Thin polyimide films, microstructural

Polyimides are an important class of polymers for high temperature aerospace applications. Thin polyimide films are ideal candidates for protective coatings on antenna reflectors and other electronic applications. Their properties, both physical and electrical, are expected to be strongly influenced by their morphology. We have developed a novel technique for monitoring microstructural characteristics of thin polymer films. It is based on the sensitivity of the positron lifetimes to the molecular architecture of the polymers. Specifically, positron lifetimes can be used to calculate free volume hole radii and free volume fractions in the test polymers. A free volume model has been developed to calculate dielectric constants of thin polyimide films. It has been tested on a series of special purpose polyimide films developed for aerospace communication networks. The results are described in the following sections. 

The fabrication of polyimide based microstructures with a single metallization layer is described. The silicon wafer is merely used as a supporting structure to perform the photolithographic steps and thin film procedures in the cleanroom. The wafer is removed at the end of the process. 

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