Multilayer ceramic capacitor and method of manufacturing the same

Abstract

Provided are a multilayer ceramic capacitor and a method of manufacturing the same, the multilayer ceramic capacitor including a capacitor body including a dielectric layer and an inner electrode layer, and an outer electrode disposed on an outer surface of the capacitor body, in which the dielectric layer includes a plurality of dielectric grains, and the inner electrode layer includes a plurality of outer electrode layers. At least one of the plurality of dielectric grains includes a dielectric composite in which a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal, and a sub-component including a rare earth element, a second transition metal, or a combination thereof.

Description

Technical Field

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

[0002] As electronic components using ceramic materials, there are capacitors, inductors, piezoelectric elements, varistors, thermistors, etc. Among ceramic electronic components, multilayer ceramic capacitors (MLCCs) can be used in various electronic devices due to advantages such as small size, high capacitance, and easy installation.

[0003] For example, a multilayer ceramic capacitor (MLCC) can be a chip capacitor mounted on a board of various electronic products (such as image devices (e.g., liquid crystal displays (LCDs), plasma display panels (PDPs), etc.), computers, personal portable terminals, smart phones, etc.) for charging or discharging therefrom.

[0004] BaTiO 3 Dielectric is mainly used as a material for MLCCs. BaTiO 3 The dielectric can achieve high capacitance, but the capacitance or effective capacitance decreases under DC (direct current) bias application conditions corresponding to the actual use conditions of the product. Recently, there has been a trend in the industry to emphasize the effective capacitance under the actual product use conditions rather than the capacitance. Summary of the Invention

[0005] An embodiment of the present disclosure provides a multilayer ceramic capacitor having improved DC bias characteristics and excellent reliability.

[0006] Another embodiment of the present disclosure provides a method for manufacturing the multilayer ceramic capacitor.

[0007] An embodiment of the present disclosure provides a multilayer ceramic capacitor, the multilayer ceramic capacitor comprising: a capacitor body including a dielectric layer and an internal electrode layer, and an external electrode disposed on an outer surface of the capacitor body, wherein the dielectric layer includes a plurality of dielectric grains, at least one of the plurality of dielectric grains includes a dielectric composite and a sub-component, in the dielectric composite, a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal, the sub-component includes a rare earth element, a second transition metal, or a combination thereof, in the result of TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis of at least one of the plurality of dielectric grains, from the center of at least one of the plurality of dielectric grains to any grain boundary, the position of a first point is different from the position of a second point, the first point has the largest atomic percentage (atomic %) value of hafnium (Hf) or the first transition metal with respect to the total number of atoms of at least one of the plurality of dielectric grains, the second point has the largest atomic % value of the rare earth element or the second transition metal with respect to the total number of atoms of at least one of the plurality of dielectric grains, and the first transition metal does not include hafnium (Hf), and the first transition metal and the second transition metal are different from each other.

[0008] In the result of TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis of at least one of the plurality of dielectric grains, from the center of at least one of the plurality of dielectric grains to any grain boundary, the second point may be located on the outer side farther from the center of at least one of the plurality of dielectric grains than the first point, the second point has the largest atomic % value of the rare earth element or the second transition metal, and the first point has the largest atomic % value of hafnium (Hf) or the first transition metal.

[0009] At least one of the plurality of dielectric grains has a core-double shell structure, the core-double shell structure including a core, a first shell, and a second shell, the first shell surrounding at least a part of the core, and the second shell surrounding at least a part of the first shell.

[0010] The first shell may include the dielectric composite, and the second shell may include the sub-component, in the dielectric composite, the barium titanate-based compound is doped with hafnium (Hf) or the first transition metal, and the sub-component includes the rare earth element, the second transition metal, or a combination thereof.

[0011] In the results of TEM-EDS (transmission electron microscopy - energy dispersive spectroscopy) line analysis of at least one of the plurality of dielectric grains, from the center of at least one of the plurality of dielectric grains to any grain boundary, the first shell may be a region including a peak of hafnium (Hf) or the first transition metal having the maximum atomic % value, the second shell may be a region including a peak of the rare earth element or the second transition metal having the maximum atomic % value, and the first shell and the second shell may have regions different from each other.

[0012] The atomic % content of hafnium (Hf) or the first transition metal in the first shell may be greater than the atomic % content of the rare earth element or the second transition metal, and the atomic % content of hafnium (Hf) or the first transition metal in the second shell may be less than the atomic % content of the rare earth element or the second transition metal.

[0013] The first transition metal may include zirconium (Zr), yttrium (Y), tantalum (Ta), niobium (Nb), or a combination thereof.

[0014] The rare earth element may include at least one selected from the group consisting of dysprosium (Dy), terbium (Tb), yttrium (Y), lanthanum (La), cerium (Ce), samarium (Sm), gadolinium (Gd), holmium (Ho), and erbium (Er).

[0015] The second transition metal may include at least one selected from the group consisting of manganese (Mn) and vanadium (V).

[0016] Based on the total amount of the dielectric composite, hafnium (Hf) or the first transition metal may be doped in an amount of about 0.1 atomic % to about 5 atomic %.

[0017] Based on the total amount of the composition of the second shell, the sub-component may be included in an amount of about 0.1 atomic % to about 2 atomic %.

[0018] The length of the core measured from the major axis passing through the center of at least one of the plurality of dielectric grains may be about 50 nm to about 150 nm.

[0019] The average length of the first shell measured from the major axis passing through the center of at least one of the plurality of dielectric grains may be about 10 nm to about 50 nm.

[0020] The average length of the second shell measured from the major axis passing through the center of at least one of the plurality of dielectric grains may be about 40 nm to about 240 nm.

[0021] The plurality of dielectric grains may have an average diameter greater than or equal to about 100 nm and less than about 266 nm.

[0022] The ratio of the number of dielectric grains having the core-double shell structure to the total number of the plurality of dielectric grains may be greater than or equal to about 50% and less than or equal to about 100%.

[0023] Another embodiment of the present disclosure provides a method for manufacturing a multilayer ceramic capacitor, the method comprising: preparing a dielectric composite powder in which a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal; manufacturing a dielectric green sheet using a dielectric slurry including the dielectric composite powder and a sub-component powder, and forming a conductive paste layer on the surface of the dielectric green sheet; manufacturing a dielectric green sheet stack by stacking the dielectric green sheets having the conductive paste layer formed thereon; manufacturing a capacitor body including a dielectric layer and an internal electrode layer by firing the dielectric green sheet stack; and forming an external electrode on the surface of the capacitor body, wherein the dielectric layer includes a plurality of dielectric grains, at least one of the plurality of dielectric grains includes a dielectric composite and a sub-component, in the dielectric composite, the barium titanate-based compound is doped with hafnium (Hf) or a first transition metal, the sub-component includes a rare earth element, a second transition metal, or a combination thereof, in the result of TEM-EDS (transmission electron microscope-energy dispersive spectroscopy) line analysis of at least one of the plurality of dielectric grains, from the center of at least one of the plurality of dielectric grains to any grain boundary, the position of a first point is different from the position of a second point, the first point has the hafnium (Hf) or the first transition metal having the maximum atomic % value with respect to the total number of atoms of at least one of the plurality of dielectric grains, the second point has the rare earth element or the second transition metal having the maximum atomic % value with respect to the total number of atoms of at least one of the plurality of dielectric grains, and the first transition metal does not include hafnium (Hf), and the first transition metal and the second transition metal are different from each other.

[0024] The dielectric composite powder may include a core portion and a shell portion, the core portion includes the barium titanate-based compound, and the shell portion surrounds at least a part of the core portion and includes Ba(Ti,Hf)O 3 or Ba(Ti,TM)O 3 , where TM represents the first transition metal, and in the dielectric composite powder, the barium titanate-based compound is doped with hafnium (Hf) or the first transition metal (TM).

[0025] The dielectric composite powder may be prepared by the following steps: preparing barium titanate seeds including barium (Ba) and titanium (Ti) by hydrothermal synthesis; and mixing the barium titanate seeds with a hafnium (Hf)-containing compound or a first transition metal-containing compound.

[0026] Based on 100 moles of titanium (Ti), the hafnium (Hf)-containing compound or the first transition metal-containing compound may be mixed in an amount of from about 0.1 mole to about 3 moles.

[0027] The first transition metal-containing compound may include at least one selected from the group consisting of a zirconium (Zr)-containing compound, a yttrium (Y)-containing compound, a tantalum (Ta)-containing compound, and a niobium (Nb)-containing compound.

[0028] The sub-component powder may include a rare earth element-containing compound, a second transition metal-containing compound, or a combination thereof.

[0029] The rare earth element-containing compound may include at least one selected from the group consisting of a dysprosium (Dy)-containing compound, a terbium (Tb)-containing compound, a yttrium (Y)-containing compound, a lanthanum (La)-containing compound, a cerium (Ce)-containing compound, a samarium (Sm)-containing compound, a gadolinium (Gd)-containing compound, a holmium (Ho)-containing compound, and an erbium (Er)-containing compound.

