WO2017057231A1

WO2017057231A1 - Ni-COATED COPPER POWDER, CONDUCTIVE PASTE, CONDUCTIVE PAINT AND CONDUCTIVE SHEET USING SAME, AND METHOD FOR MANUFACTURING Ni-COATED COPPER POWDER

Info

Publication number: WO2017057231A1
Application number: PCT/JP2016/078181
Authority: WO
Inventors: 岡田　浩
Original assignee: 住友金属鉱山株式会社
Priority date: 2015-09-28
Filing date: 2016-09-26
Publication date: 2017-04-06
Also published as: TW201726973A

Abstract

Provided is a Ni-coated copper powder which increases the number of contact points between Ni-coated copper powder particles, thereby ensuring excellent conductivity and preventing agglomeration between the copper powder particles. Thus, the Ni-coated copper powder may be preferably used for conductive pastes, electromagnetic shields or the like. The Ni-coated copper powder according to the present invention is formed via the agglomeration of copper particles having specific shapes and Ni- or Ni alloy-coated surfaces into a dendritic shape or an agglomerate of the copper particles. This Ni-coated copper powder has a larger number of contact points between copper powder particles and thus exhibits excellent conductivity.

Description

Ni-coated copper powder, and conductive paste, conductive paint, conductive sheet using the same, and method for producing Ni-coated copper powder

The present invention relates to copper powder (Ni-coated copper powder) whose surface is coated with nickel (Ni) or a Ni alloy, and more specifically, to improve conductivity by using it as a material such as a conductive paste. The present invention relates to a Ni-coated copper powder having a new shape.

For the formation of wiring layers, electrodes, and the like in electronic devices, many pastes and paints using metal fillers such as copper powder and silver powder, such as resin pastes, fired pastes, and electromagnetic wave shielding paints, are used. Metal filler pastes such as copper powder and silver powder are applied or printed on various base materials, and are subjected to heat curing or heat baking treatment to form a conductive film to be a wiring layer or an electrode.

For example, a resin-type conductive paste is made of a metal filler, a resin, a curing agent, a solvent, etc., printed on a conductor circuit pattern or terminal, and cured by heating at 100 ° C. to 200 ° C. An electrode is formed. In the resin-type conductive paste, since the thermosetting resin is cured and contracted by heat, when the metal filler is pressed and brought into contact, the metal filler overlaps and an electrically connected current path is formed. Since this resin-type conductive paste is processed at a curing temperature of 200 ° C. or less, it is used for a substrate using a heat-sensitive material such as a printed wiring board.

Firing-type conductive paste consists of a metal filler, glass, solvent, etc., printed on a conductor circuit pattern or terminal, and heated and fired at 600 ° C. to 800 ° C. to form wiring and electrodes as a conductive film. To do. The fired conductive paste is processed at a high temperature to sinter the metal filler and ensure conductivity. Although this firing-type conductive paste has a high firing temperature, it cannot be used for printed wiring boards that use resin materials, but it can realize low resistance because the metal filler is sintered by high-temperature treatment. Become. Therefore, the fired conductive paste is used for an external electrode of a multilayer ceramic capacitor.

On the other hand, electromagnetic wave shields are used to prevent the generation of electromagnetic noise from electronic equipment. Especially in recent years, personal computers and mobile phone cases have been made of resin, so that the case is made conductive. In order to secure the properties, there are a method of forming a thin metal film by a vapor deposition method or a sputtering method, a method of applying a conductive paint, a method of attaching a conductive sheet to a necessary place and shielding an electromagnetic wave, etc. Proposed. Among them, special methods are required in the processing process for the method of applying the metal filler dispersed in the resin and the method of dispersing the metal filler in the resin and processing it into a sheet and attaching it to the housing. It has excellent flexibility and is widely used.

However, in the case where such a metal filler is dispersed in a resin and applied or processed into a sheet shape, the dispersion state of the metal filler in the resin is not uniform. A method such as increasing the filling rate of the metal filler is required. However, in such a case, the addition of a large amount of metal filler causes problems such as an increase in sheet weight and a loss of flexibility of the resin sheet. Therefore, for example, in Patent Document 1, a method of using a flat metal filler has been proposed in order to solve these problems, and as a result, a thin sheet having excellent electromagnetic shielding effect and good flexibility. Can be formed.

Copper powder as a metal powder material used as a metal filler for such conductive paste and electromagnetic wave shielding material is covered with copper oxide when oxidized, causing adverse effects on sinterability, corrosion resistance, or conductivity Become. For this reason, in order to prevent oxidation of the copper powder, the surface of the copper particles is coated with a noble metal such as Pt, Pd, Ag, Au, etc., coated with a SiO ₂ oxide, or coated with Ni. Those with improved oxidation resistance are known. For example, Patent Document 2 discloses Ni-coated copper powder in which nickel (Ni) is coated on the surface of copper powder.

On the other hand, the shape of the copper powder used as the metal filler is spherical, flat, dendritic, etc., and in particular, the flat copper powder is a contact point between fillers compared to granular or dendritic copper powder. Since a large area can be secured, it is widely used as a low-resistance conductive paste. As a method for producing such a flat copper powder, Patent Document 3 discloses a method of obtaining a flaky copper powder by mechanically processing a spherical copper powder into a flat shape. Specifically, a spherical copper powder having an average particle size of 0.5 μm to 10 μm is used as a raw material, and it is mechanically processed into a flat plate shape by a mechanical energy of a medium loaded in the mill using a ball mill or a vibration mill. is there.

Also, for example, Patent Document 4 discloses a technique relating to a copper powder for conductive paste, more specifically, a disk-shaped copper powder that provides high performance as a copper paste for through holes and external electrodes, and a method for producing the same. Specifically, the granular atomized copper powder is put into a medium agitating mill, and a steel ball having a diameter of 1/8 inch to 1/4 inch is used as a grinding medium. % To 1% and processed into a flat plate shape by pulverization in air or in an inert atmosphere.

Here, silver powder is used as the metal filler used for these conductive pastes and electromagnetic wave shields, and as described above, the surface of the copper particles is coated with a noble metal such as Pt, Pd, Ag, or Au. Thus, those having sufficient oxidation resistance are used. However, since these are expensive, the cost increases. Among them, a copper powder coated with Ag can be kept at a relatively low price, but there is a problem that migration tends to occur with Ag. Also, when the surface of the copper powder is coated with a SiO ₂ -based oxide, oxidation resistance can be secured, but there are problems such as poor sinterability.

A method for coating copper powder with Ni is mentioned as a low cost and relatively good sinterability while ensuring oxidation resistance and the like.

As a method for coating the surface of the copper powder with Ni, a method by electroless nickel plating may be mentioned. The coating method by electroless nickel plating is to perform nickel coating on the copper powder surface by reducing nickel ions in the plating solution with a reducing agent. The types of reducing agents are hypophosphites and borohydrides. And hydrazine compounds. Specifically, in nickel coating treatment using hypophosphite as a reducing agent, a Ni—P alloy coating is formed because phosphorus is contained in the coating during the reduction reaction. Further, in the nickel coating treatment using a borohydride compound as a reducing agent, a Ni—B alloy coating is formed because boron is contained in the coating during the reduction reaction. Further, in the nickel coating process using a hydrazine compound as a reducing agent, a high-purity Ni coating with few impurities is formed.

Now, as copper powder, electrolytic copper powder deposited in dendritic shape called dendritic shape is known, and since the shape is dendritic, it is characterized by a large surface area. Due to the dendritic shape as described above, when this is used for a conductive film or the like, the dendritic branches are overlapped with each other, conduction is easy, and the number of contact points between particles is larger than that of spherical particles. Therefore, there is an advantage that the amount of conductive filler such as conductive paste can be reduced. For example, Patent Document 5 discloses a technique for ensuring oxidation resistance by forming an Ni alloy layer on a copper surface and performing Ag coating thereon, and the copper powder used here is a dendritic electrolytic copper powder. Is preferable from the viewpoint of entanglement between particles.

On the other hand, when developing a branch of electrolytic copper powder, when used in conductive paste, etc., the electrolytic copper powder is entangled more than necessary and agglomeration occurs, so that it does not disperse uniformly in the resin, and the fluidity is It is pointed out in Patent Document 6 that it decreases and becomes very difficult to handle, causing problems in wiring formation by printing or the like and reducing productivity. In addition, in patent document 6, in order to raise the intensity | strength of electrolytic copper powder itself, the intensity | strength of electrolytic copper powder itself is improved by adding tungstate in the copper sulfate aqueous solution of the electrolyte solution for depositing electrolytic copper powder. It is said that it is difficult to break the branches and can be molded with high strength.

As described above, it is not easy to use the dendritic copper powder as a metal filler such as a conductive paste, and the improvement of the conductivity of the paste has been difficult.

JP 2003-258490 A JP-A-5-342908 Japanese Patent Laid-Open No. 2005-200734 JP 2002-15622 A Japanese Patent Laid-Open No. 2002-075057 JP 2011-58027 A

The present invention has been proposed in view of such circumstances, and agglomeration between copper powders while ensuring excellent conductivity by increasing the number of contacts when the copper powders coated with Ni are in contact with each other. An object of the present invention is to provide a Ni-coated copper powder that can be suitably used for applications such as conductive paste and electromagnetic wave shielding.

The inventor has conducted intensive examinations to solve the above-described problems. As a result, the copper particles of a specific shape coated with Ni or Ni alloy on the surface are gathered, and the Ni-coated copper powder having a dendritic shape or an aggregate form of the copper particles, It has been found that the number of contacts between the copper powders increases and exhibits excellent conductivity, and the present invention has been completed. That is, the present invention provides the following.

[1] A first aspect of the present invention is a tree branch having a main trunk that is linearly grown with copper particles coated with nickel (Ni) or Ni alloy on the surface and a plurality of branches separated from the main trunk. The copper particles having a Ni-shaped copper powder having a surface shape coated with Ni or a Ni alloy have an average cross-sectional thickness of 0.02 μm to 5.5 mm as determined by scanning electron microscope (SEM) observation. The Ni-coated copper powder, which has a flat shape of 0 μm and is constituted by aggregating the copper particles, has an average particle diameter (D50) of 1.0 μm to 100 μm, and is equal to the flat surface of the copper particles. Thus, the maximum height in the vertical direction is 1/10 or less of the maximum length in the horizontal direction of the flat plate-like surface.

[2] A second invention of the present invention is a Ni-coated copper powder in which copper particles whose surfaces are coated with nickel (Ni) or Ni alloy are assembled to form a dendritic shape having a plurality of branches. The copper particles coated with Ni or Ni alloy on the surface have a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. The Ni-coated copper powder that is an ellipsoid and is configured by aggregating the copper particles is Ni-coated copper powder having an average particle diameter (D50) of 5.0 μm to 20 μm.

[3] A third invention of the present invention is the Ni-coated copper powder according to the second invention, wherein the average thickness of the branch portions constituting the dendritic shape is 0.5 μm to 2.0 μm.

[4] A fourth aspect of the present invention is a tree branch having a main trunk that is linearly grown with copper particles coated with nickel (Ni) or Ni alloy on the surface and a plurality of branches separated from the main trunk. A copper particle having a Ni-shaped copper powder having a surface shape, the surface of which is coated with Ni or a Ni alloy is a flat plate having a cross-sectional average thickness of 0.2 μm to 5.0 μm. The Ni-coated copper powder composed of the above is Ni-coated copper powder having an average particle diameter (D50) of 1.0 μm to 100 μm.

[5] A fifth invention of the present invention is a Ni-coated copper powder in which a plurality of individual copper particles whose surfaces are coated with nickel (Ni) or a Ni alloy are aggregated to have an aggregate form. The copper particles coated with Ni or Ni alloy have an average major axis diameter determined by observation with a scanning electron microscope (SEM) of 0.5 μm to 5.0 μm and an average cross-sectional thickness of 0.02 μm to The Ni-coated copper powder, which has a flat plate shape of 1.0 μm and is configured by the aggregation of the copper particles, is an Ni-coated copper powder having an average particle diameter (D50) of 1.0 μm to 30 μm.

[6] A sixth aspect of the present invention is a tree branch having a main trunk that is linearly grown with copper particles coated with nickel (Ni) or Ni alloy on the surface and a plurality of branches separated from the main trunk. The copper particles having a Ni-shaped copper powder having a surface shape coated with Ni or a Ni alloy are dendritic having a main trunk grown in a dendritic shape and a plurality of branches separated from the main trunk. The Ni-coated copper powder, which is a flat plate having a cross-sectional average thickness of the main trunk and branches of the copper particles of 0.02 μm to 0.5 μm and is configured by aggregating the copper particles, has an average particle diameter ( D50) is a Ni-coated copper powder having a thickness of 1.0 to 30 μm.

[7] A seventh invention of the present invention is the Ni according to the sixth invention, wherein the surface of the copper particles has fine convex portions, and the average height of the convex portions is 0.01 μm to 0.4 μm. Coated copper powder.

[8] The eighth invention of the present invention is the entire Ni-coated copper powder coated with Ni or Ni alloy in which the Ni content coated as Ni or Ni alloy in any of the first to seventh inventions The Ni-coated copper powder is 1 to 50% by mass with respect to 100% by mass.

[9] According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the surface of the copper particles is coated with a Ni alloy, and cobalt, zinc, tungsten, molybdenum, palladium, platinum, Coated with a Ni alloy containing at least one selected from the group consisting of tin, phosphorus, and boron at a content of 0.1% by mass to 20% by mass with respect to 100% by mass of the Ni alloy. Ni-coated copper powder.

[10] A tenth aspect of the present invention is the Ni-coated copper powder according to any one of the first to ninth aspects, wherein the bulk density is in the range of 0.5 g / cm ³ to 5.0 g / cm ^3. is there.

[11] Eleventh aspect of the present invention, in any one of the first to 10, BET specific surface area is 0.2m ^² /g~5.0m ² / g, a Ni-coated copper powder is there.

[12] A twelfth invention of the present invention is a metal filler containing the Ni-coated copper powder according to any one of the first to eleventh inventions in a proportion of 20% by mass or more of the whole.

[13] A thirteenth invention of the present invention is a conductive paste obtained by mixing a metal filler according to the twelfth invention with a resin.

[14] A fourteenth aspect of the present invention is a conductive paint for electromagnetic wave shielding using the metal filler according to the twelfth aspect of the present invention.

[15] A fifteenth aspect of the present invention is an electromagnetic wave shielding conductive sheet using the metal filler according to the twelfth aspect of the present invention.

[16] A sixteenth invention of the present invention is a method for producing a Ni-coated copper powder according to the first invention, wherein the copper powder is deposited on the cathode from the electrolyte by an electrolytic method, and the copper powder A step of coating nickel (Ni) or a Ni alloy, and the electrolytic solution is represented by the following formula (2), a copper ion and a compound having a phenazine structure represented by the following formula (1): One or more selected from the group consisting of a compound having an azobenzene structure and a compound having a phenazine structure and an azobenzene structure represented by the following formula (3), and one or more nonionic surfactants: Is a method for producing Ni-coated copper powder.

[In Formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, ═O, CN, SCN. , SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl, R ₅ is hydrogen, halogen , Amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, and aryl. And A ⁻ is a halide anion. ]

[In the formula (2), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ are each independently hydrogen, halogen, amino, OH, = O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, a group selected from the group consisting of benzenesulfonic acid, lower alkyl, and aryl. ]

[In the formula (3), R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each independently hydrogen, Selected from the group consisting of halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl R ₃ is hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, A group selected from the group consisting of lower alkyl and aryl, and A ⁻ is a halide anion. ]

[17] The seventeenth invention of the present invention is the method for producing Ni-coated copper powder in the sixteenth invention, wherein the electrolytic solution further contains chloride ions.

[18] An eighteenth invention of the present invention is a method for producing a Ni-coated copper powder according to the second or third invention, wherein the copper powder is deposited on the cathode from the electrolytic solution by an electrolysis method, A process for coating nickel powder with nickel (Ni) or a nickel alloy, wherein the electrolytic solution contains copper ions and a polyether compound for electrolysis. is there.

[19] A nineteenth invention of the present invention is a method for producing a Ni-coated copper powder according to the fourth invention, wherein the copper powder is deposited on the cathode from the electrolyte by an electrolytic method, and the copper powder A step of coating nickel (Ni) or a Ni alloy on the electrolyte solution, and the electrolytic solution includes one or two selected from copper ions and a compound having a phenazine structure represented by the following formula (1) This is a method for producing Ni-coated copper powder in which electrolysis is carried out.

[20] A twentieth invention of the present invention is a method for producing a Ni-coated copper powder according to the sixth or seventh invention, wherein the copper powder is deposited on the cathode from the electrolytic solution by an electrolysis method, A step of coating copper powder with nickel (Ni) or Ni alloy, and the electrolytic solution is selected from compounds having a phenazine structure and an azobenzene structure represented by the following formula (3): copper ions The manufacturing method of Ni coat | court copper powder which electrolyzes containing 1 type, or 2 or more types.

[In the formula (3), R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each independently hydrogen, Selected from the group consisting of halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl It is a group. R ₃ is hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion. ]

According to the present invention, it is possible to secure a large number of contacts and a large contact area, to ensure excellent conductivity, and to prevent agglomeration between copper powders. It can utilize suitably for uses, such as a shield.

It is the figure which showed typically the specific shape of the dendritic Ni coat | court copper powder which concerns on 1st Embodiment. It is the figure which showed typically the specific shape of the dendritic Ni coat | court copper powder which concerns on 1st Embodiment. In 1st Embodiment, it is a photograph figure which shows an observation image when the dendritic copper powder before coat | covering Ni is observed by SEM with 1000-times multiplication factor. In 1st Embodiment, it is a photograph figure which shows an observation image when dendritic copper powder before coat | covering Ni is observed by SEM with a magnification of 5,000 times. It is a photograph figure which shows an observation image when the dendritic Ni coat copper powder which concerns on 1st Embodiment is observed by 1000-times multiplication factor by SEM. It is a photograph figure which shows an observation image when the dendritic Ni coat copper powder which concerns on 1st Embodiment is observed by 1000-times multiplication factor by SEM. In 2nd Embodiment, it is the figure which showed typically the specific shape of the dendritic copper powder before coat | covering Ni. In 2nd Embodiment, it is a photograph figure which shows an example of an observation image when the dendritic copper powder before coat | covering Ni is observed by SEM with a magnification of 5,000 times. It is a photograph figure which shows an example of an observation image when the dendritic Ni coat | court copper powder which concerns on 2nd Embodiment is observed by 5,000 times by SEM. It is a photograph figure which shows an example of an observation image when the dendritic Ni coat | court copper powder which concerns on 2nd Embodiment is observed by 10,000 times with SEM. It is the figure which showed typically the specific shape of the dendritic Ni coat | court copper powder which concerns on 3rd Embodiment. In 3rd Embodiment, it is a photograph figure which shows an example of an observation image when the dendritic copper powder before coat | covering Ni is observed by SEM with a magnification of 5,000 times. It is a photograph figure which shows an example of an observation image when the dendritic Ni coat | court copper powder which concerns on 3rd Embodiment is observed by 5,000 times magnification by SEM. It is a photograph figure which shows an example of an observation image when the dendritic Ni coat | court copper powder which concerns on 3rd Embodiment is observed by 1000-times multiplication factor by SEM. It is the figure which showed typically the specific shape of the Ni coat copper powder which concerns on 4th Embodiment. It is a photograph figure which shows an example of an observed image when the Ni coat copper powder which concerns on 4th Embodiment is observed by SEM with a magnification of 5,000 times. It is a photograph figure which shows an example of an observation image when the Ni coat copper powder which concerns on 4th Embodiment is observed by 10,000 times by SEM. It is the figure which showed typically the specific shape of the copper particle with which Ni or Ni alloy which comprises the dendritic Ni coat copper powder concerning 5th Embodiment was coat | covered. In 5th Embodiment, it is a photograph figure which shows an example of an observation image when dendritic copper powder before coat | covering Ni is observed by SEM by 10,000 time magnification. It is a photograph figure which shows an example of an observation image when the dendritic Ni coat | court copper powder which concerns on 5th Embodiment is observed by 5,000 times magnification by SEM. It is a photograph figure which shows an example of the observation image when another location of the dendritic nickel coat copper powder which concerns on 5th Embodiment is observed by magnification by 10,000 times with SEM. It is a photograph figure which shows an example of an observed image when another location of the dendritic nickel coat copper powder which concerns on 5th Embodiment is observed by 1000-times multiplication factor by SEM. It is a photograph figure which shows an observation image when the Ni coat copper powder obtained in the comparative example 7 is observed by 5,000 times by SEM. It is a photograph figure which shows an observation image when the Ni coat copper powder obtained in the comparative example 10 is observed by 5,000 times by SEM. It is a photograph figure which shows an observation image when Ni coat copper powder obtained in the comparative example 13 is observed by 1000-times multiplication factor by SEM.

Hereinafter, specific embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments, and Various modifications can be made without departing from the scope of the invention. In this specification, the notation “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less”.

<< 1. Nickel (Ni) coated copper powder >>
The nickel-coated copper powder according to the present invention is a copper powder having a surface coated with nickel (Ni) or a Ni alloy. In this specification, nickel-coated copper powder is referred to as “Ni-coated copper powder”. Further, nickel or nickel alloy to be coated is expressed as “Ni” and “Ni alloy”, respectively, and when Ni is coated on the surface of copper powder or Ni alloy is coated on the surface of copper powder, “Ni coating” is generally used. ".

<1-1. First Embodiment>
[Configuration of Ni-coated copper powder]
When the Ni-coated copper powder according to the first embodiment is observed using a scanning electron microscope (SEM), the Ni-coated copper powder has a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. The main trunk and the branch are constituted by a collection of tabular copper particles having a specific cross-sectional average thickness, and the surface of the tabular copper particles is coated with Ni or a Ni alloy. Hereinafter, this Ni-coated copper powder is also referred to as “dendritic Ni-coated copper powder”.

More specifically, in this dendritic Ni-coated copper powder, the main trunk and branches are composed of flat copper particles having an average cross-sectional thickness of 0.02 μm to 5.0 μm determined by SEM observation. Thus, the average particle diameter (D50) of the Ni-coated copper powder composed of flat copper particles is 1.0 μm to 100 μm. In this dendritic Ni-coated copper powder, the height of the flat copper particles in the vertical direction with respect to the flat surface is 1/10 or less with respect to the maximum length in the horizontal direction. It has a smooth surface that suppresses growth in the vertical direction.

Although such dendritic Ni-coated copper powder will be described in detail later, for example, the anode and the cathode are immersed in a sulfuric acid acidic electrolyte solution containing copper ions, and a direct current is applied to perform electrolysis so that the copper is deposited on the cathode. It can be produced by depositing powder and coating the surface of the obtained copper powder with Ni or a Ni alloy by an electroless plating method or the like.

1 and 2 are diagrams schematically showing a specific shape of the dendritic Ni-coated copper powder according to the first embodiment. As shown in FIG. 1, the dendritic Ni-coated copper powder 11 has a dendritic shape having a main trunk 12 grown linearly and a plurality of branches 13 separated from the main trunk 12. Note that the branches 13 in the dendritic Ni-coated copper powder 11 mean not only the branches 13a branched from the main trunk 12 but also the branches 13b further branched from the branches 13a.

As described above, the main trunk 12 and the branch 13 are constituted by a collection of tabular copper particles having an average cross-sectional thickness of 0.02 μm to 5.0 μm determined by SEM observation. The formation of such flat copper particles is caused by the fact that specific additives added to the electrolytic solution when electrolytically depositing copper powder are adsorbed on the surface of the copper particles, as will be described later. As a result, it is thought that it grows flat. The Ni-coated copper powder 11 is constituted by coating the surface of such flat copper particles with Ni or a Ni alloy.

However, for example, when copper powder grows in a direction perpendicular to the flat surface shown in FIG. 2 (the Z direction in FIG. 2), the copper particles of the grown branches themselves become flat, but the vertical Copper powder in which copper particles grow like protrusions is also formed in the direction. FIG. 2 is a diagram showing a horizontal direction (flat plate direction) to the flat plate surface and a direction perpendicular to the flat plate surface. The flat plate direction indicates the XY direction, and the vertical direction. Indicates the Z direction.

Here, FIG. 3 shows an observation image when the copper powder grown in the direction perpendicular to the flat plate-like surface is observed by SEM (magnification 1,000 times) in the dendritic copper powder before coating with Ni. It is a photograph figure which shows an example. In the dendritic copper powder shown in this photograph, copper particles grow in a direction perpendicular to the flat surface to form protrusions, and some flat surfaces are bent to have a height in the vertical direction. It has a shape.

When the copper particles grow in the vertical direction as shown in the photograph of FIG. 3, for example, when the Ni-coated copper powder produced based on the copper powder is used for a conductive paste or conductive paint, the vertical Since the copper powder becomes bulky due to the growth of the copper particles in the direction, the filling density cannot be obtained, and there is a problem that sufficient conductivity cannot be ensured.

On the other hand, in the Ni-coated copper powder 11 according to the first embodiment, the growth in the vertical direction with respect to the flat plate-like surface is suppressed, and the copper powder has a substantially smooth surface. Specifically, as shown in FIG. 2, the Ni-coated copper powder 11 has a maximum height in the vertical direction (reference numeral “15” in FIG. 2) with respect to the plate-like surface. It becomes 1/10 or less with respect to the maximum length (symbol “14” in FIG. 2) that is long in the direction. Note that the maximum height 15 in the direction perpendicular to the flat surface is not the thickness of the flat surface, but, for example, when the protrusion is formed on the flat surface, the height of the protrusion. Yes, it means the “height” in the direction opposite to the thickness direction with respect to the flat “surface”. Moreover, the maximum length 14 in the horizontal direction with respect to the flat surface means the major axis length of the flat surface.

Here, FIG. 4 shows an observation image when the dendritic copper powder before being coated with Ni or Ni alloy is observed by SEM (magnification 1,000 times), that is, in a direction perpendicular to the flat surface. It is a photograph figure which shows an example of the observation image of the flat dendritic copper powder which suppressed the growth. FIG. 5 is a graph showing the dendritic Ni-coated copper powder in which Ni or Ni alloy is coated on the dendritic copper powder whose growth in the vertical direction shown in FIG. It is a photograph figure which shows the observation image of. In addition, FIG. 6 is similar to FIG. 6 for another part of the dendritic Ni-coated copper powder obtained by coating Ni or Ni alloy on the dendritic copper powder whose growth in the vertical direction is suppressed by SEM (magnification 1,000 times). It is a photograph figure which shows the observation image when it observes. As shown in these photographic diagrams, it can be seen that the growth in the vertical direction with respect to the flat surface is suppressed, and a dendritic and flat copper powder having a substantially smooth surface is obtained.

Such a flat dendritic Ni-coated copper powder 11 in which the growth in the vertical direction is suppressed can ensure a large contact area between the copper powders. And since the contact area becomes large, low resistance, that is, high conductivity can be realized. Thereby, it is further excellent in electroconductivity, can maintain the electroconductivity favorably, and can be used suitably for the use of an electroconductive coating material or an electroconductive paste. Moreover, when the dendritic Ni-coated copper powder 11 is formed by aggregating flat copper particles, it can contribute to thinning of the wiring material and the like.

As described above, the tabular copper particles coated with Ni or Ni alloy constituting the main trunk 12 and the branches 13 in the dendritic Ni-coated copper powder 11 have an average cross-sectional thickness of 0.02 μm to 5.0 μm. It is. As for the cross-sectional average thickness of the flat copper particles coated with Ni or Ni alloy, the thinner one will exhibit the effect as a flat plate. That is, the trunk 12 and the branches 13 are constituted by flat copper particles coated with Ni having a cross-sectional average thickness of 5.0 μm or less, so that the copper particles and dendritic Ni formed thereby are formed. A large area where the coated copper powders 11 come into contact with each other can be secured.

In addition, as the cross-sectional average thickness of the tabular copper particles coated with Ni or Ni alloy becomes thinner, the number of contacts when the dendritic Ni-coated copper powders 11 come into contact with each other decreases. If the cross-sectional average thickness of the copper particles coated with Ni or Ni alloy is 0.02 μm or more, a sufficient number of contacts can be secured, and more preferably 0.2 μm or more. Can be increased effectively.

Further, in the dendritic Ni-coated copper powder 11 according to the first embodiment, the average particle diameter (D50) is 1.0 μm to 100 μm. The average particle diameter can be controlled by changing the electrolysis conditions described later. Further, if necessary, it can be further adjusted to a desired size by adding mechanical crushing or crushing such as a jet mill, a sample mill, a cyclone mill, or a bead mill. In addition, an average particle diameter (D50) can be measured by the laser diffraction scattering type particle size distribution measuring method, for example.

Here, as pointed out in, for example, Patent Document 1, as a problem of dendritic Ni-coated copper powder, when used as a metal filler such as a conductive paste or a resin for electromagnetic wave shielding, the metal in the resin It is mentioned that when the filler has a dendritic shape, the dendritic copper powders are entangled with each other and agglomerate occurs and is not uniformly dispersed in the resin. In addition, the agglomeration increases the viscosity of the paste and causes problems in wiring formation by printing. This occurs because the dendritic Ni-coated copper powder has a large shape (particle diameter). In order to solve this problem while effectively utilizing the dendritic shape, the dendritic Ni-coated copper powder is used. It is necessary to reduce the shape of the. However, if the particle diameter of the dendritic Ni-coated copper powder is too small, the dendritic shape cannot be secured. Therefore, the effect of being in a dendritic shape, that is, a three-dimensional shape, has a large surface area and excellent moldability and sinterability, and can be molded with high strength by being firmly connected via a branch-like portion. In order to secure the effect, it is necessary that the dendritic Ni-coated copper powder has a size larger than a predetermined size.

In this respect, in the dendritic Ni-coated copper powder 11 according to the first embodiment, the average particle diameter is 1.0 μm to 100 μm, so that the surface area is increased and good moldability and sinterability are ensured. can do. The dendritic Ni-coated copper powder 11 has a dendritic shape because the main trunk 12 and the branch 13 are composed of an aggregate of tabular copper particles in addition to the dendritic shape. Due to the three-dimensional effect and the effect that the copper particles constituting the dendritic shape are flat, more contacts between copper powders can be secured.

As a method for producing a flat Ni-coated copper powder, Patent Document 3 and Patent Document 4 show that a flat plate is formed by a mechanical method such as pulverization. In this mechanical method, for example, when spherical copper powder is formed into a flat plate shape, it is necessary to prevent copper oxidation during mechanical processing. Therefore, fatty acid is added and pulverized in air or in an inert atmosphere. This is processed into a flat plate shape. However, it cannot be completely prevented from oxidation, and the fatty acid added at the time of processing may affect the dispersibility when it is made into a paste. The fatty acid may firmly adhere to the copper surface due to the pressure during machining, which causes a problem that it cannot be completely removed. Then, when it uses as metal fillers, such as an electrically conductive paste and resin for electromagnetic wave shielding, the adhesion of the oxide film or fatty acid becomes a cause of increasing resistance.

