Analysis of large area Trench-IGBT current distribution under UIS test with the aid of lock-in thermography

Abstract

In this contribution we focus on an innovative use of the well known lock-in thermography (LIT) technique. The main purpose of this paper is to show the possible use of the LIT technique in transient analysis of power devices. We show how the LIT technique can be used to image the current distribution in Unclamped Inductive Switching (UIS) tests and experimentally verify if current filamentation occurs. A significant number of experimental measurements on 1000 A peak current – 900 V maximum sustainable voltage Trench-IGBT is reported and discussed. The correlation between the sudden decrease in collector voltage during UIS test and filamentary current conduction inside the device has been demonstrated. Given the results of this analysis, an improved understanding of the reliability in UIS tests for the analyzed devices has been obtained confirming LIT technique as a useful tool for power devices analysis.