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'[OT] Sharing my BGA pain'
2010\12\16@161208 by Nathan Nottingham

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I can't offer as much as others in contributing to the list, but hopefully I can brighten someone's day with my (self-inflicted) misery...

My day has gone something like this:

1.) Removed a ~1000 ball (0.6mm) BGA GPU
2.) Cleaned old solder off board and chip
3.) Used a stencil to replace lead-free solder with leaded solder
4.) Aligned BGA back into place and started to heat gun it
6.) Decided it could use more flux so reached for the nearest syringe
7.) Injected a bunch of Chipquik SMD 291AX solder paste between the chip and the board

>From now on, I'm storing the solder paste very far from my flux.  :)

- Nat

2010\12\16@190853 by Philip Pemberton

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On Thu, 2010-12-16 at 14:12 -0700, Nathan Nottingham wrote:
> 6.) Decided it could use more flux so reached for the nearest syringe
> 7.) Injected a bunch of Chipquik SMD 291AX solder paste between the chip and the board

OWWWWWW! I feel your pain, man! That's HARSH.

Dare I ask if you were operating with a blood caffeine level somewhat
below optimum? :)

> >From now on, I'm storing the solder paste very far from my flux.  :)

My solution:
 Solder paste -- goes in a little mini-fridge (y'know, those tiny
little thermoelectric things that'll take two or three beer cans at a
push). If it's not in use, it's in there. When it's done with, it goes
STRAIGHT BACK.
 Flux -- lying around in a "convenient location" on the workbench.
Usually on top of the hot-air station or next to the soldering iron.

-- Phil.
spam_OUTpiclistTakeThisOuTspamphilpem.me.uk
http://www.philpem.me.uk/

2010\12\16@191355 by Oli Glaser

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On 16/12/2010 21:12, Nathan Nottingham wrote:
> I can't offer as much as others in contributing to the list, but hopefully I can brighten someone's day with my (self-inflicted) misery...
>
> My day has gone something like this:
>
> 1.) Removed a ~1000 ball (0.6mm) BGA GPU
> 2.) Cleaned old solder off board and chip
> 3.) Used a stencil to replace lead-free solder with leaded solder
> 4.) Aligned BGA back into place and started to heat gun it
> 6.) Decided it could use more flux so reached for the nearest syringe
> 7.) Injected a bunch of Chipquik SMD 291AX solder paste between the chip and the board
>
> > From now on, I'm storing the solder paste very far from my flux.  :)
>
> - Nate

Ouch! I understand how that could be a tad depressing.. :-)
It's so easy to make silly mistakes when reworking or populating boards though, especially if you're a bit tired - I managed to put a SMD tantalum the wrong way round the other day, fired the board up and couldn't work out why nothing was working, even got the hot air gun and removed a PIC and a few other components, before working out what it was. Sorted it out, then did exactly the same thing again later on with another one on the same board.. :-)
All good fun..

2010\12\16@193406 by peter green

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Oli Glaser wrote:
{Quote hidden}

>   Hmm, my experiance when screwing up with tantalums (e.g. putting them in backwards or overheating them during installation) is that you know about it from the bang and in some cases, fireworks display and then the massive stink left afterwards

2010\12\16@221546 by Oli Glaser

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On 17/12/2010 00:34, peter green wrote:
{Quote hidden}

Yes, had that before.. :-)
When prototyping/populating boards I often use my bench supply initially with current limit turned on, so in the event of this kind of thing less or no damage is done (I usually set it for about twice the expected consumption so I can tell if something is wrong) Of course you have to allow for initial current surges and the fact some things (e.g. switchers) may not start properly with too much limiting, it's just a very basic initial precaution.
The problem with that here was that the cap didn't quite fail completely (no fireworks or short) which made it a bit difficult to pin down (no bang with the second one either - no current limit this time but on a low current LDO) Mind you, it shouldn't have been really, but that was kind of my point, in that when tired or not concentrating you can easily make silly mistakes, or spend ages solving a simple problem.. :-)

In my experience, 90% of errors like these happen when I'm tired, so usually at the first sign of them I call it a day, or at least have a break (neither of which I did above, which quite probably led to the further foolishness... :-)  )
 I'm a fan of "sleeping on a problem", letting the subconscious go to work on it - amazing how very often something that baffles you last thing is solved first thing the next day.

2010\12\17@045151 by alan.b.pearce

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> Ouch! I understand how that could be a tad depressing.. :-)

I think I would promptly retire that PCB... it rather reminds me of one that the factory manager had where I worked, from a car radio that fell into the flow solder bath - came out fully encapsulated. I don't know how they got it out, presumably they emptied the bath periodically.

> It's so easy to make silly mistakes when reworking or populating boards
> though, especially if you're a bit tired - I managed to put a SMD
> tantalum the wrong way round the other day, fired the board up and
> couldn't work out why nothing was working, even got the hot air gun and
> removed a PIC and a few other components, before working out what it
> was. Sorted it out, then did exactly the same thing again later on with
> another one on the same board.. :-)
> All good fun..