On the other hand, the dendritic Ni-coated copper powder 11 according to the first embodiment can be grown by direct electrolysis to form a flat plate without performing mechanical processing. Therefore, the problem of oxidation and the problem due to the remaining fatty acid, which are problems in this method, do not occur, the surface state of the copper powder becomes good, and the electrical conductivity can be made extremely good. Thereby, when using as metal fillers, such as electroconductive paste and resin for electromagnetic wave shielding, low resistance is realizable. In addition, the manufacturing method of the dendritic Ni-coated copper powder 11 will be described in detail later.

Also, in order to realize further low resistance, the filling rate of the metal filler becomes a problem. In order to further increase the filling rate, the smoothness of the flat dendritic Ni-coated copper powder is required. That is, the form of the dendritic Ni-coated copper powder 11 is such that the maximum height in the direction perpendicular to the flat surface is 1/10 of the maximum length in the direction horizontal to the flat surface. By being below, since smoothness is high and a filling rate rises, since the contact in the surface of copper powder increases, further low resistance is realizable.

If the dendritic Ni-coated copper powder having the above-mentioned shape is occupied at a predetermined ratio in the obtained Ni-coated copper powder when observed with an electron microscope, Ni of other shapes Even if the coated copper powder is mixed, the same effect as that of the copper powder composed only of the dendritic Ni-coated copper powder can be obtained. Specifically, when observed with an electron microscope (for example, 500 to 20,000 times), the dendritic Ni-coated copper powder having the shape described above is 65% by number or more, preferably 80% of the total Ni-coated copper powder. As long as it occupies a ratio of several percent or more, more preferably 90 percent or more, Ni-coated copper powder of other shapes may be included.

[Ni coating]
As described above, the dendritic Ni-coated copper powder 11 according to the first embodiment is a flat plate having a cross-sectional average thickness of 0.02 μm to 5.0 μm, and the surface is coated with Ni or a Ni alloy. It is constituted in a dendritic shape by copper particles.

The dendritic Ni-coated copper powder 11 is preferably 1% by mass as Ni content with respect to 100% by mass of the entire Ni-coated copper powder 11 coated with Ni on the dendritic copper powder before being coated with Ni or Ni alloy. Ni or Ni alloy is coated at a ratio of ˜50 mass%, and the thickness of Ni (coating thickness) is 0.1 μm or less, preferably 0.05 μm or less. From this, the dendritic Ni-coated copper powder 11 has a shape that retains the shape of the dendritic copper powder before coating with Ni or Ni alloy. Therefore, the shape of the copper powder before coating Ni or Ni alloy and the shape of the Ni-coated copper powder after coating Ni or Ni alloy on the copper powder are both dendritic shapes.

The content of Ni coated as Ni or Ni alloy in the dendritic Ni-coated copper powder 11 is 1% by mass to 50% by mass with respect to 100% by mass of the Ni-coated copper powder 1 as a whole as described above. % Is preferable. The content of Ni coated as Ni or Ni alloy is preferably as low as possible because the conductivity of Ni itself is lower than copper, but if it is too small, a uniform Ni or Ni alloy film cannot be secured on the copper powder surface. As a result, copper is oxidized to cause a decrease in conductivity. Therefore, the content of Ni coated as Ni or Ni alloy is preferably 1% by mass or more with respect to 100% by mass of the entire Ni-coated copper powder 11 coated with Ni, and is 2% by mass or more. It is more preferable that the content is 5% by mass or more.

On the other hand, if the content of Ni coated as Ni or Ni alloy is increased, the conductivity is not preferable. Therefore, the coating amount of Ni or Ni alloy is preferably 50% by mass or less, more preferably 20% by mass or less, with respect to 100% by mass of the Ni-coated copper powder 11 coated with Ni. More preferably, it is 10 mass% or less.

In the dendritic Ni-coated copper powder 11 according to the first embodiment, the average thickness of Ni or Ni alloy coated on the surface of the dendritic copper powder is about 0.0003 μm to 0.1 μm, and 0.005 μm. More preferably, it is about 0.02 μm. If the coating thickness of Ni or Ni alloy is less than 0.0003 μm on average, a uniform Ni or Ni alloy coating cannot be secured on the surface of the copper powder, and copper conductivity cannot be suppressed, resulting in a decrease in conductivity. Cause. On the other hand, when the coating thickness of Ni or Ni alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of decreasing the electrical conductivity.

Thus, the average thickness of Ni coated on the surface of the dendritic copper powder is 0.1 μm or less, and the cross-sectional average thickness of the flat copper particles constituting the dendritic copper powder before coating the Ni or Ni alloy Is smaller than 0.02 μm to 5.0 μm. Therefore, before and after coating the surface of the dendritic copper powder with Ni or Ni alloy, the cross-sectional average thickness of the tabular copper particles does not substantially change.

Further, as will be described later, in the dendritic Ni-coated copper powder 11, the Ni covered with the dendritic copper powder may be a Ni alloy. The element added as the Ni alloy is preferably an element from Group 6 to Group 14 of the periodic table, and particularly one or more selected from zinc, cobalt, tungsten, molybdenum, palladium, platinum, and tin. preferable. In addition, as will be described later, when using electroless plating in the step of coating Ni on the dendritic copper powder, and further using hypophosphite and borohydride as the reducing agent, the resulting Ni coating is They are Ni-P alloy and Ni-B alloy, respectively.

[About bulk density]
The bulk density of the dendritic Ni-coated copper powder 11 is not particularly limited, but is preferably in the range of 0.5 g / cm ³ to 5.0 g / cm ³ . If the bulk density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the dendritic Ni-coated copper powders 11 cannot be secured. On the other hand, if the bulk density exceeds 5.0 g / cm ³ , the average particle diameter of the dendritic Ni-coated copper powder 11 also increases, and the surface area decreases and the moldability and sinterability deteriorate. is there.

[BET specific surface area]
In dendritic Ni-coated copper powder 11 is not particularly limited, it is preferable the value of the BET specific surface area of 0.2m ^² /g~5.0m ² / g. When the BET specific surface area value is less than 0.2 m ² / g, the copper particles coated with Ni or Ni alloy may not have the desired flat plate shape as described above, and high conductivity is obtained. There may not be. On the other hand, when the BET specific surface area value exceeds 5.0 m ² / g, the Ni coating on the surface of the dendritic Ni-coated copper powder becomes non-uniform and high conductivity may not be obtained. Moreover, the copper particle which comprises Ni coat | court copper powder may become too fine, Ni coat copper powder may become a fine beard-like state, and electroconductivity may fall. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

<1-2. Second Embodiment>
[Configuration of Ni-coated copper powder]
The Ni-coated copper powder according to the second embodiment forms a dendritic shape having a plurality of branches when observed using a scanning electron microscope (SEM), and has an ellipsoidal shape having a specific size. The copper particles are assembled and the surfaces of these copper particles are coated with Ni or a Ni alloy. Hereinafter, this Ni-coated copper powder is also referred to as “dendritic Ni-coated copper powder”.

More specifically, in this dendritic Ni-coated copper powder, a copper powder having a dendritic shape having a plurality of branches has a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter. The ellipsoid has a size in the range of 0.5 μm to 2.0 μm, and is composed of copper particles whose surfaces are coated with Ni or a Ni alloy. The average particle diameter (D50) of the Ni-coated copper powder formed by aggregating copper particles coated with Ni or Ni alloy on the surface is 5.0 μm to 20 μm.

Here, FIG. 7 is a diagram schematically showing a specific shape of the dendritic copper powder before the Ni or Ni alloy is coated on the surface, which constitutes the Ni-coated copper powder according to the second embodiment. It is. As shown in the schematic diagram of FIG. 7, the dendritic copper powder 21 constituting the Ni-coated copper powder has a dendritic shape having a plurality of branches and is composed of an aggregate of fine copper particles 22. The Ni-coated copper powder is formed by coating the surface of dendritic copper powder 21, which is an aggregate of such copper particles 22, with Ni or a Ni alloy.

The copper particles 22 constituting the dendritic copper powder 21 have an ellipsoid having a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. It is the copper particle of the shape. The dendritic copper powder 21 which is an aggregate of the ellipsoidal copper particles 22 has an average particle diameter (D50) of 5.0 μm to 20 μm. Even after the surface of the dendritic copper powder 21 is coated with Ni or Ni alloy, the minor axis average diameter and major axis average diameter of the copper particles coated with Ni constituting the Ni-coated copper powder, and the Ni The average particle diameter of the coated copper powder is almost the same.

Although such dendritic copper powder 21 will be described in detail later, for example, the anode and the cathode are immersed in a sulfuric acid acidic electrolyte solution containing copper ions, and a DC current is applied to cause electrolysis to deposit on the cathode. Can be obtained. That is, the dendritic copper powder 21 having a small shape as described above can be deposited and formed by electrolysis without performing physical treatment such as pulverization and crushing. In addition, since the conventional dendritic copper powder has a very large shape and cannot be used as it is, it was used as a small shape by performing a pulverization process. In this case, the crushed shape is a rod-shaped copper powder having a size of 10 μm or less. Therefore, the shape of the conventional dendritic copper powder is considered to be a dendritic copper powder in which shapes of 10 μm or less are assembled.

FIG. 8 is a photograph showing an example of an observation image obtained by SEM (magnification: 5,000 times) of the dendritic copper powder before coating with Ni or Ni alloy. 9 and 10 are SEM observations of the dendritic Ni-coated copper powder according to the second embodiment, that is, the dendritic Ni-coated copper powder obtained by coating the surface of the dendritic copper powder with Ni or a Ni alloy. It is a photograph figure which shows an example of an image (FIG. 9: 5,000 times magnification, FIG. 10: 10,000 times magnification).

As observed in FIG. 8, the copper powder before coating with Ni exhibits a dendritic precipitation state. And this dendritic copper powder has formed the dendritic shape which has a some branch by gathering the fine copper particle which has an elliptical shape, as typically shown in FIG. Here, the size of the copper particles is an ellipsoidal shape having a minor axis average diameter of 0.5 μm or less and a major axis average diameter of 2.0 μm or less.

Increasing the number of contacts when dendritic Ni-coated copper powders are in contact with each other by having a long axis average diameter of the shape of the copper particles 2 constituting the dendritic copper powder 1 is 2.0 μm or less. Can do. That is, by being an aggregate of copper particles 2 having a long axis average diameter of 2.0 μm or less, it can be confirmed from the observation results shown in FIG. 9 and FIG. As a result, fine protrusions are formed, which can secure many contacts between the dendritic Ni-coated copper powders.

However, when the long axis average diameter is longer than 2.0 μm, the distance between the branches of the dendritic copper powder becomes narrower and becomes a dense shape on the whole, so that the contacts between the dendritic copper powders tend to decrease. Become. Conversely, when the major axis average diameter of the copper particles becomes too short, formation of protrusions cannot be obtained. Therefore, the major axis average diameter of the copper particles 2 is preferably 0.5 μm to 2.0 μm.

Further, the minor axis average diameter of the copper particles 2 is 0.5 μm or less. When the minor axis average diameter of the copper particles 2 is thicker than 0.5 μm, when the copper particles are assembled to form a dendritic copper powder, the thickness of the branch portion of the dendritic copper powder (for example, FIG. 7). “D1”) in the schematic diagram increases. When the thickness of the branch portion is increased, the interval between the branches of the dendritic Ni-coated copper powder in which the surface of the dendritic copper powder is coated with Ni or Ni alloy is narrowed, resulting in a dense shape as a whole. No dendritic effect. Conversely, if the diameter of the branch part of the dendritic copper powder composed of copper particles is too thin, it becomes a fine whisker-like state, ensuring sufficient conductivity when the dendritic Ni-coated copper powders are in contact with each other become unable. For this reason, it is preferable that the minor axis average diameter of the copper particles 2 is 0.2 μm to 0.5 μm, thereby providing sufficient conductivity while exhibiting a three-dimensional dendritic effect. Can be secured.

Furthermore, the average thickness (D1) of the branch portion of the dendritic copper powder 1 constituted by the aggregation of the copper particles 2 is preferably 2.0 μm or less. When the average thickness of the branch portion exceeds 2.0 μm, the interval between the branches of the dendritic copper powder is narrowed and the shape becomes dense as a whole. On the other hand, if the thickness of the branch portion is too small, the strength of the dendritic Ni-coated copper powder in which the surface of the dendritic copper powder is coated with Ni or Ni alloy will be insufficient, especially when molded into a conductive sheet In consideration of the flexibility, since the strength of the dendritic Ni-coated copper powder is low, there is a possibility that it breaks at the branch portion of the copper powder and loses conductivity. Therefore, the thickness of the branch portion of the dendritic copper powder 1 is preferably 0.5 μm to 2.0 μm.

Further, in the Ni-coated copper powder according to the second embodiment, the average particle diameter (D50) is 5.0 μm to 20 μm. The average particle diameter can be controlled by changing the electrolysis conditions described later. Further, if necessary, it can be further adjusted to a desired size by adding mechanical crushing or crushing such as a jet mill, a sample mill, a cyclone mill, or a bead mill. With such a size of the Ni-coated copper powder, it is possible to secure a large number of contact points between the copper powders by the effect of the three-dimensional dendritic shape, and to suppress the aggregation in the resin and disperse it well. And increase in paste viscosity can be suppressed. In addition, an average particle diameter (D50) can be measured by the laser diffraction scattering type particle size distribution measuring method, for example.

[Ni coating]
In the dendritic Ni-coated copper powder according to the second embodiment, the surface of the dendritic copper powder 21 (see FIG. 7) is coated with Ni or a Ni alloy as described above.

The dendritic Ni-coated copper powder has a Ni content of 1% by mass to 100% by mass of the entire Ni-coated copper powder coated with Ni on the dendritic copper powder 21 before being coated with Ni or Ni alloy. Ni or Ni alloy is coated at a ratio of 50% by mass, and the thickness of Ni (coating thickness) is 0.1 μm or less, preferably 0.02 μm or less. From this, the resinous Ni-coated copper powder has a shape that retains the shape of the dendritic copper powder 21 before being coated with Ni or Ni alloy. Therefore, both the shape of the copper powder before coating Ni or Ni alloy and the shape of the Ni-coated copper powder after coating the copper powder with Ni or Ni alloy are both dendritic shapes.

The content of Ni coated as Ni or Ni alloy in the dendritic Ni-coated copper powder is 1% by mass to 50% by mass with respect to 100% by mass of the entire Ni-coated copper powder coated with Ni as described above. A range is preferable. The content of Ni coated as Ni or Ni alloy is preferably as low as possible because the conductivity of Ni itself is lower than copper, but if it is too small, a uniform Ni or Ni alloy film cannot be secured on the copper powder surface. As a result, copper is oxidized to cause a decrease in conductivity. Therefore, as content of Ni coat | covered as Ni or Ni alloy, it is preferable that it is 1 mass% or more with respect to 100 mass of the whole Ni coat | covered Ni-coated copper powder, and it is 2 mass% or more. Is more preferable, and it is further more preferable that it is 5 mass% or more.

On the other hand, if the content of Ni coated as Ni or Ni alloy is increased, the conductivity is not preferable. Therefore, the coating amount of Ni or Ni alloy is preferably 50% by mass or less, more preferably 20% by mass or less, with respect to 100% by mass of the entire Ni-coated copper powder coated with Ni. More preferably, it is at most mass%.

In the dendritic Ni-coated copper powder according to the second embodiment, the average thickness of Ni or Ni alloy coated on the surface of the copper particles is about 0.0003 μm to 0.1 μm, and 0.005 μm to 0.00. It is preferably about 02 μm. If the coating thickness of Ni or Ni alloy is less than 0.0003 μm on average, a uniform Ni coating cannot be ensured on the surface of the copper powder, and copper oxidation cannot be suppressed, resulting in a decrease in conductivity. Become. On the other hand, when the coating thickness of Ni or Ni alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of decreasing the electrical conductivity.

Thus, the average thickness of the Ni or Ni alloy coated on the surface of the dendritic Ni-coated copper powder is about 0.0003 μm to 0.1 μm, and constitutes the dendritic copper powder 21 before coating the Ni or Ni alloy. It is smaller than the size of the copper particles 22 (an ellipsoid having a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm). Therefore, the form of the copper powder is not substantially changed before and after the surface of the dendritic copper powder 21 is coated with Ni or Ni alloy.

As described further below, in the dendritic Ni-coated copper powder, the Ni covered with the dendritic copper powder 21 may be a Ni alloy. The element added as the Ni alloy is preferably an element from Group 6 to Group 14 of the periodic table, and particularly one or more selected from zinc, cobalt, tungsten, molybdenum, palladium, platinum, and tin. preferable. Further, as will be described later, when using electroless plating in the step of coating Ni on the dendritic copper powder 21, and further using hypophosphite and borohydride as the reducing agent, the Ni coating obtained Are a Ni—P alloy and a Ni—B alloy, respectively.

[About bulk density]
The bulk density of the dendritic Ni-coated copper powder according to the second embodiment is not particularly limited, but is preferably in the range of 0.5 g / cm ³ to 5.0 g / cm ³ . If the bulk density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the dendritic Ni-coated copper powders cannot be ensured. On the other hand, if the bulk density exceeds 5.0 g / cm ³ , the average particle diameter of the dendritic Ni-coated copper powder also increases, and the surface area may decrease, and the formability and sinterability may deteriorate. .

[BET specific surface area]
The dendritic Ni-coated copper powder according to the second embodiment is not particularly limited, it is preferable the value of the BET specific surface area of 0.2m ^² /g~5.0m ² / g. If the BET specific surface area value is less than 0.2 m ² / g, the copper particles 22 coated with Ni or Ni alloy (see FIG. 7) may not have the desired size and shape as described above. High conductivity may not be obtained. On the other hand, if the BET specific surface area value exceeds 5.0 m ² / g, the Ni or Ni alloy coating on the surface of the dendritic Ni-coated copper powder becomes non-uniform and high conductivity may not be obtained. In addition, the copper particles 2 constituting the Ni-coated copper powder become too fine, and the Ni-coated copper powder may be in a fine whisker-like state, resulting in a decrease in conductivity. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

<1-3. Third Embodiment>
[Configuration of Ni-coated copper powder]
When the Ni-coated copper powder according to the third embodiment is observed using a scanning electron microscope (SEM), the Ni-coated copper powder has a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. The main trunk and the branch are constituted by a collection of tabular copper particles having a specific cross-sectional average thickness, and the surface of the tabular copper particles is coated with Ni or a Ni alloy. Hereinafter, this Ni-coated copper powder is also referred to as “dendritic Ni-coated copper powder”.

More specifically, in this dendritic Ni-coated copper powder, the main trunk and branches are composed of flat copper particles having an average cross-sectional thickness of 0.2 μm to 5.0 μm determined by SEM observation. The average particle diameter (D50) of the Ni-coated copper powder composed of flat copper particles is 1.0 μm to 100 μm.

FIG. 11 is a diagram schematically showing a specific shape of the Ni-coated copper powder according to the third embodiment. As shown in FIG. 11, the dendritic Ni-coated copper powder 31 has a dendritic shape having a main trunk 32 that grows linearly and a plurality of branches 33 that are separated from the main trunk 32. The branch 33 in the dendritic Ni-coated copper powder 31 means both a branch 33a branched from the main trunk 32 and a branch 33b further branched from the branch 33a.

The dendritic Ni-coated copper powder 31 is a flat plate having a predetermined average cross-sectional thickness, and is composed of copper particles whose surface is coated with Ni or a Ni alloy.

More specifically, in the dendritic Ni-coated copper powder 31, the main trunk 32 and the branch 33 are configured by aggregating tabular copper particles having a cross-sectional average thickness of 0.2 μm to 5.0 μm. The formation of such flat copper particles is caused by the fact that specific additives added to the electrolytic solution when electrolytically depositing copper powder are adsorbed on the surface of the copper particles, as will be described later. As a result, it is thought that it grows flat. The Ni-coated copper powder 31 is constituted by coating the surface of such flat copper particles with Ni or a Ni alloy.

FIG. 12 is a photograph showing an example of an observation image of the dendritic copper powder 31 constituting the dendritic Ni-coated copper powder 31 before being coated with Ni, when observed by SEM (magnification 5,000 times). FIG. 13 is a photograph showing an example of an observation image when the dendritic Ni-coated copper powder obtained by coating the dendritic copper powder of FIG. 12 with Ni is observed by SEM (magnification 5,000 times). Similarly, FIG. 14 is a photograph showing an example of an observation image when dendritic Ni-coated copper powder obtained by coating Ni on dendritic copper powder by SEM (magnification 1,000 times).

The dendritic Ni-coated copper powder forms a two-dimensional or three-dimensional dendritic shape having a main trunk and branches branched from the main trunk, as shown in the observation images of FIGS.

Here, in the dendritic Ni-coated copper powder 31, the flat copper particles constituting the main trunk 32 and the branches 33 have an average cross-sectional thickness of 0.2 μm to 5.0 μm as described above. The thinner the cross-sectional average thickness of the flat copper particles, the more the flat plate effect is exhibited. That is, since the main trunk 32 and the branch 33 are composed of flat copper particles having a cross-sectional average thickness of 5.0 μm or less, an area where the Ni-coated dendritic Ni-coated copper powders 31 are in contact with each other is increased. Since the contact area can be ensured and the contact area becomes large, low resistance, that is, high conductivity can be realized. By this, it is more excellent in electroconductivity, can maintain the electroconductivity favorably, and can use it suitably for the use of an electroconductive coating material or an electroconductive paste. Further, since the dendritic Ni-coated copper powder 31 is composed of fine copper particles coated with a flat-plate Ni, it can contribute to thinning of the wiring material and the like.

In addition, even if the cross-sectional average thickness of the copper particles coated with Ni or Ni alloy is as thin as 5.0 μm or less, the unevenness is reduced if the size of the flat copper particles is too small. When the dendritic Ni-coated copper powders 31 come into contact with each other, the number of contacts decreases. Therefore, as described above, the lower limit value of the average cross-sectional thickness of the copper particles is preferably 0.2 μm or more, which can increase the number of contacts.

The dendritic Ni-coated copper powder 31 has an average particle diameter (D50) of 1.0 to 100 μm. The average particle diameter can be controlled by changing the electrolysis conditions described later. Further, if necessary, it can be further adjusted to a desired size by adding mechanical pulverization such as a jet mill, a sample mill, a cyclone mill, and a bead mill. In addition, an average particle diameter (D50) can be measured by the laser diffraction scattering type particle size distribution measuring method, for example.

Thus, when the average particle diameter is 1.0 μm to 100 μm, the surface area is increased, and good moldability and sinterability can be ensured. The dendritic Ni-coated copper powder 31 has a dendritic shape and, in addition, the main trunk 32 and the branch 33 are made of flat copper particles. As a result of the effect that the copper particles constituting the dendritic shape are flat, more contacts between the dendritic Ni-coated copper powders 31 can be secured.

[Ni coating]
As described above, the dendritic Ni-coated copper powder 31 according to the third embodiment is a flat plate having a cross-sectional average thickness of 0.2 μm to 5.0 μm, and the surface is coated with Ni or a Ni alloy. It is constituted in a dendritic shape by copper particles.

The dendritic Ni-coated copper powder 31 preferably has a Ni content of 1% by mass to 100% by mass of the entire Ni-coated copper powder coated with Ni on the dendritic copper powder before coating with Ni or Ni alloy. Ni or Ni alloy is coated at a ratio of 50% by mass, and the thickness of Ni (coating thickness) is 0.1 μm or less, preferably 0.05 μm or less. From this, the dendritic Ni-coated copper powder 31 has a shape that retains the shape of the dendritic copper powder before coating with Ni or Ni alloy. Therefore, the shape of the copper powder before coating Ni or Ni alloy and the shape of the Ni-coated copper powder after coating Ni or Ni alloy on the copper powder are both dendritic shapes.

As described above, the content of Ni coated as Ni or Ni alloy in the dendritic Ni-coated copper powder 31 is 1% by mass to 50% by mass with respect to 100% by mass of the Ni-coated copper powder 31 as a whole. % Is preferable. The content of Ni coated as Ni or Ni alloy is preferably as low as possible because the conductivity of Ni itself is lower than that of copper, but if it is too small, a uniform Ni or Ni alloy film can be secured on the copper surface. As a result, copper is oxidized, resulting in a decrease in conductivity. Therefore, the content of Ni coated as Ni or Ni alloy is preferably 1% by mass or more with respect to 100% by mass of the entire Ni-coated copper powder 31 coated with Ni, and is 2% by mass or more. It is more preferable that the content is 5% by mass or more.

On the other hand, if the content of Ni coated as Ni or Ni alloy is increased, the conductivity is not preferable. Accordingly, the coating amount of Ni or Ni alloy is preferably 50% by mass or less, more preferably 20% by mass or less, with respect to 100% by mass of the Ni-coated copper powder 31 coated with Ni. More preferably, it is 10 mass% or less.

In the dendritic Ni-coated copper powder 31 according to the third embodiment, the average thickness of Ni or Ni alloy coated on the surface of the dendritic copper powder is about 0.0003 μm to 0.1 μm, and 0.005 μm. More preferably, it is about 0.02 μm. When the coating thickness of Ni or Ni alloy is less than 0.0003 μm on average, a uniform Ni or Ni alloy coating cannot be secured on the surface of the copper powder, and copper oxidation cannot be suppressed, resulting in a decrease in conductivity. Cause. On the other hand, when the coating thickness of Ni or Ni alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of decreasing the electrical conductivity.

Thus, the average thickness of Ni coated on the surface of the dendritic copper powder is about 0.0003 μm to 0.1 μm, compared with the cross-sectional average thickness of the tabular copper particles constituting the dendritic copper powder. Very small. Therefore, before and after coating the surface of the dendritic copper powder with Ni or Ni alloy, the cross-sectional average thickness of the tabular copper particles does not substantially change.

Further, as will be described later, in the dendritic Ni-coated copper powder 31, the Ni covered with the dendritic copper powder may be a Ni alloy. The element added as the Ni alloy is preferably an element from Group 6 to Group 14 of the periodic table, and particularly one or more selected from zinc, cobalt, tungsten, molybdenum, palladium, platinum, and tin. preferable. In addition, as will be described later, when using electroless plating in the step of coating Ni on the dendritic copper powder, and further using hypophosphite and borohydride as the reducing agent, the resulting Ni coating is They are Ni-P alloy and Ni-B alloy, respectively.

[About bulk density]
The bulk density of the dendritic Ni-coated copper powder 31 is not particularly limited, but is preferably in the range of 0.5 g / cm ³ to 5.0 g / cm ³ . If the bulk density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the dendritic Ni-coated copper powders 31 cannot be secured. On the other hand, if the bulk density exceeds 5.0 g / cm ³ , the average particle diameter of the dendritic Ni-coated copper powder 31 also increases, and the surface area decreases and the formability and sinterability deteriorate. is there.

[BET specific surface area]
In dendritic Ni-coated copper powder 31 is not particularly limited, it is preferable the value of the BET specific surface area of 0.2m ^² /g~5.0m ² / g. When the BET specific surface area value is less than 0.2 m ² / g, the copper particles coated with Ni or Ni alloy may not have the desired flat plate shape as described above, and high conductivity is obtained. There may not be. On the other hand, when the BET specific surface area value exceeds 5.0 m ² / g, the Ni coating on the surface of the dendritic Ni-coated copper powder becomes non-uniform and high conductivity may not be obtained. Moreover, the copper particle which comprises Ni coat | court copper powder may become too fine, Ni coat copper powder may become a fine beard-like state, and electroconductivity may fall. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

<1-4. Fourth Embodiment>
[Configuration of Ni-coated copper powder]
When the Ni-coated copper powder according to the fourth embodiment is observed using a scanning electron microscope (SEM), a plurality of individual copper particles whose surfaces are coated with Ni or Ni alloy are aggregated and aggregated. It has the form of a collection.

Here, FIG. 15 is a schematic diagram showing a specific shape of the Ni-coated copper powder according to the fourth embodiment. As shown in the schematic diagram of FIG. 15, the Ni-coated copper powder 41 is made of Ni or Ni alloy on the surface of the copper powder having a form in which the separated flat copper particles 42 are aggregated two-dimensionally or three-dimensionally. The copper particles 42 have a flat plate shape. Hereinafter, this Ni-coated copper powder is also referred to as “flat Ni-coated copper particle aggregated powder 41”.

More specifically, the plate-like Ni-coated copper particle aggregated powder 41 is in the form of an aggregated copper powder in which a plurality of copper particles 42 whose surfaces are coated with Ni or Ni alloy are aggregated to form an aggregate. The copper particles 42 are in the form of a flat plate having an average major axis diameter d (average major axis diameter) of 0.5 μm to 5.0 μm and an average cross-sectional thickness of 0.02 μm to 1.0 μm. The tabular Ni-coated copper particle aggregated powder 41 obtained by aggregating a plurality of tabular copper particles 2 into an aggregate is characterized in that the average particle diameter (D50) is 1.0 μm to 30 μm. Yes.

The flat Ni-coated copper particle agglomerated powder 41 is described later in detail. For example, the anode and the cathode are immersed in a sulfuric acid electrolyte containing copper ions, and the cathode is electrolyzed by flowing a direct current. The agglomerated powder is deposited on the surface, and the surface of the obtained agglomerated powder can be produced by coating Ni or a Ni alloy by an electroless plating method or the like.

FIG.16 and FIG.17 is a photograph figure which shows an example of the observation image when it observes by SEM (FIG. 16: 5,000 times magnification, FIG. 17: 10,000 times magnification) about the tabular Ni coat copper particle aggregated powder 41. It is.

As observed in FIG. 16, the tabular Ni-coated copper particle aggregated powder 41 has a form in which tabular copper particles are aggregated. Moreover, as observed in FIG. 17, the flat copper particles are singulated and have a flat shape having a flat surface or a curved surface.

Here, as shown in the schematic diagram of FIG. 15, the flat copper particles 42 have a flat surface having a smooth periphery, such as a substantially oval shape, an oval shape, or a so-called corn flake shape, which will be described later. The shape has a cross-sectional average thickness within a specific range. Of course, the surface having a substantially elliptic shape or the like may have protrusions and attached particles having a height of about twice or less the average cross-sectional thickness.

As described above, the average major axis diameter d of the copper particles 42 which are flat and whose surfaces are coated with Ni or Ni alloy is 0.5 μm to 5.0 μm, more preferably 0.7 μm to 4 μm. 0.0 μm. The average cross-sectional thickness of the copper particles 42 is 0.02 μm to 1.0 μm, more preferably 0.05 μm to 0.4 μm. Here, the average major axis diameter d of the flat copper particles 42 indicates the maximum width of a flat surface having a shape such as an ellipse, as shown in FIG. Further, the average major axis diameter d and the cross-sectional average thickness can be obtained by SEM observation.

