Plasma surface treatment of polyimide for adhesive Cu/80Ni20Cr/PI flexible copper clad laminate

Two different methods of surface treatment, a low pressure plasma treatment and an atmospheric plasma treatment, on polyamide (PI) substrate were investigated from the point of view of adhesion of a Cu/80Ni20Cr layer on PI in flexible copper clad laminate (FCCL). The specimen treated with atmospheric plasma had high peel strength properties before and after aging. The root-mean-squared (rms) roughness with samples exposed to both kinds of plasma treatment was almost the same at 0.68 nm and 0.65 nm respectively, but the contact angle was different at 14.5° and 5.9°. We interpret this to mean that a more hydrophilic surface can be obtained using atmospheric plasma treatment. Observing the XPS spectra, more C-O binding rate was identified on the FCCL sample treated with the atmospheric plasma. From these results, it is suggested that the better adhesion achieved with atmospheric plasma treatment is not due to the mechanical roughness on the PI but due more to the activated C-O chemical bonding.