Electricity: electrical systems and devices – Electrostatic capacitors – Fixed capacitor
Reexamination Certificate
2000-06-06
2001-11-27
Reichard, Dean A. (Department: 2831)
Electricity: electrical systems and devices
Electrostatic capacitors
Fixed capacitor
C361S303000, C361S306100, C361S306300, C361S508000
Reexamination Certificate
active
06324047
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-layer ceramic capacitor or varistor adapted to be mounted on the surface of a circuit board. In particular, the invention relates to a square chip design for a capacitor or varistor for mounting on an electronic circuit board with corner terminations. More precisely, the present invention relates to a symmetrical multi-layer capacitor or varistor chip design for mounting on a circuit board to act as a filter therefore, with corner terminations and unoriented feed-thrus placed diagonally across the chip.
2. Description of the Prior Art
With today's push toward miniaturization, Electromagnetic Interference (EMI) could potentially render a circuit useless or worse still it could cause an incorrect answer to be generated from a computer by randomly powering a gate up or down. As a result filtering out undesirable signal noise (i.e., unwanted frequencies) has become a major design consideration for new electronic devices.
To solve this problem, designers have used capacitors and varistors for some time. Additionally they have been using specifically design electrical devices known as feed-thru filters to specifically solve these problems. Feed-thru filter devices are well know in the art. They have been used in everything from cellular phones and laptop computers to implantable medical devices such as cardiac pacemakers. Their primary function is to attenuate undesirable or transient voltage frequencies or EMI from a signal passing through a circuit. They can be either capacitor- or varistor-based devices.
There are two primary capacitor/varistor geometries in use in the industry—the rectangular chip and the discoidal chip. The monolithic or multi-layer rectangular chip configuration is produced in very high volumes in highly automated facilities around the world. One example of such a rectangular chip is disclosed in commonly owned U.S. Pat. No. 5,880,925 entitled “Surface Mount Multilayer Capacitor.”
In many instances, a chip requires a significant amount of care be exercised during the manufacture, packaging, and installation of the chip. Sometimes a chip requires additional machinery or man-hours to ensure that the chip is oriented properly throughout the manufacturing process.
The termination process is the widely-used industry process in which chips are oriented to form the terminals on the sides of the chip and then re-oriented to form the terminals on the ends of the chip. The electrically conductive terminals allow for electrical connection between the lead structures of the electrode plates and the circuitry in which the chip is ultimately placed.
The complete disclosure of U.S. Pat. No. 5,880,925 (including all figures and discussion thereof) is fully incorporated herein by reference.
Additional United States Patents provide examples of capacitor-based feed-thru filters for use in attenuating undesired signal frequencies. Examples include U.S. Pat. Nos. 3,255,396; 3,320,557; 3,426,257; 3,989,988; 4,747,019; 4,908,590; 5,097,389; 5,650,759; and 5,595,829. The complete disclosures of all such patents (including all figures and descriptions thereof) are fully incorporated herein by reference.
SUMMARY OF THE INVENTION
The present invention recognizes and addresses various of the foregoing limitations and drawbacks concerning feed-thru filter manufacturing. Thus, broadly speaking, a principal object of the subject invention is an improved design for feed-thru filters with respect to manufacturing difficulties. More particularly, a main concern is improved design layouts for feed-thru filters that enhance manufacturing ease and require less printed circuit board (PCB) space while maintaining at least the same capabilities as prior art feed-thru filters.
Another more particular object of the subject invention is to provide a feed-thru filter that by design requires no side or end orientation for manufacturing and implementation. In such a context, it still a further object to provide such a feed-thru filter which is square in shape.
Still another more particular object of the subject invention is to provide a square feed-thru filter with terminals in each of the four corners, wherein the terminals extend along the entirety of the height of the chip. It is a further more particular object of the subject invention to provide a feed-thru filter wherein the feed-thrus are oriented diagonally across the chip.
Additional objects and advantages of the invention are set forth in, or will be apparent to those of ordinary skill in the art from, the detailed description herein. Also, it should be appreciated that modifications and variations to the specifically illustrated, referenced, and discussed steps, features, materials, or devices hereof may be practiced in various uses and embodiments of this invention without departing from the spirit and scope thereof, by virtue of present reference thereto. Such variations may include, but are not limited to, substitution of equivalent steps, materials, means, or features for those shown, referenced or discussed, and the functional, operational, or positional reversal of various features, steps, parts, or the like.
Still further, it is to be understood that different embodiments, as well as different presently preferred embodiments, of this invention may include various combinations or configurations of presently disclosed steps, features, or elements, or their equivalents (including combinations of steps or features or configurations thereof not expressly shown in the figures or stated in the detailed description). One exemplary such embodiment of the present invention relates to an improved design for a feed-thru filter for electrical circuitry.
Such a design includes a symmetrical, square design employing a multi-layer capacitor/varistor based feed-thru filter. The feed-thru filter comprises an interleaved series of electrode plates made of any capacitor/varistor material well known in the industry, for example zinc oxide. Other examples of such materials would be barium titanate or tantillum for use with the capacitor based variation of the subject invention.
At one set of opposing corners of each plate extend electrode tab structures for electrical connection to the terminals of the device. Each plate has its electrode tab structures in the opposite set of opposing corners from the plate either above, below, or both above and below it. In other words, the plates are interdigitated.
The feed-thru filter, itself, has four terminals total, one in each corner of the device. The terminals extend along the entirety of the height of the device. It is these terminals, to which, the electrode tab structures of each electrode plate are attached. They are arranged in such a way so that the polarity of a set of terminals in opposing corners is the same. That set of terminals, however, will have a different polarity from the remaining set of terminals.
The feed-thru filter of the subject invention utilizes less space with greater capability while enhancing the ease of manufacturing and implementation of itself. The present invention's symmetric square-shape leaves greater room on the PCB than does a discoidal or rectangular design. With today's push toward miniaturization, integration of components into smaller and smaller areas is absolutely mandatory. In its shape alone, the present invention has solved problems for circuit designers.
Additionally, the instant invention enables manufacturers to create the corner terminals on existing machinery without concern as to the orientation of the chip. Unlike rectangular chips which have distinctive length-to-width ratios, a square chip with corner terminals can be processed through the termination process without end or side orientation. The termination process merely adds the terminals at the corners. It is not required that the terminals be placed at an exact location along the length of the rectangular chip. The use of just four terminals, one for each corner, allows for the termination process t
AVX Corporation
Dority & Manning P.A.
Ha Nguyen T
Reichard Dean A.
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