Most boards can be washed safely but there are some components that can be damaged. Safest method is to use distilled, deoxygenated water (aka electronic water

Most boards can be washed safely but there are some components that can be damaged. Safest method is to use distilled, deoxygenated water (aka electronic water) to remove most contaminants, followed by 99% isopropyl alcohol or 96% ethyl alcohol to remove the rest and also water. Don't skimp on water and alcohol, submerge the board and use brush while submerged, to pull and dilute contaminants. Just never use tap or mineral water. You can use regular distilled water as long as you do it quickly, but unless it is deoxygenated it will be corroding so don't leave it in water for long. Alcohol is there mostly to dilute water so that it dries out very quickly. Without alcohol water could stay under components for a long time and kill or damage your board. Alcohols can damage some plastic components, so don't keep it in alcohol fo too long, either.