[0030] The second transition metal-containing compound may include a manganese (Mn)-containing compound, a vanadium (V)-containing compound, or a combination thereof.

[0031] The multilayer ceramic capacitor according to some embodiments of the present disclosure may improve DC bias characteristics and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a perspective view showing a multilayer ceramic capacitor according to an embodiment.

[0033] Figure 2 is along Figure 1 A cross-sectional view of the multilayer ceramic capacitor taken along line I-I'.

[0034] Figure 3 is along Figure 1 A cross-sectional view of the multilayer ceramic capacitor taken along line II-II'.

[0035] Figure 4 is a schematic view showing a dielectric grain according to an embodiment.

[0036] Figure 5 is a schematic view showing a dielectric composite powder according to an embodiment.

[0037] Figure 6 is a TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis diagram of the dielectric grain according to Example 1.

[0038] Figure 7 is a TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) analysis image of the dielectric layer according to Example 1.

[0039] Figure 8 It is a scanning electron microscope (SEM) analysis image of the effective region of the multilayer ceramic capacitor according to Example 1.

[0040] Figure 9 It is a scanning electron microscope (SEM) analysis image of the effective region of the multilayer ceramic capacitor according to Comparative Example 1.

[0041] Figure 10 It is a graph showing the DC bias characteristics of the multilayer ceramic capacitors according to Example 1 and Comparative Example 1. Detailed Description of the Invention

[0042] Hereinafter, the present disclosure will be described in detail with reference to the accompanying drawings, in which embodiments of the present disclosure are shown. The drawings and the description are considered to be illustrative rather than restrictive in nature. Throughout the specification, the same reference numerals denote the same elements. In the drawings, some components are exaggerated, omitted, or schematically shown, and the dimensions of each component do not exactly reflect the actual dimensions.

[0043] The drawings are only intended to facilitate the understanding of the embodiments disclosed in this specification, and it should be understood that the technical ideas disclosed herein are not limited by the drawings, and include all modifications, equivalents, or alternatives within the scope of the ideas and technologies of the present disclosure.

[0044] Although terms such as "first", "second", etc. are used to explain various components, the components are not limited to these terms. These terms are only used to distinguish one component from another.

[0045] In addition, it should be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element, or there can also be an intermediate element. More precisely, when an element is referred to as being "directly on" another element, there is no intermediate element. In addition, when an element is referred to as being "on" or "above" a reference element, it can be positioned above or below the reference element, and it is not necessarily referred to as being positioned "on" or "above" in the direction opposite to the direction of gravity.

[0046] Throughout the specification, the terms "comprising" or "having" are intended to list the presence of the stated features, numbers, steps, operations, components, and / or combinations thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, components, and / or combinations thereof. Therefore, unless explicitly described to the contrary, the words "comprising" or "having" will be understood to imply the inclusion of the stated elements but not the exclusion of any other elements.

[0047] Furthermore, throughout the specification, the phrase "in a plan view" or "on a plane" means observing the target part from the top, and the phrase "in a sectional view" or "on a section" means observing a section formed by vertically cutting the target part from the side.

[0048] Throughout the specification, the term "connected" not only means that two or more constituent components are directly connected, but also may mean that two or more constituent components are indirectly connected through another constituent component, two or more constituent components are electrically connected and physically connected, or two or more constituent components are referred to by different names but are united by position or function.

[0049] Hereinafter, reference will be made to Figures 1 to 3 describe a multilayer ceramic capacitor according to an embodiment.

[0050] Figure 1 is a perspective view showing a multilayer ceramic capacitor according to an embodiment, Figure 2 is along Figure 1 a sectional view of the multilayer ceramic capacitor taken along line I-I', and Figure 3 is along Figure 1 a sectional view of the multilayer ceramic capacitor taken along line II-II'.

[0051] Figures 1 to 3 The L-axis direction, W-axis direction, and T-axis direction shown in are the length direction, width direction, and thickness direction of the capacitor body 110, respectively. Here, the thickness direction (T-axis direction) may be a direction perpendicular to the wide surface (main surface) of the sheet-like component. For example, it can be used as the same concept as the stacking direction of the stacked dielectric layers 111. The length direction (L-axis direction) may be a direction extending parallel to the wide surface (main surface) of the sheet-like component and may be substantially perpendicular to the thickness direction (T-axis direction). For example, the length direction (L-axis direction) may be the direction along which the outer electrodes 131 and 132 face each other. The width direction (W-axis direction) may be a direction extending parallel to the wide surface (main surface) of the sheet-like component and may be substantially perpendicular to the thickness direction (T-axis direction) and the length direction (L-axis direction). The length of the sheet-like component in the length direction (L-axis direction) may be longer than the width in the width direction (W-axis direction).

[0052] Referring to Figures 1 to 3 , the multilayer ceramic capacitor 100 according to an embodiment includes a capacitor body 110 and outer electrodes 131 and 132 provided on the outer surface of the capacitor body 110. The outer electrodes 131 and 132 may include a first outer electrode 131 and a second outer electrode 132 provided at opposite ends of the capacitor body 110 in the length direction (L-axis direction).

[0053] For example, the capacitor body 110 may have a substantially hexahedral shape.

[0054] For the convenience of describing the embodiments, two surfaces that face each other in the thickness direction (T-axis direction) of the capacitor body 110 are referred to as the first surface and the second surface, two surfaces that are connected to the first surface and the second surface and face each other in the length direction (L-axis direction) are referred to as the third surface and the fourth surface, and two surfaces that are connected to the first surface and the second surface and are connected to the third surface and the fourth surface and face each other in the width direction (W-axis direction) are referred to as the fifth surface and the sixth surface.

[0055] According to some embodiments of the present disclosure, the first surface as the lower surface may be the mounting surface. Additionally, the first surface to the sixth surface may be flat, but the embodiments are not limited thereto. For example, the first surface to the sixth surface may be curved surfaces having convex central portions, and the edges serving as the boundaries of each surface may be rounded.

[0056] The shape and 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 embodiments.

[0057] The capacitor body 110 includes a plurality of dielectric layers 111 and inner electrode layers 121 and 122. Specifically, the capacitor body 110 includes a plurality of dielectric layers 111 and a first inner electrode layer 121 and a second inner electrode layer 122, and the first inner electrode layer 121 and the second inner electrode layer 122 are alternately arranged in the thickness direction (T-axis direction) with the dielectric layer 111 interposed therebetween.

[0058] At this time, adjacent dielectric layers 111 of the capacitor body 110 may be integrated to such an extent that it is difficult to identify the boundary between them without using a scanning electron microscope (SEM).

[0059] The capacitor body 110 may have an effective region. The effective region is a region where the dielectric layers 111 and the inner electrode layers 121 and 122 are alternately arranged, which helps to form the capacitance of the multilayer ceramic capacitor 100. Specifically, the effective region may be a region where the first inner electrode layer 121 and the second inner electrode layer 122 stacked along the thickness direction (T-axis direction) overlap.

[0060] Additionally, the capacitor body 110 may further include a covering portion and a side edge portion.

[0061] The covering portion is an edge portion of the multilayer ceramic capacitor 100 in the thickness direction, and may be located on the upper surface and the lower surface of the effective region in the thickness direction (T-axis direction), respectively. Such a covering portion may be a single dielectric layer or two or more dielectric layers stacked on the upper surface and the lower surface of the effective region, respectively. The dielectric layers in the covering portion may be formed of the same material as the dielectric layer 111.

[0062] The side edge portions can be regarded as side covering portions and can be located at each of the two opposite ends of the active region in the width direction (W-axis direction) (i.e., the surfaces of the active region corresponding to the fifth surface and the sixth surface). The side edge portions can be formed in the following manner: when the conductive paste for the inner electrode layer is coated on the surface of the dielectric green sheet, the conductive paste is coated only in a partial region of the surface of the dielectric green sheet and not coated on the portions of the surface of the dielectric green sheet adjacent to both sides in the width direction, stack the dielectric green sheets, and then fire, but the forming method is not limited thereto.

[0063] The covering portion and the side edge portions are used to prevent damage to the first inner electrode layer 121 and the second inner electrode layer 122 caused by physical stress or chemical stress.

[0064] The dielectric layer 111 may include a plurality of dielectric grains.

[0065] At least one of the plurality of dielectric grains includes a dielectric composite and a sub-component. In the dielectric composite, a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal. The first transition metal can be any transition metal other than hafnium (Hf). The sub-component includes a rare earth element, a second transition metal, or a combination thereof, and the second transition metal is different from the first transition metal.

