JP4033616B2 - Manufacturing method of copper plating material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a copper plating material made of easily soluble copper oxide using basic copper carbonate as a raw material .
[0002]
[Prior art]
As one of the methods of performing copper plating treatment on the object to be plated, there is an electrolytic plating method in which a copper plating material is supplied in sulfuric acid, which is an electrolytic solution, and electricity is passed between the object to be plated that forms an insoluble anode and a cathode. As a copper plating material used in this method, it is known to use copper oxide obtained by thermally decomposing basic copper carbonate (Japanese Patent No. 2753855).
[0003]
Copper oxide is widely used as a raw material for ferrite materials, and is also used as a copper ion replenisher for electroless copper plating baths as described in JP-A-3-80116. In general, it is produced by heat treatment of copper mill scale, cuprous oxide or copper hydroxide, but copper mill scale system is difficult to dissolve, so it cannot be used as a copper plating material, and cuprous oxide system is Cl. Since there are a lot of ions (chlorine ions), plating is poor and cannot be used. In the above-mentioned publication (Japanese Patent Laid-Open No. 3-80116), it is described that copper hydroxide is obtained by heating copper hydroxide at 60 to 100 ° C., but cupric hydroxide is used for Cl ions and SO4 bodies. Since there is much S, when it uses for electrolytic plating, it will become a plating defect. On the other hand, copper oxide obtained by thermally decomposing basic copper carbonate can be used as a copper plating material because it contains less Cl ions and S in SO4 form.
[0004]
[Problems to be solved by the invention]
However, the use of copper oxide obtained by thermally decomposing basic copper carbonate as a copper plating material has the following problems.
[0005]
a. Since copper oxide is usually used as a raw material for ferrite, it is required that the weight of the ferrite be reduced, particularly in the sintering process, so that the heating temperature when the raw material is pyrolyzed or heat-treated is generally 900 ° C. or higher. However, although the obtained copper oxide is more soluble than general copper oxide, the degree of solubility is not so high. For this reason, it takes a long time for the copper plating material to dissolve in the electrolytic solution when the copper plating material is replenished to the copper plating bath (the solution in which the copper plating material is supplied to the electrolytic solution), resulting in uneven copper ion concentration. This causes variations in quality and causes a reduction in processing efficiency.
[0006]
b. As a normal cracking furnace, a rotary kiln with direct heating using a frame that emphasizes thermal efficiency is commonly used, but when the reducing flame of the frame comes into contact with copper carbonate or copper oxide, cuprous oxide or metallic copper is unified. Will be generated. These cuprous oxides and metallic copper lead to an increase in insoluble residues as impurities when dissolved in sulfuric acid, which is an electrolytic solution, and the copper concentration in the electrolytic solution becomes unstable, that is, the copper plating material that should be at a constant concentration. The quality is lost and the quality of the plated product becomes unstable.
[0007]
c. Impurities contained in the basic copper carbonate itself brought from the raw material of the basic copper carbonate, such as a small amount of alkali metals (Na and K) and alkaline earth metals (Mg and Ca), Cl ions and SO4 form S, etc. In the copper oxide obtained by thermal decomposition, for example, it is concentrated about 1.4 to 1.5 times. If Cl ions are accumulated in the plating bath, the surface of the object to be plated becomes rough or precipitates in the form of knobs or needles occur, resulting in a product defect. If S in the SO4 body accumulates, it not only adversely affects the plating state but also makes it difficult to control the SO4 concentration in the plating bath, resulting in unstable quality of the plated product. Furthermore, when alkali metal or alkaline earth metal accumulates, there is a concern about the precipitation of those sulfates on the plating surface, and there is a concern that the frequency of building baths will increase.
[0008]
For this reason, in the case of continuous operation using copper oxide as a direct plating material, these impurities are accumulated in the plating bath. If the accumulated amount reaches the upper limit for management, plating failure will occur, so it is necessary to build a plating bath earlier than planned, but the plating bath is very expensive, so it is costly to operate the system. It will lead to up.
[0009]
The present invention has been made under such a background. The object of the present invention is to provide an easily soluble copper oxide that is highly soluble and can suppress the formation of insoluble residues, and further has less impurities. It is to provide an easily soluble copper oxide. Another object is to provide a copper plating material that is highly soluble and can suppress the formation of insoluble residues. Still another object is to provide a copper plating method using high-purity, readily soluble copper oxide.
