Effect of Contact Characteristics on Thermal Contact Resistance of Grease-Less Uniform Contact Surfaces

A high-power electronic device such as ceramic resistor is often in contact with a housing of an electronic equipment by using bolts. This mounting method without the thermal grease that allows heat transfer through the device to the housing, realizes a low-cost design, however, has challenges in predicting and stabilizing a thermal contact resistance (TCR). In the authors' previous studies [1], [2], we have been developing a prediction method of the TCR based on a topography data of a grease-less uniform contact surface measured by using a confocal laser scanning microscopy. In this work, the TCR of the grease-less uniform contact surface between an alumina substrate with a surface roughness Sa = 0.504 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{m}$</tex> and an aluminum plate with a polished surface was predicted under the mean contact pressure <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0\leqq p_{\mathrm{m}}\leqq 10$</tex> MPa. And the predicted result was shown to be valid by comparison with a Test-Head style TCR measurement system [3]. In addition, the determining factors of the TCR were analyzed based on a thermal resistance ratio of an air layer and real contact points for achieving a low TCR of the contact interface.