Polygons automatically filled with copper?

No, Ratsnest does the job.

r

John Bachman wrote on Mon, 22 February 2010 14:32

If I create a polygon and name it (GND for instance) will it be

automatically filled with copper?  I think that is what the manual says

 

but want to be sure.

Hi John,

It actually depends on the situation.  For display purposes it won't always

update the screen.  For that you need to run the ratsnest command (and have

the bit set in the options to process polygons).

If you mean during the CAM file generation then that is done automatically.

I know that confused me when I started.  All polygons are processed

automatically before the CAM processor creates gerbers.

Cheers,

James.

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John Bachman wrote on Mon, 22 February 2010 14:32

If I create a polygon and name it (GND for instance) will it be

automatically filled with copper?

If you mean on the final board, then yes, sortof.  That's what polygons

are: filled regions of whatever the layer represents, which is copper for

the signal layers.  This has nothing to do with the name of the polygon.

That indicates which net it is part of.  If you name the polygon GND, then

vias to ground within the polygon's area will connect to it, for example.

Vias for other signals will not.

The reason I said "sortof" above is that polygons can have other traces

within their areas, and can get broken up.  This is one difference between

planes and polygons.  A plane will never have other signals.  At most it

will contain holes for vias not of the same net.

Polygons on the other hand can have other signals routed thru their areas,

and they don't have to extend over a whole plane of a board.  A common

trick with two layer boards is to make the bottom layer a ground polygon.

By setting the layer cost high and a few other tricks, you can get most of

the other net connections on the top layer.  The bottom layer will be

mostly a ground plane, with other signals using the space for short

jumpers.  If the board is too complex or dense, it may be impossible to

prevent large islands of other signals within the ground polygon or prevent

it from being broken up.  Then it's time to think hard about your grounding

strategy and whether it's time to go to multiple layers.

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