In order to be able to do visual inspections of PCB’s or components I normally use a magnifier glass. Where the magnifier glass offers a magnification of 5X, a low-cost USB microscope can give you 20..500X.
The USB microscope I ordered for about 15 euro gives interesting results. It contains 8 white LEDs that illuminate the object to be investigated from above. The focus range and magnification can be adjusted. LED Light intensity can be changed. It really turned out to be a plug-and-play device. Plug in the USB connector, install the software and enjoy the pictures (and even moving images). Great fun.
USB Microscope set-up and PCB:
5 cents Euro coin
30 pF capacitor