How to Design the 4 Layer PCB Stack Up

How to Design the 4 Layer PCB Stack Up

How to design the stack up when designing a 4 layer PCB board?

 

In theory, there are three options.

 

Programme I:

One power supply layer, one ground layer and two signal layers, those are arranged as below:

TOP (signal layer);

L2 (ground layer);

L3 (power layer);

BOT (signal layer).

 

Programme 2:

One power supply layer, one ground layer and two signal layers, those are arranged as below:

TOP (power layer);

L2 (signal layer);

L3 (signal layer;

BOT (ground layer).

 

Programme 3:

One power supply layer, one ground layer and two signal layers, those are arranged as below:

TOP (signal layer);

L2 (power layer);

L3 (ground layer);

BOT (signal layer).

pcb design

Signal layer

single layer

Ground layer

 pcb stack up

Power layer

 pcb layer

Signal layer

stack up pcb

 

What are the advantages and disadvantages of these three options?

 

Programme I, the main stack design of the four-layer PCB, there is a ground plane under the component surface, the key signal is preferably the TOP layer; as for the layer thickness setting, there are the following suggestions: the impedance control core board (GND to POWER) should not be too thick In order to reduce the distribution impedance of the power supply and the ground plane; to ensure the decoupling effect of the power plane.

 

 

Programme 2, In order to achieve a certain shielding effect, the power and ground planes are placed on the TOP and BOTTOM layers. However, this programme must achieve the desired shielding effect.  At least the following defects:

 

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

2. The power supply and ground plane are extremely incomplete due to the influence of component pads. Because the reference surface is incomplete, the signal impedance is not continuous.

 

In fact, due to the large number of surface-mount devices, the power supply and ground of the solution can hardly be used as a complete reference plane. The expected shielding effect is very good. It is difficult to implement; it has a limited scope of use. However, in individual boards, it is the optimal layer setting programme.

 

Programme 3, is similar to programme 1, and is applicable to the case where the main device is wired in the BOTTOM layout or the underlying signal.