Issue link: https://iconnect007.uberflip.com/i/306762
14 The PCB Magazine • May 2014 GRAPHITE-BASED DIRECT METALLIzATION continues ite based processes, the equipment footprint is quite small when compared to a conventional electroless copper line of equal productivity. This is indeed an advantage with respect to ca- pex utilization and return on assets. Graphite-Based Direct Metallization Colloidal graphite direct metallization pro- cesses have proven their usefulness as a replace- ment for electroless copper. This is especially the case in high-technology and quick-turn ap- plications. The ability of the colloidal graphite to successfully enable the direct electroplating of difficult to metalize materials such as polyimide, PTFE, ceramic-filled resins, PPO and PPE is well documented. Aiding this has been the improve- ment of the consistency of colloidal graphite di- rect metallization processes. This is accomplished through a better understanding of the influence of conditioning agents, the stability of the disper- sion, and other process refinements that will be detailed in this article. The implementation of polyelectrolyte surface active agents that enhance the adsorption of the graphite to the non-con- ductive surfaces without causing excessive film thickness is quite critical. And the introduction of fixer technology further enhances the uniformity and conductivity of the graphite coating. These improvements are necessary as the industry mi- grates to more complex designs (Figure 1). Process Overview The colloidal graphite direct metallization process involves the following steps: 1. Cleaner/conditioner 2. Colloidal graphite 3. Fixer 4. Dry 5. Microetchant 6. Anti-tarnish (optional) The purpose of the cleaner/conditioner is to coat the hole-walls with a compound hav- table 1: (source: IPc technology roadmap, 2013) Figure 1: complex HdI build-up.