JP2009224503A - Multilayer capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer capacitor which is increased in capacity and suppresses cracking. <P>SOLUTION: The multilayer capacitor C1 includes a capacitor element body 1, terminal electrodes 11 and 12, internal electrodes 20 and 30, and protection portions 25 and 26, and 35 and 36. The capacitor element body 1 is formed by laminating dielectric layers 9, and has side faces 2 and 3 orthogonal to the laminating direction of the dielectric layers 9 and opposite to each other, and side faces 6 and 7 orthogonal to the opposing direction of the side faces 2 and 3 and opposed to each other. The terminal electrodes 11 and 12 are disposed on the side faces 2 and 3 of the capacitor element body 1. The internal electrodes 20 and 30 are disposed in the capacitor element body 1 alternately with the dielectric layer 9 and connected to the terminal electrodes 11 and 12. The protection portions 25 and 26, and 35 and 36 are disposed between the side faces 6 and 7 and internal electrodes 20 and 30 in the same layers with the internal electrodes 20 and 30 to be exposed on the side surfaces 6 and 7 along side portions of the internal electrodes 20 and 30 opposed to the side faces 6 and 7. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a multilayer capacitor.

As a multilayer capacitor, a capacitor including a multilayer body in which dielectric layers and internal electrodes are alternately stacked is known (for example, see Patent Document 1).
JP 2005-302977 A

  Incidentally, the multilayer capacitor may be used as a decoupling capacitor in digital electronic equipment. In this case, the multilayer capacitor preferably has a large capacity. In the multilayer capacitor described in Patent Document 1, the capacity can be increased by increasing the number of internal electrodes and dielectric layers. However, increasing the number of dielectric layers increases the mechanical strain caused by the electrostrictive effect. Therefore, cracks are likely to occur in the laminate.

  Therefore, it is an object to provide a multilayer capacitor that can increase the capacity and suppress the occurrence of cracks.

  The multilayer capacitor of the present invention is formed by laminating dielectric layers, and is laminated with first and second side surfaces orthogonal to each other and facing each other, and opposite directions of the first and second side surfaces. A capacitor element body having third and fourth side surfaces orthogonal to each other and facing each other, terminal electrodes disposed on the first and second side surfaces, a dielectric layer inside the capacitor element body, Alternatingly arranged internal electrodes connected to the terminal electrodes, and in the same layer as the internal electrodes, along the side portions of the internal electrodes facing the third and fourth side surfaces and the third and fourth side surfaces And a protective part including a metal oxide, which is disposed between the third and fourth side surfaces and the internal electrode so as to be exposed to the surface.

  In the multilayer capacitor according to the present invention, a protective portion is provided between the side surface of the capacitor body and the internal electrode. Between the side surface of the capacitor body and the internal electrode is a region in which displacement due to the electrostrictive effect appears prominently because there is no internal electrode. The protective layer placed in this region serves as a cushion as a dielectric layer. Absorbs the displacement. This makes it difficult for cracks due to displacement to occur inside the multilayer capacitor. Moreover, the protection part is exposed from the side surface. Therefore, cracks due to displacement are less likely to occur on the surface of the multilayer capacitor. Since the protective part is arranged in the same layer as the internal electrode, it can be arranged alternately with the dielectric layer like the internal electrode. By alternately arranging the protective portions and the dielectric layers, it is possible to more effectively suppress the occurrence of cracks due to displacement.

  Incidentally, in order to increase the capacity of the multilayer capacitor, it is also effective to widen the internal electrodes in addition to increasing the number of internal electrodes and dielectric layers. However, when the internal electrode is expanded, the internal electrode may be exposed from the side surface of the capacitor body where the terminal electrode is not provided, and the insulating property may be lowered. In the multilayer capacitor according to the present invention, the protective portion formed between the internal electrode and the side surface of the capacitor body serves to prevent the internal electrode from being exposed. Moreover, since the protective part contains a metal oxide, it has insulating properties. Therefore, the insulation of the internal electrode can be ensured. As described above, by providing the protective portion, the internal electrode can be enlarged without worrying about the exposure and the deterioration of the insulating property, so that the capacity of the multilayer capacitor can be increased.

