gEDA-user: bending design rules for TSSOP20 -- need advice

[Dave N6NZ]

Thanks, very helpful.  That seems like the correct interpretation of 
their use of the word "swell".

-dave


DJ Delorie wrote:
> Below a certain pitch, mask becomes almost useless, because the solder
> will bride from pin to pin anyway.  The challenge boards are 0.50m and
> 0.40mm pitch and neither has mask between the pins.  What seems to
> work for me is to just glob on the solder, then go over it with a
> desolder braid where needed.  That removes the glob on top, but leaves
> the solder under the pin.  This is with a 20 mil needle tip, not the
> oft-recommended hoof tip.
> 
> PCB-Pool wants mask to be 0.15mm bigger, then they clarify that it's
> mask size minus pad size. That means the gap between copper and mask
> edge is 0.075mm (3mil).  They also specify a minimum 0f 0.15mm
> remaining between masks (6mil).  That means you need at least 0.3mm
> (12 mil) between pad copper to get a mask.  I know I interpreted these
> right because of two 0.65mm pitch parts on my other board, both with
> "exactly" the minimum mask, one had mask between pins and the other
> didn't (implying that one was a little off one way, and the other a
> little off the other way).
> 
> Interpreting your data the same way, they want the distance between
> mask edge and pad copper to be 4 mils, leaving 8 mils for mask.
> 
>