如何设计 4-layer PCB 堆

In theory, there are three options.

程序1：

A power supply layer, a ground layer and two signal layers are arranged as follows:

TOP (signal layer); L2 (formation); L3 (power supply layer); BOT (signal layer).

程序2：

A power supply layer, a ground layer and two signal layers are arranged as follows:

TOP (power supply layer); L2 (signal layer); L3 (Signal layer; BOT (ground floor).

方案3：

A power supply layer, a ground layer and two signal layers are arranged as follows:

TOP (signal layer); L2 (power layer); L3 (connecting strata); BOT (signal layer).

Signal layer

底楼

功率

Signal layer

What are the advantages and disadvantages of these three options?

Procedure 1, the main stack of four layers of PCB design, there is a ground underneath the component surface, the key signal is best TOP layer; For layer thickness Settings, the following recommendations are recommended: Impedance control core plates (GND to POWER) should not be too thick to reduce the distributed impedance of POWER supply and grounding; Ensure power plane decoupling.

Procedure 2, in order to achieve a certain shielding effect, the power supply and grounding are placed on the TOP and BOTTOM layers. However, the program must achieve the desired masking effect. At least the following defects exist:

1, the power supply and the ground are too far apart. The plane impedance is very large.

2, due to the influence of the component pad, the power supply and grounding is very incomplete. Signal impedance is discontinuous due to incomplete reference surface.

In practice, the power supply and grounding of the solution are difficult to use as a complete reference plane due to the large number of surface-mounted devices. The expected shielding effect is very good. Difficult to implement; Its use is limited. However, it is the best layer-setting procedure on a single circuit board.

Procedure 3, similar to procedure 1, is used where the main equipment is laid out with a BOTTOM or base signal wiring.