[0066] According to some embodiments, in the result of the TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis of the dielectric grains, from the center of the dielectric grains to any grain boundary, the position of the first point of hafnium (Hf) or the first transition metal having the maximum atomic % value (or maximum atomic %) relative to the total number of atoms of the dielectric grains is different from the position of the second point of the rare earth element or the second transition metal having the maximum atomic % value (or maximum atomic %). That is, the first point and the second point in the dielectric grains are located at different positions. In this way, by suppressing defects near the center of the dielectric grains, the crystallinity of the dielectric grains having a structure in which the first point and the second point are located at different positions can be increased. Therefore, fine dielectric grains can be achieved, and the DC bias characteristics of the multilayer ceramic capacitor can be improved. Here, the improvement of the DC bias characteristics means an increase in the DC effective capacitance, which means that when a DC voltage is applied, the degree of capacitance reduction is reduced.

[0067] Specifically, the second point of the rare earth element or the second transition metal having the maximum atomic % value may be located on the outer side farther from the center of the dielectric grains than the first point of hafnium (Hf) or the first transition metal having the maximum atomic % value. In this way, since the dielectric grains having a structure in which the first point is located inside and the second point is located on the outer side farther from the center of the dielectric grains have increased crystallinity, fine dielectric grains can be achieved and the DC bias characteristics of the multilayer ceramic capacitor can be improved.

[0068] According to some embodiments, at least one of the plurality of dielectric grains may have a core-double shell structure. Reference will be made to Figure 4 describe dielectric grains having a core-double shell structure.

[0069] Figure 4 is a schematic diagram showing a dielectric grain according to an embodiment.

[0070] Reference is made to Figure 4 , according to some embodiments, the dielectric grain 10 may have a core-double shell structure, and the core-double shell structure includes a core 20, a first shell 30 surrounding at least a part of the core 20, and a second shell 40 surrounding at least a part of the first shell 30.

[0071] The core 20 may include a barium titanate-based compound.

[0072] The barium titanate-based compound is a dielectric matrix material, has a high dielectric constant, and contributes to forming the dielectric constant of the multilayer ceramic capacitor 100.

[0073] The barium titanate-based compound may include a compound containing barium (Ba) and titanium (Ti). For example, the barium titanate-based compound includes from the group consisting of BaTiO 3 , Ba(Ti,Zr)O 3 , Ba(Ti,Sn)O 3 , (Ba,Ca)TiO 3 , (Ba,Ca)(Ti,Ca)O 3 , (Ba,Ca)(Ti,Zr)O 3 , (Ba,Ca)(Ti,Sn)O 3 , (Ba,Sr)TiO 3 , (Ba,Sr)(Ti,Zr)O 3 and (Ba,Sr)(Ti,Sn)O 3 at least one selected from the group.

[0074] The first shell 30 may include a barium titanate-based compound and hafnium (Hf) or a first transition metal.

[0075] Specifically, the first shell 30 may include a dielectric composite, that is, a dielectric composite in which a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal.

[0076] The first transition metal may be any transition metal other than hafnium (Hf). The first transition metal may include, for example, at least one selected from the group consisting of zirconium (Zr), yttrium (Y), tantalum (Ta), and niobium (Nb).

[0077] The second shell 40 may include a barium titanate-based compound (as a main component) and a sub-component. The sub-component may include a rare earth element, a second transition metal, or a combination thereof.

[0078] The rare earth element may include, for example, at least one selected from the group consisting of dysprosium (Dy), terbium (Tb), yttrium (Y), lanthanum (La), cerium (Ce), samarium (Sm), gadolinium (Gd), holmium (Ho), and erbium (Er).

[0079] The second transition metal is different from the first transition metal and may include, for example, at least one selected from the group consisting of manganese (Mn) and vanadium (V).

[0080] According to some embodiments, the dielectric grain 10 has a core-double shell structure, that is, a structure in which the first shell 30 includes a dielectric composite, that is, a dielectric composite in which a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal. Thus, during firing in the manufacturing process of the capacitor body 110, hafnium (Hf) or the first transition metal present in the first shell 30 can prevent sub-components (such as rare earth elements) present in the second shell 40 from diffusing into the core 20. Therefore, defects in the core 20 are suppressed, thereby increasing the crystallinity of the core 20, and fine dielectric grains can be achieved, thereby improving the DC bias characteristics of the multilayer ceramic capacitor.

[0081] The core-double shell structure of the dielectric grain 10 can be confirmed by TEM-EDS (transmission electron microscopy - energy dispersive spectroscopy) line analysis. That is, in the result of the TEM-EDS (transmission electron microscopy - energy dispersive spectroscopy) line analysis of the dielectric grain 10, from the center of the dielectric grain to any one grain boundary, the first shell 30 can be defined as the region including the peak of hafnium (Hf) or the first transition metal having the maximum atomic % value. In addition, the second shell 40 can be defined as the region including the peak of the rare earth element or the second transition metal having the maximum atomic % value. At this time, the first shell 30 and the second shell 40 have different regions.

[0082] Specifically, in the first shell 30, the atomic % content of hafnium (Hf) or the first transition metal may be greater than the atomic % content of the rare earth element or the second transition metal. In addition, in the second shell 40, the atomic % content of hafnium (Hf) or the first transition metal may be less than the atomic % content of the rare earth element or the second transition metal.

[0083] According to some embodiments, the first shell 30 may include a dielectric composite in which a barium titanate-based compound is doped with hafnium (Hf).

[0084] Hafnium (Hf) has a high melting temperature, and the ionic radius of Hf 4+ is 0.71 nm, which is larger than the ionic radius of Ti with an ionic radius of 0.61 nm 4+ such that hafnium (Hf) in barium titanate (BaTiO 3), and can suppress the diffusion of sub-components (such as rare earth elements) as additives into the core. Therefore, when barium titanate (BaTiO 3 ) is doped with hafnium (Hf) and applied to the dielectric layer, the diffusion of additives into the core during firing can be suppressed, and a fine grain size can be obtained, thereby improving the DC bias characteristics.

[0085] When manufacturing the dielectric layer, a dielectric composite in which a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal can be used in the form of a powder having a core-shell structure. Specifically, the core includes a barium titanate-based compound, and when the first transition metal is TM, the shell may include Ba(Ti,Hf)O 3 or Ba(Ti,TM)O 3 .

[0086] Generally, a dielectric having a core-shell structure is manufactured by adding an additive to barium titanate powder and then controlling the firing conditions. The core-shell structure can be formed by adjusting the firing conditions, but since the grain growth behavior varies according to the firing conditions, it is difficult to form a core-shell structure while having fine grains. In addition, some additives present in the shell diffuse into the core, forming defects in the core.

[0087] According to some embodiments, a dielectric is manufactured by synthesizing a dielectric composite powder having a core-shell structure in the step of synthesizing barium titanate powder. Therefore, the dielectric layer 111 according to some embodiments may have dielectric grains 10 having a core-double shell structure manufactured by this method, thereby improving the DC bias characteristics and reliability.

[0088] TEM-EDS (transmission electron microscope-energy dispersive spectroscopy) analysis can be used to measure the core-double shell structure of the dielectric grains 10, as well as the components and contents present in each of the core 20, the first shell 30, and the second shell 40.

[0089] Specifically, the multilayer ceramic capacitor 100 is placed in an epoxy resin mixture and cured. The surface of the capacitor body 110 in the W-axis direction - T-axis direction (WT surface) is polished along the L-axis direction to a depth of 1 / 2, and then the obtained cross-sectional sample is fixed and held in a vacuum atmosphere chamber, so that the effective region where the dielectric layer 111 and the inner electrode layers 121 and 122 are stacked on each other can be observed. Subsequently, the effective region of the cross-sectional sample can be measured using a transmission electron microscope (TEM) such that at least one layer (e.g., one to five layers) in the dielectric layer 111 is visible. For example, a TEM image can be obtained using a focused ion beam (Xe-FIB) in a region of about 800 nm × 800 nm where at least one layer in the dielectric layer 111 is visible in the effective region under the condition of an acceleration voltage of 200 kV. Then, in the TEM image of the measured cross-sectional sample, an EDS (energy dispersive spectroscopy) line analysis is performed on a straight line segment passing through the center of an arbitrary dielectric grain from one outermost point to another outermost point. Through the EDS line analysis, the presence of the core-double shell structure and the composition in each region can be confirmed.

[0090] Based on the total amount of the dielectric composite, hafnium (Hf) or the first transition metal included in the first shell 30 can be doped into the barium titanate-based compound in an amount of about 0.1 atomic % to about 5 atomic % (e.g., about 0.5 atomic % to about 4 atomic %). When hafnium (Hf) or the first transition metal is doped into the barium titanate-based compound within the above content range, the diffusion of sub-components (such as rare earth elements) into the core 20 during firing can be prevented, thereby improving the crystallinity of the core. Therefore, fine dielectric grains can be achieved, thereby improving the DC bias characteristics and reliability of the multilayer ceramic capacitor.

