Flexible polytetrafluoroethylene (PTFE) composite film with enhanced thermal conductivity and low interface thermal resistance for high frequency electronics

The significant degradation in mechanical properties and filling-gap performance of thermal interface materials (TIMs) under high filling ratios remained a prevalent problem. Here, a polytetrafluoroethylene (PTFE) based composite film with excellent flexibility at ultra-high hybrid fillers content (up to 90 wt%) was developed through the mechanical interlocking strategy. Due to the sufficient fibrosis of PTFE under shear stress, boron nitride (BN) and aluminum nitride (AlN) were firmly constrained inside the fiber cage. The hybrid fillers arranged into a seesaw-like structure during the calendering process, which facilitated the formation of thermal conductive network in both horizontal and vertical directions. Importantly, this unique embedded structure allowed for direct contact between the fillers and the heat source, resulting in a 90.45% decrease in interfacial thermal resistance. The resultant film possessed a high thermal conductivity (4.3 W/m·K, in-plane, 0.75 W/m·K, out-plane), low dielectric constant (3.1, 10 GHz), and excellent flexibility, making it suitable for application of interface heat dissipation in high-frequency electronic devices.