Polytetrafluoroethylene composites for high-frequency microwave applications: Balancing thermal conductivity, adhesion and dielectric properties

Polytetrafluoroethylene (PTFE) is widely used as a polymer substrate for high-frequency microwave copper cladding due to its low dielectric loss and high stability. However, its inherently low thermal conductivity requires the use of high-content fillers, which complicates efforts to balance thermal conductivity, adhesion strength, and dielectric loss of the composite materials. Herein, we introduce PTFE composites with a hybrid filler network, where the synergistic alignment and interaction of two-dimensional hexagonal boron nitride (h-BN) and granular β-silicon nitride (Si 3 N 4 ) forms interconnected pathways in the vertical direction. The spatial arrangement of large-sized h-BN can bridge and shorten the thermal conduction path within the Si 3 N 4 network, forming robust vertical thermal pathways, achieving an out-of-plane thermal conductivity of 1.6 W/m K. Additionally, the complementary properties of h-BN and Si 3 N 4 enhance the overall performance. Si 3 N 4 reduces stress concentration, improving adhesion strength, while h-BN's wide bandgap and weak polarity help minimize dielectric loss. This combination results in a peeling strength of 1.3 N/mm with copper foil and a remarkably low dielectric loss (<0.0011) at 10 GHz. The ultimate PTFE composite ensures reliable, stable, and secure signal transmission in high-frequency communication devices, making it a highly promising material for the electronics sector.