Forcing via placement/ignore clearance

I am trying to fanout a BGA and can’t place any via between the pads, probably because of the low clearance.

Is there a way to temporarily ignore clearance and force via placement?

What pitch bga?
What grid are you using?
Is the bga aligned to the grid.

NOTE I recently tracked a 484 bga and one thing I noticed is I could place a 0.6:0.3 in the middle of a group of 4 pads. But if I tracked out (especially with a 0.5mm grid for consistency) I could place a via

This is a 0.8mm pitch VGA with a 0.2mm grid which is aligned.

Change the router to “Highlight Collisions” mode and check the “Allow DRC Violations” checkbox. (Those are the 6.0 names, so they might be slightly different on 5.1.x.)


Note that in 6.0 you can also define different clearance rules under the BGA. But you’d have to be willing to use a nightly for that…

Start with making via’s and clearances smaller until you can route them under your BGA. That at least verifies that it is a clearance issue. It also gives you some real life parameters of what you’ll need.

Next step is to find out if those settings are supported by your board manufacturer. If those settings fit comfortably with your PCB manufacturer there is no need to different settings for the rest of the tracks.

The current solution for the stable KiCad V5.1.8 to use different track width and clearance settings for a single net is to split the whole net into sections with the “net-tie” symbols.

Thanks for your help. Changing router mode works well when using “Route tracks” but does not allow to place a via using “Add vias”. Is this the expected behavior?

Anyways, using the router works well for my use case. Thank you very much.

No, not expected. However, I can’t reproduce it. It allows me to place vias where they’re clearly in violation of DRC:


I am using KiCad 5.1.6. I think you are using a nightly 6.0 meaning that it was later fixed. If you think I should open an issue anyways I will happily do it.


If what you are describing is the issue I have, it would appear to still be a problem with the nightlies as well

1mm pitch BGA, grid on 0.5mm to easily land between the balls. vias are 0.3:0.6
You are unable to manually place a via but if you track out from a pad you can.

Guessing here, but it might be that the default via size used when just placing vias with the place via tool is too large to fit, but the via size on the track’s netclass you are placing does fit.

I originally thought that but…

Yes, that is exactly what I experienced on 5.1.x. I tried the nightly today (which is amazing :heart_eyes:) but placing via under BGA is even worse as I can’t even place them while tracking out from a pad.

Edit: ignore this comment. I forgot to allow DRC violations.

This feels like a bug as the vias definitely fit

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