Multilayer ceramic capacitor and manufacturing method thereof

Abstract

To provide a multilayer ceramic capacitor having excellent moisture resistance that can be manufactured at a relatively low firing temperature.SOLUTION: A multilayer ceramic capacitor includes a capacitive portion in which dielectric layers and internal electrode layers are alternately stacked, and a cover layer arranged on the outside of the capacitive portion in the stacking direction, the cover layer includes a perovskite compound represented by the general formula ABO3 and contains one or more elements in a metallic state selected from the group consisting of Cu, Au, Ag, Al, Ir, and W, and the number of atoms of the elements is 0.002 to 0.15 per 100 atoms of the B-site elements in the general formula.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a multilayer ceramic capacitor and a method for manufacturing a multilayer ceramic capacitor. [Background technology]

[0002] A multilayer ceramic capacitor (MLCC) comprises a capacitance section formed by alternately stacking dielectric layers and internal electrode layers, and a cover layer disposed on the outer side of the capacitance section in the stacking direction. The cover layer tends to be slow to densify due to factors such as a small amount of metal diffusing from the internal electrodes reaching the cover layer during the firing process. If the cover layer constituting the surface is not sufficiently densified, the moisture resistance of the multilayer ceramic capacitor is likely to decrease, potentially resulting in reduced reliability.

[0003] In response to this, it is known that moisture resistance can be improved by adding more sintering agent to the cover layer than to the dielectric layer of the capacitance section, and making the sintering temperature as uniform as possible between the cover layer and the dielectric layer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-170526 Summary of the Invention [Problem to be solved by the invention]

[0005] If a large amount of sintering agent is added to the cover layer, the diffusion of the sintering agent into the capacitance section may impair the electrostatic properties of the dielectric layer. Therefore, as a means of promoting densification of the cover layer without relying on sintering agent, it is considered to perform firing at a higher temperature. However, if the firing temperature is too high, the internal dielectric layer may be over-sintered, resulting in insufficient reliability. Furthermore, from the perspective of reducing energy consumption, firing at as low a temperature as possible is desirable.

[0006] An object of the present disclosure is to provide a multilayer ceramic capacitor that can be manufactured at a relatively low firing temperature and has excellent moisture resistance. [Means for solving the problem]

[0007] The capacitor has a capacitive section in which dielectric layers and internal electrode layers are alternately stacked, and a cover layer arranged on the outside of the capacitive section in the stacking direction, wherein the cover layer contains a perovskite compound represented by the general formula ABO3 and contains one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in a metallic state, and the number of atoms of the elements is 0.002 to 0.15 per 100 atoms of the B-site elements in the general formula. [Effects of the Invention]

[0008] According to one aspect of the present disclosure, it is possible to provide a multilayer ceramic capacitor that can be manufactured at a relatively low firing temperature and has excellent moisture resistance. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a multilayer ceramic capacitor according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along line BB in FIG. [Figure 4] An enlarged view of part C in FIG. 2 is shown. [Figure 5] 1 is a flowchart showing a first embodiment of a method for manufacturing a multilayer ceramic capacitor. [Figure 6] 6 is a flowchart showing second and third embodiments of the method for manufacturing a multilayer ceramic capacitor. DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiments of the present disclosure will be described in detail below, but the present disclosure is not limited thereto. In this specification and drawings, components having substantially the same functional configurations may be denoted by the same reference numerals to avoid redundant description. The drawings also show X-, Y-, and Z-axes, which are mutually orthogonal, as appropriate. The X-, Y-, and Z-axes define a fixed coordinate system fixed with respect to the multilayer ceramic capacitor. When the multilayer ceramic capacitor has an approximately rectangular parallelepiped outer shape, the X-, Y-, and Z-axes may correspond to its length, width, and height.

[0011] [Multilayer ceramic capacitors] (Structure of multilayer ceramic capacitors) FIG. 1 is a perspective view showing a multilayer ceramic capacitor 100 according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB in FIG. 1. As shown in FIGS. 1 to 3, the multilayer ceramic capacitor 100 includes an element body 10 having a substantially rectangular parallelepiped shape. Two opposing surfaces of the element body 10 are referred to as the upper surface and the lower surface, and four surfaces connecting the upper surface and the lower surface are referred to as side surfaces. Typically, when the multilayer ceramic capacitor is mounted on a circuit board, the surface facing the board is referred to as the lower surface, but this is not limited to this.

[0012] In the example shown in FIGS. 1 to 3, a first external electrode 20a and a second external electrode 20b are provided on two opposing side surfaces of the element body 10, namely, a first side surface 10a and a second side surface 10b (see FIG. 2). The first external electrode 20a extends from the first side surface 10a to four surfaces adjacent to the first side surface 10a, and the second external electrode 20b extends from the second side surface 10b to four surfaces adjacent to the second side surface 10b. The first external electrode 20a and the second external electrode 20b are spaced apart from each other. The external electrodes may be provided on any surface of the element body 10, not limited to the two opposing side surfaces.

[0013] The element body 10 has a capacitive section 14 in which dielectric layers 11 containing a ceramic material that functions as a dielectric and internal electrode layers 12 are alternately stacked. The internal electrode layers 12 include a plurality of first internal electrode layers 12a and a plurality of second internal electrode layers 12b. The first internal electrode layers 12a and the second internal electrode layers 12b are alternately stacked. The edges of the first internal electrode layers 12a are extended to the surface of the element body 10 on which the first external electrode 20a is provided, i.e., the first side surface 10a in the example shown in FIGS. 1 to 3. The edges of the second internal electrode layers 12b are extended to the surface of the element body 10 on which the second external electrode 20b is provided, i.e., the second side surface 10b in the example shown in FIGS. 1 to 3. As a result, the first internal electrode layers 12a and the second internal electrode layers 12b are alternately electrically connected to the first external electrode 20a and the second external electrode 20b. Therefore, the multilayer ceramic capacitor 100 has a configuration in which capacitor units are stacked.

[0014] The lamination direction in which the dielectric layers 11 and the internal electrode layers 12 are stacked is the first axis, and in Figures 1 to 3, the first axis, which is the lamination direction in which the dielectric layers 11 and the internal electrode layers 12 are stacked, is the Z axis, and is the direction in which the above-mentioned internal electrode layers face each other. The axis perpendicular to the first axis, which is the lamination direction, is the second axis. In Figures 1 to 3, the second axis, which is perpendicular to the first axis, which is the lamination direction, is the X axis, and is the direction in which the internal electrode layers 12 are pulled out, and is the direction in which the first side surface 10a and the second side surface 10b of the element body 10 face each other, or the direction in which the first external electrode 20a and the second external electrode 20b face each other. In the example shown in Figures 1 to 3, this electrode pull-out direction (X-axis direction) is the direction along the longitudinal direction of the element body 10. The axis perpendicular to the first axis, which is the lamination direction, and perpendicular to the second axis is the third axis. 1 to 3, the third axis, which is perpendicular to the first axis, which is the stacking direction, and perpendicular to the second axis, is the Y axis, which is the axis along the direction in which the third side surface 10c and the fourth side surface 10d (see FIG. 3), among the four side surfaces of element body 10, face each other, and in the example shown in FIGS. 1 to 3, is the direction along the width direction of element body 10. The X axis direction, Y axis direction, and Z axis direction are mutually orthogonal. The stacking direction is not limited to the Z direction, and can be any direction. Therefore, for example, the first axis, which is the stacking direction, may be the X axis in the X direction or the Y axis in the Y direction.

[0015] In the present application, for the purpose of explaining general embodiments, figures illustrating a specific embodiment may be used, and the content explained using the coordinate axis system used in one embodiment is applied in the general embodiment by being read as a general coordinate system in which the stacking direction is the first axis. For example, what is explained as the X-axis, Y-axis, and Z-axis used in Figures 1 to 3 in the specific embodiment, where the stacking direction coincides with the Z-axis, can be read as the second axis, third axis, and first axis in the general embodiment.

[0016] In other words, the capacitive portion 14 is a region where the first internal electrode layer 12a connected to the first external electrode 20a and the second internal electrode layer 12b connected to the second external electrode 20b face each other, and is a region that generates capacitance in the multilayer ceramic capacitor 100. In other words, the capacitive portion 14 is a region where adjacent internal electrode layers connected to different external electrodes face each other with a dielectric layer interposed therebetween.

[0017] In the capacitive section 14 formed by laminating the dielectric layers 11 and the internal electrode layers 12, the outermost in the lamination direction (Z-axis direction) is composed of the internal electrode layers 12. The cover layer 13 is disposed on the outer surface of the capacitive section 14 in the lamination direction, i.e., on the outer surface of the outermost internal electrode layer 12 in the lamination direction. As described above, the multilayer ceramic capacitor according to this embodiment has the capacitive section 14 formed by laminating the dielectric layers 11 and the internal electrode layers 12, and the cover layer 13 disposed on the outer side of the capacitive section in the lamination direction. In the example shown in FIGS. 1 to 3, the cover layer 13 includes a cover layer 13a disposed on the upper surface of the capacitive section 14 and a cover layer 13b disposed on the lower surface.

[0018] The configuration of the element body 10 is not limited to that shown in FIGS. 1 to 3, as long as the first internal electrode layer 12a and the second internal electrode layer 12b are exposed in different regions on the surface of the element body 10 and are connected to different external electrodes. The different regions on the surface of the element body 10 may be surface regions on opposing faces of the surface of the element body 10, surface regions on adjacent faces, or different surface regions on the same face. As long as the different external electrodes are spaced apart from each other, the first internal electrode layer 12a and the second internal electrode layer 12b may extend from the faces exposed on the surface region of the laminate to other faces. The element body 10 may have multiple intermediate regions between the dielectric layer 11 and the internal electrode layer 12.

[0019] The region where the first internal electrode layers 12a connected to the first external electrode 20a face each other in the stacking direction without the second internal electrode layer 12b connected to the second external electrode 20b intervening therebetween is referred to as the first end margin 15a. The region where the second internal electrode layers 12b connected to the second external electrode 20b face each other in the stacking direction without the first internal electrode layer 12a connected to the first external electrode 20a intervening therebetween is referred to as the second end margin 15b. Each end margin is a region where internal electrode layers connected to the same external electrode face each other in the stacking direction without the internal electrode layer connected to a different external electrode intervening therebetween. The first end margin 15a and the second end margin 15b are regions that do not generate capacitance.

