Effect of displacement and humidity on contact resistance of copper electrical contacts

The effect of displacement and humidity on fretting-induced instability of electrical contact resistance (R_c) was studied. A fretting tester was used to examine R_c in partial and gross slip modes. Under the partial slip regime the contact failure was susceptible to the displacement and moisture effectively increased contact stability, which was pronounced at smaller displacements. In the gross slip mode, however, humidity effect was relatively small. The early contact failure at low humidity was attributed to the wear debris agglomeration within the sliding interface, suggesting a high propensity of electrical contact failure at dry conditions.