Accelerated testing of tin plated copper alloy contacts

Thermal cycling tests conducted on tin plated contacts were used in conjunction with materials aging data to develop a fretting degradation model. Parameters such as thermal swing, temperature extremes, dwell times and number of cycles are incorporated in the model to account for aging processes such as micro-motion, oxidation rate and stress relaxation. In addition, algorithms were developed to simulate the levels of oxidation, stress relaxation and intermetallic compound formation that occur under various field and accelerated test conditions. These algorithms and the fretting model were used to evaluate various test exposures of tin plated copper base alloy contacts in comparison to typical field conditions. The results indicate three of the four aging processes (fretting corrosion, oxidation and stress relaxation) can be simulated using standard test conditions. Moreover it was found that intermetallic compound formation could not be simulated without excessively accelerating the other processes. These results reveal oxidation rate and stress relaxation per cycle as important thermally activated processes that accelerate the rate of fretting corrosion degradation.