Multilayer ceramic capacitor

Abstract

Provided is a multilayer ceramic capacitor that can suppress breakage of a laminated body while ensuring moisture resistance reliability.　Provided is a multilayer ceramic capacitor 1, wherein an end-surface outer electrode 3 comprises: an electrode body 31 disposed on an end surface C; and a folded-back section 32 that extends from the electrode body 31 in a direction toward the electrode. The folded-back section 32 comprises a base electrode layer 33 that contains copper. The base electrode layer 33 of the folded-back section 32 comprises: a concave section 331 where the thickness of the base electrode layer 33 is less than the thickness of a portion of the base electrode layer 33 adjacent in the direction toward the electrode and no greater than the thickness of a portion of the base electrode layer 33 adjacent in a direction away from the electrode; a first convex section 332 that is a portion of the base electrode layer 33 on the side further away from the electrode than the concave section 331; and a second convex section 333 that is a portion of the base electrode layer 33 on the side further toward the electrode than the concave section.

Description

Multilayer ceramic capacitors

[0001] The present invention relates to a multilayer ceramic capacitor.

[0002] There are multilayer ceramic capacitors that include a laminate formed by stacking dielectric layers and internal electrodes, and external electrodes that include a metal-containing base electrode layer and a plating layer. For example, in the multilayer ceramic capacitor disclosed in Patent Document 1, the external electrodes are provided so as to cover the end faces of the laminate and portions of the main surfaces and side surfaces. The external electrodes have the function of suppressing moisture penetration into the laminate and suppressing mechanical stress acting on the laminate. This allows the multilayer ceramic capacitor to maintain various performance characteristics, such as capacitance characteristics and insulation resistance.

[0003] Japanese Patent Application Laid-Open No. 2020-072246

[0004] However, the underlying electrode layer may cause cracks near the surface of the laminate due to internal stress in the metal. To prevent this problem, for example, the underlying electrode layer may be made of a resin. However, in such an external electrode, the hygroscopicity of the resin may impair the function of preventing moisture from penetrating into the laminate.

[0005] An object of the present invention is to provide a multilayer ceramic capacitor that can prevent damage to the laminate while ensuring moisture resistance reliability.

[0006] In order to solve the above-mentioned problems, the present invention provides a multilayer ceramic capacitor comprising: an inner layer portion including a plurality of dielectric layers and a plurality of internal electrodes; a laminate having first and second main surfaces opposed to each other in a stacking direction; first and second side surfaces opposed to each other in a width direction perpendicular to the stacking direction; and first and second end surfaces opposed to each other in a length direction perpendicular to the stacking direction and the width direction; and external electrodes arranged in pairs on at least either of the side surfaces and the end surfaces, wherein the direction in which the external electrodes arranged in pairs are arranged is defined as an electrode arranging direction, and the direction in which the paired external electrodes approach each other in the electrode arranging direction is defined as an electrode proximity direction, and the direction in which the paired external electrodes are separated from each other is defined as an electrode approaching direction. When the electrode separation direction is taken as the electrode separation direction, the external electrode has a connection portion arranged on one of the side surfaces and the end surface facing the electrode arrangement direction, and a folded portion extending from the connection portion toward the electrode approach direction, and the folded portion has a base electrode layer containing Cu, and the base electrode layer of the folded portion has a recess where the thickness of the base electrode layer is less than the thickness of the base electrode layer in a portion adjacent to the electrode approach direction and is equal to or less than the thickness of the base electrode layer in a portion adjacent to the electrode separation direction, a first convex portion which is a portion of the base electrode layer of the folded portion that is closer to the electrode separation direction than the recess, and a second convex portion which is a portion of the base electrode layer of the folded portion that is closer to the electrode approach direction than the recess.

[0007] According to the present invention, it is possible to provide a multilayer ceramic capacitor that can suppress damage to the laminate while ensuring moisture resistance reliability.

[0008] 1 is a schematic perspective view of a multilayer ceramic capacitor 1 according to an embodiment; FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1; FIG. 3 is a cross-sectional view taken along line III-III of FIG. 1; FIG. 4 is a cross-sectional view taken along line III-III of FIG. 1; FIG. 5 is an enlarged view of a portion V of FIG. 2; and FIG. 6 is an enlarged view of a portion VI of FIG.

[0009] A multilayer ceramic capacitor 1 according to an embodiment of the present invention will now be described with reference to FIGS.

[0010] (Multilayer Ceramic Capacitor 1) As shown in Fig. 1, the multilayer ceramic capacitor 1 is a so-called three-terminal multilayer ceramic capacitor. The multilayer ceramic capacitor 1 includes a laminate 2, a pair of end surface external electrodes 3, and a pair of side surface external electrodes 4. The laminate 2 is substantially rectangular parallelepiped-shaped and has six outer surfaces. As shown in Figs. 2 and 3, the laminate 2 includes an inner layer portion 11 in which dielectric layers 14 and internal electrodes 15 are stacked.

[0011] In this specification, the direction in which the dielectric layers 14 and the internal electrodes 15 are stacked in the multilayer ceramic capacitor 1 is referred to as the stacking direction T. One of the directions perpendicular to the stacking direction T is referred to as the length direction L. The direction perpendicular to both the length direction L and the stacking direction T is referred to as the width direction W.

[0012] Of the six outer surfaces of the laminate 2, a pair of outer surfaces on both sides in the stacking direction T are referred to as the first main surface AA and the second main surface AB, a pair of outer surfaces extending in the stacking direction T and on both sides in the width direction W are referred to as the first side surface BA and the second side surface BB, and a pair of outer surfaces extending in the stacking direction T and on both sides in the length direction L are referred to as the first end surface CA and the second end surface CB. The first main surface AA and the second main surface AB may be collectively referred to as "each main surface A." The first side surface BA and the second side surface BB may be collectively referred to as "each side surface B." The first end surface CA and the second end surface CB may be collectively referred to as "each end surface C."

[0013] In the length direction L, the direction from each end face C toward the center of the length direction L of the laminate 2 is referred to as the "inner length direction L1," and the direction from the center of the length direction L of the laminate 2 toward each end face C is referred to as the "outer length direction L2." In the width direction W, the direction from each side face B toward the center of the width direction W of the laminate 2 is referred to as the "inner width direction W1," and the direction from the center of the width direction W of the laminate 2 toward each side face B is referred to as the "outer width direction W2."

