Preparation And Study Of Diamond/Copper Composite With High Thermal Conductivity

Diamond/copper composites are considered to be one of the most promising electronic packaging materials because of their good thermal conductivity,adjustable thermal expansion coefficient,low cost and flexible material manufacturing.Moreover,the synthetic diamond has been industrialized,and the cost is greatly reduced.Therefore,the preparation of diamond/copper composites with high thermal conductivity has important research significance and practical application value for the development of packaging technology.In this paper,the surface modification of diamond particles by electroless Cu plating and Ni-Cu-P alloy plating was carried out,and then the dense diamond/copper composite was prepared by SPS sintering with mixture of diamond and copper powder in different proportion.The morphology of the coating,the natural surface and fracture section of the composite were observed by SEM.XPS was used to analyze the elements type of the diamond surface before and after coarsening and after sensitizing.The thermal conductivity of the composites were measured by laser thermal conductivity tester.The effects of diamond surface modification,heat treatment,volume fraction of diamonds and sintering temperature on the thermal conductivity and density of diamond/copper composites were analyzed.The main results are as follows:?1?The coarsening treatment increased the surface roughness of the diamond and formed hydrophilic groups such as C-O.After sensitization and activation,uniform activation centers were formed uniformly on the diamond surface.The optimal process parameters of electroless copper plating were:the concentration of silver nitrate is 5g/L in activator solution,the temperature of electroless plating was 50? and the plating time was 80 min.For the electroless Ni-Cu-P plating,the coating became more uniform and denser with the increase of sensitization frequency;the best plating temperature is70?;heat treatment transferred the Ni-Cu-P coating from amorphous to crystalline Ni and Cu,and formed chemical bonding between the diamond and coating layer.?2?The diamond/copper composites prepared by pressureless sintering have a relatively low relative density of only 82.3%,and no graphitization of diamond has been found in the composites.?3?Diamond/copper composites with different volume fraction of diamond were prepared by SPS sintering,when the volume fraction of diamond increased from 20%to 40%,the relative density changed little,and the thermal conductivity increased from148.2 W·m^-1·K^-1 to 361 W·m^-1·K^-1.When the volume fraction increased to 50%,the relative density decreased,some diamond particles accumulated,and the thermal conductivity dropped to 260.8 W·m^-1·K^-1.With the increasing of sintering temperature of SPS,the relative density of diamond/copper composite increased,and diamond graphitization occurred at 900?,the thermal conductivity of the composite material obtained at 800? was the highest.The diamond surface modification could effectively improve the combination at the interface of diamond/copper composite,improve the density of the composite and prevent the diamond surface graphitization at 800?.