Not only that, there is also diffusion caused by difference of concentration, which is increased by heat. And you have that concentration difference at the p-n boundaries/junctions in an IC.

Though I'm not sure how much actual damage you'd see in practice, whether the ICs tend to die with intense use before e.g. the capacitors mentioned above.

Takes 100yrs on current processes to break a particularly weak bond wire.

Sorry, not bond wires. A weak cross section in the metal layer.

But how big of an issue is that really in practice? You still see 20+ years old machines chugging along just fine.

That's a bit of survivor bias. I used to buy truckloads of old PCs and recycle them when I was a teenager. I initially thought that this old tech was just really built to last, but in reality I was selecting the 1% or less that could survive being shoved around a rat-feces-infested warehouse at freezing temperatures before ending up in my parents' garage, to their dismay. Those survivors seemed to last freaking forever afterward, but again, that's because they were the random fraction that just happened to have that perfect balance of durability.

When I started buying new parts as an adult, the failure rates of e.g. GPUs were pretty disappointing in comparison to the biased expectations I had from those survivor PCs.

Haha, I also noticed that used parts that lasted ~2-4 years have a lower failure rate than new ones. All the ones that fail, fail early, and the surviving ones go through a sort of "extended burn-in" so to say.

I have a longstanding habit of buying my laptops refurbished - so, a few months of wear and sometimes a "scratch and dent". To date, every one of them has been a winner on longevity.

Same, only had a problem twice, with a failed USB/audio daughterboard on an Elitebook ($20 replacement) and a failed VRM capacitor on an MXM card (replaced it but the GPU itself failed after a year so I just got a new card, $100).

I'm really sad about new laptops having everything soldered on. If something fails, you either need a good reflow station (and skills) or you have to toss the whole thing, which is insane.

It also makes parts ridiculously expensive, like a system board for a Dell Precision now goes for ~$500 where it used to be under $100. All because the CPU, GPU, VRAM and even RAM are soldered on.

Honestly, I hate where all of this is going. So much for everyone going green.

Process size matters, so older computers are less affected.