Spring metals for terminals and connectors in harsh environments

Copper alloy strip used for terminal and connector springs must often provide requisite contact forces in the harsh environments of elevated temperatures, for quite long times. A number of innovative metals and several traditional metals were tested for stress relaxation at temperatures up to 200°C for up to 3000 h. Recognizing that resistance to degradation at elevated temperatures is but one facet of the requirements of a spring metal, strength and formability were also measured for each of the alloys. Yield strength was measured in the bending mode to better simulate the way stress is developed in actual spring members of terminals and connectors. Formability was determined with standard methods but, more importantly, was related to the bending strengths of the alloys. Because conductivity plays a role in material selection, it is reported for each of the materials studied. It is noted that there are copper alloys in strip form that possess sufficient strengths to provide high initial contact forces, are formable enough for sophisticated geometries, have desirable conductivities, and can provide contact forces that withstand service temperatures approaching 200°C