How to go about desoldering?
March 31, 2022 1:39 AM Subscribe
What tool(s) should I get for a small desoldering project?
Although the recommendations in this previous question about desolderers arrived at a consensus on the Hakko FR-301, the project I have in mind is limited and unlikely to be carried out more than twice, so a full-on desoldering station would be overkill.
I want to desolder three factory-soldered keyboard switches (see the lower left of this image of the underside of the PCB). When I first got the switches I intend to use as replacements, I tried doing it with a cheap soldering iron and the wick that came with it, but didn't have much success and stopped as I was concerned I'd damage the board by leaving the iron in contact too long while trying to melt the solder. The packaging doesn't say, but I imagine the wick lacks flux. It's also a possibility that the heat of the iron itself is insufficient, it being a basic model with no temperature control (40 W; the packaging states that it reaches temperatures of 300°C or higher).
Given the above, I'm considering the following, from cheapest to most expensive, but am not certain which would be the best approach insofar as cost versus difficulty.
Although the recommendations in this previous question about desolderers arrived at a consensus on the Hakko FR-301, the project I have in mind is limited and unlikely to be carried out more than twice, so a full-on desoldering station would be overkill.
I want to desolder three factory-soldered keyboard switches (see the lower left of this image of the underside of the PCB). When I first got the switches I intend to use as replacements, I tried doing it with a cheap soldering iron and the wick that came with it, but didn't have much success and stopped as I was concerned I'd damage the board by leaving the iron in contact too long while trying to melt the solder. The packaging doesn't say, but I imagine the wick lacks flux. It's also a possibility that the heat of the iron itself is insufficient, it being a basic model with no temperature control (40 W; the packaging states that it reaches temperatures of 300°C or higher).
Given the above, I'm considering the following, from cheapest to most expensive, but am not certain which would be the best approach insofar as cost versus difficulty.
- Get flux-coated wick and try it again with the current iron, adding solder to the existing joints as necessary, the factory joints likely being lead-free.
- Get a solder sucker and do as above.
- Get both wick and the solder sucker to use in combination.
- Get a desolderer that combines a soldering iron and a solder sucker.
I like using a combination desoldering iron and sucker as then you don't have to switch tools half way through. The other tool I like to have on hand is some sort of pick to clean out the hole once the part is removed.
posted by drezdn at 4:08 AM on March 31, 2022
posted by drezdn at 4:08 AM on March 31, 2022
I would buy a tube of flux and try again with the soldering iron & wick that you already have. Something like this is what I would buy here in the States. I don't know Japanese, so you'll probably want to review this, but I saw a similar product on one of the sites you linked to.
I've never used the SS-02 but Adafruit seems to think that it's really nice.
I agree with McNulty that it's pretty hard to damage the board.
posted by gregr at 6:16 AM on March 31, 2022
I've never used the SS-02 but Adafruit seems to think that it's really nice.
I agree with McNulty that it's pretty hard to damage the board.
posted by gregr at 6:16 AM on March 31, 2022
With an unregulated iron I would myself be worried about overheating the board. If the joint gets too hot you can burn the epoxy that holds the copper to the board and find yourself with a pad peeling off. Because this operation is tricky (it looks like you need to free two joints to make the switch mechanically free, so it's two or nothing) it's going to encourage frustrated lingering with the iron.
The best solution is to find someone who will let you use the right tool for a few minutes - tragically that is indeed a $200 desoldering pump. If you're near Cambridge MA that could be me, I have a bunch in my teaching lab and you'd be done in five minutes, feel free to memail me. I'm pretty sure our local (large) library has a makerspace that would have the right tool; you might look around to see if you have something like that nearby.
Otherwise I'd be tempted to lay the iron across the two pads whole gently tugging on the switch, then pull the switch free and clear the holes with a solder sucker afterwards - those solder suckers are way more effective at clearing a solder plug than freeing a pin. The solder plug usually ends up recessed in the hole so you will paradoxically need to add solder in order to make thermal contact with the plug.
If this is a commercial product and that's lead-free solder then it's going to be more frustrating because you have to work at higher temperatures that are closer to the burnt-epoxy danger zone. Because it's hotter (further away from room temp) it would also mean that the temperature will fall faster after you remove the iron, so getting two melted joints at the same time is a little harder too with deleaded solder.
posted by range at 6:41 AM on March 31, 2022
The best solution is to find someone who will let you use the right tool for a few minutes - tragically that is indeed a $200 desoldering pump. If you're near Cambridge MA that could be me, I have a bunch in my teaching lab and you'd be done in five minutes, feel free to memail me. I'm pretty sure our local (large) library has a makerspace that would have the right tool; you might look around to see if you have something like that nearby.
