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I don't do much lead-free work at all, so I'm asking this question out of ignorance. I have been using leaded solder as long as I have been soldering, and I have never had an issue with a soldering iron tip. The plated part of the tip always stays shiny, I'm OCD about cleaning the iron, careful with the temperatures used, and never leave my iron on long without using it.

I went to borrow an iron from a lab, and the tip was dark grey and rough. It would not accept any solder unless I tried to rub off some of this material, and even then it would only be a small spot that oxidized very quickly. I concluded that the tip was ruined, and went to get another iron with a better tip, but all the irons in that lab had the same condition, or worse. I got a brand new tip and installed it, and the tip lasted for about 15 minutes before it had a perfect coating and could not be cleaned. This whole time, I had been using the available solder: a 99.3% Tin, 0.7% Copper blend with a rosin core.

To further the ancedote, I came across another lab that used the same iron, but only had lead based solder. The tips in this lab ranged from perfect to moderately abused, but all would have been able to easily melt solder. Many irons were set to 450 degrees C, and their tip looked just fine. I'm not sure how much I would trust the temperature though, the iron is just about the cheapest "temperature controlled" iron I've seen.

Taking another new tip and using lead based solder, I was able to end up with a tip that I would classify "used, in good condition" after a soldering session. My conclusion is that the lead free solder is either more corrosive or less protective than normal lead solder. Which (finally) leads to my questions:

  • Is there a lead free metallurgy that is more forgiving to soldering iron tips?
  • Is there something inherently wrong in my handling of the soldering iron?
  • What would I need to solder with this composition?
  • Is there any hope for these tips that have been used with the lead free stuff? (My gut says no)

The soldering iron is a Stahl Tools SSVT Variable Temperature Soldering Station.

The solder is Elenco LF-99: 99.3% Sn, 0.7% Cu; Rosin core.

EDIT:

The other oxidized irons used were used to assemble simple kits; nothing very fancy or exotic as far as I know. They were handled by novices, which made me originally believe that the students had destroyed the tips. When I ended up with an oxidized tip that was otherwise clean, I thought it was less likely that the students had killed the iron. As I was using the lead-free solder, applying solder never seemed to clean the tip. I wasn't setting the iron to temperatures that were excessively high in my opinion (400 degrees C), but I don't know what the actual temperature of the iron was.

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  • \$\begingroup\$ One would not usually expect a lead free solder to react with std iron tips. Importantly - you need to say what solder was being used in the lab and it would help to say the brand of the irons and the use they were being put to. Also, stating the brand and composure of your lead free solder would help. There are MANY types of lead free solders, although most are not commonly met in most circles. They MAY have been clever and used a tip plating less active than tin or lead but more so that new-solder-additive-metal. \$\endgroup\$
    – Russell McMahon ♦
    Feb 28, 2012 at 4:03
  • \$\begingroup\$ @RussellMcMahon I have restated the information as requested. It seems that the cheaper you get, the less information is available =\ \$\endgroup\$
    – W5VO
    Feb 28, 2012 at 5:12
  • \$\begingroup\$ @W5VO Interesting. I've had a similar experience with a tip cleaner. From the package, it is supposed to have Sn96.4 Ag3.6 solder. While it does remove oxidation from the tip of the iron, it leaves it covered in exactly what you described: dark gray, rough covering which needs to be removed (with some difficulty) from the tip or otherwise the tip will not get wet with or easily melt the leaded solder I'm using (Sn60 Pb40). \$\endgroup\$
    – AndrejaKo
    Feb 28, 2012 at 7:15
  • \$\begingroup\$ When I tried lead free solder at home, I found my iron looked dull and damaged after using it. But it still seemed to work perfectly well. I think that perhaps lead free solder just isn't as shiney as traditional solder. Although I guess there is more to it than that for you, as you said that it wouldn't accept solder. \$\endgroup\$
    – John Burton
    Dec 10, 2012 at 10:25
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    \$\begingroup\$ I found an article from Kester titled "Lead-free Hand-soldering, Ending the Nightmares". Quoting: "Tip life will be reduced with lead-free solders... High tin solders like to dissolve iron and this reduces tip life... a manufacturer reported that with 63/37 the tips lasted 3 months with lead-free the tip-life was only 3 weeks". \$\endgroup\$
    – MV.
    Mar 21, 2015 at 22:23

4 Answers 4

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Lead-free solder requires higher heat. Lead has a lower melting point which one of the reason it was used in the first place.

You can find more information here:

http://en.wikipedia.org/wiki/Solder

which discusses both lead and lead-free solder.

I hate lead-free solder and do not use it when I am not forced.

