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I’ve found one topic on this forum about this but it doesn’t answer my question fully.

From the information I’ve gathered, you should wash your hands after touching lead, even if it’s a cooled-down joint.

I make a keyboard, it doesn’t have a fully closed case, you can’t touch lead directly, but it has holes and it is open to air. Lead is kind of there and I want to take this keyboard with me everywhere. It will be in my backpack, on a train, etc., and of course it will shake and bump and all sorts of stuff.

My question is, how solid are lead joints? If the lead is not enclosed, does it pose any risk?

ocrdu
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JFJGDX8372
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    You should wash your hands after touching leaded solder. Is this keyboard designed in such a way that you can touch the soldering in normal use? Or just open to the air but not touchable? – user1850479 Dec 18 '22 at 14:39
  • Always a good idea to wash your hands after touching anything that you wouldn't want to ingest, such as solder. That being said, I am not particularly afraid of getting lead poisoning simply by touching solder. Absorption through the skin is, AFAIK negligible, but someone may have hard data on that. I don't. – Math Keeps Me Busy Dec 18 '22 at 15:08
  • @user1850479 you can’t touch lead directly, all joints are inside a case, but it has holes and yes - it’s open to air – JFJGDX8372 Dec 18 '22 at 15:38
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    @JFJGDX8372 You could paint over the lead. The usual sort of thing to use would be "conformal coating" - it will have the advantage of preventing corrosion too, although it might not be such a good idea if it can get into the switch mechanisms. Or you could use lead-free solder. Note that the fumes from the flux are bad for you regardless of the solder type, and you definitely want to wash flux off your hands. – Andrew Morton Dec 18 '22 at 15:58
  • I’m aware of flux fumes, thank you for your care. Would lead free solder be safe to touch after cooling down? Or touching flux is also dangerous? I’ve read about flux and it doesn’t give you neurological damage, but respiratory system problems – JFJGDX8372 Dec 18 '22 at 16:26
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    I don't understand why you need to ask this. If you make a keyboard, and worry about the lead, then why can't you simply use unleaded solder? It has been in common use for about 20 years now. Many places won't even sell solder with lead. You can manufacture your keyboard so that you get it soldered and flux washed off. – Justme Dec 18 '22 at 16:26
  • I’m handwiring switches. It’s not a commercial project and I don’t use a manufacturer. Does flux need to be washed off? By flux I mean the core inside solder. I will order a non-lead solder. Poland allows leaded solders and it’s difficult to find a non leaded one. I will order it online though. – JFJGDX8372 Dec 18 '22 at 16:30
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    It's usually harder to buy leaded solder in Europe since the EU restricts the use of leaded solders. I'm sure you can buy lead free almost anywhere that sells solder. Since you're concerned about lead and don't seem to have a reason to use it over lead free, I would switch to lead free. – user1850479 Dec 18 '22 at 16:44
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    @JFJGDX8372 I'm confused. Your question asks whether you can touch lead, your comment says the lead is safely in a box. So, what's the problem then? – Marcus Müller Dec 18 '22 at 18:09
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    Does this answer your question? What type of solder is safest for home (hobbyist) use? – Lundin Dec 19 '22 at 09:21
  • This has been debated over and over like in the linked duplicate. The conclusion is always that flux (vapor) is what's most harmful. Whereas lead is one of the heaviest matters there is and it won't magically make it inside your body unless you actively digest it (don't eat solder, don't lick on your PCB... and indeed wash your hands after soldering). Additionally, all commercial electronic products use lead-free solder since some 15 years back. – Lundin Dec 19 '22 at 09:23
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    "Poland allows leaded solders" Poland needs to follow the RoHS directive as a member of the EU. – Lundin Dec 19 '22 at 09:26

2 Answers2

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It's not clear what your concern is, or, how big the holes in your enclosure are; why mention them if you still can't touch it? I guess they are too small to reach through, but open to air. So maybe you were thinking it can emit spontaneously?

If you can't touch the lead, it's fine. It does not evaporate, it does not produce dust on its own, and even if so, it's only an ingestion hazard (mind, ingestion includes dust inhalation). It's not absorbed by the skin.

Regarding touch, it's only anything that causes material loss: abrasion, cutting, etc. Solder is very soft, soft enough that stroking it with your fingers typically leaves a black streak on you -- this should be washed away. That's all. Incidental handling is unlikely to be a problem (you'd have to really rub on it to get anything to see -- mind, invisible amounts should still be avoided). And with no contact, it's no problem at all.

I would be more worried about the keyboard's health itself, if it were so exposed -- all those electrical contacts would be prime ESD targets.

Tim Williams
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Yes and no. It's possible you contaminated some of the surfaces with lead during soldering if the solder was sputtering or the tip was way too hot, but wiping down the exterior of the keyboard with soap and water should be sufficient to take care of that.

If you do that I would consider the keyboard to be perfectly safe to use.

As others have said, the finished solder joints will not emit any lead if they don't get wet and corrode.

..However when the keyboard inevitably gets land-filled, the lead will be there, leaching into the ground water or otherwise contaminating the environment.

Lead free solder is totally usable with just a little bit more practice, so to me there's no reason to ever use the lead stuff, except maybe in life support applications where the absolute best material properties are required.

I would wipe down this keyboard and not worry about it, but I would get yourself a roll of lead free solder and a temperature controlled soldering iron for the future.

Drew
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