Preparation Of Nano Hexagonal Boron Nitride And Its Application In High Thermal Conductivity Paper-based CCL

With the rapid development of the electronic information industry,printed circuit boards,which are substrates for electronic information products,are increasingly used in electronic products.However,there are also many new challenges.Recently,light,thin,small and high density have become the development of printed circuit boards.It also imposes certain requirements on heat dissipation.Therefore,more performance requirements of its special base material copper clad laminates are also requested.Ordinary copper clad laminates have been unable to meet the requirements of some high-end electronic products due to low thermal conductivity,high dielectric constant,and large dielectric loss.Therefore,the development of thermal copper clad laminates is imminent.In recent years,thermal two-dimensional nanomaterials have become the current research hotspot due to their many structural and performance advantages.This paper focuses on the preparation,modification and application of hexagonal boron nitride nanosheets,and we carried out the following research:1.One-step stripping preparation of hexagonal boron nitride nanosheets and functional modification thereof.The bulk hexagonal boron nitride is stripped by ultrasonic assisted organic solvent isopropanol（IPA）,and then centrifuged to obtain a few layer（<10）of hexagonal boron nitride nanosheet.Then a silane coupling agent is needed.The agent is added to the suspension of hexagonal boron nitride nanosheets,and the intermittent mode of the ultrasonic wave is controlled to be modified to obtain modified hexagonal boron nitride nanosheets（kh570-BNNSs）.Compared with other preparation methods,the process has obvious advantages,not only the preparation process is simple,the production cycle is short,but also has reference value and significance for large-scale preparation of single-layer hexagonal nanosheets in the future and expanding their applications.2.Preparation of flexible thermally conductive low dielectric nano-aramid/boron nitride nanosheets（ANFs/BNNSs）composite paper.The nano-aramid fibers（ANFs）are prepared by dissolving the para-aramid fibers by an organic solvent-strong alkali（DMSO/KOH）system,and then the nano-aramid which has been deprotonated is dialyzed to realize the reprotonation of the nano-aramid.Finally,the stripped BNNSs were added to the nano-aramid-water solution,and flexible high thermal conductivity low dielectric aramid nano paper（ANFs/BNNSs）was prepared by vacuum filtration.In the structure of aramid nano paper,the mixing of nano-aramid and boron nitride nanosheets is uniform,and the doping of nano-aramid greatly improves the strength of boron nitride nanofilm and reduces its dielectric constant.The prepared flexible high thermal conductivity low dielectric aramid nano paper has good mechanical properties,thermal insulation and excellent dielectric properties.The preparation process is simple and the paper can be used in miniaturized electronic equipment,especially in high frequency communication equipment with certain requirements on application frequency.3.Precision molding of flexible thermal conductive low dielectric prepreg and its application in copper clad laminates（CCL）.The kh570-BNNSs are added to an epoxy resin for impregnating the above ANFs/BNNSs paper.By vacuum impregnating and drying,a prepreg was obtained.Adding a very small amount of kh570-BNNSs（2.0 wt%）to obtain a resin composite with a thermal conductivity of 0.484 W·m^-1·K^-1,which is a 2.22 times of the pure epoxy resin(0.218 W·m^-1·K^-1).The obtained aramid nano paper-based prepreg（ANFs-prepreg）is insulated and excellent in dielectric properties.The dielectric constant and dielectric loss of the ANFs-prepreg were 2.97 and 0.011 at a test frequency of 1 MHz.