By on February 27, 2010

A number of articles have appeared implicating tin whiskers as a potential source or complicating factor in Toyota’s (and other manufacturers’) unintended acceleration issues. The phenomenon of tin whiskers, a crystalline metallurgical phenomenon involving the spontaneous growth of tiny, filiform hairs from a metallic surface, can cause short circuits and arcing in electric equipment. First discovered in phone switching equipment in the 1940′s, the addition of lead to tin solder largely eliminated the problem. But the push to eliminate lead from electronic assemblies has led to a nasty re-growth of the pesky whiskers. And some are pointing fingers.

Satellites, including the failure of Galaxy IV, nuclear power facilities,pacemakers, and numerous other electronic assemblies have suffered from the effects of tin whiskering (here’s an explanation). In an article at TechEYE.net, a document that details the issues with lead-free soldering is referred to. Another expert in the field Henning Leidecker, chief engineer of the electronic parts office of NASA’s Goddard Space Flight Center in Greenbelt, Md., and an expert on tin whiskers, said in the last four years his office has been contacted by seven major suppliers of automotive electronics inquiring about failures in their products caused by tin whiskers.

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61 Comments on ““Tin Whiskers” Implicated In Unintended Acceleration Problems...”


  • avatar
    Dynamic88

    Interesting.

  • avatar
    Robert Schwartz

    And that explains the brake failures and the inability to put transmissions into neutral. When are you guys going to wise up and realize that yōkai are real.

  • avatar
    panzerfaust

    I guess you can file this under ‘there’s no such thing as a free lunch.’ We see the same issues with fire retarding materials, adhesives, and solvents. Some metalurgist, or chemist didn’t sit in a lab years ago and say to himself “aha, this will really pollute the enviornment, I’ll use lead (or asbestos or Trichloroethane).” Rather those substances were chosen because they worked. The choice to elimiate them was a good one, yet the substitutes have their own problems. The substitutes are sometimes not as good and this can result in property loss, injury and loss of life.

  • avatar
    pgcooldad

    As a Metallurgist …. I knew this was a Metallurgical issue but nooobody believed me. Ok, I never brought this up here!
    Interesting, very interesting …. I’ll have to get back to this later. I love my science.

  • avatar
    segfault

    The guy who wrote the dBi paper seems to know what he’s talking about, but he did make a recommendation against buying electronics during the early ROHS-compliance period (January 2006 through mid-2007), suggesting that there would be widespread failures and that many of the products would have a useful life of less than one year. Years later, this hasn’t happened.

    I still don’t deny that Toyota’s SUA issues may be metallurgical in nature.

    • 0 avatar
      potatobreath

      Consumer electronics have failed due to lead-free solder problems. See iBook Radeon video warranty extensions, MacBook Pro video warranty extensions, NVIDIA 8600 solder problems, Xbox 360 red ring of death, and PS3 yellow light of death.

      They’re not quite the electronic apocalypse, but failures are there.

  • avatar
    JGlanton

    As an electronics equipment manufacturer, tin whiskers has caused serious problems for my business, including a major recall and repair program. I took almost a year to identify the root cause of the intermittent problem, hidden deep inside a power controller circuit board provided by a 3rd party that had recently switched to a lead-free process without notifying customers. They figured that the product was identical, except for the solder and lead finish of course. It took up to two years for the whiskers to grow and cause strange, intermittent problems to products that were mature, well-tested, high quality systems. It took another 6 months to recall and replace the faulty product.

    So, if this is the problem, I can understand how Toyota couldn’t ID for a long time. On the other hand, my little company did.

  • avatar
    crackers

    I understand that some independent agencies that approve the use of electronics for certain applications, ie the FAA, still won’t accept the use of non-lead based solders because of issues like this.

  • avatar
    vww12

    The whiskers thing was predicted yet the Eurocracy wanted their lead-free RoHS headline.

    Well, they got it, and we got the consequences.

  • avatar
    Jimal

    So you’re saying this isn’t a conspiracy between the government and the domestic auto unions to take down Toyota? Fascinating.

  • avatar
    gslippy

    When my company modified all its products to comply with the European RoHS rules in early 2006, tin whiskers was a concern for us. Such a phenomenon can explain the early deaths of numerous electronic devices. Tin whiskers may be part of the blame for “why they don’t make them like they used to”.

