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

With the rapid development of electronic devices towards miniaturization,lightweight and high performance,the increasing power density and generated heat have become the key problems restricting the reliability and efficiency of electronic equipment.The thermal conductivity(TC)of some traditional electronic packaging materials such as Invar,Kovar,SiC/Al and Si/Al could no longer fulfill the requirements of high-power electronic devices.In order to dissipate heat effectively and timely,it is urgent to develop electronic packaging materials with high TC.In recent years,Graphite/Al composites have become a research hotspot because of its high TC,easy processing and lightweight.In this paper,graphite film with high TC was used as the reinforcement,on the basis of summarizing the TC mechanism and influencing factors of Graphite/Al composites,the optimization and research of its preparation process,interface optimization and composites configuration were carried out.The relationship between the preparation process,configuration and performance characteristics of the composites were compared and established.The main conclusions are listed as follows:Based on the acoustic phonon mismatch model,the effects of different carbide modified layers on the interfacial heat transfer coefficient of Graphite/Al composites were calculated.and representative carbide intermediate layers were selected.TiC modified layers with average thickness of 183 nm and SiC modified layers with average thickness of 167 nm were successfully prepared on the graphite surface by reactive sputtering mothod.Taking laminate material as research object,the effects of different modified layers on TC and mechanical properties were discussed.It is found that the modified layers can improve the interfacial bonding and properties of the composites.When the volume of graphite is 28.7%,the in-plane TC of the composites reinforced by SiC and TiC modified graphite can reach 499 W/m·K and 486 W/m·K,comparing with uncoated graphite,which increased by 10.4%and 7.5%,and the interfacial heat transfer coefficient increased by 9.8 times and 3.4 times,respectively,the tensile strength can reach 39 MPa and 44 MPa,respectively.Through the rolling process,the layered composites were transformed into discontinuous configuration,which could improve the mechanical properties while sacrificing part of the TC.The effects of different rolling processes on the composite were investigated.It is found that the greater the initial thickness and single deformation of the material are,the easier it is to produce the phenomenon of uneven distribution of graphite;with the decrease in single deformation and the rolling passes,the graphite in the composites tends to be arranged in parallel.Based on the effective medium model,the effects of the size distribution of reinforcement and the value of spatial distribution function on TC of the composites were calculated,under the same average size,the TC of composites was negative influenced when the size distribution of graphite is large and the proportion of small-size graphite is high.Combined with the EMA model,the properties of the rolled material were analyzed,by controlling the thickness of the rolled piece and prefabricating pores on the graphite surface,the size distribution and spatial arrangement of the reinforcement can be improved,and the TC was effectively improved.At 19.8%volume fraction of graphite,the in-plane TC can reach 377 W/m·K and the tensile strength can reach 87 MPa.By pre-perforation on the graphite,the effects of pore parameters on the properties were compared.combined with the theoretical models,it is found that the smaller the penetration and the larger the pore diameter,the higher the TC and the lower the mechanical properties of the composites will be.The prepared composites can maintain high TC and high mechanical properties under low graphite content,when the penetration is 13.4%and the graphite content is 19.8%,the in-plane TC of the composites is 362 W/m·K and the tensile strength can reach 122 MPa.In this paper,composites with varies configuration were prepared through different processes,and the performance characteristics of composites were summarized and compared,which provides the theoretical basis for the process preparation and performance design for Graphite/Al composites...