Folks,
After my recent post on the fact that there was no data linking tin whiskers to the Toyota sudden acceleration issues, there continue to be more posts saying things like “Tin Whiskers Implicated in Unintended Acceleration Problems.” Many of these posts link back to the earlier TechEye post. The basis for all of the posts, is a paper written by EurIng Keith Armstrong . Armstrong’s paper is titled: “Toyota ‘sticking pedals’ recall is a smokescreen, Their sudden unintended acceleration problem is caused by electronics either due to EMI, lead-free soldering or software ‘bugs.’” It does not appear that Armstrong’s paper was sponsored or refereed.
Since it appears that this entire wave of reporting implicating tin whiskers, in this important issue, emanates from Armstrong's paper, it is helpful to quote his
entire comments on Tin Whiskers:
"9.0 Lead-free soldering:
In recent years, various countries and trade blocs (including the European Union) have banned the use of lead on electrical solder, on the basis that lead going into landfill when electrical and electronic products are disposed of is bad for the environment, and hence for people.
But many accuse them of being shortsighted – lead has been added to solder in quite large amounts for many decades because it made the other main constituent, tin, behave much better, considerably improving reliability.
Now that lead has been removed from solder, which is now mainly tin (with a little silver and copper added) all sorts of new possibilities arise for short-circuits and open-circuits, and intermittent shorts and opens, mainly on printed circuit boards (PCBs) and mainly associated with small-footprint integrated circuits (ICs), especially ball-grid arrays (BGAs).
Its really just another cause of intermittent or fixed short-or-open circuits in electronic PCBs and modules - but one that would not have been any problem until a few years ago, and so could have caught Toyota by surprise.
John R Barnes has created a monumentally huge library of references to the problems of lead-free soldering, especially tin whiskering, see www.dbicorporation.com/rohsbib.htm. Prepare to be totally overwhelmed!
Removing lead from solder has the following effects:
9.1 Tin whiskers
These will grow out of soldered joints and can contact other conductors, causing short-circuits between PCB copper traces and the pins of connectors. They are often no longer than 0.5mm (about 1/50th of an inch) but can grow to 1mm (about 1/24th of an inch) or longer, especially in damp conditions.
Even at 1/50th of an inch they can short between the pins on a modern integrated circuit (IC). And the process of removing the PCB for inspection can brush them off, so you never find them.
And if you didn't accidentally brush them off, they are so thin they are very hard to see - you need a powerful microscope. They are as fine as the finest spider-web threads, yet can carry sufficient current to short-out the electronics. You won’t see them unless you are looking for them.
Being so thin, they can wave around in the breeze and/or due to shocks, vibration and acceleration, causing intermittent short-circuits.
The iNEMI organisation has published guidelines (www.inemi.org) on how to ensure that tin whiskers don’t grow too long, but I don’t know to what extent these are followed by suppliers of electronics to the car industry in general, or Toyota in particular."
Note that, in this paper, there is no data or any evidence re: tin whiskers discussed from investigating any of the vehicles in question. All of this paper is an opinion. In addition, the title of Armstrong’s paper leaves no room for any other cause, it has to be electronics or software. This position is very strong indeed for having no supporting data.
More recently Bob Landman added these comments to the tin whisker discussion:
“the increased use of electronics in automobiles when mixed with RoHS can make for a deadly cocktail. We don’t know what the causative agent [in regard to the Toyota recalls] was, but I have heard recently of new autos showing up at dealers that will not start. That cause has been linked to tin whiskers.”
Bob heard this. There is no report and no data. Until Bob gives us a reference for some analysis and data, his comments are little more than hearsay. I searched the web in vain to find information related to Bob’s quote. In addition this comment is a little surprising, tin whiskers are usually associated with a certain amount of aging, hence not usually found in new products.
That tin whiskers exist and cause failures is irrefutable. NASA has an excellent website related to tin whiskers and failures caused by them. However, the total number of tin whisker fails reported is less than 100. Many other types of electronic failure modes would appear to be much more common.
My purpose of writing this post is not to suggest that tin whiskers are not a concern in lead-free electronics. However, it is a fundamental principle in engineering and science to only make pronouncements on how something failed, when they can be supported with data. No data supports implicating tin whiskers in the Toyota incidents. It is also troubling how readily many people referenced the work of Armstrong without apparently reading what he said and checking his sources and lack of data.
