Fabrication and thermal properties of hot press sintered Cr-coated carbon fiber/Cu composites

The mesophase pitch-based short carbon fibers (CFs) with ultra-high thermal conductivity and negative coefficient of thermal expansion (CTE) were compounded with Cu via hot press sintering. In order to improve the bonding state between CFs and Cu, Cr was pre-coated on CFs by chemical vapor deposition technique. The microstructure and thermal properties of the Cr-coated CFs/Cu composites were studied. The results show that most of Cr coating reacts with C forming to a thin, continuous and uniform Cr7C3 interfacial layer, and small amount of them diffuses into Cu matrix during the preparation process, which causes the interface structure between CFs and Cu to change from week mechanical bonding into good metallurgical bonding. Consequently, the thermal properties of the composites are improved effectively. The Cr-coated CFs/Cu composites with 40vol%-55vol% CFs achieve the relative densities higher than 97.5%, the in-plane thermal conductivities to 393-419 W(mK)-1 and the in-plane CTE ranging of 5.1×10-6-8.4×10-6 K-1. The composites are promising materials for electronic packaging applications due to their high thermal conductivities, low CTE and good machinabilities.