  Preferably, the protective portion is formed by firing the conductive paste and includes a portion obtained by oxidizing the ends of the third and fourth side surfaces in the metal layer extending from the third side surface to the fourth side surface, Consists of the remaining part excluding the oxidized part.

  In this case, the edge of the metal layer is oxidized, and the oxidized part is used as a protective part and the remaining part is used as an internal electrode. Therefore, the protective part forming process and the internal electrode forming process can be shared. As a result, the manufacturing cost can be suppressed. Further, by changing the oxidation condition, the width of the oxidized portion, that is, the width of the protective portion can be adjusted. If the width of the protective part is narrowed, the internal electrode can be widened. Therefore, the capacity of the multilayer capacitor can be increased more reliably.

  ADVANTAGE OF THE INVENTION According to this invention, the capacity | capacitance increase can be aimed at and the multilayer capacitor which can suppress generation | occurrence | production of a crack can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  FIG. 1 is a perspective view of the multilayer capacitor in accordance with the present embodiment. FIG. 2 is an exploded perspective view of the capacitor body included in the multilayer capacitor in accordance with the present embodiment. FIG. 3 is a perspective view and a cross-sectional view of the capacitor body shown in FIG.

  As shown in FIG. 1, the multilayer capacitor C <b> 1 according to the present embodiment includes a capacitor body 1 and first and second terminal electrodes 11 and 12.

  The capacitor element body 1 has a substantially rectangular parallelepiped shape, a pair of opposing rectangular side surfaces 2 and 3, a pair of opposing side surfaces 4 and 5 (first and second side surfaces), and a pair of opposing sides. And side surfaces 6 and 7 (third and fourth side surfaces). The side surfaces 4 and 5 extend in the short side direction of the side surfaces 2 and 3 so as to connect the side surfaces 2 and 3. The side surfaces 6 and 7 extend in the long side direction of the side surfaces 2 and 3 so as to connect the side surfaces 2 and 3.

  As shown in FIG. 2, the capacitor body 1 has a plurality of dielectric layers 9. Each dielectric layer 9 extends in a direction parallel to the side surfaces 2 and 3, and is laminated in a direction opposite to the side surfaces 2 and 3. Each dielectric layer 9 is composed of a sintered body of a ceramic green sheet containing a dielectric ceramic. In the actual multilayer capacitor C1, each dielectric layer 9 is integrated to such an extent that the boundary between the dielectric layers 9 cannot be visually recognized.

  A first terminal electrode 11 is disposed on the side surface 4 of the capacitor body 1. The first terminal electrode 11 is formed over the side surfaces 2 and 3 and the side surfaces 6 and 7 so as to cover the side surface 4. A second terminal electrode 12 is disposed on the side surface 5 of the capacitor body 1. The second terminal electrode 12 is formed over the side surfaces 2 and 3 and the side surfaces 6 and 7 so as to cover the side surface 5. The first and second terminal electrodes 11 and 12 are formed, for example, by applying a conductive paste containing conductive metal powder and glass frit to the corresponding outer surface of the capacitor body 1 and baking it. If necessary, a plating layer may be formed on the baked electrode.

  2 and 3, the multilayer capacitor C1 includes a plurality (three in the present embodiment) of first internal electrodes 20 and a plurality (three in the present embodiment) of second internal electrodes 30. A plurality (three in the present embodiment) of first protection sections 25, a plurality (three in the present embodiment) of second protection sections 26, and a plurality (three in the present embodiment) of third protection sections. And a plurality of (three in the present embodiment) fourth protection units 36. In the capacitor body 1, the first internal electrodes 20 and the second internal electrodes 30 are alternately arranged in the stacking direction of the dielectric layers 9, that is, in the opposing direction of the side surfaces 2 and 3.

