Laminated electronic component

Abstract

This laminated electronic component includes an effective section, a cover, and an external electrode. The effective section includes dielectric layers and internal electrodes which are alternately laminated. The cover overlaps the effective section in a lamination direction of the dielectric layers and the internal electrodes. The external electrode covers a side surface along a lamination direction of the effective section and the cover, and is connected to a partial edge section that is a section of an outer edges of the internal electrodes. In a section of the external electrode that expands in the lamination direction and that is wide in the length of the partial edge section, a section covering the side surface of the effective section is referred to as a first section, and a section covering the side surface of the cover is referred to as a second section. Here, a volume ratio of an oxide phase in the first section is smaller than the volume ratio of the oxide phase in the second section.

Description

Multilayer electronic components

[0001] The present disclosure relates to multilayer electronic components such as multilayer ceramic capacitors.

[0002] Multilayer ceramic capacitors are known as multilayer electronic components (see, for example, Patent Document 1 below). A multilayer ceramic capacitor includes, for example, a main body that directly functions as a capacitor and external electrodes for mounting the capacitor on a circuit board or the like. The main body includes alternately stacked dielectric layers and flat internal electrodes. The edges of the internal electrodes are exposed from the side surfaces (surfaces along the stacking direction) of the main body. The external electrodes are formed, for example, by metal layers covering the side surfaces of the main body. Patent Document 1 proposes forming an oxide on the external electrodes to improve the adhesive strength of the external electrodes to the main body (ceramics).

[0003] JP 2009-170875 A

[0004] A capacitor according to one aspect of the present disclosure includes an effective portion, a cover, and an external electrode. The effective portion includes dielectric layers and internal electrodes that are alternately stacked. The cover overlaps the effective portion in the stacking direction of the dielectric layers and the internal electrodes. The external electrode covers the side surfaces of the effective portion and the cover along the stacking direction and is connected to a partial edge portion that is a part of the outer edge of the internal electrode. In a portion of the external electrode that extends in the stacking direction with a width equal to the length of the partial edge portion, the portion that covers the side surface of the effective portion is referred to as a first portion, and the portion that covers the side surface of the cover is referred to as a second portion. In this case, the volume fraction of the oxide phase in the first portion is smaller than the volume fraction of the oxide phase in the second portion.

[0005] 6. A perspective view showing a capacitor according to the first embodiment. A schematic exploded perspective view of the capacitor of FIG. 1. A cross-sectional view taken along line III-III of FIG. 1. An enlarged view of region R4 of FIG. 3. A view of a portion of the capacitor shown in FIG. 4, viewed from the +D1 side. An enlarged view of region R6 of FIG. 4. An enlarged view of region R7 of FIG. 6. A cross-sectional view showing another example of an external electrode. A view showing yet another example of an external electrode. A perspective view showing a capacitor according to a second embodiment. A table showing the characteristics of capacitors according to examples and comparative examples. A cross-sectional view showing another example of a dummy layer.

[0006] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The drawings used in the following description are schematic. Therefore, for example, the dimensional ratios in the drawings do not necessarily correspond to the actual ones. Furthermore, the dimensional ratios may not match between drawings. Certain shapes and / or dimensions may be exaggerated, and details may be omitted. However, the above does not deny that the actual shapes and / or dimensions may be as shown in the drawings, or that features of shapes and / or dimensions may be extracted from the drawings.

[0007] Regarding the embodiments described relatively later, basically, only the differences from the embodiments described relatively earlier will be described. Matters not specifically mentioned may be considered to be the same as the embodiments described earlier or may be inferred from the embodiments described earlier. For convenience, the same reference numerals may be used for corresponding components between different embodiments, even if there are differences.

[0008] In the following description, when referring to a "rectangle" (or rectangular shape), a "square" (or square shape), and a "rectangle" (or rectangular shape), the corners may be chamfered by a curved surface or the like, as long as the concept of the shape is valid. For example, a corner formed by two sides may be chamfered to a length of 1 / 5 or less, 1 / 10 or less, or 1 / 20 or less of the length of the shorter of the two sides. It goes without saying that, when viewed microscopically, the corners may be rounded due to manufacturing precision (errors). The same applies to other polygons, etc.

[0009] (Overview of the Embodiments) Fig. 1 is a perspective view showing a capacitor 1 (an example of a multilayer electronic component) according to a first embodiment. For convenience, Fig. 1 and other figures described below are illustrated with a Cartesian coordinate system D1D2D3. The capacitor 1 may be used with either side designated as upper or lower. However, in the description of the embodiments, for convenience, the +D3 side may be designated as upper, and terms such as upper surface and lower surface may be used.

[0010] The capacitor 1 is, for example, a multilayer ceramic capacitor. The capacitor 1 has a roughly rectangular parallelepiped body 3 and four external electrodes 5 located at the four corners of the body 3 in a plan view (as viewed in the direction D3). The external electrodes 5 contribute to electrical connection between the capacitor 1 and other electronic components (for example, a circuit board (not shown)).

[0011] 3 is a cross-sectional view taken along line III-III in FIG. 1. The main body 3 has, for example, an effective portion 13 and two covers 15 respectively overlapping the upper and lower surfaces of the effective portion 13. The effective portion 13 has a plurality of dielectric layers 7 and a plurality of internal electrodes 9 that are alternately overlapped. In other words, the effective portion 13 directly functions as a capacitor. The covers 15, for example, contribute to improving the strength of the main body 3.

[0012] Of the outer surfaces of the main body 3, the surfaces along the stacking direction (direction D3) of the multiple dielectric layers 7 and multiple internal electrodes 9 are referred to as side surfaces. Parts of the edges of the multiple internal electrodes 9 (sometimes referred to as partial edge portions 9c) are exposed from the side surfaces of the main body 3. The external electrodes 5 cover the side surfaces of the main body 3 and are fixed to the partial edge portions 9c. This electrically connects the internal electrodes 9 and the external electrodes 5. The internal electrodes 9 that face each other via the dielectric layers 7 are connected to different external electrodes 5.

[0013] Of the portions of the external electrode 5 that cover the side surfaces of the main body 3, the portion that covers the side surfaces of the active portion 13 is referred to as the first portion 5a, and the portion that covers the side surfaces of the cover 15 is referred to as the second portion 5b. In this case, the volume fraction of the oxide phase in the first portion 5a is smaller than the volume fraction of the oxide phase in the second portion 5b. This can improve, for example, the electrical characteristics.

[0014] More specifically, for example, the oxide phase generally has a higher electrical resistivity than the non-oxidized phase. Therefore, by reducing the volume fraction of the oxide phase in the first portion 5a, the resistance between the outside of the capacitor 1 and the internal electrode 9 can be reduced. As a result, for example, a reduction in equivalent series resistance (ESR), an improvement in the Q value, a reduction in heat generation, and an improvement in high-frequency performance can be expected.

[0015] 4 to 6, for example, the reduction in the volume fraction of the oxide phase in the first portion 5a does not necessarily result in a reduction in ESR, due to the method for reducing the volume fraction of the oxide phase in the first portion 5a, as will be described in detail later. However, the above method improves the bonding strength of the external electrode 5 to the main body 3. As a result, it is easier to achieve both an improvement in bonding strength and suppression of an increase in ESR, compared to, for example, an embodiment in which the volume fraction of the oxide phase in the first portion 5a is increased to improve bonding strength.

[0016] Furthermore, for example, when the main component of the external electrode 5 is copper, the oxide phase exhibits a rectifying effect, which may destabilize the characteristics of the capacitor 1. However, by reducing the volume fraction of the oxide phase in the first portion 5a, the likelihood of such a problem occurring can be reduced.

[0017] The comparison of the volume proportions may be performed within the length range of the partial edge portion 9c of the internal electrode 9 in the direction along the outer periphery of the main body portion 3 (the direction along the outer edge of the dielectric layer 7). Specifically, the comparison is as follows.

[0018] 1 illustrates one partial edge portion 9c that is joined to the external electrode 5 on the -D1 side and the -D2 side on the -D2 side of the main body 3. In the illustrated example, the length of the partial edge portion 9c (in the D1 direction) and the length of the external electrode 5 in the direction along the partial edge portion 9c (in the D1 direction) are roughly equivalent. However, as shown by the two-dot chain line, the external electrode 5 can also be extended further toward the +D1 side than the length of the partial edge portion 9c. In such a case, comparing the portion of the external electrode 5 that covers the side surface of the active portion 13 with the portion that covers the side surface of the cover 15 over the entire length of the external electrode 5 in the D1 direction is not necessarily reasonable in light of the above-described effects.

[0019] Therefore, the volume fractions of the oxide phase may be compared for a portion of the external electrode 5 that extends in the D3 direction (the stacking direction of the dielectric layers 7) with the length of the partial edge portion 9c as its width (hereinafter, this portion may be referred to as the "target portion 5c"). That is, the above-mentioned first portion 5a may be the portion of the target portion 5c that covers the side surface of the effective portion 13. The second portion 5b may be the portion of the target portion 5c that covers the side surface of the cover 15. Typically, the lengths of the partial edge portions 9c of multiple internal electrodes 9 are the same, but if they are different from each other, the length of the smallest range that includes all of the partial edge portions 9c may be used as the length of the partial edge 9c (the width of the target portion 5c).

[0020] The above is an overview of the embodiment. As can be understood from the above, the capacitor (1) may have various configurations as long as it has an active portion 13, a cover 15, and an external electrode 5 covering the side surfaces thereof. In other words, the overall configuration of the capacitor 1 (first embodiment) shown in FIG. 1 is merely an example. However, for convenience, the following will first describe the overall configuration of the capacitor 1, and then, based on the configuration of the capacitor 1, will describe the oxide phase of the external electrode 5, etc. After that, the overall configurations of other capacitors (second embodiment, etc.) will also be described.

