Making contact to aged surfaces

A Monte Carlo analysis of aged crossed rod copper (Cu) contacts was conducted to evaluate the effects from a number of variables such as film thickness, contact force, microhardness and geometry. The analysis was conducted using two previously developed models that employ material properties and design parameters as constraints in a statistical model of degradation. It was shown, using a power law model to describe the surface concentration of oxides, that the degradation model could be calibrated to produce results that showed good agreement with a wide range of laboratory data. In addition it was found that the recently observed difference in performance of soft and hard Cu contacts could be explained within the framework of the degradation model. It was concluded that the mechanism which causes oxide accumulation in the surface layer is affected by microhardness in a way which is less favorable to the performance of soft Cu contacts. The reason for this type of behavior was not determined and warrants further investigation.>