Non-interfacial growth of Cu3Sn in Cu/Sn/Cu joints during ultrasonic-assisted transient liquid phase soldering process

Abstract The non-interfacial growth of Cu 3 Sn intermetallic compounds (IMCs) in a Cu/Sn/Cu interconnection structure during the ultrasonic-assisted transient liquid phase (TLP) soldering process was investigated. In the traditional TLP soldering process, the Cu 3 Sn phase always nucleated at Cu 6 Sn 5 /Cu interfaces and grew at the expense of the Cu 6 Sn 5 phase and towards the joint centre, eventually forming a full intermetallic joint consisting of a single Cu 3 Sn phase with columnar grains. While in the ultrasonic-assisted TLP soldering process, the Cu 3 Sn phase nucleated and grew randomly within the whole joint, the resulting intermetallic joint consisted of a single Cu 3 Sn phase with equiaxed grains. This anomalous behaviour can be wholly ascribed to the effects ultrasonic on the nucleation and growth mechanisms of Cu 3 Sn.