Polygon minimum width?

[Anonymous]

Have been drawing some polygons as power/ground/signals and as it's quite busy at some places (some chip pins etc) I decreased the polygon width to "0". Then I get a warning like this when running a check with the ULP "STATISTIC-BRD.ulp". Is this warning relevant, or is polygon width "0" ok?

[Pieter.Jan.Van.de.Maele]

Hey this is a common issue.

The way polygons are drawn in gerber files is by a set of lines that describe the polygon. This means that the interior of the polygon is filled with lines, and because of the line bevel, the fill-lines have the same width as the polygon outline. Because of this, a very small line-width can result in very big file size. To prevent this, EAGLE decides to throw an error. 

As more recent versions of gerber do support proper polygons, this check is irrelevant for those formats. We will start to phase it out in the next big EAGLE version by implementing it as a checkbox in the DRC settings so the user has control over this himself. 

Currently you can just ignore this error or if the check makes sense for you increase the line-width :).

Thanks for reporting!

[Anonymous · Accepted solution]

Pieter, thanks for this quick and clear reply!

[marcoJTHQQ]

When I create a new complex footprint I normally use polygons with a width of 0. I just ignore the error messages, however it takes much longer to generate the gerber files. 

I am using width 0 because it is much easier to create complex polygons. This way you do not need to substract the width:

Taking width into account

Original spec

[Anonymous]

But no problem with the board house/final result(s)?

[marcoJTHQQ]

The gerbers become much larger, but I haven't had any complains from any PCB mfr (gold Phoenix, euro circuits, VPS) Also the results are good.

At the moment I make my footprints with a polygon width not equal to 0 to avoid high gerber generation times. However creating a footprint this way takes me much longer than when I use polygon width=0.

I hope autodesk finds a solution for this "problem" since the footprints are becoming more complex and smaller where a higher precision is needed. And then a width of 0 will certainly help.

Greetings,

Marco

[jorge_garcia2 · Accepted solution]

Hi @marcoJTHQQ,

For now just use 0.01mil line width its small enough that you can effectively treat it as a 0 width but you will avoid the large amounts of gerber data being generated. In EAGLE 0 width is really 0.03um. Using a 0.01 mil line you are using a 3um width. So 2 orders of magnitude larger than EAGLE's limit. This would be the best compromise.

In general you should never use 0 width polygons.
Let me know if there is anything else I can do for you.

Best Regards,