METHOD AND APPARATUS FOR ELECTRODEPOSITION OF GOLD ALLOYS

摘要

1381192 Semi-conductor circuits SCHERING AG 29 March 1972 [24 April 1971] 14808/72 Heading H3T [Also in Division C7] A gold alloy, e.g. Au-Cu-, Au-Cu-Cd or Au-Ag-Ni-Pd, is electrodeposited by causing to act upon a gold plating electrolyte of constant composition, preferably containing alkali metal (e.g. K) dicyanoaurate-I and one or more complex-bound elements of Group IVa or Va or Group Ib, IIb or VIIb of the Periodic Table or mixtures thereof, a succession of periodically recurring voltage impulses having durations of 10-3 to 10-4 seconds preceded by deposition potentials of not less than 0À1 seconds and followed by virtually potential-less periods of 10-1 to 10-3 seconds. The amplitudes of the impulses may be the same or different and greater than the deposition potentials by 1 to 5 volts. The complex-bound element may be present in the electrolyte as cyanide with free KCN, or when As, Sb, Sn or Pb, as a hexahydroxy complex. Gold alloys specified are (a) 70-85% Au, 12-22% Cu and 3-8% Cd; and (b) 83-90% Au, 7-11% Ag, 0À5-1À0% Pd and 2À5-5À0% Ni. A variable polarizing voltage for electrodeposition is produced by stepping a switching signal in cyclic succession along conductors with first switches and second switches connected thereto and responsive to the signal to generate respective polarizing voltages and timing signals changing at respective rates, preferably adjusted by potentiometers connected to the switches. An integrator, reset with each stepping of the switching signal, may be connected to the second switches to produce the timing signals.