Edit:

http://en.wikipedia.org/wiki/Soldering_iron#Tips

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    \$\begingroup\$ I agree with the sentiment that lead free solder is more difficult to work with, but I haven't ever seen it eat up a soldering iron tip like this. Lead was also introduced to help stop tin whiskers. I read through the Wikipedia article, and did not find anything relevant to my question. \$\endgroup\$
    – W5VO
    Feb 28, 2012 at 3:43
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    \$\begingroup\$ I think that W5VO (and most readers) understand these basic facts. However, many people (myself included) use lead-free solder every day without damage to irons, and turn irons up to more than enough to heat lead-free solder on troublesome ground planes and such all the time. The question is not "why does lead-free solder do this to soldering iron tips", it's "Why does this variety of lead-free solder do this to these soldering iron tips at this temperature?" \$\endgroup\$
    – Kevin Vermeer
    Feb 28, 2012 at 3:43
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    \$\begingroup\$ @W5VO: I think you are failing to realize that the additional heat causes premature aging of the tips. You don't have to melt the tip to ruin it. I've added an additional link that backs up this claim. \$\endgroup\$
    – Uiy
    Feb 28, 2012 at 3:56
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    \$\begingroup\$ It could be a combination of the additional temperature, cheap tips, and exact solder composition that cause this but it the temperature is almost surly the primary factor. You can ruin a tip by using too high heat on lead solder. The change in composition increased the melting point which gets one ever closer to tip failure. It is always possible something else is going on but highly unlikely. Temperature is almost surely the cause and maybe cheap tips are more susceptible to this than expensive ones. \$\endgroup\$
    – Uiy
    Feb 28, 2012 at 4:07
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    \$\begingroup\$ Well, maybe in both cases your temperature is too high? I don't know what to tell you. It is a temperature issue and it is simple as that. At low enough temperatures there will not be any problem. There may be confounding factors involved but the temperature is the catalyst. If you have 2 new tips and 2 irons you could setup a side by side experiment and see how they compare. Run them at the same temperature, gradually increase it over time, and do the same things(setup little simple soldering runs). My best guess is you are already running them too hot. \$\endgroup\$
    – Uiy
    Feb 28, 2012 at 7:28
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I have been having this problem as well. At my business I have been buying lead free solder for the electronics we manufacture. I use weller Soldering stations with Weller Tips. I have been using them for years with no issues at work using lead free solder.

Once I started using the same iron at my second business we bought some lead free from radio shack and i have wasted about $30 in weller tips, I have tried multiple heat setting and it doesnt matter what I do it ruins tips. Maybe its cheap radio shack solder, but if I use their leaded solder i have no issues. So you are not the only one seeing this.

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    \$\begingroup\$ The problem is that "leaded solder" is the same stuff everywhere: 60:40 Pb:Sn, give or take some percentages. But there is no real standard for what substance "lead free solder" refers to. There are multiple recipes. \$\endgroup\$
    – Kaz
    Aug 20, 2013 at 23:42
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See "solder alloys" on this Wikipedia solder page for many lead-free and lead-containing options. Hours of browsing fun :-). However ...

The iron ad says "... iron-plated solid copper tip ...". Everything points to something being chemically wrong with this specific mix of tips and Pb free solder.

The solder claims to be tin + copper which is standard enough.
Tip claims to be copper covered with iron which is standard enough.
Of the two it seems most likely that the iron makers are being "creative" somehow.
They say spare tips are available. If this was me I'd get a few more tips and try a solder that claimed to be the same to "prove" it was the tip at fault.

Trying solder that "fails" with a tip from another supplier should provide the final proof, if it is in fact the tip at fault.

Trace elements at quite a small level could cause problems. And if the tip was not iron plated but nickel plated or whatever they "anything could happen".
The irons look very good value for money IF they work as you'd hope. But ...

Superb HP paper on low temperature solders These are not necessarily lead free. The temperature diagrams are a superb introduction to what can be achieved with various alloys.

An example super solder (not lead free) is 40% Sn, 40% In, 20% Pb.
Rather expensive alas. They say:

  • 40Sn40In20Pb.
    The solidus temperature of this alloy is 121°C and the liquidus temperature is 130°C.
    It is soft and ductile. It doesn’t have the problem of embrittlement when soldering to thick gold surfaces, like PbSn, because of the high In content.
    Unfortunately, the high In content drives the price of this alloy up because In is extremely expensive right now
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  • \$\begingroup\$ IF they work as you'd hope. But...*what*? Seems like you're missing something. While you're about fixing that, you might also want to correct In is extremely expensive right no-w. \$\endgroup\$
    – Kevin Vermeer
    Feb 28, 2012 at 13:30
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At work (high tech electronics) we use "SAC" solder which is SnAgCu (Tin/Silver/Copper). I have never used solder with only SnCu. Certainly the contract assembly shops that do reflow soldering do not use SnCu solder. Typical SAC solder is SAC305 (3% Silver, 0.5% Copper). Our Metcal soldering iron (pick one up used on ebay for < USD$200 if you plan on soldering a lot, it's worth it!) has no issue corrosion issues with it, but it is hard to keep it clean and shiny. A copper brillo pad and lead-free tip cleaner will help.

It is possible that the solder you used is dissolving the finish on your iron, molten solder dissolves many metals such as gold and copper. It only dissolves small amounts but for a plating perhaps only a few atoms thick it would remove it. I believe that is why the copper is added to the solder (to reduce copper loss from the PCB trace) but I can't find a supporting reference at the moment.

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