The fabrication of 8 layer PCB involves the stack design. Any error in the stack design will seriously affect the PCB performance. So next, we need to know some knowledge about the stack design involved in the fabrication of 8 layer PCB.
As the first step of stack design, the number of power supply layer and signal layer is very important to analyze and solve the ground plane that PCB may need.
Ground planes are an important part of any stack because they provide better shielding for your PCB. Moreover, they minimize the need for external canned tanks.
Here are some proven 8 layer PCB stack designs for various applications:
For compact boards with smaller footprint: if you plan to wire a smaller dense board, you can install four signal planes, one ground plane, and one power plane.
For more intensive boards that will use a mixture of wireless and analog signals: on this type of board, you can choose layers that look like this: signal layer / ground / power layer / ground / signal layer / ground plane. In this type of stack, the internal and external signal layers are separated by two encapsulated ground planes. This stack design helps to suppress the mixing of EMI and internal signal layers. The stack design is also ideal for RF devices, as the AC power supply and ground plane provide excellent decoupling.
For printed circuit boards with sensitive wiring: if you want to build a printed circuit board with many sensitive traces, it is best to choose a stack that looks like this: signal layer / power layer / 2 signal layer / grounding / signal layer. This stack will provide excellent protection for sensitive traces. The stack is suitable for circuits using high-frequency analog signals or high-speed digital signals. These signals will be isolated from the low speed signals in the outer layer. This shielding is accomplished by the inner layer, which also allows the routing of signals with different frequencies or switching speeds.
For boards to be deployed near strong radiation sources: for this type of board, the stacking of ground / signal layer / power / ground / signal layer / ground type is ideal. This stack can effectively suppress EMI. This stack is also suitable for circuit boards used in noisy environments.
Changes of 8 layer PCB
Although 8 layer PCB has many potential benefits and use cases, the actual design may not be sustainable in some cases. Instead, there are two major changes in the use of 8 layer PCB.
The first change is that the routing of the circuit board will run vertically to the adjacent routing layer. Therefore, 8 layer PCBs tend to have minimum crosstalk and increased wiring efficiency.
Other changes are due to the speed of the 8 layer PCB. For example, if you are considering a high-speed design, this means that the ground plane and power layer must remain on adjacent layers. While this helps to decouple, other ground planes can also be used to shield designs that may require low electromagnetic radiation.