Re: gEDA: Problems with connection scanning

[Karel Kulhavý <clock@twibright.com>]

On Sun, Aug 08, 2004 at 10:38:49AM -0400, Stuart Brorson wrote:
> > For example some board have tons of tiny squares that are not connected
> > together to perform coverage equalization, copper savings etc. My manufacturer
> > didn't want any such thing. It's probably necessary only in very big series or
> > in some extra cheapo processes or I don't know what. I can see it on PCI cards.
> 
> That's called "thieving".  Usually, PCB manufacturers *do* want that
> -- they place it into the design themselves.  And not just cheapo
> boards use it.  My biggest board was a 20 layer SONET interface board
> for a major router (not done with gEDA, BTW  :-( ) which would retail
> for $20,000.00.  (Or maybe the BOM cost was $20K. . . .  I forget.)
> It had thieving. 
> 
> I would be curious to know why your mfr doesn't want thieving.  Maybe
> they will put it in themselves?
> 

Actually, I forget that there isn't any place left for the thieving at all
;-)
http://ronja.twibright.com/twister/pcb.php
Maybe the little place at lower left corner ;-)

Doesn't thieving degrade HF performance? The squares must behave like a medium
in which electromagnetic waves can propagate, don't they?

> My understanding is that manufacturers want theiving because it means
> they need to dissolve less Cu in their etch baths, which means they
> have to change the bath less often.  Also, it helps with the
> mechanical strains on the board if you have an even copper balance on
> both sides of the board.  If you have a copper imbalance, your board
> can tend to warp.
> 
> Stuart