Tin in solder or some other meals can form spiky crystals when under stress. These whiskers can form short circuits if not properly insulated or not alloyed with other metals.
Fun fact: Leaded solder is still required in aircraft because it doesn’t grow whiskers like this, while pure tin solder does.
Tin whiskers have also been identified as the cause of some satellites going down too, so spacecraft definitely still using leaded solder.
https://nepp.nasa.gov/whisker/failures/index.htm
Also recommend looking at the homepage of that site. Lots of cool pictures and research papers on metal whiskering.
And the thermal properties in general are better (or better known) too for leaded I think.
It’s a real shame about the brain damage, lead really is an amazing metal
This can happen inside ICs and has been a known failure mode for high frequency processors for many years. I work in chip design, and we use software tools to simulate it. It’s called electromigration.
This statement is not fully accurate. Whiskers in OP’s case are about (usually) tin whiskers that grow, often visibly, and then can connect (short) to unintended areas.
Electromigration is effectively when a large potential difference encourages ions to relocate to reduce the potential difference.
Big Whiskers have two methods of formation. The first way is that tin ions are able to move by becoming soluble in some form of water so they’re mobile. The other way whiskers can form is from stress alone. (Stress being force per area that compresses or tensions the metal in question, applied through a multitude of ways) Whiskers can be directed by electromigration so they form tendrils to a differing potential, basically purposefully ruining stuff instead of randomly shorting things.
Now in integrated circuits (ICs), there are extremely high currents running through extremely small regions. Electromigration in ICs is caused by electrons getting yeeted at extremely fast speeds, giving them significant momentum. They collide with ions in their path and dislodge the ions from their matrix. This can result in voids of ions preventing current from flowing (open circuits) or tendrils of ions making a path to an unintended area and connecting to it (shorting it). The tendrils here are also called whiskers, but are generated in a very different way (e.g., no water solubility or inherent stresses required) and on a significantly smaller scale. And probably not in tin.
The more you know!
The mechanism behind metal whisker growth is not well understood, but seems to be encouraged by compressive mechanical stresses. According to Wikipedia.
Electrons in metal always move the same speed, and potential differences in modern high perf applications are never above 3.3V. There are mechanical stresses in ICs introduced during manufacturing. So these cases aren’t as different as you let on.
Anyway, point is, metal moves, we have some ideas why and can model some of them. From an engineering perspective these are both tin whiskers. We call whiskers made of copper and aluminum tin whiskers. You’re describing a distinction without a difference.
The metal moves due to very different reasons. I would not say whiskers due to mechanical/residual stresses are due to “electromigration” - electromigration isn’t even there since the wiki definition is “transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms”. You build stresses and strains into semiconductors for better mobility profiles, and I’m sure that can cause whiskers - but again, it’s not electromigration.
Electromigration, as noted, plays a role in the form of encouraging stress whiskers to grow in a direction (with a very relaxed definition).
But in ICs, with their very unique extremely small scales, electromigration can directly form whiskers by moving individual ions via electron collisions. But the generation mechanism for those whiskers shares nothing with Big Whiskers generation mechanism. That’s my point.
Electrons in metal do not always move at the same speed; they move at v=mu*E where v is the velocity, mu is the electron mobility, and E is the electric field. Crank the E, you go faster. At very high E fields you reach the electron saturation velocity where slowing factors limit the maximum speed - I assume in your IC world you’re basically always there due to the extremely small regions (E = V/m; any V with m at nanometers is big E) which is why you claim that. But even then the electrons are accelerating due to the E field, smashing into ions and losing their momentum (mass static, so it’s just velocity), and then re-accelerating. The saturation velocity is the average bulk motion of electrons but it’s not a smooth highway, it’s LA traffic (constant crashes).
Electrons can gain significant momentum, which is just their static mass times their velocity. Limited at velocity by the saturation velocity, current density is important for significant momentum exchange. Luckily ICs are so tiny that the currents they drive are massive current densities.
What you said originally is correct; it’s just in ICs electromigration can cause whiskers. In the Big World it can’t. But it can influence Big Whiskers to grow to the worst places and fuck up things optimally if you take an extremely relaxed view of electromigration that defines it as “movement of ions encouraged by an electric field”.
Check out https://en.wikipedia.org/wiki/Hot-carrier_injection hot carrier degredation, it’s in the vicinity of electron mobility but in a semiconductor setting. Key link is it’s electrons with momentum doing the work. In this case electrons (much hotter than in electron mobility, which are limited by the saturation velocity) smash into the gate dielectric, making it a worse dielectric. Hot carrier injection doesn’t have to end in damage to the dielectric, but when it does it’s hot carrier degredation. There’s a lot going on though, semiconductors are really complex - like electron tunneling also exists.
Electromigration in ICs typically occurs in metal interconnect, so there are no dopants there to move. Dopants are added to the silicon substrate.
This is like saying an SUV isn’t a car.
OP: Look at my car
Me: I have one too. It’s an SUV
You: SUV’s aren’t cars.
If you understand “car” as “hardware degradation” there is something to it, despite calling it “electromigration”.
You said it (= whiskers) can be simulated and that it’s called electromigration. From what I understood, this statement is wrong, since they are both different in both cause and effect. Metal whiskering can be simulated to a certain extent, yes. But that’s vastly different to what electromigration is and how it works.
What happens if I eat one? Do I gain computational powers?
Someone’s been on !unix_surrealism@lemmy.sdf.org
Hey, tin whiskers! I haven’t seen this happen in person since my Jerry rigged Celeron 333A killed itself. I’d created a monstrous homebrew cooler with raw bar stock aluminum as an IHS with a big fat peltier cooler and a huge heatsink so I could run the thing at 550mhz. The aluminum eventually grew a tin whisker after the machine had been running in my closet for a good 4 or so years and shorted the Celeron carrier board.
Apparently this was a pretty big problem in aerospace back in the early days, their electronics were particularly prone to this failure mode.
I’m not as tech minded as others on this platform. I think you said you were building a space ship in your closet that grew whiskers, and comitted suicide.
That seems like the kind of thing Disney would make an animated film about in the 60s. A child sized rocket thats grown depressed. So instead of flying to space with a kid inside, it instead goes into the closet for so long that it grows whiskers, and then ends it all.
It would be like that scene where bambis mom dies. It’s ONLY there to traumatize kids, and punish parents who now have to deal with a crying kid.
Because Disney is evil.
