What are these round pads on the bottom of a PCB marked ScX?
I don't think these are test points – this board has some (not in the picture) and they're labelled with TP and the pad size and shape are different.
My best guess is that they're termination pads, but googling it didn't turn up many results so I can't verify that.
Best Answer
As mentioned in some of the comments, these are test pads designed for use with a pogo-pin test fixture, also known as a bed-of-nails test fixture. These fixtures have a specially-shaped array of pogo-pins which press down and make contact with the test pads on the board under test:
These test pads and the test points are probably used in different parts of the manufacturing process. For example, the test points may be used for board-level testing and the test pads may be used for system-level testing. Or, perhaps, the test pads are used for programming and/or debugging firmware, when the device under test is clamped into the bed-of-nails fixture.