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I'm asking this in the context of desoldering consumer PCBs, with lead vs. lead-free solder. My concern is twofold:

  • lead-free solder usually has a higher melting point, so the temperature should be set slightly higher to shorten the desoldering time and hence reduce the total heat transfer.
  • since solder wets/tins the soldering tip, there's a chance you'll have a solder tip tinned with a different type of solder than the one your are processing, which might be a bad thing.

Are those concerns important enough to consider them when desoldering, and, if so, how can leaded solder be told apart from lead-free solder?

Note that answers with a fairly surefire solution are preferred over heuristics (e.g. visual identification).

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  • \$\begingroup\$ I believe the important question here is if you care about RoHS compliance after your repairs. If you don't care, just do your thing. If you do care .. then things get a bit more complicated as you don't want to contaminate an RoHS compliant board (or your compliant soldering iron!). \$\endgroup\$ – jippie Aug 11 '13 at 16:35
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Anything using lead-free solder would (or should) have a ROHS compliancy symbol. Otherwise why would they bother going with lead-free. It's not particularly easy to work with compared to old industry standard leaded solder.

Melting or remelting points vary depending on solder compositions, and there plenty of mixtures that are lead-free that have a lower melting point than leaded.

Practical solution, treat everything you are desoldering as if it has lead-free if its been produced in the last say 10 or 13 years, and don't use your regular soldering iron for desoldering.

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