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Lead free solder - exposed in a UK national newspaper

Discussion in 'Electronic Repair' started by N_Cook, Apr 3, 2008.

  1. N_Cook

    N_Cook Guest

    http://www.guardian.co.uk/technology/2008/apr/03/research.engineering

    Within a whisker of failure

    Removing lead from solder may seem a smart idea environmentally, but the
    resulting microscopic growths called tin whiskers could be just as
    problematic

    * Kurt Jacobsen
    * The Guardian,
    * Thursday April 3 2008
    * Article history

    This article appeared in the Guardian on Thursday April 03 2008 on p1 of the
    Technology news & features section. It was last updated at 00:05 on April 03
    2008.
    Tin whiskers

    On April 17 2005, the Millstone nuclear generating plant in Connecticut shut
    down when a circuit board monitoring a steam pressure line short-circuited.
    In 2006, a huge batch of Swatch watches, made by the eponymous Swiss
    company, were recalled at an estimated cost of $1bn (£500m). In both cases,
    "tin whiskers" - microscopic growths of the metal from soldering points on a
    circuit board - were blamed for causing the problems.

    It's not the first time these mysterious growths have been blamed for
    electronics failures. In 1998 the Galaxy IV communications satellite
    sputtered out after just five years; engineers diagnosed its failure as due
    to "whiskers".

    The US military blamed them for malfunctioning F-15 radar systems and
    misguided Phoenix and Patriot missiles. In 1986, the US Food and Drug
    Administration recalled a number of pacemakers because of these same
    whiskers. In fact, they've been known about since the 1940s, and happen with
    cadmium and zinc, too: during the second world war, similar whiskers would
    short the cadmium tuning capacitors in aircraft radios. A decade later,
    tin-based relays in AT&T telephone switching centres were found to cause
    shorts.


    The solution to "whiskering"? Mix lead into the solder, as was done from the
    1950s. Colin Hughes, a physicist who worked on the first British nuclear
    bomb, told me that the whiskering problem never came up during his career.

    But now the lead is gone, by legal mandate, and whiskers are back - causing
    potential problems for us all.

    Since 2006, lead has been banned from solder in the European Union under the
    2003 Reduction of Hazardous Substance (RoHS) directive, which gave
    manufacturers three years to phase out lead.

    The logic seemed reasonable. Removing lead from petrol (where it was used to
    prevent engine mistiming) brought clear environmental and health benefits,
    taking a harmful chemical that can affect intelligence out of the
    atmosphere. Removing lead from solder, the 37% lead, 63% tin alloy used to
    join metal objects in everything from plumbing to circuit boards, was an
    obvious next step to prevent it leaching into ground water from dumped items
    in landfills.

    Meanwhile, the US and Japan have also been moving to lead-free solders. It's
    a huge shift; the US Environmental Protection Agency (EPA) estimates that
    80m kilograms of lead solder was used worldwide in 2002. Environmental
    groups have applauded the move. "In the US we've been surviving without lead
    solder for many years," says Rick Hind, legislative director of Greenpeace's
    toxics campaign. "With less exposure to lead we will all benefit by being
    smarter and making safer and more durable products." (The US has not made
    lead-free solder obligatory, but does offer tax benefits for doing so.)

    But without lead to tame it, tin behaves oddly on circuit boards. Left
    alone, tin plating, like cadmium and zinc, spontaneously generates
    microscopic shreds of metal - about one to five microns in diameter, or less
    than one-tenth as wide as a human hair - which push up from the base. If
    they grow far enough to touch another current-carrying location, they'll
    cause a short that can wreck the equipment while leaving barely any trace.

    The cause is becoming clearer. "I believe the mechanism of whisker formation
    is now understood: it is due to compressive stress - caused by, say,
    diffusion of copper into the tin - being built up in the tin layer which
    breaks through the tin oxide barrier layer [to the air]," says Steve Jones
    of Circatex, in South Shields. Critics cite reports that solder
    substitutes - pure tin, tin-zinc, tin-silver-copper - simply cannot match
    the lead mixture for reliability, coverage ("wetting" terminals), and cost
    (silver is especially pricey). Therefore, the US military, Nasa and medical
    and high-level research equipment are exempt from what authorities view as
    untrustworthy commercial components.

    "I still use lead-tin solder - it works better," says John Ketterson, a
    solid state physicist at Northwestern University in Illinois. He notes the
    tradeoffs of "cost, materials, strength of the solder and all that" during
    this mandated changeover, and that manufacturers "have to get an experience
    base" with new processes.

    { snipped as lengthy }

    Tin whiskers: coming to a PC near you?

