Interfacial interactions affecting polyimide reliability

An X-ray photoelectron spectroscopy (XPS) study of the interfacial chemistry of the polyimide PMDA-ODA on exposure to air, water, and NaCl solution for extended periods of time is discussed. A spin-coated polyimide layer is oxygen deficient and possibly contains peaks due to the solvent. In the present work one carbonyl moiety per repeat unit was found to be deficient and could not be regenerated by water immersion. On immersing spin-coated PMDS-ODA in water, the solvent peaks were eliminated. For PMDA-ODA in NaCl, although no ions were detected on the backside of the polyimide, substantial reaction of the polyimide was observed that was different from the interaction of polyimide with water, in spite of the near neutrality in pH of both aqueous solutions, indicating the influence of ions on the reaction.