MEASUREMENT OF RELATIVE ADHESION AND SURFACE-PROPERTIES OF POLYIMIDE FILMS USING A SURFACE-ACOUSTIC-WAVE SENSOR

A surface acoustic wave (SAW) sensor is used to study the relative-hum idity response of thin polyimide films on quartz, where interfacial an d surface properties are varied. The results show differences in the c omparative SAW humidity response for films applied with and without ad hesion promoter and with and without a chromium interface layer deposi ted between the substrate and the polyimide film after temperature and humidity aging. Polyimide films were examined that were both sputter cleaned and non-sputter cleaned. The humidity response is particularly sensitive to the surface treatment of the polyimide film. A theoretic al analysis has been done to obtain information on the physical mechan isms responsible for the SAW sensor humidity response. The analysis id entifies three primary film properties that can influence this respons e. These properties are changes in density, elastic constants and stre ss of the film as a function of humidity. The more dominant of these f actors appear to be density and elastic-constant changes.