THE POLYIMIDE (PMDA-ODA) TITANIUM INTERFACE .2. XPS STUDY OF POLYIMIDE TREATMENTS AND AGING

The interface between evaporated Ti and PMDA-ODA polyimide has been examined by XPS after several pretreatments of the polymer surface. The only pretreament to modify the chemistry and properties of the interface is oxygen plasma treatment. Introduction of oxygenated groups into the polymer chain increases the adhesion and durability of the interface. The failure mode is always cohesive in the polymer layer. However, when adhesion is increased, the locus of failure shifts further from the interface within the polyimide. When the polymer has undergone plasma treatment, the failure occurs at the modified/unmodified polymer boundary, as shown by a comparison of the XPS spectra on the Ti side and on the polymer side of the interface. When this interface is aged in a wet atmosphere, the concentration of oxygen at the interface increases, adhesion decreases and the locus of failure becomes closer to the Ti layer.