Vapor deposited thin gold coatings for high temperature electrical contacts

Using electron beam evaporation, thin films of Au over Ni and Au over Pd₈₀Ni₂₀ have been deposited on stainless steel and copper alloy substrates for high temperature electrical contact studies. The structure and composition of the films were studied in detail using electron probe microanalysis (EPMA) and x-ray photoelectron spectroscopy (XPS) with sputter depth profiling. The contact properties, such as contact resistance, fretting wear resistance, and thermal stability have been measured. The Ni and Pd₈₀Ni₂₀ layers of about 200 to 300 nm thickness have been shown to be effective in maintaining high temperature stability up to 340°C in air by blocking the diffusion of elements in the substrates to the Au surface. These coatings also show good fretting wear resistance. These desired properties have been achieved with the thickness of the Au, Ni, and Pd₈₀Ni₂₀ layers substantially less than that of the conventional electroplated coatings.