[0014] A pair of end surface external electrodes 3 is provided on each end surface C. A pair of side surface external electrodes 4 is provided on each side surface B.

[0015] In this specification, the direction in which the external electrodes arranged in pairs are lined up is referred to as the “electrode line-up direction.” Within the electrode line-up direction, the direction in which the paired external electrodes approach each other is referred to as the “electrode line-up direction,” and the direction in which the paired external electrodes are separated from each other is referred to as the “electrode line-up direction.”

[0016] The electrode arrangement direction of the end surface external electrodes 3 is referred to as "electrode arrangement direction D1", the electrode approach direction of the end surface external electrodes 3 is referred to as "electrode approach direction D11", and the electrode separation direction of the end surface external electrodes 3 is referred to as "electrode separation direction D12".

[0017] The electrode arrangement direction of the side surface external electrodes 4 is referred to as "electrode arrangement direction D2", the electrode approach direction of the side surface external electrodes 4 is referred to as "electrode approach direction D21", and the electrode separation direction of the side surface external electrodes 4 is referred to as "electrode separation direction D22".

[0018] The electrode arrangement direction D1 of the end surface external electrodes 3 corresponds to the length direction L. In the description of the end surface external electrodes 3, the electrode approach direction D11 corresponds to the inner side L1 in the length direction, and the electrode separation direction D12 corresponds to the outer side L2 in the length direction.

[0019] The electrode arrangement direction D2 of the side surface external electrodes 4 is the width direction W. In the description of the side surface external electrodes 4, the electrode approach direction D21 is the inner width direction W1, and the electrode separation direction D22 is the outer width direction W2.

[0020] A cross section of the laminate 2 parallel to the length direction L and the stacking direction T is referred to as an "LT cross section." A cross section of the laminate 2 parallel to the width direction W and the stacking direction T is referred to as a "WT cross section." A cross section of the laminate 2 parallel to the length direction L and the width direction W is referred to as an "LW cross section."

[0021] 2 shows an LT cross section passing through the center of the width direction W of the laminate 2. Fig. 3 shows a WT cross section passing through the center of the length direction L of the laminate 2. Fig. 4 shows an LW cross section along the internal electrode 15 (more specifically, a side internal electrode 50, which will be described later).

[0022] (Laminate 2) The laminate 2 has an inner layer portion 11 and a pair of outer layer portions 12 arranged on either side of the inner layer portion 11 in the stacking direction T. The laminate 2 preferably has rounded corners and ridges. The corners are portions where three surfaces of the laminate intersect. The ridges are portions where two surfaces of the laminate intersect.

[0023] 2 and 3, the inner layer portion 11 has a plurality of dielectric layers 14 and a plurality of internal electrodes 15. The dielectric layers 14 and the internal electrodes 15 are alternately stacked.

[0024] (Dielectric Layer 14) The dielectric layer 14 is formed of a dielectric ceramic containing, for example, BaTiO3 as a main component. The dielectric ceramic may contain a Mn compound, an Fe compound, a Cr compound, a Co compound, a Ni compound, or the like as a secondary component.

[0025] (Internal electrode 15) The internal electrode 15 is formed of a metal material such as Ni, Cu, Sn, Ag, Pd, an Ag-Pd alloy, or Au. The internal electrode 15 has a plurality of end face internal electrodes 20 and a plurality of side face internal electrodes 50. The end face internal electrodes 20 and the side face internal electrodes 50 are alternately arranged in the stacking direction T. The end face internal electrodes 20 and the side face internal electrodes 50 may be collectively referred to as "internal electrodes 15."

[0026] (End surface internal electrode 20) The end surface internal electrode 20 extends between both end surfaces C in the length direction L of the laminate 2. Each end of the end surface internal electrode 20 in the length direction L is exposed at each end surface C. The end surface internal electrode 20 is spaced a certain distance from both side surfaces B in the width direction W. The end surface internal electrode 20 has a first opposing portion 21 and two first lead portions 22.

[0027] The first opposing portion 21 is a portion of the end face internal electrode 20 that faces the side face internal electrode 50 adjacent to it in the stacking direction T. The first opposing portion 21 is located in the center between the end faces C. Each first lead portion 22 is a portion of the end face internal electrode 20 that is led out from the first opposing portion 21 toward each end face C. Each first lead portion 22 is exposed at each end face C.

[0028] 4 , each end of the side surface internal electrode 50 in the width direction W is exposed to each side surface B. The side surface internal electrode 50 is spaced a certain distance from both end surfaces C in the length direction L. The side surface internal electrode 50 has a second opposing portion 51 and two second lead portions 52.

[0029] The second opposing portion 51 is a portion of the side surface internal electrode 50 that faces the end face internal electrode 20 adjacent to it in the stacking direction T. The second opposing portion 51 is located in the center between the side surfaces B. Each second extraction portion 52 is a portion of the side surface internal electrode 50 that is extracted from the second opposing portion 51 to each side surface B side. Each second opposing portion 51 is exposed to each side surface B.

[0030] The first opposing portion 21 and the second opposing portion 51 may be collectively referred to as "opposing portions 21, 51." The first drawn-out portion 22 and the second drawn-out portion 52 may be collectively referred to as "draw-out portions 22, 52."

[0031] When the internal electrode 15 contains Sn, it is possible to alleviate the electric field concentration at the interface between the internal electrode 15 and the dielectric layer 14, leading to an improvement in high-temperature load reliability. In this case, even if Sn is contained in only one of the internal electrodes, either the end face internal electrode 20 or the side face internal electrode 50, it can sufficiently exhibit its effect.

[0032] (Outer Layer Portion 12) The outer layer portion 12 may be formed of the same material as the dielectric layer 14 of the inner layer portion 11. Note that no inner electrode 15 is disposed in the outer layer portion 12.

[0033] (End surface external electrodes 3) Each end surface external electrode 3 is disposed on a respective end surface C of the laminate 2. A first lead portion 22 is connected to each end surface external electrode 3. Each end surface external electrode 3 covers not only the end surface C but also a portion of the end surface C side of the main surface A and the side surface B. Each end surface external electrode 3 has an electrode main body portion 31 disposed on the respective end surface C, and a folded portion 32 extending from the electrode main body portion 31 toward the electrode approaching direction D11 (inward inward in the longitudinal direction L1).

