Modelling of thermal fatigue failure in soft-soldered semiconductor devices using the internal variable method

Abstract A physical model of thermal fatigue failure in soft-soldered semiconductor devices has been proposed by introducing the internal variable method of thermodynamics. Based on the analysis of experimental results of device power cycling and solder mechanical behaviour, a fatigue damage lifetime diagram for 95% Pb-Sn solder is given. This diagram can be used for estimating the thermal fatigue lifetime of devices.