Study On Diamond/Copper Composites Fabricated By Surface Metallization-Chemical Co-Deposition Method In Electronic Packaging Application

This investigation aims at preparation electronic packaging material with highTC and low CTE matched to semi-conductor materials, synthetic micron diamondsparticle reinforced Diamond/Cu composite were fabricated by surface metallizationand chemical co-deposition method. The microstructures of Diamond/Cu compositewere studied by X-ray diffraction, optical microscope, scanning electron microscopeand transmission electron microscope. The physical properties of Diamond/Cucomposite were analyzed by thermal expansion tester and thermal conductivity tester,great emphasis was given to the effect of diamond particle size and surfacemodification on TC and CTE. The following results were obtained:D/Cu composite powders were prepared by surface metallization and chemicalco-deposition route, and D/Cu composites were fabricated by powder metallurgy. Thepretreatment process of electroless plating of copper was optimized throughexperiment. Some petty concave pits were eroded on the surface of diamond byconcentrated nitric acid through roughening pretreatment process, which wasbeneficial to the growth of coating, The optimal weight ratio interval of Diamond to Tiand Cr were 1:3～1:4 and 1:8～1:10 through contrast experiment use salt bath platingprocess.Electroless plating and salt bath plating were adopted on the surface modificationof diamond. An layer consist of even and compact copper was plated on the surface ofdiamond by electroless plating, which improved the wettability between diamond andcopper. Experiment results indicated that good metallurgical bonding can be obtainedbetween diamond and copper after salt bath, it was found that the interface of thediamond in the salt bath was closer than that of Cu plating diamond. The structuremodel of carbide after salt bath Ti and Cr plating has been proposed and the growthmechanism of carbide on the surface of diamond was validated. The carbide not onlystrengthened the bonding between diamond and copper as transition layer, but alsomade a bridge grafting role to improved the TC and CTE performance betweendiamond and copper in the Cu matrix composite.The experimental results indicated that diamond particles homogeneouslydispersed in copper matrix, the interface was clean and tight, grains were fine,dislocations and twins could be found. The influence of D particle size and surface modification on composites performances was studied. With the increase of D particlesize, composites'conductivity could be improved, but the density and hardness andtensile strength were decreased. D/Cu composites have the best combinedperformances with salt bath Ti plating and thermal conductivity can reach to 310 W/(m·K),The CTE (coefficient of thermal expansion) of D/Cu composites with salt bathTi and Cr plating were between 6.2～13.5℃and 6.5～14.5×10^-4 /×10^-4 /℃.