Through-plane assembly of carbon fibers into 3D skeleton achieving enhanced thermal conductivity of a thermal interface material

Thermal management has become one of the most important issues for electronic devices due to the continual increase in power density and consumption. Thermal interface materials (TIMs), applied between heat sources and heat sinks, are essential ingredients of thermal management. Carbon fibers are promising fillers because of its numerous advantages including high thermal conductivity, high strength-to-weight ratio, desired fatigue resistance, and corrosion resistance. However, they are rarely considered in preparing TIMs at present, because the one-dimensional structure of carbon fibers largely enhance the viscosity of the composites using conventional methods, and thus increase the complexity of processing. Herein, we report a thermally conductive TIM based on the construction of three dimensional and vertically aligned carbon fibers (3D-CFs) skeleton. The 3D-CFs skeleton is fabricated by vertical freezing the solution of CFs followed by freeze-dying to remove the ice and then infiltrating them with epoxy resin matrix. At a relatively low CFs loading of 13.0 vol%, the composites show an enhanced through-plane thermal conductivity (2.84 W m−1 K−1) compared to that of a neat epoxy resin (0.19 W m−1 K−1). Theoretical models qualitatively demonstrate that the interfacial thermal resistance is mainly originated from CFs–CFs interface not CFs–epoxy interface in oriented CFs/epoxy composites. In addition, the composites also possess a low thermal expansion coefficient (CTE) of 23.63 ppm K−1, and an increased glass transition temperature of 222.8 °C at a relatively small CFs loading (13.0 vol%) compared to that of pure epoxy resin. Our fabrication of through-plane assembly of carbon fibers skeleton has broad application prospects in TIMs.