Otherwise I'd be tempted to lay the iron across the two pads whole gently tugging on the switch, then pull the switch free and clear the holes with a solder sucker afterwards - those solder suckers are way more effective at clearing a solder plug than freeing a pin. The solder plug usually ends up recessed in the hole so you will paradoxically need to add solder in order to make thermal contact with the plug.
If this is a commercial product and that's lead-free solder then it's going to be more frustrating because you have to work at higher temperatures that are closer to the burnt-epoxy danger zone. Because it's hotter (further away from room temp) it would also mean that the temperature will fall faster after you remove the iron, so getting two melted joints at the same time is a little harder too with deleaded solder.
posted by range at 6:41 AM on March 31, 2022
Best answer: Flux is magical for soldering/desoldering.
Solder sucker is much better than wick.
It's much easier to desolder one joint at a time, consider cutting the switch apart so you can desolder and remove on pin at a time. This is destructive obviously and the parts won't be reusable.
posted by jclarkin at 6:48 AM on March 31, 2022
Solder sucker is much better than wick.
It's much easier to desolder one joint at a time, consider cutting the switch apart so you can desolder and remove on pin at a time. This is destructive obviously and the parts won't be reusable.
posted by jclarkin at 6:48 AM on March 31, 2022
Best answer: For desoldering fairly heavy wires like typical switch pins off boards with the tiny pads that are fashionable these days, I've always found that reasonably wide wick plus added, good flux works way better than any mechanical solder sucker that isn't a self-heated vacuum power desoldering tool. Teeny tiny 1.5mm wide wick is uniformly useless, though. Go for wick at least 3mm wide, and add your own flux rather than relying on whatever dodgy crap is embedded in the wick.
As well as using a good flux, desoldering stuff off commercial boards is way easier if you dilute the existing lead-free solder joint with a goodly blob of old fashioned multi-cored 60/40 tin/lead alloy before trying to remove it. The resulting molten mixture has a much lower melting point than lead-free solder does, and will therefore want to go further up the wick before solidifying in it and clogging it. You might need to do this a few times if the pin is tight in the hole, so that the new leaded alloy actually makes it all the way in to where the last of the lead-free stuff is hiding.
For wick desoldering you want to dump a lot of heat into the joint fairly quickly, because the wick will be sucking heat back out again along with the molten solder. A 60W iron will work noticeably better than a 40W for this, unless the 40W has an unusually chunky tip with plenty of thermal mass.
posted by flabdablet at 7:58 AM on March 31, 2022 [1 favorite]
As well as using a good flux, desoldering stuff off commercial boards is way easier if you dilute the existing lead-free solder joint with a goodly blob of old fashioned multi-cored 60/40 tin/lead alloy before trying to remove it. The resulting molten mixture has a much lower melting point than lead-free solder does, and will therefore want to go further up the wick before solidifying in it and clogging it. You might need to do this a few times if the pin is tight in the hole, so that the new leaded alloy actually makes it all the way in to where the last of the lead-free stuff is hiding.
For wick desoldering you want to dump a lot of heat into the joint fairly quickly, because the wick will be sucking heat back out again along with the molten solder. A 60W iron will work noticeably better than a 40W for this, unless the 40W has an unusually chunky tip with plenty of thermal mass.
posted by flabdablet at 7:58 AM on March 31, 2022 [1 favorite]
Best answer: The Engineer SS-02 is very good. We sell it, and it's spectacularly well made. Solder braid, even good stuff, is of limited use for lead-free solder removal, though.
flabdablet's suggestion of using a lower-melting point alloy to ease the last of the solder out the joint is a good one. In countries where lead is properly regulated, you can get bismuth-based alloys that work really well. ChipQuik is one of the brands, but that might not be one you can get in Japan.
posted by scruss at 8:18 AM on March 31, 2022 [1 favorite]
flabdablet's suggestion of using a lower-melting point alloy to ease the last of the solder out the joint is a good one. In countries where lead is properly regulated, you can get bismuth-based alloys that work really well. ChipQuik is one of the brands, but that might not be one you can get in Japan.
posted by scruss at 8:18 AM on March 31, 2022 [1 favorite]
Best answer: Oh, and don't try to pull out the switch pins until you've wicked out enough solder that you can make them wobble in the holes after the joint's cooled down. If you wobble them while it does that you'll deliberately create a weak "dry" joint from whatever tiny remnants the wick leaves behind, and that will make achieving the cold wobble easier.
Pulling out tight-fitting pins that aren't properly wobbly risks ripping the through-hole plating out of the board, which will make reliable replacement of the components involved way way harder.