[0021] Specifically, the embodiments will be described roughly in the following order: 1. Structure of the capacitor according to the first embodiment (FIGS. 1 to 3) 1.1. Overall structure 1.2. Active portion 1.3. Cover 1.3.1. General cover 1.3.2. Insulating layer 1.3.3. Dummy electrode 1.4. General structure of the external electrode 2. Specific structure of the external electrode (FIGS. 4 to 9) 2.1. Oxide phase 2.2. Pattern of the first metal layer 2.3. Materials and dimensions of the first metal layer and the second metal layer 2.4. Other examples of specific electrode structures 2.4.1. Other examples of partial edges of the internal electrode (FIG. 8) 2.4.2. Other examples of laminated structures of the external electrode (FIG. 8) 2.4.3. Other examples of the pattern of the first metal layer (FIG. 9) 3. Method of manufacturing the capacitor 3.1. Procedure for manufacturing the entire capacitor 3.2. Method of forming the pattern of the first metal layer 3.3. 3. Method for forming a specific shape of an internal electrode 3.4. Method for reducing the volume fraction of an oxide phase 4. Structure of a capacitor according to another embodiment (FIG. 10) 5. Example (FIG. 11) 6. Summary of the embodiment

[0022] (1. Configuration of the Capacitor According to the First Embodiment) (1.1. Overall Configuration) The capacitor 1 according to the first embodiment shown in FIG. 1 is configured, for example, as a surface-mounted chip component. Specifically, for example, the capacitor 1 is placed with the −D3 side or +D3 side facing a circuit board (not shown). Then, the four pads on the circuit board and the four external electrodes 5 are respectively joined with a conductive bonding material (for example, solder) (not shown), thereby mounting the capacitor on the circuit board.

[0023] The configuration (internal structure and external shape) of the capacitor 1 is, for example, approximately plane-symmetric with respect to a plane of symmetry (not shown) that is parallel to the D1D2 plane and passes through the center of the capacitor 1 in the thickness direction. Also, the configuration of the capacitor 1 is, for example, 180° rotationally symmetric when viewed in the D3 direction. Of course, the capacitor 1 does not have to have such symmetry.

[0024] The shape of the main body 3 is, for example, a generally thin rectangular parallelepiped. This rectangular parallelepiped may be square (as in the illustrated example) or rectangular (excluding squares; the same applies below) in plan view. For convenience, in the description of the embodiments, a square shape may be assumed unless otherwise specified.

[0025] The specific dimensions of the main body 3 (or the capacitor 1) are arbitrary. For example, when the capacitor 1 is relatively small, the lengths of the main body 3 (or the capacitor 1) in the D1 direction and the D2 direction are each 300 μm or more and 1000 μm or less, and the thickness in the D3 direction is 30 μm or more and 100 μm or less.

[0026] Note that, unless otherwise specified or unless a contradiction occurs, multiple components of the same type (e.g., 5, 7, 9, 15, 17, 19, or 21) may be provided with the same (or corresponding) shape, size, material, and position. For example, multiple dielectric layers 7 may be configured with the same shape, size, and material, and may overlap each other exactly in a planar perspective. Therefore, unless otherwise specified or unless a contradiction occurs, a description of one component may be considered to be common to multiple components of the same type. Furthermore, individual mention of multiple components of the same type overlapping exactly in a planar perspective may be omitted.

[0027] A layer (film) of a component (e.g., 5, 7, 9, 17, or 21) may be entirely made of a single material, but may also be made of layers of different materials stacked on top of each other.

[0028] (1.2. Effective portion) The shape of the effective portion 13 shown in FIG. 3 is, for example, roughly a thin rectangular parallelepiped. Its planar shape is the same as that of the main body portion 3. The specific thickness of the effective portion 13 is arbitrary. For example, the thickness of the effective portion 13 may be 0.2 to 0.9 times the thickness of the main body portion 3 (both thicknesses are based on the surface of the insulating portion).

[0029] The dielectric layer 7 is basically a layer having a constant thickness (at least between the internal electrodes 9). The thickness of the dielectric layer 7 may be set appropriately depending on the characteristics required of the capacitor 1. Examples of a relatively thin thickness include a thickness between the internal electrodes 9 of 3 μm or less or 1 μm or less. The shape and dimensions of the dielectric layer 7 in a planar view are the same as those of the active portion 13 in a planar view. The material of the dielectric layer is, for example, ceramics, and the specific type is also optional. The number of laminated dielectric layers 7 (internal electrodes 9) is optional. For example, the number is 10 to 30 layers.

[0030] The internal electrodes 9 are layer-shaped and have a constant thickness. The thickness of the internal electrodes 9 is arbitrary, and may be thinner, the same as, or thicker than the thickness of the region of the dielectric layer 7 between the internal electrodes 9. The material of the internal electrodes 9 is, for example, a metal. The specific type of metal is arbitrary, and may be, for example, a base metal (e.g., Ni or Cu).

[0031] Fig. 2 is an exploded perspective view of the capacitor 1. Fig. 2 is a schematic diagram for understanding the shapes and relative positions of the internal electrodes 9, etc. Therefore, Fig. 2 shows a smaller number of various layers than Fig. 3.

[0032] The internal electrode 9 has, for example, a rectangular (square in the illustrated example) electrode body 9a in a plan view and a pair of lead electrodes 9b extending from a pair of opposing corners of the electrode body 9a. The internal electrode 9 is located inside the outer edge of the dielectric layer 7 and is not exposed from the side surface of the effective portion 13. The pair of lead electrodes 9b reach the outer edge of the dielectric layer 7 and are connected to a pair of external electrodes 5 located at a pair of opposing corners of the main body portion 3.

[0033] In two internal electrodes 9 that face each other with the dielectric layer 7 interposed therebetween (that are adjacent to each other with the dielectric layer 7 interposed therebetween), a pair of lead electrodes 9b of one internal electrode 9 and a pair of lead electrodes 9b of the other internal electrode 9 are located on different diagonal lines in a planar perspective view, and are connected to different pairs of external electrodes 5.

[0034] The electrode body 9 a and the extraction electrode 9 b may have any dimensions. For example, the length of the extraction electrode 9 b on one side of the dielectric layer 7 (i.e., the length of the partial edge 9 c) is approximately the same as the length of the external electrode 5 along the side.

[0035] (1.3. Cover) (1.3.1. Covers in general) The cover 15 shown in Figure 3 is provided on both the upper and lower surfaces of the effective portion 13, for example. Unlike the example shown, the cover 15 may be provided on only one of the upper and lower surfaces of the effective portion 13. The cover 15 is, for example, a layer having a shape and dimensions that overlap the effective portion 13 exactly in planar perspective. The thickness of the cover 15 is approximately constant. The proportion of the thickness of the cover 15 to the thickness of the main body portion 3 is the reverse of the proportion of the thickness of the effective portion 13 to the thickness of the main body portion 3 (as described above), and therefore specific examples of this proportion will be omitted.

[0036] Each cover 15 has, for example, at least one insulating layer 17 (plurality in the illustrated example) and at least one dummy layer 21 (plurality in the illustrated example) overlapping the insulating layer 17. Each dummy layer 21 has, for example, four dummy electrodes 19, as shown in FIG. 2 . The dummy electrodes 19 contribute to, for example, reinforcing the cover 15 and / or improving the connection strength between the main body 3 and the external electrodes 5. Unlike the illustrated example, the cover 15 may have only one or more insulating layers 17 (it may not have the dummy layer 21).

[0037] When the dummy layer 21 is provided, for example, a metal can be deposited on the surface of the dummy layer 21 by electroless plating or electrolytic plating to form the external electrode 5. Furthermore, regardless of whether the dummy layer 21 is provided or not, the external electrode 5 can be formed by a dipping method or a printing method.

[0038] The insulating layers 17 and the dummy layers 21 are alternately stacked one on top of the other. In other words, the dummy layers 21 are provided at the boundaries of all the insulating layers 17. Unlike the illustrated example, the dummy layers 21 may be provided only at some of the boundaries. For example, the dummy layers 21 may not be provided at one or more boundaries relatively close to the effective portion 13, and the dummy layers 21 may be provided only at one or more boundaries relatively far from the effective portion 13. In such a case, however, two or more insulating layers 17 that are in close contact with each other without a dummy layer 21 interposed therebetween may be regarded as a single insulating layer 17.

[0039] There may be only one dummy layer 21. FIG. 12 shows an example different from the example shown in FIG. 3. In this example, one dummy layer 21 is provided on each of the upper and lower surfaces of the main body 3. More specifically, this dummy layer 21 is exposed from the upper or lower surface of the main body 3 and is insulated from the internal electrode 9 by one insulating layer 17 or one dielectric layer 7. In the example shown in FIG. 12, the dummy layer 21 is thicker than in the example shown in FIG. 3, for example, having a thickness of at least half or two-thirds the thickness of the cover 15 (although it is of course not necessary for the dummy layer 21 to have such a thickness). For convenience, the description of the embodiments may assume the configuration shown in FIG. 12 without any particular mention.

[0040] (1.3.2. Insulating Layer) The insulating layer 17 is a layer having a substantially constant thickness, excluding variations in thickness resulting from the presence or absence of overlap with the conductor layers (9 and 19). The planar shape of the insulating layer 17 is, for example, the same as the planar shape of the dielectric layer 7. The material of the insulating layer 17 is arbitrary. For example, the material of the insulating layer 17 may be the same as or different from the material of the dielectric layer 7. Furthermore, the material of the insulating layer 17 may be, for example, ceramics or a material other than ceramics.

[0041] The thickness of the insulating layer 17 is arbitrary. For example, the thickness of the insulating layer 17 may be thicker (in the illustrated example), equal to, or thinner than the thickness of the dielectric layer 7 (both of which are thicknesses between conductor layers or thicknesses of regions not overlapping with conductor layers; the same applies hereinafter in this paragraph). For example, the thickness of the insulating layer 17 may be two or more times, five or more times, or ten or more times the thickness of the dielectric layer 7, and may be 5 μm or more and 20 μm or less.

[0042] 3, the top layer of the effective portion 13 is a conductor layer including an internal electrode 9. The internal electrode 9 in the top layer is covered with an insulating layer 17 in the bottom layer of the upper cover 15. However, as long as the internal electrode 9 in the top layer and the dummy electrode 19 in the upper cover 15 are insulated from each other, the configuration at the boundary may be different from that shown in the illustrated example.

[0043] For example, the top layer of the effective portion 13 may be the dielectric layer 7. The top dielectric layer 7 may overlap the bottom insulating layer 17 of the upper cover 15, or the top dielectric layer 7 may overlap the bottom dummy electrode 19. Furthermore, all of the dielectric layers 7 and all of the insulating layers 17 do not need to be distinguishable from each other in terms of their materials, thicknesses, etc. From another perspective, the boundary between the effective portion 13 and the cover 15 may be vague.

