Design method of thermal connector for electronic equipment cooling

Abstract

We have developed the evaluation method for two performance factors to design the thermal connector: Insertion force of thermal grease and thermal conductance. The thermal connector was comprised of a thermal plug and a thermal socket, and the thermal grease which was filled into the gap between the thermal plug and the thermal socket connected the thermal plug and the thermal socket thermally. Firstly, the insertion force was theoretically calculated using the Bingham plastic model for rheology characteristics of the thermal grease and the slip model on the surfaces of the thermal plug and the thermal socket. The calculated results were in good agreement with the experimental results. Secondly, the experimental results of the thermal conductance between the thermal plug and the thermal sockets at the first connection to the 20 times connection were -1 to +26 percent greater than the theoretical value. The reason why some experimental results exceed the theoretical results is the eccentricity between the thermal plug and the thermal socket. In addition, the filling status of the thermal grease in the gap was visualized by ultrasonic testing. The results after the 20 times connections showed there were some voids in the thermal grease and the area of voids was 4 percent of the heat transfer area. Therefore, the thermal conductance was mostly not influenced by the voids. Finally, it was found that the proposed methods to predict the insertion force and thermal conductance were reasonable.