Rapid formation of intermetallic joints through ultrasonic assisted die bonding with Sn 0.7Cu solder for high temperature packaging application
Abstract Rapid formation of complete intermetallic phases (IPs) composed joints during die bonding for high temperature applications was achieved by pressureless and fluxless ultrasonic assisted soldering in air within seconds. The joint consisted of sole (Cu,Ni) 6 Sn 5 plus a thin layer of Cu 3 Sn possessed a rather low thermal resistance of 0.252 mm 2 K W 1 and a high shear strength of 69 MPa. This rapid formation of fully IPs composed structures was probably accelerated by ultrasonic cavitation and streaming effects through supersaturation of copper in the melted solder. Compared with transient liquid phase soldering, this method dramatically reduces the processing time and there was no external force acted on the dies.