Preparation And Properties Of PTFE Based High Frequency Copper Clad Laminate

5G communication has the characteristics of high-speed transmission,low time delay and high connection density,which requires that the copper clad laminate widely used in5 G equipment has the characteristics of low dielectric constant,low high-frequency loss,high thermal conductivity,good heat resistance and high reliability.Polytetrafluoroethylene(PTFE)has very low dielectric loss at high frequency,but its poor thermal conductivity and large coefficient of thermal expansion limit its wide application.In this paper,PTFE based high frequency and high thermal conductivity composite substrate with excellent comprehensive performance parameters was prepared by impregnation and gluing process,and high thermal conductivity ceramic powder was selected for filling and modification.The main research contents and results were as follows:1.Research on filling modification of high thermal conductivity filler.Firstly,a single Al₂O₃ filler was selected to modify the PTFE substrate,and the effect of Al₂O₃ filler content on the dielectric and thermal properties of PTFE composite substrate was studied.The results showed that with the increasing of Al₂O₃ thermal conductive filler content,the thermal conductivity and dielectric constant of the composite substrate gradually increased,while the coefficient of thermal expansion(CTE)gradually decreased.When the mass fraction of alumina ceramic powder was 40%,the comprehensive performance of the composite substrate was the best: the dielectric constant was 3.49;the dielectric loss was0.0027;the water absorption was 0.040%;the thermal conductivity was 0.61W/m · K.In order to further improve the thermal conductivity of the composite substrate,based on the study of Al₂O₃/GFS/PTFE composite substrate,Al₂O₃ and h BN composite ceramic powder were further selected for the modification of PTFE based composite substrate.The results showed that when the mass ratio of Al₂O₃: h BN: PTFE was 20%: 20%: 60%,the maximum thermal conductivity of the composite substrate was 1.05 W/m·K(50?),which was 5.3times that of pure PTFE.At the same time,the dielectric constant was 3.53;the dielectric loss was 0.0022;the water absorption was 0.054%;the density was 2.26g/cm3.2.Research on blending modification for PTFE.The compatibility between PFA and PTFE and the effect of PFA content on the properties of Al₂O₃-h BN/GFS/PTFE composite substrate were investigated.The results showed that the blend of PFA and PTFE had a single Tg;the compatibility between them was very good;a uniform phase could be formed.The water absorption of the composite substrate could be improved by blending.The experimental results showed that the best comprehensive properties of the composite substrate were as follows: dielectric constant 3.55,dielectric loss 0.0021,water absorption0.042%,peel strength 1.66 N/mm,bending strength 92.9 MPa and thermal conductivity1.10 W/m·K.3.Research on hot pressing sintering process.The effects of different hot pressing pressure,hot pressing temperature and hot pressing holding time on the bending strength,water absorption and peel strength of the composite substrate were studied.The optimum hot pressing sintering process conditions of composite substrate were as follows: hot pressing pressure was 6 MPa;hot pressing temperature was 360?;hot pressing holding time was 2.5h.The high frequency and high thermal conductivity copper clad laminate prepared in this paper had low dielectric constant,low dielectric loss,high thermal conductivity,low water absorption and excellent mechanical properties.It could be used in 5G base station antenna,millimeter wave radar,microwave power amplifier and other equipment.