JPS6039167A - Method for regenerating chemical copper plating solution - Google Patents

Abstract

PURPOSE:To recover and reuse a chelating agent by adjusting a deteriorated plating soln. to a specified pH or below to deposit a chelating agent, adjusting the deposited chelating agent to a specified pH or below, and carrying out deposition and purification. CONSTITUTION:A deteriorated chemical copper plating soln. contg. Cu ions, a Cu ion chelating agent, a Cu ion reducing agent and an alkali metallic hydroxide as a pH adjusting agent is adjusted to <=4pH by adding sulfuric acid or hydrochloric acid to deposit the chelating agent, and the agent is precipitated and separated. The separated chelating agent is adjusted to <=4pH by adding sulfuric acid or hydrochloric acid to prepare a mixed aqueous soln. contg. a deposit of the chelating agent. A soln. contg. no deposit is taken selectively and continuously out of the mixed aqueous soln., and it is passed through an electrodialytic vessel and returned to the mixed aqueous soln. Thus, the chelating agent is recovered, purified, and is reused.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating a chemical copper plating solution, and more particularly to a method for purifying and recovering a chelating agent from a used and degraded chemical copper plating solution.

Chemical copper plating and the like are widely used in the electronic industry as a means of imparting electrical conductivity to the surface of electrically insulating substrates such as glass and epoxy resin. Sodium salt of ethylenediaminetetraacetic acid for chemical copper plating.

Copper ion chelating agents such as Rossell's salt, copper sulfate.

A chemical copper plating solution that is an alkaline aqueous solution containing a copper compound such as copper chloride and a reducing agent such as formaldehyde or paraformaldehyde is used.

Continuous use of such a chemical copper plating solution consumes the main components in the plating solution.

As a result, copper ions are consumed by the reaction of chemical copper plating, and copper ions are replenished to maintain the optimum concentration of copper ions in the plating solution. In this case, the copper ions to be replenished are supplied as an aqueous solution of a copper compound.

Therefore, when the copper compound is repeatedly replenished, the counter anion of the copper ion is accumulated in the plating solution.

Since copper sulfate or copper chloride is used as the copper compound, sulfate ions or chloride ions accumulate.

On the other hand, formaldehyde or paraaldehyde is used as a reducing agent for copper ions, but the reducing agent changes to formic acid as a result of an oxidation reaction in the plating solution.

This formic acid change in the reducing agent is also accumulated due to the replenishment of the copper ion reducing agent as the plating solution is continuously used.

Furthermore, since chemical copper plating solutions are generally alkaline solutions, they absorb carbon dioxide gas in the air and accumulate carbonate ions in the entire plating solution. These accumulated ions increase the ionic strength of the plating solution and trap divalent copper ions, causing a total loss of stability of the plating solution, decomposing the plating solution, and impairing the mechanical properties of the plated copper film. lower. Therefore, when the anions accumulate, part or all of the plating solution is replaced with a new one, and the old plating solution is discarded.

For this reason, there is a drawback that the cost of chemicals used for plating and the cost of treating degraded liquid are extremely high. Furthermore, looking at the breakdown of costs in detail, the cost of the chelating agent is generally relatively high among the chemicals required to prepare and replenish a new plating solution. Furthermore, since it is almost impossible to treat all of the degraded liquid contained in the chelating agent using the general neutralization method, it has been necessary to incinerate it. For this reason, chelating agent 1
The conventional method of encapsulation is to first recover the metallic copper in the degraded plating solution through electrolytic treatment, then use an acid such as sulfuric acid to lower the P value of the plating solution, precipitate a chelating agent, and separate and recover it. There was a way. However, with this method, most of the metals and other impurities contained in the plating solution cannot be removed, so it has been almost impossible to reuse the recovered chelating agent.

An object of the present invention is to provide a method that overcomes the drawbacks of the conventional methods for regenerating chemical copper plating solutions and recovering chelating agents.

