From: William Donzelli <aw288_at_osfn.org>
>I would think the thermal shock of the chips hitting the hot water would
>be a failure mechanism. Hot air and hot water are different things, even
>at the same temperature. The thermal resistance of a water to ceramic
(or
Not an issue as the temps are well blow boiling (nominal 145f).
>plastic) junction is much, much lower, than one with air, so during the
>first seconds of the wash cycle, the chips go from ambient
>temperature to something rather high. Lots of stress results, especially
>if only some of the chip's package gets wet. Preheating the boards would
>help reduce the shock greatly, but home dishwashers do not do that (not
a
>good idea to cook the food onto the plates before trying to wash them!).
Not required.
>The above is one of the reasons why liquid cooled electronics are a bit
>tricky. The cooling units *never* just start pumping cold water when the
>power is applied. There is always a stabilization period, so the shock
is
>reduced.
Some do, other run the cooling first and let the coolant temp climb to
operating temp gradually. Others preheat the coolant to working temp
so the system can come on line faster.
Allison
Received on Sat Dec 29 2001 - 13:32:10 GMT