When the average major axis diameter d of the tabular copper particles 42 is less than 0.5 μm, or the cross-sectional average thickness exceeds 1.0 μm, the aggregated powders formed by aggregation of these particles are aggregated. A large contact area cannot be secured, and the electrical conductivity may decrease. On the other hand, the upper limit value of the average major axis diameter d of the tabular copper particles 42 is not particularly limited. However, in the method of depositing on the cathode by electrolysis described later, the upper limit is about 5.0 μm. Further, the lower limit value of the cross-sectional average thickness of the flat copper particles 42 is not particularly limited, but in the same method of depositing on the cathode by electrolysis, the lower limit is about 0.02 μm.

The size of the tabular Ni-coated copper particle aggregated powder 41 obtained by aggregating the tabular copper particles 42 into an aggregate is 1.0 μm to 30 μm in average particle diameter (D50). The average particle diameter can be controlled by changing the electrolysis conditions described later. Further, if necessary, it can be further adjusted to a desired size by adding mechanical pulverization such as a jet mill, a sample mill, a cyclone mill, and a bead mill. The average particle diameter (D50) of the tabular Ni-coated copper particle aggregated powder 41 can be measured by a laser diffraction / scattering particle size distribution measurement method.

In this way, the tabular copper particles 2 having an average cross-sectional thickness of 0.02 μm to 1.0 μm are aggregated to form the tabular Ni-coated copper particle aggregated powder 41, so that the copper having a desired size described above is formed. It becomes a powder, and it is possible to secure a large area where the flat Ni-coated copper particle aggregated powders 41 and the copper particles 42 on the flat plate contact each other. And since the contact area becomes large, low resistance, that is, high conductivity can be realized. By this, it is more excellent in electroconductivity and can be used suitably for the use of a conductive paint and a conductive paste.

Here, as pointed out in Patent Document 1, for example, when used as a metal filler such as a conductive paste or a resin for electromagnetic wave shielding, the metal filler in the resin has a dendritic shape, Dendritic copper powders are entangled with each other and agglomeration occurs, which may not be uniformly dispersed in the resin. In addition, the agglomeration increases the viscosity of the paste and causes problems in wiring formation by printing. This is because the shape of the dendritic copper powder grows in a needle shape, and when trying to prevent agglomeration, the shape of the dendritic copper powder is reduced. It becomes impossible to obtain the effect of securing the contact by eliminating.

Further, in the case where the plate is formed by the mechanical method of Patent Document 3 or Patent Document 4, it is necessary to prevent copper oxidation at the time of mechanical processing. For example, after adding a fatty acid, in the air or inactive It is crushed in an atmosphere and processed into a flat plate shape. However, oxidation cannot be completely prevented, and the fatty acid added at the time of processing needs to be removed after processing to affect dispersibility when it is made into a paste. There is a problem that the fatty acid cannot be completely removed because it may firmly adhere to the copper surface. Moreover, it becomes difficult to make the flat copper powder obtained to make a flat plate by mechanical pressure flat because it becomes flat by mechanical processing, and it becomes warped. . Since copper powder with a smooth and warped surface is difficult to secure contact points, when using it as a metal filler, not only flat copper powder but also granular copper powder can be mixed with other metal fillers. It is necessary to secure the contact points.

On the other hand, in the tabular Ni-coated copper particle aggregated powder 41, since the tabular copper particles 42 are aggregated, the respective tabular copper particles 42 are aggregated in a three-dimensional shape. It has a structure that simultaneously satisfies a two-dimensional contact effect and a three-dimensional contact effect. Further, the flat Ni-coated copper particle aggregated powder 41 has an average particle size (D50) of 1.0 μm to 30 μm, thereby increasing the surface area and ensuring good moldability and sinterability. be able to.

This demonstrates the same effect that the contact rate between metal fillers is improved by using silver powder having a shape described in, for example, Japanese Patent No. 4059486, and is a flat Ni-coated copper particle aggregated copper powder. Since 41 is a three-dimensional uneven structure, the contact rate between metal fillers is improved, the filler weight contained in the paste can be reduced, and the cost can be greatly reduced.

If the Ni-coated copper powder having the above-mentioned shape is occupied at a predetermined ratio in the obtained Ni-coated copper powder when observed with an electron microscope, Ni-coated copper of other shapes Even if the powder is mixed, the same effect as the copper powder consisting only of the Ni-coated copper powder can be obtained. Specifically, when observed with an electron microscope (for example, 500 to 20,000 times), the Ni-coated copper powder having the shape described above is 65% by number or more, preferably 80% by number, of the total Ni-coated copper powder. As described above, Ni-coated copper powder having other shapes may be included as long as it accounts for 90% by number or more.

[Ni coating]
As described above, the flat Ni-coated copper particle aggregated powder 41 according to the fourth embodiment has an average major axis diameter of 0.5 μm to 5.0 μm and an average cross-sectional thickness of 0.02 to 1.0 μm. A plurality of copper particles 42 having a flat plate shape and coated with Ni or Ni alloy are aggregated to form an aggregate.

The flat Ni-coated copper particle aggregated powder 41 has a Ni content with respect to 100% of the total mass of the Ni-coated copper powder 41 coated with Ni on the tabular copper particle aggregated powder before being coated with Ni or Ni alloy. The Ni or Ni alloy is coated at a ratio of 1% by mass to 50% by mass, and the thickness of Ni (coating thickness) is 0.1 μm or less, preferably 0.02 μm or less. It is covered. From this, the flat-plate Ni coat copper particle aggregated powder 41 becomes a shape which maintained the shape of the flat-plate copper particle aggregated powder before Ni or Ni alloy coat | covers as it is. Accordingly, the shape of the tabular copper particle aggregated powder before coating with Ni or Ni alloy and the shape of the tabular Ni-coated copper particle aggregated powder 41 after coating with Ni or Ni alloy are both two-dimensional or It is the shape which the flat plate which is a three-dimensional form aggregated.

As described above, the content of Ni coated as Ni or Ni alloy in the flat Ni-coated copper particle aggregated powder 41 is 1% by mass to 100% by mass of the Ni-coated copper powder 41 coated with Ni. A range of 50% by mass is preferred. The content of Ni coated as Ni or Ni alloy is preferably as low as possible because the conductivity of Ni itself is lower than that of copper, but if it is too small, a uniform Ni or Ni alloy film can be secured on the copper surface. As a result, copper is oxidized, resulting in a decrease in conductivity. Therefore, the content of Ni coated as Ni or Ni alloy is preferably 1% by mass or more with respect to 100% by mass of the entire Ni-coated copper powder 41 coated with Ni, and is 2% by mass or more. It is more preferable that the content is 5% by mass or more.

On the other hand, when the content of Ni coated as Ni or Ni alloy increases, it is not preferable from the viewpoint of decreasing the electrical conductivity. As the content of Ni coated as Ni or Ni alloy, the Ni coated copper powder 41 It is preferably 50% by mass or less, more preferably 20% by mass or less, and further preferably 10% by mass or less with respect to 100% of the total mass.

In the flat Ni-coated copper particle aggregated powder 41 according to the fourth embodiment, the average thickness of Ni or Ni alloy coated on the surface of the flat copper particles is about 0.0003 μm to 0.1 μm. The thickness is preferably about 0.005 μm to 0.02 μm. When the Ni or Ni alloy coating thickness is less than 0.0003 μm on average, a uniform Ni or Ni alloy coating cannot be secured on the surface of the copper powder, and copper oxidation cannot be suppressed, resulting in a decrease in conductivity. Cause. On the other hand, when the coating thickness of Ni or Ni alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of decreasing the electrical conductivity.

Thus, the average thickness of the Ni or Ni alloy coated on the surface of the tabular Ni-coated copper particle aggregated powder 41 is about 0.0003 μm to 0.1 μm, and the tabular copper before coating the Ni or Ni alloy. It is smaller than the cross-sectional average thickness (0.02 μm to 0.5 μm) of the flat copper particles 42 constituting the particle aggregated powder. Therefore, the form of the tabular copper particles is not substantially changed before and after the surface of the tabular copper particle aggregated powder is coated with Ni or Ni alloy.

Further, as will be described later, in the tabular Ni-coated copper particle agglomerated powder 41, the Ni coated with the tabular copper particles 42 may be a Ni alloy. The element added as the Ni alloy is preferably an element from Group 6 to Group 14 of the periodic table, and particularly one or more selected from zinc, cobalt, tungsten, molybdenum, palladium, platinum, and tin. preferable. Further, as will be described later, when electroless plating is used in the step of coating Ni on the flat copper particle agglomerated powder, and hypophosphite and a borohydride compound are used as the reducing agent, the Ni obtained The coatings are Ni—P alloy and Ni—B alloy, respectively.

[About bulk density]
The tabular Ni-coated copper particle aggregated powder 41 according to the fourth embodiment is not particularly limited, but its bulk density (tap density) is in the range of 0.5 g / cm ³ to 5.0 g / cm ^3. preferable. If the tap density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the Ni-coated copper powders cannot be secured. On the other hand, when the tap density exceeds 5.0 g / cm ³ , the average particle diameter of the Ni-coated copper powder increases, the surface area decreases, and the moldability and sinterability may deteriorate.

[BET specific surface area]
As the BET specific surface area of the tabular Ni-coated copper particles agglomerated powder 41 is not particularly ^limited, it is preferably in the range of 0.2m ² /g~5.0m 2 / g. When the BET specific surface area exceeds 5.0 m ² / g, there is a possibility that sufficient contact between the Ni-coated copper powders cannot be ensured. On the other hand, when the BET specific surface area is less than 0.2 m ² / g, the average particle diameter of the Ni-coated copper powder is also increased, the surface area is decreased, and the formability and the sinterability may be deteriorated. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

<1-5. Fifth Embodiment>
[Configuration of Ni-coated copper powder]
When the Ni-coated copper powder according to the fifth embodiment is observed using a scanning electron microscope (SEM), the Ni-coated copper powder has a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. The main trunk and branches are dendritic having a main trunk grown in a dendritic manner and a plurality of branches separated from the main trunk, and copper particles coated with Ni or Ni alloy on the surface are assembled. It is configured. Hereinafter, this Ni-coated copper powder is also referred to as “dendritic Ni-coated copper powder”.

FIG. 18 is a schematic diagram showing the specific shape of the copper particles whose surface is coated with Ni or Ni alloy, which constitutes the Ni-coated copper powder according to the fifth embodiment. As shown in the schematic diagram of FIG. 18, the copper particles 51 coated with Ni or Ni alloy have a dendritic shape that is a two-dimensional or three-dimensional form.

More specifically, the copper particles 51 coated with Ni or Ni alloy have a shape having a main trunk 52 grown in a dendritic shape and a plurality of branches 53 separated from the main trunk 52. The plate has a flat cross-sectional average thickness of 0.02 μm to 0.5 μm. The branch 53 in the copper particle 51 means both a branch 53a branched from the main trunk 52 and a branch 53b further branched from the branch 53a.

The Ni-coated copper powder according to the fifth embodiment is a dendritic copper powder (dendritic copper powder) having a main trunk and a plurality of branches, which is configured by aggregating such flat copper particles 51. Ni-coated copper powder with Ni or Ni alloy coated on its surface (see SEM images of Ni-coated copper powder in FIGS. 20 to 22), and dendritic Ni-coated copper composed of the flat copper particles 51 The average particle size (D50) of the powder is 1.0 μm to 30 μm.

Although the dendritic Ni-coated copper powder according to the fifth embodiment will be described in detail later, for example, by immersing an anode and a cathode in a sulfuric acid acidic electrolyte solution containing copper ions and flowing a direct current to perform electrolysis It can be produced by depositing dendritic copper powder on the cathode and coating the surface of the obtained dendritic copper powder with Ni or a Ni alloy by an electroless plating method or the like.

FIG. 19 is a photograph showing an example of an observation image when the dendritic copper powder before being coated with Ni or Ni alloy is observed by SEM (magnification 10,000 times). 20 is a photographic diagram showing an example of an observation image when the dendritic Ni-coated copper powder obtained by coating the dendritic copper powder of FIG. 19 with Ni or a Ni alloy is observed by SEM (5,000 times magnification). is there. FIG. 21 and FIG. 22 show SEM (FIG. 21: Magnification 10,000 times, FIG. 22: Magnification) of another part of dendritic Ni-coated copper powder in which dendritic copper powder is similarly coated with Ni or Ni alloy. It is a photograph figure which shows an example of an observation image when it observes by 1,000 times.

As shown in the observation images of FIGS. 19 to 22, the Ni-coated copper powder exhibits a two-dimensional or three-dimensional dendritic precipitation state having a main trunk and branches branched from the main trunk. Further, the main trunk and the branch are formed in a flat plate shape and have a dendritic shape and are formed by aggregation of copper particles covered with Ni or Ni alloy, and the copper particles 1 are fine on the surface. It has a convex part.

Here, the flat copper particles 51 constituting the dendritic Ni-coated copper powder and coated with Ni or Ni alloy having the main trunk 52 and the branches 53 have an average cross-sectional thickness of 0.02 μm to 0.5 μm. is there. The thinner the cross-sectional average thickness of the flat copper particles 51 coated with Ni or Ni alloy, the more effective the flat plate will be. That is, the main trunk and the branch of the dendritic copper powder are constituted by the flat copper particles 51 having a cross-sectional average thickness of 0.5 μm or less, so that the copper particles 51 and the dendritic Ni-coated copper constituted thereby. A large area where the powders come into contact with each other can be secured. And since the contact area becomes large, low resistance, that is, high conductivity can be realized. Thereby, it is more excellent in electroconductivity, can maintain the electroconductivity favorably, and can be used suitably for the use of an electroconductive coating material or an electroconductive paste. Further, since the dendritic Ni-coated copper powder is composed of the flat copper particles 51, it is possible to contribute to thinning of the wiring material and the like.

In addition, as the cross-sectional average thickness of the tabular copper particles 51 coated with Ni or Ni alloy becomes thinner, the number of contacts when the dendritic Ni-coated copper powders contact with each other decreases. If the cross-sectional average thickness of the copper particles 51 is 0.02 μm or more, a sufficient number of contacts can be ensured, and more preferably 0.2 μm or more, thereby effectively increasing the number of contacts. .

Further, in the dendritic Ni-coated copper powder according to the fifth embodiment, the average particle diameter (D50) is 1.0 μm to 30 μm. The average particle diameter can be controlled by changing the electrolysis conditions described later. Further, if necessary, it can be further adjusted to a desired size by adding mechanical pulverization such as a jet mill, a sample mill, a cyclone mill, and a bead mill. In addition, an average particle diameter (D50) can be measured by the laser diffraction scattering type particle size distribution measuring method, for example.

Thus, when the average particle size is 1.0 μm to 30 μm, the surface area is increased, and good moldability and sinterability can be ensured. And in this dendritic Ni coat copper powder, in addition to being dendritic shape, the dendritic shape which has the main trunk 2 and the branch 3 and the copper particle 51 which has a flat plate shape is comprised, and is comprised. More contact points between the copper powders can be secured by the three-dimensional effect of being dendritic and the effect that the copper particles 1 constituting the dendritic shape are flat.

Further, in the dendritic Ni-coated copper powder according to the fifth embodiment, the flat copper particles 51 have fine convex portions on the surface. The average height of the convex portions on the surface is preferably 0.01 μm to 0.4 μm.

Here, as described in Patent Document 3 and Patent Document 4, when spherical copper powder is flattened by a mechanical method, for example, it is necessary to prevent copper oxidation during mechanical processing. It is processed into a flat plate shape by adding a fatty acid and pulverizing it in air or in an inert atmosphere. However, it cannot be completely prevented from oxidation, and the fatty acid added at the time of processing may affect the dispersibility when it is made into a paste. The fatty acid may firmly adhere to the copper surface due to the pressure during machining, which causes a problem that it cannot be completely removed. Further, since the surface is flattened by mechanical processing, the surface becomes smooth, and the flat copper powder formed for flattening by mechanical pressure is not a horizontal surface but a warped shape. Therefore, when using as a metal filler such as conductive paste and resin for electromagnetic wave shielding, when trying to secure the contact between the metal fillers, the mechanically flattened copper powder has a smooth and warped surface. Therefore, it becomes difficult to secure the contacts, and when used, the contacts between the metal fillers must be secured by a method of mixing not only the flat copper powder but also the granular copper powder.

On the other hand, the flat copper particles 51 constituting the dendritic Ni-coated copper powder according to the fifth embodiment have fine convex portions on the surface, and the average height of the convex portions is preferably The dendritic Ni-coated copper powder has a feature that the contact between the metal fillers can be easily secured as compared with the plate-like copper powder obtained by mechanical processing, by being 0.01 μm to 0.4 μm. Have. That is, in this dendritic Ni-coated copper powder, since there are fine convex portions on the surface of the flat copper particles 51 constituting the dendritic Ni-coated copper powder, when used as a metal filler such as a conductive paste or a resin for electromagnetic wave shielding The contact point can be easily secured by the convex portions on the surface of the flat copper particles 51. Furthermore, this dendritic Ni-coated copper powder is produced by depositing tabular copper particles by direct electrolysis and growing into the shape of dendritic copper powder without performing mechanical processing. Occurrence of oxidation and removal of fatty acids are not necessary, and the electrical conductivity characteristics can be made extremely good.

As described above, the average height of the fine protrusions on the surface of the flat copper particles 51 is preferably 0.01 μm to 0.4 μm. When the average height is less than 0.01 μm, a sufficient effect cannot be obtained as a shape for securing the contacts. On the other hand, when the average height exceeds 0.4 μm, it is used for a conductive paste or the like. In some cases, the filling rate of the metal filler in the paste does not increase, and a satisfactory resistance value may not be obtained.

[Ni coating]
As described above, the dendritic Ni-coated copper powder according to the fifth embodiment is a dendritic shape having a main trunk 52 and a branch 53, and has a plate-like shape with a cross-sectional average thickness of 0.02 μm to 0.5 μm. The copper particles 51 are configured in a dendritic shape, and the surfaces of the copper particles 51 are coated with Ni or a Ni alloy.

This dendritic Ni-coated copper powder is preferably 1% by mass as Ni content with respect to 100% by mass of the entire Ni-coated copper powder coated with Ni on the dendritic copper powder before coating with Ni or Ni alloy. Ni or Ni alloy is coated at a ratio of ˜50% by mass, and the Ni thickness (coating thickness) is 0.1 μm or less, preferably 0.02 μm or less. . From this, the dendritic Ni-coated copper powder has a shape that retains the shape of the dendritic copper powder before being coated with Ni or Ni alloy. Therefore, the shape of the dendritic copper powder before coating with Ni or Ni alloy and the shape of the dendritic Ni-coated copper powder after coating Ni or Ni alloy on the copper powder are both two-dimensional or three-dimensional. It is a dendritic shape that is a form of

The content of Ni coated as Ni or Ni alloy in the dendritic Ni-coated copper powder is 1% by mass to 50% by mass with respect to 100% by mass of the entire Ni-coated copper powder coated with Ni as described above. It is preferable that it is the range of these. The content of Ni coated as Ni or Ni alloy is preferably as low as possible because the conductivity of Ni itself is lower than that of copper, but if it is too small, a uniform Ni or Ni alloy film can be secured on the copper surface. In other words, copper is oxidized to cause a decrease in conductivity. Therefore, as content of Ni coat | covered as Ni or Ni alloy, it is preferable that it is 1 mass% or more with respect to 100 mass of the whole Ni coat | covered Ni-coated copper powder, and it is 2 mass% or more. Is more preferable, and it is further more preferable that it is 5 mass% or more.

On the other hand, when the content of Ni coated as Ni or Ni alloy increases, it is not preferable from the viewpoint of decreasing the electrical conductivity. The content of Ni coated as Ni or Ni alloy is the Ni coated Ni coating. It is preferable that it is 50 mass% or less with respect to 100 mass of the whole copper powder, It is more preferable that it is 20 mass% or less, It is further more preferable that it is 10 mass% or less.

In the dendritic Ni-coated copper powder according to the fifth embodiment, the average thickness of Ni or Ni alloy coated on the surface of the copper particles is about 0.0003 μm to 0.1 μm, and 0.005 μm to 0.00. It is preferably about 02 μm. When the Ni or Ni alloy coating thickness is less than 0.0003 μm on average, a uniform Ni or Ni alloy coating cannot be secured on the surface of the copper powder, and copper oxidation cannot be suppressed, resulting in a decrease in conductivity. Cause. On the other hand, if the coating thickness of Ni or Ni alloy exceeds 0.1 μm on average, it is not preferable from the viewpoint of decreasing the electrical conductivity.

Thus, the average thickness of the Ni or Ni alloy coated on the surface of the dendritic Ni-coated copper powder is about 0.0003 μm to 0.1 μm, and constitutes the dendritic copper powder before coating the Ni or Ni alloy. This is smaller than the average cross-sectional thickness (0.02 μm to 0.5 μm) of the dendritic copper particles 51. Therefore, before and after coating the surface of the dendritic copper powder with Ni or Ni alloy, the form of the dendritic copper powder does not substantially change.

Further, as will be described later, in the dendritic Ni-coated copper powder, the Ni coated with the dendritic copper powder may be a Ni alloy. The element added as the Ni alloy is preferably an element from Group 6 to Group 14 of the periodic table, and particularly one or more selected from zinc, cobalt, tungsten, molybdenum, palladium, platinum, and tin. preferable. In addition, as will be described later, when using electroless plating in the step of coating Ni on the dendritic copper powder, and further using hypophosphite and borohydride as the reducing agent, the resulting Ni coating is They are Ni-P alloy and Ni-B alloy, respectively.

[About bulk density]
The bulk density of the dendritic Ni-coated copper powder according to the fifth embodiment is not particularly limited, but is preferably in the range of 0.5 g / cm ³ to 5.0 g / cm ³ . If the bulk density is less than 0.5 g / cm ³ , there is a possibility that sufficient contact between the dendritic Ni-coated copper powders cannot be ensured. On the other hand, if the bulk density exceeds 5.0 g / cm ³ , the average particle diameter of the dendritic Ni-coated copper powder also increases, and the surface area may decrease, and the formability and sinterability may deteriorate. .

[BET specific surface area]
The dendritic Ni-coated copper powder according to the fifth embodiment is not particularly limited, it is preferable the value of the BET specific surface area of 0.2m ^² /g~5.0m ² / g. If the value of the BET specific surface area is less than 0.2 m ² / g, the copper particles coated with Ni or Ni alloy may not have the desired shape as described above, and high conductivity cannot be obtained. Sometimes. On the other hand, if the value of the BET specific surface area exceeds 5.0 m ² / g, the Ni or Ni alloy coating on the surface of the dendritic Ni-coated copper powder becomes non-uniform and high conductivity may not be obtained. In addition, the copper particles constituting the dendritic Ni-coated copper powder become too fine, and the dendritic Ni-coated copper powder becomes a fine whisker-like state, and the conductivity may decrease. The BET specific surface area can be measured in accordance with JIS Z8830: 2013.

≪2. Manufacturing method of Ni-coated copper powder >>
Next, the manufacturing method of Ni coat copper powder concerning the present invention is explained. Below, the manufacturing method of the copper powder before Ni coating | cover which comprises Ni coat | court copper powder is demonstrated first, Then, Ni or Ni alloy is coat | covered with respect to the copper powder, and the method of obtaining Ni coat copper powder Will be described.

In addition, the manufacturing method of the Ni coat copper powder which concerns on the 1st-5th embodiment mentioned above is demonstrated in order, and description is abbreviate | omitted suitably about the item which is common in each embodiment.

<2-1. Manufacturing Method of Ni Coated Copper Powder According to First Embodiment>
The Ni-coated copper powder according to the first embodiment has a dendritic shape in which copper particles whose surfaces are coated with Ni or a Ni alloy are aggregated and have a main trunk that grows linearly and a plurality of branches that are separated from the main trunk. It is Ni coat copper powder which constituted the shape. The copper particles whose surfaces are coated with Ni or Ni alloy have a flat plate shape with an average cross-sectional thickness of 0.02 μm to 5.0 μm determined by SEM observation, and the copper particles are assembled to form a copper particle. The Ni-coated copper powder has an average particle diameter (D50) of 1.0 μm to 100 μm, and the maximum height in a direction perpendicular to the flat surface of the copper particles is in the horizontal direction of the flat surface. It is 1/10 or less with respect to the maximum length.

<2-1-1. Manufacturing method of copper powder>
As described above, the Ni-coated copper powder (dendritic Ni-coated copper powder) according to the first embodiment is coated with Ni or a Ni alloy on the surface of the dendritic copper powder. For example, it can be manufactured by a predetermined electrolytic method using a sulfuric acid acidic solution containing copper ions as an electrolytic solution.

In electrolysis, for example, a sulfuric acid electrolytic solution containing copper ions is accommodated in an electrolytic cell in which metallic copper is used as an anode (anode) and a stainless steel plate or titanium plate is used as a cathode (cathode). Electrolysis is performed by passing a direct current through the liquid at a predetermined current density. Thereby, a fine dendritic copper powder can be deposited (electrodeposited) on the cathode with energization. In particular, in the first embodiment, a specific additive and a nonionic surfactant are added to the sulfuric acid electrolytic solution containing a water-soluble copper salt serving as a copper ion source to perform electrolysis. A flat dendritic copper powder composed of flat copper particles can be deposited. Further, it is preferable that the electrolytic solution further contains chloride ions.

(1) Copper ions The water-soluble copper salt is a copper ion source that supplies copper ions, and examples thereof include copper sulfate such as copper sulfate pentahydrate and copper nitrate, but are not particularly limited. Alternatively, copper oxide may be dissolved in a sulfuric acid solution to make a sulfuric acid acidic solution. The copper ion concentration in the electrolytic solution can be about 1 g / L to 20 g / L, preferably about 5 g / L to 10 g / L.

(2) Sulfuric acid Sulfuric acid is for making a sulfuric acid electrolyte. The concentration of sulfuric acid in the electrolytic solution can be about 20 g / L to 300 g / L, preferably about 50 g / L to 150 g / L, as the free sulfuric acid concentration. Since the sulfuric acid concentration affects the conductivity of the electrolyte, it affects the uniformity of the copper powder obtained on the cathode.

(3) Additive As the additive, one kind of compound selected from the group consisting of a compound having a phenazine structure, a compound having an azobenzene structure, and a compound having a phenazine structure and an azobenzene structure, or this group Two or more compounds selected from the group consisting of different molecular structures are used in combination. By adding such an additive to the electrolytic solution together with a nonionic surfactant described later and performing electrolysis, copper powder that suppresses growth in a direction perpendicular to the flat surface, that is, copper having a smooth surface Powder can be produced.

The concentration in the electrolyte of one or more additives selected from the group consisting of a compound having a phenazine structure, a compound having an azobenzene structure, and a compound having a phenazine structure and an azobenzene structure may be added. It is preferable that the total amount is about 1 mg / L to 1000 mg / L.

(Compound having phenazine structure)
A compound having a phenazine structure can be represented by the following formula (1). In the first embodiment, one or more compounds having a phenazine structure represented by the following formula (1) can be contained as an additive.

Here, in Formula (1), R ₁ , R ₂ , R ₃ , R ₄ , R ₆ , R ₇ , R ₈ , R ₉ are each independently hydrogen, halogen, amino, OH, ═O, It is a group selected from the group consisting of CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl. R ₅ is hydrogen, halogen, amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion.

Specifically, examples of the compound having a phenazine structure include 5-methylphenazine-5-ium, eruginosine B, aeruginosine A, 5-ethylphenazine-5-ium, 3,7-diamino-5-phenylphenazine-5. -Ium, 5-ethylphenazine-5-ium, 5-methylphenazine-5-ium, 3-amino-5-phenyl-7- (diethylamino) phenazine-5-ium, 2,8-dimethyl-3,7- Diamino-5-phenylphenazine-5-ium, 1-methoxy-5-methylphenazine-5-ium, 3-amino-7- (dimethylamino) -1,2-dimethyl-5- (3-sulfonatophenyl) Phenazine-5-ium, 1,3-diamino-5-methylphenazine-5-ium, 1,3-diamino-5-phenylphenol Nadin-5-ium, 3-amino-7- (diethylamino) -2-methyl-5-phenylphenazine-5-ium, 3,7-bis (diethylamino) -5-phenylphenazine-5-ium, 2,8 -Dimethyl-3,7-diamino-5- (4-methylphenyl) phenazine-5-ium, 3- (methylamino) -5-methylphenazine-5-ium, 3-hydroxy-7- (diethylamino) -5 -Phenylphenazine-5-ium, 5-azoniaphenazine, 1-hydroxy-5-methylphenazine-5-ium, 4H, 6H-5-phenyl-3,7-dioxophenazine-5-ium, anilinoap Safranin, phenosafranine, neutral red and the like can be mentioned.

(Compound having azobenzene structure)
The compound having an azobenzene structure can be represented by the following formula (2). In 1st Embodiment, the 1 type (s) or 2 or more types of the compound which has an azobenzene structure represented by following formula (2) can be contained as an additive.

Here, in formula (2), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ are each independently hydrogen, halogen, amino A group selected from the group consisting of OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, and aryl. is there.

Specifically, examples of the compound having an azobenzene structure include azobenzene, 4-aminoazobenzene-4'-sulfonic acid, 4- (dimethylamino) -4 '-(trifluoromethyl) azobenzene, C.I. I. Acid Red 13, Mercury Orange, 2 ', 4'-Diamino-5'-methylazobenzene-4-sulfonic acid sodium, methyl red, methyl yellow, methyl orange, azobenzene-2,4-diamine, alizarin yellow GG, 4- Dimethylaminoazobenzene, orange I, salazosulfapyridine, 4- (diethylamino) azobenzene, orange OT, 3-methoxy-4-aminoazobenzene, 4-aminoazobenzene, N, N, 2-trimethylazobenzene-4-amine, 4 -Hydroxyazobenzene, Sudan I, 4-amino-3,5-dimethylazobenzene, N, N-dimethyl-4-[(quinolin-6-yl) azo] benzenamine, o-aminoazotoluene, alizarin yellow R, 4 '-(Aminosulfonyl) 4-hydroxy-azobenzene-3-carboxylic acid, Congo red, vital red, Metanil Yellow, Orange II, Disperse Orange 3, C. I. Direct orange 39, 2,2'-dihydroxyazobenzene, azobenzene-4,4'-diol, naphthyl red, 5-phenylazobenzene-2-ol, 2,2'-dimethylazobenzene, C.I. I. Examples include Mordant Yellow 12, Mordant Yellow 10, Acid Yellow, Disperse Blue, New Yellow RMF, Vistramine Brown G, and the like.

