Phil,
Do the photos show the top side of the capacitor or the bottom side
after it was removed? Do you know what cracked the capacitor? My first
reaction is that I think I'd be more concerned about the crack than the
dendrites.
Regards,
George
George M. Wenger (908)-546-4531 [log in to unmask]
Distinguished Member Technical Staff
Celiant Corporation, FMA Lab, 40 Technology Drive, NJ 07059
-----Original Message-----
From: phil bavaro [mailto:[log in to unmask]]
Sent: Monday, February 25, 2002 12:53 PM
To: [log in to unmask]
Subject: Re: [TN] Dendritic Growth...
OK, here is the background on this particular dendrite growth:
It is a field failure unit and upon closer inspection, this dendrite
follows a crack in the capacitor from one termination to the other. In
my
opinion, the crack was there first, and was filled with contaminated
moisture while the cap had battery voltage (5V) across it, causing the
near
perfect dendrite to form along the walls of the crevice.
This CCA was produced on our no clean assembly line, of which the
cleanliness is monitored on each lot of boards produced. We believe
that
the solder flux residues are not related to this defect. The soldering
residues do not migrate to this area of the capacitor.
The condensation moisture alone would not seem to be enough to have
generated this dendritic growth so we are investigating other possible
contamination that may have been present such as moisture dripping off
of a
dirty shelf above, and also the component cleanliness itself. If the
crack
was there from the beginning then the contamination could have been as
well.
We have seen shorts across this capacitor before but usually only as
random
faint carbon tracks that are nowhere as defined as this one was.
This one is so perfect, it almost looks like an organic plant like a
small
fern.
This is an ongoing investigation so all comments are welcome and I will
provide an update at some point in the future.
Phil
At 06:51 AM 2/25/02 -0700, [log in to unmask] wrote:
>Doug,
>Isn't that known as the Mountain "Dew"lution Test?
>Dewey
>
> > -----Original Message-----
> > From: [log in to unmask] [SMTP:[log in to unmask]]
> > Sent: Monday, February 25, 2002 6:31 AM
> > To: [log in to unmask]
> > Subject: Re: [TN] Dendritic Growth...
> >
> > Sunny asks:
> > I'd like to know which type of Ion Chromatography can measure the
local
> > dot ionic cleanliness. Anyone can tell me which company produce
this
> > equipment?
> >
> > Doug Pauls responds:
> >
> > No company that I know of builds ion chromatography equipment to do
spot
> > ionic checks. IC equipment merely analyzes extract solutions. If
you
> > want
> > to measure localized ion concentrations, you have to develop a
localized
> > extraction technique. This might involve immersion of a portion of
the
> > assembly in extract solution, or building some time of
non-contaminating
> > enclosure around the area to be extracted. Once you can localize
the
> > extraction, collect the solution an analyze it with the IC equipment
> >
> >
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