    The hysteria over lead consumption in electronics is way overblown. Electronics used to account for something like 3% of lead consumption, yet things like lead-acid batteries are exempt. So a car might have a few grams of lead mixed in with its circuitry, but 20 pounds of it in the starter battery.

    While nobody doubts the negative effects of lead on the body, most of the benefit from lead cleanup has been through eliminating lead piping, leaded plumbing solder, leaded gasoline, leaded paint, and lead content in dinnerware. This has eliminated nearly all means of entry into the body via drinking, breathing, or eating.

    The concern about lead in electronics stems from their disposal into landfills even though the lead content is microscopically small compared to other substances.

    And a reminder: lead comes from… the ground.

    Too bad it’s such a wonderful substance that improves numerous manufacturing processes and the appearance of many goods.

    • 0 avatar
      Jimal

      There is/was a big deal in the powersports industry when (IIRC) the Consumer Product Safety Commission banned the sale of dirtbikes to kids because they contained lead. The lead was the lead in the battery, which would only be a hazard to the young rider if he took the battery out of the bike, broke open the battery, drained the acid (which I think would be more hazardous than the lead but wasn’t cited) and chewed on the lead plates.

      Seriously?

  • avatar
    redmondjp

    I believe that the military has exempted itself from the leadfree requirements, for obvious reasons. This is a serious issue, and these tin whiskers can easily grow to 1/4″ or longer. It’s fascinating, and LEAD is the best prevention for this, not to mention that lead provides other benefits (easier wetting, lower melting point which means less damage to the heat-sensitive ICs and other components) in the soldering process.

    It’s too bad that we are rolling back so many of the advances of the 20th century in the name of preserving the environment. Meanwhile, our use of Chinese-made products helps trash the other side of the world, where the EPA, OSHA, and so on don’t exist. How many people have died in the past 35 years from mosquito-borne malaria since we have banned the use of DDT, which is very safe if used PROPERLY. But that’s another story . . .

    • 0 avatar
      gslippy

      +1 on your comments, redmondjp, particularly the one on DDT.

      The malaria thing is a bit off-topic, but National Geographic magazine (of all sources) had a fascinating article about the mosquito some time ago (http://science.nationalgeographic.com/science/health-and-human-body/human-diseases/raging-malaria.html), which includes the following quote: “The ban on DDT,” says Gwadz of the National Institutes of Health, “may have killed 20 million children.”

      Thanks a lot, Rachel Carson.

      Similarly, the zeal to reduce lead content in electronics may have unintended consequences in numerous industries, including automotive.

    • 0 avatar
      Adamatari

      We aren’t “rolling back advances”, we’re logical concluding that they were a bad idea with unintended consequences and looking for safer alternatives. Do you REALLY want to go back to lead paint and leaded gasoline? Are you willing to give up those IQ points, or have your kids give up IQ points, because lead does some things nicely? We protect the environment because a) we can’t replace it (some things can come back if the damage is light, but once you’ve laid waste to it…) and b) we have to live in it. We screw it up, we have to live in what’s left. We poison it, we poison ourselves.

      As for the DDT issue, the US banned it for good reason – we have the ability to do without and it kills things we would rather have living when the only thing we want dead are mosquitoes. Notably many countries around the world continue to use DDT – it’s the prerogative of the individual countries to ban or use DDT. There are often better alternatives, as can be seen by history – the United States eliminated malaria from Cuba after the Spanish-American war long before DDT existed, basically by being extremely thorough in eliminating standing water near settlements. In modern times there are examples like Vietnam, where moving away from DDT to a different strategy has been more successful. Good governance is the real key to controlling or eliminating malaria, not randomly using huge amounts of DDT.

      As for trashing the third world for cheap trinkets, well, I’m as much for ending that as you. But trashing (what’s left of) the environment in the first world isn’t going to clean up or save the environment in the third world, only not buying unsustainable crap produced by questionable methods will.

    • 0 avatar
      Morea

      Actually most of the people writing on this board grew up in houses painted inside and out with lead paint. Are we all mentally handicapped because of it? In fact virtually all of these poisoning scares are generated to give the media, the EPA, and environmental groups bigger budgets. If any of these effects were truly dangerous it would be immediately apparent. Instead studies with massive numbers of participants with significant time and effort in statistical “data mining” are needed to perhaps, possibly, maybe see a slight effect.

    • 0 avatar
      geeber

      If I recall correctly, the problem with lead paint in houses was that the paint chipped as it aged, and children would somehow eat the chips. There were also problems if the paint was removed by sanding, and children (or adults) inhaled the dust generated as a result.

