Fill zone within a fill zone - vias connecting

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1

Hi,

I have two fill zones, the middle one shown on the picture is priority 6 and is a power net, the outer zone is GND and is priority 1.

There are some GND vias inside the power zone and the software is trying to connect them together with a pour, then giving me a warning about the copper being too thin.

Why is the software trying to connect them together? They don’t need to be. There is another plane that is a solid GND pour.
Is there a way to stop this happening please?

Thanks,

G

Screenshot 2024-11-22 at 12.33.20
Screenshot 2024-11-22 at 12.33.20850×819 36.2 KB

2

Without a attached example project the following is only a (educated) guess.

  • kicad fills the inner zone with priority==6
  • due to the clearance-setting of that zone there remains some unfilled space between the GND-vias
  • now kicad fills the next lower priority zone. And because there is some empty space between the GND-vias kicad tries to flood this space with GND
  • kicad does not know that it generally should fill GND zones, but exceptionally this empty space should not be filled. The arbitrary intelligence to detect which empty space of a zone should be filled and that some empty space should not be filled is not implemented yet in kicad.
  • There is currently no real way to prevent you from this happening.
  • As you know that these “copper too thin” warnings are not important in your case: ignore these DRC-errors/warnings

Some parameters may influence the behaviour and improve the situation:

  • more/less clearance values on the zones, maybe different values for power-zone/GND-zone
  • more/less “minimum width” for GND zone
  • moving the GND-vias, so the power-zone can better fill between the vias
  • reduce the “minimum conenction width” for the DRC
3

Hi,

Thanks for your answer.
What does the parameter “minimum width” mean for a fill zone? What does it affect?

Thanks,
G

4

You could imagine the filling works like painting with a pencil with round tip. The “minimum width” parameter is the diameter of this drawing pencil. So the width of this drawing pencil determines how good the filling works between obstacles (filling flows through connector-pads or not).
This “minimum width” parameter should be set at least higher than the minimum copper width from the board constraints.

5

So it’s a bad idea to wet minimum width to zero?

Thanks,
G

6

The more I’ve looked through my warnings, the more of these I’ve found on lots of pours.
Is there really not a way to stop pours pouring tiny slivers of copper that are thinner than the minimum thickness?

Thanks,
G

7

You can reduce the number of such warnings if you increase the “minimum width” value of your zone fills.