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| Shelf life of assembled electronics |
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| lasmux:
Most devices out there, including flash storage etc aren't really tested for 'shelf life' when the device isn't powered on, as it's normally so long to make it an irrelevant problem, so it's a difficult question. Anything with a chemical process will have a more defined shelf life, such as already mentioned electrolytics, but also things like gas sensors etc. Another factor is dendrite growth due to ROSH compatible solders. Since everyone started using SAC305 for everything, we may in future years start seeing a lot of devices starting to fail in unexpected ways. That said the device has to be powered on for this to happen, so it's not fully applicable to your question. |
| Kasper:
--- Quote from: Siwastaja on December 01, 2022, 12:09:33 pm ---I call bullshit about Berni's comments about the flash. If the camera designers are not total morons (which they could be, though, in which case I will stand corrected), for the firmware, they use the kind of flash which 1) is NOT unreliable, and does NOT hide the unreliability by ECC. Might not have ECC at all. 2) has data retention of at least 50 years or so guaranteed by manufacturer, and this is at elevated temperature. --- End quote --- Are you assuming designers make 50 year lifespan at elevated temperature their top priority? How many consumers do you think care about 50 year reliability? The number of people who purchase phones without replaceable batteries is evidence that many consumers do not care for even a 10 year lifespan. |
| iJoseph2:
This is an interesting thread... I really hope the flash in older cars lasts over 50 years. The engine ECU is obviously important, but the ABS units have the ability to actuate the brakes ... I can imagine a failure mode could even actuate the brake on just one wheel and be very dangerous. |
| tom66:
The good news is that I can't think of an ECU that would not checksum its main flash memory and bail out if the checksum fails to match. In the ABS case, that would light the fault lamp and land you a repair bill for a new ABS computer, but probably not end up with you in a ditch. Also the flash in these systems tends to be of a higher grade and much lower density, the program for an ABS computer or ECU is probably under 1MB and would be stored in NOR flash rather than the higher density NAND. NOR flash has much better lifespan. If it is NAND, it will be infrequently written and will be of a higher standard, SLC or pseudo-SLC or similar. Automotive systems have much higher standards generally but then you have manufacturers like Tesla using eMMC in important infotainment systems (big touchscreen that controls the speedo and defogger) which can still go bad. I am most worried about those because they are probably quite expensive to repair and nowadays they control a lot about a car, I know for instance on an EV you wouldn't be able to change charging settings if the head unit went bad. |
| Siwastaja:
--- Quote from: Kasper on December 01, 2022, 03:03:17 pm ---Are you assuming designers make 50 year lifespan at elevated temperature their top priority? How many consumers do you think care about 50 year reliability? --- End quote --- It's not about 50 years, it's about the fact that if designers fuck this up, it happens like tom66 described - snarky, overconfident designers go on dismissing the problem interns bring up by going "oh well, 50 years at elevated temperature is not our top priority" strawman, while failing to actually define what their lifetime target is or provide any calculation of it whatsoever, and as a result, it lasts only a year, and company loses a lot of money fixing the problem, maybe resulting in failure of the company. No need to be "top priority". Normal design practices are enough - use internal MCU flash for firmware, check the ratings of any external flash -, and flash life is not a problem. And if you fail to do that, who knows how badly you failed it? 50 years was just an example of being completely normal rating by nearly all MCU manufacturers, nothing expensive or special about that, contrary to what you seem to think. |
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