Investigation on the melting and tensile properties of Bi-containing SAC105 lead-free solder alloys

Sn-Ag-Cu (SAC) solder is one of the most promising candidates to replace Sn-Pb (SnPb) solder alloys. Reducing the amount of Ag phase is an important approach to obtain new SAC solders with lower cost. In this article, different proportions of Bi element were added into Sn-1.0Ag-0.5Cu (SAC105) lead-free solders. The melting points of these alloys are examined and the corresponding tensile properties are also characterized under various strain rates. Further more, the SAC305 solder is also studied for comparison. The results of our work indicate significant reduction of melting temperature with the addition of Bi into SAC105 solder while the melting range increases at the same time. Moreover, it has also been found that the tensile strength of all the SAC solder alloys increases approximately monotonically with the increment of strain rate. According to the microstructure analysis by scanning electron microscope (SEM), Bi addition can significantly increased the ultimate tenslile strength (UTS) of Bi micro-alloyed SAC105 lead-free solders linearly by solid solution hardening or precipitations strengthen mechanism.