Unsoldering a Pentium 3?

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Tricky problem - I've got to unsolder a Pentium 3 from where it is soldered
(not socketed!). That's about 400 little delicate pins.

Is there a way other then carefully unsoldering every pin - and hoping for
the best?


Re: Unsoldering a Pentium 3?
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There are a few ways.  But first you want to ask yourself if you want to
possibly be able to use the device after its removal.  If the answer is
no things become a lot easier.

One destructive way (to the chip, not the board) to remove pins from a
surface mount component with leads is to use a sharp utility knife
(exacto and the like) and cut off each pin from the body of the chip.
This will create some stress on the pad and can knock pads off if they
aren't well connected but my experience is that this doesn't happen if
you're careful and since there is no heat at this point its easier on
the board overall.   Then use a soldering iron and remove the pins and
excess solder off the pads.  And voila you are done.  You can do a
PQFP208 in about 10 minutes this way--and I have.

Another option that works pretty well is to heat up the entire area
until the solder turns to liquid and then take the chip off all at once.
This can work with through-hole components as well as surface mount.
You have to be careful not to bump the neighbouring pins or the entire
assembly when the solder is liquid because they may move and make a big
mess that takes a lot of time to clean up.  Also, you want to make sure
that you don't increase the temperature too quickly at any one point or
have a large gradiant so you need to heat up the entire board slowly and
as uniformly as possible.  I replaced a chip in my satellite receiver
this way that had non-accessible leads.  Things got pretty hot but it
worked well in the end.  You can also use this method to solder the new
chip back on if you want.  I do this with a simple heat gun that is
intended for removing wall paper but I don't have a great control on the
heat transfer.  There are more professional tools available that wil do
a better job for more money.

Or you could buy the exact right desoldering tools with the exact
extraction head for the component you have and you'll have the chip off
in a matter of minutes (assuming it has leads).  But you'll be set back
4 or 5 digits in your bank account.  I'm not sure they even make those
for that type of package.

Those are some options.  I'm sure there are more but these are what I
would suggest.



Re: Unsoldering a Pentium 3?
Hey, James, thanks for the help. No, I don't need the Pentium III I'm
removing, so I don't mind if the desoldering is destructive to the P3. But
I'd really mind if it was destructive to the board.

One issue about the 'right desoldering tool". No, I don't want to be set
back $1K+ for that tool, but I'm wondering if there's a company that has
this tool that provides this service?


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Re: Unsoldering a Pentium 3?
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There definitely are companies that have the right equipment.  Where are
you located?  Any PCB Assembly shop worth its salt should have something
that could be used.  Any of the big boys (Celestica et al) won't be
bothered with anything less that 100000 units or more so don't waste
your time.  Try to find a small company.


Re: Unsoldering a Pentium 3?
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Try this: Use aluminium foil to make a cone (or square tube) just about the
size of P3, on the component side, think of a way to apply even pull force on
all sides (try using mag-wire), use your hair-dryer and blow into the hollow
of the aluminum tube. Be careful not to hurt yourself - it can be very hot!
It is best done with another person help to apply the pull force evenly and
gradually. Be careful not to heat up the area at one go - it will damage
the plate-throughs.  Be careful not to pull too hard too - all the plate
through will get removed too.  The biggest risk here is that you typically
have just one chance - too fast, you melt the plate through, too much
force, the plate-through comes out, too slow, nothing move, loose focus,
you hurt your hand.  Do this *at your own risk*!!!

I have tried this couple of times few years back, now, I think the risk
is not worth taking anymore - boards are very affordable now.  I am
sure you have reasons why you want the board apart from saving couple
of bucks.

One more thing, be prepared to resolder some SMT resistors and caps -
the smart thing to do is to color code them with inked color dots so
that you can figure out which goes where.

Juz recall another trick I used many years back with more fragile
packaging - a little more expensive, but it works; instead of
heating the solder side, heat the chip surface till you practically
cannot touch it, then, get lots of cold freeze, spray on it abundantly.
The packaging of some chips in yester-years will crack, and depend
on how it crack, you may have the openings to do the 'snip' job.
You can also find out how good is the Intel packaging these days!
Warning - this has high chance of failing, you have to get a hang
of different materials behavior and make on-the-spot judgement
on how to abuse it to break.

Have abundant of luck ... and don't, don't hurt yourself for goodness sake!


Re: Unsoldering a Pentium 3?

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I've also head about flodding the area with lower and lower melting
point solders.

Eventually one can easily remove the device.


Re: Unsoldering a Pentium 3?
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And all pads/traces as well....


Re: Unsoldering a Pentium 3?
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Hot air gun? Toaster oven?


Re: Unsoldering a Pentium 3?
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And last but not least, the rubbish bin ;)

Thanks, Frank.
(remove 'q' and 'invalid' when replying by email)

Re: Unsoldering a Pentium 3?
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Here is a Weller WQB2000 hot air repair station. Its a job of 3 Minutes with
guarantee for CPU and PCB. If you like to come for a visit in Stuttgart ...

regards from Germany

Re: Unsoldering a Pentium 3?

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I think Jurgen has the essence of the solution.
Get the right tool for the Job.
If it is a one-off, then get a company that has the right tool and
expertise to do the job. If you are going to do it often, then find
and purchase the appropriate tool.

   Anton Erasmus

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