The number of layers of PCB depends on the complexity of the circuit board. PCB stack design is an important part of PCB design, which directly affects the quality of PCB finished products. So, what are the general rules of PCB stack design?

1. The stratum and the signal layer shall be closely coupled, that is, the distance between the stratum and the power layer shall be as small as possible, and the dielectric thickness shall be as small as possible to increase the capacitance between the power layer and the stratum.

2. The two signal layers shall not be directly adjacent as far as possible, otherwise signal crosstalk is easy to occur and affect the performance of the circuit.

3. For multilayer circuit boards, such as 4-layer and 6-layer boards, the signal layer is generally required to be adjacent to an internal electric layer (layer or power layer) as far as possible. In this way, the large-area copper coating of the internal electric layer can be used to shield the signal layer, so as to effectively avoid crosstalk between the signal layers.

4. For the high-speed signal layer, it is generally located between the two internal electrical layers. On the one hand, it provides an effective shielding layer for the high-speed signal, on the other hand, it limits the high-speed signal between the two internal electrical layers to reduce the interference to other signal layers.

5. The symmetry of the laminated structure should be considered.

6. Multiple grounded internal electric layers can effectively reduce the grounding impedance.

7. Use even layer PCBs and avoid odd layers. Because odd layer circuit boards are easy to bend.