Multilayer capacitor

Abstract

To provide a multilayer capacitor capable of simultaneously and excellently implementing an effective dielectric constant (DC, a high frequency, a low electric field, etc.), reliability (high temperature / a moisture resistance load), and temperature (high temperature) characteristics.SOLUTION: A multilayer capacitor includes: a capacitor body including a dielectric layer and an internal electrode; and an external electrode disposed outside of the capacitor body. The dielectric layer includes a plurality of dielectric crystal grains. The dielectric crystal grains have a cube shape and include a core containing a barium (Ba) titanium (Ti) oxide.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventional multilayer ceramic capacitors (MLCCs) have mainly been high-capacity products with a high nominal dielectric constant. Therefore, it has been required to increase the size of dielectric crystal grains obtained by sintering BaTiO3, which is a dielectric material, in order to ensure a high dielectric constant.

[0003] On the other hand, recently, in the MLCC industry, as end products become smaller and more high-performance, ensuring the effective dielectric constant (DC, high frequency, low electric field, etc.) has become more important than simply ensuring a high dielectric constant. It is necessary to develop technologies in the direction of controlling the overall microstructure including the size and composition of dielectric crystal grains in the thinned dielectric layer to simultaneously achieve excellent effective dielectric constant (DC, high frequency, low electric field, etc.), reliability (high temperature / humidity load), and temperature characteristics.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, one problem of the present invention is to provide a multilayer capacitor capable of simultaneously achieving excellent effective dielectric constant (DC, high frequency, low electric field, etc.), reliability (high temperature / humidity load), and temperature (high temperature) characteristics.

Means for Solving the Problems

[0005] One embodiment of the present invention provides a multilayer capacitor including a capacitor body including a dielectric layer and internal electrodes; and external electrodes disposed outside the capacitor body, wherein the dielectric layer includes a plurality of dielectric crystal grains, the dielectric crystal grains have a cube form, and include a core containing barium (Ba) titanate (Ti) oxide.

[0006] The core surface of the dielectric crystal grains may predominantly exist as a (001) plane crystal face.

[0007] The average size of the dielectric crystal grains may be 160 nm or less.

[0008] The standard deviation of the size of the dielectric crystal grains may be 40 nm or less.

[0009] The core within the dielectric crystal grains may have an average size of 120 nm or less.

[0010] The standard deviation of the size of the core within the dielectric crystal grains may be 30 nm or less.

[0011] The average fraction of the core within the dielectric crystal grains may be 60% or more.

[0012] The multilayer capacitor may satisfy the following formula 1.

[0013] [Formula 1] D s / D avg ≧0.7 (% / nm) In the above formula 1, D s is the sintered relative density of the dielectric layer, and D avg is the average size of the dielectric crystal grains.

[0014] When the sintered relative density of the dielectric layer of the multilayer capacitor is 98%, the average size of the dielectric crystal grains may be 200 nm or less.

[0015] The dielectric crystal grains may further include a shell located on the core, and the shell may contain Dy, Mg, Mn, Tb, Sm, Si, Ba, Al, V, Nb, Sn, or a combination thereof.

[0016] The barium titanate may be represented by the following chemical formula 1.

[0017] [Chemical formula 1]

[0018] Ba (1-x) D1 x Ti (1-y) D2 y O3 In Chemical Formula 1, D1 is Ba, Dy, Tb, Sm, Nb, or a combination thereof, D2 is Mg, Mn, Si, Al, V, Dy, Tb, Sm, Sn, or a combination thereof, 0 ≦ x ≦ 0.3, and 0 ≦ y ≦ 0.3.

Advantages of the Invention

[0019] In the multilayer capacitor according to an embodiment of the present invention, by appropriately controlling the form of barium titanate-containing dielectric crystal grains, it is possible to simultaneously achieve excellent effective dielectric constant (DC, high frequency, low electric field, etc.), reliability (high temperature / humidity load), and temperature characteristics.

Brief Description of the Drawings

[0020]

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Mode for Carrying Out the Invention

[0021] Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement it. In the drawings, parts that are unnecessary for explanation for clearly explaining the present invention are omitted, and the same reference numerals are given to the same or similar components throughout the specification. Also, the accompanying drawings are merely for facilitating easy understanding of the embodiments disclosed in this specification, and the technical idea disclosed in this specification is not limited by the accompanying drawings, and it should be understood to include all modifications, equivalents, or alternatives included in the idea and technical scope of the present invention.

[0022] Terms including ordinals such as first, second, etc. can be used to describe various components, but the components are not limited by the terms. The terms are only used for the purpose of distinguishing one component from another.

[0023] When a component is referred to as being "coupled" or "connected" to another component, it should be understood that it can be directly coupled or connected to the other component, or opposed to it, or there can also be other components in between. In contrast, when a component is referred to as being "directly coupled" or "directly connected" to another component, it should be understood that there are no other components in between.

[0024] Throughout the specification, terms such as "including" or "having" are intended to specify the presence of the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should not be understood to preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof. Therefore, when a part "includes" a certain component, this means that it does not exclude other components and can further include other components unless there is a contrary description.

[0025] One embodiment of the present invention provides a multilayer capacitor including a capacitor body including a dielectric layer and internal electrodes; and external electrodes disposed outside the capacitor body, the dielectric layer including a plurality of dielectric crystallites having a cube form and including a core containing barium titanate oxide.

[0026] FIG. 1 is a perspective view showing a multilayer capacitor 100 according to an embodiment, FIG. 2 is a cross-sectional view of the multilayer capacitor 100 taken along line I-I' of FIG. 1, and FIG. 3 is an exploded perspective view showing the laminated structure of the internal electrodes in the capacitor body 110 of FIG. 1.

