[ghayes]

Curious if anyone has tips on lead-free soldering. I basically always see in online forums "just use lead," but never any tips on how to actually become capable on using lead-free solder. Esp. as my son is around a lot, it seems prudent to stay lead-free, even if you can generally handle lead safely. Thanks.

[throwup238]

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.

[jdietrich]

I don't want to start a holy war, but the JBC system with integrated cartridge tips is at least comparable to Metcal for high thermal mass joints and (IMO) superior for very fine SMD work. The JBC system has the advantage of allowing one-handed tip changes while the tip is still hot. It's also very affordable to get in the door, thanks to the proliferation of cheap Chinese stations that are fully compatible with JBC tips. I do agree that the traditional style of iron with a separate heater cartridge and tip is obsolete.

https://www.aliexpress.com/item/1005006568050453.html

[kevin_thibedeau]

The MX-500s have a design misfeature where power is constantly on internally. The switch only controls the output driver to the handpiece. Put these on a switched circuit for part time hobbyist use.

[opwieurposiu]

Metcal inductive irons are so much better then resistive, use one once and you will understand.

I pugged my Metcal into a power meter the other day. The instant you the tip touches copper, the power jumps from ~4W to ~40W. The power goes back down as soon as the solder melts.

If you can not find good deal on a Metcal, JBC irons are ok. Probably 80% as good soldering experience and often have a better (shorter) handpiece.

[Kirby64]

The same responsiveness happens with a JBC iron in my experience. Temp hardly overshoots, and you can punch all 120W into a ground plane if you get good enough contact (and have a large enough tip). I've used both Metcal irons and JBC irons, and I would agree with the other poster that JBC is the better overall package.

Key benefits:

* JBC tips are cheaper, and clones are widely available that are just as performant and even cheaper ($10/tip)

* JBC tips have adjustable temp; you can argue this isn't useful, but if you typically solder leaded but need to desolder something unleaded then this is a problem since you need to bump temp to desolder properly.

* You mentioned this already, but handpieces are shorter generally. In my opinion this makes a huge difference to soldering experience, especially as I get shakier in my older age.

[SequoiaHope]

I’d never used Metcal or JBC until recently. I’ve managed 15 plus years of SMT work with Hakko style irons. I recently got a new job, and the guy who manages our lab and does our soldering previously did soldering for military satellites for 20 years. He said he has something like thirty satellites in orbit.

When I asked for a soldering station I could use in the lab, I saw a lot of JBC machines around. I said “could I get a JBC?”. He said “oh the JBC is a Ferrari. I don’t think you need a Ferrari. I’ll get you a Metcal. That’s the Toyota of soldering irons.”

I can’t comment on exactly what he means, but he seems very experienced and has good things to say about JBC.

[opwieurposiu]

The JBC has adjustable temperature, which lets you solder faster if you crank it up. The risk is that you will cook either the board or the component you are attaching to the board. This decreases the reliability of the finished assembly, and it is not always visually obvious when you have cooked something. So it is like the gas pedal on a Ferrari, dangerous if you overdo it.

The Metcal does not have adjustable temperature, the temperature is set by the tips you choose. So it only has one "speed" and this reduces the risk of cooking the board.

Both Metcal and JBC are good, ultimately it turns into a sort of Vim vs. Emacs sort of thing, aka personal preference.

[sitharus]

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.

[zrobotics]

One thing I didn't see brought up in the sibling comments about vapor is that the real hazard of using leaded solder is small particles which can end up on clothing or your hands and later ingested. It is definitely a hazard to be aware of, you want to wash your hands after working with it and keep your workspace cleanliness in mind.

For hobby work, I've switched to lead-free simply because that's what 99% of the boards I work on we're originally soldered with, but I still have some leaded solder around. That being said, it can be used safely, I cast my own bullets which generates a far larger amount of lead particulate and my blood lead levels were not at all elevated when I had them checked 2 years ago. But since it bioacumulates, you do want to keep exposure in mind.

[sitharus]

Good point, I totally forgot that because cleaning my workbench and hand washing after work is just second nature to me now.

