Dishwashers are not a good idea. There are too many unknowns. Dishwashers splash so much water around, it is essentially the same as
submerging the board and all its mounted components into a tub of "
heated" water. It is important to remember, dishwashers use hot water
only and then they
heat the water even further!
And dishwashers use pumps to pressurize that hot water into "jets"
forcing that water into every crack and crevice - over and over again.
Do you know for a fact, each and every "electrical" device mounted on the motherboard is sealed? Impervious to water? Do you know for a fact, all the edges of the layered motherboard (including the edges of the drilled mounting holes) are still properly sealed by the resins?
Do you know for a fact, all the components, metals, plastic materials,
labeling, and the PCB itself is impervious to the highly caustic detergents - detergents that are known to interact with some metals, that can "etch" crystal?
Even if no detergent is used, there is still the pressurized "hot" water issue.
Then of course, what if you forget to set the dishwasher to air dry - and then the heating element for the dryer comes on? And even if you do remember that, what if you don't ensure, with 200% certainty, that there is absolutely no trace of water left - anywhere - before applying power again?
Are there anecdotal examples of people washing motherboards in dishwashers with good results? Yes. But that does not mean that is the best or proper way to clean electronics. If a simple wipe with a "damp" (not wet) cloth is not enough, I recommend the use electrical contact cleaner - which is specifically designed to be used on electronics. I recommend
CRC QD Electronic Cleaner.