JPH04323380A - Electroless plating method - Google Patents

Abstract

PURPOSE:To suppress the accumulation of waste matter in a plating soln. in a plating soln. tank by mixing an excess plating soln. overflowing the tank with waste water used to wash a plated body, recovering valuable components from the mixture by electrodialysis and feeding the recovered soln. to the tank. CONSTITUTION:A body to be treated is plated in a plating soln. tank 1 and the plated body is washed. A fresh plating soln. is then fed from a fresh soln. tank 2 to the plating soln. tank 1 and an excess plating soln. 3 overflowing the tank 1 is mixed with waste water 7 used to wash the plated body. Valuable components are recovered from the mixture 8 by electrodialysis with an electrodialyzer 4 and the recovered soln. is fed to the tank 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electroless plating.

0002

[Prior Art] Electroless plating is being reconsidered in recent years as a surface treatment technology that can form a uniform film on any shape of material and can impart various electrical and mechanical properties. The amount tends to increase year by year. However, compared to electroplating, waste products (reaction products) tend to accumulate, making it difficult to maintain constant film quality. Conventionally, in order to prevent quality deterioration due to the accumulation of waste products, part of the plating solution in use has been replaced with new plating solution in batches. The liquid is a difficult-to-process waste liquid that contains harmful components, and the amount of the liquid is quite large, which has posed a problem.

[0003] It is possible to recover valuable components from the waste liquid using electrodialysis, but if the plating stock solution is directly treated with electrodialysis, it will be further concentrated (H2
(O also migrates), this causes problems such as precipitation of the contained components in the equipment piping and on the ion exchange membrane, making it practically unusable.

0004

[Problems to be Solved by the Invention] In view of the above circumstances, an object of the present invention is to provide an electroless plating method that can easily suppress the accumulation of waste products in the plating solution and reduce the amount of waste solution generated. shall be.

[0005]

[Means for Solving the Problems] In order to solve the above problems, in the electroless plating method according to the present invention, after plating the workpiece in a plating solution tank filled with an electroless plating solution, In a method in which the object to be treated is washed with water, a new plating solution is continuously supplied to the plating solution tank, and surplus plating solution overflows from the plating solution tank as the new plating solution is supplied and waste water generated from the washing. The system is configured such that a valuable component recovery solution is obtained from this mixed solution by electrodialysis, and this recovery solution is supplied to the plating solution tank.

[0006] The electroless plating method of the present invention will be specifically explained below with reference to the drawings. FIG. 1 is a block diagram showing an electroless plating system to which an example of the electroless plating method according to the present invention is applied. The plating solution tank 1 is filled with an electroless plating solution for plating a processed object (an object to be plated) to be immersed. This electroless plating solution contains metal ions, a complex of metal ions, a reducing agent, p
Although it contains an H adjuster and additives, the metal ions, reducing agent, pH adjuster, additives, etc. that are consumed by the plating reaction are replenished by the controller 5. Although the electroless plating solution used in this invention is not limited, specifically, those having the following compositions are exemplified.

(A) Electroless copper plating solution Copper sulfate pentahydrate (for metal ions)
...10g/liter
Disodium ethylenediaminetetraacetate (complexing agent)...
30g/liter Sodium hydroxide (pH adjuster)
...Amount to adjust pH to 12.8 Formalin solution - 35% (reducing agent)
...5ml/liter Sulfur-based additive (for stability)
...small amount surfactant

...small amount Bath temperature conditions
・・・
・65℃ (B)
Electroless nickel phosphor plating solution Nickel sulfate hexahydrate (for metal ions)...30g
/liter Sodium hypophosphate (reducing agent)
...30g/liter glycine (complexing agent)
...20g/liter sodium citrate (complexing agent)
...20g/liter Sodium hydroxide (p
H adjuster) ・・・pH5
．． 5 Amount of lead-based additive (for stabilization)
...a small amount
surfactant
...small amount Bath temperature conditions
... A fixed amount of new plating solution is continuously supplied to the 90° C. plating tank 1 from the new solution tank 2 by a pump 6 or the like. Continuous supply of new plating solution can be divided into two types: continuous supply, which continues to flow all the time, and intermittent supply, which flows a predetermined amount at predetermined time intervals; however, the former continuous supply is preferable. The amount of fresh plating solution supplied is, for example, about 1/20 of the capacity of the plating solution tank 1 per hour.