[0044] In either embodiment, however, the material between the internal electrodes 9 functions as a dielectric for increasing capacitance. Also, the material between the uppermost of the multiple internal electrodes 9 and the lowermost of the multiple dummy electrodes 19 of the upper cover 15 functions as an insulating layer for insulating them. From this perspective, the insulating layer between the uppermost of the multiple internal electrodes 9 and the lowermost of the multiple dummy electrodes 19 may be considered as the insulating layer 17 of the cover 15, regardless of whether it has the same configuration as the dielectric layer 7 between the internal electrodes 9 or the insulating layer 17 between the dummy layers 21, or whether it is a combination of the previous two layers.

[0045] Although the upper cover 15 is taken as an example, the same applies to the lower cover 15. However, the terms "top layer" and "bottom layer" are interchangeable.

[0046] (1.3.3. Dummy Electrode) The dummy electrode 19 (in other words, the dummy layer 21) is, for example, a layer having a certain thickness. The material of the dummy electrode 19 is, for example, a metal. The specific type of metal is arbitrary, and is, for example, a base metal (e.g., Ni and Cu). The material of the dummy electrode 19 may be the same as or different from the material of the internal electrode 9.

[0047] In a plan view, the position, shape, and size of the dummy electrodes 19 are arbitrary. In the example of Fig. 2, the dummy electrodes 19 are located at the four corners of the dielectric layer 7 in a planar perspective view. From another perspective, the positions of the dummy electrodes 19 correspond to the positions of the external electrodes 5. Furthermore, the planar shape of the dummy electrodes 19 is rectangular (more specifically, square). The size of the dummy electrodes 19 in a planar view is approximately the same as the size of the external electrodes 5 in a planar view.

[0048] The dummy electrode 19 may overlap the electrode body 9a in planar perspective (in the illustrated example, it overlaps the corner of the internal electrode 9), or it may not overlap. In the latter case, the dummy electrode 19 may be formed, for example, in an L-shape along a corner (two intersecting sides) of the dielectric layer 7. When the dummy electrode 19 overlaps the internal electrode 9, for example, a large area of ​​the dummy electrode 19 is ensured, thereby improving the effect of improving strength provided by the dummy electrode 19. When the dummy electrode 19 does not overlap the internal electrode 9, for example, the electrical influence of the dummy electrode 19 on the internal electrode 9 is reduced.

[0049] The dummy electrode 19 is exposed, for example, on the side surface of the main body 3. This exposed portion is fixed to the external electrode 5. As a result, the dummy electrode 19 contributes to improving the bonding strength between the main body 3 and the external electrode 5. Unlike the example shown in the figure, the dummy electrode 19 does not have to be connected to the external electrode 5. For example, the dummy electrode 19 may be provided so as not to be exposed from the side surface of the main body 3, and may contribute to improving the strength of the main body 3 without contributing to improving the connection strength with the external electrode 5.

[0050] The thickness of the dummy electrode 19 is arbitrary. For example, the thickness of the dummy electrode 19 may be thicker than (in the illustrated example), may be approximately the same as, or may be thinner than the thickness of the internal electrode 9. For example, the thickness of the dummy electrode 19 may be two or more times, five or more times, or ten or more times the thickness of the internal electrode 9. Furthermore, the thickness of the dummy electrode 19 may be thinner than (in the illustrated example), may be the same as, or may be thicker than the thickness of the insulating layer 17.

[0051] 3, a dummy layer 21 is provided on the top layer of the upper cover 15. The four dummy electrodes 19 are covered with the external electrodes 5. Unlike the illustrated example, the dummy layer 21 does not have to be provided on the top layer of the upper cover 15. As described above, the dummy layer 21 affects the method of forming the external electrodes 5, and therefore, whether or not to provide the dummy layer 21 on the top layer may be determined taking this effect into consideration.

[0052] As described above, the layered (film-like) component may be composed of two or more layers. The external electrode 5 may also be composed of two or more layers. In this case, the lower layer of the external electrode 5 and the uppermost dummy electrode 19 may or may not be distinguishable from the viewpoint of thickness and / or material. Therefore, the presence or absence of the dummy electrode 19 may be determined by the presence or absence of the dummy electrode 19 covered by the insulating layer 17 from the side opposite to the effective portion 13 (dielectric layer 7).

[0053] In the illustrated example, the four dummy electrodes 19 overlap the internal electrodes 9 in a planar perspective view, and are connected to external electrodes 5 at different potentials. Therefore, the dummy layers 21 and the internal electrodes 9 need to be separated by the dielectric layer 7 and / or the insulating layer 17. However, this does not apply in cases where some or all of the four dummy electrodes 19 do not overlap the internal electrodes 9 in a planar perspective view, or where some or all of the four dummy electrodes 19 are not connected to the external electrodes 5.

[0054] 1 is, for example, generally in the form of a layer covering the four surfaces (top surface, bottom surface, and two side surfaces) of the main body 3 at the corners in a plan view of the main body 3. This allows one external electrode 5 to be connected to one extraction electrode 9b on two side surfaces of the main body 3, and also makes it possible to surface mount the capacitor 1 on either the top surface or the bottom surface. Note that, ignoring the reduction in practicality, the external electrode 5 may cover only two surfaces (a combination of the top surface or bottom surface and one side surface), for example.

[0055] The shape, dimensions, and material of the portions on each surface of the external electrode 5 are arbitrary. The planar shape of the portion of the external electrode 5 located on the upper or lower surface of the main body 3 is, for example, rectangular (square in the illustrated example). The planar shape and dimensions of the portion of the external electrode 5 located on the side surface of the main body 3 are, for example, rectangular with the same lateral length as the portion located on the upper or lower surface. The thickness of the external electrode 5 (film) may be, for example, thicker than the thicknesses of the internal electrode 9 and the dummy electrode 19.

[0056] (2. Specific Configuration of External Electrode) The specific configuration of the external electrode 5 with respect to the volume fraction of the oxide phase, etc. will be described. As described above, in the capacitor 1 according to the first embodiment, one external electrode 5 overlaps two side surfaces of the main body portion 3. However, for convenience, the following description will focus only on the portion of one external electrode 5 that overlaps one side surface. On this premise, the number of each portion, etc. may be mentioned. Furthermore, the requirements with respect to the volume fraction of the oxide phase, etc. for one external electrode 5 only need to be met for one side surface. However, they may also be met for the entire two side surfaces.

[0057] As explained with reference to FIG. 1 in the description of the overview of the embodiment, the requirements regarding the volume fraction of the oxide phase, etc., only need to be met within the range of the length of the partial edge portion 9c (target portion 5c of the external electrode 5) in the direction along the outer periphery of the main body portion 3 (direction D1 or D2). However, in the first embodiment, the length of the external electrode 5 and the length of the partial edge portion 9c are approximately equal in the above direction. In other words, the entire portion of the external electrode 5 located on one side surface may be considered as the target portion 5c. Therefore, reference to the target portion 5c may be omitted.

[0058] (2.1. Oxide Phase) Figure 4 is an enlarged view of region R4 in Figure 3. As shown in this figure, the external electrode 5 has a laminated structure consisting of a first metal layer 23 and a second metal layer 25. The first metal layer 23 is in close contact with (or directly overlaps with) the outer surface (e.g., side surface) of the main body portion 3. The second metal layer 25 is overlapped on the side surface of the main body portion 3 from above the first metal layer 23. From another perspective, the second metal layer 25 is in close contact with the outer surface of the first metal layer 23.

[0059] Figure 5 is a view of a portion of the area shown in Figure 4 from the +D1 side. In other words, Figure 5 is a view of the external electrode 5 located on the +D1 side and the +D2 side and its surroundings as viewed in the direction indicated by arrow a1 in Figure 1. The second metal layer 25 is omitted from Figure 5. Also, the internal electrode 9 (more specifically, the partial edge portion 9c of the lead electrode 9b) and the dummy electrode 19, which are covered by the external electrode 5 and cannot be seen, are shown by dotted lines. Note that Figure 4 is a cross-sectional view taken along line IV-IV in Figure 5.

[0060] 4 and 5 , the first metal layer 23 does not extend continuously (in other words, without gaps) across the region where the external electrodes 5 are arranged, but rather extends discontinuously. In other words, a non-arrangement region A1 of the first metal layer 23 is formed on the side surface of the main body portion 3. The non-arrangement region A1 is mainly located on the side surface of the effective portion 13. In the non-arrangement region A1, the second metal layer 25 is in close contact with the side surface of the main body portion 3, not with the first metal layer 23.

[0061] 6 is an enlarged view of region R6 in FIG. 4. As shown in this figure, the outer surface of the first metal layer 23 (the surface opposite to the main body portion 3) is oxidized. From another perspective, the first metal layer 23 has a first material layer 23a and a first oxide layer 23b covering the first material layer 23a. The material of the first oxide layer 23b is an oxide of the material that constitutes the first material layer 23a.

[0062] Similar to the first metal layer 23, the outer surface of the second metal layer 25 is oxidized. From another perspective, the second metal layer 25 has a second material layer 25 a and a second oxide layer 25 b covering the second material layer 25 a. The material of the second oxide layer 25 b is an oxide of the material that constitutes the second material layer 25 a.

[0063] As described above, the non-disposition area A1 of the first metal layer 23 is located mainly on the side surface of the effective portion 13 among the side surfaces of the main body portion 3. Therefore, the area ratio of the first oxide layer 23b on the side surface of the effective portion 13 is smaller than the area ratio of the first oxide layer 23b on the side surface of the cover 15. As a result, in the external electrode 5, the volume ratio of the oxide phase in the first portion 5a is smaller than the volume ratio of the oxide phase in the second portion 5b.

[0064] Here, the volume ratio of the oxide phase in the first portion 5a is the ratio of the volume of the oxide phase present in the first portion 5a to the volume of the external electrode 5 present in the first portion 5a, and the volume ratio of the oxide phase in the second portion 5b is the ratio of the volume of the oxide phase present in the second portion 5b to the volume of the external electrode 5 present in the second portion 5b. Furthermore, the area ratio of the first oxide layer 23b on the side surface of the effective portion 13 is the ratio of the area of ​​the first oxide layer 23b present in the first portion 5a to the area of ​​the first portion 5a, and the area ratio of the first oxide layer 23b on the side surface of the cover 15 is the ratio of the area of ​​the first oxide layer 23b present in the second portion 5b to the area of ​​the second portion 5b.

[0065] For ease of explanation, the first material layer 23 a and the first oxide layer 23 b are clearly distinguished from each other, but the boundary between them does not have to be clear. From another perspective, the first material layer 23 a may contain an oxide phase, and conversely, the first oxide layer 23 b may contain a phase other than the oxide phase. The same applies to the second material layer 25 a and the second oxide layer 25 b.

