JPS6225749B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating a chemical copper plating solution by removing ions that interfere with chemical copper plating accumulated in the solution, and an apparatus used therefor.

A chemical copper plating solution contains copper ions, a copper ion reducing agent, a copper ion chelating agent, and an alkali metal hydroxide as essential components. In order to continuously perform chemical copper plating, when the copper ions, reducing agents, and hydroxide ions consumed in the plating reaction are replenished, the plating solution contains counteranions and ring atoms of the replenished copper ions. Ions generated by the oxidation reaction of the agent and alkali metal ions accumulate, and carbonate ions accumulate because the alkaline plating solution absorbs carbon dioxide gas in the air.

Accumulation of the above ions causes deterioration and decomposition of the chemical copper plating solution, but until now there has been no effective method to solve the accumulation of ions that interfere with the chemical copper plating reaction. Nakatsuta. Even when a method of renewing deteriorated plating solution by continuously adding new plating solution is used, a large amount of expensive chemical copper plating solution is required, and deterioration cannot be sufficiently suppressed. There were problems and it was not an effective countermeasure.

As mentioned above, the purpose of the present invention is to regenerate chemical copper plating solution that could not be recycled conventionally, to prevent deterioration of mechanical properties of chemical copper plating film due to accumulation of plating-interfering ions, To provide a homogeneous chemical copper plating.

A feature of the present invention is that electrodialysis removes plating-interfering ions that accumulate in a chemical copper plating solution containing copper ions, copper ion reducing agents, copper ion chelating agents, and alkali metal hydroxides. Carbonate ions, which have a low selective permeability due to carbonate ions, are decarboxylated by setting the pH of the chemical copper plating solution to 2 to 8 in advance, and adjusting the selective permeability of the accumulated ion group contained in the chemical copper plating solution to the same level. After that, only the accumulated ions are removed by electrodialysis, or the pH of the chemical copper plating solution is adjusted to 8 to 11 or less, and then only the accumulated ions are removed by electrodialysis.

The chemical copper plating solution to be treated in the present invention includes copper ions, a reducing agent for copper ions, a chelating agent for copper ions, and an alkali metal hydroxide as well as copper ions that are supplied to the solution used for chemical copper plating. It contains a counter anion, an ion produced by the oxidation reaction of the reducing agent, an alkali metal ion, and, in addition, a carbonate ion.

As described above, the ions accumulated in the main plating solution are counteranions of copper ions, ions produced by oxidation reactions of reducing agents, alkali metal ions, and carbonate ions. If copper sulfate is used as a counter anion to the above copper ions, sulfate ions will accumulate. If formaldehyde (or formalin in an aqueous formaldehyde solution) is used as the reducing agent, formate ions will accumulate as ions produced by the oxidation reaction. If sodium hydroxide is used as a hydroxide ion source, sodium ions will accumulate. It has been found that when a chemical copper plating solution containing such accumulated ions is directly regenerated by electrodialysis without any treatment, the following problems occur.

In the chemical copper plating solution, as mentioned above, the only type of cation that accumulates is sodium ion, so there is no problem with electrodialysis. Regarding anions, in addition to the above-mentioned sulfate ions, formate ions, and carbonate ions, there is a copper ion chelating agent that is an essential component of the plating solution, so it can be used in electrodialysis without dialysis. , it becomes necessary to dialyze only sulfate ions, formate ions, and carbonate ions. When a copper ion chelating agent is dialyzed together with the accumulated ions mentioned above, not only is it necessary to carry out special disposal treatment to dispose of the effluent (concentrated solution described later), but also the expensive chelating agent is wasted. . Therefore, it is necessary to make the dialysis of carbonate ions, which are the most difficult to electrodialyze among accumulated ions, much easier than the dialysis of copper ion chelating agents. For this purpose, before electrodialysis, an acid is added externally to the chemical copper plating solution, which is generally used in the pH range of 11.6 to 13.0, to adjust the pH to 2 to 11, and the divalent carbonate ions are converted into carbonate. The removal efficiency of interfering ions can be significantly improved by eliminating them as a gas or converting them into monovalent carbonate ions, which are extremely easy to electrodialyze, and electrodialysis without dialyzing copper ion chelating agents. It provides law.

In the PH treatment in the present invention, the amount of carbonic acid that can exist in the chemical copper plating solution is determined by the dissociation equilibrium of carbonic acid in an aqueous solution and the dissolution equilibrium of carbon dioxide in the air into the plating solution. It is decarboxylated or converted to HCO ₃ ^- by taking advantage of the relationship.
In other words, when the pH of the plating solution is set to 2 to 8, the carbonate ions dissolved in the alkaline chemical copper plating solution will be released into the air as carbon dioxide gas in excess of the equilibrium dissolved amount. The amount of carbon dioxide in the plating solution can be significantly reduced. When the pH is greater than 8 and less than 11, carbonate ions become HCO ₃ ^- and are removed by subsequent electrodialysis.

