I agree Bev. We used to make spectrofluorometers. Oxygen also will quench fluorescence. As will Cu2+ and amines and a lot of organic chemicals. A good reference is Joseph R. Lakowicz's book "Principles of Fluorescence Spectroscopy".
Could the current, however small, with the spilled coffee, somehow created an ionized copper trail?
Having just returned from Costa Rica where I went on a coffee plantation tour, I'm chock full of caffene and the knowledge that coffee is an incredibly complex organic stew. Perhaps the caffene is the quencher?
And what does this tell us about the conformal coating's qualities that it can be penetated by coffee?
Bob Landman
H&L Instruments, LLC
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Wednesday, October 27, 2010 8:38 AM
To: [log in to unmask]
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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