[0034] The electrode main body portion 31 is disposed on the end face C. The electrode main body portion 31 is connected to the end face internal electrode 20. The folded portion 32 is disposed on the main face A and on the side face B. More specifically, if an imaginary plane extending from the end face C in the stacking direction T and the width direction W is defined as an "imaginary plane VC," the electrode main body portion 31 is a portion of the end face external electrode 3 that is closer to the electrode separating direction D12 than the imaginary plane VC, and the folded portion 32 is a portion of the end face external electrode 3 that is closer to the electrode approaching direction D11 than the imaginary plane VC.

[0035] The end of the folded portion 32 in the electrode approach direction D11 may be referred to as the "folded edge portion 32a." Of the folded portion 32, the portion extending from the electrode main body 31 toward the main surface A may be referred to as the "main surface folded portion 32A," and the portion extending from the electrode main body 31 toward the side surface B may be referred to as the "side surface folded portion 32B."

[0036] The folded portion 32 has, for example, a substantially rectangular cylindrical shape. The main surface folded portion 32A extends over the entire width direction W of the edge portion on the edge face C side of the main surface A. The side surface folded portion 32B extends over the entire height direction T of the edge portion on the edge face C side of the side surface B. The main surface folded portion 32A and the side surface folded portion 32B are continuous with each other.

[0037] However, the configuration of the folded portion 32 is not limited to this. For example, the main surface folded portion 32A does not have to extend over the entire width direction W of the edge portion on the edge face C side of the main surface A. The side surface folded portion 32B does not have to extend over the entire height direction T of the edge portion on the edge face C side of the side surface B. Furthermore, the folded portion 32 only needs to be disposed on at least one of the main surfaces A and the side surfaces B, and does not have to be disposed on all of the main surfaces A and the side surfaces B.

[0038] The end surface external electrode 3 includes a base electrode layer 33 formed in contact with the surface of the laminate 2, a first plating layer 35 disposed on the base electrode layer 33, and a second plating layer 36 disposed on the first plating layer 35. The electrode main body portion 31 and the folded portion 32 each include the base electrode layer 33, the first plating layer 35, and the second plating layer 36.

[0039] The base electrode layer 33 is a baked layer containing, for example, a conductive metal such as Cu (copper) and glass. The first plating layer 35 is, for example, a Ni (nickel) plating layer. The second plating layer 36 is, for example, a Sn (tin) plating layer.

[0040] The first plating layer 35 and the second plating layer 36 each have a substantially uniform thickness. Therefore, the outer surface of the end surface external electrode 3 has substantially the same shape as the outer surface of the base electrode layer 33.

[0041] (Side surface external electrode 4) Each side surface external electrode 4 is disposed on each side surface B of the laminate 2. A second lead portion 52 is connected to each side surface external electrode 4. Each side surface external electrode 4 covers not only the side surface B but also a portion of the side surface B side of the main surface A. Each side surface external electrode 4 has an electrode main body portion 41 disposed on each side surface B and a folded portion 42 extending from the electrode main body portion 41 toward the electrode approach direction D21 (widthwise inward W1).

[0042] The electrode main body 41 is disposed on the side surface B. The electrode main body 41 is connected to the side surface internal electrode 50. The folded portion 42 is disposed on the main surface A. More specifically, if an imaginary plane extending the side surface B in the stacking direction T and the length direction L is defined as an "imaginary plane VB," the electrode main body 41 is a portion of the side surface external electrode 4 that is closer to the electrode separating direction D22 than the imaginary plane VB, and the folded portion 42 is a portion of the side surface external electrode 4 that is closer to the electrode approaching direction D21 than the imaginary plane VB. The folded portion 42 is disposed, for example, on each main surface A. Note that the edge portion of the folded portion 42 in the electrode approaching direction D21 may be referred to as the "folded edge portion 42a."

[0043] Each side surface external electrode 4 includes a base electrode layer 43 formed in contact with the surface of the laminate 2, a first plating layer 45 disposed on the base electrode layer 43, and a second plating layer 46 disposed on the first plating layer 45. The electrode main body portion 41 and the folded portion 42 each include the base electrode layer 43, the first plating layer 45, and the second plating layer 46.

[0044] The base electrode layer 43 is a baked layer containing, for example, a conductive metal such as Cu and glass. The first plating layer 45 is, for example, a Ni plating layer. The second plating layer 46 is, for example, a Sn plating layer.

[0045] The first plating layer 45 and the second plating layer 46 each have a substantially uniform thickness. Therefore, the outer surface of the side surface external electrode 4 has substantially the same shape as the outer surface of the base electrode layer 43.

[0046] The end surface external electrode 3 and the side surface external electrode 4 may be collectively referred to as the "external electrodes 3, 4." The electrode main body portion 31 and the electrode main body portion 41 may be collectively referred to as the "electrode main body portions 31, 41." The folded portion 32 and the folded portion 42 may be collectively referred to as the "folded portion 32, 42." The folded edge portion 32a and the folded edge portion 42a may be collectively referred to as the "folded edge portions 32a, 42a." The base electrode layer 33 and the base electrode layer 43 may be collectively referred to as the "base electrode layer 33, 43." The first plating layer 35 and the first plating layer 45 may be collectively referred to as the "first plating layer 35, 45." The second plating layer 36 and the second plating layer 46 may be collectively referred to as the "second plating layer 36, 46."

[0047] In this specification, the shortest distance from a point on the lower surface (the joint surface with the laminate 2) of the external electrode 3, 4 to the outer surface (the surface away from the laminate 2) of the external electrode 3, 4 is defined as the thickness of the external electrode 3, 4 at that point. The shortest distance from a point on the lower surface (the joint surface with the laminate 2) of the base electrode layer 33, 43 to the outer surface (the joint surface with the first plating layer 35, 45) of the base electrode layer 33, 43 is defined as the thickness of the base electrode layer 33, 43 at that point. The shortest distance from a point on the lower surface (the joint surface with the base electrode layer 33, 43) of the first plating layer 35, 45 to the outer surface (the joint surface with the second plating layer 36, 46) of the first plating layer 35, 45 is defined as the thickness of the first plating layer 35, 45 at that point. The shortest distance from a point on the underside of the second plating layer 36, 46 (the joint surface with the first plating layer 35, 45) to the outer surface of the second plating layer 36, 46 (the outer surface of the external electrode 3, 4) is defined as the thickness of the second plating layer 36, 46 at that point.

