Thermal contact conductance across filled polyimide films at cryogenic temperatures

Thermal contact resistance arises in the region of contact where two solid specimens are pressed together. The thermal resistance can be controlled by inserting an interstitial material at the interface, such as Kapton MT, a polyimide film containing alumina particles, which has a relatively low thermal resistance, but yet a high voltage standoff capability. The thermal resistance consists of two components: thermal contact resistance at the copper/Kapton MT interfaces, and the thermal conduction resistance across the Kapton MT film. The measured thermal resistance at low temperatures indicates that increasing the contact pressure reduces the thermal resistance, to a limit determined by the film conduction resistance. The effects of the contact pressure, the average interface temperature and the thickness of the interstitial layer are evaluated. A novel dimensionless correlation is derived from the experimental results that describes the thermal contact conductance of joints which include a soft interstitial material, at cryogenic temperatures.