Steve,
Had the same problem with some boards that had a White Solder Resist on them.  Mask would peel off in a tape test at our facility.  We suspected that it was either uncured or not cured enough or possibly solder resist that was near end or past it's shelf life that was applied in too thin a layer.  Or a combination of both. We had the fab shop take some samples and do a 300deg. F bake for an hour.  They also took some additional samples and applied a thicker coat of resist.  It turned out that with both re-works it solved the problem.  When we re-tested they passed the tape test, although some samples still showed very marginal peeling in isolated areas.  Conclusion was that lack of sufficient cure was the problem given that the  samples that peeled prior to cure came back good and that the samples that were additionally coated had to go through cure again as well.
Hope this helps.
Tom Burek


 -----Original Message-----
From: [log in to unmask] [SMTP:MIME :[log in to unmask]]
Sent: Friday, February 11, 2000 9:44 AM
To: [log in to unmask]
Subject: [TN] Solder mask failing tape test..

 << File: ENVELOPE.TXT >>
 --------------------------------------------------------------------------  --
Mornin' all!!

This morning I got a email from one of our buyers telling me that one of
the
boards at one of our fab shops is being held-up because it doesn't pass
their
solder mask tape test. My buyer said that they told him that the mask is
only
coming off the via's, and it was because of uncured mask. The mask is a
LPI
and the via's aren't meant to be tented. Also the board doesn't go through
wave solder as the only through-hole is hand soldered because it goes up
through the board from the bottomside.

My buyer is asking me if we should accept the boards. I have a few
concerns.
One thing is that if there is uncured mask at the via's, what guarantees
are
there that there isn't more at other places on the board? Shouldn't
uncured
mask be a simple thing to fix by either baking the PCB (if it's a thermal
cure), or exposing it to more UV (if it's a UV cure)?

Further still, does uncured mask come off in a tape test? Or is mask
coming
off from a tape test more an indication of an adhesion problem from
contamination?

Thanks in advance for all replies,

 -Steve Gregory-

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with
following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################