Preparation And Application Of Heat Dissipation Of Graphite-based Composite Films

With the rapid development of electronic devices,traditional materials are increasingly difficult to meet the heat dissipation of electronic equipments.Composite materials prepared by dispersing highly thermally conductive fillers in a polymer matrix have become the mainstream of heat dissipation materials.In this thesis,graphite nanoplatelets(GNP)/polyurethane(PU)composite materials with orientation structure and graphene/polyimide(PI)composite materials with sandwich structure are prepared by using the high thermal conductivity of graphite-based fillers.The effect of process parameters on performance is studied.A flexible substrate was designed and manufactured,and its heat dissipation performance was studied.First,graphite nanoplatelets(GNP)/polyurethane(PU)composite materials with an oriented structure were prepared at room temperature by gap coating.Under the action of the gravity field,GNP exhibited a highly oriented structure in the PU matrix.With the increase of GNP content,the in-plane thermal conductivity of the GNP/PU composite films continues to increase,and the Cross-plane thermal conductivity is much smaller than the in-plane thermal conductivity.When the GNP content is 50%,the in-plane thermal conductivity of the composite film reaches 53.03 W/(m·K).The factors affecting the orientation structure of GNP were studied,and it was found that the solid content of the slurry had a small effect on the thermal conductivity of the material,and the drying temperature could change the orientation of GNP by affecting the solidification rate of the polyurethane matrix.The composite film with 40% GNP content,after drying at 30?,60? and 90?,the in-plane thermal conductivity is38.12 W/(m·K),32.82 W/(m·K)and 28.81 W/(m·K).Laminating the prepared composite film by hot pressing to prepare a composite thermal conductive substrate with a laminated structure,and conducting a heat dissipation comparison experiment with a same thickness conventional substrate,simulating a chip temperature of about31.5°C,showing excellent heat dissipation effect.Secondly,graphene oxide(GO)films were prepared by gap coating,and the prepared GO films were graphitized at 3000°C,and rolled to obtain pure graphene films(GF).The strength of the pure graphene film is only 6.66 MPa,so the multilayer pure graphene film is rolled and combined with mechanical force to prepare a multilayer graphene film(M-GF),and the tensile strength is increased to 39.41 MPa.Due to the reduction in voids and the increase in density due to rolling,the in-plane thermal conductivity of M-GF at room temperature reaches 739.56 W/(m·K).The M-GF is placed between two polyimide(PI)films with an adhesive layer and hot pressed to prepare a sandwich flexible composite substrate(G-FPC).The heat dissipation comparison experiment of G-FPC and same thickness traditional flexible substrate(FPC),the simulated chip temperature is about 10°C lower,with excellent heat dissipation effect.Finally,ANSYS Workbench software was used to simulate and optimize GNP/PU and M-GF composite materials.The effects of preparing GNP/PU composite materials as substrates and heat sinks on the heat dissipation of the chip,and the influence of the process parameters of the composite flexible substrate on the heat dissipation of the chip were studied.