(Compound having phenazine structure and azobenzene structure)
A compound having a phenazine structure and an azobenzene structure can be represented by the following formula (3). In the first embodiment, one or more compounds having a phenazine structure and an azobenzene structure represented by the following formula (3) can be contained as an additive.

Here, in Formula (3), R ₁ , R ₂ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ are each separately , Hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, and C1-C8 alkyl Is a group selected from R ₃ is hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO ₃ H, SO ₃ salt, SO ₃ ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A ⁻ is a halide anion.

Specifically, as a compound having a phenazine structure and an azobenzene structure, for example, 3- (diethylamino) -7-[(4-hydroxyphenyl) azo] -2,8-dimethyl-5-phenylphenazine-5-ium , 3-[[4- (dimethylamino) phenyl] azo] -7- (diethylamino) -5-phenylphenazine-5-ium, Janus Green B, 3-amino-7-[(2,4-diaminophenyl) Azo] -2,8-dimethyl-5-phenylphenazine-5-ium, 2,8-dimethyl-3-amino-5-phenyl-7- (2-hydroxy-1-naphthylazo) phenazine-5-ium, 3 -[[4- (dimethylamino) phenyl] azo] -7- (dimethylamino) -5-phenylphenazine-5-ium, 3-amino-7-[[ -(Dimethylamino) phenyl] azo] -5-phenylphenazine-5-ium, 2- (diethylamino) -7- [4- (methylpropargylamino) phenylazo] -9-phenyl-9-azonia-10-azaanthracene 2- (diethylamino) -7- [4- (methyl-4-pentynylamino) phenylazo] -9-phenyl-9-azonia-10-azaanthracene, 2- (diethylamino) -7- [4- (methyl-2 , 3-dihydroxypropylamino) phenylazo] -9-phenyl-9-azonia-10-azaanthracene.

(4) Surfactant A nonionic surfactant is contained as the surfactant. By adding a nonionic surfactant to the electrolyte together with the above-mentioned additives, it is possible to produce copper powder that suppresses growth in a direction perpendicular to the flat surface, that is, copper powder having a smooth surface. it can.

As the nonionic surfactant, one kind can be used alone, or two or more kinds can be used in combination, and the total concentration in the electrolytic solution can be about 1 mg / L to 10,000 mg / L.

The number average molecular weight of the nonionic surfactant is not particularly limited, but is preferably from 100 to 200,000, more preferably from 200 to 15,000, and preferably from 1,000 to 10,000. Further preferred. When the surfactant has a number average molecular weight of less than 100, fine electrolytic copper powder that does not exhibit a dendritic shape may be deposited. On the other hand, when the surfactant has a number average molecular weight exceeding 200,000, electrolytic copper powder having a large average particle size is precipitated, and only dendritic copper powder having a specific surface area of less than 0.2 m ² / g is obtained. There is no possibility. The number average molecular weight is a molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

The type of nonionic surfactant is not particularly limited, but is preferably a surfactant having an ether group, for example, polyethylene glycol, polypropylene glycol, polyethyleneimine, pluronic surfactant, tetronic surfactant. , Polyoxyethylene glycol / glycerin ether, polyoxyethylene glycol / dialkyl ether, polyoxyethylene polyoxypropylene glycol / alkyl ether, aromatic alcohol alkoxylate, polymer compound represented by the following formula (x), and the like. These nonionic surfactants can be used alone or in combination of two or more.

More specifically, as the polyethylene glycol, for example, one represented by the following formula (i) can be used.

(In the formula (i), n1 represents an integer of 1 to 120.)

Further, as the polypropylene glycol, for example, one represented by the following formula (ii) can be used.

(In the formula (ii), n1 represents an integer of 1 to 90.)

Moreover, as polyethyleneimine, what is represented, for example by a following formula (iii) can be used.

(In the formula (iii), n1 represents an integer of 1 to 120.)

Further, as the pluronic surfactant, for example, one represented by the following formula (iv) can be used.

(In the formula (iv), n2 and l2 represent an integer of 1 to 30, and m2 represents an integer of 10 to 100.)

Further, as the tetronic surfactant, for example, one represented by the following formula (v) can be used.

(In formula (v), n3 represents an integer of 1 to 200, and m3 represents an integer of 1 to 40.)

Moreover, as polyoxyethylene glycol glyceryl ether, for example, those represented by the following formula (vi) can be used.

(In the formula (vi), n4, m4, and l4 each represent an integer of 1 to 200.)

Moreover, as polyoxyethylene glycol dialkyl ether, for example, those represented by the following formula (vii) can be used.

(In the formula (vii), R ₁ and R ₂ represent a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, and n5 represents an integer of 2 to 200.)

As the polyoxyethylene polyoxypropylene glycol / alkyl ether, for example, those represented by the following formula (viii) can be used.

(In the formula (viii), R ₃ represents a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, and m6 or n6 represents an integer of 2 to 100.)

Moreover, as an aromatic alcohol alkoxylate, what is represented, for example by a following formula (ix) can be used.

(In the formula (ix), m7 represents an integer of 1 to 5, and n7 represents an integer of 1 to 120.)

Further, as the nonionic surfactant, a polymer compound represented by the following formula (x) can be used.

(In the formula (x), R ₁ has a higher alcohol residue having 5 to 30 carbon atoms, an alkylphenol residue having an alkyl group having 1 to 30 carbon atoms, or an alkyl group having 1 to 30 carbon atoms. A residue of alkyl naphthol, a residue of fatty acid amide having 3 to 25 carbon atoms, a residue of alkyl amine having 2 to 5 carbon atoms, or a hydroxyl group, and R ₂ and R ₃ are each a hydrogen atom or a methyl group. M and n are integers of 1 to 100.)

(5) Chloride ions Furthermore, the electrolyte solution can contain chloride ions. Chloride ions contribute to the shape control of the precipitated copper powder together with the above-described additives and nonionic surfactants. Thus, by containing chloride ions in the electrolytic solution, it is possible to more effectively produce a copper powder having a smooth surface that suppresses growth in a direction perpendicular to the flat surface. .

As the chloride ions, compounds that supply chloride ions such as hydrochloric acid and sodium chloride (chloride ion source) can be added to the electrolyte solution. The chloride ion concentration in the electrolytic solution is not particularly limited, but can be about 1 mg / L to 500 mg / L.

In the first embodiment, for example, electrolysis is performed using the electrolytic solution having the composition as described above, whereby copper powder is deposited on the cathode to produce dendritic copper powder. As the electrolysis method, a known method can be used. For example, the current density is preferably in the range of 5 A / dm ² to 30 A / dm ² in electrolysis using a sulfuric acid electrolytic solution, and the electrolytic solution is energized while stirring. The liquid temperature (bath temperature) of the electrolytic solution can be, for example, about 20 ° C. to 60 ° C.

<2-1-2. Ni Coating Method (Production of Ni Coated Copper Powder)>
The Ni-coated copper powder according to the first embodiment is formed on the surface of the dendritic copper powder prepared by the above-described electrolytic method using, for example, Ni or a Ni plating solution (electroless Ni plating solution) by an electroless plating method. It can be manufactured by coating a Ni alloy.

In order to coat Ni or Ni alloy with a uniform thickness on the surface of the dendritic copper powder, it is preferable to wash before the Ni plating, and the dendritic copper powder is dispersed in the cleaning liquid and washed while stirring. It can be carried out. The washing treatment is preferably performed in an acidic solution. After washing, filtration, separation and washing with water of the dendritic copper powder are repeated as appropriate to obtain a water slurry in which the dendritic copper powder is dispersed in water. In addition, what is necessary is just to use a well-known method about filtration, isolation | separation, and water washing.

Specifically, when Ni coating is performed by the electroless plating method, the electroless Ni plating solution is added to the copper slurry obtained after washing the dendritic copper powder, or the copper slurry is added to the electroless Ni plating solution. By uniformly stirring, the surface of the dendritic copper powder can be coated more uniformly with Ni or Ni alloy.

The electroless Ni plating solution is not particularly limited. The electroless Ni plating solution performs Ni coating by reducing Ni ions in the plating solution with a reducing agent. Examples of the reducing agent include hypophosphites, borohydrides, and hydrazine compounds. It is done.

Specifically, examples of hypophosphites include hypophosphites such as potassium hypophosphite and sodium hypophosphite, and phosphites such as potassium phosphite and sodium phosphite. Can be mentioned.

Examples of the borohydride compound include dimethylhexaborane, dimethylamineborane (DMAB), diethylamineborane, morpholineborane, pyridineamineborane, piperidineborane, ethylenediamineborane, ethylenediaminebisborane, t-butylamineborane, imidazoleborane, methoxy Examples include ethylamine borane and sodium borohydride.

As the hydrazine compound, hydrazine and hydrates thereof, hydrazine salts such as hydrazine sulfate and hydrazine hydrochloride, hydrazine derivatives such as pyrazoles, triazoles and hydrazides, and the like can be used. Among these hydrazine derivatives, pyrazoles such as 3,5-dimethylpyrazole and 3-methyl-5-pyrazolone can be used in addition to pyrazole. Further, as triazoles, 4-amino-1,2,4-triazole, 1,2,3-triazole, and the like can be used. As hydrazides, adipic hydrazide, maleic hydrazide, carbohydrazide, and the like can be used. As hydrazines, hydrazine sulfate, hydrazine hydrochloride, adipic hydrazide, maleic hydrazide, carbohydrazide, and the like can be used.

Nickel sources include nickel salts such as nickel sulfate, nickel chloride, nickel acetate and nickel sulfamate.

In addition, the plating solution can contain a complexing agent, a pH buffering agent, and a pH adjusting agent.

Specifically, a known complexing agent can be used as the complexing agent. For example, amino acids such as glycine, citrates such as sodium citrate and ammonium citrate, lactic acid, oxalic acid, malonic acid, malic acid, tartaric acid, aspartic acid, glutamic acid, gluconic acid, sodium salts or ammonium salts, ammonia, etc. Is mentioned.

A known complexing agent can be used as the pH buffering agent. For example, ammonium chloride, ammonium sulfate, boric acid, sodium acetate and the like can be mentioned.

A known complexing agent can be used as the pH adjuster. For example, an acid or alkali compound can be used, and examples thereof include alkali metal hydroxides such as ammonia and sodium hydroxide, nickel carbonate, sulfuric acid, and hydrochloric acid. In addition, when using ammonia, it can supply as ammonia water.

Further, if necessary, an antifoaming agent or a dispersing agent may be used.

Furthermore, in order to improve the permeability of the plating solution, a surfactant can be contained. As the surfactant, any of nonionic, cationic, anionic and amphoteric surfactants can be used, and one kind can be used alone, or two or more kinds can be used in combination.

Here, in Ni coating by electroless plating, the Ni coating deposited differs depending on the hypophosphorous acid bath salt, borohydride compound, and hydrazine compound which are reducing agents in the electroless Ni plating solution. Specifically, when hypophosphorous acid bath salt is used as the reducing agent, a Ni—P alloy film is formed because phosphorus is contained in the film during the reduction reaction. Further, when a borohydride compound is used as the reducing agent, since the boron is contained in the coating during the reduction reaction, a Ni—B alloy coating is formed. Further, when a hydrazine compound is used as the reducing agent, a high-purity Ni film with few impurities is formed.

Furthermore, by making the Ni film to be formed contain other elements, that is, by forming a “Ni alloy” film on the surface of the copper powder, the Ni-coated copper powder can be used for heat resistance. In addition, a conductive paste having excellent corrosion resistance can be realized.

Specifically, as an element to be included in the Ni film, that is, as an element other than Ni constituting the Ni alloy, elements of Groups 6 to 14 of the periodic table can be mentioned, and among them, zinc, palladium, Examples include cobalt, rhodium, iron, platinum, iridium, tungsten, molybdenum, chromium, and tin. In particular, one or more elements selected from zinc, cobalt, tungsten, molybdenum, palladium, platinum, and tin are preferable, and a Ni alloy film having excellent conductivity is formed by using an Ni alloy containing these elements. be able to.

The content of the elements constituting these Ni alloys is preferably 0.1% by mass to 20% by mass with respect to 100% by mass of the Ni alloy, from the viewpoint of conductivity and dispersibility, and preferably 1% by mass to 15%. More preferably, it is more preferably 2% by mass to 10% by mass. In addition, regarding the Ni—P alloy and Ni—B alloy respectively formed according to the kind of the reducing agent described above, the content of phosphorus and boron is also 0.1% by mass with respect to 100% by mass of the Ni alloy film. It is preferably ˜20% by mass, more preferably 1% by mass to 15% by mass, and further preferably 2% by mass to 10% by mass.

When the Ni alloy is used, if the content of elements other than Ni is too large, the conductivity is lowered, so that the content is preferably 20% by mass or less. On the other hand, if the content is less than 0.1% by mass, the effect of improving the heat resistance and corrosion resistance cannot be sufficiently obtained even if these elements are contained together with Ni to form a Ni alloy. In addition, content of the element in Ni alloy can be measured by converting content of each element which comprises Ni coat | court copper powder, for example by a high frequency inductively coupled plasma (ICP) emission spectroscopy analysis method. In addition, each element in the Ni alloy coating can be quantitatively analyzed from the cross section of the Ni-coated copper powder or the like by energy dispersive X-ray spectroscopy (EDX) method or Auger electron spectroscopy (AES) method.

As a method for forming a Ni alloy coating, ions such as cobalt, zinc, tungsten, molybdenum, palladium, platinum, and tin are added to the above-described electroless Ni plating solution, and electroless plating using the plating solution is performed. Can be formed. The ion source such as cobalt, zinc, tungsten, molybdenum, palladium, platinum, and tin is not particularly limited as long as it is a soluble metal salt.

Specifically, the cobalt ion source can be used without particular limitation as long as it is soluble in a plating solution as a cobalt compound and can obtain an aqueous solution having a predetermined concentration. Examples thereof include cobalt sulfate, cobalt chloride, and cobalt sulfamate. These cobalt compounds can be used individually by 1 type or in mixture of 2 or more types.

The zinc ion source is not particularly limited as long as it is soluble in the plating solution as a zinc compound and can obtain an aqueous solution having a predetermined concentration. For example, zinc chloride, zinc sulfamate, zinc sulfate, zinc acetate and the like can be mentioned. These zinc compounds can be used singly or in combination of two or more.

The tungsten ion source is not particularly limited as long as it is soluble in the plating solution as a tungsten compound and can obtain an aqueous solution having a predetermined concentration. Examples thereof include sodium tungstate, potassium tungstate, and ammonium tungstate. These tungsten compounds can be used singly or in combination of two or more.

The molybdenum ion source is not particularly limited as long as it is soluble in the plating solution as a molybdenum compound and can obtain an aqueous solution having a predetermined concentration. Examples thereof include molybdenum trioxide, sodium molybdate, diammonium molybdate, calcium molybdate, molybdic acid, phosphomolybdic acid, and molybdate gluconic acid complex. These molybdenum compounds can be used singly or in combination of two or more.

The palladium ion source is not particularly limited as long as it is soluble in a plating solution as a palladium compound and can obtain an aqueous solution having a predetermined concentration. For example, water-soluble palladium compounds such as palladium sulfate, palladium chloride, palladium acetate, dichlorodiethine rediamine palladium, and tetraammine palladium dichloride can be used. Further, as the palladium compound, a so-called palladium solution in which palladium is made into a solution can also be used. As the palladium solution, for example, a dichlorodiethylenediamine palladium solution or a tetraammine palladium dichloride solution can be used. These palladium compounds can be used individually by 1 type or in mixture of 2 or more types.

The platinum ion source is not particularly limited as long as it is soluble in a plating solution as a platinum compound and can obtain an aqueous solution having a predetermined concentration. For example, platinum chloride, chloroplatinic acid, chloroplatinic acid salt, hydraulic platinum acid, hydraulic platinum acid salt, dinitrodiammine platinum complex salt, dinitrosulfitoplatinum complex salt, tetraammine platinum complex salt, hexaammine platinum complex salt. A platinum compound can be used individually by 1 type or in mixture of 2 or more types.

The tin ion source is not particularly limited as long as it is soluble in a plating solution as a tin compound and can obtain an aqueous solution having a predetermined concentration. For example, stannous chloride, stannic chloride, stannous sulfate, stannic sulfate, stannous pyrophosphate, and other inorganic acid salts of tin, stannous citrate, stannous citrate, stannous oxalate Of tin carboxylates such as stannic oxalate, tin methanesulfonate, tin 1-ethanesulfonate, tin 2-ethanesulfonate, tin 1-propanesulfonate, tin 3-propanesulfonate Alkane sulfonate, tin methanol sulfonate, tin hydroxyethane-1-sulfonate, tin 1-hydroxypropane-1-sulfonate, tin hydroxyethane-2-sulfonate, tin 1-hydroxypropane-3-sulfonate, etc. Alkanol sulfonates, tin hydroxides such as stannous hydroxide and stannic hydroxide, and metastannic acid.

The method for forming the Ni alloy film is not limited to the above-described electroless plating method. For example, an element other than Ni constituting the Ni alloy is included in the dendritic copper powder before coating with Ni, and after forming a film made only of Ni (Ni film), it is added to the copper powder in advance. A Ni alloy film can also be formed by diffusing the elements previously deposited into the Ni film.

<2-2. Method for Producing Ni Coated Copper Powder According to Second Embodiment>
The Ni-coated copper powder according to the second embodiment is a Ni-coated copper powder in which copper particles whose surfaces are coated with Ni or Ni alloy are assembled to form a dendritic shape having a plurality of branches. The copper particles whose surfaces are coated with Ni or Ni alloy have an elliptical size with a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. The Ni-coated copper powder, which is a body and is constituted by aggregating the copper particles, has an average particle diameter (D50) of 5.0 to 20 μm. Further, the average thickness of the branch portions constituting the dendritic shape is preferably 0.5 μm to 2.0 μm.

<2-2-1. Manufacturing method of copper powder>
As described above, the Ni-coated copper powder (dendritic Ni-coated copper powder) according to the second embodiment is obtained by coating the surface of the dendritic copper powder with Ni or a Ni alloy. For example, it can be manufactured by a predetermined electrolytic method using a sulfuric acid acidic solution containing copper ions as an electrolytic solution.

In the case of electrolysis, a sulfuric acid-containing electrolytic solution containing copper ions is contained in an electrolytic cell in which metallic copper is used as an anode and a stainless steel plate or a titanium plate is used as a cathode, as in the electrolytic treatment in the first embodiment. Then, electrolytic treatment is performed by passing a direct current through the electrolytic solution at a predetermined current density. Thereby, a dendritic copper powder can be deposited (electrodeposition) on a cathode with electricity supply. In particular, in the second embodiment, a sulfuric acid acidic electrolytic solution containing a water-soluble copper salt serving as a copper ion source is electrolyzed by adding a polyether compound as an additive. Without using a medium such as a ball to mechanically deform the obtained granular copper powder, the ellipsoidal copper particles gathered into a dendritic shape by aggregation only by electrolysis. It can be deposited on the cathode surface.

That is, as the electrolytic solution, for example, an electrolytic solution containing a water-soluble copper salt (copper ion), sulfuric acid, and a polyether compound is used. Further, it is preferable that the electrolytic solution further contains chloride ions. Here, the water-soluble copper salt and sulfuric acid contained in the electrolytic solution are the same as those in the manufacturing method according to the first embodiment, and detailed description thereof is omitted.

In the second embodiment, a polyether compound is used as an additive in the electrolytic solution. This polyether compound, together with chloride ions described later, contributes to shape control of the deposited copper powder, and the copper powder deposited on the cathode is an ellipsoidal copper having a predetermined minor axis average diameter and major axis average diameter. A dendritic copper powder in which particles are aggregated into a dendritic shape can be obtained.

Specifically, the polyether compound is not particularly limited. For example, polyethylene glycol, polypropylene glycol, polyethyleneimine, pluronic surfactant, tetronic surfactant, polyoxyethylene glycol / glycerin ether, polyoxyethylene Examples thereof include polymer compounds such as glycol dialkyl ether, polyoxyethylene polyoxypropylene glycol alkyl ether, and aromatic alcohol alkoxylate.

Further, the number average molecular weight of the polyether compound is not particularly limited, but is preferably 100 to 200,000, more preferably 200 to 15,000, and 1,000 to 10,000. Is more preferable. If the number average molecular weight is less than 100, fine electrolytic copper powder that does not have a dendritic shape may be deposited. On the other hand, when the number average molecular weight exceeds 200,000, electrolytic copper powder having a large average particle size is precipitated, and only dendritic copper powder having a specific surface area of less than 0.6 m ² / g may be obtained. . The number average molecular weight is a molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

In addition, as a polyether compound, you may add individually by 1 type and may add it in combination of 2 or more types. Further, the addition amount of the polyether compound is preferably such that the concentration in the electrolytic solution is in the range of about 0.1 mg / L to 5,000 mg / L.

As the chloride ions, compounds that supply chloride ions such as hydrochloric acid and sodium chloride (chloride ion source) can be added to the electrolyte solution. By containing chloride ions in the electrolytic solution, the shape of the deposited copper powder can be controlled more effectively. The chloride ion concentration in the electrolytic solution can be about 1 mg / L to 1000 mg / L, preferably about 10 mg / L to 800 mg / L, more preferably about 20 mg / L to 500 mg / L.

In the second embodiment, for example, electrolysis is performed using the electrolytic solution having the composition as described above, whereby copper powder is deposited on the cathode to produce dendritic copper powder. As the electrolysis method, a known method can be used. For example, the current density is preferably in the range of 5 A / dm ² to 30 A / dm ² in electrolysis using a sulfuric acid electrolytic solution, and the electrolytic solution is energized while stirring. The liquid temperature (bath temperature) of the electrolytic solution can be, for example, about 20 ° C. to 60 ° C.

<2-2-2. Ni Coating Method (Production of Ni Coated Copper Powder)>
The Ni-coated copper powder according to the second embodiment is obtained by using Ni plating solution (electroless Ni plating solution) by using an electroless plating method on the surface of the dendritic copper powder produced by the above-described electrolysis method. It can be manufactured by coating a Ni alloy.

The specific electroless plating method, the composition of the electroless Ni plating solution (components in the plating solution), and pretreatment such as cleaning treatment before electroless plating are performed in the first embodiment. The method is the same as that of the method, and detailed description is omitted.

Moreover, it is preferable that other elements are contained in the Ni film to be formed, similarly to the formation of the Ni film in the first embodiment. By forming a Ni alloy film on the surface of the copper powder, it is possible to realize a conductive paste having excellent heat resistance and corrosion resistance using the Ni-coated copper powder.

In addition, the formation method of the Ni alloy film, the content of elements other than Ni in the Ni alloy, the element source of the elements other than Ni, and the like are the same as the aspects of the manufacturing method in the first embodiment. The detailed explanation is omitted.

<2-3. Manufacturing Method of Ni Coated Copper Powder According to Third Embodiment>
The Ni-coated copper powder according to the third embodiment has a dendritic shape in which copper particles whose surfaces are coated with Ni or a Ni alloy are aggregated and have a main trunk that grows linearly and a plurality of branches separated from the main trunk. It is Ni coat copper powder which constituted the shape. The copper particles whose surfaces are coated with Ni or Ni alloy are in the form of a flat plate having a cross-sectional average thickness of 0.2 μm to 5.0 μm, and the Ni coated copper powder formed by assembling the copper particles is The average particle diameter (D50) is 1.0 μm to 100 μm.

<2-3-1. Manufacturing method of copper powder>
As described above, the Ni-coated copper powder (dendritic Ni-coated copper powder) according to the third embodiment is coated with Ni or a Ni alloy on the surface of the dendritic copper powder. For example, it can be manufactured by a predetermined electrolytic method using a sulfuric acid acidic solution containing copper ions as an electrolytic solution.

In the case of electrolysis, a sulfuric acid-containing electrolytic solution containing copper ions is contained in an electrolytic cell in which metallic copper is used as an anode and a stainless steel plate or a titanium plate is used as a cathode, as in the electrolytic treatment in the first embodiment. Then, electrolytic treatment is performed by passing a direct current through the electrolytic solution at a predetermined current density. Thereby, a dendritic copper powder can be deposited (electrodeposition) on a cathode with electricity supply. In particular, in the third embodiment, an amine compound is added as an additive to a sulfuric acid electrolytic solution containing a water-soluble copper salt serving as a copper ion source, and thus electrolysis is obtained. The copper powder in the form of particles is formed by dendritic copper powder that is formed by aggregation of flat copper particles only by electrolysis without mechanical deformation using a medium such as a ball. Can be deposited.

That is, as the electrolytic solution, for example, an electrolytic solution containing a water-soluble copper salt (copper ion), sulfuric acid, and an amine compound is used. Further, it is preferable that the electrolytic solution further contains chloride ions. Here, the water-soluble copper salt and sulfuric acid contained in the electrolytic solution are the same as those in the manufacturing method according to the first embodiment, and detailed description thereof is omitted.

In the third embodiment, an amine compound can be used as an additive in the electrolytic solution. This amine compound contributes to shape control of the copper powder deposited together with chloride ions to be described later, and the copper powder deposited on the cathode surface is composed of flat copper particles having a predetermined cross-sectional average thickness. And a dendritic copper powder having a branch branched from its main trunk.

As the amine compound, one kind may be added alone, or two or more kinds may be added in combination. The amount of the amine compound added is preferably an amount such that the concentration in the electrolytic solution is in the range of 0.1 mg / L to 500 mg / L, and an amount in the range of 1 mg / L to 400 mg / L. More preferably.

Specifically, the amine compound is not particularly limited, but a compound having a phenazine structure that can be represented by the following formula (1) can be used. More preferably, for example, safranine (3,7-diamino-2,8-dimethyl-5-phenyl-5-phenazinium chloride, C ₂₀ H ₁₉ N ₄ Cl, CAS number: 477-73-64) is used. Can do.

As the chloride ions, compounds that supply chloride ions such as hydrochloric acid and sodium chloride (chloride ion source) can be added to the electrolyte solution. By containing chloride ions in the electrolytic solution, the shape of the deposited copper powder can be controlled more effectively. The chloride ion concentration in the electrolytic solution can be about 1 mg / L to 1000 mg / L, preferably about 5 mg / L to 800 mg / L, more preferably about 10 mg / L to 500 mg / L.

In the third embodiment, for example, electrolysis is performed using the electrolytic solution having the composition as described above, whereby copper powder is deposited on the cathode to produce dendritic copper powder. As the electrolysis method, a known method can be used. For example, the current density is preferably in the range of 5 A / dm ² to 30 A / dm ² in electrolysis using a sulfuric acid electrolytic solution, and the electrolytic solution is energized while stirring. The liquid temperature (bath temperature) of the electrolytic solution can be, for example, about 20 ° C. to 60 ° C.

<2-3-2. Ni Coating Method (Production of Ni Coated Copper Powder)>
The Ni-coated copper powder according to the third embodiment is obtained by using Ni plating solution (electroless Ni plating solution) by an electroless plating method on the surface of the dendritic copper powder produced by the above-described electrolysis method. It can be manufactured by coating a Ni alloy.

<2-4. Method for Producing Ni Coated Copper Powder According to Fourth Embodiment>
The Ni-coated copper powder according to the fourth embodiment is a Ni-coated copper powder in which a plurality of piece-like copper particles whose surfaces are coated with Ni or a Ni alloy are aggregated to form an aggregate. The copper particles coated with Ni or Ni alloy have a flat plate shape with an average major axis diameter determined by SEM observation of 0.5 μm to 5.0 μm and an average cross-sectional thickness of 0.02 μm to 1.0 μm. The Ni-coated copper powder composed of the copper particles has an average particle diameter (D50) of 1.0 μm to 30 μm.

<2-4-1. Manufacturing method of copper powder>
As described above, the Ni-coated copper powder (flat Ni-coated copper particle aggregated powder) according to the fourth embodiment is obtained by coating the surface of the tabular copper particle aggregated powder with Ni or a Ni alloy. The copper particle agglomerated powder can be produced, for example, by a predetermined electrolytic method using a sulfuric acid acidic solution containing copper ions as an electrolytic solution.

In the case of electrolysis, a sulfuric acid-containing electrolytic solution containing copper ions is contained in an electrolytic cell in which metallic copper is used as an anode and a stainless steel plate or a titanium plate is used as a cathode, as in the electrolytic treatment in the first embodiment. Then, electrolytic treatment is performed by passing a direct current through the electrolytic solution at a predetermined current density. Thereby, flat copper particle aggregation copper powder can be deposited (electrodeposition) on a cathode with electricity supply. In particular, in the fourth embodiment, an amine compound or a nonionic surfactant is added as an additive to the sulfuric acid acidic electrolyte solution containing a water-soluble copper salt serving as a copper ion source. The granular copper powder obtained by electrolysis is not subjected to mechanical deformation processing using a medium such as a ball, and the tabular copper particle aggregated powder in which tabular copper particles are aggregated is obtained only by electrolysis. It can be deposited on the surface.

That is, as the electrolytic solution, for example, a material containing a water-soluble copper salt (copper ion), sulfuric acid, and an additive such as an amine compound or a nonionic surfactant is used. Further, it is preferable that the electrolytic solution further contains chloride ions. Here, the water-soluble copper salt and sulfuric acid contained in the electrolytic solution are the same as those in the manufacturing method according to the first embodiment, and detailed description thereof is omitted.

In the fourth embodiment, for example, an amine compound or a nonionic surfactant is used as an additive in the electrolytic solution. The amine compound added as an additive contributes to the shape control of the copper powder deposited together with the chloride ions and nonionic surfactants described later, and the copper powder deposited on the cathode has a flat cross-sectional shape having a predetermined average thickness. It can be set as the tabular copper particle aggregation powder comprised from a copper particle.

Specifically, the amine compound is not particularly limited, and for example, Janus Green B (C ₃₀ H ₃₁ N ₆ Cl, CAS number: 2869-83-2) can be used.

As the amine compound, one kind may be added alone, or two or more kinds may be added in combination. Further, the addition amount of the amine compound is preferably an amount that is in the range of about 0.1 mg / L to 500 mg / L in terms of concentration in the electrolytic solution.

The nonionic surfactant is not particularly limited, but those having an ether group are preferred. Specific examples include polyethylene glycol, polypropylene glycol, polyethyleneimine, pluronic surfactant, tetronic surfactant, polyoxyethylene glycol / glyceryl ether, polyoxyethylene glycol / dialkyl ether, polyoxyethylene polyoxypropylene glycol. -Alkyl ether, aromatic alcohol alkoxylate, the compound represented by following formula (x), etc. are mentioned.

(In the formula (x), R ₁ has a higher alcohol residue having 5 to 30 carbon atoms, an alkylphenol residue having an alkyl group having 1 to 30 carbon atoms, or an alkyl group having 1 to 30 carbon atoms. A residue of an alkyl naphthol, a residue of a fatty acid amide having 3 to 25 carbon atoms, a residue of an alkyl amine having 2 to 5 carbon atoms or a hydroxyl group, R ₂ and R ₃ represent a hydrogen atom or a methyl group, m And n represents an integer of 1 to 100.)

