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I know it is bad to solder lead-free devices, such as resistors, with lead. However, is it possible (with less effort) to remove this lead-free coating on the resistors to make it possible to solder with lead? PCB has also a chemical coating.

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    \$\begingroup\$ Why is it bad?? \$\endgroup\$ – DKNguyen May 21 '20 at 15:39
  • \$\begingroup\$ I have boards soldered with Pb all the time and most of the components available today are all Pb Free. There is no issue (unless it's a BGA type). \$\endgroup\$ – Aaron May 21 '20 at 15:41
  • \$\begingroup\$ I should have add that I intent to use it at low temperature - where it is better to solder with lead. Well, I can't imagine that it is good to have different materials. The question is if that tiny amount of coating can make problems \$\endgroup\$ – Jeres May 21 '20 at 15:42
  • \$\begingroup\$ Is -55C cold enough? That's what we test to. \$\endgroup\$ – Aaron May 21 '20 at 15:58
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    \$\begingroup\$ You seem to think having lead-free parts are made to be incompatible with lead solder. Why is that? Using lead free components does not mean they are incompatible with lead solder. The resistors are just marked as lead free because they are lead free, it does not mean that they ever contained any lead or have been changed in any way. \$\endgroup\$ – Justme May 21 '20 at 15:59
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The coating on the leads is typically tin.

For Pb-free components, the manufacturer will have used Pb-free Sn, for example the datasheet for some resistors I picked at random says:

Pure tin plating provides compatibility with lead (Pb)-free and lead containing soldering processes.

Presumably by "solder with lead" you mean solder with tin/lead solder (e.g. 60/40 or 63/37). There will be no need to remove the coating.

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  • \$\begingroup\$ I agree, I know places that produce thousands of circuit cards every year using leaded solder and a mix of leaded and lead-free parts. I have not heard of them having any problems. \$\endgroup\$ – user4574 May 21 '20 at 16:01
  • \$\begingroup\$ But Bb-free = lead free ?! I have seen some resistors where Pb-free is not specified, which for me means they have a lead coating \$\endgroup\$ – Jeres May 21 '20 at 16:05
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    \$\begingroup\$ @Jeres Pb-free means they are sure there is no Pb in them. Not saying Pb-free does not mean that there is Pb in them. A pure Pb coating would not be used anyway, even in the old days, AFAIK. \$\endgroup\$ – Andrew Morton May 21 '20 at 16:10
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There are many resistors out there which have lead free terminals, you just have to search in mouser ticking the ROHS compliant.

The problem of using leaded + unleaded solder is that the melting point can go down dramatically, in some cases below water boiling point creating reliability issues, however these days most components have pure tin contacts, and pure tin + leaded shouldn't pose a problem the same way pure tin + unleaded shouldnt.

YET... there is more to the story, because it's not only the terminals that may contain lead, also the ceramic substrate of the resistor. You can tell which have leaded ceramic as in the ROHS certificate it says compliant by exception.

This won't affect the performance of the circuit however for environmental consciousness you may want to avoid them if the specs allow you to.

There are options without leaded ceramic such as RC0603FR series, i guess more will pop up in the future

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