Synthesis and characterization of ultra-thick negative photosensitive polyimide

Photosensitive polyimide (PSPI) is one of the great interesting engineering polymers, especially for microelectronic industry. We studies and optimized the synthesis conditions for a PSPI that can be used as lithography material. Negative photosensitive polyimide (NPSPI) have been synthesized by reaction of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) with hexamethylenediamine (HMDA) and 4,4′-oxydianiline (ODA) at stoichiometric dianhydride/diamine ratio of 100:30:70 in N-methyl-2-pyrrolidinone (NMP) solutions by using solution condensation polymerization at room temperature and further imidization at 250°C. The photoinitiator and photo precursor were bis(2,4,6-trimethyl benzoyl) phenylphosphine oxide (Irgacure-819) and 2-hydroxyethyl methacrylate (HEMA), respectively. In this study, we used photosensitive polyimide for insulation layer that created as cover film with the thickness of cover film approximately controlled at 12.5 micron, thus the thickness of cover film was called, as “Ultra-thick” and the area opening of NPSPI films are 4 mm2 was prepared. The silica domains are responsible for reducing the volume shrinkage of NPSPI films after the curing process by synthesis of negative photosensitive polyimide/silica (POSS) hybrid films. The synthesized NPSPI and NPSPI/silica hybrid films were characterized by FTIR and 1H-NMR while their morphologies were evaluated by Optical and Confocal Microscope. The thermal stability of the polyimide films was analyzed by TGA and their dielectric constants were confirmed by LCR meter. These results indicated that the prepared NPSPI/silica hybrid films would have the high potential for applications in electrical devices.