| Polytetrafluoroethylene?PTFE?-based composite substrate has excellent high frequency and low loss characteristics,stable dielectric constant,ultra-low water absorption,corrosion resistance and other characteristics.It is one of the key materials in5G communication field and is widely used in power amplifiers,base station antennas and so on.Ceramic-filled PTFE composite substrates have become the focus of current research due to their adjustable dielectric properties.Domestic manufacturers have also made more corresponding products,but at present,most of them have the problem of low thermal conductivity???0.5W/?m·K??.With the increasingly numerous and jumbled devices on PTFE substrates and the development towards multi-layer stacking and high integration,the heat dissipation problem is becoming increasingly serious.Although some manufacturers have made products with high thermal conductivity,the dielectric loss is on the high side,thus reducing the practicability.Therefore,Si3N4 and Al2O3ceramic powders are selected to study and prepare high frequency composite substrates with good thermal conductivity and other performance parameters.At the same time,by filling Si3N4 or Al2O3 on SiO2/PTFE system,the effect of filling content on thermal conductivity and other properties of SiO2/PTFE composite substrate was studied.The following are the details of this study:1.Study on surface modification of Si3N4 powder and Al2O3 powder by F8261 silane coupling agent:Through modification of different contents of coupling agent,it is found that 1.2 wt%F8261 modified Si3N4 powder has the best effect and the maximum surface contact angle is 156.4°.FTIR also proves that this content of coupling agent is the best content of modified Si3N4 powder.Water immersion test also shows that Si3N4 powder has better water resistance.XPS analysis also confirmed that F8261 coupling agent was successfully grafted on the surface of Si3N4 powder.Using the same method to measure the surface contact angle of Al2O3 powder,the optimal content of F8261 modified by Al2O3 powder is 1.4 wt%.2.Research on Si3N4/PTFE and Al2O3/PTFE composite substrates:The ceramic dispersion in the composite substrate prepared by modified Si3N4 powder is more uniform,PTFE coating effect is better,and dielectric loss is lower.After changing the ceramic filling content,Si3N4 powder and Al2O3 powder directly affects the dielectric properties of the composite substrate.The thermal conductivity,dielectric constant and dielectric loss of 70 wt%Si3N4 composite substrate are 1.3 W/?m·K?,4.03 and 0.0014 respectively.The thermal conductivity,dielectric constant and dielectric loss of the composite substrate made of 60 wt%Al2O3 are 0.682 W/?m·K?,3.96 and 0.0021 respectively.Comparing the experimental heat conduction data with various heat conduction theoretical models,it is found that the W.D Kingery theoretical model is closer to the actual heat conduction data.3.Research on Si3N4/SiO2/PTFE and Al2O3/SiO2/PTFE composite substrates:Compared with SiO2/PTFE???0.45W/?m·K??,the thermal conductivity of the composite substrates prepared by filling Si3N4 or Al2O3 on the basis of SiO2/PTFE is improved.In the Si3N4/SiO2/PTFE system,the thermal conductivity of the composite substrate is 0.614W/?m·K?,the dielectric constant is 3.855,and the dielectric loss is 0.0017.In the Al2O3/SiO2/PTFE substrate,the maximum thermal conductivity is 0.558 W/?m·K?,the dielectric constant is 4.125,and the dielectric loss is 0.0020. |
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