A symmetrical feed-thru filter construction is provided in a square-shaped chip with corner terminations and unoriented feed-thrus running diagonally across the chip for suppressing transient or undesired frequencies from a signal. The construction can be of either a capacitor or varistor based design and can be altered during manufacture to handle signals of specified strengths.

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 to create the terminals in
 just one pass through the machinery as opposed to multiple passes for
 other chips. Similarly, due to its symmetrical design, the chip requires
 less effort in packaging and installation, yet provides equal or greater
 performance.
 Those of ordinary skill in the art will better appreciate the features and
 aspects of such embodiments and others, upon review of the remainder of
 the specification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The miniaturization of cellular phones, laptop computers, and other
 electronic devices pushed passive electronic component manufacturers to
 begin developing integrated components into smaller surface mountable
 packages or arrays. In addition to space and cost savings, these
 integrated components fathered generations of smaller, more powerful
 electronic components.
 These newer, more powerful components brought with them there own problems
 which needed correction. Among these problems was the very physics behind
 the functionality of some of these components. For example, as capacitors
 grew smaller, the reduction in volumetric area reduced the capacitance of
 the capacitor. In order to overcome this problem, manufacturers have been
 combining passive components into built-in arrays. Other manufacturers
 began looking for optimal space saving shapes with maximum volumetric area
 while still capable of manufacture with existing machinery.
 While the particulars of the subject invention may be adapted for use in
 other electronic components, the example discussed herein are in the
 context of a capacitor/varistor feed-thru filter.
 With more specific reference to the subject invention, FIG. 1B represents
 an overhead view of a multi-layer symmetrical chip showing corner
 terminations. The subject invention comprises a feed-thru filter
 construction 10 having a square-shaped symmetrical body 11 (i.e., a
 length-to-width ratio of 1:1) with an electrically conductive terminal 12,
 14 in each corner of the construction 10. An exemplary measurement of one
 embodiment is approximately 40 mils by 40 mils with a height of up to 35
 mils maximum. As the construction 10 is a passive component, it can be
 either a capacitor or a varistor based component.
 As seen in FIGS. 1A and 1C, the feed-thru paths are unoriented until
 installation of the chip 10. While the pathway (as indicated by the arrows
 in the figures) is diagonal across each electrode plate 16, 18, 20, only
 installation determines the direction of the flow of current through the
 construction 10. Additionally, the construction 10 has four electrically
 conductive terminals 12, 14. There is one terminal 12, 14 in each corner
 of the construction 10. It is these terminals 12, 14 that provide the
 electrical connection between the construction 10 and the circuitry into
 which it is ultimately placed.
 As represented to those of ordinary skill in the art from present FIG. 3,
 the internal composition of the construction 10 comprise a plurality of
 electrode plates 16, 18, 20 stacked, pressed, and sintered together in a
 spaced apart arrangement to form the filter through which the signal
 passes. These electrode plates 16, 18, 20 can be made of any material used
 in the industry in the construction of either a capacitor or varistor.
 Examples of such materials include zinc oxide and barium titanate.
 Between the electrode plates 16, 18, 20 is a dielectric material 15 to
 electrical insulate the plates 16, 18, 20 from each other and from the
 body 11 of the construction 10. Similarly, in order to electrically
 insulate the edges of the electrode plates 16, 18, 20 from the body 11,
 each electrode plate 16, 18, 20 has at least a five mil border 28 of the
 dielectric material 15 except where the electrical connection between the
 electrode plates 16, 18, 20 and the terminals 12, 14 is made.
 For example, the first electrode plate 16, shown in FIG. 3, is designed to
 have a main electrode portion 30 and two electrode tab structures 22
 extending therefrom. The electrode tab structures 22 extend into a set of
 opposing corners. The second electrode plate 18 has an identical main
 electrode portion 32 and two identical electrode tab structures 24. The
 electrode tab structures 24 of the second electrode plate 18, however,
 extend into the opposite set of opposed corners. The third electrode plate
 20, is identical in all respects to the first electrode plate 16. The
 fourth electrode plate (not shown) would be identical in all respects to
 the second electrode plate 18. In this manner, the multiple electrode
 plates 16, 18, 20 are interdigitated to alternating sets of opposed
 corners. It is in those two sets of opposed corners where the electrode
 tab structures 22, 24, 26 and the terminals 12, 14 are electrically
 connected.
 In order to ease the manufacturing of the construction 10 and to ensure the
 electrical connection with each electrode plate 16, 18, 20, the terminals
 12, 14 extend along the entirety of the height of the body 11. As can be
 seen in FIG. 2, each of the sets of terminals 12, 14 gain an opposing
 polarity once installed. As the construction 10 is symmetrical and
 unoriented prior to its installation, one of ordinary skill in the art
 would recognize that either terminal set 12, 14 could become positive and
 either could become negative.
 While most stacked capacitor/varistor components have limiting
 length-to-width characteristics, the ease of manufacturing, packaging, and
 installation of the present invention are due to its symmetrical
 unoriented design. The use of just four corner terminals allows for
 reduced manufacturing time. The symmetric shape and unoriented layout
 allow for "pick and place" packaging and installation. As a result, the
 subject invention solves several problems facing electrical component
 designers today. It reduces the real estate required by an individual
 component on PCBs while maintaining equal or better capabilities.
 It will be understood by those skilled in the art that modification may be
 made in the structures and methods set forth herein without departing from
 the spirit and scope of the invention as defined in the claims that
 follow, and it is intended that the structures and methods described above
 and shown in the accompanying drawings are to be construed as illustrative
 only.