Flexible boron nitride composite membranes with high thermal conductivity, low dielectric constant and facile mass production

With the ever-increasing development of 5G technology, high signal propagation loss and high heating flux in miniaturizing devices bring about simultaneous and urgent requirement for thermal management materials with insulating, flexible, highly thermal conductive and low dielectric properties. However, these properties are not easy to simultaneous implement due to the phonon scattering and interfacial polarization, bringing a negative impact on working efficiency and service life of high-power electronics and portable devices. Herein, the flexible boron nitride composite membranes with high thermal conductivity, low dielectric constant and facile mass production was successfully prepared by coating directional forming and vacuum pressure technology. The directional arrangement of 2D boron nitride nanosheets (BNNS) in boron nitride-enhanced heat spreaders (BNHS) made the heat diffuse along in-plane direction and effectively improve the TC as high as 81.49 Wm−1K−1. In addition, the BNHS had a series of advantages of good electric insulation (the order of 1013 Ω cm), low dielectric constant (ϵ＜3) and low dielectric loss in the frequency range of 1 MHz–1 GHz. The BNHS also exhibited excellent flexibility (bending 20,000 times), high thermal stability and low water absorption. Distinguishing from electroconductive and heat-conducting graphite or graphene films, such superior BNHS with electric insulation but high TC and low dielectric constant will carve a distinctive path in the application of thermal management materials, such as RF antenna, filter, resonator and wireless charger.