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I know "solder won't melt" is a pretty common issue, but after hours of research online I don't know what else to try. I've attached a couple pics to hopefully help.

Scenario: I'm repairing some handheld Motorola radios. There is an audio jack with a casing that is soldered to the ground-plane of the PCB using 4 pins and the audio jack itself is using several other pins. The audio jack itself cam off fairly easily. I cut the metal casing off to just nubs so that it wouldn't dissipate so much heat, however I still cannot get those nubs solder to melt.

What I've tried:

  1. Multiple solder tips - currently using biggest/fattest I can practically use.
  2. Adding lots of flux
  3. Adding solder to the nubs - I can add, but it doesn't mix with the old.
  4. Using multiple solder irons on both sides of the PCB.
  5. Using pin-point hot air in conjunction with the iron
  6. Higher iron heat - Up to 400+ degrees C
  7. Preheating PCB to about 100C
  8. Used Solder Wick, Solder Sucker, and Solder Vacuum.

The the regular pic I've circled the joints I'm referring to - all the brown is just flux on the board. I've not damaged the board in any way that I can tell.

The other pic is from a thermal camera and is circled where those joints are, roughly.

Can anyone provide any other ideas/techniques to try? I've run out of ideas.

Thanks so much!

enter image description here

enter image description here

EDIT: Sorry for my late response to everyone - I didn't realize so many people had replied. I didn't get any notifications of it - so sorry about that.

I'm currently using an X-Tronic 5040-XTS-XR3 soldering station and a METCAL SP200 soldering iron. Neither one of them, nor both of them together, have been able to melt the solder - hence my original post.But like I said, my biggest tip is a 2.4mm.

The X-Tronic seems like a generic brand, but maybe I'm wrong? I can't find any larger tips for it - but maybe it's a generic/universal style tip? I'm not incredibly familiar with soldering equipment - I'm still learning.

The SP200 is pretty old, but seems to work well for other projects. But I think it is auto-adjusting. There is no manual adjustments for it.

Do any of you feel like either of these products are sufficient?

Thank you all for your input!

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  • \$\begingroup\$ You listed pretty much everything so it's probably not what you're doing but how you're doing it. Adding wick will make heating more difficult. "biggest/fattest I can practically use" How big is big and how are you defining the limit of practical? Because if you're using the pad size, that is not the limit. I use a 6.6mm wide blunt chisel tip for this. Clearing holes can be a pain even if it melts. You might just not be making contact with the solder indent in the hole. Normally you add solder so you get better contact and remove that. \$\endgroup\$
    – DKNguyen
    Commented Jun 12, 2022 at 1:53
  • \$\begingroup\$ @DKNguyen The tip is about as big as I can use without damaging other nearby components by physically touching them. I can't really get a bigger tip in there to work with - I'm not sure if I even have a larger one. It's not that I'm unable to clear the holes - the pic does sort of look that way. But those joints are not concave - they are small nubs sticking out with solder built up around them. I can melt any solder I add to it, but it is not mixing with what is deeper into the hole. \$\endgroup\$
    – csharp1321
    Commented Jun 12, 2022 at 1:55
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    \$\begingroup\$ Incidental contact is not an issue. Especially when ground planes, Pb-Free solder and wick are all present. If added solder is not mixing it means you're not heating enough or not wetting (insufficient flux). Period. I use a monster like this with wick even with small pads, let alone a large pad: howardelectronics.com/soldering/soldering-tips/jbc-tools/… \$\endgroup\$
    – DKNguyen
    Commented Jun 12, 2022 at 1:56
  • \$\begingroup\$ Wow - I don't have anything nearly that big. Measuring my biggest is 2.5mm - which is bigger than anything I've ever needed. I'm using Sn63Pb37 solder \$\endgroup\$
    – csharp1321
    Commented Jun 12, 2022 at 2:06
  • \$\begingroup\$ You would have trouble with a 2.5mm tip and wick with lead-free solder on a ground plane. I know I did. That's why I no longer use the my 2.4mm with wick, and it's worse if it's a thin, knife edge 2.4mm. The 2.4mm is reserved for through-hole soldering. You want a big, blunt blocky tip with wick. And if you're working through the wick, it helps shield adjacent areas from the tip where you're not actively pressing the tip. Shorter pieces of wick will reduce heating required as well in case you did not know. Use hemostats so you don't burn your fingers. \$\endgroup\$
    – DKNguyen
    Commented Jun 12, 2022 at 2:14

5 Answers 5

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This will take:

  1. A 100W soldering iron set to 800F or 430C.

  2. 60-40 solder with rosin core.

