[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 I do agree that the traditional style of iron with a separate heater cartridge and tip is obsolete.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.

[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.

[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.

[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?

[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.

[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.

[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.

[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.

[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?

[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.