[0020] 3, the region provided adjacent to the outside of the capacitive section 14 in the Y-axis direction is called a side margin 16. This is the outer region adjacent to the capacitive section 14 on the side where the internal electrode layer 12 is not drawn out. The side margin 16 is also a region that does not generate electrical capacitance.

[0021] The size of the multilayer ceramic capacitor 100 is not particularly limited, and may be, for example, 0.25 mm long, 0.125 mm wide, and 0.125 mm high; 0.4 mm long, 0.2 mm wide, and 0.2 mm high; 0.6 mm long, 0.3 mm wide, and 0.3 mm high; 1.0 mm long, 0.5 mm wide, and 0.5 mm high; 3.2 mm long, 1.6 mm wide, and 1.6 mm high; or 4.5 mm long, 3.2 mm wide, and 2.5 mm high. However, the above-listed sizes of the multilayer ceramic capacitor 100 are merely examples, and the multilayer ceramic capacitor is not limited to these sizes. The size of the multilayer ceramic capacitor 100 may be, for example, length > width ≥ height; width > length ≥ height; height > length ≥ width; or height > width ≥ length. The ceramic capacitor 100 shown in FIGS. 1 to 3 has a length in the X-axis direction (electrode lead-out direction), a width in the Y-axis direction, and a height in the Z-axis direction (lamination direction).

[0022] (dielectric layer) The dielectric layer 11 contains a ceramic material as a main component, and preferably contains a compound having a perovskite structure represented by the general formula ABO3 (also referred to as a perovskite-type compound) as a main component. The dielectric layer 11 may contain the perovskite-type compound at, for example, 50 at% or more, 60 at% or more, 80 at% or more, 90 at% or more, or 95 at% or more. The perovskite structure may have an oxygen deficiency relative to the stoichiometric composition. In other words, the ABO3 deviates from the stoichiometric composition. 3-α (0≦α≦1: α represents an amount that deviates from the stoichiometric composition.) In addition, in this specification, "containing a specific component as a main component" means that the specific component is contained in the largest amount in terms of the proportion of substance amount among the components contained.

[0023] Perovskite compounds include barium titanate (BaTiO3), calcium zirconate (CaZrO3), calcium titanate (CaTiO3), strontium titanate (SrTiO3), magnesium titanate (MgTiO3), and BaTiO3, which forms a perovskite structure. 1-x-y Ca x Sr y Ti 1-z Zr z O3 (0≦x≦1, 0≦y≦1, 0≦z≦1), etc. can be used. 1-x-y Ca x Sr y Ti 1-z Zr z O3 may be barium strontium titanate, barium calcium titanate, barium zirconate, barium titanate zirconate, calcium titanate zirconate, barium calcium titanate zirconate, etc. The B site of the perovskite compound may contain hafnium (Hf).

[0024] Among the above compounds, barium titanate (BaTiO3) is preferable. Barium titanate has excellent dielectric properties such as a high dielectric constant and low dielectric loss, and therefore, when the dielectric layer 11 contains barium titanate as a perovskite compound, the capacitance of the multilayer ceramic capacitor 100 can be increased. The ceramic material in the dielectric layer 11 preferably contains barium titanate as a main component, but may be composed solely of barium titanate.

[0025] The dielectric layer 11 may contain additives other than the above-mentioned ceramic materials. Examples of additives include zirconium (Zr), magnesium (Mg), manganese (Mn), molybdenum (Mo), vanadium (V), chromium (Cr), rare earth elements (scandium (Sc), cerium (Ce), neodymium (Nd), yttrium (Y), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and yttrium (Y). Examples of the glass include a glass containing an oxide containing one or more elements selected from cobalt (Co), nickel (Ni), lithium (Li), boron (B), sodium (Na), potassium (K) and silicon (Si), a glass containing an oxide containing one or more elements selected from cobalt, nickel, lithium, boron, sodium, potassium and silicon, and the like.

[0026] Among the additives listed above, elements such as manganese (Mn), magnesium (Mg), silicon (Si), and boron (B), as well as compounds and glasses, are known as additives (sintering agents or sintering aids) that promote sintering. To maintain the dielectric properties of the multilayer ceramic capacitor 100, it is preferable that the dielectric layer 11 be substantially free of the additives that promote sintering, particularly Mn. In this specification, the expression "substantially free of" a specific element or "substantially absent" a specific element refers to a ratio of the number of atoms of the specific element to 100 atoms of B-site elements in the perovskite-type ceramic material represented by the general formula ABO3 being 0.001 or less, preferably 0.0001 or less. Even if the dielectric layer 11 contains an additive that promotes sintering, as long as the ratio is below the above atomic ratio, the additive does not substantially affect the sintering function of the dielectric layer 11.

[0027] (Internal electrode layer) The internal electrode layers 12 contain a metal or an alloy as a main component. The internal electrode layers 12 may contain, for example, a base metal such as nickel (Ni), copper (Cu), or tin (Sn), or an alloy containing these, as a main component. The internal electrode layers 12 may also contain, as a main component, a noble metal such as platinum (Pt), palladium (Pd), silver (Ag), or gold (Au), or an alloy containing these. The internal electrode layers 12 preferably contain Ni, and may contain Ni as a main component, because of its excellent electrical properties and ability to reduce costs.

[0028] As described later, when forming the internal electrode layers 12 in the manufacture of a multilayer ceramic capacitor, if one or more elements selected from the group consisting of Cu (copper), Au (gold), Ag (silver), Al (aluminum), Ir (iridium), and W (tungsten) are contained in the unsintered internal electrode material that becomes the internal electrode layers 12, the internal electrode may contain one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W. Also, for example, if Cu is contained in the unsintered internal electrode material, the internal electrode layers 12 may contain Cu. Furthermore, if the internal electrode layers 12 contain Ni as a main component, the internal electrode layers 12 may contain an alloy of Ni and Cu.

[0029] (cover layer) The cover layer 13 contains a ceramic material as a main component. For specific ceramic materials for the cover layer 13, please refer to the description of the ceramic material for the dielectric layer 11 above. Therefore, the cover layer 13 may contain a perovskite compound represented by the general formula ABO3. The cover layer 13 may contain the perovskite compound represented by the general formula ABO3 in an amount of, for example, 50 at% or more, 60 at% or more, 80 at% or more, 90 at% or more, or 95 at% or more. Barium titanate (BaTiO3) is preferred as the perovskite compound. In other words, the cover layer 13 preferably contains barium titanate (BaTiO3). Furthermore, the ceramic material for the cover layer 13 preferably contains barium titanate as a main component, and may be composed solely of barium titanate.

[0030] The ceramic material of the cover layer 13 may be the same as or different from the ceramic material of the dielectric layer 11. However, it is preferable that the cover layer 13 contains the same ceramic material as the dielectric layer 11, because fewer types of materials need to be prepared during manufacturing and characteristics are less likely to fluctuate even if interdiffusion occurs between the materials of the cover layer 13 and the dielectric layer 11. For example, it is preferable that the ceramic materials contained in both the cover layer 13 and the dielectric layer 11 contain barium titanate as a main component, and they may be composed solely of barium titanate.

[0031] The cover layer 13 contains, in a metallic state, one or more elements selected from the group consisting of Cu (copper), Au (gold), Ag (silver), Al (aluminum), Ir (iridium), and W (tungsten). Here, "metallic state" refers to the presence of a metal in a simple or alloyed state. Thermal conductivity can be enhanced by including one or more elements selected from the group consisting of Cu (copper), Au (gold), Ag (silver), Al (aluminum), Ir (iridium), and W (tungsten) in a "metallic state," rather than elements or compounds known as sintering-promoting additives (sintering agents or sintering aids), such as simple substances or compounds containing elements such as manganese (Mn), magnesium (Mg), silicon (Si), or boron (B), or glass. This configuration improves the moisture resistance of the cover layer 13 and, consequently, the moisture resistance of the multilayer ceramic capacitor 100, resulting in a highly reliable multilayer ceramic capacitor 100. This mechanism is thought to be due to the fact that the inclusion of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in a metallic state enhances the thermal conductivity of the cover layer 13 during the firing process (described in detail below), allowing the heat from the firing furnace to be efficiently and rapidly transferred to the entire cover layer 13, promoting uniform densification of the cover layer 13. Because the heat from the firing furnace is efficiently transferred to the entire cover layer 13, a highly reliable multilayer ceramic capacitor can be manufactured even when the firing furnace temperature is set relatively low during the firing process, i.e., even at a relatively low firing temperature. A relatively low firing temperature contributes to promoting densification of the cover layer during the firing process. Furthermore, because the heat from the firing furnace is rapidly transferred to the entire cover layer 13 during the firing process, a dielectric layer with little variation can be obtained, allowing a highly reliable multilayer ceramic capacitor to be manufactured even when the firing furnace temperature rise rate is set relatively high during the firing process, i.e., even at a relatively high temperature rise rate. A relatively high heating rate can also improve productivity by shortening the heating time required for the firing process. By reducing both the heating temperature and heating time, energy consumption in the firing process can also be reduced, which is desirable from the perspective of cost reduction and the realization of a sustainable society, which is one of the SDGs.

[0032] Among the one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W, Cu is preferred because it has high thermal conductivity in the form of a single element or an alloy, and is inexpensive.

[0033] Furthermore, the atomic number of the one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W is 0.002 or more and 0.15 or less relative to the atomic number of 100 B-site elements of the perovskite compound represented by the general formula ABO3 contained in the cover layer 13. This atomic number may be preferably 0.002 or more and 0.09 or less, more preferably 0.003 or more and 0.075 or less, and even more preferably 0.005 or more and 0.05 or less. By having the atomic number of the one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W be 0.002 or more relative to the atomic number of 100 B-site elements, the thermal conductivity of the cover layer 13 is appropriately increased, and a cover layer with excellent moisture resistance, and therefore a multilayer ceramic capacitor 100 with excellent moisture resistance, can be obtained at a relatively low firing temperature. Furthermore, by setting the atomic number of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W to 0.15 or less per 100 atoms of the B-site elements, electrical defects such as leakage current can be suppressed.

