gEDA project

Plane Areas With Poor Connection

Bug #699335 reported by dcole07
20
This bug affects 4 people
Affects Status Importance Assigned to Milestone
gEDA project
Confirmed
Medium
Unassigned
pcb
Confirmed
High
Peter Clifton
pcb future-feature-release

Bug Description

PCB does not remove part of a plane when the only location connecting it to the rest of the plane is less than the minimum trace width. That means it is currently possible to connect components to a plane that is not isolated in PCB, but will be when it is fabricated.

To explain this more, consider a large plane that has a large traces breaking it in half, but the last 1 Mil of the plane remains, even after the copper spacing is taken into account. Both side of the plane will remain because there is a connection between them. When this design goes to fabrication, a minimum traces width of 10 Mils will lead the two halves of the plane to be isolated, because a 1 Mil section of the plane is not considered in the DRC.

Tags: core sf-bugs
Revision history for this message
Martin Kupec (martin-kupec) wrote :

I am experiencing the same problem. DRC is not complaining when connection is made thorugth thin polygon.

Revision history for this message
Peter Clifton (pcjc2) wrote :

This is a known problem, and one which is actually quite hard to fix.

I'm looking into it when I get some spare time, and I believe the (initial) fix, will be to introduce code which clips away pieces of polygons which aren't thick enough to meet the design rules.

I don't know if this would be applied to "solid" polygons, so it would also be helpful to create a DRC check for too thin polygons. This will almost certainly require similar code to the above fix.

Revision history for this message
Peter Clifton (pcjc2) wrote :

Due to the implications for breaks on produced PCBs, I'm marking this "High" importance.

(I'm sure I've had a shorted board back from production due to a whisp of thin polygon breaking free from the FR4 too!)

Changed in pcb:
importance: Undecided → High
status: New → Confirmed
assignee: nobody → Peter Clifton (pcjc2)
milestone: none → future-feature-release
Traumflug (mah-jump-ing)
Changed in geda-project:
importance: Undecided → Medium
status: New → Confirmed
Chad Parker (parker-charles)
Changed in pcb:
milestone: pcb-4.2.0 → future-feature-release
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