JPH0533146A - Electroless plating method - Google Patents

Abstract

PURPOSE:To obtain a stabilized-quality plating film over a long period by this electroless plating method with the amt. of waste liq. reduced. CONSTITUTION:A material to be treated is electroless-plated in a tank 1 filled with an electroless plating soln., and the plated material is cleaned with water. In this case, a fresh plating soln. is successively supplied to the tank 1, the excess plating soln. overflowing the tank 1 as the fresh soln. is supplied is mixed with the waste water generated by the cleaning, a liq. contg. valuable components is recovered from the liq. mixture by electrodialysis, the recovered liq. is supplied to the tank 1, and at least one among the excess plating soln., liq. mixture and recovered liq. is treated with activated carbon.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electroless plating method.

[0002]

2. Description of the Related Art Electroless plating is capable of forming a uniform film on any shape and material, and its application is expanding year by year as a surface treatment technology that can impart various electrical and mechanical properties. .. However, electroless plating has a problem that it is difficult to maintain the quality of the plating film in a constant state and a large amount of waste liquid is generated because reaction products are more likely to accumulate than electroplating. To prevent the deterioration of the quality of the plating film due to the accumulation of the reaction products, a method of replacing a part of the plating solution in use with a new solution can be dealt with, but in that case, a large amount of plating waste solution is generated.

As the waste liquid generated in the plating process, in addition to the liquid in which the reaction product is accumulated, there is waste water which is a diluted plating liquid generated in the process of washing the plated object to be treated. As a method for reducing the amount of wastewater, Japanese Patent Laid-Open No. 47-3
As disclosed in Japanese Patent No. 4128, there is known a method of performing concentration operation by electrodialysis and returning the obtained concentrated liquid to a plating tank.

In order to reduce the amount of waste liquid generated by the liquid in which the reaction product has accumulated, it has been considered to reuse the liquid in which the reaction product has accumulated by using an electrodialysis method. If it is treated as it is by the dialysis method, it is concentrated, so that there is a problem that the contained components are deposited in the apparatus piping and in the ion exchange membrane, and it could not be put to practical use. Therefore, as described in Japanese Patent Application No. 3-092422, the inventors of the present application apply the plating to the object to be processed in a plating solution tank filled with an electroless plating solution, and then wash the object to be plated with water. In the electrolytic plating method, the new plating solution is continuously supplied to the plating solution tank, and the excess plating solution overflowing from the plating solution tank with the supply of the new plating solution and the waste water discharged by the water washing are mixed, and this mixed solution The electroless plating method has been developed in which a recovery liquid containing valuable components is obtained by electrodialysis and the recovery liquid is supplied to the plating liquid tank. However, subsequent studies have revealed that this electroless plating method causes a problem that a plating film of stable quality cannot be obtained for a long period of time. The reason for this is that the electrodialysis method removes ionic wastes in the solution, but non-ionic wastes are not removed, so the non-ionic wastes not removed remove the plating solution. I confirmed the fact that it was unstable.

[0005]

The problem to be solved by the present invention is to find an electroless plating method which produces a small amount of waste liquid and can obtain a plating film of stable quality for a long period of time.

[0006]

The present invention provides an electroless plating method in which an object to be processed is plated in a plating solution tank filled with an electroless plating solution and then the plated object is washed with water. New plating solution is continuously supplied to the plating solution tank,
The excess plating solution overflowing from the plating solution tank with the supply of the new plating solution is mixed with the waste water discharged from the water washing, and a recovery solution containing a valuable component is obtained from this mixed solution by electrodialysis. The electroless plating method is characterized in that the surplus plating solution, the mixed solution, and / or the recovered solution is supplied to a plating solution tank and treated with activated carbon.

The present invention will be described below with reference to the drawings. FIG. 1 is a conceptual 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 the object to be dipped.
This electroless plating solution contains a metal ion, a metal ion complex, a reducing agent, a pH adjusting agent, an additive, and the like.
Regulators, additives, etc. are replenished by the controller 5. The electroless plating solution used in the present invention is not limited, but specifically, the following compositions and bath temperature conditions are exemplified.

Electroless copper plating solution Copper sulfate pentahydrate (for metal ions) ・ ・ ・ 10 g / liter Disodium ethylenediaminetetraacetate (complexing agent) ・ ・ ・ 30 g / liter Sodium hydroxide (pH adjuster) ・・ ・ Adjusted to pH 12.8 35% HCHO solution (reducing agent) ・ ・ ・ 5 ml / liter Sulfur additive (for stabilization) ・ ・ ・ Small amount Polyethylene glycol (surfactant) ・ ・ ・ Small bath temperature condition ・ ・65 ° C. A constant amount of new plating solution is continuously supplied from the new solution tank 2 to the plating solution tank 1 by using a means such as a pump 6. The form of continuous supply of the new plating solution may be continuous supply or intermittent supply, but continuous supply is preferable in order to stabilize the plating solution. The supply amount of the new plating solution is determined by the consumption amount, and is, for example, about 1/20 of the capacity of the plating solution tank 1 per hour.

