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Polygons automatically filled with copper?

autodeskguest

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.

--

John Bachman, W1JGB

AnaTek Corporation

 

  • 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.

    --

    James Morrison  ~~~  Stratford Digital

     

    email:  james@eaglecentral.ca

    web: http://www.eaglecentral.ca

     

    Specializing in CadSoft EAGLE

    • Online Sales to North America

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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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