Oxidation of liquid solders for die attachment

► This paper investigates the high temperature oxidation behavior and reaction products of the die-attach solder, Pb-Sn and its potential Pb-free replacements, Zn-Sn and Bi-Ag alloys. This is the first report investigating this issue systematically. ► The additions of Ag can significantly reduce the oxidation of Bi and thus Bi-11 Ag has a comparable performance with Pb-5Sn. ► Among the die-attach solders investigated, the Zn-Sn alloys exhibit a superior oxidation resistance in the liquid state. This is because the thermodynamically stable ZnO has low free energy of formation, as well as slow growth rate, and thus protects the liquid solder from further oxidation.