  The first internal electrode 20 has a substantially rectangular shape, and has a main electrode portion 21 and a lead portion 22. The main electrode portion 21 and the lead portion 22 are integrally formed. The lead portion 22 extends from the edge on the side surface 4 side of the main electrode portion 21 so that the end is exposed on the side surface 4. The first internal electrode 20 includes a base metal, and more specifically includes Ni.

  The first protection part 25 is formed integrally with the first internal electrode 20. The first protection portion 25 has a substantially rectangular shape, extends along the side portion of the first internal electrode 20 facing the side surface 6, and one end portion is exposed from the side surface 4. Further, as shown in FIG. 3A, the first protection part 25 is exposed from the side surface 7. The length of the first protection part 25 in the opposing direction of the side surfaces 4 and 5 is the same as the length of the first internal electrode 20 in the direction. The first protection unit 25 includes NiO.

  As shown in FIG. 2, the second protection part 26 is formed integrally with the first internal electrode 20. The second protection portion 26 has a substantially rectangular shape, extends along the side portion of the first internal electrode 20 facing the side surface 7, and one end portion is exposed from the side surface 4. Further, as shown in FIG. 3A, the second protection part 26 is exposed from the side surface 7. The length of the second protection part 26 in the facing direction of the side surfaces 4 and 5 is the same as the length of the first internal electrode 20 in the direction. The second protection unit 26 includes NiO.

  As shown in FIG. 2, the second internal electrode 30 has a substantially rectangular shape and includes a main electrode portion 31 and a lead portion 32. The main electrode portion 31 and the lead portion 32 are integrally formed. The lead portion 32 extends from the edge on the side surface 5 side of the main electrode portion 31 so that the end is exposed on the side surface 4. The second internal electrode 30 is made of the same material as that of the first internal electrode 20. That is, in the present embodiment, the second internal electrode 30 includes Ni as a base metal.

  As shown in FIG. 2, the third protection part 35 is formed integrally with the second internal electrode 30. The third protection portion 35 has a substantially rectangular shape, extends along the side portion of the second internal electrode 30 facing the side surface 6, and one end portion is exposed from the side surface 5. Further, as shown in FIG. 3A, the third protection portion 35 is exposed from the side surface 6. The length of the first protection part 25 in the opposing direction of the side surfaces 4 and 5 is the same as the length of the first internal electrode 20 in the direction. The 3rd protection part 35 contains NiO.

  As shown in FIG. 2, the fourth protection part 36 is formed integrally with the second internal electrode 30. The fourth protection portion 36 has a substantially rectangular shape, extends along the side portion of the second internal electrode 30 facing the side surface 7, and one end portion is exposed from the side surface 5. Further, as shown in FIG. 3A, the fourth protection part 36 is exposed from the side surface 7. The length of the fourth protection part 36 in the facing direction of the side surfaces 4 and 5 is the same as the length of the first internal electrode 20 in the direction. The fourth protection unit 36 includes NiO.

  The first terminal electrode 11 described above is formed so as to cover all the portions exposed to the side surface 4 of the lead portion 22 of the first internal electrode 20, the first protection portion 25, and the second protection portion 26. The lead portion 22 is physically and electrically connected to the first terminal electrode 11. As a result, the first internal electrode 20 is connected to the first terminal electrode 11. Further, the second terminal electrode 12 is formed so as to cover all portions exposed to the side surface 5 of the lead portion 32 of the second internal electrode 30, the third protection portion 35, and the fourth protection portion 36. The lead portion 32 is physically and electrically connected to the second terminal electrode 12. As a result, the second internal electrode 30 is connected to the second terminal electrode 12.

  As shown in FIG. 3B, the main electrode portion 21 of the first internal electrode 20 and the main electrode portion 31 of the second internal electrode 30 are at least one part of the capacitor body 1. It includes regions facing each other in the stacking direction of the dielectric layers 9 with the two dielectric layers 9 interposed therebetween. That is, the first internal electrode 20 and the second internal electrode 30 have regions that overlap each other when viewed from the opposing direction of the side surfaces 2 and 3. Therefore, a portion of the dielectric layer 9 that overlaps the main electrode portion 21 of the first internal electrode 20 and the main electrode portion 31 of the second internal electrode 30 is a region that substantially generates a capacitance component. Become.

