Preparation And Application Of Graphite Film-based Thermal Conductive Composites

With the continuous advancement of computer microelectronics and new materials,electronic devices are developing toward high integration and high functionality.The packaging environment for electronic devices continues to decrease while the power density of electronic devices continues to increase.The increasingly narrow environment has brought serious problems to the heat dissipation of the chips.Therefore,the thermal management of electronic devices has become increasingly serious.In order to deal with increasingly stringent thermal management issues,this article uses graphite film as the substrate for the preparation of high thermal conductivity composite materials.A composite material with a layered structure was prepared by applying a coating method such as a brush film and the like using a binder of an epoxy resin and a polyurethane system,respectively.This kind of composite material has both excellent properties of light weight and high thermal conductivity.First,the ordinary low-thermal graphite film was selected as the heat-conducting matrix,which was compounded with epoxy resin by means of vacuum hot pressing.Through the exploration of the hot-pressing process,it is analyzed that the process mainly affects the influence of the parameter curing pressure on the prepared composite material.With the increase of curing pressure,the content of interlayer epoxy resin gradually decreased,and the content of graphite film as a heat-conducting matrix in the composite material gradually increased.In composite materials,thermosetting epoxy resin is mainly used as a carrier for mechanical properties to improve the mechanical properties of composites such as tensile strength and flexural strength;The low thermal conductivity graphite film acts as a thermal matrix to increase the thermal conductivity of the composite.When the curing pressure reaches 30MPa,the content of graphite film in the composite material reaches the maximum,and the graphite film layer is best bonded.Its thermal conductivity reaches 198 W/(m·K),its tensile strength is 17~23MPa,and its bending strength is 26~36MPa.The density is only 1.8g/cm~3,similar to the magnesium alloy,only 67%of the aluminum alloy.Secondly,on the basis of the preparation of low thermal conductivity graphite film/epoxy resin composite materials,the thermal conductivity of the composite material is optimized by replacing the polymer adhesive with better thermal conductivity.A system consisting of a graphite nanosheet and polyurethane(GNP/PU)was explored and used to produce a thermally conductive paste with good thermal conductivity as an interlayer adhesive.A slurry with a ratio of GNP:PU=4:10 was selected as a binder for both high thermal conductivity and adhesiveness.The low thermal conductivity graphite film/GNP-PU composite material was prepared based on the previously worked out process parameters.The vertical thermal conductivity was 3.4 W/(m·K),and the density was about 1.7 g/cm~3with the low thermal conductivity graphite film/epoxy composite cold plate.The actual thermal conductivity was investigated through heat dissipation experiments and simulation analysis.The experimental results show that the prepared low thermal conductivity graphite film/GNP-PU composite also has excellent thermal conductivity.Finally,a high-quality,high-thermal-conductivity graphite film with better thermal conductivity was used,and a high-thermal-conductivity graphite film/PU composite material was prepared by using the same coating brush process using a polyurethane system as a binder.Its thermal diffusivity is 494mm~2/s,density is only1.8g/cm~3,and thermal conductivity is 630 W/(m·K).Through comparative tests of heat dissipation experiments,when the power of the heating element is 28W,the heat dissipation effect of the 2 mm composite material is 22°C lower than the heat dissipation performance of the 2 mm thick 6061 aluminum alloy plate of the same size.The experimental results show that the composite material has a good heat dissipation effect.At the same time,the practical application of the composite material was studied.It was embedded into the aluminum alloy casing to prepare a graphite-based core-shell heat sink cold plate that can be assembled in the chassis.Through comparison of heat dissipation experiments,the core-shell cold plate exhibits excellent characteristics of high thermal conductivity and weight reduction in practical applications.