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Tin-lead and nickel plating outlawed in the US?

Discussion in 'Electronic Design' started by Joerg, Apr 26, 2013.

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  1. Joerg

    Joerg Guest

    Hello Folks,

    Got a big project done and goes into fab now. A surprise just popped up
    where the turn-key fab house said they can't get boards tin-lead plated
    and nickel-plated anymore. So we are going with gold immersion since
    some areas are mechanically contacted and thus can't have HASL. The rest
    could be HASL but that makes it complicated and black-pad isn't really
    an issue these days anymore.

    Did nickel-plating become totally outlawed by now? How about Canada and
    other countries?
     
  2. I don't think you would have a useful gold-plated board without a
    nickel barrier layer between the Cu and the Au, so I call B.S.

    (AFAIUI, without a barrier, the copper atoms migrate through the few
    hundred atoms of gold and do bad things in a relatively short time)
     
  3. Joerg

    Joerg Guest

    Not so sure about that one:

    http://www.uyemura.com/library-3.htm

    There seem to be issues with lead-free solder but we won't use that.

    I was puzzled in the past as well when Ni-Au was the usual process.
    Whenever I requested Ni-only lately there was balking. Back in the late
    80's there never were any issues with that, we did it a lot. It was
    nice, you could also have parts of the chassis nickel-plated and thus
    had no dissimilar metals problems.
     
  4. That page says that you can wirebond to a _heavy_ gold layer deposited
    over an electrolytic gold layer directly onto copper- not quite as
    good as Cu-Ni-Au, but acceptable.

    Again, AFAIUI, heavy gold is not great for soldering- I remember
    dealing with some of the old Tek boards that had a very thick gold
    layer and the solder tended to fracture easily at the interface. Flash
    gold just disappears into the solder*. Even at today's bargain price
    of < $1,500 USD/oz, it's also not cheap.

    Interesting note here:
    http://www.polarinstruments.com/support/cits/AP171.html

    ... pointing out that the usual (ferromagnetic) Ni layer causes
    increased losses, and that confining the nickel to selective areas
    such as contacts and pads can help mitigate the issue.

    * years ago I did a lot of single-sided stamped boards that used an
    organic coating similar to liquid flux directly over the bare copper
    to protect it. That's how you could get a 3 x 4" board for maybe 15
    cents in moderate quantities.


    Best regards,
    Spehro Pefhany
     
  5. Robert Baer

    Robert Baer Guest

    You do NOT want to F with gold due to corrosion (purple plague)
    created by the inter-metallic potential (copper-gold) created.
     
  6. Phil Allison

    Phil Allison Guest

    "Joerg = Jerk "
    ** Nickel and tin are not " outlawed " anywhere.

    Lead based solder is outlawed in the EU - with exceptions for things like
    avionics and medical apps.

    99% tin solder is the main alternative.

    Nickel plated connectors are used everywhere.



    .... Phil
     
  7. Heavy gold is very bad for soldering, hand or machine.

    It gets dissolved into the solder alloy and causes embrittlement.

    Even mil contacts which have solder cups require that the assembler
    fill and release the solder tinning a couple times to release any loose
    gold molecules in the solder cup to tinning interface. That way, the
    solder joint does not get made with gold mixed into it, since you already
    suspended and released or wicked it out.

    I have seen the differences and the embrittlement, and the broken
    contact leads. It is a real concern. The assembly steps are required
    since the contact gets plated evenly, and the desired gold thickness out
    on the pin or socket itself needs to be thicker, so that means one has to
    thin it in the area where the connection gets made.
     
  8. Joerg

    Joerg Guest

    It's AAPCB the turn-key house in Colorado. They usually try a fairly
    large number of PCB places.
     
  9. Joerg

    Joerg Guest

    Black pads issues? Those are long gone with controlled processes, I
    think. I have solder NiAu boards a lot, worked well. On this one I have
    to trust the circuit assembly house. It's a pretty big place, they
    should know because they'll get the heat (and lose a contract) if it
    doesn't work.
     
  10. Yup.

    http://www.protostack.com/download/NASA Student Handbook for Hand Soldering.pdf

    The removal of gold from connector pins is mentioned in Procedure 7.


    Best regards,
    Spehro Pefhany
     
  11. josephkk

    josephkk Guest

    Then there is something deuced odd with this one response. Check a few
    board houses, if your responses are different challenge the assembler.

    ?-)
     
  12. Joerg

    Joerg Guest

    Well, we went with ENIG. Ni-only was not possible for whatever reason,
    even though that would merely be the leaving out of one step.
     
  13. There's the Nicholson approach:-



    Come to think of it, he never got his toast either.
     
  14. Joerg

    Joerg Guest

    Cool. But then my client wouldn't get any boards :)
     
  15. josephkk

    josephkk Guest

    Amazing, or not. You got some short lived enviro-twit the first time.

    ?-)
     
  16. Joerg

    Joerg Guest

    Reminds me of a case where some sort of zinc plating was no longer
    allowed in California and we had to do it farther east. Heavy stuff, so
    there were regular truck transports back and forth. Picture Diesel
    plumes belching towards the sky at every steep pass when shifting gears.
    Which of course in its net effect was an environmental shot into the
    foot. Of course politicos cannot understand even such simple things.
     
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