PCB007 Magazine

PCB007-Nov2024

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What is minimum space and trace? The answer depends on the starting copper weight. This is because we must do an etch comp on the traces in CAM to compensate for known etch loss. The space between traces after compensation will play a role in whether a board can be manufactured. The lower the spacing width, the higher the cost. Designers don't always account for the proper starting copper weight after edge compensation. For accurate starting copper weight, add a half mil (.0005") to all copper features. Start with 3/8 or 1/4 oz. foil, reducing etch comp and less likely to cause a spacing issue. Boards that call for full body electrolytic gold are not comped to avoid gold slivers occurring during the etching process. • • • Design tips: DESIGN TIPS #124: ETCH COMPENSATION After etching Before etching During etching, trace width expands beyond the width of the resist. TRACE WIDTH

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