[0010]
[Means for Solving the Problems]
The present invention, in a method for producing a copper plating material comprising a readily soluble copper oxide,
A step of mixing copper chloride or copper sulfate with an alkali metal, alkaline earth metal or NH ₄ carbonate aqueous solution and reacting while heating to obtain basic copper carbonate;
A step of obtaining easily soluble copper oxide by heating to 250 ° C. to 800 ° C. in an atmosphere that is not a reducing atmosphere and thermally decomposing basic copper carbonate, and then washing the easily soluble copper oxide with water; It is a manufacturing method of the copper plating material characterized by including . Heating in an atmosphere that does not become a reducing atmosphere is, for example, heating using an electric furnace or the like, not directly by a burner.
[0011]
As the basic copper carbonate, commercially available ones may be used, while mixing and heating an aqueous solution of copper chloride, copper sulfate or copper nitrate and an aqueous solution of an alkali metal, alkaline earth metal or NH4 carbonate, for example. The reaction product thus precipitated may be obtained by filtration and separation. In this case, mixing the carbonate aqueous solution with the copper chloride, copper sulfate or copper nitrate aqueous solution means that the carbonate is added to the copper chloride, copper sulfate or copper nitrate aqueous solution in a solid state to convert the carbonate into the aqueous solution. On the contrary, the case where a solid solution of copper chloride, copper sulfate or copper nitrate is added to an aqueous carbonate solution to form an aqueous solution is also included. Since the easily soluble copper oxide according to the present invention has high solubility, for example, it is preferably used as a copper plating material supplied to an electrolytic solution provided with an insoluble anode and a body to be plated. Can do. In this case, if the copper plating material contains a large amount of the above-mentioned impurities, the quality of the plated product is deteriorated, so that the basic copper carbonate is alkali metal (Na or K), alkaline earth metal (Mg or Ca), and When many impurities such as anions (Cl ions and SO4 ions) are contained, it is preferable to wash the readily soluble copper oxide obtained by thermal decomposition with water.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a commercially available product may be purchased as basic copper carbonate, which is a raw material for easily soluble copper oxide, but in this embodiment, it is manufactured on the factory side without purchasing basic copper carbonate. And FIG. 1 is an explanatory view showing the production flow in this case. For example, an aqueous solution of cupric chloride (CuCl2) having a copper concentration of 10% by weight and an alkali metal carbonate, for example, a carbonic acid having a carbonic acid concentration of 7% by weight. An aqueous solution of sodium (Na2 CO3) is introduced into the reaction vessel 1 so that the pH of the mixed solution becomes, for example, 7-9, and is stirred by the stirring means 11 while being heated so that the temperature of the mixed solution becomes, for example, 70 ° C. Stir for 30 minutes to react. The liquid mixture is heated by, for example, providing bubbling means such as an air diffuser (not shown) in the reaction tank 1 and bubbling vapor from the bubbling means into the liquid mixture.
[0014]
The above reaction proceeds as follows. First, copper carbonate is generated as in equation (1),
Na2 CO3 + CuCl2 → CuCO3 + 2NaCl (1)
Subsequently, copper carbonate is hydrated as shown in formula (2) to produce basic copper carbonate dihydrate,
CuCO3 + 3 / 2H2 O → 1/2 {CuCO3 · Cu (OH) 2 · 2H2 O} + 1 / 2CO2 (2)
Furthermore, as shown in the formula (3), water is released from the dihydrate, and anhydrous basic copper carbonate is generated.
[0015]
CuCO3 · Cu (OH) 2 · 2H 2 O → CuCO 3 · Cu (OH) 2 + 2H 2 O (3)
In this way, basic copper carbonate is precipitated and formed into a powder. And the valve | bulb 12 is opened, the slurry which is a deposit is extracted, and it sends to the centrifuge 2, and solid content is isolate | separated from mother liquor here by centrifugation, The solid content is put into the dryer 3, and it is dried, and is basic. Obtain copper carbonate powder.
[0016]
As a copper ion source which is a raw material of basic copper carbonate, an aqueous solution of a copper salt such as copper sulfate or copper nitrate can be used in addition to copper chloride. Sources of carbonate ions include sodium carbonate, alkali metal carbonates such as sodium bicarbonate and potassium carbonate, alkaline earth metal carbonates such as calcium carbonate, magnesium carbonate, and barium carbonate, or ammonium carbonate ((NH4) 2 CO3) or the like can be used.
