Plane Areas With Poor Connection

[dcole07]

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.

[Martin Kupec (martin-kupec)]

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

[Peter Clifton (pcjc2)]

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.

[Peter Clifton (pcjc2)]

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!)