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Recognizing lead-free solder

Discussion in 'Electronic Repair' started by mc, Jun 15, 2006.

  1. mc

    mc Guest

    Given that it's desirable to do repairs with the same type of solder as was
    used originally, in order to avoid alloy mixing or partial melting
    problems...

    (1) How do I recognize lead-free solder when I see it?

    (2) What temperature should I set my iron to, when working with SnSb or SnAg
    solder?

    Thanks!
     
  2. Pooh Bear

    Pooh Bear Guest

    Gawd knows mate. The politicians probably didn't think of that one.
    About 50C higher. Hang on, you said " SnSb or SnAg " ! Where do you think you're
    going to find those ?

    Graham
     
  3. g. beat

    g. beat Guest

    Georgia ?

    How about starting with an Alloy Temperature Chart??
    http://www.kester.com/en-us/technical/alloy.aspx

    Kester Lead Free Solutions
    http://www.kester.com/en-us/leadfree/index.aspx


    NPL: UK's National Measurement Labs
    http://www.npl.co.uk/ei/research/leadfree.html
     
  4. g. beat

    g. beat Guest

    BTW, Kester lists 5 eutectic solder alloys on this chart -- can you find
    them?
    http://www.kester.com/en-us/technical/alloy.aspx

    http://en.wikipedia.org/wiki/Eutectic
     
  5. Arfa Daily

    Arfa Daily Guest

    It has been recommended by the creators of the half-arsed RoHS directive,
    that manufacturers mark their boards with the alloy that has been used. To
    date, I think I have probably seen about 2 or 3. In general, boards made
    with lead-free, look as though every joint is bad ( and often, this is
    pretty much the case !! ). Instead of the joints having a shiny appearance,
    and being domed or meniscus-shaped, they are dull and grey, decidedly
    'crystalline' looking, and tend to be volcano-shaped, with straight sides.

    Pretty much any commercial equipment from the big far east manufacturers -
    Pan, Sony, Hitachi etc - built in the last two or so years, can be assumed
    to have been built in lead-free.

    When you get a lead-free board for repair, as well as finding your fault,
    which may well be joint-related, check the solder joints on anything large
    such as connectors, power transistors, heatsinks etc. It's also worth
    checking the soldering on any LSIs fitted to the board - particularly the
    rows of legs on the downstream side of the soldering process, which is often
    marked on the board by an arrow. Give anything suspicious, a good rocking.
    Bad joints just don't look the same as with leaded solder. I have had
    components just come out in my hand, leaving behind a perfect-looking
    volcano of solder. This is because the manufacturers run their solder
    process plants at as low a temperature as they can, to avoid damage to LSIs
    etc. With the known inferior wetting properties of lead-free, this tends to
    result in insufficient heat to properly solder components with a high
    thermal inertia. SM LSIs seem to suffer as a result of the inferior flowing
    properties of lead-free, resulting in poorer capilliary 'draw-in' of the
    solder, under the legs.

    As Graham says in this thread, 50 deg C hotter is about right. The
    difference in actual melting temperature, is around 30 - 40 deg, depending
    on the exact mix. As a matter of interest, the recommended alloy for general
    bench rework, is Tin-Copper-3% Silver. This has a melting point about 10 deg
    lower, and apparently, rather better wetting properties, but I can't vouch
    for this, not having tried any yet.

    Arfa
     
  6. mc

    mc Guest

  7. mc

    mc Guest

    How about starting with an Alloy Temperature Chart?? Actually, that gives the melting points, which weren't hard to find in the
    first place. What I'm looking for is advice about how to set the
    temperature-controlled iron.
     
  8. mc

    mc Guest

    Thanks -- that's useful!
     
  9. ian field

    ian field Guest

    Dead easy - lead free solder joints fall apart in less than a year!!!
     
  10. ian field

    ian field Guest

    <snip>

    Any chance the half-arsed RoHS directive was thought up by the stuck up gits
    who pepper the countryside with 12bore lead shot?
     
