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Without a rule of thumb for determining which designs will be enhanced by the addition of buried capacitance, each must be individually evaluated to establish the merits.

Presently, there are several techniques for forming a buried capacitor in the core of a multilayer board. For purposes of this discussion, attention will be directed toward a sheet capacitor, though most of what is presented below can be extended to the other techniques as well.
A buried sheet capacitor is essentially a thin innerlayer. The core is composed of an organic material often reinforced with a woven glass structure; a classic example is FR-4. The copper weight is normally one ounce, and the thickness of the dielectric is typically two mils or less. The innerlayer is biased top to bottom, creating a large capacitor in the interior of the multilayer board. Except for through-hole connecting pads and antipads, the innerlayer is normally not imaged. A cross section is shown in FIGURE 1.

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