JP2018161674A - Solder composition and electronic substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solder composition being excellent in meltability, capable of sufficiently suppressing a void and having sufficient printability even when performing a reflow process in an air atmosphere.SOLUTION: In a solder composition including a flux composition containing (A) a rosin-based resin, (B) an activator and (C) a solvent and (D) a solder powder having a melting point of 200°C or higher and 250°C or lower, the (A) component contains (A1) the hydrogenated product of an unsaturated organic acid modified rosin, the (C) component contains (C1) a hexane diol-based solvent having a melting point of 40°C or higher and a boiling point of 220°C or lower and (C2) a solvent having a viscosity of 10 mPa s or less and a boiling point of 270°C or higher at 20°C, and the blending amount of the (A) component is 30 mass% or more to 100 mass% of the flux composition.SELECTED DRAWING: None

Description

  The present invention relates to a solder composition and an electronic substrate.

The solder composition is a mixture obtained by kneading a flux composition (such as a rosin resin, an activator, and a solvent) into solder powder to form a paste (for example, Patent Document 1). In this solder composition, not only solderability such as solder meltability and a property that the solder easily spreads (solder wetting spread), but also suppression of voids and printability are required.
Moreover, if this solder composition is used, a solder joint can be formed between an electronic component and an electronic substrate by a reflow process. And as a reflow apparatus used for this reflow process, an air reflow apparatus, a vacuum reflow apparatus, a formic acid reflow apparatus, a plasma reflow apparatus, etc. are mentioned. From the viewpoint of the cost of the equipment, an air reflow apparatus that performs the reflow process in an air atmosphere is preferable. Therefore, the solder composition is required to have excellent solder meltability even when the reflow process is performed in an air atmosphere.

Japanese Patent No. 5756067

  However, when the reflow process is performed in an air atmosphere, the flux composition needs to contain a predetermined amount or more of rosin resin from the viewpoint of removing the oxide film and maintaining the cleanliness of the copper foil surface. On the other hand, when the content of the rosin resin in the flux composition is large, the viscosity of the flux composition is increased and voids are easily generated. From the viewpoint of suppressing voids, it is conceivable to use a low boiling point solvent as the solvent in the flux composition. However, when a low boiling point solvent is used, the solvent is volatilized during printing, and the viscosity of the solder composition changes, so that the printability is lowered. Thus, suppression of voids and printability are in a trade-off relationship, and there has been no solder composition that can satisfy these simultaneously.

  Therefore, the present invention provides a solder composition that has excellent solder meltability even when the reflow process is performed in an air atmosphere, can sufficiently suppress voids, and has sufficient printability, and an electronic substrate using the same. For the purpose.

In order to solve the above problems, the present invention provides the following solder composition and electronic substrate.
The solder composition of the present invention comprises (A) a flux composition containing a rosin resin, (B) an activator and (C) a solvent, and (D) a solder powder having a melting point of 200 ° C. or higher and 250 ° C. or lower. And the component (A) contains a hydrogenated product of (A1) unsaturated organic acid-modified rosin, and the component (C) has (C1) a melting point of 40 ° C. or higher and a boiling point of 220 ° C. or lower. And (C2) a solvent having a viscosity at 20 ° C. of 10 mPa · s or less and a boiling point of 270 ° C. or more, and the blending amount of the component (A) is the flux composition 30% by mass or more with respect to 100% by mass of the product.

In the solder composition of the present invention, the component (C1) is preferably at least one selected from the group consisting of 2,5-dimethylhexane-2,5-diol and 1,6-hexanediol. .
In the solder composition of the present invention, the component (C2) is preferably tetraethylene glycol dimethyl ether.
The electronic substrate of the present invention is characterized by including a soldering portion using the solder composition.

