[Test-Equipment] Unsoldering

[Dave Brown]

Get a real hot air gun. (NOT a hair drier)
 Clamp the pcb in a bench vise or similar setup so you're looking at 
the pcb edge with it held approx vertical - components on the left (if 
you're right handed).Otherwise vice versa.

BEFORE you turn on the heat gun, have a suitable component extraction 
tool ready in your left hand (pliers, artery clamps, mini slip-jaws, 
or whatever-depends on the component size and shape) and check you can 
get a firm grip on the component you want to extract.

 Turn on the heat gun and wait for it to warm up-maybe 20-30 seconds 
or so.
 Apply heat to the copper side of the pcb in the general area of the 
component you want to remove.
 Hold the heat gun about 3-5 cm away from the pcb surface and at an 
angle such that the air flow is directed across the surface and not 
straight at it. Helps to have the hot air flow away from you and hands 
etc as well!

Most essential to keep the hot air supply moving around. Dont leave it 
in one place more than a few seconds.
After about 15 seconds or so, apply gentle extraction presure to the 
component. Time here varies depending on the heat gun, number of leads 
to be desoldered etc. All the obvious things!

Keep the heat source moving slowly and up the extraction pressure-it 
will quite suddenly release and come cleanly off the pcb. For large 
multi lead components, you may have to keep the heat on while gently 
'wiggling' the component to free up all leads. The solder will all be 
fluid at this point and it's only bent leads etc holding the component 
in place.

Once it releases, immediately take the heat gun off the pcb and turn 
it off.
Deal to putting the component down safely. It's leads are still hot!
Job done. (and the pcb will still be in good order)

73
 Dave, ZL3FJ

----- Original Message ----- 
From: "Rasputin Novgorod" <priapulus at yahoo.com>
To: <test-equipment at mailman.qth.net>
Sent: Friday, November 04, 2005 4:22 PM
Subject: [Test-Equipment] Unsoldering


> Sorry, here goes another off-topic message.
>
> I'm an electronic hobbyist with some nice, if old,
> HP test gear. A electronics service tech friend gives
> me dead and abandoned old electronics, which I like
> to disassemble for the parts. I only go after the interesting,
> expensive or rare parts; most new electronics parts
> are so cheap now that they aren't worth the effort.
>
> This works fine for single-sided pc boards, but I
> find it impossible to remove parts from double-sided
> plated thru holes w/o distroying everything. I've tried
> solder suckers, braid, fancy vacuum pump irons, etc,
> but it is very difficult to get those plated-thru holes
> clean.
>
> I've found it helps to use a big iron, 80 watts, to dump a lot
> of heat quickly and pop out the part. Smaller irons seem
> to just burnup the board w/o melting the solder. I can get out
> resistors and caps, but IC's are impossible. I've rescued
> some IC's (expensive ones that are worth the effort) by
> cutting the board with tin snips close to the pins
> and removing pins one by one.
>
> So, any suggestions for salvaging parts from double sided PCs?
>
> Sincerely
> Blair
>
>
>
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