Abstract: In this paper, quartz fiber paper was prepared by wet forming method with different ratio of micro and nano quartz fibers. After dipping in PTFE emulsion and pre-burning to remove small organic molecules, the composite substrate was prepared by hot pressing and sintering, and the dielectric, mechanical and thermal properties of the substrate were characterized and analyzed. The results show that the density and water absorption decrease with the increase of the content of quartz fiber while the proportion of total fiber remains unchanged. In terms of dielectric properties, the dielectric constant decreases with the increase of quartz fiber content. When the quartz fiber proportion reaches 80%, the dielectric constant is at its lowest to 2.21, and the dielectric loss presents a nonlinear relationship, and the lowest is 0.000 96 when the proportion of quartz fiber is 40%. In terms of thermal conductivity, the increase in quartz fiber content results in an enhancement of the composite’s thermal conductivity, and reaches a maximum of 0.232 W/(m·K) when the proportion of quartz fiber is 80%. In terms of mechanical properties, the tensile strength and elastic modulus decreased with the increase of quartz fiber content, and decreased to 17.85 MPa and 1538.76 MPa when the proportion of quartz fiber was 80%.

Key words: quartz fiber, PTFE, composite substrate, dielectric property