Multilayer coil component

Abstract

To provide a multilayer coil component with an improved inductance value.SOLUTION: In a multilayer coil component 1, the number of turns of first bottom electrode 3 and second bottom electrode 4 is increased by approximately 1 / 4 turn each, thereby achieving a high inductance value. Also, the first bottom electrode 3 and the second bottom electrode 4 increase the inner diameter of the outermost turn on a side face 2f and the outermost turn on a side face 2e compared to the inner diameter of the intermediate turn located between the two outermost turns, thereby achieving a high inductance value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a laminated coil component. [Background technology]

[0002] Known conventional multilayer coil components include, for example, the one described in Patent Document 1. The multilayer coil component described in this document includes an element body having a mounting surface and a main surface that face each other in the stacking direction, a coil conductor that is disposed within the element body and has a coil axis that is parallel to the mounting surface, and a pair of terminal electrodes that are disposed on the mounting surface of the element body and are electrically connected to a pair of ends of the coil conductor, respectively. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-141945 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors have conducted extensive research into the inductance value of multilayer coil components and have discovered a new technique for increasing the inductance value.

[0005] An object of one aspect of the present invention is to provide a laminated coil component with an improved inductance value. [Means for solving the problem]

[0006] A laminated coil component according to one aspect of the present invention is composed of a plurality of stacked insulating layers and includes: an element body having a mounting surface that intersects the stacking direction, a pair of end faces that face each other in a first direction parallel to the mounting surface, and a pair of side faces that face each other in a second direction that is perpendicular to the stacking direction and the first direction; a coil conductor provided within the element body, having a coil axis along the second direction and having a first end and a second end; and a first bottom electrode connected to the first end of the coil conductor and a second bottom electrode connected to the second end of the coil conductor, wherein the first end of the coil conductor forms part of the outermost turn on one of the pair of side faces and extends from one of the pair of end faces along the stacking direction toward the mounting surface to be connected to the first bottom electrode. The first bottom electrode has a first connection portion connected to the first end of the coil conductor on one side of the pair of end faces, a first mounting portion located on the other side of the pair of end faces, and a first extension portion extending in the first direction between the first connection portion and the first mounting portion.

[0007] In the above-described laminated coil component, the first bottom electrode functions as part of the outermost turn on one of the pair of side surfaces, and the number of turns of the coil conductor increases by the amount of the first bottom electrode, thereby increasing the inductance value. [Effects of the Invention]

[0008] According to one aspect of the present invention, there is provided a laminated coil component having an improved inductance value. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a laminated coil component according to one embodiment. [Figure 2] FIG. 2 is an exploded perspective view showing the configuration of each layer of the laminated coil component shown in FIG. [Figure 3] FIG. 2 is a side view of the laminated coil component shown in FIG. [Figure 4] 2 is a diagram showing a bottom electrode of the laminated coil component shown in FIG. 1. FIG. [Figure 5] 10A and 10B are diagrams showing different aspects of bottom electrodes. [Figure 6] 10A and 10B are diagrams showing different aspects of bottom electrodes. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or corresponding elements are designated by the same reference numerals, and redundant description will be omitted.

[0011] The laminated coil component according to the present embodiment will be described with reference to Fig. 1. Fig. 1 is a perspective view of the laminated coil component according to one embodiment. As shown in Fig. 1, the laminated coil component 1 includes an element body 2, a pair of bottom electrodes 3 and 4, and a coil conductor 5.

[0012] The element body 2 has a rectangular parallelepiped shape. The rectangular parallelepiped shape includes a rectangular parallelepiped shape with chamfered corners and ridges, and a rectangular parallelepiped shape with rounded corners and ridges. The element body 2 has, as its outer surfaces, a pair of end faces 2a and 2b, a pair of main faces 2c and 2d, and a pair of side faces 2e and 2f. The end faces 2a and 2b face each other. The main faces 2c and 2d face each other. The side faces 2e and 2f face each other. Hereinafter, the opposing direction of the end faces 2a and 2b is referred to as a first direction D1, the opposing direction of the side faces 2e and 2f is referred to as a second direction D2, and the opposing direction of the main faces 2c and 2d is referred to as a third direction D3. The first direction D1, the third direction D3, and the second direction D2 are substantially perpendicular to each other.

