Influence of Antimony on Reliability of Solder Joints Using Sn-Sb Binary Alloy for Power Semiconductor Modules

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.