A study of modified polyimide surfaces as related to adhesion

Abstract

Surfaces of fully imidized pyromellitic, dianhydride–oxydianiline (PMDA-ODA) based polyimide films have been studied after argon ion-beam bombardment or treatment with either oxygen or nitrogen plasmas. The treated surfaces were characterized by x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and surface energy measurements. The XPS spectrum of the C1s level showed that intensity related to carbonyl and imide ring structure decreases while that related to carbon-to-carbon bonding increases with argon ion bombardment. Oxygen plasma treatment resulted in an increase by a factor of two in the atomic concentration of oxygen and a decrease of carbon concentration. Polycarbonate and/or peroxy type carbon–oxygen structures were formed as indicated by the C1s level. Treatment with a nitrogen plasma caused an increase in the atomic percent of nitrogen by a factor of three, a decrease in carbon and no change in the oxygen. The N1s level was resolved into three peaks that are assigned in part to imide and nitrile moieties. All of the modified polyimide surfaces show significant improvement in adhesion to a overcoated chromium film. This enhancement in adhesion is attributed to the increased surface energy and number of bonding sites. Surface topography studies by SEM show the relative smoothness of the surface is reduced slightly after ion bombardment and plasma treatments.