According to the invention, in chemical copper plating that mainly contains copper ions, copper ion chelating agents, copper ion reducing agents, and alkali metal hydroxides as pH adjusters, sulfuric acid or hydrochloric acid is added to the deteriorated plating solution. Added P) T value wo 4
．． A step of precipitating and separating the chelating agent by adjusting the pH value to 0 or less, and adding sulfuric acid or hydrochloric acid again to the separated chelating agent to adjust the pH value to 4.0 or less to produce a mixed aqueous solution containing the chelating agent precipitate. and a step of selectively and continuously taking out all of the solution to remove the chelating agent precipitates from this mixed aqueous solution, passing it through an electrodialysis tank, and returning it to the mixed aqueous solution. A method for regenerating a chemical copper plating solution is obtained, which comprises a step of recovering and purifying a chelating agent by removing iron and other metal ions, sulfate ions, chloride ions, and other anions.

Hereinafter, the invention will be explained with reference to examples.

Prior to the examples, the test methods used in the examples will be described.

A stainless steel plate with a thickness of 1 mm x width of 100 mm x length of 15 Q mm was used as a copper plating sample. It was activated in advance with an acidic aqueous solution of a mixed salt of tin(II) chloride, and the entire surface was coated with copper to a thickness of approximately 30 μm. After applying.

Peel off the copper plating film to create an area of 5mm x 100mm.
The sample was cut into a size of 5-2 to prepare a sample for a tensile test, and the tensile strength of the copper plating film was completely measured using a tensile tester.

The concentration of the components in the chemical copper plating solution is automatically detected during the plating process, and using a plating solution automatic management device (not shown) that automatically replenishes the missing amount of the main component, The concentration was controlled. Regarding the stability of the plating solution, the time when the plated surface was visually observed to exhibit a brownish color was determined to be the point at which the plating solution decomposed. and details with drawings.

Table 1 Table 1 shows the standard composition of the plating solution used in the invention, and the volume is 2.
01! It is. This plating solution was designated as I41. Step 1 is a step of forming a 30 μm thick plating layer on a stainless steel plate using this plating solution.

Next, 3 ppm of iron sulfate (pe804°782
0)'i plus 20+)I) as a primary nickel ion
m units of nickel sulfate (Ni804.7H20) were added.

Next, in the same way, 500 ppm as anion impurities.
Salt ['(r) was added as a unit of chlorine ion, and hydrofluoric acid was added as a fluorine ion in units of sooppm.The plating solution containing this known concentration of impurities was designated as sample Na2.This sample Na2-104 Sample No. 3 is a plating solution prepared by recovering the chelating agent from the plating solution using the conventional method and using the recovered chelating agent again. Measurements were taken to analyze the type and concentration.
The step of providing a 0 μm plating layer is the second step.

Next, the same type and amount of impurities were added to the plating solution of Sample No. 3 in the same manner as described above, and the chelating agent was recovered from the solution using a conventional method.

The plating solution used in the plating bath using the recovered Clean-1 agent was designated Sample 4, and the sample obtained by repeating the operation sound was designated as the plating solution No. 5.

Measurements were taken to analyze the type and concentration of impurities. These samples Na4. A process of forming a 30 μm thick plating layer on each stainless steel plate using a Na5 plating solution The third step and the fourth step were performed depending on the order of the metals.

Each of the above plating solution samples 1. Na3. 4. FIG. 1 shows the types and concentration changes of each impurity corresponding to the number 5.

Furthermore, the changes in tensile strength and stability of the plating solution plated in each of the first to fourth steps are shown in Figure 2 and Table 2, respectively.

WJz table Next, all of the same types and amounts of impurities were added to the remaining plating solution of sample Na2 as in the conventional method.

The chelating agent was recovered by the method of the present invention and used again to prepare a plating solution, and the process of forming a 30 μm thick plating layer on a stainless steel plate was repeated. Figure 3 shows the changes in the type and concentration of each impurity corresponding to the plating solution sample in each step) h3', 4', and 5', and further in each of the steps 2/, 3/, and 4/. The changes in tensile strength and stability of the plating solution are shown in Figure 4 and Table 3, respectively.

