At a former employer we had a similar problem where a few solderings looked rubbish after cleaning. Turned out that all bad looking solderings where connected to a cooler made of a material that made a galvanic element in the cleaning process.
Fortunately, this was discovered before coating so I don't know if that solderingsurface would have caused defluorescence.
// Fredrik
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: den 27 oktober 2010 14:55
To: [log in to unmask]
Subject: Re: [TN] Disappearing Fluorescence
I had asked the technicians whether the traces in question could be
carrying a lot of current, thereby possibly generating a lot of heat, but
he said they did not. Low current line, so presumably low heat. And yes,
they look normal under regular light.
Doug Pauls
Mike Sewell <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
10/27/2010 07:42 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Mike Sewell <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] Disappearing Fluorescence
I've broken down the tracer by repeated exposure to a UV curing oven
(Dymax UV cured coating) but never seen it on just a trace. So what is
special with just those traces? Do they look "normal" under white
light?
Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Wednesday, October 27, 2010 7:30 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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