Interfacial microstructure between thick aluminium wires and aluminium alloy pads formed by ultrasonic bonding

Abstract

Interfacial microstructures between thick Al wires and pads formed by ultrasonic bonding were analysed to investigate the behaviour of bond preventing phases. The wire and the substrate form direct bond interface in the central region of the bond area, whereas the surfaces of them in the peripheral region are covered by amorphous Al2O3 bond preventing layer. The amorphous Al2O3 layer is chipped off the surfaces by application of ultrasonic vibration and forms a number of spherical particles intervening between the wire and the substrate. The particles consist of amorphous Al2O3 matrix and lamellae of Al. The particles grow by accumulating the amorphous Al2O3 on the surfaces of the wire and the substrate in contact, moving outward the bond area. The bond area expands through the area where the bond preventing layer has been removed. © 2013 Institute of Materials, Minerals and Mining.