Removing Copper Pour from outside PCB boundaries

First time KiCAD user here. My PCB outline was imported from a dxf file and it has a few cutouts and irregular edges. I did a fill zone over the top layer to create a copper plane but now I’m stuck wondering how to remove the fill zones from the areas I don’t want it. I know you can use a the zone cutout tool but it’s not entirely useful (and tedious) seeing as I can’t zone out curved areas.

What is your kicad version?
Did you try to refill (shortcut B)?
Is the board outline closed and on the edge cuts layer? Closed means all segment ends are within 0.01mm (info from mailing list) to the next segment.

For complex board outlines it is suggested to use kicad stepup:

Version 5.0.0.
Tried the refill, doesn’t change anything.
Looking closely around the edges everything seems to be connected fine.
My board is on the edge.cuts layer

Thanks I’ll take a look into StepUp and see if it can help.

If you have any cutouts on the inside then these need to be closed as well.

And double check the endpoints of every arc you have on the edge cuts layer. These are the most likely place where an error could occur. (The end point of the arc must be within the tolerance of the next line segment)

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I went and checked all the way around and all the endpoints of the lines and arcs line up perfectly.

I was playing around with the zone cutout and realized it actually works for curves…sort of. Because there’s clearance from the fill layer to the cutout edge, you can approximate the curve with a polygon. The cutout zone looks ugly but the fill layer follows the PCB edge so the end result is nice. It’s just slow and inefficient this way.

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Did you give that fill area a valid net name ?(hard to tell from the image)
I think that may trigger the isolated copper removal, and so trim the ‘outer’ copper.

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Connecting to a label can solve the problem.

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That worked! The copper is actually connected to nothing so I never assigned it to a net, hence my problem. Thank you.

Actually now I’m just having an issue assigning to an empty net. I added a GND symbol to my schematic with one net labeled ‘Ground’, but the net doesn’t show up in the layout editor.

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If you connect different labels (A gnd symbol is nothing else than a global label) only one of them will appear in the netlist (the one with the highest priority)

Ah yes I see now. The GND net appears in my layout now but trying to do a zone fill around my board results in nothing. It looks like the fill zone only works if there’s something to connect to it, as in a pad in the same net as the fill zone…

So now I’m really not sure how to make the zone fill my board while also being connected to nothing.

What would be the reason for having a large copper plane that is connected to nothing?

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I don’t know his reasons, but homemade boards might be a reason. Home etching wouldn’t go through as much echant and milling all the copper from unused areas would take a long time and cause unnecesary wear on the milling bits.

I don’t think his board design is a flex board, but I remember (many decades ago, so it may be different now) being advised by a flex manufacturer to leave as much unused copper on the flex circuit to avoid warping due to differential shrinkage between copper areas and non copper areas.

Personally, I’d just connect the unused copper to ground unless I had an EMI or isolation reason not to.

This PCB has no incoming ground connections and I have no control over that aspect. I still want the additional thickness of the ground plane for various reasons.

Well I went back to the old way of manually creating zone cutouts but now KiCAD hard crashes every time I complete a zone cutout…I think I’ll just leave the copper out on this one. It’s not what I want but it seems to be fighting me too much to make it worth it.

Technically… yeah you do. Circuit ground is simply a reference at which all other signals are measured. Even if your circuit is running at a negative voltage, you still need some reverence for that negative direction and the voltage value to have any meaning. Ok, you may not have chassis ground and/or earth ground. Circuit ground can be more accurately called 0V, it is just generally called ground by convention.

Now if you need the copper for physical thickness, that actually might be an argument for a floating copper pour. Just as long as multiple things touching the floating copper pour don’t cause problems when eventually the solder mask gets worn away and the copper pour provides electrical contact between the off-board things (what ever they are).

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It’s actually a keypad grid with no passives so none of the connections go back to any kind of reference directly. All the the signal lines go back to a microprocessor or a resistor. Otherwise I’d connect the copper fill to it.

It’s unusual for none of those lines to be GND, and also unusual on a Keypad, to NOT have some ESD pathway to GND provided.
If you fail to give ESD a path, it will happily go via your MCU pins…


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