3 ms·
Invar is actually a very bad material for most uses, because having zero CTE usually won't match the rest of your system's nonzero CTE. So things will fail pret
by exmadscientist 3y ago
Invar is actually a very bad material for most uses, because having zero CTE usually won't match the rest of your system's nonzero CTE. So things will fail pretty quickly.
Matching CTE is a big deal in careful engineering. "Alloy 42" is a great example of that in action: it's an invar-like alloy with its CTE matched to silicon, so chip lead frames expand with silicon dies as they heat up during operation. Not that many things use lead frames anymore....
- Kirby64 3y agoWhat do you mean? MOST ICs use lead frames still. Although there is a large push in consumer electronics to use flip chip or CSP devices, I would suggest that most devices are still using lead frames. Any plastic packaged device is lead frame based.
- exmadscientist 3y agoSorry, you're right, I was thinking of the newer stuff (flip-chip, wafer-scale, nearly-bare-die, etc). It's also interesting just how few leadframes are magnetic these days, even for something ancient like a SOIC-8. I don't know what they use; I guess it's not very important if there isn't much power dissipation.