Now the graphics card and the motherboard are multi-layer boards, which can greatly increase the area of the wiring. The multi-layer board is provided with more single or double-sided wiring boards, and is pressed after an insulating layer is placed between each board. The number of layers of the PCB board represents several layers of independent wiring layers. Usually, the number of layers is even, and the outermost two layers are included. The common PCB board is generally a structure of 4 to 8 layers. The number of layers of many PCB boards can be seen by looking at the cut surface of the PCB board. But in fact, no one can have such a good eye. So, a method below FYI.
The circuit connection of the multi-layer board is through the buried hole and the blind hole technology. The main board and the display card mostly use the 4-layer PCB board, and some of the boards are 6, 8, or even 10 layers. To see how many layers are on the PCB, you can identify them by observing the vias, because the 4 layers used on the motherboard and the display card are the 1st and 4th layers, and the other layers have other uses (ground and power). Therefore, like the double-layer board, the via hole will penetrate the PCB board. If some of the vias appear on the front side of the PCB, but are not found on the reverse side, then it must be a 6/8 layer. If the same via hole can be found on both the front and back of the PCB board, it is naturally a 4-layer board.
Point the board to the light, and see the position of the via hole. If it can transmit light, this is the 8/6 layer board, otherwise it is the four layer board.