Highly thermal conductivity flexible composite films based on alumina-boron nitride binary fillers

Thermal interface materials (TIMs) exhibiting dual attributes of high thermal conductivity and excellent electrical insulation are urgently in demand for heat management of microelectronic devices. However, ultrahigh filler loadings that are often required for achieving high thermal conductivity would compromise the other properties such as softness and flowability of the composites. In this work, we present a straightforward and effective approach for highly thermally conductive polymer composites based on binary fillers of alumina (Al 2 O 3 ) and boron nitride (BN) through a conventional hot-press method that is potential for the scalable production. Al 2 O 3 and BN with different particle sizes and shapes are functionalized as binary fillers. By utilizing various gradation scheme based on Dinger-Funk particle stacking theory, the spherical Al 2 O 3 composites achieve a thermal conductivity of 5.12 W m −1 K −1 with a maximum packing density. Further mixing with BN leads to flexible thin films with a remarkable thermal conductivity of 9.23 W m −1 K −1 , which is ∼50 times that of pure silicon rubbers (0.18 W m −1 K −1 ). Meanwhile, the synthesized composites demonstrate electrically insulation, flexibility, compressibility , as well as remarkable stability even after cycled temperature shocks from room temperature to 120 °C, which are conducive to environmental adaptability for industrial applications. The results of this work offer a feasible strategy of synthesizing BN-based TIMs and pave the way for their large-scale practical implementation for effective thermal management.