Soldering the Tek way

Just use Metcal fixed induction soldering irons. I just saw a power supply for an MX-500 for $100 on eBay and there is the hobbyist level PS-900 on sale new for under $300 on Amazon right now (which works just as well but might not last 30 years like an MX-500). Thermaltronics was started by some Metcal engineers after their patents expired so they’re a cheaper source of tips but I haven’t looked at their power supplies recently.

Unlike wellers and other soldering irons they don’t use a PID loop. They exploit the curry effect of the alloys their tips are made of and pump 2.6 MHz RF into the handle which keeps the tip heated the entire time with zero delay, even when contacting huge copper pours. The downside is that you have to change the (expensive) tips to change the temperature, but the upside is that it’s capable of delivering much more heat. Since the iron is capable of heating so fast, temperature control doesn’t really matter because it can melt the solder long before damaging nearby chips.

If you’re not using a solder oven, that’s the best option. It’s expensive but it’ll make a night and day difference to your soldering work. I’ve got a Metcal that’s almost 25 years old that still runs like a champ, is compatible with tips sold by Metcal and Thermaltronics, heats better than any soldering iron I’ve used since, and is easily repairable if it breaks.

Leaded solder is not a big health risk for hobbyists as long as you have proper fume extraction. Metallic lead is poorly absorbed through the skin (it _is_ absorbed from what I can find, but very very slowly), the major risk is from lead vapour and at normal soldering temperatures that’s very minimal.

However, lead free tin-silver-copper (SAC) solder is fairly easy to work with. You need a hotter soldering iron at around 300°C, and if soldering PCBs preheating the board to 80-100°C may be needed for good results. It may also take a bit longer for the solder to propagate flow and wet, since the surface needs to be hotter.

If you’re using additional flux or non-fluxed solder you’ll need to check it for compatibility, that should be on the data sheet. Most fluxes are fine, but I’ve seen a couple that say not to use with some lead free solder formulations.

The main downside to SAC lead free solder is the higher temperature required which can overheat some components, particularly capacitors and ICs in my experience. It’s a case of being careful to keep the heat duration as short as possible.

Personally I went back to lead solder and manage my exposure with ventilation and HEPA filters.

Depends on the components. You need to get enough heat into the joint that both sides are hot (pad and component) but not enough that you burn up a sensitive part. The hack people use, wetting the joint with solder by touching it to the iron can lead to a cold joint. Don’t do that.

Turn your iron up (I use 675) and ensure you’re touching the pad first, it’s a much larger heat sync. Lean the tip of the iron up to the component leg, give it a second and then feed solder into the other side of the leg, letting the leg of the component melt the solder and flood the joint. I use flux if I’m really worried about the joint, the fluid transfers heat better. There should be a clear fillet arcing between the pad and leg of the component, solder should be wet 100% around the pad and gracefully blend into the component leg. The joint should not look sandy or dirty or have bad surface finish.

1) board preheat. In a pinch, heat gun or old hairdryer. But ideally get a cheap ceramic one off amazon or something. Typically set it to 75C for delicate components. For sturdy boards i start there and if that still sucks you can usually go up to ~150C. Usually its the heating element or air temp not the board temp.

2) Flux and thin solder. Solder should contain flux too. Use solder paste whenever possible and keep it refrigerated when not in use as it dries out

3) you need a high wattage iron and usually a thicker tip with more heat capacity. A slightly higher temp helps a little, but the wattage helps it stay a consistent temperature from the start to end of the joint.

4) when designing boards use ENIG and not HASL

5) remove any old solder before attempting to add more to a joint (older than a day or two).

6) sometimes an air gun on a arm helps too on thick copper

7) get really good lighting with a mix of diffise and directional sources. Brighter than you’d think

I'm hardly an expert, but when I switched to lead-free solder (for the same reason, had a young kid around), the only change that helped me was soldering at a significantly higher temperature. The lead free stuff still doesn't behave quite as well as the leaded stuff -- hey, lead is useful! -- but I do feel a lot better about my garage. Though I did backslide when I had a project that required about 500 manual solder connections; after a few days of frustration I guiltily went back to lead, briefly.

It's really OK. With modern formulations such as SAC305 and with temperature-controlled stations, there's no real difference, and no need to stick to lead.

I think the resistance to the idea has two roots. First, there's a lot of old-timers who just didn't like the idea of the government meddling with their hobby, so they go out of their way to convince others to use leaded solder.

Second, the first years of the switch were painful. You needed to upgrade some equipment, the early alloys were not performing great, there were problems with tin whiskers (which aren't specific to lead-free soldering, but were apparently happening more commonly), etc. But these days are gone. The industry has moved on.

As a child who was taught how to solder (Thanks Dad!) I can say this: making the practice of post-solder handwashing just A Thing does a lot to impart good practice.

if you're super paranoid, D-Lead hand soap is a fantastic product: https://esca-tech.com/product/d-lead-hand-soap/ -- I use it post-shooting to wash my hands of lead and residues from firearms.

Use a higher temperature and plenty of flux (I like flux pens), and you'll be fine.

Leaded isn't actually a significant health risk for you, so you might as well go with that. It's not like you are going to breathe in lead. It's a problem for the environment in general, and you do not want to consume it, but it isn't that unsafe. A bigger problem is that you should never use leaded solder to repair boards that have been soldered with lead-free, which means pretty much every board out there that has been manufactured in the last 20-30 years or so.

