Thermally Conductive Hexagonal Boron Nitride/Polymer Composites for Efficient Heat Transport

Abstract Commercial thermally conductive dielectric materials used in electronic packaging typically exhibit thermal conductivities ( κ ) ranging from 0.8 to 4.2 W m −1 K −1 . Hexagonal boron nitride (h‐BN) flakes are promising thermally conductive materials for the thermal management of next‐generation electronics. These electrically insulating yet thermally conducting h‐BN flakes can be incorporated as thermal fillers to impart high κ to polymer‐based composites. A cellulose‐based composite embedded with few‐layer h‐BN (FLh‐BN) flakes, achieving a κ ≈ 21.7 W m −1 K −1 , prepared using a cost‐effective and scalable procedure is demonstrated. This value is >5 times higher than the κ observed in composites embedded with bulk h‐BN (Bh‐BN, κ ≈ 4.5 W m −1 K −1 ), indicating the benefits of the superior κ of FLh‐BN on the κ of h‐BN polymer composites. When applied as a paste for thermal interface material (TIM), the FLh‐BN composite can reduce the maximum temperature ( T max ) by 24.5 °C of a heating pad at a power density ( h ) of 2.48 W cm −2 compared to Bh‐BN composites at the same h‐BN loading. The results provide an effective approach to improve the κ of cellulose‐based thermal pastes for TIMs and demonstrate their viability for heat dissipation in integrated circuits (ICs) and high‐power electronic devices.