  3. Liquid activated rosin flux in a suitable dispenser ("dropper" or flux pen).

Douse the nibs in flux. Apply solder, ensure it starts to wick into the hole, or at least forms a meniscus as if you were soldering those pins in place. Then pull from the other side using small side cutters or pliers. The idea is to minimize the contact area between the pulling tool and the pin, so small side cutters work well for that. Really small: blade length of 5-8mm.

As long as you have good contact from the tip through a well fluxed fresh solder to the pins/nibs, removal will be trivial. None of the preheating and other diversions are necessary. This will work, and it will work first time if done right.

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  • \$\begingroup\$ Thank you for your input! I've added more info to my original post. \$\endgroup\$
    – csharp1321
    Commented Jun 18, 2022 at 20:55
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Use a preheater for soldering. You can get inexpensive temperature controlled air preheaters where you blow hot air under the board. [edit] I normally set the preheat temperature to 180°C, 200°C for stubborn boards. The soldering iron will better able to melt the soldered connection when the board is heated. You may want to add bismuth solder to the joint to lower the melting point of the solder which will make removal easier.

In lieu of a commercial hot air heater, you can use a hot air gun with a bit of gymnastics. You need to be careful with this technique so you don't over heat the board.

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  • \$\begingroup\$ OP already mentioned trying a preheater. \$\endgroup\$
    – DKNguyen
    Commented Jun 13, 2022 at 1:00
  • \$\begingroup\$ @DKNguyen Preheating to 100°C isn't enough. Need to be closer to 180 to 200°C. \$\endgroup\$
    – qrk
    Commented Jun 13, 2022 at 1:33
  • \$\begingroup\$ I see now that was the objective of your comment. You might want to make it more direct. \$\endgroup\$
    – DKNguyen
    Commented Jun 13, 2022 at 1:42
  • \$\begingroup\$ Thank you for your input! I've added more info to my original post. \$\endgroup\$
    – csharp1321
    Commented Jun 18, 2022 at 20:55
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If it doesn't melt, you need more power than the ground plane can soak.

You don't say which soldering iron you have, but there are two kinds, and that makes a big difference when you need a lot of power.

In the older style, the heater is fixed in the handle, and you change just the tip. This means there is a thin layer of air between the heater and the tip, which prevents good heat transfer.

In the newer style, the heater is molded inside the tip in a single piece. So the tips are a bit more expensive since they include the heater and the temperature sensor, but heat transfers much better. Since the sensor is also inside the tip, temperature feedback is much quicker, and when you stick it on aground plane, the station will go to max power immediately.

I recommend this station with the blue iron (second one) and BCM2 tip. The other tips for this iron arent's so good. It needs a 24V power supply with more than 3A.

A thick short tip helps. The one I'm recommending has a cup at the tip, which is great for drag soldering, but you can also apply it to shield pins like yours, and it will kind of wrap around the pin and heat it effectively.

Applying 63/37 solder to lower the melting point of the existing lead-free also helps.

If all else fails, you can use chip-quik or other very low melting point solders designed for this use. But these solders have to get inside the joint to mix with the existing solder and melt it, I'm not sure it would work in your case since the joint isn't melting at all.