As shown in Table 3 above, the plating solution prepared by recovering the chelating agent using the conventional method and using the recovered chelating agent increases the amount of impurities as the number of plating processes increases, as shown in Figure 1. In plating solution 1, iron ions are Q, 5p as the content increases.
Plating solution N had nickel ions below 9-pm, nickel ions below o, sppm, chlorine ions below 1101) p, and fluorine ions below 5 ppm.
In No. 15, the iron ion concentration is 3.71)I)m, the nickel ion concentration is 6.8 ppmm, and the chloride ion concentration is 290 ppm.
The mm fluorine ion concentration was 270 m)I)m. Therefore, as shown in FIG. 2, the expansion force of the plated adherend plated using the above-mentioned plating solution-5 was significantly reduced. Specifically, the expansion force value of the plating deposit plated with plating solution N111 before adding impurities was 60.0 kg/mm2, whereas
The dilatation force value of the plated adherend plated from scratch is 19.0
kg/mm2.Moreover, regarding the stability of the plating solution, as shown in Table 2, the plating solution N
In plating solution a4, the plating solution slightly decomposed, and in plating solution positive 5, the company's plating solution was completely decomposed.

Next, the chelating agent is recovered using an uninvented method, and the plating solution prepared using the recovered chelating agent has almost no increase in impurity content even if the number of plating steps increases, as shown in Figure 3. In the plating solution Na5'10-, the iron ion concentration is less than (,1,51)T)m,
The nickel ion concentration was Q, 5 ppm or less, the chlorine ion concentration was 10 ppm or less, and the fluorine ion concentration was 5 ppm or less. Furthermore, the expansion force of the plated deposit plated from the plating solution 5 mentioned above is as shown in FIG. Almost no decline was observed. Specifically, the expansion force value of the plated adherend plated from the plating solution 5' was 61.0 kg/mm.

According to the present invention, the chelating agent is recovered from the deteriorated chemical copper plating solution and the recovered chelating agent is reused when preparing the chemical copper plating solution. It has been very difficult to recover and reuse the chelating agent because the accumulation causes instability of the chemical copper plating solution and reduces the expansion power of the plating deposit, but the present invention can do so.

The chelating agent can be easily recovered and reused, which has great economic effects.

[Brief explanation of drawings]

FIG. 1 shows the content of impurities accumulated in a plating solution prepared by recovering a chelating agent using the conventional method and preparing a bath using the recovered chelating agent. FIG. 2 shows the change in expansion force of the plated adherend plated with the above-mentioned plating solution. FIG. 3 shows the content of impurities accumulated in a plating solution prepared by recovering a chelating agent using the uninvented method and using the recovered A chelating agent. FIG. 4 shows the change in expansion force of the plated adherend plated using the plating solution described in M. '-11, Agent Patent Attorney Uchihara 1 ゝ・日・, 16.・ -i Meng] Layer 7 Ding Re 6 ``0 o o () θ (scent ■) zu to ζ (zw” g)/ u completed;

Claims (1)

[Claims] In chemical copper plating, which mainly contains copper ions, copper ion chelating agents, copper ion reducing agents, and alkali metal hydroxides as pH adjusters, sulfuric acid or hydrochloric acid is added to the deteriorated plating solution to reduce the pH value. A step of adjusting the P-H value to 4.0 or less, precipitating the chelating agent and separating it by precipitation, and adding sulfuric acid or hydrochloric acid again to the separated chelating agent to adjust the P-H value to 4.0 or less to remove the chelating agent precipitate. A chemical copper plating solution comprising the steps of: forming a mixed aqueous solution containing the chelating agent; and selectively and continuously extracting a solution from which chelating agent precipitates are removed from the mixed aqueous solution, passing it through an electrodialysis tank, and returning it to the mixed aqueous solution again. How to play.