Transient thermo-mechanical analysis of smart power switches by a laser Doppler vibrometer and numerical simulations

In the paper, application of a laser Doppler vibrometry (LDV) technique for the surface thermal expansion measurement of the semiconductor power devices is presented. As the LDV method can provide a signal directly proportional to the velocity of the surface deformation even for step inputs, the study of a thermal deformation transient process has been accomplished. The time dependence of surface out-of-plane displacement was obtained by integration of the measured velocity time dependences for several discrete surface points. The LDV results of transient performance were confronted with those simulated by the finite-element method. Such a numerical/experimental analysis has been carried out on a composite multilayer structure of a smart power switch device operating under short circuit conditions. A good quantitative coincidence was achieved between thermo-mechanical modelling and LDV measurements.