Printed circuit boards (PCB) are being widely applied for related electronic produces in industry. The trend in the future is toward narrower metal line, tiny via hole, and complex multilayer manufacture processed. The challenge is therefore for the difficulty of producing excellent metal thickness on substrate surface and inner surrounding of holes for high level application. This study proposed an improving method on electroless plating, and combined with the ink-jet printing of catalyst to form a high aspect ratio of metal thickness for the substrate surface and hole inner wall. This study laminated the flow direction by dynamic pressure control and modulated the velocity at divergence along the substrate surface and hole inner wall. Meanwhile, the stabilization of electroless plating was tuned by an inner flow circulation, to reduce of cavity defect in metal forming. By this system improving, high performance circuit at full reliability was made on multilayer flexible substrate with holes, the variation of aspect ratio of thickness can control within 13%, and further reduce up to 2% with the hole diameter decrease.
Jie-Kai Chang, Kevin Cheng, Ming-Huan Yang, Chung-Wei Wang, Fu-Kang Chen, Cheng-Po Yu, Chang Ming Lee, Tzyy-Jang Tseng, "Green Ink-Jet Technology for Fabrication of Multilayer Flexible Circuit Part I: System Construction & Fabrication Process" in Proc. IS&T Digital Fabrication Conf., 2006, pp 144 - 146, https://doi.org/10.2352/ISSN.2169-4451.2006.22.2.art00045_3