[SI-LIST] : Buried Capacitors

Dr. Edward P. Sayre (rharris@etdesg.trw.com)
Tue, 29 Jul 1997 17:49:11 -0700 (PDT)

I am trying to gain a better understanding on the concept of the buried
capacitors, made of two (2) internal planes on a printed circuit board.

We do not have a general agreement within the design community on the use
of this technique, so I just wanted to bounce it off of this reflector.

Multi-layer PCB's have power and ground planes as a norm. This technique
stacks some of these planes very close together (2 mil thin dielectrics)
to act as a giant capacitor.

The design uses thru-hole vias only.

Are we:
1) reducing noise
2) using this as an alternative to filter-caps
3) using this in conjunction with filter-caps.
4) At what frequencies is this practice appropriate.
5) anything else you can add.

Thanks

Bob Harrison
TRW