Nettie being a pain in the butt on gnd connection

Hey all,

I am following TI’s layout for a differential I2C buffer,

Because I don’t want to call my ‘TX-SDA’ line ‘GND’ (or rather, my GND becomes TX-SDA’, I added a net-tie. However, I don’t think net-ties work great with grounds :slight_smile: I keep getting DRC violation errors, no matter what I set my clearances (on the tie, or the pads). One reason might be, because the clearance rules are ignored. First, Here’s what happens when my net tie goes to ground. No matter what kind of connection I do, the pad is simply too close to the ‘neutral tie’ which always reports a violation, regardless if I use thermal relieves or a VIA. If I do not connect it, or connect it via a trace, it’s fine of course.

If I disable the solid fill, I get thermal spokes, but they run to the upper half of the pad, which is where the net tie lives.

Also interesting to see, is that we see the ‘pad clearance request’ in the circle, but it’s being ignored. Probably because both are GND so kicad thinks it should use the zone clearance instead of the pad clearance.

Even adding a trace, doesn’t help, because the clearance of the pad is being ignored. I’ve used 0.75 clearance on the net-tie, but that’s not enough for the lower half, if I make it slightly bigger, the upper half bumps into the through hole. I can add more traces/space, but it’s annoying and ugly :frowning:

I had the same problem putting the net tie in the through hole, so that it’s ‘mostly hidden’ but of course, it was complaining there too. I’d almost say, the PCB of the net-tie should be probably ignored on a lot of checks or something.

Perhaps its the same issue as in this thread ?

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I found this gitlab issue:
Net tie fails DRC in KiCad 7.0

Shows a Milestone of 8.0.1.

In case some users don’t read the complete linked gitlab issue: in the middle of the discussion a workaround is mentioned:

  • make the connecting graphical items (polygone) smaller than the pad
  • this can be further enhanced if the graphical copper is integrated into one of the pads (create a arbitrary custom shaped pad)

Look at nettie NT4 in this example (and compare with the original NT1): (30.1 KB)

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