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De-Soldering help: solder stuck in through-hole.

1,878 733 June 11, 2009 at 08:01 PM
I'm trying to replace some bad caps. The capacitors are through hole components on the PCB, not surface mount. I have a 40w desoldering gun 45w desoldering iron with the bulb from Radio Shack. It works very well to remove the caps except when the following occasionally happens.
If I'm desoldering a component, especially lead free, it is very hard to suck the solder up. I have a "trick" where if I add solder (leaded), this mixes with the lead free and makes it easier to suck up the solder. Sometimes I cannot get all the solder after multiple passes. Occasionally I end up with an almost clean pad but a tiny little bit of solder in the hole which proves almost impossible to remove. I've tried using my soldering gun to heat up a slim piece of metal I can fit in the hole, but this doesn't work; the solder doesn't melt.
Sometimes I can add a lot more solder to the clean pad, some goes in the hole and then the bulb can suck the hole clean. But occasionally not. What to do?

Thanks guys....


EDIT: Solved. This thread has many good suggestions. What worked for me is described in post #21.
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#2
That is a touch question to answer. Must be a small hole because I have a solder that doesn't have any bells or whistle. However...it does have a long sharp end that can be stuck in the hole. Perhaps...you just need a simple solder iron like the old days?

Oh heck, I don't know anything. I often just flip the work upside down to get the solder to melt and let gravity take hold.
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#3
I have a 15w pencil but it barely moves lead free. The holes are all really tiny. I was thinking about a toothpick to wedge in there when the solder is hot. Other than that I'm running dry on ideas.
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#4
Have you tried a desoldering braid? They are also available from Radio Shack.
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#5
Have you tried desoldering braid [radioshack.com] ?
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#6
Have you tried a spring-loaded plunger-style solder sucker? They have more powerful suction than squeeze bulbs do

I use copper desoldering braid to remove the final traces of solder, the 2-3mm size because it's wide enough to soak up almost all the solder from a joint but not so wide that it draws too much heat away from it. Also right after a section of the braid is used, even if it doesn't absorb much solder, I cut it off so the dangling length doesn't draw away heat. Braid made with the finest strands seems to absorb solder best (knit No Clean), while some other types soak up virtualy nothing. But brushing rosin flux onto the braid makes it work a whole lot better

I wouldn't use a soldering gun on a motherboard.

I've found that some irons put out more heat than others of the same power rating and tip size and shape, and a narrow chisel-shaped tip conducts heat into the joint better than a conical tip does. However 40W seems to usually be slightly underpowered for desoldering circuit boards made with more than 2 layers of copper, and 50W can be a big improvement.

Some people take the Radio Shack $11 model 206-2031 [radioshack.com] desoldering iron and modify it by replacing its suction bulb with a big vacuum tank. One person plugged it into a variac to raise the power from its normal 45W to slightly over 50W, but I don't know how long it lasted then.
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Last edited by larrymoencurly June 11, 2009 at 09:55 PM. Reason: interrupted by ninja attack
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#7
yeah I tried desoldering braid it doesn't work well on the lead free. my desoldering gun is actually the 45w 206-2031 .
the problem is getting into the hole to get that last bit. I haven't tried spring loaded. Radio Shack sells a Vacuum Desoldering Tool but the reviews aren't encouraging.
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#8
Got compressed air to blow it out? What if you heat an aluminum wire to poke through the molten solder?
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#9
That's an idea. I had heated something similar to a paper clip wire but it didn't work. Any particular reason I should go with aluminum?
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#10
The aluminum won't take the solder. When desoldering a joint we would slip a piece cut from a soda can through the molten solder to isolate the two pieces of metal. Once the solder cooled, pull out the piece of aluminum and the joint is completely broken. A toothpick might work, though.
I see you've already tried that.
I agree with Felix who said he tips the work and lets the solder run out.
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Last edited by In_Like_Tim June 12, 2009 at 12:22 AM.
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#11
I've always used one of these with 100% success http://www.radioshack.com/product...=107595528
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#12
Quote from dollarbill
:
I've always used one of these with 100% success http://www.radioshack.com/product...=107595528
I have that exact one!

Quote from larrymoencurly
:
Have you tried a spring-loaded plunger-style solder sucker? They have more powerful suction than squeeze bulbs do

I use copper desoldering braid to remove the final traces of solder, the 2-3mm size because it's wide enough to soak up almost all the solder from a joint but not so wide that it draws too much heat away from it. Also right after a section of the braid is used, even if it doesn't absorb much solder, I cut it off so the dangling length doesn't draw away heat. Braid made with the finest strands seems to absorb solder best (knit No Clean), while some other types soak up virtualy nothing. But brushing rosin flux onto the braid makes it work a whole lot better

I wouldn't use a soldering gun on a motherboard.

I've found that some irons put out more heat than others of the same power rating and tip size and shape, and a narrow chisel-shaped tip conducts heat into the joint better than a conical tip does. However 40W seems to usually be slightly underpowered for desoldering circuit boards made with more than 2 layers of copper, and 50W can be a big improvement.

Some people take the Radio Shack $11 model 206-2031 [radioshack.com] desoldering iron and modify it by replacing its suction bulb with a big vacuum tank. One person plugged it into a variac to raise the power from its normal 45W to slightly over 50W, but I don't know how long it lasted then.
Great point on the trimming of the braid bulb I'll have to try to remember that next time, as usually I trim off the used braid after I'm all done, not after each time I use it for that session.
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#13
Quote from disk
:
yeah I tried desoldering braid it doesn't work well on the lead free. my desoldering gun is actually the 45w 206-2031 .
the problem is getting into the hole to get that last bit. I haven't tried spring loaded. Radio Shack sells a Vacuum Desoldering Tool but the reviews aren't encouraging.
I've found that iron to be slightly underpowered for motherboards, but keeping the hole unclogged and the tip really clean and waiting 10-15 seconds between uses can help. To remove all traces of solder with it, I fill the hole with 60/40 and then hold the desoldering iron over the hole for a full second before releasing the suction bulb.

Have you tried the rosin trick with the braid? Big difference.
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#14
Quote from larrymoencurly
:
Have you tried the rosin trick with the braid? Big difference.
No, I can give that a shot maybe this weekend. Thanks. btw I hope you're doing ok from that ninja attack.
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#15
how about cut the pins/legs on the cap to fit the position, fill the hole with solder, heat it up and just run the pin right through one by one? When the hole is grounded it'd take a while to heat it up too.
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