Surplus plating solution overflowing from the plating solution tank 1 due to the supply of new plating solution is received in a surplus solution tank 3. Next, some or all of this surplus plating solution is combined with cleaning waste water in the cleaning tank 7 generated in the process of cleaning the object to be treated (a diluted plating solution since the object to be treated contains the plating solution taken out from the plating solution tank 1). (equivalent to) are charged into a dialysis tank 8 and mixed, and this mixed solution is passed through an electrodialyzer 4 to obtain a recovered solution containing valuable components such as metal ions, metal ion complexes, and reducing agents. Valuable components in cleaning wastewater can also be recovered. It is diluted once by adding washing waste water, but it is not concentrated by electrodialysis and becomes a suitable state. In this case, a concentration operation in which water is evaporated by heating may also be used, but care must be taken as this may destabilize the recovered liquid.

[0009] If the electroless plating solution is highly alkaline and has problems such as easily corroding the ion exchange membrane used in dialysis, the pH should be adjusted when mixing the excess plating solution and cleaning waste water. You may do so. The amount of waste liquid is reduced by sequentially supplying a fixed amount of the recovered liquid containing valuable components such as metal ions, complexing agents, and reducing agents to the plating solution tank 1 recovered by electrodialysis. but,
If the plating solution was supplied to tank 1 in this state,
■“The concentration of the metal ion and complexing agent or the concentration of the reducing agent changes to a point that exceeds the appropriate range.”■”
If some of the additives are removed during electrodialysis, the balance of the additive concentration in the plating solution will be disrupted, resulting in changes in the physical properties of the plating film and changes in the plating solution components. Decomposition may occur and large amounts of waste liquid may be generated.

[0010] Therefore, in cases where there is such a possibility, in order not to disturb the component balance in the plating solution 1,
Before supplying the recovered solution after electrodialysis to the plating tank, adjust the concentrations of metal ions, complexing agents, reducing agents, and additives (and pH adjuster if necessary) in the recovered solution to the new plating solution. It is desirable that the concentration be adjusted by the adjuster 9. Of course, it is possible to directly supply the recovered liquid to the new liquid tank 2 or the plating liquid tank 1 without performing such concentration adjustment, but in this case, the necessary concentration adjustment function is added to the controller 5. However, it is desirable to adjust the density.

[0011] The recovered solution may be supplied alone or in parallel with the new plating solution at a certain ratio. Specifically, the recovered liquid may be added to the new liquid tank 2 and mixed, and then added to the plating liquid tank 1 as part of the new plating liquid. Further, the recovered liquid may be heated to a temperature comparable to the plating bath temperature before being supplied to the plating liquid tank 1 so that the supply of the recovered liquid does not cause fluctuations in the plating bath temperature.

0012

In the electroless plating method according to claims 1 and 2, new plating solution is continuously supplied to the plating solution tank and accumulation of waste products is suppressed, so that the object to be treated can be appropriately plated. In addition, excess plating solution that overflows from the plating solution tank when new plating solution is supplied is mixed with wastewater from washing and supplied to the plating solution tank as valuable component recovery solution, reducing the amount of waste solution generated. . Excess plating solution is diluted with wastewater from washing, and excessive concentration will not cause trouble due to precipitates in the equipment piping or on the ion exchange membrane, so electrodialysis to obtain a recovered solution for valuable components can be performed without any difficulty. I can do it. Another advantage is that valuable components in the wastewater produced during washing can also be recovered.

[0013] In the electroless plating method according to claim 2, before the recovered liquid is supplied to the plating tank, metal ions in the recovered liquid,
Since the concentrations of the complexing agent, reducing agent, and additives are adjusted to match the new plating solution, changes in the physical properties of the plating film and changes in the components in the plating solution tank can be sufficiently suppressed.

[0014]

[Embodiments] Examples of the present invention will be described below. Of course, this invention is not limited to the following embodiments. - Example 1 - The electroless copper plating solution described above was applied to the system shown in FIG. 1, and the system was operated under the following conditions.

The plating solution tank 1 contains plating solution equivalent to 4 turns of plating, and the new solution tank 2 contains 1 plating solution.
Fresh plating solution equivalent to 1/20 of the capacity of plating solution tank 1 was supplied per hour. Further, the copper ions, HCOH, and sodium hydroxide consumed by the plating reaction are replenished by the pump of the controller 5. After 20 hours of operation, the surplus plating solution generated and the primary cleaning wastewater generated in the cleaning process were mixed at a ratio of approximately 4:1, and an electrodialysis device (TS-5-40 manufactured by Tokuyama Soda Co., Ltd.) was used. Dialysis is performed until the total volume of the mixed solution becomes 80%, and copper ions, EDTA,
A portion of HCHO was recovered.

Next, the concentrations of copper ions, EDTA, and HCOH in the electrodialyzed recovered solution were adjusted to be the same as in the new plating solution. In addition, since the sulfur-based additive was extracted during dialysis, the concentration of the sulfur-based additive was also adjusted at the same time so that it was the same as that of the new plating solution. After adjusting the concentration, it was mixed into new liquid tank 2, and plating processing was subsequently performed.

