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 the rmal resistance, but yet a high voltage standoff capability. The thermal re sistance consists of two components: thermal contact resistance at the copp er/Kapton MT interfaces, and the thermal conduction resistance across the K apton MT film, The measured thermal resistance at low temperatures indicate s that increasing the contact pressure reduces the thermal resistance, to a limit determined by the film conduction resistance, The effects of the con tact pressure, the average interface temperature and the thickness of the i nterstitial layer are evaluated. A novel dimensionless correlation is deriv ed from the experimental results that describes the thermal contact conduct ance of joints which include a soft interstitial material, at cryogenic tem peratures. (C) 1999 Elsevier Science Ltd. All rights reserved.