Think You Know Everything About Soldering?

[Joshua] has frequent discussions about his soldering techniques with viewers of his YouTube channel. He finally decided to interview [Randy Rubinstein] who is the president of SRA Soldering. In nearly an hour, they talk about everything from solder alloys to proper temperature. They also talk about lead exposure, flux cleaning, and lead-free solder.

They also talk about strategies for rework with lead-free and using special solder for removing SMD components. Honestly, although the first frame of the video says “your solder sucks,” we didn’t really find any earth-shattering revelations about something everyone’s doing wrong. We did, however, find a lot of good advice and some interesting details about things like the uses for different solder alloys.

The interview focuses on soldering with a contact iron, although hot air is seeing more use among hobbyists. However, using a regular iron is still a basic and necessary skill, even if you won’t use it for every job if you have hot air or a reflow oven.

If you really want a soldering tutorial, the Pace one is an oldie but a goodie. We’ve also talked about soldering metallurgy before, if you want to learn more about it.

50 thoughts on “Think You Know Everything About Soldering?

    1. Only if the IPC would offer a degree in soldering. They don’t do the normal bachelor and masters degrees in soldering, but they do offer courses for professionals that are sometimes a requirement for jobs where quality is key (i.e. medical, military, space, automotive,…).
      There is even a hand soldering competition, if you want to show off your skills. And your work will be judged by IPC-A-610 Master Instructors. :-p

        1. For me it’s less about adjustment and more about watts. Having an iron that pulls more watts allows it to respond and maintain the set temp when soldering heatsinking objects that would be impossible with a battery powered iron.

          1. But a nonregulated iron won’t generally have enough power to do difficult jobs without running way too hot when it’s idle or soldering small stuff.
            That leads to really fast tip erosion, and oxidation that can make it difficult to keep the tip tinned well.

          2. @Nick: So it’s less about adjustment, but about regulation. I also rarely deviate from the usual 350 to 360°C but I like to have something like 70 to 80W at hand that deliver the heat immediately when necessary. My AOYUE SMD station and the TS-100 (with >20V) are really good at this.

          3. Yeah. At first I thought you were saying it’s more important to have lots of watts than having a thermostat. (Big 70W weller fire-sticks meant for stained glass, etc)

            Generally, the better regulated an iron is, and the closer the temperature sensing is to the tip, the less you will need to adjust it to get that extra power. It’s not actually running any more power, it just prevents it from creating a thermal gradient from the point where the thermistor/thermocouple is to the tip. (this is why really thin and pointy tips are bad, too)

            As Martin says, high wattage with good regulation means that you rarely need to turn up the temperature. That’s not to say that it’s not a reasonable thing to do when needed, but I wouldn’t say the adjustability is as important as the thermostat.

            For a few examples. I have a cheap 70W thermostat controlled iron. It works pretty well in general. Responds quickly, and regulates well. It does have a tiny bit of lag, though, so if I need to solder something demanding, I will get a gradient, and need to turn it up to 400 or more from the usual 350.
            I have an AOYUE lead-free station with cartridge tips that regulate much more quickly. With that, playing with the temperature is rarely needed, and if I do, I’ll usually just turn it up 20deg or so.
            With my Metcal, the regulation is very fast, so there’s no need to adjust it, which is good because you can’t (other than using other tips)

            All that said, for most purposes, the $20 iron is fine.

      1. Within reason, sure, you can solder a bit quicker with a hotter iron, but you’re going to eat tips like mad.

        Seeing as you can pick up a 60W pencil iron with a thermostat on it for $20 or so, there’s no reason to put up with crappy tools.

    1. Or you just get a “real” soldering iron known as a Metcal and you let it do the thinking for you… need to do lead free and high temps? Just swap in a lead-free tip…
      Adjustable irons are slightly better than plugging an iron directly into the wall…

        1. Look at me with my fancy soldering iron…

          A reasonable iron with a thermostat is just fine. For most things there’s not a lot of difference.
          Yes, there are some awful ones out there, too, but you don’t have to spend a lot to get a pretty decent iron.

          1. That first line was me mocking the gear snobbery, in case that wasn’t obvious. :P
            I have a Metcal, and I agree that it’s really nice, but it’s not worth it for most people. It’s certainly not “awful” using something else.
            Also, I will say that there have been a few times I wished I could adjust the temperature by increments of less than 55C.
            For general use, I definitely prefer it, but I don’t think there’s many things I could do with it that I couldn’t do as well with my $20 one.

  1. I’ve worked a few days in an electronics company and has been invaluable for learning techniques and tools and how to use them properly. It was for repairing very expensive hardware so quality was everything there.
    Can you imagine cleaning power supplies with a bacteria solution, then drying in a 70 degrees oven? Using x-rays to check bga resoldered joints? Using IR thermometers to increase the PCB temperature gradually to avoid warping. I really liked the way a pre-heater makes soldering with lower temperatures much easier using either a hot air or normal soldering iron preferably with a well type tip. Of course most of this isn’t within reach for most hobbyist or hacker but a hot air iron and pre-heater certainly is.
    Or something as simple as that gel type flux, really makes many soldering or desoldering jobs a lot better and easier.
    If you ever get the chance to sit with a very skilled engineer I highly recommend to take the opportunity. I’ve learned a lot in very little time.

  2. This guy’s out to lunch. He’s pulling numbers out of his butt. It’s not even F vs C here.

    I use 350C for lead, 370C or so for lead free. Works well, and not hot enough to fry your tips.

