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Thread: Lead free solder

  1. #1
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    Default Lead free solder

    I bought upwards of 10x 1lb. rolls of Kester 96.3% tin, 3.7% Silver solder years ago, .015" diameter wire (very thin). Did I waste my money? Will I have problems down the road, whether it be electronic or simply when bonding pieces of brass together? Should I shelve it and buy leaded solder?

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    I would be concerned about it. I think the aerospace industry and medical equipment manufactures are exempt, and for very good reasons. More info here. Of course, I'm assuming you're using it for electronics, but perhaps you're not.
    WANTED: Cardinal 2450MNP modem.

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    96.3/3.7 Sn/Ag melts at 430+F, where good old 63/37 Sn/Pb melts at 361F and is a eutectic alloy.

    I've got some of your stuff in solid wire form, but I use it for plumbing with an acid flux. It doesn't flow and wet as nicely as the leaded variety, but it doesn't tarnish as much.

    There are better non-leaded solders for electronics work. Guide from Kester, but 63/37 is still the best for most work if you've got to solder.

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    One roll was exposed to a good deal of humidity I guess, and has significant black sooty oxidation. Perhaps not through the whole roll, but neither tin not silver is impervious to corrosion. That's why they use gold in ics and other critical apps, even though it's not as good a conductor as AG or copper.

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    Atmospheric sulfur is the big reason for silver going black--humidity is just part of the picture.

    Nothing wrong with silver if used correctly. Wire-wrap wire is silver-plated, but the wraps are gas-tight.

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    Quote Originally Posted by Chuck(G) View Post
    Atmospheric sulfur is the big reason for silver going black--humidity is just part of the picture.

    Nothing wrong with silver if used correctly. Wire-wrap wire is silver-plated, but the wraps are gas-tight.
    Could you describe conditions where atmospheric sulphur is significant? I'll have to find the spool and photo it.

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    Most airborne pollution has a sulfur content, as does vehicle exhaust, rotting food, eggs, sewer gas and intestinal effluence. Urban areas tend to have more of it than rural areas, unless you live near a cattle ranch, dairy farm or pig farm.

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    Quote Originally Posted by 2icebitn View Post
    I bought upwards of 10x 1lb. rolls of Kester 96.3% tin, 3.7% Silver solder years ago, .015" diameter wire (very thin). Did I waste my money? Will I have problems down the road, whether it be electronic or simply when bonding pieces of brass together? Should I shelve it and buy leaded solder?
    Depends what you want to do with it I always thought solder like that was for jewelry use, and if so it should continue to work. Leaded solder for electrical work is still pretty freely available for repairs anda ROHS regs only apply for stuff you are putting into production. Modern "Lead Free" solder is brittle, but you may need to use it on some circuits...
    Dave
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  9. #9

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    Do you, or will you ever have, an old Tektronix oscilloscope? The kind with the ceramic strips requires lead-free solder. It's not practical for anything else lectronic in my opinion.

  10. #10

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    The stuff is so scary that you should immediately send it all to me for safe disposal

    Seriously - just use it, it's fine. I think there is a lot of unjustified superstition floating around about non-lead solder. When it was introduced there was a spike in failure rates from manufacturers who hadn't got their processes dialed in for the new solder compositions. That was ages ago. (and in long-ago days cheap leaded-solder circuits came with quite a few flaws too). No idea when lead-free for consumer devices was mandated in the US (if ever) but in Europe it feels like it's been that way for about 15 years and production processes have been doing a fine job for nearly all of them. I have loads of devices, and have mended plenty of broken ones, from that timespan and I have never seen one die of non-lead solder. (Capacitor plague on the other hand...) Come to think of it, I've been using non-lead solder for hand-soldering for at least nine years now (maybe 10) and not had a failure there either. Nor have I seen one of these "whiskers". I don't doubt they're out there somewhere, but they cannot be common. I would be interested to know if a particular storage condition causes it, but I don't have any evidence. Note that the NASA paper is about pure tin and notes that even a very low % alloy can inhibit formation - non-lead solders are alloys and it seems like the small % of copper, silver or both works just as well to inhibit whisker formation as a small % of lead.

    I would say, though, that hand soldering a lead-free without a few % of silver is a bit harder. The 3% silver kind you have there should be fine. You do need a temperature-controlled iron with a decent reserve of power - the old poorly-regulated 12- or 15-watt ones are not up to the job. Delicate components don't have to get any hotter than they did with lead because the heating time remains short. It's different and takes a little getting used to, fine with anything else.

    For what it's worth I've found 95%+% tin, 5% copper/silver/other solders also really handy for non-electronic soldering (eg brass work, or even small bits of steel in model making). Your mileage, as the say, may vary.

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