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56 The PCB Magazine • March 2016 by Rita Mohanty, Albert Angstenberger, Melanie Rischka and Han Verbunt MACDERMID EnThonE ElECTRonICs soluTIons Abstract Flexible printed circuits (FPCs) are the key enabling technology in the design and fabrica- tion of advanced handheld electronic devices such as smartphones, tablets, and camcorders— not to mention their importance to the auto- motive, defense and aviation industry through- out the last decades. The rapid expansion of smartphone and tablet markets coupled with consumer demand for thinner and lighter products is causing the growth of the FPC segment to be the fastest in the PCB market. FPC provides electronic equip- ment designers greater design freedom when faced with further miniaturized circuitry (thin- ner lines/pitches and smaller vias) while simul- taneously needing to reduce overall cost and increase functionality. The limitation to further FPC adoption is due to challenges in fabrication, primarily the metallization of the flexible dielectric materials. Metallization challenges are the greatest for ad- hesiveless polyimide materials due to the high- er cross-linked material which is less receptive to standard electroless plating chemistries. Con- ventional electroless copper processes are also cost prohibitive when it comes to horizontal FPC processing. Other options such as carbon/ graphite-based direct metallization processes have had limited success for plating complex multilayer boards with microvia designs. How- ever, new conductive polymer-based direct met- allization technologies provide a breakthrough process for FPC fabrication. This paper will discuss the recent develop- ment of a conductive polymer based direct met- allization system that enables FPC fabrication of complex designs as a cost-effective alterna- tive to traditional electroless methods. Results from a series of statistically designed experi- ments to understand the interaction between conductive polymer-based systems and various advanced polyimide materials will be presented here. Guidelines will be provided to FPC fabri- cators to assist in choosing the most cost effec- tive solution to meet their customers need. Direct Metallization System for Flexible Printed Circuits artiCle