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Moral railroads (update)

I wrote in the Moral Railroads post that the key to trustable systems is that they work right. A recent post at Metblogs points out one reason they may have failed: overregulation because of the demonization of a substance.

“In the aftermath of the crash on the Red Line between the Takoma and Fort Totten stations, Metro officials analyzed track circuit data and found that one circuit in the crash area intermittently lost its ability to detect a train. The circuit would report the presence of a train one moment, then a few seconds later the train would “disappear,” only to return again.”

It sounded to me like the same problems that have been encountered on the Space Shuttle, nuclear power plants, and various military systems. And that problem is tin whiskers.
The backstory: When people first started building electric circuits, they used tin metal to solder the interconnections between the copper bits. It wasn’t long before they noticed the tin would get “furry”, growing spiky whiskers as the part was used. These spikes could grow long enough to short out the circuits, and then were so weak that they would break off right after doing so. A smart metallurgist figured out that adding a small amount of lead to the tin alloy stopped this behavior.

Then, of course, the regulators demonized lead, because yes, it is poisonous in the long run if you eat or drink it. (Personally I’ve been able to keep my appetite for circuit boards under control.) So people die, and they blame “technology” rather than overzealous regulators.

Yet the activists admit that the amount of lead in electronics isn’t at dangerous levels; they say their ultimate goal is to shut down lead production entirely. (In the interest of full disclosure, I facilitated a study back in 2005 that predicted this, and only now is the military starting to address those findings.)
Hey, guys, maybe technology might need to trump politics for once?

… or that, God forbid, regulators be held accountable for the deaths they cause?

(Ht/ Ronald Bailey at Reason)

3 Responses to “Moral railroads (update)”

  1. threedonia.com » Fall of the Machines Says:

    [...] And here’s a follow-up post. which links to this interesting post at Metblogs on a thing called “tin whiskers”. In it he comments on a Washington Post article on why the train computer systems failed. From Metblogs: It sounded to me like the same problems that have been encountered on the Space Shuttle, nuclear power plants, and various military systems. And that problem is tin whiskers. [...]

  2. Agribusinessman Says:

    The effect was noted about 30 years ago on circuit boards that were thermally cycled with power on. The thermal cycling would cause condensation on the boards from the cold part of the thermal cycle. In the presence of moisture, dendritic growth (tin is prone to electromigration) occurs between adjacent soldered joints and traces at different electrical potential (primarily between power and ground). The growth of “dendrites” eventually causes shorts at these points. Normally circuit boards used in harsh environments are conformal coated to prevent this.

  3. SteveA Says:

    Ummm, no. Solder was always 40% lead, because that gives it the lowest meltimg point. The tin-whisker problem was noticed on other things, like “tin” cans, which (in olden times) were steel plated with basically pure tin so it wouldn’t rust.

    Tin whiskers became a problem in the early days of spacecraft, because they could grow long enough in zero-G to short things out, as mentioned. In normal gravity, with vibration, they tend to break off before getting long enough to do harm.

    The Euro-crats mandated lead-free solder in most electronics starting in 2006. Google “RoHS” for details. Current lead-free solder is mostly tin, with a bit of copper (and some other things) added specifically to prevent tin-whiskering (and bring the melting point down a bit).

    That part of the Metro system was built decades ago. Unless the Metro signaling system was replaced after mid-2006, it was not built with lead-free solder.

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