Reliability assessment using modified energy based model for WLCSP solder joints

The reliability life assessment of electronic packages is a key issue to ensure the mass production quality of packaging components. To meet the time-to-market and long term reliability requirements, using finite element to predict a precise life cycle of solder joints becomes the main trend of electronic packaging product development. Thermal cycling test is a standard test and has been widely used for testing long term reliability of packaging components, however, many cases shown the ramp rate will affect the reliability life of solder joint, therefore, the strain rate and creep effect should take into account for life prediction in finite element simulation. Our previous results found the life prediction is not accurate enough when using Darveaux energy based model for solder joint's life prediction. In this research, based on the optimal mesh size, we modify the energy based model to a simplified form based on our wafer level chip-scale packaging (WLCSP) study results, and this modified empirical solution can provide a better reliability life prediction than conventional energy based model. If the dwell time and ramp rate are fixed, the effect of time dependent creep behavior become inconspicuous. Based on our optimal mesh size, Coffin-Manson strain based model can also predict a precise lifetime and even with less computing time.