[0027] To define the directions for clearly explaining this embodiment, the L-axis, W-axis, and T-axis shown in the drawings respectively indicate the length direction, width direction, and thickness direction of the capacitor body 110. Here, the thickness direction (T-axis direction) may be perpendicular to the wide surface (peripheral surface) of the sheet-shaped component. As an example, it can be used as the same concept as the stacking direction in which the dielectric layer 111 is stacked. The length direction (L-axis direction) can be approximately perpendicular to the thickness direction (T-axis direction) in a direction extending along the wide surface (peripheral surface) of the sheet-shaped component. As an example, it can be the direction in which the first external electrode 131 and the second external electrode 132 are located on both sides. The width direction (W-axis direction) may be approximately perpendicular to the thickness direction (T-axis direction) and the length direction (L-axis direction) in a direction extending along the wide surface (peripheral surface) of the sheet-shaped component. The length of the sheet-shaped component in the length direction (L-axis direction) may be even longer than the length in the width direction (W-axis direction).

[0028] Referring to FIGS. 1 to 3, the multilayer capacitor 100 according to this embodiment can include a capacitor body 110, and a first external electrode 131 and a second external electrode 132 disposed at both ends facing the length direction (L-axis direction) of the capacitor body 110.

[0029] The capacitor body 110 can be, for example, substantially hexahedral in shape.

[0030] In this example, for convenience of explanation, the two surfaces of the capacitor body 110 facing each other in the thickness direction (T-axis direction) are defined as the first surface and the second surface, the two surfaces connected to the first surface and the second surface and facing each other in the length direction (L-axis direction) are defined as the third surface and the fourth surface, the two surfaces connected to the first surface and the second surface, connected to the third surface and the fourth surface, and facing each other in the width direction (W-axis direction) are defined as the fifth surface and the sixth surface.

[0031] As an example, the first surface, which is the bottom surface, can be the surface facing the mounting direction. Also, the first to sixth surfaces may be flat, but the present embodiment is not limited thereto. For example, the first to sixth surfaces may be curved surfaces with a convex central portion, and the corner portions, which are the boundaries of the respective surfaces, may be rounded.

[0032] The shape, size of the capacitor body 110, and the number of stacked dielectric layers 111 are not limited to those shown in the drawings of the present embodiment.

[0033] The capacitor body 110 is formed by stacking a plurality of dielectric layers 111 in the thickness direction (T-axis direction) and then firing, and includes a first internal electrode 121 and a second internal electrode 122 that are alternately arranged in the thickness direction (T-axis direction) with a plurality of dielectric layers 111 interposed therebetween.

[0034] At this time, the boundaries between the respective adjacent dielectric layers 111 of the capacitor body 110 can be integrated to such an extent that it is difficult to confirm without using a scanning electron microscope (SEM).

[0035] Also, the capacitor body 110 can include an active region and cover regions 112 and 113.

[0036] The active region is a portion that contributes to the formation of the capacitance of the multilayer capacitor 100. As an example, the active region can be a region where the first internal electrode 121 or the second internal electrode 122 stacked along the thickness direction (T-axis direction) overlaps.

[0037] The cover regions 112 and 113 can be respectively positioned on the sides of the first surface and the second surface of the active region in the thickness direction (T-axis direction) as thickness direction margin portions. Such cover regions 112 and 113 can be formed by stacking a single dielectric layer 111 or two or more dielectric layers 111 on the upper surface and the lower surface of the active region, respectively.

[0038] Further, the capacitor body 110 can further include a side cover region. The side cover regions can be respectively positioned on the sides of the fifth and sixth surfaces of the active region in the width direction (W-axis direction) as width direction margin portions. Such side cover regions can be formed by applying a conductive paste layer for forming an internal electrode only to a partial region of the surface of a dielectric green sheet, laminating dielectric green sheets without applying the conductive paste layer to both side surfaces of the surface of the dielectric green sheet, and then firing.

[0039] The cover regions 112 and 113 and the side cover region serve to prevent damage to the first internal electrode 121 and the second internal electrode 122 due to physical or chemical stress.

[0040] Hereinafter, the dielectric crystal grains according to the present invention will be described in more detail.

[0041] The dielectric layer 111 according to the present invention includes a plurality of dielectric crystal grains 1111.

[0042] In the conventional multi-layered ceramic capacitor (MLCC), since high-capacity products with a high nominal dielectric constant were central, it was required to increase the size of dielectric crystal grains obtained by sintering barium titanate oxide, which is a dielectric material, to ensure a high dielectric constant. For this purpose, conventionally, the dielectric crystal grains usually included a spherical core.

[0043] On the other hand, recently, in the MLCC industry, as the final products become smaller and more high-performance, ensuring the effective dielectric constant (DC, high frequency, low electric field, etc.) has become more important than simply ensuring a high dielectric constant, and it has been required to control the overall microstructure including the size and composition of dielectric crystal grains in the thinned dielectric layer.

[0044] Therefore, as a result of repeated research on a method for equalizing the size and size distribution of dielectric crystal grains, the present inventor has found that it is important to control the form of the barium titanate oxide-containing core contained in the dielectric crystal grains, and has completed the present invention.

[0045] FIG. 4 is a conceptual diagram of the dielectric crystal grains and the dielectric layer according to the present invention.

[0046] FIG. 5 is a conceptual diagram of the core-shell structure of the dielectric crystal grains according to the present invention.

[0047] Referring to FIGS. 4 and 5, the dielectric crystal grains according to the present invention include a core containing barium (Ba) titanate (Ti) oxide, and at this time, the core has a cube form. This is a form that is clearly distinguished from the spherical or amorphous dielectric crystal grain cores that have been commonly used in the past.

[0048] Specifically, the conventional barium titanate oxide-based dielectric crystal grain cores exhibited a spherical shape, a shape similar to a sphere, or an amorphous shape.

