Re: gEDA-user: PCB: ground network common practice newbie question

[Dan McMahill <dan@xxxxxxxxxxxx>]

On Sun, Apr 24, 2005 at 11:45:13AM -0400, DJ Delorie wrote:
> 
> >   For two sided boards, Is it common practice not to draw any ground
> > lines, but to rely on the polygons to connect all grounds as the final
> > stage of pcb drawing?
> 
> If it were me, I'd use regular traces for ground lines to ensure
> connectivity, but clear the "clears polygons" flag.  Later, drop a
> polygon over the whole side and it will fill the empty space and
> happen to connect to ground wherever it can.  Not all of the plane
> would be grounded, but that's better than having a disconnect.

I typically just draw one big polygon at the end.

> >   Another quesion. If you draw big polygons to fill any empty space
> > with ground copper on the the board, how do you deal with the pieces
> > of copper that are not connected (debris?)? For example, those in
> > between lines.

those bits of copper are often called "islands".

> Normally, the spacing between traces would be sufficient for the
> polygon to go "around" the lines, but it is something you have to be
> careful about.  In general, don't put many traces on ground planes,
> but that means four or more layers.

I'd argue that the # of layers will heavily depend on the type of board.
I've done quite a few analog and RF boards where it was 2 layers and
almost no bottom side traces, just a ground plane.  Its what I call
a 1.5 layer board.  You get 1 trace layer and 1 ground layer.  I doubt
anyone but me calls it that.

-Dan

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