[0066] As described above, in the capacitor 1 according to the embodiment, the volume fraction of the oxide phase in the first portion 5a is reduced by making the first metal layer 23 discontinuous on the side surface of the active portion 13. In this case, for example, the volume fraction of the oxide phase in the first portion 5a can be easily reduced while the external electrode 5 has a laminated structure. By making the external electrode 5 have a laminated structure, for example, it is possible to address differences in the functionality required of the external electrode 5 between the inner side and the outer side. For example, the first metal layer 23 may have high adhesive strength to the internal electrode 9 and / or the dielectric layer 7. The second metal layer 25 may have a thickness that can be easily secured in terms of time and / or cost. Examples of the effects of reducing the volume fraction of the oxide phase in the first portion 5a have already been described.

[0067] Making the first metal layer 23 discontinuous in the active portion 13 and / or the cover 15 also provides advantages from different perspectives. For example, making the first metal layer 23 discontinuous increases the surface area of ​​the first metal layer 23 relative to its volume. Therefore, for example, the affinity between the first metal layer 23 and the second metal layer 25 can be improved while reducing the volume of the first metal layer 23. Also, for example, the unevenness caused by the discontinuous first metal layer 23 provides an anchoring effect. For these reasons, for example, the thickness of the external electrode 5 can be ensured by the relatively inexpensive second metal layer 25, while the strength of adhesion of the external electrode 5 to the main body portion 3 can be improved.

[0068] Whether or not the requirement that the volume fraction of the oxide phase in the first portion 5 a be smaller than the volume fraction of the oxide phase in the second portion 5 b is satisfied may be determined by an appropriate method. For example, in an embodiment in which the thicknesses of the first oxide layer 23 b and the second oxide layer 25 b can be considered to be substantially constant, the volume fraction is defined by the area of ​​the first oxide layer 23 b (i.e., the surface area of ​​the first metal layer 23). Therefore, whether or not the above requirement is satisfied may be determined by comparing the area fraction of the first metal layer 23 between the first portion 5 a and the second portion 5 b.

[0069] Here, the area ratio of the first metal layer 23 in the first portion 5a is the ratio of the area of ​​the first metal layer 23 present in the first portion 5a to the area of ​​the first portion 5a, and the area ratio of the first metal layer 23b in the second portion 5b is the ratio of the area of ​​the first metal layer 23 present in the second portion 5b to the area of ​​the second portion 5b.

[0070] In the above case, it may be determined that the above requirement is satisfied if the area ratio of the first metal layer 23 in the first portion 5a is somewhat smaller than the area ratio of the first metal layer 23 in the second portion 5b. However, taking into consideration measurement errors and the like, it may also be determined that the above requirement is satisfied when the area ratio of the former is 0.95 or less, 0.90 or less, or 0.80 or less relative to the area ratio of the latter. The area ratio may be determined based on the manufacturing process, or may be determined by analyzing the external electrode 5 after manufacturing. In the latter case, the area ratio may be determined, for example, by imaging and analyzing a mirror-polished surface or cross section of the external electrode 5.

[0071] Even when the magnitude relationship of the volume proportions of the oxide phase is not specified by the area proportion of the first oxide layer 23b, the magnitude relationship may be determined based on the manufacturing process or by analyzing the external electrode 5 after manufacturing. In the latter case, for example, an appropriate analytical device that performs qualitative and quantitative analysis of materials may be used. Measurement by the analytical device may be either a physical method or a chemical method, and may be either destructive or non-destructive. Furthermore, the measurement may be performed on the entire amount of each portion (5a and 5b) or on multiple extracted portions of each portion.

[0072] In addition, when the boundary between the first portion 5a and the second portion 5b is unclear, the volume proportions of the oxide phases in both portions may be compared by excluding the unclear portion to the minimum necessary size.

[0073] (2.2. Pattern of First Metal Layer) The specific pattern for making the first metal layer 23 discontinuous is arbitrary. In the example shown in FIG. 5 , the first metal layer 23 has, in the effective portion 13, a plurality of extending portions 23e extending along the D2 direction (a direction intersecting the stacking direction of the dielectric layers 7 and the internal electrodes 9). The positions of the plurality of extending portions 23e in the D3 direction (the stacking direction of the dielectric layers 7 and the internal electrodes 9) are different from one another. In other words, the plurality of extending portions 23e are spaced apart from one another in the D3 direction. This makes the first metal layer 23 discontinuous in the D3 direction.

[0074] At least one of the multiple extending portions 23e (all of them in the example of FIG. 5) has a discontinuity A3 midway in the D2 direction. From another perspective, the extending portion 23e has multiple separating portions 23f that are spaced apart from each other in the D2 direction. In other words, the first metal layer 23 has multiple separating portions 23f that are spaced apart from each other in the D2 and D3 directions. As a result, the first metal layer 23 is discontinuous not only in the D3 direction but also in the D2 direction.

[0075] The lumped portion of the first metal layer 23 (separation portion 23f in the illustrated example) may be single crystal or polycrystalline. In other words, in the former case, separation portion 23f may be formed by crystals growing in an island shape. Although not specifically illustrated, the island-shaped crystals may be even smaller than separation portion 23f in the illustrated example, and may not fit the concept of a portion obtained by dividing extension portion 23e in the length direction. For example, the grain size of the island-shaped crystals (in other words, crystal grains) may be smaller than the thickness of internal electrode 9. Note that, for convenience, in the description of the embodiments, separation portion 23f may be assumed to be polycrystalline unless otherwise specified.

[0076] The specific positions, shapes, and dimensions of the multiple extending portions 23e and the multiple separating portions 23f are arbitrary. In the example of Fig. 5, the extending portion 23e extends along a partial edge portion 9c (an edge portion exposed from the effective portion 13) of the internal electrode 9 while covering the partial edge portion 9c. Also, as shown in Figs. 4 and 5, the partial edge portion 9c has a non-exposed portion 9d (reference numeral shown in Fig. 4) that is not exposed from the side surface of the effective portion 13. A discontinuity A3 of the extending portion 23e overlaps the non-exposed portion 9d when viewed in the D1 direction (the normal direction of the first portion 5a).

[0077] 5, the shape of the extension portion 23e and the shape of the separation portion 23f are formed in an elongated shape extending with a generally constant width (length in the D3 direction). Unlike the illustrated example, the shape of the separation portion 23f (or the extension portion 23e) may be an ellipse with the D2 direction as the longitudinal direction. Furthermore, the shape of the separation portion 23f may be a shape in which the longitudinal direction cannot be defined (for example, a circle), or a shape with the D3 direction as the longitudinal direction.

[0078] When the extending portion 23e (or the separating portion 23f) extends in the D2 direction, it is sufficient that the maximum length in the D2 direction is somewhat longer than the maximum length in the D3 direction, although the former may be two or more times or five or more times the latter.

[0079] Furthermore, when the first metal layer 23 has a plurality of extending portions 23 e at different positions in the D3 direction (or when the plurality of extending portions 23 e are spaced apart in the D3 direction), the plurality of extending portions 23 e do not have to be completely spaced apart from one another. For example, when the extending portions 23 e (or the separating portions 23 f) are elliptical as described above, the wide portions of adjacent extending portions 23 e (separating portions 23 f) may be connected to one another.

[0080] The number of interruptions A3 in one extending portion 23e is arbitrary, and may be one (as in the illustrated example) or two or more. The length of the interruptions A3 in the direction D2 is also arbitrary. For example, in one extending portion 23e, the total length of one or more interruptions A3 may be shorter than the total length of the uninterrupted portions of the extending portion 23e.

[0081] As described above, in the first embodiment, one external electrode 5 overlaps two side surfaces of the effective portion 13, and is fixed at the two side surfaces to partial edge portions 9c of the internal electrode 9. Two extension portions 23e connected to the same internal electrode 9 and located on two side surfaces may be connected to each other (see the first, third, and fifth extension portions 23e from the top in Figure 5), or may not be connected to each other (see the other extension portions 23e in Figure 5).

[0082] The number and width of the extending portions 23e and the number and length of the interruptions A3 may be set more specifically so as to realize, for example, an example of the coverage value of the first metal layer 23 described in the examples described later. Specifically, the ratio of the area of ​​the side surface of the effective portion 13 covered by the first portion 5a (first region) to the area of ​​the first region covered by the first metal layer 23 may be set to, for example, 50% to 95%. The number and width of the extending portions 23e and the number and length of the interruptions A3 may then be set so as to realize this area ratio.

[0083] (2.3. Materials and Dimensions of the First Metal Layer and the Second Metal Layer) The thickness of the first metal layer 23 and the second metal layer 25 is arbitrary. For example, the thickness of the first metal layer 23 (e.g., the maximum thickness; the same applies hereinafter in this paragraph) may be 0.2 μm or more and 3 μm or less. The thickness of the second metal layer 25 (e.g., the minimum thickness on the first metal layer 23; the same applies hereinafter in this paragraph) may be 2 μm or more and 10 μm or less. The second metal layer 25 may be thicker than the first metal layer 23. For example, the thickness of the second metal layer 25 may be 1.5 times or more or 10 times or more the thickness of the first metal layer 23.

[0084] The material of the first metal layer 23 and the second metal layer 25 is arbitrary. For example, the material of the first material layer 23a and the second material layer 25a or its main component may be a base metal. The base metal may be, for example, Cu, Ni, or an alloy containing at least one of Cu and Ni (e.g., a Cu-Ni alloy). The main component may be, for example, a component that accounts for 60% by mass or more or 80% by mass or more of the material (the same applies to layers other than the first metal layer 23 and the second metal layer 25). When the material is Cu, Ni, or a Cu-Ni alloy, unintentional impurities may be present. The impurities may account for, for example, less than 1% by mass of the material. The material of the first oxide layer 23b and the second oxide layer 25b or its main component may be an oxide of the material exemplified above. For example, the oxide may be Cu, ２ O, CuO, NiO or Ni ２ O ３ It may be.

[0085] The materials or main components of the first metal layer 23 and the second metal layer 25 may be the same or different. The difference in materials may be, for example, based solely on the elemental ratio, or may be based on the grain size of the crystal grains in addition to the elemental ratio (the same applies to layers other than the first metal layer 23 and the second metal layer 25). Even if the elements and grain sizes of the first metal layer 23 and the second metal layer 25 are the same, the presence of the first metal layer 23 and the second metal layer 25 can be confirmed by the first oxide layer 23b in the configuration illustrated in FIG. 6. The material or main component of at least one of the first metal layer 23 and the second metal layer 25 may be the same as or different from the material or main component of the internal electrode 9.

