Electronic products need to be updated. For versatile, small-volume electronics, single-sided and double-sided PCBs are not fully compliant, and multi-layer PCBs must be used. Multi-layer PCB has many advantages, such as: high assembly density, small size; shortened connection between electronic components, fast signal transmission, convenient wiring; good shielding effect, and so on. The number of layers of the multi-layer board is not limited, and there are currently more than 100 layers of PCBs, and the common ones are four-layer and six-layer boards. When the multi-layer board is designed, the layers should be symmetrical, and it is better to have an even number of copper layers. If it is asymmetrical, it is easy to cause distortion. The multi-layer board wiring is carried out according to the circuit function. When the outer layer is wired, it is required to have multiple wiring on the soldering surface and less wiring on the component surface, which is beneficial to the maintenance and troubleshooting of the printed board. In terms of routing, the power plane, the ground plane, and the signal layer need to be separated to reduce interference between power, ground, and signals. The lines of two adjacent printed boards should be perpendicular to each other or diagonally and curved, and parallel lines should not be taken to reduce the interlayer coupling and interference of the substrate. Compared with single-sided and double-sided PCBs, which layers are composed of layers, what does each layer represent and what is the use? The multilayer PCB consists mainly of the following layers: Signal Layers, InternalPlanes, Mechanical Layers, Masks, Silkscreen, and System. The signal layer is divided into a top layer, a middle layer, and a bottom layer, and is mainly used for placing various components, or for wiring and soldering. The internal power plane, also called the inner power layer, is dedicated to arranging the power and ground lines. Mechanical layers are typically used to place instructive information about board and assembly methods, such as board physical dimension lines, data sheets, via information, and more. The solder mask also has a top layer and a bottom layer, and pads or other objects placed on the layer are copper-free regions. The silkscreen layer is mainly used to draw the outline of the component, the number of the placed component or other text information, and the system working layer is used to display information that violates the design rule check.