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64 The PCB Magazine • April 2014 by Karl Dietz karl dietZ consulting llc Green Technologies in PCB Fabrication c o l u m n karl's tech talk "Green" and "environmentally friendly" are ill-defined terms. In general, these terms refer to manufacturing that involves the replacement of toxic substances with less toxic materials, the elimination of materials or processing steps, and less consumption of chemicals (i.e., more efficient or higher yield processing, reduction of water use, reduction of energy use, less space requirement, smaller equipment foot print, and recycling and on-site recovery of materials). Direct Metallization This family of processes eliminates the elec- troless copper process. These processes typically have fewer process steps, use less rinse water, have less floor space requirement, and use less toxic chemicals. Direct metallization processes include: Palladium-based These processes pretty much follow the clas- sic electroless copper processing step sequence, except the sequence ends with the application of the palladium catalyst, followed by the acti- vation, then skips the electroless bath and pro- ceeds to copper electro-plating. Carbon or Graphite-based Using small carbon or graphite particles to render the dielectric hole-wall electro-platable, this process involves very few steps. Conductive Polymer-based The process of using a non-conductive monomer to coat the board surface follows an oxidation step that forms a conductive poly- mer from the non-conductive monomer. The Figure 1: Formation of conductive poly-"edot" elimination of chemicals.

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