Multilayer ceramic capacitor

Abstract

Provided is a multilayer ceramic capacitor capable of improving reliability while improving effective capacitance. A laminated ceramic capacitor (100) is provided with a laminated body (6) including a plurality of dielectric layers (2) and a plurality of internal electrode layers (4) laminated in the thickness direction, and a pair of external electrodes, an inner layer part (16) of a laminated body (6) is provided with a central region (16c) at the center in the width direction, a first side edge adjacent region (16a) adjacent to a first side edge part (20a), and a second side edge adjacent region (16b) adjacent to a second side edge part (20b). The area-equivalent diameter (D50) of the dielectric particles in the dielectric layer in the first side edge adjacent region (16a) and the second side edge adjacent region (16b) is larger than the area-equivalent diameter (D50) of the dielectric particles in the dielectric layer in the central region (16c).

Description

Technical Field

[0001] The present invention relates to a laminated ceramic capacitor. Background Art

[0002] With the miniaturization of electronic devices, such as mobile phones, and the increasing speed of CPUs, the demand for multilayer ceramic capacitors (MLCCs) is increasing. Multilayer ceramic capacitors have a structure in which dielectric layers and internal electrode layers are alternately stacked. Due to the thinning of the high-dielectric-constant dielectric layers, they are compact and have high capacitance. While multilayer ceramic capacitors using various materials are known, those using barium titanate (BaTiO3)-based compounds in the dielectric layer exhibit high performance and are therefore widely used. For example, Patent Document 1 discloses a multilayer ceramic capacitor using a perovskite-type (ABO3-type) barium titanate-based composite compound as the dielectric layer of the stack.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-178686 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] In multilayer ceramic capacitors, there are demands for increased effective capacitance and improved reliability. To reduce capacitance change when voltage is applied and thus increase effective capacitance, the relative permittivity of the dielectric layer is reduced. Suppressing the sintering of the dielectric particles can be considered, minimizing the grain growth of the dielectric particles after the sintering process. However, in this case, grain growth of the dielectric particles near the side edges as well as the inner layer is also suppressed, thereby inhibiting the progress of rare earth element solid solution. Consequently, the reliability of the multilayer ceramic capacitor decreases.

[0008] An object of the present invention is to provide a multilayer ceramic capacitor capable of increasing effective capacitance and improving reliability.

[0009] Technical solutions to solve problems

[0010] The multilayer ceramic capacitor according to the present invention comprises: a multilayer body having a first main surface and a second main surface opposite to each other in the thickness direction, a first side surface and a second side surface opposite to each other in the width direction, and a first end surface and a second end surface opposite to each other in the length direction, and including a plurality of dielectric layers and a plurality of internal electrode layers stacked in the thickness direction; and a pair of external electrodes, respectively provided on the first end surface and the second end surface, and connected to the plurality of internal electrode layers, wherein the multilayer body is divided into: a first side edge portion extending along the first side surface and not including the internal electrode layer; a second side edge portion extending along the second side surface and not including the internal electrode layer; a first outer layer portion sandwiched by the first side edge portion and the second side edge portion, and surrounded by the internal electrode layer closest to the first main surface and the first main surface; sandwiched; a second outer layer portion, sandwiched by the first side edge portion and the second side edge portion, and sandwiched by the internal electrode layer closest to the second main surface and the second main surface; and an inner layer portion, sandwiched by the first side edge portion and the second side edge portion, and sandwiched by the first outer layer portion and the second outer layer portion, in a cross-section of the multilayer ceramic capacitor across the center of the longitudinal direction, the inner layer portion has a central area in the center of the width direction, a first side edge adjacent area adjacent to the first side edge portion, and a second side edge adjacent area adjacent to the second side edge portion, and the area equivalent diameter D50 of the dielectric particles in the dielectric layer of the first side edge adjacent area and the second side edge adjacent area is larger than the area equivalent diameter D50 of the dielectric particles in the dielectric layer of the central area.

[0011] Effects of the Invention

[0012] According to the present invention, a multilayer ceramic capacitor capable of improving reliability while increasing effective capacitance can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a perspective view showing the outer shape of a multilayer ceramic capacitor.

[0014] Figure 2 yes Figure 1 This is a cross-sectional view of the multilayer ceramic capacitor shown along line II-II.

[0015] Figure 3 yes Figure 1 This is a cross-sectional view of the multilayer ceramic capacitor shown along line III-III.

[0016] Figure 4 It is a cross-sectional schematic diagram of the core-shell particle.

[0017] Figure 5 This is an example of an enlarged image of a cross section of an exposed inner layer.

[0018] Figure 6 The diagram shows SEM images of the side edge portion, the area adjacent to the side edge of the inner layer portion, and the central area of the inner layer portion in the form of drawings. DETAILED DESCRIPTION

[0019] A specific embodiment of the present invention (hereinafter referred to as "this embodiment") will be described. The present invention is not limited to the following embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0020] (1) Multilayer ceramic capacitors

[0021] The multilayer ceramic capacitor of this embodiment has a first main surface and a second main surface facing each other in the thickness direction, a first side surface and a second side surface facing each other in the width direction, and a first end surface and a second end surface facing each other in the length direction. The multilayer ceramic capacitor includes a laminate comprising a plurality of dielectric layers and a plurality of internal electrode layers stacked in the thickness direction, and a pair of external electrodes provided on the first end surface and the second end surface, respectively, and connected to the plurality of internal electrode layers. The dielectric layers contain dielectric particles. In addition, the stack is divided into a first side edge portion extending along the first side surface and not including the internal electrode layer, a second side edge portion extending along the second side surface and not including the internal electrode layer, a first outer layer portion sandwiched by the first side edge portion and the second side edge portion and sandwiched by the internal electrode layer closest to the first main surface and the first main surface, a second outer layer portion sandwiched by the first side edge portion and the second side edge portion and sandwiched by the internal electrode layer closest to the second main surface and the second main surface, and an inner layer portion sandwiched by the first side edge portion and the second side edge portion and sandwiched by the first outer layer portion and the second outer layer portion. Furthermore, in a cross-section of the multilayer ceramic capacitor taken across the center in the longitudinal direction, the inner layer portion includes a central region in the center in the width direction, a first side edge adjacent region adjacent to the first side edge portion, and a second side edge adjacent region adjacent to the second side edge portion, and the area-equivalent diameter D50 of the dielectric particles in the dielectric layers of the first side edge adjacent region and the second side edge adjacent region is larger than the area-equivalent diameter D50 of the dielectric particles in the dielectric layer of the central region.

[0022] use Figures 1 to 3 One embodiment of a multilayer ceramic capacitor will be described. Figure 1 It is a perspective view showing the outer shape of a multilayer ceramic capacitor. Figure 2 yes Figure 1 The cross section of the multilayer ceramic capacitor shown is taken along line II-II. Figure 3 yes Figure 1 This is a cross-sectional view of the multilayer ceramic capacitor shown along line III-III.

[0023] A laminated ceramic capacitor (100) comprises a laminate (6) comprising a plurality of laminated dielectric layers (2) and a plurality of internal electrode layers (4), and a pair of external electrodes (8a, 8b) provided on both end faces (14a, 14b) of the laminate (6). The laminated ceramic capacitor (100) and the laminate (6) have a substantially rectangular parallelepiped shape. The term "substantially rectangular parallelepiped" includes not only a rectangular parallelepiped but also a rectangular parallelepiped with rounded corners and / or ridges. Here, the corner is a portion where three faces of the laminate (6) intersect, and the ridge is a portion where two faces of the laminate intersect. Preferably, the laminated ceramic capacitor (100) and the laminate (6) have a substantially rectangular parallelepiped shape with rounded corners and / or ridges.

[0024] The stack (6) has a first main surface (10a) and a second main surface (10b) opposite to each other in the thickness direction T, a first side surface (12a) and a second side surface (12b) opposite to each other in the width direction W, and a first end surface (14a) and a second end surface (14b) opposite to each other in the length direction L. Here, the thickness direction T refers to the direction in which the dielectric layer (2) and the internal electrode layer (4) are stacked. The thickness direction T is also called the stacking direction T. The length direction L refers to the direction perpendicular to the thickness direction T and the direction in which the end surfaces (14a, 14b) are opposite to each other. The width direction W is the direction perpendicular to the thickness direction T and the length direction L. The surface including the thickness direction T and the width direction W is defined as the WT surface, the surface including the width direction W and the length direction L is defined as the LW surface, and the surface including the length direction L and the thickness direction T is defined as the LT surface.

[0025] The external electrodes (8a, 8b) include a first external electrode (8a) provided on the first end surface (14a) and a second external electrode (8b) provided on the second end surface (14b). The first external electrode (8a) may be provided not only on the first end surface (14a) but also around the first main surface (10a), the second main surface (10b), the first side surface (12a), and a portion of the second side surface (12b). In addition, the second external electrode (8b) may be provided not only on the second end surface (14b) but also around the first main surface (10a), the second main surface (10b), the first side surface (12a), and a portion of the second side surface (12b). However, the first external electrode (8a) and the second external electrode (8b) are not in contact and are electrically isolated.

[0026] The internal electrode layer (4) includes a plurality of first internal electrode layers (4a) and a plurality of second internal electrode layers (4b). The first internal electrode layer (4a) and the second internal electrode layer (4b) are respectively composed of opposing electrode portions of a substantially rectangular shape that face each other, and lead electrode portions that extend to end faces (14a, 14b) and are connected to external electrodes (8a, 8b). That is, the plurality of first internal electrode layers (4a) extend to the first end face (14a) via the lead electrode portions and are electrically connected thereto to the first external electrode (8a). In addition, the plurality of second internal electrode layers (4b) extend to the second end face (14b) via the lead electrode portions and are electrically connected thereto to the second external electrode (8b). The first internal electrode layers (4a) and the second internal electrode layers (4b) are alternately stacked so as to face each other in the thickness direction T with the dielectric layer (2) interposed therebetween. The first internal electrode layer (4a) and the second internal electrode layer (4b) that are opposed to each other with the dielectric layer (2) interposed therebetween are not electrically connected. Therefore, when a voltage is applied via the external electrodes (8a, 8b) and the lead electrode portion, electric charge accumulates between the opposing electrode portion of the first internal electrode layer (4a) and the opposing electrode portion of the second internal electrode layer (4b). The accumulated electric charge generates electrostatic capacitance, thereby exhibiting a function as a capacitance element (capacitor).

[0027] like Figure 3 As shown, the stack (6) is composed of an inner layer portion (16), a first outer layer portion (18a), a second outer layer portion (18b), a first side edge portion (20a), and a second side edge portion (20b). The first side edge portion (20a) extends along the first side surface (12a) and is a layered region that does not include the internal electrode layers (4a, 4b). In addition, the second side edge portion (20b) extends along the second side surface (12b) and is a layered region that does not include the internal electrode layers (4a, 4b). That is, the first side edge portion (20a) is a region sandwiched between the end portion of the internal electrode layers (4a, 4b) on the first side surface (12a) and the first side surface (12a), and the second side edge portion is a region sandwiched between the end portion of the internal electrode layers (4a, 4b) on the second side surface (12b) and the second side surface (12b). Furthermore, in a cross section of the multilayer ceramic capacitor (100) that passes through the center in the longitudinal direction, the inner layer portion (16) is divided into a central region (16c) in the center in the width direction, a first side edge adjacent region (16a) adjacent to the first side edge portion (20a), and a second side edge adjacent region (16b) adjacent to the second side edge portion (20b). The first side edge adjacent region (16a) is a range from the boundary between the first side edge portion (20a) and the inner layer portion (16) toward the center of the inner layer portion (16) to 20 μm. The second side edge adjacent region (16b) is a range from the boundary between the second side edge portion (20b) and the inner layer portion (16) toward the center of the inner layer portion (16) to 20 μm.

