gEDA-dev: PCB paste layer and exposed paddles

[David Carr <dc@xxxxxxxxx>]

I have the distinct (dis)pleasure of making some PCBs with QFN/MLF packages
that have exposed copper paddles.  I think I'll need to use stencils to
properly apply paste for these packages.  It appears that PCB simply uses
SMT pads (slightly shrunk) as the apertures for the paste layer.  I think
this is a simple effective design for most packages --- except exposed
ground paddles.  These require that the paste be broken into smaller
"blocks" with say 75% coverage of the paddle.  (See Analog AN-772)

Has anyone on the list dealt with this issue in the past?  If not, I wonder
if there is any way to distinguish paddle pads from regular ones so that I
could modify the paste layer code to do the right thing.  I guess we could
do something like look for square pads with a size > Xmm on a side.  That
seems a big fragile though.

Hmmm,
-DC



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