Multilayer capacitor

Abstract: A multilayer capacitor (31) whose equivalent series inductance is reduced includes a capacitor main body (38) having a generally rectangular parallelpiped shape with two principal surfaces in a face-to-face relationship with each other and four side surfaces (34 -37) connecting the principal surfaces. A capacitor unit is formed in the capacitor main body by a respective pair of first and second internal electrodes disposed in the main body (38) in a face-to-face relationship with a dielectric material layer interposed therebetween. At least three first external electrodes (48 - 53) are located on respective ones of the side surfaces (34 - 37) of the capacitor main body (38), with at least one of the first external electrodes (48 - 53) being located on each of at least three of the side surfaces (34 - 37). The first internal electrode has at least three first lead electrodes, each of which extends to and is electrically coupled to a respective one of the first external electrodes (48 - 53). A plurality of second external electrodes (60 - 65) are located on respective side surfaces (34 - 37) of the capacitor main body (38) and the second internal electrode has an equal plurality of second lead electrodes, each extending to and being electrically coupled to a respective one of the second external electrodes (60 - 65).

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer capacitor and, more particularly, to a multilayer capacitor which can be advantageously used in high frequency circuits. 2. Description of the Related Art Conventional multilayer capacitors include that described in Japanese Unexamined Patent Publication No. H2-256216 in which a multilayer capacitor 1, as shown in Figs. 15 through 17, is disclosed. Fig. 15 is a plan view of the external appearance of the multilayer capacitor 1. Fig. 16 is a plan view of a first section of the multilayer capacitor 1 showing a first electrode 10 located on one surface of one internal dielectric layer 9 of the capacitor 1. Fig. 17 is a plan view of a second section of the multilayer capacitor 1 showing a second electrode 11 located on one surface of a differential internal dielectric layer 9 of the capacitor 1. Referring to Figs. 15-17, the multilayer capacitor 1 includes a capacitor main body 8 in the form of a rectangular parallelpiped having two principal surfaces 2 and 3 in a face-to-face relationship with each other and four side surfaces 4, 5, 6 and 7 connecting the principal surfaces 2 and 3. The capacitor main body 8 includes a plurality of dielectric layers 9 (Figs. 16-17) made of, for example, a ceramic dielectric material. Each of the dielectrical layers is generally planar in shape and lies generally parallel to the principal surfaces 2 and 3. At least a pair of first and second internal electrodes 10 and 11 are provided on respective surfaces of the dielectric layers 9 in a face-to-face relationship with each other with a dielectric layer 9 interposed therebetween to form a capacitor unit. The first internal electrode 10 is formed with four lead electrodes 12, 13, 14 and 15 which extend to two opposing side surfaces 4 and 6, as shown. Each lead electrode 12, 13, 14 and 15 is coupled to a respective external terminal electrode 16, 17, 18 and 19 provided on the side surfaces 4 and 6 of the capacitor main body 8. Specifically, the lead electrodes 12 and 13 are connected to the external terminal electrodes 16 and 17, respectively, which are located on the side surface 4, and the lead electrodes 14 and 15 are connected to the external terminal electrodes 18 and 19, respectively, which are located on the side surface 6. Referring to Fig. 17, the second internal electrode 11 is also formed with four lead electrodes 20, 21, 22 and 23 which extend to the side surfaces 4 and 6, respectively. More specifically, the lead electrodes 20 and 21 extend to positions on the side surface 4 which are different from the positions to which the lead electrodes 12 and 13 extend, and the lead electrodes 22 and 23 extend to positions on the side surface 6 of the main body 8 which are different from the positions to which the lead electrodes 14 and 15 extend. The leads electrodes 20 through 23 are electrically coupled to external terminal electrodes 24, 25, 26 and 27, respectively. External terminal electrodes 24 and 25 are located on the side surface 4 at positions which are different from those of the external terminal electrodes 16 and 17. External terminal electrodes 26 and 27 are located on the side surface 6 at positions which are different from the positions of the external terminal electrodes 18 and 19. Thus, the plurality of first external terminal electrodes 16 through 19 and the plurality of second external terminal electrodes 24 through 27 are arranged on the two side surfaces 4 and 6 such that they alternate adjacently to each other. Fig. 18 illustrates current flowing through the multilayer capacitor 1 as viewed in plan view corresponding to Fig. 17. In Fig. 18, first internal electrode 10 and second internal electrode 11, shown with broken and solid lines, respectively, are shown in an overlapping relationship. In Fig. 18, the arrows indicate typical current paths and directions. In the state illustrated, current flows from each of the external terminal electrodes 24 through 27 to each of the external terminal electrodes 16 through 19. Because an alternating current is used, the direction of current flow will reverse periodically. When the currents flow, magnetic flux is induced. The direction of the flux is determined by the direction of the currents to produce self-inductance components. Since the currents flow in various directions at central regions 28 (indicated by circles) of the internal electrodes 10 and 11, the induced magnetic flux generated by the various currents is canceled and substantially no net magnetic flux is produced in those regions. The current in the vicinity of each of the external terminal electrodes 16 through 19 and 24 through 27 tends to flow toward each of the external terminal electrodes 16 through 19 and away from each of the