Oxalate-Containing Soft Gold-Plating Bath
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
A novel supporting electrolyte for gold-plating baths leads to soft, fine-grained films suitable for wire-bonding substrates. The bath is comprised of inter alia, an organic oxalate, anion, which prevents the buildup of gold (III) ions in the bath during plating and permits a uniform plating efficiency over time. More specifically, the supporting electrolyte contains mono and di-hydrogen potassium phosphate as a buffering system, thallium as a grain refiner and softening agent, and an anionic agent, potassium oxalate. Potassium gold cyanide is used as a source of gold (I) ions. The unique composition of the bath of this invention enables it to maintain the gold (III) concentration at a constant, near-zero level.