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I am trying to swap dead capacitors in my motherboard. Removing them was relatively easy, but I can not insert the new ones. The solder melted into the vias and the desoldering wire does not suck it out of the hole. Is there any safe method to remove the blocking solder from the vias?

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    \$\begingroup\$ PC motherboards seem to use some really annoying solder (some hard RoHS stuff?) IIRC. It might help to add some more normal solder and melt them together. Then try the answers. Suction might work better than capillary and poking a hot component lead through might indeed be the easiest. \$\endgroup\$ – XTL Oct 10 '10 at 9:02
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Sometimes you can just push the majority of the stuff out, by quickly pushing a couple inches of un-heated solid wire through the hole while the solder is melted. If you do it fast enough, you end up with the solder frozen on the wire sticking out the other side of the board, and you can break the solder off and then just pull the wire back through.

Another thing that sometimes works is to heat the via and then quickly tap the board against the edge of a bench, moving the board in a short swing in the direction of the via. The inertia of the molten solder will cause it to keep going forward (and probably onto the floor) when the rest of the board stops. And (obviously, I had thought) you don't want use this technique on any but the sturdiest of boards.

Like the blowing technique, the down-side of these is that they can produce tiny, loose bits of conductive material to watch out for, which can cause shorts if you don't get them all. Suction is really the way to go.

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    \$\begingroup\$ Suction before you remove the components is the way to go. \$\endgroup\$ – Kevin Vermeer Oct 9 '10 at 16:13
  • \$\begingroup\$ @reemrevnivek - well, yeah, if nothing else, because the extra mass of the component lead helps keep the solder molten longer, making it easier to get there in time with the suction tool. And besides, if the part you're de-soldering is destined for the trash can, you can really cook the joint and then even the body of the part itself will help keep things hot. \$\endgroup\$ – JustJeff Oct 9 '10 at 17:01
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    \$\begingroup\$ ah, should have added, don't go to hot for too long, or you can melt the trace off the board. \$\endgroup\$ – JustJeff Oct 9 '10 at 17:07
  • \$\begingroup\$ If you have a suction tip on your soldering station, you can put the lead inside the tip, and work around in little circles, reducing the area you have to suck air through and increasing the amount of solder which remains. You can get the joint completely dry this way. \$\endgroup\$ – Kevin Vermeer Oct 9 '10 at 20:13
  • \$\begingroup\$ I really only mentioned these methods to round out the answers a bit. I've only personally used the knock technique a couple of times, and not at all since I bought one of those spring-loaded piston solder suckers, about 20 years ago. Please, don't go banging on any board you're not ready to throw away. Get a sucker! \$\endgroup\$ – JustJeff Oct 10 '10 at 23:37
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Have you tried a desoldering pump?

alt text

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  • \$\begingroup\$ Yes I tried, but I am not sure how to use it. Because if I try it on the same side, the solder cools down as I remove the solder pen and I have no time to suck up the solder. From the opposite side, it does not work also maybe because the hole is too small. Now i am trying to blow from the opposite side with a dust blower while heating the via. \$\endgroup\$ – csadam Oct 9 '10 at 12:57
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    \$\begingroup\$ I'd recommend using it from the same side, and admittedly it's tricky, you have to practice at being quick enough. Also, you want to keep these beasties producing the maximum vacuum possible. Watch out for solder that freezes up in the tip, and if the spring/piston action seems slow, the tiniest (really, tiny) drop of WD40 can help speed that up. \$\endgroup\$ – JustJeff Oct 9 '10 at 13:11
  • \$\begingroup\$ @csdam: as JustJeff has said, it takes practice, or have someone else hold the soldering iron, that way you will be quicker. \$\endgroup\$ – volting Oct 9 '10 at 14:55
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    \$\begingroup\$ Also, I've often found solder gets inside the spring mechanism and this causes problems. You can disassemble them relatively easily and blow them out. I have to do this every few months; I do use my solder sucker a lot, though. \$\endgroup\$ – Thomas O Oct 9 '10 at 15:50
  • \$\begingroup\$ I even added a drop of machine oil inside my pump near/on the joint(s) - it really increases the speed and the suction as it makes the pump more air-tight and reduces the friction at the same time. ** If you have a small wrench for your workbench, you can fix your board vertically, but the pump on one side, the soldering iron on the other and once the solder is hot, hit the pump button! \$\endgroup\$ – le_top Oct 7 '19 at 15:10
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Beyond what has already been answered, you can try to use wick solder remove.

alt text

There is a great article at wikipedia: http://en.wikipedia.org/wiki/Desoldering

And Youtube has many videos about: http://www.youtube.com/results?search_query=desoldering&aq=f