Metallic lead is dangerous if inhaled or ingested, but not a big concern for momentary contact with your skin as metal, especially given most modern solder is only 40% lead.

Your body will remove a small amount of lead, so hobby soldering is unlikely to cause long term problems.

[TheSpiceIsLife]

You can also take lipoic acid, methionine, and n-acetyl-cysteine, to help the body remove bioaccumulated heavy metals.

This is proven to work via hair-tissue mineral analysis before starting therapy, during, and after.

[BasilofBasiley]

I cannot imagine anyone soldering with SAC at 300ºC. Not even leaded solder with pre-heating as merely an option. But somehow those values crop up from time to time.

I'm not going to debate them though, I'll just dump my values, it might help someone.

My job involves soldering at least once a week from through-holes to SMDs(mostly), 1.6mm to 0.8mm pcb thickness, from 1206 smd to 0402 (imperial) sizes. From flimsy 0402 resistors to beefy 1cm² all metal casing inductors from hell.

To do all this I use a JBC soldering station with C245 and C210 tips. I also use a non-brand hot-air station for TSSOP ICs with exposed pad on the underside for heat transfer. Sometimes I use a hot-plate as well, and a reflow oven while we're at it.

On the JBC:

For leaded solder: 350ºC on both C245 and C210 tips. I do increase it to +/- 360ºC on occasion to solder near big stubborn ground planes on the pcb. Less than that is impossible without pre-heating because I can't afford to spend more than a few seconds on each soldering op, both because have other things to do and because I can't overheat components. Overheating is also dependent on the time you spend on each component. Might bump it up to 380ºC on those inductors and switch the tips to beefier ones like the chisels and the knives.

For unleaded SAC: 360ºC to 380ºC on those same tips, and I might bump it up to 400ºC again on those inductors.

On the hot-air station:

For leaded: 275ºC

For SAC: 282ºC

On the hotplate: 240ºC for both SAC and leaded. (Mostly repair work after pcbs come out of the oven.)

On the oven: It's a temperature curve and I only use leaded solder paste. Peak at 240ºC.

NOTE1: All the soldering wire I use is flux cored. I tend to use extra flux a lot (Chipquik SMD291), even if it's not really necessary. But on lead-free SAC it's always obligatory.

NOTE2: We don't have any fancy setup where I work and it's overall barely professional in my opinion. Pre-heating is not used much if at all so, I don't have any temperature values to share in that regard.

NOTE3: The SAC solder wire I use is Sn99Cu0,7Ag0,3 EVO11 from CYNEL. I like the brand but I feel the need to try other formulations for different use-cases so I can get away with using lower temperatures on specific temperature sensitive components. On leaded I don't feel that need at all.

[stavros]

I have my Pinecil set to 320 C and it works beautifully for leaded solder. I momentarily bump it up to 400 for big ground planes, but rarely.

[BasilofBasiley]

It's curious how you use such a big temperature range. I've never used a pinecil despite having friends telling me very good things about it, which picked my interest a bit.

Can you tell us what exactly do you solder at 320ºC and what is the exact type of solder you use and/or Pb and Sn percentages?

Also, is your pinecil calibrated? And which tips do you use at that temperature?

Anecdotally, what usually happens to me at lower temps is the tip and/or the solder wire sticking a bit while I'm soldering which I take as a sign that the liquid solder won't flow correctly and that I have to spend more time giving it heat from tip, than I should.

[stavros]

I use 63/37 solder with a flux core. The Pinecil is amazing, it holds heat really well and gets to 320 C in eight seconds. I didn't calibrate my tip in boiling water, and I don't remember which tip I use now, it's the one that comes by default (B2?).

I only bump it up to 400 C because that was the default, I never use it for more than two or three seconds so the temperature hasn't mattered much. I haven't noticed solder stick, it just sometimes fail to melt properly with large ground planes, so that's when I bump the heat.

[sitharus]

That is indeed a typo, it's supposed to be 400°C.

[oasisaimlessly]

You can (/ should) edit your original comment.

