SURFACE MODIFICATIONS OF KAPTON AND CURED POLYIMIDE FILMS BY ARF EXCIMER LASER - APPLICATIONS TO IMAGEWISE WETTING AND METALLIZATION

Polymer surfaces of certain kinds, particularly polyimide, become highly hydrophilic upon irradiation by deep UV or UV laser in air. Unlike UV lamp light, laser exposure in air is extremely efficient in making polymer surfaces hydrophilic and wettable with aqueous solutions or similar liquids. The change in chemical nature of the polymer surfaces upon laser and deep UV irradiation is studied by contact-angle measurements in both advancing and receding modes. The results are compared with those of PPQ, PPES, polystyrene and PMMA. Under UV irradiation in air, polymer surfaces become highly hydrophilic, resulting in a decrease of the contact angles in both modes. Laser exposure in air makes the surfaces highly hydrophilic and wettable by both photo-induced reactions and debris/roughness formation. Water spray reduces the hysteresis by removing the debris, but the polymers still keep certain roughness and hydrophilicity on the remaining surfaces. Laser irradiation makes imagewise wetting possible with polyimide films at a low fluence. Direct imagewise metallization is also observed with polyimides and PPQ films. The laser-exposed areas cannot have electrically conducting metal films deposited on them while on unexposed surfaces uniform metal film deposition took place. Although the mechanism is still not clear, oxygen RIE is found to be possible in the exposed, non-conducting part, while galvanic plating was carried out on unexposed, conducting surfaces with a Au-Pd metallization. © 1990.