Non-cyanide silver plating bath composition

Abstract

Disclosed is an electroplating solution for the deposition of silver; said solution containing silver in the form of a complex of silver with hydantoin or a substituted hydantoin compound; said solution also containing an excess of the hydantoin or substituted hydantoin compound employed, together with an effective quantity of a nonprecipitating electrolyte salt, and also an effective quantity of 2,2′ dipyridyl for the purpose of obtaining a mirror-bright to brilliant deposit.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a continuation-in-part of commonly owned, copendng application Ser. No. 10 / 785,297, filed 24 Feb. 2004, and published as U.S. Patent Publication No. 2005 / 0183961 on Aug. 25, 2005, now ______; the disclosure of which is hereby incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] Numerous non-cyanide silver plating processes have been attempted (See Citation No. 1). Of these, the only ones to have achieved commercial success have been those employing succinimide, either as a premanufactured silver complex (See Citation Nos. 2 and 3), or as a reagent. Succinimide undergoes hydrolysis at pH values above neutrality, which in turn causes the pH of the plating solution, normally in the range of 8 to 9 or so, to become unstable; and also to require frequent replenishment of the succinimide. [0003] Hydantoin (CAS Number 461-72-3) is a cyclic diimide possessing structural features similar to succinimide, and simi...

AI Technical Summary

Benefits of technology

[0017] Accordingly, it is an object of this invention to provide a non-cyanide plating solution for the deposition of silver, said solution being capable of yielding mirror-bright to brilliant deposits. It is a further object that the plating solution thus provided be as chemically stable as possible, and free of chemical precipitants.

[0022] Preferably, the electroplating solution includes an effective quantity of a pyridine or substituted pyridine compound for the purpose of improving the overall brightness of the deposit obtained.

[0023] Preferably, the electroplating solution also includes an effective quantity of surface-active material for the purpose of further improving the overall brightness and brilliance of the deposit obtained.

[0033] Preferably, in the process of the present invention, the electroplating solution also includes an effective quantity of a pyridine or substituted pyridine compound for the purpose of improving the overall brightness of the deposit obtained.

[0034] Preferably, in the process of the present invention, the electroplating solution also includes an effective quantity of surface-active material for the purpose of further improving the overall brightness and brilliance of the deposit obtained.

Problems solved by technology

Succinimide undergoes hydrolysis at pH values above neutrality, which in turn causes the pH of the plating solution, normally in the range of 8 to 9 or so, to become unstable; and also to require frequent replenishment of the succinimide.

Large excesses of a complexing agent, however, are not incorporated into the reaction product, but remain unreacted in the reaction mixture, where they compete with and act to prevent complexation by any other reagent which may be introduced.