Physical characterization of photosensitive polyimide

Polyimides prepared from oxydiphthalic anhydride and diamine precursors can be photosensitive. The thermal, mechanical, and dielectric properties of the polyimide films have been characterized with various techniques. The thermal decomposition temperature of the cured film is 520 degrees C, and the coefficient of thermal expansion is 20 x 10(-6)/degrees C. The polymer chemistry and processing conditions result in a low stress (<26 MPa) in the polyimide film as measured in situ during the curing and cooling cycles. Pads of 6 mu m were patterned through the photosensitive polyimide at a sensitivity of 110 mJ/cm(2) to i-line wavelength. The polyimide films exhibit anisotropy with an in-plane refractive index of 1.74 and an out-of-plane index of 1.62 measured at 632.8 nm wavelength. This indicates a preferred orientation of polymer chains in the film plane. The estimated dielectric anisotropy should be considered a major factor for device design and optimization.