[0013] The end faces 2a and 2b extend in the third direction D3 to connect the principal faces 2c and 2d. The end faces 2a and 2b also extend in the second direction D2 to connect the side faces 2e and 2f. The principal faces 2c and 2d extend in the first direction D1 to connect the end faces 2a and 2b. The principal faces 2c and 2d also extend in the second direction D2 to connect the side faces 2e and 2f. The side faces 2e and 2f extend in the first direction D1 to connect the end faces 2a and 2b. The side faces 2e and 2f also extend in the third direction D3 to connect the principal faces 2c and 2d.

[0014] The main surface 2d is a mounting surface that faces another electronic device (not shown) when the laminated coil component 1 is mounted on the other electronic device (for example, a circuit board or a laminated electronic component). The end surfaces 2a and 2b are surfaces that are continuous with the mounting surface (i.e., the main surface 2d).

[0015] The length of the element body 2 in the first direction D1 is longer than the length of the element body 2 in the third direction D3 and the length of the element body 2 in the second direction D2. The length of the element body 2 in the third direction D3 is shorter than the length of the element body 2 in the second direction D2. That is, in this embodiment, the end faces 2a, 2b, main faces 2c, 2d, and side faces 2e, 2f have a rectangular shape. The length of the element body 2 in the third direction D3 may be equal to the length of the element body 2 in the second direction D2, or may be longer than the length of the element body 2 in the second direction D2.

[0016] In this embodiment, "equivalent" does not only mean equal, but also may mean values ​​that include slight differences or manufacturing errors within a preset range. For example, if multiple values ​​are within a range of ±5% of the average value of the multiple values, the multiple values ​​are defined as equivalent.

[0017] 2, the element body 2 has a configuration in which multiple element body layers are stacked in the third direction D3, and in this embodiment, the element body 2 is made up of nine element body layers 21 to 29. In other words, the stacking direction of the element body 2 coincides with the third direction D3. In an actual element body 2, the multiple element body layers 21 to 29 may be integrated to the extent that the boundaries between the layers are not visible, or may be integrated so that the boundaries between the layers are visible.

[0018] Each of the element layers 21 to 29 is mainly made of a resin material. The resin material includes at least one selected from the group consisting of liquid crystal polymer, polyimide resin, crystalline polystyrene, epoxy resin, acrylic resin, bismaleimide resin, and fluorine resin. The resin material may or may not contain a filler. The filler is, for example, an inorganic filler. An example of the inorganic filler is silica.

[0019] As shown in Figure 2, of the element layers 21-29, element layer 21, which constitutes main surface 2c, is made only of a resin material. Wiring portions 6, 7, 8a-8f, which constitute coil conductor 5, are embedded in element layers 22-27. More specifically, element layer 22 has multiple second wiring portions 6 embedded therein, element layers 23-26 have wiring portions 8a-8d, which constitute pillar portion 8 (described later), embedded therein, and element layer 27 has multiple first wiring portions 7 and wiring portion 8e, which constitutes pillar portion 8 (described later). Wiring portion 8f, which constitutes pillar portion 8 (described later), is embedded in element layer 28. A pair of bottom electrodes 3 and 4 (described later) are embedded in element layer 29, which constitutes main surface 2d.

[0020] Each of the element layers 21 to 29 may be made of a magnetic material. The magnetic material may include, for example, a Ni-Cu-Zn ferrite material, a Ni-Cu-Zn-Mg ferrite material, or a Ni-Cu ferrite material. The magnetic material may include, for example, an Fe alloy. Each of the element layers 21 to 29 may also include a non-magnetic material, which may be a glass ceramic material or a dielectric material.

[0021] The coil conductor 5 is disposed within the element body 2. The coil conductor 5 has a plurality of second wiring portions 6, a plurality of first wiring portions 7, and a plurality of pillar portions 8. The coil conductor 5 is configured by electrically connecting the second wiring portions 6, the first wiring portions 7, and the pillar portions 8. The coil axis of the coil conductor 5 is provided along the second direction D2. The second wiring portions 6, the first wiring portions 7, and the pillar portions 8 are configured of a conductive material (for example, Cu).

