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'[EE][OT] Repair goes bang?'
2007\01\19@200235 by Micro Brix

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I just worked on a circuit board (the one I need the SRAM for) and had a
very unusual thing happen.

While soldering on the vias, and on a couple of the SRAM chips, with the
board entirely removed from the system, I had several instances of what
appeared to be explosions as I heated the joints.  These were NOT any kind
of bubbling, these were bright noisy POPs, which threw red and yellow
sparks.  The board has a couple of 100uF caps, and a bunch of 0.1uF, but had
not been powered in months, and in any case, I was only touching the one
point, no possibility of a short.

The lithium coin cell had leaked over this area, which had a number of lead
solder joints, and copper traces of course.
I am wondering if there's a possible chemical reaction there that leads to
an explosive?

Never saw anything like it before.

--
Feel the power of the dark side!  Atmel AVR

2007\01\19@201412 by M. Adam Davis

face picon face
Is your iron grounded?  Is it possible that they contain high enough
voltage that the iron may bring two conductors close enough to arc?
I'm noticing a lot of static electricity in southeast michigan due to
the cold weather - perhaps you are starting a spark which provides a
path for a capacitor to discharge.

I like the chemical reaction thought - lithium is a very reactive metal.

Test a few caps with a multimeter.

Very interesting - let us know what you find if you discover the cause.

-Adam

On 1/19/07, Micro Brix <spam_OUTmicrobrixTakeThisOuTspamgmail.com> wrote:
{Quote hidden}

> -

2007\01\19@201712 by peter green

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> The lithium coin cell had leaked over this area, which had a
> number of lead
> solder joints, and copper traces of course.
> I am wondering if there's a possible chemical reaction there that leads to
> an explosive?
iirc some of the stuff in lithium batteries as pretty explosive even without something to react with.


2007\01\19@202917 by Micro Brix

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On 1/19/07, M. Adam Davis <.....stienmanKILLspamspam@spam@gmail.com> wrote:
>
> Is your iron grounded?


It is, but the board was not connected to anything else, no current path.

Is it possible that they contain high enough
> voltage that the iron may bring two conductors close enough to arc?


Not even remotely.

I'm noticing a lot of static electricity in southeast michigan due to
> the cold weather - perhaps you are starting a spark which provides a
> path for a capacitor to discharge.


No. not static, or charged capacitors.  I've shorted a lot of caps, and I'd
say what I saw, in each instance, looked like 1500+uF at 12V or more, and
this board only has a 5V rail on it, and no caps bigger than 100uF.

2007\01\19@203228 by Micro Brix

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>
>
> iirc some of the stuff in lithium batteries as pretty explosive even
> without something to react with.


I know people say they "explode", but I've always held that to be a boiling
liquid "explosion" when the vent fails.
This was a definite "BANG", which threw sparks.  Happened in several places,
notably where a lot of black "crud" had built up, in the vias, and between
the pins near VCC on the SRAM.  Some of them were address lines to the SRAM,
definitely NOT where any cap would exist to store up energy.

2007\01\19@215549 by James Newton, Host

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> From: piclist-bouncesspamKILLspammit.edu
> [.....piclist-bouncesKILLspamspam.....mit.edu] On Behalf Of Micro Brix


> --
> Feel the power of the dark side!  Atmel AVR
> --

Just a quick note to point out that "Micro Brix" is David VanHorn.

gmail apparently changed Daves outgoing email setup without his knowledge.

...in case anyone cares.

---
James Newton: PICList webmaster/Admin
EraseMEjamesnewtonspam_OUTspamTakeThisOuTpiclist.com  1-619-652-0593 phone
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2007\01\19@223312 by Jinx

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> I am wondering if there's a possible chemical reaction there that leads
> to an explosive ?

Like a fulminate sort of thing ?

http://en.wikipedia.org/wiki/Fulminate

Leaky battery + metals might be the chemical cocktail needed

2007\01\19@233629 by Dave Lag

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James Newton, Host wrote:
>>--
>>Feel the power of the dark side!  Atmel AVR

> Just a quick note to point out that "Micro Brix" is David VanHorn.
>
> gmail apparently changed Daves outgoing email setup without his knowledge.
> ...in case anyone cares.

And I was worried the "dark side" thing was spreading....

2007\01\20@005312 by Cris Wilson

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face

> I just worked on a circuit board (the one I need the SRAM for) and had a
> very unusual thing happen.
>
> While soldering on the vias, and on a couple of the SRAM chips, with the
> board entirely removed from the system, I had several instances of what
> appeared to be explosions as I heated the joints.  These were NOT any kind
> of bubbling, these were bright noisy POPs, which threw red and yellow
> sparks.  The board has a couple of 100uF caps, and a bunch of 0.1uF, but
> had
> not been powered in months, and in any case, I was only touching the one
> point, no possibility of a short.
>
> The lithium coin cell had leaked over this area, which had a number of
> lead
> solder joints, and copper traces of course.
> I am wondering if there's a possible chemical reaction there that leads to
> an explosive?

Sounds like you might have ignited a little bit of lithium.
It melts and burns rather easily and quite violently. The low
temperature burn (around 400 degrees F) is crimson red, as it
burns and reacts with oxygen the flame gets hotter and turns
white. Kind of like a magnesium flare.

It's definitely something you don't want to ignite, you can't
even put it out with water because lithium reacts with
water - not as bad as sodium, but bad enough.

--
Cris Wilson
Information Resource Consultant
College of Architecture, Arts, and Humanities
Clemson University
crisspamspam_OUTclemson.edu
Report problems to: @spam@aah_computersKILLspamspamclemson.edu


2007\01\20@023947 by Jinx

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> It's definitely something you don't want to ignite, you can't
> even put it out with water because lithium reacts with
> water - not as bad as sodium, but bad enough.

