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Q&A

Is there a particular type of lead-free solder that does not degrade soldering tips?

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I have had my soldering iron tips degrading at ridiculous rates. Granted, they are not very expensive, but sometimes it takes less than 8 hours of soldering for them to degrade to the point where they are no longer usable. I use a soft sponge for cleaning, don't leave the iron on for prolonged times and coat it with tin when not using it.

I see that the market is moving to lead-free solder (which is what I am using) and it is getting more difficult to acquire leaded solder. Yes, I have read that there are no real advantages of lead-free solder over leaded solder, except for reducing the waste that goes into the landmass.

However, assuming there are children and pets in the house, it would make sense to not have a spool of lead laying around. Naturally, it should be put away, but nobody is perfect, and you may forget etc.

Hence the question: Are there certain types of lead-free solder to look for, that are easy on the soldering iron tips? If so, are there particular chemical compounds that allow this?

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3 comments

It is probable that the temperature of your soldering iron is too high. Try reducing the temperature (e.g. with a dimer), and see if this helps. coquelicot‭ 28 days ago

The flux core in RoHS solder is very unhealthy too. So in case you worry about your kid putting it in their mouth, it's not a better alternative than leaded. Lundin‭ 28 days ago

Anyway, I would strongly suspect that the root of your problem is the solder station itself. What brand and what temperature are you using, assuming it is temperature controlled in the first place? Coating the tips when not using them is a good idea btw, so keep doing that. Lundin‭ 28 days ago

2 answers

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A different type of solder, other than using lead-based solder, is probably not going to help. There are two causes to your problem:

  1. Crappy tips.
  2. Higher temperature required due to lead-free solder.

You can fix the first by getting a good soldering tool.

Leaded solder will help with the second. You cite several reasons not to use leaded solder. The disposal issue is valid (although quite minor), but the remaining ones are not, and the use of lead-free solder may actually make things worse:

children and pets in the house, it would make sense to not have a spool of lead laying around

There are far more dangerous substances in your house than leaded solder. Pretty much any cleaning chemical is worse, not to mention medicines. Simple touching, unlike with some cleaners, isn't going to cause problems. Teaching the kids to keep their hands off your electronics stuff, and putting away the solder when not in use should really be good enough.

The big point you are missing is that the main danger of solder to humans is the vaporized flux, not the metal itself. This is made more dangerous with lead-free solder due to the high temperatures. Kids standing near you watching you solder are exposed to significantly more harm due to inhaling flux fumes, than they would be by handling leaded solder.


In what manner the higher required temperature affect the service life of the tip …?

Chemical reactions and diffusions speed up with temperature. In this case, the metal of the tip slowly "dissolves" into the molten solder. Different metals vary in this. Copper is actually quite susceptible, which is one reason solder bonds with copper so well. Good quality soldering tips are copper on the inside (for good thermal conductivity), but coated with a metal that doesn't diffuse into molten solder as well. Higher temperatures speed up all these processes.

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2 comments

no 2. In what manner the higher required temperature affect the service life of the tip according to you? coquelicot‭ 24 days ago

@coquelicot‭ You need to go some 30-40 dgr C higher for RoHS solder. However, if you have the possibility to set the temperature manually, you put it much higher than the melting point anyway, which is the temperature that affects the tip life. Leaded melts around 180, RoHS around 220 and I put the iron at 350 dgr C. If you have a station with automatic temperature control, you don't need to worry of that. I had a small Metcal station which did this and the tips lasted forever. Lundin‭ 24 days ago

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PCB's and components are expected to be used with the common SAC solder, there's little reason to use SnPb, IMO. I learned on SnPb. After a brief transition for RoHS to re-calibrate the "feel" of it, never went back. Once or twice an oddball situation needed low melting point, used SnBi (also toxic I believe).

Things to look at, many already discussed

  • Temperature... Need good temp control. Use "extra hot" only when needed. Design pcb with more thermal reliefs when possible to avoid this need. Also, IMO no need for tiny tips, just ends up needing to turn the heat up. I use 2.4mm for everything.
  • I think name-brand tips with quality plating are worth it.
  • Avoid any abrasive cleaning of the tip, that would wear away the plating. (but after tip plating is already gone, go to town)
  • I am suspicious of aggressive fluxes. I think the stuff on solder wick might be such. Would not want to leave that on there for too long. Simply displace with regular solder when done with it.
  • The water quality on the sponge may be another wildcard factor with corrosion.
  • Not sure how important it is to wipe off the slag(?) frequently, but I do it.
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2 comments

In my opinion you can't really solder 0603 or smaller with the standard tips, nor fine pitch QFP, QFN etc. I always use a small tip for most things SMD. Lundin‭ 23 days ago

My personal opinion, which I admit is not the norm. I found 2.4mm tip effective down to 1.27mm pitch with just the flux already in the solder wire (with the occasional solder bridge that's easily fixed with wick). With gel flux, 2.4mm tip does 0.65mm pitch, and with some care the 0.50mm. Technique relies entirely on surface tension effects (and for QFN's you have absolutely no choice in this IMO). 0603's are more a matter of getting them to stay still, IMO. Pete W‭ 23 days ago

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