According to the solder composition of the present invention, even when the reflow process is performed in an air atmosphere, the solder meltability is excellent, the voids can be sufficiently suppressed, and the reason for having sufficient printability is not necessarily clear. They guess as follows.
That is, in the solder composition of the present invention, as the (A) rosin resin, (A1) a hydrogenated product of an unsaturated organic acid-modified rosin is used, and the blending amount of the (A) component is a predetermined amount or more. . Therefore, even when the reflow process is performed in an air atmosphere, the oxide film can be removed, the cleanliness of the copper foil surface can be maintained, and sufficient solder meltability can be ensured. In the solder composition of the present invention, as the solvent (C), (C1) a hexanediol solvent having a melting point of 40 ° C. or higher and a boiling point of 220 ° C. or lower, and (C2) a viscosity at 20 ° C. A solvent having a boiling point of not more than 10 mPa · s and a boiling point of not less than 270 ° C. is used in combination. Since the component (C1) has a relatively low boiling point, it volatilizes into a gas before the solder is melted or when the solder is melted. This gas acts to push the gas in the solder composition to the outside. is there. Since the component (C2) has a high boiling point, it hardly volatilizes even when the solder is melted. Therefore, generation | occurrence | production of the void by vaporization of a solvent can be suppressed. In addition, since the solder composition containing the component (C2) has a certain degree of fluidity even when the solder is melted, the gas in the solder composition is released outside while gradually gathering. In this way, voids can be sufficiently suppressed. Furthermore, both the (C1) component and the (C2) component hardly volatilize at room temperature. Therefore, at the time of printing, the viscosity change of the solder composition is small, and sufficient printability can be ensured. As described above, the present inventors speculate that the effects of the present invention are achieved.

  According to the present invention, it is possible to provide a solder composition that is excellent in solder meltability even when the reflow process is performed in an air atmosphere, can sufficiently suppress voids, and has sufficient printability, and an electronic substrate using the same. .

  The solder composition of the present invention contains a flux composition described below and (D) solder powder described below.

[Flux composition]
First, the flux composition used for this invention is demonstrated. The flux composition used in the present invention is a component other than the solder powder in the solder composition, and contains (A) a rosin resin, (B) an activator, and (C) a solvent.

[(A) component]
Examples of the (A) rosin resin used in the present embodiment include rosins and rosin modified resins. Examples of rosins include gum rosin, wood rosin and tall oil rosin. Examples of rosin-based modified resins include disproportionated rosin, polymerized rosin, hydrogenated rosin (fully hydrogenated rosin, partially hydrogenated rosin, and unsaturated organic acids (aliphatic unsaturated monobasic such as (meth) acrylic acid). Unsaturated organics that are modified rosins of acid, fumaric acid, maleic acid and other aliphatic unsaturated dibasic acids such as α, β-unsaturated carboxylic acids, and unsaturated carboxylic acids having aromatic rings such as cinnamic acid) Examples include hydrogenated products of acid-modified rosin (also referred to as “hydrogenated acid-modified rosin”) and derivatives thereof. These rosin resins may be used alone or in combination of two or more.

In the present embodiment, the component (A) needs to contain a hydrogenated product of (A1) unsaturated organic acid-modified rosin. When this component (A1) is not contained, the solder meltability is insufficient even when the reflow process is performed in an air atmosphere.
The component (A) may contain a rosin resin (component (A2)) other than the component (A1) as necessary. In such a case, the mass ratio [{(A1) / (A)} × 100] of the component (A1) to the component (A) is preferably 50% by mass or more, and 70% by mass or more. It is more preferable that the content is 90% by mass or more.

  The blending amount of the component (A) needs to be 30% by mass or more with respect to 100% by mass of the flux composition. When the blending amount of the component (A) is less than 30% by mass, the solder meltability is insufficient when the reflow process is performed in the air atmosphere. Further, from the viewpoint of the balance between the solder meltability and the flux residue, the blending amount of the component (A) is preferably 30% by mass or more and 70% by mass or less with respect to 100% by mass of the flux composition. More preferably, it is at least 65% by mass, and particularly preferably at least 40% by mass and not more than 60% by mass.