The number average molecular weight of the nonionic surfactant is not particularly limited, but is preferably 100 to 200,000, more preferably 200 to 15,000, and further preferably 1,000 to 10,000. preferable. The number average molecular weight is a molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

These nonionic surfactants may be added singly or in combination of two or more. The amount of the nonionic surfactant added is not particularly limited, but is preferably about 200 mg / L to 5000 mg / L, more preferably about 500 mg / L to 2000 mg / L in terms of the concentration in the electrolytic solution. preferable.

As the chloride ions, compounds that supply chloride ions such as hydrochloric acid and sodium chloride (chloride ion source) can be added to the electrolyte solution. Chloride ions contribute to shape control of the deposited copper powder together with the above-described amine compound and nonionic surfactant additives. The chloride ion concentration in the electrolytic solution is not particularly limited, but is preferably about 200 mg / L to 1000 mg / L, and more preferably about 250 mg / L to 800 mg / L.

In the fourth embodiment, for example, by performing electrolysis using the electrolytic solution having the above-described composition, copper powder is deposited on the cathode to produce a tabular copper particle aggregated powder. As the electrolysis method, a known method can be used. For example, the current density is preferably in the range of 5 A / dm ² to 40 A / dm ² when electrolysis is performed using a sulfuric acid electrolyte, and the electrolyte is energized while stirring. The liquid temperature (bath temperature) of the electrolytic solution can be, for example, about 20 ° C. to 60 ° C.

<2-4-2. Ni Coating Method (Production of Ni Coated Copper Powder)>
The Ni-coated copper particles according to the fourth embodiment are obtained by using, for example, a Ni plating solution (electroless Ni plating solution) by an electroless plating method on the surface of the tabular copper particle aggregate powder produced by the above-described electrolytic method. It can be produced by coating Ni or Ni alloy.

<2-5. Manufacturing Method of Ni Coated Copper Powder According to Fifth Embodiment>
The Ni-coated copper powder according to the fifth embodiment has a dendritic shape in which copper particles whose surfaces are coated with Ni or a Ni alloy are aggregated and have a main trunk that grows linearly and a plurality of branches separated from the main trunk. It is Ni coat copper powder which constituted the shape. The copper particles whose surfaces are coated with Ni or Ni alloy are dendritic having a main trunk grown in a dendritic shape and a plurality of branches separated from the main trunk, and the cross-sectional average thickness of the main trunk and the branches of the copper particles. The Ni-coated copper powder, which is a flat plate having a thickness of 0.02 μm to 0.5 μm and is formed by aggregating the copper particles, has an average particle diameter (D50) of 1.0 μm to 30 μm. The surface of the copper particles has fine convex portions, and the average height of the convex portions is preferably 0.01 μm to 0.4 μm.

<2-5-1. Manufacturing method of copper powder>
As described above, the Ni-coated copper powder (dendritic Ni-coated copper powder) according to the fifth embodiment is obtained by coating the surface of the dendritic copper powder with Ni or a Ni alloy. For example, it can be manufactured by a predetermined electrolytic method using a sulfuric acid acidic solution containing copper ions as an electrolytic solution.

In the case of electrolysis, a sulfuric acid-containing electrolytic solution containing copper ions is contained in an electrolytic cell in which metallic copper is used as an anode and a stainless steel plate or a titanium plate is used as a cathode, as in the electrolytic treatment in the first embodiment. Then, electrolytic treatment is performed by passing a direct current through the electrolytic solution at a predetermined current density. Thereby, a dendritic copper powder can be deposited (electrodeposition) on a cathode with electricity supply. In particular, in the present embodiment, an amine compound is added as an additive to the sulfuric acid acidic electrolytic solution containing a water-soluble copper salt serving as a copper ion source, and thus obtained by electrolysis. Without denaturing the copper powder in a granular form using a medium such as a ball, the dendritic copper powder is formed on the surface of the cathode by gathering flat copper particles and forming a dendritic shape only by electrolysis. It can be deposited.

In the fifth embodiment, an amine compound can be used as an additive in the electrolytic solution. The amine compound contributes to shape control of the copper powder to be deposited together with chloride ions to be described later, and the copper powder to be deposited on the cathode surface is composed of flat copper particles having a predetermined cross-sectional thickness; A dendritic copper powder having branches branched from the main trunk can be obtained.

Specifically, the amine compound is not particularly limited, but a compound having a phenazine structure and an azobenzene structure, which can be represented by the following formula (3), can be used. More preferably, for example, Janus Green B (C30H31N6Cl, CAS number: 2869-83-2) can be used.

As the chloride ions, compounds that supply chloride ions such as hydrochloric acid and sodium chloride (chloride ion source) can be added to the electrolyte solution. By containing chloride ions in the electrolytic solution, the shape of the deposited copper powder can be controlled more effectively. The chloride ion concentration in the electrolytic solution can be about 30 mg / L to 1000 mg / L, preferably about 50 mg / L to 800 mg / L, more preferably about 200 mg / L to 500 mg / L.

In the fifth embodiment, for example, electrolysis is performed using the electrolytic solution having the above-described composition, so that copper powder is deposited on the cathode to produce dendritic copper powder. As the electrolysis method, a known method can be used. For example, the current density is preferably in the range of 5 A / dm ² to 30 A / dm ² in electrolysis using a sulfuric acid electrolytic solution, and the electrolytic solution is energized while stirring. The liquid temperature (bath temperature) of the electrolytic solution can be, for example, about 20 ° C. to 60 ° C.

<2-5-2. Ni Coating Method (Production of Ni Coated Copper Powder)>
The Ni-coated copper powder according to the fifth embodiment is obtained by using Ni plating liquid (electroless Ni plating liquid) by an electroless plating method on the surface of the dendritic copper powder produced by the above-described electrolysis method. It can be manufactured by coating a Ni alloy.

≪3. Use of conductive paste, conductive paint for electromagnetic wave shield and conductive sheet >>
The Ni-coated copper powder according to the present invention (Ni-coated copper powder according to the first to fifth embodiments) has a large surface area and excellent formability and sinterability, and has a specific shape. A large number of contacts between the Ni-coated copper powders can be ensured by the aggregation of the copper particles, thereby exhibiting excellent conductivity.

In addition, in the Ni-coated copper powder according to the first to fifth embodiments, the Ni-coated copper powder having a specific structure can suppress aggregation even when a copper paste or the like is used, It becomes possible to disperse uniformly in the resin, and it is possible to suppress the occurrence of poor printability due to an increase in the viscosity of the paste.

Therefore, the Ni-coated copper powder according to the first to fifth embodiments can be suitably used for applications such as conductive paste and conductive paint.

For example, as conductive paste (copper paste), Ni-coated copper powder is included as a metal filler (copper powder), and kneaded with binder resin, solvent, and additives such as antioxidants and coupling agents as required. Can be produced.

Here, in using the Ni-coated copper powder as a metal filler, the Ni-coated copper powder in the metal filler is 20% by mass or more, preferably 30% by mass or more, more preferably 50% by mass or more. To be included. By setting the ratio of the Ni-coated copper powder in the metal filler to 20% by mass or more, for example, when the metal filler is used in the copper paste, it can be uniformly dispersed in the resin, and the paste has an excessive viscosity. It is possible to prevent the printability from being increased. Moreover, the more excellent electroconductivity can be exhibited as an electrically conductive paste.

As described above, the metal filler may contain Ni-coated copper powder in a proportion of 20% by mass or more. Others include, for example, spherical copper powder of about 1 μm to 20 μm or spherical Ni-coated. You may mix copper powder etc. Also, fillers having different compositions as well as fillers such as silver powder may be mixed.

Specifically, the binder resin is not particularly limited, but an epoxy resin, a phenol resin, or the like can be used. Moreover, as a solvent, organic solvents, such as ethylene glycol, diethylene glycol, triethylene glycol, glycerol, and terpineol, can be used. Moreover, the addition amount of the organic solvent is not particularly limited, but the addition amount is adjusted in consideration of the particle size of the Ni-coated copper powder so that the viscosity is suitable for a conductive film forming method such as screen printing or a dispenser. be able to.

Furthermore, other resin components can be added to adjust the viscosity. For example, a cellulose-based resin typified by ethyl cellulose can be used, and it can be added as an organic vehicle dissolved in an organic solvent such as terpineol. In addition, it is necessary to suppress the addition amount of the resin component to an extent that does not impair the sinterability, and is preferably 5% by mass or less of the whole.

Also, as an additive, an antioxidant or the like can be added in order to improve the conductivity after firing. Although it does not specifically limit as antioxidant, For example, a hydroxycarboxylic acid etc. can be mentioned. More specifically, hydroxycarboxylic acids such as citric acid, malic acid, tartaric acid, and lactic acid are preferable, and citric acid or malic acid that has high adsorptive power to copper coated with Ni or Ni alloy is particularly preferable. The addition amount of the antioxidant can be set to, for example, about 1% by mass to 15% by mass in consideration of the antioxidant effect and the viscosity of the paste.

Next, even when Ni-coated copper powder is used as a metal filler as an electromagnetic shielding material, it is not limited to use under particularly limited conditions. For example, a metal filler is mixed with a resin. Can be used.

For example, the resin used for forming the electromagnetic wave shielding layer of the electromagnetic wave shielding conductive sheet is not particularly limited, and conventionally used vinyl chloride resin, vinyl acetate resin, vinylidene chloride resin, Thermoplastic resin, thermosetting resin, radiation curable type made of various polymers and copolymers such as acrylic resin, polyurethane resin, polyester resin, olefin resin, chlorinated olefin resin, polyvinyl alcohol resin, alkyd resin, phenol resin, etc. Resin etc. can be used suitably.

As a method for producing an electromagnetic shielding material, for example, the above-described metal filler and resin are dispersed or dissolved in a solvent to form a coating material, and the coating material is applied or printed on the substrate to form the electromagnetic shielding layer. It can be manufactured by forming and drying to such an extent that the surface solidifies. Moreover, a metal filler can also be utilized for the conductive adhesive layer of a conductive sheet.

Further, when using Ni-coated copper powder as a metal filler to form a conductive coating for electromagnetic wave shielding, it is not limited to use under particularly limited conditions, but a general method, for example, using a metal filler as a resin And mixed with a solvent, and further mixed with an antioxidant, a thickener, an anti-settling agent or the like as necessary, and then kneaded and used as a conductive paint.

The binder resin and solvent used at this time are not particularly limited, and vinyl chloride resin, vinyl acetate resin, acrylic resin, polyester resin, fluororesin, silicon resin, phenol resin, and the like that have been used in the past are used. Can be used. As the solvent, conventionally used alcohols such as isopropanol, aromatic hydrocarbons such as toluene, esters such as methyl acetate, ketones such as methyl ethyl ketone, and the like can be used. Well, conventionally used antioxidants such as fatty acid amides, higher fatty acid amines, phenylenediamine derivatives, titanate coupling agents, and the like can also be used.

Hereinafter, examples of the present invention will be described in more detail with reference to comparative examples, but the present invention is not limited to the following examples.

≪Evaluation method≫
The copper powder obtained in the following Examples and Comparative Examples was subjected to shape observation, average particle diameter measurement, specific surface area measurement, and the like by the following methods.

(Observation of shape)
With a scanning electron microscope (manufactured by JEOL Ltd., JSM-7100F type), 20 visual fields were arbitrarily observed at a predetermined magnification, and Ni-coated copper powder contained in the visual field was observed.

(Measurement of average particle size)
The average particle diameter (D50) of the obtained Ni-coated copper powder was measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., HRA9320 X-100).

(The bulk density)
The bulk density was measured as a tap density using a shaking specific gravity measuring device (manufactured by Kuramochi Scientific Instruments, Tapping machine KRS-40).

(BET specific surface area)
The BET specific surface area was measured using a specific surface area / pore distribution measuring apparatus (manufactured by Cantachrome, QUADRASORB SI).

(Specific resistance measurement)
Regarding the specific resistance value of the film, the sheet resistance value was measured by a four-terminal method using a low resistivity meter (Loresta-GP MCP-T600, manufactured by Mitsubishi Chemical Corporation), while the surface roughness shape measuring instrument ( The film thickness of the coating film was measured by SURFCOM130A, manufactured by Tokyo Seimitsu Co., Ltd., and the sheet resistance value was determined by dividing the film thickness by the film thickness.

(Electromagnetic wave shielding characteristics)
The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate of the samples obtained in the examples and comparative examples using an electromagnetic wave having a frequency of 1 GHz.

Also, in order to evaluate the flexibility of the electromagnetic wave shield, it was confirmed whether or not the electromagnetic wave shielding characteristics were changed by bending the produced electromagnetic wave shield.

≪Example, comparative example≫
(1) Test using Ni-coated copper powder according to the first embodiment [Example 1]
<Preparation of electrolytic copper powder>
In an electrolytic cell having a capacity of 100 L, an electrode plate made of titanium having an electrode area of 200 mm × 200 mm is used as a cathode, and a copper electrode plate having an electrode area of 200 mm × 200 mm is used as an anode, and an electrolytic solution is loaded in the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

At this time, as the electrolytic solution, a composition having a copper ion concentration of 15 g / L and a sulfuric acid concentration of 100 g / L was used. Further, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added to the electrolytic solution so that the chloride ion (chlorine ion) concentration in the electrolytic solution was 50 mg / L. In addition, safranin (manufactured by Kanto Chemical Co., Ltd.), which is a compound having a phenazine structure, is added as an additive to the electrolytic solution so that the concentration in the electrolytic solution is 100 mg / L, and a nonionic surfactant is further added. Polyethylene glycol (PEG) having a molecular weight of 1,000 (manufactured by Wako Pure Chemical Industries, Ltd.) was added to a concentration of 500 mg / L in the electrolytic solution.

Then, while circulating the electrolytic solution adjusted to the concentration as described above at a flow rate of 15 L / min using a pump, the temperature is maintained at 25 ° C. and the current density of the cathode is 10 A / dm ^2. Then, copper powder was deposited on the cathode plate.

The electrolytic copper powder deposited on the cathode plate was recovered by mechanically scraping it off the bottom of the electrolytic cell using a scraper, and the recovered copper powder was washed with pure water and then put in a vacuum dryer and dried. .

<Production of Ni-coated copper powder (reducing agent: borohydride)>
Next, 100 g of the obtained dendritic copper powder was used to coat the surface of the copper powder with an electroless Ni plating solution, thereby producing a Ni-coated copper powder. In addition, the electroless Ni plating solution whose reducing agent is a borohydride compound was used.

Specifically, as an electroless Ni plating solution, nickel sulfate 30 g / L, sodium succinate 50 g / L, boric acid 30 g / L, ammonium chloride 30 g / L, dimethylamine borane 4 g / L were added at each concentration, Further, 500 mL of a plating solution adjusted to pH 6.0 by adding sodium hydroxide was prepared.

In this electroless Ni plating solution, a slurry in which 100 g of electrolytic copper powder prepared by the above-described method is dispersed in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 60 ° C. for 60 minutes. Stir.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, a Ni-coated copper powder having a Ni alloy coated on the surface of the copper powder was obtained. As a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Ni-coated copper powder is a flat copper particle whose surface is uniformly coated with a Ni alloy. It was a dendritic Ni-coated copper powder that was densely gathered and exhibited a dendritic shape. When the dendritic Ni-coated copper powder was recovered and the Ni content was measured, it was 18.2% by mass with respect to 100% by mass of the entire dendritic Ni-coated copper powder. Further, the content of boron (B) contained in the Ni alloy was 6.3% by mass with respect to 100% by mass of the Ni alloy.

The obtained dendritic Ni-coated copper powder was grown in a direction perpendicular to the cross-sectional average thickness of the flat copper particles and the flat surface of the dendritic Ni-coated copper powder while observing with SEM. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. As a result, the copper particles constituting the obtained dendritic Ni-coated copper powder were in the form of a flat plate having a cross-sectional average thickness of 2.7 μm. The average particle diameter (D50) of the dendritic Ni-coated copper powder was 46.6 μm. The ratio of the maximum length of the Ni-coated copper powder grown in the vertical direction from the flat surface to the maximum length in the direction horizontal to the flat surface (flat direction) (vertical length / flat length in the flat plate direction) Was an average of 0.069.

Moreover, the bulk density of the obtained dendritic Ni-coated copper powder was 2.9 g / cm ³ . The BET specific surface area was 1.15 m ² / g.

From the result of Example 1, a compound having a phenazine structure and a nonionic surfactant were added to the electrolytic solution to prepare a dendritic electrolytic copper powder, and the surface of the obtained copper powder was coated with a Ni alloy By doing this, it was found that a plate-like dendritic Ni-coated copper powder with suppressed growth in the vertical direction could be produced.

[Example 2]
<Preparation of electrolytic copper powder>
A hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) is added to the electrolyte so that the chloride ion concentration is 150 mg / L, and methyl orange (Kanto Chemical Industries, Ltd.), which is a compound having an azobenzene structure as an additive, is added. Manufactured) was added to a concentration of 150 mg / L in the electrolytic solution. Furthermore, polyoxyethylene polyoxypropylene butyl ether having a molecular weight of 1,000, which is a nonionic surfactant, (manufactured by NOF Corporation, trade name: UNILOVE 50MB-11), as the electrolyte solution, has a concentration of 700 mg / L in the electrolyte solution. It added so that it might become. Otherwise, electrolytic treatment was performed under the same conditions as in Example 1 to produce electrolytic copper powder.

<Production of Ni-coated copper powder (reducing agent: hypophosphite)>
Next, 100 g of the obtained dendritic copper powder was used to coat the surface of the copper powder with an electroless Ni plating solution, thereby producing a Ni-coated copper powder. In addition, an electroless Ni plating solution whose reducing agent is hypophosphite was used.

Specifically, as an electroless Ni plating solution, nickel sulfate 20 g / L, sodium hypophosphite 25 g / L, sodium acetate 10 g / L, sodium citrate 10 g / L are added at each concentration, and sodium hydroxide is further added. 500 mL of a plating solution adjusted to pH 5.0 by adding the above was prepared.

In this electroless Ni plating solution, a slurry in which 100 g of electrolytic copper powder prepared by the above-described method is dispersed in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 90 ° C. for 60 minutes. Stir.

After the addition of each aqueous solution was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which Ni alloy containing phosphorus (P) was coated on the surface of dendritic copper powder was obtained. . As a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Ni-coated copper powder is a flat copper particle whose surface is uniformly coated with a Ni alloy. It was a dendritic Ni-coated copper powder that was densely gathered and exhibited a dendritic shape. When the dendritic Ni-coated copper powder was recovered and the Ni content was measured, it was 13.3% by mass with respect to 100% by mass of the entire dendritic Ni-coated copper powder. The content of P contained in the Ni alloy was 7.2% by mass with respect to 100% by mass of the Ni alloy.

The obtained dendritic Ni-coated copper powder was grown in a direction perpendicular to the cross-sectional average thickness of the flat copper particles and the flat surface of the dendritic Ni-coated copper powder while observing with SEM. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. As a result, the copper particles constituting the obtained dendritic Ni-coated copper powder were in the form of a flat plate having a cross-sectional average thickness of 1.8 μm. The average particle diameter (D50) of the dendritic Ni-coated copper powder was 34.6 μm. The ratio of the maximum length of the Ni-coated copper powder grown in the vertical direction from the flat surface to the maximum length in the direction horizontal to the flat surface (flat direction) (vertical length / flat length in the flat plate direction) Was an average of 0.034.

Moreover, the bulk density of the obtained dendritic Ni-coated copper powder was 2.1 g / cm ³ . The BET specific surface area was 1.29 m ² / g.

From the results of Example 2, a compound having an azobenzene structure and a nonionic surfactant were added to the electrolytic solution to produce a dendritic electrolytic copper powder, and the surface of the obtained copper powder was coated with a Ni alloy. By doing this, it was found that a plate-like dendritic Ni-coated copper powder with suppressed growth in the vertical direction could be produced.

[Example 3]
<Preparation of electrolytic copper powder>
To the electrolyte, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the chloride ion concentration was 80 mg / L, and Janus Green B (a compound having a phenazine structure and an azobenzene structure as an additive) Kanto Chemical Co., Ltd.) was added at a concentration of 600 mg / L in the electrolytic solution. Furthermore, polyoxyethylene polyoxypropylene butyl ether having a molecular weight of 3,000 as a nonionic surfactant (manufactured by NOF Corporation, trade name: UNILOVE 50MB-72) is added to the electrolyte solution at a concentration of 1,000 mg / liter in the electrolyte solution. It added so that it might become L. Otherwise, electrolytic treatment was performed under the same conditions as in Example 1 to produce electrolytic copper powder.

<Production of Ni-coated copper powder (reducing agent: hydrazine compound)>
Next, 100 g of the obtained dendritic copper powder was used to perform Ni coating on the surface of the copper powder by electroless Ni plating to prepare a Ni-coated copper powder. Electroless Ni plating using a hydrazine compound as a reducing agent was performed.

Specifically, nickel acetate was added to a slurry in which 100 g of the obtained electrolytic copper powder was dispersed in 500 mL of water to a concentration of 12.4 g / L, and then 6 g of an 80% by mass aqueous solution of hydrazine monohydrate was added. The solution was dropped into the bath with slow stirring over 60 minutes. At this time, the bath temperature was controlled to 60 ° C.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which Ni was coated on the surface of the electrolytic copper powder was obtained. As a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Ni-coated copper powder is densely packed with flat copper particles whose surfaces are uniformly coated with Ni. Thus, the dendritic Ni-coated copper powder aggregated and exhibited a dendritic shape. When the dendritic Ni-coated copper powder was recovered and the Ni content was measured, it was 7.5% by mass with respect to 100% by mass of the entire dendritic Ni-coated copper powder.

The obtained dendritic Ni-coated copper powder was grown in a direction perpendicular to the cross-sectional average thickness of the flat copper particles and the flat surface of the dendritic Ni-coated copper powder while observing with SEM. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. As a result, the copper particles constituting the obtained dendritic Ni-coated copper powder were flat plate having a cross-sectional average thickness of 1.3 μm. The average particle diameter (D50) of the dendritic Ni-coated copper powder was 33.7 μm. The ratio of the maximum length of the Ni-coated copper powder grown in the vertical direction from the flat surface to the maximum length in the direction horizontal to the flat surface (flat direction) (vertical length / flat length in the flat plate direction) Was an average of 0.022.

Moreover, the bulk density of the obtained dendritic Ni-coated copper powder was 1.9 g / cm ³ . Moreover, the BET specific surface area was 1.98 m < ² > / g.

From the results of Example 3, the surface of the obtained copper powder was prepared by adding a compound having a phenazine structure and an azobenzene structure and a nonionic surfactant to the electrolytic solution to form a dendritic electrolytic copper powder. It was found that a plate-like dendritic Ni-coated copper powder with suppressed growth in the vertical direction can be produced by coating Ni with Ni.

[Example 4]
<Preparation of electrolytic copper powder>
A hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) is added to the electrolyte so that the chloride ion concentration is 100 mg / L, and methyl orange (manufactured by Kanto Chemical Co., Ltd.), which is a compound having an azobenzene structure as an additive, is added. ) Is added at a concentration of 150 mg / L in the electrolytic solution, and Janus Green B (manufactured by Kanto Chemical Co., Ltd.), which is a compound having a phenazine structure and an azobenzene structure, is added at a concentration of 100 mg / L in the electrolytic solution. It added so that it might become L. Further, a nonionic surfactant having a molecular weight of 600 polyethylene glycol (PEG) (manufactured by Wako Pure Chemical Industries, Ltd.) is further added to the electrolyte so that the concentration in the electrolyte is 1,000 mg / L. Polyoxyethylene polyoxypropylene butyl ether having a molecular weight of 3,000 (manufactured by NOF Corporation, trade name: UNILOVE 50MB-72) as an agent was added so that the concentration in the electrolytic solution was 1,000 mg / L. Otherwise, electrolytic treatment was performed under the same conditions as in Example 1 to produce electrolytic copper powder.

<Preparation of Ni-coated copper powder (reducing agent: borohydride)>
Next, when the surface of the obtained electrolytic copper powder was coated with a Ni alloy in the same procedure as in Example 1, a Ni-coated copper powder in which the surface of the electrolytic copper powder was coated with the Ni alloy was obtained. .

As a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of Ni-coated copper powder is densely packed with tabular copper particles coated with a Ni alloy on the surface. The dendritic Ni-coated copper powder gathered and exhibited a dendritic shape. Moreover, when the dendritic Ni coat copper powder was collect | recovered and content of Ni was measured, it was 18.5 mass% with respect to 100 mass of the said dendritic Ni coat copper powder whole. Moreover, content of B contained in Ni alloy was 6.8 mass% with respect to 100 mass of Ni alloy.

The obtained dendritic Ni-coated copper powder was grown in a direction perpendicular to the cross-sectional average thickness of the flat copper particles and the flat surface of the dendritic Ni-coated copper powder while observing with SEM. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. As a result, the copper particles constituting the obtained dendritic Ni-coated copper powder were flat plate having a cross-sectional average thickness of 0.4 μm. The average particle diameter (D50) of the dendritic Ni-coated copper powder was 18.9 μm. The ratio of the maximum length of the Ni-coated copper powder grown in the vertical direction from the flat surface to the maximum length in the direction horizontal to the flat surface (flat direction) (vertical length / flat length in the flat plate direction) Was an average of 0.055.

Moreover, the bulk density of the obtained dendritic Ni-coated copper powder was 1.2 g / cm ³ . The BET specific surface area was 2.10 m ² / g.

From the results of Example 4, a compound having an azobenzene structure and a compound having a phenazine structure and an azobenzene structure were added and added as additives, and two or more kinds of nonionic surfactants were further added to form a dendron. It is found that a plate-like dendritic Ni-coated copper powder with suppressed growth in the vertical direction can be produced by preparing a shaped electrolytic copper powder and coating the surface of the obtained copper powder with a Ni alloy. It was.

[Examples 5 to 11]
<Manufacture of electrolytic copper powder>
To the electrolyte, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the chloride ion concentration was 80 mg / L, and Janus Green B (a compound having a phenazine structure and an azobenzene structure as an additive) Kanto Chemical Co., Ltd.) was added at a concentration of 600 mg / L in the electrolytic solution. Furthermore, polyoxyethylene polyoxypropylene butyl ether having a molecular weight of 3,000 as a nonionic surfactant (manufactured by NOF Corporation, trade name: UNILOVE 50MB-72) is added to the electrolyte solution at a concentration of 1,000 mg / liter in the electrolyte solution. It added so that it might become L. Otherwise, electrolytic treatment was performed under the same conditions as in Example 1 to produce a dendritic copper powder.

<Preparation of Ni-coated copper powder (Ni alloy)>
Next, 100 g of the obtained dendritic copper powder was used, and the copper powder surface was coated with a Ni alloy with an electroless plating solution.

As an electroless Ni plating solution for an alloy, nickel acetate is added to a slurry (copper powder slurry) in which 100 g of the obtained electrolytic copper powder is dispersed in 500 mL of water to a concentration of 12.4 g / L, and hydrazine is further added. 3.2 g was added dropwise into the bath over 60 minutes with slow stirring. The bath temperature was controlled to 60 ° C.

At this time, each metal compound was added to a bath containing a copper powder slurry and nickel acetate, and hydrazine was gradually added so that each desired Ni alloy film was formed. In Example 5, 1.5 g of sodium tungstate was added as a metal compound to form a Ni—W alloy film. In Example 6, 2 g of cobalt sulfate was added to form a Ni—Co alloy film. In Example 7, 4 g each of zinc sulfate heptahydrate and sodium citrate were added to form a Ni—Zn alloy film. In Example 8, 2 g of palladium chloride was added to form a Ni—Pd alloy film. In Example 9, 2 g of potassium tetrachloroplatinate and 1 g of glycine were added to form a Ni—Pt alloy film. In Example 10, 1 g each of sodium molybdate and trisodium citrate was added to form a Ni—Mo alloy film. In Example 11, 1 g of sodium stannate was added to form a Ni—Sn alloy film.

After each reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which Ni alloy was coated on the surface of the electrolytic copper powder was obtained. The Ni-coated copper powder was recovered and the Ni alloy coating amount was measured. Table 1 shows the results of measuring the content of Ni with respect to 100% by mass of the entire dendritic Ni-coated copper powder and the content of elements that become Ni alloys with respect to 100% by mass of the Ni alloy.

In addition, as a result of observing each of the obtained Ni-coated copper powder with a SEM field of view at a magnification of 5,000 times, at least 90% by number or more of the Ni-coated copper powder is an electrolytic copper powder before Ni coating. A dendritic Ni-coated copper powder having a two-dimensional or three-dimensional dendritic shape, the surface of which is uniformly coated with a Ni alloy, and a main trunk that grows linearly and a plurality of linear branches branched from the main trunk The dendritic Ni-coated copper powder had a dendritic shape having a branch and a branch further branched from the branch. Table 1 shows the alloy composition of the obtained dendritic Ni-coated copper powder.

The obtained dendritic Ni-coated copper powder was grown in a direction perpendicular to the cross-sectional average thickness of the flat copper particles and the flat surface of the dendritic Ni-coated copper powder while observing with SEM. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. Table 1 shows the measurement results for each dendritic Ni-coated copper powder.

From the results of Examples 5 to 11, a dendritic electrolytic copper powder was prepared by adding a compound having a phenazine structure and an azobenzene structure and a nonionic surfactant to the electrolytic solution, and the obtained copper powder. By coating the surface of Ni—W alloy, Ni—Co alloy, Ni—Zn alloy, Ni—Pd alloy, Ni—Pt alloy, Ni—Mo alloy, Ni—Sn alloy with a Ni alloy in the vertical direction It has been found that a plate-like dendritic Ni-coated copper powder with suppressed growth can be produced.

[Example 12]
<Preparation of dendritic Ni-coated copper powder (hypophosphite + tungsten compound)>
In Example 12, 100 g of the dendritic copper powder prepared in Example 2 was used, and the copper powder surface was coated with a Ni alloy with an electroless plating solution.

As the electroless Ni plating solution, a plating solution containing hypophosphite as a reducing agent was used in the same manner as in Example 1, and a metal other than Ni was added to the plating solution to produce a Ni alloy.

Specifically, as an electroless Ni plating solution, a plating solution in which nickel sulfate 20 g / L, sodium hypophosphite 25 g / L, sodium acetate 10 g / L, and sodium citrate 10 g / L are added at each concentration, 500 g of a plating solution prepared by adding 1.5 g of sodium tungstate and adjusting the pH to 5.0 by adding sodium hydroxide was prepared. The bath temperature was controlled to 60 ° C.

