Multilayer ceramic capacitor

Abstract

In a multilayer ceramic capacitor, a ceramic dielectric in an inner layer portion includes main crystal particles composed of a perovskite-type compound containing barium (Ba), calcium (Ca), and titanium (Ti), and a molar ratio of an amount of calcium (Ca) to a total amount of barium (Ba) and calcium (Ca) contained in the main crystal particles of the inner layer portion (Ca / (Ba+Ca) inner layer ratio) is 0.02 or more and 0.04 or less. A ceramic dielectric in outer layer portions covering a principal surface includes main crystal particles composed of a perovskite-type compound containing barium (Ba), calcium (Ca), and titanium (Ti), and a molar ratio of an amount of calcium (Ca) to a total amount of barium (Ba) and calcium (Ca) contained in the main crystal particles of a first outer layer portion and a second outer layer portion (Ca / (Ba+Ca) outer layer ratio) is 0.05 or more and 0.20 or less.

Description

Multilayer ceramic capacitor

[0001] This invention relates to a multilayer ceramic capacitor.

[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 growing rapidly. Multilayer ceramic capacitors have a thin, high-dielectric-constant dielectric layer. As a result, they have a large capacitance despite their small size. Multilayer ceramic capacitors using various materials are known, but barium titanate (BaTiO) is used for the dielectric layer. ３ A type of electrode that uses ceramic dielectrics such as ) and a base metal such as nickel (Ni) for the internal electrode layer is widely used because it is inexpensive and exhibits high performance.

[0003] A multilayer ceramic capacitor comprises an inner layer in which dielectric layers and internal electrode layers made of ceramic dielectric material are alternately stacked, and an outer layer that covers the top and bottom of the inner layer. The inner layer functions as a capacitive element, while the outer layer is a region that does not include the internal electrode layer and is provided above and below the inner layer. It can be said that the outer layer serves to protect the inner layer, which functions as a capacitive element, from the external environment.

[0004] Barium titanate (BaTiO) is used as a ceramic dielectric material for multilayer ceramic capacitors. ３ ) compounds are widely used. ３ Because the compound has a high dielectric constant, using it as a dielectric layer makes it possible to obtain multilayer ceramic capacitors with high capacitance.

[0005] Furthermore, as a ceramic dielectric, barium calcium titanate (BaCaTiO) ３ It has also been proposed to use ) system compounds. BaCaTiO ３ , BaTiO ３ This material is obtained by substituting a portion of the Ba with Ca in a solid solution, and it exhibits excellent reduction resistance. Therefore, it is advantageous as a ceramic dielectric material for multilayer ceramic capacitors equipped with an internal electrode layer containing a base metal such as Ni.

[0006] BaCaTiO ３Regarding the compound system, Patent Document 1 discloses a laminated ceramic capacitor in which the dielectric layer has the following composition formula: {Ba １－ｘ Ca ｘ O} ｍ TiO ２ +αRe ２ O ３ +βMgO + γMnO (where Re ２ O ３ is Y ２ O ３ etc.), and the internal electrode is made of nickel or a nickel alloy (Claim 1 of Patent Document 1). Also, it is said that a highly reliable laminated ceramic capacitor with excellent insulation breakdown voltage can be obtained, which satisfies the temperature characteristics of capacitance as B characteristics and X7R characteristics without becoming semiconductorized even when fired in a reducing atmosphere, and has high insulation resistance at room temperature and high temperature (Patent Document 1,

[0015] ).

[0007] Japanese Patent No. 3709914

[0008] Thus, although it has been conventionally proposed to produce a laminated ceramic capacitor with excellent insulation and reliability using a barium calcium titanate (BaCaTiO ３ ) - based compound, there has been room for improvement in the conventional technology.

[0009] That is, when the inventors investigated, in the dielectric layer containing a BaCaTiO ３ - based compound, it was found that although increasing the amount of Ca improves the reliability in the high - temperature load test, there is a risk of an increase in dielectric loss (tanδ). Also, the mechanical strength of the ceramic is affected by the amount of Ca, and the lower the amount of Ca, the weaker the strength. Therefore, even if one tries to control the dielectric loss and mechanical strength by the amount of Ca, it is impossible to improve the mechanical strength while reducing the dielectric loss, and it has been difficult to achieve both excellent electrical characteristics and high mechanical strength.

[0010] In view of such problems, the inventors have conducted further investigations. As a result, in a laminated ceramic capacitor, BaCaTiO having a perovskite - type crystal structure ３We have found that by constructing the inner and outer layers with a ceramic dielectric containing a compound as the main component, and by independently controlling the main component composition of the inner and outer layers within a predetermined range, it is possible to achieve both excellent electrical properties and high mechanical strength.

[0011] This invention was completed based on such findings, and aims to provide a multilayer ceramic capacitor that can achieve both excellent electrical characteristics and high mechanical strength.

[0012] The present invention encompasses the following embodiments. In this specification, the expression "~" includes the numerical values ​​at both ends. That is, "X ~ Y" is synonymous with "X or more and Y or less".

[0013] According to one aspect of the present invention, a multilayer ceramic capacitor comprising: an inner layer having a first inner electrode layer and a second inner electrode layer alternately stacked via a dielectric layer made of a ceramic dielectric, the inner layer having a first main surface which is a surface in the stacking direction, a second main surface which is the surface opposite to the first main surface, a first side surface which is a surface in the width direction perpendicular to the first and second main surfaces, a second side surface which is the surface opposite to the first side surface, a first end surface which is a surface in the length direction perpendicular to the first main surface, the second main surface, the first side surface, and the second side surface, and a second end surface which is the surface opposite to the first end surface; a first outer layer made of a ceramic dielectric that covers the first main surface from the stacking direction; a second outer layer made of a ceramic dielectric that covers the second main surface from the stacking direction; and a plurality of external electrodes connected to each of the first and second inner electrode layers, respectively, A multilayer ceramic capacitor is provided, wherein the ceramic dielectric in the inner layer includes main crystal particles composed of a perovskite-type compound containing barium (Ba), calcium (Ca), and titanium (Ti), and the molar ratio of the amount of calcium (Ca) to the total amount of barium (Ba) and calcium (Ca) contained in the main crystal particles of the inner layer (Ca / (Ba+Ca) inner layer ratio) is 0.02 or more and 0.04 or less; the ceramic dielectric in the first outer layer and the second outer layer each includes main crystal particles composed of a perovskite-type compound containing barium (Ba), calcium (Ca), and titanium (Ti), and the molar ratio of the amount of calcium (Ca) to the total amount of barium (Ba) and calcium (Ca) contained in the main crystal particles of the first outer layer and the second outer layer (Ca / (Ba+Ca) outer layer ratio) is 0.05 or more and 0.20 or less; and the thickness of the first outer layer and the second outer layer in the stacking direction is 60 μm or less.

[0014] According to the present invention, a multilayer ceramic capacitor is provided that can achieve both excellent electrical characteristics and high mechanical strength.

[0015] This is an example of a perspective view showing the external shape of a multilayer ceramic capacitor. This is a schematic cross-sectional view showing the internal structure of a multilayer ceramic capacitor. This is a schematic cross-sectional view showing the internal structure of a multilayer ceramic capacitor.

[0016] Specific embodiments of the present invention (hereinafter referred to as "this embodiment") will now be described. However, the present invention is not limited to the following embodiments, and various modifications are possible without altering the essence of the invention.

[0017] <<1. Multilayer Ceramic Capacitor>> The multilayer ceramic capacitor of this embodiment comprises an inner layer, a first outer layer, a second outer layer, and a plurality of external electrodes. The inner layer is formed by alternately stacking a first internal electrode layer and a second internal electrode layer via a dielectric layer made of ceramic dielectric, and has a first main surface which is the surface in the stacking direction, a second main surface which is the surface opposite to the first main surface, a first side surface which is the surface in the width direction perpendicular to the first and second main surfaces, a second side surface which is the surface opposite to the first side surface, a first end surface which is the surface in the length direction perpendicular to the first main surface, the second main surface, the first side surface, and the second side surface, and a second end surface which is the surface opposite to the first end surface. The first outer layer is made of ceramic dielectric and covers the first main surface from the stacking direction. The second outer layer is made of ceramic dielectric and covers the second main surface from the stacking direction. The plurality of external electrodes are connected to the first internal electrode layer and the second internal electrode layer, respectively. The ceramic dielectric in the inner layer includes main crystal particles composed of a perovskite-type compound containing barium (Ba), calcium (Ca), and titanium (Ti). The molar ratio of calcium (Ca) to the total amount of barium (Ba) and calcium (Ca) contained in the main crystal particles of the inner layer (Ca / (Ba+Ca) inner layer ratio) is 0.02 or more and 0.04 or less. The ceramic dielectric in the first outer layer and the second outer layer each includes main crystal particles composed of a perovskite-type compound containing barium (Ba), calcium (Ca), and titanium (Ti). The molar ratio of calcium (Ca) to the total amount of barium (Ba) and calcium (Ca) contained in the main crystal particles of the first outer layer and the second outer layer (Ca / (Ba+Ca) outer layer ratio) is 0.05 or more and 0.20 or less. The thickness of the first outer layer and the second outer layer in the stacking direction is 60 μm or less.

[0018] One embodiment of a multilayer ceramic capacitor will be illustrated using Figures 1 to 3. Figure 1 is a perspective view showing the external shape of a multilayer ceramic capacitor. Figure 2 is a cross-section of the multilayer ceramic capacitor shown in Figure 1, cut along line II-II, and Figure 3 is a cross-section cut along line III-III.

[0019] The multilayer ceramic capacitor (100) comprises a base body (6) and a pair of external electrodes (8a, 8b) provided on both end faces (14a, 14b) of the base body (6). The multilayer ceramic capacitor (100) and the base body (6) have a substantially rectangular parallelepiped shape. A substantially rectangular parallelepiped includes not only a rectangular parallelepiped but also a rectangular parallelepiped with rounded corners and / or edges.

[0020] The multilayer ceramic capacitor (100) and the elemental body (6) have a first main surface (10a) and a second main surface (10b) facing the thickness direction T, a first side surface (12a) and a second side surface (12b) facing the width direction W, and a first end surface (14a) and a second end surface (14b) facing the length direction L. Here, the thickness direction T is the direction in which the dielectric layer (2) and the internal electrode layer (4) contained in the elemental body (6) are stacked. The length direction L is perpendicular to the thickness direction T and is the direction in which the end surfaces (14a, 14b) face each other. The width direction W is perpendicular to the thickness direction T and the length direction L. A surface containing the thickness direction T and the width direction W is defined as the WT surface, a surface containing the width direction W and the length direction L is defined as the LW surface, and a surface containing the length direction L and the thickness direction T is defined as the LT surface.

[0021] The base body (6) is composed of an inner layer (16), a first outer layer (18a), and a second outer layer (18b). Of these, the inner layer (16) is a region that functions as a capacitive element and has a structure in which internal electrode layers (4) are alternately stacked via a dielectric layer (2). The dielectric layer (2) is made of a ceramic dielectric. The internal electrode layer (4) is composed of 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 drawn out from the first end face (14a) and the second end face (14b), respectively.

[0022] The first outer layer (18a) is a region that covers the first main surface of the inner layer (16) from the stacking direction (thickness direction T). The second outer layer (18b) is a region that covers the second main surface of the inner layer (16) from the stacking direction. The first outer layer (18a) and the second outer layer (18b) are made of ceramic dielectric material.

[0023] The external electrodes (8a, 8b) consist of a first external electrode (8a) provided on the first end face (14a) of the base body (6) and a second external electrode (8b) provided on the second end face (14b). The first external electrode (8a) is electrically connected to the first internal electrode layer (4a). The second external electrode (8b) is electrically connected to the second internal electrode layer (4b). However, the first external electrode (8a) and the second external electrode (8b) are not connected and are electrically separated.

[0024] In the above-described embodiment, external electrodes (8a, 8b) are provided on the end faces (14a, 14b) of the base body (6), and thereafter, the external electrodes (8a, 8b) are connected to the internal electrode layer (4a, 4b). However, the multilayer ceramic capacitor of this embodiment is not limited to having the above-described embodiment. It may also be an embodiment in which the external electrodes (8a, 8b) are provided on the side faces (12a, 12b). Alternatively, it may be an embodiment in which one of the external electrodes (8a, 8b) is provided on the end face (14a, 14b) and the other external electrode (8a, 8b) is provided on the side face (12a, 12b). In this case, one of the internal electrode layers (first internal electrode layer, second internal electrode layer) is connected to one of the external electrodes (8a, 8b) provided on the end faces (14a, 14b), and the other of the internal electrode layers (first internal electrode layer, second internal electrode layer) is connected to the other of the external electrodes (8a, 8b) provided on the side faces (14a, 14b).

[0025] The size of the multilayer ceramic capacitor (100) and the base body (6) is not particularly limited. However, it is preferable that the width dimension W is 0.7 mm or more and 5.1 mm or less, and the length dimension L is 1.5 mm or more and 5.8 mm or less. The multilayer ceramic capacitor of this embodiment is characterized by high mechanical strength, and in the case of a multilayer ceramic capacitor with relatively large dimensions, the effect of improved mechanical strength can be utilized even more.

[0026] <Inner Dielectric Layer> The inner layer is a region in which internal electrode layers (first internal electrode layer, second internal electrode layer) are alternately stacked via dielectric layers made of ceramic dielectric. The dielectric layer is composed of ceramic dielectric made by firing an inner layer green sheet containing dielectric raw materials. The ceramic dielectric consists of a sintered polycrystalline body (ceramic) in which a large number of dielectric particles are bonded via grain boundaries and triple points. In other words, it contains dielectric particles (dielectric grains) as main crystal particles. Here, the main crystal particles are the crystal particles that are the main components of the ceramic dielectric. Furthermore, the main component of the ceramic dielectric is the component with the largest content in the ceramic dielectric, that is, the component with a content of 50% by mass or more.

[0027] In the multilayer ceramic capacitor of this embodiment, the ceramic dielectric in the inner layer (hereinafter referred to as the "inner layer dielectric") includes main crystal particles composed of a perovskite-type compound containing barium (Ba), calcium (Ca), and titanium (Ti). In other words, the main crystal particles of the inner layer dielectric are BaCaTiO ３ It is composed of system compounds.

[0028] BaCaTiO ３ The compound is a perovskite-type compound (ABO) containing Ba and Ca at the A site and Ti at the B site. ３ ) is. BaTiO ３ It can also be described as a compound in which part of the Ba is substituted with Ca in a solid solution. BaCaTiO ３ The compound has excellent reduction resistance and is less likely to become a semiconductor. Therefore, the BaCaTiO ３ By forming an inner dielectric that acts as a capacitive element using a compound, a multilayer ceramic capacitor can be obtained that has high insulation resistance at room temperature and high temperatures, and excellent reliability and dielectric strength. In other words, when inexpensive base metals such as Ni or Ni alloys are used as the material for the internal electrode layer, it is necessary to perform firing in a reducing atmosphere during the manufacturing of the multilayer ceramic capacitor in order to prevent oxidation of the internal electrode layer. On the other hand, BaTiO is widely used as a dielectric material for multilayer ceramic capacitors. ３ The compound is easily semiconducted under a reducing atmosphere. Semiconducted BaTiO ３The compound has low insulation resistance, which can cause problems in terms of reliability and dielectric strength. BaCaTiO has excellent reduction resistance. ３ These problems can be avoided by using compound systems.

[0029] Furthermore, in the multilayer ceramic capacitor of this embodiment, the molar ratio of calcium (Ca) to the total amount of barium (Ba) and calcium (Ca) contained in the main crystal particles of the inner layer dielectric (Ca / (Ba+Ca) inner layer ratio) is 0.02 or more and 0.04 or less. In other words, the main crystal particles are given by the formula: (Ba １－ｘ Ca ｘ ) ｍ TiO ３－Δ It has a basic composition represented by (where 0.02 ≤ x ≤ 0.04, and m and Δ are any real numbers that maintain the perovskite crystal structure).

[0030] When the Ca / (Ba+Ca) inner layer ratio is between 0.02 and 0.04 (0.02 ≤ x ≤ 0.04), the effect of improving reduction resistance can be sufficiently obtained while maintaining the electrical properties of the inner layer dielectric. Therefore, the electrical properties and reliability of the multilayer ceramic capacitor can be improved. On the other hand, if the Ca / (Ba+Ca) inner layer ratio is less than 0.02, the improvement in reduction resistance by Ca will be insufficient, and the reliability of the inner layer dielectric may deteriorate. Also, if the Ca / (Ba+Ca) inner layer ratio is greater than 0.04, the dielectric loss of the inner layer dielectric may increase. From the viewpoint of further enhancing the effect of improving reliability and suppressing dielectric loss, a Ca / (Ba+Ca) inner layer ratio of 0.03 or more and 0.04 (0.03 ≤ x ≤ 0.04) is preferable.

[0031] The molar ratio of the total amount of barium (Ba) and calcium (Ca) to the amount of titanium (Ti) contained in the main crystal grains of the inner dielectric ((Ba + Ca) / Ti inner layer ratio), that is, the value of m in the basic composition described above, is not limited as long as the main crystal grains maintain a perovskite-type crystal structure. However, a value of 0.990 or more and 1.035 or less (0.990 ≤ m ≤ 1.035) is preferred. When the (Ba + Ca) / Ti inner layer ratio is within this range, the raw material for the main crystal grains is BaCaTiO ３This makes it possible to suppress variations in the particle size of the system powder. As a result, it becomes possible to further improve the electrical characteristics and reliability of multilayer ceramic capacitors. From the viewpoint of promoting densification of the inner dielectric layer, a (Ba + Ca) / Ti inner layer ratio of 1.000 to 1.015 (1.000 ≤ m ≤ 1.015) is more preferable.

[0032] Furthermore, the main crystal grain composition of the inner dielectric layer (Ca / (Ba+Ca) inner layer ratio, (Ba+Ca) / Ti inner layer ratio) is determined as the average value of the compositions of multiple particles. In other words, the main crystal grain composition may vary from particle to particle within the inner dielectric layer. Even in such cases, the overall composition of the main components of the ceramic dielectric constituting the inner layer can be evaluated by using the average composition.

[0033] The inner dielectric layer may contain minor components in addition to the main crystal grains. Examples of minor components, though not limited to them, include 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 minor components may be present individually or in combination. For example, yttrium oxide (Y) ２ O ３ ), gadolinium oxide (Gd ２ O ３ ), terbium oxide (Tb ２ O ３ ), dysprosium oxide (Dy ２ O ３ ), holmium oxide (Ho ２ O ３ ), erbium oxide (Er ２ O ３ ), and ytterbium oxide (Yb ２ O ３ It comprises at least one rare earth metal oxide selected from the group consisting of ), and further includes magnesium oxide (MgO), manganese oxide (MnO), and vanadium oxide (V ２ O ５ ) may be included. The mode of existence of the minor components is not limited. They may be contained in dielectric particles, grain boundaries, or triple points.

[0034] The dielectric particles may include core-shell particles. Core-shell particles are particles that have a structure (core-shell structure) in which at least a portion of the minor components are solid-dissolved at a high concentration in the surface layer (shell portion) of the particle, and the minor components are solid-dissolved at a low concentration or not solid-dissolved in the central portion (core portion) of the particle. Alternatively, the dielectric particles may include uniformly solid-dissolved particles.

[0035] The thickness of the dielectric layer occupying the inner layer is preferably 0.7 μm or more and less than 2.0 μm. By making the dielectric layer thickness greater than or equal to a predetermined value, it is possible to suppress the occurrence of dielectric breakdown and deterioration of lifespan when using multilayer ceramic capacitors. Conversely, by making the dielectric layer thickness less than or equal to a predetermined value, the dielectric layer is made thinner, making it possible to further increase the capacitance of the multilayer ceramic capacitor. The number of dielectric layers is not particularly limited. Preferably, the number of dielectric layers constituting the outer layer and the inner layer is between 100 and 2000.

[0036] <Inner Layer - Internal Electrode Layer> The internal electrode layer (first internal electrode layer, second internal electrode layer) is composed of a counter electrode portion and an extraction electrode portion, and together with the dielectric layer, constitutes the inner layer. The counter electrode portion sandwiches the dielectric layer and functions as a capacitive element. The extraction electrode portion extends to the end face and / or side surface of the inner layer, where it electrically connects the counter electrode portion and the external electrode (external end face electrode, external side electrode). The internal electrode layer contains 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.

[0037] Among these, it is preferable that at least one of the first internal electrode layer and the second internal electrode layer, which are internal electrode layers, contains Ni or a Ni alloy as the main component. By using Ni or a Ni alloy, which are base metals, as the material for the internal electrode layer, it is possible to reduce the cost of multilayer ceramic capacitors. In this embodiment, the multilayer ceramic capacitor has BaCaTiO, which has excellent reduction resistance, as the inner layer dielectric. ３A compound is used. Therefore, even when Ni or a Ni alloy, which requires firing in a reducing atmosphere, is used as the material for the internal electrode layer, it is possible to obtain a highly reliable multilayer ceramic capacitor.

[0038] The internal electrode layer may contain components other than conductive metals. Examples of other components include ceramic components that act as co-materials. The thickness of the internal electrode layer is preferably 0.30 μm to 0.40 μm. By making the internal electrode thickness above a predetermined value, problems such as electrode breaks can be prevented. Conversely, by making it below a predetermined value, a decrease in the proportion of the dielectric layer in the capacitor can be prevented, contributing to increased capacitance. Furthermore, the number of internal electrode layers is preferably between 10 and 1000.

[0039] <Outer Layer> The outer layers (first outer layer, second outer layer) are provided above and below the inner layer, respectively. The outer layers are made of ceramic dielectric material and do not contain an internal electrode layer. The outer layers act as protective layers that protect the above and below the inner layer, which functions as a capacitive element. The outer layers are manufactured by firing an outer layer green sheet containing dielectric material.

[0040] In the multilayer ceramic capacitor of this embodiment, the ceramic dielectric in the outer layers (first outer layer, second outer layer) (hereinafter referred to as "outer layer dielectric") includes main crystal particles composed of a perovskite-type compound containing barium (Ba), calcium (Ca), and titanium (Ti). In other words, the main crystal particles of the outer layer dielectric are BaCaTiO ３ It is composed of system compounds.

[0041] Furthermore, in the multilayer ceramic capacitor of this embodiment, the molar ratio of calcium (Ca) to the total amount of barium (Ba) and calcium (Ca) contained in the main crystal particles of the outer dielectric layer (Ca / (Ba+Ca) outer layer ratio) is 0.05 or more and 0.20 or less. In other words, the main crystal particles are given by the formula: (Ba １－ｙ Ca ｙ ) ｎ TiO ３－Δ’ It has a basic composition represented by (where 0.05 ≤ y ≤ 0.20, and m and Δ' are any real numbers that maintain the perovskite crystal structure).

[0042] BaCaTiO of a predetermined composition ３ By forming an outer dielectric layer using a compound, a multilayer ceramic capacitor with high mechanical strength can be obtained. That is, BaTiO ３ By substituting some of the Ba with Ca in a solid solution, the crystal lattice is strained, and atomic movement when stress is applied is hindered. As a result, the outer layer becomes less prone to deformation, and the flexural strength, which is a type of mechanical strength, is improved.

[0043] When the Ca / (Ba+Ca) outer layer ratio is between 0.05 and 0.20 (0.05 ≤ y ≤ 0.20), it is possible to improve the mechanical strength and reliability of multilayer ceramic capacitors. Conversely, if the Ca / (Ba+Ca) outer layer ratio is less than 0.05, the effect of Ca in preventing deformation of the outer layer becomes insufficient. As a result, the mechanical strength (flexural strength) of the multilayer ceramic capacitor decreases. Furthermore, if the Ca / (Ba+Ca) outer layer ratio exceeds 0.20, there is a risk of structural defects such as delamination occurring at the interface between the outer and inner dielectric layers. This is because the amount of Ca in the outer dielectric layer is excessively high, causing excessive sintering of the outer dielectric layer during the manufacturing of the multilayer ceramic capacitor, resulting in a large difference in the shrinkage behavior of the outer and inner dielectric layers during firing. If structural defects exist at the interface, the mechanical strength of the multilayer ceramic capacitor may decrease. In addition, moisture and other substances may penetrate from the outside through the defects, leading to a decrease in reliability. From the viewpoint of further enhancing the effects of improving mechanical strength and suppressing structural defects, a Ca / (Ba+Ca) outer layer ratio of 0.05 or more and 0.14 or less (0.05 ≤ y ≤ 0.14) is preferable.

[0044] Furthermore, the Ca / (Ba+Ca) inner layer ratio (x) is between 0.02 and 0.04, and the Ca / (Ba+Ca) outer layer ratio (y) is between 0.05 and 0.20. Therefore, the difference between the Ca / (Ba+Ca) inner layer ratio and the Ca / (Ba+Ca) outer layer ratio (|y-x|) is between 0.01 and 0.18. However, it is preferable that this difference (|y-x|) is between 0.01 and 0.10 ((0.01 ≤ |y-x| ≤ 0.10)). By suppressing the difference in composition (Ca content) between the outer and inner dielectric layers, the difference in shrinkage behavior during firing is reduced, and as a result, it becomes possible to more effectively suppress the occurrence of structural defects.

[0045] The molar ratio of the total amount of barium (Ba) and calcium (Ca) to the amount of titanium (Ti) contained in the main crystal grains of the outer dielectric layer ((Ba + Ca) / Ti outer layer ratio), that is, the value of n in the basic composition described above, is not limited as long as the main crystal grains maintain a perovskite-type crystal structure. However, a value of 0.990 or more and 1.035 or less (0.990 ≤ n ≤ 1.035) is preferred. When the (Ba + Ca) / Ti outer layer ratio is within this range, the raw material for the main crystal grains is BaCaTiO ３ This makes it possible to suppress variations in the particle size of the system powder. From the viewpoint of promoting densification of the outer dielectric layer, a (Ba + Ca) / Ti outer layer ratio of 1.000 to 1.015 (1.000 ≤ n ≤ 1.015) is more preferable.

[0046] Preferably, the (Ba+Ca) / Ti inner layer ratio is 0.990 or more and 1.035 or less, and the (Ba+Ca) / Ti outer layer ratio is 0.990 or more and 1.035 or less. More preferably, the (Ba+Ca) / Ti inner layer ratio is 1.000 or more and 1.015 or less, and the (Ba+Ca) / Ti outer layer ratio is 1.000 or more and 1.015 or less.

[0047] Furthermore, the main crystal grain composition of the outer dielectric layer (Ca / (Ba+Ca) outer layer ratio, (Ba+Ca) / Ti outer layer ratio) is determined as the average value of the compositions of multiple particles. In other words, the main crystal grain composition may vary from particle to particle within the outer dielectric layer. Even in such cases, the overall composition of the main components of the ceramic dielectric constituting the outer layer can be evaluated by using the average composition.

[0048] The outer dielectric layer may contain minor components in addition to the main crystal grains. Examples of minor components, though not limited to them, include 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. For example, yttrium oxide (Y) ２ O ３ ), gadolinium oxide (Gd ２ O ３ ), terbium oxide (Tb ２ O ３ ), dysprosium oxide (Dy ２ O ３ ), holmium oxide (Ho ２ O ３ ), erbium oxide (Er ２ O ３ ), and ytterbium oxide (Yb ２ O ３ It comprises at least one rare earth metal oxide selected from the group consisting of ), and further includes magnesium oxide (MgO), manganese oxide (MnO), and vanadium oxide (V ２ O ５ ) may be included.

[0049] In this embodiment, the thickness of each outer layer (first outer layer, second outer layer) in the stacking direction is 60 μm or less. Here, the thickness of the outer layer in the stacking direction refers to the dimension of each outer layer in the stacking direction. In a multilayer ceramic capacitor, the outer layer is a region that does not contribute to capacitance. If the thickness of the outer layer is excessively large, the capacitance per unit volume of the multilayer ceramic capacitor will decrease. By keeping the thickness of the outer layer moderately low, it is possible to suppress the occurrence of such problems. On the other hand, by making the thickness of the outer layer moderately large, it is possible to make even greater use of the effect of the outer layer in improving mechanical strength. From the viewpoint of making full use of the effect of improving mechanical strength, the thickness of each outer layer is preferably 20 μm or more and 60 μm or less.

[0050] <External Electrodes> The external electrodes (first external electrode, second external electrode) function as input / output terminals of the multilayer ceramic capacitor. The external electrodes are provided on one or both of the end face and side faces of the multilayer ceramic capacitor. Known configurations can be used for the external electrodes. For example, they may consist of a base electrode layer and a plating layer placed on top of it. Alternatively, the external electrodes may be composed only of a plating layer without a base electrode layer.

[0051] As described above, the multilayer ceramic capacitor of this embodiment has a perovskite crystal structure BaCaTiO ３ The inner and outer layers are composed of a ceramic dielectric primarily made of a compound, and the main component compositions of the inner and outer layers are independently controlled within a predetermined range. Such a multilayer ceramic capacitor suppresses structural defects at the interface between the outer and inner layers. Furthermore, it allows for improved electrical properties of the inner layer (dielectric loss, reliability under high-temperature load testing) and improved mechanical strength (flexural strength) of the outer layer. Therefore, it is possible to achieve both excellent electrical properties and high mechanical strength overall.

[0052] <<2. Method for Manufacturing Multilayer Ceramic Capacitors>> The manufacturing method of the multilayer ceramic capacitor of this embodiment is not limited as long as the above requirements are satisfied. However, a preferred manufacturing method includes the following steps: a step of making an inner layer green sheet from the main component powder for the inner layer (inner layer green sheet manufacturing step); a step of forming a patterned conductive layer on the surface of the inner layer green sheet using a conductive paste for internal electrodes (conductive layer formation step); a step of making an outer layer green sheet from the main component powder for the outer layer (outer layer green sheet manufacturing step); a step of stacking a plurality of inner layer green sheets on which conductive layers have been formed, stacking outer layer green sheets above and below them, and pressing the whole together to make a stacked block (stacking step); a step of cutting the obtained stacked block to make a stacked chip (cutting step); a step of subjecting the obtained stacked chip to a debinder treatment and a firing treatment to obtain a base body (firing step); and a step of forming external electrodes (external end face electrodes, external side electrodes) on the obtained base body to make a multilayer ceramic capacitor (external electrode formation step).

[0053] <Process for manufacturing the inner layer green sheet> In manufacturing the inner layer green sheet, first, the main component powder for the inner layer is prepared. The synthesis method for the main component powder for the inner layer is not limited. Examples include solid-phase methods in which solid-phase raw materials such as oxides and carbonates are reacted at high temperatures, or wet methods such as alkoxide methods and hydrothermal synthesis methods. For example, barium carbonate (BaCO3) ３ ), calcium carbonate (CaCO3) ３ ) and titanium dioxide (TiO ２ Using the above as raw materials, a mixture can be obtained by mixing the raw materials in a predetermined ratio, and the resulting mixture can be heated (calcined) to synthesize the main component powder. The raw material mixing can be carried out dry or wet using a known mixing device such as a ball mill. When wet mixing is performed, the mixture can be mixed in a dispersion medium such as water. The resulting mixture may be dried. It is preferable to heat (calcine) the mixture at a high temperature of 1000°C or higher. Furthermore, the synthesized main component powder may be pulverized to adjust the particle size.

[0054] The composition of the main component powder for the inner layer is such that the main crystal particles of the inner layer dielectric of the final multilayer ceramic capacitor are given by formula: (Ba １－ｘ Ca ｘ ) ｍ TiO ３－Δ The basic composition should be adjusted to have the formula shown (where 0.02 ≤ x ≤ 0.04, and m and Δ are any real numbers that maintain the perovskite crystal structure). The composition of the main component powder can be controlled by adjusting the raw material blending ratio.

[0055] A single type of powder may be used as the main component powder for the inner layer. Alternatively, a combination of multiple powders with different physical properties such as composition (Ca content x, molar ratio m) and particle size may be used. For example, a combination of a Ca-free powder with a Ca content x of 0 and a Ca-containing powder with a Ca content x greater than 0 may be used.

[0056] Next, a binder and solvent are added to the main component powder for the inner layer and mixed to form a slurry. The resulting slurry is then molded to produce a green sheet for the inner layer. As the binder, a known organic binder such as a polyvinyl butyral-based binder may be used. As the solvent, a known organic solvent such as toluene or ethanol may be used. Additives such as plasticizers may also be added as needed. Molding can be carried out by a known method such as the lip method.

[0057] During slurry formation, the main component powder for the inner layer may be mixed with the raw materials for the auxiliary components (RE, Mg, Mn, Fe, Cr, Co, Ni, Si, Al, V, etc.). Known ceramic raw materials such as oxides, carbonates, hydroxides, nitrates, organic acid salts, alkoxides and / or chelate compounds may be used as auxiliary component raw materials. In addition to the auxiliary component raw materials, a composition control agent for the main component powder may also be added. For example, barium carbonate (BaCO3) ３ The main component composition can be controlled by adding Ba raw materials such as ). The main component powder and secondary component raw materials can be mixed dry or wet using known mixing equipment such as a ball mill. When wet mixing is performed, the mixture can be mixed in a dispersion medium such as water. The resulting mixture may be dried.

[0058] <Conductive Layer Formation Process> In the conductive layer formation process, a patterned conductive layer is formed on the surface of the inner layer green sheet. The conductive layer becomes the internal electrode layer after firing. The conductive layer can be formed by methods such as printing, vapor deposition, or plating. For example, a conductive paste can be printed onto the surface of the inner layer green sheet to form a conductive paste layer as the conductive layer. In this case, a conductive material such as Ni or a Ni alloy can be used as the conductive metal contained in the conductive paste. Ceramic components that act as co-materials may also be added to the conductive paste. The printing method is not particularly limited. Examples include screen printing and gravure printing.

[0059] <Process for manufacturing the outer layer green sheet> In manufacturing the outer layer green sheet, first, the main component powder for the outer layer is prepared. The synthesis of the main component powder for the outer layer can be carried out in the same manner as the main component powder for the inner layer. The composition of the main component powder for the outer layer is such that the main crystal grains of the outer dielectric of the final multilayer ceramic capacitor are given by formula: (Ba １－ｙ Ca ｙ ) ｎ TiO ３－Δ’ The basic composition should be adjusted to have the formula shown (where 0.05 ≤ y ≤ 0.20, and n and Δ' are arbitrary real numbers that maintain the perovskite crystal structure).

[0060] The outer layer green sheet can be prepared in the same manner as the inner layer green sheet. That is, the main component powder for the outer layer is mixed with a binder and solvent to form a slurry, and the resulting slurry is then molded. Additives such as plasticizers and auxiliary component raw materials may also be added to the slurry as needed. However, unlike the inner layer green sheet, a conductive paste layer is not formed on the outer layer green sheet. In other words, no printing process is involved.

[0061] <Lamination Process> In the lamination process, multiple inner layer green sheets, each having a conductive layer, are laminated, and one or more outer layer green sheets are laminated above and below them. Then, the entire structure is compressed to create a laminated block. The inner layer green sheets become inner layer dielectrics (ceramic dielectrics in the inner layer) through a firing process. The outer layer green sheets become outer layer dielectrics (ceramic dielectrics in the outer layer). The number of green sheets to be laminated should be adjusted to obtain the required capacitance.

[0062] <Cutting Process> In the cutting process, the obtained laminated block is cut to obtain laminated chips. The cutting should be performed in such a way that chips of a predetermined size are obtained and a portion of the conductive paste layer is exposed on the end face and / or side face of the laminated chip.

[0063] If necessary, the resulting laminated chip may be subjected to barrel polishing. This process makes it possible to round the corners and / or edges of the green base material.

[0064] <Firing Process>In the firing process, the laminated chip is subjected to a debinding process and a firing process to obtain a green body. By the firing process, the conductive layer and the inner layer green sheet are co-sintered to form an internal electrode layer and an inner layer dielectric, respectively. The outer layer green sheet is sintered to form an outer layer dielectric.

[0065] The conditions for the debinding process may be determined according to the type of organic binder contained in the green sheet and the conductive paste layer. Also, the firing process may be carried out at a temperature at which the laminated chip is sufficiently densified. For example, it may be carried out under the condition of holding at a temperature of 1200 °C or higher and 1300 °C or lower for 3 hours or less. Further, the firing is carried out in an atmosphere in which the main component compound is not reduced and the oxidation of the conductive material is suppressed. For example, in an N －９ -H －１０ -H ２ -O ２ -H ２ -O gas stream. Further, an annealing process may be performed after firing.

[0066] <External Electrode Formation Process>In the external electrode formation process, an external electrode is formed on the green body to fabricate a multilayer ceramic capacitor. The formation of the external electrode may be carried out by a known method. For example, a conductive paste mainly composed of a conductive component such as Cu or Ni is applied and baked on the end face and / or side face where the internal electrode layer of the green body is drawn out and exposed to form an underlayer. The underlayer may be formed by a method in which a conductive paste is applied to both end faces of the green body before firing and then a firing process is performed. After forming the underlayer, electrolytic plating may be performed to form a plating film such as Ni or Sn on the surface of the underlayer. Thereby, a multilayer ceramic capacitor is fabricated.

[0067] The present embodiment will be further specifically described by the following examples. However, the present invention is not limited to the following examples.

[0068] (1) Fabrication of Multilayer Ceramic Capacitor [Examples 1 to 21]<Synthesis of Main Component Powder>Titanium oxide (TiO ２ ) powder, barium carbonate (BaCO ３ ) powder, and calcium carbonate (CaCO ３Using the powder as a starting material, the main component powder for the inner layer and the main component powder for the outer layer were synthesized. Specifically, after wet-mixing and pulverizing the starting material using a ball mill, it was heated at a temperature of 1000 °C or higher in an air atmosphere to synthesize BaCaTiO ３ -series compound powder (main component powder). At this time, the blending amounts of the starting materials (TiO ２ , BaCO ３ , CaCO ３ ) were adjusted to prepare eight types of powders (A to H) shown in Table 1 below.

[0069]

[0070] <Preparation of inner layer green sheet> As the main component powder for the inner layer, the powder having the composition of (Ba １－ｘ Ca ｘ ) ｍ TiO ３ shown in Table 2 below was used. In addition to the main component powder, dysprosium oxide (Dy ２ O ３ ), magnesium oxide (MgO), manganese oxide (MnO), and vanadium oxide (V ２ O ５ ) were prepared as sub-component raw materials. Next, the main component powder and the sub-component raw materials were weighed and mixed so that in the formula: (Ba １－ｘ Ca ｘ ) ｍ TiO ３ + αDy ２ O ３ + βMgO + γMnO + δV ２ O ５ , α = 2.00 mol%, β = 0.006 mol%, γ = 0.002 mol%, and δ = 0.001 mol% to prepare a dielectric raw material.

[0071] Next, ethanol as an organic solvent and a polyvinyl butyral-based binder were added to the obtained dielectric material and wet-mixed using a ball mill to prepare an inner layer ceramic slurry. Then, the obtained ceramic slurry was formed into a sheet to produce a green sheet. Subsequently, a conductive paste mainly composed of Ni was printed onto the surface of the green sheet to form a conductive paste layer for the internal electrode layer. The green sheet with the conductive paste layer was used as the inner layer green sheet.

[0072] <Preparation of outer layer green sheet> The main component powder for the outer layer is shown in Table 2 below (Ba １－ｙ Ca ｙ ) ｎ TiO ３ A powder with the specified composition was used. Furthermore, the outer layer green sheet was prepared using the same procedure as for the inner layer green sheet. However, the conductive paste layer was not formed.

[0073] <Fabrication of Multilayer Ceramic Capacitors> Next, multiple inner layer green sheets were stacked so that the leads of the conductive paste layer were staggered, and multiple outer layer green sheets were stacked on top of them, sandwiching them from above and below, and the whole thing was then compressed to obtain a laminate. In this case, the number of inner layer green sheets stacked was 320. The number of outer layer green sheets stacked was 30 on one side (one side, top or bottom). Next, the obtained laminate was N ２ After heating to 350°C in an atmosphere to burn off the binder, the oxygen partial pressure was reduced to 10 －９ ~10 －１２ H with a pressure of MPa ２ -N ２ -O ２ A ceramic sintered body was obtained by firing at 1200°C for 2 hours in a reducing atmosphere consisting of gas.

[0074] Next, B ２ O ３ -SiO ２ - An Ag paste containing BaO-based glass frit is applied to both ends of the ceramic sintered body, N ２An external electrode electrically connected to the internal electrode layer was formed by baking at 600°C in an atmosphere. Subsequently, a Ni plating solution containing Ni sulfate, Ni chloride, and boric acid was prepared, and a Ni plating layer was formed on the external electrode by barrel plating. Next, a solder plating solution consisting of an AS bath (alkanol sulfonic acid) was prepared, and solder plating was applied to the Ni plating layer by barrel plating to obtain a multilayer ceramic capacitor with an external electrode having a plated layer. The obtained multilayer ceramic capacitor had external dimensions of 0.9 mm in width and 1.8 mm in length. The thickness of each dielectric layer sandwiched between the internal electrode layers was 1.5 μm, and the thickness of the outer layer was 50 μm on one side.

[0075]

[0076] (2) The samples obtained in Evaluation Examples 1 to 21 were evaluated for various characteristics as follows.

[0077] <Composition of Main Crystal Particles> The cross-section of a multilayer ceramic capacitor was polished, and thin sections were prepared from the exposed inner and outer ceramic layers (dielectric layers) by FIB processing. Then, the composition of the main crystal particles was determined by analyzing each of the obtained thin sections using STEM-EDX. Specifically, five main crystal particles were randomly selected within the observation field of view of each inner and outer layer sample, and the composition of the central part of each particle was performed as a point analysis. Next, the average value of the analysis was calculated and determined as the main crystal particle composition of each sample.

[0078] As a result, it was confirmed that the composition of the main crystal particles contained in the inner and outer dielectric layers was consistent with the composition of the main component powders used as raw materials (A to H in Table 1).

[0079] <Dielectric Properties> The capacitance and dielectric loss (tanδ) of the multilayer ceramic capacitors were measured using an automatic bridge type measuring instrument in accordance with JIS C5102. They were then graded according to the following criteria.

[0080] Dielectric loss of 5% or less: ○ (Good product) Dielectric loss exceeding 5%: × (Defective product)

[0081] <High-Temperature Load Test> For each level, a high-temperature load test was conducted using 20 multilayer ceramic capacitors as samples. Specifically, a DC voltage of 30V was applied to each sample at a temperature of 150°C, and the change in insulation resistance over time was examined. ５ The time until the value drops below Ω was defined as the lifetime. Next, the average lifetime (Mean Time To Fifths) was calculated and graded according to the following criteria.

[0082] Average lifespan of 10 hours or more: ○ (Good product) Average lifespan of less than 10 hours: × (Defective product)

[0083] <Mechanical Strength> For each level, the mechanical strength (flexural strength) was evaluated using 20 multilayer ceramic capacitors as samples. Specifically, the flexural strength test of the samples was performed using the three-point bending method under the following conditions.

[0084] Pressing jig descent speed: 0.1 mm / sec; Pressing jig tip diameter: 0.2 mm radius; Pressing position: Center of the intersection of the length L and width W of the sample (center of the LW surface)

[0085] Next, the average flexural strength (average flexural strength) was calculated and graded according to the following criteria.

[0086] Average bending strength of 500N or more: ○ (Good product) Average bending strength less than 500N: × (Defective product)

[0087] <Structural Defects> Structural defects in ceramic sintered bodies were investigated before the external electrodes were attached. Specifically, 30 ceramic sintered bodies were analyzed using an ultrasonic flaw detection device to examine the interface between the inner and outer layers and check for the presence or absence of structural defects (delamination). Based on the results obtained (number of sintered bodies with structural defects), the bodies were graded according to the following criteria.

[0088] 0 pieces / 30 pieces: 〇 (good product) 1 piece or more / 30 pieces: × (defective product)

[0089] (3) Evaluation results The evaluation results obtained for Examples 1 to 21 (dielectric loss, mean lifetime, flexural strength, structural defects) are summarized in Table 3 below.

[0090] Examples 1 to 3 are comparative examples where the amount of Ca x in the main crystal grains of the inner layer is excessively low (x = 0.01). In these samples, the results of the high-temperature load test (average lifetime) were "×". Also, Examples 19 to 21 are comparative examples where the amount of Ca x in the main crystal grains of the inner layer is excessively high (x = 0.05). In these samples, the evaluation results of the dielectric loss were "×".

[0091] Examples 4, 9, and 14 are comparative examples where the amount of Ca y in the outer layer main crystal grains is excessively low (y = 0.03). In these samples, the evaluation result for flexural strength was "×". Also, Examples 8 and 13 are comparative examples where the amount of Ca y in the outer layer main crystal grains is excessively high (y = 0.22). In these samples, the evaluation result for structural defects was "×".

[0092] In contrast, Examples 5 to 8, 10 to 12, and 15 to 17 are example samples in which the amount of Ca x in the inner layer main crystal grains and the amount of Ca y in the outer layer main crystal grains satisfy the range defined in this embodiment (0.02 ≤ x ≤ 0.04 and 0.05 ≤ y ≤ 0.20). In these samples, the evaluation results for average lifetime, dielectric loss, flexural strength, and structural defects were all "○".

[0093]

[0094] From the above results, it can be understood that the multilayer ceramic capacitor of this embodiment makes it possible to achieve both excellent electrical characteristics and high mechanical strength.

[0095] 2 Dielectric layer 4 Internal electrode layer 4a First internal electrode layer 4b Second internal electrode layer 6 Base part 8a First external electrode 8b Second external electrode 10a First main surface 10b Second main surface 12a First side surface 12b Second side surface 14a First end surface 14b Second end surface 16 Inner layer 18a First outer layer 18b Second outer layer 100 Multilayer ceramic capacitor

Claims

1. A multilayer ceramic capacitor comprising: an inner layer having a first inner electrode layer and a second inner electrode layer alternately stacked via a dielectric layer made of ceramic dielectric, the inner layer having a first main surface which is a surface in the stacking direction, a second main surface which is the surface opposite to the first main surface, a first side surface which is a surface in the width direction perpendicular to the first and second main surfaces, a second side surface which is the surface opposite to the first side surface, a first end surface which is a surface in the length direction perpendicular to the first main surface, the second main surface, the first side surface, and the second side surface, and a second end surface which is the surface opposite to the first end surface; a first outer layer made of ceramic dielectric that covers the first main surface from the stacking direction; a second outer layer made of ceramic dielectric that covers the second main surface from the stacking direction; and a plurality of external electrodes connected to each of the first and second inner electrode layers, respectively. The ceramic dielectric in the inner layer includes main crystal particles composed of a perovskite-type compound containing barium (Ba), calcium (Ca), and titanium (Ti), and the molar ratio of the amount of calcium (Ca) to the total amount of barium (Ba) and calcium (Ca) contained in the main crystal particles of the inner layer (Ca / (Ba+Ca) inner layer ratio) is 0.02 or more and 0.04 or less. The ceramic dielectric in the first outer layer and the second outer layer each includes main crystal particles composed of a perovskite-type compound containing barium (Ba), calcium (Ca), and titanium (Ti), and the molar ratio of the amount of calcium (Ca) to the total amount of barium (Ba) and calcium (Ca) contained in the main crystal particles of the first outer layer and the second outer layer (Ca / (Ba+Ca) outer layer ratio) is 0.05 or more and 0.20 or less. The thickness of the first outer layer and the second outer layer in the stacking direction is 60 μm or less.

2. The multilayer ceramic capacitor according to claim 1, wherein the widthwise dimension W of the multilayer ceramic capacitor is 0.7 mm or more and 5.1 mm or less, and the lengthwise dimension L is 1.5 mm or more and 5.8 mm.

3. The multilayer ceramic capacitor according to claim 1 or 2, wherein at least one of the first internal electrode layer and the second internal electrode layer comprises nickel (Ni) or a nickel (Ni) alloy.

4. The multilayer ceramic capacitor according to claim 1 or 2, wherein the difference between the Ca / (Ba+Ca) inner layer ratio and the Ca / (Ba+Ca) outer layer ratio (|Ca / (Ba+Ca) outer layer ratio - Ca / (Ba+Ca) inner layer ratio|) is 0.01 or more and 0.10 or less.

5. The multilayer ceramic capacitor according to claim 1 or 2, wherein the molar ratio of the total amount of barium (Ba) and calcium (Ca) to the amount of titanium (Ti) contained in the main crystal grains of the inner layer ((Ba + Ca) / Ti inner layer ratio) is 0.990 or more and 1.035 or less, and the molar ratio of the total amount of barium (Ba) and calcium (Ca) to the amount of titanium (Ti) contained in the main crystal grains of the first outer layer and the second outer layer ((Ba + Ca) / Ti outer layer ratio) is 0.990 or more and 1.035 or less.

6. The multilayer ceramic capacitor according to claim 1 or 2, wherein the (Ba + Ca) / Ti inner layer ratio is 1.000 or more and 1.015 or less, and the (Ba + Ca) / Ti outer layer ratio is 1.000 or more and 1.015 or less.

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