Try it!!!! (Was - Re: One More PCB Dishwasher Question)

From: William Donzelli <>
Date: Sat Dec 29 11:53:01 2001

> I'm not sure its a temprature issue, as some have assumed. A dishwasher may have
> very powerful waterjets and a lot of vibration. The dammage may be mechanical,
> possibly a bonding wire detachment.

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
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!).

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

Me? I am a hand washer. Nothing is wrong with a little clean water and
(very) light detergent, a toothbrush or Q-tip and some time.

William Donzelli
Received on Sat Dec 29 2001 - 11:53:01 GMT

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