Now, a story...  Some years ago, a manufacturer's representative was
bragging to me about their state-of-the-art printed circuit board assembly
plant and their new, environmentally friendly flux removal/board cleaning
equipment.  It was a modified commercial dishwashing  machine - such as you
might see in a large restaurant or cafeteria, which handled one wire rack
loaded with boards at a time.  The trick was that the final rinse used very
high purity deionized water.  This water was saved to be used as the
second-to-last rinse of the next batch of boards. That water was saved
for use as the first deionized rinse.  Overall, there were two washes with
a biodegradable detergent solution, two rinses with filtered tap water,
and three rinses with deionized water.  All, of course were piping hot.
Afterwards, the boards were dried in a tunnel with a counterflow of warm,
filtered air.

The big trick was that no residual ionic solids were left on the board.
(No water spots!)  Also, any parts that could be damaged by residual
moisture - such as fine coils in a speaker - were supplied with a
peelable seal which was removed after cleaning.

The  above is "hearsay", but I think it explains the rumors about putting
a keyboard (or at least the circuit board) through a rather special
dishwasher.  The trick is to use deionized (or distilled) water as the
final rinse, and drying immediately to avoid corrosion.

Boyd Ramsay

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