Design and preparation of low-filled magnetic oriented BN@Fe3O4/EP insulating composite with improved thermal conductivity and thermal stability

As an excellent two-dimensional insulating material with high thermal conductivity, high temperature stability and high hardness, hexagonal boron nitride(h-BN) is widely applied in semiconductor manufacturing, aerospace, metallurgical manufacturing and other cutting-edge fields. However, the unique surface structure of h-BN leads to poor lubricity and easy agglomeration, which limits the application of h-BN especially in the field of electronic packaging. To address key issues boosted above, this study designed and prepared the BN@Fe3O4 magnetic insulating particles and doped it into the reduced viscosity epoxy resin to prepare the composites. By selecting appropriate external magnetic field strength and BN@Fe3O4 particles' content, a novel 3D structure of fillers like dominoes in epoxy resin composite was successfully constructed. The microstructure of the BN@Fe3O4 particles and composites were analyzed, the thermal conductivity, the mechanical and the electrical properties of composites were simultaneously tested. Results manifested that the core-shell structures with BN as core and Fe3O4 as shell was successfully prepared, linking through the PDA middle layer between the BN core and Fe3O4 shell. Under the influence of magnetic orientation, the BN@Fe3O4 magnetic particles were preferred an out-of-plane oriented in the epoxy resin composites, resulted an enormously enhanced on thermal conductivity of composites. At a magnetic field strength of 60 mT and 25 vol% BN@Fe3O4 content, the thermal conductivity of BN@Fe3O4/EP composites is as lofty as 1.832 W/(m K), which is 1023.46% higher than that of pure epoxy resin. Meanwhile, the thermal stability has also been slightly improved, the elastic modulus and insulation performances remain at the same level.