Back when I was working in a electronics company in 2004, we had a new directive coming in - RoHS. Since then, we were forced to use lead free solder. I understand the dangers of lead poisoning, but we always had trouble using the lead free solder. It melts at a higher temperature, so we had to heat up our iron to a higher temperature, but then, the copper tracks on the PCB became easier to peel off due to this. Further more our iron tips got corroded way faster. I read about lead free specific iron tips recently, guess that is no longer a problem. How is the latest lead free solder these days? Does it still need a higher temperature to work with? Is there any latest technology in lead free solder that maybe allow us to use at similar temperature as the leaded one?
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\$\begingroup\$ It's the same as far as temperature and heating goes. Don't use a crappy soldering station. In fact, don't even use a decent one. Use a really good station with really good tips. You're not going to get away with a one-tip-does all with lead-free. \$\endgroup\$– DKNguyenCommented Aug 3, 2022 at 0:07
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\$\begingroup\$ There are some bismuth-containing solders that melt at lower temperatures, but the bismuth tends to ruin some other properties of the solder that makes it not a good idea to use. There's germanium-doped solder, which gives you similar performance to SAC305 (better in some regards) for slightly cheaper since it contains no silver, but its melting temperature is a degree or two hotter than SAC305, so it doesn't help either. Unfortunately, there just aren't any formulations out there that can straight replace 63/37. \$\endgroup\$– HearthCommented Aug 3, 2022 at 0:19
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\$\begingroup\$ beware sac305 paste formulations in applications that see aggressive changes in temperature... The bismuth and indium containing alloys can be almost indistinguishable from 60/40 leaded solder and in some ways outperform it. \$\endgroup\$– Luke GaryCommented Aug 3, 2022 at 1:25
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\$\begingroup\$ IME, nothing is as nice as 63/37 in yielding bright well-wetting joints. Cheap lead-free (just tin with a bit of copper) is a bit nasty- dull joints, high melting point (about 50°C higher than eutectic SnPb). I think the lead-free generally might be more brittle which can cause failures in things like large BGAs with a lot of thermal cycling. \$\endgroup\$– Spehro 'speff' PefhanyCommented Aug 3, 2022 at 2:17
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1\$\begingroup\$ I am familiar with all of the concerns that you listed. We also switched to LF around the same time. I can say that the pcbs that we get handle the high temps much better now ( for both hand soldering and reflow). We did switch our medium range soldering irons a good Hakko units, and the tips last forever (and are still affordable), even with the higher temps). For rework, preheating really helps, as well as a good gel flux. Everything we do now is LF, and there’s no job that we haven’t been able to accomplish yet. Good luck! \$\endgroup\$– Chris KnudsenCommented Aug 3, 2022 at 15:41
1 Answer
But we always had trouble using the lead free solder.
Yes, nobody likes it. It's somewhat harder to work with overall, even to this day.
but then, the copper tracks on the pcb became easier to peel off due to this
This was a big problem when RoHS was new and not nearly as much of a problem nowadays. Though naturally it depends a lot of the PCB quality - some PCBs meant for mass production are simply not designed to have components re-soldered multiple times, RoHS or not.
Further more our iron tips got corroded way faster.
Higher temperature means shorter tip life. For RoHS solder you typically use around 350°C as professional setting, whereas for leaded you would do around 320°C.
I haven't noticed any major quality improvement of solder tips since the introduction of RoHS.
But how is the latest lead free solder these days? Does it still need a higher temperature to work with?
Yes. Approximately 30°C higher temperature.
Is there any latest technology in lead free solder that maybe allow us to use at similar temperature as the leaded one?
As mentioned in comments, there is specialised solder containing bismuth with lower melting points. I have no personal experience of using it, but from what I hear it is slightly more brittle and should preferably only be used for special jobs with heat-sensitive components. There are some versions of it with more silver etc that are better, but then it turns more expensive instead. Also, flux core wire might not be available. See Any drawbacks to "low temp" lead-free solder paste?