[0049] More specifically, the dielectric crystal grain cores having a spherical or spherical-similar shape can be synthesized by a hydrothermal synthesis method using water as a reaction solvent during the production of barium titanate oxide. However, in the hydrothermal synthesis method, after forming a small-sized seed, heat and pressure are applied, Ostwald ripening occurs, and grain growth occurs, so that the particle size distribution of the dielectric crystal grains becomes large during the grain growth process.

[0050] In addition, the amorphous-shaped dielectric crystal grain cores can be synthesized by a dry high-phase compatibility method without using a solvent during the production of barium titanate oxide. However, the dry high-phase compatibility method is synthesized through an in-situ mechanism, and similarly, as grain growth occurs to increase the crystal grain size, the particle size distribution becomes larger.

[0051] That is, in the case of conventional spherical, spherical-like, or amorphous-shaped core-containing dielectric crystallites, when the crystallite size is increased to achieve a high dielectric constant, there has been a problem that the particle size distribution becomes excessively large and the effective dielectric constant or reliability decreases. Further, non-uniform grain growth has the problem of reducing the fraction of the core in the dielectric crystallites and degrading the dielectric constant improvement effect.

[0052] In contrast, the dielectric crystallites according to the present invention have a cube-shaped core. Dielectric crystallites having a cube-shaped core may have a (001) plane crystal plane dominant on the core surface. When the dielectric crystallite core surface is predominantly composed of the (001) plane, the surface energy is low and normal grain growth does not occur during the sintering process for manufacturing the dielectric layer. When face contact occurs between particles, the degree of suppression of grain growth further increases, and the size and size variation of the dielectric crystallites can be effectively reduced. Further, by reducing the size variation of the dielectric crystallites, the integration degree and density of the dielectric crystallites in the dielectric layer can be improved. Thereby, it is possible to simultaneously achieve excellent effective dielectric constant (DC, high frequency, low electric field, etc.), reliability (high temperature / humidity load), and temperature characteristics of the MLLCC. Further, the fraction of the core in the dielectric crystallites can be improved through uniform grain growth.

[0053] On the other hand, the fact that the core surface of the dielectric crystallites predominantly exists as the (001) plane crystal plane can be confirmed by observing the HR-TEM image of the dielectric crystallite core and through FFT (Fast-Fourier-transform) conversion analysis. More specifically, it can be confirmed by observing the HR-TEM image of the dielectric crystallite core surface and through the fact that the (001) plane, (011) plane, (002) plane, and (022) plane predominantly appear during FFT (Fast-Fourier-transform) conversion analysis.

[0054] On the other hand, the cube-shaped dielectric crystallite core according to the present invention can be realized by manufacturing it by a liquid phase method during the production of barium titanate oxide powder and using a solvent in which water and alcohol are mixed as a reaction solvent. This will be described in more detail in the manufacturing method described later.

[0055] On the one hand, in this specification, the "Cube form" is meant to be distinguished from the conventional spherical, spherical-like or amorphous dielectric grain core forms, and means having an angular shape similar to that of a cube or a rectangular parallelepiped. Such a form can be confirmed when the dielectric layer in the MLCC is subjected to thin-film sampling by FIB and the dielectric grain core is observed by TEM (transmission electron microscope).

[0056] At this time, an index that can quantitatively evaluate the degree of the cube form of the core is the "Average Cube Shape Factor (A.C.S.F)", which can be calculated by the following method. First, the "Cube Shape Factor (C.S.F)" of the core for one dielectric grain is measured as follows. The dielectric layer in the MLCC is subjected to thin-film sampling by FIB and observed by TEM (transmission electron microscope), the outer periphery of the dielectric grain core is measured, and the area (a) of a virtual square having the same outer periphery is calculated. Then, the area (b) of the actual corresponding dielectric grain core is calculated. After that, the value of b / a is calculated to obtain the "Cube Shape Factor (C.S.F)" of the core for one dielectric grain. Next, the "Average Cube Shape Factor (A.C.S.F)" can be obtained by calculating the average of the "Cube Shape Factor (C.S.F)" derived by the same method for 20 arbitrary dielectric grain particles cores.

[0057] At this time, the "Average Cube Shape Factor (C.S.F)" of the dielectric grain core according to the present invention may be 0.80 or more or 0.85 or more, and may be close to an ideal cube form.

[0058] On the one hand, the dielectric crystal grains according to the present invention have a cube-shaped core, so that grain growth is controlled during sintering for the production of the dielectric layer, and the average dimension is 160 nm or less, more specifically, 150 nm or less, and may be sufficiently small. Thereby, it is possible to simultaneously realize excellent effective dielectric constant (DC, high frequency, low electric field, etc.), reliability (high temperature / humidity load), and temperature characteristics of the MLLCC.

[0059] In this specification, the "average dimension of the dielectric crystal grains" can be obtained by thin-film sampling the dielectric layer in the MLCC with FIB and calculating the average of the maximum diameters for 20 arbitrary dielectric crystal grains when observed with a TEM (transmission electron microscope).

[0060] On the other hand, the dielectric crystal grains according to the present invention have a cube-shaped core, so that grain growth is controlled during sintering for the production of the dielectric layer, and the standard deviation of its dimension is 60 nm or less, and may be sufficiently small, more specifically, 40 nm or less. Thereby, it is possible to simultaneously realize excellent effective dielectric constant (DC, high frequency, low electric field, etc.), reliability (high temperature / humidity load), and temperature characteristics of the MLLCC.

[0061] In this specification, the "standard deviation of the dielectric crystal grain dimension" can be obtained by thin-film sampling the dielectric layer in the MLCC with FIB and calculating the standard deviation of the maximum diameters for 20 arbitrary dielectric crystal grains when observed with a TEM (transmission electron microscope).

[0062] Moreover, the core in the dielectric crystal grains according to the present invention has controlled grain growth and the average dimension may be 120 nm or less, more specifically, 100 nm or less. Thereby, it is possible to simultaneously realize excellent effective dielectric constant (DC, high frequency, low electric field, etc.), reliability (high temperature / humidity load), and temperature characteristics of the MLLCC.