[0091] Based on the total amount of the components of the second shell 40, sub-components (such as rare earth elements) included in the second shell 40 can be included in an amount of about 0.1 atomic % to about 2 atomic % (e.g., about 0.5 atomic % to about 1.5 atomic %). When the sub-components are included in the second shell 40 within the above content range, a multilayer ceramic capacitor with high reliability can be ensured.

[0092] Referring to Figure 4 , the length L1 of the core 20 measured for the major axis passing through the center of the dielectric grain 10 can be about 50 nm to about 150 nm, for example, about 60 nm to about 140 nm, or about 70 nm to about 130 nm.

[0093] In addition, the average lengths L2 and L2' of the first shell 30 measured for the major axis passing through the center of the dielectric grain 10 can be about 10 nm to about 50 nm, for example, about 15 nm to about 45 nm, or about 20 nm to about 40 nm. Here, L2 and L2' can be different from each other, and the average length of the first shell 30 can be the average value of L2 and L2'.

[0094] In addition, the average lengths L3 and L3' of the second shell 40 measured along the major axis passing through the center of the dielectric grain 10 may be from about 40 nm to about 240 nm, for example, from about 50 nm to about 230 nm, or from about 60 nm to about 220 nm. Here, L3 and L3' may be different from each other, and the average length of the second shell 40 may be the average value of L3 and L3'.

[0095] When the core 20, the first shell 30, and the second shell 40 each have lengths within the above ranges, the core-double shell structure of the dielectric grain 10 is ensured, and the DC bias characteristics and reliability of the multilayer ceramic capacitor can be improved.

[0096] The length of each of the core 20, the first shell 30, and the second shell 40 can be obtained by TEM-EDS (transmission electron microscopy - energy dispersive spectroscopy) analysis. The TEM-EDS analysis method is the same as described above.

[0097] The average diameter of the dielectric grains may be greater than or equal to about 100 nm and less than about 266 nm, for example, from about 120 nm to about 250 nm. This is the average value measured for a plurality of dielectric grains, for example, 2 to 200 dielectric grains or 5 to 150 dielectric grains, and the average diameter may be the average value of the sum of the major axis of the dielectric grain and the axis perpendicular to the major axis. When the average diameter of the dielectric grains is within the above range, the DC bias characteristics of the multilayer ceramic capacitor can be improved by having fine dielectric grains.

[0098] The average diameter of the dielectric grains can be obtained by SEM (scanning electron microscopy) analysis.

[0099] Specifically, after placing the multilayer ceramic capacitor 100 in an epoxy resin mixture and curing it, the surface (WT surface) of the capacitor body 110 in the W-axis direction - T-axis direction is polished to a depth of 1 / 2 along the L-axis direction, and then the obtained cross-sectional sample is fixed and held in a vacuum atmosphere chamber, so that the effective region where the dielectric layer 111 and the inner electrode layers 121 and 122 are stacked on each other can be observed. Subsequently, the effective region of the cross-sectional sample can be measured using a scanning electron microscope (SEM) such that at least one layer (for example, two to five layers) in the dielectric layer 111 is visible. For example, an SEM image can be obtained using a Verios G4 product from Thermofisher Scientific under the condition of 10 kV in a region of about 2.5 μm × 2.5 μm where three visible dielectric layers 111 are in the effective region. From the SEM image of the cross-sectional sample, the average value of the sum of the major axis and the axis perpendicular to the major axis can be calculated for more than 100 dielectric grains.

[0100] According to some embodiments, the ratio of the number of dielectric grains having the above-described core-double shell structure to the total number of dielectric grains in the dielectric layer may be greater than or equal to about 50% and less than or equal to about 100%, for example, about 60% to about 100%. When the ratio of the dielectric grains having the core-double shell structure is within the above range, a multilayer ceramic capacitor having improved DC bias characteristics and reliability can be obtained.

[0101] The average thickness (average length in the T-axis direction) of the dielectric layer 111 may be about 0.1 μm to about 8.0 μm, for example, may be about 0.1 μm to about 6.0 μm. When the average thickness of the dielectric layer 111 is within the above range, the reliability of the multilayer ceramic capacitor is improved.

[0102] The average thickness of the dielectric layer 111 can be analyzed by scanning electron microscopy (SEM), and measured by putting the multilayer ceramic capacitor 100 into an epoxy resin mixture liquid and then curing, polishing, and ion milling. The scanning electron microscope can use, for example, the Verios G4 product from Thermofisher Scientific, the measurement conditions can be 10 kV, 0.2 nA, the analysis magnification can be 100 times, and the measurement can be performed on 1 layer or more, 3 layers or more, 5 layers or more, or 10 layers or more in the dielectric layer 111. In the scanning electron microscopy (SEM) image, the center point of the dielectric layer 111 in the length direction (L-axis direction) or width direction (W-axis direction) is taken as a reference point, and the arithmetic mean of the thickness of the dielectric layer 111 can be obtained for 10 points set at a predetermined interval from the reference point. The interval of the 10 points can be adjusted according to the scale of the SEM image, and can be, for example, about 1 μm to about 100 μm, about 1 μm to about 50 μm, or about 1 μm to about 10 μm. At this time, all 10 points must be located within the dielectric layer 111, and if all 10 points are not located within the dielectric layer 111, the position of the reference point can be changed, or the interval between the 10 points can be adjusted.

[0103] The first inner electrode layer 121 and the second inner electrode layer 122 are electrodes having different polarities, alternately arranged with the dielectric layer 111 interposed therebetween and opposite to each other in the T-axis direction, and may have first ends exposed through the third surface and the fourth surface of the capacitor body 110, respectively.

[0104] The first inner electrode layer 121 and the second inner electrode layer 122 can be electrically insulated from each other by the dielectric layer 111 interposed therebetween.

[0105] The end portions of the first inner electrode layer 121 exposed through the third surface of the capacitor body 110 and the end portions of the second inner electrode layer 122 exposed through the fourth surface of the capacitor body 110 may be electrically connected to the first outer electrode 131 and the second outer electrode 132, respectively.

[0106] The first inner electrode layer 121 and the second inner electrode layer 122 may include a conductive metal, for example, a metal such as Ni, Cu, Ag, Pd, Au or an alloy thereof (such as an Ag-Pd alloy).

[0107] In addition, the first inner electrode layer 121 and the second inner electrode layer 122 may include dielectric particles having the same composition as the ceramic material included in the dielectric layer 111.

[0108] The first inner electrode layer 121 and the second inner electrode layer 122 may be formed using a conductive paste including a conductive metal. The printing method of the conductive paste may be a screen printing method or a gravure printing method.

[0109] The average thickness of the first inner electrode layer 121 and the second inner electrode layer 122 may be about 0.1 μm to about 2 μm. The average thickness of the first inner electrode layer 121 and the second inner electrode layer 122 may be measured by SEM analysis. Here, since the SEM analysis is the same as the method for measuring the average thickness of the dielectric layer 111 described above, its description will be omitted.

[0110] The capacitor body 110 may be formed by firing a stacked structure in which a plurality of dielectric layers 111 and inner electrode layers 121 and 122 are stacked.

[0111] The first outer electrode 131 and the second outer electrode 132 are applied with voltages of different polarities and may be electrically connected to the exposed portions of the first inner electrode layer 121 and the second inner electrode layer 122, respectively.

[0112] According to the above configuration, when a predetermined voltage is applied to the first outer electrode 131 and the second outer electrode 132, charges accumulate between the first inner electrode layer 121 and the second inner electrode layer 122 facing each other. At this time, the capacitance of the multilayer ceramic capacitor 100 is proportional to the overlapping area of the first inner electrode layer 121 and the second inner electrode layer 122 overlapping each other in the T-axis direction in the effective region.

[0113] The first external electrode 131 may include a first connection portion and a first strip portion, and the second external electrode 132 may include a second connection portion and a second strip portion. The first connection portion and the second connection portion are respectively disposed on the third surface and the fourth surface of the capacitor body 110 and connected to the first internal electrode layer 121 and the second internal electrode layer 122. The first strip portion is disposed on the edge where the third surface of the capacitor body 110 intersects with the first surface, the second surface, and / or the fifth surface and the sixth surface, and the second strip portion is disposed on the edge where the fourth surface of the capacitor body 110 intersects with the first surface, the second surface, and / or the fifth surface and the sixth surface.

[0114] The first strip portion and the second strip portion may respectively extend from the first connection portion and the second connection portion to a part of the first surface, a part of the second surface, and / or a part of the fifth surface and a part of the sixth surface of the capacitor body 110. The first strip portion and the second strip portion can be used to improve the adhesion strength between the first external electrode 131 and the second external electrode 132 and the capacitor body 110.

[0115] Each of the first external electrode 131 and the second external electrode 132 may include a sintered metal layer in contact with the capacitor body 110, a conductive resin layer provided to cover the sintered metal layer, and a plating layer provided to cover the conductive resin layer.

[0116] The sintered metal layer may include a conductive metal and glass.