[Component (B)]
Examples of the (B) activator used in the present embodiment include organic acids, non-dissociative activators composed of non-dissociable halogenated compounds, and amine-based activators. These activators may be used individually by 1 type, and may mix and use 2 or more types. Among these, from the viewpoint of environmental measures and from the viewpoint of suppressing corrosion at the soldered portion, it is preferable to use an organic acid or an amine-based activator (one containing no halogen), and an organic acid is used. It is more preferable.

Examples of the organic acid include other organic acids in addition to monocarboxylic acid and dicarboxylic acid.
Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid Arachidic acid, behenic acid, lignoceric acid, glycolic acid and the like.
Examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, and diglycolic acid.
Examples of other organic acids include dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, and picolinic acid.

  Examples of the non-dissociative activator include non-salt organic compounds in which halogen atoms are bonded by a covalent bond. The halogenated compound may be a compound formed by covalent bonding of chlorine, bromine and fluorine, such as chlorinated, brominated and fluoride, but any two or all of chlorine, bromine and fluorine may be used. The compound which has the following covalent bond may be sufficient. In order to improve the solubility in an aqueous solvent, these compounds preferably have a polar group such as a hydroxyl group or a carboxyl group such as a halogenated alcohol or a halogenated carboxyl compound. Examples of the halogenated alcohol include 2,3-dibromopropanol, 2,3-dibromobutanediol, trans-2,3-dibromo-2-butene-1,4-diol, 1,4-dibromo-2-butanol, And brominated alcohols such as tribromoneopentyl alcohol, chlorinated alcohols such as 1,3-dichloro-2-propanol, and 1,4-dichloro-2-butanol, fluorinated alcohols such as 3-fluorocatechol, and Other compounds similar to these may be mentioned. Examples of the halogenated carboxyl compound include 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and 5-iodoanthranilic acid, iodinated carboxyl compounds, 2-chlorobenzoic acid, and Examples thereof include carboxylated carboxyl compounds such as 3-chloropropionic acid, brominated carboxyl compounds such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, and 2-bromobenzoic acid, and other similar compounds. .

  Examples of the amine-based activator include amines (polyamines such as ethylenediamine), amine salts (amines such as trimethylolamine, cyclohexylamine, and diethylamine), and organic acid salts or inorganic acid salts such as amino alcohols (hydrochloric acid, sulfuric acid). And hydrobromic acid)), amino acids (such as glycine, alanine, aspartic acid, glutamic acid, and valine), amide compounds, and the like. Specifically, diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salts (such as hydrochloride, succinate, adipate, and sebacate), triethanolamine, monoethanolamine, In addition, hydrobromides of these amines can be mentioned.

  The blending amount of the component (B) is preferably 1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, with respect to 100% by mass of the flux composition. The content is particularly preferably 2% by mass or more and 10% by mass or less. When the blending amount of the component (B) is less than the lower limit, solder balls tend to be easily formed. On the other hand, when the amount exceeds the upper limit, the insulating property of the flux composition tends to be lowered.

[Component (C)]
The (C) solvent used in the present embodiment has (C1) a hexanediol solvent having a melting point of 40 ° C. or higher and a boiling point of 220 ° C. or lower, and (C2) a viscosity at 20 ° C. of 10 mPa · s or lower. And it is necessary to contain the solvent whose boiling point is 270 degreeC or more. By using a combination of the component (C1) and the component (C2), both suppression of voids and printability can be achieved.
In addition, the upper limit of melting | fusing point of (C1) component is not specifically limited. For example, the melting point of the component (C1) may be 100 ° C. or less. Moreover, the minimum of the boiling point of (C1) component is not specifically limited. For example, the boiling point of the component (C1) may be 120 ° C. or higher. In addition, in this specification, a boiling point means the boiling point in 1013 hPa.

  As the component (C1), 2,5-dimethyl-2,5-hexanediol (melting point: 86 to 90 ° C., boiling point: 214 ° C.), 1,6-hexanediol (melting point: 40 to 44 ° C., boiling point: 215 ° C.) and (2S, 5S) -2,5-hexanediol (melting point: 52 to 56 ° C., boiling point: 212 to 215 ° C.). Among these, 2,5-dimethyl-2,5-hexanediol is more preferable from the viewpoint of the melting point of the solvent. These may be used alone or in combination of two or more.

