Development of an electroplating solution for codepositing Au–Sn alloys

A relatively stable, weakly acidic, non-cyanide electroplating solution has been developed for deposition of Au–Sn alloys over a range of compositions. The solution consists of Au and Sn chloride salts, as well as ammonium citrate as a buffering agent and sodium sulphite and ascorbic acid as stabilizers. Electrochemical studies have been conducted to examine the effects of the various additives and their concentrations on bath stability and plating behaviour. Preliminary electroplating experiments with the developed solution indicate that uniform, homogeneous deposits can be achieved over a range of compositions, including the technologically important eutectic and near eutectic values.