[0117] The conductive metal may include at least one selected from the group consisting of copper (Cu), nickel (Ni), silver (Ag), palladium (Pd), gold (Au), platinum (Pt), tin (Sn), tungsten (W), titanium (Ti), lead (Pb), and their alloys. For example, the term copper (Cu) may include the concept of elemental copper (Cu) and copper (Cu) alloys. When the conductive metal includes copper (Cu), based on 100 moles of copper (Cu), a metal other than copper (Cu) may be included in an amount less than or equal to about 5 moles.

[0118] The glass may include a composition of mixed oxides, for example, one or more selected from the group consisting of silicon oxide, boron oxide, aluminum oxide, transition metal oxides, alkali metal oxides, and alkaline earth metal oxides. The transition metal may include at least one selected from the group consisting of zinc (Zn), titanium (Ti), copper (Cu), vanadium (V), manganese (Mn), iron (Fe), and nickel (Ni). The alkali metal may include at least one selected from the group consisting of lithium (Li), sodium (Na), and potassium (K), and the alkaline earth metal may be at least one selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

[0119] Optionally, a conductive resin layer may be formed on the sintered metal layer. For example, it may be formed in a shape that completely covers the sintered metal layer. In addition, the first outer electrode 131 and the second outer electrode 132 may not include the sintered metal layer. In this case, the conductive resin layer may be in direct contact with the capacitor body 110.

[0120] The conductive resin layer extends to the first surface and the second surface and / or the fifth surface and the sixth surface of the capacitor body 110, and the length of the region (i.e., the belt portion) where the conductive resin layer extends and is disposed on the first surface and the second surface and / or the fifth surface and the sixth surface of the capacitor body 110 may be longer than the length of the region (i.e., the belt portion) where the sintered metal layer extends and is disposed on the first surface and the second surface and / or the fifth surface and the sixth surface of the capacitor body 110. That is to say, the conductive resin layer may be formed on the sintered metal layer and may be formed in a shape that completely covers the sintered metal layer.

[0121] The conductive resin layer may include a resin and a conductive metal.

[0122] The resin included in the conductive resin layer may be implemented by the following materials: having adhesive properties and shock absorption properties, and capable of forming a paste when mixed with conductive metal powder, but not limited thereto. For example, the resin may include phenolic resin, acrylic resin, silicone resin, epoxy resin, or polyimide resin.

[0123] The conductive metal included in the conductive resin layer is used for electrical connection to the first inner electrode layer 121 and the second inner electrode layer 122 or the sintered metal layer.

[0124] The conductive metal included in the conductive resin layer may have a spherical shape, a flake shape, or a combination thereof. That is to say, the conductive metal may be formed only in a flake shape, only in a spherical shape, or in a form of a mixture of a flake shape and a spherical shape.

[0125] Here, the spherical shape may also include a shape that is not a perfect sphere. For example, a shape in which the length ratio of the major axis to the minor axis (major axis / minor axis) is less than or equal to about 1.45. The flake shape refers to a flat and elongated shape, and there is no particular limitation. However, for example, the length ratio of the major axis to the minor axis (major axis / minor axis) may be greater than or equal to about 1.95.

[0126] The first outer electrode 131 and the second outer electrode 132 may also include a plating layer disposed on the outer surface of the conductive resin layer.

[0127] The coating layer may include at least one selected from the group consisting of nickel (Ni), copper (Cu), tin (Sn), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), tungsten (W), titanium (Ti), lead (Pb), and their alloys. For example, the coating layer may be a nickel (Ni) coating layer or a tin (Sn) coating layer, may be in a form where the nickel (Ni) coating layer and the tin (Sn) coating layer are stacked in sequence, or may be in a form where the tin (Sn) coating layer, the nickel (Ni) coating layer, and the tin (Sn) coating layer are stacked in sequence. Additionally, the coating layer may include multiple nickel (Ni) coating layers and / or multiple tin (Sn) coating layers.

[0128] The coating layer can improve the mountability of the multilayer ceramic capacitor 100 on the substrate, structural reliability, durability against the outside, heat resistance, and equivalent series resistance (ESR).

[0129] Hereinafter, a method for manufacturing the multilayer ceramic capacitor 100 according to an embodiment will be described.

[0130] The multilayer ceramic capacitor 100 according to some embodiments can be manufactured by: preparing a dielectric composite powder in which a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal; manufacturing a dielectric green sheet using a dielectric slurry including the dielectric composite powder and a sub-component powder, and forming a conductive paste layer on the surface of the dielectric green sheet; manufacturing a dielectric green sheet stack by stacking the dielectric green sheets on which the conductive paste layer is formed; manufacturing a capacitor body including a dielectric layer and an internal electrode layer by firing the dielectric green sheet stack; and forming an external electrode on the surface of the capacitor body.

[0131] First, a dielectric composite powder in which hafnium (Hf) or a first transition metal is doped in a barium titanate-based compound is prepared.

[0132] The first transition metal can be any transition metal other than hafnium (Hf), and may include, for example, at least one selected from the group consisting of zirconium (Zr), yttrium (Y), tantalum (Ta), and niobium (Nb).

[0133] Reference will be made to Figure 5 Describe the dielectric composite powder.

[0134] Figure 5 is a schematic diagram showing a dielectric composite powder according to an embodiment.

[0135] Reference Figure 5 shows that the dielectric composite powder 50 may have a core-shell structure, and the core-shell structure includes a core portion 60 and a shell portion 70 surrounding at least a part of the core portion 60. The core portion 60 may include a barium titanate-based compound, and when the first transition metal is TM, the shell portion 70 may include Ba(Ti,Hf)O 3 or Ba(Ti,TM)O3 。

[0136] The dielectric composite powder 50 can be prepared by the following method: preparing barium titanate seeds including barium (Ba) and titanium (Ti) by hydrothermal synthesis, and then mixing the prepared barium titanate seeds with a hafnium (Hf)-containing compound or a first transition metal-containing compound.

[0137] The temperature of the hydrothermal synthesis can be greater than or equal to about 180 °C, for example, about 180 °C to about 260 °C. When the hydrothermal synthesis is carried out within the above temperature range, the core-shell structure of the dielectric composite powder can be easily formed.

[0138] The hafnium (Hf)-containing compound and the first transition metal-containing compound can be oxides, nitrides or salt compounds respectively, or can be used in the form of sols dispersed in an organic solvent.

[0139] Based on 100 mole parts of titanium (Ti), the hafnium (Hf)-containing compound or the first transition metal-containing compound can be mixed in an amount of about 0.1 mole part to about 3 mole parts (for example, about 0.5 mole part to about 2.5 mole parts). When the hafnium (Hf)-containing compound or the first transition metal-containing compound is included within the above content range, the barium titanate-based compound can be doped at an appropriate level, thereby preventing sub-components (such as rare earth elements) as additives from diffusing into the core 20. Therefore, the crystallinity of the core 20 increases, and fine dielectric grains can be achieved, enabling the manufacture of multilayer ceramic capacitors with excellent DC bias characteristics and reliability. The first transition metal-containing compound can include at least one selected from the group consisting of a zirconium (Zr)-containing compound, a yttrium (Y)-containing compound, a tantalum (Ta)-containing compound, and a niobium (Nb)-containing compound.

[0140] Next, a dielectric slurry is prepared by mixing the prepared dielectric composite powder and the sub-component powder.

[0141] The sub-component powder can include a rare earth element-containing compound, a second transition metal-containing compound, or a combination thereof.

[0142] The rare earth element-containing compound can include at least one selected from the group consisting of a dysprosium (Dy)-containing compound, a terbium (Tb)-containing compound, a yttrium (Y)-containing compound, a lanthanum (La)-containing compound, a cerium (Ce)-containing compound, a samarium (Sm)-containing compound, a gadolinium (Gd)-containing compound, a holmium (Ho)-containing compound, and an erbium (Er)-containing compound.

[0143] The second transition metal-containing compound can include at least one selected from the group consisting of a manganese (Mn)-containing compound and a vanadium (V)-containing compound.

[0144] When an additive such as a rare earth element-containing compound is added to the aforementioned dielectric composite powder, hafnium (Hf) that has occupied the lattice during the preparation stage of the dielectric composite powder does not diffuse and forms a first shell, and then a second shell made of an additive such as a rare earth element can be formed. Therefore, hafnium (Hf) inhibits the diffusion of additives such as rare earth elements into the core, thereby reducing the defects in the core.

[0145] Based on 100 parts by mole of titanium (Ti), the sub-component powder can be included in an amount of about 0.01 part by mole to about 5 parts by mole (for example, about 0.1 part by mole to about 4 parts by mole). When the sub-component powder is included within the above content range, a highly reliable multilayer ceramic capacitor can be manufactured.