external terminal electrodes 24 through 27. There are currents that flow to the left and right as viewed in Fig. 18 to spread at an angle of about 180 degrees. As a result, a major part of magnetic flux is canceled and there is no significant generation of net magnetic flux in these areas. Therefore, in the multilayer capacitor 1 shown in Figs. 15 through 17, the generation of self-inductance is suppressed in the areas points described above to reduce equivalent series induction (hereinafter "ESL"). However, currents flow substantially in the same direction in the vicinity of each of the side surfaces 5 and 7 on which no external terminal electrodes are provided, i.e., at each of the left and right edge portions indicated by hatching in Fig. 18. This results in substantially no cancellation of magnetic flux in these areas and significant net self-inductance is created. Therefore, the measures taken to reduce ESL in the multilayer capacitor 1 shown in Figs. 15 through 17 is less than desirable. Multi-layer capacitors comparable to those described above referring to Figs. 15 to 18 are disclosed in US-4,831,494. EP-A-0191668 concerns multi-layer capacitors having an increased resonance frequency and an increased capacitance. A plurality of capacitor electrodes is arranged with dielectric layers therebetween wherein the electrodes have an elongated shape, wherein each electrode is provided with two protruding terminal portions. In addition, EP-A-0191668 discloses U-shaped internal electrodes which are provided by bending elongated electrodes so as to provide a more compact element. The U-shaped electrodes are formed of a central portion and two branch portions. Protruding terminal portions are provided at corners or different side faces of the U-shaped internal electrodes. It is the object of the present invention to provide a multi-layer capacitor which more effectively reduces equivalent series induction (ESL) and shows an improved performance. This object is achieved by a multi-layer capacitor according to claim 1. In the following, the present invention will be explained in detail with reference to the drawings enclosed, in which: Fig. 1 is a plan view of a multilayer capacitor 31 according to a first comparison example; Fig. 2 is a plan view of the multilayer capacitor 31 shown in Fig. 1 showing an internal structure thereof in the form of a section along which a first internal electrode 40 extends; Fig. 3 is a plan view of the multilayer capacitor shown 31 in Fig. 1 showing an internal structure thereof in the form of a section along which a second internal electrode 41 extends; Fig. 4 is a plan view illustrating currents flowing in the multilayer capacitor 31; Fig. 5 is a plan view of a multilayer capacitor 71 according to a second comparison example showing the external appearance thereof; Fig. 6 is a plan view of the multilayer capacitor 71 shown in Fig. 5 showing an internal structure thereof in the form of a section along which a first internal electrode 40a extends; Fig. 7 is a plan view of the multilayer capacitor 71 shown in Fig. 5 showing an internal structure thereof in the form of a section along which a second internal electrode 41a extends; Fig. 8 is a plan view of a multilayer capacitor 81 according to a third comparison example showing the external appearance thereof; Fig. 9 is a plan view of the multilayer capacitor 81 shown in Fig. 8 showing an internal structure thereof in the form of a section along which a third internal electrode 82 extends; Pig. 10 is a plan view of the multilayer capacitor 81 shown in Pig. 8 showing an internal structure thereof in the form of a section along which a first internal electrode 40b extends; Fig. 11 is a plan view of the multilayer capacitor 81 shown in Fig. 8 showing an internal structure thereof in the form of a section along which a second internal electrode 41b extends; Fig. 12 is a plan view of a multilayer capacitor 91 according to the invention showing the external appearance thereof; Fig. 13 is a plan view of the multilayer capacitor 91 shown in Fig. 12 showing an internal structure thereof in the form of a section along which a first internal electrode 40c extends; Fig. 14 is a plan view of the multilayer capacitor 91 shown in Fig. 12 showing an internal structure thereof in the form of a section along which a second internal electrode 41c extends; Fig. 15 is a plan view of a conventional multilayer capacitor 1 which is of interest to the present invention showing the external appearance thereof; Fig. 16 is a plan view of the multilayer capacitor 1 shown in Fig. 15 showing an internal structure thereof in the form of a section along which a first internal electrode 10 extends; Fig. 17 is a plan view of the multilayer capacitor 1 shown in Fig. 15 showing an internal structure thereof in the form of a section along which a second internal electrode 11 extends; Fig. 18 is a plan view illustrating currents flowing in the multilayer capacitor 1 shown in Fig. 15; Fig. 19 is a plan view of a multilayer capacitor 101 according to a fourth comparison example; Fig. 20 is a plan view of the multilayer capacitor 101 shown in Fig. 19 showing an internal structure thereof in the form of a section along which a first internal electrode 40d extends; and Fig. 21 is a plan view of the multilayer capacitor 101 shown in Fig. 10 showing an internal structure thereof in the form of a section along which a second internal electrode 41d extends. Referring now to the drawings, wherein like numerals indicate like elements, there is shown in Figs. 1 through 3 a first comparison example of a multilayer capacitor designated generally as 31. Figs. 1 through 3 correspond to Figs. 15 through 17. Fig. 1 is a plan view of the external appearance of multilayer capacitor 31. Fig. 2 is a plan view multilayer capacitor 31 showing a first internal electrode 40 located on one surface of a first internal dielectric layer 39 of the capacitor 31. Fig. 3 is a plan view of a second section of the multilayer capacitor 31 showing a second internal electrode 41 located on one surface of a second internal dielectric layer 39 of