[0028] The first outer layer portion (18a) is a region sandwiched between the first side edge portion (20a) and the second side edge portion (20b), and is sandwiched between the internal electrode layer closest to the first main surface (10a) among the multiple internal electrode layers (4a, 4b) and the first main surface (10a). The second outer layer portion (18b) is a region sandwiched between the first side edge portion (20a) and the second side edge portion (20b), and is sandwiched between the internal electrode layer closest to the second main surface (10b) among the multiple internal electrode layers (4a, 4b) and the second main surface (10b). The inner layer portion (16) is a region sandwiched between the first outer layer portion (18a) and the second outer layer portion (18b), that is, a region arranged between the internal electrode layer closest to the first main surface (10a) and the internal electrode layer closest to the second main surface (10b). This inner layer portion functions as a capacitor element. In short, the inner layer portion (16) that performs the function of the capacitor element is clamped by the first outer layer portion (18a) and the second outer layer portion (18b) in the stacking (thickness) direction, and the entire portion is clamped by the first side edge portion (20a) and the second side edge portion (20b) in the width direction. Figure 3 In the figure, the length T1 of the inner layer portion (16) indicating the range in the thickness direction T and the length W1 of the inner layer portion (16) indicating the range in the width direction W are shown. In addition, the length W2 of the first side edge portion (20a) indicating the range in the width direction W and the length W3 of the second side edge portion (20b) indicating the range in the width direction W are shown. In addition, the length T2 of the first outer layer portion (18a) indicating the range in the thickness direction T and the length T3 of the second outer layer portion (18b) indicating the range in the thickness direction T are shown.

[0029] The dimensions of the laminated ceramic capacitor (100) and the laminate (6) are not particularly limited. For example, the length direction L dimension is greater than 0.2 mm and less than 1.8 mm, the width direction W dimension is greater than 0.1 mm and less than 1.0 mm, and the thickness direction T dimension is greater than 0.1 mm and less than 1.0 mm. Figures 1 to 3 In FIG. 5 , the longitudinal dimension L is shown to be larger than the width dimension W. However, the multilayer ceramic capacitor of this embodiment is not limited to such dimensions. The longitudinal dimension L may be smaller than the width dimension W.

[0030] <Inner layer - dielectric layer>

[0031] The dielectric layer, along with the internal electrode layer, forms the inner layer of a multilayer ceramic capacitor. The dielectric layer contains dielectric particles (dielectric grains). Specifically, the dielectric layer is a sintered polycrystal (ceramic) composed of numerous dielectric particles bonded via grain boundaries and triple points. The dielectric particles are composed of perovskite oxides, forming the primary component of the dielectric layer. The dielectric layer can also be considered a dielectric ceramic primarily composed of perovskite oxides. Perovskite oxides have a composition represented by the general formula: ABO₃. At room temperature, they exhibit cubic, tetragonal, orthorhombic, and rhombohedral crystal structures similar to cubic. Furthermore, atoms of the A-site element (hereinafter referred to as "A-site atoms") and atoms of the B-site element (hereinafter referred to as "B-site atoms") are ionized and occupy the A and B sites, respectively, of the perovskite structure. The term "primary component" refers to the component with the highest proportion in the dielectric layer. The content of the dielectric particles (perovskite-type oxide) as the main component in the dielectric layer may be 50 mass % or more, 60 mass % or more, 70 mass % or more, 80 mass % or more, or 90 mass % or more.

[0032] The dielectric particles contain barium (Ba) and titanium (Ti). In other words, the perovskite oxide that constitutes the dielectric particles is a barium titanate (BaTiO3)-based compound. BaTiO3 has a large spontaneous polarization at room temperature. Therefore, it is a ferroelectric with a high dielectric constant. Using a BaTiO3-based compound as the main component can further increase the capacitance of the capacitor. BaTiO3-based compounds include not only BaTiO3 but also compounds in which a portion of the Ba in BaTiO3 is replaced with other A-site elements such as Sr and / or Ca, or compounds in which a portion of the Ti is replaced with other B-site elements such as Zr and / or Hf. However, the molar ratio of Ba in the A-site element is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. Furthermore, the molar ratio of Ti in the B-site element is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more.

[0033] The dielectric layer contains a rare earth element (Re) as a minor component. Rare earth elements (Re) are a general term for elements that form the group consisting of scandium (Sc), atomic number 21, yttrium (Y), atomic number 39, and lanthanum (La), atomic number 57, through lutetium (Lu), atomic number 71, in the periodic table. The rare earth element (Re) is preferably one or more elements selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), with dysprosium (Dy) being particularly preferred.

[0034] Rare earth elements (Re) improve the lifespan of dielectric layers and enhance reliability. In BaTiO3, Ba ions (Ba2+), with a large ionic radius, occupy the A site, while Ti ions (Ti4+), with a smaller ionic radius, occupy the B site. Rare earth elements (Re) typically form trivalent ions (Re3+), with ionic radii intermediate between those of Ba2+ and Ti4+. Therefore, rare earth elements form a solid solution in BaTiO3, replacing either or both Ba and Ti. The rare earth element occupying the Ba site (A site) acts as a donor, while the rare earth element occupying the Ti site (B site) acts as an acceptor.

[0035] BaTiO3-based dielectric ceramics contain a high concentration of oxygen vacancies in the dielectric particles, generated during the firing process. In particular, multilayer ceramic capacitors are fired in a weakly reducing atmosphere during their manufacture to suppress oxidation of the internal electrode layers. Therefore, BaTiO3 is easily reduced, generating oxygen vacancies. Oxygen vacancies have positive charges and serve as pathways for these charges. If there are many oxygen vacancies, more charges migrate, which can easily lead to insulation resistance degradation. Especially under high-temperature conditions, oxygen vacancies tend to migrate to the vicinity of the negative electrode. Therefore, when a load is applied, the amount of oxygen vacancies on the negative electrode side increases locally, degrading the insulation resistance. In contrast, adding rare earth elements that act as donors and / or acceptors to BaTiO3 suppresses the generation and movement of oxygen vacancies. This suppresses insulation resistance degradation and dielectric breakdown, resulting in a longer high-temperature load life.

[0036] The dielectric layer further includes a first additive element (Me) as a secondary component. The first additive element (Me) is one or more elements selected from the group consisting of manganese (Mn), vanadium (V), iron (Fe), copper (Cu), cobalt (Co), nickel (Ni), and chromium (Cr), and preferably includes nickel (Ni).

[0037] The first additive element (Me) has the effect of increasing the insulation resistance (IR) of the dielectric layer. As mentioned above, during the manufacture of multilayer ceramic capacitors, firing is performed in a weakly reducing atmosphere, so the BaTiO3 contained in the dielectric layer is easily reduced. When BaTiO3 is reduced to a semiconductor, its insulation resistance decreases. If the insulation resistance is low, leakage current (leakage current) tends to flow, which increases dielectric loss and easily leads to a deterioration of life. The first additive element (Me) is mainly an acceptor element that dissolves in the Ti site of BaTiO3 and has the effect of improving reduction resistance. Therefore, by adding the first additive element, the insulation resistance of the dielectric layer after firing is increased, resulting in the suppression of leakage current and the extension of high-temperature load life.

[0038] The rare earth element (Re) and the first additive element (Me) can each be a single element or a combination of multiple elements. Furthermore, it is sufficient that at least a portion of the rare earth element and the first additive element is contained in the dielectric particles. Elements not contained in the dielectric particles may be present at grain boundaries or triple points.

[0039] The dielectric layer may also contain accessory components other than the rare earth element (Re) and the first additive element (Me). Examples of such accessory components include, but are not limited to, silicon (Si), magnesium (Mg), aluminum (Al), and / or compounds thereof. These accessory components may be contained within the dielectric particles or present at grain boundaries or triple points.

[0040] In the laminated ceramic capacitor of this embodiment, in a cross-section passing through the center of its longitudinal direction, the dielectric layer contained in the inner layer portion contains both core-shell particles and uniform solid solution particles as dielectric particles. That is, the dielectric layer of the inner layer portion contains core-shell particles and uniform solid solution particles in a mixed state. By including both core-shell particles and uniform solid solution particles in a given ratio, the dielectric constant and insulation resistance of the dielectric layer become higher, and reliability is significantly improved. The reasons for this are described below.

[0041] exist Figure 4 A schematic cross-sectional view of a core-shell particle is shown in FIG. The core-shell particle (30) is a particle having a core portion (32) with a low concentration of accessory components such as rare earth elements, and a shell portion (34) provided on the surface of the core portion with a high concentration of accessory components. Specifically, the core-shell particle (30) is a dielectric particle in which the molar ratio of the rare earth element (Re) to titanium (Ti) at a distance of 10 nm from the outer surface of the particle to the inside (the outer periphery of the particle) is 1.5 times or more of the molar ratio of the rare earth element (Re) to titanium (Ti) at the center of the particle. The core-shell particle (30) can also be said to be a particle having a Re concentration distribution ratio of 1.5 or more. Here, the Re concentration distribution ratio is the ratio ((shell Re / Ti ratio) / (core Re / Ti ratio)) of the molar ratio of the rare earth element (Re) to titanium (Ti) at the outer periphery of the particle and the molar ratio of the rare earth element (Re) to titanium (Ti) at the center of the particle.

[0042] The core-shell structure of dielectric particles significantly improves high-temperature load life. This is because the inclusion of accessory components such as rare earth elements, which function as donors and acceptors, in the shell suppresses the migration of oxygen vacancies that can cause insulation degradation. The concentration distribution of the first additive element (Me) within the core-shell particles is not particularly limited.

[0043] Homogeneous solid solution particles are particles in which accessory components are uniformly dissolved within the particle, or particles in which accessory components are not dissolved. Specifically, homogeneous solid solution particles are dielectric particles in which the molar ratio of rare earth element (Re) to titanium (Ti) within a distance of 10 nm from the outer surface of the particle (the outer periphery) is less than 1.5 times the molar ratio of rare earth element (Re) to titanium (Ti) in the particle's center. Homogeneous solid solution particles can also be described as particles in which the Re concentration distribution ratio ((shell Re / Ti ratio) / (core Re / Ti ratio)) is less than 1.5. Homogeneous solid solution particles are also called non-core-shell particles.

[0044] The thickness of the dielectric layer is preferably 0.3 μm or more and 5.0 μm or less, more preferably 0.4 μm or more and 4.0 μm or less, and further preferably 0.4 μm or more and 3.0 μm or less. By setting the thickness of the dielectric layer to a given value or more, it is possible to suppress the generation of insulation breakdown and life degradation during use of the multilayer ceramic capacitor. In addition, by setting the thickness of the dielectric layer to a given value or less, the dielectric layer is thinned, and further capacitance of the multilayer ceramic capacitor can be achieved. The number of dielectric layers is not particularly limited. The number of dielectric layers constituting the outer layer and the inner layer is preferably 100 or more and 2000 or less.

[0045] <Inner layer - internal electrode layer>

[0046] The internal electrode layer (the first internal electrode layer and the second internal electrode layer) together with the dielectric layer constitute the inner layer portion. In addition, the internal electrode layer is composed of an opposing electrode portion and an extraction electrode portion. The opposing electrode portion sandwiches the dielectric layer and has the function of exhibiting the function of a capacitor element. The extraction electrode portion has the function of electrically connecting the opposing electrode portion and the external electrode. The internal electrode layer contains a conductive metal. As the conductive metal, well-known electrode materials such as nickel (Ni), copper (Cu), silver (Ag), palladium (Pd), silver (Ag)-palladium (Pd) alloy and / or gold (Au) can be used. However, from the perspective of cost reduction, Ni and Cu, which are base metals, are preferred, and Ni is particularly preferred.