Therefore, it is essentially different from known plating and PH adjustment during waste liquid discharge.

As the acid used in the above PH adjustment treatment, any acid can be used as long as the acid group does not have a significant adverse effect on the reaction of chemical copper plating, and particularly preferable ones are those in which the acid group (anion) is copper. It corresponds to the counter anion of the ion or the ion produced by the oxidation reaction of the reducing agent.

The principle of the present invention will be explained below with reference to the flow sheet shown in FIG. In FIG. 1, 1 is an electrodialysis tank, and cation exchange membranes (not shown) and anion exchange membranes (not shown) are arranged alternately, and a demineralization chamber 2 and a concentration chamber are provided. 3 and a polar chamber (not shown). As the electrodialysis tank, both known devices and devices that will be developed in the future can be used as long as they are the same in principle. The same applies to ion exchange membranes, but since a highly alkaline chemical copper plating solution is used in the present invention, membranes with particularly excellent alkali resistance are preferred.

In the chemical copper plating tank 4, the chemical copper plating solution that has accumulated interfering ions due to the replenishment solution and the plating reaction and further accumulated carbonate ions is sent to the PH adjustment tank 5, where it is removed from the acid tank 6. The supplied acid is mixed and the pH is adjusted to 2 to 8 to decarboxylate it. At a pH greater than 8 and less than 11, carbonate ions become HCO ₃ ^- which is removed by subsequent electrodialysis. The liquid subjected to the PH adjustment process is supplied to the desalting chamber 2 of the electrodialysis tank 1, electrodialyzed, and then returned to the PH adjustment tank 5. The accumulated ions discharged into the concentration chamber 3 of the electrodialysis tank 1 are returned to the concentrate tank 7. (Figure 2 is the simplest flow sheet.) In this way, the interfering ions in the chemical copper plating solution are removed and the chemical copper plating solution in the PH adjustment tank is regenerated. Become.

The flow sheet described above is an example of the present invention, and the present invention may have a configuration other than the flow sheet shown in FIG. 1 as long as the principles are the same. For example, the present invention also includes a case in which electrodialyzed chemical copper plating solution is directly supplied to a chemical copper plating tank for continuous regeneration, and also a case in which the PH adjustment tank and the chemical copper plating tank are used together. These cases are also included in the present invention.

Next, examples will be explained together with comparative examples and test examples to make the present invention easier to understand. Comparative examples are examples of conventional chemical plating to which the present invention is not applied, Test Example 1 is an example of chemical plating in which only electrodialysis treatment is applied to the plating solution, Test Example 2 is an example of pH adjustment, and Examples are examples of chemical plating according to the present invention. This is an example.

The chemical copper plating operation, the measurement of the plating film, the analysis method of the plating solution, etc. in these comparative examples, test examples, and examples are all the same and are as follows.

First, chemical copper plating is the commonly used copper pyrophosphate electroplating, which is instantaneously plated onto a stainless steel plate to generate plating nuclei for chemical copper plating. A plating film is created using a copper plating solution.

(b) Chemical copper plating liquid Cu (HCOO) ₂ 4H ₂ O 10g EDTA2Na 40g 37% formalin 5ml αα' dipyridyl 20mg Ethoxy surfactant 100mg K ₂ S 0.01mg NaOH Amount to make PH 12.3 Water Amount to make 1 Above The stainless steel plate described above was immersed in a chemical copper plating solution at a temperature of 70°C and a load of 1 d.
Chemically copper plated with m ² /. During plating, the lack of copper ions, formalin, and pH is automatically replenished using replenishment and adjustment solutions. The following compositions are used for the replenishment liquid and adjustment liquid.

(b) Copper ion replenishment solution Cu (HCOO) ₂ 4H ₂ O 100g water 1 amount (c) Formaldehyde replenishment solution 37% formalin 300ml water 1 amount (d) PH adjustment solution NaOH 200g water 1 and During chemical copper plating, air is constantly blown into the plating solution to stir it. Plating to a thickness of approximately 30μ is considered one plating process.The plating film is peeled off from the stainless steel plate, cut into pieces of 1cm x 10cm, and the mechanical properties are measured using a tensile tester. .

The amounts of Na ⁺ , HCOO ^- , and CO ₃ ^2- accumulated in the plating solution are analyzed using a sodium ion electrode and a liquid chromatograph, and the concentrations of copper ions and EDTA are measured using a spectrophotometer and atomic absorption photometer. do.

Comparative Example This comparative example is an example in which neither the PH adjustment treatment of the plating solution nor the electrodialysis of the present invention was applied.

