Blinking badge - lead free solder?

At the meeting last week there were a couple of questions raised that I didn’t get a chance to speak with the questioners further, but I didn’t want to forget about.

The question came up about using lead free solder. I confess I’m fairly ignorant about the issue besides “wash your hands after soldering.”

I figure if lead was good enough for the Romans, it’s good enough for me! *

What are the pros and cons of lead free solder?

Are we just talking about the solder that we use to teach with, or the solder used in manufacturing the boards as well?

The response in the room was “it’s too much of a hassle”, is that because it’s harder to solder, or are there other reasons not to use lead free solder?

*I don’t actually believe this.

I was at a build party last summer, and we were having all kinds of trouble making pretty solder joints. I was thinking to myself, “I don’t know what’s wrong. It’s just not working.” Trying to reduce the problem, I dug out my normal solder, which is Kester 44. It’s pretty old. Perfect solder joints. I pulled off some coils for the other three people soldering, and everyone had no more trouble.

My recommendation would be that whatever solder you pick, that you actually try it out and are comfortable that it works well and is forgiving for beginners. If I were running it, I’d probably make sure all the soldering irons had a brand-new tip as well.

I’d worry much more about lead solder as an occupational hazard (for example, doing it for 8 hours-a-day for months or years). It might be good to have a solder fume collector or some rigged-up muffin fans or something, more to demonstrate good practice and to allay fears. For some reason, the solder smoke plume always chases my nose and eyes. I go to a fair bit of trouble to not breathe solder fumes from that plume.

My mother worked a factory job where she was exposed to lead vapor from a bath of solder (many gallons). The company took baseline blood lead levels, and then checked them every few months. After 3 or 4 years, she got moved to another job. (Also, she was too old to have kids. That was part of the company policy.)


The big deal with LF is heat. It typically requires 80-180degC more heat. It also doesn’t “flow” like a good 63-37 does. It’s much more of a pain to work with, especially for beginners.

LF / ROHS is more of an issue for manufactured items for sale. There are restrictions particularly in Europe on this.

We have several pounds of Alphametals solder that I donated that is very good. I also have about another 15lbs of it.

As long as you cover the safety concerns (i.e. don’t eat this shit) I don’t see there being any issues using lead.


I am on the fence about using leaded vs lead free. On one hand lead free is a good bit more difficult to solder, but leaded solder has… lead.

I would probably be ok with leaded as long as we very clearly display that it is leaded, cover the basics of what not to do, and have a way for people to clean their hands off nearby.

Also, the issue with lead free isn’t that it is a higher temperature. The melting point of 63/37 is about 183C and that of SAC305 (probably the most common lead free solder) has a melting point of about 217C. A difference of 40C doesn’t make a difference when you have your soldering iron set to 400C. The problem with lead free is that its “wettability” isn’t nearly as good as leaded solders (that and tin whiskers, but that isn’t a problem with what we are doing). You can buy lead free that is much better at wetting than the normal stuff, but it is more expensive and more difficult to get your hands on. Because of this lead free also tends to have more and harsher flux which is where the fumes come into play. Definitely a good idea to bring a fume extraction fan for each soldering iron!