Cheers,Dr. Ron
The image is from: http://nepp.nasa.gov/WHISKER/photos/ziff/ZIFF-whisker-3.JPG
Comments for Are Solder-Related Tin Whiskers Implicated in Toyota Sudden Acceleration Issues?
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Name: Rick ShortTime: Monday, March 22, 2010I am very surprised to witness the extreme lack of "science" or "engineering" in most public discussions of this issue. As you point out, Dr. Lasky, it isn't hard to follow the literature path and to realize that there is NO research, experimentation, or evidence to lean on. It seems that yours is currently the only voice of reason on this issue.
Thank you for speaking "from one engineer to another" to all interested engineers. I hope your stance inspires others to return to science and solve this issue logically.
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Name: Bob LandmanTime: Friday, March 26, 2010My source for the dead vehicles that arrive at car dealers having whisker problems, that information comes from none other than my former professor of physics, Dr. Henning Leidecker at NASA Goddard Space Flight Center in Greenbelt MD.
Ron Lasky confirms that parts plated in pure tin will grow tin whiskers "with a certain amount of aging". As for the time it takes to grow whiskers, they can grow in hours, days, weeks, months, years. It depends on many factors including the quality of the tin plate, the stress in the coating (annealed or not), grain uniformity, temperature, humidity, and other factors we don’t yet understand.
So yes, is entirely possible that "new" products have failed quickly due to whiskers. NASA cannot tell us who the manufacturers are who call for help due to confidentiality agreements. Don't you agree that it's better to get some information than none?
You can add the following which was learned last week at CALCE at UMd. 31% of all laptops fail within 3 years. That is all I know presently except to say that the laws of physics have not brn suspended. Tin will most certainly grow whiskers; it seems to me it is "when" not "if" they will do so.
NASA continues to log failures. NASA Goddard is now, for NHTSA, studying the Toyota incidents. Again, a non-disclosure statement has been signed so Dr. Leidecker cannot comment on the study at this time.
Dr Gilbert of Southern Indiana University has demonstrated that a shorted input to the electronics control module causes Toyotas to open their throttles full, perhaps the problem is due to lead free manufacturing (which Toyota admits it began in 2002)?
If you want to learn more see pictures of the Toyota parts at www.hlinstruments.com//RoHS_articles/Toyota/
The EU was warned that this would happen but went ahead and banned lead from tin-lead solder and tin platings. The result?
Perhaps we are seeing it but are not willing to admit it? 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 www.wtop.com/?nid=108&sid=1898265
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Name: FYITime: Thursday, June 10, 2010Haven't found that software glitch, Toyota? Keep trying
http://www.latimes.com/news/opinion/opinionla/la-oew-cummings12-2010mar12,0,2595172.story
(excerpts):
An electronics problem isn't to blame for the sudden acceleration, say the carmaker's engineers. That's nearly impossible to conclusively determine through laboratory tests.
Because of Pathfinder's high reliability requirements and the probability of unpredictable hardware errors due to the increased radiation effects in space, we adopted a highly "defensive" programming style. This included performing extensive error checks in the software to detect the possible side effects of radiation-induced hardware glitches and certain software bugs.
David M. Cummings, executive vice president of the Santa Barbara-based Kelly Technology Group, spent nine years as a consultant for the Jet Propulsion Laboratory, where he worked on the Mars Pathfinder spacecraft.
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No easy answer for the Toyota problem
http://www.washingtonpost.com/wp-dyn/content/article/2010/03/15/AR2010031501693.html
By Jeremy Anwyl Tuesday, March 16, 2010
The writer is chief executive of Edmunds.com, which recently announced a competition with a
cash prize for anyone who can demonstrate in a verifiable manner the reason for unintended acceleration.
[Included chart in W. Post hardcopy issue: (Toyota and the accelerating mystery; page A19)]
Discrepancy in complaints
Consumer reports of cases of unintended acceleration by manufacturer
(Model years 2005 - Sept. 30, 2009)
Sales (in millions) Complaints per 100,000 vehicles sold
GM ....... 16.5 .......... 0.81
Toyota ... 11.0 ........... 4.81
Ford ...... 10.8 ........... 3.12
Chrysler .. 9.1 ........... 1.72
Honda ..... 7.1 ........... 1.26
Nissan .... 4.6 ........... 1.07
SOURCE: Edmunds.com analysis of National Highway Traffic Safety Administration complaints
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Name: John RoslleTime: Monday, July 26, 2010Four months or more and there is still no conclusive evidence of what is causing the sudden acceleration problem. Gotta make you wonder who’s making money of f the issue(s).
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