Solder fatigue failures in a new designed power module under Power Cycling

Today a point has been reached where lifetimes of power modules are limited by the standard packaging technologies, such as wire bonding. To surpass these limits, a new power module was designed using Cu clips as interconnects instead of Al wire bonds. With this new design the structure robustness should be improved and lead to a reliability gain but in counterpart it requires an additional solder layer in order to fix the clip onto the die. This paper studies the failure mechanisms occurring in these two solder layers under power cycling. The behavior of solder layers is precisely analyzed by performing power cycling tests and by taking advantage of Finite Elements simulations. Furthermore an experimental and numerical sensitivity study on test parameters is conducted. Results obtained enable the definition of solder lifetime prediction models.