Obviously, a single or double layer PCB cannot be classified as a multi-layer PCB. However, any PCB with number of layers greater than two is considered as a multi-layer PCB (4, 6, 8,…-layer PCB). There are various reasons that make PCB Designers to move to a multi-layer PCB. The major reason could be thought of as, to improve on the ease of routing capability and most importantly, to improve on the electromagnetic compatibility. A multi-layer PCB stack-up must be made in such a way that, the complete board shall meet the electrical signal and power needs and also meet the mechanical strength requirements. Most professional multi-layer PCB designs are able to exhibit around 15dB less emissions.
When making a multi-layer PCB, you must plan about the configuration of your PCB stack-up. Wrong multi-layer PCB configuration may give rise to undesired electromagnetic interference and poor signal integrity. Below are some of the important things to consider about signal when making a multi-layer PCB design.
- Consider the type of signals to be routed e.g. different signal frequencies
- Consider the signal rise and fall
- Sufficient return for the signal loop
Likely signal delay caused by permitivity - Possible cross-connection and overlap