Next, always be aware of your signal return path. It’s not enough to simply make sure all of your ground pins are connected; you will need to keep the return path for every signal in mind. If your signals cross a split in the reference plane, the signal return will have to find a way around that split and back to its place under the signal. Every time that happens you will add EMI to your design. Is there a practical way around signal return path issues? Yes. With PCB123, for example, you have the ability to turn off just the traces, leaving the area fills visible. This is a useful technique with 2 layer boards, since they don’t have the luxury of dedicated ground planes. With that done, you can ensure that your return path can flow directly to all areas of the board. Use vias to stitch your fills together making a more complete and direct return path for all of your signals. Finally, if your product is going to need controlled impedance, try to figure out how to achieve that impedance level with standard board construction and materials that can be built anywhere. If you get all exotic with your requirements, costs will skyrocket, and while your product may work just great, it will cost so much you can’t sell it.

Connector Considerations

An engineer prepares DFM rule checks for use in open-market PCB design tools. Using fab-created design rules can increase the success rate for all designs, including PCI boards.

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Typical PMC implementations will require exact connector placement on both ends of the daughterboard’s long axis. It is because of these close tolerances that engineers embarking on their first PMC format design should carefully research the initial setup of their PMC template. Or, better yet, use a known-good template supplied from a reputable source like your CAD tool supplier, or your PCB board fabricator.