Has anyone any tips on desoldering through-hole parts with high pin count? It seems near-impossible to get all the joints free with a solder sucker.

I have two cases in mind: one is 40-pin DIP, and the other is 68-pin PGA. In both cases, replace original parts with sockets.

I had a quick try with a small blowtorch - it's going to be easy to cause damage but I hear it can be a good way.

I also had some partial success using Field's metal: desoldering as best I could with a solder sucker, then resoldering with Field's metal, and then using hot water to free things up. I'm not sure about long-term effects there, as it won't be possible to get all the alloy out. (But for personal rather than industrial purposes, I'd take the risk)

I tried making a carefully-shaped loop of heavy-duty copper and driving it as a replacement bit on a handheld soldering gun - but it was heating unevenly and not reaching a high enough temperature.

Two other vague ideas: to build some sort of jig with a hotplate; and to make some kind of solder pool (probably on top of a hotplate...)

I've tried a few things over the years, like a heat gun, but since our very dense and complex boards have been very expensive (up to $46 bare) and the parts were cheap, it has been best to just sacrifice the part and cut all its pins then remove them from the board one by one and clear out the holes with the solder sucker after they're out. Trying to save the part presents too much risk to the board.

I don't think this will work for PGAs though since you can't even get to the pins.

Funnily enough, desoldering a 40-pin socket on a scrap board using the torch I managed to melt 5 of the pins. So melting all 68 might be an option! Not the preferred solution, of course.

And in melting the pins I surely did the board some damage.

Cheers
Ed

With a lot of patience, I've successfully used desoldering wick on 40-pin devices., combined with the occasional jiggling of a pin to break solder joints against plated-through holes as the pin cools.

Be careful though -- I've had lifted traces using this approach. This might not necessarily be a problem, as long as you don't otherwise damage the lifted trace.

ah, good point, I do have some wick - tried it in the distant past to no effect, but it's another tack.

Thanks to both of you!

I've done some desoldering back in the day when I was blowing out IC's on my C-64. I wound up socketing every single IC to make it easier for my dad's friend at his work to fix. What a nice guy, I'll never forget that.

Anyway, and forgive me if I am being simplistic here, you may have done this already...
I found that putting a fresh "dab" of solder on each pin and then using the solder sucker worked very well. Then, after I saw that most of the solder was sucked out of the holes, from the other side of the board, I would use a small flat tip screwdriver and push the pins toward the package, thereby freeing up the pin from the board. Seemed to work for most of the pins. The pins that were resistant I heated up with the soldering iron as I pried the IC off abit at a time.

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65Org16:https://github.com/ElEctric-EyE/verilog-6502

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Hakko 700, and preheating the board with a hot air gun evenly helps out

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"My biggest dream in life? Building black plywood Habitrails"

Thanks everyone.

> Hakko 700
That's a serious multi-hundred dollar station with a vacuum pump! Out of my range, unfortunately, but I bet it does the job.

> resolder before desoldering
I think I've heard of this one, also using lots of flux. Will try it.

> wiggle the pins before the remaining solder re-freezes
Certainly read of that before, and sounds worth a try if there is wiggle room.

My current case in point is the board from an Acorn Electron: they were an aggressive use of ULA technology - which had production trouble and scuppered the product's Christmas launch - and these days the ULA is quite often dead. But with some broken boards in hand, some socketing and exchanging parts might get us a working board. (The 40-pin is of course the 6502A CPU, which we'd like to try accelerating with our 65816 board.)

the hakko I used at SNK and I saved up and got one at home. 700 bucks or so, was very much weorth it.

Even a hand desoldering pump will work out better with preheating the main board as I mentioned.

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"My biggest dream in life? Building black plywood Habitrails"

I've found that it is easy to desolder DIP ICs by heating the pin on the component side of the PCB and using a solder sucker on the other side of the board. This allows the solder sucker to be placed flat against the board to form a good seal while still keeping the iron on the pin to keep the solder hot. I find that this usually completely clears the hole of solder and the chip can be removed with almost no effort.

_________________
Shift to the left,
Shift to the right,
Mask in, Mask Out,
BYTE! BYTE! BYTE!

I would think you might run into heating up your chip pins a tad more that way.

Ah, and for your sig:

LSR
ASL
AND #$00, AND #$FF
.DB .DB .DB!!!!

_________________
"My biggest dream in life? Building black plywood Habitrails"

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Nope. Either way, by the time all the solder has melted, the iron will have heated the pin up to the highest temperature it can reach.

Also, the fine gold wires connecting the pins to the die can't carry enougth thermal energy to the chip to damage it unless you take forever on each pin.

_________________
Shift to the left,
Shift to the right,
Mask in, Mask Out,
BYTE! BYTE! BYTE!

What about desoldering wick?
(Ah, that's been mentioned. Bugger.)