Preparation And Properties Of High-parallel Graphene-based Thermal Interface Materials

With the rapid development of electronic science and technology,the power and integration of electronic devices are increasing and the characteristic size of devices is decreasing.In the electronic equipment,most of the power is converted into heat.The heat of components directly leads to the increase of temperature in the electronic equipment and the increase of thermal stress,which poses a serious threat to the reliability of microelectronic equipment.Thermal failure has become one of the most important failure modes in electronic packaging.In electronic equipment,due to the rough surface of the heat sink and the heat source,there are a large number of holes which seriously hinders the conduction of heat.Thermal interface materials(TIMs)are important and indispensable part for the efficient transfer/removal of generated heat from heater to avoid electronic devices working under overheating conditions.In actual working status,TIMs with high through-plane thermal conductivity and good compressibility bridge the heater and heat sink for filling the unavoidable air gaps between their mating interface.Since graphene was discovered and exhibited a ultrahigh intrinsic thermal conductivity of 3,500–5,300 W/(m K),the penetration of polymers into three-dimensional graphene framework has considered as a promising solution to develop the composites with improved thermal conductivity for TIM applications.In this paper,two kinds of thermal interface materials with ultra-high thermal conductivity were successfully prepared by using graphene as a thermally conductive filler,and a series of characterization tests were carried out.(1)A dual-assembly strategy was proposed by utilizing a porous polyurethane(PU)film as the starting template to assemble graphene sheets on its skeletons,followed by a roll-to-roll step to prepare large scale homogeneous graphene/PU monolith.And then a thermal treatment for the monolith was performed to obtain a graphene framework with large scale.Moreover,the structural arrangement of resultant graphene framework can be further modulated by controlling the stretch ratio of the PU film in the roll-to-roll process,by which a dual-assembled graphene framework(DAGF)composed of highly ordered graphene sheets was achieved at the stretch ratio of 340%.Based on the characteristic structure,the DAGF dramatically enhances the through-plane thermal conductivity of epoxy by ? 368 times(71 W m-1 K-1)with a graphene loading of 22.4 wt%.In the thermal interface material test,the corresponding DAGF/epoxy composite achieves 30.4% improvement in cooling efficiency compared to the state-of-the-art silver/epoxy adhesive.(2)The graphene oxide fiber fabric is prepared by graphene oxide and the graphene fiber non-woven fabric is obtained by thermal reduction.The 3D graphene fiber foam is formed by a roll-to-roll process and the graphene fiber/PDMS is obtained by sealing PDMS.The thermal interface material achieved a thermal conductivity of 9.593 W/(mK)with a low graphene loading(5.76 wt%).The structure has high stability,so its structure is not destroyed after compressing 50% deformation and the thermal conductivity is still maintained at a high level.