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I want to attach a panel mount potentiometer to a PCB. But I need the bushing to be grounded. Ideally I would just make the hole for the pot thru plated but the fab does not permit really large thru plated holes. So my first attempt is two SMD pads with a thru plated hole in the middle like this:

eagle bushing contact

This obviously has issues. Can anyone recommend an alternative solution?

If not, do you think this would work if I accept all of the overlap and clearance issues with these pads? Will the hole actually be through plated so that the top and bottom pads are in fact connected?

UPDATE 1:

As suggested by Peter Bennett, a possible solution is to make a circle using the bStop layer to expose the ground plane:

eagle bStop for bushing contact

So there would be no contact on top but I think because the tin is slightly raised and soft it should make good contact with the bushing. We'll see ...

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  • \$\begingroup\$ Is that a via or a through-hole pad? If the latter, try adding it as a via in the layout rather than a hole in the footprint. Also, refer to this question for connecting the pads. \$\endgroup\$
    – Tom Carpenter
    Aug 18, 2016 at 5:01
  • \$\begingroup\$ Thanks. Append does help a lot with the schematic. But I have to manually create two vias (one from bottom to top and one from top to bottom) to resolve all routing and DRC errors. I would be fabulous if there were a more streamlined solution. \$\endgroup\$
    – squarewav
    Aug 18, 2016 at 5:43
  • \$\begingroup\$ It looks like you have a ground plane around the hole, so just creating a larger "hole" in the solder mask should allow a good connection between the pot bushing and ground. No need for an explicit pad or via. \$\endgroup\$
    – Peter Bennett
    Aug 18, 2016 at 16:25
  • \$\begingroup\$ Mmmn, that is kind of brilliant. How do I create a hole in the solder mask. What layer means "don't put solder mask here"? \$\endgroup\$
    – squarewav
    Aug 19, 2016 at 0:03

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I doubt that the potentiometer's nut will make a reliable contact with the small pad like that. To make a reliable contact, I would make the pad encircle the hole completely, and put a star washer between the pad and the nut. Alternatively, do that on the bottom layer.

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    \$\begingroup\$ The pads encompass more than 45 degrees and the pads are on both sides so at least one tooth of the washer should make contact. But I agree it is not ideal. If there is a way to make a circular "pad" with a hole in it, I'm v. interested. \$\endgroup\$
    – squarewav
    Aug 18, 2016 at 5:46

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