For small batches, the pcbs get put in a £60 ultrasonic bath with Safewash 2000, rinsed with a Hozelock garden spray gun, then dumped in a big bucket of de-ionised water. The "drying oven" is a very large cardboard box with a 3kW fan heater pointing at it. For added precision, I dangle a
Maplin digital thermometer in the box and have a peek at it every once in a while, positioning the heater accordingly. As you can see, we are at the very cutting edge of technology.
Larger batches go to an outside sub-contractor. We went round their facility ten days ago.....and yes, they do have the most expensive dish washer for cleaning boards.