[0022] Each of the second wiring portions 6 is arranged on the main surface 2c side of the element body 2. The second wiring portions 6 are arranged away from the end faces 2a, 2b, the main surface 2c, and the side faces 2e, 2f of the element body 2. Each of the second wiring portions 6 extends along the first direction D1. Each of the second wiring portions 6 connects two pillar portions 8. The second wiring portion 6 is bridged across the two pillar portions 8. One end of the second wiring portion 6 in the extension direction (the end on the end face 2a side) is connected to one end of the pillar portion 8 (the end on the main surface 2c side). The other end of the second wiring portion 6 in the extension direction (the end on the end face 2b side) is connected to one end of the pillar portion 8.

[0023] Each of the first wiring portions 7 is arranged on the principal surface 2d (mounting surface) side of the element body 2. The first wiring portions 7 are arranged spaced apart from the end surfaces 2a, 2b, the principal surface 2d, and the side surfaces 2e, 2f of the element body 2. Each of the first wiring portions 7 extends along a first direction D1. Each of the first wiring portions 7 connects two pillar portions 8. The first wiring portion 7 spans the two pillar portions 8. One end of the first wiring portion 7 in the extension direction (the end on the end surface 2a side) is connected to the other end of the pillar portion 8 (the end on the principal surface 2d side). The other end of the first wiring portion 7 in the extension direction (the end on the end surface 2b side) is connected to the other end of the pillar portion 8. The number of the multiple first wiring portions 7 is one less than the number of the multiple second wiring portions 6. In other words, if there are n second wiring portions 6, there will be n-1 first wiring portions 7. In this embodiment, the second wiring portion 6 has five wires, and the first wiring portion 7 has four wires.

[0024] In this embodiment, each first wiring portion 7 is generally inclined at a predetermined angle with respect to the first direction D1 when viewed from the third direction D3. The inclination angle with respect to the first direction D1 is the same for all first wiring portions 7. That is, the multiple first wiring portions 7 are parallel to one another.

[0025] The pillar portions 8 are respectively arranged on the end face 2a side and the end face 2b side of the element body 2. Each of the pillar portions 8 extends along the third direction D3. The pillar portions 8 are arranged spaced apart from the end faces 2a and 2b, the main surface 2c, and the side faces 2e and 2f. In this embodiment, the cross-sectional shape of the pillar portions 8 in a cross section perpendicular to the third direction D3 is substantially rectangular (specifically, substantially square). The cross-sectional shape of the pillar portions 8 may be, for example, circular, elliptical, or a polygonal shape other than a rectangle. The pillar portions 8 connect the second wiring portion 6 and the first wiring portion 7. One end of the pillar portion 8 is connected to one end and the other end of the second wiring portion 6. The other end of the pillar portion 8 is connected to one end and the other end of the first wiring portion 7. Of the multiple pillar portions 8, the pillar portion 8 close to the side surface 2f has one end connected to one end of the second wiring portion 6 and constitutes the end portion 5a of the coil conductor 5, and the pillar portion 8 close to the side surface 2e has one end connected to the other end of the second wiring portion 6 and constitutes the end portion 5b of the coil conductor 5.

[0026] As shown in Figures 3 and 4, the pair of bottom electrodes 3, 4 are provided on the main surface 2d of the element body 2. In this embodiment, the pair of bottom electrodes 3, 4 are embedded inside the element body 2 (more specifically, inside the element body layer 29) and exposed from the main surface 2d. The exposed surface of each bottom electrode 3, 4 is flush with the main surface 2d, and the exposed surface and the main surface 2d form the same plane. The pair of bottom electrodes 3, 4 is composed of a first bottom electrode 3 and a second bottom electrode 4.

[0027] The first bottom electrode 3 is configured to include a connection portion 31 (first connection portion), a mounting portion 32 (first mounting portion), and an extension portion 33 (first extension portion).