[0048] In the multilayer ceramic capacitor 1, the external electrodes 3, 4 are provided with base electrode layers 33, 43 containing a metal (specifically, Cu), respectively. Therefore, the external electrodes 3, 4 can effectively prevent moisture from penetrating into the laminate 2. This ensures the moisture resistance reliability of the multilayer ceramic capacitor 1.

[0049] However, if the external electrodes 3, 4 include the base electrode layers 33, 43 containing metal, there is a risk that cracks will easily occur near the surface of the laminate 2 due to internal stress in the metal of the base electrode layers 33, 43. Such cracks are particularly likely to occur near the portions of the laminate 2 that contact the folded edge portions 32 a, 42 a.

[0050] Therefore, as shown in Figure 5, in the end face external electrode 3, the base electrode layer 33 of the folded portion 32 has a recess 331 which is a portion where the thickness of the base electrode layer 33 is less than the thickness of the base electrode layer 33 in the portion adjacent to the electrode approaching direction D11 side and is equal to or less than the thickness of the base electrode layer 33 in the portion adjacent to the electrode separating direction D12 side, a first convex portion 332 which is a portion of the base electrode layer 33 of the folded portion 32 closer to the electrode separating direction D12 than the recess 331, and a second convex portion 333 which is a portion of the base electrode layer 33 of the folded portion 32 closer to the electrode approaching direction D11 than the recess 331.

[0051] More specifically, in the end face external electrode, the outer surface of the base electrode layer 33 of the folded portion 32 has an uneven shape in which, for example, two arcs that convex in a direction away from the laminate 2 are adjacent in the electrode arranging direction D1. The outer surface of the first convex portion 332 and the outer surface of the second convex portion 333 each have an arc shape that convex in a direction away from the laminate 2. The concave portion 331 is the boundary between the first convex portion 332 and the second convex portion 333.

[0052] With this configuration, the stress of the first convex portion 332 can be concentrated in the concave portion 331, thereby preventing the stress of the first convex portion 332 from being transmitted to the folded edge portion 32a. This reduces the stress on the folded edge portion 32a, thereby reducing the stress acting on the portion of the laminate 2 that contacts the folded edge portion 32a. This prevents damage to the laminate 2 caused by the stress of the end surface external electrode 3.

[0053] Furthermore, the area near the edge of the folded portion 32 is considered to be relatively susceptible to damage. However, with this configuration, the thickness of the second convex portion 333 is greater than the thickness of the concave portion 331. In this case, the thickness of the second convex portion 333 can be maintained at a certain level or more, thereby ensuring the strength of the area near the edge of the folded portion 32. This makes it possible to prevent damage to the external electrode 3.

[0054] 5, the thickness of the recess 331 is indicated as "d11", the thickness of the thickest portion of the first protrusion 332 is indicated as "d12", and the thickness of the thickest portion of the second protrusion 333 is indicated as "d13". Also, in FIG. 5, the internal structure of the laminate 2 is not shown.

[0055] The shape of the outer surface of the base electrode layer 33 disposed on each principal surface A generally corresponds to the shape of the outer surface of the base electrode layer 33 disposed on each side surface B. For this reason, detailed illustration of the shape of the outer surface of the base electrode layer 33 disposed on each side surface B is omitted.

[0056] Furthermore, the thickness of the recess 331 is ¾ or less of the thickness of the thickest portion of the first protrusion 332 .

[0057] According to this configuration, the stress of the first convex portion 332 can be more suitably concentrated on the concave portion 331, and therefore the transmission of stress to the folded edge portion 32a can be more suitably suppressed.

[0058] The thickness of the thickest portion of the second convex portion 333 is smaller than the thickness of the thickest portion of the first convex portion 332 .

[0059] Because the second convex portion 333 is located closer to the folded edge portion 32a than the recessed portion 331, it is considered that the stress of the second convex portion 333 is relatively easily transmitted to the folded edge portion 32a even if the recessed portion 331 is provided in the base electrode layer 33. However, with this configuration, the thickness of the second convex portion 333 can be reduced, thereby reducing the stress of the second convex portion 333. This reduces the stress transmitted to the folded edge portion 32a.

[0060] If the dimension of the underlying electrode layer 33 of the folded portion 32 in the electrode arrangement direction D1 is e, the recess 331 is located at a position where the distance from the end of the folded portion 32 in the electrode separation direction D12 is in the range of 1 / 2e to 9 / 10e.

[0061] According to this configuration, the position of the recess 331 can be made closer to the folded edge 32a in the folded portion 32. This makes it possible for the recess 331 to bear more of the stress of the entire folded portion 32. This makes it possible to more effectively suppress the transmission of stress to the folded edge 32a.

[0062] The thickness of the recess 331 is 0.5 μm or more.

[0063] It is considered that stress tends to concentrate relatively easily in the recess 331, and this configuration can ensure the strength of the recess 331. Therefore, the strength of the folded portion 32 in the end surface external electrode 3 can be ensured.

[0064] The thickness of the first convex portion 332 is 75 μm or less.

[0065] According to this configuration, the thickness of the folded portion 32 can be made relatively small, and therefore the height of the multilayer ceramic capacitor 1 can be prevented from increasing.

[0066] As shown in Figure 6, in the side external electrode 4, the base electrode layer 43 of the folded portion 42 has a recess 431 in which the thickness of the base electrode layer 43 is less than the thickness of the base electrode layer 43 in the portion adjacent to the electrode approaching direction D21 side and is equal to or less than the thickness of the base electrode layer 43 in the portion adjacent to the electrode separating direction D22 side, a first convex portion 432 in which the base electrode layer 43 of the folded portion 42 is closer to the electrode separating direction D22 side than the recess 431, and a second convex portion 433 in which the base electrode layer 43 of the folded portion 42 is closer to the electrode approaching direction D21 side than the recess 431.

[0067] More specifically, in the side external electrode 4, the outer surface of the base electrode layer 43 of the folded portion 42 has an uneven shape in which, for example, two arcs that convex in a direction away from the laminate 2 are adjacent in the electrode arranging direction D2. The outer surface of the first convex portion 432 and the outer surface of the second convex portion 433 each have an arc shape that convex in a direction away from the laminate 2. The concave portion 431 is the boundary between the first convex portion 432 and the second convex portion 433.

