Hi Doug!
Are you sure you haven't already stated the answer - heat?  Your tech
says low current, but that would be normal operation - maybe those
particular traces ran hot when the coffee incident took place.  Not hot
enough to burn perhaps, but hotter than the surrounding area?  Why else
would it follow the trace?  

regards,
 - Graham C

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Wednesday, October 27, 2010 9:30 AM
To: [log in to unmask]
Subject: [TN] Disappearing Fluorescence

Good morning all,

I posted a picture to the IPC Technet gallery.

http://ipc-technet.groupsite.com/gallery/16251

This is taken from a failure analysis effort I am working on.  Its
amazing 
what happens to electronics when you spill coffee into them.

One of the assemblies I have been looking at has a very odd visual
effect 
that I have never seen before.  The conformal coating has a fluorescing 
dye to it that glows blue under black light, which is common.  Notice
how 
the fluoresence has disappeared from the areas over one set of traces.
I 
have seen fluorescence disappear before, but it usually heat releated
and 
over a large area, nothing highly localized like this.  My first thought

was that there had been a jumper wire installed in these locations, but 
that is not the case.

I showed this to my good friend Phil Kinner at Humiseal, who is no 
stranger to the wierd and wacky world of conformal coating oddities, and

he has not seen anything like this either.

Anyone else seen this?

Doug Pauls

Maybe this could be one of Inge's Friday quiz items............

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