Multilayer ceramic capacitor

Abstract

To provide a multilayer ceramic capacitor capable of suppressing delamination.SOLUTION: A multilayer ceramic capacitor 1 includes a laminate 2 having an inner layer portion 11 including alternately stacked dielectric layers 14 and internal electrodes 15. When a cross section parallel to the stacking direction T and the length direction L and passing through the center of the multilayer ceramic capacitor 1 in the width direction W is taken as a reference cross section S, at the reference cross section S, the internal electrodes 15 have an arc-shaped convex portion that forms an arc convex toward the adjacent dielectric layer 14.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Conventionally, there has been a demand for smaller multilayer ceramic capacitors with higher capacitance. To this end, attempts have been made to reduce the thickness and increase the number of layers of dielectric layers and internal electrode layers. Furthermore, there has also been a demand for improved reliability in multilayer ceramic capacitors.

[0003] For example, in the multilayer ceramic capacitor of Patent Document 1, a cover layer is disposed between the layers of the external electrodes, thereby improving the moisture resistance reliability of the multilayer ceramic capacitor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-117364 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is a problem in that delamination within the laminate is not sufficiently suppressed.

[0006] An object of the present invention is to provide a multilayer ceramic capacitor capable of suppressing delamination. [Means for solving the problem]

[0007] In order to solve the above problems, the multilayer ceramic capacitor of the present invention is a multilayer ceramic capacitor comprising: an inner layer portion including alternately stacked dielectric layers and internal electrodes; a pair of outer layer portions sandwiching the inner layer portion in a stacking direction; a laminate having a pair of main surfaces opposing each other in the stacking direction, a pair of side surfaces opposing each other in a width direction perpendicular to the stacking direction, and a pair of 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 when a cross section parallel to the stacking direction and the length direction is taken as an LT cross section, the internal electrodes have arc-shaped convex portions that draw an arc convex toward the adjacent dielectric layer in the LT cross section. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a multilayer ceramic capacitor capable of suppressing delamination. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic perspective view of a multilayer ceramic capacitor 1 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Figure 3] FIG. 3 is an enlarged view of part III in FIG. 2. [Figure 4] FIG. 3 is an enlarged view of part IV in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0010] A multilayer ceramic capacitor 1 according to an embodiment of the present invention will now be described with reference to the drawings.

[0011] (Multilayer ceramic capacitor 1) As shown in Fig. 1, the multilayer ceramic capacitor 1 has a substantially rectangular parallelepiped shape. The multilayer ceramic capacitor 1 includes a laminate 2 and a pair of external electrodes 3 provided on both ends of the laminate 2. The laminate 2 includes an inner layer portion 11 in which a dielectric layer 14 and an internal electrode 15 are laminated. The laminate 2 has a substantially rectangular parallelepiped shape and six outer surfaces.

[0012] 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. The direction perpendicular to the stacking direction T and in which the pair of external electrodes 3 are arranged 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.

[0013] Also, a cross section parallel to the stacking direction T and the length direction L and passing through the center of the multilayer ceramic capacitor 1 in the width direction W is defined as a "reference cross section S." The cross section in FIG. 2 shows the reference cross section S. The reference cross section S corresponds to an "LT cross section."

[0014] In the following description, of the six outer surfaces of the laminate 2, a pair of outer surfaces on both sides in the stacking direction T will be 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 will be 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 will be referred to as the first end surface CA and the second end surface CB. When there is no particular need to distinguish between them, the first main surface AA and the second main surface AB will sometimes be collectively referred to as the "respective main surfaces A." The first side surface BA and the second side surface BB will sometimes be collectively referred to as the "respective side surfaces B." The first end surface CA and the second end surface CB will sometimes be collectively referred to as the "respective end surfaces C."

[0015] (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 has a generally rectangular parallelepiped shape as a whole. It is preferable that the corners and ridges of the laminate 2 are rounded. Note that the corners are the portions where three surfaces of the laminate intersect, and the ridges are the portions where two surfaces of the laminate intersect.

[0016] (Inner layer 11) 2, 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.

[0017] The dielectric layer 14 is formed of a dielectric ceramic containing BaTiO as a main component, for example, and may contain a Mn compound, an Fe compound, a Cr compound, a Co compound, a Ni compound, or the like as a secondary component.

[0018] The internal electrodes 15 are formed of a metal material such as Ni, Cu, Ag, Pd, an Ag-Pd alloy, Au, etc. The internal electrodes 15 include a first internal electrode 15A exposed only at the first end face CA and a second internal electrode 15B exposed only at the second end face CB.

[0019] The first internal electrodes 15A and the second internal electrodes 15B are arranged alternately. A portion of the first internal electrode 15A facing the adjacent second internal electrode 15B is referred to as a first opposing portion 15Aa. A portion of the second internal electrode 15B facing the adjacent first internal electrode 15A is referred to as a second opposing portion 15Ba.