[0068] With this configuration, the stress of the first convex portion 432 can be concentrated in the concave portion 431, thereby preventing the stress of the first convex portion 432 from being transmitted to the folded edge portion 42a. This reduces the stress on the folded edge portion 42a, thereby reducing the stress acting on the portion of the laminate 2 that contacts the folded edge portion 42a. This makes it possible to prevent damage to the laminate 2 caused by the stress of the side surface external electrode 4. Therefore, it is possible to provide a multilayer ceramic capacitor 1 that can prevent damage to the laminate 2 while ensuring moisture resistance reliability.

[0069] Furthermore, the area near the edge of the folded portion 42 is considered to be relatively susceptible to damage. However, with this configuration, the thickness of the second convex portion 433 is greater than the thickness of the concave portion 431. In this case, the thickness of the second convex portion 433 can be maintained at a certain level or more, thereby ensuring the strength of the area near the edge of the folded portion 42. This makes it possible to prevent damage to the side surface external electrode 4.

[0070] 6, the thickness of the recess 431 is indicated as "d21", the thickness of the thickest portion of the first protrusion 432 is indicated as "d22", and the thickness of the thickest portion of the second protrusion 433 is indicated as "d23". Also, in FIG. 6, the internal structure of the laminate 2 is not shown.

[0071] The thickness of the recess 431 is preferably ¾ or less of the thickness of the thickest portion of the first protrusion 432 .

[0072] According to this configuration, the stress of the first convex portion 432 can be more suitably concentrated on the concave portion 431, and therefore the transmission of stress to the folded edge portion 42a can be more suitably suppressed.

[0073] Furthermore, the thickness of the thickest portion of the second convex portion 433 is smaller than the thickness of the thickest portion of the first convex portion 432 .

[0074] Because the second convex portion 433 is located closer to the folded edge portion 42a than the recessed portion 431, it is considered that the stress of the second convex portion 433 is relatively easily transmitted to the folded edge portion 42a even if the recessed portion 431 is provided in the base electrode layer 43. However, with this configuration, the thickness of the second convex portion 433 can be reduced, thereby reducing the stress of the second convex portion 433. This reduces the stress transmitted to the folded edge portion 42a.

[0075] If the dimension of the underlying electrode layer 43 of the folded portion 42 in the electrode arrangement direction D1 is e, the recess 431 is located at a position where the distance from the end of the folded portion 42 in the electrode separation direction D22 is in the range of 1 / 2e to 9 / 10e.

[0076] According to this configuration, the recess 431 can be positioned closer to the folded edge 42a in the folded portion 42. This makes it easier for the recess 431 to bear more of the stress of the entire folded portion 42. This makes it possible to more effectively suppress the transmission of stress to the folded edge 42a.

[0077] The thickness of the recess 431 is 0.5 μm or more.

[0078] It is considered that stress tends to concentrate relatively easily in the recess 431, and this configuration can ensure the strength of the recess 431. Therefore, the strength of the folded portion 42 in the side surface external electrode 4 can be ensured.

[0079] The thickness of the first convex portion 432 is 75 μm or less.

[0080] According to this configuration, the thickness of the folded portion 42 can be made relatively small, and therefore the height of the multilayer ceramic capacitor 1 can be prevented from increasing.

[0081] (Method of Measuring Thickness) The thickness of the external electrodes 3, 4 and the thickness of the base electrode layers 33, 43 can be measured, for example, by observing a cross section of the multilayer ceramic capacitor 1 exposed by polishing with a scanning electron microscope.

[0082] When observing the end face external electrode 3, the cross section to be observed is, for example, an LT cross section passing through the center in the width direction W of the laminate 2 when measuring the thickness at the main face folded portion 32A, and an LW cross section passing through the center in the stacking direction T of the laminate 2 when measuring the thickness at the side face folded portion 32B. When observing the side face external electrode 4, the cross section to be observed is, for example, a WT cross section passing through the center in the length direction L of the laminate 2.

[0083] (Method for Manufacturing Multilayer Ceramic Capacitor 1) Next, a method for manufacturing the multilayer ceramic capacitor 1 according to the embodiment will be described.

[0084] (Internal electrode pattern forming process) First, a ceramic green sheet is prepared by forming a ceramic slurry into a sheet shape. Next, a pattern of the end surface internal electrode 20 and the side surface internal electrode 50 is printed on the ceramic green sheet with a conductive paste. As a result, a ceramic green sheet on which the end surface internal electrode 20 is arranged and a ceramic green sheet on which the side surface internal electrode 50 is arranged are obtained. The patterns of the end surface internal electrode 20 and the side surface internal electrode 50 are formed by printing, for example, screen printing, gravure printing, letterpress printing, or the like.

[0085] (Laminating Process) Next, the ceramic green sheets on which the end face internal electrodes 20 are arranged and the ceramic green sheets on which the side face internal electrodes 50 are arranged are laminated. Next, ceramic green sheets for outer layer portions, which will become the outer layer portions 12, are laminated on both sides of the laminated ceramic green sheets in the lamination direction T. The ceramic green sheets for outer layer portions are thermocompression bonded to the ceramic green sheets. This results in a mother block.

[0086] Each outer layer portion 12 may be formed by laminating a plurality of ceramic green sheets or by a single ceramic green sheet. The ceramic green sheets for the inner layer portion and the ceramic green sheets for the outer layer portion may contain different components.

[0087] (Mother Block Cutting Process) Next, the mother block is divided along cutting lines corresponding to the dimensions of the laminate. The mother block is cut, for example, in the length direction L and the width direction W. This results in multiple rectangular blocks (referred to as "laminated chips"). It is preferable that the corners and ridges of the laminated chips are rounded, for example, by barrel polishing.

[0088] (Laminate Firing Step) Next, the laminated chip is heated at a predetermined firing temperature in a nitrogen atmosphere for a predetermined time, thereby obtaining the laminate 2.

[0089] (Base electrode layer forming process) Next, a conductive paste containing copper and glass is applied to each side surface B of the laminate 2. As a result, a base electrode layer 43 of the side surface external electrode 4 is formed on each side surface B. Each base electrode layer 43 is formed so as to cover not only the side surface B but also a portion of the side surface B side of the main surface A.

