Re: gEDA-user: A couple o' questions

[Dan McMahill <dan@xxxxxxxxxxxx>]

Stuart Brorson wrote:
> > Is it a DRC failure? I have my boards full of such shit and I don't
> > care. I think the 1mil wide think cannot peel off and float because it's
> > held on both ends. Maybe it can get interrupted but I don't rely with
> > my groundplane connectivity on such thin places.
>
>
> This should be a failure.  A 1 mil trace can easily become a 0 mil
> trace at your PCB fab house due to their tolerances.  That is, the
> etch process used to etch out your traces has variability; if you have
> 1 mil features on your board, they might be totally eaten away during
> PCB manufacture.  Most PCB houses will specify their minimum line
> width; it seems to vary between 5mil (best case) and 10 mil or more
> (depeding upon their quality and price).   

not that I'm planning on changing the polygons to be drawn with lines, 
but I think this is also a case where with polygons you have to do extra 
stuff while with lines you can automatically get the right thing.  If 
you have a 6 mil minimum width, you would grow all of your clearances by 
3 mils and then trace the outline with a 6 mil aperture, then fill in 
the enclosed areas.  This would automatically prevent the slivers as 
well as the sharp angles.

Now I'm curious...  anyone have first hand knowledge as to what current 
commercial tools do?  I simply don't recall for most of the tools I've used.

-Dan