Research On Preparation And Properties Of Graphite/Copper Composites With High Thermal Conductivity

With the increasing of chip integration, more and more heat resulting, we need tomeet the higher requirements on the heat sink materials of electronic devices. Comparedwith traditional heat sink materials, like copper and aluminum, graphite/coppercomposites have higher thermal conductivity, lower density, and outstandingperformance. It’s the one of most potential development direction of heat sink materials.Graphite has rich resources and easy to obtain, it’s provide the material foundation forthe wide application of the composites. The research on graphite/copper composites has agreat theoretical significance and practical value.In this experiment, electrolytic copper powder and natural flake graphite were usedto prepare graphite/copper composites by re-pressing and re-sintering process. Byobserving the powder morphology, the appropriate technology of mixing powder isdetermined. First, use high-energy ball milling electrolytic copper powder to break up itsstructure, and then mixed it with graphite powder by low speed ball. Through theanalysis of the microscopic structure of the composites, study on density, bendingstrength and thermal conductivity change with the content of graphite in the composites.The study showing: because of the pressing pressure is too small, most of copper inre-sintering composites still present in powder form, the combination of copper powderis not completely; with the increasing of graphite, it fragmented copper substrate moreand more obvious; under the effect of copper powder sintering to decreases volume andgraphite heat expansion, the density of the composites increases first and then decreasesafter re-sintering; due to the mechanical coupling between the powder particles, and lowrelative density, resulting in a low bending strength of the composites, decreased rapidlywith the increasing of graphite. when the content of graphite is less than60%, it can beable to meet the requirements of the radiator on the bending strength; as a large number of pores presence, thermal conductivity of the composites reduced severely, as to theorientation of natural flake graphite, when the graphite mass fraction is40%, thermalconductivity of the composites in a direction perpendicular to the pressure is still reached252W/(m·K), and at this point, the material density is only90.4%, it’s indicating that thegraphite/copper composites have a very large cooling potential.In order to improve the thermal conductivity of the composites, while natural flakegraphite aligned, a higher density of graphite/copper composites was prepared by hotpressing. Copper and graphite is uniformly distributed in the composites, and the coppersubstrate substantially three-dimensional mesh structure, the natural flake graphiteorientation, copper and graphite contact closely. Under the given process conditions, thecomposites have a very good performance. When the graphite mass fraction is40%, thethermal conductivity of the composites reached378W/(m·K), which is equivalent withcopper, and the composites density is only45%of copper, applicable to the heat sinkmaterials.