  11. g. beat

    g. beat Guest

    OK. You mean the mind-less idiot knob on the current soldering stations?

    Personally my range is 650 to 750 degree -- the KEY is to stay in the range
    and then select the proper tip SIZE (1/64" to 1/4" in 1/32 or 1/64"
    increments) and PROFILE (screwdriver, conical, single flat) -- as well as
    solder. Works well for 63/37 Tin/Lead eutectic and 60/40 alloy.

    For the Weller WTCP, I still use 700 degree F tips, PTA, PTB for
    screwdriver, the other 3 tips that I occasionally use depending upon the
    work (reach, SMD, etc) are: PTH, PTL, PTS

    I do know some people who jump to 800 degree for the no-leads -- depending
    upon formulation being used.

    For Lead free solder, call Alpha/Cookson Electronics (Jersey City, NJ) and
    have them send you a sample of:

    96.5% TIN; 3% SILVER and 0.5% COPPER in the
    ..020 diameter either with a 3.3% flux or WRAP2 flux


    g. beat
     
  12. Arfa Daily

    Arfa Daily Guest

    Most shot used in clay shooting is no longer lead, I seem to recall. Anyway,
    the point is that if it is, it is not recycled, so remains lying where it
    is. Solder accounts for less than 1% of the world's mined lead, over 80%
    going to car battery manufacture. The car battery industry have managed to
    organise virtually 100% safe recycling, so are allowed to carry on using
    lead on this basis, and the contention that there is no suitable
    alternative. With the coming of the WEEE directive shortly, end of life
    electronic equipment will have to be safely recycled in much the same way,
    so where's the difference ? If the car battery people can do it, I'm sure
    that the electronic people can also do it with less than 1/80th the volume.

    The point about the RoHS directive as it stands with regard to leaded
    solder, is that it is forcing a changeover from a mature, tried and tested
    technology, which had reached the point of almost perfect reliability, to a
    less than satisfactory alternative, with at best, woolly reasoning to try to
    justify it. This is well understood by such people as the US military, who
    refuse to use the stuff, the avionics industry, who have obtained
    exemptions, and the medical instrument industry, likewise. Any ecological
    advantage from the poisoning angle, will probably be outweighed in the long
    run by the additional energy budget worldwide to run all those solder
    production lines and hand soldering irons 50 degrees hotter, and all the
    extra recycling brought about by electronic equipment being junked earlier
    due to owners getting fed up with all the intermittent problems from bad
    joints ...

    Just keep your fingers crossed that avionics are not finally forced down
    that route, coz that'll be the day that I stop flying.

    Arfa
     
  13. ian field

    ian field Guest

    Some good points there, I didn't know lead was no longer used for 12bore
    shot - any idea what they use instead?

    Regardless of the WEEE directive, lead was originally mined out of the
    ground and one way or another it will eventually end up back there, also I
    had always held the opinion that the common solder alloys were substantially
    less toxic than lead on its own, if this is true then the manufacture of
    lead/tin solder actually reduces the availability of lead wherever it ends
    up at end of life.

    One thing I have been trying to find out if anyone knows, is how much lead
    the petroleum industry procured annually for TEL additives before leaded
    petrol was discontinued, the figures I read somewhere (can't remember where,
    or how much!) were huge - thousands of tons of lead converted into exhaust
    particulates to be inhaled, washed onto agricultural land and into the water
    table, I suspect that lead in solder is insignificant compared to previous
    usage of TEL!
     
  14. Franc Zabkar

    Franc Zabkar Guest

    I wonder how much lead is in a typical CRT? BTW, I googled for "lead
    free CRT" but got very few hits.

    - Franc Zabkar
     
  15. Jim Land

    Jim Land Guest

    Yes, but the lead coming out of tailpipes was widely distributed in the
    air, whereas electronics that wind up in landfill dumps just sit there
    for a long time and continuously leach their chemicals into the nearby
    ground, whence it flows down into water tables and gets into drinking
    water. I'd prefer my drinking water lead-free, thank you.
     
