Thermomechanical Deformations of Power Modules with Sintered Metal Buffer Layers under Consideration of the Operating Time and Conditions

In this work an investigation of the thermomechanical deformation behaviour of power modules with sintered metal buffer layers is presented under consideration of the operating time. The thermomechanical deformation is measured during active operation of the device using an optical measurement technique. The in-plane strain and the out-of-plane curvature were evaluated in dependency of the temperature by applying different operating conditions (IC, ton, toff). In addition, comparisons of the deformations of modules are shown, which on the one hand were measured directly after the production and on the other hand have passed through several thousand active load cycles until the end-of-life (EOL). Furthermore, the relevant electrical and thermal parameters (VCE,Sat, Tvj,max, ΔTvj, Rth) were recorded during the load cycles in order to analyse the failure mechanisms. The evaluation of the electrical measurement with regard to the failure mechanism correlates with the findings of the thermomechanical deformation. The uncertainty regarding the primary failure mechanism, which exists when evaluating only VCE and Rth, can be eliminated with the additional optical method without destroying the test module.