Interface Design And Properties Of Diamond/Copper Composites

The increase in power level of high integration devices have urged the requirements for better performance of thermal management materials.Diamond particle-reinforced metal matrix composites has been the research hot spot for new generation high-performance electronic packaging materials,owing to the characteristics of high thermal conductivity,low expansion coefficient,high elastic modulus and excellent wear resistance.However,the weak interface bonding and high thermal resistance were always been the most negative factors for diamond reinforced metal matrix composites because the poor wettability between metal and diamond.A feasible solution to the problem is diamond surface metallization,The surface metallization can improve the wettability of the diamond particles and the metal matrix,which leads to large enhancement of the thermal conductivity of the composites.In this paper,Cr or Mo was deposited on the diamond particles by salt bath method to metallize the diamond surface.The influence of technological parameters on the structure and morphology of the coating was studied.Then,the diamond/copper composite was prepared by hot pressing method with the surface modified diamond and copper powder as raw materials.The characteristics of coating were investigated by Scanning Electron Microscopy(SEM),Energy Disperse Spectroscopy(EDS),X-ray Diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and Atomic Force Microscope(AFM).Part of the samples were ground and the thickness of the coating was measured by scanning electron microscope.The morphology,thermodynamic and mechanical properties of diamond/copper composites were studied.The results show that:(1)The coating obtained by RVD diamond vacuum plating Cr is discrete spots.When the weight percentage of Cr increases and the vacuum plating holding time extends,the coating gradually connects and becomes complete.RVD diamond salt bath is plated with Cr.When the weight percentage of Cr is greater than 8%,the coating is completely covered,the salt bath is evenly plated with Cr and the surface is flat.(2)Using molten salt method to deposit chromium plating on the surface of MBD diamond is faster.The chromium coating on the surface of diamond particles is mainly composed of Cr₃C₂and Cr₇C₃.As the temperature of the salt bath increases,the coating becomes rough and the probability of cracks in the coating decreases.When the Cr content reaches 6%and the salt bath time exceeds 40 minutes,a complete coating can be formed.As the heating time and Cr content increase,the coating thickness increases significantly.As the temperature increases,the thickness of the coating increases slightly.The coating thickness of the sample is between312-826 nm,and the actual thickness of the coating is lower than the theoretically predicted thickness.(3)Comparing MBD diamond and RVD diamond using the same surface modification method to make diamond/copper composite materials,the thermal conductivity of RVD diamond/copper composite materials is generally higher than that of MBD diamond/copper composite materials.It may be due to the irregular shape of the RVD diamond.When the diamond/copper composite material is prepared by hot pressing,the RVD diamond accumulates more densely in the composite material,and the volume percentage of the diamond in the composite material is higher,resulting in the RVD diamond/copper composite material.The thermal conductivity of MBD is generally higher than that of MBD diamond/copper composites.(4)Salt bath plating of Mo on the diamond surface,the formation of the coating shows preferential growth.The coating first grows on the{100}surface of the diamond and then on the{111}surface of the diamond.On the premise of ensuring the integrity of the coating,the minimum thickness of the Mo coating can be obtained as 1.191?m.(5)Plating Cr or Mo on the diamond surface greatly improves the performance of the composite material.The thermal conductivity of the composite material is increased from 162 W/(m·k)to 483 W/(m·k)at most,and the composite material is resistant to bending The strength is increased from 47 MPa to 243 MPa at most,the thermal expansion coefficient of the composite material is reduced,and the stability at high temperature is further improved.