[0047] The internal electrode layer may also contain components other than conductive metals. As such components, ceramic particles that act as common materials can be listed. By adding common materials, the shrinkage behavior of the internal electrode layer matches that of the dielectric layer during the firing process when manufacturing the stacked ceramic capacitor. As a result, the occurrence of defects such as internal electrode layer peeling can be suppressed. As ceramic particles, dielectric particles such as BaTiO3-based compounds contained in the dielectric layer are preferred. In addition, the thickness of the internal electrode layer is preferably greater than 0.2μm and less than 1.5μm, more preferably greater than 0.3μm and less than 1.0μm. By setting the internal electrode thickness to a given value or more, problems such as electrode interruption can be prevented. In addition, by setting it to less than a given value, the proportion of the dielectric layer in the capacitor can be prevented from decreasing, which helps to increase the capacitance. Furthermore, the number of layers of the internal electrode layer is preferably greater than 10 and less than 2000.

[0048] The thickness of the internal electrode layer is measured, for example, as follows. First, a cross-section (LT) passing through the center of the multilayer ceramic capacitor is polished to expose the inner layer. If necessary, the exposed cross-section may be etched to remove any internal electrode layer stretched during polishing. Figure 5 This is an example of an enlarged image of the exposed inner layer cross section. In the enlarged image shown, for example, multiple straight lines La, Lb, Lc, Ld, and Le extending in the thickness direction T are depicted at approximately equal intervals S. The interval S is preferably approximately 5 to 10 times the thickness of the internal electrode layer to be measured. For example, when measuring an internal electrode layer approximately 1 μm thick, the interval S is set to 5 μm.

[0049] Next, the thickness d1, d2, d3, d4, and d5 of each internal electrode layer is measured on each of the five straight lines La, Lb, Lc, Ld, and Le. This is performed for all five internal electrode layers, and the average value is used as the thickness of the internal electrode layer of this embodiment. However, if an internal electrode layer is missing on the lines La, Lb, Lc, Ld, and Le, resulting in the dielectric layers sandwiching the internal electrode layer being connected, or if the magnified image of the measurement location is unclear, a new straight line is drawn to measure the thickness of the internal electrode layer. Furthermore, if the number of internal electrode layers stacked is less than five, the thickness of all internal electrode layers is measured, and the average value is used as the thickness of the internal electrode layer of this embodiment. The thickness of the dielectric layer can also be measured using the same method as for the internal electrode layer. The thickness D1, D2, D3, D4, and D5 of each dielectric layer is measured on each of the five straight lines La, Lb, Lc, Ld, and Le, and the average value is used as the thickness of the dielectric layer of this embodiment.

[0050] Preferably, in a cross section of the multilayer ceramic capacitor taken across the longitudinal center, the widthwise end positions of adjacent internal electrode layers are offset by 5 μm or less. That is, the widthwise end positions of adjacent upper and lower internal electrode layers are preferably aligned.

[0051] Tin (Sn) may be present at the interface between the dielectric layer and the internal electrode layer. If Sn is present, it may exist in a layered form parallel to the internal electrode layer, or it may be dispersed. Furthermore, Sn may be dissolved in the internal electrode layer or present in the dielectric layer.

[0052] <Outer layer>

[0053] The outer layer (first and second outer layer) is composed of a dielectric material sandwiched between the first and second side edge portions, and between the internal electrode layer closest to the main surfaces (first and second main surfaces) and the main surfaces. Specifically, it is provided above and below the inner layer. The outer layer is composed of dielectric ceramic and is the region within it that does not contain the internal electrode layer. The outer layer protects the inner layer, which functions as a capacitor element, from both above and below.

[0054] The dielectric material constituting the outer layer comprises dielectric particles containing barium (Ba) and titanium (Ti), and further comprises a rare earth element (Re) and one or more first additive elements (Me) selected from the group consisting of manganese (Mn), vanadium (V), iron (Fe), copper (Cu), cobalt (Co), nickel (Ni), and chromium (Cr) as accessory components. Specifically, the dielectric layer comprises dielectric particles comprising a BaTiO3-based compound, and further comprises the rare earth element (Re) and the first additive element (Me) as accessory components. Furthermore, the dielectric material may also contain silicon (Si), magnesium (Mg), aluminum (Al), and / or compounds thereof as accessory components. Details regarding the BaTiO3-based compound and accessory components are as described for the inner layer.

[0055] The composition and microstructure of the outer layer portion may be the same as or different from the dielectric layer included in the inner layer portion. If the composition of the outer layer portion is the same as that of the inner layer portion, the dielectric green sheet used to form the inner layer portion can be used to form the outer layer portion during the manufacture of the multilayer ceramic capacitor.

[0056] Preferably, in a cross-section across the center of the length direction of the stacked ceramic capacitor, the dielectric constituting the outer layer portion (the first outer layer portion and the second outer layer portion) contains uniform solid solution particles as dielectric particles. By making the outer layer portion contain uniform solid solution particles, it is possible to further improve reliability. Unlike core-shell particles, uniform solid solution particles can grow without destroying the internal structure of the particles. Therefore, particle growth can be fully promoted during the firing process during the manufacture of the stacked ceramic capacitor, and as a result, densification of the dielectric constituting the outer layer portion can be achieved. If the densification of the outer layer portion progresses, it is possible to prevent impurities such as moisture from invading from the upper surface side, thereby improving moisture resistance reliability.

[0057] The details of the uniform solid-solution particles contained in the outer layer are the same as those described for the inner layer. Specifically, the uniform solid-solution particles are dielectric particles having a Re concentration distribution ratio ((shell Re / Ti ratio) / (core Re / Ti ratio)) of less than 1.5. More preferably, the dielectric material constituting the outer layer primarily comprises uniform solid-solution particles, and particularly preferably comprises only uniform solid-solution particles. Furthermore, the Re concentration distribution ratio is preferably greater than 1.0 and less than 1.5.

[0058] <Side edge>

[0059] The side margins (first and second side margins) extend along the side surfaces (first and second side surfaces) and are composed of a dielectric material that does not include an internal electrode layer. Specifically, they are provided along the side surfaces of the multilayer ceramic capacitor, sandwiching the inner and outer layers. The side margins are also called side gaps. The side margins (side gaps) are composed of dielectric ceramic. The provision of the side margins prevents the intrusion of impurities such as moisture from the side surfaces. The side margins can be a single layer or a multilayer structure consisting of multiple layers.

[0060] The dielectric material forming the side edge portion includes dielectric particles containing barium (Ba) and titanium (Ti), and further includes a rare earth element (Re) and one or more first additive elements (Me) selected from the group consisting of manganese (Mn), vanadium (V), iron (Fe), copper (Cu), cobalt (Co), nickel (Ni), and chromium (Cr) as accessory components. Specifically, the dielectric layer comprises a BaTiO3-based compound, and further includes the rare earth element (Re) and the first additive element (Me) as accessory components. Furthermore, the dielectric material may also include silicon (Si), magnesium (Mg), aluminum (Al), and / or compounds thereof as accessory components. Details of the BaTiO3-based compound and accessory components are as described for the inner layer portion.

[0061] The composition and microstructure of the side edge portion may be the same as or different from the dielectric layer contained in the inner layer portion. The side edge portion may also be formed integrally with the inner layer portion and the outer layer portion when the multilayer ceramic capacitor is manufactured. In this case, the composition and microstructure of the dielectric layer constituting the side edge portion are continuous with the dielectric layer constituting the inner layer portion and / or the outer layer portion. On the other hand, the side edge portion may also be formed independently from the inner layer portion and the outer layer portion. Specifically, the side edge green body is pasted on the side of the stacked chip that becomes the inner layer portion and the outer layer portion to produce the green body portion, and the green body portion is sintered to produce it. In this embodiment, in order to properly control the sintering state of the dielectric particles in each region, it is preferred that the effective molar ratio of the A position relative to the B position in the dielectric contained in the inner layer portion and the effective molar ratio of the A position relative to the B position in the dielectric contained in the side edge portion are different.

[0062] Preferably, in a cross section of the multilayer ceramic capacitor taken across the longitudinal center, the dielectric constituting the side edge portions (the first side edge portion and the second side edge portion) includes core-shell particles and uniform solid solution particles as dielectric particles.

[0063] If the applied voltage is sufficiently high, the electric field intensity between the internal electrode layers increases, and the electric field distribution expands in the width direction. As a result, the electric field is applied not only within the inner layer but also at the side edges. This promotes the solid solution of rare earth elements (Re) in the side edges and adjacent areas, thereby improving reliability. Furthermore, this promotes grain growth of the dielectric particles, further enhancing reliability.

[0064] The details of the core-shell particles included in the side edge portion are the same as those described for the inner layer portion. Specifically, the core-shell particles are dielectric particles having a Re concentration distribution ratio ((shell Re / Ti ratio) / (core Re / Ti ratio)) of 1.5 or greater. More preferably, the dielectric material constituting the side edge portion primarily comprises core-shell particles, and particularly preferably comprises only core-shell particles. Furthermore, the dielectric particles included in the dielectric material may have a Re concentration distribution ratio of 1.0 to 2.0, 1.5 to 2.0, or 1.2 to 1.8.

[0065] <External electrodes>

[0066] The external electrodes (first and second external electrodes) function as the input and output terminals of the multilayer ceramic capacitor. The external electrodes can employ known structures. For example, they may include a base electrode layer and a plating layer disposed on the base electrode layer.

[0067] The base electrode layer comprises at least one selected from the group consisting of a sintered layer, a resin layer, and a thin film layer. The sintered layer is formed by applying a conductive paste containing glass and metal to a laminate and then sintering it. Firing can be performed simultaneously with the firing of the laminate, or after the firing of the laminate. The sintered layer can be a single layer or can be composed of multiple layers. The metal contained in the sintered layer is preferably copper (Cu), nickel (Ni), silver (Ag), palladium (Pd), a silver (Ag)-palladium (Pd) alloy, and / or gold (Au). The resin layer contains conductive particles and a thermosetting resin. The resin layer can be a single layer or can be composed of multiple layers. The thin film layer is formed by a thin film forming method such as sputtering and vapor deposition, and is a layer with a thickness of less than 1 μm in which metal particles are deposited. The thin film layer is preferably a layer with a thickness of less than 0.5 μm.

[0068] The plating layer includes metals such as copper (Cu), nickel (Ni), tin (Sn), silver (Ag), palladium (Pd), silver (Ag)-palladium (Pd), and / or gold (Au). The plating layer can be a single layer or composed of multiple layers. A preferred plating layer has a two-layer structure of Ni plating and Sn plating. The Ni plating layer can prevent solder from corroding the base layer when mounting the multilayer ceramic capacitor. In addition, the Sn plating layer improves the wettability of the solder, thereby facilitating the mounting of the multilayer ceramic capacitor.

[0069] Alternatively, the external electrode layer may be formed of a plating layer instead of a base electrode layer. In this case, the plating layer is directly provided on the laminate and directly connected to the lead-out electrode portion of the internal electrode layer. However, a catalyst may also be provided on the laminate as a pretreatment. Preferably, the plating layer includes a first plating layer and a second plating layer provided on the first plating layer. The first plating layer and the second plating layer may, for example, include one metal selected from the group consisting of copper (Cu), nickel (Ni), tin (Sn), lead (Pd), gold (Au), silver (Ag), palladium (Pd), bismuth (Bi), and zinc (Zn), or an alloy containing such metals. When the internal electrode layer includes Ni, the first plating layer preferably includes Cu, which has good bonding properties with Ni. In addition, the first plating layer preferably also includes Ni, which has good solder barrier properties. The second plating layer preferably includes Sn or Au, which have good solder wettability.

