Re: [SI-LIST] : Thin Power Plane Dielectrics

Tom Woodward ([email protected])
Wed, 20 Oct 1999 09:28:55 -0400

Is there another high frequency current path that could mitigate the
effects of the slow propagation across the high-Er material?
Due to skin effect, the high frequency current should flow predominately
in the surface of the power/ground planes adjacent to the high-Er
dielectric. If the opposite sides of the planes, however, are adjacent
to normal FR-4, then a higher speed propagation path should
be available on those surfaces. Nearby power/gnd vias should
provide a wrap-around path for these currents to reach the surfaces
adjacent to the high-Er material, thereby allowing earlier access
to "patches" of higher capacitance. Is this realistic?

Tom Woodward ([email protected])
Woodward McCoach, Inc. 1180 McDermott Dr. West Chester, PA 19380
610-692-9526 Ext. 102 ( Voice) 610-436-8258 (Fax)

-----Original Message-----
From: Ingraham, Andrew <[email protected]>
To: '[email protected]' <[email protected]>
Date: Tuesday, October 19, 1999 9:49 AM
Subject: RE: [SI-LIST] : Thin Power Plane Dielectrics

>Do these techniques use only different dimensions (perhaps with a higher
>breakdown potential), or is the dielectric constant bigger as well?
>
>I have seen warnings about "buried capacitance" layers that use high-Er
>materials. While this is OK at lower frequencies, the advantage falls apart
>at higher frequencies because the propagation delay through the buried
>capacitance layer is more. Even though the capacitance per unit area is
>large, the capacitance per nanosecond (risetime) may not be.
>
>Andy
>
>
>
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