    · They can grow at ambient temperature and humidity, or in vacuum

    · They can grow in steady or varying temperatures (though the latter may
    encourage growth)

    · Whiskers' tips are atom-sharp. They will push through any coating, given
    time

    · They are a prevalent cause, only now being identified, of many past
    equipment failures

    · One whisker can carry about 30mA - more than enough to cause havoc in
    digital circuits

    · Silver-tin-copper ("SAC") solder slows but doesn't stop whisker growth

    · SAC solder has more environmental impact than the lead-tin version

    · Older 37%-63% lead-tin solder mix merely deforms, reducing stress and
    hence minimising whiskering

    · Whiskers can grow indefinitely

    Source: Howard Johnson, Signal Consulting
     
  2. Arfa Daily

    Arfa Daily Guest


    Isn't it funny how figures can be 'distorted' to make facts suit the
    context. By saying "80m kilos", the EPA make it sound like a HUGE amount,
    but put that into a more 'recognisable' form, and it becomes 80 thousand
    tonnes, which is not nearly so contentious. Then further, take that only 37%
    of that was actually lead, and you are down to 29.6 thousand tonnes. Now
    compare that to the world's lead-acid battery usage, where recycling of the
    end-of-life product to recover the lead, has been sucessfully in place for
    years. At 30th tonnes, the potential environmental impact of the lead in
    solder, even if you *did* dump it all in the ground, is minuscule.

    As I've said before, I'm glad that the avionics industry refuse to use the
    stuff. The day they do is the day I stop flying ...

    Arfa
     
  3. Eeyore

    Eeyore Guest

  4. TheM

    TheM Guest

    Its good for the way economy works nowadays. Buy, buy, buy the crap
    that dies or obsoletes every 2-3 years.

    Mark
     
  5. N_Cook

    N_Cook Guest

    Before I waste time downloading an irrelevant pdf

    would this be what you be referring to :

    Review of Directive 2002/95/EC (RoHS) Categories 8 and 9 - Final

    http://ec.europa.eu/environment/waste/pdf/era_study_final_report.pdf

    Results of vibration testing lead-free solder from different researchers ...
     
  6. And, where do these pin-heads think the lead came from, in the first place?

    Jonesy
     
  7. Eeyore

    Eeyore Guest

    Not sure if that's the one I had to be honest but looks interesting.

    Graham
     
  8. James Sweet

    James Sweet Guest


    And lead isn't the only toxic substance used in electronic equipment and the
    process used to manufacture it.

    Is a lead-free item that fails and ends up in the landfill after 2 years
    better than a lead-containing device that lasts a decade?
     
  9. exray

    exray Guest

    Welcome to California.
    I've used 'alternative' solder. I could live with it if need be. It
    handles differently but geez, I think the fumes would kill me faster
    than eating a pound of lead solder everyday at tea. I've never heard
    the proponents addressing the wicked fumes of the 'better' solder.

    -Bill (63/37)
     
  10. Guest

    You mean the fumes from the flux. You don't believe you're breathing
    solder vapors, do you? In the 40+ years I've been using solder, I
    doubt I've used 5 lbs and I do quite a bit of soldering.

    GG
     
  11. Eeyore

    Eeyore Guest

    AIUI, lead in metallic form is pretty stable and doesn't 'leach' into
    groundwater the way some would have us believe.

    Graham
     
  12. exray

    exray Guest

    I've never turned on my shop spectrometer to determine if it was the
    flux or solder. I just know that the new stuff doesn't smell as
    friendly to my human nose.


    40+ years, 5 pounds, yadda,yadda...how much 'new' solder have you used?
    I suspect you're just trying to pick a fight. I'm not playing. See ya.

    -ex
     
  13. Phil Allison

    Phil Allison Guest

    "Jay Tossers"


    ** Silly comparison.

    Glass does not break down in the environment.

    So how would any of that lead get out ??



    ....... Phil
     
  14. N_Cook

    N_Cook Guest

    One small bit from that study

    "Solder joint failure due to vibration becomes more significant as the
    frequency of vibration approaches the resonant frequency of the component or
    structure.
    Studies by Chuang et al 29 and
    Song et al 30 have sought to identify microstructural features that
    influence the performance of conventional Sn-Pb solders and candidate
    replacement lead-fre solders. The typical microstructure of conventional
    Sn-Pb solders containing coarse pro-eutectic grains reduces the ability of
    these materials to absorb energy during crack formation and hence reduces
    the vibration resistance of joints made using these solders. "

    I thoutht distributed irregularities in structures, suppressed crack
    propogation.
    Would seem NOT to be borne out for the case for premature failures of solder
    joints for unsupported dropper resistors in mucic combos - ie amplifiers
    contained within the same case as large speaker/s.
    Failure in 2 or 3 years of routine use wheras more like 20 years for failure
    in similar but older PbSn manufacture.
     