[0090] In this case, the conductive paste for the base electrode layer 43 is applied, for example, twice. The conductive paste is applied to the main surface A or the side surface B so that the positions of the ends of the conductive paste on the main surface A or the side surface B are closer to the end faces C than in the first application. As a result, a step is formed near the end of the second-applied conductive paste in the electrode approaching direction D21. As the conductive paste dries, the portion of the conductive paste closer to the electrode approaching direction D21 and the portion of the conductive paste closer to the electrode separating direction D22 rise, respectively, centered on their intermediate portions in the electrode arrangement direction D2. As a result, a recess 431 is formed in the base electrode layer 43 of the folded portion 42 in the portion where the step of the conductive paste was formed, and a first protrusion 432 and a second protrusion 433 are formed on either side of the recess 431. Furthermore, the first protrusion 432 is larger than the second protrusion 433 due to the conductive paste being applied multiple times.

[0091] The size of the bulge of the conductive paste in the portions that will become the first convex portion 432 and the second convex portion 433 can be adjusted, for example, by adjusting the viscosity of the conductive paste. The higher the viscosity of the conductive paste, the larger the bulge of the conductive paste after drying. For this reason, for example, the viscosity of the conductive paste applied the first time is set to be lower than that of the conductive paste applied the second time. This makes it easier to make the thickness of the second convex portion 433 smaller than the thickness of the first convex portion 432.

[0092] Furthermore, the method for forming the recesses, first convex portions, second convex portions, etc. is not limited to this. For example, even if the conductive paste is applied only once, the recesses, first convex portions, second convex portions, etc. can be formed on the base electrode layer of the folded portion by shaping the surface of the conductive paste applied to the laminate with a blade or the like.

[0093] Next, conductive paste is applied to each end face C of the laminate 2. As a result, a base electrode layer 33 of the end face external electrode 3 is formed on each end face C. Each base electrode layer 33 is formed so as to cover not only the end face C but also a portion of the end face C side of the main face A and the side face B. At this time, the conductive paste that will become the base electrode layer 33 is applied twice, for example, in the same way as in the case of the base electrode layer 43. As a result, a recess 331, a first convex portion 332, and a second convex portion 333 are formed in the base electrode layer 33 of the folded portion 32.

[0094] (Base Electrode Layer Baking Process) Next, the laminate 2 on which the base electrode layers 33 and 43 have been formed is heated in a nitrogen atmosphere at a predetermined firing temperature for a predetermined time. As a result, the base electrode layers 33 and 43 are baked onto the laminate 2.

[0095] (Plating Layer Forming Process) Next, the first plating layer 35, which is a Ni plating layer, is formed on the base electrode layer 33, and the first plating layer 45, which is a Ni plating layer, is formed on the base electrode layer 43. The first plating layer 35 and the first plating layer 45 are formed by, for example, barrel plating. Next, the second plating layer 36, which is a Sn plating layer, is formed on the first plating layer 35, and the second plating layer 46, which is a Sn plating layer, is formed on the first plating layer 45. The second plating layer 36 and the second plating layer 46 are formed by, for example, barrel plating. As a result, the end surface external electrode 3 and the side surface external electrode 4 are formed on the laminate 2.

[0096] As a result of the above, the multilayer ceramic capacitor 1 shown in FIG. 1 is obtained.

[0097] (Effects of the Embodiment) According to the present embodiment, the following effects can be obtained.

[0098] According to this embodiment, the folded portion 32 of the end surface external electrode 3 has a base electrode layer 33 containing Cu. The base electrode layer 33 of the folded portion 32 has a recess 331 in which the thickness of the base electrode layer 33 is less than the thickness of the base electrode layer 33 in a portion adjacent to the electrode approaching direction D11 and is equal to or less than the thickness of the base electrode layer 33 in a portion adjacent to the electrode separating direction D12, a first convex portion 332 which is a portion of the base electrode layer 33 of the folded portion 32 closer to the electrode separating direction D12 than the recess 331, and a second convex portion 333 which is a portion of the base electrode layer 33 of the folded portion closer to the electrode approaching direction D11 than the recess 331.

[0099] Furthermore, the folded portion 42 of the side surface external electrode 4 has a base electrode layer 43 containing Cu. The base electrode layer 43 of the folded portion 42 has a recess 431 in which the thickness of the base electrode layer 43 is less than the thickness of the base electrode layer 43 in a portion adjacent to the electrode approaching direction D21 and is equal to or less than the thickness of the base electrode layer 43 in a portion adjacent to the electrode separating direction D22, a first convex portion 432 which is a portion of the base electrode layer 43 of the folded portion 42 closer to the electrode separating direction D22 than the recess 431, and a second convex portion 433 which is a portion of the base electrode layer 43 of the folded portion 42 closer to the electrode approaching direction D21 than the recess 431.

[0100] With this configuration, the stress of the first protrusions 332, 432 located further in the electrode separation direction than the recesses 331, 431 can be concentrated at the recesses 331, 431, thereby suppressing the transmission of stress to the folded edge portions 32a, 42a. This suppresses the transmission of stress to the portions of the laminate 2 that contact the folded edge portions 32a, 42a. This suppresses damage to the laminate 2 caused by the stress of the external electrodes 3, 4.

[0101] Therefore, it is possible to provide a multilayer ceramic capacitor 1 that can prevent damage to the laminate 2 while ensuring moisture resistance reliability.

[0102] Furthermore, the areas near the edges of the folded portions 32, 42 are considered to be relatively susceptible to damage. However, the thickness of the second convex portions 333, 433 is greater than the thickness of the concave portions 331, 431. In this case, the thickness of the second convex portions 333, 433 can be maintained at a certain level or greater, thereby ensuring the strength of the areas near the edges of the folded portions 32, 42. This makes it possible to prevent damage to the external electrodes 3, 4.

[0103] According to this embodiment, in the end surface external electrode 3 , the thickness of the recess 331 is ¾ or less of the thickness of the thickest portion of the first protrusion 332 .

[0104] In addition, in the side surface external electrode 4 , the thickness of the recess 431 is ¾ or less of the thickness of the thickest portion of the first protrusion 432 .

