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April 2000

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Subject:
From:
Deborah Schepis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 4 Apr 2000 14:46:41 -0400
Content-Type:
text/plain
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text/plain (32 lines)
We are getting a lot of rejects back to our soldermask operation for touch
up of solder dams that have handling damage.  Most of these are between SMT
pads for passive components and the vias attached to those pads.  Since
some designs have NO solder dam on this sort of feature, the question has
come up as to what the minimum amount of soldermask is that will keep the
solder from running down the via during reflow.  It would save us a lot of
rework if we did not have to touch up all of these little dams.  Our
requirement on the dam on a BGA "dogbone" (separating the pad from via) is
3 mils, but we don't seem to have an equivalent spec on non-BGA features.

I would appreciate any input!

Deborah Schepis
OEM Printed Circuit Applications
Dept T46G / Bldg 022-2 / Office J004
Tie line 855-5558 / External phone (607) 755-5558 / Fax 857-1558
E-mail schepisd @ us.ibm.com

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