[0020] When there is no particular need to distinguish between them, the first internal electrode 15A and the second internal electrode 15B may be collectively referred to as "internal electrodes 15." The first opposing portion 15Aa and the second opposing portion 15Ba may be collectively referred to as "opposing portion 15a."

[0021] (Outer layer part 12) The outer layer portion 12 is made of the same material as the dielectric layer 14 of the inner layer portion 11. Note that the outer layer portion 12 does not have an internal electrode 15 disposed thereon.

[0022] (External electrode 3) The external electrodes 3 are disposed on the end faces C. Either the first internal electrode 15A or the second internal electrode 15B is connected to each external electrode 3. The external electrodes 3 cover not only the end faces C but also part of each principal face A and part of each side face B.

[0023] The external electrode 3 includes a base electrode layer 31 formed in contact with the surface of the laminate 2, a first plating layer 32 arranged on the base electrode layer 31, and a second plating layer 33 arranged on the first plating layer 32.

[0024] The base electrode layer 31 is, for example, a baked layer containing a conductive metal such as Cu (copper) and glass. The first plating layer 32 is, for example, a Ni (nickel) plating layer. The second plating layer 33 is, for example, a Sn (tin) plating layer.

[0025] Here, the internal electrode 15 has an arc-shaped convex portion 22 that forms an arc convex toward the adjacent dielectric layer 14. Fig. 3 is an enlarged view of part III in Fig. 2, and is an enlarged cross-sectional view based on a scanning electron microscope (SEM) photograph. Fig. 4 is an enlarged view of part IV in Fig. 2, and is an enlarged cross-sectional view based on a SEM photograph.

[0026] 3, the arc-shaped protrusion 22 has arc-shaped protrusions 22A and 22B that form arcs convex toward the first principal surface AA, and arc-shaped protrusion 22C that forms an arc convex toward the second principal surface AB. The arc-shaped protrusions 22A, 22B, and 22C are formed on the same internal electrode 15. This internal electrode 15 is sometimes referred to as the "internal electrode 151." The internal electrode 151 is located in a region near the center of the inner layer portion 11 in the stacking direction T.

[0027] The arcuate protrusions 22A and 22B are formed on the surface of the internal electrode 151 on the first principal surface AA side, and are arranged in this order from the first end face CA side toward the second end face CB side.

[0028] The arc-shaped protrusion 22C is formed on the surface of the internal electrode 151 on the second principal surface AB side. At the reference cross section S, both ends of the arc-shaped protrusion 22A in the length direction L and both ends of the arc-shaped protrusion 22C in the length direction L are aligned in the length direction L. In this case, the internal electrode 151 has a swelling portion 231 that includes the arc-shaped protrusion 22A and the arc-shaped protrusion 22C and swells in both directions in the stacking direction T. The outer shape of the swelling portion 231 at the reference cross section S is a substantially ellipse extending in the length direction L.

[0029] In this specification, "aligned positions in the length direction L" refers to a case where the separation distance in the length direction L is equal to or less than the average particle diameter of the conductive particles 21 described below, and is not limited to a case where the positions in the length direction L are the same.

[0030] The dielectric layer 14 has an arc-shaped recess 26 that recesses in an arc shape toward the inside of the dielectric layer 14 .

[0031] The arc-shaped recess 26 has an arc-shaped recess 26A and an arc-shaped recess 26B that form a concave arc on the second principal surface AB side, and an arc-shaped recess 26C that forms a concave arc on the first principal surface AA side.

[0032] The arc-shaped recess 26A and the arc-shaped recess 26B are formed in the same dielectric layer 14, and are arranged in this order from the first end face CA side toward the second end face CB side. The dielectric layer 14 is sometimes referred to as the "dielectric layer 141." The dielectric layer 141 is adjacent to the first main surface AA side of the internal electrode 151.

[0033] The arc-shaped recess 26C is formed in the dielectric layer 142, which is the dielectric layer 14 adjacent to the second main surface AB side of the internal electrode 151. The internal electrode 151 is sandwiched between the dielectric layer 141 and the dielectric layer 142.

[0034] Arc-shaped convex portion 22A fits into the recess of arc-shaped recess 26A; more specifically, arc-shaped convex portion 22A and arc-shaped recess 26A come into close contact with each other to form interface 28A. Arc-shaped convex portion 22B fits into the recess of arc-shaped recess 26B; more specifically, arc-shaped convex portion 22B and arc-shaped recess 26B come into close contact with each other to form interface 28B. Arc-shaped convex portion 22C fits into the recess of arc-shaped recess 26C; more specifically, arc-shaped convex portion 22C and arc-shaped recess 26C come into close contact with each other to form interface 28C.

[0035] These improve the bonding strength between the dielectric layer 14 and the internal electrode 15, and can prevent peeling between the dielectric layer 14 and the internal electrode 15. Note that in Fig. 3, the interfaces 28A, 28B, and 28C are indicated by virtual lines.

