Abstract
Two types of photosensitive polyimides (PSPIs) were developed as novel cover layer materials for FPC applications in this work. One of them, PSPI-1 was highly soluble in common organic solvents such as NMP in spite of its stiff backbone structure. The PSPI-1 film formed by simple solution-casting exhibited a low CTE of 19-24 ppm/K in addition to a high Tg at 292°C, high thermal stability, low water absorption (0.3%), comparatively good transparency, and sufficient film flexibility. On the other hand, another system, PSPI-2 displayed an extremely low modulus. Both PSPI systems completely inhibited curling of the PSPI/copper laminates. These PSPI systems also possessed fine positive-tone patterning ability, reliable insulation property, and the highest level of non-flammability(UL-94: V-0 or VTM-0). The results revealed that the present PSPI systems are promising candidates as novel cover layer materials.