Excessive plating solution overflowing from the plating solution tank 1 with the supply of the new plating solution is received by the excess solution tank 3, and then a part or all of the excess plating solution and the object cleaning step are generated. Waste water, which is the diluted plating solution in the wash water tank 7, is put into a dialysis tank 8 and mixed, and the mixed solution is applied to an electrodialysis device 4 to recover valuable components such as metal ions, metal ion complexes and reducing agents. Get the liquid. Here, the excess plating solution that overflows is diluted once by adding waste water that is washed out with water, but is concentrated by electrodialysis to a proper concentration. Further, a concentration operation by heating or the like may be used in combination with the electrodialysis method, but care must be taken because the composition of the obtained liquid may become unstable.

In addition, when the overflowed excess plating solution is highly alkaline and the ion exchange membrane used in the electrodialysis device 4 may be damaged, when the excess plating solution and the cleaning wastewater are mixed, You may adjust pH.

Next, a certain amount of a recovery liquid containing valuable components such as metal ions, complexing agent and reducing agent, recovered by electrodialysis, is sequentially supplied to the plating liquid tank 1 to reduce the amount of waste liquid. However, if it is supplied to the plating solution tank 1 as it is, "the concentration ratio of the metal ion and the complexing agent, or the concentration of the reducing agent changes to a point exceeding an appropriate range", "additive If a part of this is removed during electrodialysis, the balance of the additive concentration in the plating solution will be lost, etc., and the physical properties of the plating film obtained will change, and the components of the plating solution will be decomposed. It may occur and generate a large amount of new waste liquid.

Therefore, when there is such a fear,
Before supplying the recovered solution after electrodialysis to the plating solution tank 1 so that the balance of components in the plating solution tank 1 is not disturbed, metal ions in the recovered solution, complexing agents, reducing agents and additives (further It is preferable that the adjuster 9 adjusts the concentration of the pH adjusting agent) to the new plating solution, if necessary. Of course, it is possible to immediately 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, a concentration adjusting function is added to the controller 5 to perform concentration adjustment. It is desirable to do so.

The recovery solution may be supplied to the plating solution tank 1 alone, or may be supplied in parallel with the new plating solution at a certain ratio, or the recovery solution may be added to the new solution tank 2 and mixed. You may make it into a part of plating liquid, and you may make it throw it into the plating liquid tank 1.

Before the recovery liquid is supplied to the plating solution tank 1, the temperature of the plating solution tank 1 is set to the same level as the temperature of the plating solution tank 1 so that the supply of the recovery solution does not change the bath temperature condition of the plating solution tank 1. You may make it warm.

By carrying out the above, it is possible to reduce a large amount of waste liquid which has been generated in the past. However, although recovery by electrodialysis removes ionic waste products in the liquid. Since non-ionic wastes such as organic substances such as polyethylene glycol used as a surfactant and organic substances generated from the object to be treated are not removed, the non-removed non-ionic wastes in the recovery liquid are not removed. There is a case where an object is supplied to the plating solution tank 1 to make the plating solution in the plating solution tank 1 unstable.

Therefore, in the present invention, the nonionic wastes which cannot be removed by the above electrodialysis are removed by activated carbon treatment. This activated carbon treatment may be performed on at least one of the surplus plating solution, a mixed solution of the surplus plating solution and waste water discharged by washing with water, or a recovery solution after electrodialysis. However,
The mixed solution in this case also includes a mixed solution during electrodialysis. When the recovered liquid after electrodialysis is treated with activated carbon, it is preferable that the additive is adjusted with respect to the recovered liquid after the activated carbon treatment. The reason is that some types of additives are adsorbed and removed by activated carbon.

[0018]

Since the new plating solution is continuously supplied to the plating solution tank 1, accumulation of waste products is suppressed, and the object to be processed is appropriately plated. The surplus plating solution overflowing from the plating solution tank 1 with the supply of the new plating solution is mixed with the waste water discharged by washing, electrodialyzed, and supplied to the plating solution tank 1 as a recovery solution containing valuable components. ,
The amount of waste liquid generated can be suppressed. Furthermore, performing activated carbon treatment on at least one of the excess plating solution, a mixed solution of the excess plating solution and the waste water discharged by washing, or the recovery solution after electrodialysis cannot be removed by electrodialysis. The removal of this non-ionic waste material means that the plating solution in the plating solution tank 1 becomes unstable when a recovery solution containing valuable components is supplied to the plating solution tank 1. Produces the effect of preventing.

[0019]

EXAMPLES Examples of the present invention will be described below. Example 1 The above electroless copper plating solution was applied to the system shown in FIG. 1 and the system was operated under the following conditions.

The plating liquid tank 1 contains the plating liquid which has been plated for 4 turns, and the new liquid tank 2 is 1
A new plating solution corresponding to 1/20 of the capacity of the plating solution tank 1 was supplied per hour. Further, copper ions, HCHO, and sodium hydroxide consumed in the plating reaction were supplied by a pump (not shown) in the controller 5.

