Lead-free solder

I made a surprisingly neat solder joint yesterday. Then I saw that it contained lead.

I try to use lead-free but I’m now assuming that it’s harder to work with?

Is there a policy or advise on solder types?

Also, is it worth applying flux paste before soldering?

As long as you don’t eat it, lead solder is much better for hand soldering than the lead-free stuff*. With solder paste and reflow it doesn’t matter that much. Flux paste is great for soldering small pitch SMD ICs - if you absolutely drown the pins in flux, and then drag the iron tip with some solder on it over them, you’re super unlikely to get many issues and with some things you can get it right first time. I wouldn’t use it for everything though, like there’s no need to use it for 0.1" pin headers.

*However I would like to see a long-term study of health problems in people who use lead solder versus lead-free, as well as whether the flux vapour from flux core solder wire carries any lead particulate matter


Thanks. I’m only doing basic large connections atm. Although your advice will probably help me later.

Regards lead poisoning, the fumes are dangerous eg. Mad as a hatter when hat makers got poisoned

And I believe there’s some evidence that even touching it can be dangerous. I think Calefornia has some of the strictest guidance with safety notices stating health impacts from direct contact.

Please can you elaborate?

The California cancer warnings are a bit infamous, because if you actually go there and see them in every starbucks claiming that coffee contains carcinogens, you’ll realise how ridiculous some of them are.

For solder paste and reflow, the idea is that you apply solder paste to your pads, tack the components on, and then throw everything into a reflow oven - and after ten or so minutes you have a near-perfectly soldered board. Only works for single-side SMD soldering though.

I think you’re thinking of mercury. The fumes are from flux and yeah they can be nasty if you have asthma or a predisposition to asthma-like conditions, but that’s why we have fans on the electronics bench. Touching lead solder is fine, just don’t solder and eat at the same time.

I think you’re right there.

Are there extraction fans? I’ll look today. Perhaps a prominent notice would be useful?

There are some desktop soldering extraction units @electrotechs where are they?

I haven’t been in for months.

Last time I saw fans they were mounted on the desk.

it’s on his way from china…

They used to pump lead into the air via internal combustion engines. (Now we just get the nitrogen oxides and the particulates.) A little leaded solder won’t do you any harm. :slight_smile:

Recently, I got a soldering course and we used flux for everything : trough hole, CMS, to solder, to desolder, to make a joint better. At first, we worked only with lead-free. Maybe flux is more useful when we use lead-free and for beginners like me but clearly, it helps a lot.

When we passed to lead, it made a big difference and I understand why people who use it for a long time are reluctant to use lead-free. But the issue is not only for health but also for environment. It is likely it will be completely forbidden, except for some sectors like aeronautics.
So I think to use free-lead before being too “attached” to lead.

However, they told us nothing about the toxicity of the flux fume. If it is toxic, it is not a good idea to use it for everything.

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Asbestos was known to be dangerous since Roman times. Yet it was used for almost everything including floor tiles. I’ve heard blue asbestos (the most dangerous kind) is still used in train brakes.

‘Safe disposal’ is simply double-bagging and landfill.

At school we used copious amounts of mdf even though the dust was toxic.

Any idiot should have known that plastics would persist in the environment and become microscopic particles to be ingested by various lifeforms.

Antibiotics kill healthy gut bacteria leading to allergies, immune system damage and mental illness.

I could go on but I think I’ve made the point.