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

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

  1. Eeyore

    Eeyore Guest

    The debate about lead free solders seem to be nearly as politically charged as
    that about anthropogenic global warming and a casualty seems to be useful data.

    I've read plenty of comments to the effect that lead-free is less reliable in
    the long term (vibration seems to be a key weakness AIUI - maybe also thermal
    cycling) which presumably explains the exemptions for certain categories, yet
    I've also seen some studies that claim it can out-perform lead containing
    solders.

    Is there any real hard and fast information out there that one can rely on ?

    Graham
     
  2. me

    me Guest

    If it were better than lead solders there would not be any exemptions
    needed, every thing would be required to be lead free. Critical (Mil,
    Aero, etc)equipment gets an exemption though...
     
  3. Leeper

    Leeper Guest

    It is really application and chip package specific, and even makes a big
    difference on where the chip is mounted on the board. It also makes a big
    difference on the various lead finishes, process steps and how they are
    done, and which of the common 23 lead-free mixes you use. Would you believe
    ENIG finishes can even cause issues with lead-free?

    Personally, if you look there is a consortium lead by Boeing, of areospace
    industries, who have been doing a lot of testing on the subject, and ended
    up settling on just 1 or 2 alloys that perform the best in the early phases,
    to pick out which ones to run thru the gauntlet- with control subject of
    regular leaded solder.

    If you do searches on key documents/terms listed within these, you will find
    more than you ever wanted to know:
    http://www.aciusa.org/leadfree/LFS_SUMMIT-PDF/12_TOUW_AIA-AMC-GEIA_LEAP_WG_Brief.pdf
    http://www.calce.umd.edu/lead-free/SMTAExemptMay8.pdf
    http://www.jgpp.com/projects/lead_free_soldering/presentations.html - a
    whole list of documents
    http://www.jgpp.com/projects/lead_free_soldering/Dec_04_Presentations/Vianco Ag JEM-0409-991.pdf
    http://www.jgpp.com/projects/lead_free_soldering/Dec_04_Presentations/Kirkendall Voids.pdf
    http://www.jgpp.com/projects/lead_free_soldering/Dec_04_Presentations/121404Woodrow.pdf
    http://www.jgpp.com/projects/lead_f...nvironments_Testing_Status_backup_3_16_05.pdf

    Another key term to search for is Thomas Woodrow, who has dedicated years
    attempting to unravel this puzzle for best practices.

    When looking at these presentations, it is important to look hard into the
    nitty gritty of the source references, or you will easily end up with the
    wrong conclusions. Things like a good number of the tests were done with
    immersion silver, and ENIG (gold) and other board finishes can have a big
    impact on the results of the test. ENIG has it's own issues, such as a big
    increase in what is becomming known as "black pad" failures when lead-free
    solders are used with it. As I recall, it had something to do with the ENIG
    process steps, which vary from board house to board house.

    In the second one, several working groups have found the failure shown in
    page 33 of the document( pdf page 33), where you can see cracks running all
    through the BGA ball, and a rather clear separation off the pad. Caused by
    temperature cycling, and failures in less than 150 thermal cycles!

    Tin Whiskers Theory and Mitigation Practices Guideline:
    http://www.jedec.org/DOWNLOAD/search/JP002.pdf

    "The amount of damage required for
    a BGA to fail on an assembly was used to predict lifetimes for other BGAs,
    at other locations, on the same board. They tested: Sn3.9Ag0.6 for reflow
    soldering, Sn3.4Ag1.0Cu3.3Bi for reflow, Sn0.7Cu0.05Ni for wave, and
    63Sn37Pb for reflow and wave. The surprising part is that BGAs using
    tin/lead will outlast SAC BGAs by a factor of 20x. Thus, SAC BGAs in
    high-reliability electronics could be problematic in high-vibration
    environments.
    ....
    There has been no other transition to affect all aspects of our industry
    as fundamentally as lead-free. Predicting reliability will prevent future
    disasters, and that's the best reason to glean information from all
    approaches. There's still so much we need to know."
    http://listserv.ipc.org/scripts/wa.exe?A2=ind0706&L=Leadfree&P=1444


    ----- Original Message -----
    From: "Eeyore" <>
    Newsgroups: sci.electronics.design,sci.electronics.repair
    Sent: Tuesday, July 24, 2007 3:42 PM
    Subject: So what's the truth about lead-free solder ?
     
