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I intend to send a board to a PCB manufacturer and I am wondering how to mark unused components in the pick and place file. I'm using EAGLE and I saw that it includes all components in the file, but I do not want all of them to be mounted.

Can someone give me an advice on how it is better to proceed? Should I set those component's values to DNP (Do not place) so the manufacturer knows they shouldn't be mounted, and remove them from the BOM? Or should I manually remove the unused components from the pick and place file and BOM?

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    \$\begingroup\$ You could just ask the assembly house how they usually handle it for the best chance of success \$\endgroup\$ – PlasmaHH Sep 18 '18 at 7:49
  • \$\begingroup\$ Thanks. I will do that. I was wondering how other people commonly solve this problem. \$\endgroup\$ – Cristian M Sep 18 '18 at 7:53
  • \$\begingroup\$ I would always try to use the methods of the manufacturer since that gives the least possibility of things going wrong instead of trying to get them to do it your way. Of course sometimes that can mean to choose a manufacturer has the way they do it ;) \$\endgroup\$ – PlasmaHH Sep 18 '18 at 8:11
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    \$\begingroup\$ Usually you would mark the components as DNP or NM (not mounted) in the BOM. Some CAD tools exclude the DNP components from the BOM. It shouldn't be necessary to modify the pick'n'place file. The EMS will map the components from the BOM to the positions in the pick'n'place file. Unused positions in the pick'n'place file will be disregarded. \$\endgroup\$ – Peter Karlsen Sep 18 '18 at 8:26
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Personally I'd do the opposite of @CrossRoads, leave the reference designators in the BOM. If you set the value to DNI or DNP (or NM) with no other part numbers, all assembly houses will interpret this as meaning do not place.

If you want you can also add a column to your BOM which by true/false entry indicates whether a part is populated, however DNI/DNP should be enough.

The reason I'd suggest leaving the ref des in the BOM is that most assembly houses will examine your data and try to match up BOM entries to the silkscreen (even if you provide coordinate data). If they find parts on the silk that don't exist in the BOM, they may query you as to what should be done with those parts. If you mark them as unpopulated in the BOM, they have all the information they need without having to query it.

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Leave them off the BOM, or mark them as qty 0.

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