      If the children were kept away from the chipping or sanded paint, they would not ingest any lead.

    • 0 avatar
      windswords

      “How many people have died in the past 35 years from mosquito-borne malaria since we have banned the use of DDT, which is very safe if used PROPERLY.”

      Estimates I have read say millions.

      “Do you REALLY want to go back to lead paint and leaded gasoline? Are you willing to give up those IQ points, or have your kids give up IQ points, because lead does some things nicely?”

      No. We have perfectly good substitutes for paint and gas. Just let me use it 3% by volume in solder please. Whatever happened to common sense?

  • avatar

    slightly off topic, but is there any reason why putting the lever on the Toyota (or other car with a slushbox) into neutral might fail to put the car into neutral? And if so, what alternative does the driver have to stop the car from accelerating?

    • 0 avatar
      John Horner

      That depends. I suspect that on many cars the automatic transmission lever is doing little more than sending signals to the transmission’s control computer. If so, it is certainly possible for electronic malfunctions to cause the vehicle to do something other than what the selector lever says it should be doing.

    • 0 avatar
      wallace487

      Having driven a Toyota Prius, I can say that the gear selector is electronic. It requires you to hold it in the neutral position for a couple of seconds before the transmission shifts into neutral. It’s an interesting setup because the selector always returns to its starting position after selecting the “gear”. It doesn’t stay seated on the R, N, or D.

  • avatar
    John Horner

    An interesting theory. Speaking of which, tin whiskers can create highly resistive electrical shorts. You know, the kind of shorts Bertel called hokum in one of his recent editorials where he was slamming Dr. Gilbert of recent Toyota testimony fame.

  • avatar
    porschespeed

    +1 Adamatari,

    For those of you who are under 40ish, there was a time when the we-just-can’t-ever-live-without-it crowd said that horrible things would happen to automotive engines if we didn’t have lead as a gas additive.

    On the flip side, the happy-go-lucky-it’ll-all-be-ok folks said that paint would be just fine with no lead and incredibly low levels of VOCs.

    Reality? Both cases were just plain wrong.

    Hardened valve seats worked just fine without lead as a “critial lubricant”, thanks.

    House paint now doesn’t cover, takes forever to dry, and has lousy bonding qualities no matter how well prepared the substrate. Lovely.

    Life is full of case-by-case scenarios, let’s hope we deal with whiskers soon.

    Oh yeah, back on topic. This is actually a scientifically plausible causality proposition. Highly unlikely, but actually plausible.

    Ain’t that novel?

    +1 John Horner,

    Bertel’s understanding of electrical effects in a low-voltage automotive environment appears to be incomplete.

    Honestly, I highly doubt that whiskers are the issue. BUT, at least an explanation that is actually POSSIBLE is out in the public media.

  • avatar
    Robert.Walter

    “I think it is unwise to say you do not believe in anything when you can’t prove that it is either true or untrue. There is so much in the world which is always new in the way of discoveries that it is wiser to say that there may be things which we are simply unable now to fathom.” -FDR

    It is not unusual to assume that obscure and esoteric phenomia may derive from obscure and esoteric causes.

  • avatar

    John Horner: For the last time, there is no such thing as a “highly resistive electrical short.” Contradiction in terms. Porschespeed will explain it to you, he’s the expert.

    Porschespeed: If you think my understanding of E = I * R is incomplete, then please specify my shortcomings. In the meantime, I would be appreciative if you would refrain from blanket statements. Disclosure: I hand-soldered an Altair in 1975, authored some arcane articles about obscure topics in the last millennium, was a member of the IEEE-1394 Trade Association, launched an infamous website in 1997 (it’s still there, for historical reasons,) worked as a consultant for Adaptec, could at some point write assembly code for the RCA 1802 COSMAC (including the equally infamous “Standard Call and Return” technique) and the Intel 8085 microcontroller (thankfully, a forgotten skill.) In short: I know enough to be dangerous.

    Tin whiskers exist. Are they the reason for UA? Easy to find out: Pull the ECUs, open them and look at them.

    Tin whiskers can cause:

    - Solid shorts (as in SHORTS)
    - Intermittent shorts (as in SHORTS)
    - Arcs (in a high-power environment)
    - Debris (think of metal filings sprinkled over a circuit board)

    Most of these can be diagnosed by visual inspection. If the ECU of an UA victim is pulled, and there are tin whiskers present, then this MAY be the cause. Further investigation will then show that it indeed was the cause. Has this been found? Unless it has, we are grasping at – whiskers.

