[Test-Equipment] Re: Unsoldering

[John Miles]

One of my favorite tricks for removing DIPs from HP and Tek PC boards is to
melt the solder at one pin at a time from the bottom side of the board, and,
while the iron is still in contact with the pin, hit the via on the
*component* side with a short blast of compressed air from a can.  Hold the
nozzle right on the IC pin where it passed through the board.

When you're done -- and it doesn't take long, with practice -- the IC will
often just fall out of the board.  Board and IC are in pristine condition
with essentially no likelihood of heat damage.

The two drawbacks are: (1) canned air is EXPENSIVE; and (2) whatever was on
the other side of the board is now covered in aerosolized solder droplets.
But when you want to remove an irreplaceable EPROM or something like that,
it's an obvious technique to try.

Sometimes it's easier to hold both the iron and the air nozzle against the
IC pin on the component side of the board, with the board resting on the
workbench.  That works, too, but you have to watch for solder backsplash on
the other side of the board.

-- john, KE5FX

> -----Original Message-----
> From: test-equipment-bounces at mailman.qth.net
> [mailto:test-equipment-bounces at mailman.qth.net]On Behalf Of David
> DiGiacomo
> Sent: Thursday, November 03, 2005 9:30 PM
> To: test-equipment at mailman.qth.net
> Subject: [Test-Equipment] Re: Unsoldering
>
>
> The OP wants to salvage parts, and presumably doesn't care what happens to
> the circuit boards.  I have found that a propane torch works well for this
> on through-hole boards.  It should be used outdoors, since the circuit
> board tends to burn, giving off noxious fumes.
>
> I have also tried an electric heat gun, which reduced the fumes, but
> otherwise wasn't as good.
>
> Other people have reported good results with solder pots, lab hot plates,
> and toaster ovens.
>
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