Further, from the viewpoint of further suppression of voids, the viscosity at 20 ° C. of the component (C2) is more preferably 8 mPa · s or less, particularly preferably 5 mPa · s or less, and 2 mPa · s or less. Most preferred. The lower limit of the viscosity of component (C2) at 20 ° C. is not particularly limited. For example, the viscosity at 20 ° C. of the component (C2) may be 0.01 mPa · s or more. The viscosity of the solvent can be measured with a Brookfield rotary viscometer.
Furthermore, from the viewpoint of further suppressing voids, the boiling point of the component (C2) is more preferably 275 ° C. or higher and 300 ° C. or lower.

  Examples of the component (C2) include tetraethylene glycol dimethyl ether (boiling point: 275 ° C., viscosity: 3.8 mPa · s), tripropylene glycol monobutyl ether (boiling point: 274 ° C., viscosity: 8.4 mPa · s), and maleic acid And dibutyl (boiling point: 281 ° C., viscosity: 5.0 mPa · s). Among these, tetraethylene glycol dimethyl ether is more preferable from the viewpoint of the viscosity of the solvent. These may be used alone or in combination of two or more. In addition, the viscosity described in parentheses is a viscosity at 20 ° C.

  The mass ratio of the (C2) component to the (C1) component ((C2) / (C1)) is preferably 1 or more and 10 or less from the viewpoint of the balance between void suppression and printability. It is more preferably 2 or more and 8 or less, and particularly preferably 2 or more and 6 or less.

  The component (C) may contain a solvent (component (C3)) other than the component (C1) and the component (C2) within a range in which the object of the present invention can be achieved. The solid content in the solder composition can be dissolved or dispersed by the component (C3). The component (C3) is preferably liquid at 20 ° C.

  Examples of the component (C3) include diethylene glycol monohexyl ether (boiling point: 259 ° C., viscosity: 8.6 mPa · s), diethylene glycol monobutyl ether (boiling point: 230 ° C., viscosity: 6.6 mPa · s), α, β, γ Terpineol (boiling point: 217 ° C., viscosity: 67 mPa · s), benzyl glycol (boiling point: 256 ° C., viscosity: 12.6 mPa · s), diethylene glycol mono 2-ethylhexyl ether (boiling point: 272 ° C., viscosity: 10.4 mPa · s) s), tripropylene glycol (boiling point: 265 ° C., viscosity: 57.2 mPa · s), diethylene glycol monobenzyl ether (boiling point: 302 ° C., viscosity: 19.3 mPa · s), diethylene glycol dibutyl ether (boiling point: 255 ° C., viscosity) : 2.4 mPa · s), tripropylene Recall monomethyl ether (boiling point: 242 ° C., viscosity: 1 mPa · s), dipropylene glycol monobutyl ether (boiling point: 231 ° C., viscosity: 7.4 mPa · s), ethylene glycol mono 2-ethylhexyl ether (boiling point: 229 ° C., viscosity) : 7.6 mPa · s), diethylene glycol monoethyl ether acetate (boiling point: 220 ° C., viscosity: 2.8 mPa · s) and 2,2-dimethyl-1,3-propanediol (melting point: 127 to 130 ° C., boiling point: 210 ° C.). These may be used alone or in combination of two or more. In addition, the viscosity described in parentheses is a viscosity at 20 ° C.

  When the component (C3) is used, the mass ratio of the component (C3) to the component (C) ((C3) / (C)) is 1/15 from the viewpoint of the balance between void suppression and printability. It is preferable that it is 1/2 or less, more preferably 1/10 or more and 1/2 or less, and particularly preferably 1/5 or more and 1/3 or less.

  The blending amount of the component (C) is preferably 20% by mass or more and 65% by mass or less, more preferably 30% by mass or more and 60% by mass or less, with respect to 100% by mass of the flux composition. It is particularly preferable that the content is not less than 50% by mass and not more than 50% by mass. If the blending amount of the solvent is within the above range, the viscosity of the obtained solder composition can be appropriately adjusted to an appropriate range.