  Subsequently, a method of manufacturing the multilayer capacitor C1 according to this embodiment will be described. FIG. 4 is a flowchart showing the manufacturing process of the multilayer capacitor in accordance with this embodiment. FIG. 5 is an exploded perspective view of the green chip obtained in the manufacturing process. FIG. 6 is a cross-sectional view of a sintered body obtained during the manufacturing process.

In producing the multilayer capacitor C1, first, the green sheet S1 is produced (step S11). More specifically, BaTiO ₃ powder and an organic binder / organic solvent are mixed to form a slurry. The paste obtained by slurrying is applied onto a carrier film such as a PET film by a known method such as a doctor blade method, and then dried to form a film. The film thus obtained is peeled from the PET film to obtain a green sheet S1.

  Subsequently, an electrode pattern is formed on the green sheet S1 (step S12). More specifically, an electrode paste is printed on the surface of the green sheet S1 produced in step S11 so as to have a predetermined pattern by a screen printing method and dried. As the electrode paste, a paste obtained by mixing a co-material, an organic binder, a dispersant, an organic solvent and the like into Ni powder is used. By this step, as shown in FIG. 5, the green sheet S1 on which the conductor pattern EL1 is formed and the green sheet S1 on which the conductor pattern EL2 is formed are obtained. The conductor pattern EL1 is formed in a region excluding one end on the green sheet S1. The conductor pattern EL2 is formed in a region excluding the other end on the green sheet S1.

  Subsequently, the green sheet S1 on which the conductor pattern EL1 is formed, the green sheet S1 on which the conductor pattern EL2 is formed, and the green sheet S1 on which the conductor pattern is not formed are stacked in a predetermined order, and then from the stacking direction. Pressure is applied to form a green laminate (step S13).

  The green laminate thus obtained is then cut into a desired size to obtain a green chip (step S14). In the obtained green chip, as shown in FIG. 5, the green sheet S1 on which the conductor pattern EL2 is formed and the green sheet S1 on which the conductor pattern EL1 is formed are alternately stacked, and the conductor pattern EL1 is formed on the green sheet S1. The formed green sheets S1 are laminated. The green chip has a substantially rectangular parallelepiped shape, and has a pair of opposed rectangular main surfaces, a pair of opposed end surfaces, and a pair of opposed side surfaces. The pair of main surfaces of the green chip are the side surfaces 4 and 5 of the capacitor body 1. The pair of side surfaces of the green chip become the side surfaces 6 and 7 of the capacitor body 1. The conductor patterns EL1, EL2 are exposed from one end face and a pair of side faces of the green chip. However, the conductor pattern EL2 is not exposed from one end face of the green chip, and the conductor pattern EL1 is not exposed from the other end face.

  Subsequently, the green chip is subjected to heat treatment to remove the binder, and then fired (step S15) to obtain a sintered body. By this firing, as shown in FIG. 6A, the green sheet S1 in the green chip becomes the dielectric layer 9, the conductor pattern EL1 becomes the metal layer 39, and the conductor pattern EL2 also becomes the metal layer. In the sintered body, the metal layer 39 extends from the side surface serving as the side surface 6 of the capacitor body 1 to the side surface serving as the side surface 7 of the capacitor body 1. The same applies to the metal layer made of the conductor pattern EL2.

  Subsequently, the sintered body is annealed (step S16). The annealing process is performed in an oxygen atmosphere. By the annealing process, as shown in FIG. 6B, one end surface side and both side surfaces of the sintered body of the metal layer 39 are oxidized. As a result, the metal layer 39 obtained from the conductor pattern EL1 is composed of an oxidized portion 40 and a remaining portion 41 excluding the oxidized portion 40. Similarly, the metal layer obtained from the conductor pattern EL2 is also composed of an oxidized portion and a remaining portion excluding the oxidized portion.