    Lead free’s fine, too, it just oxidizes quickly and doesn’t flow as well so it takes a little bit more practice.

    The part about oxides blocking heat is wrong, both in his welding example, and for soldering. They simply prevent wetting. You can have the joint hot enough to join, but if it’s badly oxidized the melted solder will just sit on top instead of wetting.

    1. Whenever lead free comes up, I like to point out that there’s a massive difference between different lead free solders. The most common stuff (because it’s cheapest) is 99% or 100% tin, which is absolute garbage. I’ve used SAC305 forever (96.5% tin, 3% silver, 0.5% copper), which is MASSIVELY better. There are supposedly newer formulations that perform even better, but really I just stick with what’s easily available and likely to be supported by nearby assembly houses if/when stuff gets offloaded to them.

      I tend to run my Weller iron at 710 degF / 376 degC.

      I also don’t wipe my tips on a wet sponge. I wash my tips in fresh solder… at a rate that effectively wastes about 50-75% of my solder. My tips last about 800 hours maybe this way… but then the solder costs more, so maybe it’s not for everyone. I prefer this way. If the soldering iron sits more than 3 minutes, it gets re-washed in solder or turned off.

      1. You’re right on all accounts, I should have been more specific about the alloy.
        I also quit using the sponges.I’ve found that those cheap brass coil balls do a good job of removing excess solder and some burnt flux or other debris. When that’s not enough, I’ll usually just flood the tip with a bit of solder and flick it off when the crud floats loose on the solder drop.
        If it’s really stubborn, a dry paper towel will do a decent job of removing stuck-on junk. It’ll usually leave some paper fibres, but they can easily be removed by going back to flood and flick.
        Since I’ve been doing it that way my tips seem to last for ages. I used to go through them pretty quick when I was thermally shocking them all the time with the sponge.

        flooding off the bad solder after it sits is especially important with the lead free solder, since it tends to oxidize and get gummy quite quickly compared to leaded.

      2. The assembly houses of course take what they are used to. When I do manual repair, modifications or patches than I only use tin/lead solder.
        For wiping the tip I recommend this brass “sponges” made out of brass turnings. The don’t harm the surface and don’t introduce shock cooling of the tip.

        1. +1 I have been using brass sponges for the last 5 years or so and my tips last forever. I just jab the sponge a few times as needed. I don’t need to flood tips or flux them or any of that. I use a Kestor flux pen now and that is the only flux the tip ever is exposed to. I run at about 420 and work quickly.

      1. Sure. He just attributed it to the wrong factor, and the solder expert didn’t correct him.

        I’ve done a bit of aluminum tig welding too, and I can tell you that aluminum definitely will melt through the oxides. They just prevent a puddle from forming, instead the metal just falls away in an ugly blob.

  3. Also, way too click bait. Both on HAD’s title, and the video’s.

    I don’t know “everything about soldering”, but I know a lot more than these guys, and my solder certainly doesn’t suck.

      1. I’m just a fairly experienced tinkerer and haven’t had any formal training on the subject. I think I just get cranky when I see videos with a title like “your solder sucks” and then I watch the whole thing, notice some errors, and don’t learn anything new. Cracks about “They want to sell you more tips”, while saying they should be using temperatures well below the melting point of solder, And bonus points for the bit at the end talking about bad solder from china, followed immediately by shilling cheap soldering irons from china.

        I just now published some some videos I made a couple of years ago when I was thinking of selling a surface mount amp kit. It’s not all “proper”, as I’m doing some kind of hacky things to solder parts that are only meant to be reflowed, but maybe it’s useful? I did at least film the soldering, even if my choice of PCB mask wasn’t the most photogenic.

        I don’t think I’ll likely get around to ever selling the things, so I way as well post it, right?

  4. I’m not going to wade through some random video in hopes of them telling me something usable. Type the shit out here on HaD and skip the “BE SURE TO LIKE MY VIDEO” BS. I’ve been doing through-hole with Weller, Hakko and Metcal for decades and they would have to offer more than a sub $100 Chinese iron to get me to click on that.

    1. Of course my AOYUE soldering station sucks and it does it quite well, it’s desoldering gun is supposed to do that. And the soldering iron is also really good, fast and powerful. The JBCs in the lab in the office look more modern, but they are also much more expensive.

  5. chip-quik has some interesting solder in their line now. Not just for desoldering jobs, but paste that you mix yourself, saving your shelf life by a couple of years. I know people that will swear that its ok to use it chunky or attempt thining it – but it will eventually dry out on you. When you’re doing more advance boards with big BGA stencils, having paste on hand you simply mix when its time to solder is a nice selling point. keeping it cold will extend it even longer, like any other pre-mixed paste.
    I haven’t tried it yet, but I plan on giving it a go the next oven baked board I do.

    1. It took me awhile to figure out that you need to use flux with solder wick. Allegedly some has flux built in, but I’ve never seen it. Just place the wick on the joint, 1/4 to 3/8 inch from the end of the wick. Apply iron to the wick, and drag the wick through the melt puddle.

      1. I’ve had mixed luck, even with the stuff that’s supposed to have flux. Some of it needs more added, and I’ve had some that just doesn’t seem to work, no matter what I do. I’m guessing it just gets too oxidized. Chances are it had been sitting on the shelf for years before I bought it.

      2. Terrible stuff. Unless you run a flux pen down the leading inch before you use it. Then it works great and is easy to use. Push the end of the wick into the joint with the tip of your iron.

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