filled polymers, boron compounds, thermal conductivity, materials preparation, thermal stability, thermal expansion, permittivity, boron nitride microsphere-epoxy composites, needless heat removal, electronic devices, enhanced thermal conductivity, polymer composites, cross-plane thermal conductivity, peeled hexagonal boron nitride flakes, coefficient of thermal expansion, glass transition temperature, pure epoxy resin, dielectric constant, dielectric properties, BN, Electrical engineering. Electronics. Nuclear engineering, TK1-9971, Electricity, QC501-721

As modern electronics are developed towards miniaturisation, high-degree integration and intelligentisation, a large amount of heat will be generated during the operation of devices. How to efficiently remove needless heat is becoming more and more crucial for the lifetime and performance of electronic devices. Many efforts have been made to improve the thermal conductivity of polymer composites, which is an important component of electronics. Herein, the authors report on preparation of boron nitride micosphere/epoxy composites. The cross-plane thermal conductivity of the resultant composites is up to 1.03 Wm^‒1K^‒1. This is attributed to the thermally conductive network formed by the peeled hexagonal boron nitride flakes. Thanks to the superior thermal stability of boron nitride micosphere, the boron nitride micosphere/epoxy composite shows a decreased coefficient of thermal expansion (53.47 ppm/K) and an increased glass transition temperature (147.2°C) compared with the pure epoxy resin. In addition, the boron nitride micosphere/epoxy composite exhibits a lower dielectric constant compared with that of the hexagonal boron nitride/epoxy composite. This strategy can potentially pave the way for the design and fabrication of materials with high cross-plane thermal conductivity and lower dielectric properties.