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So what's the truth about lead-free solder ?

Discussion in 'Electronic Repair' started by Eeyore, Jul 24, 2007.

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  1. Actually, in the long ago past when I had the TV repair shop, I had exactly
    the same problem on old tube connectors in PCBs and also on inductiors, and old
    Philips K8 connectors, some after 2 years too I think.
    With leaded solder.
    This is also also an issue of better connections, some that allow some movement,
    like WIRES for example...
    I mean use flexible wires to connect the hot components to a PCB.
    That defeats the idea of PCB perhaps.
    But I only wanted to point out that that thermal effect is also present in leaded
    solder.
    It could be worse in leadfree, but you'd have to test in the same setup.
    He *could* have resoldered one with 60/40 and when it comes back in 2 years
    see which ones gave way ;-)




    workin gas TV repair
     
  2. Eeyore

    Eeyore Guest

    The temperature cycles would have been rather higher methinks.

    Graham
     
  3. Eeyore

    Eeyore Guest

    No, that's illegal per the rules from the idiots in Brussels. It could result in a
    fine of £2000.

    Graham
     
  4. Glen Walpert

    Glen Walpert Guest

    Don't look to this newsgroup for factual info on lead free! Instead
    look at actual test results in the trade publications such as SMT
    magazine:
    http://smt.pennnet.com/home.cfm
    They have published numerous tests comparing various lead free
    materials and processes with tin-lead. Some lead free materials and
    processes are better than others (no surprise) and picking the best
    one for your situation is non-trivial.

    My nutshell summary of the published test results is that lead free is
    significantly harder to do right than tin-lead, requiring tighter
    process controls, but if done right it can be more reliable than
    tin-lead for non-shock situations. Lead free is harder, stronger and
    more brittle than tin-lead so tin-lead will deform plastically under
    high shock when lead free will break, however lead free will withstand
    more hot-cold cycles than before failure than tin-lead (better fatigue
    resistance). So you need to know what the significant failure
    mechanisms are in your design to pick the most reliable materials.

    Glen
     
  5. Guy Macon

    Guy Macon Guest

    So all those owners of lead mines are wasting all that
    money doing things the more expensive way as a public
    service?
     
  6. mpm

    mpm Guest

    I suspect it is because these fields are considered "life-safety"
    fields.
    Even ordinance, when you think of it in terms of friendly fire
    incidents.
    They probably just don't want to recertify their processes, or don't
    have the time to do it right.

    But the "Truth"?
    That's much more elusive.
    Does RoHS result in a better environment? I don't know, but I doubt
    it.
    The sheer number of TV sets that will be obsoleted in the coming years
    due to the migration to Digital Television will probably swamp the
    RoHS "gains" by orders of magnitude.

    Ditto for the batteries used in some electric cars, and the US's
    (likely?) ultimate reliance on it's vast coal reserves to power all
    this crap. And that's if Global Warming doesn't get us first...

    Bottom line: I don't think the environment gives a sh^t about RoHS,
    or WEEE.
    I think we need fewer people, and less "disposable" crap from China.

    -mpm
     
  7. Right, I turned in a portable TV last week.
    This one was about 30 years old (seventies), and was still working OK,
    but no analog transmissions here anymore, all you get is nice equal
    distributed noise when tuning in to a digital station.
     
  8. Joe Chisolm

    Joe Chisolm Guest

    Dr Howard Johnson (High Speed Digital Design) had this article in
    his email newsletter (and posted on his site). Interesting read.
    Rollback RoHS: http://www.sigcon.com/Pubs/news/10_01.htm
     
  9. Well seems [all] we have to [do is] make some traces .65mm apart :)
     
  10. Traver

    Traver Guest

    The main issue for lead free in military and aerospace electronics is
    tin whiskers. Tin solder will
    grow conductive whiskers that even penetrate conformal coatings. In
    low power circuit,
    the whisker will short something out. In a high power circuit, it
    might burn up like a fuse,
    but if it happens in a satellite (no atmospheric pressure) the little
    whisker will cause
    a plasma arc capable of passing huge amounts of current.

    We in the defense electonics industry fight with this issue every day
    and the information
    is very confusing. Parts turn lead free midstream in production and
    seems impossible to
    keep tack of it. Every company is dealing with it differently. We stay
    away from certain
    finishes like bright tin and look at the spacing of components and
    coatings on our boards.
    This can mitigate some of the reliability risks of lead free.

    If high-rel is of upmost importance, we struggle to find tin-lead
    parts.
     
  11. Eeyore

    Eeyore Guest

    Some ? ALL !

    Goodbye microelectronics.

    I just came across this too.
    http://en.wikipedia.org/wiki/Tin_pest

    " At 13.2 degrees Celsius (about 56 degrees Fahrenheit) and below, pure tin
    transforms from the (silvery, ductile) allotrope of beta-modification white tin
    to brittle, alpha-modification grey tin. Eventually it decomposes into powder,
    hence the name tin pest."


    Graham
     
  12. More than political -- the subject could easily be viewed as troll bait.
    It's been 'discussed' many times in ser.

    http://tinyurl.com/22c6t
     
  13. AFAIK this exemption only applies to component lead finishes.

    Best regards,
    Spehro Pefhany
     
  14. Too bad....
    How about conductive glue replacing solder?
    Na, will have to wait until the first EU politician's cellphone fails in
    some emergency.
     
  15. Eeyore

    Eeyore Guest

    It's not a troll.

    New data ought be available as to the effects on actual in-service reliability of
    lead-free by now. It seems as I expected, anecdotally, that musical equipment
    products that tend to see high levels of vibration are suffering.

    Graham
     
  16. msg

    msg Guest

    Jan Panteltje wrote:

    What ever happened to 'multiwire' (or some such trade name)? It was
    a multilayered weld-bonded wiring alternative to multilayer PCBs
    in the '60s and '70s and was very rugged, easily implemented with
    NC technology, and used no solder of course.

    Since each layer is built up in succession, between power and ground
    planes, even BGAs can be accomodated.

    Regards,

    Michael
     
  17. Eeyore

    Eeyore Guest

    How about getting a clue ? You can get conductive epoxy adhesive btw. It's
    loaded with silver particles and is ridiculously expensive.

    Graham
     
  18. Eeyore

    Eeyore Guest

    Gone the same way as wire wrap it seems.

    Graham
     
  19. Alex

    Alex Guest

    I reworked all the joints with lead-free, as that is what the RoHS
    If you use leadfree solder, remember that the temperature is a bit
    higher, and this makes the fumes from resin much more dangerous to
    YOU..
    Second.. if the components is made for leadfree solder , it can happen
    that the tin/lead solder wont make a good solder-joint. ( but I agree
    that sometimes one is tempted )
    Alex
     
  20. Eeyore

    Eeyore Guest

    No, that's not true AIUI. It's the other way round.

    Graham
     
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