Processing of Photosensitive Polyimides for Packaging Applications

Photosensitive polyimides have been investigated as substitutes for a standard aqueous base-etchable polyimide. The application uses a ceramic base module on which two layers of metal circuits are separated by a polyimide dielectric. Using a photosensitive polyimide reduces the number of steps and shortens the process time required to form the via interconnections. Processing properties and material properties were studied to select a material which would give optimum throughput. The photosensitive polyimides investigated were primarily developed for IC processing; adaption to packaging applications requires adjustment of processes. Polyimide application, drying, baking, exposure, developing, and final cure must be optimized to use these materials successfully.