Steve,
If your vendor is using UV solder mask, someone most likely is forgot to
cure one of the board... or cure improperly....UV activator is
cation...The un-cured mask is rather corrosive and absorb moisture
readily...
                                          jk

-----Original Message-----
From: Guenter Grossmann [mailto:[log in to unmask]]
Sent: May 22, 2001 4:19 AM
To: [log in to unmask]
Subject: [TN] Antw: [TN] Assembly "ate-up" after temp cycling...


Steve

I have never seen something like that. Looking at your pictures I think
there is more than just a soldermask problem:
The copper leads looks like etched as well as the solder joint.
Something that's intriguing me is the fact that only some of the joints
and  leads are damaged. You see this very good on the picture where
several joints are seen: The first and the third joint from the left
hand side are like etched. The other joints are intact. Also the copper
below the soldermask looks liked etched copper. The only acid that I
know that etches Tin as well as Copper is Nitric Acid ( HNO3 ). Don't
ask me how this could happen to your board. Did you ever do any surface
analysis?

Have fun

Guenter



Guenter Grossmann

Swiss Federal Institute for Materials Testing and Research EMPA
Centre for Reliability
8600 Duebendorf
Switzerland

Phone: xx41 1 823 4279
Fax :      xx41 1823 4054
mail:     [log in to unmask]

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