Abstract
Improvement of analysis precision of thermal fatigue test is required to shorten the development period for power device products. During thermal fatigue test, thermal resistance increases more and more as the crack of solder proceeds. It causes temperature rise of the device and increase of thermal stress and leads to acceleration of the crack propagation. However, conventional crack propagation analysis does not take into account this phenomenon. We developed crack propagation analysis with the capacity of dealing with the change of thermal and electrical boundary condition resulting from the crack propagation. The developed method reproduces the drastic increase of thermal resistance in the latter part of thermal fatigue test and agrees well with the experimental result. We also confirmed that temperature distribution of the device changes as the crack propagates and revealed that thermal and electrical coupled analysis has major effect on the prediction of fatigue life of power device products.
