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I'm working on a product, a single-board computer with an expected lifetime of 10-15 years, and I'm trying to identify the correct components to focus on for this. So far electrolytic capacitors appear to be the weakest and most obvious link, but I'm finding it hard to estimate how well switch-mode converters (ICs) will survive at elevated temperatures for example. At the maximum ambient temperature I'm seeing some of the ICs approaching their maximum operating temperature. Can I possibly assume that while the ICs are within specifications they'll likely function well for years to come on average?

Should I hence focus solely on specifying the electrolytic capacitors for this lifetime and maximum expected temperatures and assume the ICs and resistors will be of little concern?

The product has been designed with low self heating in mind, low-power DDR3 memories, synchronous step-down converters, and omission of all linear regulators. The board itself however is enclosed in a 100% waterproof metal enclosure (HMI) which can not contain air vents or complex dissipating surfaces for cleaning reasons. Hence in extreme cases with ambient temperatures of 40 degrees celcius it gets hot inside the enclosure and parts need to withstand elevated temperatures.

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The absolute maximum rated values (temperature, current, voltage, etc) should in no instance be assumed to permit extended usage over time. For a part to survive, and behave within specifications, for the full expected lifetime, it should be operated within "normal" operating conditions, not all the way to the absmax. Even if a particular electronic component survives being taken close to its absmax rating, deterioration of performance over time is very likely, resulting in premature failure. –  Anindo Ghosh Jul 12 at 12:35
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40 degrees Celcius, I presume? –  Peter Mortensen Jul 12 at 15:12
    
Yes 40 degrees Celcius –  Steinar Jul 12 at 16:08

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There are standardized methods for calculating reliability such as Bellcore Telcordia. Accuracy may be questioned, but they provide a basis for comparison.

I don't imagine there is any need for electrolytic capacitors in an SBC, as the power supply would likely best be separate, and there is little need for tantalum parts with the progress in MLCC caps.

Complex things like memory chips running very hot, and large numbers of MLCC bypass caps should probably figure into your lifetime calculations. Relays have a defined life, optoelectronics generally ages, but VLSI chips also have a temperature-dependent lifetime due to some mechanisms like metal migration. MLCCs can fail shorted.

And, if you're not selling a packaged bulletproof product, the lifetime may be foreshortened by user activities. I once received a "warranty repair" temperature controller that had failed due to a forklift tine penetrating the front panel to a depth of at least 6". They'll do stuff like connect 240VAC to ADC inputs and put electronics in lightning-prone locations.

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Similar experience here, manufacturing and assembly arm of the company does stupid stuff all the time. For that reason inputs are often made to withstand 24V while usually functioning at lower voltages. The issue here is an industrial product (HMI running a ghz quad core cpu), there have been requests of installation capability at 40 degrees ambient which is awkward for a 100% sealed waterproof enclosure. There are limits to how much heat can be dissipated from the enclosure, hence the high operating temperature in these installation cases. –  Steinar Jul 12 at 13:23

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