    • 0 avatar
      Christian

      A short just means an abnormally low resistance connection across points in a circuit. What’s considered abnormally low is relative, as is the phrase “highly resistive.” But the vernacular short equates abnormally low with zero. So technically you’re both right.

    • 0 avatar
      JohnAZ

      For anyone who hasn’t put on his blinders, the situation is very simple. Dr. Gilbert has shown the way to how an electrical failure can induce the reported symptoms, and knowledge of tin whiskers shows how the electrical failure can be induced. The mystery has been explained, now all that people without blinders need to do is put their finger on the actual culprit.

      It would not take whiskers on a dead person’s car to prove it. NHTSA should be testing a large cross section of UA reported models for any evidence of whiskers and ruling on the results. Whiskers in electronically controlled two ton missiles should be banned.

      And if no whiskers are found, then start looking for something else.

    • 0 avatar
      Robert.Walter

      “…whiskers can cause:
      - Solid shorts (as in SHORTS)
      - Intermittent shorts (as in SHORTS)”

      That others have seen whiskers expose shorts, is a kind of interesting symmetry, because I’ve seen where short-shorts expose whiskers. Regarding this symmetry, JohnAZ’s last sentence also applies nicely to both.

    • 0 avatar

      There’s a cure for THAT, my friend, and comes right from Brazil …. As for the last sentence, I agree.

    • 0 avatar
      gslippy

      In a former life, we utilized a “whisker” which served as a tuneable high-frequency air capacitor. Our technicians actually bent it to produce the proper performance in our device. Its presence would never be detected by an ohmmeter. You could characterize it as a highly-resistive short, if its presence was unintended.

      It is feasible that a tin whisker could mimic the same behavior. I’d be especially concerned in a hybrid vehicle, which contains a high-frequency high-voltage switching power supply for the electric drive motor.

    • 0 avatar
      porschespeed

      Bertel, if a short is still defined as an unintended zero ohm connection between two nodes, do we do when it’s not zero ohm?

      I was not arguing that you don’t understand what a “short” is. Nor do I claim to be an electronic genius in any way. What I am saying is that EEs that I have interaction with, use a variety of more descriptive terminology that “short”, because the strict definition of a “short” is rather limited.

      “Highly resistive short” is not new art. Contradiction in terms? One could make that argument. But it is out there as a descriptor, as well as “micro short” and a host of others.

      Personally, I learned those terms from a Cal Tech educated, Lawrence Livermore engineer who helped me troubleshoot the L/LH-Jet Brain test bench that I designed and built.

      Congrats on the Altair, I wanted to get the Mark8 kit, but the parents couldn’t afford it.

      As a technician, I know that in a complex system different types of “shorts” can produce different failures. Hence, they have different descriptors. You are free to accept or reject those descriptors. Regardless, they exist in common parlance.

      Apologies that I didn’t phrase that more eloquently.

  • avatar
    chanman

    Something similar in Xbox 360 video cars has been suspected as a contributing factor in their high failure rate. Their graphics cards were in the first generation designed after a switch to lead-free solder.

  • avatar
    pgcooldad

    Nasa has an extensive page on Whiskers that I’m currently catching up on.

    http://nepp.nasa.gov/WHISKER/background/index.htm

    http://nepp.nasa.gov/whisker/

    I’m sure most don’t have time to read a lot of the findings but at least take a look at the photos to see the extent of the problem.

    http://nepp.nasa.gov/whisker/photos/index.html

  • avatar
    NickR

  • avatar
    Beta Blocker

    panzerfaust: ” ….. The substitutes are sometimes not as good and this can result in property loss, injury and loss of life.”

    Then there was the loss of the space shuttle Columbia in 2003.

    The process used to apply foam insulation to the shuttle’s external fuel tank had used CFC’s in the foam application solvent.

    When the foam application process employing CFC’s was dropped for environmental compliance reasons, a problem appeared immediately with shedding of foam pieces from the tank during launch.

    When the problem first appeared, NASA management could have requested an exemption from the CFC ban, but they were far more concerned with being politically correct than they were with maintaining a safe shuttle program.

    Not only that, they went so far as to have the NASA engineering staff pencil-whip the foam shedding problem away, even after damage to the shuttles was already occurring well before the Columbia disaster.

