Poul-Henning Kamp skrev:
In message <[email protected]>, Magnus Danielson writes:
Hal Murray skrev:
There are being books written about this. One that I have found being a
fairly short but useful one is the AT&T Reliability Manual.
It is worth pointing out that a very large fraction of all electronics
failures are not semiconductors but electrolytic capacitors.
People are often astonished when I tell them, that a "long life"
electrolytic capacitor is one which will last one year at its rated
temperature, whereas a standard consumer-grade will last only a
month.
To add insult to injury, many of them have rated temperatures of
only 85°C and much of the discount electrocrap uses 55°C grade.
For modern consumer crap, yes... for traditional pro-gear caps may
eventually need replacement, but if you look at them as standard 10000
km replacement parts it becomes less of an issue and just a matter of
remember to do it.
My experience from well-designed pro-gear is that caps could very well
survive but a silicon device might eventually fail. Vibration or
mechanical movement wear is another issue for long-term reliability
issue, where components detach from solder and move in tunnels of solder
at the end, connecting part of the time and only fractional at some time.
Modern electrolytics is a different story altogher from traditional
electrolytics. My stationary computer failed in the PSU. Sure enougth it
was caps. But looking carefully at the errupted caps you could also see
that even through there is a fan there, the air flows over the top and
often the caps sits next to the switch transistors and their heat sink.
What else to expect? The same electronics but spread over twice the
volume and with the electronics sitting more in a "wind-tunnel" than
forming a side of it would have made it last longer. The compactness of
todays electronics often come at the price of reliability. The caps is
smaller in physical size for the same reason, and guess what suffer. The
electrolytics becomes more critical, and hence the issue of stealing the
formula, where as the traditional electrolytics was a different story...
Cheers,
Magnus
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