Importantly the residual oils from ethanol may be problematic in this context as well, so the benefit of ethanol just isn’t assured. I would also note that the flux residues themselves are actually ‘salts’; add moisture and also you get potential quick circuits. Attempting to conformally coat a board with flux residues can result in poor coating adhesion and potential delamination of the coating . If you might be continuously having points with boards needing to be cleaned, there could additionally be something more vital within the design or manufacturing process that needs to be examined.