[sitharus]

It was too long since I’d posted and I couldn’t edit it, otherwise I would have.

[BasilofBasiley]

Got it. Cheers.

[TheBigSalad]

I've heard that the soldering temperatures aren't nearly enough to make the lead a gas and the fumes from the flux are what can kill you. I suppose the same advice applies in that case, but is that accurate?

[sitharus]

Yes that’s accurate for hobbyist work. There will be some lead vapour, but at the temperatures used for soldering we’re talking a few atoms. The flux is much more of a risk, and both are mitigated with proper fume extraction.

Lead does bioaccumulate so continual exposure to low levels is dangerous, but unless you’re soldering all day every day it’s not likely to be dangerous.

If you’re a factory and have multiple wave soldering baths operating it’s a different story.

[IgorPartola]

Lead has a boiling point of 1749 degrees C. That is at least 1200 degrees higher than your typical soldering temperature. If you use a propane torch you’ll almost touch that temp.

[sitharus]

Correct, but all materials have a vapour pressure so there will be a very small amount of lead vapour when soldering. Based on lead’s vapour pressure it’s in the range of a few atoms, I haven’t done the math though.

I mentioned it for completeness because someone else would if I didn’t.

[IgorPartola]

Quick math shows that vapor pressure of lead at 500 degrees C is 1/7,600,000 of an atmosphere. I don’t know how to calculate the rate of sublimation but this does seem pretty negligible.

[Aldipower]

Did you ever forgot a cup of water somewhere? It fumed away after 2 weeks! All without boiling it. :-O Same applies to lead, especially if you heat it to 360 C.

[IgorPartola]

I mean you can do an experiment: put a gram of lead onto a hotplate at 360C, then weigh it after 2 weeks. I would really love to see your results.

[hooli_gan]

Do you know how dangerous new vs old flux is? I'm using some old Канифоль from the USSR and get headaches while soldering. Fume extraction would probably be a good idea, but I solder no more than 4h a year

[sitharus]

It really depends on the flux, even modern fluxes have a range of toxicity. The only way to know is to check the MSDS.

I use Канифоль/rosin flux as well and use a fume extractor. Rosin flux is the most common for flux-cored solder in my experience.

But a few times a year is unlikely to be an issue, soldering health effects are in people who do it for work.

[IgorPartola]

There is a technique where you breathe out as you solder. No idea if канифоль is toxic or not but honestly if it gives you headaches why not try another type? Or wear a respirator?

[hooli_gan]

The answer is laziness

[jdietrich]

Most electronics fluxes aren't particularly toxic, but rosin is a sensitiser - repeated exposure will cause an increasingly severe allergic reaction. Working in a well-ventilated room is probably fine if you only solder occasionally, but anyone who is soldering regularly should be using a good fume extraction system.

https://www.hse.gov.uk/pubns/indg249.pdf

[moffkalast]

Yeah I've found that SAC solder typically doesn't contain nearly enough flux to get the job done (just 2% at most, seriously?!). Small joints like really tiny wires work great at something like 370C so I can just touch it for a split second and it's instantly done, for anything else it's dripping into flux paste time and it works almost as good as leaded used to. Would've been easier to streamline the process if the rosin core was like 10% or 15% instead.

Not all types of flux work well though, my local store sells something that has no labels but seems to be very aggressive and works exceptionally well, the more common no clean types don't do anything at all.

Tips are definitely eaten a lot faster than leaded, but it's not exactly a huge expense when they're like a dollar or two for a 10 pack on aliexpress.

[MarkMarine]

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.

[ahartmetz]

Lead-free solder will have a dull surface even on a good joint though, no? IMO worth mentioning. Not grainy or with visible "fault lines", but dull.

[MarkMarine]

yes, dull, but not rough or grainy that is exactly correct. It should be uniform, no grains or chunks, no crystal structure, no boundaries but smooth.

[Hackbraten]

> Turn your iron up (I use 675)

I felt a little puzzled about this but then it hit me that you probably meant Fahrenheit.

To spare others the conversion: 675 °F is roughly equal to 350 °C.

