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 --