[0017]
Next, the basic copper carbonate as a powder is supplied to a heating furnace, for example, a rotary kiln 4, where it is heated to a temperature of, for example, 250 ° C. to 800 ° C. and thermally decomposed. In this example, as a heating furnace, a rotating tube 41 made of, for example, stainless steel that rotates with a tube axis serving as a rotating shaft is provided with a slight inclination, the rotating tube 41 is surrounded by a heater 42, and the rotating tube 41 is rotated. Thus, a rotary kiln for transferring basic copper carbonate powder is used. If basic copper carbonate is heated in this way, the heating atmosphere does not become a reducing atmosphere. The reason why basic copper carbonate is not heated directly with a burner is that when it is in a reducing atmosphere, copper carbonate itself or copper carbonate is decomposed into copper oxide, and then partially reduced to cuprous oxide (Cu2 O) or metal This is because copper (Cu) is generated, which is avoided.
[0018]
When copper oxide is used as a copper plating material, metallic copper does not dissolve or hardly dissolves in sulfuric acid, which is an electrolytic solution, and becomes an insoluble residue and requires new filtration equipment. Further, when metallic copper or cuprous oxide is formed, the amount of copper to be supplied into the plating bath is not constant, and the quality of the plated product varies. Therefore, it is necessary not to use a reducing atmosphere when heating basic copper carbonate.
[0019]
As for the heating temperature, if it is 250 ° C., for example, copper oxide can be obtained by heating it for about 2 hours, but it is not thermally decomposed at 200 ° C. It is necessary to heat at 250 ° C. or higher because it is known that thermal decomposition is not complete at 220 ° C. even in differential thermal analysis, but in order to shorten the time of thermal decomposition and increase production efficiency Is preferably 350 ° C. or higher. If it exceeds 800 ° C., the resulting copper oxide is less readily soluble, so it is necessary that the temperature be 800 ° C. or lower. Furthermore, when it is going to obtain copper oxide with much easier solubility, it is preferable to make it 600 degrees C or less.
[0020]
After obtaining copper oxide in this way, this copper oxide is put into a washing tank 5 containing pure water as a washing liquid, and is stirred by the stirring means 51 and washed with water. Then, the valve 52 is opened, the mixed slurry of water and copper oxide is taken out from the washing tank 5, water is removed by the centrifuge 6 or the filter, and then dried by the dryer 7 to obtain copper oxide as powder. . As the cleaning liquid, pure water such as distilled water or ion-exchanged water can be used, but water having a lower impurity content than that, such as ultrapure water, can also be used.
[0021]
An example of an apparatus for carrying out a copper plating method using copper oxide as a replenisher for the copper plating material is shown in FIG. In FIG. 2, reference numeral 8 denotes a plating bath, which is filled with a plating bath in which copper oxide is dissolved in sulfuric acid, which is an electrolytic solution, and an insoluble anode 81 connected to the positive electrode side of the DC power source E, such as a titanium plate. A white metal platinum iridium coded in a ratio of 7: 3 and a material 82 to be plated, which is a cathode connected to the negative electrode side of the DC power source E, are immersed. 83 is a dissolution tank, and when the copper ions in the plating bath 8 are reduced, a predetermined amount of copper oxide powder is replenished into the dissolution tank 83 from a hopper 84 as a supply source and stirred by the stirring means 85. After dissolving in sulfuric acid, the pumps P1 and P2 are operated to circulate the plating bath, and then the next copper plating process is performed. F is a filter.
[0022]
According to the above-mentioned examples, since the basic copper carbonate is thermally decomposed at 250 to 800 ° C., the obtained copper oxide has high solubility and can be heated in a reducing atmosphere as can be seen from the examples described later. Since it is not decomposed, the formation of insoluble residue components such as cuprous oxide and metallic copper is suppressed, and when copper oxide is used as a copper plating material, the filter is hardly loaded and the copper ions in the copper plating bath The concentration of is stable.
