Before finalizing the design of multi-layer PCB circuit boards, designers need to confirm the structure of the circuit board primarily based on the scale, physical size, and the requirements of electromagnetic compatibility. Considering the above, designers are more likely to use 10 layers of circuit boards. This also decided the placement of the inner layer and the manner of distribution of different signals in these layers—the stack-up design of the multi-layer PCB. This careful planning and rational selection of the stack-up design beforehand will be saving the user a huge effort in wiring and production later.
Two major factors need to be decided once the designers have determined the number of circuit board layers. These are the distribution of the special signal layers and the distribution of the power and ground layers. Designers at EPCB follow some general principles to obtain the best combination of signal, ground, and power layers:
1. The signal layer was kept next to an internal power or ground layer, shielded by the copper film of the internal power layer.
2. To keep a tight control over the impedance, the internal power layer was integrated tightly with the ground layer, so that the thickness of the prepreg between the internal power and ground layers was kept thin.
3. To minimize crosstalk, no two signal layers were kept adjacent each other. As far as possible, the designers placed a ground layer in between two signal layers to avoid crosstalk.
4. To control the ground impedance, designers placed multiple grounded internal power layers.
5. The layer structure was designed to be symmetrical.