Capacitor method and apparatus

A method and apparatus is provided that pertains to a low inductance capacitor. The capacitor has a first surface electrically interconnected to a plurality of conductive electrodes and one or more second surfaces electrically interconnected to a plurality of electrodes interposed between the electrodes electrically interconnected to the first conductive surface. A dielectric layer separates the layered plurality of electrodes. The one or more second conductive surfaces are positioned within the body of the layered electrodes, such that the distance between the terminations of the first conductive surface and the one or more second conductive surfaces is shortened to lower inductance.

FIELD OF THE INVENTION

The present invention relates generally to capacitors and the manufacture thereof, and more particularly, to low inductance capacitors suitable for use with microelectronic circuits.

BACKGROUND OF INVENTION

Microelectronic devices are continually becoming smaller, and the circuit density, operating speeds and switching rates are continually increasing. This trend has impacted the design and manufacture of a variety of components that support the operation of microelectronic devices, such as voltage regulation devices, inductors, capacitors, and the like. In regard to capacitors, the decreased size and increased speed trend has amplified issues with respect to the inductance of capacitors, which have not previously been a critical concern.

Capacitors can be used for a variety of reasons, including as a means to store energy for use by microelectronic devices during periods of non-steady state or transient current demands, or to manage noise problems that occur in microelectronic circuit applications. Inductance is a capacitor limitation that is becoming more critical as microelectronic devices get smaller and faster. The higher the inductance, the slower the capacitor, as a power source, responds to a transient current demand. Accordingly, it is one goal of the industry to reduce inductance in capacitors, so as to allow them to timely respond to the energy demands as required by a microelectronic device (e.g. within the first few cycles).

FIG. 1is a side view of an example of a capacitor of the prior art design. Capacitors commonly consist of a first conductive plate10and a second conductive plate12. The first conductive plate10is electrically interconnected to a plurality of conductive first electrodes14. The second conductive plate12is electrically interconnected to a plurality of conductive second electrodes16. Dielectric material18is dispersed between the plurality of first electrodes and the plurality of second electrodes. The dielectric material18can be any nonconductive material, including, but not limited to air, aluminum oxide, ceramics, mica, and the like.

The charge or polarity of the first conductive plate10and the first electrodes14is opposite to the charge of the second conductive plate12and the second electrodes16, such that the electrical energy of the charged system then is stored in the polarized dielectric. First conductive plate10terminates at first terminal20and second conductive plate12terminates at second terminal22. First and second terminals20and22can then be electrically interconnected to a conductive path, such as a power trace in a printed circuit board that electrically interconnects a power source with a microelectronic device (not shown).

Inductance is dependent on factors such as the separation distance between first and second electrodes14and16, as well as the first and second conductive plates10and14. Generally, inductance is directly proportional to the distance between the oppositely charged surfaces, i.e. first and second electrodes14and16and first and second conductive plates10and14, show by terminal distance arrow24. As such, industry has attempted to reduce both distances, in order to reduce inductance. As new dielectric materials18with higher dielectric constants are developed, the distance between the conductive plates may be reduced.

New configurations and methods for reducing the distance between the conductive surfaces10and12are needed to reduce inductance of capacitors, which will increase the capacitor response time to the energy demands of the smaller, yet higher speed microelectronic devices.

DESCRIPTION

FIG. 2is a cross-sectional view of a capacitor30in accordance with an embodiment of the present invention. A plurality of conductive first electrodes34and a corresponding plurality of conductive second electrodes38are layered or interleaved to a predetermined number of layers. A dielectric material40separates each layered first electrode34and second electrode38. The layered first and second electrodes34and38, and the dielectric material40, generally comprise the body of capacitor30defining a certain shape and size. A first conductive surface32is positioned about the perimeter of the capacitor30. The first electrodes34are electrically interconnected to the first conductive surface32and extend generally perpendicular to the first conductive surface32. The first conductive surface32and the first electrodes34have a predetermined charge or polarity.

The second conductive surface36is disposed in the body of the capacitor30, generally penetrating the layers of the first and second electrodes34and38. The second electrodes38are electrically interconnected to the second conductive surface36and extend substantially perpendicular to the second conductive surface36, but are not electrically interconnected with the first conductive surface32. The second conductive surface36and the second electrodes38electrically interconnected thereto have a charge that is opposite to the charge of the first conductive surface32and the first electrodes34. The first conductive surface32terminates at the first terminal42and the second conductive surface36terminates at the second terminal44. The terminals42and44can be configured to electrically interconnect to, for example, the power and ground plane of a power delivery path for a microelectronic device. The capacitor30can be encapsulated with a dielectric material to prevent grounding or electromagnetic influence from other devices (not shown).

Though first conductive surface32is shown in the illustrated embodiment to surround the perimeter of capacitor30, the first conductive surface32may segmented and electrically interconnected to first electrodes34at different positions around the perimeter of capacitor30.