  4. John Doe

    John Doe Guest

    I dunno, but soluble core solder Rocks :)
     
  5. N Cook

    N Cook Guest

    =----

    Follow the derogations/exemptions.
    Military , aerospace & medical do have derogation from WEEE and RoSH, but
    can anyone nail down precisely why they are exempted.
    The suggestion from the following would be they are maverics putting
    themselves in an awkward position regarding spares etc.

    http://www.lboro.ac.uk/research/iemrc/pdf files/Electronics 2015 Makin
    g%20a%20Visible%20Difference%20EIGT%20Report.pdf

    "... Much equipment manufactured before the application of RoHS will suffer
    premature obsolescence, as component parts which have been modified to meet
    the RoHS requirement may not be compatible. Businesses supplying sectors
    such as defence, medical, instrumentation and control, currently have a
    derogation from the regulation in Europe.
    But this poses problems for the future availability of lead-free
    components. This issue has product lifetime implications for public sector
    purchases as well as business implications to those supplying export markets
    where RoHS standards do not yet apply. ..."


    The real conspiracy would be if it could be shown what manufacturing
    industries deliberately went with lead-free knowing that their products
    would fail due to that and not component failure, knowing they would sell
    more product.
    The engineers I have talked to in UK industry are genuinly unaware of
    in-service problems in electronic products, due to their enforced lead-free
    soldering. But the ones I know are in scientific/technical kit and
    instrumentation production so not subjected to vibrational environments.
    Do automotive electronics have a derogation ? as that would be an area that
    would soon show up lead-free solder problems.
     
  6. Arfa Daily

    Arfa Daily Guest

    I'm not sure that I would find this "surprising", having seen the general
    performance of lead-free from a service angle, for several years now. At the
    end of the day, like several other technologies we have been forced to ditch
    as a result of dubious science and conclusions, lead-based soldering was a
    mature, proven, and above all *reliable* way to construct electronic
    equipment.

    If Boeing Corporation are really leading research into the performance of
    this hateful material, then I hope that it is with a view to reinforcing the
    avionics industry's opinion that this stuff has no right to up be in the
    sky, and responsible for getting 450 people safely to their destination. If
    they are researching with the intention of determining the best compromise
    alloy to use in place of conventional solder, then I believe that is indeed
    a worrying development ...

    It would be interesting to know from someone directly involved in avionics
    or avionics service, how many in-service equipment failures are currently as
    a result of bad joints, and what sorts of levels of failures are being
    recorded in the vibration tests that must be being done on evaluation sample
    pieces, constructed with lead-free.

    Arfa
     

  7. Bullshit. Lead based solder alloys are superior in damn near all
    electronic realms, and there is no configuration where they would not be
    other than high end commercial and military applications, and they
    certainly do not include Tin.

    RoHS is a Euro-ploy to boost the Euro-dollar, and there is no health
    problem surrounding lead alloyed solders.

    It is all bullshit, and it was all bullshit when it was started.

    We already had regulations in place for such matters for DECADES.

    Get a clue.
     


  8. Absolutely. Lead based solder alloys are fucking superior, and Tin
    based, non-leaded alloys are inferior, and have VERY POOR reliability
    numbers.

    It is really quite simple math.

    A mission critical application REQUIRES a system where one does not
    have to expect some lame failure mode to creep in due to the utilization
    of a VERY POOR, failure mode prone device interconnection methodology.
     
  9. Eeyore

    Eeyore Guest

    Whilst I don't disagree with you, where's the hard comparative data ?

    I only wish it was just the EU.

    FYI, the idea(l) behind RoHS is to encourage recycling by removing elements that
    would be troublesome otherwise.

    Personally, I can think of no good reason to attempt to 'recycle' old printed
    circuit boards. For example it appears to be both uneconomic and likely energy
    wasteful too.

    Graham
     

  10. Considering the fact that we have 5 decade old circuit cards still
    operating perfectly, and that we already know what alloys containing Tin
    which is not bound by Lead do over time and temperature cycling, I do not
    think that precise numerical analysis is even needed on such a profoundly
    lopsided issue.
     

  11. Lead alloy solders in discarded circuit assemblies does NOT pose any
    "troublesome" issues for the environment.

    Fact: Metallic form lead solder alloys, or even raw metallic form Lead
    does NOT pose a problem for water tables or land fills.

    Aside from the polymer materials provided for in the "regulation", RoHS
    is total bullshit.
     