  Subsequently, as shown in FIG. 6C, both end portions of the sintered body are polished (step S17). By polishing one end of the sintered body, a region 40a located on one end side of the sintered body is scraped out of the oxidized portion 40 of the metal layer 39, and the remaining portion 41 of the metal layer 39 is obtained. To expose. Similarly, the other end portion of the sintered body is polished to expose the remaining portion of the metal layer obtained from the conductor pattern EL2. Through this polishing step, a capacitor element body 1 as shown in FIG. 3 is obtained. The remaining portion 41 of the metal layer 39 becomes the internal electrode 20. The remaining portion of the metal layer obtained from the conductor pattern EL2 becomes the internal electrode 30. A region of the oxidized portion 40 that remains without being shaved, that is, a region located on both side surfaces of the sintered body becomes the first and second protection portions 25 and 26. A region of the oxidized portion 40 that remains without being cut, that is, a region located on both side surfaces of the sintered body becomes the third and fourth protection portions 35 and 36.

  Finally, the first and second terminal electrodes 11 and 12 are formed so as to cover the side surfaces 2 and 3 of the capacitor body 1 (step S18). As a method for forming the first and second terminal electrodes 11 and 12, baking, sputtering, electroless plating, or the like is used. Thereby, the multilayer capacitor C1 is completed.

  As described above, according to the multilayer capacitor C <b> 1 of the present embodiment, the first to fourth protection portions 25 are provided between the first and second internal electrodes 20, 30 and the side surfaces 6, 7 of the capacitor body 1. , 26, 35, 36 are formed. Between the first and second internal electrodes 20 and 30 and the side surfaces 6 and 7 of the capacitor element body 1 is a region in which displacement due to the electrostrictive effect appears remarkably because there is no internal electrode. Since the fourth protective portions 25, 26, 35, and 36 serve as cushions and absorb the displacement of the dielectric layer 9, the influence of the electrostrictive effect is alleviated. As a result, cracks are less likely to occur between the first and second internal electrodes 20, 30 and the side surfaces 6, 7 of the capacitor body 1. Further, since the first to fourth protection portions 25, 26, 35, and 36 are exposed from the side surfaces 6 and 7 of the capacitor body 1, cracks based on the electrostrictive effect are less likely to occur on the surface of the multilayer capacitor C1. Since the first to fourth protection portions 25, 26, 35, 36 are arranged in the same layer as the first and second internal electrodes 20, 30, similarly to the first and second internal electrodes 20, 30 The dielectric layers 9 are alternately arranged. Therefore, the generation of cracks based on the electrostrictive effect can be more effectively suppressed.

  In order to increase the capacitance of the multilayer capacitor C1, in addition to increasing the number of the first and second internal electrodes 20, 30 and the dielectric layer 9, it is also effective to widen the first and second internal electrodes 20, 30. It is. When the first and second internal electrodes 20 and 30 are expanded, the first and second internal electrodes 20 and 30 may be exposed from the side surfaces 6 and 7 of the capacitor body 1, and the insulating property may decrease. In the multilayer capacitor C1, since the first to fourth protection portions 25, 26, 35, and 36 are disposed between the first and second inner electrodes 20, 30 and the side surfaces 6, 7, the first and second The exposure of the two internal electrodes 20 and 30 can be prevented. Further, since the first to fourth protection portions 25, 26, 35, 36 containing NiO have insulation properties, the insulation properties of the first and second internal electrodes 20, 30 with respect to the outside of the capacitor body 1. Can be secured. Therefore, by providing the first to fourth protection portions 25, 26, 35, and 36, the first and second internal electrodes 20 and 30 can be enlarged without worrying about exposure or deterioration in insulation. It is possible to increase the capacity of the multilayer capacitor C1.

