Intermetallic compounds formed during the soldering reactions of eutectic Sn-9Zn with Cu and Ni substrates

The efforts of this study aim to investigate the morphology and growth kinetics of the intermetallic compounds formed during the interfacial reactions of eutectic Sn-9Zn solders with Cu and Ni substrates at temperatures ranging from 250 to 350 degreesC. Experimental results show that the intermetallic growth rate at the Sn-9Zn/Cu interface is much higher than that at the Sn-9Zn/Ni interface. Kinetics analyses indicate that both types of interfacial reactions are diffusion-controlled. The activation energies for the intermetallic growth at the Sn-9Zn/Cu and Sn-9Zn/Ni interfaces are 8.2 and 68.9 kJ/mol, respectively. The formation mechanisms of the intermetallic compounds during the soldering reactions at both interfaces are clarified by using a Ta thin film as diffusion marker.