Liquid metal-modified boron nitride for polytetrafluoroethylene composites with enhanced thermal conductivity and peel strength

Abstract

Polytetrafluoroethylene (PTFE)/boron nitride (BN) composites has ultra-low dielectric loss and thermal conductivity, making it a suitable choice for high-frequency communication copper-clad laminate. However, the low peel strengthens of these composites restricted the further application, due to the low polarity and smooth surface of BN. Here, we assemble liquid metal (LM) on BN filler (LM-BN) via a mechanochemistry method. The surface polarity and roughness of BN can be enhanced by the oxidized layer from LM. The thermal interfacial overlap between BN sheets can be enhanced by LM droplets. Consequently, at filler content of 50 vol%, the thermal conductivity increases from 0.3 W/m⋅K of PTFE to 1.90 W/m⋅K for PTFE/BN composites, to 2.05 W/m⋅K for PTFE/LM-BN composites, and the peel strength exhibit a nearly 100% increment from 0.19 of PTFE/BN to 0.39 N/mm of PTFE/LM-BN. Along with low dielectric loss, excellent thermal conductivity, peel strength, and reduced thermal expansion, this method ensures a wider application of PTFE/LM-BN composites in electronic packaging.