  15. Arfa Daily

    Arfa Daily Guest

    Basically, there isn't a lead-free alternative that works the same, or even
    close, but you're missing the point(s). Firstly, there isn't *quite* such a
    huge amount or disposal problem as they would have you believe. Second, the
    lead in solder is pretty firmly 'locked into' the alloy, such that it
    doesn't readily come out of the solder into water. Yes, I know that acid
    rain can have some effect on that equation, but that's nothing like as bad
    as it once was. Finally, all electronic equipment in Europe at least, is now
    subject to the WEEE directive, which dictates the way it is treated at end
    of life, covering recycling and disposal of the remains that can't be
    recycled. There is no reason at all that leaded solder could not be
    recovered and recycled, in the same way as lead free solder. 80% of the
    world's metallic lead production goes to automotive battery manufacture.
    Lead recovery and reuse from that product at end of life, has been mandated
    and successfully carried out, for years.

    I think that this is the reason that most people who have to use lead-free,
    get so wound up about it. As far as I am concerned, the legislation that
    mandates its use, is ill-considered, not thought through, unnnecessary in
    the light of the legitimate WEEE directive, and effectively replaces a
    mature and reliable technology, with one that has the potential to be
    directly dangerous to human life, if it ever finds its way into avionics,
    medical, and military applications, which so far, have managed to secure
    exemptions.

    Like any sensible person, I don't want to deliberately pollute the planet
    for those who come after me, but in recent years, many badly informed
    decicisions on this sort of thing, have been made by departments 'jumping on
    the banwagon' to justify their own existence. The whole thing isn't helped
    by celebrities and ex famous politicians serving their own public eye needs
    through 'green' issues. It has actually reached the point where I am now
    sick to death of hearing the words "green" and "eco" and "carbon footprint"
    and "geenhouse gas" and "cimate change" and "global warming" every single
    time I turn on the radio or TV. So here's a new word.

    Ecobollocks. Covers what a lot of this bull actually is ...

    Arfa
     
  16. Arfa Daily

    Arfa Daily Guest

    I don't think that he's trying to pick a fight at all ... Depending on
    whether or not he's talking 'professional' use, that might be a bit of an
    underestimate, but not huge. I hand solder just about every day of my
    working life. I use predominantly 0.7mm solder wire, which I buy in 500g
    reels. I reckon that each reel lasts me probably 3 years, so in 35 years of
    professional use, I have used perhaps 6kg or 13 pounds.

    The reason that lead-free solder does not smell as nice, is that it is no
    longer a basic natural rosin flux that is contained within the solder.
    Because of the new stuff's vastly inferior wetting qualities with most
    metals used in electronics, it has to contain a far more aggressive flux to
    stand any chance of forming a metallic bond. That aggressive-ness is
    achieved by making the flux slightly acidic, so the fumes, if you are
    breathing them, are actually gently rotting the linings of your nose and
    lungs. There was always a declared H & S issue about industrial asthma with
    rosin flux fumes in quantity, but I suspect that this stuff is potentially a
    far greater health hazard than rosin fumes ever were. So, if you're having
    to use a lot of lead-free in your day to day work, I would suggest that now
    is the time to install some fume management, even if it is just an old
    computer fan blowing the smoke across to someone else ... :)

    Arfa
     
  17. Arfa Daily

    Arfa Daily Guest

    And is then properly recycled ?

    Arfa
     
  18. Arfa Daily

    Arfa Daily Guest

    Apparently, in America, they crushed the glass to powder or some such to try
    to prove this. I'm sure that someone from that side of the pond, knows the
    details. The lead which is contained in the faceplate glass to minimise x
    radiation to acceptable levels, is actually not metallic lead, but lead
    oxide, and is very firmly locked into the molecular structure of the glass,
    so wouldn't readily leach anyway. 5 pounds of lead is probably a bit on the
    enthusiastic side on average. 'Big' tubes may contain this amount, or even a
    little more, but average sized ones, and computer monitors, would probably
    be around half or a little more, than that figure. LCD displays, of course,
    do not require this radiation protection.

    Arfa
     
  19. N_Cook

    N_Cook Guest

  20. James Beck

    James Beck Guest

    Mettalic lead has been shown to have very little impact on the
    environment. Especially after it has built up an oxide layer.
    Ah, but we aren't talking about running a smelting operation, are we?
    I don't know.
    Comparing burying metallic lead VS a smelting operation, that borders on
    pinheadiness.
    Until they come up with better alternatives, I'll stick with good old
    lead/tin. When I left my last job, I had a full physical including a
    lead test, and even though I had been "exposed" to lead solder almost
    daily for 13 years, my blood lead levels were almost not measurable and
    that puts me below the national average for people that don't work with
    solder at all. Why would that be if lead/tin solder were so dangerous?

    Jim
     
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