[0036] Furthermore, if the internal electrode 15 has an arc-shaped protrusion 22 that protrudes in one direction of the stacking direction T and an arc-shaped protrusion 22 that protrudes in the other direction of the stacking direction T, and the portion of the internal electrode 15 that bulges in both directions of the stacking direction T is defined as a bulging portion 23, the internal electrode 151 has a bulging portion 231 that has an arc-shaped protrusion 22A that protrudes toward the first principal surface AA and an arc-shaped protrusion 22C that protrudes toward the second principal surface AB. The ends of the arc-shaped protrusion 22A in the length direction L and the ends of the arc-shaped protrusion 22C in the length direction L are aligned with each other. This increases the bonding strength between the internal electrode 151 and the dielectric layers 14 located on both sides of the internal electrode 151 in the stacking direction T, thereby effectively suppressing peeling between the dielectric layers 14 and the internal electrode 15.

[0037] In addition, it is preferable that a plurality of swelling portions 23 are formed continuously in one internal electrode 15 in the length direction L. This makes it possible to more suitably suppress peeling between the dielectric layer 14 and the internal electrode 15.

[0038] Furthermore, when adjacent internal electrodes 15 each have a plurality of swelling portions 23 formed continuously in the length direction L, it is preferable that the positions in the length direction L of each end of the swelling portion 23 formed on one internal electrode 15 differ from those of each end of the swelling portion 23 formed on the other internal electrode 15. This makes it possible to more effectively prevent peeling between the dielectric layer 14 and the internal electrodes 15.

[0039] In this specification, the phrase "multiple arc-shaped convex portions formed continuously" refers to a case where, in two adjacent arc-shaped convex portions in the length direction L, the conductive particle (described below) comprising the end of one arc-shaped convex portion in the length direction L and the conductive particle comprising the end of the other arc-shaped convex portion in the length direction L are either the same conductive particle or two adjacent conductive particles.

[0040] In the inner layer portion 11, the regions where the arc-shaped convex portions 22 and arc-shaped concave portions 26 are located are not particularly limited.

[0041] 4, the arc-shaped protrusion 22 has an arc-shaped protrusion 22D that forms an arc convex toward the second principal surface AB. The arc-shaped protrusion 22D is formed on an internal electrode 153 that is a different internal electrode 15 from the internal electrode 15 on which the arc-shaped protrusions 22A and 22B are formed. The internal electrode 153 is located in a region near the end of the inner layer portion 11 on the first principal surface AA side.

[0042] The arc-shaped recess 26 has an arc-shaped recess 26D that forms a concave arc on the first main surface AA side. The arc-shaped recess 26D is formed in a dielectric layer 144 that is different from the dielectric layer 14 on which the arc-shaped recess 26A, the arc-shaped recess 26B, and the arc-shaped recess 26C are formed. The dielectric layer 144 is adjacent to the internal electrode 153 on the second main surface AB side.

[0043] Arc-shaped convex portion 22D fits into the concave portion of arc-shaped concave portion 26D, and more specifically, arc-shaped convex portion 22D and arc-shaped concave portion 26D come into close contact with each other to form interface 28D. Interface 28D is indicated by a virtual line in FIG.

[0044] Interface 28A, interface 28B, interface 28C, and interface 28D may be collectively referred to as "interface 28."

[0045] The internal electrode 15 has a plurality of conductive particles 21 .

[0046] The number of conductive particles 21 aligned in the stacking direction T in one internal electrode 15 is defined as the first vertically aligned number. The first vertically aligned number is determined, for example, by dividing one internal electrode 15 into six equal parts in the length direction L on an SEM photograph (described in detail later) of a reference cross section S, measuring the first vertically aligned number at five boundaries of the six equal parts, and averaging the measured numbers. The first vertically aligned number corresponds to the "vertically aligned number" as defined in the claims.

[0047] The first vertically arranged number is preferably equal to or greater than 3, and more preferably equal to or greater than 4. This makes it possible to increase the coverage of the internal electrodes 15 with respect to the dielectric layer .

[0048] The surface of the arc-shaped protrusion 22 is formed by arranging the conductive particles 21 in an arc shape, the number of which is equal to or greater than the first vertically arranged number of the internal electrode 15 on which the arc-shaped protrusion 22 is formed. This makes it possible to form smooth arc-shaped protrusions, thereby suppressing delamination and the occurrence of local electric field concentration and stress concentration.

[0049] The surface of the arc-shaped protrusions 22 is preferably formed by arranging 5 or more conductive particles in an arc, and more preferably by arranging 5 to 15 conductive particles in an arc, which allows for the formation of smooth arc-shaped protrusions 22, thereby suppressing delamination and the occurrence of localized electric field concentration and stress concentration.

[0050] The dimension of the arc-shaped protrusion 22 in the length direction L is larger than the dimension of the internal electrode 15 on which the arc-shaped protrusion 22 is formed in the lamination direction T. This makes it possible to form smooth arc-shaped protrusions, thereby suppressing delamination and the occurrence of local electric field concentration and stress concentration.

