Browse Prior Art Database

HIGH VALUE CAPACITORS AND HIGH Z0 STRIPLINE IN THE SAME MULTILAYER CERAMIC PACKAGE

IP.com Disclosure Number: IPCOM000007474D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2002-Mar-29
Document File: 1 page(s) / 66K

Publishing Venue

Motorola

Related People

Richard S. Kommrusch: AUTHOR [+2]

Abstract

In many stripline and Multilayer Ceramic (MLC) circuits, it is desirable to have relatively high value capacitors and relatively high impedance transmis- sion lines. This can be accomplished by mixing high and low dielectric layers. When a large capacitor is desired a high dielectric layer is used between its plates. In some cases the capacitance can be increased by more than ten times while the line impedances can be maintained by using a narrower line.

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M-ROLA Technical Developments

HIGH VALUE CAPACITORS AND HIGH 20 STRiPLINE IN THE SAME MULTILAYER CERAMIC PACKAGE

by Richard S. Kommrusch and Chowdary R. Koripella

  In many stripline and Multilayer Ceramic (MLC) circuits, it is desirable to have relatively high value capacitors and relatively high impedance transmis- sion lines. This can be accomplished by mixing high and low dielectric layers. When a large capacitor is desired a high dielectric layer is used between its plates. In some cases the capacitance can be increased by more than ten times while the line impedances can be maintained by using a narrower line.

  Figure la shows a typical series capacitor made in MLC with a 7.8 dielectric constant. Note how the stack of capacitive plates extend towards the upper and lower ground planes which creates an undesired stray capacitance to ground. Figure lb shows that a capacitor of the same value as Cl can be made by changing 2 of the 10 layers to a high dielectric, K= 100. The new capacitor has 3 1% of the area, one- fourth the layers and has less than a one-tenth of the stray capacitance.

  Depending on the application and the choice of dielectric constants the characteristic impedance, Zo, of the transmission line shown in Figure 1 can be

maintained. In the Figure 1 example, a centered line with a width of 25 mils and a thickness of 0.3 mils gives a Zo of30 ohms and a v/c, relative veloc- ity of propagation, of 0.358. When the two center layers are replaced with a di...