Researches On The Preparation Technology And Properties Of PTFE/glass Fiber Microwave Substrate

Polytetrafluoroethylene(PTFE)has been widely used in the preparation of microwave substrate because of its excellent performance,in the wireless network,satellite communications,radar and other fields had a wide range of applications.Many scientists and experts had developed out series of composite substrate materials based on PTFE,which microwave composite substrate material developed by Rogers company is the typical representative.the typical representative.It is important that research high-performance composite substrate material based on PTFE.In this paper,PTFE/GF microwave composite substrates with specific dielectric properties and low water absorption were prepared by using PTFE as the matrix and E-glass fiber cloth(GF)as the reinforcing material.Main work as follows:1.Research on impregnation method: the effects of emulsion concentration and impregnation on the dielectric properties,densities and water absorption of composite substrates were systematically studied.(a)The GF has been impregnated by using different concentration of PTFE emulsion,it was determined that porosity of the composite substrate has been reduced by impregnating with 60% emulsion concentration,the density has been improved,water absorption was reduced and the excellent dielectric properties was obtained.(b)The different impregnation method has been studied and found that impregnation method of 60%+60%+50% can reduce the water absorption effectively,but the dielectric constant was slightly decreased.2.Study on blending modification for PTFE: the compatibility between PTFE and FEP and the effect of FEP dosage on properties of PTFE/GF composite substrate were investigated by blending modification with FEP.It was found that PTFE and FEP with good compatibility and the hybrid emulsion has formed uniform phase,which could increase the flowability of PTFE greatly and enhance the density of the composite substrate.The microwave composite substrate materials have the most excellent performance: dielectric constant is 2.234;dielectric loss is 0.0014;water absorption is0.019%.3.Study on hot-pressing sintering process:the effects of different pre-sintering process and hot pressing pressure on the water absorption,dielectric properties and denseness of composite substrates were studied.(a)Five different pre-sinteringprocesses were developed.It was found that organic molecules such as surfactants in the prepreg were eliminated completely by pre-sintering at 280 °C for 2h and stay at 210 °C for 2h.It is advantageous to form the most compact structure at hot pressing process and obtain the superior performance.The dielectric constant,dielectric loss and water absorption of the microwave composite substrate is 2.20,0.001 and 0.018%,respectively.(b)The effects of hot pressing sintering pressure on the properties of composite substrates were studied.The surface pressures were 1.25 MPa,2.5 MPa,3.75 MPa,5 MPa and 6.25 MPa,respectively.It was found that the density of composite substrate was increased first and then decreased with the pressure increased.And the maximum density was obtained at 3.75 MPa,at the same time,dielectric properties of composite substrate is also good,the dielectric constant and dielectric loss is 2.20 and0.0014,respectively..