[0070] However, the plating layer is not limited to being composed of a first plating layer and a second plating layer. It is also possible to omit the second plating layer and constitute the plating layer solely by the first plating layer. Alternatively, another plating layer may be provided on the second plating layer. In either case, the plating layer preferably does not contain glass. Furthermore, the metal content of the plating layer is preferably 99% by volume or greater. The plating layer exhibits granular growth along the thickness direction, resulting in a columnar shape.

[0071] <Details of Dielectric Particles>

[0072] Next, the dielectrics of the inner layer portion, the first side edge portion, and the second side edge portion will be described in detail.

[0073] The dielectric contained in the inner layer and side edges (the first and second side edges) includes dielectric particles containing barium (Ba) and titanium (Ti) and a rare earth element (Re) as a minor component. In this embodiment, the dielectric contained in the inner layer and side edges includes dysprosium (Dy) as a minor rare earth element. The dielectric contained in the inner layer, the first side edge, and the second side edge has a perovskite (ABO3) structure.

[0074] It is preferred that a first effective molar ratio Rm1, representing the effective molar ratio of the A site to the B site (A / B ratio), in the dielectric layer in the central region, and a second effective molar ratio Rm2, representing the effective molar ratio of the A site to the B site (A / B ratio), in the first side edge adjacent region and the second side edge adjacent region be substantially the same. The effective molar ratio Rm1 and the effective molar ratio Rm2 are preferably 1 or greater, and more preferably 1.0000 or greater and 1.0020 or less.

[0075] The third effective molar ratio Rm3 indicating the effective molar ratio of the A site to the B site (A / B ratio) in the dielectric contained in the first and second side edge portions is preferably less than 1, and more preferably 0.990 to 0.998.

[0076] Here, in the present embodiment, the A-site elements include Ba and Ca, and the B-site elements include Ti and Zr. The effective molar ratios Rm1 to Rm3 are calculated as (Ba+Ca) / (Ti+Zr).

[0077] Thus, in this embodiment, the third effective molar ratio Rm3 is smaller than the first effective molar ratio Rm1 and the second effective molar ratio Rm2. This allows for appropriate control of the sintering state of the dielectric particles in each region, thereby increasing both the effective capacitance and the reliability.

[0078] In addition, in the present embodiment, the difference between the third effective molar ratio Rm3 and the second effective molar ratio Rm2 is larger than the difference between the second effective molar ratio Rm2 and the first effective molar ratio Rm1.

[0079] Here, in a cross-section taken across the center of the lengthwise direction of the multilayer ceramic capacitor, the area-equivalent diameter (D50) of the dielectric particles in the dielectric layer in the regions adjacent to the first and second side edges is larger than the area-equivalent diameter (D50) of the dielectric particles in the dielectric layer in the central region. By minimizing the particle size of the dielectric particles in the central region of the inner layer, the capacitance change when voltage is applied can be reduced, thereby increasing the effective capacitance. This improves both the effective capacitance and reliability.

[0080] The area-equivalent diameter D50, also known as the median diameter, is the area-equivalent diameter at which the cumulative value of the cumulative distribution of the area-equivalent diameters of multiple dielectric particles reaches 50%. In other words, when multiple dielectric particles are divided into two groups based on a certain area-equivalent diameter, the area-equivalent diameter at which the number of dielectric particles larger than the reference diameter and the number of dielectric particles smaller than the reference diameter are equal is called the area-equivalent diameter D50.

[0081] The area equivalent diameter D50 of the dielectric particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region is preferably 1.1 times or more of the area equivalent diameter D50 of the dielectric particles in the dielectric layer of the central region, more preferably 1.1 times or more and 2.0 times or less, and further preferably 1.2 times or more and 1.8 times or less.

[0082] In this embodiment, the area-equivalent diameter D50 of the dielectric particles in the dielectric at the first and second side edges is larger than the area-equivalent diameter D50 of the dielectric particles in the central region of the dielectric layer. By reducing the particle size of the dielectric particles in the central region of the inner layer, the capacitance change when voltage is applied can be reduced, thereby increasing the effective capacitance. This improves both the effective capacitance and reliability.

[0083] The area-equivalent diameter D50 of the dielectric particles in the dielectric layer of the first side edge portion and the second side edge portion is preferably 1.5 times or more of the area-equivalent diameter D50 of the dielectric particles in the dielectric layer of the central region, more preferably 1.5 times or more and 3 times or less, and even more preferably 1.5 times or more and 2.5 times or less.

[0084] The area-equivalent diameter D50 of the dielectric particles in the dielectric of the first and second side edge portions is larger than the area-equivalent diameter D50 of the dielectric particles in the dielectric layer of the first and second side edge adjacent regions. This can improve both the effective capacitance and the reliability.

[0085] The area equivalent diameter D50 of the dielectric particles in the dielectric layer of the first side edge portion and the second side edge portion is preferably greater than 1.1 times the area equivalent diameter D50 of the dielectric particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region, more preferably greater than 1.1 times and less than 2.0 times, and further preferably greater than 1.2 times and less than 1.8 times.

[0086] The area-equivalent diameter D50 of the dielectric particles in the dielectric layer in the central region is preferably 150 nm to 350 nm, and more preferably 200 nm to 300 nm.

[0087] The area-equivalent diameter D50 of the dielectric particles in the dielectric layer in the first side edge adjacent region and the second side edge adjacent region is preferably greater than 200 nm and less than 500 nm. More preferably, it is greater than 200 nm and less than 400 nm. In addition, in the first side edge adjacent region and the second side edge adjacent region, the area-equivalent diameter D50 of the dielectric particles may also gradually decrease toward the central region. That is, in this region, the area-equivalent diameter D50 of the dielectric particles may also decrease the closer to the central region and increase the closer to the first side edge portion or the second side edge portion.

[0088] The area-equivalent diameter D50 of the dielectric particles in the dielectric of the first side edge portion and the second side edge portion is preferably 300 nm to 500 nm, and more preferably 350 nm to 450 nm.

[0089] Here, in a cross-section taken across the center of the lengthwise direction of the multilayer ceramic capacitor, the area-equivalent diameter D90 of the dielectric particles in the dielectric layer in the regions adjacent to the first and second side edges is larger than the area-equivalent diameter D90 of the dielectric particles in the dielectric layer in the central region. By reducing the particle size of the dielectric particles in the central region of the inner layer, the capacitance change when voltage is applied can be reduced, thereby increasing the effective capacitance. This improves both the effective capacitance and reliability.

[0090] The area-equivalent diameter D90 is the area-equivalent diameter at which the cumulative value of the cumulative distribution of the area-equivalent diameters of a plurality of dielectric particles reaches 90%. In other words, the area-equivalent diameter D90 is the value at which the ratio of dielectric particles having an area-equivalent diameter below this value reaches 90%.

[0091] The area equivalent diameter D90 of the dielectric particles in the dielectric layer of the first side edge adjacent area and the second side edge adjacent area is preferably 1.1 times or more of the area equivalent diameter D90 of the dielectric particles in the dielectric layer of the central area, more preferably 1.1 times or more and 2.0 times or less, and further preferably 1.2 times or more and 1.8 times or less.

[0092] In this embodiment, the area-equivalent diameter D90 of the dielectric particles in the dielectric at the first and second side edges is larger than the area-equivalent diameter D90 of the dielectric particles in the central region of the dielectric layer. By reducing the particle size of the dielectric particles in the central region of the inner layer, the capacitance change when voltage is applied can be reduced, thereby increasing the effective capacitance. This improves both the effective capacitance and reliability.

[0093] The area-equivalent diameter D90 of the dielectric particles in the dielectric layer of the first side edge portion and the second side edge portion is preferably 1.5 times or more of the area-equivalent diameter D90 of the dielectric particles in the dielectric layer of the central region, more preferably 1.5 times or more and 3 times or less, and even more preferably 1.5 times or more and 2.5 times or less.

[0094] The area-equivalent diameter D90 of the dielectric particles in the dielectric layer at the first and second side edges is larger than the area-equivalent diameter D90 of the dielectric particles in the dielectric layer at the first and second side edge adjacent regions. This improves both the effective capacitance and the reliability.

[0095] The area-equivalent diameter D90 of the dielectric particles in the dielectric layer of the first side edge portion and the second side edge portion is preferably greater than 1.1 times the area-equivalent diameter D90 of the dielectric particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region, more preferably greater than 1.1 times and less than 2.0 times, and further preferably greater than 1.2 times and less than 1.8 times.

[0096] The area-equivalent diameter D90 of the dielectric particles in the dielectric layer in the central region is preferably 250 nm to 600 nm, and more preferably 300 nm to 500 nm.

[0097] The area-equivalent diameter D90 of the dielectric particles in the dielectric layer in the first side edge adjacent region and the second side edge adjacent region is preferably greater than 350 nm and less than 600 nm. More preferably, it is greater than 400 nm and less than 550 nm. In addition, in the first side edge adjacent region and the second side edge adjacent region, the area-equivalent diameter D90 of the dielectric particles may also gradually decrease toward the central region. That is, in this region, the area-equivalent diameter D90 of the dielectric particles may also decrease the closer to the central region and increase the closer to the first side edge portion or the second side edge portion.

[0098] The area-equivalent diameter D90 of the dielectric particles in the dielectric of the first side edge portion and the second side edge portion is preferably 450 nm to 750 nm, and more preferably 500 nm to 700 nm.

[0099] The dielectric particles of the dielectric in the inner layer portion, the first side edge portion, and the second side edge portion include core-shell particles and uniform solid solution particles.

[0100] Here, the ratio of the area (As1) occupied by the uniform solid solution particles in the dielectric layer in the central region to the area (Ac1) occupied by the core-shell particles is set to RA1 (=As1 / Ac1). The ratio of the area (As2) occupied by the uniform solid solution particles in the dielectric layer in the first side edge adjacent region and the second side edge adjacent region to the area (Ac2) occupied by the core-shell particles is set to RA2 (=As2 / Ac2). The ratio of the area (As3) occupied by the uniform solid solution particles in the dielectric layer in the first side edge portion and the second side edge portion to the area (Ac3) occupied by the core-shell particles is set to RA3 (=As3 / Ac3).

[0101] The ratio RA2 (=As2 / Ac2) of the area (As2) occupied by the uniform solid-solution particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region to the area (Ac2) occupied by the core-shell particles is greater than the ratio RA1 (=As1 / Ac1) of the area (As1) occupied by the uniform solid-solution particles in the dielectric layer of the central region to the area (Ac1) occupied by the core-shell particles. By increasing the degree of solid solubility of the rare earth elements in the dielectric layers of the first side edge adjacent region and the second side edge adjacent region, reliability can be improved. This can improve reliability while increasing effective capacitance.

[0102] The ratio RA3 (= As3 / Ac3) of the area occupied by the uniform solid-solution particles (As3) in the dielectric layer at the first and second side edges to the area occupied by the core-shell particles (Ac3) is greater than the ratio RA1 (= As1 / Ac1) of the area occupied by the uniform solid-solution particles (As1) in the dielectric layer in the central region to the area occupied by the core-shell particles (Ac1). By increasing the degree of solid solubility of the rare earth element in the dielectric particles in the dielectric layer at the first and second side edges, reliability can be improved. This improves both effective capacitance and reliability.

[0103] The ratio RA3 (=As3 / Ac3) of the area occupied by the uniform solid-solution particles (As3) in the dielectric layer at the first and second side edges to the area occupied by the core-shell particles (Ac3) is greater than the ratio RA2 (=As2 / Ac2) of the area occupied by the uniform solid-solution particles (As2) in the dielectric layer at the first and second side edges to the area occupied by the core-shell particles (Ac2). By increasing the degree of solid solubility of the rare earth element in the dielectric particles in the dielectric layer at the first and second side edges, reliability can be improved. This improves both effective capacitance and reliability.

