Positive-type Photosensitive Polyimide Based on Poly(amide acid), Vinyl Ether Crosslinker, and a Photoacid Generator

A positive-type photosensitive polyimide (PSPI) based on poly(amic acid) (PAA), 1,3,5-tris[(2-vinyloxy)ethoxy]benzene (TVEB) as a crosslinking dissolution inhibitor and a photoacid generator (PAG) has been developed. PAA was prepared from pyromellitic dianhydride (PMDA), 2,5(6)-bis(aminomethyl)bicyclo[2.2.1]heptane (NBDA) and 4,4'-oxydianiline (ODA) in N,N-dimethylacetamide (DMAc), which has moderate transparency above 365 nm and solubility for 1 % sodium carbonate aqueous solution (aq.). Without isolation of PAA, the photosensitive resist solution was formulated with the polymerization solution (23 wt% in DMAc), TVEB (15 wt% for polymer) and PAG (3 wt% for polymer). No anomaly was recognized after the flexural endurance test by use of the 16 6mu;m PSPI film, which was cured at 2506 C, on a Kapton(r) film. Furthermore a positive image featuring 30 μm line and space patterns was observed by the contact mode when a 9 μm thick film of the PSPI system was exposed to broadband UV light followed by development in a 1 % sodium carbonate aq. at room temperature.