Or not as the case may be. A colleague was very lucky not lose an eye due to a reverse tantalum. We had a printer arrive from our supplier, but it wouldn't work. Said colleague pulled the back off and was eyeballing the PCB with it powered up, leaning over the bench so he could look inside the chassis containing the PCB. A few seconds later there was this bang and the body of a teardrop tantalum went past his ear. The unit had worked long enough to get past factory test, but the resultant rest period during shipping had allowed the tantalum to go real bad after its initial mistreatment.
-- Scanned by iCritical.

2010\12\17@062637 by Mike Harrison

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On Fri, 17 Dec 2010 09:51:39 +0000, you wrote:

>> Ouch! I understand how that could be a tad depressing.. :-)
>
>I think I would promptly retire that PCB... it rather reminds me of one that the factory manager had where I worked, from a car radio that fell into the flow solder bath - came out fully encapsulated. I don't know how they got it out, presumably they emptied the bath periodically.

Pretty much anything will float on solder...

2010\12\17@081019 by RussellMc

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> >I think I would promptly retire that PCB... it rather reminds me of one that the factory manager had where I worked, from a car radio that fell into the flow solder bath - came out fully encapsulated. I don't know how they got it out, presumably they emptied the bath periodically.
>
> Pretty much anything will float on solder...

A good idea  would be to NOT drop in anything that wouldn't float that
had a core that "volatilised" at temperatures below solder melting
point.

I was shown around an aluminum manufacturing plant by a friend. Not a
smelter - they took ingots from a smelter and
cast/rolled/milled/melted ... them into other product.

They had a largish induction furnace - 50 Hz mains was used to induce
umpteen kiloWatts into a load of Al to be smelted. They recycled
material using it. He said the trick was to always very very very
carefully remove rubbish from incoming Al before melting. A bottle of
water or softdrink could be lethal - carried into midst of scrap and
buried and then Al is induction melted around it. Steam bomb :-(.
Apparently people have died that way. A big enough solder bath should
make a 'good' substitute for that.


Russell

2010\12\17@130625 by Vitaliy

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RussellMc wrote:
{Quote hidden}

My first experience with tinning pins resulted in a mini-explosion with burning material sprayed everywhere. Put lots of flux on the pins (14 total). Rapidly dip the pins in molten solder. Sh-plat!

Vitaliy

2010\12\18@141302 by Sean Breheny

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One of my co-workers experimented with Aluminum casting in his
basement while at university. I don't remember what his heat source
was (perhaps forced air plus propane? forced air over coal?) but he
once made the mistake of dumping molten aluminum into water. The water
instantly turned to steam and shot the still-molten aluminum past his
head and into the ceiling!

On Fri, Dec 17, 2010 at 8:09 AM, RussellMc <.....apptechnzKILLspamspam@spam@gmail.com> wrote:
{Quote hidden}

>

2010\12\18@210202 by YES NOPE9

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I was repairing a power supply where someone had reversed a very large electrolytic capacitor.  The cap had two terminals with bolts ( plus and minus ).  The cap bolts had been used to secure the cap to a PCB.  This also allowed the PCB to restrain the pressure release plug on the cap.  I was peering at the supply.... determining what I would probe with the DMM.  I sat back and the capacitor exploded and sent a really cool looking load upward which hit the ceiling.  The capacitor contents "unwound" as they shot upward.  My face had been in the path seconds before.

Gus in Denve

2010\12\22@164310 by Spehro Pefhany

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At 04:12 PM 16/12/2010, you wrote:

>I can't offer as much as others in contributing to the list, but
>hopefully I can brighten someone's day with my (self-inflicted) misery...
>
>My day has gone something like this:
>
>1.) Removed a ~1000 ball (0.6mm) BGA GPU
>2.) Cleaned old solder off board and chip
>3.) Used a stencil to replace lead-free solder with leaded solder
>4.) Aligned BGA back into place and started to heat gun it
>6.) Decided it could use more flux so reached for the nearest syringe
>7.) Injected a bunch of Chipquik SMD 291AX solder paste between the
>chip and the board
>
> >From now on, I'm storing the solder paste very far from my flux.  :)
>
>- Nate

From another forum, far, far away..

[..]

A similar incident happened in my family. They quit storing the Crazy
Glue and the eye medicine next to each other.  The doctors said the
mistake was sort of common.  Let that be a warning for ya...

Bill

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspamKILLspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

2010\12\22@234308 by RussellMc

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> A similar incident happened in my family. They quit storing the Crazy
> Glue and the eye medicine next to each other.  The doctors said the
> mistake was sort of common.  Let that be a warning for ya...

Right up there with the looking eagerly upwards in the darkened
workshop while bottle of conc hydrochloric acid with wholly eaten away
cork (what's that?) loops off shelf and provides a faceful of its
contents. Pain. Most immensely strong lemon taste ever. Runs for
garden tap. No permanent damage. If it had been H2SO4 ... :-.(.


     Russell

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