Power semiconductor devices for electric power conversion must be able to operate at high temperatures and with high levels of reliability. Therefore, heat resistance and long fatigue lifetime are necessary for the solder joints of these devices.In this paper, we discuss the mechanical properties and the thermal cycling lifetime evaluation of a Sn-Sb binary alloy whose melting temperature can be controlled relatively, and which has excellent high temperature properties. Tensile tests are conducted to determine how the reliability of solder joints using the Sn-Sb alloy is affected by the amount of Sb.We used a Sn-13 wt.% Sb binary alloy as the joint material of a power semiconductor device and investigated the thermal cycling lifetime of the solder joint. It was clarified that the tensile strength of the Sn-Sb binary alloy is proportional to the Sb content and the thermal cycling lifetime increases with increasing tensile strength of the solder. The precipitation strengthening of a SbSn compound leads to improvement of the tensile strength and thermal cycling lifetime.

Tensile and low cycle fatigue properties of Sn-5Sb (mass%) solder were investigated with miniature size tensile specimens. The effect of temperature and strain rate on tensile properties and the effect of temperature on low cycle fatigue properties were examined. Tensile strength increases with increasing strain rate regardless of temperature investigated. For elongation, the effect of temperature on it is negligible although it slightly increases with increasing strain rate. The low cycle fatigue life of Sn-5Sb obeys by the Manson-Coffin’s equation. The effect of temperature on the fatigue life is negligible in the temperature range from 25 oC to 150 oC. In the low cycle fatigue test with a high total strain range of 4%, cracking at phase boundary mainly occurs regardless of temperature investigated. In the case of a low total strain range of 0.4%, ductile fracture mainly occurs, and cracking at phase boundary with generation of grooves also occurs at high temperature.

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