Intermetallic compounds at aluminum-to-copper and copper-to-tin electrical interfaces

The effects of intermetallic compounds on the electrical and mechanical properties of bimetallic friction welded Al-Cu joints and tin-plated copper wire conductors are studied. The formation and growth of intermetallic compounds are studied in the temperature range 200-525 degrees C for the Al-Cu system, and 80 degrees -200 degrees C for the Cu-Sn system. The formation and growth of intermetallic phases exert a pronounced effect on the mechanical (microhardness) and electrical integrity of these systems. In the case of aluminum-to-copper bimetallic contacts, the contact resistance increases linearly with the thickness of the intermetallics, while in the tin-plated copper system, the resistance shows a tendency towards stabilization when the thickness of intermetallic phases approaches that of the plating. In the aluminum-to-copper joints, the presence of an electrical field greatly accelerates the kinetics of formation of intermetallic phases and significantly alters their morphology.