Silicon Chip Aging

Silicon aging is a thing, especially at high voltage.

Do they fail from thermal stress or electromigration?

Aren't the smaller transistors going to be more susceptible to damage and bit flips though?

Probably. From a follow on article,"The biggest factor is heat. “Higher speeds tends to produce higher temperatures and temperature is the biggest killer,” says Rita Horner, senior product marketing manager for 3D-IC at Synopsys. “Temperature exacerbates electron migration. The expected life can exponentially change from a tiny delta in temperature.”"https://semien

this and heat are the main issues, not shrinking the transistors AFAIK.

Is the copper or the silicon responsible for most of the heat in a chip?

Transistor aging: https://spectrum.ieee.org/semiconductors/processors/transist...(Not likely to affect anything you'd mount on a bicycle, over any span of time relevant to a bicycle.)

Counter counter point, chips break down over time even though they’re solid state. The flow of electricity through a chip will slowly degrade the metal traces inside it. At the nanometer scale, it doesn’t take much to ruin a logic gate. This is called electromigration.You can care for that car (or chip) all you want, but chips aren’t cars. It’s a slow process, and may not happen on the timescale of mining, but it happens.<a href="https://en.wikipedia.org/wiki/Tra

Silicon chips age due to electromigration, which is exacerbated by small feature sizes. Chips made 20 year ago could take decades for enough migration to cause failure which is why you’ve never known or cared before. Today due to the much smaller processes we use it’s closer to a few years.

24x7 heavy use decreases lifespan. It's not just the chip that's stress it's everything else on the PCB as well, fans,etc.