[0034] When the perovskite compound represented by the general formula ABO3 is barium titanate, the B-site element is Ti. In this case, the number of atoms of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the cover layer 13 is 0.002 to 0.15 per 100 Ti atoms. When the perovskite compound is Ba 1-x-y Ca x Sr y Ti 1-z Zr zWhen the formula is O3 (0≦x≦1, 0≦y≦1, 0≦z≦1), the B-site elements are Ti and Zr. In this case, the number of atoms of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the cover layer 13 is 0.002 to 0.15 per 100 atoms, which is the total number of Ti and Zr atoms.

[0035] The one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W present in the cover layer 13 in the above-mentioned predetermined amount may be those added to the unsintered cover material for forming the cover layer 13 during the manufacturing process of the multilayer ceramic capacitor 100, or may be those added to the unsintered internal electrode material for forming the internal electrode layer 12 and diffused into the cover layer 13 during the firing process, or may include both.

[0036] The cover layer 13 may also contain an additive containing an element other than one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W. Such an additive may be one or more of the additives described above as being contained in the dielectric layer 11. However, it is preferable that the amount of additives having a sintering aid function (additives known as sintering agents) in the cover layer 13 be reduced. Because additives having a sintering aid function degrade the dielectric properties of the multilayer ceramic capacitor 100, reducing such additives allows the dielectric properties to be maintained.

[0037] For example, in the cover layer 13, the number of Mn (manganese) atoms serving as a sintering-aid additive relative to 100 atoms of the B-site elements of the perovskite compound represented by the general formula ABO3 is preferably 1.2 or less. This reduces the amount of Mn diffusing from the cover layer 13 to the capacitance portion 14 during the firing process, thereby suppressing deterioration in the dielectric properties of the multilayer ceramic capacitor 100. The ratio of Mn atoms relative to 100 atoms of the B-site elements is preferably 1.0 or less, more preferably 0.5 or less, even more preferably 0.1 or less, and even more preferably 0.05 or less. It is also preferable that the cover layer 13 be substantially free of Mn.

[0038] Furthermore, in the cover layer 13, the number of atoms of the sintering-aid additive element, including Mn (the total number of atoms when there are two or more elements) is preferably 1.2 or less relative to the number of B-site elements of the perovskite compound represented by the general formula ABO3 contained in the cover layer 13. This reduces the diffusion of the sintering-aid additive from the cover layer 13 to the capacitance portion 14 during the firing process, further suppressing deterioration of the dielectric properties of the multilayer ceramic capacitor 100. The number of atoms of the sintering-aid additive element may be preferably 1.0 or less, more preferably 0.5 or less, even more preferably 0.1 or less, and even more preferably 0.05 or less relative to the number of B-site elements (100). Furthermore, it is preferable that the cover layer 13 be substantially free of sintering-aid additives.

[0039] Note that a substance containing one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W present in the cover layer 13 also diffuses toward the capacitive section 14 during the firing process. However, when the element reaches the internal electrode layer 12 adjacent to the element cover layer 13, it alloys with the metal constituting the internal electrode layer 12, making it difficult to diffuse further into the capacitive section 14. FIG. 4 is a schematic enlarged view of portion C in FIG. 2. As shown in FIG. 4, a substance 30 containing one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W diffuses toward the center in the stacking direction (Z-axis direction), but this diffusion is blocked by the outermost alloyed internal electrode layer 12 in the stacking direction, making it difficult to diffuse further in the stacking direction. Therefore, the addition of a substance containing one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W, particularly Cu, suppresses degradation of capacitance characteristics.

[0040] The concentration of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the uppermost internal electrode layer and / or the lowermost internal electrode layer of the internal electrode layers 12 adjacent to the cover layer 13 may be higher than the concentration of the above elements in the internal electrode layer at the center in the stacking direction.

[0041] When the one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W contained in the cover layer 13 originate solely from those added to the unsintered cover material for forming the cover layer 13 in the manufacturing process of the multilayer ceramic capacitor 100, the concentration of the substance containing one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the internal electrode layer 12 adjacent to the cover layer 13, i.e., the uppermost internal electrode layer and / or the lowermost internal electrode layer, may be higher, at least twice, preferably at least three times, than the concentration of the substance in the internal electrode layer at the center in the stacking direction. Furthermore, it is preferable that the internal electrode layer at the center in the stacking direction is substantially free of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W. For example, the number of atoms of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the internal electrode layer at the center in the stacking direction may be preferably 0.001 or less, more preferably 0.0001 or less, relative to 100 atoms of the main component elements of the internal electrode layer in the central internal electrode.

[0042] The one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W contained in the cover layer 13 may be derived from elements added to the unsintered internal electrode material for forming the internal electrode layer 12, i.e., elements added to the unsintered internal electrode material may be diffused into the cover layer 13 during the firing process.

[0043] As an example, one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W contained in the cover layer may be obtained by adding only to the internal electrode material for forming the internal electrode layer closer to the cover layer 13 among the unsintered internal electrode materials for forming the internal electrode layer 12. In this case, one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W are not added to the internal electrode layer at the center in the stacking direction before firing. Therefore, even after firing, the concentration of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the internal electrode layers 12 closer to the cover layer, for example, the uppermost internal electrode layer and / or the lowermost internal electrode layer, can be higher than the concentration of the above elements in the internal electrode layer at the center in the stacking direction. Furthermore, even after firing, the internal electrode layer at the center in the lamination direction preferably has substantially no atomic number of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W. "Substantially no atomic number" may be preferably 0.001 or less, more preferably 0.0001 or less, relative to 100 atoms of the main component elements of the internal electrode layer in the central internal electrode.

[0044] As a modified example, a dummy electrode may be provided as an internal electrode layer close to the cover layer 13, and one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W may be added to the internal electrode material used to form this dummy electrode. In this case, the elements added to the unsintered internal electrode material diffuse into the cover layer 13 during the sintering process. A dummy electrode is defined as two electrode layers that are adjacent to each other via a dielectric layer and connected to the same external electrode. Since no potential difference occurs between the two dummy electrodes, the dummy electrode does not contribute to capacitance. Even when a dummy electrode is provided as an internal electrode layer close to the cover layer 13, the concentration of a substance containing one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the upper and / or lower dummy electrodes close to the cover layer 13 can be made higher than the concentration of the above elements in the internal electrode layer at the center of the stacking direction, as in the case of a typical internal electrode layer. It is preferable that the number of atoms of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W is substantially absent in the internal electrode layer at the center in the lamination direction even after firing. "Substantially absent" may be preferably 0.001 or less, more preferably 0.0001 or less, relative to 100 atoms of the main component elements of the internal electrode layer in the central internal electrode.

[0045] The concentration of a substance containing one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the uppermost internal electrode layer and / or the lowermost internal electrode layer of the internal electrode layers 12 adjacent to the cover layer 13 may be lower than the concentration of the substance in the internal electrode layer at the center in the stacking direction.

[0046] When the one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W contained in the cover layer are derived from those added to the unsintered internal electrode material for forming the internal electrode layer 12, i.e., those that were added to the unsintered internal electrode material and diffused into the cover layer 13 during the firing process, the concentration of the substance containing one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the internal electrode layer adjacent to the cover layer among the internal electrode layers 12, i.e., the uppermost internal electrode layer and / or the lowermost internal electrode layer, may be higher, and is 1.1 times or more, preferably 1.5 times or more, 2 times or more, and more preferably 4 times or more. This is because, even though the content of the substance containing one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the internal electrode layers 12 is equal in each layer of the internal electrode layers 12 before diffusion occurs, when diffusion occurs, the amount of diffusion into the cover layer 13 increases in the internal electrode layers 12 adjacent to the cover layer 13, and the remaining content decreases significantly, whereas in the internal electrode layers not adjacent to the cover layer 13, there is almost no diffusion into the cover layer 13, and so the majority of the content remains.

[0047] The number of atoms of a predetermined element relative to 100 atoms of the B-site element of the perovskite compound represented by the general formula ABO3 in the cover layer 13 can be calculated by analyzing a cross section of the resulting multilayer ceramic capacitor. For example, the multilayer ceramic capacitor is polished from the external electrode 20 side toward the center, i.e., along the X-axis direction, to near the center in the X-axis direction to expose a YZ cross section, and elemental analysis is performed on the central portion of the cover layer 13 in the Z-axis direction. If the perovskite compound contained in the cover layer 13 is barium titanate, the number of atoms of the predetermined element relative to 100 Ti atoms is determined. The amount of the predetermined element can also be determined based on analysis by wavelength dispersive X-ray spectroscopy (EPMA-WDX) or laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). However, if any doubt arises, the measurement value by wavelength dispersive X-ray spectroscopy shall be used. The amount of elements in layers other than the cover layer 13, for example, the internal electrode layer 12, can also be determined in a similar manner.

[0048] The multilayer ceramic capacitor 100 according to one embodiment has been described above, but the configuration of the multilayer ceramic capacitor according to the present disclosure can be used as a multilayer ceramic electronic component. Specific examples of multilayer ceramic electronic components other than multilayer ceramic capacitors include chip varistors and chip thermistors.

[0049] [Manufacturing method for multilayer ceramic capacitors] Next, a description will be given of a method for manufacturing the above-mentioned multilayer ceramic capacitor 100. The manufacturing method according to one embodiment of the present disclosure is a method for manufacturing a multilayer ceramic capacitor having a capacitive section in which dielectric layers and internal electrode layers are alternately stacked, and a cover layer arranged on the outer side of the capacitive section in the stacking direction, the cover layer containing a perovskite compound represented by the general formula ABO3, and includes a lamination step of alternately stacking unsintered dielectric materials that will become the dielectric layers and unsintered internal electrode materials that will become the internal electrode layers, and further arranging an unsintered cover material that will become the cover layer to obtain a laminate, and a firing step of firing the laminate, wherein after the firing step, the cover layer contains one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in a metallic state, and the atomic number of the element is 0.002 to 0.15 relative to the atomic number of 100 of the B-site elements.

