Electrodeposition of Cu-Ag films in ammonia-based electrolyte

Electrodeposition of Cu-based alloys has been researched for a variety of applications due to Cu-based alloys having superior properties compared to pure Cu, including higher chemical resistance, mechanical hardness, and electrocatalytic activity. Cu-Ag is the most electrically conductive among Cu-based alloys, and it has higher mechanical hardness and oxidation resistance compared to pure Cu. Cu-Ag co-deposition in cyanide-based electrolytes has been previously reported; however, the toxicity of cyanide limited its use. In this study, we introduce an ammonium hydroxide-based electrolyte for Cu-Ag electrodeposition and the properties of Cu-Ag films deposited in this electrolyte. Electrochemical measurements were performed to determine the potential range for co-electrodeposition of Cu and Ag, and the effect of nitrate reduction on the film deposition was examined. The effects of deposition potential and concentration of Ag ions in the electrolytes on the electrical resistivity and Ag contents of the films were investigated. The modulation of Ag ion concentration was found to be a more effective way to control Ag contents in the deposited films. Co-deposition of 4 at% Ag with Cu in the ammonium-hydroxide electrolyte markedly improved mechanical hardness and oxidation resistance compared to a pure Cu film without severe deterioration of electrical conductivity.