Electrodeposition of nano-diamond/copper composite platings: Improved interfacial adhesion between diamond and copper via formation of silicon carbide on diamond surface

Although copper is an effective heat-dissipation material, a material with a higher thermal conductivity is required to meet the demands of future electronics. Carbon materials (CMs) are of great interest owing to their excellent thermal conductivities; however, it is difficult to apply CMs individually because of their brittleness and low formability. CM/copper composites are expected to overcome these drawbacks. Diamond is of special interest for preparing composites because they do not require control of orientation owing to their isotropic thermal conductivity, but unfortunately, diamond and copper generally show poor interfacial adhesion. Therefore, designing an interface to improve their adhesion is essential to realizing high thermal conductivity. In this study, SiC-coated diamonds were adopted to fabricate diamond/copper composite platings by electro-deposition for the first time. Electrodeposition was carried out in a copper sulfate bath containing pristine and SiC-coated diamonds. The formation of SiC slightly decreased the current efficiency but did not significantly affect the diamond content of the plating. The sample with the nano-diamond/copper composite plating containing 1.07 mass% (2.72 vol%) of SiC-coated nano-diamonds exhibited a thermal conductivity 46 Wm(-1) K-1 higher than that of the sample with pure copper plating. From observations of the diamond/copper interface using micron-sized diamonds as a model, an obvious gap was observed between the diamonds and the copper when using pristine diamonds, whereas no gaps were observed when using the SiC-coated diamonds. SiC formation significantly improved the adhesion between the diamonds and copper. In addition, copper was directly deposited onto the surfaces of the SiC-coated diamonds in contrast to pristine diamonds, which showed no sign of deposition.