Direct Additive Copper Plating on Polyimide Surface with Silver Ammonia Via Plasma Modification

In this paper, a facile method of fully additive process to manufacture copper lines on flexible polyimide (PI) substrates was developed. The selective modification on film, involving silver ammonia solution and plasma treatment, was performed to produce Ag particles that catalyze electroless copper plating. It was found that reductive aldehyde groups (R-CHO) were generated at the treated PI surface to reduce silver ammonia ion to Ag particles, which is supported by the of chemical and morphological characterizations. The obtained solid copper deposition demonstrates highly reliable features including limited oxidation, lower roughness and compact crystalline grain with low resistivity of 3.83 x 10-6 omega.cm. The practical fabricated flexible circuits with designed pattern have passed the mechanical and electrical property tests, confirming the compatibility of the developed additive method with the flexible PI substrate.