JPH0867987A - Electroless plating method - Google Patents

Abstract

PURPOSE: To provide an electroless plating method by which the waste plating soln. is reduced and the plating soln. is continuously regnerated and used. CONSTITUTION: The surface of a material to be treated is electroless-plated while continuosuly regenerating the plating soln. in this method. Namely, the plating soln. is pumped out from a plating tank 1 and then sprayed into a low-temp. tank 5 to recrystallize a reaction product in the soln. The recrystallized material is separated from the soln. by filrration, and the plating soln. is returned to the tank 1. Consequently, a plating film stable over a long period of time is formed on the material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless plating method in which a plating solution is continuously regenerated and used.

[0002]

2. Description of the Related Art Electroless plating is capable of forming a uniform film on any shape or material, and is used as a surface treatment technique capable of imparting various mechanical and electrical characteristics.
However, in electroless plating, reaction products are more likely to be accumulated than in electroplating, and as a result, it is difficult to form a uniform coating and the amount of plating waste liquid is large. In order to form a uniform coating, a method of replacing the plating solution with a new bath has been taken, but this method has a problem of producing a large amount of waste solution. In addition, it has been proposed to reuse the plating solution with accumulated reaction products by electrodialysis in order to reduce the amount of waste liquid with accumulated reaction products. If the treatment is carried out as it is, the plating solution is concentrated, so that there are problems that the contained components are precipitated in the piping of the apparatus and in the ion exchange membrane, and that ions necessary for the plating reaction are taken out at the same time as the reaction products. .

[0003]

The problem to be solved by the present invention is to find an electroless plating method which produces a small amount of plating waste liquid and can obtain a plating film of stable quality for a long period of time. . That is, an object of the present invention is to provide an electroless plating method in which the amount of waste plating solution generated is small and the plating solution can be continuously regenerated and used.

[0004]

The electroless plating method of the present invention is an electroless plating method in which electroless plating is performed on a surface of an object to be treated while continuously regenerating a plating solution. The solution is pumped out, the sprayed plating solution is sprayed into a low temperature tank in an atomized form to recrystallize the reaction product in the plating solution, and the recrystallized product is separated from the plating solution by filtration, and then the plating solution Is returned to the plating tank again.

Further, the electroless plating method according to the invention of claim 2 is characterized in that the plating solution is a copper plating solution.

The present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an electroless plating method according to the present invention.

The plating solution tank 1 is filled with an electroless plating solution for plating an object to be treated. This electroless plating solution contains a metal ion, a metal ion complex, a reducing agent, a pH adjusting agent, and an additive. Metal ion, metal ion complex, reducing agent, p consumed in plating reaction
The H regulator and the additive are replenished by the controller 2. The plating solution is continuously pumped out of the plating solution tank 1 by using a pumping means 3 or the like, sprayed into a low temperature tank 5 by atomizing the plating solution by using a discharging pump 4 or the like, and recrystallized. The reaction product thus obtained is filtered by the filtration tower 6 to separate the plating solution and the reaction product, and the obtained plating solution is returned to the plating solution tank 1. At this time, the temperature of the low temperature tank 5 is preferably within the range of 0 to 5 ° C. The reason for this is that the temperature of the low temperature tank 5 is 0 ° C.
If it is less than 5, the plating solution may be frozen, and if it is higher than 5 ° C, the reaction product is difficult to recrystallize. The method of filtration is not particularly limited, and a cartridge filter, a resin filter, or the like may be used.

[0008]

The present invention is characterized by the method of recrystallizing the reaction product, and the reaction product can be recrystallized speedily by cooling the atomized plating solution.
By using this recrystallization method to continuously remove the reaction products in the plating solution, the accumulation of reaction products is suppressed and a plating film of stable quality can be obtained for a long period of time on the object to be treated. Can be formed. Further, since the plating can be performed for a long period of time, the amount of waste liquid generated with respect to the plating processing time can be suppressed.

[0009]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples.

Example 1 An electroless plating method, the outline of which is shown in FIG. 1, was applied, and electroless copper plating was performed under the following plating solution conditions.

<Composition and Conditions of Electroless Copper Plating Solution> Copper Sulfate Pentahydrate (for Metal Ions) ... 10 g / L Disodium Ethylenediaminetetraacetate (Complexing Agent) ... 30 g / L Water Sodium oxide (pH adjuster) ・ ・ ・ ・ Amount to adjust to pH 12.0 35% HCHO solution (reducing agent) ・ ・ ・ ・ 5mL / L Sodium cyanide (stabilizer) ・ ・ ・ ・ Small amount Polyethylene glycol (surfactant ) ... Small amount of bath temperature condition ... 60 ° C Put the electroless copper plating solution having the above composition into the plating solution tank 1, draw out the plating solution at a flow rate of 20 L / min by the drawing pump 3, and discharge it. The plating solution was atomized using the pump 4 for spraying into the low temperature tank 5 (tank temperature 3 ° C.) to recrystallize the reaction product. Next, the plating solution and the recrystallized product coming out of the low temperature tank 5 were introduced into a filtration tower 6 and filtered, and the plating solution in which the recrystallized product after filtration was separated was returned to the plating solution tank 1. Further, the controller 2 was used to replenish the copper ions, HCHO, and sodium hydroxide consumed in the plating reaction. Then, the alumina substrate treated with the palladium-based catalyst was plated under the above conditions.

(Comparative Example 1) A plating process was performed in the same manner as in Example 1 except that the discharge pump 4 in Example 1 was removed and the plating solution was directly introduced into the low temperature tank 5 without being atomized. In this case, the recrystallization of the reaction product occurred although it was a small amount.

(Comparative Example 2) Example 1 except that the discharge pump 4, the low temperature tank 5 and the filtration tower 6 in Example 1 were removed and the plating solution was simply circulated by the pump 3 for pumping out.
The plating process was performed in the same manner as in.

(Results of Example 1, Comparative Example 1 and Comparative Example 2) In Comparative Example 2, the plating solution became unstable 60 hours after the start of plating, and in Comparative Example 1, after 80 hours. The plating solution began to become unstable, but in Example 1, the plating solution was stable even after the plating treatment was continued for 120 hours or more. Whether or not the plating solution became unstable was determined by observing the appearance of the plating film formed on the alumina substrate which was the object to be processed and when the roughness occurred, the plating solution became unstable. From the above results, the amount of waste liquid generated with respect to the plating treatment time in Example 1 was
It can be said that it could be 67% or less in the case of, and 50% or less in the case of Comparative Example 1.

[0015]

INDUSTRIAL APPLICABILITY According to the electroless plating method of the present invention, the reaction product can be recrystallized speedily by cooling the atomized plating solution. Since the accumulation of substances can be suppressed, the electroless plating method of the present invention can form a plating film of stable quality on an object to be treated for a long period of time, and also enables plating for a long period of time. As a result, the amount of waste liquid generated with respect to the plating processing time can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic view showing an electroless copper plating method according to the present invention.

[Explanation of symbols]

 1 plating solution tank 2 controller 3 pump for pumping out 4 pump for discharge 5 low temperature tank 6 filtration tower

Claims (2)

[Claims] 1. An electroless plating method in which electroless plating is performed on the surface of an object to be treated while continuously regenerating the plating solution, wherein the plating solution is drawn out from a plating tank, and then the drawn-out plating solution is atomized. Electroless characterized by spraying into a low temperature tank to recrystallize the reaction product in the plating solution, then separating the recrystallized product from the plating solution by filtration, and then returning the plating solution to the plating tank again Plating method. 2. The electroless plating method according to claim 1, wherein the plating solution is a copper plating solution.