"Tom Bruhns" ha scritto nel messaggio
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I know there are some pretty good PCB-capacitor aplets on the web.
Try a Google or similar search for them.

"RFSim99" is free for the downloading and has lots of tools, including
a component calculator that covers, among other components,
capacitors. It lets you just select FR4 dielectric (or any of several
others, or your specific relative dielectric constant), thickness, and
plate area, and will tell you the capacitance. Beware of fringing
effects, though, if your capacitor plate dimensions are not large
compared with the board thickness. RFSim99 doesn't do anything to
account for fringing as far as I can see. The capacitance is mainly
dependent on the plate area, but beware also of making one that is
long and narrow, because it will act like a transmission line. Also,
a problem with FR4 is that the dielectric constant is not well
controlled, so the capacitance may not be very consistent from
manufacturer to manufacturer.

Fantastic, bellissimo, thankx
Massimo