Integrating a thermo-mechanical solver into the DJOSER analytical thermal simulator for multilayer power electronic assemblies. Preliminary results

The DJOSER analytical thermal solver for multilayer mounting structures has been tested as a useful and friendly tool for the thermal analysis of power electronic devices and their packages, able to replace the onerous programs based on the finite element (FEM) calculations. The other problem connected with the packaging evaluation is the calculation of the thermally induced stresses and strains in the various layers composing the assembling structures. This paper deals with the first step of the implementation of a thermo-mechanical solver to be connected with the DJOSER program, which may be able to calculate the stresses at the layer interfaces, using the same strategy, i.e. a semi-analytical mathematical approach, and the same DJOSER structural constrains (stepped pyramidal structures, homogeneous layers). The basic theory is briefly exposed and the method is applied to some two-layers virtual structures. The obtained results are compared with those obtained using standard FEM analyses, revealing a substantial agreement but also some local disagreements.