Characterisation of Thermal Interface Materials under Sustained Cyclic Thermo-Mechanical Loading

In modern power electronics, the push for high density power converters and resulting increase in loss densities within semiconductor devices necessitate the optimization of Thermal Interface Materials (TIMs). This need is particularly critical with the adoption of wide-bandgap semiconductors, where the reduction in active semiconductor volume heightens the influence of TIMs on overall system performance. The TIM plays a pivotal role in thermal management, directly affecting the electrical performance, thermal behaviour at the semiconductor junction, and ultimately, the system's longevity. In the context of top-side-cooled packages, thermal gap pads are used to facilitate thermal performance, while maintaining electrical isolation properties. A typical optimization method is to select the thinnest material possible, at highest possible thermal conductivity. However, typically these materials are stiffer and more porous compared to thicker, less conducting materials, which significantly impacts the thermo-mechanical performance of the gap pad, especially towards end-of-life. This work aims to characterize this behaviour for selected commercially available materials, giving a guideline for material selection and thermo-mechanical design of the target power electronics assembly.