Study On Preparation And Performance Of High Thermal Conductivity Graphite/Copper Composite

The development of electronic devices towards miniaturization,multi-function,and high integration,causing heat congregation in electronic system.To avoid thermal failure of electronic system,thermal management materials with high thermal conductivity(TC),low coefficient of thermal expansion(CTE),and applicable strength are required to transfer heat to the heat sink or external space in time to ensure the stable operation of the electronic system.In this study,graphite with high thermal conductivity and copper were used as the reinforcement and the matrix to prepare the graphite/Cu composite.SEM,EBSD,TEM,XRD,XPS,and thermal/mechanical performance testing were used to study and optimize the preparation process,composite configuration,interface structure of the composite.The preparation technology of graphite/copper composite was systematically studied and optimized,including the preparing high solid content slurry,designing debinding process,and specifying sintering process.The results showed that after 50?60 wt%of mixed powder was added to the organic additives(mass ratio of ethanol,polyvinyl butyral,dibutyl phthalate was 13.2:1.2:1),the as-prepared slurry with viscosity of 1.0 Pa·s was obtained.The composite green tape could easily separate from the substrate,and had good flexibility and aligned graphite flakes.The high temperature anaerobic degreasing process contributed to about 0.384 wt%residual amorphous carbon in the 50 vol%graphite flake/copper(GF/Cu)composite.As a result,the in-plane TC of the composite was lowered by 12.75%.and the thickness CTE decreased to-8.34×10-6/K,and the bending strength was increased by 10.84%.The GF/Cu composite with tight interface bonding and 98-99%density was prepared by hot-pressing sintering at 1000? for 2 h,under 10 MPa axial pressure.The discontinuous phase(graphite flake)and continuous phase(graphite film)reinforced graphite/copper composites were prepared and their properties were comparative studied.The results showed that the in-plane TC of 50 vol%GF/Cu with orientation configuration was increased by about 25.6%compared to the GF/Cu composite without orientation configuration.With the same graphite content(30?50 vol%),in-plane TC of GM/Cu composite was 28.8%?36.9%higher than that of the GF/Cu composite,which attributed to the establishment of graphite high-speed thermal conduction channels.The effect of Zr and Mo on the microstructure and properties of GF/Cu composites was studied in detail.The results showed that the Cu5Zr,Zr,and ZrC particles about 50 nm strengthened the interface bonding and enhanced the copper matrix.The in-plane TC of the composite increases by 2.1%with 0.5 wt%Zr addition,and the in-plane CTE decreased to 13.8×10-6/K.At the same time,the thickness CTE was lowered to-5.95×10-6/K(25?250?),and the bending strength was increased by 42.2%.Fine crystal strengthening of the Cu matrix by the in-situ Mo particles,as well as the interfacial bonding enhancement by the in-situ Mo2C both improved the properties of the composite.The 50 vol%GF/Cu composite with 1 wt%Mo content showed the in-plane TC of 598 W/(m-K),and the thickness CTE of-2.92×10-6/K(25?250?),and the bending strength was 40%higher than the 50 vol%GF/Cu composite.