Interdiffusion coefficients of various cobalt base alloy coatings for Cu/Au system

The interdiffusion coefficients of electrodeposited Co-Mo, Co-P, Co-Mo-P with Cu substrate were studied at temperature ranging from 400 to 800°C, by micro-profiling method using energy dispersive X-ray spectroscopy (EDS). Chemical interdiffusion coefficients were derived using the Boltzmann-Matano method. At 400-500°C, the interdiffusion coefficients for Cu/Co-P couples have the same order of magnitude as the Cu/Co-Mo couples. It was found that the interdiffusion coefficients for nickel are higher than that of the cobalt base alloys. The Co-Mo coating becomes poor in term of barrier property when the temperature is above 700°C.