If it was Li, would humidity hydrate it over a period and make
it safe ?

2007\01\20@064259 by Peter P.

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Micro Brix <microbrix <at> gmail.com> writes:

> The lithium coin cell had leaked over this area, which had a number of lead
> solder joints, and copper traces of course.
> I am wondering if there's a possible chemical reaction there that leads to
> an explosive?

This is common with boards that got lithium battery electrolyte leaked on them.
I do not know what the chemical is but it goes bang from heat. Wear safety lab
glasses when doing such jobs, and close all solvent bottles etc.

Peter P.



2007\01\20@064514 by Peter P.

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Micro Brix <microbrix <at> gmail.com> writes:

> I know people say they "explode", but I've always held that to be a boiling
> liquid "explosion" when the vent fails.

Lithium batteries vent burning lithium not 'liquid'.

Peter P.


2007\01\22@000635 by Cris Wilson

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face

>> It's definitely something you don't want to ignite, you can't
>> even put it out with water because lithium reacts with
>> water - not as bad as sodium, but bad enough.
>
> If it was Li, would humidity hydrate it over a period and make
> it safe ?

Pure Lithium will react with high humidity and spontaneously ignite.
So the pure stuff is usually stored in oil, and held down under the
oil by a weight of some kind  (because lithium will float)

Lithium doesn't stay pure very long, it reacts with just about
everything and oxidizes in a matter of minutes to normal air
exposure. Once it has reacted with air, nitrogen, oxygen, whatever
it is harmless.
BUT, if you heat it up (like from a soldering iron) it melts and
becomes highly reactive again. Since it is an alklai metal - it
definitely doesn't react well to the acidity of solder flux and
will ignite when in contact with it.

To remove the stuff that leaks out of Lithium batteries, I usually
do repeated alcohol washes and scrub out as much of it as I can
before soldering near it.
And even after the washes, if I have to solder near a Lithium spill
I wear glass safety glasses, welding gloves, and a long sleeve shirt.
The stuff feels like molten solder when it lands on you while it's
still burning. It's not likely to lit anything on fire, but you
will probably drop your soldering iron in your lap and get a worse
burn from that - in a place you don't really want to be burned.

So the final point is, remove as much of the lithium junk from
the board as possible before soldering, be ready for the popping
noise and sparks, and where long sleeves.
--
Cris Wilson
Information Resource Consultant
College of Architecture, Arts, and Humanities
Clemson University
KILLspamcrisKILLspamspamclemson.edu
Report problems to: RemoveMEaah_computersTakeThisOuTspamclemson.edu


2007\01\22@104926 by Martin Klingensmith

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Do you feel somber and indifferent after it lands on you?
--
Martin K

Cris Wilson wrote:
{Quote hidden}

2007\01\22@112225 by David VanHorn

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I just found the whole thing interesting.  After working with millions of
systems with these batteries, this is the first one I've seen where lithium
escaped from the cell.  I've only seen a couple cells rupture.  I suppose
this is because we were very careful with our design, not allowing any
measurable current back into the cells, and buying quality cells.

2007\01\22@123451 by Cris Wilson

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face
If it did that I probably would solder naked around it  ;-)

Seriously, though, the lithium used for depression is usually in the form
of lithium carbonate or lithium citrate - and you have to take it orally.
I don't think I'm going to try and catch a burning/molten piece of metal
on my tongue.

I'm not really sure what type of lithium salt you end up with after the
batteries leak onto the board. Next time I have to repair one, I'll try
to remember to scrap the goop off and have it analyzed.

At 10:48 AM 1/22/2007, you wrote:
{Quote hidden}

>

2007\01\22@123740 by Cris Wilson

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At 11:14 AM 1/22/2007, you wrote:
>I just found the whole thing interesting.  After working with millions of
>systems with these batteries, this is the first one I've seen where lithium
>escaped from the cell.  I've only seen a couple cells rupture.  I suppose
>this is because we were very careful with our design, not allowing any
>measurable current back into the cells, and buying quality cells.

The majority of the repairs I have had to do with leaking Li batteries were
because someone had spilt a drink or beaker of something into the equipment.


_____________________________________________________________
Cris Wilson
Information Resource Consultant
College of Architecture, Arts, and Humanities
Clemson University
spamBeGonecrisspamBeGonespamclemson.edu
To report problems email: TakeThisOuTaah_computersEraseMEspamspam_OUTclemson.edu




                               

2007\01\22@125210 by David VanHorn

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>
>
> The majority of the repairs I have had to do with leaking Li batteries
> were
> because someone had spilt a drink or beaker of something into the
> equipment.


Hmm.. We had tons of those, "guess the beverage" became a game in the repair
department.
But the vast majority of our battery failures were simply "dead".

I only remember one coming back with a ruptured battery, and it was reported
to have caused the device to partially disassemble, but they put it back
together before they shipped it to us.

2007\01\22@125439 by Bob Axtell

face picon face
David VanHorn wrote:
> I just found the whole thing interesting.  After working with millions of
> systems with these batteries, this is the first one I've seen where lithium
> escaped from the cell.  I've only seen a couple cells rupture.  I suppose
>  

> this is because we were very careful with our design, not allowing any
> measurable current back into the cells, and


> buying quality cells.
>  
That's the key.

--Bob

2007\01\22@155602 by Martin Klingensmith

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Just a little joke...
--
Martin K

Cris Wilson wrote:
{Quote hidden}

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