[0050] First Embodiment The manufacturing method according to the first embodiment includes forming an unsintered cover material so as to contain one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W. In the first embodiment, one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W are present in the cover layer 13 even before firing, making it possible to more reliably ensure that the cover layer 13 in the fired multilayer ceramic capacitor 100 contains a predetermined amount of one or more elements selected from the predetermined group. FIG. 5 is a flowchart illustrating a method for manufacturing the multilayer ceramic capacitor 100 according to the first embodiment.

[0051] (Unfired dielectric material preparation step (S1)) In the green dielectric material preparation step (S1), ceramic green sheets (green dielectric material) that will become the dielectric layers 11 when fired are prepared.

[0052] First, ceramic powder for forming the dielectric layer is prepared. The ceramic powder can be any of the ceramic materials described above for the dielectric layer 11 of the multilayer ceramic capacitor 100. Therefore, the ceramic powder may contain powder of a perovskite-type compound represented by the general formula ABO3, and preferably contains barium titanate. Barium titanate can generally be obtained by reacting a titanium source such as titanium dioxide with a barium source such as barium carbonate. Conventional methods, such as a solid-phase method, a sol-gel method, or a hydrothermal method, can be used to synthesize the ceramic powder that will be the ceramic material that will be the main component of the dielectric layer 11.

[0053] The ceramic powder for forming the dielectric layers may contain predetermined additives depending on the purpose. For example, additives having a sintering aid function (additives known as sintering aids) may be added, or may not be added. However, from the viewpoint of improving the dielectric properties of the multilayer ceramic capacitor 100, it is preferable that the ceramic powder for forming the dielectric layers contains substantially no additives having a sintering aid function, and in particular, does not contain substantially Mn.

[0054] The dielectric layer-forming ceramic powder is wet-mixed with or without additives, dried, and pulverized. The obtained dielectric layer-forming powder is then wet-mixed with a binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer to prepare a dielectric layer-forming slurry. When additives are added, they can be added during the preparation of the slurry rather than being added to the dielectric layer-forming ceramic powder in advance. The obtained dielectric layer-forming slurry is applied to a substrate such as a polyethylene terephthalate (PET) film by a die coater method, a doctor blade method, or the like, and dried to obtain a ceramic green sheet (unfired dielectric layer material).

[0055] (Unfired cover material preparation step (S2)) In the green cover material preparation step (S2), a cover sheet (green cover material) that will become the cover layer is prepared.

[0056] The ceramic powder for forming the cover layer may be the same as the ceramic powder for forming the dielectric layer described in the above-mentioned step (S1) of preparing the unsintered dielectric material. Therefore, the ceramic powder may contain a powder of a perovskite-type compound represented by the general formula ABO3, preferably containing barium titanate. Furthermore, the same powder as the ceramic powder for forming the dielectric layer may be used.

[0057] The ceramic powder for forming the cover layer contains, as an additive, one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W. Of these, Cu is preferred. The elements may be added in the form of simple substances, alloys, compounds, or organic complexes, but oxides are preferred because they are easier to handle and more easily distributed uniformly through diffusion during the firing process. For example, in the case of Cu, it is preferable to use surface-oxidized copper (Cu) powder or copper oxide (CuO or CuO) powder with a particle size of 500 nm or less.

[0058] In this way, by adding elements containing one or more selected from the group consisting of Cu, Au, Ag, Al, Ir, and W to the ceramic powder for forming the cover layer in the unsintered cover material preparation step (S2), it is possible to improve moisture resistance and prevent electrical defects such as leakage current, thereby obtaining a highly reliable multilayer ceramic capacitor 100.

[0059] By adding the predetermined elements to the unsintered cover material as described above, after the firing step (S6), a multilayer ceramic capacitor 100 is obtained in which the cover layer 13 contains, in a metallic state, one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W, and the number of atoms of the elements is 0.002 to 0.15 per 100 atoms of the B-site elements of the compound represented by the general formula ABO3 that is the main component of the cover layer 13. In other words, in the unsintered cover material preparation step (S2), the amount of the predetermined elements to be contained in the cover layer-forming slurry can be set so as to obtain the configuration of the multilayer ceramic capacitor 100 described above in which the cover layer 13 contains a predetermined amount of the predetermined elements in a metallic state.

[0060] The amount of elements added to the green cover material in the green cover material preparation step (S2) may be such that the atomic number of the element is 0.2 to 5.0, preferably 0.4 to 4.5, relative to 100 atoms of the B-site elements of the perovskite compound represented by the general formula ABO3. The atomic number of the element containing one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W, relative to 100 atoms of the B-site elements, may be preferably 4.0 or less, more preferably 2.0 or less. By setting the atomic number of the element containing one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W to 0.2 or more relative to 100 atoms of the B-site elements, the moisture resistance of cover layer 13 and, ultimately, the moisture resistance of multilayer ceramic capacitor 100 itself can be improved. By setting the atomic number of elements including one or more selected from the group consisting of Cu, Au, Ag, Al, Ir, and W to 5.0 or less per 100 atoms of the B-site elements, electrical defects such as leakage current can be prevented, thereby providing a highly reliable multilayer ceramic capacitor 100.

[0061] When the perovskite compound represented by the general formula ABO3 is barium titanate (BaTiO3) and the above element is Cu, the amount of Cu in the cover layer forming slurry is 0.2 or more and 5.0 or less, preferably 0.4 or more and 4.5 or less, per 100 Ti atoms.

[0062] It is preferable that no sintering-aid additives (additives known as sintering agents) be added to the ceramic powder for forming the cover layer, or that only a small amount be added. Because sintering-aid additives degrade the dielectric properties of the multilayer ceramic capacitor 100, reducing the amount of such additives can maintain the dielectric properties. For example, even if Mn is added to the ceramic powder for forming the cover layer, it is preferable that the ratio of Mn atoms to 100 atoms of the B-site elements of the perovskite-type compound represented by the general formula ABO3 is 1.5 or less. This prevents degradation of the dielectric properties of the multilayer ceramic capacitor 100 when Mn diffuses from the cover layer 13 to the capacitance section 14 during the firing step (S6). Furthermore, the ratio of Mn atoms to 100 atoms of the B-site elements in the ceramic powder for forming the cover layer is preferably 1.0 or less, more preferably 0.5 or less. It is also preferable that the ceramic powder for forming the cover layer is substantially free of Mn.

[0063] As in the unsintered dielectric material preparation step (S1), the ceramic powder for forming the cover layer is wet-mixed with a binder, an organic solvent, and a plasticizer to prepare a slurry for forming the cover layer. The resulting slurry for forming the cover layer is applied to a substrate such as a polyethylene terephthalate (PET) film by a die coater method, a doctor blade method, or the like, and dried to obtain a cover sheet (unsintered cover layer).

[0064] (Unfired internal electrode material preparation process (S3)) In the green internal electrode material preparation step (S3), green internal electrode materials that will become the internal electrode layers 12, i.e., the first internal electrode layers 12a and the second internal electrode layers 12b, are prepared. The metal that is the main component of the green internal electrode material may be the same metal material as the materials described above for the internal electrode layers 12 of the multilayer ceramic capacitor 100, for example, base metals such as Ni and Sn, or alloys containing these. Furthermore, noble metals such as Pt, Pd, Ag, and Au, or alloys containing these, may also be used. In view of excellent electrical properties and cost reduction, the above metal material preferably contains Ni, and more preferably has Ni as the main component.

[0065] The metal material, organic binder, and solvent can be kneaded to obtain a metal paste (unfired internal electrode material).

[0066] Ceramic powder can also be added to the metal paste as a co-material. The main component of the ceramic powder is not particularly limited, but it is preferable that it has the same composition or consists of the same constituent elements as the ceramic powder used in the unsintered dielectric material preparation step (S1) and / or the unsintered cover material preparation step (S2). When ceramic powder is added as a co-material, it can be added when the metal paste is mixed.

[0067] (Lamination process (S4)) In the lamination step (S4), the metal paste obtained in the unsintered internal electrode material preparation step (S3) is printed on the surface of the ceramic green sheet obtained in the unsintered dielectric material preparation step (S1) by screen printing, gravure printing, etc. This allows the first internal electrode pattern to become the first internal electrode layer 12a and the second internal electrode pattern to become the second internal electrode layer 12b to be arranged on the surface of the ceramic green sheet. Note that the method for forming the internal electrode patterns is not limited to printing, and they can also be formed by plating, vacuum deposition, sputtering, CVD, etc. using a mask.

[0068] The ceramic green sheets on which the metal paste is printed are stacked so that the internal electrode layers 12 are alternately drawn to a pair of external electrodes 20a, 20b arranged in the longitudinal direction (X-axis direction) of the dielectric layer 11. A known technique can be used for this stacking. For example, to form a side margin 16, which is the outer region in the Y-axis direction, in the capacitive section 14 on the side on which the internal electrode layer 12 is not drawn, an unfired dielectric material can be placed in the peripheral region where the internal electrode pattern made of metal paste is not printed. Using ceramic green sheets on which the metal paste is printed as a stacking unit, the number of stacked layers in the stacking unit can be 100 to 500 layers.

[0069] Next, the cover sheets obtained in the unsintered cover material preparation step (S2) are laminated on the top and bottom of the laminate having the ceramic green sheets and the internal electrode pattern, i.e., on both sides in the lamination direction (Z-axis direction). The number of cover sheets laminated on each side may be 2 to 10 layers.

[0070] The laminate with the cover sheet laminated thereon can be pressed in the stacking direction (Z-axis direction), thereby obtaining a pressed body.

[0071] (Singulating process (S5)) Furthermore, the pressure-bonded body can be cut into individual pieces to a predetermined size by dicing with a dicer, laser cutting, etc. As the method for dividing, any existing technology can be used.