From the composition of the chemical copper plating solution and replenishment solution mentioned above,
The ions that accumulate as the plating reaction progresses are
They are Na ⁺ , SO ₄ ^2- , HCOO ^- and CO ₃ ^2- . The relationship between the mechanical properties of the plating film, the concentration of accumulated components in the plating solution, and the stability of the plating solution when plating was repeated was as shown in the table of FIG.

As is clear from the table in Figure 3, the accumulation of the four component ions described above deteriorates the mechanical properties of the plating film, deteriorates the stability of the plating solution, and reduces The dripping liquid separated.

Test Example 1 In this example, in the chemical copper plating described above, the plating solution was regenerated by performing only electrodialysis without performing the PH adjustment process. That is, this is the case where the acid tank is missing in contrast to the PH adjustment tank in the flow sheet of FIG.

The electrodialysis tank was a DU-Ob type electrodialysis tank manufactured by Asahi Glass Co., Ltd., and the ion exchange membranes were CMU and AMU (manufactured by Asahi Glass Co., Ltd.: strong acidic cation exchange membrane, strong basic anion exchange membrane). ), and is divided into 9 demineralization chambers and 10 concentration chambers alternately. The effective membrane area was 2.09 dm ² and dialysed for 2-3 hours at a current density of 4 A/dm ² . The compositions of the concentrated solution and polar solution used for dialysis were as follows.

(a) Concentrated liquid HCOONa 34g water Amount to make 1 (b) Extremely liquid HCOONa 68g Water Amount to make 1 Initial plating using the above electrodialyzer 4
After the plating was completed, the chemical copper plating solution was regenerated after the plating was completed three times, that is, the number of plating was 4, 7, 10, 13, 16, . . . .

As a result of the above, the measured values shown in the table of FIG. 4 were obtained. In other words, the mechanical properties of the plated film deteriorate due to the accumulation of HCOO ^- , CO ₃ ^2- , and Na ⁺ ions, but electrodialysis can remove HCOO ^- and Na ⁺ ions. It was found that the mechanical properties of the plated film were also recovered by the subsequent plating cycles of 5, 8, 11, 14, 17, . . . . After a total of 10 regenerations, the plating solution was always stable, and the plating film had an elongation of 3% and a tensile strength of 45 kg/mm ² or more.

However, according to this electrodialysis, the selective permeability coefficients based on HCOO ^- are SO ₄ ^2- 1.1 and CO ₃ ^2-
0.5, Cu-EDTA ^2- 0.15, and EDTA ^4- 0.15. Here, Cu−EDTA ²⁻ indicates a chelated copper ion.

In other words, in electrodialysis, the order of dialysis from the demineralization chamber to the concentration chamber is SO ₄ ^2- , HCOO ^- for anions.
≫CO ₃ ^2- ≫Cu−EDTA ^2- , EDTA ^4- ,
SO ₄ ^2- , HCOO ^- can be easily removed from the plating solution, but CO ₃ ^2- is relatively difficult to remove and is an essential component of the plating solution when dialyzed to a concentration as shown in the table in Figure 4. It was found that about 8 to 10% of some Cu-EDTA ^2- and EDTA ^4- plating solutions were removed and lost. (After the 11th plating, the results of dialysis performed before plating are shown in parentheses.) Test Example 2 The chemical copper plating solution described above, that is, the same chemical copper plating solution as in Test Example 1, was used. In the same chemical copper plating operation, formic acid was added to the plating solution with a pH of 12.3 after four platings to bring the pH to 11-2, and the effect of adjusting the pH was investigated. Figure 5 shows when the pH is lower than 8.
This is the relationship between pH, the rate of carbon dioxide removal, and the amount of carbon dioxide remaining in the plating solution. From this, it was found that carbonic acid can be removed in about 30 minutes when the pH of the plating solution is set to 8 or lower, and that a pH of 7 or lower is desirable for removing carbonic acid most efficiently. Note that setting the pH to 2 or less is not good because the chelating agent in the plating solution will precipitate.

Next, add a chemical copper plating solution with a pH of 12.3 to
Chemical copper plating solutions adjusted to 11, 10, 9, and 8 were electrodialyzed in the same manner as in Test Example 1, and the selective permselectivity of carbonic acid in electrodialysis was determined. As a result, the selection of carbonic acid based on HCOO ^- The permeability coefficients were approximately 0, 0.2, 0.6, 0.8, and 1.0 for the above pHs. In other words, if electrodialysis is performed without adjusting the pH of a chemical copper plating solution containing carbonate, carbonate ions will not be removed at all;
It has been found that carbonate ions can be efficiently dialyzed by electrodialysis at a pH of 8 to 11, preferably 8 to 10.