After 20 hours of operation, the excess plating solution generated and the waste water discharged from the washing of the material to be treated were mixed at a ratio of 4: 1 and the electrodialyzer (TS-5 manufactured by Tokuyama Soda Co., Ltd.) was mixed. -4
The mixture was dialyzed with 0) until the total amount of the mixed solution became 80% to obtain a recovered solution containing valuable components of copper ion, disodium ethylenediaminetetraacetate (EDTA), and HCHO.

A cartridge filter containing activated carbon was set in the circulation system of the concentrated solution of the electrodialysis device 4 to adsorb and remove the nonionic accumulated substance in the concentrated solution which could not be removed by electrodialysis.

Next, the concentration of copper ions, EDTA and HCHO in the electrodialyzed recovered solution was adjusted to be the same as that of the new plating solution. Since the sulfur-based additive was extracted during the dialysis, the concentration of the sulfur-based additive was adjusted at the same time so that the concentration of the sulfur-based additive was the same as that of the new plating solution. The recovered liquid whose concentration was adjusted was mixed in the new liquid tank 2 and subsequently plated.

By carrying out the above plating method, the amount of waste liquid generated could be suppressed within 30% as compared with the case where the conventional excess plating liquid and the waste water generated by washing the object to be treated were used as the waste liquid. Further, when plastic was used as the object to be treated, the plating solution began to become unstable after 60 hours when the activated carbon treatment was not carried out.
The plating solution was stable even after the plating treatment was performed for 00 hours or more. (Example 2) The same plating treatment as in Example 1 was performed, except that the recovered liquid obtained by the electrodialysis treatment was directly mixed into the new liquid tank 2 without adjusting the concentration.

In this case, however, an analytical replenishing device for sulfur type additives was added to the controller 5 to control and adjust the plating solution in the plating solution tank 1.

As a result, as in the case of Example 1, the amount of waste liquid generated could be suppressed to within 30% as compared with the case where the conventional excess plating liquid and the waste water discharged by washing the object to be treated were used as the waste liquid. Further, when plastic was used as the object to be treated, the plating solution began to become unstable after 60 hours when the activated carbon treatment was not carried out. It was stable. (Example 3) Instead of the set of the cartridge filter containing activated carbon in the circulation system of the concentrated solution of the electrodialysis device 4 in Example 1, a filtration device in which a cartridge filter containing activated carbon was attached to the excess liquid tank 3 ( (Not shown) was provided, and the plating treatment was performed in the same manner as in Example 1 except that the activated carbon treatment of the excess plating liquid in the excess liquid tank 3 was performed until the excess plating liquid and the waste water discharged by water washing were mixed. ..

As a result, as in the case of Example 1, it was possible to suppress the amount of waste liquid generated to within 30% as compared with the case where the conventional excess plating liquid and the waste water discharged by washing the object to be treated were used as the waste liquid. When plastic is used as the object to be processed,
In the case where the activated carbon treatment was not carried out, the plating solution began to become unstable after 60 hours, but in the present example, the plating solution was stable even after the plating treatment was carried out for 100 hours or more.

[0028]

According to the present invention, since the new plating solution is continuously supplied to the plating solution tank 1, the accumulation of waste products is suppressed and the object to be processed is appropriately plated. And
The surplus plating solution overflowing from the plating solution tank 1 with the supply of the new plating solution is mixed with the waste water discharged by washing with water, electrodialyzed, and supplied to the plating solution tank 1 as a recovery solution containing valuable components. The amount generated can be suppressed. Furthermore, performing activated carbon treatment on at least one of the excess plating solution, the mixed solution of the excess plating solution and the waste water discharged by washing, or the recovery solution after electrodialysis is a non-ionic substance that cannot be removed by electrodialysis. Since it is possible to remove toxic waste products, there is an effect that the plating solution in the plating solution tank 1 does not become unstable even if the recovery solution is supplied to the plating solution tank 1.

[Brief description of drawings]

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

[Explanation of symbols]

 1 Plating liquid tank 2 New liquid tank 3 Surplus liquid tank 4 Electrodialysis device 5 Controller 6 Pump 7 Washing tank 8 Dialysis tank 9 Regulator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C25D 21/16 A 7179-4K 21/18 B 7179-4K

Claims (1)

Claim: What is claimed is: 1. An electroless plating method in which an object to be processed is plated in a plating solution tank filled with an electroless plating solution and then the plated object is washed with water. The new plating solution is continuously supplied to the tank, and the excess plating solution overflowing from the plating solution tank with the supply of the new plating solution is mixed with the waste water discharged from the washing, and the valuable component is contained from this mixed solution by electrodialysis. Is obtained, and the collected solution is supplied to the plating solution tank, and at least one of the excess plating solution, the mixed solution, and the recovered solution is treated with activated carbon. And electroless plating method.