the capacitor 31. Multilayer capacitor 31 includes a capacitor main body 38 in the form of a rectangular parallelpiped having two opposed principal surfaces 32 and 33 and four side surfaces 34, 35, 36 and 37 extending therebetween. The capacitor main body 38 includes a plurality of generally planar dielectric layers 39 made of, for example, a ceramic dielectric material. The main surfaces of the dielectric layers 39 are situated generally parallel to the principal surfaces 32, 33 of the capacitor main body 38. At least a pair of first and second internal electrodes 40 and 41 are provided in a face-to-face relationship with each other with a dielectric material layer 39 interposed therebetween, each such pair of internal electrodes forming a respective capacitor unit. As shown in Fig. 2, the first internal electrode 40 has six lead electrodes 42, 43, 44, 45, 46 and 47, each of which extends to a respective one of the four side surfaces 34 through 37. Particularly, the lead electrodes 42 and 43 extend to the side surface 34; the lead electrode 44 extends to the side surface 35; the lead electrodes 45 and 46 extend to the side surface 36; and the lead electrode 47 extends to the side surface 37. Each lead electrode 42-47 is electrically coupled to a respective external terminal electrodes 48-53. The external terminal electrodes 48 and 49, connected to the lead electrodes 42 and 43, respectively, are located on the side surface 34; the external terminal electrode 50, connected to the lead electrode 44, is located on the side surface 35; the external terminal electrodes 51 and 52, connected to the lead electrodes 45 and 46, respectively, are located on the side surface 36; and the external terminal electrode 53, connected to the lead electrode 47, is located on the side surface 37. As shown in Fig. 3, the internal electrode 41 is formed with six second lead electrodes 54, 55, 56, 57, 58 and 59, each of which extend to a respective one of the four side surfaces 34 through 37. More specifically, the lead electrodes 54 and 55 extend to side surface 34; lead electrode 56 extends to side surface 35; lead electrodes 57 and 58 extend to side surface 36; and lead electrode 59 extends to the side surface 37. The positions on the side surfaces 34 through 37 to which the respective lead electrodes 54 through 59 extend are different from the positions to which the respective lead electrodes 42 through 47 extend. External terminal electrodes 60, 61, 62, 63, 64 and 65, which are electrically coupled to respective lead electrodes 54 through 59, are provided on the side surfaces 34 through 37 a positions which are different than the positions of the external terminal electrodes 48 through 53. External terminal electrodes 60 and 61, connected to lead electrodes 54 and 55, respectively, are located on side surface 34; external terminal electrode 62, connected to lead electrode 56, is located on side surface 35; external terminal electrodes 63 and 64, connected to lead electrodes 57 and 58, respectively, are located on side surface 36; and external terminal electrode 65, connected to lead electrode 59, are located on side surface 37. The external terminal electrodes 48 through 53 are arranged in an interleaved manner such that no two external electrodes which are electrically coupled to the same internal electrode 40 or 41 are adjacent one another. In operation, the polarization of the first and second internal electrodes 40, 41 are preferably opposite to one another. In order to increase the capacity of the multilayer capacitor 31, additional pairs of internal electrodes can be provided to define additional capacitor units. For example, the multilayer capacitor 31 can include two sets of capacitor units, each set being defined by a respective pair of first and second internal electrodes 40, 41 separated by a respective dielectric layer. The plurality of capacitor units are preferably connected in parallel by at least either appropriate ones of the first external terminal electrodes 48 through 53 or the second external terminal electrodes 60 through 65. Each of the external terminal electrodes 48 through 53 and 60 through 65 is preferably formed so as to extend not only on the side surfaces 34 through 37 but also onto a part of each of the principal surfaces 32 and 33. Fig. 4 illustrates various currents flowing in the multilayer capacitor 31. In Fig. 4, the first internal electrode 40 is indicated by a broken line and the second internal electrode 41 is indicated by a solid line, the two electrodes being illustrated in an overlapping relationship. As apparent from these typical paths and the directions of current flow indicated by the arrows in Fig. 4 (the direction of current flow indicates that direction of each of the noted current paths at a given point in time, the direction of the flow of current through these paths will alternate periodically), a current flows from each of the second external terminal electrodes 60 through 65 to each of the first external terminal electrodes 48 through 53. When such currents flow, induced magnetic flux is generated. As in the prior art, the various components of the induced flux at the central regions 66 indicated by the circles cancel one another out because currents flow in various directions. Similarly, the various components of the induced flux in the areas of the side surfaces 34 and 36 tend to cancel one another. In this connection, current flow in the area of side surfaces 34 and 36 is very similar to that of the prior art of Fig. 18. However, the comparison example of Figs. 1-4 produces a much more desirable result in the areas 67 adjacent the side surfaces 35, 37. Since the first external terminal electrodes 50 and 53 and the second external terminal electrodes 62 and 65 are provided at the side surfaces 34 and 36, there is no significant net current flow in the areas 67 and no significant generation of net magnetic flux. As a result, the degree of net induced magnetic flux generated over the entire region of the multilayer capacitor 31 is significantly reduced, thereby allowing the ESL to be suppressed to a very low