Effect Of Surface Treatment On The Thermal Conductivity Of Diamond/Cu Composites

With the advent of the 5th generation communication technology,electronic devices have higher requirements for heat dissipation.Diamond/Cu composites with high thermal conductivity(TC)and adjustable thermal expansion coefficient are known as the first choice for the next generation of electronic packing materials.But the low interfacial thermal conductance(ITC)between the diamond and copper becomes the severe problem to further improve the TC of Diamond/Cu composites.Based on the analysis made above,in this paper,diamond particles are etched via a molten salt method to obtain different surface areas.And diamond/Cu composites are prepared by a hot pressed sintering method.Subsequently,the effect of surface areas on the TC of composites is investigated deeply by experiments and finite element simulations.The effect of etching temperatures on the morphologies and phase structure of diamond particles was investigated systematically by adjusting the molten salt etching parameters.The morphologies of etched pits on the{111}and{100}planes are triangular and quadrilateral respectively,and the size of this pits on the{111}planes is about 1.5 times comparing to the{100}planes.Also,there is no graphitization transformation during the etching process,and the sp² carbon,C-H bond and graphite cluster are largely eliminated by etching,but the C=O bond has a slightly increase.After the etching,the raw and etched diamond particles were coated by the double-layer to further strengthen the interfacial combination of the diamond and copper matrix.The tungsten(W)and copper(Cu)double-layer introduced by a thermal diffusion method and a electroless method respectively.The W-coating is uniform,complete and continuous and even is not oxidized,and its phases were composed of W,W₂C and WC.Additionally,the thickness of tungsten a nd copper layer was about 170nm and 2.4?m respectively.The Diamond/Cu composites with excellent interfacial bonding are prepared by a vacuum hot pressing sintering method.With the change of etching temperatures,the TC of the composites increases first and then decreases.The TC of the composites has a maximum of 602 W·m^-1·K^-1,and the ITC reaches to 2.27×10⁷ W·m^-2·K^-1.The finite element method is successfully employed to construct different interface models to show that the increase of interface area provides more efficient channels for heat transfer.In other words,the etched pits may significantly increase the coupling area between the diamond and the Cu matrix,therefore providing more heat transfer channels and a secondary heat transfer process at the interface.In conclusion,the feasibility of this idea is demonstrated expe rimentally and theoretically,thus it is expected to provide experiences for improving the TC of other particles reinforced metal matrix composites.