[Pcb-bugs] [Bug 1843834] Re: New DRC flags zero-clearance pads

[Chad P. <par...@gm...>]

Hi guys-

Sorry, I just noticed this. It didn't get prioritized in my inbox. I'll
try to take a deeper look at it this coming weekend.

I fixed a lot of DRC issues in 4.2.0, and this may have been one of
them. I believe it will flag any object with a clearance less than the
global minimum copper clearance as an error.

I believe the "correct" way to connect a surface mount pads to a plane
is to set an appropriate clearance for the pad and then use a line
without the "clearline" flag set. This can be done by changing a setting
in the Settings menu: "New lines, arcs clear polygons". I don't remember
off the top of my head if there is a hotkey for this.

I agree that the thermal tool should work for pads. I actually started
looking at implementing this a couple months ago. It turns out that it's
not as trivial as one might hope. There is a branch you can try if
you're interested: LP699495. However, in my opinion it's not ready for
prime time. I think it works for pads that are horizontally or
vertically aligned, but non-90-degree rotations will cause seg-faults.

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https://bugs.launchpad.net/bugs/1843834

Title:
  New DRC flags zero-clearance pads

Status in pcb:
  New

Bug description:
  As of version 4.2.0 my PCB layout has 176 new DRC errors.  I have many
  pads which are connected to polys by setting the pad clearance to
  zero.  The DRC previously ignored theses.  I understand that this
  looks like a legitimate clearance violation but there is no way, as
  far as I can tell, to tell PCB that the connection from the pad to the
  poly is intentional.

  I believe the DRC should just ignore zero-clearance pads as it did in
  previous versions.  If the resulting connections were errors, they
  would be detected as such anyway because they would violate the
  netlist.

  An alternative but less ideal solution would be to add a flag, say
  "noclear", that could be added to the pad to indicate connection to
  the poly was intentional.

  This is fairly easy to reproduce.

    1. Start a new project
    2. Add a poly rectangle on the top layer.
    3. Add a component that has a pad.
    4. Set the clearance of a pad to zero (Shift-K).
    5. Run the DRC.

  See attached file.

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