[0146] For example, the rare earth element-containing compound can include a dysprosium (Dy)-containing compound. Based on 100 parts by mole of titanium (Ti), the dysprosium (Dy)-containing compound can be included in an amount of about 0.5 part by mole to about 1.5 parts by mole (for example, about 0.7 part by mole to about 1.3 parts by mole). When the dysprosium (Dy)-containing compound is included within the above content range, a highly reliable multilayer ceramic capacitor can be manufactured.

[0147] The dielectric slurry can be prepared by further mixing a solvent and additives such as a dispersant, a binder, a plasticizer, a lubricant, or an antistatic agent.

[0148] The dispersant can include, for example, a phosphate ester-based dispersant, a polycarboxylic acid-based dispersant, or a combination thereof. Based on 100 parts by weight of the barium titanate-based compound, the dispersant can be mixed in an amount of about 0.1 part by weight to about 5 parts by weight, for example, in an amount of about 0.3 part by weight to about 3 parts by weight.

[0149] When the dispersant is mixed within the above content range, the dielectric slurry can exhibit excellent dispersibility and the amount of impurities included in the manufactured dielectric layer can be reduced.

[0150] The binder can be, for example, an acrylic resin, a polyvinyl butyral resin, a polyvinyl acetal resin, an ethyl cellulose resin, etc. Based on 100 parts by weight of the barium titanate-based compound, 0.1 part by weight to 50 parts by weight (for example, 3 parts by weight to 30 parts by weight) of the binder can be added. When the binder is mixed within the above content range, the dielectric slurry exhibits excellent dispersibility and the amount of impurities included in the manufactured dielectric layer can be reduced.

[0151] The plasticizer can be, for example: phthalic acid compounds such as dioctyl phthalate, benzyl butyl phthalate, dibutyl phthalate, dihexyl phthalate, bis(2-ethylhexyl) phthalate, and bis(2-ethylbutyl) phthalate; adipic acid compounds such as dihexyl adipate and bis(2-ethylhexyl) adipate; ethylene glycol compounds such as ethylene glycol, diethylene glycol, and triethylene glycol; ethylene glycol ester compounds such as triethylene glycol dibutyrate, triethylene glycol bis(2-ethylbutyrate), and triethylene glycol bis(2-ethylhexanoate); and so on. Based on 100 parts by weight of the barium titanate-based compound, the plasticizer can be added in an amount of about 0.1 part by weight to about 20 parts by weight (for example, about 1 part by weight to about 10 parts by weight). When the plasticizer is mixed within the above content range, the dielectric slurry can exhibit excellent dispersibility and can reduce the amount of impurities included in the manufactured dielectric layer.

[0152] The solvent can be: aqueous solvents such as water; alcohol solvents such as ethanol, methanol, benzyl alcohol, and methoxyethanol; ethylene glycol solvents such as ethylene glycol and diethylene glycol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as butyl acetate, ethyl acetate, carbitol acetate, and butyl carbitol acetate; ether solvents such as methyl cellosolve, ethyl cellosolve, butyl ether, and tetrahydrofuran; aromatic solvents such as benzene, toluene, and xylene, etc. Considering the solubility or dispersibility of various additives included in the dielectric slurry, the solvent can be, for example, an alcohol solvent or an aromatic solvent. Based on 100 parts by weight of the barium titanate-based compound, the solvent can be mixed in an amount of about 50 parts by weight to about 1000 parts by weight, or for example, in an amount of about 100 parts by weight to about 500 parts by weight. When the solvent is mixed within the above content range, the components of the dielectric slurry can be fully mixed, and subsequently the solvent can be easily removed.

[0153] The above dielectric slurry can be mixed by using a wet ball mill or a stirring mill. When using zirconia balls in a wet ball mill, multiple zirconia balls with a diameter of about 0.1 mm to about 10 mm can be used for wet mixing for about 8 hours to about 48 hours, or about 10 hours to about 24 hours.

[0154] The prepared dielectric slurry forms a dielectric layer after firing.

[0155] As a method of forming the prepared dielectric slurry into a sheet, a tape casting method such as a doctor blade method or a calender roll method can be used. For example, a roll coater with a head discharge method can be used, and then a dielectric green sheet can be obtained by drying the molded body.

[0156] To form a conductive paste layer that becomes an internal electrode layer after firing, a conductive paste can be prepared by mixing conductive powder made of a conductive metal or their alloy, a binder, and a solvent. Additionally, if necessary, barium titanate powder can be mixed as a common material. The common material can serve to inhibit sintering of the conductive powder during the firing process. The conductive paste layer is formed by coating the conductive paste in a predetermined pattern onto the surface of a dielectric green sheet using various printing methods such as screen printing or transfer printing.

[0157] The conductive powder can include nickel (Ni) or a nickel (Ni) alloy.

[0158] Next, a dielectric green sheet stack is prepared by stacking multiple dielectric green sheets on which internal electrode patterns are formed, and then pressing the multiple dielectric green sheets in the stacking direction. At this time, dielectric green sheets on which no internal electrode pattern is formed can be stacked on the upper and lower surfaces of the dielectric green sheet stack to form a covering portion.

[0159] The following step can be selectively performed: cutting the prepared dielectric green sheet stack into a predetermined size by cutting or the like.

[0160] Additionally, if necessary, the dielectric green sheet stack can be cured and dried to remove plasticizers and the like, and after curing and drying, the dielectric green sheet stack can be barrel polished using a horizontal centrifugal barrel machine or the like. In barrel polishing, the dielectric green sheet stack, a medium, and a polishing liquid are placed in a barrel container, and a rotational motion or vibration is applied to the barrel container, so that unnecessary parts such as burrs generated during cutting can be polished. Additionally, after barrel polishing, the dielectric green sheet stack can be washed with a cleaning solution such as water and dried.

[0161] Subsequently, a capacitor body can be obtained after the binder removal treatment and firing of the dielectric green sheet stack.

[0162] The conditions for binder removal can be appropriately adjusted according to the composition of the dielectric layer or the internal electrode layer. For example, the heating rate during the binder removal treatment can be about 5 °C / hour to about 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. Binder removal can be performed in an air atmosphere or a reducing atmosphere.

[0163] The firing conditions can be appropriately adjusted according to the main component composition of the dielectric layer or the main component composition of the internal electrodes. For example, firing can be carried out at a temperature of about 1100°C to about 1400°C, and can be carried out at a temperature of about 1200°C to about 1350°C. In addition, firing can be carried out for about 0.5 to about 8 hours, for example, about 1 to about 3 hours. Further, firing can be carried out in a reducing atmosphere, for example, in a mixed gas of humidified nitrogen and hydrogen. When the internal electrodes include nickel (Ni) or a nickel (Ni) alloy, the oxygen partial pressure in the firing atmosphere can be about 1.0×10 -14 MPa to about 1.0×10 -10 MPa.

[0164] After firing, annealing can be carried out as needed. Annealing is a process of re-oxidizing the dielectric layer, and if firing is carried out in a reducing atmosphere, annealing can be carried out. The conditions of the annealing treatment can also be appropriately adjusted according to the composition of the dielectric layer. For example, the annealing temperature can be about 950°C to about 1150°C, the time can be about 0 to about 20 hours, and the heating rate can be about 50°C / hour to about 500°C / hour. The annealing atmosphere can be a humidified nitrogen (N 2 2) atmosphere, and the oxygen partial pressure can be about 1.0×10 - 9 MPa to about 1.0×10 -5 MPa.

[0165] In the adhesive removal treatment, firing treatment, or annealing treatment, for example, a wetting agent can be used to humidify nitrogen or the mixed gas. In this case, the temperature of the wetting agent can be about 5°C to about 75°C. The adhesive removal treatment, firing treatment, and annealing treatment can be carried out sequentially, or can be carried out independently.

[0166] Optionally, surface treatments such as sandblasting, laser irradiation, barrel polishing, etc. can be carried out on the third surface and the fourth surface of the prepared capacitor body 110. By carrying out this surface treatment, the ends of the first internal electrode and the second internal electrode can be exposed to the third surface and the fourth surface, so that the electrical connection between the first external electrode and the first internal electrode and between the second external electrode and the second internal electrode can be improved, and an alloy part can be easily formed.

[0167] Subsequently, an external electrode is formed on the surface of the manufactured capacitor body 110.

[0168] According to some embodiments of the present disclosure, a paste for forming a sintered metal layer can be coated on the surface of the capacitor body 110, and then sintered to form a sintered metal layer.

[0169] The paste for forming a sintered metal layer may include a conductive metal and glass. Since the descriptions of the conductive metal and glass are the same as those above, the repeated descriptions will be omitted. Additionally, the paste for forming a sintered metal layer may selectively include a binder, a solvent, a dispersant, a plasticizer, an oxide powder, etc. The binder may be, for example, ethyl cellulose, acrylate, butyral, etc., and the solvent may be an organic solvent or an aqueous solvent, such as terpineol, butyl carbitol, ethanol, methyl ethyl ketone, acetone, toluene, etc.

