Ultra-low permittivity HSM/PTFE composites for high-frequency microwave circuit application

With the development of new generation 5G communication technology, the demands for the ceramic/polymer dielectric composites with ultra-low dielectric constant and low coefficient of thermal expansion become imperative. In order to reduce the dielectric constant of the composites, the air with the lowest dielectric constant is introduced into the composites. In this study, the hollow silica microspheres (HSM) used as the fillers are introduced in polytetrafluoroethylene (PTFE) matrix to fabricate HSM/PTFE composites, and the effect of HSM on the structure, dielectric properties, and thermal properties of the composites have been investigated. The dielectric constant and CTE of the composites gradually decrease as the fillers increases, and HSM/PTFE composites with filler content of 40 vol% exhibit the excellent properties ( ε ≈ 1.94,, tan δ ≈ 0.83 × 10 −3 ) at high frequency (≥ 10 GHz) and lower coefficient of thermal expansion (CTE ≈ 95 ppm/°C).