The Effect of the Surface Roughness Characteristics of the Contact Interface on the Thermal Contact Resistance of the PP-IGBT Module

In this article, the correlation between the thermal contact resistance and the surface roughness characteristics of the contact interface in the press-pack insulated-gate bipolar transistor (PP-IGBT) modules during power cycling was studied by experimental measurements and finite-element (FE) simulation-based factorial design analysis. Thermal transient test technology was applied to examine the change in the thermal characteristic parameters of the PP-IGBT module. This shows that the increase in the thermal contact resistance of the Al metallization/emitter Mo contact interface occurs more dramatically during power cycling. A 3-D surface profilometer was used to evaluate the surface morphology parameters of the Al metallization/emitter Mo contact interface. The equivalent root-mean-square (RMS) roughness increases during power cycling, and the equivalent asperity slope and the equivalent spacing between asperities increase slightly. Additionally, the surface roughening in the corner area of the chip is more obvious than in other regions. A fractional factorial design analysis based on FE simulations was performed. The results indicate that the thermal contact resistance strongly depends on the main effects of the real contact area and the spacing between the asperities, and the RMS roughness and the asperity slope interaction.