The higher temperature is the main source of difficulty: it can be harder to heat up a joint to the right temperature without overheating the iron tip or the components. So it's mainly a case of getting good thermal contact between the iron and the joint, and having a powerful enough iron and the right size tip.

(One trick that can be very helpful is pre-heating: e.g. placing a board on a hot-plate at ~150C or so, or using a hot air gun to do the same. This means the iron doesn't need to heat a much. But of course this makes placing and holding the components more difficult)

I use lead free solder and haven’t had issues though admittedly I have been soldering as an amateur for decades. You want flux and higher temperature. That’s about the only adjustments. It goes without saying that you should use clean tips and a quality iron.

Don't equate solder to (liquid) metal touching other metal. Soldering is a chemical reaction between metals, and it needs a pretty high temperature for that to occur. The solder simply touching the other metals isn't enough, those are commonly called cold joints, because the chemical reaction didn't happen, only the mechanical melting and freezing did.

Don't forget that many of us grew up in an era when leaded gasoline was widely used, and if anything the population today does not seem any smarter, so whatever effects leaded solder has is going to be miniscule in comparison.

I suggest practicing on perfboards, TH and SMT. Chipquik has boards for about $2 each. Compare different solders (SAC305, K100LD, SN100C), temperatures, pad sizes, fluxes, etc.

I say this as someone who has been soldering their entire life, but lead-free is fine. The differences between leaded and lead free are minimal these days.

The best way I can describe lead-free solder is like using some old and really crappy leaded solder. It can get kinda gummy and ugly, but usually only when you touch a joint for the tenth time.

The way to make lead free solder flow and work like leaded is simple: flux. Flux pens are alright, but your world will be forever changed by gel flux in a syringe. Clean up with rubbing alcohol and a toothbrush or paper towel.

Modern solder alloys are pretty good. Just don't buy the cheapest thing you can find. Always, always get your solder from a good manufacturer like MG chemicals. Also buy fluxed (not no-clean) solder wick from those guys.

I used to be in the "just use lead" camp, but there's really no benefit. I've been exposed to far more than enough lead in my career. Lead-free is totally fine.

Some people fret about solder whiskers, but I'm unconvinced that this is a real problem worth discussing. It seems to be myth more than a practical problem that anyone but NASA should care about.

Just use good lead-free. It's only trivially worse than leaded. It's fine.

The first time I've heard of vacuum desoldering, so simple and yet looks like magic compared to struggling with wicks. I have gotta get myself one of those spring loaded plunger things.

Keeping a thin layer of solder on the tip when shutting down helps keep the tip from oxidizing, especially if you solder infrequently.

It's more likely that your iron is under powered for your application, and frankly a copper tip will likely make the problem even worse. There are three dimensions that impact heat transfer (temperature being equal): Thermal mass of the tip, thermal conductivity of the tip, and power transfer to the tip.

If your iron cannot support a regular tip, it's likely that it cannot get enough power to the tip to sustain the heat being pulled from it (copper will just expedite this). You can try a beefier tip (or load up a tip with wet solder which can kinda give the same effect) or you can get a higher power iron.

I've been soldering for 15 years with all manner of irons, I've never needed a copper tip, but I often need more than your standard hakko or weller. 400C on a the hakko is not at all close to being equal to 400C on a Metcal for instance.

My best guess is that your soldering iron is running too hot, or that you're using the wrong kind of solder. It's generally not an issue.

You probably have a shitty soldering iron which can’t deliver heat consistently. Try grabbing a used Metcal PS900 or MX500 on eBay. I have done zero maintenance or tinning on either of mine. They just work. I do SMD and TH stuff and rework no problems at all.

Literally everyone who gets one goes “oh so that’s what soldering is supposed to be like”

Also might be crap solder. Get some decent Felder or Multicore stuff. Leaded is easier to work with and harmless if you wash your hands and don’t lick your PCBs. Silver bearing leaded from Felder is what I tend to use. But it’s about $70 a roll

Edit: I see that you have a Hakko. Buy genuine tips. Or replace it with a different iron. The cheaper Hakkos are terrible.

Sodder is the common American pronunciation, most of the rest of the world says solder.

Interesting. My experience is the opposite. Sodder, soddering is the norm. Every lab, every tech at every company has said it that way. I'm from the west coast USA if thats relevant. If I ever heard someone say "sold-er" I probably dismissed it as someone who only ever read the word, and was sounding it out phonetically.

Use a fume hood or extractor and really learn how to solder properly. It sounds like you are either running your iron too hot and/or you are trying to melt your solder on the iron and pass it to the joint. The pros use a TON of flux because it practically solves the oxidization issue and helps a lot with spreading the heat to where you want it to go. Half of your temperature issues can be solved by either preheating your boards or spot heating with a hot air rework tool.

Soldering makes a metal-metal connection, with the flux ensuring oxides are removed. This makes a very low resistance connection, mechanically it’s very strong, and it’s easy to automate. As a bonus it’s also very easy to undo.

Other technologies like glues and crimping have their uses but are less reliable, higher resistance, or difficult to automate.

This may change but there’s little demand. Glues have lower conductivity and are harder to remove, mechanical connectors are bulky and not as strong.

You could do wire wrapping like nasa still does; there will definitely be a high quality tutorial somewhere. Or if building a squashed bug circuit you could use crimps (with or w/o the insulator to be pretty)

But besides breadboards you're kinda stuck with facilitating a clean soldering setup, which is fairly easy - if you're really worried build a gloved-box. I just wear a respirator and open a window

Technically I think there are conductive glues, but they aren't right for everything.