Control of PTFE/PFA Surface Free Energy by Atmospheric Multi-Gas Plasma Treatment

With the spread of next-generation high-speed communication systems, materials with low transmission loss are required for printed circuit boards. Fluoropolymers such as polytetrafluoroethylene (PTFE) and perfluoroalkoxyalkane (PFA) are attracting attention as low-loss materials with low relative permittivity. On the other hand, it is very difficult to bond them with other materials because of their chemically stable structure. We considered that the adhesive characteristics of PTFE and PFA could be improved by controlling the surface conditions using atmospheric multi-gas plasmas. In this study, the effects of reactive species generated in various gas plasmas on PTFE and PFA surfaces were investigated. Surface treatment was performed with an atmospheric multi-gas plasma jet developed in our laboratory. Molecular gases such as nitrogen and oxygen were used as plasma generating gases. This treatment was applied continuously by using a motor stage driven at 1 mm/s. The effect of plasma treatment was evaluated by measuring the water contact angle, which indicates the hydrophilicity of the solid surface, before and after plasma irradiation. The diiodomethane contact angle was also measured, and the surface free energy was calculated from the contact angles of these two liquids. In this presentation, in addition to these results, adhesion strength between PTFE and polyimide tapes will be reported.