[0086] 7 is an enlarged view of region R7 in FIG. 6. In this figure, crystal grains are depicted for the first metal layer 23 and the second metal layer 25. However, whether or not they are oxide phases is not shown. Furthermore, crystal grains are not depicted for portions other than the first metal layer 23 and the second metal layer 25.

[0087] As shown in this figure, the first metal layer 23 and the second metal layer 25 are made of, for example, polycrystalline materials. That is, the first metal layer 23 has a plurality of first crystal grains 23p, and the second metal layer 25 has a plurality of second crystal grains 25p. The grain sizes of the two may be larger than each other (as in the illustrated example) or may be the same. In the illustrated example, the grain size of the first crystal grains 23p is smaller than the grain size of the second crystal grains 25p.

[0088] The particle size referred to here may be, for example, the circle-equivalent diameter in the cross section (or, from another perspective, a two-dimensional image) of the metal layers (23 and 25). Furthermore, the particle sizes compared between the first metal layer 23 and the second metal layer 25 may be average particle sizes unless otherwise specified. For example, the average particle size may be the particle size at which the area ratio becomes 50% when the areas of the particles in the above-mentioned two-dimensional image are integrated in ascending order of particle size. In other words, the average particle size may be an area-based average value. The particle sizes of the first metal layer 23 and the second metal layer 25 may be determined without distinguishing whether they are oxide phases or not.

[0089] The specific values ​​of the grain size of the first crystal grains 23p and the grain size of the second crystal grains 25p, and the difference between them, are arbitrary. For example, the average grain size of the first crystal grains 23p may be less than 1 μm, more specifically, 0.1 μm or more and less than 1 μm. The average grain size of the second crystal grains 25p may be 1 μm or more, more specifically, 1 μm or more and less than 10 μm. The average grain size of the second crystal grains 25p may be two or more times or five or more times the average grain size of the first crystal grains 23p.

[0090] The grain size may be measured, for example, by mirror-finishing the surface or cross section of the metal layers (23 and 25), appropriately chemically etching the surface to clarify the grain boundaries, and then imaging the mirror surface with an electron microscope. More specifically, for example, the first metal layer 23 is imaged at a scale where the number of first crystal grains 23p is 30 to 50. The second metal layer 25 is imaged at a scale where the number of second crystal grains 25p is 30 to 50. The two scales may be different. Then, known image processing is performed on the image of each metal layer to calculate the circle-equivalent diameter. Multiple images may be taken until the variation due to the imaging position converges, and the average value of the average grain size may be calculated.

[0091] Unlike the above, there are cases where it is desired to confirm the presence of the first metal layer 23 and the second metal layer 25 by identifying the presence of regions with different crystal grain sizes. In such cases, for example, in an embodiment where the difference in grain size between the first crystal grains 23p and the second crystal grains 25p is large as shown in FIG. 7 , the presence of the difference in grain size can be identified by visual inspection of the image, and thus the presence of the first metal layer 23 and the second metal layer 25 can be confirmed. In other embodiments, for example, images of multiple consecutive regions can be taken while appropriately changing the scale so that the number of crystal grains included is 30 to 50, and the grain size (circle equivalent diameter) of each crystal grain can be measured. Then, the presence of the first metal layer 23 and the second metal layer 25 can be confirmed by analyzing the change in grain size of crystal grains located on a predetermined straight line spanning the multiple regions. For example, when the moving average of the particle sizes of five or ten consecutive crystal grains along a straight line is calculated, the presence of the first metal layer 23 and the second metal layer 25 can be confirmed when the particle size at the peak (second metal layer 25) is more than two or five times the particle size at the valley (first metal layer 23).

[0092] (2.4. Other Examples of Specific Electrode Configurations) The following describes other examples of specific configurations of the internal electrode 9 and the external electrode 5. The examples already described and the other examples to be described below may be combined as appropriate.

[0093] (2.4.1. Other Examples of Partial Edge Portions of Internal Electrodes) FIG. 8 shows other examples of the internal electrode 9 and the external electrode 5, and corresponds to FIG.

[0094] In the internal electrode 9, the thickness of the partial edge portion 9c (the portion exposed from the side surface of the effective portion 13) may be thicker than the portion located more inward than the partial edge portion 9c. From another perspective, the exposed area of ​​the partial edge portion 9c may be increased. The first metal layer 23 may cover the entire thickness of the partial edge portion 9c. That is, the bonding area between the partial edge portion 9c and the first metal layer 23 may be expanded in the thickness direction (direction D3) of the internal electrode 9 compared to the embodiment of FIG. 4 . Note that, hereinafter, the partial edge portion 9c that is thickened as described above may be referred to as the expanded edge portion 9e.

[0095] In the illustrated example, only two types of edge portions are shown as edge portions constituting the partial edge portion 9c: the extended edge portion 9e and the previously described non-exposed portion 9d. However, three types of edge portions, including these edge portions and an edge portion having the same thickness as the inner portion of the internal electrode 9 (see FIG. 4 ; hereinafter referred to as the “normal edge portion 9f”), may be provided as appropriate. For example, embodiments other than those shown in FIGS. 4 and 9 include an embodiment in which the above three types of edge portions are provided, an embodiment in which the normal edge portion 9f and the extended edge portion 9e are provided, an embodiment in which only the normal edge portion 9f is provided, and an embodiment in which only the extended edge portion 9e is provided. In an embodiment in which both the normal edge portion 9f and the extended edge portion 9e are provided, the two may be provided on different partial edge portions 9c or on the same partial edge portion 9c.

[0096] The specific shape and dimensions of the extended edge portion 9e are arbitrary. In the illustrated example, the extended edge portion 9e is gradually thickened by equal amounts on both the top and bottom sides as it moves outward (toward the external electrode 5). Other examples of shapes include a shape that thickens only upward or downward, a shape that thickens on both the top and bottom sides but with a greater thickness on one side than on the other, and a shape that thickens not gradually but creates a step and / or a shape that bends the edge of the internal electrode 9. The thickness (e.g., maximum thickness) of the extended edge portion 9e may be, for example, 1.2 times or more, 1.5 times or more, or 2 times or more the thickness of the inner portion of the internal electrode 9.

[0097] (2.4.2. Other Examples of Stacked Structure of External Electrodes) The external electrode 5A shown in FIG. 8 is obtained by adding a third metal layer 27 and a fourth metal layer 29 to the external electrode 5 shown in FIG. 4 . The third metal layer 27 and the fourth metal layer 29 contribute to, for example, reducing solder erosion of the second metal layer 25, reducing oxidation of the second metal layer 25, and / or improving the bonding strength to a bonding material (e.g., solder). Only one of the third metal layer 27 and the fourth metal layer 29 may be provided, or another metal layer may be provided. The materials and thicknesses of the third metal layer 27 and the fourth metal layer 29 may be appropriately set depending on the purpose of these layers. For example, in the embodiment in which the first metal layer 23 and the second metal layer 25 are made of Cu as described above, the third metal layer 27 may be made of Ni, and the fourth metal layer 29 may be made of Sn.

[0098] 8, the outer electrode 5A is combined with an inner electrode 9 having an extended edge portion 9e and an unexposed portion 9d, although it is clear that the outer electrode 5A may be combined with an inner electrode 9 that does not have the extended edge portion 9e and / or the unexposed portion 9d.

[0099] (2.4.3. Other Examples of Patterns of First Metal Layer) FIG. 9 is a diagram showing another example of the pattern of the first metal layer 23, and corresponds to FIG.

[0100] 9, the extending portion 23e does not have the gap A3. In other words, the first metal layer 23 is discontinuous in the direction D3 (the stacking direction) but is continuous in the direction D2 (the direction intersecting the stacking direction). Furthermore, the partial edge 9c of the internal electrode 9 does not have an unexposed portion 9d.

[0101] 9 may be a normal edge portion 9f (FIG. 4) or an extended edge portion 9e (FIG. 8), or a combination thereof. Also, depending on the method for forming the pattern of the first metal layer 23 (described later), the first metal layer 23 in the pattern shown in FIG. 9 may be combined with a non-exposed portion 9d.

[0102] (3. Manufacturing Method of Capacitor) (3.1. Manufacturing Procedure of the Entire Capacitor) The manufacturing method of the capacitor 1 may be various methods. For example, the outline of the manufacturing procedure may be the same as a known procedure. An example is shown below.

[0103] First, ceramic green sheets that will become the dielectric layers 7 and insulating layers 17 are prepared. Next, a conductive paste that will become the internal electrodes 9 or dummy electrodes 19 is applied (e.g., printed) to the ceramic green sheets. Next, the ceramic green sheets are stacked to prepare a laminate that will become the main body portion 3. Note that the stacking of the laminate that will become the active portion 13 and the stacking of the portion that will become the cover 15 on the laminate may be performed together or separately.

[0104] The process up to the production of the laminate is carried out, for example, on a mother substrate the size of which will be used to produce a large number of main body portions 3. After the laminate is produced, the mother substrate including the laminate is diced (e.g., cut) into pieces each having a size roughly corresponding to the size of the main body portion 3. Next, the laminate having the size of the main body portion 3 is fired. After that, a metal film is formed on the main body portion 3, and the external electrodes 5 are formed.

[0105] Degreasing may be performed before firing. Firing may be performed, for example, in a reducing atmosphere. Re-oxidation heat treatment may be performed after firing. Polishing (e.g., barrel polishing) of the main body portion 3 may be performed before and / or after firing. In polishing, for example, the ridges of the main body portion 3 may be chamfered or the side surfaces of the main body portion 3 may be polished. By polishing, partial edge portions 9 c of the internal electrodes 9 and edges of the dummy electrodes 19 may be exposed from the side surfaces of the main body portion 3.

[0106] (3.2. Method of forming a pattern of the first metal layer) Any method may be used to make the first metal layer 23 discontinuous. An example is shown below.

[0107] The first metal layer 23 may be formed by depositing metal by electroless plating or electrolytic plating on the surfaces of the internal electrodes 9 and dummy electrodes 19 that are exposed to the outside of the main body 3 (hereinafter, sometimes referred to as "exposed surfaces"). In this case, the pattern of the first metal layer 23 depends on the patterns of the exposed surfaces of the internal electrodes 9 and dummy electrodes 19. Therefore, by appropriately shaping the patterns of the exposed surfaces of the internal electrodes 9 and dummy electrodes 19 and by preventing the metal deposited on the exposed surfaces from connecting via non-placement areas of the exposed surfaces, the first metal layer 23 can be formed into any pattern.

