Homebrew PCBs

On Tue, 26 Jan 2010, Stefan Trethan wrote:
>> I'm told that taping the stencils face-to-face to create a pouch makes for
>> good registration.  Any opinions on this?

> The problem with this is the non-zero width of the PCB. Depending on
> how you hold things together the films can shift one side relative to
> the other. A better method is to stick the films to PCB cutoff strips,
> or an L-shape. Insert a piece of clear acrylic or glass while aligning
> the two sides instead of the PCB. This gives very exact results,
> probably the best you can get without alignment pegs.
>
> Vacuum holddown is highly recommended, it is easy to make by covering
> the film/artwork stack with a framed sheet of flexible clear plastic
> and applying vauum to that.

I see.  The L-shape sounds like a good idea.  My reasoning is that if you 
leave enough space beyond the edge of the board, that space will bow out 
slightly thus allowing the very edges to be fastened together.

-- 
David Griffith
dgriffi@...

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