Measuring Specificities of Thermal Resistance of IGBT Power Modules

This article shows that the results of experimental studies of thermoelectric properties of the insulated gate bipolar transistor (IGBT) power modules aimed at developing methods and means for measuring cross-couple thermal resistances between module transistors. The research has shown that the modulation method, which uses heating of a measured object with power modulated according to the harmonic law, has a number of advantages over standard methods based on measuring the transient thermal characteristics. It was possible to measure thermal resistance components “junction-top copper layer of the direct bond copper (DBC) board,” “junction-Al2O3 layer of the DBC board,” “junction-baseplate of the module body,” and “junction-heatsink” using the modulation method for all the IGBTs of the GD35PIT1205SN power module. Analysis of the results showed that the cross-couple thermal resistance between the transistors of the module may contain one or two components. If the transistors are located on the same DBC board and the heat flows between the module transistors within the same DBC board, then only one component appears. If the transistors are located on different DBC boards separated by a gap, then two components of thermal resistance appear.