[0063] In this specification, the "average size of the core within the dielectric crystal grains" can be obtained by performing thin-film sampling on the dielectric layer in the MLCC using FIB and calculating the average of the maximum diameters for 20 cores within any dielectric crystal grain when observing with TEM (transmission electron microscope).

[0064] Also, the core within the dielectric crystal grains according to the present invention may have its grain growth controlled, and the standard deviation of its size may be 30 nm or less, and more specifically, it may be 25 nm or 20 nm or less. Thereby, it is possible to simultaneously and excellently realize the effective dielectric constant (DC, high frequency, low electric field, etc.), reliability (high temperature / humidity resistance load), and temperature characteristics of the MLLCC.

[0065] In this specification, the "standard deviation of the size of the core within the dielectric crystal grains" can be obtained by performing thin-film sampling on the dielectric layer in the MLCC using FIB and calculating the standard deviation of the maximum diameters for 20 cores within any dielectric crystal grain when observing with TEM (transmission electron microscope).

[0066] On the other hand, the dielectric crystal grains according to the present invention can induce uniform grain growth by having cube-shaped cores, and the fraction of the cores within the dielectric crystal grains can be improved. Thereby, the average fraction of the cores within the dielectric crystal grains according to the present invention may be 60% or more, and more specifically, it may be 65% or more. Since the average fraction of the cores within the dielectric crystal grains is sufficiently large in this way, it is possible to realize a high dielectric constant.

[0067] In this specification, the "average fraction of the cores within the dielectric crystal grains" can be obtained by performing thin-film sampling on the dielectric layer in the MLCC using FIB and calculating the average of the ratio of the core area to the total area of the dielectric crystal grains for 20 arbitrary dielectric crystal grains when observing with TEM (transmission electron microscope).

[0068] Also, the multilayer capacitor according to the present invention can additionally satisfy the following formula 1.

[0069] [Formula 1] D s / D avg≧0.7(% / nm)

[0070] In the above formula (1), D s is the sintered relative density of the dielectric layer, and D avg is the average size of the dielectric crystal grains.

[0071] More specifically, generally, as the sintering temperature for manufacturing the dielectric layer increases, the average size of the dielectric crystal grains increases, and the sintered relative density also tends to improve simultaneously.

[0072] However, for conventional spherical or amorphous core-containing dielectric crystal grain particles, in order to obtain a high sintered relative density at a level of 80% or more, a minimum level of 200 nm or more is required as the average size of the dielectric crystal grains. In this case, there is a problem that the sintered relative density may become good, or the particle size distribution may become non-uniform, resulting in a decrease in the effective dielectric constant or reliability.

[0073] On the other hand, the dielectric layer in the multilayer capacitor according to the present invention contains cube-shaped core-containing dielectric crystal grains, thereby controlling grain growth and enabling dense sintering, improving the integration degree of the dielectric crystal grains in the dielectric layer. As a result, a high sintered relative density can be achieved even when the average size of the dielectric crystal grains is small, and formula (1) can be satisfied. As a result, the effective dielectric constant and reliability of the MLCC can be improved.

[0074] In one embodiment, in the multilayer capacitor according to the present invention, the average size of the dielectric crystal grains when the sintered relative density of the dielectric layer is 98% may be 200 nm or less, and more specifically, it may be 150 nm or less or 137.5 nm or less. Thereby, a high sintered relative density can be achieved even when the average size of the dielectric crystal grains is small. As a result, the effective dielectric constant and reliability of the MLCC can be improved.

[0075] The more preferable realization of the reduction in the average size and size standard deviation of the dielectric crystal grains described above, the reduction in the average size and size standard deviation of the cores within the dielectric crystal grains, and the excellent sintered relative density at a relatively small average dielectric crystal grain size is obtained by more precisely controlling the average particle size (D50) of the titanium raw material used as the barium titanate oxide raw material substance. This will be described in more detail in the manufacturing method described later.

[0076] On the other hand, the dielectric crystal grains according to the present invention further include a shell located on the core, and the shell can contain Dy, Mg, Mn, Tb, Sm, Si, Ba, Al, V, Nb, Sn, or a combination thereof. When the shell consists of the above composition, the control effect of grain growth can be more preferably realized.

[0077] Furthermore, the barium titanate oxide according to the present invention can be more specifically represented by the following Chemical Formula 1.

[0078] [Chemical Formula 1] Ba (1-x) D1 x Ti (1-y) D2 y O3

[0079] In Chemical Formula 1, D1 is Ba, Dy, Tb, Sm, Nb, or a combination thereof, D2 is Mg, Mn, Si, Al, V, Dy, Tb, Sm, Sn, or a combination thereof, 0 ≦ x ≦ 0.3, and 0 ≦ y ≦ 0.3.

[0080] A method for manufacturing a multilayer capacitor according to another embodiment of the present invention will be described.

[0081] Another embodiment of the present invention includes the steps of manufacturing dielectric powder; manufacturing a dielectric green sheet using the dielectric powder and forming a conductive paste layer on the surface of the dielectric green sheet; laminating the dielectric green sheets with the conductive paste layer formed thereon to manufacture a dielectric green sheet laminate; firing the dielectric green sheet laminate to manufacture a capacitor body including a dielectric layer and internal electrodes; and forming an external electrode on one surface of the capacitor body. The dielectric layer includes a plurality of dielectric crystal grains, and the dielectric crystal grains have a cube form, thereby providing a method for manufacturing a multilayer capacitor.

[0082] Hereinafter, the method for manufacturing a multilayer capacitor according to the present invention will be described in detail step by step.

[0083] First, dielectric powder is manufactured.

[0084] The step of manufacturing the dielectric powder may include the step of forming core particles containing barium titanate oxide and having a cube form.

