Hal Murray wrote:
The reason for the fans is to prevent premature failures of the
silicon devices due to thermal degradation. The life of a silicon
chip is halved for every 10C temperature increase, more or less.
I was going to make a similar comment, but got sidetracked poking around
google. I didn't find a good/clean article. Does anybody have a good URL?
Doubling every 10C is the normal recipe for chemical reactions. I think that
translated to IC failure rate back in the old days. Is that still correct?
Has modern quality control tracked down and eliminated most of the
temperature dependent failure mechanisms?
Hal,
The old standby is MIL-HDBK-217F:
http://assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=53939
It is quaint, but they based it on years of experience. They did a lot of
testing of the chips and created mathematical models that worked as well as any
model can, given the clumpiness of failures.
P.5-13 gives the temperature failure rate multiplier for ECL chips:
25C 0.10
45C 0.27
55C 0.42
65C 0.63
75C 0.94
85C 1.4
95C 1.9
So my off-the-cuff guess of failures doubling for every 10C rise is not too
wrong.
--David Forbes, Tucson
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