Hi Doug,
Is it possible there is a support made for this board that contacts
right along these lines? In other applications I have seen a hard
rubber gasket type of material used as a backstop/support for military
applications. Maybe this caused the marks.
Jerry Dengler
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Wednesday, October 27, 2010 8:54 AM
To: [log in to unmask]
Subject: Re: [TN] Disappearing Fluorescence
Something actually factual in Wikipedia. Who'd a thunk it.
Maybe the pilots are drinking ruthenium enhanced coffee.....
Doug Pauls
Bev Christian <[log in to unmask]>
10/27/2010 07:37 AM
To
TechNet E-Mail Forum <[log in to unmask]>, "[log in to unmask]"
<[log in to unmask]>
cc
Subject
RE: [TN] Disappearing Fluorescence
Doug,
It was a looong time ago, but I did take a fourth year course in
photochemistry. Fluorescence can be "quenched" in a variety of ways.
For
instance quinine fluorescence can be quenched by chloride. See the
Wikipedia link.
http://en.wikipedia.org/wiki/Quenching_(fluorescence)
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Wednesday, October 27, 2010 8:30 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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