To this electroless Ni plating solution, a slurry in which 100 g of the dendritic copper powder prepared in Example 2 was dispersed in 100 mL of water was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 90 ° C. to 60 Stir for minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder coated with a Ni—WP alloy was obtained. As a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Ni-coated copper powder is densely packed with flat copper particles whose surfaces are uniformly coated with Ni. Thus, the dendritic Ni-coated copper powder aggregated and exhibited a dendritic shape. When the dendritic Ni-coated copper powder was recovered and the Ni content was measured, it was 12.2% by mass with respect to 100% by mass of the entire dendritic Ni-coated copper powder. Moreover, content of P contained in Ni alloy was 7.0 mass% with respect to 100 mass of Ni alloy. Furthermore, the content of W contained in the Ni alloy was 5.6% by mass with respect to 100% by mass of the Ni alloy.

The obtained dendritic Ni-coated copper powder was grown in a direction perpendicular to the cross-sectional average thickness of the flat copper particles and the flat surface of the dendritic Ni-coated copper powder while observing with SEM. The ratio between the maximum length and the long axis length in the horizontal direction with respect to the flat surface was measured. As a result, the copper particles constituting the obtained dendritic Ni-coated copper powder were in the form of a flat plate having a cross-sectional average thickness of 1.8 μm. The average particle diameter (D50) of the dendritic Ni-coated copper powder was 36.1 μm. The ratio of the maximum length of the Ni-coated copper powder grown in the vertical direction from the flat surface to the maximum length in the direction horizontal to the flat surface (flat direction) (vertical length / flat length in the flat plate direction) Was an average of 0.037.

Moreover, the bulk density of the obtained dendritic Ni-coated copper powder was 2.2 g / cm ³ . The BET specific surface area was 1.26 m ² / g.

From the results of Example 12, a compound having an azobenzene structure and a nonionic surfactant were added to the electrolytic solution to prepare a dendritic electrolytic copper powder, and Ni—W— was formed on the surface of the obtained copper powder. It was found that by coating a Ni alloy made of P, a plate-like dendritic Ni-coated copper powder with suppressed growth in the vertical direction can be produced.

[Example 13]
To 55 parts by mass of dendritic Ni-coated copper powder having a specific surface area of 1.15 m ² / g obtained in Example 1, 15 parts by mass of phenol resin (PL-2211 manufactured by Gunei Chemical Co., Ltd.), butyl cellosolve ( Paste by mixing 10 parts by mass of Kanto Chemical Co., Ltd., deer special grade) and repeating kneading 3 times at 1200 rpm for 3 minutes using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1). did. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing was 7.6 × 10 ⁻⁵ Ω · cm.

[Example 14]
To 55 parts by mass of the dendritic Ni-coated copper powder having a specific surface area of 1.29 m ² / g obtained in Example 2, 15 parts by mass of a phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211), butyl cellosolve ( Paste by mixing 10 parts by mass of Kanto Chemical Co., Ltd., deer special grade) and repeating kneading 3 times at 1200 rpm for 3 minutes using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1). did. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing was 8.1 × 10 ⁻⁵ Ω · cm.

[Example 15]
To 55 parts by mass of dendritic Ni-coated copper powder having a specific surface area of 2.10 m ² / g obtained in Example 4, 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211), butyl cellosolve ( Paste by mixing 10 parts by mass of Kanto Chemical Co., Ltd., deer special grade) and repeating kneading 3 times at 1200 rpm for 3 minutes using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1). did. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing was 7.9 × 10 ⁻⁵ Ω · cm.

[Example 16]
2 different between the Ni-coated copper powder having a specific surface area of 1.15 m ² / g obtained in Example 1 and the Ni-coated copper powder having a specific surface area of 1.29 m ² / g obtained in Example 2. 55 parts by mass (total amount) of Ni-coated copper powder mixed at a ratio of 50:50, 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211), butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., 10 parts by weight of deer (special grade) were mixed and paste-formed by repeating kneading at 1200 rpm for 3 minutes three times using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1). The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing was 8.0 × 10 ⁻⁵ Ω · cm.

[Example 17]
Dendritic Ni-coated copper powder having a specific surface area of 1.15 m ² / g obtained in Example 1 was dispersed in a resin to obtain an electromagnetic wave shielding material.

That is, 40 g of the dendritic Ni-coated copper powder obtained in Example 1 was mixed with 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone, and kneading was performed at 1200 rpm for 3 minutes using a small kneader. The paste was made by repeating the process once. During pasting, the Ni-coated copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried on a base material made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm using a Mayer bar to form an electromagnetic wave shielding layer having a thickness of 25 μm.

The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Table 1 shows the results of the characteristic evaluation.

[Example 18]
Dendritic Ni-coated copper powder having a specific surface area of 1.29 m ² / g obtained in Example 2 was dispersed in a resin to prepare an electromagnetic wave shielding material.

That is, 40 g of dendritic Ni-coated copper powder obtained in Example 2 was mixed with 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone, and kneading was performed at 1200 rpm for 3 minutes using a small kneader. The paste was made by repeating the process once. During pasting, the Ni-coated copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried on a base material made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm using a Mayer bar to form an electromagnetic wave shielding layer having a thickness of 25 μm.

[Example 19]
Dendritic Ni-coated copper powder having a specific surface area of 2.10 m ² / g obtained in Example 4 was dispersed in a resin to obtain an electromagnetic wave shielding material.

That is, 40 g of dendritic Ni-coated copper powder obtained in Example 4 was mixed with 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone, and kneading was performed at 1200 rpm for 3 minutes using a small kneader. The paste was made by repeating the process once. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried on a base material made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm using a Mayer bar to form an electromagnetic wave shielding layer having a thickness of 25 μm.

[Comparative Example 1]
Copper powder under the same conditions as in Example 1 except that safranin, which is a compound having a phenazine structure, and polyethylene glycol (PEG) having a molecular weight of 1,000, which is a nonionic surfactant, are not added as additives. Was deposited on the cathode plate. Then, Ni was coated on the surface of the obtained copper powder under the same conditions as in Example 1 to obtain a Ni-coated copper powder.

As a result of observing the shape of the obtained Ni-coated copper powder by the method using the scanning electron microscope (SEM) described above, the obtained Ni-coated copper powder had a dendritic shape, but the granular copper particles were It was an aggregate and was not a flat dendritic Ni-coated copper powder. The specific surface area of the Ni-coated copper powder obtained was 0.14 m ² / g. Moreover, when content of Ni of Ni coat copper powder was measured, it was 18.9 mass% with respect to 100 mass of the said Ni coat copper powder whole. Furthermore, the content of P contained in the Ni alloy was 8.2% by mass with respect to 100% by mass of the Ni alloy.

Next, 55 parts by mass of the dendritic Ni-coated copper powder was mixed with 15 parts by mass of a phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Then, using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing was 65.2 × 10 ⁻⁵ Ω · cm.

[Comparative Example 2]
The characteristic of the conductive paste by Ni coat copper powder which coat | covered Ni with the conventional flat copper powder was evaluated, and it compared with the characteristic of the conductive paste produced using the dendritic Ni coat copper powder in an Example.

The flat copper powder was prepared by mechanically flattening granular electrolytic copper powder. Specifically, 5 g of stearic acid was added to 500 g of granular atomized copper powder (manufactured by Mekin Metal Powders Co., Ltd.) having an average particle diameter of 7.9 μm, and flattened with a ball mill. The ball mill was charged with 5 kg of 3 mm zirconia beads, and flattened by rotating for 90 minutes at a rotation speed of 500 rpm.

The obtained flat copper powder was coated with Ni in the same manner as in Example 2. The content of Ni in the produced tabular Ni-coated copper powder was 13.8% by mass with respect to 100% by mass of the tabular Ni-coated copper powder. Moreover, content of P contained in Ni alloy was 8.6 mass% with respect to 100 mass of Ni alloy.

The plate-like Ni-coated copper powder thus produced was measured with a laser diffraction / scattering particle size distribution analyzer, and as a result, the average particle size (D50) was 21.8 μm. Moreover, as a result of observing with SEM, the cross-sectional average thickness was 0.4 micrometer.

Next, 20 g of a phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the obtained flat Ni-coated copper powder. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

As a result of measuring the specific resistance value of the film obtained by curing, it was 31.6 × 10 ⁻⁵ Ω · cm, and the specific resistance value was higher than that of the copper paste obtained in Example 1, and the conductivity was high. It was inferior.

[Comparative Example 3]
Similar to the one used in Comparative Example 2, a Ni-coated copper powder in which Ni was coated on a flat copper powder prepared by mechanically flattening a granular electrolytic copper powder was prepared. And the characteristic of the electromagnetic wave shield by the Ni coat copper powder was evaluated, and compared with the characteristic of the electromagnetic wave shield produced using the dendritic Ni coat copper powder in an Example, the dendritic shape effect was investigated. In addition, content of Ni of the used flat Ni coat copper powder was 13.8 mass% with respect to 100 mass of the flat Ni coat copper powder. Moreover, content of P contained in Ni alloy was 8.6 mass% with respect to 100 mass of Ni alloy.

Specifically, 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone are mixed with 40 g of flat Ni-coated copper powder, respectively, and kneading at 1200 rpm for 3 minutes is repeated three times using a small kneader. Pasted. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried using a Mayer bar on a substrate made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm to form an electromagnetic wave shielding layer having a thickness of 25 μm.

The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Specifically, the level of Comparative Example 3 in which no dendritic Ni-coated copper powder is used is “△”, and the level worse than that of Comparative Example 3 is “×”. The case where it was better than the level was evaluated as “◯”, and the case where it was superior was evaluated as “◎”. Table 1 shows the results.

≪Example, comparative example≫
(2) Test using Ni-coated copper powder according to the second embodiment [Example 20]
<Preparation of electrolytic copper powder>
An electrolytic cell with a capacity of 100 L is used with a titanium electrode plate having an electrode area of 200 mm × 200 mm as a cathode and a copper electrode plate with an electrode area of 200 mm × 200 mm as an anode, and an electrolytic solution is charged into the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

At this time, an electrolytic solution having a composition with a copper ion concentration of 10 g / L and a sulfuric acid concentration of 100 g / L was used. Further, polyethylene glycol (PEG) having a molecular weight of 400 (manufactured by Wako Pure Chemical Industries, Ltd.) as an additive was added to this electrolytic solution so that the concentration in the electrolytic solution was 500 mg / L, and a hydrochloric acid solution (Wako Pure Chemical Industries, Ltd.) was further added. Yakuhin Kogyo Co., Ltd.) was added at a chloride ion (chlorine ion) concentration of 50 mg / L.

Then, the current density of the cathode is 20 A / dm ² under the condition that the temperature is maintained at 30 ° C. while circulating the electrolytic solution whose concentration is adjusted as described above at a flow rate of 10 L / min using a metering pump. In this way, copper powder was deposited on the cathode plate.

The electrolytic copper powder deposited on the cathode plate was mechanically scraped and collected on the bottom of the electrolytic cell, and the collected copper powder was washed with pure water, and then placed in a vacuum dryer and dried.

As a result of observing the shape of the copper powder thus obtained with a scanning electron microscope (SEM) in the field of view of a magnification of 5,000, the deposited copper powder had a minor axis average diameter of 0.2 μm to 0 μm. It was a dendritic copper powder having a dendritic shape composed of ellipsoidal copper particles having a major axis average diameter of 0.5 μm to 2.0 μm. The average particle diameter (D50) of the dendritic copper powder formed by aggregation of the copper particles was 5.0 μm to 20 μm. It was also confirmed that the copper particles were aggregated to form a dendritic copper powder having an average thickness of the branch portion of 0.5 μm to 2.0 μm.

<Preparation of dendritic Ni-coated copper powder (reducing agent: borohydride)>
Using 100 g of the obtained dendritic copper powder, Ni was coated on the surface of the copper powder by electroless plating to prepare a Ni-coated copper powder. In addition, the electroless Ni plating solution whose reducing agent is a borohydride compound was used.

Specifically, as an electroless Ni plating solution, nickel sulfate 30 g / L, sodium succinate 50 g / L, boric acid 30 g / L, ammonium chloride 30 g / L, dimethylamine borane 4 g / L were added at each concentration, 500 mL of a plating solution adjusted to pH 6.0 by adding sodium hydroxide was prepared.

In this electroless Ni plating solution, a slurry in which 100 g of the dendritic copper powder prepared by the above method is dispersed in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 60 ° C. to 60 ° C. Stir for minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which the surface of the dendritic copper powder was coated with Ni was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 18.6% by mass with respect to 100% by mass of the entire Ni-coated copper powder. Further, the content of boron (B) contained in the Ni alloy was 6.1% by mass with respect to 100% by mass of the Ni alloy.

Moreover, as a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Ni-coated copper powder has a dendritic shape in which copper particles are aggregated, It was dendritic Ni-coated copper powder in which the Ni alloy was uniformly coated on the surface of the copper particles. The copper particles constituting the Ni-coated copper powder and coated with a Ni alloy on the surface have a minor axis average diameter of 0.2 μm to 0.5 μm and an average of 0.39 μm. It was an ellipsoid having a diameter of 0.5 μm to 2.0 μm and an average size of 1.6 μm.

The average particle diameter (D50) of the dendritic Ni-coated copper powder formed by aggregating ellipsoidal copper particles coated with these Ni alloys is 21.2 μm, and the average thickness of the branch portion is 1 It was 5 μm.

Furthermore, the bulk density of the obtained Ni-coated copper powder was 1.25 g / cm ³ . The BET specific surface area was 1.7 m ² / g.

[Example 21]
<Manufacture of electrolytic copper powder>
As the electrolytic solution, a composition having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L is used, and polyethylene glycol (PEG) as an additive is 150 mg / L as an additive in the electrolytic solution. Copper powder (dendritic copper powder) on the cathode plate under the same conditions as in Example 20, except that the hydrochloric acid solution was added to a concentration of 100 mg / L as the chloride ion concentration in the electrolyte solution. Precipitated.

<Production of dendritic Ni-coated copper powder (reducing agent: hypophosphite)>
Next, using the electrolytic copper powder produced by the method described above, Ni-coated copper powder was produced by electroless plating. In addition, an electroless Ni plating solution whose reducing agent is hypophosphite was used.

Specifically, as an electroless Ni plating solution, nickel sulfate 20 g / L, sodium hypophosphite 25 g / L, sodium acetate 10 g / L, sodium citrate 10 g / L were added at each concentration, and sodium hydroxide was further added. 500 mL of a plating solution adjusted to pH 5.0 by addition was prepared.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which the surface of the dendritic copper powder was coated with Ni alloy containing phosphorus (P) was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 13.1% by mass with respect to 100% by mass of the entire Ni-coated copper powder. Moreover, content of P contained in Ni alloy was 8.1 mass% with respect to 100 mass of Ni alloy.

Moreover, as a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Ni-coated copper powder has a dendritic shape in which copper particles are aggregated, It was Ni coat copper powder by which Ni alloy was uniformly coat | covered on the surface of the copper particle. The copper particles constituting the Ni-coated copper powder and coated with a Ni alloy on the surface have a minor axis average diameter of 0.2 μm to 0.5 μm and an average of 0.27 μm. It was an ellipsoid having a diameter of 0.5 μm to 2.0 μm and an average size of 1.2 μm.

The average particle diameter (D50) of dendritic Ni-coated copper powder formed by agglomeration of ellipsoidal copper particles coated with these Ni alloys is 8.3 μm, and the average thickness of the branch portion is 1 .1 μm.

Furthermore, the bulk density of the obtained Ni-coated copper powder was 2.77 g / cm ³ . The BET specific surface area was 1.2 m ² / g.

[Example 22]
<Preparation of dendritic Ni-coated copper powder (reducing agent: hydrazine compound)>
Using 100 g of the dendritic copper powder obtained in Example 21, Ni was coated on the surface of the copper powder by electroless plating to prepare a Ni-coated copper powder. Electroless Ni plating using a hydrazine compound as a reducing agent was performed.

Specifically, nickel acetate was added to a slurry in which 100 g of the dendritic copper powder obtained in Example 21 was dispersed in 500 mL of water to a concentration of 12.4 g / L, and an aqueous solution of 80% by mass of hydrazine monohydrate. 6 g was added dropwise into the bath with slow stirring over 60 minutes. At this time, the bath temperature was controlled to 60 ° C.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which the surface of the dendritic copper powder was coated with Ni was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 7.7% by mass with respect to 100% by mass of the entire Ni-coated copper powder.

Moreover, as a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Ni-coated copper powder has a dendritic shape in which copper particles are aggregated, It was Ni coat copper powder by which Ni was uniformly coat | covered on the surface of the copper particle. Further, the copper particles constituting the Ni-coated copper powder and coated with Ni on the surface have a minor axis average diameter of 0.2 to 0.5 μm and an average of 0.24 μm, and a major axis average diameter. Was an ellipsoid having a size of 0.5 μm to 2.0 μm and an average size of 1.1 μm.

The average particle diameter (D50) of the dendritic Ni-coated copper powder formed by agglomeration of ellipsoidal copper particles coated with Ni is 9.6 μm, and the average thickness of the branch portion is 1.3 μm. Met.

Furthermore, the bulk density of the obtained Ni-coated copper powder was 2.92 g / cm ³ . Further, the BET specific surface area was 1.6 m ² / g.

[Examples 23 to 29]
<Preparation of dendritic Ni-coated copper powder (Ni alloy)>
Using 100 g of the dendritic copper powder obtained in Example 21, the surface of the copper powder was coated with a Ni alloy by electroless plating.

As an electroless Ni plating solution for an alloy, nickel acetate was added to a slurry in which 100 g of the dendritic copper powder obtained in Example 2 was dispersed in 500 mL of water to a concentration of 12.4 g / L, and hydrazine 3. 2 g was added dropwise into the bath over 60 minutes with slow stirring. The bath temperature was controlled to 60 ° C.

At this time, each metal compound was added to a bath containing a copper powder slurry and nickel acetate, and hydrazine was gradually added so that each desired Ni alloy film was formed. As the metal compound, in Example 23, 1.5 g of sodium tungstate was added to form a Ni—W alloy film. In Example 24, 2 g of cobalt sulfate was added to form a Ni—Co alloy film. In Example 25, 4 g each of zinc sulfate heptahydrate and sodium citrate were added to form a Ni—Zn alloy film. In Example 26, 2 g of palladium chloride was added to form a Ni—Pd alloy film. In Example 27, 2 g of potassium tetrachloroplatinate and 1 g of glycine were added to form a Ni—Pt alloy film. In Example 28, 1 g each of sodium molybdate and trisodium citrate was added to form a Ni—Mo alloy coating. In Example 29, 1 g of sodium stannate was added to form a Ni—Sn alloy film.

After completion of the respective reactions, the powder was filtered, washed with water and dried through ethanol. As a result, Ni-coated copper powder in which the surface of the dendritic copper powder was coated with Ni alloy was obtained. The Ni-coated copper powder was recovered and the Ni alloy coating amount was measured. Table 1 shows the results of measuring the content of Ni with respect to 100% by mass of the entire Ni-coated copper powder and the content of elements that become Ni alloys with respect to 100% by mass of the Ni alloy.

In addition, as a result of observing each of the obtained Ni-coated copper powders with a field of view of 5,000 times by SEM, at least 90% by number or more of Ni-coated copper powders are aggregated with copper particles in a dendritic shape. It was a Ni-coated copper powder that had a shape and was uniformly coated with a Ni alloy on the surface of the copper particles. The copper particles constituting the Ni-coated copper powder and coated with Ni on the surface have an average minor axis diameter of 0.2 μm to 0.5 μm and an average major axis diameter of 0.5 μm to 2.0 μm. It was an ellipsoid of the size.

Further, the average particle diameter (D50), bulk density, and BET specific surface area of the dendritic Ni-coated copper powder formed by aggregating ellipsoidal copper particles coated with these Ni alloys were measured. Table 1 summarizes these measurement results.

[Example 30]
<Preparation of dendritic Ni-coated copper powder (hypophosphite + tungsten compound)>
In Example 30, 100 g of the dendritic copper powder produced in Example 20 was used, and the copper powder surface was coated with a Ni alloy by electroless plating.

As the electroless Ni plating solution, a plating solution containing hypophosphite as the same reducing agent as in Example 20 was used, and a metal other than Ni was added to the plating solution to produce a Ni alloy.

In this electroless Ni plating solution, a slurry in which 100 g of the dendritic copper powder prepared in Example 1 was dispersed in 100 mL of water was added and stirred at 25 ° C. for 10 minutes, and then the bath temperature was heated to 90 ° C. Stir for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder coated with a Ni—WP alloy was obtained. When the obtained Ni-coated copper powder was recovered and the content of Ni was measured, it was 12.3% by mass with respect to 100% by mass of the entire Ni-coated copper powder. The content of P contained in the Ni alloy was 7.1% by mass with respect to 100% by mass of the Ni alloy. Moreover, content of W contained in Ni alloy was 5.5 mass% with respect to 100 mass of Ni alloy.

Moreover, as a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% by number or more of the Ni-coated copper powder has a dendritic shape in which copper particles are aggregated, It was Ni coat copper powder by which Ni alloy was uniformly coat | covered on the surface of the copper particle. The copper particles constituting the Ni-coated copper powder and coated with Ni alloy on the surface have a minor axis average diameter of 0.2 μm to 0.5 μm and an average of 0.34 μm. It was an ellipsoid having a diameter of 0.5 μm to 2.0 μm and an average size of 1.6 μm.

[Example 31]
30 g of the dendritic Ni-coated copper powder obtained in Example 20 was mixed with 15 g of a phenol resin (PL-2211 manufactured by Gunei Chemical Co., Ltd.) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Using a kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.0 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited. Table 2 shows these results.

[Example 32]
30 g of dendritic Ni-coated copper powder obtained in Example 21 was mixed with 20 g of a phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Using a kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.2 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited. Table 2 shows these results.

[Example 33]
The dendritic Ni-coated copper powder obtained in Example 20 was dispersed in a resin to obtain an electromagnetic wave shielding material.

That is, 30 g of dendritic Ni-coated copper powder obtained in Example 20 was mixed with 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone, and kneaded at 1200 rpm for 3 minutes using a small kneader. The paste was made by repeating the process once. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried using a Mayer bar on a substrate made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm to form an electromagnetic wave shielding layer having a thickness of 25 μm.

The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Table 2 shows these results.

[Comparative Example 4]
Copper powder was deposited on the cathode plate in the same manner as in Example 20 except that PEG as an additive and chlorine ions were not added to the electrolytic solution. Subsequently, in the same manner as in Example 1, the surface of the obtained copper powder was coated with a Ni alloy to obtain a Ni-coated copper powder.

The Ni content of the Ni-coated copper powder was 18.3% by mass with respect to 100 as the total weight of the Ni-coated copper powder coated with the Ni alloy. Moreover, content of B contained in Ni alloy was 6.0 mass% with respect to 100 mass of Ni alloy.

As a result of observing the shape of the obtained Ni-coated copper powder with a field of view of 10,000 times by SEM, the obtained Ni-coated copper powder had a dendritic shape, but the thickness of the branch portion was 10 μm. It was confirmed that this was a very large dendritic Ni-coated copper powder. Moreover, the average particle diameter (D50) of the Ni-coated copper powder was 22.3 μm.

Next, with respect to 60 g of dendritic Ni-coated copper powder produced by the above-described method, 15 g of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) Were mixed using a small kneader (Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1) and kneaded at 1200 rpm for 3 minutes three times to form a paste. During pasting, the viscosity increased every time kneading was repeated. This is considered to be caused by a part of the copper powder being aggregated, and uniform dispersion was difficult. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing is 6.7 × 10 ⁻⁴ Ω · cm, and the specific resistance value is extremely high and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 5]
The characteristic of the conductive paste by spherical Ni coat copper powder was evaluated, and it compared with the characteristic of the conductive paste produced using the dendritic Ni coat copper powder in an Example. The spherical Ni-coated copper powder used was obtained by pulverizing electrolytic copper powder into a granular form.

That is, an electrolytic copper powder having an average particle size of 30.5 μm (trade name: electrolytic copper powder Cu-300, manufactured by Nexel Japan) was applied to a high-pressure jet airflow swirl vortex jet mill (manufactured by Tokusu Kogakusha Co., Ltd., NJ Nanogrine) Using a Ding mill NJ-30), spherical copper powder was prepared by grinding and pulverizing by performing 8 passes at an air flow rate of 200 liters / minute, a grinding pressure of 10 kg / cm ² and about 400 g / hour. The obtained spherical copper powder was observed by SEM with a field of view of 5,000 times magnification and confirmed to be granular. Moreover, the average particle diameter (D50) of the spherical copper powder was 5.6 μm.

The obtained spherical copper powder was coated with Ni on the surface of the copper powder by electroless plating in the same manner as shown in Example 22. And when spherical Ni coat copper powder after electroless plating was collect | recovered and content of Ni was measured, it was 7.4 mass% with respect to the weight 100 of the said Ni coat copper powder whole.

The obtained spherical Ni-coated copper powder had an average particle size (D50) of 5.8 μm and a bulk density of 3.83 g / cm ³ . Further, the BET specific surface area was 0.16 m ² / g.

Next, 60 g of this spherical Ni-coated copper powder was mixed with 15 g of a phenol resin (PLE 2211, manufactured by Gunei Chemical Co., Ltd.) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade), and a small kneader. Using a non-bubbling kneader NBK-1 (manufactured by Nippon Seiki Seisakusho Co., Ltd.), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing is 8.2 × 10 ⁻⁴ Ω · cm, which is extremely high in specific resistance value and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 6]
The characteristics of the electromagnetic shielding material by the spherical Ni-coated copper powder were evaluated and compared with the characteristics of the electromagnetic shielding material produced using the dendritic Ni-coated copper powder in Example 20. In addition, the spherical Ni coat copper powder produced in the comparative example 5 was used for the used spherical Ni coat copper powder.

Specifically, 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone are mixed with 50 g of spherical Ni-coated copper powder, and the mixture is made into a paste by repeating kneading at 1200 rpm for 3 minutes three times using a small kneader. did. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was applied and dried on a substrate made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm using a Mayer bar to form an electromagnetic wave shielding layer having a thickness of 30 μm.

The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Specifically, the level of Comparative Example 6 that does not use dendritic Ni-coated copper powder is set as “Δ”, and the level worse than the level of Comparative Example 6 is set as “X”. The case where it was better than the level was evaluated as “◯”, and the case where it was superior was evaluated as “◎”. Table 2 shows the results.

≪Example, comparative example≫
(3) Test using Ni-coated copper powder according to the third embodiment [Example 34]
<Preparation of electrolytic copper powder>
An electrolytic cell with a capacity of 100 L is used with a titanium electrode plate having an electrode area of 200 mm × 200 mm as a cathode and a copper electrode plate with an electrode area of 200 mm × 200 mm as an anode, and an electrolytic solution is charged into the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

At this time, as the electrolytic solution, a composition having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L was used. In addition, safranin (manufactured by Kanto Chemical Co., Inc.) as an additive is added to the electrolytic solution so that the concentration in the electrolytic solution is 85 mg / L, and a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) is further added to the electrolytic solution. It added so that it might become 55 mg / L as a chloride ion (chlorine ion) density | concentration in it.

Then, the current density of the cathode is 18 A / dm ² under the condition that the temperature is maintained at 25 ° C. while circulating the electrolytic solution whose concentration is adjusted as described above at a flow rate of 15 L / min using a metering pump. Was energized to deposit copper powder on the cathode plate.

As a result of observing the shape of the copper powder thus obtained in the field of view with a magnification of 1,000 times by the method using the scanning electron microscope (SEM) described above, the deposited copper powder was a main chain that grew linearly and the main trunk. It was a dendritic copper powder having a two-dimensional or three-dimensional dendritic shape having a plurality of branches branched linearly from and branches further branched from the branches.

<Production of dendritic Ni-coated copper powder (reducing agent: hypophosphite)>
Next, using the dendritic copper powder produced by the above-described method, Ni was coated on the surface of the copper powder by electroless Ni plating to produce Ni-coated copper powder. In addition, an electroless Ni plating solution whose reducing agent is hypophosphite was used.

In this electroless Ni plating solution, a slurry in which 100 g of the dendritic copper powder prepared by the above method is dispersed in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 90 ° C. to 60 ° C. Stir for minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which the surface of the dendritic copper powder was coated with Ni alloy containing phosphorus (P) was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 13.5% by mass with respect to 100% by mass of the entire Ni-coated copper powder. Moreover, content of P contained in Ni alloy was 8.2 mass% with respect to 100 mass of Ni alloy.

Further, as a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Ni-coated copper powder is uniformly on the surface of the dendritic copper powder before Ni coating. A Ni-coated copper powder coated with a Ni alloy and having a two-dimensional or three-dimensional dendritic shape, the main trunk growing linearly, a plurality of branches linearly branched from the main trunk, and the branches It was a dendritic Ni-coated copper powder having a dendritic shape having branches further branched from.

Further, the copper particles constituting the main trunk and branches of the dendritic Ni-coated copper powder had a flat plate shape with an average cross-sectional thickness of 0.42 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Ni-coated copper powder was 25.1 μm.

Furthermore, the bulk density of the obtained dendritic Ni-coated copper powder was 0.53 g / cm ³ . Moreover, the BET specific surface area was 0.82 m < ² > / g.

<Conductive paste>
Next, the obtained dendritic Ni-coated copper powder was made into a paste to produce a conductive paste.

That is, 20 g of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Ni-coated copper powder, Using a small kneader (Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.8 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 35]
<Preparation of electrolytic copper powder>
As the electrolytic solution, a composition having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L is used, and safranin is added to the electrolytic solution so that the concentration in the electrolytic solution is 150 mg / L. Further, an electrolytic copper powder (dendritic copper powder) was deposited on the cathode plate under the same conditions as in Example 34 except that a hydrochloric acid solution was added so that the chloride ion concentration in the electrolytic solution was 100 mg / L. It was.

<Preparation of dendritic Ni-coated copper powder (reducing agent: borohydride)>
Next, 100 g of the obtained dendritic copper powder was used to perform Ni coating on the surface of the copper powder by electroless Ni plating to prepare a Ni-coated copper powder. In addition, the electroless Ni plating solution whose reducing agent is a borohydride compound was used.

In this electroless Ni plating solution, a slurry in which 100 g of the dendritic copper powder prepared by the above-described method is dispersed in 100 mL of water is placed in the Ni plating solution and stirred at 25 ° C. for 10 minutes, and then the bath temperature is set to 60 ° C. And stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which the surface of the dendritic copper powder was coated with Ni alloy was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 18.8% by mass with respect to 100% by mass of the entire Ni-coated copper powder. Further, the content of boron (B) contained in the Ni alloy was 6.4% by mass with respect to 100% by mass of the Ni alloy.

Further, as a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Ni-coated copper powder is uniformly on the surface of the dendritic copper powder before Ni coating. Ni-coated copper powder having a Ni-coated two-dimensional or three-dimensional dendritic shape, the main trunk growing linearly, a plurality of branches linearly branching from the main trunk, and further from the branches Furthermore, it was a dendritic Ni-coated copper powder having a dendritic shape having branched branches.