[0108] 4 and 5, for example, the gaps between the exposed surfaces of the plurality of dummy electrodes 19 in the direction D3 are made smaller than the gaps between the exposed surfaces of the plurality of internal electrodes 9. Then, the plating conditions (e.g., deposition time) are adjusted so that the deposited metal connects between the exposed surfaces of the plurality of dummy electrodes 19 but does not connect between the exposed surfaces of the plurality of internal electrodes 9. In this way, the first metal layer 23 having the plurality of extensions 23e is formed.

[0109] Also, for example, the previously described non-exposed portion 9d is provided on the partial edge portion 9c of the internal electrode 9. That is, the exposed surface of the internal electrode 9 is interrupted halfway. Then, the plating conditions (e.g., deposition time) are adjusted so that the metal deposited on the exposed surface of the internal electrode 9 does not continue beyond the interruption of the exposed surface. This forms an extension portion 23e having an interruption A3. When the non-exposed portion 9d is provided in a position where adjacent extension portions 23e are likely to be connected, the non-exposed portion 9d also makes it difficult for multiple extension portions 23e to be connected to each other.

[0110] Various methods other than those described above are possible for making the first metal layer 23 discontinuous. For example, the first metal layer 23 may be formed through a mask, or the first metal layer 23 may be formed and then etched through a mask. Etching may be performed, for example, by laser processing or blasting. As can be understood from this, the first metal layer 23 does not necessarily have to cover the exposed surface (partial edge portion 9 c) of the internal electrode 9, and does not necessarily have a pattern corresponding to the pattern of the exposed surface of the internal electrode 9. The first metal layer 23 may also be formed by a method other than electroless plating and electrolytic plating (e.g., sputtering).

[0111] When the first metal layer 23 is formed by electroless plating or electrolytic plating, either method may be used. For example, the first metal layer 23 may be formed by electroless plating. Also, the second metal layer 25 may be formed by electrolytic plating. By doing so, for example, the adhesive strength between the internal electrode 9 and the first metal layer 23 can be improved, while ensuring the thickness of the second metal layer 25 in a short time and / or at low cost.

[0112] (3.3. Method of Forming Specific Shape of Internal Electrode) The method of forming the non-exposed portion 9d of the internal electrode 9 (partial edge portion 9c) is arbitrary.

[0113] For example, the non-exposed portion 9 d may be formed by a pattern when a conductive paste that becomes the internal electrode 9 is printed on a ceramic green sheet. That is, in a plan view of the internal electrode 9, the non-exposed portion 9 d may be formed by forming the shape of the partial edge portion 9 c to have a part that is separated from the edge of the dielectric layer 7, rather than forming the shape of the partial edge portion 9 c in a straight line parallel to the edge of the dielectric layer 7.

[0114] And / or, for example, the side surface of the effective portion 13 (dielectric layer 7 (or insulating layer 17)) may be partially removed after (or before) firing to partially expose the partial edge portion 9c. That is, the part of the partial edge portion 9c located in the region of the side surface of the effective portion 13 that has not been removed may be the non-exposed portion 9d. The removal may be performed by, for example, blasting or laser processing, or a mask may be used.

[0115] As described above, barrel polishing may be performed before and / or after firing. In barrel polishing, the chip (main body portion 3) is housed in a barrel, and polishing is performed by rotating the barrel, etc. Therefore, the ridges of the main body portion 3 are likely to be chamfered, and as a result, the dummy electrodes 19 are more likely to be exposed on the outer surface of the main body portion 3 than the internal electrodes 9. As a result, when the first metal layer 23 is formed by depositing metal on the exposed surfaces of the internal electrodes 9 and dummy electrodes 19, the first metal layer 23 is more likely to spread continuously on the dummy electrodes 19 than on the internal electrodes 9.

[0116] The method for forming the extended edge portion 9e (FIG. 8) of the internal electrode 9 is also arbitrary. For example, the extended edge portion 9e may be formed by stretching and deforming the internal electrode 9 by blasting after (or before) firing. The blasting may also serve as a process for partially removing the side surface of the above-mentioned effective portion 13. Alternatively, the extended edge portion 9e may be formed by thickening only the portion that will become the extended edge portion 9e when applying the conductive paste that will become the internal electrode 9.

[0117] When blasting is performed to partially remove the side surface of the effective portion 13 and / or form the extended edge portion 9e, the material of the projected powder and the direction in which the powder is projected may be arbitrary. For example, the projection direction may be inclined in the direction D3 with respect to the normal to the side surface of the effective portion 13. In this case, for example, it is easy to extend and deform the edge portion of the internal electrode 9 in the direction D3. The specific magnitude of the inclination angle may be arbitrary.

[0118] (3.4. Method of reducing the volume fraction of the oxide phase) As can be understood from the above explanation, in the external electrode 5, a method of making the volume fraction of the oxide phase in the first portion 5a (portion covering the effective portion 13) smaller than the volume fraction of the oxide phase in the second portion 5b (portion covering the cover 15) may be achieved by making the area fraction of the first metal layer 23 in the first portion 5a smaller than the area fraction of the first metal layer 23 in the second portion 5b. As already described, a method of reducing the area fraction of the first metal layer 23 in the first portion 5a is achieved by forming the first metal layer 23 into an appropriate pattern.

[0119] The first oxide layer 23b is formed, for example, by exposing the first metal layer 23 to an oxidizing atmosphere after the first metal layer 23 is formed from the material of the first material layer 23a and before the second metal layer 25 is formed. At this time, the thickness of the first oxide layer 23b (or, from another perspective, the volume fraction of the oxide phase in the first metal layer 23) may be adjusted by adjusting the time of exposure to the oxidizing atmosphere, etc. Furthermore, the volume fraction of the oxide phase may be adjusted using an oxidizing agent or a reducing agent.

[0120] Similarly, the second oxide layer 25b is formed by forming the second metal layer 25 using the material of the second material layer 25a and then exposing the second metal layer 25 to an oxidizing atmosphere. When the third metal layer 27 is provided, the thickness of the second oxide layer 25b (or, from another perspective, the volume fraction of the oxide phase in the second metal layer 25) may be adjusted by adjusting the time for which the second metal layer 25 is exposed to the oxidizing atmosphere. The volume fraction of the oxide phase may also be adjusted by using an oxidizing agent or a reducing agent.

[0121] The method for making the volume fraction of the oxide phase in the first portion 5 a smaller than the volume fraction of the oxide phase in the second portion 5 b is not limited to adjusting the area fraction of the first metal layer 23. From another perspective, the first metal layer 23 does not need to extend discontinuously, and may extend without gaps.

[0122] For example, the first metal layer 23 may be formed without any gaps over the entire area of ​​the side surface of the main body portion 3 that is to be covered by the external electrode 5. After the first oxide layer 23b is formed, and before the second metal layer 25 is formed, the first oxide layer 23b may be removed from part or all of the side surface of the effective portion 13 in the above-mentioned area using a reducing agent.

[0123] Alternatively, for example, the first portion 5a may be formed after the second portion 5b is formed. Then, after the second portion 5b is formed and before the first portion 5a is formed, a heat treatment may be performed to form an oxide phase in the region of the second portion 5b on the main body 3 side. In this case, for example, the oxide phase in the second portion 5b improves the bonding strength of the second portion 5b to the main body 3.

[0124] (4. Configuration of Capacitor According to Other Embodiments) FIG. 10 is a perspective view of a capacitor 201 according to a second embodiment. In the following description, FIG. 3 according to the first embodiment may be referred to as a cross-sectional view taken along line IIIB-IIIB in FIG. 10. However, reference numerals 1 and 3 in FIG. 3 are replaced with reference numerals 201 and 203. It should also be noted that the specific dimensions of each part in FIG. 3 do not necessarily match those in FIG. 10.

[0125] Generally speaking, capacitor 201 differs from capacitor 1, which is a four-terminal type, in that it is a two-terminal type. In other words, capacitor 201 has the same basic configuration for functioning as a capacitor as capacitor 1, and is also similar to capacitor 1 in that the volume fraction of the oxide phase in first portion 5a is smaller than the volume fraction of the oxide phase in second portion 5b. Specifically, this is as follows.

[0126] The shape of the main body 203 (or the capacitor 201) is, for example, a roughly rectangular parallelepiped. For example, the height (length in the D3 direction) of this rectangular parallelepiped may be equal to or smaller than the width (length in the D2 direction) (as in the illustrated example). The length (D1 direction) of the rectangular parallelepiped is, for example, greater than the width. The dimensions of the main body 203 are arbitrary. Examples of relatively small dimensions include a length of 0.4 mm or more and 3.2 mm or less, and a width and height of 0.2 mm or more and 2.5 mm or less. The external electrode 5 is generally a layer covering the longitudinal ends of the main body 203 over five faces of the rectangular parallelepiped.

[0127] Similar to the first embodiment (see FIG. 3 ), the main body 203 has an effective portion 13 and a cover 15. The effective portion 13 is configured by alternately stacking dielectric layers 7 and internal electrodes 9. The cover 15 has at least one insulating layer 17 and at least one dummy layer 21. The dummy layer 21 includes a plurality of dummy electrodes 19.

[0128] However, the position and shape of the internal electrodes 9 in a plan view differ from those in the first embodiment. Specifically, for example, in a plan view, the shape of the internal electrodes 9 is generally a rectangle having four sides parallel to the four sides of the rectangular main body portion 203 (dielectric layer 7). Of the four sides of the internal electrode 9, two long sides and one short side are located inside the side surface of the main body portion 203 (not exposed). The remaining short side is exposed from the side surface on the +D1 side or -D1 side of the main body portion 203 and connected to the external electrode 5 on the +D1 side or -D1 side. The internal electrodes 9 connected to different external electrodes 5 are alternately stacked. The region of each internal electrode 9 that overlaps with another internal electrode 9 in a planar perspective view is the electrode main body 9a. The portion extending from the electrode main body 9a to the external electrode 5 is the extraction electrode 9b.

[0129] The position and shape of the dummy electrodes 19 in a plane may be different from those in the first embodiment. Specifically, for example, in a plan view, each dummy layer 21 has two dummy electrodes 19 at both ends in the longitudinal direction of the main body portion 203. The dummy electrodes 19 are rectangular across the entire width (length in the D2 direction) of the main body portion 203, and are exposed, for example, from the side surface on the +D1 side or −D1 side of the main body portion 203 and also from the side surface on the +D2 side and the −D2 side.

