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

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    \$\begingroup\$ Bring it to the EU or California and see if you get arrested? \$\endgroup\$ – Olin Lathrop Sep 20 '11 at 19:01
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    \$\begingroup\$ If you knew the supposed percentage of lead/tin you could weigh it... \$\endgroup\$ – Toby Jaffey Sep 20 '11 at 19:09
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    \$\begingroup\$ If you have a reasonably well calibrated temperature controlled iron, you could test the melting point. \$\endgroup\$ – Olin Lathrop Sep 20 '11 at 19:17
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    \$\begingroup\$ @Joel B - Lead certainlt does all that anywhere. Sounds like california have got their head screed on right on that one. BUT if you keep it out of your body it doesn't do your body much harm. \$\endgroup\$ – Russell McMahon Sep 21 '11 at 15:59
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    \$\begingroup\$ @Russell - "...it doesn't do your body much harm." Skin cancer, maybe? Only in California, of course! \$\endgroup\$ – stevenvh Sep 21 '11 at 16:07
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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.

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  • \$\begingroup\$ 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? \$\endgroup\$ – joeforker Sep 22 '11 at 15:02
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    \$\begingroup\$ @joeforker - that eutectic thing only happens for eutectic solder (63/37). Other proportions go through a plastic phase on their way to solid. \$\endgroup\$ – Pete Becker Jan 8 '16 at 21:19
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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.

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    \$\begingroup\$ +1 for :-) value. Some people would find that test failed regardless :-) \$\endgroup\$ – Russell McMahon Sep 21 '11 at 11:17
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    \$\begingroup\$ @Fake Name: BLASPHEMY! flux is life! \$\endgroup\$ – SingleNegationElimination Sep 21 '11 at 23:18
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    \$\begingroup\$ 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. \$\endgroup\$ – Kevin Vermeer Sep 22 '11 at 13:47
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    \$\begingroup\$ My point is serious: if you experience both kinds of solder, you will find the difference in wetting is pretty dramatic. \$\endgroup\$ – markrages Sep 22 '11 at 15:39
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    \$\begingroup\$ 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. \$\endgroup\$ – markrages Sep 22 '11 at 15:42
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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

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  • \$\begingroup\$ 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. \$\endgroup\$ – Kevin Vermeer Sep 21 '11 at 10:53
  • \$\begingroup\$ @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. \$\endgroup\$ – Russell McMahon Sep 21 '11 at 11:16
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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

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  • \$\begingroup\$ 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% :-) ). \$\endgroup\$ – Russell McMahon Sep 21 '11 at 11:41
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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.

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