Summary of PCB multi-board design-layer distribution settings

Summary of PCB multilayer Design

Reprinted: PCB multi-board design suggestions and examples (, 12)

Design requirements:

A. The component plane and welding plane are complete ground planes (shielded );

B. There is no adjacent parallel wiring layer;

C. All signal layers should be adjacent to the ground plane as much as possible;

D. The key signal is adjacent to the formation and does not span the segmentation zone.

4 layers

Solution 1: There is a ground plane under the component plane, and the key signal is preferentially distributed on the top layer. For the layer thickness setting, the following suggestions are provided:

1: impedance control

2: compaction (Gnd to power) should not be too thick, to reduce the distribution impedance of the power supply and ground plane; Ensure the decoupling effect of the power supply plane.

Solution 2: Defects

1: Power Supply and ground are too far apart, and the power supply plane impedance is too large

2: the power supply and ground plane are extremely incomplete due to the influence of component pad.

3: Signal impedance is not continuous due to incomplete reference surface

Solution 3:

Similar to solution 1, this solution is suitable for the bottom-layer cabling of Main devices in the bottom layout or key signals.

6 layers

Solution 3: reduces a signal layer and an internal electrical layer. Although the layers available for cabling are reduced, this solution solves the Common Defects in solution 1 and solution 2.

Advantages:

1: The power supply layer is closely coupled with the ground layer.

2: Each signal layer is directly adjacent to the inner electrical layer, which is effectively isolated from other signal layers and is not prone to crosstalk.

3: siganl_2 (inner_2) is adjacent to two inner electrical layers Gnd (inner_1) and power (inner_3), which can be used to transmit high-speed signals. The two inner electrical layers can effectively shield external interference on the siganl_2 (inner_2) layer and siganl_2 (inner_2) external interference.

Solution 1: The layer-4 signal layer and layer-2 internal power supply/access layer are used, and there are many signal layers, which is conducive to wiring between components.

Defects:

1: The power supply layer and ground layer are separated far from each other and are not fully coupled.

2: The signal layer siganl_2 (inner_2) and siganl_3 (inner_3) are directly adjacent, the signal isolation is poor, and it is easy to produce crosstalk.

8 layers

10 layers

12 layers

Personal summary:
1. The key signal layer must be adjacent to the ground, and the Gnd must be adjacent to the power to reduce the plane impedance of the power supply.
2. The signal layer should not be adjacent to each other, increasing the isolation between signals to avoid Crosstalk
3. The signal layer should be adjacent to the ground plane as much as possible. Do not route the adjacent layers in parallel.
4. For transmission lines, the underlying layer of the transmission line uses the microline model for analysis, and the internal signal layer uses the linear line model. Software Simulation is recommended for signal layers on both sides of 6/10/14/18 substrates.

5. If there are other power supplies, the signal layer should first go through the coarse line. Do not split the electric strata as much as possible. It is best to use the inner layer for high-speed lines. The bottom layer is vulnerable to external temperature, humidity, and air, and is not stable.

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