level. Another advantage of this comparison example is that the current paths between each of the electrodes is reduced. Particularly, each of the first lead electrodes 42 through 47 (and the first external terminal electrodes 48 through 53) is located relatively close to its adjacent second lead electrode 54 through 59 (and the second external terminal electrode 60 through 64) compared to the prior art of Fig. 18. This reduces the lengths of the current paths and thereby reduces self-inductance components produced between them. Figs. 5 through 7 show a multilayer capacitor 71 according to a second comparison example. Fig. 5 is a plan view of the external appearance of the multilayer capacitor 71. Fig. 6 is a plan view showing one surface of an internal dielectric layer 39 of the multilayer capacitor 71 having a first internal electrode 40a located thereon. Fig. 7 is a plan view showing one surface of a different one of the internal dielectric layers 39 of the multilayer capacitor 71 having a second internal electrode 41a located thereon. Figs. 5 through 7 respectively correspond to Figs. 1 through 3 of the first comparison example. In Figs. 5 through 7, elements corresponding to elements shown in Figs. 1 through 3 are indicated by like reference numbers and will not be described here to avoid duplication. Referring to Fig. 6, the first internal electrode 40a is formed with five lead electrodes 42, 43, 45, 46 and 47a which extend to respective side surfaces 34, 36 and 37. The multilayer capacitor 71 is different from the multilayer capacitor 31 of the first comparison example in that the multilayer capacitor 71 has no lead electrode extending to side surface 35. Additionally, lead electrode 47a extends to the middle of the side surface 37, whereas lead electrode 47 extends to the upper half of side surface 37. The five lead electrodes 42 through 47a are electrically coupled to five external terminal electrodes 48, 49, 51, 52 and 53a, respectively. The five external electrodes 48, 49, 51, 52 and 53a, are each located on one of the three side surfaces 34, 36 and 37. The multilayer capacitor 71 is different from the multilayer capacitor 31 of the first comparison example in that the multilayer capacitor 71 has no external terminal corresponding to the first external terminal electrode 50 and in that the external terminal electrode 53a is different in location from the external terminal electrode 53. Referring to Fig. 7, a second internal electrode 41a has five lead electrodes 54, 55, 56a, 57 and 58 which extend to respective side surfaces 34 through 36. The multilayer capacitor 71 is different from the multilayer capacitor 31 of the first comparison example in that it has no lead electrode extending to the side surface 37 and in that the lead electrode 56a which extends to the side surface 35 extends to the middle of the side surface 35, rather than the bottom of the side surface 35 as is the case with lead electrode 56 of the first comparison example. Each of the lead electrodes 54 through 58 is electrically coupled to a respective external terminal electrode 60, 61, 62a, 63 and 64. Each of these terminal electrodes are provided on a respective side surface 34 through 36. The multilayer capacitor 71 is different from the multilayer capacitor 31 of the first comparison example in that it has no external terminal corresponding to the external terminal electrode 65 and in that the external terminal electrode 62a is located in a different position than the external terminal electrode 62. If desired, the capacity of multilayer capacitor 71 can be increased by providing a plurality of capacitive units, each defined by a respective set of internal electrodes 40a, 41a, separated by a respective dielectric layer 38. The plurality of capacitor units are then connected in parallel by appropriate ones of the external terminal electrodes 48 through 53a or 60 through 64. In the second comparison example, each of the external terminal electrodes 48, 49, 51 and 52 coupled to the first internal electrode 40a is located adjacent at least one of the external terminal electrodes 60, 61, 63 and 64 coupled to internal electrode 41a. Further, only the second external terminal electrode 62a is located on the side surface 35, and only the first external terminal electrode 53a is located on the side surface 37. By providing the external terminal electrodes 62a and 53a on the side surfaces 35 and 37, respectively, it is possible to direct the flow of the currents on the internal electrodes 40a and 41a in various directions to achieve a level of cancellation of magnetic flux that is higher than that which is achievable in the conventional multilayer capacitor 1 shown in Figs. 15 through 17. It is also possible to reduce the length of the path of these currents thereby further reducing the induced inductance components. Figs. 8 through 11 show a multilayer capacitor 81 according to a third comparison example. Fig. 8 is a plan view of the external appearance of the multilayer capacitor 81. Fig. 9 is a plan view of the surface of one of the internal dielectric layers 39 of the multilayer capacitor 81 having a first internal electrode 82 formed thereon. Fig. 10 is a plan view of the surface of one of the internal dielectric layers 39 of the multilayer capacitor 81 having a second internal electrode 40b formed thereon. Fig. 11 is a plan view of the surface of one of the internal dielectric layers 39 of the multilayer capacitor 81 having a third internal electrode 41b formed thereon. In Figs. 8 through 11, elements corresponding to elements shown in Figs. 1 through 3 are indicated by like reference numbers and will not be described here to avoid duplication. The multilayer capacitor 81 of the third comparison example includes a third internal electrode 82 facing at least either the first internal electrode 40b or second internal electrode 41b with a dielectric material layer 39 interposed therebetween. The third internal electrode 82 is formed with four lead electrodes 83, 84, 85 and 86, each of which extends to a respective side surface 34 and 36. More specifically, lead