Modeling transient thermal response of pulsed power electronic packages

Steady-state power conversion applications have benefited from numerous packaging and cooling improvements, and there has been a push to apply the same techniques to pulsed power electronic systems and devices. However, the unique aspects of pulsed systems create a trade-off between high package thermal capacity for mitigating rapid temperature rise and low thermal resistance for rapid heat rejection. This report details a numerical study of several electronics packages with varying levels of cooling integration. Using finite element equivalent thermal circuit models to perform transient simulations of the packages, the effect of convective improvement and a reduced thermal path upon junction temperature response was examined. Results showed that while a reduced thermal stack and high convection rate speeds the return to steady state after a pulse, the ability for improved convection to mitigate junction temperature rise diminishes significantly as pulse widths approach the thermal time constant of the package. In addition, the reduced thermal capacity of the integrated packages causes them to exhibit higher junction temperature rise and larger temperature swings than basic, non-integrated packages for certain pulse conditions. The worst case examined showed a direct die-cooling package exhibit a 3x increase in peak temperature and a 5x increase in pulse-to-pulse temperature swing over a standard, non-integrated package.