Studies On High Performance Of Copper Clad Laminates Based On Polytetrafluoroethylene

The copper clad laminates based on polytetrafluoroethylene,which possess the low dielectric constant and dielectric loss tangent, are ideal high-frequency microwave circuit boards. The demand for the copper clad laminates based on polytetrafluoroethylene is rapidly increasing in the market of high-speed digital and high-frequency microwave electrical products such as mobile communication devices and new satellite broadcasting system, so high-frequency copper clad laminates based on polytetrafluoroethylene are expected to be more widely used in the future.There are some major shortcomings existing in polytetrafluoroethylene products, such as poor mechanical performance, low flexural strength and rigidity, high thermal expansion coefficient, and low peel strength between copper and prepregs. These shortcomings limit their application in many fields. At present, few products of copper clad laminates based on polytetrafluoroethylene were manufactured independently in China. Most products or semi-products were introduced from foreign companies. Therefore, it is necessary to research the manufacturing of high performance copper clad laminates based on polytetrafluoroethylene.Considering the low adhesion of glass fibre and polytetrafluoroethylene, the effect mechanism of silane coupling agents on flexural strength of composites was discussed based on the interface adhesion mechanism. The result shows that Z6032 enhances the adhesion of glass fibre and polytetrafluoroethylene, and improves the flexural strength and thermal properties of composites. F8261 debases the adhesion of glass fibre and polytetrafluoroethylene although it should enhance the adhesion in theory.A copolymer of tetrafluoroethylene and hexafluoropropylene has the similar molecule structure to polytetrafluoroethylene, but possesses lower melting temperature, better liquidity and higher adhesion to metal. Applying appropriate blending technology, they are consistent and can depress the operation temperature and press. The effect of silane coupling agents, emulsion composition and glass cloth on flexural strength of composites was studied. Furthermore, the effect of glass cloth content on peel strength of composites and effect of fluororesin content on dielectric of composites were also investigated. Thermal press technology of products was discussed and the parameters were optimized by orthogonal test considering the flexural strength of composites. Under the optimized technological conditions, the main performances of the copper clad laminates produced in this research are better than those of foreign products. The theoretical forecasts of dielectric constant and dielectric loss tangent were compared with the results of the experiment.Additives in the fluororesin have important effects on the performance of copper clad laminates. The thermal degradation properties and dynamics of additives were studied by the DSC. The result demonstrates that thermal degradation of additives mainly occurs in two phases. Parameters of dynamic equations were calculated for providing theoretical guidance for sintering and heat-pressure in the process of the CCL.Aiming at the high thermal expansion coefficient of polytetrafluoroethylene, the composites of polytetrafluoroethylene and hollow microbeads were also prepared based on the low dielectric constant, high rigidity, and low thermal expansion coefficient of hollow microbeads. The effect of silane coupling agent type and content on water absorption and tensile strength of composites and on dispersing of hollow microbeads, the effect of thermal profile on tensile strength, and the effect of hollow microbeads type and content on tensile strength, water absorption, thermal expansion coefficient, dielectric properties of composites were also studied. Hollow microbeads can equably disperse in the fluororesin after being dealt with Z6032 and F8261. The thermal expansion coefficient equation of composites was obtained as follows:The tensile strength equation of composites:Utilizing the characters of hollow glass microbeads and short glass fibre, the new method of reinforced polytetrafluoroethylene with short glass fibre and hollow glass microbeads was advanced and high frequency composites were prepared. The interface effect mechanism of polytetrafluoroethylene, short glass fibre and hollow glass microbeads was studied. The effect of coupling agent type and structure, lasting time, pH, temperature, solvents and solution content on glass fibre surface treatment quantity was studied. The surface treatment coupling agent content may keep stable at 1%(wt) when 2%(wt) F8261 solution was used. The tensile modulus can be predicted by regression equations , HalpinTsai model or Nielsen model. The predicting results are consistent with the experimental results. The tensile strength, however, calculated by Stereology model could not be proved by experiment.