Interplane Capacitance

[hioyo]

I know that the power and ground plane acts as a bypass capacitor.
I have two cases
1)PWR and GND planes are tightly coupled together
2)There is a signal layer in between PWR and GND planes

May I know in both cases the bypass capacitor action of PWR and GND planes will be the same or different?
I mean in which case it acts as a good bypass capacitor

 

[senilicus]

In general, from an EMI view, it is not a good practice to put a signal layer between the PWR and GND plane.
The energy is not in the copper, remember. It is between the planes,

For high speed signals this can be the root cause for problems.

The closer the two planes are, the higher the capacitance will be. But it is still very small.


The get an idea of the numbers, have a look at,

https://www.emisoftware.com/calculator/biplanar-capacitance/