DIRECT METALLIZATION SYSTEM FOR FLEXIBLE PRINTED CIRCUIT BOARD

摘要

Flexible Printed Circuits (FPC) are the key enabling technology in the design and fabrication of advanced handheld electronic devices such as smartphones, tablets, camcorders - not to mention their importance to the automotive, defense and aviation industry throughout 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 equipment designers greater design freedom when faced with further miniaturized circuitry (thinner line/pitch and smaller via) while simultaneously 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 adhesiveless polyimide materials due to the higher cross-linked material which is less receptive to standard electroless plating chemistries. Conventional 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. However, new conductive polymer based direct metallization technologies provide a breakthrough process for FPC fabrication. This paper will discuss the recent development of a conductive polymer based direct metallization system that enables FPC fabrication of complex designs as a cost effective alternative to traditional electroless methods. Results from a series of statistically designed experiments to understand the interaction between conductive polymer based systems and various advanced polyimide materials will be presented here. Guidelines will be provided to FPC fabricators to assist in choosing the most cost effective solution to meet their customers need.