[0085] At this time, the step of forming the core particles may more specifically include the step of mixing a barium raw material substance, a titanium raw material substance, water, and alcohol to form a reaction solution; and the step of heat-treating the reaction solution.

[0086] By using a mixed alcohol aqueous solution of water and alcohol as the solvent of the reaction solution in this way, the form of the dielectric crystal grain core can be realized in a cube form.

[0087] The alcohol may more specifically be methanol, ethanol, propanol, butanol, pentanol, or a combination thereof.

[0088] The average particle size of the titanium raw material substance may be 10 to 40 nm, more specifically, it may be 15 to 35 nm or 25 to 35 nm. When the average particle size of the titanium raw material substance satisfies the above range, the reduction of the average size and size standard deviation of the dielectric crystal grains, the reduction of the average size and size standard deviation of the cores in the dielectric crystal grains, and the realization effect of excellent sintered relative density with a relatively small average dielectric crystal grain size can be more preferably realized. On the other hand, the average particle size of the titanium raw material substance can be obtained by calculating the average of the lengths of the longest sides of any 30 particles during SEM or TEM image observation of the titanium raw material substance powder.

[0089] The barium raw material substance is not particularly limited, and can be, for example, Ba(OH)2, Ba(OH)2·8H2O, BaCl2, or a combination thereof.

[0090] The titanium raw material substance is not particularly limited, and can be, for example, TiO2, TTIP, TALH, TiCl4, or a combination thereof.

[0091] On the other hand, the step of manufacturing the dielectric powder may further include a step of forming a shell on the core particles after the step of forming core particles containing barium titanate oxide and having a cube form.

[0092] The step of forming a shell on the core particles may include a step of forming a coating solution containing a coating raw material substance; and a step of forming a shell by performing a coating heat treatment after introducing the core particles into the coating solution.

[0093] The coating raw material substance can be a Dy compound, an Mg compound, an Mn compound, a Tb compound, a Sm compound, an Si compound, a Ba compound, an Al compound, a V compound, a Nb compound, a Sn compound, or a combination thereof.

[0094] Next, the manufacture of the capacitor body will be described.

[0095] In the manufacturing process of the capacitor body, a dielectric paste that becomes a dielectric layer after firing and a conductive paste that becomes an internal electrode after firing are prepared.

[0096] The dielectric paste is manufactured, for example, by the following method. The manufactured dielectric powder doped with hafnium (Hf) is uniformly mixed by means such as wet mixing, dried, and then heat-treated under predetermined conditions to obtain plastic powder. An organic vehicle or an aqueous vehicle is added to the obtained plastic powder and kneaded to prepare a dielectric paste.

[0097] The obtained dielectric paste is formed into a sheet by a technique such as the doctor blade method to obtain a dielectric green sheet. The dielectric paste may also contain additives selected from various dispersants, plasticizers, dielectrics, sub-component compounds, or glass, etc., as necessary.

[0098] The conductive paste for the internal electrode is prepared by kneading conductive powder made of a conductive metal or its alloy with a binder and a solvent. The conductive paste for the internal electrode may contain ceramic powder (for example, barium titanate powder) as a co-material, if necessary. The co-material can play a role in suppressing the sintering of the conductive powder during the firing process.

[0099] The conductive paste for the internal electrode is applied in a predetermined pattern on the surface of the dielectric green sheet by various printing methods such as screen printing or transfer methods. Then, after laminating the dielectric green sheet with the formed internal electrode pattern in multiple layers, the dielectric green sheet laminate is obtained by pressing in the lamination direction. At this time, the dielectric green sheet and the internal electrode pattern can be laminated so that the dielectric green sheet is located on the upper and lower surfaces in the lamination direction of the dielectric green sheet laminate.

[0100] Optionally, the obtained dielectric green sheet laminate can be cut into a predetermined size by dicing or the like.

[0101] Further, the dielectric green sheet laminate can be solidified and dried to remove a plasticizer or the like as necessary, and after the solidification and drying, it can be barrel-polished using a horizontal centrifugal barrel machine or the like. In barrel polishing, the dielectric green sheet laminate is put into a barrel container together with media and a polishing liquid, and by applying rotational motion, vibration, or the like to the barrel container, unnecessary portions such as burrs generated during cutting can be polished. Further, after barrel polishing, the dielectric green sheet laminate can be washed with a cleaning liquid such as water and dried.

[0102] The dielectric green sheet laminate is subjected to a debinding process and a firing process to obtain a capacitor body.

[0103] The conditions of the debinding process can be appropriately adjusted according to the main component composition of the dielectric layer and the main component composition of the internal electrode. For example, the heating rate during the debinding process can be 5 °C / hour to 300 °C / hour, the holding temperature can be 180 °C to 400 °C, and the temperature holding time can be 0.5 hour to 24 hours. The debinding atmosphere can be air or a reducing atmosphere.

[0104] The conditions of the firing process can be appropriately adjusted according to the main component composition of the dielectric layer and the main component composition of the internal electrode. For example, the temperature during firing can be 1200 °C to 1350 °C, or 1220 °C to 1300 °C, and the time can be 0.5 hour to 8 hours, or 1 hour to 3 hours. The firing atmosphere can also be a reducing atmosphere, for example, an atmosphere in which a mixed gas of nitrogen gas (N2) and hydrogen gas (H2) is humidified. When the internal electrode contains nickel (Ni) or a nickel (Ni) alloy, the oxygen partial pressure in the firing atmosphere is 1.0×10 -14 MPa to 1.0×10 -10 MPa.

[0105] After the firing process, annealing can be performed as necessary. Annealing is a process for re-oxidizing the dielectric layer, and can be performed when the firing process is carried out in a reducing atmosphere. The conditions of the annealing process can also be appropriately adjusted according to the main component composition of the dielectric layer, etc. For example, the temperature during annealing may be 950°C to 1150°C, the time may be 0 hours to 20 hours, and the heating rate may be 50°C / hour to 500°C / hour. The annealing atmosphere may be a humidified nitrogen gas (N2) atmosphere, and the oxygen partial pressure may be 1.0×10 -9 MPa to 1.0×10 -5 MPa.