  In the present embodiment, a thixotropic agent may be further contained from the viewpoint of printability and the like. Examples of the thixotropic agent used in the present embodiment include hardened castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. These thixotropic agents may be used alone or in combination of two or more.

  When using the thixotropic agent, the blending amount is preferably 3% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less with respect to 100% by mass of the flux composition. . If the blending amount is less than the lower limit, thixotropy cannot be obtained and the sagging tends to occur. On the other hand, if it exceeds the upper limit, the thixotropy tends to be too high and printing tends to be poor.

[Other ingredients]
In the flux composition used in the present embodiment, in addition to the component (A), the component (B), the component (C) and the thixotropic agent, if necessary, other additives, and other Of resin can be added. Other additives include antifoaming agents, antioxidants, modifiers, matting agents, and foaming agents. As a compounding quantity of these additives, it is preferable that they are 0.01 mass% or more and 5 mass% or less with respect to 100 mass% of flux compositions. Examples of other resins include acrylic resins.

[Solder composition]
Next, the solder composition of this embodiment will be described. The solder composition of this embodiment contains the above-described flux composition of this embodiment and (D) solder powder described below.
The blending amount of the flux composition is preferably 5% by mass to 35% by mass, more preferably 7% by mass to 15% by mass, and more preferably 8% by mass with respect to 100% by mass of the solder composition. It is particularly preferable that the content is not less than 12% and not more than 12% by mass. When the blending amount of the flux composition is less than 5% by mass (when the blending amount of the solder powder exceeds 95% by mass), the flux composition as the binder is insufficient, so the flux composition and the solder powder are mixed. On the other hand, when the blending amount of the flux composition exceeds 35% by mass (when the blending amount of the solder powder is less than 65% by mass), when the obtained solder composition is used, It tends to be difficult to form a sufficient solder joint.

[(D) component]
The solder powder (D) used in this embodiment is a solder powder having a melting point of 200 ° C. or higher and 250 ° C. or lower. In the present embodiment, the boiling points of the component (C1) and the component (C2) are defined on the premise that solder powder having a melting point of 200 ° C. or higher and 250 ° C. or lower is used.
As the solder alloy in the solder powder, an alloy containing tin (Sn) as a main component is preferable. Examples of the second element of the alloy include silver (Ag), copper (Cu), zinc (Zn), bismuth (Bi), indium (In), and antimony (Sb). Furthermore, you may add another element (after 3rd element) to this alloy as needed. Examples of other elements include copper, silver, bismuth, indium, antimony, and aluminum (Al).
Here, the lead-free solder powder refers to a solder metal or alloy powder to which lead is not added. However, it is allowed that lead is present as an inevitable impurity in the lead-free solder powder, but in this case, the amount of lead is preferably 300 mass ppm or less.

  Specific examples of the solder alloy in the lead-free solder powder include Sn—Ag series and Sn—Ag—Cu series. Among these, Sn—Ag—Cu-based solder alloys are preferably used from the viewpoint of solder joint strength. The melting point of the Sn—Ag—Cu solder is usually 200 ° C. or higher and 250 ° C. or lower (preferably 200 ° C. or higher and 240 ° C. or lower). Note that among the Sn-Ag-Cu-based solders, the melting point of the solder having a low silver content is 210 ° C. or higher and 250 ° C. or lower (preferably 220 ° C. or higher and 240 ° C. or lower).

  The average particle size of the component (D) is usually 1 μm or more and 40 μm or less, but is more preferably 1 μm or more and 35 μm or less from the viewpoint that it can be applied to an electronic substrate having a narrow solder pad pitch. More preferably, it is 30 μm or less, and particularly preferably 3 μm or more and 20 μm or less. The average particle size can be measured with a dynamic light scattering type particle size measuring device.

[Method for producing solder composition]
The solder composition of the present embodiment can be manufactured by blending the above-described flux composition and the above-described (D) solder powder at the predetermined ratio and stirring and mixing them.

