A personal anecdote: I am pretty sure that lead-free solder gets a lot of hate for two reasons.
First, lots of us learned how to solder with leaded solder. That’s what my dad had in his workshop and that’s what I learned to solder on, and what I continued to use pretty much until I moved out of my parents’ house. My dad had a big box of solder rolls. He still has a few (I kept one because nostalgia is one hell of a drug but I hardly use it anymore – and when I do, it’s still pretty because its smell is a fantastic mixture of childhood and lead poisoning).
It took me a while to adjust to lead-free solder. For a few days I did nothing bot solder components at random, and it was a few weeks before I could solder things well again. But based on my experience teaching interns how to solder, I’d say there’s hardly any difference in difficulty. They pick it up as quickly as I picked it up from my dad.
Second: lots of RoHS (and lead-free solder) hate trickled down from management back when RoHS hit. Even with all the exemptions and temporary suspensions and advanced warnings and debates and whatnot, RoHS still put a dent in some pockets, and there was a lot of backroom PR being fought about it. Honestly, why people who are exposed to leaded-solder fumes would back it up is beyond me – I certainly liked leaded solder better than lead-free solder but I like being healthy even more than that! – but backroom PR works in strange ways.
I suspect that it is also partly due to a lot of the early lead-free solder either being really terrible or at least not behaving in the way engineers were used to. I had (I think) 6 replacements for the logic board of my 2003 PowerBook because the SO-DIMM sockets kept detaching from the board when the machine got warm. This was apparently a known fault… caused by the manufacturer’s move to lead-free solder with a lower softening point than the board designers were expecting. They had enough thermal conductivity and cooling to keep the solder below its design tolerances, but then those tolerances changed. Those replacements probably cost someone (maybe Apple, maybe the manufacturer) more than the profit on the machine. I can imagine that kind of experience prejudicing people against lead-free solder.
Honestly, saying this is like saying “drinking bleach is better than drinking bleach with arsenic mixed into it.”
The healthiness of solder should not be a concern. It shouldn’t be entering your body at all! These are laboratory-grade materials. You wouldn’t eat a sandwich immediately after handing dangerous chemicals in a chemistry lab, would you? At least I hope not.
You should be practicing proper lab safety with these materials, like any other for goodness sake.
The healthiness of solder should be a non-issue if people actually took proper precautions. Unfortunately, the widespread adoption of the hobby made possible by cheap electronics kits, easy programming, etc. has made folks ignorant to the proper safety precautions that must be taken when handling these materials.
From a friend who solders a lot:
Yes, this. Leaded solders are fine (and often preferred) if you use proper safety precautions like fume extractors. The three most valuable things that people don’t use enough when soldering are:
Oh, and you should also consider setting up a good fume extractor.
Any refs from your friend on a fume extractor?
Brand isn’t super important as long as it does the job. I mean, unless you’re handling something ridiculous like plutonium dust (but then you’d probably be the kind to give advice, not take it). If you know what you’re doing, even a makeshift one can work. Just make sure it has decent fans and filters (0.1 microns to be extra safe). You can replace the filters if they’re old/shitty. After all, a fume extractor is basically a fan, tube, and filter.
A mask can complement this, especially if there are some shortcomings in you ventilation setup.
I’ve written a bit of a response to this now, Lab Safety.
I’ve read somewhere that leaded solder is still preferred in space and medical products. Does anybody here work in these industries and can tell more that?
Not sure about the space industry, but in the case of the medical industry: yep, albeit it’s not really for technical reasons most of the time. When RoHS was adopted, a number of exemptions were granted, and among these exemptions are several exemptions related to the use of leaded solder in medical devices. They don’t apply to all medical devices but the exemption is pretty broad (I think it applies to all in-vitro diagnostic devices, for example).
In most cases there isn’t any major technical reason why you couldn’t use lead-free solder (or at least I know of companies that have moved to a fully RoHS-compliant line, including lead-free solder). However, the exemption is useful because it means you don’t need to re-assess and change your supply chain and manufacturing line. This is sort of a big deal because a lot of medical devices are long-lived products. It’s not uncommon for a device to be manufactured for 10-15 years, and supported for 15-20 years. Also, many of them aren’t sold in great numbers. I’ve worked on devices that saw sales volume of 5-6 per year, and that was pretty good. (Edit, to clarify: the exemption is very useful because it means you don’t have to change the established – and well-tested – manufacturing process of a device. What most companies did was that when product X reached its end of life, they designed it successor to be RoHS-compliant, including lead-free soldering where feasible. But it’s not a rule, I think at least one company I worked with actually changed its manufacturing process and revised an existing product).
This exemption was supposed to be temporary and short-lived but it got extended. I think it’s supposed to go away in the 2020s (but take it with a grain of salt – I’ve not been really involved in the manufacturing side for about four years now so I haven’t really kept a close eye).
Most devices that don’t really fit that description, like simple thermometers which you can find in drugstores, tend to use lead-free solder.by now. Their manufacturers really don’t have a reason to stick to leaded solder anymore – they are effectively “consumer” devices, and the supply and manufacturing lines are pretty much lead-free-first in this line of work.
I very appreciate you describing your professional experience! This is much better than my hearsay comment.
Your hearsay comment is spot on! You were right on the “what”, I just elaborated on the “why” :-D.
I have heard that aviation prefers through hole pcbs versus surface mount.
Yes, this! Anecdotally most of the people I know who “hate lead-free solder” bought some of the more janky formulations that were common on the market over a decade ago, and (understandably) never tried again.
SAC305 (the Sn96.5Ag03Cu.5 formulation that the post mentions for both solder wire and paste) is pretty good, if you haven’t tried it then I reckon it’s worth a shot.
The only downside to switching is that it’s better to go all-in, mixing leaded & unleaded tends to mess up iron tips and joints with both solders mixed can become faulty (although I’ve reworked a bunch of not-really-important leaded solder boards with SAC305 and they’re all OK so far.)