[0105] According to this configuration, the stress of the first convex portions 332, 432 can be more suitably concentrated on the concave portions 331, 431, and therefore the transmission of stress to the folded edge portions 32a, 42a can be more suitably suppressed.

[0106] In this embodiment, in the end surface external electrode 3 , the thickness of the thickest portion of the second convex portion 333 is smaller than the thickness of the thickest portion of the first convex portion 332 .

[0107] In the side surface external electrode 4 , the thickness of the thickest portion of the second convex portion 433 is smaller than the thickness of the thickest portion of the first convex portion 432 .

[0108] Because the second convex portions 333, 433 are located closer to the folded edge portions 32a, 42a than the recessed portions 331, 431, it is considered that the stress of the second convex portions 333, 433 is relatively easily transmitted to the folded edge portions 32a, 42a even if the recessed portions 331, 431 are provided in the base electrode layers 33, 43. However, with this configuration, the stress of the second convex portions 333, 433 can be reduced by reducing the thickness of the second convex portions 333, 433. This reduces the stress transmitted to the folded edge portions 32a, 42a, thereby more effectively suppressing damage to the laminate 2.

[0109] According to this embodiment, in the end face external electrode 3, if the dimension of the folded portion 32 in the electrode arrangement direction D1 is e, the recess 331 is provided at a position where the distance from the end of the folded portion 32 in the electrode separation direction D12 is in the range of 1 / 2e to 9 / 10e.

[0110] Furthermore, in the side external electrode 4, if the dimension of the folded portion 42 in the electrode arrangement direction D2 is e, the recess 431 is provided at a position where the distance from the end of the folded portion 42 in the electrode separation direction D22 is in the range of 1 / 2e to 9 / 10e.

[0111] With this configuration, stress in the portion of the folded portion 32, 42 that is closer to the electrode separation direction than the recessed portion 331, 431 is less likely to be transmitted to the folded edge portion 32a, 42a than the recessed portion 331, 431. However, in the folded portion 32, 42, the recessed portion 331, 431 can be positioned closer to the folded edge portion 32a, 42a. This makes it possible for the recessed portion 331, 431 to bear a larger portion of the overall stress of the folded portion 32, 42. This makes it possible to more effectively suppress the transmission of stress to the folded edge portion 32a, 42a.

[0112] According to this embodiment, the thickness of the end surface external electrode 3 at the recess 331 is 0.5 μm or more.

[0113] Furthermore, the thickness of the side surface external electrode 4 at the recess 431 is 0.5 μm or more.

[0114] Although it is considered that stress tends to concentrate relatively easily in the recesses 331, 431, this configuration can ensure the strength of the recesses 331, 431. Therefore, the strength of the folded portions 32, 42 of the external electrodes 3, 4, respectively, can be ensured.

[0115] According to this embodiment, the thickness of the first convex portion 332 of the end surface external electrode 3 is 75 μm or less.

[0116] In addition, in the side surface external electrode 4, the thickness of the first convex portion 432 is 75 μm or less.

[0117] According to this configuration, the thickness of the folded portions 32, 42 can be made relatively small, and therefore the height of the multilayer ceramic capacitor 1 can be prevented from increasing.

[0118] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various changes and modifications are possible.

[0119] In the above embodiment, the folded portion 32 of the end surface external electrode 3 and the folded portion 42 of the side surface external electrode 4 each have an uneven shape on their outer surface. However, the outer surface of one of the folded portions 32 and 42 may be flat. However, in the laminate 2, the dimension of the internal electrode 15 in the width direction W is smaller than the dimension of the internal electrode 15 in the length direction L. Therefore, the mechanical strength of the multilayer ceramic capacitor 1 in the width direction W is weaker than the mechanical strength of the multilayer ceramic capacitor 1 in the length direction L. Therefore, when providing an uneven shape on only one of the base electrode layer 33 of the end surface external electrode 3 and the base electrode layer 43 of the side surface external electrode 4, it is more preferable to provide an uneven shape on the base electrode layer 43 of the side surface folded portion 32B. This makes it easier to ensure the strength of the multilayer ceramic capacitor 1.

[0120] In the above embodiment, the base electrode layer 33 of the end surface external electrode 3 has a portion disposed on each main surface A and a portion disposed on each side surface B that have shapes that generally correspond to each other, but these shapes do not necessarily have to correspond to each other. For example, in the above embodiment, the main surface folded portion 32A and the side surface folded portion 32B of the base electrode layer 33 each have an uneven shape on the outer surface, but neither the main surface folded portion 32A nor the side surface folded portion 32B needs to have the uneven shape of the above embodiment. However, in the case of the multilayer ceramic capacitor 1, which is a three-terminal multilayer ceramic capacitor, it is mounted on a mounting board with the main surface A side facing the mounting board, so it is preferable that at least the main surface folded portion 32A has the uneven shape of the above embodiment.

[0121] In the above embodiment, the base electrode layer 33 of the end surface external electrode 3 has an uneven shape in both the portion arranged on the first principal surface AA and the portion arranged on the second principal surface AB, but it is not necessary for both principal surfaces A to have the uneven shape of the above embodiment. However, the configuration of the above embodiment is preferable in that the desired effect can be obtained regardless of which of the principal surfaces A is faced toward the mounting substrate when the multilayer ceramic capacitor 1 is mounted on the mounting substrate.

[0122] In the above embodiment, the external electrodes 3, 4 have the first plating layer 35, 45 and the second plating layer 36, 46, respectively, but the first plating layer 35, 45 and the second plating layer 36, 46 are not essential components. If the external electrodes 3, 4 are not provided with the first plating layer 35, 45 and the second plating layer 36, 46, the outer surfaces of the external electrodes 3, 4 become the outer surfaces of the base electrode layers 33, 43.

[0123] In the above embodiment, the external electrodes 3, 4 are external electrodes of a three-terminal multilayer ceramic capacitor 1, but this is not limited thereto. For example, in a multilayer ceramic capacitor (a so-called two-terminal multilayer ceramic capacitor) including a laminate and a pair of external electrodes provided as a pair on either one of the side faces or each end face of the laminate, and the laminate having an internal electrode connected to only one of the pair of external electrodes and an internal electrode connected to only the other, the base electrode layer of the external electrode may have an uneven shape corresponding to the above embodiment. Furthermore, the internal structure of the laminate (for example, the shape of the internal electrodes) is not particularly limited.

