As far as I know venting and thieving are used to balance the copper on the
board.
Say that you have a board, one part with very dense pattern i.e. a
address-bus and a data-bus
0.2 mm tracks and 0.2 mm clearance and planes.
On the other side you have a power supply with mains voltage, 2 mm tracks
and up to 5 mm clearance and no planes.
In order to balance the copper, so it etches evenly over the board, with no
over- or under-etching, they have to apply some venting and thieving areas,
normally outside the board.

With best regards

Tomas Larsson
Sweden

Verus Amicus Est Tamquam Alter Idem

> -----Original Message-----
> From: piclist-bounces@mit.edu 
> [mailto:piclist-bounces@mit.edu] On Behalf Of David VanHorn
> Sent: Tuesday, January 31, 2006 1:46 AM
> To: Microcontroller discussion list - Public.
> Subject: Re: [EE] PCB Layout - Dos and Do nots
> 
> 
> On 1/30/06, alan smith <micro_eng2@yahoo.com> wrote:
> >
> > it was open space.......fair game for them to put the artist touch?
> >
> > I got back an analog board..same thing....copper thieving 
> all around 
> > the finely crafted analog layout.  Turned out 
> ok....just...wasnt what 
> > I expected
> 
> 
> I splain it to them very clearly. NO CHANGES TO THE GERBERS.
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