Influence of the Uneven Temperature Distribution on the Electrode Warpage of PP IGBTs

Abstract

The pressure and junction temperature distribution within press-pack insulated gated bipolar transistors had been proven uneven due to the thermomechanical coupling effect caused by electrode warpage. However, the root reason for the electrode warpage remains unclear, and therefore leads to confusion in optimization. In this article, the influence of vertical and lateral temperature difference on the electrode warpage is first separated and analyzed through the proper combination of boundary conditions in finite element simulation. The lateral temperature difference is found to be the main reason for the electrode warpage, which is different from the perception state of the art and provides the possibility to suppress the electrode warpage directly. Furthermore, the role of the lateral temperature difference is analyzed by a simplified model and it is found that the lateral temperature difference could be decreased by only pure thermal design rather than thermomechanical design. The electrode size and pedestal layout are discussed to alleviate the lateral temperature difference of the electrode and the simulation results also show great improvement in pressure and junction temperature distribution. Finally, the junction temperature distribution is measured by the sequential <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CE</sub> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> ) method to verify the root reason and also the effectiveness of the improvement.