Can I safely use one soldering iron tip for both leaded and lead-free solders?

[PointyOintment]

I work on a large variety of devices, some of which were made with leaded solder and some of which were made with lead-free. I've read that mixing the two types in joints can result in brittle joints, tin whiskers, etc. (especially if the two solders don't mix into a homogeneous alloy). Okay, fine. I won't deliberately make mixed joints. But what about contamination transferred by the soldering iron? I only have one tip of each style, so I can't designate one for leaded and one for lead-free. It doesn't seem to have caused problems yet, but I haven't done, and don't plan to do, any long-term reliability tests, vibration tests, etc. So, can I safely continue using one tip for both types? Should I wipe it off and re-tin it (and maybe even wipe it off and re-tin it a second time) with the appropriate type of solder when I switch from one to the other? (I'm not doing stuff that has to be RoHS-compliant, so a tiny amount of contamination is not a problem—as long as it doesn't affect the quality of the joints.)

P.S. Any tips on how to tell whether the solder in a device is leaded or lead-free if it doesn't have a RoHS label and isn't really old?

[zapta]

+1

And possibly similar mixup problem when soldering HASL boards or removing SMDs with that Chip Quik alloy.

[Psi]

i've always just cleaned the tip when moving between lead and leadfree.

[nanofrog]

Yes.

Just rinse the tip with the appropriate alloy before making any joints (tin the iron first with the alloy you intend to use a few times before actually soldering with it).

Quick, cheap, and easy. 

[Rick Law]

...I've read that mixing the two types in joints can result in brittle joints, tin whiskers, etc. (especially if the two solders don't mix into a homogeneous alloy)....

What I have read is lead free solder has alloys that is more prone to whiskers.

If there is someone with more definitive info, please share.

Thanks
Rick

[RobertHolcombe]

This reminded me of the following video, it is quite dated and I'm unsure if it is still practiced

[rob77]

i just clean the tip as nanofrog does, never changing the tip. just tin the tip with the alloy you're switching to and clean it off - do it twice to be sure you'll not contaminate the board.

regarding chipquick - that's a nasty stuff - you have to clean it off as much you can, otherwise it will mess up the melting point of the solder and will make the solder joints brittle.

and yes, tin whiskers might be a problem with some lead-free alloys (but it takes "ages" while the whiskers grow).
btw.. the lead was the anti-whisker agent in the soldering alloy - lead is slowing down the formation of whiskers. in the lead-free era the anti-whisker agent is copper - that's why you have copper in the lead-free soldering alloys.

[PointyOintment]

Thanks everybody! That's exactly what I wanted to hear.

This reminded me of the following video, it is quite dated and I'm unsure if it is still practiced

OMG, the editing was so bad… and he introduced every rinse iteration as if it was a new procedure. Oh well; at least it confirms that rinsing works.

[RobertHolcombe]

Yeah the delivery isn't great

[con-f-use]

The whole premise is flawed. Didn't he say to use a tip for leaded solder and convert it to lead free? Lead-free solder is much heavier on the tip. Lead-free tips have thicker plating that's made of another alloy because:
a) lead-free solder is more aggressive and will pull metal out from your tip plating and
b) lead-free solder needs more aggressive flux that corrodes the tip.
Therefore you shouldn't convert use tips for leaded solder with lead-free. It will shorten its life drastically. The other way around is fine though. Or am I mistaking here?

But back to topic: Cleaning, rinsing the tip one time and then cleaning it again should dilute the other type of solder sufficiently for it not to be a mechanical problem. If you want to rework an existing joint, you should remove the other type of solder thoroughly but the alloys are not that sensitive to small changes.

[sacherjj]

The whole premise is flawed. Didn't he say to use a tip for leaded solder and convert it to lead free? Lead-free solder is much heavier on the tip. Lead-free tips have thicker plating and another alloy because a) lead-free solder is more aggressive and will pull metal out from your tip plating and b) lead-free solder needs more aggressive flux that corrodes the tip. Therefore you shouldn't convert use tips for leaded solder with lead-free. It will shorten its life drastically. The other way around is fine though. Or am I mistaking here?

I think the assumption is made that the tips are lead-free compatible, but just if it is OK to use both types of solder on that tip.  Most tips from reputable makes are up to lead-free standards these days.

[tszaboo]

I was in a Japanese assembly factory for some extended amount of time. They specifically marked stations with a big red unremovable sticker, if they weren't ROHS. If you used a station with not lead free solder, the station was marked with the red sticker, removed from the production area, the board was scrapped. I guess this is a bit extreme but if you have to comply, I would replace the tip and the barrel section, or have two separate irons for lead-free and leaded.

[Neilm]

I was in a Japanese assembly factory for some extended amount of time. They specifically marked stations with a big red unremovable sticker, if they weren't ROHS. If you used a station with not lead free solder, the station was marked with the red sticker, removed from the production area, the board was scrapped. I guess this is a bit extreme but if you have to comply, I would replace the tip and the barrel section, or have two separate irons for lead-free and leaded.

At a proper factory the non-RoHS station would be clearly marked to prevent contamination. IIRC Apple got caught out when RoHS came in due to that scenario.

One thing to note is you should use different bits for leaded and unleaded as the flux for unleaded can damage the tips as the flux is quite aggressive. Also combining the two types of solder could cause reliability problems.