Tin whiskers and electronics

I was just watching Modern Marvels Engineering Disasters 12 and they talked about these "tin whiskers". I was thinking "WTF are those?" and apparently tin plating, which is used in a lot of electronics, has this strange phenomenon in which microscopic filaments grow out of the surface and can cause spontaneous shorts between pins of chips and whatnot. They have been implicated in many failures of satellites and probably likely something in your own life. But, using a lead alloy (which is non-RoHS compliant now) greatly prevents this.

Here's a link to some info on NASA's website:
http://nepp.nasa.gov/WHISKER/background/index.htm

And the obligatory wikipedia entry:
http://en.wikipedia.org/wiki/Whisker_(metallurgy)

I've never heard of this before and thought it was pretty crazy. Probably explains why I have so many electronics that just went crap.

EDIT: wikipedia link fixed... automatic linking didn't include the end parenthesis before

hah, yeah i recall reading or watching someting about that somewhere.
i was just as perplexed as you, its truely an odd phenomenon.
but that whole lead alloy thing is good to hear

I remember one professor telling me about how a student came to him and asked him why his board, which had been working perfectly before, suddenly didn't work anymore. After some questions, he learned that the student had soldered some new components on, and to clean the board of the excess residue, he wiped the board down with alcohol. The problem was that the student didn't allow the alcohol to properly evaporate before he turned it on, and the board began to suffer from metal migration much like described in the article above. Those kinds of problems are the worst too, because they're really hard to locate.

Metal migration happens in microelectronics as well, especially in conditions where there is a lot of current and there are bends in the conductor. The metal will actually migrate across such that it smooths out the curves, sometimes causing shorts. With semiconductor devices shrinking all the time, and the current/power densities so high, it becomes a major problem. Detecting such issues at the functional level keeps a lot of companies in business too.

As for RoHS components. Considering all the lead sinkers from fishing that find their way into our freshwater lakes and rivers, I'm not too concerned about whatever lead is mixing in with all the other garbage at the landfill. I'm glad such solder is not banned in the USA like it is elsewhere, or I'd have to stock up on it.

I saw the same episode! Really neat stuff, especially the pictures they showed of the tin whiskers under microscope. too cool!

I'm sure you could make a lot of money figuring out how to stop this from occuring since EVERYTHING electronic would utilize the technology.

GooeyGus said:

I saw the same episode! Really neat stuff, especially the pictures they showed of the tin whiskers under microscope. too cool!

Click to expand...

yeah, it was pretty cool since I had no idea this occured. Watching the History Channel is fun I watch the Modern Marvels a lot and actually learn a lot of stuff I never knew before.

I read about this many years ago but I have never seen it happen.

Mike

Ha ha, this is great

No longer must we admit to crappy handiwork, for now we have a microscopic excuse to why it isn't working!

I've seen it on tin indium gold alloy solder in multi laser diode stack arrays.