抄録
Thermal fatigue damage of solder joint is considered to be closely associated with microstructural phase growth. The authors have proposed a new method to evaluate the fatigue crack initiation life time by introducing the phase growth parameter S_c, which represents strain induced phase growth. This is an application study of the method to actual thermal cyclic tests using fabricated PCBs. As a result, microstructurally measured S_c data show Weibull's distribution. And it becomes possible to estimate the average life time with upper and lower limits corresponding to the standard deviation of observed S_c. It is very useful for the reliability of solder joint that the average life time is estimated by using shorter period data under 100 cycles.
