Preparation And Application Of Heat Dissipation Of Graphite Film/Aluminium Thermal Conductive Substrates

With the continuous development of integrated circuit technology,the power density of electronic equipments is also increasing.The performance and lifetime of electronic products has a great relationship with their operating temperature,so the thermal management of electronic devices becomes more and more important.In this work,graphite film and aluminum are used to prepare high thermal conductive composite substrates with sandwich structure.The composite substrates have high thermal conductivity,low density,excellent mechanical properties and reliability,can be widely used in the heat dissipation of electronic equipments.First,the graphite film/epoxy resin/aluminum(G-E-A)thermal conductive substrate with sandwich structure was prepared.Graphite film is used as the thermal conduction reinforcement of the composite substrate.It is a new type of thin film heat dissipation material,the graphite is oriented in in-plane direction of the film,and its in-plane thermal conductivity can up to 800W/(m·K).G-E-A substrate was prepared through a series of processes such as assembling,pressing,hot pressing,and packaging,and the thermal properties of G-E-A substrate was tested and evaluated through experiments and simulations.We studied the effect of the pressing process on the properties of the graphite film,a certain pressure can increase the in-plane thermal conductivity and density of the graphite film,at the same time,the change of the size of the graphite film under pressure can make the interface between the graphite film side and the aluminum closer.The coating process of epoxy resin adhesive was explored,making the thickness of the single-layer adhesive was only about 10?m,which greatly reduced the impact of low thermal conductivity of the adhesive itself and the impact to packaging process.Using hot pressing process to make the epoxy resin cure at high temperature,and packaging the G-E-A substrate through friction stir welding with small heat-affected zone finally.The G-E-A substrate has high thermal conductivity and low density(2.2g/cm³),exhibiting excellent performance in heat dissipation experiments and simulations.At 10W?30W chip power in experiments,the chip temperature on G-E-A substrate is 6.5^oC?22^oC lower than that on the aluminum substrate,and the temperature difference increases as the chip power increases.The thermal conductivity of G-E-A substrate at room temperature is estimated to be between448.1W/(m·K)?491.1W/(m·K)by Fourier's Law and Parallel Compound Theory.The high thermal conductivity of the G-E-A substrate is due to the higher thermal conductivity of the graphite film and the adhesion of the epoxy resin to the interface.In addition,the cross-plane thermal conductivity of the graphite film is extremely low(3W/(m·K)),so the cross-plane thermal conductivity of G-E-A thermally conductive substrate is also low,and the heat dissipation ability is poor when applied to the environment of bottom convection.At the same time,the presence of epoxy resin also limits the application of substrates in high temperature environments.Herein,the structure of the substrate was optimized,without epoxy resin,and cross-plane thermal conductive structure was added inside to prepare VG-A(with cross-plane thermal conductive structure)substrate with sandwich structure.In order to determine the size,position and distribution density of the cross-plane thermal conductive structure accurately,ANSYS finite element simulation was used to simulate and analyze the heat dissipation ability of different types of VG-A substrate.Combined with cost and the difficulty of the process,the program of 4-VG-A(the diameter of thermal conductive column is 2mm,and the distribution density is 4/cm²)substrate was determined.The4-VG-A substrate was prepared by drilling on graphite films,assembling,pressing,and packaging by brazing.A good metallurgical bond is formed between aluminum/aluminum interface in the substrate,and the graphite film/aluminum interface are tightly bonded and interpenetrating.analysis of the interface reveals that there is no obvious Al₄C₃.The cross-plane thermal conductive structure in 4-VG-A substrate increased the theoretical cross-plane thermal conductivity from 5.2W/(m·K)to35.9W/(m·K).At the same time,the thermal conductive structure form many micro-connections similar to the"honeycomb"structure in 4-VG-A substrate,which makes the mechanical properties of the substrate more excellent.