Stephen :
        If it is isolated to the vias ,by chance would these boards be
Immersion gold plated?
I have seen this phenomena in the past where the mask is thin at the knee
and the Ni/Au process undercuts the mask resulting in adhesion failures of
the via cap. Usually it only happens on one side, Since the air that is in
the via migrates to one side as the mask liquefies in the curing process, It
also will flow away from the knee slightly.
        As for un-cured mask, If it is  a thermal "curing" system, chances
of "Un-cured" mask in only the  vias is quite remote.

Russell Smith
 ----------

From: Stephen R. Gregory
To: [log in to unmask]
Subject: [TN] Solder mask failing tape test..
Date: Friday, February 11, 2000 9:12AM

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-

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