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

[Joseph C. <18...@bu...>]

Chad,

As a developer of many large code bases, I appreciate your concern for
the purity of the code.  As a user, I just want it to work.  Allowing
thermals on pads would solve the problem.  A separate clearance
parameter for pads might be useful for other reasons but would not work
well for my use case because I still want the DRC to catch other non-
zero pad clearance violations.

Still, adding back the exception for zero clearance pads in the DRC
seems like the simplest solution.  I checked out the code and this
change was all I needed:

    @@ -637,7 +637,7 @@ drc_callback (DataType *data, LayerType *layer, PolygonType *polygon,
         /* fall-through */
       case PAD_TYPE:
       case PIN_TYPE:
    -    if (clearance < 2 * PCB->Bloat)
    +    if (clearance && clearance < 2 * PCB->Bloat)
         {
           /* The clearance is too small, but it could be cleared by other
            * objects.

You could add a checkbox in the DRC config to toggle this behavior.

Thanks for all your hard work.

Joseph

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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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