By carrying out the above plating method, it was possible to suppress the accumulation of waste products and to suppress the amount of waste liquid generated to 30% of the conventional amount. Furthermore, since expensive reagents such as EDTA can be recovered and used, the cost of plating solution can be reduced. -Example 2- The same plating process as in Example 1 was performed except that the recovered liquid obtained by the electrodialysis process was directly mixed into the new liquid tank 2 without adjusting the concentration.

However, in this case, a sulfur-based additive analysis and replenishment device was added to the controller to manage the plating bath, but the plating process could be performed without any problems. As in Example 1, the amount of waste liquid generated was able to be suppressed to 30% of the conventional amount while suppressing the accumulation of waste products. Furthermore, EDTA
Since expensive reagents such as those described above can be recovered and used, the cost of plating solutions can also be reduced. Compared to Example 1, there is an advantage that the processing can be simplified because the concentration of the recovered liquid obtained by dialysis is not adjusted.

Example 3 The electroless nickel-phosphorus plating solution described above was applied to the system shown in FIG. 1, and the system was operated under the following conditions. The plating solution tank 1 contained plating solution that had been used for plating equivalent to four turns, and the new plating solution equivalent to 1/20 of the capacity of the plating solution tank 1 was supplied from the new solution tank 2 per hour. Further, the nickel ions, sodium hypophosphite, and sodium hydroxide consumed by the plating reaction are replenished by the pump of the controller 5.

After 20 hours of operation, the surplus plating solution generated and the primary cleaning wastewater generated in the cleaning process were mixed at a ratio of about 4:1, and an electrodialysis device (ST- manufactured by Tokuyama Soda Co., Ltd.) was used.
5-40) until the total amount of the mixed solution became 80%, and a portion of nickel ions, citric acid, glycine, and hypophosphorous acid were recovered. Next, the concentrations of nickel ions, citric acid, glycine, and hypophosphorous acid in the electrodialyzed recovered solution were adjusted to be the same as in the new plating solution. In addition, since the lead-based additive was extracted during dialysis, the concentration of the lead-based additive was also adjusted at the same time so that it was the same as the new plating solution. After adjusting the concentration, it was mixed into new liquid tank 2, and plating processing was subsequently performed.

By carrying out the above plating method, it was possible to suppress the accumulation of waste products and to suppress the amount of waste liquid generated to 30% of the conventional amount. Furthermore, since the reagents can be recovered and used, the cost of plating solution can be reduced.

[0022]

[Effects of the Invention] In the electroless plating method according to claims 1 and 2, new plating solution is continuously supplied to the plating solution tank, and accumulation of waste products is suppressed, so that appropriate plating can be performed on the object to be processed. In addition, excess plating solution that overflows from the plating solution tank when new plating solution is supplied is mixed with wastewater from washing and supplied to the plating solution tank as a recovery solution for valuable components, reducing the amount of waste solution generated. Moreover, since the excess plating solution is diluted with waste water from washing, there is no problem with precipitates in the equipment piping or on the ion exchange membrane due to excessive concentration, and electrodialysis to obtain the recovered solution of valuable components is not necessary. It can be done without any difficulty and is very practical.

In the electroless plating method according to claim 2, in addition to the above, the concentrations of metal ions, complexing agents, reducing agents, and additives in the recovered liquid are refreshed before the recovered liquid is supplied to the plating tank. Since the concentration is adjusted to match the plating solution, there is an advantage that variations in the physical properties of the plating film and variations in the components in the plating solution tank can be sufficiently suppressed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of an electroless plating system to which the electroless plating method according to the present invention is applied.

[Explanation of symbols]

1 Plating solution tank 2 New liquid tank 3 Surplus liquid tank 4 Electrodialysis device 5 Controller 7 Washing tank 8 Dialysis tank 9 Adjuster

Claims (2)

[Claims] [Claim 1] In an electroless plating method in which a workpiece is plated in a plating solution tank filled with an electroless plating solution and the plated workpiece is then washed with water, At the same time, the surplus plating solution that overflows from the plating solution tank due to the supply of the new plating solution is mixed with the waste water generated from the water washing, and valuable components are recovered from this mixed solution by electrodialysis. An electroless plating method characterized in that the collected liquid is supplied to the plating liquid tank. [Claim 2] Before supplying the recovered solution to the plating tank, the concentrations of metal ions, complexing agents, reducing agents, and additives in the recovered solution are adjusted to match the new plating solution. [Claim 1] Electroless plating method as described.