from a youtube comment by andy4102 on How to Solder Correctly

I relly like your video!! It’s clear that you have spent some time on it! Very nice..
You mentioned that a typical soldering iron, heats to 600-750 Fahrenheit. I have recently bought a 6 watt soldering iron, witch claims to have a max temperature of 870 Fahrenheit. Then my question is: do you think I’m exposed to lead?

I’m assuming you meant 60 Watt? My reference for saying “soldering above 850 degrees F can make it more likely that solder will atomize into smaller particles that you can breathe” is based off an instructional video from IPC, the industry organization that makes specifications.

Check out just about everything on I know on the risks of lead in solder fumes (click expand at the top of the page after it loads—it’s a biggie). That link also includes a link to the IPC video and other sources.

If you don’t want to read the short bit at the end of that link, the basic summary is that I looked for a long time trying to find studies on airborne lead poisoning risks from hand soldering, and just didn’t find much of anything. Licking your fingers is a different matter, though. The lack of any big hand-soldering airborne lead poisoning scare leads me to believe that even if you solder up at 900 degrees, your risks are probably minimal, although multiple sources (at link) indicate that more lead is in the air at those temperatures. How much more? Is it harmful? Who knows.

Now, soldering past 700 degrees F for lead-based solder or 800 degrees F for lead-free is not a great idea. There’s obviously more risk of component or board damage, but also risk of weaker joints. The intermetallic bond that forms between the solder and joint is critical, but also brittle, and the longer and hotter things are heated, the larger this gets. Again, how hot or long is too much? I’m not sure. Check out the Time subsection of under heat and solder the joint from our guide.

Finally, flux will get used up faster at hotter temperatures, making timing more important.

If that’s not more than you wanted to know, I can’t help you :)

what is the average temperature in celsius recommended for lead and lead free soldering?

In Fahrenheit, I usually recommend 600-700 for lead, and 700-800 for lead free. In Celsius that would correspond to 316-371 for lead based, and 371-427 deg C for lead-free.

Two notes: the ideal temperature depends a lot on technique, the size of the component, flux, etc, and generally lower is safer. Cheaper unregulated irons are less capable at lower temperatures because they deliver constant heat, and will quickly drop in temperature when you begin soldering. More expensive soldering stations can solder effectively even at 540 degrees F (282 deg C) (in my experience) because they ramp up the heat delivery as soon as the tip temperature drops.

All this being said, I haven’t had a lot of experience burning components—even sensitive ones, with a wide range of temperatures. The board is most at risk during desoldering when you may be applying heat for a long time.

In production environments, “lockable” stations are often used to keep employees from turning the temperature too hot. A hotter iron makes the soldering process seem easier, but this is riskier. It’s preferable to use a lower temperature and make sure parts are clean.