From: Ethan Dicks (erd_at_infinet.com)
Date: 2003-07-08 22:38:41
> If you know for sure that a chip is dead/defective and needs to be
> replaced, just cut the body off and then remove each pin separately.
Good advice. Typically, I'll use dikes (diagonal cutters) held
up-and-down with respect to the board, and clip the pin as close
to the IC body as possible, leaving nearly all the pin on the board.
You need *good* cutters to do this - Xcelite is a good brand.
I will then typically hold the iron up against the shoulder of the
pin, not even touching the board. When the pin warms up enough to
melt the solder, lift gently with the iron and it will slip out of
the hole.
Once the pin is out of the hole, it's easier to clean the solder
out with a solder sucker. Don't use solder wick - if you heat the
hole enough to wick the solder out of it, you've probably already
cooked the board enough to lift traces and pads.
> In case the pin hole won't open, don't "cook" it with the soldering
> iron over and over -- instead, get a gauge needle of appropriate
> size, heat the pin hole and put the needle through (from the
> component side). The solder won't stick to medical steel.
I haven't tried that, but it sound interesting.
Mostly, with two and even four-layer boards, data pins are no problem.
It's the power and ground pins on four-layer and thicker boards that
are ever stubborn. One trick that works (with practice) is to
mount the board vertically (best done in a vise meant to hold circuit
boards, not a vise for lumber), put the heat in from one side, and
suck the solder out from the other.
> And in case you want to save the chip for further use you still can
> cut off the pins: leave them a bit longer and solder the "torso"
> onto a precision socket.
I haven't tried that, but it might be easier with side-cutters (rather
than diagonal cutters).
-ethan
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