Hi Steve,
		It looks to me that you are using no-clean flux though
you mentioned DI washes (water base flux).
While it seems to me more like a delamination at the screw nut area.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: Wednesday, 21 January 2009 3:59 AM
To: [log in to unmask]
Subject: Re: [TN] Strange Mask Appearance

Steve- I'm probably the culprit that put that report on TN long ago- and

again recently. Liquid solder masks often use fumed silica as
filler/thickener  
to keep it in place. This is often sold under the Cab-O-Sil tradename.  
Aggressive cleaning agents can dissolve off part of the under or un
cured solder  
mask polymer, exposing the while silica filler. When you heat the
undercured  
mask, it will soften and allow the filler to sink down into the polymer,
so the  
solder mask all looks green again. 
Re the curing from wave solder, this may not work if you are working
with a  
UV cured mask. That's why it is important to monitor the output of UV
lamps,  
which not all shops do, thinking that UV lamps behave the same as
incandescent 
 lamps- which they don't. 
Yes, the heat gun is a very inexpensive $0.05 test, quick, easy and
requires 
no instrumentation. 
 
(Steve- I have some photos of the differences between one, two and three

passes under UV lamps to show the difference if you'd like them. If so,
pls give  
me a mailing address.)  

Bill  Kenyon
Global Centre Consulting
3336 Birmingham Drive
Fort Collins, CO  80526
Tel: 970.207.9586   Cell:  970.980.6373

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