[0124] In the case of a two-terminal multilayer ceramic capacitor, when the multilayer ceramic capacitor is mounted on a mounting substrate, not only the main surface A but also the side surface B can be the surface facing the mounting substrate. Therefore, in the case of a two-terminal multilayer ceramic capacitor, it is preferable that the base electrode layer has an uneven shape corresponding to the above embodiment on both the folded portion on the main surface A and the folded portion on the side surface B. This makes it possible to obtain the desired effect in the two-terminal multilayer ceramic capacitor regardless of the orientation of the multilayer ceramic capacitor when mounted.

[0125] In the above embodiment, the external electrodes 3, 4 have the first plating layer 35, 45 and the second plating layer 36, 46, but the plating layer is not limited to a two-layer structure. Furthermore, the type of metal contained in the plating layer is not limited to that in the above embodiment. The configuration of the plating layer of the external electrode is not particularly limited, as long as the outer surface of the external electrode has substantially the same shape as the outer surface of the base electrode layer.

[0126] The present invention also includes the following combinations:

[0127] <1> A multilayer ceramic capacitor comprising: an inner layer portion including a plurality of dielectric layers and a plurality of internal electrodes; a laminate having first and second main surfaces opposing each other in a stacking direction; first and second side surfaces opposing each other in a width direction perpendicular to the stacking direction; and first and second end surfaces opposing each other in a length direction perpendicular to the stacking direction and the width direction; and external electrodes arranged in pairs on at least either of the side surfaces and the end surfaces, wherein the direction in which the external electrodes arranged in pairs are arranged is defined as an electrode arranging direction, and the direction in which the external electrodes in pairs approach each other is defined as an electrode approaching direction, and the direction in which the external electrodes in pairs are separated from each other is defined as an electrode separating direction, a connecting portion disposed on one of the side surfaces and the end surface facing each other in the electrode arrangement direction, and a folded portion extending from the connecting portion toward the electrode approaching direction, wherein the folded portion has a base electrode layer containing Cu, and the base electrode layer of the folded portion has a recess where the thickness of the base electrode layer is less than the thickness of the base electrode layer in a portion adjacent to the electrode approaching direction and is equal to or less than the thickness of the base electrode layer in a portion adjacent to the electrode separating direction, a first convex portion which is a portion of the base electrode layer of the folded portion closer to the electrode separating direction than the recess, and a second convex portion which is a portion of the base electrode layer of the folded portion closer to the electrode approaching direction than the recess.

[0128] <2> The multilayer ceramic capacitor according to <1>, wherein the thickness of the recess is ¾ or less of the thickness of the thickest portion of the first protrusion.

[0129] <3> The multilayer ceramic capacitor according to <1> or <2>, wherein the thickness of the thickest portion of the second protrusion is smaller than the thickness of the thickest portion of the first protrusion.

[0130] <4> The multilayer ceramic capacitor according to any one of <1> to <3>, wherein, when a dimension of the folded portion in the electrode arrangement direction of the base electrode layer is e, the recess is provided at a position where a distance between the folded portion and an end of the folded portion in the electrode separation direction is in a range of 1 / 2e to 9 / 10e.

[0131] <5> The multilayer ceramic capacitor according to any one of <1> to <4>, wherein the recess has a thickness of 0.5 μm or more.

[0132] <6> The multilayer ceramic capacitor according to any one of <1> to <5>, wherein the thickness of the first protrusion is 75 μm or less.

[0133] REFERENCE SIGNS LIST 1 Multilayer ceramic capacitor 2 Laminate 3 End face external electrode (external electrode) 4 Side face external electrode (external electrode) 14 Dielectric layer 20 End face internal electrode (internal electrode) 31, 41 Connection portion 32, 42 Folded portion 33, 43 Base electrode layer 50 Side face internal electrode (internal electrode) 331, 431 Recess 332, 432 First convex portion 333, 433 Second convex portion AA First main surface AB Second main surface BA First side surface BB Second side surface CA First end surface CB Second end surface

Claims

1. A multilayer ceramic capacitor comprising: an inner layer portion including a plurality of dielectric layers and a plurality of internal electrodes; a laminate having first and second main surfaces opposing each other in the stacking direction, first and second side surfaces opposing each other in a width direction perpendicular to the stacking direction, and first and second end surfaces opposing each other in a length direction perpendicular to the stacking direction and the width direction; and external electrodes arranged in pairs on at least either of the side surfaces and end surfaces, wherein the direction in which the external electrodes arranged in pairs are arranged is defined as an electrode arranging direction, the direction in which the paired external electrodes approach each other in the electrode arranging direction is defined as an electrode approaching direction, and the direction in which the paired external electrodes are separated from each other is defined as an electrode separating direction, the external electrodes have connection portions arranged on the surfaces of the side surfaces and end surfaces facing the electrode arranging direction, and folded portions extending from the connection portions toward the electrode approaching direction, and the folded portions have an underlying electrode layer containing Cu, the base electrode layer of the folded portion has a recess in which the thickness of the base electrode layer is less than the thickness of the base electrode layer in a portion adjacent to the electrode approaching direction and is equal to or less than the thickness of the base electrode layer in a portion adjacent to the electrode separating direction, a first convex portion which is a portion of the base electrode layer of the folded portion on the electrode separating direction side of the recess, and a second convex portion which is a portion of the base electrode layer of the folded portion on the electrode approaching direction side of the recess.

2. The multilayer ceramic capacitor according to claim 1, wherein the thickness of said recess is 3 / 4 or less of the thickness of the thickest portion of said first protrusion.

3. The multilayer ceramic capacitor according to claim 1 or 2, wherein the thickness of the thickest portion of said second protrusion is smaller than the thickness of the thickest portion of said first protrusion.

4. A multilayer ceramic capacitor according to any one of claims 1 to 3, wherein the recess is provided at a position where the distance between the end of the folded portion in the electrode separation direction and the end of the folded portion is in the range of 1 / 2e to 9 / 10e, where e is the dimension of the base electrode layer in the electrode arrangement direction of the folded portion.

5. The multilayer ceramic capacitor according to any one of claims 1 to 4, wherein the thickness of the recess is 0.5 μm or more.

6. The multilayer ceramic capacitor according to any one of claims 1 to 5, wherein the thickness of the first protrusion is 75 μm or less.

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