electrodes 83 and 84 extend to side surface 34, and lead electrodes 85 and 86 extend to side surface 36. External terminal electrodes 87, 88, 89 and 90, which are electrically coupled to the lead electrodes 83 through 86, respectively, are provided on respective side surfaces 34 and 36. The multilayer capacitor 81 is different from the multilayer capacitor 31 of the first comparison example in that it includes the third external terminal electrodes 87 and 90 provided, respectively, in the positions where the first external terminal electrodes 48 and 52 are provided on the multilayer capacitor 31 of the first embodiment and includes the third external terminal electrodes 88 and 89 provided respectively in the positions where the second external terminal electrodes 61 and 63 are provided on the multilayer capacitor 31. Referring to Fig. 10, a first internal electrode 40b has four first lead electrodes 42b, 44, 45b and 47 which extend to respective side surfaces 34 through 37. The first internal electrode 40b of the multilayer capacitor 81 is different from the multilayer capacitor 31 of the first comparison example in that it has only one lead electrode 42b which extends to side surface 34 and one lead electrode 45b which extends to side surface 36. Four first external terminal electrodes 48b, 50, 51b and 53 are electrically coupled to the four first lead electrodes 42b through 47, respectively, and are provided on the four side surfaces 34 through 37, respectively. The multilayer capacitor 81 is different from the multilayer capacitor 31 of the first comparison example in that it includes the first external terminal electrodes 48b and 51b provided respectively in the positions where the second external terminal electrodes 60 and 64 are provided on the multilayer capacitor 31. Referring to Fig. 11, a second internal electrode 41b has four second lead electrodes 54b, 56, 57b and 59 which extend to respective side surfaces 34 through 37. The second internal electrode of the multilayer capacitor 81 is different from the second internal electrode 41 of the multilayer capacitor 31 of the first comparison example in that only one lead electrode 54b extends to the side surface 34 and only one lead electrode 57b extends to side surface 36. Four second external terminal electrodes 60b, 62, 63b and 65 are electrically coupled to the four first lead electrodee 54b through 59, respectively. The four second external terminal electrodes are provided on the four side surfaces 34 through 37, respectively. The multilayer capacitor 81 is different from the multilayer capacitor 31 of the first comparison example in that the second external terminal electrodes 60b and 63b provided, respectively, in the positions where the first external terminal electrodes 49 and 51 are provided on the multilayer capacitor 31. By way of example, the multilayer capacitor 81 can be formed by locating the third internal electrode 82, the first internal electrode 40b and the second internal electrode 41b, one above the other with respective dielectric layers being located therebetween. Irrespective of the relative locations of the internal electrodes, the external terminal electrodes are arranged such that each of the third external terminal electrodes 87 through 90 is followed by one of the first external terminal electrodes 48b through 53 and then followed by one of the second external terminal electrodes 60b through 65. This alternating arrangement is repeated throughout the four side surfaces 34 through 37. The above-described order of stacking the internal electrodes 82, 40b and 41b may be changed arbitrarily. In order to increase the capacity of the multilayer capacitor 81, a plurality of third internal electrodes 82, first internal electrodes 40b and second internal electrodes 41b may be provided to form a plurality of capacitor units. For example, a plurality of third internal electrodes 82 and a plurality of first internal electrodes 40b may be provided; a plurality of second internal electrodes 41b and a plurality of third internal electrodes 82 may be provided; or a plurality of third internal electrodes 82, a plurality of first internal electrodes 40b and a plurality of second internal electrodes 41b may be provided. The resultant capacitor units are connected in parallel by at least any of the third external terminal electrodes 87 through 90, the first external terminal electrodes 48b through 53 and the second external terminal electrodes 60b through 65. Like the first comparison example, external terminal electrodes connected to different internal electrodes (that is, external terminal electrodes having different polarities) are located on each of the four side surfaces 34 through 37. More specifically, first external terminal electrode 48b, second external terminal electrode 60b and third external terminal electrodes 87 and 88 are located on the side surface 34; first external terminal electrode 50 and second external terminal electrode 62 are located on side surface 35; first external terminal electrode 51b, second external terminal electrode 63b and third external terminal electrodes 89 and 90 are located on side surface 36; and first external terminal electrode 53 and second external terminal electrode 65 are located on side surface 37. Therefore, according to the third comparison example, since the flow of currents on the internal electrodes 40b and 41b can be directed in various directions to effectively cancel magnetic flux and to reduce the lengths of the current paths, the induced inductance components can be reduced. Although the arrangement of the third comparison example is different from that in the first comparison example in that external terminal electrodes having different polarities are not necessarily adjacent to each other in all locations, the directions of the current flows on the internal electrodes 40b and 41b is more diverse than those in the conventional multilayer capacitor 1 shown in Figs. 15 through 17 and the lengths of the current paths are shorter. This makes it possible to achieve a higher reduction of the induced inductance components. As