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The reason it isn't killing that 7nm interconnect is that those semiconductor physical implementation designers run lots of EM simulations to determine the reli
by jgeada 7y ago
The reason it isn't killing that 7nm interconnect is that those semiconductor physical implementation designers run lots of EM simulations to determine the reliability and lifetime of all traces, taking into account the trace dimensions, electrical properties and the expected current flows and the design is only signed off when those metrics meet or exceed the design requirements.
Note also that specialized metals (tungsten, ruthenium) are used on really fine lower level traces of advanced nodes, due both to their resistance to EM as well their better compatibility with silicon (smaller passivation thickness).
- ajross 7y agoI think you missed the sarcasm. Electromigration is simply not an issue for PCB design, period. The relative scales of the devices are separated by many orders of magnitude. The effect wasn't even discovered until photolithography pushed scales to values much smaller than we see on even the tiniest printed circuit. Maybe, just maybe, there's a high current, high voltage board out there with tiny traces that was designed with some kind of trivial electromigration mitigation. But if there is, I've never heard of it. And electromigration is absolutely not a reason to avoid 90 degree turns on your digital logic board, don't be ridiculous.
- madengr 7y agoElectrochemical migration is an issue in high-rel PCBs, though I don’t think that is true electro migration from charge carriers. Silver and tin dendrites have failed satellites.
- ajross 7y agoYeah, different things. Electrochemistry involves motion of charge carriers through some kind of medium, and can happen over very large distances even if the medium is just the polymer surface of the board. And needless to say it doesn't care about junction angle at all. "Electromigration" is the motion of individual conductor nuclei out of the wire due to scattering with electron momentum. Effectively, when electrons are asked (by the electric field in the conductor) to make ultra-sharp turns at nanometer scales, they sometimes collide with the aluminum/copper/tungsten/whatever nucleus instead, knocking that nucleus away from where it should be in the crystal. Over time, this erodes the junction, increasing electrical resistance, and eventually the chip starts to fail at voltages and clock rates it used to handle well.