Thermal and Structural Simulation Techniques for Estimating Fatigue Life of an IGBT Module

Two techniques, one for estimating fatigue life of aluminum bonding wires and one for estimating fatigue life of solders under repeated thermal load, were developed. In one method, fracture mechanics with strain intensity factor (Delta
K

_epsiv
) is used to estimate the fatigue life of aluminum bonding wires. In the other method, "electrical-thermal-structural coupled analysis" is used to estimate fatigue life of solders. The simulated crack propagation in aluminum bonding wires agrees well with the experimentally measured propagation. Moreover, the simulations show that fatigue life of aluminum bonding wires has a lower fatigue limit at a temperature-cycling range of 30degC.