an alternative to the third comparison example, a multilayer capacitor may be provided in which only the first and second internal electrodes 40b and 41b are provided and the third internal electrode 82 is excluded. Further, the third internal electrode 82 may be formed with lead electrodes which extend to the side surfaces 35 and 37. Figs. 12 through 14 show a multilayer capacitor 91 according to the present invention. Fig. 12 is a plan view of the external appearance of the multilayer capacitor 91. Fig. 13 is a plan view of the surface of one of the dielectric layers of the multilayer capacitor 91 having a first internal electrode 40c formed thereon. Fig. 14 is a plan view of the surface of one of the dielectric layers of the multilayer capacitor 91 having a second internal electrode 41c formed thereon. Figs. 12 through 14 respectively correspond to Figs. 1 through 3 of the first comparison embodiment. In Figs. 12 through 14, elements corresponding to elements shown in Figs. 1 through 3 are indicated by like reference numbers and will not be described here to avoid duplication. The multilayer capacitor 91 of the invention resembles the multilayer capacitor 71 of the second comparison example in its external appearance. A first internal electrode 40c has five first lead electrodes 42, 43, 44c, 45c and 46c which extend to respective side surfaces 34, 35 and 36. The multilayer capacitor 91 is different from the multilayer capacitor 31 of the first comparison example in that does not include a lead electrode corresponding to the lead electrode 47 which extends to the side surface 37 and in that the positions at which the lead electrodes 44c, 45c and 46c respectively extends to the side surfaces 35 and 36 are different from the positions that the lead electrodes 44 through 46 extend to those surfaces. Five external terminal electrodes 48, 49, 50c, 51c and 52c are electrically coupled to the five lead electrodes 42 through 46c, respectively. These external electrodes are provided on the side surfaces 34 through 36. The multilayer capacitor 91 is different from the multilayer capacitor 31 of the first comparison example in that it does not include an external terminal electrode corresponding to the first external terminal electrode 53 and in that the positions of the external terminal electrodes 50c, 51c and 52c are different from the positions of the external terminal electrodes 50 through 52, respectively. Referring to Fig. 14, a second internal electrode 41c has five lead electrodes 54, 55, 57c, 58c and 59c, each of which extends to a respective side surfaces 34, 36 and 37. The multilayer capacitor 91 is different from the multilayer capacitor 31 of the first comparison example in that it does not include a lead electrode corresponding to the lead electrode 59 which extends to the side surface 35 and in that the positions of the lead electrodes 57c, 58c and 59c are different from the positions of the lead electrodes 57 through 59, respectively. The external terminal electrodes 60, 61, 63c, 64c and 65c which are electrically coupled to second lead electrodes 54 through 59c, respectively, are provided on the side surfaces 34, 36 and 37. The multilayer capacitor 91 is different from the multilayer capacitor 31 of the first comparison example in that it does not include an external terminal electrode corresponding to the second external terminal electrode 62 and in that the positions of the external terminal electrodes 63c, 64c and 65c are different from the positions of the external terminal electrodes 63 through 65, respectively. In order to increase the capacity of multilayer capacitor 91, a plurality of first internal electrodes 40c and a plurality of second internal electrodes 41c can be provided. Pairs of internal electrodes 40c, 41c will face one another with a dielectric layer formed therebetween so as to form respective capacitor units. These capacitor units will be connected in parallel by at least either the first external terminal electrodes 48 through 52c or the second external terminal electrodes 60 through 65c. Like the first comparison example described above, each of the first external terminal electrodes 48 through 52c of the multilayer capacitor of the invention is arranged so as to alternate with respective ones of the second external terminal electrodes 60 through 65c throughout the four side surfaces 34 through 37. The fourth multilayer capacitor of the invention is different from the second comparison example in this regard. Therefore, according to the invention, since the flow of currents on the internal electrodes 40c and 41c can be directed in various directions, the various components of induced magnetic flux will be cancelled and the lengths of the current paths will be shortened relative to the prior art of Figs. 15-17. The fourth embodiment will effectively reduce the induced inductance components to a degree which is similar to that of the first comparison example. Figs. 19 through 21 show a multilayer capacitor 101 according to a fourth comparison example. Fig. 19 is a plan view of the external appearance of the multilayer capacitor 101. Fig. 20 is a plan view of the surface of one of the dielectric layers of the multilayer capacitor 101 having a first internal electrode 40d formed thereon. Fig. 21 is a plan view of the surface of one of the dielectric layers of the multilayer capacitor 101 having a second internal electrode 41d formed thereon. Figs. 19 through 21 respectively correspond to Figs. 1 through 3 of the first comparison example. In Figs. 19 through 21, elements corresponding to elements shown in Figs. 1 through 3 are indicated by like reference numbers and will not be described here to avoid duplication. Referring to Fig. 20, a first internal electrode 40d has three first lead electrodes 44d, 45d and 47d which extend to respective side surfaces 35, 36 and 37. The multilayer capacitor 101 is different from the multilayer capacitor 31 of the first comparison example in that it does not include lead electrodes 42 and 43 which extends to the side surface 34, does not include a lead electrode 46 which extends