When designing a multilayer PCB, the stackup is a crucial step, and its quality directly impacts product performance. Below, we'll review some basic principles of multilayer board stackup.

First, signal layers must be stacked adjacent to ground layers. An adjacent ground layer effectively reduces crosstalk and electromagnetic radiation between signals. Ground layers provide current loops and shield electromagnetic radiation from signal layers. Especially in high-frequency, high-speed PCB designs, the presence of adjacent ground layers can prevent signal crossover. Therefore, when designing a PCB, important signals should be placed in signal layers close to the ground layer.

Second, layer symmetry must be maintained during stackup. Whether the stackup is symmetrical affects the curvature of the final PCB. Asymmetrical stacking can cause warping in the finished board, further impacting board placement and potentially leading to weak solder joints and cold solder joints.

Third, layers adjacent to components should be ground planes. This provides shielding for the components and prevents cross-splitting of signals between the top and bottom layers (cross-splitting refers to the situation where adjacent reference layers of a signal pass through multiple planes).

Fourth, power planes should be as close to the ground plane as possible to form a plane capacitor, thereby reducing the power plane impedance.

Fifth, avoid adjacent parallel wiring layers. Crosstalk between adjacent parallel wiring layers can be significant, affecting signal quality and board performance. If adjacent wiring layers do exist, run one horizontal layer and one vertical layer, or increase the thickness between the two layers. Increasing the spacing can also effectively address crosstalk, such as in the so-called "fake eight-layer" design.