  12. If one (read a business) had an incinerator for refuse, which is common
    in the US, one could very easily have enough heat energy "left over" to
    reflow, and "Smack and Gather" soldered assemblies after they reach
    reflow temperatures.

    It would not take long to gather a ton of "solder".

    A ton is a ton is a ton, and gathering several grams from each assembly
    one has for salvage makes the planet more "green", because reprocessing
    lead, and lead alloys is far easier and less costly than mining it.
     
  13. N Cook

    N Cook Guest

    The next time I get a year or 2 year old 800 GBP/1500 USD combo in for
    repair with loose simple, thermally un-stressed,but vibrationally stressed
    components, I will actually measure the extraction force of the obviously
    suspect ones and some of the remaining ones, with a spring balance and a
    hook of wire. I would never have expected otherwise well-soldered (but
    obviously lead-free solder) very basic "components" like soldered wire
    links,1/3W resistors,TO92 transistors, to have solder failures after
    decades, let alone a couple of years.

    Some more relevant background text from
    http://www.lboro.ac.uk/research/iemrc/pdf files/Electronics 2015 Makin
    g%20a%20Visible%20Difference%20EIGT%20Report.pdf
    nothing about failure rates in the bullet-points though

    "..... The lead-free solder proposal was introduced at short notice by the
    EU in
    1998 as a revision to the WEEE Directive under Article 175 (environment),
    and is the subject of qualified majority voting, so the UK has no power of
    veto. The UK was the only member state represented by its industry
    ministry, and other member states were represented by environmental
    ministries. No rigorous fiche d'impact was undertaken. The proposals take
    effect from 1 July 2006.
    Subsequently, the Removal of Hazardous Substances (RoHS) provisions,
    which deal with other hazardous substances, were made under Article 95
    (single market). So interdependent legislation will be introduced under
    different agreement arrangements.
    Unintended consequences include:
    * Increased material and component costs because some PCB material
    and some components cannot be used with higher temperature solder;
    * Re-certification costs for safety critical products;
    * Damage to soldering equipment from electrochemical corrosion,
    following use of tin-rich solder in machines previously used with lead-
    based solder;
    * Increased capital equipment cost as equipment life shortens;
    * Increased costs associated with inspection, testing and tracking to
    demonstrate compliance;
    * Training and retraining costs for staff working with new materials;
    * Increased capital and inventory costs as manufacturers keep separate
    lines and stocks for defence and exempt products. ....."
     
  14. Eeyore

    Eeyore Guest

    So pony up your data !

    Graham
     
  15. Eeyore

    Eeyore Guest

    Whilst I agree with you, bureacrats tend not to be very receptive to anecdotal
    comment. And make no mistake, the bureacrats are the ones in control of this.

    Graham
     
  16. Eeyore

    Eeyore Guest

    Incinerators are now deprecated since the greenies say they make dioxins.

    Actually, I'd expect a lot of solder to turn to oxides and go up the smoke stack if
    subjected to high temps.

    Graham
     
  17. Eeyore

    Eeyore Guest

    I agree. I imagine you've seen a number of these then ? Do you tell your
    customers about the lead-free thing and its consequences ?

    Graham
     
  18. Arfa Daily

    Arfa Daily Guest

    I have just this minute finished repairing a Panasonic DAB / FM radio which
    was dying as soon as it was switched on, with a "F76 Pdet" error in the
    display. I took this to be "power detect", which seemed reasonable, given
    the symptoms. When I took the main board out to have a look at the
    underside, I found the power supply section riddled with poor and
    'cracked-right-round' lead-free solder joints ( the board actually has
    "PbF" silk-screened on it ). The poor joints were particularly well defined
    on the main free-air cooled regulator transistor, which is obviously subject
    to thermal cycling.

    I reworked all the joints with lead-free, as that is what the RoHS
    legislation legally charges me to do as a commercial repair outfit, but boy,
    the temptation was strong to just reach for the leaded solder, and do the
    job 'properly' ...

    Arfa
     
  19. Eeyore

    Eeyore Guest

    Have you considered documenting this stuff ? With a scan or a pic for example ?

    What do you tell the customer ? That Greenpeace is to blame ?

    Graham
     
  20. N Cook

    N Cook Guest

    What was the chipcode dates on that DAB ?
    No more than 2 years old no doubt.

    If you had not repaired it than also no doubt it would have ended in
    landfill taking with it ,perhaps not lead, but antimony, bismuth, tin,
    copper, barium , phthalates etc
     
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