[0051] In the reference cross section S1, a straight line parallel to the longitudinal direction L that passes through the end of the arc-shaped convex portion 22 that is located on the opposite side of the protruding direction of the arc-shaped convex portion 22 is defined as the first reference line.

[0052] The "dimension in the longitudinal direction L of the arc-shaped protrusion 22" refers to the distance between two points on the first reference line at the reference cross section S, where the positions of each end of the arc-shaped protrusion 22 in the longitudinal direction L are the same as those of the end of the arc-shaped protrusion 22 in the longitudinal direction L.

[0053] The dimension of the internal electrode 15 in the stacking direction T is determined by, for example, dividing one internal electrode 15 into six equal parts in the length direction L on an SEM photograph of the reference cross section S (described in detail later), measuring the dimension of the internal electrode 15 in the stacking direction T at five boundaries of the six equal parts, and averaging the measured values.

[0054] The dimension of the arc-shaped protrusions 22 in the stacking direction T is larger than the average particle diameter of the conductive particles 21 in the internal electrode 15 on which the arc-shaped protrusions 22 are formed. This makes it possible to more effectively suppress delamination.

[0055] The average particle diameter of the conductive particles 21 is preferably 0.1 μm or more and 0.3 μm or less.

[0056] The "dimension of the arc-shaped convex portion 22 in the stacking direction T" refers to the distance in the stacking direction T between the first reference line and the part of the surface of the arc-shaped convex portion 22 that is most convex in the stacking direction T at the reference cross section S.

[0057] Furthermore, the term "average particle diameter" as used herein refers to the median diameter in an areal particle size distribution, and is the area-equivalent diameter at which the cumulative value in the cumulative distribution of the area-equivalent diameters of a plurality of particles is 50%. In other words, the average particle diameter is the area-equivalent diameter at which, when a plurality of particles are divided into two groups based on a certain area-equivalent diameter, the number of particles larger than the standard and the number of particles smaller than the standard are the same.

[0058] The radius of curvature of the arc of the arc-shaped protrusion 22 (sometimes referred to as the "radius of curvature r1") is preferably 1 μm or more and 3 μm or less. The radius of curvature of the arc of the arc-shaped protrusion 22 is preferably 1 to 5 times the dimension in the stacking direction T of the internal electrode 15 on which the arc-shaped protrusion 22 is formed. This makes it possible to suppress delamination while also suppressing the occurrence of local electric field concentration and stress concentration. The radius of curvature r1 of the arc-shaped protrusion 22 can be calculated as the radius of curvature of a circle that passes through both ends of the arc-shaped protrusion 22 in the length direction L and the point on the surface of the arc-shaped protrusion 22 that is most convex toward the adjacent dielectric layer 14.

[0059] The dielectric layer 14 also includes a plurality of dielectric particles 25 .

[0060] The number of dielectric particles 25 aligned in the stacking direction T in a portion of one dielectric layer 14 sandwiched between adjacent opposing portions 15a is defined as the second vertically aligned number. The second vertically aligned number is determined, for example, by dividing the portion of one dielectric layer 14 sandwiched between adjacent opposing portions 15a into six equal parts in the length direction L on a scanning electron microscope (SEM) photograph (described in detail later) of the reference cross section S, measuring the number of dielectric particles 25 aligned in the stacking direction T at five boundaries of the six equal parts, and averaging the measured numbers.

[0061] The surface of the arc-shaped recess 26 is formed by arranging dielectric particles 25 in an arc shape, the number of which is at least half the second vertically arranged number of the dielectric layer 14 in which the arc-shaped recess 26 is formed. This makes it possible to form a smooth arc-shaped recess 26, thereby suppressing delamination and the occurrence of local electric field concentration and stress concentration. The second vertically arranged number is preferably 4 or more, and more preferably 5 or more.

[0062] The surface of the arc-shaped recess 26 is preferably formed by arranging five or more dielectric particles 25 in an arc, and more preferably by arranging five to fifteen dielectric particles 25 in an arc. This allows for the formation of a smooth arc-shaped recess 26, which can suppress delamination and the occurrence of local electric field concentration and stress concentration.

[0063] The dimension of the arc-shaped recess 26 in the length direction L is larger than half the dimension in the stacking direction T of the dielectric layer 14 in which the arc-shaped recess 26 is formed. This makes it possible to form a smooth arc-shaped recess 26, thereby suppressing delamination and the occurrence of local electric field concentration and stress concentration.

[0064] In addition, in the reference cross section S1, the second reference line is a straight line that passes through the end of the arc-shaped recess 26 that is located on the opposite side of the recession direction of the arc-shaped recess 26 in the longitudinal direction L and extends parallel to the longitudinal direction L.

[0065] The "dimension in the longitudinal direction L of the arc-shaped recess 26" refers to the distance between two points on the reference cross section S that are located at the same position as each end of the arc-shaped recess 26 in the longitudinal direction L on the second reference line.

