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46 The PCB Magazine • January 2015 by Michael Carano omg eleCTroniC CHemiCals Fine Lines and Spaces with Half-Etch Processes trouble in your tanK Introduction It is all about circuit density. If your cus- tomer or customers are pushing the envelope with respect to greater circuit densities, how are the fabricators adapting to these requirements? I do not want to oversimplify the task at hand, but there are a number of things one can do to improve the yields on finer lines. These include laser direct imaging, semi-additive processing, use of ultra-thin foils, and special processes. An- other and perhaps lesser known application is termed "half-etch." Here the fabricator utilizes a specially formulated copper etching process to remove a minimal amount of copper. The goal is to remove the copper uniformly, but not completely from the surface as is performed during the final etch-process step. For example, by reducing 1 ounce copper foil (35 microns) down to ½-ounce or ¼-ounce, one maintains the adhesion of the original foil. In addition, the fabricator is presented with a much thinner substrate foil that can be easily etched during the final etch process. There are several good reasons for this approach: Column

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