Unsoldering IC's

[Vincent]

I have a small 16(?) pin IC that I want to unsolder from a circuit board and replace it with another one. How can I do this? It's a double-sided board so it's hard to suck the solder out from each pin's socket. I am unable to warm each leg up quick enough to be able to pull it out.<p>Thanks!

[Chris Smith]

For difficult de-soldering jobs I use a air nozzle. You heat up one leg position at a time, and blast the solder away from the bottom or top, or both with a controlled air blast similar to what mechanics use for cleaning parts. <p>It has a two fold bonus in that it blows all the solder out and cools it down at the same time. <p>Wear safety glasses.

[Dave Dixon]

Vincent,
If the chip is bad, just use a good pair of wire cutters. Cut the leads off where they enter the IC. Once the IC is off of the board, desolder the leads one at a time. Hope this helps.
Dave

[bridgen]

Dave's suggesion is the best way if you haven't got any special tools.<p>If this is something you think you will do very often it is worthwhile looking for a special tip for your iron. For some irons you can get a tip which is basically a channel, or "U" section. The two parallel sides of the U are placed on the two rows of chip's pins to heat them up simultaneously.

[chapter30]

I've had good luck using solder wick on the bottom of the board. It seems to pull all of the solder out of the hole.

[Vincent]

hey...thanks. Great ideas. <p>I'll try to pick up a can of compressed air for now. I can cut the bad one, but I have an identical board I am using for parts, so I can't cut the IC off of it. <p>Any idea on where to find that tool, David?

[sofaspud]

On a related topic, I was reading an old Don Lancaster column on products using "Elegant Simplicity" design. He mentions some all-time finalists and among them is a Heathkit "integrated circuit extractor that can be approximated with a bent nail." Can anyone provide (or point me to) more details or perhaps a simple drawing?

[Dean Huster]

We often call those persons who use compressed air to blow solder from holes "blind fools". In this case, the foolish part comes right before the blind part. This is the most dangerous method there is for desoldering, especially with larger holes in older boards. I'd have gotten fired in a heartbeat for letting students try that stunt. PLEASE, if you're going to use this method, wear safety glasses, or better yet, a full face shield. Solder splatters to the face are not pleasant. A long-sleeve, cotton shirt would be a good idea, too. <p>A method not mentioned is to heat the pin from the component side while sucking from the opposite side. This is especially effective for multi-layer boards having ground planes. If you work both tools from the same side of the board, pins connected to ground planes will reharden before you can get the iron swapped with the solder sucker.<p>Dean

[sofaspud]

A technique that I've used successfully to remove DIPs is to use a small shirt pocket-type flat screwdriver (I use a 2mm Xcelite). Do this after you've removed the majority of the solder with wick or sucker.
Use the screwdriver blade as a wedge, pushing it under one side of the IC. Be gentle; you only want to put a very small amount of tension on the pins. Now apply your iron on the pins starting on the same end where the wedge is located, but on the solder side. The tension will release when the IC raises off the board. Continue pushing the screwdriver further under the IC and heating the pins. The IC will work it's way out.
The secret here is to be patient, gentle, and don't overheat the pins. It's probably easier than the explanation reads.

[Bernius1]

mpja.comhas an SMD rework station that seems nice. If you look at the tips listed under the unit, one may fit for DIP's.
Hmmm. 'good luck'? No 'cheers'? Nah..
Ahhh... Später !

[haklesup]

FLUX Flux Flux FLux<p>(No, I didn't just burn myself with a soldering iron)<p>Whatever method you use (especially copper braid), coat the rework area with paste or liquid flux first. The solder will flow better, resist sticking to the adjascent board areas and stick to your iron or braid better. <p>Desoldering without flux is like washing your hands without soap. You can do it, but not as well.

[Chris Smith]

Dean, my last line covered that.......!
*Only for hard to clean jobs*
Wear safety glasses. <p>Actually one of my favorites is a long plastic tube and a pen tip atttached to it. Your mouth power air supply usually works for all but the worst jobs. <p>My second favorite is to heat it up and slap the board on a soft object like a bunched up cloth, letting inertia clean out the hole.

[Enzo]

I am not a fan of blowing either, aside from the obvious safety issues, it blows solder all over. All you need is a tiny bead of it to get under something on the board and now you have a problem to solve over and above whatever the IC was doing.<p>I wear glasses on the bench, and I have on numerous occasions found myself looking at a layer of molten ssolder splashed on the lens where a moment before they were clear. When a wire is under some tension, you heat the solder adn it can fling the end free, tossing hot solder in the process. My glasses have saved my vision numerous times.<p>Safety is not just something the shop teacher yammers about. And safety is not just for you, it is for the stuff you work on as well.

[Dean Huster]

Chris:
"Actually one of my favorites is a long plastic tube and a pen tip atttached to it. Your mouth power air supply usually works for all but the worst jobs."<p>Chris, there ain't no way you're getting me to suck molten solder up a plastic tube!! Oh. You're talking positive pressure, not "vacuum", huh? In that case, the blowing would be all for the worst jobs. Then you'd suck on it for the worst job, right? Then you'd learn really quickly why it would be called the worst job.<p>Dean

[Chris Smith]

Dean, you hold your breath for a second, and give a tiny hard shot of air. <p>I use this method when the area in question is hard to access. <p>You cant suck on it, I think the max vacuum is only around two negative pounds, but the tiny focused air steam when you blow on it usually dislodges the solder, and gives you a clean shot at removal. <p>The slapping motion on small boards onto a rag actually has more force, [inertia] and its my number one process for troublesome jobs. <p>Safety glasses, should not be just glasses, but goggles. <p>Hot solder, ahh, you should try hot transmission oil on a lube job,.... a real test of when you should cry? <p> Couple of drops of solder on my arm doesn’t even make me flinch.