Electronic – How much space should be left between a PCB’s edge and traces and holes

pcbpcb-designpcb-fabrication

I am designing a PCB for use with an Arduino mega and I am wondering if there is a good rule for how much space I should leave between the edge of the PCB and various items like:

  • traces (ground, 5v supply, 9v supply, and 5v digital signals)
  • surface mounts
  • small through holes (capacitors)
  • mounting holes (for screws)
  • large through holes (power supplies)

I currently have 0.1" around everything except of a through hole for a DC jack, which comes .05" from the edge. Can I remove some of this space and not hurt my design?

Best Answer

traces (ground, 5v supply, 9v supply, and 5v digital signals)
surface mounts
small through holes (capacitors)

Collectively, all these are covered by the minimum copper to board edge clearance parameter.

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The value is driven by the precision with which the PCB fab can register the board before it's routed. Typical value is 0.020". Narrower clearance is possible, but the fab may charge extra for additional precision. So, check with the fab, the clearance should be on their "capabilities" page (like this one).

mounting holes (for screws)

Distance of mounting holes for screws is driven by a mechanical considerations. My rule of thumb is to keep the distance between the edge of the hole and edge of the board at least as big as the diameter of the hole. But this can vary greatly depending on how much vibration your assembly will see, and how heavy are the components on the board.
[hint: Separate question.]

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