The inductance of the capacitor30is influenced by the separation distance between the first and second electrodes34and38. The separation distance between first conductive surface32and second conductive surface36, shown by termination distance arrow46, directly impacts the inductance. Comparing termination distance46ofFIG. 2with the termination distance24ofFIG. 1, the inductance of capacitor30will be lower as the terminal distance46is reduced, in this case to approximately one half in reference to FIG.1. This reduction is due to the positioning the second conductive surface36into the body of capacitor30, such that it is no longer on the opposite edge of the perimeter. The lower inductance allows the capacitor30to respond more quickly to the increased energy demand of a microelectronic device.

FIG. 3is a perspective view of the capacitor30shown in the embodiment of FIG.2. The first conductive surface32is electrically interconnected to the first electrodes34(not shown), and comprises at least a portion of the perimeter of the capacitor30. The first conductive surface32terminates at first terminal42and has a charge. The second conductive surface36extends into the layers of the first and second electrodes34and38(not shown), and is electrically interconnected with the second electrodes38(not shown). The second conductive surface36terminates at the second terminal44and is opposite in polarity to the first terminal42and the first conductive surface32. As shown, the termination distance46, again, is roughly half what it would be if the capacitor30was of conventional design.

The capacitor30can be constructed in a variety of ways. In one embodiment in accordance with the present invention, individual sheets of the first electrodes34and the second electrodes38in the form of sheets can be layered with inserting a dielectric material40between each first electrode34and second electrode38. Once the desired number of first and second electrode layers is reached, the capacitor30can be cut to any desired shape or size. The first conductive surface32can then be secured to the perimeter of the body of the capacitor30and electrically interconnected to the first electrodes34. An opening within the body of the capacitor30can be created, for example but not limited to by drilling, and a second conductive surface36can be inserted in the opening and electrically interconnected with the second electrodes38.

Alternatively, in another embodiment of the present invention, the first conductive surface32and the second conductive surface36can be pre-positioned. Pre-sized first electrodes34and second electrodes38can be alternately layered, with placing a dielectric material40between each electrode layer. As each first electrode34is placed it can be electrically interconnected with first conductive surface32and as each second electrode38is placed, it can be electrically interconnected with second conductive surface36.

FIG. 4is a side view of a capacitor50in accordance with another embodiment of the present invention. A plurality of first electrodes54and a corresponding plurality of second electrodes58are interleaved or layered with a dielectric material60placed between each first and second electrode54and58, such that the body of capacitor50is defined. The first electrodes54are electrically interconnected to first conductive surface52in a substantially perpendicular manner. A plurality of second conductive surfaces56are disposed within the body of capacitor50in the layered first and second electrodes54and58. The second electrodes58electrically interconnect to the plurality of second conductive surfaces56and have an opposite charge as that of the first conductive surface52and first electrodes54. First conductive surface52terminates at first terminal62and second conductive surfaces56terminate at second terminal64.

Termination distance66is reduced by the plurality of second conductive surfaces56disposed within the capacitor50, which in turn proportionally decreases the inductance. Like the embodiment described inFIG. 2, first conductive surface52need not entirely surround the perimeter of capacitor50, but can be at a portion or multiple portions at spaced apart intervals.

FIG. 5is a perspective view of the capacitor shown in the embodiment of FIG.4. The first conductive surface52is electrically interconnected to the first electrodes54(not shown), and comprises at least a portion of the perimeter of the capacitor50. The first conductive surface52terminates at first terminal62. The second conductive surfaces56are disposed through the layers of first and second electrodes54and58(shown in FIG.4), and only electrically interconnect with the second electrodes58(shown in FIG.4). The second conductive surfaces56terminate at the second terminals64, and are oppositely charged to the first terminal62and first conductive surface52. Termination distances66, again, are roughly half what it would be if the second conductive surface56was on the perimeter at a position opposite to the first conductive surface52.

The terminals62and64can be configured to electrically interconnect to, for example but not limited to, the power and ground plane of a power delivery path for a microelectronic device, or any other electronic device. Though not shown, the capacitor50can be encapsulated with a dielectric material to prevent grounding or influence from other devices. Methods of manufacturing the capacitor50or capacitors having a plurality of second conductive surfaces disposed within the body of the capacitor is the same as those methods described in regards to the embodiments ofFIGS. 2 and 3, except multiple second conductive surfaces56are provided.

Though the second conductive surfaces36and56in the embodiments described herein inFIGS. 2 through 5are cylindrical in shape with a hollow core, which helps with heat dissipation, it is within the scope of the invention for the second conductive surfaces36and56to be a polygonal, oblong or any other shape that allows for the second conductive surfaces to be disposed in the plurality of layered first electrodes34and54and second electrodes38and58, such that the second electrodes38and58are electrically interconnected to the second conductive surfaces36and56, and the second conductive electrodes38and58are electrically interconnected to the second conductive surfaces36and56. The second conductive surfaces36and56can be solid, and their shape, as well as the shape and size of the capacitor itself can be varied depending on the desired configuration and taking into account manufacturing constraints.