A negative-type photosensitive polyimide (PSPI) based on a chain extendable poly(amic acid) (PAA) and a photo-base generator (PBG) (E)-1-piperidino-3-(2-hydroxyphenyl)-2-propen-1-one (PHPP) have been developed. The chain extendable PAA was prepared from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) and end-capped with di-tert-butyl dicarbonate (DIBOC) in N-methyl-2-pyrrolidone (NMP), which has a controlled molecular weight for developing in a 2.38 wt% tetramethyl ammonium hydroxide aqueous solution (TMAHaq) and underwent a chain-extending reaction during a curing stage. The PSPI was formulated with the polymerization solution (20 wt% in NMP) and PHPP (15 wt% for the polymer). The PSPI showed a sensitivity of 152 mJ cm−2 and a contrast of 5.9 when exposed to the i-line, followed by post exposure baking at 160°C for 2 minutes and development with the 2.38 wt% TMAHaq containing 10 wt% iPrOH at room temperature. A fine negative image with 2-μm pattern was obtained on a 3-μm thick film in the contact-printed mode. After thermal curing at 200°C for 1 hour, the resulting PSPI features low curable temperature, high resolution and excellent mechanical properties.
- low-temperature imidization
- photo-base generator