Thermo-mechanical solver for multi layer packages of power electronic devices and systems. Preliminary results

The DJOSER code has been tested as a useful and friendly tool for the thermal analysis of power electronic devices constituted by multilayer structures. The other problem connected with the packaging evaluation is the calculation of the thermally induced stresses and strains in the various layers of the assembling structures. This paper deals with the thermo-mechanical behaviour of 1-dimensional structures made up of layers with different geometrical and thermo-mechanical properties subjected to thermal loads. A first version of the thermo-mechanical solver connected with the DJOSER program has been implemented. The solver is able to calculate the stresses at the layer interfaces, using the same strategy of DJOSER, i.e. a semi-analytical mathematical approach, as well as the same structural models (stepped pyramidal structures, homogeneous layers). The basic theory is briefly exposed and the method is applied to a two-layers structure whose results are compared with those obtained using standard FEM analyses.