[0170] The method of coating the paste for forming a sintered metal layer on the outer surface of the capacitor body 110 may include various printing methods such as screen printing, dipping methods, coating methods using a dispenser, etc., and spraying methods using a sprayer. The paste for forming a sintered metal layer may be coated on at least the third surface and the fourth surface of the capacitor body 110, and selectively coated on the portions of the first surface, the second surface, the fifth surface, and / or the sixth surface where the belt portions on which the first outer electrode and the second outer electrode are formed are located.

[0171] Thereafter, the capacitor body 110 coated with the paste for forming a sintered metal layer is dried and sintered at a temperature of about 700 °C to about 1000 °C for about 0.1 hour to about 3 hours to form a sintered metal layer.

[0172] Optionally, the paste for forming a conductive resin layer is coated on the outer surface of the obtained capacitor body 110 and then cured to form a conductive resin layer.

[0173] The paste for forming a conductive resin layer may include a resin and selectively include a conductive metal or a non-conductive filler. Since the descriptions of the conductive metal and the resin are the same as those above, the repeated descriptions will be omitted. Additionally, the paste for forming a conductive resin layer may selectively include a binder, a solvent, a dispersant, a plasticizer, an oxide powder, etc. The binder may be, for example, ethyl cellulose, acrylate, butyral, etc., and the solvent may be an organic solvent or an aqueous solvent, such as terpineol, butyl carbitol, ethanol, methyl ethyl ketone, acetone, and toluene.

[0174] For example, the conductive resin layer may be formed by dipping the capacitor body 110 into the paste for forming a conductive resin layer and then curing it, or by printing the paste for forming a conductive resin layer on the surface of the capacitor body 110 by screen printing or gravure printing, or by coating the paste for forming a conductive resin layer on the surface of the capacitor body 110 and then curing it.

[0175] Next, a plating layer is formed outside the conductive resin layer.

[0176] For example, the plating layer may be formed by plating methods, sputtering, or electroplating (electrodeposition).

[0177] In the following, embodiments are described in more detail with reference to examples. However, these examples are illustrative, and the scope of the claims is not limited thereto.

[0178] (Manufacture of Multilayer Ceramic Capacitor) Example 1 Barium titanate (BaTiO 2 ) seed crystals are prepared by hydrothermally synthesizing titanium dioxide (TiO 2 ) sol and barium hydroxide (Ba(OH) 3 ) at 260 °C, and then the barium titanate (BaTiO 3 ) seed crystals are mixed with hafnium oxide (HfO 2 ) to prepare Hf-doped BaTiO 3 powder, i.e., dielectric composite powder.

[0179] Dielectric composite powder having a core-shell structure made of a BaTiO 3 core and a Ba(Ti,Hf)O 3 shell is prepared. At this time, 1 mole part of hafnium oxide (HfO 2 ) is mixed per 100 mole parts of titanium (Ti).

[0180] Based on 100 mole parts of titanium (Ti), the prepared dielectric composite powder is mixed with 1 mole part of dysprosium oxide (Dy 2 O 3 ), 0.24 mole part of manganese oxide (MnO), and 0.46 mole part of vanadium oxide (V 2 O 5 ) sub-component powders to prepare a dielectric slurry.

[0181] When preparing the dielectric slurry, zirconia balls (ZrO 2 balls) are used as a dispersion medium, ethanol / toluene and polyvinyl butyral (PVB) resin are added as a wetting dispersant and a binder, and then mixed by mechanical grinding.

[0182] Using a head discharge type roll-on former coater, a dielectric green sheet is manufactured using the prepared dielectric slurry.

[0183] A conductive paste layer including nickel (Ni) is printed on the surface of the dielectric green sheet, and the dielectric green sheets printed with the conductive paste layer thereon are stacked and pressed to manufacture a dielectric green sheet stack.

[0184] The dielectric green sheet stack is subjected to a curing process in a nitrogen atmosphere at a temperature of 400 °C or lower, and then fired at a firing temperature of 1300 °C or lower and a hydrogen concentration of 1.0% H 2 or lower.

[0185] Subsequently, an external electrode is formed by a process such as plating to manufacture a multilayer ceramic capacitor.

[0186] Comparative Example 1 A multilayer ceramic capacitor is manufactured in the same manner as in Example 1, except that the dielectric paste is prepared as follows: Barium titanate (BaTiO 3 powder and TiO 2 powder are mixed to prepare barium titanate (BaTiO 3 ), which is the main component powder, and based on 100 mole parts of titanium (Ti), 1 mole part of dysprosium oxide (Dy 2 O 3 ), 0.24 mole parts of manganese oxide (MnO), and 0.46 mole parts of vanadium oxide (V 2 O 5 ) are used as sub-component powders.

[0187] Evaluation 1: TEM-EDS Analysis The multilayer ceramic capacitor manufactured in Example 1 is subjected to TEM-EDS (transmission electron microscopy - energy dispersive spectroscopy) analysis, and the results are shown in Figure 6 and Figure 7 .

[0188] Specifically, the multilayer ceramic capacitor manufactured in Example 1 is placed in an epoxy resin mixture and cured, and then the surface of the capacitor body in the W-axis direction - T-axis direction (WT surface) is polished to a depth of 1 / 2 in the L-axis direction. Then, the obtained cross-sectional sample is fixed and held in a vacuum atmosphere chamber so that the effective region where the dielectric layer and the internal electrode layer are stacked on each other can be observed. Subsequently, the effective region of the cross-sectional sample is measured using a transmission electron microscope (TEM) to ensure that at least one dielectric layer is visible. A TEM image is obtained in a region of approximately 800 nm × 800 nm in the effective region where at least one layer of the dielectric layer 111 is visible under the condition of an acceleration voltage of 200 kV using a focused ion beam (Xe-FIB). Then, in the TEM image of the measured cross-sectional sample, EDS (energy dispersive spectroscopy) line analysis is performed on a straight line segment that passes through the center of a dielectric grain from one outermost point of an arbitrary dielectric grain to another outermost point to confirm the structure and composition content of the dielectric grain.

[0189] Figure 6 is a TEM-EDS (transmission electron microscopy - energy dispersive spectroscopy) line analysis diagram of the dielectric grain according to Example 1, and Figure 7 is a TEM-EDS (transmission electron microscopy - energy dispersive spectroscopy) analysis image of the dielectric layer according to Example 1.

[0190] Refer to Figure 6, in the results of TEM-EDS (transmission electron microscopy - energy dispersive spectroscopy) line analysis of the dielectric grains, from the center of the dielectric grains to any grain boundary, the position of the first point of hafnium (Hf) with the maximum atomic % value is different from the position of the second point of dysprosium (Dy) with the maximum atomic % value with respect to the total number of atoms in the dielectric grains, and the second point of dysprosium (Dy) with the maximum atomic % value is located on the outer side farther from the center of the dielectric grains than the first point of hafnium (Hf) with the maximum atomic % value. It can be seen from this that the dielectric grains according to Example 1 have a core-double shell structure, and the first shell includes a dielectric composite in which barium titanate is doped with hafnium (Hf).

[0191] Moreover, referring to Figure 7 , it can be seen that the dielectric grains in the dielectric layer according to Example 1 include hafnium (Hf) in the first shell and dysprosium (Dy) in the second shell.

[0192] Evaluation 2: SEM Analysis SEM (scanning electron microscopy) analysis was performed on the multilayer ceramic capacitors manufactured in Example 1 and Comparative Example 1, and the average diameter of the dielectric grains was measured. The results are shown in Figure 8 and Figure 9 .

[0193] Specifically, the multilayer ceramic capacitor was placed in an epoxy resin mixture and cured. Then, the surface (WT surface) of the capacitor body in the W-axis direction - T-axis direction was polished to a depth of 1 / 2 in the L-axis direction. Then, the obtained cross-sectional sample was fixed and held in a vacuum atmosphere chamber so that the effective region where the dielectric layer and the internal electrode layer were stacked on each other could be observed. Subsequently, a transmission electron microscope (TEM) was used to measure the effective region of the cross-sectional sample to ensure that at least three dielectric layers were visible. Using the Verios G4 product from Thermofisher Scientific, SEM images were obtained in a region of approximately 2.5 μm × 2.5 μm in the effective region where at least three dielectric layers were visible under the condition of 10 kV. In the SEM image of the cross-sectional sample, the average value of the sum of the major axis and the axis perpendicular to the major axis of more than 100 dielectric grains was calculated.

[0194] Figure 8 is a scanning electron microscope (SEM) analysis image of the effective region of the multilayer ceramic capacitor according to Example 1, Figure 9 is a scanning electron microscope (SEM) analysis image of the effective region of the multilayer ceramic capacitor according to Comparative Example 1.

[0195] Referring to Figure 8 and Figure 9, it can be seen that the average diameter of the dielectric grains in Example 1 is 229 nm, while the average diameter of the dielectric grains in Comparative Example 1 is 266 nm. This can be regarded as the result of hafnium (Hf) with high thermal stability suppressing the grain growth caused by heat. Thus, the dielectric grains according to the embodiment (i.e., the dielectric grains having a core-double shell structure and including a dielectric composite in the first shell, wherein barium titanate is doped with hafnium (Hf)) are micronized and the defects in the core are suppressed.

[0196] Evaluation 3: DC Bias Characteristics The DC bias characteristics of the multilayer ceramic capacitors manufactured in Example 1 and Comparative Example 1 were measured by the following method, and the results are shown in Figure 10 .

[0197] The effective capacitance was measured after maintaining DC biases of 1 V and 3 V for 60 seconds each under the conditions of 1 kHz and AC (alternating current) 0.5 V.

[0198] Figure 10 is a graph showing the DC bias characteristics of the multilayer ceramic capacitors according to Example 1 and Comparative Example 1.

[0199] Referring to Figure 10 it can be seen that the DC bias characteristics of Example 1 are excellent compared to Comparative Example 1. Thus, the multilayer ceramic capacitor according to the example (i.e., the multilayer ceramic capacitor including dielectric grains having a core-double shell structure and including a dielectric composite in the first shell, wherein barium titanate is doped with hafnium (Hf)) has improved DC bias characteristics.

[0200] Although the present disclosure has been described in connection with what are presently considered to be practical embodiments, it is to be understood that the disclosure is not limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0201] <Description of Reference Numerals> 10: Dielectric grains 20: Core 30: First shell 40: Second shell 50: Dielectric composite powder 60: Core part 70: Shell part 100: Multilayer ceramic capacitor 110: Capacitor body 111: Dielectric layer 121: First inner electrode 122: Second inner electrode 131: First outer electrode 132: Second outer electrode.

Claims

1. A multilayer ceramic capacitor comprising: a capacitor body including a dielectric layer and an inner electrode layer, and An outer electrode is disposed on an outer surface of the capacitor body, Wherein, the dielectric layer includes a plurality of dielectric grains. At least one of the plurality of dielectric grains includes a dielectric composite in which a barium titanate-based compound is doped with hafnium or a first transition metal and a subcomponent includes a rare earth element, a second transition metal, or a combination thereof, According to transmission electron microscopy-energy dispersive spectroscopy line analysis of the at least one of the plurality of dielectric grains, from a center of the at least one of the plurality of dielectric grains to a grain boundary, a first point has a maximum atomic percentage of hafnium or the first transition metal relative to a total number of atoms of the at least one of the plurality of dielectric grains, and a second point has a maximum atomic percentage of the rare earth element or the second transition metal relative to the total number of atoms of the at least one of the plurality of dielectric grains, and The first transition metal does not include hafnium, and the first transition metal and the second transition metal are different from each other.

2. The multilayer ceramic capacitor according to claim 1, wherein According to a transmission electron microscopy-energy dispersive spectroscopy line analysis of the at least one of the plurality of dielectric grains, The second point is located further outside from the center of the at least one of the plurality of dielectric grains than the first point.

3. The multilayer ceramic capacitor according to claim 1, wherein The at least one of the plurality of dielectric grains has a core-double shell structure including a core, a first shell surrounding at least a portion of the core, and a second shell surrounding at least a portion of the first shell.

4. The multilayer ceramic capacitor according to claim 3, wherein: The first shell includes the dielectric composite, and The second shell includes the subcomponent.

5. The multilayer ceramic capacitor according to claim 4, wherein: According to transmission electron microscopy-energy dispersive spectroscopy line analysis, The first shell is a region including a peak having the maximum atomic percentage of hafnium or the first transition metal, The second shell is a region including a peak of the rare earth element or the second transition metal having the maximum atomic percentage, The region of the first shell and the region of the second shell are different from each other.

6. The multilayer ceramic capacitor according to claim 5, wherein: The first shell includes a higher atomic percentage of hafnium or the first transition metal than an atomic percentage of the rare earth element or the second transition metal, and The second shell includes an atomic percentage of hafnium or the first transition metal lower than an atomic percentage of the rare earth element or the second transition metal.

7. The multilayer ceramic capacitor according to claim 1, wherein: The first transition metal includes at least one selected from the group consisting of zirconium, yttrium, tantalum, and niobium.

8. The multilayer ceramic capacitor according to claim 1, wherein The rare earth element includes at least one selected from the group consisting of dysprosium, terbium, yttrium, lanthanum, cerium, samarium, gadolinium, holmium, and erbium.

9. The multilayer ceramic capacitor according to claim 1, wherein: The second transition metal includes manganese, vanadium, or a combination thereof.

10. The multilayer ceramic capacitor according to claim 1, wherein Hafnium or the first transition metal is doped in an amount of 0.1 atomic % to 5 atomic % based on the total amount of the dielectric composite.

11. The multilayer ceramic capacitor according to claim 4, wherein: The sub component is included in an amount of 0.1 atomic % to 2 atomic % based on the total amount of the components of the second shell.

12. The multilayer ceramic capacitor according to claim 3, wherein: A length of the core measured from a major axis passing through the center of the at least one of the plurality of dielectric grains is 50 nm to 150 nm.

13. The multilayer ceramic capacitor according to claim 3, wherein: An average length of the first shell measured from a major axis passing through the center of the at least one of the plurality of dielectric grains is 10 nm to 50 nm.

14. The multilayer ceramic capacitor according to claim 3, wherein: An average length of the second shell measured from a major axis passing through the center of the at least one of the plurality of dielectric grains is 40 nm to 240 nm.

15. The multilayer ceramic capacitor according to claim 1, wherein The plurality of dielectric grains have an average diameter greater than or equal to 100 nm and less than 266 nm.

16. The multilayer ceramic capacitor according to claim 3, wherein: A ratio of the number of dielectric grains having the core-double shell structure in the plurality of dielectric grains relative to the total number of the plurality of dielectric grains is greater than or equal to 50% and less than or equal to 100%.

17. A method of manufacturing a multilayer ceramic capacitor, comprising: preparing a dielectric composite powder in which a barium titanate-based compound is doped with hafnium or a first transition metal; manufacturing a dielectric green sheet using a dielectric slurry including the dielectric composite powder and the sub-component powders, and forming a conductive paste layer on a surface of the dielectric green sheet; manufacturing a dielectric green sheet stack by stacking the dielectric green sheets on which the conductive paste layers are formed; manufacturing a capacitor body including a dielectric layer and an internal electrode layer by firing the dielectric green sheet stack; and forming external electrodes on a surface of the capacitor body, Wherein, the dielectric layer includes a plurality of dielectric grains. At least one of the plurality of dielectric grains includes a dielectric composite in which a barium titanate-based compound is doped with hafnium or a first transition metal, and a subcomponent includes a rare earth element, a second transition metal, or a combination thereof, According to transmission electron microscopy-energy dispersive spectroscopy line analysis of the at least one of the plurality of dielectric grains, from a center of the at least one of the plurality of dielectric grains to a grain boundary, a first point has a maximum atomic percentage of hafnium or the first transition metal relative to a total number of atoms of the at least one of the plurality of dielectric grains, and a second point has a maximum atomic percentage of the rare earth element or the second transition metal relative to the total number of atoms of the at least one of the plurality of dielectric grains, and The first transition metal does not include hafnium, and the first transition metal and the second transition metal are different from each other.

18. The method according to claim 17, wherein: The dielectric composite powder includes a core portion including the barium titanate-based compound and a shell portion surrounding at least a portion of the core portion and including Ba(Ti,Hf)O3 or Ba(Ti,TM)O3, wherein TM represents the first transition metal.

19. The method according to claim 18, wherein: The dielectric composite powder is prepared by the following steps: preparing barium titanate seeds comprising barium and titanium by hydrothermal synthesis; and The barium titanate seed crystals are mixed with a hafnium-containing compound or a first transition metal-containing compound.

20. The method according to claim 19, wherein: The hafnium-containing compound or the first transition metal-containing compound is mixed in an amount of 0.1 parts by mol to 3 parts by mol based on 100 parts by mol of titanium.

21. The method according to claim 19, wherein: The first transition metal-containing compound includes at least one selected from the group consisting of a zirconium-containing compound, a yttrium-containing compound, a tantalum-containing compound, and a niobium-containing compound.

22. The method according to claim 17, wherein: The subcomponent powder includes a rare earth element-containing compound, a second transition metal-containing compound, or a combination thereof.

23. The method according to claim 22, wherein: The rare earth element-containing compound includes at least one selected from the group consisting of dysprosium-containing compounds, terbium-containing compounds, yttrium-containing compounds, lanthanum-containing compounds, cerium-containing compounds, samarium-containing compounds, gadolinium-containing compounds, holmium-containing compounds and erbium-containing compounds.

24. The method according to claim 22, wherein: The second transition metal-containing compound includes at least one selected from the group consisting of a manganese-containing compound and a vanadium-containing compound.

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