Reducing electroless silver plating solution and reducing electroless silver plating method

Abstract

Provided are a reducing electroless silver plating solution and a reducing electroless silver plating method using the silver plating solution, the reducing electroless silver plating solution being capable of preventing decomposition of silver in the plating solution thereby to maintain stability of the solution and also being capable of preventing excessive roughening of an underlying metal or the like thereby to form a plating film having good film characteristics and a good appearance. The reducing electroless silver plating solution according to the present invention comprises a water-soluble silver salt and a reducing agent, wherein cyanide ions in a concentration of 0.006×10⁻³ mol/L to 12.5×10⁻³ mol/L are contained.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a reducing electroless silver plating solution and a reducing electroless silver plating method, more specifically, relates to a reducing electroless silver plating solution and a reducing electroless silver plating method using the silver plating solution, the reducing electroless silver plating solution being stable and being capable of forming a good plating film without excessive roughening of an underlying metal or the like.[0002]The present application asserts priority rights based on JP Patent Application 2011-235559 filed in Japan on Oct. 27, 2011. The total contents of disclosure of the patent application of the senior filing date are to be incorporated by reference into the present application.BACKGROUND OF THE INVENTION[0003]Silver plating has been long used for ornamental purposes and the like, and in recent years, with making use of its electrical characteristics and high reflectivity, it has been frequently u...

AI Technical Summary

Benefits of technology

[0023]The reducing electroless silver plating solution and the reducing electroless silver plating method according to the present invention are capable of preventing decomposition of silver in the plating solution thereby to make the stability of the solution good and also capable of preventing excessive roughening of metal or the like as an underlying plating material thereby to form a plating film having good film characteristics and a good appearance.

Problems solved by technology

However, since substituting electroless silver plating is performed in such a manner that silver plating is precipitated by a substitution reaction with an underlying metal, there is a problem that a limited kind of underlying material is used for substituting electroless silver plating.

However, while excessive cyanogen in the prior plating solution makes it possible to control decomposition of silver in the plating solution and improve the stability as mentioned above, the excessive cyanogen dissolves a plated material which is made of, metal of nickel, copper, or the like, and excessively roughens a surface of the material, whereby a plating film having good film characteristics cannot be formed.

In such cyanogen-free electroless silver plating solution, cyanogen is not present in the plating solution and therefore an underlying metal or the like is not dissolved, and accordingly, a surface thereof is not excessively roughened, however, with respect to the solution stability, the cyanogen-free electroless silver plating solution has been remarkably inferior to that of a plating solution containing cyanogen.

As disclosed in Patent Literatures 4 and 5, there has been proposed a technique to improve the stability of a cyanogen-free silver plating solution by adding an additive thereto, but the cyanogen-free silver plating solution has not yet had sufficient stability.

Furthermore, in such cyanogen-free electroless silver plating, the thicker a silver film becomes, the more the silver film becomes yellowish, and thus a problem arises also in view of appearance of a plating film.

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