[0066] Furthermore, the dimension of the dielectric layer 14 in the stacking direction T is determined by, for example, dividing a portion of the dielectric layer 14 sandwiched between adjacent opposing portions 15a into six equal parts in the length direction L on an SEM photograph of the reference cross section S (described in detail later), measuring the dimension of the dielectric layer 14 in the stacking direction T at five boundaries of the six equal parts, and averaging the measured values.

[0067] The dimension of the arc-shaped recess 26 in the stacking direction T is larger than the average particle size of the dielectric particles 25 in the dielectric layer 14 in which the arc-shaped recess 26 is formed, thereby making it possible to more effectively suppress delamination.

[0068] The average particle size of the dielectric particles 25 is preferably 0.1 μm or more and 0.3 μm or less.

[0069] The radius of curvature of the arc of the arc-shaped recess 26 (sometimes referred to as the "radius of curvature r2") is preferably 1 μm or more and 3 μm or less. The radius of curvature r2 of the arc of the arc-shaped recess 26 is preferably 1 / 2 or more and 2.5 times or less the dimension in the stacking direction T of the dielectric layer 14 in which the arc-shaped recess 26 is formed. This makes it possible to suppress delamination while also suppressing the occurrence of local electric field concentration and stress concentration. The radius of curvature r2 of the arc-shaped recess 26 can be calculated as the radius of curvature of a circle that passes through both ends of the arc-shaped recess 26 in the length direction L and the point on the surface of the arc-shaped recess 26 that is most concave toward the inside of the dielectric layer 14.

[0070] In FIG. 3, the radius of curvature of the arc of arc-shaped convex portion 22A is shown as radius of curvature r1A, and the radius of curvature of the arc of arc-shaped concave portion 26A is shown as radius of curvature r2A. Radius of curvature r1A and radius of curvature r2A are substantially the same. Similarly, the radius of curvature of the arc of arc-shaped convex portion 22B is shown as radius of curvature r1B, and the radius of curvature of the arc of arc-shaped concave portion 26B is shown as radius of curvature r2B. Radius of curvature r1B and radius of curvature r2B are substantially the same. Similarly, in FIG. 4, the radius of curvature of the arc of arc-shaped convex portion 22D is shown as radius of curvature r1D, and the radius of curvature of the arc of arc-shaped concave portion 26D is shown as radius of curvature r2D. Radius of curvature r1D and radius of curvature r2D are substantially the same. For convenience, the radius of curvature of the arc of the arc-shaped convex portion 22C and the radius of curvature of the arc of the arc-shaped concave portion 26C are omitted from the illustration.

[0071] (Measurement method) Next, the method for measuring each value will be described.

[0072] First, the multilayer ceramic capacitor 1 is polished up to the center position in the width direction W. This exposes the reference cross section S.

[0073] Next, the reference cross section S is observed under a microscope, and each value is measured. The dimension of the internal electrode 15 in the stacking direction T, the dimension of the arc-shaped convex portion 22 in the length direction L, the dimension in the stacking direction and the radius of curvature, the first vertically arranged number, the dimension of the arc-shaped concave portion 26 in the length direction L, the dimension in the stacking direction and the radius of curvature, and the second vertically arranged number can be measured by observing the reference cross section S on a scanning electron microscope (SEM) photograph.

[0074] The average particle diameter of the conductive particles 21 and the dielectric particles 25 can be determined by taking an SEM photograph of the reference cross section S at a magnification of 10,000 times and using image processing software. The SEM photograph is binarized using a predetermined threshold value to extract only the crystal particles, and their particle diameters (diameter equivalent to a circle with an area) can be evaluated.

[0075] (Manufacturing Method of Multilayer Ceramic Capacitor 1) Next, a method for manufacturing the multilayer ceramic capacitor 1 according to the embodiment will be described.

[0076] First, ceramic green sheets for lamination are prepared by forming ceramic slurry into sheets. The patterns of the internal electrodes 15 are printed on the ceramic green sheets using a conductive paste. This results in ceramic green sheets for lamination. In this process, increasing the viscosity of the conductive paste makes it easier to form irregularities on the surfaces of the internal electrodes 15. The dimension of the internal electrodes 15 in the lamination direction T can be adjusted by adjusting the amount of conductive paste applied.

[0077] The ceramic green sheets for lamination are stacked so that the internal electrode patterns are shifted by half a pitch between adjacent material sheets in the length direction L. On both sides of the stacked ceramic green sheets for lamination in the stacking direction T, ceramic green sheets for outer layer portions, which will become the outer layer portions 12, are stacked. The ceramic green sheets for outer layer portions are thermocompression bonded to the ceramic green sheets for lamination. This produces a mother block.

[0078] The mother block is divided along cutting lines corresponding to the dimensions of the laminate, thereby obtaining a plurality of laminated chips. Preferably, the laminated chips are rounded at the corners and edges by barrel polishing.

[0079] The laminated chip is heated in a nitrogen atmosphere at a predetermined firing temperature for a predetermined time. This sinters the ceramic and metal materials contained in the laminated chip, resulting in the laminate 2. During sintering, particles grow in the dielectric layers 14 and internal electrodes 15. This forms dielectric particles 25 and conductor particles 21.

