Low DK & DF and High Reliable Polyimide for Redistribution Layer of Advanced Package

ABSTRACT Advanced package requires polyimide to be low Dk & Df properties for low loss. In this paper, we report low temperature curable (minimum 200°C), low Dk (2.7) and low Df (0.007) negative tone type photo-definable polyimides for redistribution layer of advanced package. Those materials, which were in states of liquid or B-stage sheet, were able to be patterned by photolithography process with i-line stepper and g,h,i aligner, and revealed high resolution. Cured film of our novel polyimides showed excellent dielectric and mechanical properties, and good results on reliability tests. Chemical resistance of the materials for back end process of polyimide was also good. Our developed polyimides kept enough insulating performance after a biased HAST, and kept enough adhesion and mechanical properties after MSL-1 test. Finally, in collaboration with DIE. a test package of which mounted our novel polyimide as redistribution layers was fabricated. Flat Cu wiring was fabricated because of high flatness of B-stage type of novel polyimide. Thermal cycle test of the package was conducted and we observed no crack and delamination fail.