Contribution of N2 Ion on Polar Group Introduction at PTFE Surface by the High E/n Discharge

PTFE (Poly-tetra-fluoro-ethylene) has superior characteristic such as low dielectric constant, low dielectric tangent and chemistry stability. However, it has low adhesion force. In order to improve adhesion force, we have studied on surface modification of PTFE by using discharge under high E/n (E: electric field, n: particle density) condition in nitrogen. Under high E/n condition, electron and ions gain energy up to 100eV or more. It is deduced that improvement of adhesion is brought about by introduction of the polar groups at the surface. However, it does not understand clearly which particle (ion, atom, excited molecule etc.) in discharge space contributes to introduce the polar groups on the PTFE surface. We assume that ion with high kinetic energy rather than the binding energy of PTFE contributes on introduction of chemical bonds by cutting of the C-C or C-F bonds. It is expected that cutting the bonds is a rate-determining step in surface modification.Then, we measured contact angle of samples irradiated by various ion energy and exposure dose. From the results, the increase of the exposure dose make fast to introduce polar groups. In addition, it is deduced that ion energy around 40eV is effective for polar groups introduction.