[sdiy] Desoldering techniques for chips that you want to keep?

[Rykhaard D.A.M.I.A.N.]

On 1/30/06, rude66 <rude66 at gmail.com> wrote:
>  the better way: use a small gas burner and do it outside.. i have a small
> thing, it's like a portable soldering gun running on gas, it's fairly easy
> to get it to run the flame over all the soldered pins and get the solder to
> flow on all pint, then flip board over and tap on something. 99% of the time
> the ic comes out.
>
>  r./

A couple of ways as well - first related to Rude's. :)

A blow torch waved over the chip area quickly, and then immediately
slapping the board against a hard surface at one of it's edges, will
pop the chips out.

For solder braid, if you're wishing to keep the board still:

- Keep your temperature at about 700F (600F for SMT)
- Use a thinner braid.  About 1/16th - 1/8'th of an inch wide
- Apply the very end of the braid, for ease in applying it right to the pin/pad
- Hold the tip of the iron to it (not the side of the tip) moving the
braid, left and right slightly, to encourage more solder inTO it
- Cut off the end of the braid containing solder as WELL as another
1/8th of an inch or so, as contaminant (heated flux from the braid?)
seems to make it worthless in picking up more solder
- Start again, after a couple of seconds, of letting the pad cool
- Go to the next pad, and repeat
- Once you've done all of the pads - don't worry if some of the pins
are still attached to the throughhole plating, place a prying tool
under 1 edge of the chip
- Apply a LITTLE bit of pressure to the plying tool; start heating the
pins that are still attached to the through hole plating, moving those
pins with the iron to the center of the solder hole
- Change your lifting tool to the other end of the chip and repeat the
above step
- Once you've done this, if there's still any solder inside of the
hole, cut off the end of the braid, and remove it, quickly and then
start lifting the chip again

This is assuming, it's a double sided, plated through holes board. 
I've done 14, 16, 20, 24 and 40 pins chips regularly at work, in these
regards.  I've only ever lost, 1 or 2 chips. :)

If you're doing 2 or 3 legged parts in this regard - give the pads
MORE solder, with the part side aimed down; whack the board against
the table.  Chances of the part falling out, are higher. :)  (This is
IF - the parts pins are NOT bent.  In such cases for ANYthing, trim
the bends off.  If they're left on - your chances of ripping the
plated through core from the board, are MUCH greater. :O :( )

--
Take care,
Warmth and Peace,
Ryk

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Jan. 2706 update