[0106] In order to humidify nitrogen gas, a mixed gas, etc. in the debinding process, the firing process, or the annealing process, for example, a wetter can be used. In this case, the water temperature can be 5°C to 75°C. The debinding process, the firing process, and the annealing process can be performed continuously or independently.

[0107] Optionally, surface treatment such as sandblasting, laser irradiation, or barrel polishing can be performed on the third and fourth surfaces of the obtained capacitor body. By performing such surface treatment, the ends of the first internal electrode and the second internal electrode may be exposed on the outermost surface of the third and fourth surfaces, thereby improving the electrical connection between the first external electrode and the second external electrode and the first internal electrode and the second internal electrode, and making it easier to form an alloy part.

[0108] A sintered metal layer can be formed by applying a paste for forming a sintered metal layer with an external electrode on the outer surface of the obtained capacitor body and then sintering it.

[0109] The paste for forming a sintered metal layer can contain a conductive metal and glass. Since the descriptions of the conductive metal and glass are the same as those described above, repetitive explanations are omitted. Further, the paste for forming a sintered metal layer can selectively contain sub-components such as a binder, a solvent, a dispersant, a plasticizer, or oxide powder. For example, as the binder, ethyl cellulose, acrylic, or butyral can be used, and as the solvent, an organic solvent such as terpineol, butyl carbitol, alcohol, methyl ethyl ketone, acetone, or toluene, or an aqueous solvent can be used.

[0110] As a method of applying the paste for forming a sintered metal layer to the outer surface of the capacitor body, dipping method, various printing methods such as screen printing, an application method using a dispenser, or a spraying method using a spray can be used. The paste for the sintered metal layer is applied to at least the third and fourth surfaces of the capacitor body, and can also be applied to a part of the first surface, the second surface, the fifth surface, or the sixth surface where the band portions of the first external electrode and the second external electrode are selectively formed.

[0111] Thereafter, the capacitor body coated with the paste for forming a sintered metal layer is dried and sintered at a temperature of 700°C to 1000°C for 0.1 hour to 3 hours to form a sintered metal layer.

[0112] Optionally, a conductive resin layer can be formed by applying a paste for forming a conductive resin layer to the outer surface of the obtained capacitor body and then curing it.

[0113] The paste for forming a conductive resin layer can contain a resin and, optionally, a conductive metal or a non-conductive filler. Since the descriptions of the conductive metal and the resin are the same as those described above, repetitive explanations are omitted. Further, the paste for forming a conductive resin layer can optionally contain auxiliary components such as a binder, a solvent, a dispersant, a plasticizer, or oxide powder. For example, as the binder, ethyl cellulose, acrylic, or butyral can be used, and as the solvent, an organic solvent such as terpineol, butyl carbitol, alcohol, methyl ethyl ketone, acetone, or toluene, or an aqueous solvent can be used.

[0114] As an example, the method for forming a conductive resin layer can be to dip the capacitor body 110 into the paste for forming a conductive resin layer and then cure it, or to print the paste for forming a conductive resin layer on the surface of the capacitor body 110 by a screen printing method or a gravure printing method, or to apply the paste for forming a conductive resin layer on the surface of the capacitor body 110 and then cure it to form.

[0115] Next, a plating layer is formed outside the conductive resin layer.

[0116] As an example, the plating layer may be formed by a plating method, or may be formed by sputtering or electroplating.

[0117] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred examples of the present invention, and the present invention is not limited by the following examples.

[0118] Example 1 (1) Production of dielectric powder (Reaction solution formation) First, Ba(OH)2 and TiO2 powder were added to an aqueous alcohol reaction solution solvent in which water and ethanol were mixed, and the input amounts were adjusted so as to match the stoichiometric ratio of BaTiO3, which is the final core compound, and the reaction solution was formed. At this time, the average particle size of TiO2 was 29 nm.

[0119] (Heat treatment and drying) Thereafter, the reaction solution was heat-treated and then dried to form BaTiO3 powder (core).

[0120] (Coating solution formation) Thereafter, a coating raw material substance containing any one or more of Dy, Mg, Mn, Tb, Sm, Si, Ba, Al, V, and Nb was added to ethanol or an ethanol-toluene mixed solvent to form a coating solution.

[0121] (Coating heat treatment) Thereafter, the core particles were added to the coating solution, and then coating heat treatment was performed at 400 °C for 2 hours to produce dielectric crystal grains having a shell containing any one or more of the elements Dy, Mg, Mn, Tb, Sm, Si, Ba, Al, V, and Nb.

[0122] (2) Manufacture of multilayer capacitor As a dielectric base material, the dielectric crystal grains, ethanol / toluene, a dispersant, and a binder were mixed, and then mechanically milled to produce a dielectric slurry.

[0123] Thereafter, the produced dielectric slurry was used to manufacture a dielectric green sheet using an on-roll coater of the head discharge method.

[0124] Thereafter, a conductive paste layer containing nickel (Ni) was printed on the surface of the dielectric green sheet, and the dielectric green sheet (width × length × height = 3.2 mm × 2.5 mm × 2.5 mm) having the conductive paste layer formed thereon was laminated and pressure-bonded to manufacture a dielectric green sheet laminate.

[0125] Thereafter, the dielectric green sheet laminate was subjected to a plasticizing process in a nitrogen atmosphere at 400°C or lower, and then fired (sintered) at a firing (sintering) temperature of 1300°C or lower and a hydrogen concentration of 1.0% H2 or lower to produce a capacitor body. Thereafter, an external electrode was formed on the outside of the capacitor body to produce a multilayer capacitor.