[0130] As explained with reference to FIG. 1 in the description of the overview of the embodiment, the requirements regarding the volume fraction of the oxide phase, etc., only need to be met within the length range of the partial edge portion 9c of the internal electrode 9 (the target portion 5c of the external electrode 5). Therefore, with regard to the above requirements, the portions of the external electrode 5 that cover the upper and lower surfaces, the +D2 side surface, and the −D1 side surface of the main body portion 203 may be ignored. Furthermore, when focusing on the portion of the external electrode 5 that covers the side surface on the +D1 side (or the −D1 side), the portion that covers the so-called side margin portion from the +D1 side (or the −D1 side) may also be ignored. The side margin portion is the portion of the main body portion 203 that extends from the edge portion on the +D2 side (or the −D2 side) of the internal electrode 9 to the side surface on the +D2 side (or the −D2 side) of the main body portion 203.

[0131] Although not specifically shown, another example of the capacitor configuration will be given below.

[0132] The capacitor may have an exterior resin that covers the entire structure illustrated in Fig. 1 or 10, and lead wires that are connected to the external electrodes 5 and extend from the exterior resin. From another perspective, the capacitor may be a through-hole mount type rather than a surface mount type. In such an embodiment, one external electrode 5 may cover only one side surface.

[0133] Two types of internal electrodes 9 connected to different external electrodes 5 may be alternately stacked two by two, rather than one by one. In this case, for example, the thickness of the dielectric layer 7 between the mutually opposing internal electrodes 9 connected to the same external electrode 5 may be thinner than the thickness of the dielectric layer 7 between the mutually opposing internal electrodes 9 connected to different external electrodes 5. As can be understood from this, the multiple dielectric layers 7 do not need to have the same shape and size.

[0134] Furthermore, two types of internal electrodes 9 connected to different external electrodes 5 do not have to face each other. For example, two types of internal electrodes 9 connected to different external electrodes 5 may be provided in the same layer, and an internal electrode 9 facing the two types of internal electrodes 9 may be provided, thereby forming a circuit in which two parallel plate capacitors are connected in series. Also, a circuit in which three or more parallel plate capacitors are connected in series may be formed.

[0135] In the second embodiment, the side margin portion was mentioned. The side margin portion is configured, for example, by a portion of the dielectric layer 7 that extends further toward the +D2 side or the −D2 side than the internal electrode 9. However, the side margin portion may also be configured by overlapping another dielectric layer on the +D2 side or the −D2 side of the laminate configured by the dielectric layer 7. From another perspective, the main body portion 203 does not need to have a laminated structure in its entirety.

[0136] 11 is a table showing the results of examining the characteristics of a prototype capacitor according to the embodiment (more specifically, the capacitor 201 according to the second embodiment). This figure shows that, for example, by making the first metal layer 23 discontinuous and reducing the volume fraction of the oxide phase in the first portion 5a, it is possible to achieve both improved adhesion strength and reduced ESR. Specifically, this is as follows.

[0137] In this figure, "No." denotes an identification number assigned to each example and comparative example. As will be understood from the explanation below, No. 1 to No. 6 are examples, and No. 7 is a comparative example.

[0138] With the exception of No. 8, the "first metal layer coverage" indicates the area ratio (%) of the first metal layer 23 in the region of the side surface of the effective portion 13 where the target portion 5c of the external electrode 5 should overlap (i.e., the region where the first portion 5a should be formed). The "second metal layer coverage" indicates the area ratio of the second metal layer 25 in the above region. Note that, for convenience, hereinafter, the above area ratio may be simply referred to as the area ratio on the side surface of the effective portion 13, without mentioning that it is in the region where the target portion 5c should overlap.

[0139] "Electrode peeling (number of pieces)" indicates the number of pieces in which the external electrodes 5 peeled off in an experiment on 100 samples, expressed as a fraction. "ESR (mΩ)" indicates the measured ESR value.

[0140] 11, in all of the examples (No. 1 to No. 8), the first metal layer 23 and the second metal layer 25 were each formed over the entire area of ​​the side surface of the cover 15 that would overlap the target portion 5c of the external electrode 5. That is, in the second portion 5b, the area ratio of each layer is 100%, and from another perspective, the area ratios of the two layers are the same.

[0141] 11 , in Examples (No. 1 to No. 6), the area ratio of the first metal layer 23 to the side surface of the effective portion 13 is less than 100% (specifically, 40% to 95%). Also, the area ratio of the second metal layer 25 to the side surface of the effective portion 13 is 80% to 100%. From another perspective, the area ratio of the first metal layer 23 in the first portion 5a is smaller than the area ratio of the second metal layer 25.

[0142] In the second portion 5b, the area proportions of the first metal layer 23 and the second metal layer 25 are the same, so in examples (No. 1 to No. 6) in which the area proportion of the first metal layer 23 in the first portion 5a is smaller than the area proportion of the second metal layer 25, the volume proportion of the oxide phase in the first portion 5a is smaller than the volume proportion of the oxide phase in the second portion 5b.

[0143] In No. 7 (comparative example), the area ratio of each of the first metal layer 23 and the second metal layer 25 on the side surface of the effective portion 13 is 100%. From another perspective, in the first portion 5a, as in the second portion 5b, the area ratios of the two layers are the same. Therefore, the volume ratio of the oxide phase in the first portion 5a is the same as the volume ratio of the oxide phase in the second portion 5b.

[0144] In No. 8, the volume fraction of the oxide phase is increased by subjecting the first metal layer 23 to an oxidation treatment (a treatment not performed in Nos. 1 to 7) with the intention of forming the first metal layer 23 over a relatively wide area on the side surface of the effective portion 13. As a result, in No. 8, the volume fraction of the oxide phase in the first portion 5 a and the second portion 5 b is larger than in the other examples (Nos. 1 to 7).

[0145] The first metal layer 23 is formed by electroless plating, and the second metal layer 25 is formed by electroless plating. In Nos. 1 to 8, the second metal layers 25 are intended to have the same thickness. In Nos. 1 and 2, the area ratio of the second metal layer 25 does not reach 100% due to the small area ratio of the first metal layer 23.

[0146] In the experiment to determine whether electrode peeling occurs, a force of 5 N was applied to capacitor 201 mounted on a circuit board in direction D2 (direction along the surface of the circuit board) to check whether external electrode 5 peels off. ESR was determined based on impedance measurement at 1 MHz.

[0147] The specifications of the capacitor 201 used in the experiment are as follows: Length in the D1 direction: 1.0 mm Length in the D2 and D3 directions: 0.5 mm Thickness of the cover 15 (D3 direction): 30 μm Width of the side margin portion (D2 direction): 30 μm Thickness of the dielectric layer 7: 1.0 μm Number of layers of the internal electrode 9: 20

[0148] The number of cases in which electrode peeling occurred was 0 / 100 when the coverage of the first metal layer 23 was 40% or more and 80% or less (Nos. 1 to 5), and 1 / 100 when it was 95% (No. 6). In contrast, when the coverage of the first metal layer 23 became 100%, the number of cases in which electrode peeling occurred increased sharply (10 / 100). Therefore, it can be said that when the coverage of the first metal layer 23 was 40% or more and 95% or less (or 40% or more and 80% or less), the effect of reducing electrode peeling is easily achieved.

[0149] In the example, as described in the first embodiment, the partial edge 9c of the internal electrode 9 is provided with a non-exposed portion 9d that is not exposed from the side surface of the main body 203, thereby preventing the first metal layer 23 from being deposited, thereby reducing the area ratio of the first metal layer 23 and, consequently, the volume ratio of the oxide phase (first oxide layer 23b). Therefore, when the coverage of the first metal layer 23 is reduced, the volume ratio of the oxide phase with high electrical resistivity is reduced, but the cross-sectional area of ​​the connection between the internal electrode 9 and the external electrode 5 is reduced. As a result, the smaller the coverage of the first metal layer 23, the higher the ESR.

[0150] However, as can be seen from a comparison with No. 8, ESR was reduced compared to when oxidation treatment was performed. On the other hand, in No. 8, the adhesion strength of the external electrode 5 to the main body portion 203 was improved by oxidation treatment, and the number of external electrodes 5 that peeled off was 0 / 100. Therefore, it can be said that by reducing the area proportion of the first metal layer 23 in the effective portion 13, it is possible to improve adhesion strength without performing oxidation treatment, thereby achieving both improved adhesion strength and reduced ESR.

[0151] An example of the coverage range of the first metal layer 23 is 40% to 95%, which is the range in the embodiment. Furthermore, from the viewpoint of a range in which no peeling occurs, 40% to 80% is also an example. Since the ESR roughly doubles when the coverage of the first metal layer 23 increases from 50% to 40%, from this viewpoint, 50% to 95% is an example. An overlapping portion of the previous two viewpoints is 50% to 80%.

[0152] 11 is based on the capacitor 201 according to the second embodiment and on a sample of the capacitor 201 having specific specifications. However, it is clear that within the above range, a better effect can be obtained, even if it is not the best effect.

[0153] (6. Summary of the embodiment) As described above, the capacitor 1 (or 201) has an effective portion 13, a cover 15, and an external electrode 5. The effective portion 13 has dielectric layers 7 and internal electrodes 9 that are alternately stacked. The cover 15 overlaps the effective portion 13 in the stacking direction (D3 direction) of the dielectric layers 7 and the internal electrodes 9. The external electrode 5 covers the side surfaces of the effective portion 13 and the cover 15 along the D3 direction and is connected to a partial edge portion 9c that is a part of the outer edge of the internal electrode 9. In the portion of the external electrode 5 (target portion 5c) that extends in the D3 direction with the length of the partial edge portion 9c as its width, the portion covering the side surface of the effective portion 13 is referred to as a first portion 5a, and the portion covering the side surface of the cover 15 is referred to as a second portion 5b. In this case, the volume fraction of the oxide phase in the first portion 5a is smaller than the volume fraction of the oxide phase in the second portion 5b.

[0154] In this case, for example, as described in the overview of the embodiment, it is possible to reduce the ESR, achieve both an improvement in the adhesive strength of the external electrode 5 and a reduction in the ESR, and / or stabilize the electrical characteristics.

