Microstructure and solderability of Sn-3.5Ag-0.5Cu-xBi-ySb solders

Lead-free solders were prepared by adding a small quantity of Bi, Sb element into Sn-3.5Ag-0.5Cu alloy. By means of OM, SEM, EDS, DTA and solderability test, effects of Bi and Sb elements on microstructure, solderability and melting characteristic were investigated. The results show that with the increase of Bi and Sb addition into Sn-3.5Ag-0.5Cu solder, the primary β-Sn phrase decreased gradually and tiny inter-metallic compounds increased. Bi presents obvious effects on depressing the melting temperature but broadening the melting range. And the addition of Sb has little effect on melting temperature but broadens the melting range too. Adding suitable amount of Bi and Sb into the solder alloy may help improve the solderability.