New screen printable polyimide for IC devices

To develop a new screen-printable polyimide paste, structures, properties, and the ratios of three major paste components (filler, binder, and solvent) were studied and a new film-forming strategy was established. This strategy comprises a new type of polyimide particle filler which can be dissolved in the binder and the solvent under the curing condition. Using this strategy, the new screen-printable polyimide paste was developed. This paste produces a uniform film with better mechanical properties than conventional polyimide paste which is comprised of an insoluble polyimide particle filler. The effect of the solubility parameter of the solvent on mask swelling and moisture resistance was also examined. It was found that a lactone with a solubility parameter value of 18-20 (MJ/M³)^1/2 is suitable as a paste solvent and the lifetime of the stencil is extended over that of the conventional paste