  16. Arfa Daily

    Arfa Daily Guest

    First to Jim two posts above. You are missing the point. The electronic
    waste will no longer sit in landfill, because the new WEEE directive, in
    Europe at least, will make sure that the equipment is recycled, and any lead
    content removed. Electronic equipment in landfill will soon become a thing
    of the past. Anyway, just how soluble is lead in water ? I'm not too sure,
    but I expect some clever chemistry graduate will tell us. In the past, water
    was delivered to all households in the UK via lead pipes. In a lot of older
    properties, it still is. Certainly, the house that I grew up in had lead
    pipework. I am not aware of people of my generation all dying of lead
    poisoning, or having suffered intelligence lowering due to lead-induced
    brain damage. In fact, since lead piping has been being removed here, the
    kids have been getting progressively thicker ... !! I have heard people say
    that delivering water via lead pipes is of no consequence, because the pipes
    quickly get an internal coating of limescale, that insulates the water from
    the lead, but some areas of the country have very soft water, with little or
    no calcium content, so I'm not sure that this argument " holds water " (
    ouch !! ).

    Even if lead is soluble in water, I can't imagine that it is extremely so,
    and I would have thought that water treatment plants would have removed any
    in their raw input, or could be made to do so fairly easily. Of much more
    concern, I would have thought, must be the organic fertilizers and such that
    get into the water supply. I don't know what the situation is your side of
    the pond ( I'm assuming you are US based ) regarding landfill. All we ever
    hear over here, is that your glorious leader is not a very eco-friendly guy,
    but I'm sure from what I've seen on my frequent visits, that isn't the case
    amongst the general population.

    To Franc. I'm not sure what the percentage of lead is in the lead-glass that
    is used for CRT faceplates, but as far as I am aware, it's another
    technology that has been deemed not to have a viable alternative, so has
    been granted an exemption from the RoHS directive. Total recycling of this
    glass should be possible, with no lead-to-environment contamination. As well
    as the faceplate glass, I seem to recall that there is some issue also, with
    getting a vacuum-proof seal between the CRT pins and the glass, that
    involves possibly some other hazardous substance covered by the directive.
    Interesting stuff. If anyone has any strong objections on the grounds of
    this being off-topic, say so, and I'll stop raising new points ...

    Arfa
     
  17. Arfa Daily

    Arfa Daily Guest


    I have a friend who owns a clay range. A few years back, there was a big
    thing locally about shot from his range ending up in a wheat field behind.
    This also lead to complaints on the noise issue. As far as I recall, they
    changed over to a different cartridge, that has a non-lead shot content, and
    a lower velocity powder charge, which cuts down on the noise, making more of
    a soft whumph noise than the previous sharp bangs. I haven't seen him for a
    while, nor been to the range, so I don't know what the effects of this have
    been on the sport, but I will try to find out, if you like.

    I think that the issue with ' out of the ground / back to the ground '
    that's usually quoted, is that it came out of the ground as a naturally
    occuring ore, but goes back as refined lead. But I'm still not convinced
    that this whole thing is not just an eco smokescreen, keeping beaurocrats in
    a job. I'm sure that there are much more hazardous substances getting into
    the eco system, than lead from solder.

    Arfa

    Arfa
     
  18. Jim Yanik

    Jim Yanik Guest

    I believe the lead in CRT glass does not leach out.
    It's probably the monitor electronics is where the lead is coming from.
    Also,it's not just the faceplate the lead-glass is used,as the lead is
    intended to attenuate X-rays which I believe scatter BACK from the target.
     
  19. See:
    http://www.floridacenter.org/publications/lead_leachability_99-5.pdf
    The proceedure is to test for leaching using moderately acidic water
    (Ph = 5.0) and to literally pulverize the glass to accellerate the
    leaching (See Method Phase I). As expected this yielded the worst
    case results at about 3 times the US limits.
     
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