The Research On The Preparation And Thermal Conductivity Of Boron Nitride/Poly (Vinylidene Fluoride) Composites

In recent years,due to the rapid development of science and technology,electronic devices are developing toward miniaturization and integration,which leads to a substantial increase in the power density of the device and a sharp increase in the amount of heat generated.The accumulated heat will affect the safety of electronic devices during operation and the life of the equipment.How to effectively transmit the accumulated heat has become an urgent problem to be solved.Polymer materials are widely used in various electronic devices,but their thermal conductivity is very low,which is not conductive to heat transfer.At present,the commonly used method to improve the thermal conductivity is to add fillers with high thermal conductivity into the polymer matrix.Recently,boron nitride nanosheets（BNNS s）have attracted extensive attention because of their high thermal conductivity in the in-plane direction.In this paper,a series of the composite paper s were prepared by a simple and efficient method.The selected fillers include one-dimensional silicon carbide wires（Si Cw）and two-dimensional BNNS.The silver nanoparticles（Ag NPs）were deposited on the surface of the fillers,then the Ag NPs were sintered by hot-pressing to reduce the interfacial thermal resistance of the composites.Firstly,BNNS was used as thermal conductive filler,and polyvinylidene fluoride（PVDF）was used as matrix.To orient the BNNS in the horizontal direction,the BNNS/PVDF composites were prepared through doctor-blading followed by hot-pressing.The effect of BNNS content on the thermal conductivity of the BNNS/PVDF composites was studied.This results showed that when the content of BNNS was 70wt.%,the thermal conductivity of BNNS/PVDF composites reached the maximum(23.1 W·m^-1·k^-1).Next,to further improve the thermal conductivity of the composites,the Ag NPs were deposited on the surface of BNNS,and the thermal conductivity of the BNNS-Ag/PVDF composites after sintering was compared with the BNNS-Ag/PVDF composites before sintering.The results showed that the thermal conductivity of the composites increased by 12%after sinterin g.To further enhance the thermal conductivity of the composites,BNNS and Si Cw were used as hybrid fillers,and the content of the BNNS was 70 wt.%.Based on the previous research,the effect of Si Cw content on the thermal conductivity of the composites was explored.The results showed that when the Si Cw content was 8.4wt.%,the thermal conductivity of the BNNS/Si Cw/PVDF composites reached the highest value(32.3 W·m^-1·k^-1).Next,the influence of the distribution and content of Ag NPs on the thermal conductivity of the composites was studied.The results illustrated when the Ag NPs content was low,the distribution of Ag NPs on the surface of fillers is more uniform with the increase of the Ag NPs content,and the thermal conductivity of the composites increases.When the content of the Ag NPs was 11.2wt.%,thermal conductivity of the composites reached the maximum(47 W·m^-1·k^-1).When the content of the Ag NPs exceeded 11.2 wt.%,the thermal conductivity decreased.And the composites had excellent insulating properties.This work provides an effective idea for the preparation of high thermal conductive polymer composites,which is suitable for mass production and has good application prospects in the field of electronic packaging.