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Hartley gave a brief introduction to the circuit board manufacturing process, taking a basic four-layer multilayer as an example, and proceeding step by step through all of the principal stages, with his explanations aided by clear graphics. He made a particular point about non-uniform plating distribution on outer layers with unbalanced copper but advised against allowing the fabricator to fill spaces with thieving copper to even-out the plating because of potential induction effects. The designer would need to make modifications with manufacturability in mind whilst maintaining the signal integrity of the design. A copper pour, attached to ground or power, could help but might not be the answer.
On the subject of etch-compensation, he advised designing at nominal conductor width and leaving it to the fabricator to calculate the appropriate etch-factors. “Don’t compensate for the fabricator’s needs. Make sure you design so they can produce your board. Know what they can and can’t produce, and design around their needs, then send them the design and leave them alone.”
There were many more details to understand—he could easily have filled the other seven hours he mentioned—and many more questions to ask the fabricator: “Don’t assume. Talk to the fabricator, ask the questions, get to know the most knowledgeable person at every fab shop your company uses—someone who understands.”
Listening to Rick Hartley was like a breath of fresh air. And his one-hour (and a bit) session provided a wealth of advice on how to accomplish the goal of optimising designs for cost-effective, high-quality manufacturing.
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