Effect of Indium, Bismuth and Copper Doping on Microstructure and Mechanical Properties of Sn5Sb and Sn3.5Ag Lead free Solder Alloys

In this study, effect of Cu, In and Bi doping on microstructure and tensile properties of Sn-5Sb and Sn-3.5Ag solder alloys was investigated. It was found that In and Bi doping could transfer the fracture mode to ductile fracture with dimples. Solder alloys showed viscoplastic behavior during the whole tensile tests. The addition of In and Bi increased the ultimate tensile strength but decreased the elongation of Sn-5Sb based solder alloys compared with that of Sn-5Sb. The improvement of ultimate tensile strength attributed to the formation of InSb and Sn
₃
Sb
₂
particles which blocked the motion of dislocations. Furthermore, InSb particles improved the creep resistance of Sn-5Sb based solder alloys effectively. In addition, the minor addition of Cu, In and Bi had a slight effect on the E-modulus and ultimate tensile strength of Sn-3.5Ag based solder alloys. However, Cu, In and Bi doping improved elongation of Sn-3.5Ag based solder alloys.