Oxidation thermodynamics and oxidation kinetics analysis of Au-20Sn solder

In this paper, the oxidation thermodynamics and oxidation kinetics of Au-20Sn solder at various temperatures were analyzed. The results indicated that the critical oxygen partial pressure to form SnO and SnO2 in Au-20Sn solder could be 1 × 10-44 Pascal (Pa) and 1 × 10-91 Pa at the temperature of 298 K, respectively. The oxidation kinetics analysis results indicated that the oxide on the surface of Au-20Sn solder consists mainly SnO2, while the major constituent of internal oxide is SnO. The reliability test results under salt spray environment have showed that the hermeticity of the package device gradually decreased with the increasing oxygen content in Au-20Sn solder. Meanwhile, the measured leakage rate of the packaging device could be lowered than 5 × 10-9 Pa·m-3·s-1 when the oxygen content in Au-20Sn solder is less than 28 ppm after high temperature aging.