[0080] During sintering, it is preferable to set the firing temperature as low as possible and the heating time as short as possible within the range in which the laminate 2 is sufficiently densified. This makes it possible to suppress melting of the conductive particles 21 and the dielectric particles 25, and therefore to suppress a decrease in the number of conductive particles 21 and the dielectric particles 25.

[0081] Furthermore, it is preferable to add auxiliary components containing elements such as silicon (Si) and magnesium (Mg) to the dielectric raw material constituting the laminated ceramic green sheets and the laminated ceramic green sheets for the outer layer portions. For example, Si acts as a grain growth promoter, and Mg acts as a grain growth inhibitor. Therefore, the particle size of the dielectric particles 25 can be adjusted by adjusting the type and amount of the element added as an auxiliary component to the dielectric raw material.

[0082] An external electrode 3 is formed on each end face C of the laminate 2. First, a base electrode layer 31 is formed. The base electrode layer 31 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. The base electrode layer 31 is formed, for example, by applying a conductive paste containing a conductive metal and glass to each end face C of the laminate 2 and baking it. A first plating layer 32 is formed on the base electrode layer 31. A second plating layer 33 is formed on the first plating layer 32. The first plating layer 32 and the second plating layer 33 are formed, for example, by electrolytic plating.

[0083] In this way, the multilayer ceramic capacitor 1 is obtained.

[0084] (Effects of the embodiment) According to this embodiment, the following effects can be obtained.

[0085] According to this embodiment, in the reference cross section S, the internal electrode 15 has an arc-shaped convex portion 22 that forms an arc convex toward the adjacent dielectric layer 14 side.

[0086] This increases the bonding strength between the dielectric layer 14 and the internal electrode 15, making it possible to prevent the dielectric layer 14 from peeling off from the internal electrode 15.

[0087] According to this embodiment, the dielectric layer 14 has an arc-shaped recess 26 that recesses in an arc shape toward the inside of the dielectric layer 14, and the arc-shaped recess 26 and the arc-shaped protrusion 22 of the internal electrode 15 are in close contact with each other to form an interface 28.

[0088] This makes it possible to more effectively suppress delamination.

[0089] According to this embodiment, the internal electrode 15 has a plurality of conductive particles 21 , and the dielectric layer 14 has a plurality of dielectric particles 25 .

[0090] This allows the arc-shaped convex portion 22 and the arc-shaped concave portion 26 to be formed appropriately.

[0091] According to this embodiment, the first vertically aligned number is three or more.

[0092] This makes it possible to increase the coverage of the internal electrodes 15 with respect to the dielectric layers 14 .

[0093] According to this embodiment, it is preferable that the surface of the arc-shaped convex portion 22 is formed by arranging conductive particles 21 in an arc shape in a number equal to or greater than the first vertical arrangement number of the internal electrode 15 in which the arc-shaped convex portion 22 is formed.

[0094] This allows for the formation of smooth arc-shaped convex portions 22, which in turn makes it possible to suppress delamination and the occurrence of localized electric field concentration and stress concentration.

[0095] According to this embodiment, the surface of the arc-shaped convex portion 22 is preferably formed by five or more conductive particles 21 arranged in an arc shape.

[0096] This allows for the formation of smooth arc-shaped convex portions 22, which in turn makes it possible to suppress delamination and the occurrence of localized electric field concentration and stress concentration.

[0097] According to this embodiment, the dimension of the arc-shaped protrusion 22 in the length direction L is preferably larger than the dimension of the internal electrode 15 on which the arc-shaped protrusion 22 is formed in the stacking direction T.

[0098] This allows for the formation of smooth arc-shaped convex portions 22, which in turn makes it possible to suppress delamination and the occurrence of localized electric field concentration and stress concentration.

[0099] According to this embodiment, the dimension of the arc-shaped protrusions 22 in the stacking direction T is preferably larger than the average particle diameter of the conductive particles 21 in the internal electrode 15 in which the arc-shaped protrusions 22 are formed.

[0100] This makes it possible to more effectively suppress delamination.

[0101] According to this embodiment, the radius of curvature r1 of the arc of the arc-shaped convex portion 22 is preferably 1 μm or more and 3 μm or less.

[0102] This makes it possible to suppress delamination and also to suppress the occurrence of local electric field concentration and stress concentration.

[0103] According to this embodiment, the radius of curvature r1 of the arc of the arc-shaped protrusion 22 is preferably two to five times the dimension in the stacking direction T of the internal electrode 15 on which the arc-shaped protrusion 22 is formed.

[0104] This makes it possible to suppress delamination and also to suppress the occurrence of local electric field concentration and stress concentration.