[andrelaszlo]

I solder very rarely and quite badly, but switching to non-lead solder just made it impossible to get good joints. I had to get a better iron, nothing fancy but with higher effect, meaning I can get to a higher temperature faster without turning the whole PCB into mush.

[ryandamm]

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.

[breckenedge]

Ditto. I switched to lead-free for custom keyboards and it didn’t seem too terrible, just had to dial in the temperature more closely to avoid damaging components.

[serviceberry]

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.

[jeffbee]

The government did not meddle with the hobby, though. You, hobbyist, can acquire and use as much lead as you want. You can order an 4kg bar of 60/40 lead solder on the internet right now. That's enough lead to measurably lower the IQ of 15 million children, if optimally applied. Nobody will stop you.

[lazide]

The hard part is holding them down while you apply it. They squirm like crazy!

Also, you can buy pure lead in 1000 lb quantities (and leaded solder) at places like [https://www.rotometals.com/] with no paperwork.

[giantg2]

I will say, you need to use high quality lead-free solder when you could get away with decent lead solder. The cheaper lead-free stuff has been junk in my experience.

[marcus0x62]

Do you have any recommendations? I was soldering earlier today and noticed a particular joint wasn’t flowing well at all. I looked over and had grabbed the lead-free solder from my spool holder. All the other joints with my crappy Radio Shack leaded solder were fine.

[Ccecil]

With lead free use SAC305 with "no clean" flux (I prefer the name "low solids"...since you still need to clean it).

For leaded Kester44 is my favorite.

Set the iron temp to the datasheet of the solder...then never touch it.

For larger pads use larger tips...a lot of people get into trouble cranking things out of range.

[giantg2]

I don't. I have a roll of lead-free that works OK, but I got it so long ago that I don't know. I think it's an off-brand that doesn't even have a name on it, or the sticker peeled off. It's still more temperature sensitive than lead, but not bad. I think my better quality lead roll is from them too. I wish I knew the name so I could order more of each.

On a related note, I've had terrible luck with any of the Chinese solders off of places like Temu or Banggood. Even the lead ones were junky.

[syntheticgate]

I'll second the Kester recommendation, the stuff is a bit expensive but if you've used bad solder you know it's worth it! I'm using Kester 275 on the bench and have been very happy with it, and as it's a true no-clean flux, it's a bit less messy than Kester 44 without much performance difference (lead free vs lead differences are real still- Lead-free is still not as easy to work with, but the world went lead free so my bench did too). You can find some comparisons here (since kester's website is down currently for some reason) https://www.jameco.com/Jameco/Products/ProdDS/2188246.pdf

[photon_rancher]

Chipquik works fine. There’s probably better stuff but it is consistently good and doesn’t seem to go bad (i can’t tell much performance stuff between a roll that’s old enough to have the label rubbed off and a brand new one).

[photon_rancher]

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

[indrora]

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.

[Taniwha]

Yeah, I teach kids how to solder, we use unleaded solder, but always insist they wash their hands after

[jwr]

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.

[giantg2]

I agree. The rosin/flux comprises the majority of the fumes. It's still a good idea to have ventilation.

I have a setup in my garage with a vent fan connected to a dryer vent and a rubber flexible hose I can put near the solder station. I also hook it up to my 3D printer enclosure if I'm doing ABS.

[phaer]

> 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.

I am unlikely to every try this, but curious: Why is that, what would happen?

[jwr]

It results in unreliable joints that will cause problems over time.

[Kirby64]

Source? If you’re doing board repairs and adequately clean the previous components then I see little reason why adding leaded solder to the very small amount of remaining lead free solder would be a problem. If you have a full lead free joint and then add a bit of leaded solder, sure… but how many people are doing board repairs like that?

[mystified5016]

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.

[rcxdude]

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)

[IgorPartola]

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.

[randunel]

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.

[userbinator]

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.

[lrasinen]

I'm a fan of the SnCuNiGe alloys. I've got a roll of Felder Sn100Ni+ and the feel is quite close to lead tin. Of course you need more heat, I've found 340 °C best on my iron.

[amavect]

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.