Tensile properties of Sn-5Sb (mass%) and Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge (mass%) were investigated using miniature size specimens and obtained results were compared. Tensile strength of both alloys increase with increasing the strain rate and decrease with increasing the temperature. Although similar dependency to the temperature is observed in 0.1% proof stress, the effect of the strain rate on it is obscure. The tensile strength and the 0.1% proof stress of Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge are higher than those of Sn-5Sb. The elongation of Sn-5Sb is relatively stable at the range from 0.4 to 0.6. The elongation of Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge which is approximately 0.3, is inferior to that of Sn-5Sb. On the basis of investigation of stress exponent, n, it was clarified that dispersion strengthening by Ag3Sn particulates in Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge is effective to prevent the degradation of creep resistance compared with Sn-5Sb that is strengthened by solid-solution of Sb in β-Sn phases and dispersion of SbSn compounds.

Tensile and low cycle fatigue properties of Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge (mass%) lead-free solder were investigated using miniature size specimens and obtained data were compared to those of Sn-3.0Ag-0.5Cu (mass%). The microstructure of Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge consists of dendritic β-Sn phases and ternary eutectic phases surrounding them which are composed of β-Sn, (Cu,Ni)6Sn5 and Ag3Sn. Tensile strength and 0.1% proof stress of Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge are superior to those of Sn-3.0Ag-0.5Cu at 25°C and 150°C. However, elongation of it is inferior to that of Sn-3.0Ag-0.5Cu at both temperatures. Fatigue lives of both alloys obey the Manson-Coffin equation and are analogous at 25°C. Although fatigue lives of both alloys decrease at 150°C, the fatigue life of Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge is inferior to that of Sn-3.0Ag-0.5Cu. At 150°C, the crack mainly progresses at grain boundaries of recrystallized grains. Sn-3.5Ag-0.5Cu-0.07Ni-0.01Ge has several grain boundaies which can be the origin of the crack so that fatigue lives degrade at 150°C.