[0105] According to this embodiment, the internal electrode 151 has swelling portions 231 that swell in both directions of the stacking direction T. The swelling portions 231 have arc-shaped protrusions 22A that are convex toward the first principal surface AA side and arc-shaped protrusions 22C that are convex toward the second principal surface AB side. Each end of the arc-shaped protrusion 22A in the length direction L and each end of the arc-shaped protrusion 22C in the length direction L are aligned with each other.

[0106] This increases the bonding strength between the internal electrode 151 and the dielectric layers 14 located on both sides of the internal electrode 151 in the stacking direction T, thereby effectively suppressing peeling between the dielectric layers 14 and the internal electrode 15.

[0107] In addition, it is preferable that a plurality of swelling portions 23 are formed continuously in the length direction L in one internal electrode 15.

[0108] This makes it possible to more effectively prevent the dielectric layer 14 from peeling off from the internal electrode 15.

[0109] Furthermore, when adjacent internal electrodes 15 each have a plurality of swelling portions 23 formed continuously in the longitudinal direction L, it is preferable that the positions in the longitudinal direction L of each end of the swelling portion 23 formed in one internal electrode 15 and each end of the swelling portion 23 formed in the other internal electrode 15 are different from each other.

[0110] This makes it possible to more effectively prevent the dielectric layer 14 from peeling off from the internal electrode 15.

[0111] 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.

[0112] According to the above embodiment, the LT cross section is a cross section (reference cross section S) that is parallel to the stacking direction T and the length direction L and passes through the center of the width direction W of the multilayer ceramic capacitor 1, but it does not necessarily have to be a cross section that passes through the center of the width direction W of the multilayer ceramic capacitor 1. The LT cross section may be any cross section that is parallel to the stacking direction T and the length direction L of the multilayer ceramic capacitor, and the position in the width direction W is not particularly limited.

[0113] The present invention also includes the following combinations:

[0114] <1> a laminate having an inner layer portion including dielectric layers and inner electrodes stacked alternately; a pair of outer layer portions sandwiching the inner layer portion in a stacking direction; a pair of main surfaces opposing each other in the stacking direction; a pair of side surfaces opposing each other in a width direction perpendicular to the stacking direction; and a pair of end surfaces opposing each other in a length direction perpendicular to the stacking direction and the width direction; and outer electrodes arranged in pairs on at least either of the side surfaces and the end surfaces, wherein when a cross section parallel to the stacking direction and the length direction is taken as an LT cross section, the inner electrodes have arc-shaped convex portions that draw an arc convex toward the adjacent dielectric layer in the LT cross section.

[0115] <2> the dielectric layer has an arc-shaped recess that is recessed in an arc shape toward the inside of the dielectric layer, and the arc-shaped recess and the arc-shaped protrusion of the internal electrode are in close contact with each other to form an interface; <1> The multilayer ceramic capacitor according to claim 1.

[0116] <3> the internal electrodes have a plurality of conductive particles, and the dielectric layers have a plurality of dielectric particles; <1> or <2> The multilayer ceramic capacitor according to claim 1.

[0117] <4> When the number of the conductive particles aligned in the stacking direction in one of the internal electrodes is defined as a vertically aligned number, the vertically aligned number is 3 or more. <3> The multilayer ceramic capacitor according to claim 1.

[0118] <5> When the number of the conductive particles arranged in the stacking direction in one of the internal electrodes is defined as a vertically arranged number, the surface of the arc-shaped convex portion is formed by the conductive particles arranged in an arc shape, the number of which is equal to or greater than the vertically arranged number of the internal electrode in which the arc-shaped convex portion is formed. <3> or <4> The multilayer ceramic capacitor according to claim 1.

[0119] <6> the surface of the arc-shaped convex portion is formed by five or more of the conductive particles arranged in an arc shape; <3> ~ <5> 10. The multilayer ceramic capacitor according to claim 9, wherein

[0120] <7> the dimension in the length direction of the arc-shaped protrusion is larger than the dimension in the stacking direction of the internal electrode on which the arc-shaped protrusion is formed; <1> ~ <6> 10. The multilayer ceramic capacitor according to claim 9, wherein

[0121] <8> a dimension of the arc-shaped protrusion in the stacking direction is larger than an average particle diameter of the conductive particles in the internal electrode in which the arc-shaped protrusion is formed; <3> ~ <7> 10. The multilayer ceramic capacitor according to claim 9, wherein

[0122] <9> The radius of curvature of the arc of the arc-shaped convex portion is 1 μm or more and 3 μm or less. <1> ~ <8> 10. The multilayer ceramic capacitor according to claim 9, wherein

[0123] <10> the radius of curvature of the arc of the arc-shaped convex portion is 1 to 5 times the dimension in the stacking direction of the internal electrode on which the arc-shaped convex portion is formed; <1> ~ <9> 10. The multilayer ceramic capacitor according to claim 9, wherein

[0124] <11> the internal electrode has swelling portions that swell in both directions of the stacking direction, the swelling portions having arc-shaped protrusions that are convex in one direction of the stacking direction and arc-shaped protrusions that are convex in the other direction of the stacking direction, and of the arc-shaped protrusions that constitute the swelling portions, both ends of one of the arc-shaped protrusions in the length direction and both ends of the other of the arc-shaped protrusions in the length direction are aligned in the length direction. <1> ~ <10> 10. The multilayer ceramic capacitor according to claim 9, wherein

[0125] <12> The swelling portion is formed in plurality in the longitudinal direction. <11> The multilayer ceramic capacitor according to claim 1.

