Determining the layer arrangement
After determining the number the layers, you need to determine how they should be arranged or stacked. Good rules to follow here are:
- Route high-speed on minimum thickness microstrips.
- Place signal layers next to internal power layers for tight coupling.
- Power and ground layers should have minimal spacing between them.
- Avoid having two signal layers adjacent to each other.
- Make the stackup symmetric from the top and bottom layers inward
Determining routing and vias
Completing the PCB stackup design is the determination and routing of the traces. This includes determining copper weights, where to put vias and what type of vias to implement. As for all specifications for your design, you should work with your CM in making these determinations as some CMs avoid certain via types, such as via-in-pads.
Know the advantages of multilayer PCB stackup
Having multiple layers (see figure 1) increases the board’s ability to distribute energy, reduces cross-interference, eliminates electromagnetic interference and supports high-speed signals. While a stackup level allows you to get multiple electronic circuits on a single board through the various layers of PCB board, the structure of the PCB stackup design provides many other advantages:
- A stack of PCB layers can help minimize the circuit vulnerability to external noise, as well as minimize radiation and decrease impedance and crosstalk problems on high-speed systems;
- Good PCB stacking can also contribute to efficient and low-cost final production;
- A correct stack of PCB layers can improve the electromagnetic compatibility of the project.
Rules to process best stackup of PCB
The rules and criteria for managing a good stackup are hundreds. Let’s just see a few:
- Ground plane boards are better because they allow signal routing in a microstrip or stripline configuration. It also significantly reduces the ground impedance and, therefore, the ground noise;
- High speed signals should be “routed” on intermediate layers located between the various levels. In this way, ground planes can act as a shield and contain the radiation coming from the tracks at high speed
- The signal layers should be very close to each other, even in adjacent planes.
- A signal layer must always be adjacent to a plane
- Multiple ground planes are very advantageous, since they lower the board’s ground impedance and reduce radiation in a common way
- The power and mass planes must be rigorously coupled together