[0028] The connecting portion 31 is positioned so as to overlap the end portion 5a of the coil conductor 5 when viewed from the third direction D3. Specifically, the connecting portion 31 is located on the end surface 2a side and the side surface 2f side of the element body 2, and is close to the corner formed by the end surface 2a and the side surface 2f. The mounting portion 32 is a portion that is externally connected to another electronic device when the laminated coil component 1 is mounted on the other electronic device. For example, the laminated coil component 1 can be electrically connected to a terminal electrode of the electronic device by solder mounting. The mounting portion 32 is located on the end surface 2b side of the element body 2 when viewed from the third direction. The mounting portion 32 in this embodiment has a rectangular shape extending along the second direction D2 and has a first end portion 32a located on the side surface 2f side of the element body 2 and a second end portion 32b located on the side surface 2e side. The first end portion 32a is located alongside the connecting portion 31 in the first direction D1. Although second end 32b extends close to connection portion 41 of second bottom electrode 4, it is spaced apart from second bottom electrode 4, and therefore there is no electrical continuity between first bottom electrode 3 and second bottom electrode 4. Extension portion 33 extends along first direction D1 and connects connection portion 31 and first end 32a of mounting portion 32. As connection portion 31 and mounting portion 32 are connected by extension portion 33, first bottom electrode 3 has an L-shape when viewed from the third direction.

[0029] By connecting first bottom electrode 3 to end 5a of coil conductor 5, first bottom electrode 3 is continuous with outermost turn T1 on side 2f of coil conductor 5 in the winding direction and therefore functions as part of outermost turn T1. In this case, first bottom electrode 3 extends outermost turn T1 by approximately 1 / 4 turn. In other words, when first bottom electrode 3 extends from end face 2a to end face 2b of element body 2, the number of turns increases by approximately 1 / 4 turn compared to when outermost turn T1 terminates at end 5a of coil conductor 5 and is externally connected at end face 2a.

[0030] Furthermore, first bottom electrode 3 is provided on element layer 29 that constitutes main surface 2d, and is located closer to main surface 2d than first wiring portion 7 that is provided on element layer 27. Therefore, as shown in Figure 3, the inner diameter of outermost turn T1 is larger than the inner diameter of the adjacent turn (middle turn T3) in second direction D2, and is expanded mainly in third direction D3.

[0031] Similar to the first bottom electrode 3, the second bottom electrode 4 includes a connection portion 41 (second connection portion), a mounting portion 42 (second mounting portion), and an extension portion 43 (second extension portion).

[0032] The connecting portion 41 is positioned so as to overlap the end portion 5b of the coil conductor 5 when viewed from the third direction D3. Specifically, the connecting portion 41 is located on the end portion 2b side and the side portion 2e side of the element body 2, and is close to the corner formed by the end portion 2b and the side portion 2e (i.e., the diagonal corner of the corner formed by the end portion 2a and the side portion 2f). Like the mounting portion 32 of the first bottom surface electrode 3, the mounting portion 42 is a portion that is externally connected to another electronic device when the laminated coil component 1 is mounted on the other electronic device. The mounting portion 42 is located on the end portion 2a side of the element body 2 when viewed from the third direction. The mounting portion 42 in this embodiment has a rectangular shape extending along the second direction D2 and has a first end portion 42a located on the side portion 2e side of the element body 2 and a second end portion 42b located on the side portion 2f side. The first end portion 42a is located alongside the connecting portion 41 in the first direction D1. Second end 42b extends close to connection portion 31 of first bottom electrode 3, but is spaced apart from first bottom electrode 3, and therefore is not electrically connected to first bottom electrode 3 and second bottom electrode 4. Extension portion 43 extends along first direction D1 and connects connection portion 41 and first end 42a of mounting portion 42. As connection portion 41 and mounting portion 42 are connected by extension portion 43, second bottom electrode 4 has an L-shape when viewed from the third direction.

[0033] In this embodiment, the first bottom electrode 3 and the second bottom electrode 4 have a relationship of 180-degree rotational symmetry about the center O of the element body 2 when viewed from the third direction. That is, the first bottom electrode 3 and the second bottom electrode 4 are perfectly aligned when rotated 180 degrees about the center O, and have the same shape and dimensions.

[0034] Like the first bottom electrode 3, the second bottom electrode 4 is connected to the end 5a of the coil conductor 5, and is continuous with the outermost turn T2 on the side 2e of the coil conductor 5 in the winding direction, thereby functioning as part of the outermost turn T2. ​​In this case, the second bottom electrode 4 extends the outermost turn T2 by approximately 1 / 4 turn. In other words, with the second bottom electrode 4 extending from the end 2b side to the end 2a side of the element body 2, the number of turns increases by approximately 1 / 4 turn compared to when the outermost turn T2 terminates at the end 5b of the coil conductor 5 and is externally connected at the end 2b side.

