I don't see any reason why pcb *shouldn't* al= low overlapping parts, so long as other design rules aren't violated. A= nd anyway, it's somewhat difficult to define what that actually means. = Overlapping bounding boxes, for example, is not necessarily an indicator of= parts that might interfere with each other.

The o= ne thing that I would like to see at some point is the addition of keepout = zones. If you were to add a keepout zone to a part and then try to put some= thing else inside that zone, I would like that to generate a warning.

At some point I would also like pcb to start throwi= ng warnings about overlapping holes, or holes too close together, or too cl= ose to the edge of the board.

--Chad

On T= ue, Oct 27, 2020 at 7:05 AM Richard Rasker (rasker AT linetec DOT nl) [via = geda-user AT delorie DOT com] <ged= a-user AT delorie DOT com> wrote:

Op 26-10-20 om 16:55 schreef Peter Stuge (peter AT stuge DOT se) [via
geda-user AT delori= e.com]:
> gene glick (geneglick AT optonline DOT net) [via geda-user AT delorie DOT com] wrote:
>> I want to do this on purpose. One part, a 2X16 character display h= as 10
>> connections to the PCB. Problem is, they are just holes. It is mea= nt to
>> have a 10 pin header on the PCB, and then the display gets positio= ned over
>> the header and soldered in place.
> Rather than having to deal with two footprints on top of each other I&= #39;d
> recommend this:
>
> Create one 2X16LCD footprint which has no electrical connections but > only silk lines+text and any mounting holes (Pin with attribute "= hole").
> I'd recommend to draw silk lines around where the electrical conne= ctions
> will go.
>
> Then place one 1x10 header footprint for the electrical connections. >
> That way you can have both parts in schematic and BOM without having > redundant connections in the netlist and layout, and no problems with<= br> > two footprints with electrical connections on top of each other.

This had occurred to me as well, but the major caveat here is alignment: even a minute unnoticed nudge of either part may spell very serious trouble= .

At the very least, I'd recommend combining the connector pins and
mounting holes in the same footprint when adopting this approach. After all, a slightly shifted silk screen symbol isn't much of a problem, but=
mounting holes in the wrong place usually boil down to an unusable board.
> In addition to local simplicity I can imagine that fabs might be unhap= py
> or at the very least confused with two drills on top of each other..
Yes, that might indeed be an issue, depending on the fab house.

My standard approach here is actually to NOT use a separate header
symbol in the schematic, but simply put a warning in the display
symbol's comment attribute to manually add the header to the bom afterw= ards.

My final boms (LibreOffice spreadsheet files) contain lots of other
parts that aren't entered in the schematic anyway, e.g. mounting studs,=
washers, screws, and nuts, bezels, brackets etcetera. So manually adding this header is a minor issue.

But it is interesting to see that PCB allows these overlapping parts.

Richard

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