Abstract: A printed circuit board (PCB) includes an electronic element, a signal line, an input/output (I/O) interface, and a varistor. The I/O interface is connected to the electronic element through the signal line. The varistor includes a first terminal connected to the I/O interface, and a grounded second terminal. The varistor is close to the I/O interface, to eliminate static electricity flowing into the PCB from the I/O interface.

Abstract: A printed circuit board (PCB) includes a ground layer, a number of conductive mount holes extending through the PCB, and a number of electromagnetic wave absorption elements located on a top surface of the PCB and aligning with corresponding mount holes. Each mount hole is lined with a conductive material to electrically connect to the ground layer. Each electromagnetic wave absorption element includes an absorption layer to absorb high-frequency noise, and a conductive layer sandwiched between the absorption layer and the top surface of the PCB, and electrically connected to a corresponding mount hole. Each conductive layer is electrically connected to the ground layer though the conductive material of the corresponding mount hole. High-frequency noise of the PCB flows into the conductive layers through the ground layer and the conductive material of the mount holes, and is absorbed by the absorption layers.

Abstract: A printed circuit board (PCB) includes a switch mounted on a signal layer of the PCB. A plurality of grounding copper foils are formed at opposite sides of the switch. A first end of each of the grounding copper foils is adjacent to the switch. The switch includes an electroplated button and a switch component under the electroplated button. An inner surface connected to the switch component of the electroplated button is coated with lacquer.