Preparation And Properties Of Boron Nitride Thermally Conductive Composite Based On Biomimetic Mineralization

In recent years,with the rapid development of microelectronic packaging and assembly technology,electronic products have been continuously developed in the direction of small size,thinness and multifunction.The heat generated by electronic products during work has increased significantly,which has brought more prominent heat dissipation problems.Therefore,the thermal management design of electronic products and how to develop materials with high thermal conductivity that can be used in electronic packaging have attracted wide attention from researchers.Among several common materials used in electronic packaging,polymer-based thermally conductive composite materials prepared by compounding fillers and polymer have become a hot spot for researchers and developers due to their advantages of lower cost and excellent processability.In this work,we use hexagonal boron nitride as thermally conductive filler,inspired by the polymer-induced liquid-precursor step in the process of biomineralization,using a poly(acrylic acid)/calcium carbonate system,boron nitride/poly(acrylic acid)thermally conductive polymer composite and boron nitride/epoxy thermally conductive polymer composite were prepared.(1)After thermally conductive filler hexagonal boron nitride and poly(acrylic acid)were mixed,poly(acrylic acid)are physically cross-linked by the reaction of calcium ion and carbonate ion,the bionic mineralized composite was prepared.After the composite was cold-pressed and dried,a boron nitride/poly(acrylic acid)thermally conductive composite was prepared.The chemical structure and microscopic morphology of the composite were characterized by infrared spectroscopy,X-ray diffraction and scanning electron microscope.The influence of the particle size and content of hexagonal boron nitride on the thermal conductivity of the composite was studied,found that with the increase of the filler content,the thermal conductivity gradually increased.At the same loading,the thermal conductivity of composite prepared from 15 ?m hexagonal boron nitride is the highest,when the loading is 62.5 wt%,the thermal conductivity of the composite material can reach 10.3 W/(m·K).Combined with the changes in the morphology of the composite and the process and effect of the bionic mineralization reaction,the thermal conductivity enhancement mechanism of the composite was studied.(2)The boron nitride bionic mineralized composite material prepared in(1)was put into a mold for compressed molding,and after freeze-dried,ablated at high temperature under an inert atmosphere to form the boron nitride thermally conductive network.Finally,under vacuum assistance,epoxy resin was poured into the boron nitride thermally conductive network to prepare boron nitride/epoxy thermally conductive composite.We studied the effect of the molding pressure,ablation temperature and boron nitride size to three-dimensional network structure,found that the smaller molding pressure in pressed the sample,the higher ablation temperature,the larger size of boron nitride,the prepared three-dimensional network is looser and its porosity is higher,while the network structure still retains a certain strength.The thermal conductivity analysis results show that the thermal conductivity of the composite can reach 2.8 W/(m·K)when the 15 ?m sized hexagonal boron nitride filling is 48.8 wt%.We use thermal mechanical analyzer and precision impedance analyzer to characterize the thermal expansion and dielectric properties of the material.