Interfacial microstructure between copper ribbon and nickel-coated copper plate formed by ultrasonic bonding

Abstract

The present paper reports the bondabiliy and the interfacial microstructure between copper ribbons and nickel-coated copper plates by ultrasonic bonding. The ultrasonic bondability of copper to nickel is significantly improved by heating up to 423 K. On the other hand, the bondability of copper to itself is deteriorated by surface oxidation. It is also shown that the nickel coating suppresses the deterioration. The nickel layer at the central part of the bond area shows S-curved morphology, whereas it is torn and/or folded in the peripheral part of the bond interface, indicating that a complicated deformation is induced during bonding. Although ultrasonic bonding at 423 K allows lowering of the ultrasonic power to one-third of that required for bonding at room temperature, it is difficult to avoid tearing of the Ni layer.