[0023]
And basic copper carbonate contains the anion and cation according to the raw material. For example, when an aqueous solution of cupric chloride (CuCl2) and an aqueous solution of sodium carbonate (Na2 CO3) are used as raw materials, Cl ions and Na ions are contained in the basic copper carbonate. When dicopper (CuSO4) is used, Na ions and SO4 ion bodies S are contained. These Cl ions or SO4 ions such as S, Na, and K can hardly be reduced or purified even by washing the basic copper carbonate, but the basic copper carbonate is supported by the examples described later. When these are thermally decomposed and changed to copper oxide and then washed, these impurities can be reduced. Therefore, when used as a copper plating material, the time until the impurity concentration reaches the upper limit in management becomes longer, so the time until reaching the building bath becomes longer, and the cost increase can be suppressed.
[0024]
【Example】
( Reference Example 1-1)
In the previous embodiment, the basic copper carbonate was heated at 400 ° C. for about 60 minutes and thermally decomposed to obtain copper oxide.
[0025]
( Reference Example 1-2)
In the previous embodiment, the basic copper carbonate was heated at 600 ° C. for about 60 minutes and thermally decomposed to obtain copper oxide.
[0026]
( Reference Example 1-3)
In the previous embodiment, basic copper carbonate was heated at 700 ° C. for about 60 minutes to thermally decompose to obtain copper oxide.
[0027]
( Reference Example 1-4)
In the previous embodiment, basic copper carbonate was heated at 750 ° C. for about 60 minutes to thermally decompose to obtain copper oxide.
[0028]
( Reference Example 1-5)
In the previous embodiment, basic copper carbonate was heated at 800 ° C. for about 60 minutes to thermally decompose to obtain copper oxide.
[0029]
(Comparative Example 1)
In the previous embodiment, basic copper carbonate was heated at 900 ° C. for about 60 minutes and thermally decomposed to obtain copper oxide.
[0030]
In order to grasp the solubility when copper oxide is supplied to the copper plating bath as a copper plating material, the copper oxides of Reference Examples 1-1 to 1-5 and Comparative Example 1 each have a H2 S04 concentration of 245 g / liter. 550 g was added to 10 liter of sulfuric acid aqueous solution and dissolved. When the electric conductivity of the solution in the dissolution process in each sample was measured, the results shown in FIG. 3 were obtained. 4 and 5 are graphs of the results as changes in conductivity over time. When the conductivity value becomes constant, the dissolution is completed, and the time from the addition of the copper oxide powder to the dissolution end time is measured and taken as the dissolution time. The dissolution time in each sample is as shown in FIG. is there. From this result, it can be seen that the solubility at the time of thermal decomposition of the basic copper carbonate is high up to 800 ° C., but the solubility is low at 900 ° C. Further, since the dissolution time is shortened as the temperature during pyrolysis is decreased from 800 ° C. to 600 ° C. (the solubility is increased), the temperature is lower than 800 ° C., for example, 600 ° C. or less. More preferred. The reason why the solubility becomes lower at higher temperatures is considered to be due to the progress of solid-phase sintering of the copper oxide produced by decomposition.
( Reference Example 2)
In the previous embodiment, the basic copper carbonate was heated at 400 ° C. for about 60 minutes and thermally decomposed to obtain copper oxide.
[0031]
(Comparative Example 2-1)
Copper oxide was obtained in the same manner as in Example 2 except that a rotary kiln having a reducing atmosphere that could be directly heated by a burner was used.
[0032]
(Comparative Example 2-2)
Copper oxide was obtained in the same manner as in Example 2 except that the thermal decomposition temperature of basic copper carbonate was 900 ° C.
[0033]
550 g of the copper oxides of Reference Example 2, Comparative Example 2-1, and Comparative Example 2-2 were added to 10 liters of an aqueous sulfuric acid solution having an H2 SO4 concentration of 245 g / liter, and dissolved. After dissolution, the solution was filtered and the amount of insoluble residue remaining on the filter paper was measured. The result shown in FIG. 7 was obtained. From this result, when the basic copper carbonate is pyrolyzed in a reducing atmosphere, there is a large amount of insoluble residue. In contrast to this, it can be seen that according to the present invention, the amount of insoluble residue can be greatly reduced.
[0034]
(Example 3) In the previous embodiment, basic copper carbonate was heated at 400 ° C for about 60 minutes to thermally decompose to obtain copper oxide, washed with water under the following water washing conditions, and contained in the copper oxide before and after water washing. When the concentrations of Na and Cl were examined using ICP-AES (Induction Plasma Emission Spectrometer) or a titrator, the results shown in FIG. 8 were obtained. Washing conditions: 500 g of copper oxide powder is put into 4500 g of water, stirred for 10 minutes, then filtered and washed with water. The water washing used 5000 g of water for 500 g of copper oxide powder. In the case of basic copper carbonate, the concentration of Na and Cl cannot be reduced by washing with water. However, in the case of copper oxide, the washing with water is very effective in reducing the impurity concentration.
