Study on electrolytically deposited copper film on stainless steel surface for RF input couplers

A copper (Cu) film is electrolytically deposited on a stainless steel-made RF coupler used in a particle accelerator machine. The coupler after electroplated with a Cu film goes to a heat-treatment process for the brazing of components of the coupler. The brazing is performed at a temperature of ∼800degC in a high-temperature vacuum furnace. A residual resistivity ratio (RRR) of the Cu film decreases owing to the high-temperature heat-treatment process. We have been aiming to achieve a desired RRR value after the heat-treatment process. In this study, we have conducted an analysis of a Cu film, which was electrolytically deposited on a stainless-steel surface with an intermediate Cu strike layer, to find atomic diffusion from stainless steel to the Cu film due to heat-treatment. The impact of heat-treatment on the RRR value of the Cu film was evaluated. (author)