[0072] (Firing process (S6)) In the firing process, the singulated laminate is fired. First, degreasing is performed by heating in an N2 atmosphere at approximately 300°C to 600°C for 2 to 10 hours. Next, in the first embodiment, firing is performed in a strongly reducing atmosphere with a hydrogen concentration of 0.08% to 1.0% by volume, preferably 0.1% to 0.5% by volume. The other components of the strongly reducing atmosphere besides hydrogen are nitrogen or argon. This firing is also called main firing or strong reduction firing. This promotes the transformation of elements previously added to the unsintered material (including at least one element selected from the group consisting of Cu, Au, Ag, Al, Ir, and W) into a metallic state, i.e., into a metal or alloy. For example, if Cu is added in the form of an oxide, the copper oxide is reduced to metallic Cu. This results in a state in which the additive, a metal or alloy, is dispersed in the cover layer 13.

[0073] The firing temperature in the strong reduction firing is relatively low, preferably 900°C to 1270°C, more preferably 1000°C to 1250°C, even more preferably 1100°C to 1200°C, and even more preferably 1120°C to 1150°C. Firing at such low temperatures is preferable from the viewpoint of reducing energy consumption. A firing temperature within the above range can promote densification of the cover layer 13. A relatively low firing temperature is also preferable from the viewpoint of energy efficiency. The "firing temperature" refers to the temperature of the firing furnace. The temperature rise rate can be 20,000°C / h to 30,000°C / h. The firing time in the firing step (S6) in the first embodiment, including the temperature rise and fall processes, may be 30 minutes to 2 hours.

[0074] (External electrode formation process (S7)) In the external electrode forming step, the first external electrode 20a and the second external electrode 20b can be formed by plating etc. In this way, the multilayer ceramic capacitor 100 described above is completed.

[0075] Although the first embodiment has been described in detail above, the present disclosure is not limited to a specific embodiment, and various modifications and variations are possible within the scope of the claims. For example, a metal film that serves as a base layer of the external electrode may be formed after degreasing, and then the base layer of the external electrode may be sintered simultaneously with the firing of the dielectric portion by strong reduction firing, and the base layer of the external electrode may be plated in the external electrode formation process to form the final external electrode.

[0076] Second Embodiment The manufacturing method according to the second embodiment includes forming the unsintered internal electrode material so as to contain one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W. That is, in the second embodiment, one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W are added in the unsintered internal electrode material preparation step (S3). Also, since the predetermined elements such as Cu are added in the unsintered internal electrode material preparation step (S3), the firing step (S6) includes a pre-firing step (weak reduction firing step, S6a) and a main firing step (strong reduction step, S6b).

[0077] FIG. 6 is a flowchart illustrating a method for manufacturing a multilayer ceramic capacitor 100 according to the second embodiment. In the manufacturing method according to the second embodiment, the unsintered dielectric material preparation step (S1), the lamination step (S4), the singulation step (S5), and the external electrode formation step (S7) are the same as those in the first embodiment. Below, steps in the manufacturing method according to the second embodiment that differ from those in the first embodiment are described. As with the first embodiment, the present disclosure is not limited to a specific embodiment in the second embodiment, and various modifications and alterations are possible within the scope of the claims. For example, similar to the first embodiment, a metal film that serves as an underlayer for the external electrodes is formed after degreasing, and then the underlayer for the external electrodes is sintered simultaneously with the firing of the dielectric portion by strong reduction firing. In the external electrode formation step, the underlayer for the external electrodes is plated to form the final external electrodes.

[0078] (Unfired cover material preparation step (S2)) As described above, in the green cover material preparation step (S2) of the first embodiment, an additive is added, which includes at least one element selected from the group consisting of Cu, Au, Ag, Al, Ir, and W, preferably Cu, but this addition is omitted in the green cover material preparation step (S2) of the second embodiment. In all other respects, this step is the same as the green cover material preparation step (S2) of the first embodiment.

[0079] (Unfired internal electrode material preparation process (S3)) Meanwhile, in the unsintered internal electrode material preparation step (S3), a metal paste is prepared by adding at least one element selected from the group consisting of Cu, Au, Ag, Al, Ir, and W to a metal that is the main component of the unsintered internal electrode material, for example, a base metal such as Ni or Sn, or an alloy containing these. Of these elements, Cu is preferred because of its high thermal conductivity and low cost. To promote diffusion into the cover, it is preferable to use copper oxide (CuO or CuO) powder with a particle size of 500 nm or less, but this is not limiting; surface-oxidized copper (Cu) powder or Cu resinate may also be used.

[0080] Instead of adding metal of an element containing one or more selected from the group consisting of Cu, Au, Ag, Al, Ir, and W to the metal paste, it may be formed on the ceramic green sheets by sputtering in the lamination step (S4). When sputtering is used, the same target of Ni and Cu / CuO / CuO may be used, or the respective targets may be sputtered simultaneously. For example, after printing Ni paste, metal of the above elements such as Cu / CuO / Cu may be deposited on the metal pattern of the Ni paste by a sputtering method or the like. In the second embodiment, an element containing one or more selected from the group consisting of Cu, Au, Ag, Al, Ir, and W is added to all of the unsintered internal electrode materials to be laminated in the lamination step (S4).

[0081] The elements added to the unsintered internal electrode material, including one or more selected from the group consisting of Cu, Au, Ag, Al, Ir, and W, diffuse into adjacent layers in the firing step (S6).

[0082] By adding the above-mentioned elements, after the firing step (S6), the cover layer 13 contains, in a metallic state, one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W, and the number of atoms of the element is 0.002 to 0.15 per 100 atoms of the B-site elements of the compound represented by the general formula ABO3. Therefore, a highly reliable multilayer ceramic capacitor 100 can be obtained, which has excellent moisture resistance and is free from electrical defects such as leakage current. In other words, in the unsintered internal electrode material preparation step (S3), the amount of the predetermined element added to the unsintered internal electrode material can be set so as to obtain the above-mentioned multilayer ceramic capacitor 100 configuration in which the cover layer 13 contains a predetermined amount of the predetermined element in a metallic state.

[0083] The amount of elements including one or more selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the unsintered internal electrode material may be an amount that results in a ratio of 0.1 to 10.0 atoms per 100 atoms of the main component elements of the unsintered internal electrode material. The ratio of the atoms per 100 atoms of the main component elements may be preferably 0.5 to 5.0, more preferably 1.0 to 3.0. By setting the ratio of the atoms per 100 atoms of the main component elements to 0.1 or more, the moisture resistance of the cover layer 13 and, ultimately, the moisture resistance of the multilayer ceramic capacitor 100 itself can be improved. By setting the ratio of the atoms per 100 atoms of the Ni atoms to 10.0 or less, electrical defects such as leakage current can be prevented. Therefore, a highly reliable multilayer ceramic capacitor 100 can be obtained.

[0084] When the main component of the unsintered internal electrode material is Ni and the element containing one or more selected from the group consisting of Cu, Au, Ag, Al, Ir, and W is Cu, the number of Cu atoms per 100 Ni atoms is 0.3 or more and 8.0 or less.

[0085] Other points are the same as the unsintered internal electrode material preparation step (S3) in the first embodiment.

[0086] (Firing process (S6)) As described above, in the manufacturing method of the second embodiment, one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W are added in the preparation step (S3) of the unsintered internal electrode material, and it is preferable to sufficiently diffuse the elements from the internal electrode layer 12 to the cover layer 13. For this purpose, in the firing step (S6) in the second embodiment, a pre-firing step (weak reduction firing step, S6a) is performed before the firing step (S6) in the first embodiment, i.e., the main firing step.

[0087] =Pre-firing step (weak reduction firing step, S6a)= The laminate obtained through the singulation step (S5) is first fired in a weakly reducing atmosphere with a hydrogen concentration of 0.01% by volume to 0.08% by volume, preferably 0.02% by volume to 0.05% by volume. The firing temperature in the pre-firing step (S6a) is lower than the firing temperature in the main firing step (S6b), and may be preferably 600°C to 950°C, more preferably 700°C to 900°C, and even more preferably 750°C to 850°C. The firing time in the pre-firing step (S6a) may be 10 minutes to 2 hours.

[0088] By performing the pre-firing step (S6a), one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W contained in the unsintered internal electrode material can be diffused into the cover layer 13.

[0089] = Main firing step (strong reduction firing step, S6b) = This is the same as the firing step (S6) in the manufacturing method of the first embodiment.

[0090] It is preferable that the above pre-firing step (S6a) and main firing step (S6b) are carried out consecutively, i.e., without removing the individualized molded body from the firing furnace, by changing the hydrogen concentration in the firing furnace and the temperature of the firing furnace.

[0091] <Third embodiment> The manufacturing method of the third embodiment, like the second embodiment, includes adding one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W to the unsintered internal electrode material for forming the internal electrode layer 12, but includes adding one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W only to the unsintered internal electrode material for forming the internal electrode layer closer to the cover layer.

[0092] As a modification of the third embodiment, the internal electrode layer closer to the cover layer can be used as a dummy electrode, and only this dummy electrode can be doped with one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W. The dummy electrodes refer to two of the internal electrode layers that are adjacent to each other via a dielectric layer and connected to the same external electrode, and since no potential difference occurs between the two dummy electrodes, they do not contribute to capacitance.

[0093] In the third embodiment, one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W are added in the preparation step (S3) of the unsintered internal electrode material, and one or more elements are not added. Then, in the lamination step (S4), one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W are added only to the internal electrode layer of the unsintered internal electrode material closer to the cover layer, or in a modified example, the internal electrode layer closer to the cover layer becomes a dummy electrode, and one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W are added to the dummy electrode, and the laminated order is determined to produce the laminated material.

[0094] In addition, since the predetermined elements such as Cu are added in the preparation step (S3) of the unsintered internal electrode material, the firing step (S6) includes a pre-firing step (weak reduction firing step, S6a) and a main firing step (strong reduction firing step, S6b), which is the same as in the second embodiment, and other points are the same as in the first embodiment. Figure 6 is a flowchart showing a manufacturing method according to the third embodiment.

[0095] While the manufacturing methods according to the first to third embodiments have been specifically described above, in the present disclosure, manufacturing methods other than those of the above embodiments are also possible as long as a multilayer ceramic capacitor can be obtained in which the cover layer contains a perovskite compound represented by the general formula ABO3 and contains one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in a metallic state, and the number of atoms of the above elements is 0.002 to 0.15 per 100 atoms of the above B-site elements. For example, the above elements may be added to any layer of the unsintered internal electrode material laminated in the lamination step (S4). [Example]

[0096] The present disclosure will be described in more detail below based on examples.

[0097] <Measurement and evaluation> (Measurement of Cu and Mn content in cover layer, etc.) The fabricated multilayer ceramic capacitor was polished from the external electrode side toward the center (along the X-axis direction) to expose the cross section. Then, elemental analysis was performed on the center of one of the cover layers in the Z-axis direction using laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), and the number of Cu atoms per 100 Ti atoms and the number of Mn atoms per 100 Ti atoms were calculated. The Cu content in the internal electrode layer was also measured and calculated in the same manner as above.

[0098] (Evaluation of moisture resistance) A voltage of 6.3 V was applied to the fabricated multilayer ceramic capacitors for 500 hours in an environment of 40°C temperature and 90% RH, and then the insulation resistance was measured using an LCR meter (HP4284A manufactured by Keysight Technologies). The insulation resistance was measured after leaving the capacitors at room temperature (25°C) and 40% RH humidity for 24 hours. An insulation resistance of 500 MΩ or more after 500 hours of voltage application was marked "Good", and an insulation resistance of less than 500 MΩ was marked "Poor".

[0099] (Leakage current measurement) A voltage of 9 V was applied to the fabricated multilayer ceramic capacitor at 125° C., and the current value was measured using an ammeter (ADCMT 5450).

[0100] (Capacitance measurement) The fabricated multilayer ceramic capacitor was left at 150°C for 1 hour, and then left under standard conditions (temperature 25°C, 1 atmosphere) for 24 hours, after which the capacitance was measured using the above LCR meter under conditions of a voltage of 0.5 V and a frequency of 1 kHz.

[0101] [1. Example of adding Cu to ceramic slurry for creating cover layer] (Example 1-1) A ceramic slurry for creating a cover layer was prepared, with barium titanate as the main component. Cu was added to the ceramic slurry so that the ratio of Cu atoms to Ti atoms was 0.5 per 100, and Mn was added so that the ratio of Mn atoms to Ti atoms was 0.5 per 100. Cu was added in the form of oxide (CuO), and Mn was added in the form of carbonate (MnCO3). A cover sheet for the cover layer was created from the ceramic slurry.

[0102] Ni paste was printed on a dielectric green sheet that would become a dielectric layer composed primarily of barium titanate. Five hundred of the Ni paste-printed dielectric green sheets were stacked to obtain a laminate, and a cover sheet was placed on each outer side of the laminate in the stacking direction, followed by cutting to a specified size to obtain a compact. The obtained compact was subjected to a binder removal treatment in an N2 atmosphere, and then nickel paste that would become the base layer of the external electrodes was applied by dipping to obtain a compact (unfired compact).

[0103] The resulting compact was placed in a furnace with an atmosphere of 0.1% H2 by volume and 99.9% N2. The furnace temperature (firing temperature) was raised to 1150°C at a rate of 20,000°C / h, and the compact was fired for 10 minutes. After that, the base layer of the external electrodes was plated, yielding a multilayer ceramic capacitor (MLCC) with approximate dimensions of 1.0mm x 0.5mm x 0.5mm. Based on the firing conditions, it was estimated that the Cu in the cover layer was in a metallic state, more specifically, in the form of elemental Cu. The Cu and Mn contents in the cover layer were measured as described above, and the above-mentioned evaluations were also performed.

[0104] (Example 1-2) A multilayer ceramic capacitor was fabricated in the same manner as in Example 1-1, except that the amount of Cu added to the ceramic slurry for forming the cover layer was 2.0 atoms relative to 100 Ti atoms, and the amount of Mn added was 0.5 atoms relative to 100 Ti atoms.

[0105] (Examples 1-3) A multilayer ceramic capacitor was fabricated in the same manner as in Example 1-1, except that the amount of Cu added to the ceramic slurry for forming the cover layer was 2.0 atoms relative to 100 Ti atoms, and the amount of Mn added was 1.5 atoms relative to 100 Ti atoms.

[0106] (Examples 1-4) A multilayer ceramic capacitor was fabricated in the same manner as in Example 1-1, except that the amount of Cu added to the ceramic slurry for forming the cover layer was 4.0 atoms relative to 100 Ti atoms, and the amount of Mn added was 0.5 atoms relative to 100 Ti atoms.

[0107] (Examples 1-5) A multilayer ceramic capacitor was fabricated in the same manner as in Example 1-1, except that the amount of Cu added to the ceramic slurry for forming the cover layer was 2.0 atoms relative to 100 Ti atoms, and the amount of Mn added was 0.2 atoms relative to 100 Ti atoms.

[0108] (Examples 1 to 6) A multilayer ceramic capacitor was fabricated in the same manner as in Example 1-1, except that the amount of Cu added to the ceramic slurry for forming the cover layer was 1.0 atomic number relative to 100 Ti atoms, and the amount of Mn added was 0.5 atomic number relative to 100 Ti atoms.

[0109] (Examples 1-7) A multilayer ceramic capacitor was fabricated in the same manner as in Example 1-1, except that the amount of Cu added to the ceramic slurry for forming the cover layer was 3.0 atoms relative to 100 Ti atoms, and the amount of Mn added was 0.5 atoms relative to 100 Ti atoms.

[0110] (Examples 1-8) A multilayer ceramic capacitor was fabricated in the same manner as in Example 1-1, except that the amount of Cu added to the ceramic slurry for forming the cover layer was 2.0 atoms relative to 100 Ti atoms, and the amount of Mn added was 3.0 atoms relative to 100 Ti atoms.

[0111] (Comparative Example 1-1) A multilayer ceramic capacitor was fabricated in the same manner as in Example 1-1, except that the amount of Cu added to the ceramic slurry for forming the cover layer was 0.3 atoms relative to 100 Ti atoms, and the amount of Mn added was 0.5 atoms relative to 100 Ti atoms.

[0112] (Comparative Example 1-2) A multilayer ceramic capacitor was fabricated in the same manner as in Example 1-1, except that the amount of Cu added to the ceramic slurry for forming the cover layer was 5.0 atoms relative to 100 Ti atoms, and the amount of Mn added was 0.5 atoms relative to 100 Ti atoms.

[0113] (Comparative Examples 1-3) A multilayer ceramic capacitor was fabricated in the same manner as in Example 1-1, except that the amount of Cu added to the ceramic slurry for forming the cover layer was 2.0 in terms of the number of Ti atoms per 100, the amount of Mn added was 0.5 in terms of the number of Ti atoms per 100, and the H concentration in the atmosphere during firing was 0.03% by volume. In this example, it was estimated from the firing conditions that Cu in the cover layer was present in the form of an oxide.

[0114] (Comparative Examples 1-4) A multilayer ceramic capacitor was fabricated in the same manner as in Example 1-1, except that Cu was not added to the ceramic slurry for forming the cover layer, and Mn was added so that the number of atoms was 0.5 relative to 100 Ti atoms.

[0115] Table 1 summarizes the preparation conditions and evaluation results for each example.

[0116] [Table 1]

[0117] The leakage current of the multilayer ceramic capacitor may be suppressed to preferably 1500 μA or less, more preferably 1000 μA or less, even more preferably 800 μA or less, and even more preferably 500 μA or less.

[0118] The capacitance of the multilayer ceramic capacitor may be preferably 15 μF or more, more preferably 17 μF or more, even more preferably 20 μF or more, and even more preferably 21 μF or more.

[0119] Table 1 shows that in Examples 1-1 to 1-8, in which the Cu in the cover layer was present in a metallic state in an amount ranging from 0.002 to 0.15 relative to 100 Ti atoms, multilayer ceramic capacitors with excellent moisture resistance and reduced leakage current were obtained, even at lower firing temperatures. Furthermore, in the multilayer ceramic capacitors of Examples 1-1 to 1-7, in which the Mn content in the cover layer was 1.2 or less relative to 100 Ti atoms, the capacitance was sufficiently maintained (a capacitance of 20 μF or more). However, the capacitances of Examples 1-3, 1-4, and 1-7 were somewhat low. The capacitance of Example 1-3 was likely influenced by the slightly high Mn content in the cover layer, while the capacitance of Examples 1-4 and 1-7 was likely influenced by the slightly high Cu content in the cover layer, resulting in a slight increase in leakage current. On the other hand, in Comparative Examples 1-1 to 1-4, no multilayer ceramic capacitors exhibiting both good moisture resistance and leakage current suppression effect were obtained.

[0120] [2. Example of adding Cu to paste for forming internal electrode layers that corresponds to all internal electrode layers] Example 2-1 A ceramic slurry for creating a cover layer was prepared, with barium titanate as the main component. Mn was added to the ceramic slurry for creating the cover layer so that the ratio of Mn atoms to Ti atoms was 0.5 per 100. The Mn was added in the form of carbonate (MnCO3). A cover sheet was produced from this ceramic slurry. Furthermore, in preparing a metal paste for forming internal electrodes, Cu-containing Ni paste was prepared by adding Cu atoms to Ni atoms at a ratio of 1.0 per 100.

[0121] The Cu-containing Ni paste was printed on a dielectric green sheet that would become a dielectric layer primarily composed of barium titanate. Five hundred dielectric green sheets with the Cu-containing Ni paste printed on them were stacked to obtain a laminate, and a cover sheet was placed on each outer side of the laminate in the stacking direction, followed by cutting to a predetermined size to obtain a compact. The resulting compact was debindered in an N2 atmosphere, and then nickel paste that would become the base layer of the external electrodes was applied by dipping to obtain a compact (unfired compact).

[0122] The resulting compact was placed in a furnace containing 0.03% H2 by volume and 99.97% N2 by volume. The furnace temperature (firing temperature) was increased to 900°C and fired for 10 minutes (weak reduction firing). The atmosphere was then switched to 0.1% H2 by volume and 99.9% N2 by volume. The furnace temperature was increased to 1150°C at a heating rate of 20,000°C / h and fired for 10 minutes (strong reduction firing). Subsequently, the base layer of the external electrodes was plated to obtain a multilayer ceramic capacitor (MLCC) measuring approximately 1.0 mm x 0.5 mm x 0.5 mm. Based on the firing conditions, it was estimated that the Cu in the cover layer was present in a metallic state, more specifically, as elemental Cu. The Cu and Mn contents in the cover layer were measured as described above, and the above-mentioned evaluations were also performed.

[0123] (Example 2-2) A multilayer ceramic capacitor was fabricated in the same manner as in Example 2-1, except that the amount of Cu added to the Ni paste that would become the internal electrode layer was set to 3.0 atoms relative to 100 Ni atoms, and the amount of Mn added to the ceramic slurry for creating the cover layer was set to 0.5 atoms relative to 100 Ti atoms.

[0124] (Example 2-3) A multilayer ceramic capacitor was fabricated in the same manner as in Example 2-1, except that the amount of Cu added to the Ni paste that would become the internal electrode layer was set to 3.0 atoms relative to 100 Ni atoms, and the amount of Mn added to the ceramic slurry for creating the cover layer was set to 1.5 atoms relative to 100 Ti atoms.

[0125] (Examples 2-4) A multilayer ceramic capacitor was fabricated in the same manner as in Example 2-1, except that the amount of Cu added to the Ni paste that would become the internal electrode layer was set to 5.0 atoms relative to 100 Ni atoms, and the amount of Mn added to the ceramic slurry for creating the cover layer was set to 0.5 atoms relative to 100 Ti atoms.

[0126] (Examples 2-5) A multilayer ceramic capacitor was fabricated in the same manner as in Example 2-1, except that the amount of Cu added to the Ni paste that would become the internal electrode layer was set to 3.0 atoms relative to 100 Ni atoms, and the amount of Mn added to the ceramic slurry for creating the cover layer was set to 0.2 atoms relative to 100 Ti atoms.

[0127] (Examples 2-6) A multilayer ceramic capacitor was fabricated in the same manner as in Example 2-1, except that the amount of Cu added to the Ni paste that would become the internal electrode layer was 1.5 atoms relative to 100 Ni atoms, and the amount of Mn added to the ceramic slurry for creating the cover layer was 0.5 atoms relative to 100 Ti atoms.

[0128] (Examples 2-7) A multilayer ceramic capacitor was fabricated in the same manner as in Example 2-1, except that the amount of Cu added to the Ni paste that would become the internal electrode layer was set to 4.0 atoms relative to 100 Ni atoms, and the amount of Mn added to the ceramic slurry for creating the cover layer was set to 0.5 atoms relative to 100 Ti atoms.

[0129] (Examples 2-8) A multilayer ceramic capacitor was fabricated in the same manner as in Example 2-1, except that the amount of Cu added to the Ni paste that would become the internal electrode layer was set to 3.0 atoms relative to 100 Ni atoms, and the amount of Mn added to the ceramic slurry for creating the cover layer was set to 3.0 atoms relative to 100 Ti atoms.

[0130] (Comparative Example 2-1) A multilayer ceramic capacitor was fabricated in the same manner as in Example 2-1, except that the amount of Cu added to the Ni paste that would become the internal electrode layer was set to 0.2 atoms relative to 100 Ni atoms, and the amount of Mn added to the ceramic slurry for creating the cover layer was set to 0.5 atoms relative to 100 Ti atoms.

[0131] (Comparative Example 2-2) A multilayer ceramic capacitor was fabricated in the same manner as in Example 2-1, except that the amount of Cu added to the Ni paste that would become the internal electrode layer was 10 atoms relative to 100 Ni atoms, and the amount of Mn added to the ceramic slurry for creating the cover layer was 0.5 atoms relative to 100 Ti atoms.

[0132] (Comparative Example 2-3) A multilayer ceramic capacitor was fabricated in the same manner as in Example 2-1, except that the amount of Cu added to the Ni paste that would become the internal electrode layer was set to 3.0 atoms relative to 100 Ni atoms, the amount of Mn added to the ceramic slurry for creating the cover layer was set to 3.0 atoms relative to 100 Ti atoms, and the H concentration in the atmosphere during weak reduction firing was set to 0.10 volume %.

[0133] (Comparative Example 2-4) A multilayer ceramic capacitor was fabricated in the same manner as in Example 2-1, except that the amount of Cu added to the Ni paste that would become the internal electrode layers was 3.0 atoms relative to 100 Ni atoms, the amount of Mn added to the ceramic slurry for creating the cover layer was 0.5 atoms relative to 100 Ti atoms, and the H concentration in the atmosphere during strong reduction firing was 0.03 volume %. In this example, it was estimated from the firing conditions that Cu in the cover layer was present in the form of an oxide.

[0134] (Comparative Example 2-5) A multilayer ceramic capacitor was fabricated in the same manner as in Example 2-1, except that Cu was not added to the Ni paste that would become the internal electrode layer, and the amount of Mn added to the ceramic slurry for creating the cover layer was set to 0.5 atoms relative to 100 Ti atoms.

[0135] Table 2 summarizes the preparation conditions and evaluation results for each example.

[0136] [Table 2]

[0137] Table 2 shows that in Examples 2-1 to 2-8, in which the Cu in the cover layer was present in a metallic state with a ratio of Cu atoms per 100 Ti atoms between 0.002 and 0.15, multilayer ceramic capacitors with excellent moisture resistance and suppressed leakage current were obtained. Furthermore, in the multilayer ceramic capacitors of Examples 2-1 to 2-7, in which the Mn content in the cover layer was 1.2 or less per 100 Ti atoms, sufficient capacitance was maintained. However, in Examples 2-3, 2-4, and 2-7, the capacitance was somewhat low. This was likely due to the slightly high Mn content in the cover layer in Example 2-3, and the slight increase in leakage current due to the slightly high Cu content in the cover layer in Examples 2-4 and 2-7. On the other hand, in Comparative Examples 2-1 to 2-6, multilayer ceramic capacitors exhibiting both excellent moisture resistance and leakage current suppression were not obtained.

[0138] = Cu concentration in the outermost layer and center of the internal electrode layer = Table 3 shows the Cu content in the outermost internal electrode layer in the stacking direction and the Cu content in the central internal electrode in the stacking direction for some of the samples listed in Tables 1 and 2. In Example 1-4, in which Cu was added to the ceramic slurry for forming the cover layer, the Cu content in the outermost internal electrode layer in the stacking direction was more than twice the Cu content in the central internal electrode in the stacking direction. Furthermore, in Example 1-1, Cu diffusion from the cover layer was observed up to the outermost internal electrode layer, but it was below the detection limit in the central internal electrode layer, indicating that Cu was essentially absent in the central portion. Conversely, in Example 2-4, in which Cu was added to the paste material for the internal electrode, the Cu content in the central internal electrode in the stacking direction was 1.1 times the Cu content in the outermost internal electrode layer in the stacking direction, and in Example 2-1, it was 4 times the Cu content. This is thought to be because, even though the Cu content in the internal electrode layers is equal in each layer of the internal electrode layers before diffusion occurs, diffusion into the cover layer occurs during firing, so that in the internal electrode layers adjacent to the cover layer, the amount of Cu diffused into the cover layer increases and the amount of remaining Cu decreases significantly, whereas in the central internal electrode layers not adjacent to the cover layer, there is almost no diffusion into the cover layer, so most of the Cu remains close to the initial value.

[0139] [Table 3]

[0140] [3. Example of adding Cu only to the paste for forming the internal electrode layers that will become the top and bottom layers] Example 3-1 A ceramic slurry for creating a cover layer was prepared, primarily composed of barium titanate. Mn was added to the ceramic slurry for creating the cover layer so that the ratio of Mn atoms to Ti atoms was 0.5 per 100. The Mn was added in the form of carbonate (MnCO3). A cover sheet was produced from this ceramic slurry. Furthermore, in preparing the metal paste for forming the internal electrodes, Cu-containing Ni paste was prepared by adding Cu to Ni atoms so that the ratio was 1.0 per 100. A Cu-free Ni paste was also prepared without adding Cu.

[0141] The Cu-containing Ni paste and the Cu-free Ni paste were printed on dielectric green sheets, each of which would become a dielectric layer primarily composed of barium titanate. 498 dielectric green sheets printed with the Cu-free Ni paste were stacked, and a dielectric green sheet printed with the Cu-containing paste was stacked on top of and below them, to obtain a laminate. Cover sheets were placed on the outer sides of the laminate in the stacking direction, and the laminate was cut to a specified size to obtain a compact. The resulting compact was debindered in an N2 atmosphere, and then a nickel paste, which would become the base layer of the external electrodes, was applied by dipping to obtain a compact (unfired compact).

[0142] The resulting compact was placed in a furnace containing 0.03% H2 by volume and 99.97% N2 by volume. The furnace temperature (firing temperature) was increased to 900°C and fired for 10 minutes (weak reduction firing). The atmosphere was then switched to 0.1% H2 by volume and 99.9% N2 by volume. The furnace temperature was increased to 1150°C at a heating rate of 20,000°C / h and fired for 10 minutes (strong reduction firing). The outer electrode underlayer was then plated to obtain a multilayer ceramic capacitor (MLCC) measuring approximately 1.0 mm x 0.5 mm x 0.5 mm. Based on the firing conditions, it was estimated that the Cu in the cover layer was present in a metallic state, more specifically, as elemental Cu. The Cu and Mn contents in the cover layer were measured as described above, and the above-mentioned evaluations were also performed.

[0143] (Example 3-2) A multilayer ceramic capacitor was fabricated in the same manner as in Example 3-1, except that in preparing the Cu-containing Ni paste, the amount of Cu added was adjusted so that the number of atoms was 3.0 relative to the number of atoms of Ni, 100.

[0144] (Example 3-3) A multilayer ceramic capacitor was fabricated in the same manner as in Example 3-1, except that in preparing the Cu-containing Ni paste, the amount of Cu added was adjusted to 5.0 atoms relative to 100 atoms of Ni.

[0145] (Comparative Example 3-1) A multilayer ceramic capacitor was fabricated in the same manner as in Example 3-1, except that in preparing the Cu-containing Ni paste, the amount of Cu added was adjusted to 0.2 atoms per 100 atoms of Ni.

[0146] (Comparative Example 3-2) A multilayer ceramic capacitor was fabricated in the same manner as in Example 3-1, except that in preparing the Cu-containing Ni paste, the amount of Cu added was set to 10 atoms per 100 atoms of Ni.

[0147] (Comparative Example 3-3) A multilayer ceramic capacitor was produced in the same manner as in Example 3-1, except that Cu was not added to the Ni paste, that is, only a Cu-free Ni paste was used as the paste for forming the internal electrode layers.

[0148] Table 4 summarizes the preparation conditions and evaluation results for each example.

[0149] [Table 4]

[0150] From Table 4, it can be seen that even in the case where Cu is added only to the paste for forming the internal electrode layers that become the top and bottom layers, a multilayer ceramic capacitor having excellent moisture resistance and suppressed leakage current can be obtained, as in Examples 3-1 to 3-3, where the Cu in the cover layer is in an amount within the range of 0.002 to 0.15 inclusive per 100 Ti atoms and exists in a metallic state.

[0151] Although the embodiments have been described in detail above, the present disclosure is not limited to the above embodiments. Furthermore, the above embodiments can be subject to various changes, modifications, substitutions, additions, deletions, and combinations within the scope of the claims.

[0152] Aspects of the present disclosure are, for example, as follows.

[0153] <1> a capacitance section in which dielectric layers and internal electrode layers are alternately stacked; a cover layer disposed on the outer side of the capacitance section in the stacking direction, the cover layer contains a perovskite compound represented by the general formula ABO3 and contains one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in a metallic state; The number of atoms of the element is 0.002 or more and 0.15 or less relative to 100, the number of atoms of the B-site element in the general formula.

[0154] <2> There are a plurality of the internal electrode layers, and among the plurality of internal electrode layers, a concentration of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in an internal electrode layer adjacent to the cover layer is higher than a concentration of the element in an internal electrode layer at a center in the stacking direction. <1> The multilayer ceramic capacitor according to claim 1.

[0155] <3> The concentration of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the internal electrode layer adjacent to the cover layer is 1.2 times or more the concentration of the element in the internal electrode layer at the center in the stacking direction. <2> The multilayer ceramic capacitor according to claim 1.

[0156] <4> One or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W are substantially absent in the internal electrode layer at the center in the lamination direction. <2> The multilayer ceramic capacitor according to claim 1.

[0157] <5> There are a plurality of the internal electrode layers, and among the plurality of internal electrode layers, a concentration of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in an internal electrode layer adjacent to the cover layer is lower than a concentration of the element in an internal electrode layer at a center in the stacking direction. <1> The multilayer ceramic capacitor according to claim 1.

[0158] <6> The concentration of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the internal electrode layer adjacent to the cover layer is 1.1 times or more the concentration of the element in the internal electrode layer at the center in the stacking direction. <5> The multilayer ceramic capacitor according to claim 1.

[0159] <7> One or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W are substantially absent in the internal electrode layer at the center in the lamination direction. <5> The multilayer ceramic capacitor according to claim 1.

[0160] <8> the number of Mn atoms in the cover layer relative to 100 atoms of the B-site elements is 1.2 or less; <1> or <2> The multilayer ceramic capacitor according to claim 1.

[0161] <9> The cover layer includes metallic Cu. <1> or <2> or <5> The multilayer ceramic capacitor according to claim 1.

[0162] <10> The perovskite compound contained in the cover layer includes barium titanate. <1> or <2> or <5> The multilayer ceramic capacitor according to claim 1.

[0163] <11> A method for manufacturing a multilayer ceramic capacitor, comprising: a capacitance section in which dielectric layers and internal electrode layers are alternately laminated; and a cover layer disposed on an outer side of the capacitance section in a lamination direction, the cover layer containing a perovskite compound represented by a general formula ABO3, a lamination step of alternately laminating unsintered dielectric materials to become the dielectric layers and unsintered internal electrode materials to become the internal electrode layers, and further arranging an unsintered cover material to become the cover layer, to obtain a laminate; a firing step of firing the laminate, the cover layer contains, after the firing step, one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in a metallic state, and the number of atoms of the elements is 0.002 or more and 0.15 or less relative to 100, the number of atoms of the B-site elements in the general formula.

[0164] <12> forming the green cover material to include one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W; <11> The manufacturing method described in

[0165] <13> As the unsintered internal electrode material, a first internal electrode material formed so as to contain one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W, and a second internal electrode material formed so as not to contain an element selected from the group consisting of Cu, Au, Ag, Al, Ir, and W are prepared; forming an uppermost and / or lowermost internal electrode layer in the stacking direction from the first internal electrode material, and forming a central internal electrode layer in the stacking direction from the second internal electrode material, <11> The manufacturing method described in

[0166] <14> preparing a first internal electrode material formed to contain one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W as the unsintered internal electrode material, and forming all of the internal electrode layers using the first internal electrode material; <11> The manufacturing method described in

[0167] <15> The firing step is carried out at 1200°C or less. <11> from <14> 1. The manufacturing method according to any one of the preceding claims.

[0168] <16> The firing step includes a main firing step performed at 900 ° C. or higher and 1270 ° C. or lower in an atmosphere with an H concentration of 0.08 vol.% or higher and 1.0 vol.% or lower, <12> The manufacturing method described in

[0169] <17> The firing step includes: A pre-baking process performed at 950°C or less in an atmosphere with a H2 concentration of 0.01% by volume or more and 0.08% by volume or less; A firing process is carried out at 900 ° C or higher and 1270 ° C or lower in an atmosphere with an H concentration of 0.08 vol% or higher and 1.0 vol% or lower, <13> or <14> The manufacturing method described in [Explanation of symbols]

[0170] 10 Base 10a First side 10b Second side 11 Dielectric layer 12 Internal electrode layer 12a 1st internal electrode layer 12b Second internal electrode layer 13 Cover Layer 13a Upper cover layer 13b Lower cover layer 14 Capacity part 15a First End Margin 15b Second End Margin 16 Side Margin 20a 1st external electrode 20b 2nd external electrode 100 Multilayer ceramic capacitors

Claims

1. a capacitance section in which dielectric layers and internal electrode layers are alternately stacked; a cover layer disposed on the outer side of the capacitance section in the stacking direction, The cover layer may be a compound of the general formula ABO ３ and containing, in a metallic state, one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W, The number of atoms of the element is 0.002 or more and 0.15 or less relative to 100, the number of atoms of the B-site element in the general formula.

2. 2. The multilayer ceramic capacitor according to claim 1, wherein the internal electrode layers include a plurality of internal electrode layers, and a concentration of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in an internal electrode layer adjacent to the cover layer among the plurality of internal electrode layers is higher than a concentration of the element in an internal electrode layer at a center in the stacking direction.

3. 3. The multilayer ceramic capacitor according to claim 2, wherein a concentration of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the internal electrode layers adjacent to the cover layers is 1.2 times or more higher than a concentration of the element in the internal electrode layer at a center in the stacking direction.

4. 3. The multilayer ceramic capacitor according to claim 2, wherein the internal electrode layer at the center in the stacking direction is substantially free of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W.

5. 2. The multilayer ceramic capacitor according to claim 1, wherein the internal electrode layers are plural, and a concentration of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in an internal electrode layer adjacent to the cover layer among the plural internal electrode layers is lower than a concentration of the element in an internal electrode layer at a center in the stacking direction.

6. 6. The multilayer ceramic capacitor according to claim 5, wherein a concentration of one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in the internal electrode layers adjacent to the cover layers is 1.1 times or more of a concentration of the element in the internal electrode layer at a center in the stacking direction.

7. 6. The multilayer ceramic capacitor according to claim 5, wherein one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W are substantially absent in the internal electrode layer at the center in the stacking direction.

8. 6. The multilayer ceramic capacitor according to claim 1, wherein the number of Mn atoms per 100 atoms of the B-site elements in the cover layer is 1.2 or less.

9. 6. The multilayer ceramic capacitor according to claim 1, wherein the cover layer contains metallic Cu.

10. 6. The multilayer ceramic capacitor according to claim 1, wherein the perovskite compound contained in the cover layer includes barium titanate.

11. The capacitor has a capacitor portion in which dielectric layers and internal electrode layers are alternately stacked, and a cover layer disposed on the outer side of the capacitor portion in the stacking direction, and the cover layer is represented by the general formula ABO ３ A method for producing a multilayer ceramic capacitor containing a perovskite compound represented by the formula: a lamination step of alternately laminating unsintered dielectric materials to become the dielectric layers and unsintered internal electrode materials to become the internal electrode layers, and further arranging an unsintered cover material to become the cover layer, to obtain a laminate; a firing step of firing the laminate, the cover layer contains, after the firing step, one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W in a metallic state, and the number of atoms of the elements is 0.002 or more and 0.15 or less relative to 100, the number of atoms of B-site elements in the general formula.

12. The method of claim 11 , comprising forming the green cover material to include one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W.

13. As the unsintered internal electrode material, a first internal electrode material formed so as to contain one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W, and a second internal electrode material formed so as not to contain an element selected from the group consisting of Cu, Au, Ag, Al, Ir, and W are prepared; 12. The manufacturing method according to claim 11, comprising forming an uppermost and / or lowermost internal electrode layer in the stacking direction from the first internal electrode material, and forming a central internal electrode layer in the stacking direction from the second internal electrode material.

14. 12. The manufacturing method according to claim 11, comprising preparing a first internal electrode material formed to contain one or more elements selected from the group consisting of Cu, Au, Ag, Al, Ir, and W as the unsintered internal electrode material, and forming all of the internal electrode layers using the first internal electrode material.

15. The method according to any one of claims 11 to 14, wherein the firing step is carried out at 1270°C or less.

16. The firing step is performed at 900°C or higher and 1270°C or lower. ２ The method according to claim 12 , further comprising a firing step carried out in an atmosphere having a concentration of 0.08% by volume or more and 1.0% by volume or less.

17. The firing step includes: At 950°C or less, H ２ a pre-baking step performed in an atmosphere having a concentration of 0.01% by volume or more and 0.08% by volume or less; At 900°C or higher and 1270°C or lower, H ２ and a main firing step performed in an atmosphere having a concentration of 0.08% by volume or more and 1.0% by volume or less.

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