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Castellated edge support in v5.99


KiCad doesn't have any specific support for castellations, and doesn't
need anything special because it's basically PTH pad on the edge. It
works so-and-so in 5.1: it doesn't complain about pad copper which is
too close to the edge, and it's even possible to add SMD pads to the
footprint so that it's possible to route without DRC problems. (See
https://forum.kicad.info/t/how-to-design-castellated-pins/23945 .)

However, this doesn't work so well in 5.99. DRC check handles pads
like other copper and the only way to turn off errors is to ignore
"Board edge clearance violations" altogether.

We could of course have some specific support for castellation, like
marking footprints as castellation and then allowing copper and
routing there. But I doubt this is what the team wants because it's a
special case which can be solved otherwise (like local neckdown for
tight IC's).

It' not clear to me how the local rules is going to be implemented.
Will there be some kind of graphical polygon where I can define the
rules with the DRC Rules editor? That would work for me if it's made
easy enough.

I thought about being able to add certain kind of predefined rules
without a need to write them. For example
* Add a box around the area
* Open the context menu on the box
* It reveals menu item "Add Rules"
* -> "Castellation"

Then it would allow the pads on the edge, and also routing and zone
filling fully without caring about the edge line inside the pad
boundaries (the rule system must of course support this!).

On the other hand, castellation is pretty much a de facto standard and
it wouldn't hurt to support it as a special case. Even allowing THT
pads on an edge where the hole is on the edge, too, would be enough to
allow the same workflow than in 5.1.

Splitting board edge violations into two, pad and other, would also
work. I never want to violate with traces, but sometimes in a tight
design I have placed pads very near to the edge and trusted that the
manufacturer removes copper if they want and there's still enough room
for the component. This would also allow non-castellated edge plating
with a footprint (which must otherwise be handled with local rules,
like castellation).

Finally, being able to select a bunch of violation markers - for
example for one footprint - and excluding them permanently could also

Eeli Kaikkonen

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