Electroless gold plating solution

Abstract

An electroless gold plating solution comprising an aqueous solution containing as ingredients (a) chloroauric (III) acid or a salt thereof or a sulfite or thiosulfate gold (I) complex salt as a gold source, (b) an alkali metal or ammonium sulfite or thiosulfate, (c) ascorbic acid or a salt thereof and (d) a pH buffer, characterized in that (e) a compound selected from 2-mercaptobenzothiazole, 6-ethoxy-2-mercaptobenzothiazole, 2-mercaptobenzimidazole, 2-mercaptobenzoxazole and salts thereof, and optionally (f) an alkylamine compound are further incorporated. The solution prevents the bath made up thereof from forming any precipitate during the storage and usage of the bath and the bath can be stably used for long periods of time. Furthermore, the bath gives a significantly high plating rate, which does not decrease even at high bath loads. Thus the bath renders it possible to plate a number of substrate items within a short period of time and also to perform thick plating within a short period of time.

Dependencies are inferred from the claim text.