[Electronic substrate]
Next, the electronic substrate of this embodiment will be described. The electronic substrate of this embodiment is characterized by including a soldering portion using the solder composition described above. The electronic board of the present invention can be manufactured by mounting an electronic component on an electronic board (such as a printed wiring board) using the solder composition.
The solder composition of this embodiment described above can sufficiently suppress voids having a large diameter even when the printing area of the solder composition is large. Therefore, as an electronic component, an electronic component (for example, a power transistor) having a large electrode terminal area may be used. Further, the printed area of the solder composition may be, for example, 20 mm ² or more, 30 mm ² or more, or 40 mm ² or more. The printed area corresponds to the area of the electrode terminal of the electronic component.
Examples of the coating apparatus used here include a screen printer, a metal mask printer, a dispenser, and a jet dispenser.
In addition, the electronic component is placed on the solder composition applied by the coating device, heated under a predetermined condition by a reflow furnace, and the electronic component is mounted on the printed wiring board by a reflow process. Can be implemented.

In the reflow process, the electronic component is placed on the solder composition and heated in a reflow furnace under predetermined conditions. By this reflow process, sufficient soldering can be performed between the electronic component and the printed wiring board. As a result, the electronic component can be mounted on the printed wiring board.
What is necessary is just to set reflow conditions suitably according to melting | fusing point of solder. For example, the preheat temperature is preferably 140 ° C. or higher and 200 ° C. or lower, and more preferably 150 ° C. or higher and 160 ° C. or lower. The preheating time is preferably 60 seconds or more and 120 seconds or less. The peak temperature is preferably 230 ° C. or higher and 270 ° C. or lower, and more preferably 240 ° C. or higher and 255 ° C. or lower. The holding time at a temperature of 220 ° C. or higher is preferably 20 seconds or longer and 60 seconds or shorter.

Further, the solder composition and the electronic substrate of the present embodiment are not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the electronic board, the printed wiring board and the electronic component are bonded by the reflow process, but the invention is not limited to this. For example, instead of the reflow process, the printed wiring board and the electronic component may be bonded by a process of heating the solder composition using laser light (laser heating process). In this case, the laser light source is not particularly limited, and can be appropriately selected according to the wavelength matched to the metal absorption band. Examples of the laser light source include a solid-state laser (ruby, glass, YAG, etc.), a semiconductor laser (GaAs, InGaAsP, etc.), a liquid laser (pigment, etc.), and a gas laser (He—Ne, Ar, CO ₂ , and the like) Excimer).

EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples. In addition, the material used in the Example and the comparative example is shown below.
((A1) component)
Rosin resin A: hydrogenated acid-modified rosin, trade name “Pine Crystal KE-604”, Arakawa Chemical Industries rosin resin B: polymerized rosin, trade name “Chinese polymerized rosin 140”, Arakawa Chemical Industries (( B) Ingredient)
Activator A: Suberic acid Activator B: Dibromobutenediol, manufactured by Air Brown (component (C1))
Solvent A: 2,5-dimethyl-2,5-hexanediol (melting point: 86-90 ° C., boiling point: 214 ° C.)
Solvent B: 1,6-hexanediol (melting point: 40-44 ° C., boiling point: 215 ° C.)
((C2) component)
Solvent C: Tetraethylene glycol dimethyl ether (boiling point: 275 ° C., viscosity: 3.8 mPa · s), trade name “Hisolv MTEM”, solvent D: tripropylene glycol monobutyl ether (boiling point: 274 ° C., viscosity: 8) .4 mPa · s)
((C3) component)
Solvent E: Diethylene glycol monohexyl ether (boiling point: 259 ° C., viscosity: 8.6 mPa · s)
Solvent F: 2,2-dimethyl-1,3-propanediol (melting point: 127 to 130 ° C., boiling point: 210 ° C.)
Solvent G: Diethylene glycol monobutyl ether (boiling point: 230 ° C., viscosity: 6.6 mPa · s)
Solvent H: α, β, γ-Terpineol (boiling point: 217 ° C., viscosity: 67 mPa · s), trade name “Turpineol C”, manufactured by Nippon Terpene Chemical Co., Ltd. (component (D))
Solder powder: Alloy composition is Sn-3.0Ag-0.5Cu, particle size distribution is 20-38 μm, solder melting point is 217-220 ° C.
(Other ingredients)
Thixotropic agent: hydrogenated castor oil, trade name “Himakou”, manufactured by KF Trading Co., Ltd .: trade name “Irganox 245”, manufactured by BASF