[0126] <13> each end portion in the length direction of the swelling portion formed on one of the adjacent internal electrodes is located at a different position in the length direction from each end portion in the length direction of the swelling portion formed on the other internal electrode; <12> The multilayer ceramic capacitor according to claim 1. [Explanation of symbols]

[0127] 1. Multilayer ceramic capacitors 2. Laminate 3 External electrode 11 Inner layer 12 Outer layer 14 Dielectric layer 15 Internal electrode 21 Conductive particles 22 Arc-shaped convex part 23 Ampulla 25 Dielectric particles 26 Arc-shaped recess 28 Interface A pair of principal surfaces B. A pair of sides C A pair of end faces r1 Radius of curvature of the arc of the arc-shaped convex part S Standard section (LT section)

Claims

1. a laminate having an inner layer portion including dielectric layers and internal electrodes stacked alternately, a pair of outer layer portions provided on either side of the inner layer portion in a stacking direction, a pair of main surfaces opposed to each other in the stacking direction, a pair of side surfaces opposed to each other in a width direction perpendicular to the stacking direction, and a pair of end faces opposed to each other in a length direction perpendicular to the stacking direction and the width direction; external electrodes arranged in pairs on at least one of the side surfaces and the end surfaces; A multilayer ceramic capacitor comprising: If a cross section parallel to the lamination direction and the length direction is defined as an LT cross section, In the LT cross-sectional view, the internal electrodes have arc-shaped convex portions that form a convex arc toward the adjacent dielectric layer.

2. the dielectric layer has an arc-shaped recess that is recessed in an arc shape toward an inner side of the dielectric layer, 2. The multilayer ceramic capacitor according to claim 1, wherein the arc-shaped recess and the arc-shaped protrusion of the internal electrode are in close contact with each other to form an interface.

3. The internal electrode includes a plurality of conductive particles, The multilayer ceramic capacitor according to claim 1 , wherein the dielectric layer comprises a plurality of dielectric particles.

4. If the number of the conductive particles aligned in the stacking direction in one of the internal electrodes is defined as the vertical alignment number, The multilayer ceramic capacitor according to claim 3 , wherein the number of the vertically arranged capacitors is three or more.

5. If the number of the conductive particles aligned in the stacking direction in one of the internal electrodes is defined as the vertical alignment number, 4. The multilayer ceramic capacitor according to claim 3, wherein a surface of the arc-shaped convex portion is formed by arranging the conductive particles in an arc, the number of the conductive particles being equal to or greater than the number of the vertically arranged internal electrodes in which the arc-shaped convex portion is formed.

6. 4. The multilayer ceramic capacitor according to claim 3, wherein the surface of said arc-shaped convex portion is formed by five or more of said conductive particles being arranged in an arc.

7. 3. The multilayer ceramic capacitor according to claim 1, wherein a dimension in the length direction of the arc-shaped protrusion is greater than a dimension in the lamination direction of the internal electrode in which the arc-shaped protrusion is formed.

8. 4. The multilayer ceramic capacitor according to claim 3, wherein a dimension of the arc-shaped protrusion in the lamination direction is larger than an average particle diameter of the conductive particles in the internal electrode in which the arc-shaped protrusion is formed.

9. 3. The multilayer ceramic capacitor according to claim 1, wherein the radius of curvature of the arc of said arc-shaped convex portion is not less than 1 [mu]m and not more than 3 [mu]m.

10. 3. The multilayer ceramic capacitor according to claim 1, wherein the radius of curvature of the arc of each of the arc-shaped convex portions is from 1 to 5 times the dimension in the lamination direction of the internal electrode in which the arc-shaped convex portion is formed.

11. the internal electrodes each have a swelling portion that swells in both directions of the lamination direction, the swelling portion has an arc-shaped convex portion that is convex in one direction of the stacking direction and an arc-shaped convex portion that is convex in another direction of the stacking direction, 3. The multilayer ceramic capacitor according to claim 1, wherein, of the arc-shaped protrusions constituting the bulge portion, both ends in the length direction of one of the arc-shaped protrusions and both ends in the length direction of the other of the arc-shaped protrusions are aligned in the length direction.

12. The multilayer ceramic capacitor according to claim 11 , wherein the swollen portion is a plurality of swollen portions formed continuously in the longitudinal direction.

13. 13. The multilayer ceramic capacitor according to claim 12, wherein, of adjacent internal electrodes, each end in the longitudinal direction of the swelling portion formed in one internal electrode and each end in the longitudinal direction of the swelling portion formed in the other internal electrode are located at different positions in the longitudinal direction.

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