GB2174842A

GB2174842A - Monolithic ceramic capacitor for high frequency applications

Info

Publication number: GB2174842A
Application number: GB08510088A
Authority: GB
Inventors: Matthew L S Birchall
Original assignee: John Robin Musham
Current assignee: John Robin Musham
Priority date: 1985-04-19
Filing date: 1985-04-19
Publication date: 1986-11-12
Also published as: GB8510088D0

Abstract

A monolithic ceramic capacitor comprises two sets of intercollated parallel electrodes. The electrodes of a first set extend to a first pair of opposite faces of the ceramic, and the electrodes of a second set extend to a second pair of opposite faces. The capacitor may be utilised as a four terminal device, each face being a terminal T joining the edges of a respective set of electrodes (Figure 2), or the faces of a pair may be jointed T1, T2 to form a three or two terminal device (Figures 3, 4 respectively) which will act as a resonant filter or L-C resonant circuit at the appropriate high frequency. <IMAGE>

Description

SPECIFICATION Monolithic ceramic capacitor for high frequency applications The invention provides a monolithic ceramic capacitor having a ceramic body with two sets of mutually parallel interdigitated electrodes buried therein.

In a preferred structure mutually perpendicular axes X and Y of the body define a plane coincident with a film electrode, to which plane all other electrodes are parallel. Electrodes 'A' extend in an Xaxis direction to the east and west edge faces of the body and are recessed from the north and south faces. Electrodes 'B' extend in a Y-axis direction to the north and south edge faces. An electrode termination is provided on each edge face of the body.

The edge terminations may be extended to the top and bottom faces of the ceramic body.

A preferred arrangement has four discrete edge terminations although alternative styles may use three or two discrete terminations.

Thus the edge terminations of opposing edges are connected through the body by the multiple electrode layers. The electrode layers may be capable of carrying appreciable electric currents.

Capacitance is realised in the dielectric layers between the film electrodes.

Different types of electrode and dielectric material may be used depending on application design requirements.

The design may possess advantages over the conventional MLC design in that inductance may be turned to the designers advantage by the present invention.

The design may also have higher consistency owing to the way errors in the placement of layers over each other are less critical in this design than in preceding designs.

EXAMPLES 1. A four terminal device A body comprises alternate layers as seen in Figure 1. A pile of layers is assembled, laminated and fired to form a ceramic body which forms the basis of the subsequent examples. In this particular example the ends of the electrode sheets which are exposed at the edges of the ceramic body may be connected by simple end terminations. (see Figure 2).

2. Three terminal device Based on the basic ceramic body described in Example 1 the edge terminations are formed according to Figure 3. In this case the top and bottom surfaces of the ceramic body are utilised as electrode surfaces.

3. Two terminal device Based on the basic ceramic body described in Example 1 the edge terminations are formed according to Figure 4. Again, the top and bottom surfaces of the body are used to carry electrical terminations.

The four terminal structure should behave as a low pass filter device. The cutoff frequency then depends on the individual design and materials used.

The three terminal design (Example 2) should operate as a resonant filter network whose resonant frequency shall be higher than a conventional multilayer ceramic capacitor of the same dimensions and materials.

The two terminal design (Example 3) should operate as a L-C resonant circuit whose resonant frequency is higher than that of a simple MLC of similar dimensions and materials.

Each design offers a higher reproducibility of capacitance value between components from the same design owing to the fact that the overlap area of the electrodes A and B is independent of their exact relative positions.

The four terminal MLC (Example 1) may be used as a smoothing element in a power or signal circuit, as seen in Figure 5.

The three terminal MLC (Example 2) may be used as a smoothing element in a circuit as seen in Figure 6.

The two terminal MLC design (Example 3) may be used as a smoothing capacitor in an electronic circuit as seen in Figure 7.

1. A ceramic capacitor having two sets of substantially mutually parallel interdigitated electrodes buried therein.

2. A capacitor as claimed in claim 1, wherein a first set of electrodes extends to first and second opposite faces of said body and a second set extends to third and fourth opposite faces of the body.

3. A capacitor as claimed in claim 2, wherein the electrodes of each set are conductively joined at each said face to form four terminations.