[Example 1]
Rosin resin A 40% by mass, activator A 2% by mass, activator B 2% by mass, solvent A 5% by mass, solvent C 26.5% by mass, solvent E 14.5% by mass, thixotropic agent 6% by mass and antioxidant 4% by mass. Was put into a container and mixed using a planetary mixer to obtain a flux composition.
Thereafter, 11% by mass of the obtained flux composition and 89% by mass (100% by mass in total) of the solder powder were put into a container and mixed with a planetary mixer to prepare a solder composition.

[Examples 2 to 5]
A solder composition was obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 1.
[Comparative Examples 1 to 11]
A solder composition was obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 1.

<Evaluation of solder composition>
Evaluation of the solder composition (void, printability, solder meltability, adhesion, viscosity change during continuous printing, copper plate corrosion) was performed by the following method. The obtained results are shown in Table 1.
(1) Void power transistor (size: 5.5 mm × 6.5 mm, thickness: 2.3 mm, land: tin plating, land area: 30 mm ² ) and QFN (size: 6 mm × 6 mm, land: tin plating) A solder composition was printed on a substrate having electrodes capable of mounting a land area (36 mm ² ) using a metal mask (thickness: 0.13 mm) having a corresponding pattern. After that, a power transistor and QFN are mounted on the solder composition, and reflow (in the atmosphere) is performed under conditions of preheating 150 to 180 ° C. for 80 seconds, peak temperature 240 ° C. and melting time for 40 seconds, and a test substrate is manufactured. did. The solder joints in the obtained test substrate were observed using an X-ray inspection apparatus (“NLX-5000”, manufactured by NAGOYA ELECTRIC WORKS). Then, the void ratio [(void area / land area) × 100] in the power transistor and QFN after reflow was measured.
And the void was evaluated according to the following criteria.
○: The void area ratio is 15% or less.
X: The void area ratio is more than 15% and 20% or less.
Xx: Void area ratio is more than 20%.
(2) Printability Diameter 0.2mmφ, 0.22mmφ, 0.24mmφ, 0.26mmφ, 0.28mmφ, 0.3mmφ, 0.32mmφ, 0.34mmφ, 0.36mmφ, 0.38mmφ and 0.4mmφ A test plate was obtained by printing a solder composition on a substrate under conditions of a printing speed of 50 mm / sec and a printing pressure of 20 N using a plate having 100 holes each having a thickness of 0.13 mm. . And the obtained test board was analyzed with the image inspection machine, the volume ratio (missing volume ratio) of the solder composition which pierced was measured about 100 places, and printability was evaluated according to the following references | standards.
○: Out of 100 portions having a diameter of 0.24 mmφ, the missing volume ratio is 70% or more.
Δ: Among 100 places having a diameter of 0.24 mmφ, there are places where the missing volume ratio is less than 70%, but there are places where the missing volume ratio is 70% or more.
X: Out of 100 portions having a diameter of 0.24 mmφ, all missing volume ratios are less than 70%. On the other hand, out of 100 places having a diameter of 0.26 mmφ, the missing volume ratio is 70% or more.
(3) Solder meltability 0.2 mmφ, 0.22 mmφ, 0.24 mmφ, 0.26 mmφ, 0.28 mmφ, 0.3 mmφ, 0.32 mmφ, 0.34 mmφ, 0.36 mmφ, 0.38 mmφ and 0. A test plate was obtained by printing a solder composition on a substrate under conditions of a printing speed of 50 mm / sec and a printing pressure of 20 N using a plate having a diameter of 0.13 mm, each having 100 4 mmφ holes. It was. Thereafter, the obtained test plate was reflowed (in the atmosphere) under conditions of preheating 150 to 180 ° C. for 80 seconds, a peak temperature of 240 ° C. and a melting time of 40 seconds. And the test board after reflow was observed visually, and solder melting property was evaluated according to the following references | standards.
A: Solder melting was confirmed in the printed portion having a diameter of 0.22 mmφ.
○: Solder melting did not occur in the printed portion having a diameter of 0.22 mmφ, but solder melting was confirmed in the printed portion having a diameter of 0.24 mmφ.
X: Solder melting was not observed in the printed portion having a diameter of 0.26 mmφ or less, but solder melting was confirmed in the printed portion having a diameter of 0.28 mmφ.
(4) Tackiness Tackiness was evaluated according to the following criteria by the method described in Appendix 9 of JIS Z3284 (1994).
○: Adhesive strength after printing is 1 N or more, and the adhesive strength after standing for 12 hours under the condition of 25 ° C. and 50% is 1 N or more.
X: Although the adhesive strength after printing is 1 N or more, the adhesive strength after standing for 12 hours under the condition of 25 ° C. and 50% is less than 1 N.
(5) Viscosity change during continuous printing First, the initial viscosity is measured using a solder composition as a sample. After that, the sample is placed on a metal mask that has been sealed, and a continuous printing test is performed in which the squeegee is continuously moved for 12 hours. And the viscosity of the sample after a continuous printing test is measured. Next, the rate of change in viscosity [{(η2−η1) / η1} × 100] between the initial viscosity value (η1) and the viscosity value (η2) of the sample after the continuous printing test is obtained. The viscosity is measured by spiral viscosity measurement (measurement temperature: 25 ° C., rotation speed: 10 rpm).
And the viscosity change at the time of continuous printing was evaluated according to the following reference | standard based on the result of the viscosity change rate.
○: Viscosity change rate is 10% or less.
X: Viscosity change rate is more than 20%.
(6) Copper plate corrosion A test based on the method described in JIS Z 3197 (1999) was performed. Specifically, the test was conducted by the method described in JIS Z 3197 (1999) except that the test time was changed to 120 hours. And copper plate corrosion was evaluated according to the following reference | standard.
○: No corrosion or discoloration.
Δ: Some corrosion or slight discoloration.