[0035] Second bottom electrode 4 is provided on element layer 29 that constitutes main surface 2d, and is located closer to main surface 2d than first wiring portion 7 that is provided on element layer 27. Therefore, as shown in Figure 3, the inner diameter of outermost turn T2 is larger than the inner diameter of the adjacent turn (middle turn T3) in second direction D2, and is expanded mainly in third direction D3.

[0036] In the above-described laminated coil component 1, the number of turns of each of the first bottom surface electrode 3 and the second bottom surface electrode 4 is increased by approximately 1 / 4 turn (total increase of 1 / 2 turn), thereby realizing a high inductance value. An embodiment in which only one of the first bottom surface electrode 3 and the second bottom surface electrode 4 is provided may also be used, and in this case, the inductance value of the laminated coil component 1 will also increase.

[0037] Furthermore, in the laminated coil component 1, the first bottom surface electrode 3 and the second bottom surface electrode 4 make the inner diameter of the outermost turns T1, T2 larger than the inner diameter of the middle turn T3 located between the outermost turns T1, T2, thereby achieving a high inductance value. In an embodiment having only either the first bottom surface electrode 3 or the second bottom surface electrode 4, the inner diameter of only one of the outermost turns T1, T2 is larger, but even in this case the inductance value of the laminated coil component 1 increases.

[0038] The pair of bottom electrodes 3, 4 may be either entirely embedded within element body 2 as described above, or at least partially protruding from main surface 2d of element body 2.

[0039] In the embodiment shown in FIG. 5, a portion of each bottom electrode 3, 4 protrudes from the main surface 2d of the element body 2, and the remainder is buried within the element body 2. In this case, each bottom electrode 3, 4 may be configured to include a first layer L1 protruding from the main surface 2d and a second layer L2 buried within the element body 2. The first layer L1 may be a plating layer formed on the exposed surface of the second layer L2 exposed from the main surface 2d. In the embodiment shown in FIG. 6, each bottom electrode 3, 4 protrudes entirely from the main surface 2d of the element body 2. In this case, each bottom electrode 3, 4 may be configured with a plating layer.

[0040] The present invention is not necessarily limited to the above-described embodiment, and various modifications are possible without departing from the spirit and scope of the present invention.

[0041] For example, the shapes of bottom electrodes 3, 4 are not limited to those described above and can be modified as appropriate. First bottom electrode 3 and second bottom electrode 4 do not necessarily have to be 180-degree rotationally symmetric with respect to center O of element body 2, and they do not necessarily have to have the same shape or dimensions. Connection portions 31, 41, mounting portions 32, 42, and extension portions 33, 43 constituting bottom electrodes 3, 4 can also be modified as appropriate. For example, mounting portions 32, 42 may have a shape that reaches adjacent end faces 2a, 2b and is exposed from end faces 2a, 2b. Furthermore, the number of windings (turns) of coil conductor 5 can be increased or decreased as appropriate.

