Microstructure and mechanical properties of Sn–Zn–Bi–Cr lead-free solder

In this paper, the effect of trace addition of Cr on the mechanical properties and reliability on Sn–8Zn–3Bi solder alloys was investigated. It has been demonstrated that the microstructure of solder alloys was refined after doping traces of Cr. The elongation reaches up to 40.63% after doping 0.1% Cr; and the fracture mechanism converts from quasi-cleavage fracture into ductile fracture. With aging time of 0, 4, 9 and 16 days, mechanical property of Sn–8Zn–3Bi–0.3Cr alloy was improved slightly. It was found that the Sn–Zn–Cr phase was increased and Zn in alloy was consumed after aging, so that the amount of primary Zn phase was reduced and microstructure was improved.