[0104] As described above, the degree of solid solubility of the rare earth elements in the dielectric layer in the first side edge region and the second side edge region relative to the dielectric particles is preferably higher than the degree of solid solubility of the rare earth elements in the dielectric layer in the central region relative to the dielectric particles. The degree of solid solubility of the rare earth elements in the dielectric layer in the first side edge region and the second side edge region relative to the dielectric particles is preferably higher than the degree of solid solubility of the rare earth elements in the dielectric layer in the first side edge region and the second side edge region.

[0105] The ratio RA1 (=As1 / Ac1) of the area occupied by the uniform solid solution particles (As1) to the area occupied by the core-shell particles (Ac1) in the central region of the dielectric layer is preferably less than 1, more preferably 0.8 or less.

[0106] The ratio RA2 (=As2 / Ac2) of the area (As2) occupied by the uniform solid solution particles to the area (Ac2) occupied by the core-shell particles in the dielectric layer in the first side edge adjacent region and the second side edge adjacent region is preferably greater than 1, more preferably greater than 1.2.

[0107] The ratio RA3 (=As3 / Ac3) of the area occupied by the uniform solid solution particles (As3) to the area occupied by the core-shell particles (Ac3) in the dielectric at the first and second side edges is preferably greater than 1, more preferably not less than 1.

[0108] <Measurement method>

[0109] (Area equivalent diameter D50 and area equivalent diameter D90)

[0110] The method for measuring the area-equivalent diameter D50 and the area-equivalent diameter D90 will be described. Figure 3This is a cross-sectional view showing a cross section (WT plane) taken through the longitudinal center of a multilayer ceramic capacitor. The multilayer ceramic capacitor is first processed to expose a plane (WT plane) that passes through the longitudinal center and includes both the width and thickness directions. Next, the WT plane is observed using a scanning electron microscope (SEM).

[0111] SEM observation of the central area of the inner layer Figure 3 The observation was conducted at the position P1 shown in the figure. More specifically, the observation was conducted at both the center of the inner layer in the thickness direction and the center of the inner layer in the width direction. The observation was conducted over a field of view of 5000 nm x 5000 nm. However, if only the internal electrode layer is present at the position P1 and the dielectric layer cannot be observed, SEM observation was conducted on the dielectric layer adjacent to the internal electrode layer.

[0112] SEM observation of the adjacent area of the side edge of the inner layer Figure 3 The observations were conducted at the two locations (P2) shown in the figure. More specifically, at the center of the thickness of the inner layer and the center of the width of the area adjacent to the side edge (a position 10 μm from the boundary between the inner layer and the side edge toward the center of the inner layer). The observations were conducted over a field of view of 5000 nm x 5000 nm. However, if only the internal electrode layer is present at the P2 location and the dielectric layer cannot be observed, SEM observations were conducted on the dielectric layer adjacent to the internal electrode layer.

[0113] SEM observation of the side edge Figure 3 SEM observations were conducted at the two locations (P3) shown in the figure. More specifically, SEM observations were conducted at the center of the side edge in the thickness direction and furthest from the end of the internal electrode layer in the width direction, i.e., near the surface of the laminate (near the first side surface of the first side edge and near the second side surface of the second side edge). The observations were conducted within a viewing field of 5000 nm x 5000 nm.

[0114] The average particle size, the area-equivalent diameter D50, and the area-equivalent diameter D90 can be determined based on the cross-sectional area of each dielectric particle within a viewing field of 5000 nm×5000 nm during the above-mentioned SEM observation.

[0115] First, for each dielectric particle within the field of view, the area-equivalent diameter of the dielectric particle is calculated based on the cross-sectional area of the dielectric particle. The area-equivalent diameter is the diameter of a perfect circle having an area equal to the area of the dielectric particle defined by the dielectric particle's outline.

[0116] The area equivalent diameter D50 is calculated based on the area equivalent diameter data for each dielectric particle within the field of view. The area equivalent diameter D50, also known as the median diameter, is calculated as the area equivalent diameter at which the cumulative value of the cumulative distribution of the area equivalent diameters of the multiple dielectric particles within the field of view reaches 50%. Furthermore, the area equivalent diameter D90 is calculated based on the area equivalent diameter data for each dielectric particle within the field of view. The area equivalent diameter D90 is calculated as the area equivalent diameter at which the cumulative value of the cumulative distribution of the area equivalent diameters of the multiple dielectric particles within the field of view reaches 90%.

[0117] Furthermore, the area-equivalent diameter D50 and area-equivalent diameter D90 of the dielectric particles in the dielectric contained in the central region of the inner layer are calculated based on the dielectric particles in the dielectric in the SEM image of the position P1 described above. Furthermore, the area-equivalent diameter D50 and area-equivalent diameter D90 of the dielectric particles in the dielectric contained in the region adjacent to the side edge of the inner layer are calculated as the average of the values calculated at P2 at the two locations described above. Furthermore, the area-equivalent diameter D50 and area-equivalent diameter D90 of the dielectric particles contained in the dielectric near the surface of the laminate in the side edge portion are calculated as the average of the values calculated at P3 at the two locations described above.

[0118] (core-shell particles and uniform solid solution particles)

[0119] Next, a method for distinguishing core-shell particles from uniform solid solution particles and a method for calculating the ratio of the area occupied by the uniform solid solution particles to the area occupied by the core-shell particles will be described. Figure 3 This is a cross-sectional view showing a cross-section (WT surface) of a multilayer ceramic capacitor that passes through the center of the length direction. First, the multilayer ceramic capacitor is processed to expose the surface (WT surface) that passes through the center of the length direction and includes the width direction and thickness direction. Next, a thin sheet sample is taken out with the WT surface as the observation surface. The thin sheet samples are collected from the above-mentioned positions P1, P2 (two locations), and P3 (two locations). However, when only the internal electrode layer exists in the center of the width direction and the center of the thickness direction of the inner layer and the dielectric layer cannot be observed, a thin sheet sample is collected from the dielectric layer adjacent to the internal electrode layer. The collected thin sheet sample is then observed using a transmission electron microscope (TEM). The observation is performed on a field of view of 1000nm×1000nm.

[0120] Elemental analysis was then performed using TEM-EDX on each of the dielectric particles in the dielectric layer within the field of view. Elemental analysis was performed on the center of each particle (particle center) and the area 10 nm inward from the outer surface of the particle (particle periphery). However, particles with such distorted shapes that the center could not be identified were excluded from the analysis, or the area 20 nm inward was analyzed. Particles with a Re concentration distribution ratio of 1.5 or greater were identified as core-shell particles, while particles with a Re concentration distribution ratio of less than 1.5 were identified as uniform solid solution particles.

[0121] Next, at each of the aforementioned positions P1, P2 (two locations), and P3 (two locations), the area occupied by each of the multiple uniform solid solution particles in the cross section was measured based on the TEM image. These areas were then summed to form the area occupied by the uniform solid solution particles (As1, As2, As3). Similarly, at each of the aforementioned positions P1, P2 (two locations), and P3 (two locations), the area occupied by each of the multiple core-shell particles in the cross section was measured based on the TEM image. These areas were then summed to form the area occupied by the core-shell particles (Ac1, Ac2, Ac3). Then, for the three locations P1, P2 (two locations), and P3 (two locations) mentioned above, the ratio of the area occupied by the uniform solid solution particles to the area occupied by the core-shell particles (RA1 = As1 / Ac1, RA2 = As2 / Ac2, RA3 = As3 / Ac3) was calculated by dividing the area occupied by the uniform solid solution particles (As1, As2, As3) by the area occupied by the core-shell particles (Ac1, Ac2, Ac3).

[0122] The ratio RA1 = As1 / Ac1 in the central region of the inner layer is calculated based on the dielectric particles in the dielectric in the TEM image of the position P1. Furthermore, the ratio RA2 = As2 / Ac2 in the region adjacent to the side edge of the inner layer is calculated as the average of the values calculated at the two locations P2. Furthermore, the ratio RA3 = As3 / Ac3 in the side edge is calculated as the average of the values calculated at the two locations P3.

[0123] (Concentration of each element in the dielectric)

[0124] From the multilayer ceramic capacitor, samples were collected by scraping portions of the dielectric layer at the aforementioned locations P1, P2 (two locations), and P3 (two locations). These samples were then analyzed by ICP analysis to determine the concentrations of various elements in the dielectric. Specifically, the scraped samples were subjected to a solution treatment using an alkali fusion method, and the resulting solution was subjected to ICP analysis. The ICP analysis calculated the effective molar ratios of position A to position B (Rm1, Rm2, and Rm3) for each of the three locations: P1, P2 (two locations), and P3 (two locations). Specifically, the calculations included a first effective molar ratio Rm1, representing the effective molar ratio of position A to position B (A / B ratio), in the dielectric layer in the central region; a second effective molar ratio Rm2, representing the effective molar ratio of position A to position B (A / B ratio), in the regions adjacent to the first and second side edges; and a third effective molar ratio Rm3, representing the effective molar ratio of position A to position B (A / B ratio), in the dielectric layer contained in the first and second side edges.

[0125] The effective molar ratio Rm1 in the central region of the inner layer is calculated based on the analysis of the sample at the position P1. Furthermore, the effective molar ratio Rm2 in the adjacent side edge region of the inner layer is calculated as the average of the values calculated at the two locations P2. Furthermore, the effective molar ratio Rm3 in the side edge region is calculated as the average of the values calculated at the two locations P3.

[0126] (2) Manufacturing method of multilayer ceramic capacitors

[0127] The multilayer ceramic capacitor of this embodiment is not limited in its manufacturing method as long as it satisfies the above-mentioned requirements. However, a preferred manufacturing method includes the following steps: preparing a main component raw material (preparation step); mixing auxiliary component raw materials with the main component raw material to form a dielectric raw material (mixing step); adding and mixing a binder and a solvent to the dielectric raw material to form a slurry, and molding a dielectric green sheet from the resulting slurry (molding step); printing a patterned paste layer of conductive paste for internal electrodes on the surface of the dielectric green sheet (printing step); laminating and pressure-bonding multiple dielectric green sheets to form a stacked block (lamination step); cutting the resulting stacked block to form stacked small sheets (cutting step); forming side edge green bodies and attaching the resulting side edge green bodies to the sides of the stacked small sheets to form a green body (side edge forming step); subjecting the resulting green body to a binder removal treatment and firing to form a stacked body (firing step); and forming external electrodes on the resulting stacked body to form a multilayer ceramic capacitor (external electrode forming step). Details of each step are described below.

[0128] <Preparation process>

[0129] In the preparation step, the main component raw materials are prepared. These are the raw materials that form the main components of the dielectric layer included in the inner layer and the dielectric layer of the outer layer. BaTiO3-based compound powders having a perovskite structure (ABO3) can be used as the main component raw materials. BaTiO3-based compounds can be synthesized using known methods such as solid-phase reaction, hydrothermal synthesis, oxalate method, and alkoxide method. Furthermore, a first additive element (Me) may be added during the synthesis of the main component raw materials.

[0130] <Mixing process>

[0131] In the mixing process, the remaining auxiliary component (e.g., Re) raw materials are mixed with the main component raw materials to form the dielectric raw materials. As auxiliary component raw materials, known ceramic raw materials such as oxides, carbonates, hydroxides, nitrates, organic acid salts, alkoxides, and / or chelate compounds can be used. The mixing method is not particularly limited. For example, a method can be used in which the weighed main component raw materials and auxiliary component raw materials are wet mixed and pulverized in a ball mill along with a grinding medium and pure water. If wet mixing is performed, the mixture can be dried.

[0132] Molding process

[0133] In the molding process, a binder and a solvent are added and mixed to the dielectric raw material to form a slurry. The resulting slurry is then molded into a dielectric green sheet. After firing, the dielectric green sheet becomes the dielectric layer comprising the inner layer portion and the dielectric layer portion of the multilayer ceramic capacitor. As the binder, a known organic binder such as a polyvinyl butyral-based binder can be used. As the solvent, a known organic solvent such as toluene or ethanol can be used. Additives such as plasticizers can also be added as needed. Molding can be performed using known methods such as rubber isostatic pressing (RIP). The thickness of the formed sheet is, for example, 10 μm or less.

[0134] <Printing process>

[0135] In the printing process, a patterned paste layer is formed on the surface of the dielectric green sheet using a conductive paste. The paste layer becomes the internal electrode layer after firing. As the conductive metal contained in the conductive paste, conductive materials such as nickel (Ni), copper (Cu), silver (Ag), palladium (Pd), and alloys containing them can be used. However, nickel (Ni) is preferred. In addition, ceramic particles that act as a common material can also be added to the conductive paste. As ceramic particles, the main component raw material of the dielectric layer can be used. The method for forming the paste layer is not particularly limited. For example, methods such as screen printing and gravure printing can be mentioned.

[0136] <Lamination process>

[0137] In the lamination process, multiple dielectric green sheets are stacked and pressure-bonded to create a laminated block. The dielectric green sheets with a paste layer are stacked so that they are sandwiched from above and below by dielectric green sheets without a paste layer. The green sheets without a paste layer become the outer layers of the multilayer ceramic capacitor after firing. Meanwhile, the green sheets with a paste layer become the inner layers of the multilayer ceramic capacitor. The number of stacked green sheets can be adjusted to achieve the desired capacitance.

[0138] <Cutting process>

[0139] In the cutting step, the obtained stacked block is cut into stacked small pieces. The cutting step is performed so that small pieces of a predetermined size are obtained and at least a portion of the paste layer is exposed at the end surface of the stacked small piece.

[0140] <Side Edge Forming Step>

[0141] In the side edge forming step, a side edge green body is produced, which is then attached to the side of the stacked small pieces to form the green body body. After firing, the side edge green body becomes the side edge of the multilayer ceramic capacitor. The raw materials for the side edge green body (side edge raw material) can be the main component raw materials and auxiliary component raw materials used to produce the dielectric layer of the inner layer. However, the composition of the side edge does not need to be the same as that of the inner layer; a different composition may be used.

[0142] The production and attachment of the side edge green body can be carried out by a known method. For example, a method of producing a green sheet from side edge raw material powder and bonding the green sheet to the side of the stacked small piece can be cited. At this time, in order to make the bonding of the green sheet reliable, an adhesive auxiliary agent such as an organic solvent can also be applied to the side of the stacked small piece in advance. Alternatively, a method of producing a paste from side edge raw material powder, applying the paste to the side of the stacked small piece and drying can be cited. In addition, the side edge green body can be a single layer, or it can be a stack comprising multiple layers. The side edge green body comprising a stack can be obtained by a method of stacking multiple green sheets on the side of the stacked small piece, repeatedly applying the paste and drying. The paste layer exposed on the side of the stacked small piece is covered by the side edge green body.

[0143] If necessary, the green body is subjected to a barrel grinding process, which can round the corners and / or ridges of the laminate.

[0144] <Firing process>

[0145] In the firing process, the green body is subjected to a debinding treatment and a firing treatment to produce a laminate. The paste layer and the dielectric green sheet are co-sintered by the firing treatment to form an internal electrode layer and a dielectric layer, respectively. The conditions for the debinding treatment can be determined according to the type of organic binder contained in the green sheet and the paste layer. In addition, the firing treatment can be carried out at a temperature that fully densifies the stacked small pieces. For example, it can be carried out under the condition of maintaining a temperature of 1200°C or more and 1300°C or less for a given time. In addition, the firing is carried out in an atmosphere in which the BaTiO3-based compound as the main component is not reduced and the oxidation of the conductive material is suppressed. For example, at an oxygen partial pressure of 1.8×10 -9 ~8.7×10 -10 It can be carried out in a N2-H2-H2O gas flow of 100 MPa. Furthermore, annealing can be performed after firing. In this way, a multilayer ceramic capacitor can be produced.

[0146] In the manufacturing method of this embodiment, it is preferred to add a secondary component containing one or more elements including silicon (Si), magnesium (Mg), and aluminum (Al) along with the rare earth element (Re) to the dielectric materials forming the outer and inner layers, and the side edge materials forming the side edge portions. Here, Si acts as a grain growth promoter, and Mg acts as a grain growth inhibitor.

[0147] If the grain growth of the dielectric particles is promoted during the firing process, the particles become larger while the surrounding accessory elements are taken into the surface layer. Therefore, there is a tendency to form uniform solid solution particles. On the other hand, if the grain growth is suppressed, the intake of the accessory elements is suppressed, so it is easy to form core-shell particles. Therefore, if Si and / or Mg with grain growth promoting and suppressing effects are added and the amount of addition is adjusted, it is possible to control the ratio of the core-shell particles and the uniform solid solution particles in the inner layer, outer layer, and the first side edge portion.

[0148] In particular, it is preferred that the dielectric raw material forming the outer layer contains more Si. Thus, the particle growth in the outer layer can be promoted so that it contains more uniform solid solution particles. In addition, since Si diffuses from the outer layer to the inner layer during firing, the proportion of uniform solid solution particles in the inner region of the inner layer near the interface with the outer layer becomes larger. In addition, in this embodiment, in order to properly control the sintering state of the dielectric particles in each region, the amount of the side edge raw material is adjusted and the firing conditions are adjusted so that the effective molar ratio of the A position relative to the B position in the dielectric contained in the side edge portion is less than the effective molar ratio of the A position relative to the B position in the dielectric contained in the inner layer.

[0149] External electrode formation process

[0150] In the external electrode forming step, external electrodes are formed on the laminate to produce a laminated ceramic capacitor. The external electrodes can be formed by a known method. For example, a conductive paste containing conductive components such as Cu and Ni as the main component is applied and sintered to the end surface of the laminate where the internal electrodes are exposed to form a base layer. The base layer can also be formed by applying a conductive paste to both end surfaces of the green body before firing and then performing a firing treatment. After the base layer is formed, electrolytic plating is performed to form a plated film of Ni, Sn, etc. on the surface of the base layer. In this way, a laminated ceramic capacitor can be produced.

[0151] According to the multilayer ceramic capacitor 100 of this embodiment, the following effects are achieved.

[0152] (1) The laminated ceramic capacitor (100) of this embodiment comprises: a laminate (6) having a first main surface (10a) and a second main surface (10b) opposite to each other in the thickness direction, a first side surface (12a) and a second side surface (12b) opposite to each other in the width direction, and a first end surface (14a) and a second end surface (14b) opposite to each other in the length direction, and including a plurality of dielectric layers (2) and a plurality of internal electrode layers (4) stacked in the thickness direction; and a pair of external electrodes (8a, 8b) respectively provided on the first end surface (14a) and the second end surface (14b) and connected to the plurality of internal electrode layers (4), wherein the laminate (6) is divided into: a first side edge portion (20a) extending along the first side surface (12a) and not including the internal electrode layers; a first outer layer portion (18a) which is sandwiched between the first side edge portion (20a) and the second side edge portion (20a), and is sandwiched between the internal electrode layer (4) closest to the first main surface (10a) and the first main surface (10a); a second outer layer portion (18b) which is sandwiched between the first side edge portion (20a) and the second side edge portion (20b), and is sandwiched between the internal electrode layer (4) closest to the second main surface (10b) and the second main surface (10b); and an inner layer portion (16) which is sandwiched between the first side edge portion (20a) and the second side edge portion (20b), and is sandwiched between the first outer layer portion (18a) and the second outer layer portion (18b). Furthermore, in the laminated ceramic capacitor (100) of this embodiment, in a cross section passing through the center in the longitudinal direction of the laminated ceramic capacitor (100), the inner layer portion (16) includes a central region (16c) in the center in the width direction, a first side edge adjacent region (16a) adjacent to the first side edge portion (20a), and a second side edge adjacent region (16b) adjacent to the second side edge portion (20b), and the area equivalent diameter D50 of the dielectric particles in the dielectric layer (2) in the first side edge adjacent region (16a) and the second side edge adjacent region (16b) is larger than the area equivalent diameter D50 of the dielectric particles in the dielectric layer (2) in the central region (16c). Thus, the effective capacitance can be increased while the reliability can be improved.

[0153] (2) In the multilayer ceramic capacitor (100) of this embodiment, the area-equivalent diameter D50 of the dielectric particles in the dielectric of the first side edge portion (12a) and the second side edge portion (12b) is larger than the area-equivalent diameter D50 of the dielectric particles in the dielectric layer (2) in the first side edge adjacent region (16a) and the second side edge adjacent region (16b). This can improve reliability while increasing effective capacitance.

[0154] (3) The dielectric contained in the inner layer portion (16) of the multilayer ceramic capacitor (100) of this embodiment contains dielectric particles containing barium (Ba) and titanium (Ti), and a rare earth element (Re) as a minor component. The dielectric particles of the dielectric of the inner layer portion (16) contain core-shell particles and uniform solid solution particles. The ratio RA2 (=As2 / Ac2) of the area (As2) occupied by the uniform solid solution particles in the dielectric layer (2) of the first side edge adjacent region (16a) and the second side edge adjacent region (16b) to the area (Ac2) occupied by the core-shell particles is greater than the ratio RA1 (=As1 / Ac1) of the area (As1) occupied by the uniform solid solution particles in the dielectric layer (2) of the central region (16c) to the area (Ac1) occupied by the core-shell particles. Thus, reliability can be further improved.

[0155] (4) The dielectric contained in the first side edge portion (20a) and the second side edge portion (20b) of the multilayer ceramic capacitor (100) of this embodiment contains dielectric particles containing barium (Ba) and titanium (Ti), and a rare earth element (Re) as a minor component, the dielectric particles of the dielectric of the first side edge portion (20a) and the second side edge portion (20b) contain core-shell particles and uniform solid solution particles, and the ratio RA3 (=As3 / Ac3) of the area (As3) occupied by the uniform solid solution particles in the dielectric of the first side edge portion (20a) and the second side edge portion (20b) to the area (Ac3) occupied by the core-shell particles is greater than the ratio RA2 (=As2 / Ac2) of the area (As2) occupied by the uniform solid solution particles in the dielectric layer (2) of the first side edge adjacent region (16a) and the second side edge adjacent region (16b) to the area (Ac2) occupied by the core-shell particles. Thereby, reliability can be further improved.

[0156] (5) The rare earth element (Re) in the multilayer ceramic capacitor (100) of this embodiment includes dysprosium (Dy), thereby further improving reliability.

[0157] (6) The dielectric contained in the inner layer portion (16), the first side edge portion (20a) and the second side edge portion (20b) of the multilayer ceramic capacitor (100) of the present embodiment has a perovskite (ABO3) structure, and the third effective molar ratio Rm3 showing the effective molar ratio of the A position to the B position (A / B ratio) in the dielectric contained in the first side edge portion (20a) and the second side edge portion (20b) is smaller than that in the first side edge adjacent region (16a) and the second side edge adjacent region (16b). The second effective molar ratio Rm2, which represents the effective molar ratio of the A site to the B site (A / B ratio), in the edge adjacent region (16b), and the third effective molar ratio Rm3, which represents the effective molar ratio of the A site to the B site (A / B ratio), in the dielectric contained in the first side edge portion (20a) and the second side edge portion (20b), are smaller than the first effective molar ratio Rm1, which represents the effective molar ratio of the A site to the B site (A / B ratio) in the dielectric layer of the central region (16c). Thus, the sintering state of the dielectric particles in each region can be appropriately controlled, thereby improving reliability while increasing effective capacitance.

[0158] Example

[0159] The present embodiment will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

[0160] (1) Production of multilayer ceramic capacitors

[0161] [Examples 1 to 5]

[0162] Multilayer ceramic capacitors containing BaTiO3-based compounds as the main components of the inner layer, outer layer, and side edge portions were produced and evaluated. Dysprosium (Dy), a rare earth element (Re), and manganese (Mn), vanadium (V), and nickel (Ni) as the primary additive element (Me) were used as auxiliary components. Silicon (Si), magnesium (Mg), and aluminum (Al) were also used.

[0163] As a main component raw material powder, BaCO 3 and TiO 2 were stirred and then heat-treated to prepare BaTiO 3 powder.

[0164] Auxiliary raw materials were prepared separately from the main raw materials. Compounds of dysprosium (Dy), nickel (Ni), silicon (Si), magnesium (Mg), manganese (Mn), aluminum (Al), and vanadium (V) were used as auxiliary raw materials.

[0165] Next, the auxiliary raw materials were added to the main raw material, wet-mixed using a ball mill, and then dried to produce a dielectric raw material. A polyvinyl butyral-based binder and ethanol as an organic solvent were added to the resulting dielectric raw material and wet-mixed using a ball mill for a predetermined time to produce a slurry. This slurry was then sheet-molded to produce a dielectric green sheet.

[0166] Next, a conductive paste primarily composed of Ni is screen-printed onto the surface of the resulting dielectric green sheet, patterning the paste layer that will become the internal electrode layer. Multiple green sheets with the paste layer are then stacked, with green sheets without the paste layer placed above and below them, and the entire stack is press-bonded to create a stacked block. The resulting stacked block is then cut with a dicing saw to create small stacked sheets. Stacking is performed so that the ends of the paste layer are different from each other. Furthermore, the sheets are cut so that the paste layer is exposed at the side surfaces.

[0167] Separately from the laminated small pieces, side edge green sheets were fabricated to form the side edge green body. Fabrication of the side edge green sheets was performed in the same manner as for the dielectric green sheets, except for varying the amounts of the main and auxiliary raw materials. In this example, the amounts were adjusted so that the effective molar ratio (Rm3) of the dielectric material contained in the side edge portions of the manufactured multilayer ceramic capacitor was lower than the effective molar ratios (Rm1, Rm2) of the dielectric material contained in the inner layer. Next, the side edge green sheets were attached to both sides of the cut laminated small pieces where the paste layer was exposed, to form the green body.

[0168] The green body was heat treated in N2 gas flow at a maximum temperature of 270°C, and then in N2-H2O-H2 gas flow at a maximum temperature of 800°C. -9 ~8.7×10 -10 MPa. During firing, the material was cooled to near room temperature immediately after reaching the maximum temperature. -12 ~1.5×10 -11 MPa, heat treatment was performed at a temperature lower than the maximum temperature. Thus, a laminated body of a laminated ceramic capacitor was obtained.

[0169] A conductive paste primarily composed of copper (Cu) was applied to the end surfaces of the fired laminate, where the internal electrode layers were drawn out. The applied conductive paste was then sintered at 900°C to form the base layer for the external electrodes. Furthermore, the surface of the base layer was sequentially plated with Ni and Sn using wet plating. In this manner, a multilayer ceramic capacitor was fabricated.

[0170] The manufactured multilayer ceramic capacitor had a length L of 1.0 mm, a width W of 2.5 mm, and a thickness T of 0.5 mm. Furthermore, the thickness of the inner dielectric layer was 1.0 μm, the thickness of the internal electrode layer was 0.6 μm, and the number of dielectric layers was 350.

[0171] (2) Evaluation

[0172] Various characteristics of the produced multilayer ceramic capacitors were evaluated as follows.

[0173] <SEM observation>

[0174] The WT surface of the multilayer ceramic capacitor was observed using a scanning electron microscope (SEM), and the area equivalent diameter D50 and area equivalent diameter D90 of the dielectric particles contained in the central area of the inner layer, the side edge adjacent areas of the inner layer (the first side edge adjacent area, the second side edge adjacent area), and the side edge near the surface of the multilayer body (near the first side surface of the first side edge and near the second side surface of the second side edge) were investigated. Specifically, the multilayer ceramic capacitor was ground to the center of its length (L) direction to expose the cross section (WT surface). Then, SEM observation was performed on the exposed cross section. SEM observation of the inner layer is to Figure 3 The observation was conducted at the positions P1, P2 (two locations), and P3 (two locations) shown in FIG. Observation was conducted in a field of view of 5000 nm×5000 nm.

[0175] The area equivalent diameter D50 and the area equivalent diameter D90 are calculated based on the cross-sectional area of each dielectric particle within the field of view of 5000nm×5000nm during the above-mentioned SEM observation. First, for each dielectric particle within the field of view, the area equivalent diameter of the dielectric particle is calculated based on the cross-sectional area of the dielectric particle. Next, based on the data of the area equivalent diameter of each dielectric particle within the field of view, the area equivalent diameter D50 and the area equivalent diameter D90 are calculated. In addition, the area equivalent diameter D50 and the area equivalent diameter D90 of the dielectric particles in the dielectric contained in the central area of the inner layer are calculated based on the dielectric particles in the dielectric in the SEM image with the position of P1 as the object. In addition, the area equivalent diameter D50 and the area equivalent diameter D90 of the dielectric particles in the dielectric contained near the surface of the stack in the area near the side edge are calculated as the average value of the values calculated at P2 at the above two locations. Furthermore, the area-equivalent diameter D50 and the area-equivalent diameter D90 of the dielectric particles contained in the dielectric near the surface of the laminate in the side edge portion are calculated as the average of the values calculated at P3 at the two locations.

[0176] TEM observation

[0177] The cross section (WT surface) of the multilayer ceramic capacitor was observed using a transmission electron microscope (TEM), and the dielectric particles contained in the central area of the inner layer, the side edge adjacent areas of the inner layer (the first side edge adjacent area, the second side edge adjacent area), and the side edge areas near the surface of the multilayer body (near the first side surface of the first side edge and near the second side surface of the second side edge) were investigated. Specifically, the multilayer ceramic capacitor was ground to the center of its length (L) direction to expose the WT surface, and then processed to collect a thin sheet sample with the WT surface as the observation surface. The thin sheet sample was obtained from Figure 3 Samples were collected at positions P1, P2 (two locations), and P3 (two locations) as samples of the inner layer and the side edge surface. Observations were performed within a 1000 nm x 1000 nm field of view.

[0178] Then, for each sample, elemental analysis was performed on each dielectric particle within the field of view using TEM-EDX. Elemental analysis was performed on the center of each particle and the area 10 nm inward from the outer surface of the particle (the outer periphery of the particle). However, particles whose shapes were so distorted that the center could not be determined were excluded from the analysis. Then, the concentrations of rare earth elements (Re) and titanium (Ti) were investigated for the outer periphery and the center of each particle, and the Re concentration distribution ratio ((shell Re / Ti ratio) / (core Re / Ti ratio)) was calculated. Then, particles with a Re concentration distribution ratio of 1.5 or more were judged to be core-shell particles, and particles with a Re concentration distribution ratio of less than 1.5 were judged to be uniform solid solution particles.

[0179] Next, at each of the aforementioned positions P1, P2 (two locations), and P3 (two locations), the area occupied by each of the multiple uniform solid solution particles in the cross section was measured based on the TEM image. These areas were then summed to form the area occupied by the uniform solid solution particles (As1, As2, As3). Similarly, at each of the aforementioned positions P1, P2 (two locations), and P3 (two locations), the area occupied by each of the multiple core-shell particles in the cross section was measured based on the TEM image. These areas were then summed to form the area occupied by the core-shell particles (Ac1, Ac2, Ac3). Then, for each of the three locations mentioned above, P1, P2 (two locations), and P3 (two locations), the area occupied by the uniform solid solution particles (As1, As2, As3) was divided by the area occupied by the core-shell particles (Ac1, Ac2, Ac3), and the ratio of the area occupied by the uniform solid solution particles to the area occupied by the core-shell particles was calculated (RA1 = As1 / Ac1, RA2 = As2 / Ac2, RA3 = As3 / Ac3). Furthermore, the ratio RA1 = As1 / Ac1 in the central region of the inner layer was calculated based on the dielectric particles in the dielectric in the TEM image of the location P1. Furthermore, the ratio RA2 = As2 / Ac2 in the adjacent side edge region of the inner layer was calculated as the average of the values calculated for the two locations P2. Furthermore, the ratio RA3 = As3 / Ac3 in the side edge was calculated as the average of the values calculated for the two locations P3.

[0180] ICP analysis

[0181] From the multilayer ceramic capacitor, samples were collected by scraping portions of the dielectric layer at locations P1, P2 (two locations), and P3 (two locations) described above. These samples were then analyzed by ICP analysis to determine the concentrations of various elements in the dielectric. Specifically, the scraped samples were treated with an alkali fusion method, and the resulting solution was subjected to ICP analysis. The ICP analysis calculated the effective molar ratios of position A to position B (Rm1, Rm2, and Rm3) for each of the three locations: P1, P2 (two locations), and P3 (two locations). Specifically, the calculations included a first effective molar ratio Rm1, representing the effective molar ratio of position A to position B (A / B ratio) in the dielectric layer in the central region; a second effective molar ratio Rm2, representing the effective molar ratio of position A to position B (A / B ratio) in the regions adjacent to the first and second side edges; and a third effective molar ratio Rm3, representing the effective molar ratio of position A to position B (A / B ratio) in the dielectric layer contained in the first and second side edges.

[0182] Furthermore, the first effective molar ratio Rm1, representing the effective molar ratio of the A site to the B site (A / B ratio), in the dielectric layer in the central region of the inner layer of each Example, and the second effective molar ratio Rm2, representing the effective molar ratio of the A site to the B site (A / B ratio) in the first and second side edge adjacent regions, were approximately the same, ranging from 1.0000 to 1.0020. Furthermore, the third effective molar ratio Rm3, representing the effective molar ratio of the A site to the B site (A / B ratio) in the dielectric layer contained in the side edge regions (first and second side edge regions) of each Example was 0.990 to 0.998, less than both the first effective molar ratio Rm1 and the second effective molar ratio Rm2. In this Example, the A-site elements included Ba and Ca, and the B-site elements included Ti and Zr. The effective molar ratios Rm1 to Rm3 were calculated as (Ba + Ca) / (Ti + Zr). The effective molar ratio Rm1 in the central region of the inner layer is calculated based on the analysis of the sample at the position P1. Furthermore, the effective molar ratio Rm2 in the adjacent side edge region of the inner layer is calculated as the average of the values calculated at the two locations P2. Furthermore, the effective molar ratio Rm3 in the side edge region is calculated as the average of the values calculated at the two locations P3.

[0183] Effective capacitance

[0184] Effective capacitance was evaluated through a DC bias characteristic measurement test. For the multilayer ceramic capacitors of the examples, capacitance was measured without a DC bias and with a DC bias (12.5V) applied, and the percentage of capacitance drop due to the DC bias was examined. The multilayer ceramic capacitors of the examples were then judged as "OK" if they exhibited good DC bias characteristics and high effective capacitance, compared to multilayer ceramic capacitors in which the area-equivalent diameter (D50) of the dielectric particles in the dielectric layers in the first and second side edge adjacent regions was smaller than the area-equivalent diameter (D50) of the dielectric particles in the dielectric layer in the central region. Furthermore, the multilayer ceramic capacitors used for comparison were manufactured by adjusting the compounding ratio so that the effective molar ratio (Rm3) of the A site to the B site in the dielectric contained in the side edge portions of the manufactured multilayer ceramic capacitor was greater than the effective molar ratios (Rm1, Rm2) of the A site to the B site in the dielectric contained in the inner layer.

[0185] Reliability test

[0186] As a reliability test, an accelerated life test (HALT) was conducted at an elevated ambient temperature (170°C) by applying a predetermined DC voltage (30V). The point at which the insulation resistance dropped below a predetermined value was considered a failure, and the results were subjected to Weibull analysis to calculate the mean time to failure (MTTF). The multilayer ceramic capacitors of the examples were judged to have "OK" reliability if their MTTF was higher than that of multilayer ceramic capacitors in which the area-equivalent diameter D50 of the dielectric particles in the dielectric layers in the first and second side edge adjacent regions was smaller than the area-equivalent diameter D50 of the dielectric particles in the central region. Furthermore, the multilayer ceramic capacitors used in this comparison were manufactured by adjusting the compounding ratio so that the effective molar ratio (Rm3) of the A site to the B site in the dielectric contained in the side edge portions of the manufactured multilayer ceramic capacitors was greater than the effective molar ratios (Rm1, Rm2) of the A site to the B site in the dielectric contained in the inner layer.

[0187] (3) Evaluation results

[0188] Table 1 shows the evaluation results obtained for Examples 1 to 5.

[0189] [Table 1]

[0190]

[0191] Figure 6 The figure schematically shows SEM images of the side edge portion, the side edge adjacent region of the inner layer portion, and the central region of the inner layer portion of the embodiment in a cross section across the center of the longitudinal direction of the multilayer ceramic capacitor. Figure 6 , a diagram schematically showing an SEM image of Example 2, which is a representative example. Figure 6 The side edge of the figure and Figure 3 The position of P3 on the second side of the image corresponds to the position of P3 on the second side of the image. Figure 6 The adjacent area of the side edge of the inner part is Figure 3 The position of P2 on the second side of the spherical surface is roughly the same as that of the spherical surface of FIG. Figure 6 The left side of the figure of the side edge region of the inner layer portion also shows a portion of the side edge portion (20b). Figure 6 The central area of the inner layer and Figure 3 The position of P1 in . Figure 6 , it can be confirmed that the particle size of the dielectric particles in each region is different.

[0192] As shown in Table 1, the area-equivalent diameter D50 of the dielectric particles in the dielectric layer in the first and second side edge adjacent regions of Examples 1-5 is larger than the area-equivalent diameter D50 of the dielectric particles in the central region. The area-equivalent diameter D90 of the dielectric particles in the dielectric layer in the first and second side edge adjacent regions of Examples 1-5 is larger than the area-equivalent diameter D90 of the dielectric particles in the central region.

[0193] Here, regarding Example 2, the area equivalent diameter D50 and the area equivalent diameter D90 of the dielectric particles in the dielectric of the side edge portion were measured. The area equivalent diameter D50 of the dielectric particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region in Example 2 was 442 nm. The area equivalent diameter D90 of the dielectric particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region in Example 2 was 600 nm. The area equivalent diameter D50 of the dielectric particles in the dielectric of the first side edge portion and the second side edge portion was larger than the area equivalent diameter D50 of the dielectric particles in the dielectric layer of the central region. The area equivalent diameter D50 of the dielectric particles in the dielectric of the first side edge portion and the second side edge portion was larger than the area equivalent diameter D50 of the dielectric particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region. The same tendency was also found in the other examples.

[0194] Here, for Example 2, the ratio of the area occupied by the uniform solid solution particles in each region to the area occupied by the core-shell particles was calculated. In Example 2, the ratio RA1 (=As1 / Ac1) of the area occupied by the uniform solid solution particles in the dielectric layer of the central region (As1) to the area occupied by the core-shell particles (Ac1) was 0.4. The ratio RA2 (=As2 / Ac2) of the area occupied by the uniform solid solution particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region to the area occupied by the core-shell particles (Ac2) was 1.5. The ratio RA3 (=As3 / Ac3) of the area occupied by the uniform solid solution particles in the dielectric layer of the first side edge portion and the second side edge portion to the area occupied by the core-shell particles (Ac3) was 3.5. The ratio RA2 (=As2 / Ac2) of the area (As2) occupied by the uniform solid solution particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region to the area (Ac2) occupied by the core-shell particles is greater than the ratio RA1 (=As1 / Ac1) of the area (As1) occupied by the uniform solid solution particles in the dielectric layer of the central region to the area (Ac1) occupied by the core-shell particles. The ratio RA3 (=As3 / Ac3) of the area (As3) occupied by the uniform solid solution particles in the dielectric layer of the first side edge portion and the second side edge portion to the area (Ac3) occupied by the core-shell particles is greater than the ratio RA2 (=As2 / Ac2) of the area (As2) occupied by the uniform solid solution particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region to the area (Ac2) occupied by the core-shell particles. The same tendency is also present in other embodiments.

[0195] Compared to the multilayer ceramic capacitor in which the area-equivalent diameter D50 of the dielectric particles in the dielectric layers in the first and second side edge adjacent regions was smaller than the area-equivalent diameter D50 of the dielectric particles in the central region, Examples 1 to 5, in which the area-equivalent diameter D50 of the dielectric particles in the dielectric layers in the first and second side edge adjacent regions was larger than the area-equivalent diameter D50 of the dielectric particles in the central region, all achieved good DC bias characteristics and good effective capacitance evaluation results. Furthermore, the reliability test results were also good.

[0196] In the central area of the inner layer, the progress of sintering of the dielectric particles is suppressed, and the grain growth of the dielectric particles after the sintering process is suppressed to a low level. At the same time, in the adjacent area of the side edge, the progress of sintering is promoted, and the grain growth of the dielectric particles after the sintering process is increased, thereby improving the effective capacitance and the reliability.

[0197] Furthermore, in the central region of the inner layer, the progress of sintering of the dielectric particles is suppressed, and the grain growth of the dielectric particles after the sintering process is suppressed to a low level. At the same time, in the side edge portion, the progress of sintering is promoted, and the grain growth of the dielectric particles after the sintering process is further increased compared to the adjacent region of the side edge. This can further improve reliability while increasing effective capacitance.

[0198] Furthermore, in the central region of the inner layer, the progress of sintering of the dielectric particles is suppressed, while in the side edge adjacent regions, the progress of sintering is promoted, thereby increasing the progress of solid solution of rare earth atoms, thereby increasing effective capacitance and reliability.

[0199] In addition, in the central area of the inner layer, the progress of sintering of dielectric particles is suppressed, while in the side edge part, the progress of sintering is promoted, and the progress of solid solution of rare earth atoms is further improved compared with the adjacent area of the side edge, thereby further improving reliability while increasing effective capacitance.

[0200] The present invention is not limited to the configuration of the above embodiment, and can be applied with appropriate modifications within the scope of the present invention. In addition, a configuration combining two or more of the preferred configurations described in the above embodiment also constitutes the present invention.

[0201] Description of Reference Numerals

[0202] 2 Dielectric layer

[0203] 4 Internal electrode layer

[0204] 6 laminate

[0205] 8a 1st external electrode

[0206] 8b Second external electrode

[0207] 10a 1st main side

[0208] 10b 2nd main side

[0209] 12a Side 1

[0210] 12b Side 2

[0211] 14a 1st end face

[0212] 14b Second end face

[0213] 16 Inner layer

[0214] 16a First side edge adjacent area

[0215] 16b Second side edge adjacent area

[0216] 16c Central Area

[0217] 18a First outer layer

[0218] 18b Second outer layer

[0219] 20a First side edge

[0220] 20b Second side edge

[0221] 30 Core-shell particles

[0222] 32 Nuclear Department

[0223] 34 Shell

[0224] 100 multilayer ceramic capacitors.

Claims

1. A multilayer ceramic capacitor comprising: a laminate having a first main surface and a second main surface opposing each other in a thickness direction, a first side surface and a second side surface opposing each other in a width direction, and a first end surface and a second end surface opposing each other in a length direction, and including a plurality of dielectric layers and a plurality of internal electrode layers stacked in the thickness direction; and a pair of external electrodes provided on the first end surface and the second end surface, respectively, and connected to the plurality of internal electrode layers, wherein: The stacks are divided into: a first side edge portion extending along the first side surface and excluding the internal electrode layer; a second side edge portion extending along the second side surface and excluding the internal electrode layer; a first outer layer portion sandwiched by the first side edge portion and the second side edge portion, and sandwiched by the internal electrode layer closest to the first main surface and the first main surface; a second outer layer portion sandwiched by the first side edge portion and the second side edge portion, and sandwiched by the internal electrode layer closest to the second main surface and the second main surface; and The inner layer portion is sandwiched between the first side edge portion and the second side edge portion, and is also sandwiched between the first outer layer portion and the second outer layer portion. In a cross section taken across the longitudinal center of the multilayer ceramic capacitor, The inner layer portion includes a central region in the width direction, a first side edge adjacent region adjacent to the first side edge portion, and a second side edge adjacent region adjacent to the second side edge portion. An area-equivalent diameter D50 of dielectric particles in the dielectric layer in the first side edge adjacent region and the second side edge adjacent region is larger than an area-equivalent diameter D50 of dielectric particles in the dielectric layer in the central region.

2. The multilayer ceramic capacitor according to claim 1, wherein The area-equivalent diameter D50 of dielectric particles in the dielectric layer of the first side edge portion and the second side edge portion is larger than the area-equivalent diameter D50 of dielectric particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region.

3. The multilayer ceramic capacitor according to claim 1 or 2, wherein The dielectric contained in the inner layer portion includes dielectric particles containing barium (Ba) and titanium (Ti), and a rare earth element (Re) as a minor component. The dielectric particles of the inner layer dielectric include core-shell particles and uniform solid solution particles. The ratio RA2 (=As2 / Ac2) of the area (As2) occupied by the uniform solid solution particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region to the area (Ac2) occupied by the core-shell particles is greater than the ratio RA1 (=As1 / Ac1) of the area (As1) occupied by the uniform solid solution particles in the dielectric layer of the central region to the area (Ac1) occupied by the core-shell particles.

4. The multilayer ceramic capacitor according to claim 3, wherein The dielectric contained in the first side edge portion and the second side edge portion includes dielectric particles containing barium (Ba) and titanium (Ti), and a rare earth element (Re) as a minor component. The dielectric particles of the dielectric in the first side edge portion and the second side edge portion include core-shell particles and uniform solid solution particles. The ratio RA3 (=As3 / Ac3) of the area (As3) occupied by the uniform solid solution particles in the dielectric of the first side edge portion and the second side edge portion to the area (Ac3) occupied by the core-shell particles is greater than the ratio RA2 (=As2 / Ac2) of the area (As2) occupied by the uniform solid solution particles in the dielectric layer of the first side edge adjacent region and the second side edge adjacent region to the area (Ac2) occupied by the core-shell particles.

5. The multilayer ceramic capacitor according to claim 3 or 4, wherein The rare earth element (Re) includes dysprosium (Dy).

6. The multilayer ceramic capacitor according to claim 1 or 2, wherein The dielectric contained in the inner layer portion, the first side edge portion, and the second side edge portion has a perovskite (ABO3) structure. A third effective molar ratio Rm3 representing an effective molar ratio of the A site to the B site (A / B ratio) in the dielectric contained in the first side edge portion and the second side edge portion is smaller than a second effective molar ratio Rm2 representing an effective molar ratio of the A site to the B site (A / B ratio) in the first side edge adjacent region and the second side edge adjacent region. A third effective molar ratio Rm3 indicating an effective molar ratio of the A site to the B site (A / B ratio) in the dielectric layer included in the first side edge portion and the second side edge portion is smaller than a first effective molar ratio Rm1 indicating an effective molar ratio of the A site to the B site (A / B ratio) in the dielectric layer in the central region.

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