Effect of strain rate on tensile properties of miniature size lead-free alloys

Tensile properties of several lead-free solder were investigated at a strain rate ranging from 2 × 10⁻³ s⁻¹ to 2 × 102 s⁻¹ at room temperature using micro-size specimens. Five kinds of lead-free solder which are Sn-3mass%Ag-0.5mass%Cu, Sn-0.7mass%Cu, Sn-5mass%Sb, Sn-8.5mass%Sb and Sn-13mass%Sb were prepared. Sn-37mass%Pb solder was also prepared as a comparison. Tensile strength increases with increasing the strain rate and is proportional to the logarithm of the strain rate. In Sn-3Ag-0.5Cu and Sn-37Pb solder, specimens were necked uniformly and dimple fracture mainly occurred. Tensile strength became relatively high in those solder. In Sn-0.7Cu, Sn-5Sb and Sn-8.5Sb solder, specimens were not necked uniformly and chisel point fracture was observed. Tensile strength of such solder became relatively low compared with those of Sn-3Ag-0.5Cu and Sn-37Pb solder. In Sn-13Sb solder, brittle fracture occurred and elongation decreased compared with other solder. For elongation, Sn-5Sb and Sn-8.5Sb solder showed an excellent value of approximately 90% at the maximum strain rate investigated.