rkarlqu@hpscdc.HP.COM (Rick Karlquist) (06/10/88)
Does anyone out there know what is the precise difference between Commercial temperature range and Military temperature range IC's? The question came up: If the ambient is say 69 degrees C, is a 54XX logic IC more reliable because it has been "derated from 125 degrees C" that a Commercial one that is only rated to go from 0 to 70 degrees C? Let's assume both are in a frit seal ceramic package so we are not confused with comparisons between plastic and hermetic package reliability. My understanding is that there is _no_ increase in reliability in the above case and in fact there is no permanent damage done to the commercial IC if it is operated at temperatures up to 125 C, it just won't meet its specs, may not even "play". But once returned to normal temperatures, it will be fine. The only problem is that reliability decreases a factor of 2 for each 10 degrees increase, but then that would also be true of a 54XX part. My understanding is that 54XX parts get built on the same line as 74XX parts, and the design is the same. For example, they don't design 54XX parts to use less power to compensate for the greater temperatures involved. Now we're talking about plain vanilla 54XX parts here, not 54XXJANTX parts which _do_ get special T.L.C. treatment. By the way, are JANTX parts really more reliable that commercial parts (on the average) or is it merely that more is known about the reliability? I have heard that some JANTX parts are actually less reliable. Can anyone out there shed some light on this?
henry@utzoo.uucp (Henry Spencer) (06/14/88)
> ... If the ambient is say 69 degrees C, is a > 54XX logic IC more reliable because it has been "derated from > 125 degrees C" that a Commercial one that is only rated to go > from 0 to 70 degrees C? Let's assume both are in a frit seal > ceramic package so we are not confused with comparisons between > plastic and hermetic package reliability... My impression is that the difference between 54XX and 74XX *is* the packaging, period. I could be wrong. JANTX parts are a different story, of course. -- "For perfect safety... sit on a fence| Henry Spencer @ U of Toronto Zoology and watch the birds." --Wilbur Wright| {ihnp4,decvax,uunet!mnetor}!utzoo!henry