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Old 31st March 2004, 08:03 PM   #1
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Default Any advice on replacing SMD Opamps

Should I try this, or is it too hard.

I have steady hands, and a very fine tipped soldering iron, however, not any advanced desoldering tools, just the basics.

-Paul Hilgeman
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Old 1st April 2004, 12:38 AM   #2
BrianL is offline BrianL  United States
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Assuming that you are talking about op-amps in SOIC package...

I'd suggest getting a VERY small diagonal cutters, snip the
leads off then remove the "foot" that's still attached to the
board with the soldering iron and soldering wick.

Of course, this doesn't work well if you want to keep the
part intact.
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Old 1st April 2004, 01:10 AM   #3
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Default Re: Any advice on replacing SMD Opamps

Quote:
Originally posted by PHilgeman
Should I try this, or is it too hard.

I have steady hands, and a very fine tipped soldering iron, however, not any advanced desoldering tools, just the basics.

-Paul Hilgeman

Speaking from my own experience with SMD, I would say that if reasonable care is taken it can be done. I have about 12 years experience with SMD assembly/rework/protototyping. I would proceed as follows. I am assuming a 8 or 14 pin SOIC package.

1) Wick off as much excess solder as possible. This will make it easier to remove the part.

2) Once the excess solder is removed, use your soldering iron and a new fine tip X-Acto blade to carefully lift each pin from it's pad. Apply heat to the pad, and lift the pin. Work your way around the IC until it is free.

3) Clean the excess solder off the pads and clean with denatured alcohol.

I have used this method many times when I don't want or don't have time to seek out a hot-air desoldering station, and I have never damaged a pad. YMMV.

I also recommend that you use as low of a heat as possible. If you have one, a magnifying lamp is quite useful for this. I have a stereo microscope on my bench at work, and I can say the more light and magnification you have, the better.

Also, your finest tip may not be the best shoice for desoldering. It's difficult to get heat into a pad with a very fine point tip, since they have a very low thermal mass. A 1/16" or 3/32" tip may make things simpler.

Cheers,

bg


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Old 1st April 2004, 01:12 AM   #4
jwb is offline jwb  United States
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Pre-heat some copper wick to 275C. Slather a lot of flux on the pads of the part. Put a 1/4" tip on your soldering iron. Place the wick and the iron on all four pads of one side of the package, and pull all the solder into the wick. You might need to move the wick, depending on how much solder is there. Then pry up gently on the part to separate the pads and the leads. Let the part cool, then do the same thing on the other side.

Try to keep each side to less than 5 seconds, unless you plan to throw out the part.
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Old 1st April 2004, 12:18 PM   #5
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If I am removing a SMD IC from a board, I usually do so because it is stuffed. Therefore I cut the legs off the IC close to its body using a sharp hobby knife. The pins are then easy to remove with a quick wipe of the iron without damaging any pads. This works very well for those 100pin plus ICs.

When installing new part, apply some liguid flux to the IC pins, position it, and use the soldering iron to sweat the pins to the pads. Don't apply additional solder as you will end up with shorted pins.

Cheers
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Old 1st April 2004, 01:34 PM   #6
Stocker is offline Stocker  United States
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If you want to reuse the part, you can use guitar or piano wire to pull up the pins from behind. Also, if you can get at an edge of the package, sometimes you can use a razor blade to GENTLY pry the thing up while heating a whole side's leads.
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