[0042] As can be understood from the above description, the present specification discloses the following. [Appendix 1] an element body formed of a plurality of laminated insulating layers, the element body having a mounting surface that intersects with a lamination direction, a pair of end faces that face each other in a first direction that is parallel to the mounting surface, and a pair of side faces that face each other in a second direction that is perpendicular to the lamination direction and the first direction; a coil conductor provided within the element body, the coil conductor having a coil axis along the second direction and a first end and a second end; a first bottom electrode provided on a mounting surface of the element body and connected to a first end of the coil conductor, and a second bottom electrode connected to a second end of the coil conductor; Equipped with a first end of the coil conductor forms a part of an outermost turn on one side of the pair of side faces, extends toward the mounting surface along the stacking direction on one side of the pair of end faces, and is connected to the first bottom electrode; a first bottom surface electrode having a first connection portion connected to a first end portion of the coil conductor on one side of the pair of end surfaces, a first mounting portion located on the other side of the pair of end surfaces, and a first extension portion extending in the first direction between the first connection portion and the first mounting portion. [Appendix 2] a second end of the coil conductor forms a part of the outermost turn on the other side of the pair of side faces, extends toward the mounting surface along the stacking direction on the other side of the pair of end faces, and is connected to the second bottom electrode; 2. The laminated coil component according to claim 1, wherein the second bottom surface electrode has a second connection portion connected to a second end of the coil conductor on the other side of the pair of end surfaces, a second mounting portion located on one side of the pair of end surfaces, and a second extension portion extending in the first direction between the second connection portion and the second mounting portion. [Appendix 3] 3. The laminated coil component according to claim 1, wherein the first bottom electrode and the second bottom electrode are at least partially embedded in the element body. [Appendix 4] The laminated coil component according to Appendix 3, wherein the first bottom electrode and the second bottom electrode are entirely embedded in the element body and exposed from the mounting surface. [Appendix 5] 4. The laminated coil component according to claim 3, wherein the first bottom electrode and the second bottom electrode are partially embedded in the element body, and the remainder protrudes from the mounting surface of the element body. [Appendix 6] 6. The laminated coil component according to claim 5, wherein the portions of the first bottom electrode and the second bottom electrode that protrude from the mounting surface of the element body are formed of a plating layer. [Appendix 7] 3. The laminated coil component according to claim 1, wherein the first bottom surface electrode and the second bottom surface electrode entirely protrude from the mounting surface of the element body. [Appendix 8] 8. The laminated coil component according to claim 7, wherein the first bottom electrode and the second bottom electrode are formed of plating layers. [Explanation of symbols]

[0043] 1...multilayer coil component, 2...element body, 3...first bottom electrode, 4...second bottom electrode, 5...coil conductor, 5a, 5b...end portion, 6...second wiring portion, 7...first wiring portion, 8...pillar portion, D1...first direction, D2...second direction, D3...third direction.

Claims

1. an element body formed of a plurality of laminated insulating layers, the element body having a mounting surface that intersects with a lamination direction, a pair of end faces that face each other in a first direction that is parallel to the mounting surface, and a pair of side faces that face each other in a second direction that is perpendicular to the lamination direction and the first direction; a coil conductor provided within the element body, the coil conductor having a coil axis along the second direction and a first end and a second end; a first bottom electrode provided on a mounting surface of the element body and connected to a first end of the coil conductor, and a second bottom electrode connected to a second end of the coil conductor; Equipped with a first end of the coil conductor forms a part of an outermost turn on one of the pair of side surfaces, extends toward the mounting surface along the stacking direction on one of the pair of end surfaces, and is connected to the first bottom electrode; the first bottom electrode has a first connection portion connected to a first end of the coil conductor on one side of the pair of end faces, a first mounting portion located on the other side of the pair of end faces, and a first extension portion extending along the first direction between the first connection portion and the first mounting portion.

2. a second end of the coil conductor forms a part of an outermost turn on the other side of the pair of side surfaces, extends toward the mounting surface along the stacking direction on the other side of the pair of end surfaces, and is connected to the second bottom electrode; 2. The laminated coil component according to claim 1, wherein the second bottom electrode has: a second connection portion connected to a second end of the coil conductor on the other side of the pair of end faces; a second mounting portion located on one side of the pair of end faces; and a second extension portion extending along the first direction between the second connection portion and the second mounting portion.

3. The laminated coil component according to claim 1 , wherein the first bottom electrode and the second bottom electrode are at least partially embedded in the element body.

4. 4. The laminated coil component according to claim 3, wherein the first bottom electrode and the second bottom electrode are entirely embedded in the element body and exposed from the mounting surface.

5. 4. The laminated coil component according to claim 3, wherein the first bottom electrode and the second bottom electrode are partially embedded in the element body, and the remaining portions protrude from a mounting surface of the element body.

6. 6. The laminated coil component according to claim 5, wherein portions of the first bottom electrode and the second bottom electrode that protrude from the mounting surface of the element body are formed of a plating layer.

7. The laminated coil component according to claim 1 , wherein the first bottom surface electrode and the second bottom surface electrode entirely protrude from the mounting surface of the element body.

8. The laminated coil component according to claim 7 , wherein the first bottom electrode and the second bottom electrode are formed of plating layers.

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