Further, the copper particles constituting the main trunk and branches of the dendritic Ni-coated copper powder had a flat plate shape with an average cross-sectional thickness of 0.23 μm. Moreover, the average particle diameter (D50) of this dendritic Ni coat copper powder was 9.4 micrometers.

Furthermore, the bulk density of the obtained dendritic Ni-coated copper powder copper powder was 0.53 g / cm ³ . Further, the BET specific surface area was 1.94 m ² / g.

That is, 20 g of a phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of the prepared dendritic Ni-coated copper powder to produce a small size. Using a kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.4 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 36]
<Production of dendritic Ni-coated copper powder (reducing agent: hydrazine compound)>
Using 100 g of the dendritic copper powder obtained in Example 35, Ni was coated on the surface of the copper powder by electroless Ni plating to prepare a Ni-coated copper powder. Electroless Ni plating using a hydrazine compound as a reducing agent was performed.

Specifically, nickel acetate was added to a slurry in which 100 g of the dendritic copper powder obtained in Example 35 was dispersed in 500 mL of water to a concentration of 12.4 g / L, and an 80% by mass aqueous solution of hydrazine monohydrate. 6 g was added dropwise into the bath with slow stirring over 60 minutes. At this time, the bath temperature was controlled to 60 ° C.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which the surface of the dendritic copper powder was coated with Ni was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 7.6% by mass with respect to 100% by mass of the entire Ni-coated copper powder.

Further, as a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Ni-coated copper powder is uniformly on the surface of the dendritic copper powder before Ni coating. A dendritic Ni-coated copper powder coated with Ni and having a two-dimensional or three-dimensional dendritic shape, the main trunk growing linearly, and a plurality of branches linearly branched from the main trunk, and The dendritic Ni-coated copper powder had a dendritic shape having branches further branched from the branches.

Further, the copper particles constituting the main trunk and branches of the dendritic Ni-coated copper powder had a flat plate shape with an average cross-sectional thickness of 0.23 μm. Moreover, the average particle diameter (D50) of this dendritic Ni coat copper powder was 9.6 micrometers.

Moreover, the bulk density of the obtained dendritic Ni-coated copper powder was 0.52 g / cm ³ . Moreover, the BET specific surface area was 1.98 m < ² > / g.

The specific resistance value of the film obtained by curing was 6.2 × 10 ⁻⁵ Ω · cm, and it was found that the film exhibited excellent conductivity.

[Examples 37 to 43]
<Manufacture of dendritic Ni-coated copper powder (Ni alloy)>
Using 100 g of the dendritic copper powder obtained in Example 35, the surface of the copper powder was coated with a Ni alloy by electroless plating.

As an electroless Ni plating solution for alloys, nickel acetate was added to a slurry in which 100 g of the dendritic copper powder obtained in Example 35 was dispersed in 500 mL of water to a concentration of 12.4 g / L, and hydrazine 3. 2 g was added dropwise into the bath over 60 minutes with slow stirring. The bath temperature was controlled to 60 ° C.

At this time, each metal compound was added to a bath containing a copper powder slurry and nickel acetate, and hydrazine was gradually added so that each desired Ni alloy film was formed. In Example 37, as the metal compound, 1.5 g of sodium tungstate was added to form a Ni—W alloy film. In Example 38, 2 g of cobalt sulfate was added to form a Ni—Co alloy film. In Example 39, 4 g each of zinc sulfate heptahydrate and sodium citrate were added to form a Ni—Zn alloy coating. In Example 40, 2 g of palladium chloride was added to form a Ni—Pd alloy film. In Example 41, 2 g of potassium tetrachloroplatinate and 1 g of glycine were added to form a Ni—Pt alloy film. In Example 42, 1 g of each of sodium molybdate and trisodium citrate was added to form a Ni—Mo alloy film. In Example 43, 1 g of sodium stannate was added to form a Ni—Sn alloy film.

After the reaction was completed, the powder was filtered, washed with water and dried through ethanol. As a result, Ni-coated copper powder in which the surface of the dendritic copper powder was coated with Ni was obtained. The Ni-coated copper powder was recovered and the Ni alloy coating amount was measured. Table 3 shows the results of measuring the content of Ni with respect to 100% by mass of the entire Ni-coated copper powder and the content of elements that become Ni alloys with respect to 100% by mass of the Ni alloy.

In addition, as a result of observing each of the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Ni-coated copper powder is dendritic copper powder before Ni coating. A Ni-coated copper powder having a two-dimensional or three-dimensional dendritic shape in which Ni is uniformly coated on the surface of the main body, and a plurality of linearly branched main trunks and a plurality of linear branches from the main trunk The dendritic Ni-coated copper powder had a dendritic shape having a branch and a branch further branched from the branch.

Further, the average particle diameter (D50), bulk density, and BET specific surface area of these dendritic Ni-coated copper powders were measured. Table 3 summarizes these measurement results.

<Conductive paste>
Next, each obtained dendritic Ni-coated copper powder was made into a paste to produce a conductive paste.

Table 3 shows the result of measuring the specific resistance value of the coating obtained by curing. As shown in Table 3, it was found that all the coating films showed excellent conductivity.

[Example 44]
<Manufacture of dendritic Ni-coated copper powder (hypophosphite + tungsten compound)>
In Example 44, 100 g of the dendritic copper powder prepared in Example 34 was used, and the copper powder surface was coated with a Ni alloy by electroless plating.

As the electroless Ni plating solution, a plating solution containing hypophosphite as the same reducing agent as in Example 1 was used, and a metal other than Ni was added to the plating solution to produce a Ni alloy.

Specifically, as an electroless Ni plating solution, a plating solution in which nickel sulfate 20 g / L, sodium hypophosphite 25 g / L, sodium acetate 10 g / L, and sodium citrate 10 g / L are added at each concentration, 500 g of a plating solution prepared by adding 1.5 g of sodium tungstate and adjusting the pH to 5.0 by adding sodium hydroxide was prepared.

In this electroless Ni plating solution, a slurry obtained by dispersing 100 g of the dendritic copper powder prepared in Example 34 in 100 mL of water was stirred for 10 minutes at 25 ° C., and then the bath temperature was heated to 90 ° C. Stir for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder coated with a Ni—WP alloy was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 12.4% by mass with respect to 100% by mass of the entire Ni-coated copper powder. The content of P contained in the Ni alloy was 7.4% by mass with respect to 100% by mass of the Ni alloy. Moreover, content of W contained in Ni alloy was 5.4 mass% with respect to 100 mass of Ni alloy.

As a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 by SEM, at least 90% Ni-coated copper powder is uniformly Ni alloy on the surface of the dendritic copper powder before Ni coating. A two-dimensional or three-dimensional dendritic Ni-coated copper powder coated with a main body that grows linearly, a plurality of branches that branch linearly from the main trunk, and the branches It was a dendritic Ni-coated copper powder having a dendritic shape having branches further branched from.

Further, the copper particles constituting the main trunk and branches of the dendritic Ni-coated copper powder had a flat plate shape with an average cross-sectional thickness of 0.43 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Ni-coated copper powder was 25.6 μm.

Moreover, the bulk density of the obtained dendritic Ni-coated copper powder was 1.87 g / cm ³ . Moreover, the BET specific surface area was 0.88 m < ² > / g.

That is, 10 g of the prepared dendritic Ni-coated copper powder and 30 g of spherical Ni-coated copper powder having a spherical shape, 20 g of phenol resin (PL-2211 manufactured by Gunei Chemical Co., Ltd.) and butyl cellosolve (Kanto) 10g made by Kagaku Co., Ltd., deer special grade), and paste using a small kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1) by repeating kneading at 1200 rpm for 3 minutes three times. did. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.8 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 45]
<Preparation of electrolytic copper powder>
As the electrolytic solution, a composition having a copper ion concentration of 5 g / L and a sulfuric acid concentration of 150 g / L was used, and safranin was added to the electrolytic solution so that the concentration in the electrolytic solution was 100 mg / L. Further, an electrolytic copper powder (dendritic copper powder) was deposited on the cathode plate under the same conditions as in Example 34 except that a hydrochloric acid solution was added so that the chloride ion concentration in the electrolytic solution was 10 mg / L. It was.

<Production of dendritic Ni-coated copper powder (reducing agent: hypophosphite)>
Next, using the dendritic copper powder produced by the method described above, a Ni—P alloy film was formed on the surface of the dendritic copper powder under the same conditions as in Example 34.

After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which Ni alloy containing P was coated on the surface of dendritic copper powder was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 13.1% by mass with respect to 100% by mass of the entire Ni-coated copper powder. The content of P contained in the Ni alloy was 8.6% by mass with respect to 100% by mass of the Ni alloy.

Moreover, as a result of observing the obtained dendritic Ni-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Ni-coated copper powder was found on the surface of the dendritic copper powder before Ni coating. A Ni-coated copper powder having a two-dimensional or three-dimensional dendritic shape uniformly coated with Ni, and a main trunk that grows linearly, and a plurality of branches that linearly branch from the main trunk, and further The dendritic Ni-coated copper powder had a dendritic shape having branches further branched from the branches.

Further, the copper particles constituting the main trunk and branches of the dendritic Ni-coated copper powder had a flat plate shape with an average cross-sectional thickness of 3.7 μm, and the copper particles were formed into a dendritic shape. . The average particle diameter (D50) of the dendritic Ni-coated copper powder was 61.8 μm.

Moreover, the bulk density of the obtained dendritic Ni-coated copper powder was 3.2 g / cm ³ . The BET specific surface area was 1.02 m ² / g.

The specific resistance value of the film obtained by curing was 9.2 × 10 ⁻⁵ Ω · cm, and it was found that excellent electrical conductivity was exhibited.

[Example 46]
The dendritic Ni-coated copper powder produced in Example 34 was dispersed in a resin to obtain an electromagnetic wave shielding material. The preparation of the dendritic copper powder for producing the dendritic Ni-coated copper powder, and the conditions until the dendritic copper powder is coated with a Ni alloy to produce the dendritic Ni-coated copper powder are described in the Examples. 1, the Ni content of the dendritic Ni-coated copper powder is 13.5% by mass with respect to 100% by mass of the entire dendritic Ni-coated copper powder, and the content of P contained in the Ni alloy The amount of dendritic Ni-coated copper powder was 8.2% by mass with respect to 100% by mass of the Ni alloy.

A 40 g of this dendritic Ni-coated copper powder was mixed with 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone, and paste was made by repeating kneading at 1200 rpm for 3 minutes three times using a small kneader. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried using a Mayer bar on a substrate made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm to form an electromagnetic wave shielding layer having a thickness of 25 μm.

The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Table 3 shows these results.

[Example 47]
The dendritic Ni-coated copper powder produced in Example 38 was dispersed in a resin to obtain an electromagnetic wave shielding material. The preparation of the dendritic copper powder for producing the dendritic Ni-coated copper powder, and the conditions until the dendritic copper powder is coated with a Ni alloy to produce the dendritic Ni-coated copper powder are described in the Examples. 38. The Ni content of the dendritic Ni-coated copper powder is 12.4% by mass with respect to 100% by mass of the entire dendritic Ni-coated copper powder, and the content of P contained in the Ni alloy The dendritic Ni-coated copper powder is 7.4% by mass with respect to 100% by mass of the Ni alloy, and the W content in the Ni alloy is 5.4% by mass with respect to 100% by mass of the Ni alloy. used.

[Example 48]
The dendritic Ni-coated copper powder produced in Example 45 was dispersed in a resin to obtain an electromagnetic wave shielding material. The preparation of the dendritic copper powder for producing the dendritic Ni-coated copper powder, and the conditions until the dendritic copper powder is coated with a Ni alloy to produce the dendritic Ni-coated copper powder are described in the Examples. 45. The Ni content of the dendritic Ni-coated copper powder is 13.1% by mass with respect to 100% by mass of the entire dendritic Ni-coated copper powder, and the content of P contained in the Ni alloy The amount of dendritic Ni-coated copper powder was 8.6% by mass with respect to 100% by mass of the Ni alloy.

[Example 49]
Spherical Ni-coated copper powder was mixed with the dendritic Ni-coated copper powder prepared in Example 34, and these were dispersed in a resin to obtain an electromagnetic wave shielding material.

The preparation of the dendritic copper powder for producing the dendritic Ni-coated copper powder, and the conditions until the dendritic copper powder is coated with a Ni alloy to produce the dendritic Ni-coated copper powder are described in the Examples. 34, and the Ni content of the dendritic Ni-coated copper powder is 13.5% by mass with respect to 100% by mass of the entire dendritic Ni-coated copper powder, and the content of P contained in the Ni alloy The amount of dendritic Ni-coated copper powder was 8.2% by mass with respect to 100% by mass of the Ni alloy.

In addition, the spherical Ni-coated copper powder uses a granular atomized copper powder (manufactured by Mekin Metal Powders Co., Ltd.) having an average particle size of 7.9 μm, and Ni is coated in the same manner as in Example 34 to form a spherical Ni-coated copper powder. Was made. The Ni content of the spherical Ni-coated copper powder is 12.8% by mass with respect to 100% by mass of the entire Ni-coated copper powder, and the content of P contained in the Ni alloy is 100% by mass of the Ni alloy. Spherical Ni-coated copper powder having a mass of 8.8% by mass was used.

Specifically, 15 g of dendritic Ni-coated copper powder and 25 g of spherical Ni-coated copper powder are mixed with 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone, and mixed at 1200 rpm for 3 minutes using a small kneader. Paste was made by repeating smelting three times. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried using a Mayer bar on a substrate made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm to form an electromagnetic wave shielding layer having a thickness of 25 μm.

[Comparative Example 7]
The electrolytic copper powder was deposited on the cathode plate in the same manner as in Example 34, except that the conditions were such that safranin as an additive and chlorine ions were not added to the electrolytic solution. Then, the surface of the obtained electrolytic copper powder was coated with a Ni alloy in the same manner as in Example 34 to obtain a Ni-coated copper powder. When the Ni content of the Ni-coated copper powder was measured, it was 12.6% by mass relative to 100% by mass of the entire Ni-coated copper powder. Moreover, content of P contained in Ni alloy was 7.9 mass% with respect to 100 mass of Ni alloy.

FIG. 23 shows the result of observing the shape of the obtained Ni-coated copper powder with a SEM field of view at a magnification of 1,000 times. As shown in the photograph of FIG. 23, the obtained Ni-coated copper powder had a dendritic shape but was formed by aggregation of particulate copper. Moreover, it was in the state by which the surface of the copper powder was coat | covered with Ni, and the average particle diameter (D50) of Ni coat copper powder was 18.6 micrometers.

Next, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of Ni-coated copper powder produced by the above-described method. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the viscosity increased every time kneading was repeated. This is considered to be caused by a part of the copper powder being aggregated, and uniform dispersion was difficult. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

[Comparative Example 8]
The characteristic of the conductive paste by Ni coat copper powder which coat | covered Ni with the conventional flat copper powder was evaluated, and it compared with the characteristic of the conductive paste produced using the dendritic Ni coat copper powder in an Example.

The obtained flat copper powder was coated with Ni in the same manner as in Example 34. The content of Ni in the produced tabular Ni-coated copper powder was 13.8% by mass with respect to 100% by mass of the tabular Ni-coated copper powder. The content of P contained in the Ni alloy was 8.6% by mass with respect to 100% by mass of the Ni alloy.

The plate-like Ni-coated copper powder thus produced was measured with a laser diffraction / scattering particle size distribution measuring instrument. As a result, the average particle size (D50) was 21.8 μm, and the cross-section was observed by SEM. The average thickness was 0.4 μm.

The specific resistance value of the film obtained by curing is 2.6 × 10 ⁻⁴ Ω · cm, which is extremely high in specific resistance value and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 9]
Similar to the one used in Comparative Example 8, a Ni-coated copper powder in which Ni was coated on a flat copper powder prepared by mechanically flattening a granular electrolytic copper powder was prepared. And the characteristic of the electromagnetic wave shield by the Ni coat copper powder was evaluated, and compared with the characteristic of the electromagnetic wave shield produced using the dendritic Ni coat copper powder in an Example, the dendritic shape effect was investigated. In addition, content of Ni of the used flat Ni coat copper powder was 13.8 mass% with respect to 100 mass of the flat Ni coat copper powder. The content of P contained in the Ni alloy was 8.6% by mass with respect to 100% by mass of the Ni alloy.

The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Specifically, the level of Comparative Example 9 in which no dendritic Ni-coated copper powder is used is “△”, and the level worse than that of Comparative Example 9 is “×”. The case where it was better than the level was evaluated as “◯”, and the case where it was superior was evaluated as “◎”. Table 3 shows the results.

≪Example, comparative example≫
(4) Test using Ni-coated copper powder according to the fourth embodiment [Example 50]
<Preparation of flat copper particle agglomerated powder>
An electrolytic cell with a capacity of 100 L is charged with an electrolytic solution in the electrolytic cell using a titanium electrode plate with an electrode area of 200 mm × 200 mm as a cathode and a copper plate with an electrode area of 200 mm × 200 mm as an anode. Then, a direct current was passed through this to deposit copper powder on the cathode plate.

At this time, an electrolytic solution having a composition with a copper ion concentration of 10 g / L and a sulfuric acid concentration of 100 g / L was used. In addition, Janus Green B (manufactured by Wako Pure Chemical Industries, Ltd.) as an additive was added to the electrolyte so as to have a concentration of 120 mg / L in the electrolyte, and polyethylene glycol having a molecular weight of 2,000 (Wako Pure Chemical Industries, Ltd.) was added. Yakuhin Kogyo Co., Ltd.) was added so that the concentration in the electrolyte was 850 mg / L. Furthermore, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the chloride ion (chlorine ion) concentration in the electrolyte solution was 50 mg / L.

Then, while circulating the electrolyte adjusted to the concentration as described above at a flow rate of 10 L / min using a pump, the temperature is maintained at 30 ° C. and the current density of the cathode is 25 A / dm ^2. Then, copper powder was deposited on the cathode plate.

As a result of observing the shape of the obtained electrolytic copper powder in a field of view with a magnification of 1,000 times by the method using the scanning electron microscope (SEM) described above, the deposited copper powder has a shape in which flat copper particles are aggregated. It was the presented copper powder (flat copper particle aggregated powder).

The flat copper particles have an average cross-sectional thickness of 0.3 μm, and an average major axis diameter (equivalent to the diameter indicated by “d” in the schematic diagram of FIG. 1) is 2.7 μm. there were. And the magnitude | size of the tabular copper particle aggregated powder which the aggregate of the tabular copper particle became the aggregate was the average particle diameter (D50) measured with the laser diffraction and the scattering method particle size distribution measuring device 7.9 micrometer. Met.

<Production of flat Ni-coated copper particle aggregated powder (reducing agent: hypophosphite)>
Next, Ni was coated on the surface of the copper powder by electroless Ni plating using the tabular copper particle aggregated powder prepared by the above-described method to prepare a Ni-coated copper powder. An electroless Ni plating solution that is a reducing agent hypophosphite was used.

In this electroless Ni plating solution, a slurry obtained by dispersing 100 g of tabular copper particle agglomerated powder prepared in the above-described method in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 90 ° C. And stirred for 60 minutes.

After completion of the reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which Ni alloy containing phosphorus (P) was coated on the surface of the tabular copper particle aggregated powder was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 13.4% by mass with respect to 100% by mass of the entire Ni-coated copper powder. The content of P contained in the Ni alloy was 7.8% by mass with respect to 100% by mass of the Ni alloy.

In addition, as a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, the Ni-coated copper powder was uniformly coated with the Ni alloy on the surface of the copper powder before being coated with the Ni alloy. A flat Ni-coated copper particle aggregated powder having a shape of agglomerated powder in which a plurality of Ni-coated copper particles having a flat plate shape are aggregated to form an aggregate.

Moreover, since the Ni-coated copper powder obtained had a thin Ni alloy coating thickness, the shape was the same as the flat copper particle aggregated powder before coating the Ni alloy. Specifically, the plate-like Ni-coated copper particles constituting the Ni-coated copper powder have a plate-like shape with a cross-sectional thickness (cross-sectional average thickness) of 0.3 μm, and the size is the average major axis diameter (see FIG. (Diameter indicated by “d” in the schematic diagram of FIG. 1) was 2.7 μm. The size of the aggregated copper powder formed by aggregating a plurality of the flat plate-like Ni-coated copper particles into an aggregate is 7.9 μm in average particle diameter (D50). The same value as the flat copper particle aggregated powder before coating was shown.

Furthermore, the tap density of the obtained Ni-coated copper powder was 2.9 g / cm ³ . The BET specific surface area was 2.5 m ² / g.

[Example 51]
<Preparation of flat copper particle agglomerated powder>
An electrolytic solution having a copper ion concentration of 8 g / L and a sulfuric acid concentration of 110 g / L is used, and Janus Green B as an additive is added to the electrolytic solution to a concentration of 160 mg / L in the electrolytic solution. Further, polyethylene glycol having a molecular weight of 2,000 (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the concentration in the electrolytic solution was 800 mg / L. Further, a hydrochloric acid solution was added so that the chloride ion concentration in the electrolytic solution was 125 mg / L.

Then, while circulating the electrolyte adjusted to the concentration as described above at a flow rate of 20 L / min using a pump, the temperature is maintained at 35 ° C. and the current density of the cathode is 30 A / dm ^2. Except for these, copper powder was deposited on the cathode plate in the same manner as in Example 50.

As a result of observing the shape of the obtained electrolytic copper powder by the SEM method described above, the deposited copper powder was a copper powder (plate copper particle aggregated powder) having a shape in which flat copper particles were aggregated. It was. The tabular copper particles had an average cross-sectional thickness of 0.2 μm and an average major axis diameter of 3.8 μm. The size of the agglomerated copper powder in which a plurality of tabular copper particles aggregated to form an aggregate was 12.9 μm in terms of the average particle diameter (D50) measured with a laser diffraction / scattering particle size distribution analyzer. .

<Production of flat Ni-coated copper particle agglomerated powder (reducing agent: borohydride)>
Next, using the obtained tabular copper particle aggregate powder 100g, Ni coating was performed on the surface of the copper powder by electroless Ni plating to prepare a Ni-coated copper powder. In addition, the electroless Ni plating solution whose reducing agent is a borohydride compound was used.

Specifically, as the electroless Ni plating solution, nickel sulfate 30 g / L, sodium succinate 50 g / L, boric acid 30 g / L, ammonium chloride 30 g / L, dimethylamine borane 4 g / L are added at each concentration. Further, 500 mL of a plating solution adjusted to pH 6.0 by adding sodium hydroxide was prepared.

Into this electroless Ni plating solution, a slurry in which 100 g of the tabular copper particle aggregate powder prepared by the above-described method is dispersed in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 60 ° C. And stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which the surface of the tabular copper particle aggregated powder was coated with Ni alloy was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 18.5% by mass with respect to 100% by mass of the entire Ni-coated copper powder. The content of B contained in the Ni alloy was 6.5% by mass with respect to 100% by mass of the Ni alloy.

In addition, as a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, the Ni-coated copper powder was uniformly coated with the Ni alloy on the surface of the copper powder before being coated with the Ni alloy. The Ni-coated copper particles were in the form of agglomerated powder formed by aggregating a plurality of Ni-coated copper particles in which the shape of the Ni-coated copper particles was flat.

Further, since the Ni-coated copper powder produced had a thin Ni alloy coating thickness, the shape was the same as the flat copper particle aggregated powder before coating the Ni alloy. Specifically, the plate-like Ni-coated copper particles had a plate shape with a cross-sectional thickness (average cross-sectional thickness) of 0.2 μm, and the size thereof had an average major axis diameter of 3.8 μm. The size of the aggregated copper powder formed by aggregating a plurality of the flat Ni-coated copper particles into an aggregate is 12.9 μm in terms of the average particle diameter (D50). The same value as the flat copper particle aggregated powder before coating was shown.

Furthermore, the tap density of the obtained Ni-coated copper powder was 3.8 g / cm ³ . The BET specific surface area was 1.8 m ² / g.

[Example 52]
<Preparation of flat copper particle agglomerated powder>
In an electrolytic cell having a capacity of 100 L, an electrode plate made of titanium having an electrode area of 200 mm × 200 mm is used as a cathode, and a copper electrode plate having an electrode area of 200 mm × 200 mm is used as an anode, and an electrolytic solution is loaded in the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

At this time, as the electrolytic solution, a composition having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L was used. In addition, Janus Green B (manufactured by Wako Pure Chemical Industries, Ltd.) as an additive was added to the electrolyte so as to have a concentration of 130 mg / L in the electrolyte, and polyethylene glycol having a molecular weight of 2,000 (Wako Pure Chemical Industries, Ltd.). Yakuhin Kogyo Co., Ltd.) was added as a concentration in the electrolyte solution to 900 mg / L. Furthermore, a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the chlorine ion concentration in the electrolytic solution was 50 mg / L.

As a result of observing the shape of the obtained electrolytic copper powder in a field of view with a magnification of 5,000 times by the method using the scanning electron microscope (SEM) described above, the deposited copper powder has a shape in which flat copper particles are aggregated. It was the exhibited copper powder (plate-like copper particle aggregated powder).

The tabular copper particles have a cross-sectional thickness (average cross-sectional thickness) of 0.1 μm and an average major axis diameter (equivalent to the diameter indicated by “d” in the schematic diagram of FIG. 15). Was 2.9 μm. The size of the agglomerated copper powder in which a plurality of the tabular copper particles were aggregated to form an aggregate was 7.1 μm as an average particle diameter (D50) measured with a laser diffraction / scattering particle size distribution analyzer. .

<Production of flat Ni-coated copper particle aggregated powder (reducing agent: hydrazine compound)>
Next, using the obtained tabular copper particle aggregate powder 100g, Ni coating was performed on the surface of the copper powder by electroless Ni plating to prepare a Ni-coated copper powder. Electroless Ni plating using a hydrazine compound as a reducing agent was performed.

Specifically, nickel acetate was added to a slurry in which 100 g of the tabular copper particle aggregated powder obtained in Example 51 was dispersed in 500 mL of water to a concentration of 12.4 g / L, and hydrazine monohydrate 80 mass. 6 g of a% aqueous solution was added dropwise to the bath over 60 minutes with slow stirring. At this time, the bath temperature was controlled to 60 ° C.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder in which Ni was coated on the surface of the tabular copper particle aggregated powder was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 7.5% by mass with respect to 100% by mass of the entire Ni-coated copper powder.

In addition, as a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, the Ni-coated copper powder was uniformly coated with the Ni alloy on the surface of the copper powder before being coated with the Ni alloy. The shape of the agglomerated powder was formed by aggregating a plurality of Ni-coated copper particles having a flat plate shape.

Moreover, since the Ni-coated copper powder obtained had a thin Ni alloy coating thickness, the shape was the same as the flat copper particle aggregated powder before coating the Ni alloy. Specifically, the plate-like Ni-coated copper particles constituting the Ni-coated copper powder have a plate-like shape with a cross-sectional thickness (cross-sectional average thickness) of 0.1 μm, and the size is an average major axis diameter (see FIG. 15) (diameter indicated by “d” in the schematic diagram) was 2.9 μm. The size of the aggregated copper powder formed by aggregating a plurality of the flat plate-like Ni-coated copper particles into an aggregate is 7.1 μm in terms of the average particle diameter (D50). The same value as the flat copper particle aggregated powder before coating was shown.

Furthermore, the tap density of the obtained Ni-coated copper powder was 2.8 g / cm ³ . The BET specific surface area was 2.4 m ² / g.

[Examples 53 to 59]
<Manufacture of flat Ni-coated copper particle agglomerated powder (Ni alloy)>
Using 100 g of the tabular copper particle aggregate powder obtained in Example 52, the surface of the copper powder was coated with a Ni alloy by electroless plating.

As an electroless Ni plating solution for an alloy, nickel acetate was added to a slurry in which 100 g of the tabular copper particle aggregate powder obtained in Example 52 was dispersed in 500 mL of water to a concentration of 12.4 g / L, and hydrazine was added. 3.2 g was added dropwise into the bath over 60 minutes with slow stirring. The bath temperature was controlled to 60 ° C.

At this time, each metal compound was added to a bath containing a copper powder slurry and nickel acetate, and hydrazine was gradually added so that each desired Ni alloy film was formed. As the metal compound, in Example 53, 1.5 g of sodium tungstate was added to form a Ni—W alloy film. In Example 54, 2 g of cobalt sulfate was added to form a Ni—Co alloy film. In Example 55, 4 g each of zinc sulfate heptahydrate and sodium citrate were added to form a Ni—Zn alloy film. In Example 56, 2 g of palladium chloride was added to form a Ni—Pd alloy film. In Example 57, 2 g of potassium tetrachloroplatinate and 1 g of glycine were added to form a Ni—Pt alloy film. In Example 58, 1 g each of sodium molybdate and trisodium citrate was added to form a Ni—Mo alloy coating. In Example 59, 1 g of sodium stannate was added to form a Ni—Sn alloy film.

After each reaction, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder with Ni coated on the surface of the tabular copper particles was obtained. The Ni-coated copper powder was recovered and the Ni alloy coating amount was measured. Table 4 shows the results of measuring the content of Ni with respect to 100% by mass of the entire Ni-coated copper powder and the content of elements that become Ni alloys with respect to 100% by mass of the Ni alloy.

In addition, as a result of observing the obtained Ni-coated copper powder with a field of view at a magnification of 5,000 times by SEM, the Ni coating in which the Ni alloy was uniformly coated on the surface of the copper powder before coating the Ni alloy. It was a copper powder and was a flat Ni-coated copper particle aggregated powder in the form of an aggregated powder in which a plurality of Ni-coated copper particles having a flat plate shape were aggregated to form an aggregate.

Moreover, about these Ni coat copper powder, the cross-sectional average thickness of a flat copper particle, the average major axis diameter (diameter shown by "d" in the schematic diagram of FIG. 15), the average of flat Ni coat copper particle aggregated powder The particle diameter (D50), tap density, and BET specific surface area were measured. Table 4 summarizes these measurement results.

[Example 60]
<Production of flat Ni-coated copper particle aggregated powder (hypophosphite + tungsten compound)>
In Example 60, Ni alloy coating was performed on the surface of the copper powder by electroless plating using 100 g of the tabular copper particle aggregate powder prepared in Example 1.

In this electroless Ni plating solution, a slurry obtained by dispersing 100 g of the tabular copper particle aggregate powder prepared in Example 50 in 100 mL of water was stirred for 10 minutes at 25 ° C., and then the bath temperature was heated to 90 ° C. And stirred for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder coated with a Ni—WP alloy was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 12.5% by mass with respect to 100% by mass of the entire Ni-coated copper powder. Moreover, content of P contained in Ni alloy was 7.3 mass% with respect to 100 mass of Ni alloy. The content of W contained in the Ni alloy was 5.2% by mass with respect to 100% by mass of the Ni alloy.