If such tear-out happens despite your best and most careful efforts, you'll need to insert two or three single strands of hookup wire through the hole, bent over and trimmed to only just go over the pads on both sides, and fill the hole with flux before re-inserting the new component and soldering the joint. That will usually be enough to wick solder onto the pad on the inaccessible side of the board even if there's some degree of damage to the through-hole plating.
posted by flabdablet at 8:21 AM on March 31, 2022
Pulling out tight-fitting pins that aren't properly wobbly risks ripping the through-hole plating out of the board, which will make reliable replacement of the components involved way way harder.
If such tear-out happens despite your best and most careful efforts, you'll need to insert two or three single strands of hookup wire through the hole, bent over and trimmed to only just go over the pads on both sides, and fill the hole with flux before re-inserting the new component and soldering the joint. That will usually be enough to wick solder onto the pad on the inaccessible side of the board even if there's some degree of damage to the through-hole plating.
posted by flabdablet at 8:21 AM on March 31, 2022
In my experience, one-shot spring-loaded vacuum tools like scruss's Engineer SS-02 are really good for sucking the last remnants of solder out of PC board holes that either don't still have pins in them or have pin remnants left behind after clipping off the components first. They're quite frustrating to use for stuff like wide flat switch or socket pins that occupy much of the internal volume of a plated-through hole, especially when there's a chunky component like a switch body or electrolytic capacitor base blocking access to air on the colder, upstream side of the board. I've always found that good wick, good flux and good technique works better, faster and more reliably.
posted by flabdablet at 8:26 AM on March 31, 2022
posted by flabdablet at 8:26 AM on March 31, 2022
One more point on wick technique: molten solder generally wants to move toward the heat source. Poking a hole into a wide wick to admit the end of the pin you're trying to desolder, then pressing the hot iron onto the reel side of the wick to transfer heat through the wick into the joint, will work quite a lot better than just sticking the tip of the wick into one side of the joint while you heat the other with the iron.
If you're stuck with shitty tiny wick you can double it up to make a hairpin loop, surround the pin with that, then press the iron onto the side away from the bend.
None of this works particularly well without added flux, though.
posted by flabdablet at 8:38 AM on March 31, 2022 [1 favorite]
If you're stuck with shitty tiny wick you can double it up to make a hairpin loop, surround the pin with that, then press the iron onto the side away from the bend.
None of this works particularly well without added flux, though.
posted by flabdablet at 8:38 AM on March 31, 2022 [1 favorite]
Also also: keep your wick in a small, airtight ziploc bag when you're not using it. Oxidized wick is no damn good at all, and will struggle to absorb solder even with help from decent flux.
posted by flabdablet at 8:45 AM on March 31, 2022 [1 favorite]
posted by flabdablet at 8:45 AM on March 31, 2022 [1 favorite]
40W is plenty. Using solder wick is something of a black art. The stuff doesn't work and then all of a sudden it's pulling solder up for fun. In my experience the key is getting the wick hot. The way you do that is to get enough clean solder on the tip at the start to make a good thermal connection to the wick. As soon as the solder starts flowing on the board you'll have enough to keep going.
posted by StephenB at 10:55 AM on March 31, 2022
posted by StephenB at 10:55 AM on March 31, 2022
ORANGE JUICE ATE ZELDA?? Can it be repaired? Gameboy color game repair! - YouTube -- a bit of desoldering porn.
posted by zengargoyle at 10:57 AM on March 31, 2022 [1 favorite]
posted by zengargoyle at 10:57 AM on March 31, 2022 [1 favorite]
Response by poster: I just received the Engineer SS-02, flux, 3 mm soldering wick, and 60/40 tin/lead solder to try in combination with my existing soldering iron. Now it will just be the "good technique" that I'm lacking.
In addition to the answers here, I was also motivated to get the solder sucker and wick because of a blog post I found (apologies for this also being in Japanese) where the HSK-300 did work for the same task, but also resulted in burns on the board and a video from the same source as that posted by zengargoyle showing that this can be done with just a soldering iron, solder, and wick, though I won't use tweezers to break sweat joints.
posted by Strutter Cane - United Planets Stilt Patrol at 10:56 PM on April 1, 2022 [1 favorite]
In addition to the answers here, I was also motivated to get the solder sucker and wick because of a blog post I found (apologies for this also being in Japanese) where the HSK-300 did work for the same task, but also resulted in burns on the board and a video from the same source as that posted by zengargoyle showing that this can be done with just a soldering iron, solder, and wick, though I won't use tweezers to break sweat joints.
posted by Strutter Cane - United Planets Stilt Patrol at 10:56 PM on April 1, 2022 [1 favorite]
The person in the Reddit video you linked to there is using wick the hard way, leaving the wick in one spot while the iron just makes the joint hotter and hotter. The natural tendency of molten solder is to flow toward the heat source, and using wick the way the video shows makes the wick's capillary action have to work against that. There's also some careless placement of the iron tip in such a way as to melt some plastic, generally to be avoided.
