Optimising the thermal path for your power module
Summary
This article looks at a variety of ways to achieve good interfacing between heat sources and heatsinks while focusing on solutions for power modules, including a new material that solves many of the challenges faced by design and production engineers. Sheets are sandwiched between the heating elements and heatsinks; they are easy to handle but, due to their hardness, they require pressure to achieve adequate contact. With the power module in a vertical position, thermal greases, or even PCMs, are likely to discharge due to the gravitation accompanying temperature changes, leading to a medium-to-long-term degradation in performance. Lastly, they must be easy to attach and remove from the heatsink and power module without any significant investment in production in order to be simple to change in the field as well. The optimal sheet thickness mainly depends on three parameters: Table 2: Sheet thickness recommendation based on size of the module and contact pressure Panasonic currently offers GraphiteTIM in 56 standard shapes that are compatible with several hundred power modules, including products from Semikron, Hitachi, Fuji, Infineon and Mitsubishi, as detailed in the GraphiteTIM selector tool at https://industrial.panasonic.com/ww/soft-pgs-cross.