    Even after the Columbia disaster, the source of the foam shedding issue — NASA’s decision not to use a CFC solvent in applying the foam insulation — was never identified in the mainstream media as being a key root cause in the loss of the shuttle.

    Thank heaven for the Internet and for its ability to keep us well-informed as to the real facts behind our public policy debates.

    • 0 avatar
      Steven02

      Actually, the media did report this problem. They said the foam had been changed to be more environmentally friendly. But, the foam change actually didn’t cause the problem. Foam falling off happened before the change, it was only on this flight where the foam caused a large hole in a crucial part of the wing.

      You can find more information here.

      http://en.wikipedia.org/wiki/Space_Shuttle_Columbia_disaster#Initial_investigation

    • 0 avatar
      Beta Blocker

      Steven02, the Wikipedia article on the Columbia disaster and some of its reference documents make for very interesting reading.

      The external tank had been shedding foam since the very beginning of the program. Reading the references, there were periods where the foam shedding problem was worse than the norm, and one of those periods followed the CFC decision.

      However, after eight or ten more flights, the rate of foam loss incidents fell to a more-or-less average level of activity. As I understand the article, the problem exists to this day.

      There is a body of opinion among some space enthusiasts that the space shuttle is an inherently weak system overall, from both a systems engineering and a systems management perspective, and that the program should have been cancelled years ago in favor of some other technical and operational approach.

    • 0 avatar
      Steven02

      I agree and understand why people would think it is a weak system. It was supposed to be a cheap reusable vehicle with high reliability and low expenses to operate… well I guess those were all gov’t approved descriptions because it turned out to be none of those.

  • avatar
    golden2husky

    Adamatari: Well said. Often materials that were once thought of as safe turn out to not be. Comments like we lived with lead paint and don’t have six heads are meaningless. I’m willing to bet the vast majority of those “healthy with lead paint” people didn’t spend 30 years sanding it on an occupational basis. Same for other things like asbestos, which easily jumped into mainstream exposure with such uses as brake pads for cars and subway trains.

    The reality is that often we just don’t know what latent hazards exist, or what performance problems may crop up. In the old days, material selection was made primarily on cost. Back then nobody cared about hurting workers or the environment. Those were just things to be manipulated to the benefit of the ruling industrialists of the time. Today we should know, and act better. And sometimes, it may be true that the new method/material may possess their own set of problems. That may very well play out with fiberglass as a substitute for asbestos. However, once a product is know by sound science to be a hazard, it would be most negligent to ignore the facts.

    Also, keep in mind what happens to most electronic consumer items. No, they are not typically recycled, though a growing amount are. They typically end up being buried in a landfill or incinerated with household garbage. Either way, the heavy metals end up in the air or water. So, to minimize the effect of waste electronics is foolish.

    Lastly, we should be thankful for people with insight and selflessness like Rachel Carson (who wrote “Silent Spring” and warned about the severe hazards of irresponsible use of pesticides). She flew in the face of the “what’s good for GM is good for the country” crowd…something that was not readily accepted back in the “good old days”…

  • avatar
    psarhjinian

    I wouldn’t have thought tin whiskers would turn up in an environment like this. I know they’re murder in sound studios and (in my experience) datacentres where the unchanging environment and fixed airflow patterns pretty much guaranteed their formation.

    DCs go to a lot of measures to prevent tin whiskers because they form really easily if you’re not careful. I’m probably mislead, but I have trouble seeing how they’d form in a consumer automobile, which is about as unlike a DC as possible.

    On the topic of environmental lead: it’s a good thing we’ve taken the steps we have. Environmental lead is a really bad thing: there’s been studies that suggest that a) the use and discontinuation of lead in fuel and it’s removal from the environment more or less tracks the incidence of violent crime, especially in youth and b) that lead poisoning might have been a significant factor in the fall of Rome.

  • avatar

    Availability of abortion is also found to correlate with reductions in violent crime. I’m absolutely not saying that you are wrong about lead, I agree with you completely that lead in the environment is a bad thing, as it is found to reduce IQ.

  • avatar
    Michal

    Early last decade Fujitsu had serious problems with their computer hard drive products due to tin whiskers through the phasing out of leaded solder. Pretty much every hard drive in their consumer product line was expected to fail within a few years. I personally had two out of two die. It pretty much killed Fujitsu’s desktop hard drive business.

  • avatar
    RogerB34

    That is a science and engineering issue.
    Otherwise BS.

