Is it necessary to clean PCB before visual inspection?

[angy]

My question is before  visual inspection at 40x lens of PCbs  is it necessary to clean the PCB with alcohol.What happens is after cleaning with alcohol flux residue starts to accumulate between micro controller pins.Which doesn't go off easily .
So is it o.k to first to  Visual inspect the PCB for solder balls,extra solder etc and if necessary then clean the PCB.

[SimonWasAnEngineer]

We always cleaned the PCB´s before the visual inspection. I think defects are easier to find without flux residue. But instead of alcohol/isopropanol we used a special flux cleaning solution and deionized water in two separate ultrasonic baths.