Interdiffusion at Bimetallic Electrical Interfaces

The compatibility of two dissimilar electric-contact materials in a bimetallic junction is determined in part by the metallurgical stability of the interface generated. Materials which interdiffuse to form significant quantities of (brittle) intermetallics at this interface in the early life of an electrical junction, and hence generate a potentially unreliable electric contact, must obviously be avoided. An investigation is described of the rate of growth, composition, and hardness of interdiffusion layers formed by Zn, In, and Sn platings on brass and phosphor-bronze at temperatures ranging from 80°C to 150°C. Data on iutermctallics formation at Al/brass interfaces at temperatures ranging from 150°C to 450°C are reported. Also discussed is the expected effect of intermetallics growth on the performance of electrical junctions in which these combinations of materials are used.