Re: gEDA-user: next PCB release - 1.99za vs 4.0

[Peter Clifton <pcjc2@xxxxxxxxx>]

On Sat, 2010-09-11 at 21:44 +0200, kai-martin knaak wrote:
> Peter Clifton wrote:
> 
> > Just how useful is anti-copper?
> 
> I'd use it for text in copper (less space demanding than regular, 
> positve text). Anti-text in mask would be neat, too. It is even less 
> space hungry. Letters look fine if the exposed copper surface is HAL or 
> even better, gold plated.
> 
> Real anti-objects in mask would be useful with regular text in copper, 
> too. Currently, I expose the copper with a zero width line converted to 
> footprint and equipped with massive clearance. In addition, I tell the 
> fab to just ignore the zero width lines. 
> 
> Yes, this is a hassle. But I really like to have the purpose of the 
> board stand out in large and friendly letters, even on prototypes 
> without silk print.

I've done it before too. (I first encountered the idea on a board one of
my students, made using Protel I think).


> > Is it mitigated by allowing holes in polygons?
> 
> Can a footprint contain such a hole?

No, the hole is a part of the definition of the polygon, not an object
in its own right.

I think you just gave me the most solid reason I've heard yet for
explicit anti-objects / anti-layers.

We probably need to define some rules as to which objects take
precedence  over others. One way might just for a "keepout" object to
auto-clear polygons, and perhaps just flag a DRC warning for other
objects the user places in the area.

We wouldn't want a component's keep-out erasing tracks leading to the
component, or the component's pads etc.. At first sight, I can't quite
envisage how those will be differentiated from a keep-out violation.

(Can someone who uses / has used keepouts on another package describe
for me how they work, or how you use them?)

Best wishes,


-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)
Tel: +44 (0)1223 748328 - (Shared lab phone, ask for me)



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