Solder.

[kalee20]

Originally Posted by bluepilot

Isn't there some problem with mixing leaded and lead-free solder? I remember reading that if you repair a modern lead-free joint with leaded solder then after a while it may well break. I would have thought that the best solder to use depends on what you're doing, so if you're mending old radios better to use leaded.

Yes there is. You need either no lead, or quite a bit. There's a sort of no-man's-land, between 0.05% and 3% lead, where the joint is really duff. Might be more than 3% and less than 0.05%, so don't quote me on figures!

So, it's OK to use leaded solder on a joint formerly made with lead-free (60/40 just gets a bit diluted with tin maybe making 70/30). But to use lead-free on a joint previously made with leaded, you need to suck off all the solder, flood it with lead-free, suck all THAT off, repeat a couple of times, before you can be sure you've got the lead content below the critical lower limit.

60/40 is the default stuff to have. 63/37 is available, and melts even better. Savbit is fine too. Lead-free just does not flow so well, wet so well, or do anything so well. But if you throw it away into landfill, it does not poison the environment, which is the reason for its introduction.

[emeritus]

Another reason for the reluctance of the solder of 1940's equipment to melt could be the reduction of the Tin content under wartime conditions. The attached "Multicore" ad from the WW Sept 1943 WW explicitly mentions this. 60/40 was not normally available, while solder having as much as 81.5% Lead and only 18.5% Tin was produced.

['LIVEWIRE?']

I, too, am not a great fan of unleaded solder - I have a reel of it somewher, but haven't attempted to use it yet. As others do, I remove the leaded solder from the component which needs replacing, using good old 60/40 to solder in the new one. I have been working with 60/40 for the best part of 50 years, with no known ill-efffects. Obviously some lead is absorbed through the fingers when handling 'old-fashioned' solder, but I'm now over 74 and still reasonably fit!

[avocollector]

Oh great - after doing very little work, I came back to electronics about a decade ago and wondered why the solder on the latest stuff did not melt easily when trying to remove components. Nice to know it was not just me going doolally. I have a trick of heating up the lead free with the iron for a few seconds, then putting a small blob of multicore (the rosin type flux one) on the iron tip (all my solder is leaded) and putting that blob first back on the joint and it seems to melt easily then.