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20 The PCB Magazine • May 2014 GRAPHITE-BASED DIRECT METALLIzATION continues is the inherent ability of the graphite system to readily adhere to a wide variety of laminate substrates and materials, including polyimide, PTFE, ceramic filled materials, PPO, PPE, halo- gen free and many other materials. As laminate suppliers continue to reinvent themselves in order to stake out a position in higher technol- ogy, a versatile metallization process is critical to success. So why be concerned with the different laminate materials? Aside from the obvious, successful metallization requires that excellent adhesion between the conductive coating (ei- ther electroless copper or conductive graphite) be achieved. It is well documented that adhe- sion is favored when there is sufficient surface topography to promote the bond. This is espe- cially true for electroless copper as the seeding of the palladium required to initiate the copper deposition. However, as one views the SEM in Figure 8, the topography visible after perman- ganate desmear is rather smooth and unre- markable, further impacting the adhesion fac- tor. A critical advantage for the graphite-based system is that the colloidal graphite binds to resin and glass without the need for a high sur- face area. It is important to recognize that elec- troless copper is a plating process, whereby a series of reactions take place in order to affect a deposit. In the case of the graphite based met- allization system presented herein, the mecha- nism is primarily a coating process whereby the binder technology acts to promote adhesion of the graphite particles to even the smoothest of surfaces [3] . With growth in flexible circuit fabrication outpacing that of rigid and the continued trend towards miniaturization (tablets, smart phones, Figure 9: reel-to-reel flexible circuit metallization system.