Novice questions about lead-free soldering

[MrQuan]

Up until recently I've only ever used lead/tin solder but I'm having to deal with lead-free a bit these days (repairs and modding) and have a few questions...

• I've noticed some solder stations are advertised as 'lead-free' and sometimes categorised that way - What's the practical difference? Can a station not specifically marked lead-free be used for this, and vice versa?
• To remove a component that is soldered in lead-free I've found heating the joints, applying a little 60/40 (for extra viscosity), and then solder-sucking is effective. Is there any issues mixing the solders like this (i.e. oxidisation/corrosion problems)?
• Should I try to keep iron tips separated for lead-free and lead usage, or can I safely mix and match?

Any feedback or suggestions are appreciated! Many thanks

[IanB]

I think it's a good idea in general to keep the iron tips separate and not mix them up. The performance of lead free solders is tuned for the exact composition and it's best not to contaminate them.

Lead free soldering is characterized in general by higher soldering temperatures and more aggressive fluxes.

For desoldering the use of additional flux on the joint may help the solder to suck or wick more readily.

[Neilm]

According to some things I have heard, the more aggressive fluxes in lead free solder can damage the soldering iron tip of a tip made for leaded solder.

If you are repairing items then there is no legal issue to mixing the solders, but if you work in a production environment then mixing leaded and unleaded solder will contaminate the unleaded solder and (technically) your company could get in trouble.

Neil

[mikeselectricstuff]

There's no reason to use leadfree for repairs etc. Fluxes are more unpleasant, higher temps are more likely to damage PCBs, and it eats tips.
 A good way to make LF joints easier to unsolder is to flood them with leaded.

[saturation]

I'd concur with Mike, the only reason to use lead free is to be RoHS compliant during manufacture, and for whatever truth or untruth is behind lead free solder, the volume you'd use to do repairs is a tiniest fraction of the whole content of the assembly.  Unless there is some regulation required that compels you to use it, you can opt for the simpler to use Pb based solder.

You can find discussions about Pb free and its impact on soldering irons, but in general, there is no need to make any adjustments except for insuring you keep your irons preferably under 350C whenever possible, lower the better to whatever is effective.

A reason is tip wear is faster with Pb free.  From a Hakko study, a measure of erosion at different temps after 2000 tip cycles:



In general, the relationship of tip temp to tip life, the cross over is ~ 350C: