Multilayer ceramic capacitors

Abstract

Provided is a multilayer ceramic capacitor having a high dielectric constant, a reduced size, and an increased capacitance, and also having a flat temperature characteristic of the dielectric constant and high reliability. This multilayer ceramic capacitor comprises: a multilayer body that has 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 that includes a plurality of dielectric layers and a plurality of internal electrode layers that are laminated 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. The dielectric layers include dielectric particles. The multilayer body is partitioned into: a layered first side portion extending along the first side surface and not including the internal electrode layers; a layered second side portion extending along the second side surface and not including the internal electrode layers; a first outer layer portion sandwiched between the first side portion and the second side portion and also sandwiched between an internal electrode layer closest to the first main surface and the first main surface; a second outer layer portion sandwiched between the first side portion and the second side portion and also sandwiched between an internal electrode layer closest to the second main surface and the second main surface; and an inner layer portion sandwiched between the first side portion and the second side portion and also sandwiched between the first outer layer portion and the second outer layer portion. In a cross section taken across the longitudinal direction at the center of the multilayer body, a dielectric layer at the center in the thickness direction of the inner layer portion includes particles having holes as the dielectric particles.

Description

[Technical Field]

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

[0002] As electronic devices such as mobile phones become smaller and CPU speeds increase, 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, and due to the thin, high-dielectric-constant dielectric layers, they have a large capacitance despite their small size. While multilayer ceramic capacitors made from a variety of materials are known, those that use barium titanate (BaTiO3)-based compounds for the dielectric layers and base metals such as nickel (Ni) for the internal electrode layers are widely used due to their low cost and high performance.

[0003] For example, Patent Document 1 discloses a compound having the composition formula (Ba 1-x-y Sr x Ca y ) m (Ti 1-z Zr z Regarding a dielectric ceramic composition containing a main component made of a perovskite-type compound represented by the formula (I)O3, a first subcomponent made of an oxide of a rare earth element R, a second subcomponent made of an oxide of Mg, a third subcomponent made of an oxide of at least one element M selected from Mn, Cr, Co, and Fe, and a fourth subcomponent as a sintering aid, it is described that the composition can be used in the dielectric layers of a multilayer ceramic capacitor, and that Ni or a Ni alloy is preferable as the conductive material contained in the internal electrode layers (Claim 1,

[0017] and

[0039] of Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-178686 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to achieve miniaturization and increased capacitance of multilayer ceramic capacitors, it is important to increase the dielectric constant of the dielectric layers while also reducing their thickness. However, increasing the dielectric constant by adjusting the composition of the main components constituting the dielectric layers tends to increase temperature variation. A large temperature variation in the dielectric constant deteriorates the capacitance-temperature characteristics of the multilayer ceramic capacitor. Furthermore, reducing the thickness of the dielectric layers shortens the insulation resistance life between the internal electrode layers, leading to a decrease in reliability. While conventional technologies have been effective to a certain extent, they have limitations in achieving multilayer ceramic capacitors with high dielectric constants, flat temperature characteristics, and excellent reliability.

[0006] The present invention was completed to solve these conventional problems, and an object of the present invention is to provide a multilayer ceramic capacitor that has a high dielectric constant, can be made smaller and has a larger capacitance, has a flat temperature characteristic of dielectric constant, and is highly reliable. [Means for solving the problem]

[0007] The present invention encompasses the following embodiments. In this specification, the expression "to" includes the numerical values ​​on both ends of the expression. In other words, "X to Y" is synonymous with "at least X and at most Y."

[0008] According to one aspect of the present invention, there is provided a multilayer ceramic capacitor comprising: a laminate having first and second main surfaces opposing each other in a thickness direction, first and second side surfaces opposing each other in a width direction, and first and second end surfaces opposing each other in a length direction, the laminate 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, the dielectric layer includes dielectric particles; The laminate is a laminar first side portion extending along the first side surface and not including an internal electrode layer; a laminar second side portion extending along the second side surface and not including an internal electrode layer; a first outer layer portion sandwiched between the first side portion and the second side portion and sandwiched between the first main surface and an internal electrode layer closest to the first main surface; a second outer layer portion sandwiched between the first side portion and the second side portion and sandwiched between the second main surface and an internal electrode layer closest to the second main surface; and an inner layer portion sandwiched between the first side portion and the second side portion and between the first outer layer portion and the second outer layer portion; In a cross section of the laminate taken across the center in the longitudinal direction, the dielectric layer at the center in the thickness direction of the inner layer portion contains particles having voids as dielectric particles, thereby providing a multilayer ceramic capacitor. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a multilayer ceramic capacitor that has a high dielectric constant, can be made smaller and has a larger capacitance, has a flat temperature characteristic of the dielectric constant, and is highly reliable. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a perspective view showing the external shape of the multilayer ceramic capacitor. [Figure 2] FIG. 1 is a cross-sectional view schematically showing the internal structure of a multilayer ceramic capacitor. [Figure 3] FIG. 1 is a cross-sectional view schematically showing the internal structure of a multilayer ceramic capacitor. [Figure 4] TEM-HAADF image showing particles with voids. DETAILED DESCRIPTION OF THE INVENTION

[0011] A specific embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described. Note that the present invention is not limited to the following embodiment, and various modifications are possible within the scope of the present invention.

[0012] (1) Multilayer ceramic capacitors The multilayer ceramic capacitor of this embodiment has first and second main surfaces facing each other in the thickness direction, first and second side surfaces facing each other in the width direction, and first and second end surfaces facing each other in the length direction. This multilayer ceramic capacitor includes a laminate 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 and second end surfaces, respectively, and connected to the plurality of internal electrode layers. The dielectric layers contain dielectric particles. The laminate is divided into a first side portion extending along the first side surface and having a laminar shape and not including an internal electrode layer, a second side portion extending along the second side surface and having a laminar shape and not including an internal electrode layer, a first outer layer portion sandwiched between the first side portion and the second side portion and sandwiched between the first main surface and the internal electrode layer closest to the first main surface, a second outer layer portion sandwiched between the first side portion and the second side portion and sandwiched between the second main surface and the internal electrode layer closest to the second main surface, and an inner layer portion sandwiched between the first side portion and the second side portion and sandwiched between the first outer layer portion and the second outer layer portion. Furthermore, in a cross section transverse to the center in the longitudinal direction of the laminate, the dielectric layer at the center in the thickness direction of the inner layer portion contains particles having voids as dielectric particles.

[0013] One embodiment of the multilayer ceramic capacitor will be described with reference to Fig. 1 to Fig. 3. Fig. 1 is a perspective view showing the outer shape of the multilayer ceramic capacitor. Fig. 2 is a cross-sectional view of the multilayer ceramic capacitor shown in Fig. 1 taken along line II-II, and Fig. 3 is a cross-sectional view of the multilayer ceramic capacitor shown in Fig. 1 taken along line III-III.

[0014] The multilayer ceramic capacitor (100) includes a laminate (6) including 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 surfaces (14a, 14b) of the laminate (6). The multilayer ceramic capacitor (100) and the laminate (6) have a substantially rectangular parallelepiped shape. The term "substantially rectangular parallelepiped" includes not only rectangular parallelepipeds but also rectangular parallelepipeds with rounded corners and / or ridges. Here, a corner is a portion where three faces of the laminate (6) intersect, and a ridge is a portion where two faces of the laminate intersect. Preferably, the multilayer ceramic capacitor (100) and the laminate (6) have a rectangular parallelepiped shape with rounded corners and / or ridges.

[0015] The multilayer ceramic capacitor (100) and the laminate (6) have a first main surface (10a) and a second main surface (10b) facing in the thickness direction T, a first side surface (12a) and a second side surface (12b) facing in the width direction W, and a first end surface (14a) and a second end surface (14b) facing in the length direction L. Here, the thickness direction T refers to the direction in which the dielectric layers (2) and the internal electrode layers (4) are stacked. The length direction L refers to the direction perpendicular to the thickness direction T and in which the end surfaces (14a, 14b) face each other. The width direction W is a direction perpendicular to the thickness direction T and the length direction L. A plane including the thickness direction T and the width direction W is defined as a WT plane, a plane including the width direction W and the length direction L is defined as an LW plane, and a plane including the length direction L and the thickness direction T is defined as an LT plane.

[0016] 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 extend not only to the first end surface (14a) but also to parts of the first main surface (10a), second main surface (10b), first side surface (12a), and second side surface (12b). The second external electrode (8b) may extend not only to the second end surface (14b) but also to parts of the first main surface (10a), second main surface (10b), first side surface (12a), and second side surface (12b). However, the first external electrode (8a) and the second external electrode (8b) are not in contact with each other and are electrically separated from each other.

[0017] 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 layers (4a) and the second internal electrode layers (4b) each include a substantially rectangular opposing electrode portion and a lead electrode portion extending to the end face (14a, 14b) and connecting to the external electrodes (8a, 8b). That is, the first internal electrode layers (4a) extend to the first end face (14a) via the lead electrode portion and are electrically connected to the first external electrode (8a) there. The second internal electrode layers (4b) extend to the second end face (14b) via the lead electrode portion and are electrically connected to the second external electrode (8b) there. The first internal electrode layers (4a) and the second internal electrode layers (4b) are alternately stacked in the thickness direction T so as to face each other with the dielectric layer (2) sandwiched therebetween. The first internal electrode layer (4a) and the second internal electrode layer (4b), which face each other across the dielectric layer (2), are not electrically connected. Therefore, when a voltage is applied via the external electrodes (8a, 8b) and the lead-out electrode portions, electric charge accumulates between the opposing electrode portions of the first internal electrode layer (4a) and the second internal electrode layer (4b). The accumulated electric charge generates electrostatic capacitance, which causes the device to function as a capacitive element (capacitor).

[0018] The laminate (6) is composed of an inner layer portion (16), a first outer layer portion (18a), a second outer layer portion (18b), a first side portion (20a), and a second side portion (20b). The first side portion (20a) is a layered region that extends along the first side surface (12a) and does not include the internal electrode layers (4a, 4b). The second side portion (20b) is a layered region that extends along the second side surface (12b) and does not include the internal electrode layers (4a, 4b). In other words, the first side portion (20a) is a region sandwiched between the first side surface (12a) and the end portions of the internal electrode layers (4a, 4b) on the first side surface (12a) side, and the second side portion is a region sandwiched between the second side surface (12b) and the end portions of the internal electrode layers (4a, 4b) on the second side surface (12b) side.

[0019] The first outer layer portion (18a) is a region sandwiched between the first side portion (20a) and the second side portion (20b), and is sandwiched between the first main surface (10a) and an internal electrode layer of the plurality of internal electrode layers (4a, 4b) that is closest to the first main surface (10a). The second outer layer portion (18b) is a region sandwiched between the first side portion (20a) and the second side portion (20b), and is sandwiched between the second main surface (10b) and an internal electrode layer of the plurality of internal electrode layers (4a, 4b) that is closest to the second main surface (10b). The internal layer portion (16) is a region sandwiched between the first outer layer portion (18a) and the second outer layer portion (18b), i.e., a region disposed 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 capacitance element. In other words, the inner layer portion (16) that functions as a capacitance element is sandwiched in the stacking (thickness) direction between the first outer layer portion (18a) and the second outer layer portion (18b), and the entirety of these is sandwiched in the width direction between the first side portion (20a) and the second side portion (20b).

[0020] The size of the multilayer ceramic capacitor (100) or the laminate (6) is not particularly limited. For example, the lengthwise dimension L is 0.2 mm or more and 3.2 mm or less, the widthwise dimension W is 0.1 mm or more and 2.5 mm or less, and the stacking direction T dimension is 0.1 mm or more and 2.5 mm or less. Although FIGS. 1 to 3 show the lengthwise dimension L being larger than the widthwise dimension W, the multilayer ceramic capacitor of this embodiment is not limited to those having such dimensions. The lengthwise dimension L may be smaller than the widthwise dimension W.

[0021] <Inner layer - dielectric layer> The dielectric layer, together with the internal electrode layers, constitutes the inner layer of the multilayer ceramic capacitor. This dielectric layer contains dielectric particles (dielectric grains). The dielectric particles are made of perovskite oxide and are the main component of the dielectric layer. The dielectric layer is made of a sintered polycrystalline body (ceramic) in which a large number of dielectric particles are bonded via grain boundaries and triple junctions. The dielectric layer can be said to be a dielectric ceramic whose main component is perovskite oxide. The main component refers to the component that is contained in the dielectric layer at the largest ratio. The content of the dielectric particles (perovskite oxide) as the main component in the dielectric layer may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more.

[0022] Perovskite oxides have a composition represented by the general formula ABO3 and have a cubic-like crystal structure, such as cubic, tetragonal, orthorhombic, or rhombohedral, at room temperature. A-site element atoms (hereinafter "A-site atoms") and B-site element atoms (hereinafter "B-site atoms") ionize to occupy the A and B sites of the perovskite structure. Examples of A-site elements include elements with relatively large ionic sizes, such as barium (Ba), calcium (Ca), and strontium (Sr). Examples of B-site elements include elements with relatively small ionic sizes, such as titanium (Ti), zirconium (Zr), and hafnium (Hf). The combination of A-site and B-site elements is not particularly limited as long as the perovskite structure is maintained. Each of the A-site and B-site elements may contain only one element or a combination of multiple elements. Furthermore, the molar ratio of A-site elements to B-site elements may deviate from 1:1 as long as the perovskite structure is maintained.

[0023] Specific examples of perovskite oxides include barium titanate (BaTiO3)-based compounds, calcium titanate (CaTiO3)-based compounds, strontium titanate (SrTiO3)-based compounds, and mixed crystals and solid solutions thereof. Preferably, the A-site element contains barium (Ba) and the B-site element contains titanium (Ti). That is, the perovskite oxide is preferably a barium titanate (BaTiO3)-based compound. BaTiO3 has a large spontaneous polarization at room temperature. Therefore, it is a ferroelectric material exhibiting a high dielectric constant. By using a BaTiO3-based compound as the main component, it is possible to achieve even greater capacitance of the capacitor. Note that BaTiO3-based compounds include not only BaTiO3 but also BaTiO3 compounds in which a portion of the Ba in BaTiO3 is replaced with other A-site elements such as Sr and / or Ca, or Ba is replaced with other B-site elements such as Zr and / or Hf. However, the proportion of Ba among the A-site elements is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more, by molar ratio. The proportion of Ti among the B-site elements is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more, by molar ratio. The A-site elements do not have to contain any components other than Ba ​​and inevitable impurity elements, and the B-site elements do not have to contain any components other than Ti and inevitable impurity elements. Here, inevitable impurities are components that are inevitably mixed in during the manufacturing process.

[0024] The dielectric layer may contain a secondary component. Examples of the secondary component include, but are not limited to, rare earth elements (RE), magnesium (Mg), manganese (Mn), iron (Fe), chromium (Cr), cobalt (Co), nickel (Ni), silicon (Si), aluminum (Al), vanadium (V), and compounds thereof. The rare earth elements (RE) are a collective term for elements that belong to the group consisting of scandium (Sc) with atomic number 21, yttrium (Y) with atomic number 39, and lanthanum (La) with atomic number 57 to lutetium (Lu) with atomic number 71 in the periodic table. The rare earth element (RE) is preferably one or more 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), lutetium (Lu), and yttrium (Y). As the auxiliary component, the above-mentioned component may be contained alone or in combination.

[0025] When the dielectric layer contains a minor component, the form in which the minor component exists is not limited. The minor component may be contained in any of the dielectric particles, grain boundaries, and triple points. When contained in the dielectric particles, the minor component may be contained in a solid solution state. In this case, the minor component may occupy the A site of the perovskite-type oxide (ABO3), the B site, or both sites simultaneously. The minor component may be distributed uniformly or non-uniformly in the dielectric particles.

[0026] The dielectric particles may include core-shell particles. Core-shell particles are particles having a structure (core-shell structure) in which at least a portion of the auxiliary components are dissolved in a high concentration in the surface layer (shell portion) of the particle and the auxiliary components are dissolved in a low concentration or not dissolved at all in the center (core portion) of the particle. By imparting a core-shell structure to the dielectric particles, it is possible to flatten the temperature characteristics of the dielectric constant and improve reliability. That is, in core-shell particles, the concentrations of the auxiliary components differ between the core and shell portions, resulting in different dielectric constant-temperature characteristics. Therefore, it is possible to flatten the temperature characteristics of the dielectric constant throughout the particle. Furthermore, by dissolving auxiliary components such as rare earth elements that act as donors or acceptors in the shell portion, it is possible to suppress the migration of oxygen vacancies that cause insulation degradation, thereby significantly improving the reliability of multilayer ceramic capacitors.

[0027] Whether or not a particle has a core-shell structure can be determined by comparing the concentration of each subcomponent at the particle center (core) with the concentration of the subcomponent at a location inside the particle at a distance of about 10 nm from the interface between the particle and the grain boundary phase (shell). If the concentration of the subcomponent in the shell is 150% or more of the concentration in the core, the particle can be determined to be a core-shell particle.

[0028] The dielectric particles may include homogeneously dissolved particles. Homogeneously dissolved particles are particles in which the minor component is homogeneously dissolved within the particle, or particles in which the minor component is not dissolved. Homogeneously dissolved particles are also called non-core-shell particles. To achieve a homogeneous solution, it is desirable to incorporate the minor component into the particle as the particle grows, and for this purpose, it is desirable to grow the particle to a certain size. By using particles in which the minor component is homogeneously dissolved in this way, it is possible to further increase the dielectric constant. Core-shell particles have the advantage of being able to flatten the temperature characteristics of the dielectric constant and improve reliability, but there is a limit to how much the dielectric constant can be increased. In contrast, by using homogeneously dissolved particles, it is possible to significantly increase the dielectric constant.

[0029] In the multilayer ceramic capacitor of this embodiment, in a cross section across the longitudinal center of the laminate, the dielectric layer at the thickness center of the inner layer portion contains particles having voids (voided particles) as dielectric particles (dielectric grains). That is, when the multilayer ceramic capacitor is processed to expose a surface (WT surface) that crosses the longitudinal center of the laminate and includes the width and thickness directions, some or all of the dielectric particles in the dielectric layer at a predetermined position on this WT surface are voided particles. In the voided particles, the voids are present inside the particle.

[0030] The provision of voided particles can improve the properties of the dielectric layer, such as the dielectric constant, the temperature characteristic of the dielectric constant, and reliability. That is, dielectric particles without voids may have low crystallinity. Low particle crystallinity can lead to excessive diffusion of minor component elements into the particles during the firing process in the manufacture of multilayer ceramic capacitors, resulting in degradation of various properties. For example, when the objective is to form core-shell particles, the minor component elements may diffuse through the shell to the core, destroying the core-shell structure. Furthermore, when the objective is to form homogeneous solid-solution particles, the minor component elements may dissolve excessively within the particles, making it difficult to achieve the desired properties. In contrast, the high crystallinity of the voided particles prevents excessive diffusion of the minor component elements. For example, when the dielectric particles are core-shell particles, grain growth during the firing process does not unduly promote diffusion and dissolution of the minor component elements. Because grain growth is possible without destroying the core-shell structure, it is possible to achieve both a high dielectric constant, flat temperature characteristics, and excellent reliability.

[0031] The number of voids in a particle with voids is not particularly limited. A particle may contain one void or multiple voids within itself. The distribution of voids within the particle is also not particularly limited. Typically, voids are present near the center of the particle.

[0032] The presence and proportion of voided particles can be investigated as follows. First, a multilayer ceramic capacitor is processed by polishing, grinding, and / or cutting to expose its cross section. This cross section is a plane that crosses the center of the multilayer ceramic capacitor in the length (L) direction and includes the width (W) and thickness (T) directions, i.e., the WT plane. Next, the obtained cross section is observed using a transmission electron microscope (TEM) to obtain a high-angle annular dark-field (HAADF) image. Based on this image, the presence and proportion of voided particles are investigated. Voids appear as black dots within the particles and are easy to identify. Observation is performed on approximately the center of the thickness (T) direction in the WT plane. If a dielectric layer is present in the center of the thickness direction, observation of that dielectric layer is sufficient. On the other hand, if an internal electrode layer is present in the center of the thickness direction, observation of the dielectric layer adjacent to that internal electrode layer is sufficient. Observation is performed on more than 100 dielectric particles. For example, observation is performed in a 1000 nm x 1000 nm field of view, and the number of void-containing particles among the dielectric particles present within this field of view is counted. If there are less than 100 dielectric particles within this field of view, it is sufficient to examine multiple adjacent fields of view as well. For example, it is sufficient to connect multiple fields of view and perform observation in a total field of view of 3 μm x 3 μm. Then, the number of dielectric particles (N) and the number of void-containing particles (n) are counted, and the ratio of the number of void-containing particles (n / N) is calculated from these.

[0033] Preferably, the voided particles are present near the widthwise center of the inner layer portion. That is, in a cross section of the laminate transverse to the longitudinal center, the dielectric layer at the thicknesswise center of the inner layer intermediate region desirably contains voided particles as the dielectric particles. The inner layer intermediate region is a region located in the widthwise center of the inner layer portion. Specifically, when the laminate is divided into a first inner layer side region, a second inner layer side region, and an inner layer intermediate region, the region sandwiched between the first inner layer side region and the second inner layer side region is the inner layer intermediate region. The first inner layer side region is a region within the inner layer portion that occupies a portion of the inner layer portion that is equal to or less than the edge distance from the interface between the inner layer portion and the first side region. Here, the edge distance is the smaller of W / 10 and 40 μm, where W is the width of the laminate. The first inner layer side region can also be said to be a region within the inner layer portion that is sandwiched between the interface between the inner layer portion and the first side region and a surface spaced from this interface by the edge distance. The second inner layer side region is a region within the inner layer portion that occupies a portion of the inner layer portion that is no more than the edge distance from the interface between the inner layer portion and the second side portion. The second inner layer side region can also be described as a region within the inner layer portion that is sandwiched between the interface between the inner layer portion and the second side portion and a surface that is spaced from this interface by the edge distance.

[0034] Preferably, there are many voided particles near the widthwise center of the inner layer portion. Specifically, in a cross section of the laminate transverse to the longitudinal center, the number ratio (Cn / CN) of voided particles among the dielectric particles at the thicknesswise center of the inner layer intermediate region is desirably 15% or more. Increasing the ratio of voided particles in the inner layer intermediate region makes it possible to further improve the dielectric constant, temperature characteristics of the dielectric constant, and reliability of the dielectric layer. The number ratio (Cn / CN) may be 20% or more, 25% or more, 30% or more, 35% or more, or 40% or more. There is no particular upper limit to the number ratio (Cn / CN). It may be 100% or less, 80% or less, or 60% or less.

[0035] Preferably, void-containing particles are present near the widthwise ends of the inner layer portion. That is, in a cross section across the longitudinal center of the laminate, it is desirable that the dielectric layer at the thicknesswise center of at least one of the first inner layer side region and the second inner layer side region contains void-containing particles as dielectric particles. This makes it possible to further improve reliability. During operation of the multilayer ceramic capacitor, an electric field concentrates near the ends of the internal electrode layers, making dielectric breakdown likely to occur near the ends. By providing highly crystalline void-containing particles in the dielectric layer near the ends, it is possible to suppress the progression of dielectric breakdown, thereby significantly improving reliability.

[0036] Preferably, there are many void-containing particles near the widthwise ends of the inner layer portion. That is, in a cross section that traverses the longitudinal center of the laminate, the number ratio (Wn / WN) of void-containing particles among the dielectric particles at the thickness direction center of at least one of the first inner layer side region and the second inner layer side region is desirably greater than the number ratio (Cn / CN) of void-containing particles among the dielectric particles at the thickness direction center of the inner layer middle region. Furthermore, in a cross section that traverses the longitudinal center of the laminate, the number ratio (Wn / WN) of void-containing particles among the dielectric particles at the thickness direction center of at least one of the first inner layer side region and the second inner layer side region is desirably 25% or more. Increasing the ratio of void-containing particles in the dielectric layer near the end in this way makes it possible to further significantly improve reliability. The number ratio (Wn / WN) may be 30% or more, 35% or more, or even 40% or more. There is no particular upper limit to the number ratio (Wn / WN). It may be 100% or less, 80% or less, or 60% or less.

[0037] The average pore size of the pores is preferably 1 nm or more and 50 nm or less, and particularly preferably 10 nm or more and 30 nm or less. By limiting the pore size to a predetermined value or more, the effect of improving the crystallinity of the particles can be fully exerted, and the capacitance-temperature characteristics can be significantly suppressed. Furthermore, by limiting the pore size to a predetermined value or less, the deterioration of the dielectric properties due to the pores can be suppressed, and the dielectric constant can be significantly increased.

[0038] The average particle size of the dielectric particles is preferably 100 nm or more and 500 nm or less, and particularly preferably 130 nm or more and 300 nm or less. By limiting the average particle size to a predetermined value or more, the effect of improving the crystallinity of the particles can be fully exerted, and the capacitance-temperature characteristics can be significantly suppressed. Furthermore, by limiting the average particle size to a predetermined value or less, the dielectric layers can be made thinner, which contributes to increasing the capacitance of the multilayer ceramic capacitor and has the effect of improving reliability. Note that the above-mentioned average particle size refers to the average particle size of all dielectric particles, including not only particles with voids but also particles without voids.

[0039] The thickness of the dielectric layer is preferably 0.30 μm or more and 1.00 μm or less, more preferably 0.40 μm or more and 0.50 μm or less, and even more preferably 0.40 μm or more and 0.45 μm or less. By making the thickness of the dielectric layer a predetermined value or more, it is possible to suppress the occurrence of dielectric breakdown and deterioration of the lifespan of the multilayer ceramic capacitor when it is used. Furthermore, by making the thickness of the dielectric layer a predetermined value or less, the dielectric layer is made thinner, enabling the multilayer ceramic capacitor to have a further increased capacitance. The number of dielectric layers is not particularly limited. Preferably, the number of dielectric layers constituting the outer layer portion and the inner layer portion is 100 to 2000.

[0040] The composition of the dielectric layer occupying the inner layer portion is not particularly limited. However, a suitable composition includes barium titanate (BaTiO3) as a main component, and further includes the following minor components in amounts relative to 100 mol parts of titanium (Ti): 0.6 to 2.0 mol parts of dysprosium (Dy), 0.08 to 0.4 mol parts of manganese (Mn), 0.01 to 0.2 mol parts of magnesium (Mg), 0.6 to 2.0 mol parts of silicon (Si), 0.2 to 5.0 mol parts of nickel (Ni), 0.04 to 0.3 mol parts of aluminum (Al), and 0.04 to 0.2 mol parts of vanadium (V).

[0041] <Inner layer - internal electrode layer> The internal electrode layers (first internal electrode layer, second internal electrode layer) and the dielectric layer constitute the internal layer portion. The internal electrode layers are also composed of a counter electrode portion and an extraction electrode portion. The counter electrode portion sandwiches the dielectric layer and functions as a capacitive element. The extraction electrode portion electrically connects the counter electrode portion and the external electrode. The internal electrode layers contain a conductive metal. As the conductive metal, known electrode materials such as nickel (Ni), copper (Cu), silver (Ag), palladium (Pd), silver (Ag)-palladium (Pd) alloy and / or gold (Au) may be used. However, from the viewpoint of cost reduction, base metals such as Ni and Cu are preferred, and Ni is particularly preferred.

[0042] The internal electrode layers may contain components other than conductive metals. Examples of such components include ceramic components that function as co-materials. Adding co-materials allows the shrinkage behavior of the internal electrode layers to match that of the dielectric layers during the firing process of multilayer ceramic capacitor manufacturing. This prevents defects such as peeling of the internal electrode layers due to differences in shrinkage behavior. Dielectric particles such as BaTiO3-based compounds contained in the dielectric layers are preferred as ceramic components. The thickness of the internal electrode layers is preferably 0.30 μm to 0.40 μm, more preferably 0.30 μm to 0.35 μm. Maintaining the internal electrode thickness above a predetermined value can prevent problems such as electrode breakage. Maintaining the thickness below a predetermined value can prevent a decrease in the proportion of the dielectric layers in the capacitor, contributing to increased capacitance. The number of internal electrode layers is preferably 10 to 1,000.

[0043] Tin (Sn) may be present at the interface between the dielectric layer and the internal electrode layer. When Sn is present, Sn may be present in the form of a layer parallel to the internal electrode layer, or may be scattered. Sn may also be dissolved in the internal electrode layer, or may be dissolved in the dielectric particles that make up the dielectric layer.

[0044] <Outer layer> The outer layer portions (first outer layer portion, second outer layer portion) are provided above and below the inner layer portion. The outer layer portions are made of dielectric ceramic and are regions that do not include internal electrode layers. The composition of the outer layer portions may be the same as or different from the dielectric layers included in the inner layer portions. When the composition of the outer layer portions is the same as that of the inner layer portions, the dielectric green sheet used to form the inner layer portions can also be used to form the outer layer portions during the manufacture of the multilayer ceramic capacitor.

[0045] <Side> The side portions (first side portion, second side portion) are provided along the side surfaces of the multilayer ceramic capacitor so as to sandwich the inner layer portion and the outer layer portion. The inner layer portion side portions are also called side gaps. The side portions (side gap portions) are made of dielectric ceramic and are areas that do not include internal electrode layers. By providing the side portions, it is possible to prevent moisture from penetrating into the inner layer portion from the side surfaces.

[0046] The side portions may be formed integrally with the inner and outer layer portions during the manufacture of the multilayer ceramic capacitor. In this case, the dielectric layers constituting the side portions are continuous in composition and microstructure with the dielectric layers constituting the inner and / or outer layer portions. On the other hand, the side portions may be formed separately from the inner and outer layer portions. Specifically, a green element portion is produced by attaching a side green body to the side surface of the laminated chip that will become the inner and / or outer layer portions, and this green element portion is then fired. In this case, the dielectric layers constituting the side portions are not continuous in composition and / or microstructure with the dielectric layers constituting the inner and / or outer layer portions. Therefore, a physical and chemical boundary exists between the side portions and the inner and / or outer layer portions.

[0047] Preferably, the first and second side portions contain dielectric particles containing barium (Ba) and titanium (Ti), and further contain at least one of 1.00 to 3.00 mol parts of magnesium (Mg) and 0.50 to 2.00 mol parts of manganese (Mn) per 100 mol parts of titanium (Ti), with the total content of magnesium (Mg) and manganese (Mn) being 5.00 mol parts or less. By setting the Mg content to 1.00 mol parts or more or the Mn content to 0.50 mol parts or more, it is possible to further improve humidity load resistance characteristics. Furthermore, by setting the Mg content to 3.00 mol parts or less and the Mn content to 2.00 mol parts or less, it is possible to suppress capacity degradation.

[0048] <External electrode> The external electrodes (first external electrode, second external electrode) function as input / output terminals of the multilayer ceramic capacitor. Known configurations can be used for the external electrodes. For example, the multilayer ceramic capacitor may include a base electrode layer and a plating layer disposed on the base electrode layer. The base electrode layer includes at least one layer selected from a baking layer, a resin layer, and a thin film layer. The baking layer is formed by applying a conductive paste containing glass and metal to the laminate and then baking it. Baking may be performed simultaneously with or after firing the laminate. The baking layer may be a single layer or may be composed of multiple layers. The metal contained in the baking layer is preferably copper (Cu), nickel (Ni), silver (Ag), palladium (Pd), a silver (Ag)-palladium (Pd) alloy, and / or gold (Au). The resin layer includes conductive particles and a thermosetting resin. The resin layer may be a single layer or may be composed of multiple layers. The thin film layer is formed by a thin film formation method such as sputtering or vapor deposition, and is a layer of deposited metal particles with a thickness of 1 μm or less. The plating layer contains metals such as copper (Cu), nickel (Ni), tin (Sn), silver (Ag), palladium (Pd), silver (Ag)-palladium (Pd), and / or gold (Au). The plating layer may be a single layer or may be composed of multiple layers. A suitable plating layer has a two-layer structure consisting of Ni plating and Sn plating. The Ni plating layer can prevent erosion of the base layer by solder when mounting a multilayer ceramic capacitor. The Sn plating layer also improves solder wettability, making it easier to mount the multilayer ceramic capacitor.

[0049] The external electrode layer may be formed of a plating layer without providing a base electrode layer. In this case, the plating layer is provided directly on the laminate and directly connected to the lead electrode portion of the internal electrode layer. However, a catalyst may 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. Alternatively, another plating layer may be provided on the second plating layer. The first plating layer and the second plating layer include, for example, 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 a metal. When the internal electrode layer includes Ni, the first plating layer preferably includes Cu, which has good bonding properties with Ni. It is also preferable that the first plating layer includes Ni, which has good solder barrier properties. The second plating layer preferably includes Sn or Au, which have good solder wettability.

[0050] However, the plating layer is not limited to one composed of a first plating layer and a second plating layer. The plating layer may be composed of only the first plating layer without providing the second plating layer. Another plating layer may be provided on the second plating layer. In either case, it is preferable that the plating layer does not contain glass. It is also preferable that the metal content of the plating layer is 99% by volume or more. The plating layer has grain growth along the thickness direction and is columnar.

[0051] (2) Manufacturing method of multilayer ceramic capacitors The multilayer ceramic capacitor of this embodiment can be manufactured by any method as long as it satisfies the above-mentioned requirements. However, it is preferably manufactured by the following method. The preferred manufacturing method includes the following steps: a synthesis step of synthesizing the main component raw materials for the dielectric layers; a mixing step of mixing the main component raw materials with the subcomponent raw materials to form a dielectric raw material; a molding step of adding and mixing a binder and a solvent to the dielectric raw material to form a slurry, and molding the resulting slurry into a dielectric green sheet; a printing step of printing a patterned conductive paste layer on the surface of the dielectric green sheet using a conductive paste for internal electrodes; a stacking step of stacking and pressing multiple dielectric green sheets to form a laminated block; a cutting step of cutting the resulting laminated block into a laminated chip; a side green body attached to the side of the resulting laminated chip to form a green element portion; a side portion forming step of subjecting the resulting green element portion to a binder removal treatment and a firing treatment to form an element portion; and a firing step of forming external electrodes on the resulting element portion to form a multilayer ceramic capacitor. Each step will be described in detail below.

[0052] <Synthesis process> In the synthesis process, the main component raw materials used in forming the dielectric layer are synthesized. The main component raw materials are oxide powders with a perovskite structure, such as BaTiO3-based compounds. Preferably, the main component raw materials are synthesized by a liquid-phase method, such as the sol-gel method, alkoxide method, solvothermal method, or hydrothermal synthesis method. In the sol-gel method, sol or gel of inorganic or organic salts of Ba and Ti are used as raw materials, which are mixed and fired to produce oxide powder. In the alkoxide method, alkoxides of Ba and Ti are used as raw materials, which are mixed and fired to produce oxide powder. In the solvothermal method, inorganic or organic compounds of Ba and Ti are placed in a sealed container together with a solvent, and high temperature and pressure are applied to synthesize the oxide powder. The hydrothermal method is a type of solvothermal method that uses water as the solvent.

[0053] <Mixing process> In the mixing step, the main component raw material is mixed with the subcomponent raw material (Ni, Re, Mg, Mn, Si, Al, V, etc.) to produce a dielectric raw material. Known ceramic raw materials such as oxides, carbonates, hydroxides, nitrates, organic acid salts, alkoxides, and / or chelate compounds may be used as the subcomponent raw material. The mixing method is not particularly limited. For example, the main component raw material and the subcomponent raw material may be wet mixed and ground using a ball mill together with grinding media and pure water. If wet mixing is performed, the mixture may be dried.

[0054] <Forming process> In the molding process, a binder and a solvent are added to and mixed with the dielectric raw material to form a slurry, and the resulting slurry is molded into a dielectric green sheet. After firing, the dielectric green sheet becomes the dielectric layers that form the inner and outer layers of the multilayer ceramic capacitor. A known organic binder such as a polyvinyl butyral binder can be used as the binder. Furthermore, a known organic solvent such as toluene or ethanol can be used as the solvent. Additives such as a plasticizer can be added as needed. Molding can be performed using a known method such as the lip method. The thickness of the molded sheet is, for example, 1 μm or less.

[0055] <Printing process> In the printing process, a conductive paste is used to form a patterned conductive paste layer on the surface of the dielectric green sheet. The conductive paste layer becomes the internal electrode layer after firing. The conductive metal contained in the conductive paste may be a conductive material such as nickel (Ni), copper (Cu), silver (Ag), palladium (Pd), or an alloy containing these. However, nickel (Ni) is preferred. A ceramic component that acts as a co-material may also be added to the conductive paste. The main component raw material of the dielectric layer may be used as the ceramic component. The method for forming the conductive paste layer is not particularly limited. Examples include screen printing and gravure printing.

[0056] <Lamination process> In the lamination process, multiple dielectric green sheets are stacked and pressed together to produce a laminated block. At this time, multiple dielectric green sheets with conductive paste layers are stacked so that they are sandwiched from above and below by dielectric green sheets without conductive paste layers. The green sheets without conductive paste layers undergo a firing process to become the outer layers of the multilayer ceramic capacitor. Meanwhile, the green sheets with conductive paste layers become the dielectric layers that form the inner layers of the multilayer ceramic capacitor. The number of green sheets to be stacked can be adjusted to obtain the required capacitance.

[0057] <Cutting process> In the cutting step, the obtained laminated block is cut into laminated chips. The cutting may be performed so that chips of a predetermined size are obtained and at least a part of the conductive paste layer is exposed on the end surfaces of the laminated chips.

[0058] <Side portion forming process> If necessary, a side portion forming process is provided. In this process, the side portions are formed separately from the inner layer portion and the outer layer portion. In the side portion forming process, side green bodies are attached to the side surfaces of the laminated chip to form green element portions. The side green bodies cover the conductive paste layers exposed on the side surfaces of the laminated chip. The side green bodies also become the side portions of the multilayer ceramic capacitor after firing. The main component raw materials and subcomponent raw materials used to prepare the dielectric layers can be used as raw materials for the side green bodies. However, the composition of the side portions does not need to be the same as the composition of the dielectric layer, and a different composition may be used. For example, only a portion of the subcomponents of the dielectric layer may be used, or a subcomponent different from the dielectric layer may be added. On the other hand, the composition of the side portions may be the same as that of the dielectric layer.

[0059] The preparation and attachment of the side green bodies may be performed by known methods. For example, a method may be used in which a green sheet is prepared from the side raw material powder and then bonded to the side of the laminated chip. To ensure the green sheet is adhered, an adhesive agent such as an organic solvent may be applied to the side of the laminated chip in advance. Alternatively, a method may be used in which a paste is prepared from the side raw material powder and then applied and dried to the side of the laminated chip. The side green bodies may be single-layered or may be laminated bodies consisting of multiple layers. A laminated side green body can be obtained by stacking multiple green sheets on the side of the laminated chip or by repeatedly applying and drying a paste. When the side portions are integrally formed with the inner and outer layer portions, a portion of the dielectric green sheets laminated in the lamination process becomes the side portions. In this case, a separate side portion formation process is not required.

[0060] If necessary, the laminated chip or green element is subjected to barrel polishing, which makes it possible to round the corners and / or ridges of the laminated chip or green element.

[0061] <Firing process> In the firing process, the laminated chip or green element part is subjected to a binder removal process and a firing process to form an element part. The firing process causes the conductive paste layer and the dielectric green sheet to be co-sintered, becoming the internal electrode layer and the dielectric layer, respectively. The conditions for the binder removal process can be determined according to the type of organic binder contained in the green sheet and the conductive paste layer. The firing process can be carried out at a temperature at which the laminated chip is sufficiently densified. For example, the firing process can be carried out at a temperature of 1200°C to 1300°C, and maintained for 0 to 10 minutes. The firing process is carried out in an atmosphere in which the BaTiO3-based compound, which is the main component, is not reduced and the oxidation of the conductive material is suppressed. For example, an oxygen partial pressure of 1.8 x 10 -9 ~8.7×10 -10 The firing can be performed in a N2-H2-H2O gas flow at 100 MPa. Annealing may also be performed after firing.

[0062] <External electrode formation process> In the external electrode formation process, external electrodes are formed on the element body to create a multilayer ceramic capacitor. The external electrodes can be formed using a known method. For example, a conductive paste containing a conductive component such as Cu or Ni is applied and baked to form a base layer on the end surfaces of the element body where the internal electrodes are drawn out. The base layer can also be formed by applying a conductive paste to both end surfaces of the green element body before firing, followed by a firing process. After the base layer is formed, electroplating can be performed to form a plating film of Ni, Sn, or the like on the surface of the base layer. This completes the multilayer ceramic capacitor. [Example]

[0063] 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.

[0064] (1) Fabrication of multilayer ceramic capacitors [Comparative Examples 1 to 3 and Examples 1 to 20] For Comparative Examples 1 to 3 and Examples 1 to 20, the manufacturing conditions and the composition of the dielectric layers were changed to fabricate multilayer ceramic capacitors, and the capacitors were evaluated.

[0065] <Synthesis of barium titanate powder> Barium titanate powder was produced by the so-called hydrothermal synthesis method. First, titanium oxide (TiO2) powder and barium hydroxide (Ba(OH)2) powder were weighed, and pure water was added to produce a slurry. The produced slurry was then placed in a sealed container, and the temperature of the slurry was raised to 200-250°C while stirring. The temperature was then maintained at 200-250°C for 4-24 hours to allow a liquid-phase reaction to proceed. After that, the pressure inside the sealed container was returned to atmospheric pressure, heating of the sealed container was stopped, and the slurry was left to stand. After cooling, the slurry was removed from the sealed container and placed in a dryer to evaporate the water. The barium titanate powder obtained in this way was used as the main component raw material.

[0066] Separately from the main component raw materials, the raw materials for the secondary components (Ni, Re, Mg, Mn, Si, Al, V) were weighed out. The secondary component raw materials used were nickel oxide (NiO), rare earth oxides (Dy2O3, etc.), magnesium carbonate (MgCO3), manganese carbonate (MnCO3), silicon oxide (SiO2), aluminum oxide (Al2O3), and vanadium oxide (VO5).

[0067] Next, the subcomponent raw materials were added to the main component raw materials, and the mixture was wet-mixed using a ball mill, followed by drying and heat treatment to obtain a dielectric raw material. A polyvinyl butyral binder and ethanol, an organic solvent, were added to the obtained dielectric raw material, and the mixture was wet-mixed using a ball mill for a predetermined time to produce a slurry. This slurry was formed into a sheet to produce a dielectric green sheet.

[0068] Next, a Ni-based conductive paste was screen-printed onto the surface of the obtained dielectric green sheet to form a pattern of conductive paste layers that would become internal electrode layers. After that, multiple green sheets with conductive paste layers formed on them were stacked, and green sheets without conductive paste layers were placed above and below them, and the whole was pressed together to form a laminated block. The obtained laminated block was then cut with a dicing saw into laminated chips. The stacking was performed so that the ends from which the conductive paste layers were drawn out were staggered. The cutting was also performed so that the conductive paste layers were exposed on the side surfaces.

[0069] The green body was made by attaching side green sheets (side green bodies) to both sides of the cut laminated chip where the conductive paste layer was exposed. The side green sheets were produced in the same manner as the dielectric green sheets, except that the blending amounts of the main component raw materials and the subcomponent raw materials were changed.

[0070] The obtained green compact was heat-treated in a nitrogen gas stream under the condition of a maximum temperature of 270 °C, and further heat-treated in a nitrogen - water - hydrogen gas stream under the condition of a maximum temperature of 800 °C. Then, it was fired in a nitrogen - water - hydrogen gas stream. In the comparative example, the firing was carried out under the conditions of a maximum temperature of 1050 - 1090 °C, a heating rate of 50 °C / min, a holding time of 60 minutes, and an oxygen partial pressure of 7.8×10 -11 ~3.3×10 -9 MPa. In the example, the firing was carried out under the conditions of a maximum temperature of 1230 - 1400 °C, a heating rate of 20 - 60 / second, a holding time shorter than that in the comparative example, and an oxygen partial pressure of 5.0×10 -13 ~1.7×10 -12 MPa. Subsequently, a heat treatment was carried out for 60 minutes in a nitrogen - water - hydrogen gas stream under the condition of a maximum temperature of 1050 °C. Thus, a laminate of a multilayer ceramic capacitor was obtained.

[0071] On the end face where the internal electrode layer of the laminate obtained by firing was drawn out, a conductive paste mainly composed of copper (Cu) was applied. Then, the applied conductive paste was baked at 900 °C to form an underlayer of the external electrode. Further, on the surface layer of the underlayer, Ni plating and Sn plating were performed in this order by wet plating. In this way, a multilayer ceramic capacitor was manufactured.

[0072] The manufactured multilayer ceramic capacitor had a length L dimension of 1.0 mm, a width direction W dimension of 0.5 mm, and a thickness direction T dimension of 0.5 mm. Also, the thickness of the dielectric layer in the inner layer part was 0.48 μm, the thickness of the internal electrode layer was 0.38 μm, and the number of layers of the dielectric layer was 50 layers.

[0073] (2) Evaluation Regarding the manufactured multilayer ceramic capacitor, evaluations of various characteristics were carried out as follows.

[0074] <G <SEM Observation> Using a scanning electron microscope (SEM), the WT surface of the multilayer ceramic capacitor was observed to examine the thickness of the dielectric layer and the diameter of the dielectric particles. Specifically, the multilayer ceramic capacitor was polished to the center in the length (L) direction to expose the cross-section (WT surface). Next, on a total of five lines including the center line in the width direction W and two lines equally spaced on both sides from this center line in the width direction W in the exposed cross-section, the thickness of the dielectric layer of the inner layer portion located near the center in the thickness direction was measured, and the average value was taken as the thickness of the dielectric layer.

[0075] Also, under the conditions of a magnification of 5000 times, an acceleration voltage of 15 kV, and a field of view of 30 μm × 30 μm, an SEM image of the dielectric particles in the dielectric layer in the exposed cross-section was taken. Then, using image processing software, the edges of all the dielectric particles were recognized to calculate the cross-sectional area of the particles, and the equivalent circle diameter was calculated from this area as the diameter of the particles. Excluding the dielectric particles that were imaged with chips missing, the diameters of all the dielectric particles included within the imaged range were measured, and the average value was obtained.

[0076] <TEM Observation> Using a transmission electron microscope (TEM), the WT surface of the multilayer ceramic capacitor was observed to examine the presence and ratio of particles with voids. Specifically, the multilayer ceramic capacitor was polished to the center in the length (L) direction to expose the WT surface, and further processed to collect a thin-film sample including the WT surface. Then, the thin-film sample was observed using TEM to obtain a high-angle annular dark-field (HAADF) image. During the observation, the cross-section (WT surface) of the multilayer ceramic capacitor was divided into a side portion, an outer layer portion, and an inner layer portion, and the inner layer portion was further divided into an inner layer intermediate region and an inner layer side region. Then, observations were made in a field of view of 1000 nm × 1000 nm at the center of each of the inner layer intermediate region and the inner layer side region. The observations were made for 100 or more dielectric particles. When 100 or more dielectric particles were not included in one field of view, observations were made by connecting multiple fields of view.

[0077] The number of dielectric particles (CN, WN) and the number of voided particles (Cn, Wn) in the dielectric particles were counted for each of the inner layer middle region and the inner layer side region, and the ratio of the number of voided particles (Cn / CN, Wn / WN) was calculated. In addition, the pore diameters of multiple voided particles were measured and their average values ​​were calculated.

[0078] <Dielectric constant> The capacitance of the dielectric layer was measured using an automatic bridge type measuring instrument. The measurement was carried out on 100 samples under the conditions of a temperature of 25°C, an effective voltage of 0.5 Vrms, and a frequency of 1 kHz. From the obtained capacitance, the relative dielectric constant (ε r ) was calculated and the average value was calculated. Based on the obtained relative dielectric constant value, the samples were ranked according to the following criteria.

[0079] A: Dielectric constant is between 3000 and 4800 B: Relative dielectric constant is 2500 or more but less than 3000, or 4800 or more but less than 5000 C: Dielectric constant less than 2500 or more than 5000

[0080] <Temperature coefficient of capacitance> The capacitance of five samples was measured within a temperature range of -55°C to 105°C under conditions of an effective voltage of 1Vrms and a frequency of 1kHz, and the temperature coefficient (rate of change) of capacitance was calculated based on the value at 25°C.The samples were then ranked according to the following criteria based on the obtained temperature coefficient values.

[0081] A: The absolute value of the rate of change at 85°C is 10% or less B: The absolute value of the rate of change at 85°C is more than 10% and 15% or less C: The absolute value of the rate of change at 85°C is more than 15%

[0082] <Reliability> Twenty samples were subjected to a high temperature load test (HALT) at a temperature of 150°C and an applied voltage of 5V. The time to failure was calculated as the time until the insulation resistance reached 10,000 Ω, and the mean time to failure (MTTF) was calculated from the failure time using Weibull analysis. Based on the MTTF values ​​obtained, the samples were ranked according to the following criteria.

[0083] A: MTTF is 80 hours or more B: MTTF is between 60 and 80 hours C: MTTF is less than 60 hours

[0084] (3) Evaluation results The cross-sectional TEM-HAADF image obtained for the sample of Example 9 is shown in Figure 4. Voids are present in the areas indicated by arrows (black dots) in the figure. It was confirmed that voids exist inside some of the dielectric particles.

[0085] The evaluation results for the multilayer ceramic capacitors obtained in Comparative Examples 1 to 3 and Examples 1 to 20 are summarized in Table 1. As shown in Table 1, the samples of Examples 1 to 20 in which the dielectric layers of the inner layers contained void-containing particles had a relative dielectric constant (ε r ) was high, the capacitance-temperature characteristic was flattened, and reliability (high-temperature accelerated life) was improved. Furthermore, the greater the proportion of the number of voided particles, the more remarkable the effect obtained. In particular, the samples of Examples 8 to 12 and 17 to 20, in which the proportion of the number of voided particles in the inner layer intermediate region was 15% or more, the proportion of the number of voided particles in the inner layer side region was 25% or more, the average pore size of the voided particles was 10 nm or more and 30 nm or less, and the average particle size of the voided particles was 130 nm or more and 300 nm or less, were excellent in all of the relative dielectric constant, capacitance-temperature characteristic, and reliability. In contrast, the samples of Comparative Examples 1 to 3, which did not have voided particles, were inferior in any of the relative dielectric constant, capacitance-temperature characteristic, and reliability.

[0086] [Table 1]

Claims

1. a laminate having first and second main surfaces opposing each other in a thickness direction, first and second side surfaces opposing each other in a width direction, and first and second end surfaces opposing each other in a length direction, the laminate 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, the dielectric layer includes dielectric particles; The laminate is a laminar first side portion extending along the first side surface and not including an internal electrode layer; a laminar second side portion extending along the second side surface and not including an internal electrode layer; a first outer layer portion sandwiched between the first side portion and the second side portion and sandwiched between the first main surface and an internal electrode layer closest to the first main surface; a second outer layer portion sandwiched between the first side portion and the second side portion and sandwiched between the second main surface and an internal electrode layer closest to the second main surface; and the inner layer portion is sandwiched between the first side portion and the second side portion and is sandwiched between the first outer layer portion and the second outer layer portion; In a cross section of the laminate taken along the center in the longitudinal direction, the dielectric layer at the center in the thickness direction of the inner layer portion contains particles having voids as dielectric particles, When the width of the laminate is W, the inner layer portion is a first inner layer side region having a distance from an interface between the inner layer portion and the first side portion of W / 10 or less or 40 μm or less; a second inner layer side region whose distance from the interface between the inner layer portion and the second side portion is W / 10 or less or 40 μm or less; and an inner layer intermediate region sandwiched between the first inner layer side portion and the second inner layer side portion; In the cross section, the dielectric layer at the center in the thickness direction of the inner layer intermediate region contains particles having voids as dielectric particles, In the cross section, the ratio of the number of particles having voids (Cn / CN) to the number of dielectric particles at the center in the thickness direction of the inner layer intermediate region is 15% or more and 42% or less, In the cross section, the dielectric layer at the center in the thickness direction of at least one of the first inner layer side region and the second inner layer side region contains particles having voids as dielectric particles, a ratio (Wn / WN) of the number of particles having voids among the dielectric particles at the thickness center of at least one of the first inner layer side region and the second inner layer side region in the cross section is greater than a ratio (Cn / CN) of the number of particles having voids among the dielectric particles at the thickness center of the inner layer middle region.

2. 2. The multilayer ceramic capacitor according to claim 1, wherein in the cross section, a ratio of the number of particles having voids (Wn / WN) among the dielectric particles at the center in the thickness direction of at least one of the first inner layer side region and the second inner layer side region is 25% or more.

3. 3. The multilayer ceramic capacitor according to claim 1, wherein the average pore size of the pores is 10 nm or more and 30 nm or less.

4. 3. The multilayer ceramic capacitor according to claim 1, wherein the average particle size of the dielectric particles is 130 nm or more and 300 nm or less.

5. 3. The multilayer ceramic capacitor according to claim 1, wherein the thickness of the dielectric layer is 0.40 μm or more and 0.50 μm or less.

6. 3. The multilayer ceramic capacitor according to claim 1, wherein the thickness of the dielectric layer is 0.40 μm or more and 0.45 μm or less.

7. 3. The multilayer ceramic capacitor according to claim 1, wherein the thickness of the internal electrode layers is 0.30 [mu]m or more and 0.40 [mu]m or less.

8. 3. The multilayer ceramic capacitor according to claim 1, wherein the thickness of the internal electrode layers is 0.30 μm or more and 0.35 μm or less.

9. a laminate having first and second main surfaces opposing each other in a thickness direction, first and second side surfaces opposing each other in a width direction, and first and second end surfaces opposing each other in a length direction, the laminate 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, the dielectric layer includes dielectric particles; The laminate is a laminar first side portion extending along the first side surface and not including an internal electrode layer; a laminar second side portion extending along the second side surface and not including an internal electrode layer; a first outer layer portion sandwiched between the first side portion and the second side portion and sandwiched between the first main surface and an internal electrode layer closest to the first main surface; a second outer layer portion sandwiched between the first side portion and the second side portion and sandwiched between the second main surface and an internal electrode layer closest to the second main surface; and the inner layer portion is sandwiched between the first side portion and the second side portion and is sandwiched between the first outer layer portion and the second outer layer portion; In a cross section of the laminate taken along the center in the longitudinal direction, the dielectric layer at the center in the thickness direction of the inner layer portion contains particles having voids as dielectric particles, When the width of the laminate is W, the inner layer portion is a first inner layer side region having a distance from an interface between the inner layer portion and the first side portion of W / 10 or less or 40 μm or less; a second inner layer side region whose distance from the interface between the inner layer portion and the second side portion is W / 10 or less or 40 μm or less; and an inner layer intermediate region sandwiched between the first inner layer side portion and the second inner layer side portion; In the cross section, the dielectric layer at the center in the thickness direction of the inner layer intermediate region contains particles having voids as dielectric particles, In the cross section, the ratio of the number of particles having voids (Cn / CN) to the number of dielectric particles at the center in the thickness direction of the inner layer intermediate region is 15% or more, In the cross section, the dielectric layer at the center in the thickness direction of at least one of the first inner layer side region and the second inner layer side region contains particles having voids as dielectric particles, a ratio (Wn / WN) of the number of particles having voids among the dielectric particles at the thickness center of at least one of the first inner layer side region and the second inner layer side region in the cross section is greater than a ratio (Cn / CN) of the number of particles having voids among the dielectric particles at the thickness center of the inner layer middle region.

10. 10. The multilayer ceramic capacitor according to claim 9, wherein in the cross section, a ratio of the number of particles having voids (Wn / WN) among the dielectric particles at the center in the thickness direction of at least one of the first inner layer side region and the second inner layer side region is 25% or more.

11. 11. The multilayer ceramic capacitor according to claim 9, wherein the thickness of the dielectric layer is 0.40 μm or more and 0.50 μm or less.

12. 11. The multilayer ceramic capacitor according to claim 9, wherein the thickness of the internal electrode layers is 0.30 μm or more and 0.40 μm or less.

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