  • avatar
    George B

    I believe that fear of tin wiskers is overblown. My wireless telecom infrastructure employer switched over to SAC lead-free solder and RoHS-compliant components in 2005 and I don’t think we’ve had a field failure that can be blamed on tin wiskers. However, we also conformal coat the boards after they are stuffed. We went RoHS because it was clear that cutting edge microprocessors, DSP, and FPGAs wouldn’t be available with BGA (solder ball connection) packages compatible with tin-lead solder. Only the RoHS compliant parts would be available at reasonable prices in the future.

    If Europe had been less absolute in their “lead is evil” ban, solder with a small percentage of lead could have been used to suppress tin wiskers.
    http://www.scribd.com/doc/16702146/JP002-Tin-Whiskers-Theory
    Low-lead would have been a much better choice than no-lead. However, I personally prefer to work with eutectic 63% tin 37% lead solder. Wonderful ductile stuff with a low melting point.

    RoHS background info.
    http://en.wikipedia.org/wiki/Restriction_of_Hazardous_Substances_Directive

    • 0 avatar

      Good comment, George B. Conformal coating should be standard issue with PCB used in harsh environments such as an ECU. Conformal coating is known to pretty much mitigate the ill effects of whiskers. Let’s move on to the next theory …..

  • avatar
    psuahr

    Vehicles in Europe are covered by ELV, not RoHS, and the “Solder in electronic circuit boards and other applications” are exempt from the restrictions on lead. The article referenced in this post referes to an article that talks about tin whiskers in its title, but the content deals primarily with EMI. Let’s first have some evidence that lead free solder is being used in Toyota vehicles before we blame tin whiskers for these failures.

  • avatar

    There is a quick fix for the tin whisker problem:

    http://www.hybridplastics.com/docs/tds/ShortStop.pdf

  • avatar
    William C Montgomery

    Funny, when I posted this news blog about tin whiskers a couple years ago, most commentators didn’t think it would be a problem.

    http://www.thetruthaboutcars.com/auto-electronics-could-get-buggier-still/

    • 0 avatar
      rockford_il

      I’ve performed failure analysis a number of years, and am still on the lookout for my first tin whisker. The transition from HASL (Hot Air Solder Level, tin-lead coating on circuit boards) to electroless tin and immersion silver was a definite cause for worry.

      But electromigration / dendrites could be just as likely to occur as tin whiskers.

      Then there are the odd failures, such as high-temperature stabilizers in plastics that can leach out and cause electrical leakage and corrosion.

      Worst-case, there are multiple “needles in the haystack” to be found.

  • avatar
    tkb01029

    Having recently purchased a 2010 Flex, I experienced a brief unintended acceleration incident. Actually it was the second occurrence within a week, the first occurring during a test drive of the same model vehicle from a different Ford store.

    That said, I was engaged as a Materials Scientist by a very large computer firm back in the 1970s. Metal migration (whiskers / fibers) was a great cause for concern. It was a well known failure mechanism within semiconductors and their packages. This was particularly troublesome in industrial or environmentally hostile operation environments (like under the hood of a car.)

    The rapid advances in manufacturing technology allowed increasing device densities but also increased the propensity for this failure mode at the device level. Many proprietary changes in metallurgy and fabrication methods were tried before satisfactory solutions were implemented.

    Now nearly 50 years later, reading of this phenomena, is mind boggling. We do seem to be constantly having to reinvent things because we fail to be willing to borrow from history lessons.