Once the solder has melted and started to flow into the wick, keep the wick moving under the iron tip so as to feed a slow but continuous supply of fresh wick into the joint. This helps the fully tinned, spent part of the wick physically carry solder away from the joint instead of relying so completely on an ever-lengthening melt/capillary zone. The iron tip should press onto the joint on the wick exit side, giving the solder the chance to flow up the wick's temperature gradient as it gets pulled into the joint and under the tip. Don't go too fast, though, lest you over-cool the joint.
Doing it that way, you'll find you can get more solder out in less time and at lower risk of overheating the joint.
Using tweezers to wobble the pins is also best done immediately after pulling away the wick, so that any solder remaining in the joint is never given a chance to set properly. Solder is very weak if thoroughly disturbed while freezing, and much less like to damage pads or through-hole plating as the pin is eased out.
posted by flabdablet at 11:54 AM on April 2, 2022
Once the solder has melted and started to flow into the wick, keep the wick moving under the iron tip so as to feed a slow but continuous supply of fresh wick into the joint. This helps the fully tinned, spent part of the wick physically carry solder away from the joint instead of relying so completely on an ever-lengthening melt/capillary zone. The iron tip should press onto the joint on the wick exit side, giving the solder the chance to flow up the wick's temperature gradient as it gets pulled into the joint and under the tip. Don't go too fast, though, lest you over-cool the joint.
Doing it that way, you'll find you can get more solder out in less time and at lower risk of overheating the joint.
Using tweezers to wobble the pins is also best done immediately after pulling away the wick, so that any solder remaining in the joint is never given a chance to set properly. Solder is very weak if thoroughly disturbed while freezing, and much less like to damage pads or through-hole plating as the pin is eased out.
posted by flabdablet at 11:54 AM on April 2, 2022
Response by poster: Desoldering is a land of contrasts, as I didn't find the wick all that effective, even with added flux, but the Engineer SS-02 did the job, though it did take me (much) longer to clear some through holes than others. Adding additional 60/40 solder was very helpful. Only for one switch did I do it well enough that it just fell out due to gravity once I triggered the sucker, but I made sure to wobble the pins for the other two and didn't damage any of the through holes.
I typed this very comment on a keyboard that now has clicky switches for the TrackPoint buttons instead of linear switches. Thanks to everyone for your answers.
posted by Strutter Cane - United Planets Stilt Patrol at 1:36 AM on April 3, 2022 [1 favorite]
I typed this very comment on a keyboard that now has clicky switches for the TrackPoint buttons instead of linear switches. Thanks to everyone for your answers.
posted by Strutter Cane - United Planets Stilt Patrol at 1:36 AM on April 3, 2022 [1 favorite]
I didn't find the wick all that effective, even with added flux
It always works perfectly for me, but that might well be because the iron I use for desoldering is a grunty 60 watt brute that has a nice square chisel tip with bags of thermal mass. It looks like something better suited to plumbing than electronics although it's actually completely useless for plumbing.
I use plenty of flux with my wick. Also, when I'm adding the diluting 60/40 solder, I always pull the solder through a pinched fold of dry paper towel a few times to polish off the oxide layer (this makes marks that look like pencil lines), then clip off the very tip of the solder to expose the flux core, then wipe the iron's tip onto a sopping wet sponge immediately before flowing the cleaned solder into the joint. The less oxide the flux has to destroy the better.
This kind of obsessive cleaning also improves solder joint quality generally - it's not only good for desoldering.
Anyway, glad you got a good result with your pTHOOP sucker. Enjoy your clicky, you've earned it.
posted by flabdablet at 4:36 AM on April 3, 2022 [2 favorites]
It always works perfectly for me, but that might well be because the iron I use for desoldering is a grunty 60 watt brute that has a nice square chisel tip with bags of thermal mass. It looks like something better suited to plumbing than electronics although it's actually completely useless for plumbing.
I use plenty of flux with my wick. Also, when I'm adding the diluting 60/40 solder, I always pull the solder through a pinched fold of dry paper towel a few times to polish off the oxide layer (this makes marks that look like pencil lines), then clip off the very tip of the solder to expose the flux core, then wipe the iron's tip onto a sopping wet sponge immediately before flowing the cleaned solder into the joint. The less oxide the flux has to destroy the better.
This kind of obsessive cleaning also improves solder joint quality generally - it's not only good for desoldering.
Anyway, glad you got a good result with your pTHOOP sucker. Enjoy your clicky, you've earned it.
posted by flabdablet at 4:36 AM on April 3, 2022 [2 favorites]
This thread is closed to new comments.
posted by McNulty at 1:43 AM on March 31, 2022