Micro-mechanical characterization of lead-free solder joints in power electronics

The following study is motivated by the need to capture the elasto-viscoplastic behavior of a “real” industrial power module lead-free solder joint. In this work, we carried out a numerical design of experiments in order to forecast the ability of an experimental bending system to identify the specimen material properties. As a proof of principle, the micro-mechanical elastic behavior of power module copper substrates was then characterized thanks to the development of an innovative in-situ micro-mechanical bending test under an optical profilometer. An inverse Finite-Element Method has been applied in order to identify the material properties of test specimens designed directly out of industrial assemblies and not from bulk solder for good representativity. The results show that identified copper Young's modulus values are lower than that of a bulk material. It will be defined as such in the next identificatio n step targeting the solder joint.