remove soldered chips

[The Dark force of dance]

Y-ellow Zsolt 'n' y'all.
	Having done way more than my fair share of this I can probably be of some
assistance.

If you are looking at salvaging a single chip, De-solder the pins using a
solder-sucker as you have described. Get a vary fine set of needle nosed
pliers and waggle the protruding ends of each pin till it comes free. The
chip should be pull-able then. Problems arise when they are soldered top
and bottom on a double sided board. Then you have to make a decision. Are
you going to save the chip or the board? You can, and often do, pull the
plate-throughs right out of the board. If the chip is a CMOS chip or would
otherwise be susceptible to static damage, get a suitably size, all-metal
bull-dog-clip and clip it over the chip's pins. This will short them out
and you can work on it safely. However, it should be noted that this also
works as a suitable heatsink.

The operation to replace a chip and save the board is quite different. You
have to clip all the pins from the IC. (ruining the IC of course) then heat
up and remove the pins one by one. Finally you get the solder-sucker and
suck the excess solder from the holes. The idea is not to stress the PCB
too much otherwise you can destroy tracks. But if you do, have some kynar
wire (Wire wrap wire) on hand with which to repair them.

Finally. If harvesting chips from old boards is your thing, and you don't
care about the board it self then the following works with around about a
90% yield. Get yourself a cheap hot air gun. As used for stripping paint.
Like a hair drier but pushes out hot air at over 400 degrees. I fashioned
myself a concentrating nozzle out of an old soup can and some pop-rivets
but sometimes they come with a concentrating nozzle of their own. You'll
also need a suitable IC-pulling tool. ICs are usually rated at about 10
seconds @ 300 degrees per pin.

With that in mind you have about 5 -7 seconds to heat the solder side of
the board to melting point and pop the IC. Because all the pins are heated
at the same time the IC will generally just slip out of the board. Some are
harder than others but no matter how hard or easy you _WILL_ stuff the board.

Do this in a well ventilated area. I have been known to set the board on
fire at times. Lotza fun! The beauty of harvesting in this way is that it
doesn't matter if the IC is soldered top-side. Once the solder melts you
just extract the IC. I have successfully harvested CMOS and even 64 pin
devices this way. When I first experimented with this technique I was
getting about 70-75% success rate. After a while you get use to it and I
now get 90% and above. Ergo, you might wanna practice on a board that is of
little importance to you first.

Extracting IC sockets and other similar devices are a little more tricky.
The plastic surrounds on an IC socket tend to become a little liquid when
you heat them up. Often you leave behind some of the pins. Likewise with
dip switches. But you get use to this kind of behavior and you have to
accept that you're not going to get a very good yield of these devices.

Another note. I usually do this sitting in my back veranda on a cold
winter's day. Literally a rainy day project. The reason is that the chips
cool down much faster in the winter time. Less chance of heat stress.
Especially when there's an icy wind blowing. You won't get too cold holding
a 1600 watt heat gun. :)

Hope this helps.

Be absolutely Icebox.

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