For hybrid circuits, there are also ways of arranging analog and digital circuits on both sides of the printed board, using different layers of wiring, and isolating them with ground layers in the middle.
Control rules for isolated copper areas: The appearance of isolated copper areas will bring some unpredictable problems. Therefore, connecting the isolated copper areas with other signals will help to improve the signal quality. Usually, the isolated copper areas are grounded or deleted. In actual production, PCB manufacturers add some copper foil to the vacant parts of some boards, which is mainly to facilitate the processing of printed boards, and also has a certain effect on preventing the warping of printed boards.