Minimizing gold amount by alloying silver in hard gold

A novel Au–Ag alloy coating was investigated as a contact in electrical circuits to reduce Au usage. The Ag content in the coating varied with the current density and Ag concentration in the plating solution, and the effects of different Ag concentrations on the coating characteristics were explored to optimize the Ag content. Increasing the current density to 1 A/dm² decreased the Ag atomic percentage, which remained stable at current densities higher than 1 A/dm². The addition of Ag to the plating solution increased the amount of Ag in the electrodeposit, and the current efficiency of alloy electrodeposition increased with increasing Ag concentration. The structure of the coatings was investigated via phase identification, morphological observation, and surface roughness determination. The Au–Ag alloy coatings generally showed decreasing contact resistance with increasing Ag content, and the Au–Ag alloy coating with 6.9 at.% Ag showed higher hardness than pure Au. The hardness was slightly reduced with the addition of more than 6.9 at.% Ag, before abruptly decreasing at 58.2 at.% Ag. The influence of Ag content integrated with self-assembled monolayer as a corrosion inhibitor on corrosion resistance was also ascertained.