Determination on the thermal conductivity and thermal contact resistance of thin composite phase change films as a thermal interfacial material

Sub-millimeter thick phase change material (PCM) composites have been utilized in the thermal management of micro-electronics serving as a novel thermal interfacial material. However, there is a lack of appropriate measuring methods and precise data for the thin-film PCM composites' intrinsic thermal conductivity, as well as the thermal contact resistance (TCR) at interfaces between those thin-films and metal. In this work, the out-of-plane thermal conductivity of thin-film PCM35, which is a paraffin composite showing the melting point of 35 °C, was first gauged through the commercialized transient plane source (TPS) method, followed by a correction process to deduct the TCR between thin films/temperature sensor interfaces. The direct TPS readings were corrected based on the proportional relation between samples’ thickness and inherent thermal resistance. An improved steady-state heat flow apparatus designed for thin-walled samples was then utilized to examine the reliability of the corrected TPS technique, with a relative deviation between them being only ∼7%. In order to test the applicability of the corrected TPS method, the thermal conductivities of thin polytetrafluoroethylene films were also determined. Furthermore, the TCR between thin PCM35 film and thin 1060Al plate was identified by performing the improved steady-state apparatus. The contribution of overheated PCM35 film on fitting the interfacial voids and reducing the TCR were elucidated, which can guide the thermal design with the use of such thin-film PCMs.