gEDA-user: Solder Mask Clearances

[Tony Radice <tradice1@xxxxxxxxxxx>]

Luke - 
    You should talk to your contract manufacturer regarding what kind of
mask clearance they recommend. Two guidelines I can provide that I got
from my CM recently:

1) There should be at least a 100 mil clearance to the edge of the board
or cuts in the board to prevent the solder mask from peeling away once
the board edges are cut. Since the tool (PCB) is not set up to do this,
you can ask your fab house to manually edit the gerbers to do so.

2) On vias / Holes: To prevent chemical entrapment in the via barrel my
fab house recommended a "doughnet" type clearance on vias / plated
holes: ie: The solder mask at 8 mils above the drill size, but SMALLER
than the pad - so the solder mask DOES cover part of the via pad, but
leaves the hole of the barrel open.  I ended up manually editing my PCB
file for this.

I typically allow 10 mils clearance between features and solder mask,
but I again recommend talking to the fab house!

Good Luck!

Tony Radice



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