  • avatar

    Has anyone here seen a tin whisker?  I have (I have some samples from NASA).  Until I saw them, I had no idea what I was looking for.
    Thanks to an invitation from a scientist at NIST, I have been participating in an aerospace industry weekly teleconference on tin whiskers for the past two years.  Participants, including myself have consider it possible that tin whiskers could be responsible for sudden acceleration and other odd behavior in automobiles manufactured after 2002-2003. Dr. Gilbert of Southern Indiana University has participated in the teleconference and shared with us what he had learned (I was the one who invited him to attend).
    Dr. David Gilbert has demonstrated that a low resistance or shorted input between the wires  from the pedal electronics to the electronics control module will cause  Toyotas to open their throttles full.  A tin whisker could induce such a short and as Dr. Gilbert proved, pushing as hard as you can on the brake pedal will not overcome the throttle being held full open.
    Perhaps the problem is due to  leadfree manufacturing (which Toyota states on its website it began in 2002-3)?   Perhaps it is software?  We don’t yet know but we can be reasonably  certain that not all the accidents are caused by the owners of the  vehicles.  You can see pictures of the Toyota parts at my website  [www.hlinstruments.com//RoHS_articles/Toyota/]
    The pedal assembly has a printed circuit board layout that is not as well designed as it could be.  In particular,  the tiny integrated circuit that converts the signals from the Hall effect sensors  (that senses pedal position via a magnet attached to the pedal arm) into 1-5Vdc signals sent to the electronic  control module is very close to the edge of the board.  The board has  serrated edges which indicates it was snapped out of a large panel of  these boards after the parts were soldered to it.  It’s possible a trace  or lead has fractured or one of the capacitors or resistors.  We know  that leadfree solder is more brittle than tin-lead. Perhaps a few boards  are marginal and over time a lead opens or becomes intermittent?
    Whiskers are very hard to find. Only about 20% of them are visible to the naked eye and only in light reflecting off them at a certain angle.  The remainder require a microscope and to see them in great detail you need a scanning electron microscope with an X-ray fluorescence detector. Not something you average auto repair shop has.
    Even if tni-lead solder is still being used, the components themselves, thanks to RoHS, are now mostly pure tin plated.  Some companies have the gall to advertise their tin platings won’t grow whiskers.  Only time will tell if that’s true.  The standard (industry approved test) for whisker proof tin finish (JESD-201) is 4000 hours and the resulting whiskers can be no longer than 50 microns (0.002″).  4000 hours is less than a year.  What happens after 4000 hours?  Your guess is as good as mine.  To quote a NASA researcher friend (Lyudmyla Panashchenko), “sometimes tin whiskers”.

    Auto dealers call another friend of mine (Dr Henning Leidecker) at NASA Goddard Space Flight Center, who is one of the world’s experts on the subject of tin whiskers.
    This is why the US DOT contacted NASA to investigate Toyota’s problems.  And, by the way, DOT may have said they found no problems, but NASA isn’t finished with it’s investigation nor is the National Academy of Sciences.

    Dr.  Leidecker said that in the last four years his office has been contacted  by seven major suppliers of automotive electronics inquiring about  failures in their products caused by tin whiskers. He said his office  has contacted Toyota offering to help analyze its acceleration problem,  but hasn’t heard back. For full context, read the rest of the article  [http://wtop.com/?nid=108&sid=1898265].

    It’s not just the removal of lead from tin-lead solder that is a potential whisker problem, its’ that parts are now being plated in pure tin and they can grow tin whiskers “with a certain  amount of aging”. According to NASA, whiskers can grow in hours, days,  weeks, months or years. It depends on at least six factors; the quality  of the tin plating, the residual stress in the coating, was the coating  annealed or not, grain uniformity, temperature, humidity, and unknown  other factors we don’t yet understand which is what makes it so  difficult to stop whiskers from growing and is why there are so many  papers published on the subject yet we still do not understand why or how they grow.

    So  yes, is entirely within the realm of possibility that “new” products  have failed due to tin whiskers or perhaps dendritic growth.

    NASA  cannot tell us who the manufacturers are who reported these events due  to confidentiality agreements.  Dr. Leidecker says they get these calls  from other industries as well and most request a non-disclosure  agreement.  NASA feels it’s better to get some information rather than  none, don’t you agree?

    A few months ago I was at  the 4th International Conference on Tin Whiskers at CALCE at the University of Maryland where it was  reported that 31% of all laptops fail within 3 years. This is the link  to the report http://www.squaretrade.com/pages/laptop-reliability-1109/   No information is given as to what has failed. Is it due to whiskers?   We do not know.

    What we do know is that the laws of physics have  not been repealed.  Tin will most certainly grow whiskers so using  leadfree solder and tin plated components has to result in tin whiskers  growing.

    NASA continues to log failures.  NASA Goddard has signed a non-disclosure  statement so they cannot comment on the study at this  time.

    The  EU was warned that tin whiskers and brittle joints would result if lead  was banned from electronic assemblies but went ahead and banned lead  from tin-lead solder and platings on parts. They acknowledged the  possibility of reduced reliability under intense pressure from hi  reliability industries and did exempt some products (military,  aerospace, etc…).  What difference did it make since the majority of  component manufacturers refused to continue to offer tin-lead plated  leads?  That is why NASA replates it’s components with tin-lead at  Corfin Industries and uses only tin-lead solder.


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