Surface accumulation rate of diffusing species on thin gold electroplates

The accumulated species on the surface of Co-hardened gold electroplates were analyzed. The samples were aged in a basement air environment at 85, 125, and 150°C for periods of 1-12 mo. Different gold coating thicknesses were used, 0.3 and 1.0 μm, on phosphor bronze substrates with or without 5-μm nickel underplate. The accumulation rates of surface films were evaluated using contact resistance probing. Auger electron spectroscopy was employed to characterize the surface species. The values of contact resistance recorded are consistent with parabolic growth kinetics and have been utilized to extrapolate estimated lifetimes based on the failure criteria of increases in contact resistance to 20, 50, and 100 mΩ