  As is clear from the results shown in Table 1, the solder compositions (Examples 1 to 5) of the present invention have good voids, printability, solder meltability, adhesiveness, and viscosity change results during continuous printing. It was confirmed that. Therefore, it was confirmed that the solder composition of the present invention has excellent solder meltability even when the reflow process is performed in an air atmosphere, can sufficiently suppress voids, and has sufficient printability.

  The solder composition of the present invention can be suitably used as a technique for mounting an electronic component on an electronic board such as a printed wiring board of an electronic device.

Claims (4)

(A) a flux composition containing a rosin resin, (B) an activator and (C) a solvent, and (D) a solder powder having a melting point of 200 ° C. or higher and 250 ° C. or lower,
The component (A) contains (A1) a hydrogenated product of an unsaturated organic acid-modified rosin,
The component (C) includes (C1) a hexanediol solvent having a melting point of 40 ° C. or higher and a boiling point of 220 ° C. or lower, and (C2) a viscosity at 20 ° C. of 10 mPa · s or lower and a boiling point of Containing a solvent that is 270 ° C. or higher,
The solder composition, wherein the blending amount of the component (A) is 30% by mass or more with respect to 100% by mass of the flux composition. The solder composition according to claim 1,
The component (C1) is at least one selected from the group consisting of 2,5-dimethylhexane-2,5-diol and 1,6-hexanediol. In the solder composition according to claim 1 or 2,
The solder composition, wherein the component (C2) is tetraethylene glycol dimethyl ether.   An electronic board comprising a soldering portion using the solder composition according to any one of claims 1 to 3.