From now on, the regeneration method of the present invention will reduce the pH of carbonate ions in the chemical copper plating solution to 2 through the pH adjustment step.
It has been found that electrodialysis can be carried out by either removing it in advance at a pH of 8 to 11, or adjusting the pH to a value greater than 8 and less than 11 to facilitate electrodialysis.

In addition to the formic acid and sulfuric acid mentioned above, we tried using perchloric acid and acetic acid as acids for pH adjustment, but perchloric acid and acetic acid had the disadvantage of making the plating somewhat unstable because they contained impurities, but they had extremely negative effects. It was also found that it can be used because it does not give any

Example 1 A regeneration method according to the present invention in which a chemical copper plating solution was subjected to a combination of PH adjustment treatment and electrodialysis was carried out as follows. That is, chemical copper plating was performed using the same materials and the same operations as in Comparative Example and Test Example 1, and after the first four platings and the subsequent three platings, the plating solution was cooled to room temperature and placed in a PH adjustment tank. After adjusting the pH of the plating solution to 8 to 9 by adding about 10 to 20 ml of formic acid per chemical copper plating solution, the process was carried out under the same conditions as in Test Example 1 as shown in the flowchart in Figure 1. As such, electrodialysis was performed.

The results are as shown in the table of FIG. 6, and the regeneration by the method of the present invention brought about a remarkable recovery of the mechanical properties of the plated film. In this case, the selective permeability coefficient of carbonate ions in electrodialysis was approximately 1.0 with respect to formate ions. In addition, Cu−, an essential component of plating solution, is produced by electrodialysis.
Discharge of EDTA ^2- and EDTA ^4- to the concentrate (metsuki 14
(The results of electrodialysis performed before plating are shown in parentheses) were also able to be suppressed to 1 to 2% of the original plating solution concentration per electrodialysis. The chelating agent concentration and copper ion concentration in the wastewater generated from dialysis were at a level that could be discharged without reprocessing.

Example 2 Chemical copper plating was performed using the same materials and the same operations as in Comparative Example and Test Example 1. Formic acid was added to the chemical copper plating solution used for plating, the pH was adjusted to 4 to 5, and carbon dioxide in the solution was removed as carbon dioxide gas. Thereafter, electrodialysis was performed under the same conditions as Test Example 1 as shown in the flowchart of FIG.

In this case as well, the mechanical properties of the plating film are stable as in Example 1, and the chelating agent concentration and copper ion concentration in the wastewater generated from dialysis are at a level that can be discharged without reprocessing. Ta.

As can be seen from the above explanation and the results of comparative examples, test examples, and examples, according to the method and apparatus for deionizing chemical copper plating solution of the present invention, chemical copper plating containing carbonate ions, which could not be achieved with the conventional technology, can be deionized. Since it is possible to selectively eliminate accumulated ions that interfere with the plating reaction of the plating solution, the permanent stability of the plating solution and the good mechanical properties of the plating film can be maintained, and the active ingredients can be recovered. Therefore, it can be said that the effects of the present invention are extremely large.

[Brief explanation of the drawing]

FIGS. 1 and 2 are flow sheets showing the deionization operation of a chemical copper plating solution in one example of the present invention. Figure 3 is a table showing the relationship between the accumulation of ions in the chemical copper plating solution and the deterioration of the mechanical properties of the plating film, and Figure 4 shows the relationship between the accumulation of ions in the chemical copper plating solution and the deterioration of the mechanical properties of the plating film. 2 is a table showing the recovery of mechanical properties of a film and the amount of a chelating agent for copper ions discharged by dialysis. FIG. 5 is a graph showing the relationship between PH and carbon dioxide amount when the PH of a chemical copper plating solution is adjusted. FIG. 6 is a table showing the effects of regenerating a chemical copper plating solution by applying both the PH adjustment treatment and electrodialysis according to the present invention. 1...Electrodialysis tank, 2...Demineralization room, 3...Concentration room, 4...Chemical copper plating tank, 5...PH adjustment tank, 6
...Acid tank, 7...Concentrated liquid tank.

Claims (1)

[Claims] 1. The pH of a solution used for chemical copper plating containing copper ions, a copper ion reducing agent, a copper ion chelating agent, and an alkali metal hydroxide as essential components is 2 to 11 with an acid. The solution is adjusted to remove divalent carbonate ions as carbon dioxide gas or convert them into monovalent carbonate ions, and this solution is supplied to the demineralization chamber of the electrodialysis tank to remove chemical copper metal produced and accumulated during chemical copper plating in the solution. A method for removing interfering ions from a chemical copper plating solution, which comprises removing interfering ions and deionizing them. 2 Acids that adjust PH include sulfuric acid, perchloric acid, formic acid,
The method for removing interfering ions from a chemical copper plating solution according to claim 1, which is an acid containing at least one type of acetic acid.