The circuit connection of the multi-layer board is through the buried hole and blind hole technology. Most motherboards and display cards use 4-layer PCB boards, and some use 6, 8-layer or even 10-layer PCB boards. To see how many layers there are on the PCB, it can be identified by observing the via holes, because the 4-layer board used on the motherboard and the graphics card is the first and fourth layer traces, and the other layers have other uses (ground wire And power). Therefore, like the double-layer board, the guide hole will penetrate the PCB board. If some guide holes appear on the front of the PCB, but cannot be found on the back, then it must be a 6/8 layer board. If the same guide holes can be found on the front and back sides of the PCB board, it is naturally a 4-layer board. Tip: Point the motherboard or graphics card to the light source. If the position of the guide hole can transmit light, it means 6/8-layer board; otherwise, it is 4-layer board.