Enhancing the electrical insulation of highly thermally conductive carbon fiber powders by SiC ceramic coating for efficient thermal interface materials

Mesophase pitch-based carbon fibers (MPCFs), which have ultrahigh intrinsic thermal conductivity and one-dimensional morphology with high-aspect ratios, can act as excellent fillers for improving the oriented heat dissipation rate of thermal interface materials (TIMs). However, the high electrical conductivity hinders their application in some electronic packaging fields. Herein, a SiC ceramic layer is uniformly and firmly coated on the surface of the powder-like MPCFs by a dynamic chemical vapor deposition method to obtain the high thermal conductivity and suitable electrical insulation. The ceramic coating layer exhibits a porous structure, complete encapsulation and adjustable thickness in the range of 90–600 nm. Employed as the thermal conductive fillers, the SiC-coated MPCF-derived TIMs exhibit comparable thermal conductivity and significantly enhanced electrical insulation performance compared with that from original carbon fiber. For instance, the pad prepared from the coated carbon fiber with a medium coating thickness of 200 nm shows a high through-plane thermal conductivity of 12.8 W m−1 K−1, high electrical resistivity of 3.4 × 1010 Ω cm and satisfactory breakdown voltage value of 1100 V mm−1. This work opens a new avenue to integrate the thermal conductivity and electrical insulation of carbon materials as thermal conductive fillers for electronic packaging.