Gold electroplating process
 Electrolytic deposition of gold results in the formation of undesirable reducible gold III species in the electroplating bath which interfere with the current efficiency and make the prediction of gold thickness based on applied current impossible. Addition of a small quantity of hypophosphorous acid to the plating bath when the current efficiency has dropped below a certain minimum, chemically reduces accumulated gold III species and scavenges dissolved oxygen. Thus, the current efficiency is restored to about 100%. The hypophosphorous acid treatment is particularly advantageous in a phosphate buffered bath because no foreign ions are introduced into the solution. 
Bell Telephone Laboratories, Incorporated
C
C25D
inventional
Kei
Yoshida