10

Is there a test to determine whether solder is leaded or lead-free? Perhaps conductivity/resistance?

Kevin Vermeer
  • 19,989
  • 8
  • 57
  • 102
Joe Stavitsky
  • 1,149
  • 2
  • 15
  • 26

5 Answers5

12

Try soldering a 0.5mm pitch component with it. If you get frustrated and want to throw it across the room, it's lead-free solder.

markrages
  • 19,905
  • 7
  • 59
  • 96
  • 6
    +1 for :-) value. Some people would find that test failed regardless :-) – Russell McMahon Sep 21 '11 at 11:17
  • Hmmm.. I just soldiered some joints with what I *know* to be lead free solder, and yet I didn't throw it across the room. Can you suggest some other tests? – SingleNegationElimination Sep 21 '11 at 18:03
  • @TokenMacGuy - Stop using additional flux? – Connor Wolf Sep 21 '11 at 21:48
  • 4
    @Fake Name: BLASPHEMY! flux is life! – SingleNegationElimination Sep 21 '11 at 23:18
  • 4
    Note that there are legitimate ways to do this test further down. Please don't upvote the funnies to the point where they hinder usability of the site. – Kevin Vermeer Sep 22 '11 at 13:47
  • 2
    My point is serious: if you experience both kinds of solder, you will find the difference in wetting is pretty dramatic. – markrages Sep 22 '11 at 15:39
  • 1
    Also, I don't know if you can generalize, but the lead-free fluxes I've smelled have had a much sharper chemical smell, and the leaded flux is more fragrant. Lead-free really makes you want a fume extractor. – markrages Sep 22 '11 at 15:42
  • 1
    This is demonstrably false. It’s not that difficult to solder even finer pitch stuff. Use more/better flux. No reason to recommend leaded solder. If you still do, maybe you’ve used too much leaded solder... – Cameron Tacklind Feb 27 '21 at 03:05
  • Strong agree with @CameronTacklind, funny but demonstrably false. Any high-quality lead-free solder is not much harder to work with than leaded (noticeable side by side? Yes, but quite a small difference, you'd not be able to tell reliably at all), even on very tiny pitch components. It also has some advantages aside from health, such as that lead-free joints are said to have greater longevity, even more so in high-stress and high temp environments. Not to mention you get ROHS compliance. I even work with tiny pitch BGAs and have never had an issue with lead-free. – Pecacheu Apr 16 '23 at 22:13
10

Use one of these lead-check swabs:

[edit: link updated] http://leadcheck.com/

https://web.archive.org/web/20160203163608/http://leadcheck.com/

Here is a new link to the same product. 3M Lead Check Swabs

nabulator
  • 648
  • 1
  • 7
  • 20
Leon Heller
  • 38,774
  • 2
  • 60
  • 96
  • See Sodium Sulphide test addition to my answer. Not the test in your cited swabs - but your link led me to the NaS solution (5% :-) ). – Russell McMahon Sep 21 '11 at 11:41
10

Keen or desperate? - measure it's specific gravity.
Compare with published or calculated data.

Take a large enough sample and weigh it = M1.
Suspend in water and weigh again = M2.
SG = M1 / (M1-M2)

or

Weigh = M1.
Then measure volume by water displaced when inserted into a just full container.
Water mass = M2.
SG as above.

Lead solder makes "shiny" joints when properly used.
Lead free solder makes more matte appearance joints.

Melting points vary.

Lead chemistry, various.

Based on Leon Heller's link

Various lead test kits are available.
These are usually intended for testing for lead paint but should be very effective with solder.

You can do DIY test solutions using Sodium Sulphide solution. Here is an excellent article explaining Sodium Sulphide testing for lead. This test can be used on hands etc to check for lead contamination and to show how effective cleaning proceures are.

Excellent discussion -Science Fair project starter on lead testing

Russell McMahon
  • 147,325
  • 18
  • 210
  • 386
  • I'd have used either the shiny vs. matte test, or the melting point test. The specific gravity test is a general way to compare almost any two alloys, but shouldn't be your first resource. – Kevin Vermeer Sep 21 '11 at 10:53
  • @Kevin Vermeer - That's why it was headed "Keen or desperate? - measure it's specific gravity." :-). The restare more "boring" and liable to be replicated by others. The SG test is less usual. I have used water-weighing to measure the SG of plastic product bodies to try to see if they have added calcium carbonate filler to the ABS. Lots of fun. Lots of mess. – Russell McMahon Sep 21 '11 at 11:16
7

Lead-free solder has a much higher melting point than leaded. If you have a soldering iron and some leaded solder, set your iron to a temperature where it just melts the leaded stuff. Then, try heating up a component on the board at that temperature (make sure it isn't connected to a large copper pour).

If you're having trouble getting the solder to melt, there's a good chance that it's lead-free.

Lemtronix
  • 271
  • 1
  • 4
  • Doesn't leaded solder do a eutectic thing where it goes straight from liquid to solid, while the unleaded solder goes through a soft state? Could you tell the difference by carefully watching it cool? – joeforker Sep 22 '11 at 15:02
  • 2
    @joeforker - that eutectic thing only happens for eutectic solder (63/37). Other proportions go through a plastic phase on their way to solid. – Pete Becker Jan 08 '16 at 21:19
  • This is a great idea and worked for me to identify all my leaded and lead-free solders in a big unlabeled pile – Pecacheu Apr 16 '23 at 22:15
3

Unreliable yet simple test. If you rub it between your fingers and play with it a while and your fingers turn dark gray or black from the deposits,, it's probably lead solder.

JustSomeOldDude
  • 31
  • 1