to the side surface 36, and in that the positions at which the lead electrodes 44d, 45d, and 47d respectively extends to the side surfaces 35, 36 and 37 are different from the positions that the lead electrodes 44, 45 and 47 extend to those surfaces. The three lead electrodes 44d, 45d and 47d are electrically coupled to three external terminal electrodes 50d, 51d and 53d respectively. These external terminal electrodes are provided on the side surfaces 35 through 37. The multilayer capacitor 101 is different from the multilayer 31 of the first comparison example in that it does not include external terminal electrodes corresponding to the first external terminal electrodes 48, 49 and 52 in that the positions of the external terminal electrodes 50d, 51d and 53d are different from the positions of the external terminal electrodes 50, 51 and 53, respectively. Referring to Fig. 21, a second internal electrode 41d has two lead electrodes 54d and 57d, each of which extends to respective side surfaces 34 and 36. The multilayer capacitor 101 is different from the multilayer capacitor 31 of the first comparison example in that it does not include lead electrodes corresponding to the lead electrodes 61, 62, 64 and 65 which extends to the side surfaces 34 through 37, respectively, and in that the positions of the lead electrodes 54d and 57d are different from the positions of the lead electrodes 54 and 57, respectively. Two external terminal electrodes 60d and 63d are electrically coupled to the two lead electrodes 54d and 57d, respectively, and are provided on the side surfaces 34 and 36. The multilayer capacitor is different from the multilayer capacitor 31 of the first comparison example in that it does not include external terminal electrodes corresponding to the second external terminal electrodes 61, 62, 64 and 65, and in that the positions of the external terminal electrodes 60d and 63d are different from the positions of the external terminal electrodes 60 and 63, respectively. In order to increase the capacity of multilayer capacitor 101, a plurality of first internal electrodes 40d and a plurality of second internal electrodes 41d can be provided. Therefore, according to the fifth embodiment of the invention, since the flow of the currents on the internal electrodes 40b and 41b can be directed in various directions to effectively cancel magnetic flux and to reduce the lengths of the current paths, the induced inductance components can be reduced. Although the arrangement of the fifth comparison example is different from that in that first comparison example in that external terminal electrodes having different polarities are not necessarily adjacent to each other in all locations the directions of the current flows on the internal electrodes 40d and 41d is more diverse than those in the conventional multilayer capacitor 1 shown in Figs. 15 and 17 and the lengths of the current paths are shorter. Therefore, this makes it possible to achieve a higher reduction of the induced inductance components. Test Results A sample of each of the multilayer capacitor 31 according to the first comparison example (example 1), the multilayer capacitor 71 according to the second comparison example (example 2), the multilayer capacitor 81 according to the third comparison example (example 3), the multilayer capacitor 91 according to the invention and the conventional multilayer capacitor 1 was fabricated and ESL of each of them was evaluated. Each sample was formed with outer plan dimensions of 3.2 mm X 2.5 mm. For samples having six layers of internal electrodes in total, i.e., those having two kinds of internal electrodes such as the multilayer capacitors 31, 71, 91 and 1 (examples 1, 2, conventional example and invention), the stacking of the two kinds of internal electrodes was repeated three times (i.e., three pairs of internal electrodes where used to form three capacitance units). For the sample having three kinds of internal electrodes, i.e., the multilayer capacitor 81 (comparison example 3), the stacking of the three kinds of internal electrodes was repeated twice. ESL was obtained using the resonance method. The resonance method is a method wherein the impedance frequency characteristics of each of the sample multilayer capacitor is measured and ESL is obtained from a frequency f 0 at a minimum point (referred to as series resonance point between the capacity component C s and ESL of the capacitor) using the following equation. ESL = 1/[(2πf 0 ) 2 X C s ] The measured value of ESL of each sample is shown in the Table 1 below. ESL Value (pH) Example 1 40 Example 2 72 Example 3 85 Invention 51 Conventional Example 95 It is apparent from Table 1 that ESL was suppressed to a greater degree in each of the comparison examples 1 through 3 and according to the invention than in the conventional example. The comparison example 1 was most advantageous in reducing ESL. The embodiment of the invention was more advantageous than the comparison examples 2 and 3 in reducing ESL, although it was less advantageous than the comparison example 1. With the inventive structure, a high resonance frequency can be achieved and the frequency band of the capacitor can be increased. Accordingly, a multilayer capacitor according to the invention can accommodate electronic circuits at higher frequencies than was possible with the conventional example and can be advantageously used, for example, as a bypass capacitor or decoupling capacitor in a high frequency circuit. Further, while a decoupling capacitor used in an MPU (microprocessing unit) must also have the function of a quick power supply (a function of supplying power from an amount of electricity charged in the capacitor when there is a sudden need for power as in the case of power-up), a multilayer capacitor according to the invention can be used for such an application because it has low ESL. In the embodiment of the present invention described herein, the cancellation of magnetic fluxes as described above is further improved and the lengths of currents are further reduced to achieve more effective reduction of ESL.