4. A capacitor as claimed in claim 3, wherein a pair of opposed terminations are conductively joined to form a single termination.

5. A capacitor as claimed in claim 4, wherein the opposed terminations of both pairs are conductively joined to form two single terminations.

6. A low pass filter comprising a capacitor as defined in claim 3.

7. A resonant filter comprising a capacitor as defined in claim 4.

8. An L-C resonant circuit comprising a capacitor as defined in claim 5.

9. A monolithic ceramic capacitor substantially as hereinbefore described with reference to Figure 1, 2, 3 or 4 of the accompanying drawings.

10. A capacitor comprising a plurality of first substantially parallel layers of conductive material interleaved with a plurality of second substantially parallel layers of conductive material, the layers being separated from one another by a dielectric material and having a configuration whereby the area of overlap of the layers is substantially constant for a limited variation in the relative positions

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Monolithic ceramic capacitor for high frequency applications The invention provides a monolithic ceramic capacitor having a ceramic body with two sets of mutually parallel interdigitated electrodes buried therein. In a preferred structure mutually perpendicular axes X and Y of the body define a plane coincident with a film electrode, to which plane all other electrodes are parallel. Electrodes 'A' extend in an Xaxis direction to the east and west edge faces of the body and are recessed from the north and south faces. Electrodes 'B' extend in a Y-axis direction to the north and south edge faces. An electrode termination is provided on each edge face of the body. The edge terminations may be extended to the top and bottom faces of the ceramic body. A preferred arrangement has four discrete edge terminations although alternative styles may use three or two discrete terminations. Thus the edge terminations of opposing edges are connected through the body by the multiple electrode layers. The electrode layers may be capable of carrying appreciable electric currents. Capacitance is realised in the dielectric layers between the film electrodes. Different types of electrode and dielectric material may be used depending on application design requirements. The design may possess advantages over the conventional MLC design in that inductance may be turned to the designers advantage by the present invention. The design may also have higher consistency owing to the way errors in the placement of layers over each other are less critical in this design than in preceding designs. EXAMPLES 1. A four terminal device A body comprises alternate layers as seen in Figure 1. A pile of layers is assembled, laminated and fired to form a ceramic body which forms the basis of the subsequent examples. In this particular example the ends of the electrode sheets which are exposed at the edges of the ceramic body may be connected by simple end terminations. (see Figure 2). 2. Three terminal device Based on the basic ceramic body described in Example 1 the edge terminations are formed according to Figure 3. In this case the top and bottom surfaces of the ceramic body are utilised as electrode surfaces. 3. Two terminal device Based on the basic ceramic body described in Example 1 the edge terminations are formed according to Figure 4. Again, the top and bottom surfaces of the body are used to carry electrical terminations. The four terminal structure should behave as a low pass filter device. The cutoff frequency then depends on the individual design and materials used. The three terminal design (Example 2) should operate as a resonant filter network whose resonant frequency shall be higher than a conventional multilayer ceramic capacitor of the same dimensions and materials. The two terminal design (Example 3) should operate as a L-C resonant circuit whose resonant frequency is higher than that of a simple MLC of similar dimensions and materials. Each design offers a higher reproducibility of capacitance value between components from the same design owing to the fact that the overlap area of the electrodes A and B is independent of their exact relative positions. The four terminal MLC (Example 1) may be used as a smoothing element in a power or signal circuit, as seen in Figure 5. The three terminal MLC (Example 2) may be used as a smoothing element in a circuit as seen in Figure 6. The two terminal MLC design (Example 3) may be used as a smoothing capacitor in an electronic circuit as seen in Figure 7. CLAIMS

6. A low pass filter comprising a capacitor as defined in claim 3.

7. A resonant filter comprising a capacitor as defined in claim 4.

8. An L-C resonant circuit comprising a capacitor as defined in claim 5.

10. A capacitor comprising a plurality of first substantially parallel layers of conductive material interleaved with a plurality of second substantially parallel layers of conductive material, the layers being separated from one another by a dielectric material and having a configuration whereby the area of overlap of the layers is substantially constant for a limited variation in the relative positions of said layers.

11. A capacitor as claimed in claim 10, wherein the layers are parallel sided.