Issue : why VIA not connected to zone

Layout
1

After I use the “Remove Unused Pads …”, this VIA does not connect to the zone
Both are same signal.

This via is connected in both layer 2 and layer 3

If I change the VIA annular ring to '‘all copper layer’ in properties dialog , it connects!
But this does not happen for the other VIA and it is connected with the same default properties.

via-insize-zone_all
via-insize-zone_all1042×626 105 KB

2

What does your screenshot mean? I’m seeing half a dialog window.

Vias can be placed in two ways, either with automatic net names (convenient when laying down tracks), or with a fixed net name (convenient for via stitching). Your screenshot is apparently from the via properties, and that section is cut off the window.

image
image872×666 73.6 KB

3

I suspect the following . . .

In that position you don’t have GND planes on the Front and Back copper, KiCad doesn’t do buried vias so cannot have a via that doesn’t connect to the Front and Back copper so it cannot place the via.

. . . but I could be wrong.

4

Are you sure about that? I have not ordered a PCB with > 2 layers yet myself, but it appears to be supported:

image
image872×666 74.4 KB

5

Both ٰVIAs have same properties , but the the zone connections behaves differently!

2-via-propertis
2-via-propertis1400×740 238 KB

6

Maybe there is some interference with multiple overlapping zones and zone priorities, but it’s a guess.
Are you sure that at least one of the zones on the right side is connected to GNDD?

7

zone is the same for both vias
As mentioned in the first post, if the via properties changed (VIA annular ring → 'all copper layer’), it will be fixed

via-insize-zone_fix
via-insize-zone_fix671×701 65.3 KB

8

OK, so perhaps the zones on the right hand example are isolated so are not actually connected to GNDD ? can you zoom out and check in both examples please . . . it might be the difference.

9

This may be a bug.

Think about this for a while. You have told KiCad to create annular ring only if the via is connected to something else on the layer.

  1. The via requires the zone to be connected to it so that the ring can be created.
  2. The zone needs the annular ring so that it can fill to and connect to the via if the via hole itself isn’t close enough.

I don’t know how KiCad works in this respect. You can try to move the via in small steps and fill the zone again to see if there’s some threshold.

1 Like
10

I’m trying to repeat this, but can’t. Can you provide an example board file, maybe remove everything but the zones and the via. This may depend on other than just the connecting zone, so all zones may be necessary.