Hi Gary (et al),

Andy wrote:


Every integrated circuit data sheet specifies thermal tolerances for the chip. Most say something to the effect that the chip will withstand being heated to X °C for Y seconds, enough to survive reflow or wave soldering. Lately I've noticed some now add the caveat, "one time," implying that the chip won't survive a second soldering.

In point of fact, it's desoldering that chips have trouble surviving, simply because you have to heat the chip up more and for longer than you do when soldering. Especially with surface mount parts, where you have to melt the solder on multiple pins and pads at the same time, desoldering is a far more difficult skill than soldering.

And even if you do it well, it still becomes a numbers game. If I need one chip to complete a circuit board, I will try to scavenge one from an earlier board. If the odds are 1 in 10 that I might damage the chip, it is probable that I'll have my new board up and running in no time. But if I need 10 chips to complete the new board, now the odds are that if I try to take the chips from an old board it's a near certainty that one of the chips won't work. Then I get the added pleasure of wasting time troubleshooting the new board (even more than if I didn't have to question whether my parts were okay).

So if you just want to populate your parts stores, and you have the equipment to test each chip after you desolder it, so that when you use it again you can know it works, then yes. You can get lots of parts cheap (assuming your time isn't worth much).

Good luck,
Joe