A photochemical process was applied to form an active surface layer on cyclo-olefine polymer (COP) for improved immobilization of palladium. A Xe excimer lamp irradiating vacuum ultraviolet (VUV) light of 172 nm wavelength was used as a light source for surface modification. COP samples placed in dry air with atmospheric pressure were irradiated with VUV light. Because of the dissociative excitation of oxygen molecules, atomic oxygen species were generated along with ozone molecules formed through the following chemical reactions of the oxygen atoms. These active oxygen species served as oxidants for COP surface modification. Based on VUV photochemistry assisted with oxygen, known as the oxygen-amplified VUV process, an oxidized COP layer with thickness of several tens of nanometers was formed on each COP sample. The layer, which contained highly concentrated hydrophilic functional groups such as -OH, -CHO, and -COOH, functioned as an adsorbing site for palladium catalysts. Consequently, this technique has been found to be effective as a pre-treatment of Ni-P electroless plating. Electroless Ni films with sufficient adhesion to pass the cross-cut tape test were deposited on the VUV-modified COP substrates. Direct patterning without photolithography has been demonstrated for fabricated Ni micropatterns.
