Covalent-assisted construction of "scale-like" boron nitride/polyimide thermal interface materials with high thermal conductivity

Polyimide (PI) is a special engineering plastic with high strength, high modulus, high temperature resistance and corrosion resistance, but its poor thermal conductivity limits its application in high-power miniaturized electric and electronic equipment. In this study, surface-activated and modified boron nitride (m-BN) is polymerized in situ and coated to form a "scale-like" composite thermal interface material (m-BN/PI) with PI. Moreover, the mBN@PI composite films obtained by a simple co-blending process of m-BN and PI are used as a comparison. The in-plane thermal conductivity of m-BN/PI composite reached 4.43 W m-1 K-1, when the filler content is 30 wt %, which is about 12 times higher than that of the pure PI film (0.37 W m-1 K-1). At this load, the in-plane thermal conductivity of m-BN@PI is only 3.94 W m-1 K-1. In addition, the covalent bonding between m-BN and PI molecular chains in m-BN/PI effectively reduces the interfacial thermal resistance by fitting the EMT and Foygel models. Finally, using the m-BN/PI composite film as a thermal interface material placed at the CPU location, its role in the heat dissipation process of electronic devices is demonstrated.