Rapid hot pressing of copper composites for electronics' cooling applications

The control of the interfacial reactions is crucial to enable manufacture of Cu/diamond heat sinks with high thermal conductivity. Interesting high thermal conductivities are possible with diamond reinforced CuCr or CuB matrix composites. The preparation of the most promising Cu/diamond composite resulted in a thermal conductivity of about 600 W/mK combined with a CTE of about 9 -10x10-6/K. Further decrease of CTE can be realized by increasing diamond content. More detailed characterisation of the interfaces confirms the need for a chemically reacted interface to enable the heat conduction across the metal-diamond interface. The interfacial carbide formation is different in morphology depending on the pressing technology. Obviously, the rapid heating (during the directly heated hot pressing) can cause a higher number of nuclei for carbide formation resulting in finer and smoother interfacial structures compared to the conventional hot pressing process. This can presumably correlate with the achieved higher thermal conductivity of these composites.