I have a board that has fairly high working voltages up to 100V with small clearances down to 12 mil between the high voltage and ground or low voltage nets. This is unavoidable because the whole board is tiny and in some cases the HV and low voltage are adjacent pads on the same component.
This is currently assembled using a water wash cleaning step.
Is it possible to assemble this using no-clean? What are the possible problems with having flux residue on a high voltage board like this? Is it better to clean (with the possible ionic contamination from the detergents) or not clean (with flux residue)? Could I do conformal coating over flux residue?