Claims: A multi-layer capacitor (91) comprising: a substantially rectangular capacitor body (38) having four sides including a first pair of opposed sides (34, 36) and a second pair of opposed sides (35, 37), the capacitor body including at least one dielectric layer (39) and at least one pair of first and second internal electrodes (40c, 41c) having a substantially rectangular main portion that oppose each other via said dielectric layer (39) to define a capacitor unit, said first internal electrode (40c) having first lead-out portions (42, 43, 44c, 45c, 46c), said second internal electrode (41c) having second lead-out portions (54, 55, 57c, 58c, 59c), the first and second lead-out portions being arranged to interdigitate with each other; first polarity external electrode terminals (48, 49, 50c, 51c, 52c) being electrically connected to said first lead-out portions (42, 43, 44c, 45c, 46c), a plurality of the first polarity external electrode terminals being arranged on each of the first pair of opposed sides (34, 36) and one (50c) of the first polarity external electrode terminals being arranged on one (35) of the second pair of opposed sides of the capacitor body (38); and second polarity external electrode terminals (60, 61, 63c, 64c, 65c) being electrically connected to said second lead-out portions, a plurality of the second polarity external electrode terminals being arranged on each of the first pair of opposed sides (34, 36) and one (65c) of the second polarity external electrode terminals being arranged on the other one (37) of the second pair of opposed sides of the capacitor body, wherein each of the first polarity external electrode terminals (48, 49) located along one (34) of the first pair of opposed sides of the capacitor body (38) is directly opposite to one of the first polarity external electrode terminals (51c, 52c) located along the other one (36) of the first pair of opposed sides of the capacitor body (38) across a width of the capacitor body and each of the second polarity external electrode terminals (60, 61) located along one (34) of the first pair of opposed sides of the capacitor body (38) is directly opposite to one of the second polarity external electrode terminals (63c, 64c) located along the other (36) of the first pair of opposed sides of the capacitor body (38) across a width of the capacitor body. The multi-layer capacitor (91) according to claim 1, comprising a plurality of first internal electrodes (40c) and a plurality of second internal electrodes (41c), wherein respective pairs of first and second internal electrodes face one another with a dielectric layer formed therebetween so as to form respective capacitor units connected in parallel via at least either said first or second external terminal electrodes. The multi-layer capacitor (91) according to claim 1 or 2, wherein said first and second external electrodes (48, 49, 50c, 51c, 52c; 60, 61, 63c, 64c, 65c) are arranged alternately along said side of surfaces such that no two external electrodes electrically coupled to the same internal electrode (40c, 41c) are located next to each other. The multi-layer capacitor (91) according to any of claims 1 to 3, wherein two of said first external electrodes (48, 49, 50c, 51c, 52c) are located on each of the first pair of opposed sides (34, 36) and two of said second external electrodes (60, 61, 63c, 64c, 65c) are located on each of the first pair of opposed sides (34, 36). The multi-layer capacitor (91) according to any of claims 1 to 4, wherein said first and second internal electrodes (40c, 41c) are planar and lie in planes which are parallel to one another. The multi-layer capacitor (91) according to claim 5, wherein said planes are parallel to the principal surfaces of said capacitor main body (38). The multi-layer capacitor (91) according to any of claims 1 to 6, wherein said first polarity external electrode terminal arranged on one (35) of the second pair of opposed sides of the capacitor body (38) is directly opposite to said second polarity external electrode terminal arranged on the other one (37) of the second pair of opposed sides of the capacitor body (38) across a length of the capacitor body. The multi-layer capacitor (91) according to any of claims 1 to 7, wherein two of the second polarity external electrode terminals, each of which is located on one of the first pair of opposed sides (34, 36) of the capacitor body (38), are located on each side of said first polarity external electrode terminal arranged on one (35) of the second pair of opposed sides of the capacitor body (38) along an outer periphery of the capacitor body (38). The multi-layer capacitor (91) according to any of claims 1 to 8, wherein two of the first polarity external electrode terminals, each of which is located on one of the first pair of opposed sides (34, 36) of the capacitor body (38), are located on each side of said second polarity external electrode terminal arranged on the other one (37) of the second pair of opposed sides of the capacitor body (38) along an outer periphery of the capacitor body (38). A multi-layer capacitor (91) according to any of claims 1 to 9, wherein the multi-layer capacitor is arranged to define a decoupling capacitor for a multiprocessing unit. A high frequency circuit comprising at least one multi-layer capacitor according to any of claims 1 to 9. A high frequency circuit according to claim 11, wherein the at least one multi-layer capacitor is arranged to define one of a bypass capacitor and a decoupling capacitor.

Inventors: KONDO TAKANORI, KURODA YOICHI, NAITO YASUYUKI, TANIGUCHI MASAAKI, KONDO, TAKANORI, KURODA, YOICHI, NAITO, YASUYUKI, TANIGUCHI, MASAAKI
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1998
Main classification: H01G4
IPC codes: H01G4, H05K3, H05K1