When using an OSP coating on a double sided circuit board (plated thru),
should the topside annular ring of a via (not the area over the hole) be
covered with soldermask?  I am told by the designer that this is done to
prevent the copper from corroding during the lifetime of the product (no
conformal coat used).  Is it acceptable to have the soldermask go to the
edge of the via hole(over the annular ring) and allow some of the mask to
coat the upper portion inside the via hole.  I am having ICT failures on
probes that probe the bottomside of the via hole. Soldermask either covers
the via hole or bleeds down into the via hole, and then particles of this
soldermask are trapped in the solder "fillet" on the bottom of the board
that fills the via after the wave soldering process, and the probe does not
make contact.

Thanks

Ed Holton
Hella Electronics

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