  Further, in the multilayer capacitor C1 of the present embodiment, a conductive paste containing NiO is used for forming the first to fourth protection parts 25, 26, 35, and 36. Since the conductive paste containing NiO is easily oxidized, the first to fourth protective portions 25, 26, 35, and 36 can be easily formed. Of the metal layer 39 obtained by firing the conductive paste, the oxidized portion 40 becomes the first to fourth protection portions 25, 26, 35, and 36, and the remaining portion 41 excluding the oxidized portion 40 is the first. Since the second internal electrodes 20 and 30 are formed, the formation process of the first to fourth protection parts 25, 26, 35 and 36 and the formation process of the first and second internal electrodes 20 and 30 are made common. can do. As a result, the manufacturing cost can be suppressed. The widths of the first to fourth protection parts 25, 26, 35, and 36 can be easily adjusted by changing the annealing conditions (for example, annealing time, annealing temperature, oxygen concentration, etc.) of the sintered body. it can. If the widths of the first to fourth protection portions 25, 26, 35, and 36 are reduced, the first and second internal electrodes 20 and 30 can be expanded to a greater extent, so that the capacity of the multilayer capacitor C1 can be increased. It will definitely be possible.

  The preferred embodiments of the present invention have been described above. However, the present invention is not necessarily limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

  For example, the numbers of the first and second internal electrodes 20 and 30 and the first to fourth protection units 25, 26, 35, and 36 are not limited to the numbers shown in the present embodiment.

  Further, although the conductive paste forming the first and second internal electrodes 20, 30 and the first to fourth protective portions 25, 26, 35, 36 contains Ni, it may be other base metals. . For example, Cu may be used. By using a conductive paste containing a base metal, a metal layer that can be easily oxidized can be obtained.

  Further, when the green sheet S1 to be the dielectric layer 9 is manufactured, Mg may be added. By changing the amount of Mg added, it is possible to adjust the ease of oxidation of the metal layer during the annealing process in step S16.

1 is a perspective view of a multilayer capacitor according to an embodiment. It is a disassembled perspective view of the capacitor body with which the multilayer capacitor concerning this embodiment is provided. FIG. 3 is a perspective view and a sectional view of the capacitor body shown in FIG. 2. It is a flowchart which shows the manufacturing process of the multilayer capacitor which concerns on this embodiment. It is a disassembled perspective view of a green chip. It is sectional drawing of the sintered compact obtained in the middle of a manufacturing process.

Explanation of symbols

  C1 ... multilayer capacitor, 1 ... capacitor body, 1 ... multilayer capacitor, 1 ... capacitor body, 2-7 ... side face, 9 ... dielectric layer, 11 ... first terminal electrode, 12 ... second terminal electrode, DESCRIPTION OF SYMBOLS 20 ... 1st internal electrode, 30 ... 2nd internal electrode, 25 ... 1st protection part, 26 ... 2nd protection part, 35 ... 3rd protection part, 36 ... 4th protection part, 39 ... Metal layer.

Claims (2)

A dielectric layer is laminated, and the first and second side surfaces that are orthogonal to the stacking direction of the dielectric layer and that face each other, and the opposing direction of the first and second side surfaces and the stacking direction are orthogonal to each other. And a capacitor body having third and fourth side surfaces facing each other;
Terminal electrodes respectively disposed on the first and second side surfaces;
The internal electrodes connected alternately to the dielectric layers and connected to the terminal electrodes inside the capacitor body;
In the same layer as the internal electrode, the third and fourth sides are exposed along the side portion of the internal electrode facing the third and fourth side surfaces and exposed to the third and fourth side surfaces. A multilayer capacitor, comprising: a protective portion that is disposed between a side surface and the internal electrode and includes a metal oxide. The protective part is formed by firing conductive paste and is formed by oxidizing portions of the third and fourth side faces in a metal layer extending from the third side face to the fourth side face,
The multilayer capacitor according to claim 1, wherein the internal electrode includes a remaining portion excluding the oxidized portion.

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