[0155] The external electrode 5 may have a first metal layer 23 and a second metal layer 25. The first metal layer 23 may be in close contact with the side surfaces of the effective portion 13 and the cover 15. The second metal layer 25 may overlap the first metal layer 23 and the side surfaces of the effective portion 13 and the cover 15. In the first portion 5a, the first metal layer 23 may extend discontinuously. This may form a non-disposition area A1 of the first metal layer 23. The second metal layer 25 may be in close contact with the side surfaces of the effective portion 13 in the non-disposition area A1.

[0156] In this case, for example, according to a typical metal film formation process, there is a high probability that the first oxide layer 23b is formed on the surface of the first metal layer 23. Therefore, by making the first metal layer 23 discontinuous on the side surface of the effective portion 13, the volume fraction of the oxide phase in the first portion 5a can be reduced. This provides the above-mentioned effect of reducing ESR, etc. Furthermore, for example, by making the first metal layer 23 discontinuous, as already mentioned, the bonding strength between the first metal layer 23 and the second metal layer 25 can be improved. As shown with reference to the examples, it is easy to achieve both a reduction in ESR and an improvement in bonding strength.

[0157] The first metal layer 23 and the second metal layer 25 may each be made of a polycrystalline material. The average grain size of the first crystal grains 23p in the first metal layer 23 may be smaller than the average grain size of the second crystal grains 25p in the second metal layer 25.

[0158] In this case, the surface area of ​​the first metal layer 23 is likely to be larger than in a case where the average grain size of the first crystal grains 23p is relatively large (such a case is also included in the technology disclosed herein). As a result, the affinity between the first metal layer 23 and the second metal layer 25 is improved, and the bonding strength between them is likely to be improved. On the other hand, the relatively large average grain size of the second crystal grains 25p can reduce the number of grain boundaries. As a result, for example, the likelihood of moisture penetration from outside can be reduced.

[0159] The ratio of the area of ​​the side surface of the effective portion 13 where the first metal layer 23 covers the first region to the area of ​​the first region covered by the first portion 5a may be 50% or more and 95% or less.

[0160] In this case, for example, as described with reference to FIG. 11, it is easy to achieve both a reduction in ESR and an improvement in adhesive strength.

[0161] When the first portion 5a is viewed in the normal direction, the first metal layer 23 may have a plurality of extending portions 23e extending in a direction intersecting the stacking direction (D3 direction) (D2 direction in FIG. 5) at different positions in the stacking direction (D3 direction). Note that the separating portion 23f may also be regarded as a type of extending portion depending on its shape.

[0162] In this case, for example, the first metal layer 23 and the second metal layer 25 are engaged in the stacking direction, which facilitates improving the bonding strength between them in the D3 direction. Typically, the capacitor 1 (201) often faces the circuit board on which the capacitor 1 is mounted in the D3 direction, which increases the likelihood of the capacitor 1 being peeled off from the circuit board in the D3 direction. Therefore, by improving the bonding strength in the D3 direction, it becomes easier to efficiently improve the strength of the external electrode 5.

[0163] At least one of the plurality of extending portions 23e may have a break A3 midway in the intersecting direction (direction D2 in FIG. 5).

[0164] In this case, for example, the first metal layer 23 and the second metal layer 25 are engaged in two directions, namely, the direction D3 and a direction intersecting the direction D3, which makes it easier to improve the bonding strength in various directions.

[0165] The plurality of extension portions 23 e may extend along the partial edge portions 9 c so as to cover the partial edge portions 9 c of the plurality of internal electrodes 9 .

[0166] In this case, for example, it is easy to ensure the bonding area between the first metal layer 23 and the partial edge portion 9c while making the first metal layer 23 discontinuous. As a result, for example, it is easy to achieve the effect of improving the bonding strength between the internal electrode 9 and the second metal layer 25 by reducing the average particle size of the first metal layer 23. Furthermore, for example, the extension portion 23e can be formed by forming the first metal layer 23 on the partial edge portion 9c by electroless plating or electrolytic plating. In other words, the first metal layer 23 can be made discontinuous easily.

[0167] In at least one of the multiple internal electrodes 9, the partial edge portion 9c may have, midway in the intersecting direction (direction D2 in FIG. 5), a non-exposed portion 9d (FIG. 4) that is not exposed from the side surface of the effective portion 13. The extension portion 23e covering the partial edge portion 9c having the non-exposed portion 9d may have a break A3 at a position overlapping the non-exposed portion 9d.

[0168] In this case, for example, the extension portion 23e can be discontinuous in its extension direction while ensuring a sufficient bonding area between the extension portion 23e and the partial edge portion 9c. Also, for example, the extension portion 23e having the discontinuity A3 can be formed by depositing the first metal layer 23 on the partial edge portion 9c by electroless plating or electrolytic plating. That is, the extension portion 23e can be easily made discontinuous in its extension direction.

[0169] The thickness of the partial edge portion 9c may be thicker than the portion of the internal electrode 9 located inside the partial edge portion 9c.

[0170] In this case, for example, the bonding area between the external electrode 5 (e.g., the first metal layer 23) and the partial edge portion 9c is increased, thereby improving the bonding strength between them. Also, for example, when the side surface of the dielectric layer 7 is removed by blasting to expose the partial edge portion 9c from the side surface of the main body 3, the internal electrode 9 can be stretched and deformed to thicken the partial edge portion 9c while performing the step of exposing it, thereby reducing the likelihood of an increase in the number of processes.

[0171] The effective portion 13 may have a rectangular shape when viewed in the stacking direction (D3 direction). The cover 15 may have four dummy electrodes 19 and an insulating layer 17. The four dummy electrodes 19 may be located at four corners of the effective portion 13 when viewed in the D3 direction. The insulating layer 17 may cover the four dummy electrodes 19 from the side opposite to the effective portion 13. Four external electrodes 5 may be fixed to the four dummy electrodes 19.

[0172] In this case, for example, the strength of adhesion of the external electrode 5 to the main body 3 can be improved. Furthermore, for example, when forming the first metal layer 23 by electroless plating or electrolytic plating, depositing metal on the dummy electrode 19 facilitates forming the first metal layer 23 without gaps on the side surface of the cover 15. Since the dummy electrode 19 is located on a diagonal line of the rectangular main body 3, which makes it easy to ensure the length, the dummy electrode 19 can be easily separated from the electrode main body 9a. Consequently, the influence of the dummy electrode 19 on the characteristics of the effective portion 13 can be easily reduced.

[0173] The technology according to the present disclosure is not limited to the above-described embodiments and may be implemented in various forms.

[0174] For example, the multilayer electronic component is not limited to a capacitor. For example, in a multilayer electronic component, some of the internal electrodes may constitute a capacitor, and other parts of the internal electrodes may constitute an inductor or a resistor. The multilayer electronic component may also constitute an appropriate circuit (e.g., a resonant circuit) as a whole. Furthermore, it is sufficient that at least a part of the multilayer electronic component is constituted by laminating dielectric layers and internal electrodes, and it is not necessary that all or most of the multilayer electronic component is constituted by a laminate.

[0175] From the present disclosure, a concept may be extracted that does not require that the volume fraction of the oxide phase in the first portion 5 a be smaller than the volume fraction of the oxide phase in the second portion 5 b. For example, a concept characterized by the first metal layer 23 extending discontinuously may be extracted, or a concept characterized by the partial edge portion 9 c of the internal electrode 9 being thicker than the inner portion of the internal electrode 9 may be extracted.

[0176] DESCRIPTION OF SYMBOLS 1... Capacitor, 5... External electrode, 5a... First part, 5b... Second part, 7... Dielectric layer, 9... Internal electrode, 9c... Part edge.

Claims

1. A multilayer electronic component comprising: an effective portion having alternately stacked dielectric layers and internal electrodes; a cover overlapping said effective portion in the stacking direction of said dielectric layers and said internal electrodes; and an external electrode covering side surfaces of said effective portion and said cover along said stacking direction and connected to a partial edge portion that is a part of the outer edge of said internal electrode, wherein, in a portion of said external electrode extending in said stacking direction with a width equal to the length of said partial edge portion, a portion covering the side surface of said effective portion is referred to as a first portion and a portion covering the side surface of said cover is referred to as a second portion, wherein the volume fraction of an oxide phase in said first portion is smaller than the volume fraction of an oxide phase in said second portion.

2. A multilayer electronic component as claimed in claim 1, wherein the external electrode has a first metal layer in close contact with a side surface of the effective portion and a side surface of the cover, and a second metal layer overlapping the first metal layer and the side surface of the effective portion and the side surface of the cover, wherein in the first portion, the first metal layer extends discontinuously, thereby forming a non-placement area of ​​the first metal layer, and the second metal layer is in close contact with the side surface of the effective portion in the non-placement area.

3. The multilayer electronic component according to claim 2, wherein the first metal layer and the second metal layer are each composed of a polycrystalline body, and the average grain size of the crystal grains in the first metal layer is smaller than the average grain size of the crystal grains in the second metal layer.

4. A multilayer electronic component according to claim 2 or 3, wherein the ratio of an area of ​​the first metal layer covering the first region to an area of ​​the side surface of the effective portion that is covered by the first portion is 50% or more and 95% or less.

5. A multilayer electronic component according to any one of claims 2 to 4, wherein, when the first portion is viewed in a normal direction thereof, the first metal layer has a plurality of extending portions at mutually different positions in the stacking direction and extending in a direction intersecting the stacking direction.

6. The multilayer electronic component according to claim 5, wherein at least one of the plurality of extending portions has a discontinuity midway in the intersecting direction.

7. The multilayer electronic component according to claim 5 or 6, wherein the plurality of extension portions extend along the partial edge portions so as to cover the partial edge portions of the plurality of internal electrodes.

8. The multilayer electronic component according to claim 7, wherein in at least one of said plurality of internal electrodes, said partial edge portion has a non-exposed portion midway in the intersecting direction that is not exposed from a side surface of said effective portion, and an extension portion covering the partial edge portion having said non-exposed portion has an interruption at a position overlapping said non-exposed portion.

9. The multilayer electronic component according to any one of claims 1 to 8, wherein the thickness of the partial edge portion is greater than that of a portion of the internal electrode located more inward than the partial edge portion.

10. A multilayer electronic component according to any one of claims 1 to 9, wherein the effective portion has a rectangular shape when viewed in the stacking direction, the cover has four dummy electrodes located at the four corners of the effective portion when viewed in the stacking direction, and an insulating layer covering the four dummy electrodes from the opposite side to the effective portion, and the four external electrodes are fixed to the four dummy electrodes.

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