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  • \$\begingroup\$ This is what I use. You need to wet the wick first and drag it across the hole to get it wick up. \$\endgroup\$ – endolith Oct 9 '10 at 19:07
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    \$\begingroup\$ Don't forget - "wet" means "with solder" :-) \$\endgroup\$ – Toby Jaffey Oct 9 '10 at 19:37
  • \$\begingroup\$ Another technique that has served me well is to first cut the solder braid/wick at a very acute angle. Then, poke it into the through hole/via, and apply both the soldering iron and a bit of solder. It sounds counter intuitive but it works well. You will need to repeat this several times to clear the holes, especially for capacitors (which are often connected to ground and power planes). \$\endgroup\$ – John Lopez Oct 10 '10 at 3:06
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Thanks for your tips. Here are my observations:

  • desoldering pump - After cleaning and oiling my pump I had still no luck with it. Maybe I have to practice more :)
  • desoldering braid - Adding some fresh solder before using this definitely improves the cleaning effect, but it leaves the solder inside the hole. I've tried three different types of solder wick without success.
  • tap-tap method - It seems usable for smaller boards but not for a computer motherboard so I have not tried it.
  • Pushing out - I had no thin solid wire here, so I added a little extra solder and heated the via while pushing in the new capacitor from the opposite side. Sometimes worked but this thing has two legs and I have only 1 soldering iron :)
  • Blowing out - I tried to blow with my mouth without any effect. Then I tried a dust blower, but I cannot aim it precisely into the hole.

Then I found something in my drawer: alt text

It is a plastic bottle with metal needle head, 1 USD from DX. I inserted it to the hole from the opposite side then I heated the hole. After removing the soldering iron I quickly squeezed the bottle. It cleaned out the via! 8 of 10 times I was able to insert the new component to the hole without problem. For the remaining two holes I used a sewing needle to broaden the hole.

Still not the best method, but it worked for me better than any others mentioned here. However I am considering to buy a vacuum desoldering tool to save a whole day next time :)

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If you can justify it, look into a desoldering iron, such as the Pace SX-90. I've found them very useful because you don't have to remove your heat source to suck out solder, they're temperature-controlled, and they also can pull vacuum indefinitely. (They use a vacuum pump, instead of a spring piston.) Granted, the Pace iron requires a controller, but that controller can also control a temp-regulated iron as well.

SX-90

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  • \$\begingroup\$ Looks good, sadly it costs three times more than the whole computer I am trying to repair :) \$\endgroup\$ – csadam Oct 10 '10 at 13:06
  • \$\begingroup\$ I know what you mean. I've been looking on eBay for the past year or so putting together a Pace setup. So far I have one SX-90 iron and an older 2-channel controller. I'm waiting for one of these to show up at the right price. One other item you might try is a bulb arrangement that goes on an iron like a regular tip, except it has the thru-hole so you can do hot suction. Lots cheaper, but not as convenient as the too-expensive Pace. \$\endgroup\$ – Jesse Oct 10 '10 at 18:31
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Try melting the solder and blowing it out. You might find that desoldering braid works better if you add some more solder to the pad, first.

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What soldering Iron are you using?

This sound suspiciously like the pad's your having a problem with are tied directly to the ground plane and your iron isn't transferring enough heat effectively. Or more specifically the ground plane is sinking enough heat to not get the solder up to the proper temperature.

I use a metcal MX500 and when i have this issue stepping up to a larger tip usually transfers enough heat to solve the problem. As a last step you can try a hotter tip, or if your using an adjustable iron, turn the heat up, just be careful not to go too high, if it gets too hot the pad will separate from the board.

Failing that, hold the board on edge, apply heat to the back side of the pad while pushing the cap in the top side, move the cap in as you move the iron out. This usually works for me.

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Here's a cheap and easy technique which works better than any other method I've tried. First, get a good quality turkey baster which can withstand high heat. Amazon sells silicone hear resistant ones for cheap under $5.00. Make sure you are using an iron capable of a wide heat range. Most simple plug in type irons just can't deliver enough heat.

enter image description here

Apply a blob of solder to both sides of the via. Add paste flux to both blobs, but wait until they are sufficiently cool. You don't want the flux to liquify and run off the hot blob.

Anchor the PCB vertically between vice jaws or two heavy objects. Using the iron at a high setting, heat one side until it melts and immediately place your turkey baster's tip over it and hold it there. Then immediately heat the other side of the with the iron. As soon as both sides liquified suction in quicky squeeze the turkey baster's blub to blow out the solder.

Make sure you cleanup and solder droplets when you're done. You could use a vacuum action, but unless you form a really good seal around the via, it doesn't work very well.

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