[0035]
( Reference Example 4)
Electroplating was performed under the following conditions using copper oxide having a chlorine concentration (Cl concentration) of about 20 ppm as a copper supplement.
[0036]
Electroplating conditions / Anode: Titanium covered with platinum group (Pt: Ir = 7: 3) Cathode: Copper plate / electrode area: 10 cm × 10 cm
・ Current density, current, voltage: 1A / dm2, 1A, 2,2 V
-Copper concentration 18 g / liter as Cu-Sulfuric acid concentration The chlorine concentration in the plating bath at the start of 180 g / liter as H2 S04 was adjusted to about 20 ppm. When copper oxide was supplied so as to keep the copper concentration constant, the chlorine concentration in the bath did not increase but decreased. For this reason, in order to keep the chlorine concentration in the bath constant, the chlorine content is added at 5 to 20 ppm / day. From this result, it is considered that the amount of chlorine generated from the anode is larger than the amount of chlorine contained in the supplied copper oxide. The surface of the finally obtained cathode was very flat and smooth.
[0037]
( Reference Comparative Example 4)
Electroplating was performed under the same conditions as in Reference Example 4 above using copper oxide having a chlorine concentration of about 140 ppm as a copper replenisher.
[0038]
The chlorine concentration in the plating bath at the start was adjusted to about 20 ppm. When copper oxide was supplied so as to keep the copper concentration constant, an increase in the chlorine concentration of 2-4 ppm / day occurred in the plating bath. This is considered to be because the amount of chlorine contained in the supplied copper oxide is larger than the amount of chlorine generated from the anode. After 40 days, the chlorine concentration in the plating bath was about 150 ppm. The surface of the finally obtained cathode was rough as compared with Reference Example 4.
[0039]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a readily soluble copper oxide that has high solubility and can suppress the formation of insoluble residues. Moreover, a highly purified thing is obtained by wash | cleaning easily soluble copper oxide, For example, it can use suitably as a copper plating material in electrolytic plating. When electrolytic plating is performed using this easily soluble copper oxide as a copper plating material, a good plating process can be performed, and the time until reaching a building bath is lengthened, thereby suppressing an increase in cost.
[Brief description of the drawings]
FIG. 1 is a process diagram showing an embodiment of a method for producing a readily soluble copper oxide of the present invention.
FIG. 2 is a configuration diagram showing an example of a plating apparatus used in the plating method of the present invention.
FIG. 3 is an explanatory diagram showing, as a table, changes in conductivity with time when the thermal decomposition temperature of basic copper carbonate is a parameter and copper oxide is added to sulfuric acid.
FIG. 4 is an explanatory diagram showing the change over time of the conductivity shown in FIG. 3 as a graph.
FIG. 5 is an explanatory diagram showing, as a graph, the temporal change in conductivity shown in FIG.
6 is an explanatory diagram showing the dissolution time of copper oxide obtained at each thermal decomposition temperature based on the result of FIG. 3. FIG.
FIG. 7 is an explanatory diagram showing the relationship between the thermal decomposition conditions of basic copper carbonate and the amount of insoluble residue.
FIG. 8 is an explanatory diagram showing the relationship between the presence or absence of copper oxide washing and the amount of impurities.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reaction tank 2 Centrifuge 3 Dryer 4 Heating furnace 5 Washing tank 6 Centrifuge 7 Dryer 8 Electrolyzer 81 Insoluble anode 82 To-be-plated object 83 which is a cathode Dissolution tank 84 Hopper

Claims (1)

In a method for producing a copper plating material made of easily soluble copper oxide,
A step of obtaining a basic copper carbonate by mixing an aqueous solution of copper chloride or copper sulfate with an aqueous solution of alkali metal, alkaline earth metal or NH ₄ carbonate and reacting while heating;
A step of obtaining easily soluble copper oxide by heating the basic copper carbonate to 250 ° C. to 800 ° C. in an atmosphere that is not a reducing atmosphere and thermally decomposing it;
Then, the process of washing this easily soluble copper oxide with water, The manufacturing method of the copper plating material characterized by the above-mentioned.

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