Re: gEDA-user: Clearing mask to mount shields

[Dan McMahill <dan@xxxxxxxxxxxx>]

Darrell Harmon wrote:
> What is a good way to expose a ground plane for mounting a shield?
> I have a board which needs to be very well shielded, and am planning
> on making a machined aluminum plate with compartments for each 
> section of the circuit. The board will screw to this instead of
> standoffs. What is a good way to clear the soldermask in strips so
> that the aluminum can be in contact with the copper?
>
> PCB won't let me convert a polygon to an element. It will not allow
> traces wider than 250 mils, so creating the pattern with traces is 
> not a good option. Is there any way to use one of the spare layers
> as a mask keepout layer? The only way I see right now to make it 
> work is to create several traces side by side in the larger areas.

Can you create a footprint with some pads that are the right 
width/length for the shield?  That way if you move the shield around on 
the board you'll keep all the pieces together.

Don't forget, its the largest dimension of a gap, not the area which 
matters the most.  So if it is a 2 layer board with ground on the 
bottom, components on top and a can attached to the top, you'll want 
lots of vias around the edge where the can sits.

-Dan