Moreover, since the Ni-coated copper powder obtained had a thin Ni alloy coating thickness, the shape was the same as the flat copper particle aggregated powder before coating the Ni alloy. Specifically, the plate-like Ni-coated copper particles constituting the Ni-coated copper powder have a plate-like shape with a cross-sectional thickness (cross-sectional average thickness) of 0.3 μm, and the size is the average major axis diameter (see FIG. 15) (diameter indicated by “d” in the schematic diagram) was 2.7 μm. The size of the aggregated copper powder formed by aggregating a plurality of the flat Ni-coated copper particles into an aggregate is 7.2 μm in terms of the average particle diameter (D50). The same value as the flat copper particle aggregated powder before coating was shown.

[Example 61]
15 g of a phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 30 g of the tabular Ni-coated copper particle aggregated powder obtained in Example 50. Using a small kneader (manufactured by Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.3 × 10 ⁻⁵ Ω · cm, and it was found that the film exhibited excellent conductivity. Table 4 shows these results.

[Example 62]
20 g of a phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Kagaku Co., Ltd., deer special grade) are mixed with 30 g of the tabular Ni-coated copper particle aggregated powder obtained in Example 51. Using a small kneader (manufactured by Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), the mixture was kneaded at 1200 rpm for 3 minutes three times to make a paste. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 8.9 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited. Table 4 shows these results.

[Example 63]
The tabular Ni-coated copper particle aggregate powder produced in Example 50 was dispersed in a resin to obtain an electromagnetic wave shielding material.

That is, 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone are mixed with 30 g of the obtained tabular Ni-coated copper particle agglomerated powder, and kneading at 1200 rpm for 3 minutes is repeated three times using a small kneader. To make a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried using a Mayer bar on a substrate made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm to form an electromagnetic wave shielding layer having a thickness of 25 μm.

The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Table 4 shows these results.

[Comparative Example 10]
<Preparation of electrolytic copper powder>
Copper powder was deposited on the cathode plate under the same conditions as in Example 50 except that Janus Green B as an additive, polyethylene glycol, and chloride ions were not added to the electrolytic solution.

As a result of observing the shape of the obtained electrolytic copper powder in the field of view of 5,000 times magnification by the method by SEM described above, the obtained copper powder is a copper powder having a dendritic shape, and in the examples It was not a shape in which flat pieces were aggregated like the obtained copper powder.

<Production of Ni-coated copper powder (reducing agent: hypophosphite)>
Next, Ni coat copper powder was produced using the obtained copper powder.

In this electroless Ni plating solution, a slurry in which 100 g of the copper powder prepared by the above-described method is dispersed in 100 mL of water is stirred and stirred at 25 ° C. for 10 minutes, and then the bath temperature is heated to 90 ° C. and stirred for 60 minutes. did.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, a Ni-coated copper powder in which a Ni alloy containing P was coated on the surface of the copper powder was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 13.7% by mass with respect to 100% by mass of the entire Ni-coated copper powder. Moreover, content of P contained in Ni alloy was 7.9 mass% with respect to 100 mass of Ni alloy.

FIG. 24 shows the result of observing the shape of the obtained Ni-coated copper powder with a SEM field of view at a magnification of 5,000 times. As shown in the photograph of FIG. 24, the obtained Ni-coated copper powder is a copper powder having a dendritic shape, and the surface of the copper powder before being coated with the Ni alloy is uniformly coated with the Ni alloy. It is. It was not a shape in which flat pieces were aggregated like the copper powder obtained in the examples. The average particle size (D50) of this Ni-coated copper powder was 17.6 μm.

Next, 55 parts by mass of the obtained Ni-coated copper powder was mixed with 15 parts by mass of phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 parts by mass of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Using a small kneader (manufactured by Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing is 68.2 × 10 ⁻⁵ Ω · cm, which is extremely high in specific resistance value and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 11]
<Production of mechanically flattened flat copper powder>
The characteristics of the conductive paste by Ni-coated copper powder obtained by coating Ni on a conventional flat copper powder were evaluated and compared with the characteristics of the conductive paste prepared using the flat Ni-coated copper particle agglomerated powder in the examples. .

The flat copper powder was prepared by mechanically flattening granular electrolytic copper powder. Specifically, 5 g of stearic acid was added to 500 g of granular atomized copper powder (manufactured by Mekin Metal Powders Co., Ltd.) having an average particle size of 5.4 μm, and flattened with a ball mill. The ball mill was charged with 5 kg of 3 mm zirconia beads and rotated for 90 minutes at a rotation speed of 500 rpm.

As a result of measuring the obtained flat copper powder with a laser diffraction / scattering particle size distribution analyzer, the average particle diameter was 21.8 μm. Moreover, the thickness (cross-sectional average thickness) of the flat copper powder measured by SEM observation was 0.4 μm.

<Production of Ni-coated copper powder (reducing agent: borohydride)>
Using 100 g of flat copper powder produced by flattening, the surface of the copper powder was coated with Ni by electroless Ni plating.

In this electroless Ni plating solution, a slurry in which 100 g of the flat copper powder prepared by the above-described method is dispersed in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 60 ° C. to 60 ° C. Stir for minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder (flat Ni-coated copper powder) in which a Ni alloy was coated on the surface of the flat copper powder was obtained. When the Ni-coated copper powder was recovered and the Ni alloy coating amount was measured, it was 18.3% by mass relative to 100% by mass of the entire Ni-coated copper powder. Moreover, content of B contained in Ni alloy was 6.8 mass% with respect to 100 mass of Ni alloy.

Further, the obtained flat copper powder was measured with a laser diffraction / scattering particle size distribution measuring instrument, and as a result, the average particle size was 21.8 μm. Moreover, the thickness (cross-sectional average thickness) of the flat copper powder measured by SEM observation was 0.40 μm.

The specific resistance value of the film obtained by curing is 26.2 × 10 ⁻⁵ Ω · cm, which is extremely high in specific resistance value and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 12]
The tabular Ni-coated copper powder produced in Comparative Example 11 was dispersed in a resin to obtain an electromagnetic wave shielding material.

Specifically, 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone are mixed with 40 g of the obtained tabular Ni-coated copper powder, and kneading at 1200 rpm for 3 minutes is repeated three times using a small kneader. To make a paste. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried using a Mayer bar on a substrate made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm to form an electromagnetic wave shielding layer having a thickness of 25 μm.

The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Specifically, the level in the case of the comparative example 12 in which the surface of the flat copper powder produced by mechanically flattening is coated with Ni is set as “Δ”, and the case where the level is lower than the level of the comparative example 12 is “×”. The case where the level was better than the level of Comparative Example 12 was evaluated as “◯”, and the case where the level was even better was evaluated as “◎”. Table 4 shows these results.

≪Example, comparative example≫
(5) Test using Ni-coated copper powder according to the fifth embodiment [Example 64]
<Preparation of electrolytic copper powder>
An electrolytic cell with a capacity of 100 L is used with a titanium electrode plate having an electrode area of 200 mm × 200 mm as a cathode and a copper electrode plate with an electrode area of 200 mm × 200 mm as an anode, and an electrolytic solution is charged into the electrolytic cell. Then, a direct current was applied thereto to deposit copper powder on the cathode plate.

At this time, as the electrolytic solution, a composition having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L was used. In addition, Janus Green B (manufactured by Kanto Chemical Co., Inc.) as an additive is added to the electrolytic solution so that the concentration in the electrolytic solution is 80 mg / L, and a hydrochloric acid solution (manufactured by Wako Pure Chemical Industries, Ltd.) is further added. It added so that it might become 30 mg / L as chloride ion (chlorine ion) density | concentration in electrolyte solution.

Then, while circulating the electrolytic solution whose concentration is adjusted as described above at a flow rate of 15 L / min using a pump, the current density of the cathode is 15 A / dm ² under the condition that the temperature is maintained at 25 ° C. Current was applied to deposit copper powder on the cathode plate.

As a result of observing the shape of the copper powder thus obtained in the field of view with a magnification of 1,000 times by the method using the scanning electron microscope (SEM) described above, the deposited copper powder was a main chain that grew linearly and the main trunk. It was a dendritic copper powder exhibiting a two-dimensional or three-dimensional dendritic shape in which copper particles having a shape having a plurality of branches branched linearly from the branch and branches further branched from the branch were collected. .

<Preparation of dendritic Ni-coated copper powder (reducing agent: borohydride)>
Next, using the dendritic copper powder produced by the above-described method, Ni was coated on the surface of the copper powder by electroless Ni plating to produce Ni-coated copper powder. In addition, the electroless Ni plating solution whose reducing agent is a borohydride compound was used.

Further, as a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Ni-coated copper powder was found on the surface of the dendritic copper powder before coating the Ni alloy. A two-dimensional or three-dimensional dendritic shape uniformly coated with a Ni alloy, a main trunk that has grown into a dendritic shape, a plurality of branches branched from the main trunk, and a branch further branched from the branch The dendritic Ni-coated copper powder had a dendritic shape.

Further, the copper particles constituting the main trunk and branches of the dendritic Ni-coated copper powder had a flat cross-sectional thickness of 0.09 μm on average, and had fine convex portions on the surface. In addition, the average height of the convex portions formed on the surface was 0.06 μm.

The average particle diameter (D50) of the dendritic Ni-coated copper powder was 21.2 μm.

Furthermore, the bulk density of the obtained dendritic Ni-coated copper powder was 1.25 g / cm ³ . The BET specific surface area was 1.7 m ² / g.

[Example 65]
<Preparation of electrolytic copper powder>
An electrolytic solution having a copper ion concentration of 10 g / L and a sulfuric acid concentration of 125 g / L is used, and Janus Green B as an additive is added to the electrolytic solution to a concentration of 150 mg / L in the electrolytic solution. Copper powder was deposited on the cathode plate under the same conditions as in Example 64 except that the hydrochloric acid solution was further added so that the chlorine ion concentration in the electrolytic solution was 100 mg / L.

Moreover, the copper particles constituting the main trunk and branches of the dendritic Ni-coated copper powder were flat plate having an average cross-sectional thickness of 0.11 μm and had fine convex portions on the surface. The height of the convex portions formed on the surface was 0.23 μm on average.

The average particle diameter (D50) of the dendritic Ni-coated copper powder was 8.3 μm.

Furthermore, the bulk density of the obtained dendritic Ni-coated copper powder was 2.77 g / cm ³ . The BET specific surface area was 1.2 m ² / g.

[Example 66]
<Preparation of dendritic Ni-coated copper powder (reducing agent: hydrazine compound)>
Using 100 g of the dendritic copper powder obtained in Example 65, Ni was coated on the surface of the copper powder by electroless Ni plating to prepare a Ni-coated copper powder. Electroless Ni plating using a hydrazine compound as a reducing agent was performed.

Specifically, nickel acetate was added to a slurry in which 100 g of the dendritic copper powder obtained in Example 65 was dispersed in 500 mL of water to a concentration of 12.4 g / L, and an aqueous solution of 80% by mass of hydrazine monohydrate. 6 g was added dropwise into the bath with slow stirring over 60 minutes. At this time, the bath temperature was controlled to 60 ° C.

Further, as a result of observing the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of Ni-coated copper powder was found on the surface of the dendritic copper powder before coating the Ni alloy. A two-dimensional or three-dimensional dendritic shape uniformly coated with Ni, having a main trunk grown into a dendritic shape, a plurality of branches branched from the main trunk, and branches further branched from the branch The dendritic Ni-coated copper powder had a dendritic shape.

Further, the copper particles constituting the main trunk and branches of the dendritic Ni-coated copper powder had a flat shape with an average cross-sectional thickness of 0.15 μm and had fine convex portions on the surface. The height of the convex portions formed on the surface was 0.27 μm on average.

The average particle diameter (D50) of the dendritic Ni-coated copper powder was 9.6 μm.

Furthermore, the bulk density of the obtained dendritic Ni-coated copper powder was 2.92 g / cm ³ . Further, the BET specific surface area was 1.6 m ² / g.

[Examples 67 to 73]
<Manufacture of dendritic Ni-coated copper powder (Ni alloy)>
Using 100 g of the dendritic copper powder obtained in Example 65, the surface of the copper powder was coated with a Ni alloy by electroless plating.

As an electroless Ni plating solution for alloys, nickel acetate was added to a slurry in which 100 g of the dendritic copper powder obtained in Example 65 was dispersed in 500 mL of water to a concentration of 12.4 g / L, and hydrazine 3. 2 g was added dropwise into the bath over 60 minutes with slow stirring. The bath temperature was controlled to 60 ° C.

At this time, each metal compound was added to a bath containing a copper powder slurry and nickel acetate, and hydrazine was gradually added so that each desired Ni alloy film was formed. As a metal compound, in Example 67, 1.5 g of sodium tungstate was added to form a Ni—W alloy film. In Example 68, 2 g of cobalt sulfate was added to form a Ni—Co alloy film. In Example 69, 4 g each of zinc sulfate heptahydrate and sodium citrate were added to form a Ni—Zn alloy coating. In Example 70, 2 g of palladium chloride was added to form a Ni—Pd alloy film. In Example 71, 2 g of potassium tetrachloroplatinate and 1 g of glycine were added to form a Ni—Pt alloy film. In Example 72, 1 g each of sodium molybdate and trisodium citrate was added to form a Ni—Mo alloy film. In Example 73, 1 g of sodium stannate was added to form a Ni—Sn alloy film.

After the reaction was completed, the powder was filtered, washed with water and dried through ethanol. As a result, Ni-coated copper powder in which the surface of the dendritic copper powder was coated with Ni was obtained. The Ni-coated copper powder was recovered and the Ni alloy coating amount was measured. Table 5 shows the results of measuring the content of Ni with respect to 100% by mass of the entire Ni-coated copper powder and the content of elements that become Ni alloys with respect to 100% by mass of the Ni alloy.

In addition, as a result of observing each of the obtained Ni-coated copper powder with a field of view of 5,000 times by SEM, at least 90% by number or more of the Ni-coated copper powder is dendritic before coating with the Ni alloy. A two-dimensional or three-dimensional dendritic Ni-coated copper powder in which the Ni powder is uniformly coated on the surface of the copper powder, and the main trunk that grows linearly and the main trunk that branches linearly The dendritic Ni-coated copper powder had a dendritic shape having a plurality of branches and a branch further branched from the branches.

Further, the average particle diameter (D50), bulk density, and BET specific surface area of these dendritic Ni-coated copper powders were measured. Table 5 summarizes these measurement results.

[Example 74]
<Preparation of dendritic Ni-coated copper powder (hypophosphite + tungsten compound)>
In Example 74, 100 g of the dendritic copper powder prepared in Example 64 was used, and the copper powder surface was coated with a Ni alloy by electroless plating.

As the electroless Ni plating solution, a plating solution containing hypophosphite as the same reducing agent as in Example 64 was used, and a metal other than Ni was added to the plating solution to produce a Ni alloy.

In this electroless Ni plating solution, a slurry obtained by dispersing 100 g of the dendritic copper powder prepared in Example 64 in 100 mL of water was stirred for 10 minutes at 25 ° C., and then the bath temperature was heated to 90 ° C. Stir for 60 minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, Ni-coated copper powder coated with a Ni—WP alloy was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 12.3% by mass relative to 100% by mass of the entire Ni-coated copper powder. The content of P contained in the Ni alloy was 7.1% by mass with respect to 100% by mass of the Ni alloy. Moreover, content of W contained in Ni alloy was 5.5 mass% with respect to 100 mass of Ni alloy.

[Example 75]
30 g of the dendritic Ni-coated copper powder obtained in Example 64 was mixed with 15 g of a phenol resin (PL-2211 manufactured by Gunei Chemical Co., Ltd.) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Using a kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing was 9.0 × 10 ⁻⁵ Ω · cm, and it was found that excellent conductivity was exhibited.

[Example 76]
30 g of the dendritic Ni-coated copper powder obtained in Example 65 is mixed with 20 g of a phenol resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade). Using a kneader (Nippon Seiki Seisakusho, non-bubbling kneader NBK-1), kneading at 1200 rpm for 3 minutes was repeated three times to form a paste. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

[Example 77]
The dendritic Ni-coated copper powder produced in Example 64 was dispersed in a resin to obtain an electromagnetic wave shielding material.

That is, 100 g of vinyl chloride resin and 200 g of methyl ethyl ketone were mixed with 30 g of the dendritic Ni-coated copper powder obtained in Example 64, and kneading was performed at 1200 rpm for 3 minutes using a small kneader. The paste was made by repeating the process once. During pasting, the copper powder was uniformly dispersed in the resin without agglomeration. This was coated and dried using a Mayer bar on a substrate made of a transparent polyethylene terephthalate sheet having a thickness of 100 μm to form an electromagnetic wave shielding layer having a thickness of 25 μm.

The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Table 5 shows these results.

[Comparative Example 13]
<Preparation of electrolytic copper powder>
Copper powder was deposited on the cathode plate in the same manner as in Example 64 except that Janus Green B as an additive and chlorine ions were not added to the electrolytic solution. The shape of the obtained Ni-coated copper powder was a dendritic shape in which particulate copper was aggregated, and no fine convex portions were formed.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, a Ni-coated copper powder in which a Ni alloy containing P was coated on the surface of the copper powder was obtained. Moreover, when the Ni-coated copper powder was recovered and the Ni content was measured, it was 13.6% by mass relative to 100% by mass of the entire Ni-coated copper powder. The content of P contained in the Ni alloy was 7.8% by mass with respect to 100% by mass of the Ni alloy.

FIG. 25 shows the result of observing the shape of the obtained Ni-coated copper powder with a SEM field of view at a magnification of 1,000 times. As shown in the photograph of FIG. 25, the shape of the obtained Ni-coated copper powder is a dendritic shape in which particulate copper particles are aggregated, and the surface of the copper powder is coated with a Ni alloy. It was. Moreover, the average particle diameter (D50) of the Ni-coated copper powder was 22.5 μm. In addition, the fine convex part was not formed in the dendritic part.

<Evaluation of conductive paste>
Next, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of Ni-coated copper powder produced by the above-described method. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the viscosity increased every time kneading was repeated. This is considered to be caused by a part of the copper powder being aggregated, and uniform dispersion was difficult. The obtained conductive paste was printed on glass with a metal squeegee and cured at 200 ° C. for 30 minutes in the air atmosphere.

The specific resistance value of the film obtained by curing is 63.8 × 10 ⁻⁵ Ω · cm, which is higher in specific resistance value and inferior in conductivity than the conductive paste obtained in the examples. there were.

[Comparative Example 14]
<Production of mechanically flattened flat copper powder>
The characteristic of the conductive paste by Ni coat copper powder which coat | covered Ni with the conventional flat copper powder was evaluated, and it compared with the characteristic of the conductive paste produced using the dendritic Ni coat copper powder in an Example.

<Production of Ni-coated copper powder (reducing agent: borohydride)>
With respect to 100 g of the obtained flat copper powder, the surface of the copper powder was coated with Ni by electroless plating.

In this electroless Ni plating solution, a slurry in which 100 g of copper powder on a flat plate prepared by the above method is dispersed in 100 mL of water is stirred for 10 minutes at 25 ° C., and then the bath temperature is heated to 60 ° C. to 60 ° C. Stir for minutes.

After the reaction was completed, the powder was filtered, washed with water, and dried through ethanol. As a result, a Ni-coated copper powder in which the surface of the flat copper powder was coated with a Ni alloy was obtained. When the Ni-coated copper powder was recovered and the Ni content was measured, it was 18.2% by mass with respect to 100% by mass of the entire Ni-coated copper powder. Moreover, content of B contained in Ni alloy was 6.7 mass% with respect to 100 mass of Ni alloy.

The plate-like Ni-coated copper powder produced in this way was measured with a laser diffraction / scattering particle size distribution analyzer, and as a result, the average particle size (D50) was 21.8 μm. Moreover, the thickness (cross-sectional average thickness) of the plate-like Ni-coated copper powder measured by SEM observation was 0.40 μm. In the flat Ni-coated copper powder, no fine protrusions were observed on the surface.

<Evaluation of conductive paste>
Next, 20 g of phenolic resin (manufactured by Gunei Chemical Co., Ltd., PL-2211) and 10 g of butyl cellosolve (manufactured by Kanto Chemical Co., Ltd., deer special grade) are mixed with 40 g of Ni-coated copper powder produced by the above-described method. Then, using a small kneader (manufactured by Nippon Seiki Seisakusho Co., Ltd., non-bubbling kneader NBK-1), it was made into a paste by repeating kneading at 1200 rpm for 3 minutes three times. During pasting, the viscosity increased every time kneading was repeated. This is considered to be caused by a part of the copper powder being aggregated, and uniform dispersion was difficult. The obtained conductive paste was printed on a glass with a metal squeegee and cured at 200 ° C. for 30 minutes in an air atmosphere.

The specific resistance value of the film obtained by curing is 26.5 × 10 ⁻⁵ Ω · cm, which is extremely high in specific resistance value and inferior in conductivity compared to the conductive paste obtained in the examples. Met.

[Comparative Example 15]
The plate-like Ni-coated copper powder produced in Comparative Example 14 was dispersed in a resin to obtain an electromagnetic wave shielding material.

The electromagnetic shielding characteristics were evaluated by measuring the attenuation rate using an electromagnetic wave having a frequency of 1 GHz. Specifically, the level in the case of Comparative Example 15 that does not use the dendritic Ni-coated copper powder is set as “Δ”, and the level that is worse than the level of Comparative Example 15 is set as “X”. The case where it was better than the level was evaluated as “◯”, and the case where it was superior was evaluated as “◎”. Table 5 shows these results.

11 Ni-coated copper powder (dendritic Ni-coated copper powder)
12 Main trunk 13, 13a, 13b Branch 14 Maximum length in horizontal direction (XY direction) with respect to flat plate surface 15 Maximum height in vertical direction with respect to flat plate surface (XY plane) 21 Copper powder (dendritic copper powder)
22 Copper particle D1 Thickness of branch part 31 Ni-coated copper powder (dendritic Ni-coated copper powder)
32 backbone 33, 33a, 33b branch 41 Ni-coated copper powder (flat Ni-coated copper particle agglomerated powder)
42 Copper particles d Major axis diameter of flat Ni-coated copper particles 51 Copper particles 52 Main trunks (of copper particles) 53, 53a, 53b (copper particles) branches

Claims

This is a Ni-coated copper powder in which copper particles coated with nickel (Ni) or Ni alloy are gathered on the surface to form a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. And
The copper particles coated with Ni or Ni alloy on the surface are in the form of a flat plate having a cross-sectional average thickness of 0.02 μm to 5.0 μm determined by scanning electron microscope (SEM) observation.
The Ni-coated copper powder constituted by the aggregation of the copper particles has an average particle diameter (D50) of 1.0 μm to 100 μm,
The Ni coat copper powder whose maximum height to the perpendicular direction with respect to the flat surface of the said copper particle is 1/10 or less with respect to the maximum length to the horizontal direction of this flat surface.
Copper particles coated with nickel (Ni) or Ni alloy on the surface are assembled to form a dendritic shape having a plurality of branches, Ni-coated copper powder,
The copper particles coated with Ni or Ni alloy on the surface have an ellipsoid having a minor axis average diameter of 0.2 μm to 0.5 μm and a major axis average diameter of 0.5 μm to 2.0 μm. And
The Ni-coated copper powder composed of the copper particles is an Ni-coated copper powder having an average particle diameter (D50) of 5.0 μm to 20 μm.
The Ni-coated copper powder according to claim 2, wherein an average thickness of the branch portions constituting the dendritic shape is 0.5 μm to 2.0 μm.
This is a Ni-coated copper powder in which copper particles coated with nickel (Ni) or Ni alloy are gathered on the surface to form a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. And
The copper particles coated with Ni or Ni alloy on the surface are in the form of a flat plate having a cross-sectional average thickness of 0.2 μm to 5.0 μm,
The Ni-coated copper powder composed of the copper particles is an Ni-coated copper powder having an average particle diameter (D50) of 1.0 μm to 100 μm.
A Ni-coated copper powder comprising a plurality of pieces of individual copper particles coated with nickel (Ni) or Ni alloy on the surface and having an aggregate form,
The copper particles coated with the Ni or Ni alloy have an average major axis diameter determined by observation with a scanning electron microscope (SEM) of 0.5 μm to 5.0 μm and an average cross-sectional thickness of 0.02 μm to 1.0 μm. Is a flat plate shape,
The Ni-coated copper powder composed of the copper particles is an Ni-coated copper powder having an average particle diameter (D50) of 1.0 μm to 30 μm.
This is a Ni-coated copper powder in which copper particles coated with nickel (Ni) or Ni alloy are gathered on the surface to form a dendritic shape having a main trunk that grows linearly and a plurality of branches separated from the main trunk. And
The copper particles coated with Ni or Ni alloy on the surface have a dendritic shape having a main trunk grown in a dendritic shape and a plurality of branches separated from the main trunk, and the cross-sectional average thickness of the main trunk and the branches of the copper particles Is a flat plate of 0.02 μm to 0.5 μm,
The Ni-coated copper powder composed of the copper particles is an Ni-coated copper powder having an average particle diameter (D50) of 1.0 μm to 30 μm.
The Ni-coated copper powder according to claim 6, wherein the surface of the copper particles has fine convex portions, and the average height of the convex portions is 0.01 μm to 0.4 μm.
The Ni content coated as Ni or Ni alloy is 1% by mass to 50% by mass with respect to 100% by mass of the entire Ni-coated copper powder coated with Ni or Ni alloy. 2. Ni-coated copper powder according to item 1.
Ni alloy is coated on the surface of the copper particles,
At least one selected from the group consisting of cobalt, zinc, tungsten, molybdenum, palladium, platinum, tin, phosphorus, and boron is 0.1% by mass to 20% by mass with respect to 100% by mass of the Ni alloy. The Ni-coated copper powder according to any one of claims 1 to 8, wherein the Ni-coated copper powder is coated with a Ni alloy contained in a content.
The Ni-coated copper powder according to any one of claims 1 to 9, wherein a bulk density is in a range of 0.5 g / cm 3 to 5.0 g / cm 3 .
Ni-coated copper powder according to any one of claims 1 to 10 BET specific surface area is 0.2m 2 /g~5.0m 2 / g.
Metal filler which contains the Ni coat copper powder in any one of Claims 1 thru | or 11 in the ratio of 20 mass% or more of the whole.
An electrically conductive paste obtained by mixing the metal filler according to claim 12 with a resin.
A conductive paint for electromagnetic wave shielding, comprising the metal filler according to claim 12.
A conductive sheet for electromagnetic wave shielding, comprising the metal filler according to claim 12.
A method for producing the Ni-coated copper powder according to claim 1,
A step of depositing copper powder on the cathode from the electrolyte by an electrolytic method;
Coating the copper powder with nickel (Ni) or Ni alloy,
In the electrolyte,
Copper ions,
A compound having a phenazine structure represented by the following formula (1), a compound having an azobenzene structure represented by the following formula (2), and a compound having a phenazine structure and an azobenzene structure represented by the following formula (3) One or more selected from the group consisting of:
One or more types of nonionic surfactants;
The manufacturing method of the Ni coat copper powder which electrolyzes by containing.

[In Formula (1), R 1 , R 2 , R 3 , R 4 , R 6 , R 7 , R 8 , R 9 are each independently hydrogen, halogen, amino, OH, ═O, CN, SCN. , SH, COOH, COO salt, COO ester, SO 3 H, SO 3 salt, SO 3 ester, benzenesulfonic acid, and C1-C8 alkyl, R 5 is hydrogen, halogen , Amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO 3 H, SO 3 salt, SO 3 ester, benzenesulfonic acid, lower alkyl, and aryl. And A − is a halide anion. ]

[In the formula (2), R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 are each independently hydrogen, halogen, amino, OH, = O, CN, SCN, SH, COOH, COO salt, COO ester, SO 3 H, SO 3 salt, SO 3 ester, a group selected from the group consisting of benzenesulfonic acid, lower alkyl, and aryl. ]

[In the formula (3), R 1 , R 2 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 are each independently hydrogen, Selected from the group consisting of halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO 3 H, SO 3 salt, SO 3 ester, benzenesulfonic acid, and C1-C8 alkyl R 3 is hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO 3 H, SO 3 salt, SO 3 ester, benzenesulfonic acid, A group selected from the group consisting of lower alkyl and aryl, and A − is a halide anion. ]
The method for producing Ni-coated copper powder according to claim 16, further comprising chloride ions in the electrolytic solution.
A method for producing the Ni-coated copper powder according to claim 2 or 3,
A step of depositing copper powder on the cathode from the electrolyte by an electrolytic method;
Coating the copper powder with nickel (Ni) or Ni alloy,
In the electrolyte,
The manufacturing method of Ni coat copper powder which electrolyzes containing a copper ion and a polyether compound.
A method for producing the Ni-coated copper powder according to claim 4,
A step of depositing copper powder on the cathode from the electrolyte by an electrolytic method;
Coating the copper powder with nickel (Ni) or Ni alloy,
In the electrolyte,
Copper ions,
One or more selected from compounds having a phenazine structure represented by the following formula (1);
The manufacturing method of the Ni coat copper powder which electrolyzes by containing.

[In Formula (1), R 1 , R 2 , R 3 , R 4 , R 6 , R 7 , R 8 , R 9 are each independently hydrogen, halogen, amino, OH, ═O, CN, SCN. , SH, COOH, COO salt, COO ester, SO 3 H, SO 3 salt, SO 3 ester, benzenesulfonic acid, and C1-C8 alkyl, R 5 is hydrogen, halogen , Amino, OH, —O, CN, SCN, SH, COOH, COO salt, COO ester, SO 3 H, SO 3 salt, SO 3 ester, benzenesulfonic acid, lower alkyl, and aryl. And A − is a halide anion. ]
A method for producing the Ni-coated copper powder according to claim 6 or 7,
A step of depositing copper powder on the cathode from the electrolyte by an electrolytic method;
Coating the copper powder with nickel (Ni) or Ni alloy,
In the electrolyte,
Copper ions,
One or more selected from compounds having a phenazine structure and an azobenzene structure represented by the following formula (3);
The manufacturing method of the Ni coat copper powder which electrolyzes by containing.

[In the formula (3), R 1 , R 2 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 are each independently hydrogen, Selected from the group consisting of halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO 3 H, SO 3 salt, SO 3 ester, benzenesulfonic acid, and C1-C8 alkyl It is a group. R 3 is hydrogen, halogen, amino, OH, ═O, CN, SCN, SH, COOH, COO salt, COO ester, SO 3 H, SO 3 salt, SO 3 ester, benzenesulfonic acid, lower alkyl, And a group selected from the group consisting of aryl. A − is a halide anion. ]