Desoldering question

I started doing hobby electronics again fairly recently, and recycling/ scavenging is a big draw for me. As it happens, my company throws away
lots of useful stuff, and over the past year I've brought home lots of circuit boards with various useful parts on them.
I've got a solder sucker and solder wick/braid, but components with more than two or three leads continue to be a problem for me. I have a little soldering station with a soldering iron, but I've been thinking that I probably need some hot tweezers or a heat gun of some kind. Most of the stuff that I'm recovering from these boards are through- hole components ... I haven't graduated to SMT-at-home just yet.
I don't mind springing for the right tools, but I don't want to buy something only to find that it still isn't very effective.
I'd like to hear from the folks that do a significant amount of this kind of thing (desoldering), and which tools/methods they favor.
Thanks!
Mr. INTJ San Diego, CA
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On Thu, 28 Aug 2008 18:55:12 -0700, Mr. INTJ wrote:

It's been a while, but I remember an Ungar screw-in tip that hit all the pins of a 16-pin DIP at once. Usually though, a spring-loaded solder sucker would remove almost all of the solder from each pin, leaving such a small area of contact that it could be broken with a sharp probe. For cheap SSI parts, a heat gun is probably best, though I never had one.
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"Mr. INTJ" wrote:

Well there's no substitute for a de-solder tool (manual or vacuum). If you have a Weller TCP, I think there's an accesory for it. There's still a knack to it though.
Graham
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I have all the tools to do this, but since I hardly use it the Weller sucker it gets all messed up leaving it on. Its a major effort to reclean the tip. Regardless, the recommended method of removal is to cut all the pins first, and removing many components with intact leads is a chore. I can't live without solder wick, fresh, or freshly refluxed. Get a liquid flux pen and apply to pins regardless of tool.
greg
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Use the solder wick on multipin items just wick the bottom of the board and then wiggle the pins to be sure that they are loose. When you are using surface mount multipin items use the solder wick on top of the pins and then touch each one with the iron tip and lift the pin off the surface with a small tool. You must be careful not to over heat the pin... you know where it goes and the over heating of the connector wires from the pin to the chip element is a very bad thing.
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On Thu, 28 Aug 2008 21:03:49 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

While you are completely right, it is normally not very critical. When the board was assembled, the entire component was probably immersed in molten solder for a couple of seconds.
--
RoRo


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Robert Roland wrote:

Try desoldering it in a couple of seconds and see how many tracks lift, PTHs break etc etc.
Graham
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Wave solder is stamdard. boards are pre-heated and then go surfing... so to speak. But a percentage don't come through it alive... they must be re-animated. To borrow one from the Cthulster. Any way its best to be careful. Also with your primary tool... fingers.
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snipped-for-privacy@gmail.com wrote:

Yes. And the temperature and time of the solder wave or hot-air reflow was controlled to stay within the limits of the parts.
                John Nagle
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snipped-for-privacy@gmail.com wrote:

If the device is dead )or low cost) you simply cut every pin and them remove the debris pin by pin. The PCB is 10000 x more valuable than a dead bug.
Graham
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it's a lot of work for little gain. but it's a game I've played too.

those tools aren't really suited to scavenging, more to repair.

get a propane blow torch, a box, and some safety glasses
heat a section of the board until the solder is liquid an then bang it on the edge of the box, repeat until the solder/components come of.
the trick is to heat rapidly so the heat doesn't have time to damage the components.
I find with the the fibreglass boards with plate-thru holes you need to heat until the layers just start to separate. (you hear a popping sound)
the boards will be destroyed in this process but you're after the parts right?
probably best to do this outside, or in the garage: all sorts of evil smelling fumes come out of the overheated fibreglass resin, and solder droplets stick to synthetic carpet real well.
another way is to cut the board up with a hacksaw or side cutters and then extract the pins one at a time
Bye. Jasen
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On Thu, 28 Aug 2008 18:55:12 -0700 (PDT), "Mr. INTJ"

Hobby Lobby (the craft folks, not the radio control guys) has a hot air tool for embossing (less than $20) that will melt solder in its air blast. Be careful, I can see all kinds of danger with this thing! John Ferrell W8CCW
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"Mr. INTJ" wrote:

Useful to whom ? If you're just hoarding forget it. I generally won't ever use recycled semiconductors anyway. Too risky.
Graham
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I used a propane torch, till I found out the an electric paintstripper give a more controllable heat. Watch out for all the SMD resistors and transistors blown around ;-) I still have to remove heavy leaded component from multilayer boards with a biggish (60 Watt) soldering iron.
Wim
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