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JefW
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re: Toyota accelerations revisited—hanging by a (tin) whisker
JefW   7/18/2012 11:30:20 AM
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Sigh. These whiskers clearly don't grow from the solder joints but the tin plating. Although I've heard that corrosion can generate them on any tin surface, I've only seen whiskers on bent component leads some distance from the solder.

divide_by_zero
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re: Toyota accelerations revisited—hanging by a (tin) whisker
divide_by_zero   1/18/2012 5:03:42 PM
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What's really scary is the RoHS Recast, where the category called Control and Monitoring Equipment will be lose its exemption for consumer goods in mid-2014, with industrial equipment phased in at later dates. This category includes all kinds temperature, humidity, gas, fluid level, etc. sensors and alarms, including smoke, carbon monoxide, burglar and other types of security equipment. It also covers devices like PID controllers and motion sensors. Typical installed lifetimes for these devices in homes is up to 10 years. I'm a tree-hugger myself, but I think the mandatory use of lead-free solder is extremely wrong-headed, especially where human safety is involved. These types of products should maintain their exemptions until such time that whisker-free solder is available in the market. Expecting working solutions to gnarly technical problems to appear by legislative fiat doesn't always work.

DrQuine
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re: Toyota accelerations revisited—hanging by a (tin) whisker
DrQuine   1/14/2012 4:45:43 PM
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The law of unintended consequences: when direct mechanical linkages are replaced with "fly-by-wire" connections some very subtle failure modes can arise.

tb1
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re: Toyota accelerations revisited—hanging by a (tin) whisker
tb1   1/11/2012 5:42:15 PM
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So is this European bureaucratic push to lead-free solder a mistake? The argument they always made to the various problems it creates was "The engineers will figure it out. They always have in the past." Consider: -Lead is a neurotoxin, and having it in the environment is a bad thing. But my understanding is that lead solder doesn't leach into the environment. -Using lead-free solder requires higher assembly temperatures, using much more energy. -The higher soldering temperatures requires more exotic materials to prevent damage--some of which may have their own environmental problems. -Even with the more exotic material, there are still going to be more damage occuring during assembly due to the higher temps, resulting in more failures (and more trash), and reduced reliablility. The lead-free tin-whisker problem is better understood and controlled than it had been in the past, but it is not eliminated. That's good for companies selling consumer goods, because the equipment is more likely to fail over time so they will be able to sell more products. But it isn't so good for the environment (more trash) and, as this article shows, for safety. You could argue that you could still use lead solder for safety critical components. But it doesn't work that way. Processor and memory chip companies don't want to build their products both ways, so they ONLY offer them in lead-free packages. Even with exemptions, there's no choice but to build products lead-free. That's true for car brake systems and for nuclear reactors.

markhahn0
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re: Toyota accelerations revisited—hanging by a (tin) whisker
markhahn0   1/10/2012 7:47:08 PM
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the first 'A' in NASA is for aeronautics, which field has a long history of sensor use and forensic post-mortems. I guess it's the latter expertise that made NASA a good choice for this. and bravo to them!

nicolas.mokhoff
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re: Toyota accelerations revisited—hanging by a (tin) whisker
nicolas.mokhoff   1/10/2012 4:16:13 PM
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pixies: if I read the NASA report correctly, the request for NASA to step in was made by the Department of Transportation based on a complaint submitted to DOT by a driver of a 2003 Toyota Camry who experienced the problem (see page 13 of the pdf): http://nepp.nasa.gov/whisker/reference/tech_papers/2011-NASA-GSFC-whisker-failure-app-sensor.pdf

pixies
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re: Toyota accelerations revisited—hanging by a (tin) whisker
pixies   1/10/2012 2:55:00 PM
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Why is NASA working on this earthly problem?



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As data rates begin to move beyond 25 Gbps channels, new problems arise. Getting to 50 Gbps channels might not be possible with the traditional NRZ (2-level) signaling. PAM4 lets data rates double with only a small increase in channel bandwidth by sending two bits per symbol. But, it brings new measurement and analysis problems. Signal integrity sage Ransom Stephens will explain how PAM4 differs from NRZ and what to expect in design, measurement, and signal analysis.

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