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  • 1
    \$\begingroup\$ I find the uncupped/flat oval tip with untinned sides is much better at drag soldering because the solder ball is much more convex doming out of the tip than a cup/spoon tip. I can never use the full capacity of the reservoir in the spoon tip because it domes out less even while holding more solder, and when it runs just a little low much of the remaining the solder is concave and doesn't make contact. I find the cup, especially large 4mm, actually better at thru-hole soldering where you face the cup upwards and just let it wet onto the joint so you free up a hand fro holding solder wire. \$\endgroup\$
    – DKNguyen
    Commented Jun 12, 2022 at 18:56
  • \$\begingroup\$ With such a large solder dome and high surface tension it's like a T1000 liquid metal tip that conforms to everything for contact, even under pressure that deforms the dome. Lets you get right under chip components and QFNs. \$\endgroup\$
    – DKNguyen
    Commented Jun 12, 2022 at 19:01
  • \$\begingroup\$ @DKNguyen Yeah, I know, in theory. For some reason on the cheap brand I linked in the message, the tip I recommended works best. It's also their most expensive tip. There's probably something "cost-optimized" in the other cheaper tips that makes them less effective... \$\endgroup\$
    – bobflux
    Commented Jun 13, 2022 at 6:28
  • \$\begingroup\$ Interesting.... \$\endgroup\$
    – DKNguyen
    Commented Jun 13, 2022 at 15:18
  • \$\begingroup\$ Thank you for your input! I've added more info to my original post. \$\endgroup\$
    – csharp1321
    Commented Jun 18, 2022 at 20:55
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Try using an even bigger tip than the one you are using. Lead-free is already difficult to melt. Then ground planes makes it even more difficult. Then you have solder wick which is also a heatsink.

I have a tip like this specifically for this kind of thing because my 2.4mm and 4mm chisel wide tips which were 1mm thick at the edge were insufficient against both planes and wick. You want, big, wide, and blunt: enter image description here

https://www.jbctools.com/c245966-cartridge-chisel-66-x-18-ht-product-351.html

It is far larger than the pad and there is little concern about incidental contact against other solder joints due to size because it is all lead-free and heatsunk by the ground plane. Plus the solder wick tends to shield the enormous tip from incidental contact since it is flexible and only really makes good thermal contact where you are applying pressure with the iron.

And to help things along, always cut a small piece of wick maybe an inch or two, and hold it with hemostats so you don't burn your hands. Don't leave it on the spool because it just makes a giant heatsink.

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  • \$\begingroup\$ Thank you for your input! I've added more info to my original post. \$\endgroup\$
    – csharp1321
    Commented Jun 18, 2022 at 20:55
  • \$\begingroup\$ @csharp1321Metcal or Metcaf? One is high end, one is a knockoff. However Metcal SP200 is lower power: 35W. I use a JBC which is 150W and I still need a big tip. \$\endgroup\$
    – DKNguyen
    Commented Jun 18, 2022 at 21:04
  • \$\begingroup\$ It is Metcal - thank you for pointing that out. I fixed my typo in the post. What model iron are you using? \$\endgroup\$
    – csharp1321
    Commented Jun 18, 2022 at 21:05
  • \$\begingroup\$ I spoil myself with JBC DDU/DDE dual tool station and a T245 handpiece. The non-modular self-contained stations like the CDB/CD-1B are much more affordable though and functions identically if all you need is the T245 handpiece. The only reason I have the dual tool station instead of that is to accommodate hot tweezers but you pay for the stand for the hand pieces separately the central unit isn't any cheaper than the entire self-contained unit. \$\endgroup\$
    – DKNguyen
    Commented Jun 18, 2022 at 21:19
  • \$\begingroup\$ Nice! Wish I could afford that, haha. I don't think I'm advanced enough to justify it yet though. What do you think of the other unit I mentioned - the X-Tronic? Looks like the iron is a 70W - do you feel this is sufficient for my problem if I buy a 6mm tip? \$\endgroup\$
    – csharp1321
    Commented Jun 18, 2022 at 21:21
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I'm currently using an X-Tronic 5040-XTS-XR3 soldering station and a METCAL SP200 soldering iron. Neither one of them, nor both of them together, have been able to melt the solder

Neither of these soldering irons is powerful enough. For jobs like this I use a Goot TQ-77 200W pistol grip soldering iron on one side, and an SS350 SOLDAPULLT solder sucker on the other side. The conical iron tip gets right into the hole to heat the solder up quicker than a bevel or spade tip.

Put some fresh 60/40 tin/lead rosin-cored solder on the tip, pull the trigger for about 10 seconds, apply the tip to the hole and suck immediately. The idea is to heat up a small area quickly, with enough heat capacity to raise the temperature above melting point before the board copper sucks it away.

The 60/40 tin/lead solder should melt in with the existing solder to lower its melting point. It may take several goes to clean the hole out, getting easier as the original solder is replaced.

If that doesn't do it then you could try an ultra-low temperature solder such as Chip Quik SMDIN52SN48, which melts at 118 °C.

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