Analytic thermal modelling of power electronic components: The Diffusive Representation

Abstract:
The paper deals with so-called “diffusive representation” method and its application to efficient thermal modelling. The interest of this approach is to build a compact electro-thermal model as an input-output state-space model, accurate and easy to simulate compared with finite-element (FEM) or finite-difference (FDM) approaches. In the first part, a diffusive thermal model has been developed for a Direct Bonding Copper (DBC) package with a wire-bonding attached IGBT die (600v / 50A). The obtained state-space thermal model is implemented in SABER simulator and allows transient thermal responses. The hottest point in the die is the channel extremity and adequate thermal measurement methods have been implemented to validate the developed diffusive thermal model. In the second part of the paper, a fast and accurate analytic thermal model of self-heating VDMOSFET was developed from only one result of a 2D finite element electro-thermal simulation with ISE-TCAD. The diffusive thermal model is then simulated in SABER and compared with FEM simulations.