[0126] Other examples and comparative examples A multilayer capacitor was produced in the same manner as in Example 1, except that the process conditions for Example 1 were modified as shown in Table 1 below and implemented.

[0127] (In Table 1 below, Examples 1 and 2, Examples 3 and 4, and Comparative Examples 1 and 2 were each implemented multiple times, twice, under the same process conditions.)

[0128]

Table 1

[0129] Tables 2 to 5 below are tables summarizing the results of the evaluation of the physical properties of the dielectric crystal grains and the results of the evaluation of the performance of the MLCC according to Experimental Examples 2 to 4 described later.

[0130]

Table 2

[0131]

Table 3

[0132] Experimental Example 1: HR-TEM image and surface crystal plane analysis of barium titanate oxide powder The barium titanate oxide powders produced in Example 1 and Comparative Example 1 were subjected to HR-TEM image analysis, which are shown in FIGS. 6 and 7, respectively. Also, surface crystal plane analysis was performed on the HR-TEM images through FFT (Fast-Fourier-transform) conversion analysis.

[0133] In the case of Example 1, by having a cube-shaped core or through the analysis of the FFT (Fast-Fourier-transform) conversion results where the surface is analyzed as the (001) plane and the (011) plane, it was confirmed that the core surface predominantly exists as the (001) plane crystal face.

[0134] In contrast, in the case of Comparative Example 1, a cube-shaped core could not be confirmed. During the FFT conversion analysis, in addition to the (001) plane and the (011) plane, low-index faces such as the (111) plane were also analyzed, and it was confirmed that the degree of predominance of the (001) plane on the core surface was lower compared to Example 1.

[0135] Experimental Example 2: Evaluation of the Dielectric Crystal Grain Morphology and Physical Properties in the Dielectric Layer (1) Evaluation of Dielectric Crystal Grains and Core Morphology The dielectric layers of the MLCCs manufactured according to Example 1, Example 3, and Comparative Example 1 were sampled into thin films by FIB, and TEM-EDS images were observed, which are shown in FIGS. 8 to 9 (Example 1), FIGS. 10 to 11 (Example 3), and FIGS. 12 to 13 (Comparative Example 1).

[0136] (2) Evaluation of the Average Cube Shape Factor (A.C.S.F) As a method for quantitatively evaluating the degree of cube shape of the dielectric crystal grain core, the "Average Cube Shape Factor (A.C.S.F)" was calculated by the following method.

[0137] First, the "Cube Shape Factor (C.S.F)" of the core for a single dielectric crystal grain is measured as follows. The dielectric layer in the MLCC is sampled into a thin film by FIB and observed with a TEM (transmission electron microscope). The outer perimeter of the dielectric crystal grain core is measured, and the area (a) of a virtual square having the same outer perimeter is calculated. Then, the area (b) of the actual corresponding dielectric crystal grain core is calculated. After that, the value of b / a is calculated to obtain the "Cube Shape Factor (C.S.F)" of the core for a single dielectric crystal grain. Next, the "Average Cube Shape Factor (A.C.S.F)" can be obtained by calculating the average of the "Cube Shape Factor (C.S.F)" derived in the same way for 20 arbitrary dielectric crystal grain particles cores.

[0138] (3) Evaluation of the average size of dielectric crystal grains When the dielectric layer in the MLCC was sampled into a thin film by FIB and observed with a TEM (transmission electron microscope), the average of the maximum diameters for 20 arbitrary dielectric crystal grains was calculated and obtained.

[0139] (4) Evaluation of the standard deviation of the dielectric crystal grain size When the dielectric layer in the MLCC was sampled into a thin film by FIB and observed with a TEM (transmission electron microscope), the standard deviation of the maximum diameters for 20 arbitrary dielectric crystal grains was calculated and obtained.

[0140] (5) Evaluation of the average size of the dielectric crystal grain core When the dielectric layer in the MLCC was sampled into a thin film by FIB and observed with a TEM (transmission electron microscope), the average of the maximum diameters for 20 cores within arbitrary dielectric crystal grains was calculated and obtained.

[0141] (6) Evaluation of the standard deviation of the dielectric crystal grain core size The dielectric layer inside the MLCC was sampled into a thin film by FIB, and when observed with a TEM (transmission electron microscope), the standard deviation of the maximum diameter with respect to 20 cores in an arbitrary dielectric crystal grain was calculated and obtained.

[0142] (7) Evaluation of the average fraction of dielectric crystal grain cores The dielectric layer inside the MLCC was sampled into a thin film by FIB, and when observed with a TEM (transmission electron microscope), the average of the ratio of the core area to the total area of the dielectric crystal grains with respect to 20 arbitrary dielectric crystal grains was calculated and obtained.

[0143] Referring to FIGS. 8 to 13, in the case of the examples, it was confirmed that the dielectric crystal grain cores had a cube form, while in the case of the comparative examples, the dielectric crystal grain cores showed a spherical shape. Also, in the case of the examples, it was confirmed that the area ratio of the cores in the dielectric crystal grains was surely improved even visually as compared with the comparative examples.

[0144] Referring to Table 2, in the case of Examples 1 to 4 produced using an aqueous alcohol solution as a reaction solvent during the production of barium titanate oxide powder, it was confirmed that the dielectric crystal grain cores had a cube (shape) form and the average cube shape factor (A.C.S.F) also showed an appropriate level. Also, it was confirmed that grain growth was suppressed during the sintering process and the average size of the dielectric crystal grains and the like were appropriate and realized within the range according to the present invention.

[0145] On the other hand, in the case of Comparative Examples 1 and 2, as a result of being produced using conventional water as a reaction solvent during the production of barium titanate oxide powder (hydrothermal synthesis method), it was confirmed that the dielectric crystal grain cores had a spherical (sphere) form and the average cube shape factor (A.C.S.F) deviated from the appropriate level. Also, it was confirmed that grain growth became excessive during the sintering process and grain growth proceeded unevenly, and the average size of the dielectric crystal grains and the like deviated from the range according to the present invention.

[0146] On the other hand, when comparing Example 1 to 2 with Example 3 to 4, it was confirmed that in the case of Example 1 to 2 where the average particle size of the titanium raw material substance and the like were more appropriately controlled, the standard deviation of the dielectric crystal grain size and the like were more preferably realized as compared with Example 3 to 4.

[0147] Experimental Example 3: Evaluation of the change in the average size of dielectric crystal grains and the change in the sintered relative density of the dielectric layer due to the change in the sintering temperature of the dielectric layer By changing the sintering temperature during the production of the multilayer capacitor using the dielectric powders produced by Example 1, Example 3, and Comparative Example 1, the average size of the dielectric crystal grains in the dielectric layer and the sintered relative density of the dielectric layer were evaluated, and these are shown in FIG. 14 and Table 2.

[0148] Referring to FIG. 14 and Table 2, it was confirmed that the dielectric crystal grains of Example 1 and Example 3 having a cube-shaped core can achieve an excellent sintered relative density of the dielectric layer even at a relatively low sintering temperature and average size of the dielectric crystal grains as compared with the dielectric crystal grains of Comparative Example 1 having a spherical core.

[0149] On the other hand, when comparing Example 1 with Example 3, it was confirmed that in the case of Example 1 where the average particle size of the titanium raw material substance was more appropriately controlled, the above effect was more preferably realized as compared with Example 3.

[0150] Experimental Example 4: Evaluation of MLCC performance (1) Evaluation of DC change rate (1V, 3V / um) The DC change rate was evaluated by measuring with a 1 kHz 1V AC electric field and maintaining the DC for 60 seconds.

[0151] (2) Evaluation of Step IR MTTF The Step IR MTTF was evaluated by maintaining for 1200 seconds for each step under the conditions of 125 °C and 1.5 Vr.

[0152] (3) Evaluation of TCC capacitance change rate (-55 °C / 125 °C) After heat treatment at 150°C for 2 hours, it was aged for 24 hours, maintained at -55, 25, and 85°C under the conditions of 1 kHz and 0.5 V, and measured after 5 minutes to evaluate the TCC capacitance change rate.

[0153] Referring to Table 3, in the case of Examples 1 to 4 having a core containing barium titanate oxide in the form of a cube (Cube) and with the average size of dielectric crystal grains and the like appropriately controlled within the scope of the present invention, it was confirmed that the MLCC performance was generally excellent.

[0154] On the other hand, in the case of Comparative Examples 1 and 2 having a conventional spherical core containing barium titanate oxide and with the average size of dielectric crystal grains and the like outside the scope of the present invention, it was confirmed that the MLCC performance was generally very inferior compared to the examples.

[0155] Comparing each example in more detail, in the case of Examples 1 and 2 where the standard deviation of the dielectric crystal grain size and the like were more appropriately controlled, it was confirmed that the DC change rate and the Step IR MTTF characteristics were more preferably realized compared to Examples 3 and 4.

[0156] As described above, the preferred embodiments of the present invention have been explained. However, the present invention is not limited thereto, and it can be variously modified and implemented within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is natural that this also belongs to the scope of the present invention.

[0157] Therefore, it can be said that the substantial scope of the rights of the present invention is defined by the appended claims and their equivalents.

Explanation of Reference Numerals

[0158] 100: Multilayer capacitor 110: Capacitor body 111: Dielectric layer 112, 113: Cover region 121: First internal electrode 122: Second internal electrode 131: First external electrode 132: Second external electrode

Claims

1. A capacitor body including a dielectric layer and internal electrodes; and External electrodes disposed outside the capacitor body, The dielectric layer includes a plurality of dielectric crystallites, The dielectric crystallites have a cube form and include a core containing barium (Ba) titanate (Ti) oxide, A multilayer capacitor.

2. The surface of the dielectric crystallites predominantly exists as a (001) plane crystal plane, the multilayer capacitor according to claim 1.

3. The dielectric crystallites have an average dimension of 160 nm or less, the multilayer capacitor according to claim 1.

4. The standard deviation of the dimensions of the dielectric crystallites is 40 nm or less, the multilayer capacitor according to claim 1.

5. The core in the dielectric crystallites has an average dimension of 120 nm or less, the multilayer capacitor according to claim 1.

6. The standard deviation of the dimensions of the core in the dielectric crystallites is 30 nm or less, the multilayer capacitor according to claim 1.

7. The average fraction of the core in the dielectric crystallites is 60% or more, the multilayer capacitor according to claim 1.

8. The multilayer capacitor according to claim 1 that satisfies the following formula 1. 【Formula 1】 D ｓ / D ａｖｇ ≥0.7 (% / nm) In the above formula (1), D ｓ is the sintered relative density of the dielectric layer, and D ａｖｇ is the average size of the dielectric crystallites.

9. The average dimension of the dielectric crystallites when the sintered relative density of the dielectric layer is 98% is 200 nm or less, the multilayer capacitor according to claim 1.

10. The dielectric crystallites further include a shell located on the core, and the shell contains Dy, Mg, Mn, Tb, Sm, Si, Ba, Al, V, Nb, Sn or a combination thereof, the multilayer capacitor according to claim 1.

11. The barium titanate oxide is represented by the following chemical formula 1, the multilayer capacitor according to claim 1. 【Chemical Formula 1】 Ba （１－ｘ） D1 ｘ Ti （１－ｙ） D2 ｙ O ３ In the chemical formula 1, D1 is Ba, Dy, Tb, Sm, Nb or a combination thereof, D2 is Mg, Mn, Si, Al, V, Dy, Tb, Sm, Sn or a combination thereof, 0 ≦ x ≦ 0.3, and 0 ≦ y ≦ 0.3.

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