Electrodeposited Cu Coated Low-Dimensional Carbon Materials For Preparation Of Composite Thermal Management Materials By Hot Press Sintering

With the rapid development of electronic industry,the power density of electronic devices increases sharply,and carbon/Cu composite thermal management materials with high thermal conductivity and tailorable coefficient of thermal expansion are urgently required to ensure efficient heat dissipation.The composite thermal management materials are usually obtained by solid phase sintering using mechanically mixed powders or coated powders.Compared with mechanically mixed powders,coated powders could realize more homogeneous distribution of carbon materials in Cu phases,which is beneficial to improve performance of composite.Nevertheless,the traditional electroless plating method to prepare Cu-coated powders,requires a two-step pretreatment process of sensitization and activation and it takes a long time to achieve a given thickness of coating deposition.Additionally,electroless plating is inferior in cost effectiveness due to complicated composition and limited lifetime of the plating solution,which hinders its large-scale utilization in plating Cu.In this work,the intermittently electroplated method,which possess easy-to-operation process,controllable deposition rate,stable and recycleable electroplating solution,was proposed to prepare homogeneous Cu-coated carbon materials.The uniform Cu coated was successfully prepared on the surface of three kind of low-dimensional carbon materials,which includes diamond particles,short-graphite fibers and graphite flakes.The nucleation process of Cu deposition on the surface of three kinds of low-dimensional carbon materials follow the instantaneous nucleation mechanism of Skarifker-Hills model.The overpotential of carbon material fixed bed electrode has uneven distribution characteristics owing to electrodeposition equipment characteristics.The surface of carbon materials could be uniformly plated with Cu by intermittent stirring,and a Cu content controllable coating materials could be obtained.Subsequently,the 45-65 vol%diamond particle/Cu composite materials with diamond particles uniformly distributed in the Cu network structure were obtained by hot-pressing sintering Cu-coated diamond particles.The distribution uniformity,appropriate content of diamond particles and low interfacial thermal resistance between diamond particles and Cu,are the main reasons for the enhancement of thermal properties of the materials.The thermal conductivity of 55 vol%diamond particle/Cu composite material reached the highest value of 638 W·m-1·K-1,and its coefficient of thermal expansion value and bending strength could reach 4.11 ppm·K-1 and 243 MPa,respectively,which could meet the heat dissipation requirement of high power electronic components.The 20?50 vol%short-graphite fiber/Cu composite materials,where short graphite fibers are uniformly distributed in the Cu phase in the plane direction,were obtained by hot-pressing sintering Cu-coated short-graphite fibers.The composite materials with high thermal conductivity and low thermal expansion coefficient is attributed to the intrinsic properties of short graphite fibers.The coefficient of thermal expansion value of 50 vol%short graphite fibers/Cu composite material could reach 6.03 ppm·K-1,its thermal conductivity could reach 263 W·m-1·K-1,and bending strength is 107 MPa.The 40?90 vol%graphite flake/Cu composites materials,in which graphite flakes are uniformly arranged in the Cu phase with a parallel to each other and perpendicular to the pressing direction,were obtained by hot-pressing sintering Cu-coated graphite flakes.The effect of volume content of graphite flake on the thermal and mechanical properties of composite was studied.When the volume fraction of graphite flakes increased from 40%to 90%,the planar thermal conductivity of graphite flake/Cu composite materials increase from 506 W·m-1·K-1 to 710 W·m-1·K-1.The bending strength of composite materials decreased from 93 MPa to 15 MPa.In order to further improve the mechanical property of the composite,the interfacial bonding strength between graphite flakes and Cu was improved by titanium coating.When the volume fraction of titanium-plated graphite flakes was 40%,the bending strength of titanium-plated graphite flake/Cu composite materials was as high as 103 MPa,which was 10 MPa higher than that of the non-titanium-plated composite.By taking full advantage of the advantages of graphite flake with high thermal conductivity in plane direction,it has potential applications in the field of thermal management materials.