Preparation And Performance Research Of Spherical SiO₂ Filled PTFE Composite Substrate

Microwave composite substrate,refers to the microwave circuit substrate material that can achieve large-scale information processing in the microwave range.The material was found widespread application in diverse fields such as military,communications,and aerospace.As novel 5G technologies continue to gain traction and adoption,there has been an upswing in the development of signal transmission techniques that prioritize low latency and high speed.Composite substrate materials based on polytetrafluoroethylene（PTFE）are the material of choice for electronic components in high-frequency,high-speed applications due to their low dielectric constant and low dielectric loss.In this thesis,PTFE composite substrates with low dielectric,low loss and good thermal properties are prepared using spherical SiO₂ and h-BN ceramics as fillers.The main studies are as follows:（1）Surface modification study of spherical SiO₂ ceramics.In this thesis,The SiO₂surface was modified using coupling agents F8261 and Z6124,and the best coupling agent was determined to be Z6124 by comparing the modification effect of different coupling agents.The modification effects of different coupling agents were compared to determine the most effective agent.The surface modification treatment of spherical SiO₂ with different particle sizes was carried out by the optimum coupling agent.Comparing the contact angles of the modified ceramics with different coupling agent contents and the properties of the prepared composite substrates,it can be seen that the optimum amount of Z6124 to modify 5μm and 10μm spherical SiO₂ is 2 wt.%.（2）Proportioning study of spherical SiO₂/PTFE composite substrates.The composite substrates were prepared by compounding two kinds of spherical SiO₂ with different D₅₀ and PTFE at different contents.The performance of the composite substrates was tested,and the composite substrates had good performance indices(dielectric constant:2.956;dielectric loss:9.1×10^-4;water absorption:0.045%;thermal conductivity 0.538 W/（m·K）;dielectric constant temperature coefficient 16.8 ppm/°C)when the 5μm spherical SiO₂ filling content was 65 wt.%;the composite substrates had good performance indices(dielectric constant:2.937;dielectric loss:1.0×10^-3;water absorption:0.055%;thermal conductivity:0.517 W/（m·K）;temperature coefficient:25.8ppm/°C)when the 10μm spherical SiO₂ filling content was 65 wt.%.（3）Proportioning study of h-BN/SiO₂/PTFE composite substrate.In this part,KH550 was selected for the surface modification of h-BN ceramics.The thermal performance of the composite substrate was improved by adding the modified h-BN ceramic,but this resulted in an increase in dielectric loss and water absorption of the h-BN/SiO₂/PTFE composite substrate.The highest thermal conductivity of the h-BN/SiO₂/PTFE composite substrate was obtained when the filled h-BN ceramic content was 10 wt.%and the SiO₂ content was 55 wt.%,with a thermal conductivity of0.661 W/（m·K）.The h-BN/SiO₂/PTFE composite substrate had an increase of 22.9%over the pure SiO₂/PTFE composite substrate and 2.64 times the thermal conductivity of a pure PTFE substrate.