HN Explorer

Ask HN: How to design a PCB for 50-100 years?

1 points by owenversteeg ↗ HN
Let’s say you want to do 50-100 years of constant operation indoors.

I’m trying to design a PCB to last, and there’s very little information publicly available. There’s the obvious - no electrolytic caps, no pure tin, sure - but beyond that, what would you do?

7 comments

[ 3.1 ms ] story [ 27.3 ms ] thread
Salmonfisher11
100 years in a 100% controlled environment is easy.

Meaning: you are missing a lot of variables in your game that will mess with your plans.

So spend some times and do requirements engineering on an abstract level. Then select the techniques to solve them.

owenversteeg
OK, say constant operation at room temperature indoors.

No matter how well temperature and moisture controlled your environment is, I highly doubt that 100 years is easy. 100 years? 876,000 continued hours of operation? Large companies regularly have expensive recalls because of premature failures for all kinds of reasons. Components fail for myriad reasons and I think to get 100 years you’ll need careful component selection, de-rating, plating, thoughtful solder selection, conformal coating, etc.

Salmonfisher11
>OK, say constant operation at room temperature indoors.

Suddenly a wild humidity change appeared.

You must spend a lot of time defining your environmental parameters.

owenversteeg
Yes, obviously humidity changes with temperature. I don’t see how that’s important. 99% of dead boards out there are not dead because of indoor, room temperature level humidity fluctuations, and the plenty of PCBs still working from the 70s don’t seem much affected by them either. There’s thermal cycling concerns, but that’s dominated by the board’s own heat generation. Do you have some data that would indicate that modern boards are sensitive to this?
owenversteeg
One thing I’ve heard repeated all over the internet is that NASA has great studies and guides on electronics longevity, but I can’t seem to find much online and most of what I find is about radiation, temperature or motion hardening which isn’t as relevant on Earth. If anyone has specific links I’d love to read them.
pickle-wizard
One suggestion I have is to make the components as simple and generic as possible so they will still be available to repair it in the future. Getting a working ASIC in 50 years may be near impossible, but through hole resistors, caps, and 7400 series logic chips will still be easy to find.

Also think this question would be good for retro computing groups. They can tell you what their common failures are so you could avoid them.

owenversteeg
Yes, I’ll definitely be making it as repairable as possible.

Great idea on the retro computing groups, thank you! Only problem is that a lot of the more modern high-speed components haven’t really been tested and a lot of those have a significant benefit over their older counterparts. Take the LM2576 vs the newer AP63300. You’ll waste double the power with the old chip, but the new one has only been out for five years or so, so it’s hard to know if it’ll really last - and even the old one is only from the 90s.