however on the circuit board as long as it evaporates before you put it back into service isopropyl alcohol is probably the preferred method, it’s regularly used to clean electronics components. I used 70% rubbing alcohol to clean my digitone buttons once and they were fine but hawk is probably correct, and the case graphic may fade with 90% but I don’t know so I say err on the side of caution. the board though you could literally soak in alcohol and it would be fine.