What is dead copper (PCB island)?

Whether dead copper (islands) should be removed in PCB design.

Some people say that it should be removed, the reason is probably: 1, it will cause EMI problems. 2, enhance the ability to engage in interference. 3, dead copper is useless.
Some people say that they should be retained. The reason is probably: 1. Going sometimes large blanks are not good. 2, increase the mechanical properties of the board to avoid the phenomenon of uneven bending.

First, we don't want to die of copper (island), because this island forms an antenna effect here. If the surrounding radiation intensity is large, it will enhance the surrounding radiation intensity; and it will form an antenna receiving effect and will walk around. The line introduces electromagnetic interference.

Second, we can delete some small islands. If we wish to retain copper, the island should be well connected to GND through the ground hole to form a shield.

Third, at high frequencies, the distributed capacitance of the wiring on the printed circuit board will work. When the length is greater than 1/20 of the corresponding wavelength of the noise frequency, an antenna effect will occur, and the noise will be emitted through the wiring. In the case of copper with poor grounding in the PCB, copper is a tool for propagating noise. Therefore, in high-frequency circuits, don't think that somewhere on the ground is connected to the ground. This is the ground. "Be sure to make a hole in the wiring at a pitch less than λ/20, and "good grounding" with the ground plane of the multilayer board. If the copper coating is properly treated, the copper cladding not only has an increased current, but also plays a dual role of shielding interference.

Fourth, by playing the ground hole, retaining the copper coating of the island, not only can play the role of shielding interference, it can also prevent PCB deformation.