Multilayer ceramic capacitor and method of manufacturing the same

Abstract

To provide a multilayer ceramic capacitor with improved DC-bias characteristics and reliability, and a method of manufacturing the same.SOLUTION: There is provided a multilayer ceramic capacitor 100 including a capacitor body 110 and external electrodes 131, 132 disposed outside the capacitor body. In the multilayer ceramic capacitor, a 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 (Hf) or a first transition metal, and a subcomponent including a rare earth element, a second transition metal, or a combination thereof. Among results from the TEM-EDS line analysis of the dielectric grains from a center of the dielectric grains to either grain boundary, a first point having a maximum atomic percent value of hafnium (Hf) or the first transition metal is different from a location of a second point having a maximum atomic % value of the rare earth element or the second transition metal. The first transition metal excludes hafnium (Hf), and the first transition metal and the second transition metal are different from each other.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] As electronic components using ceramic materials, there are capacitors, inductors, piezoelectric elements, varistors, thermistors, and the like. Among such ceramic electronic components, a multilayer ceramic capacitor (MLCC) can be used in various electronic devices because of its advantages of being small in size, having a high capacitance, and being easy to mount.

[0003] For example, a multilayer ceramic capacitor (MLCC) can be used as a chip-shaped capacitor that is mounted on a substrate of various electronic products such as a liquid-crystal-display (LCD), a plasma display panel (PDP), an organic light-emitting diode (OLED) and other video devices, a computer, a personal digital assistant, and a smartphone, and serves to charge or discharge electricity.

[0004] BaTiO 3 is mainly used as the dielectric material of the MLCC. BaTiO 3 dielectric can achieve a high capacitance, but the capacitance, that is, the effective capacitance, decreases under the application conditions of a DC bias corresponding to the actual use conditions of the product. In recent years, the industry has been paying more attention to the effective capacitance under the actual use conditions of products that are not electrostatic capacitance.

Summary of the Invention

Problems to be Solved by the Invention

[0005] One embodiment provides an excellent multilayer ceramic capacitor with improved DC-bias characteristics and reliability.

[0006] Another embodiment provides a method for manufacturing the multilayer ceramic capacitor. **Means for Solving the Problems**

[0007] One embodiment includes a capacitor body including a dielectric layer and an internal electrode layer, and an external electrode disposed outside the capacitor body. The dielectric layer includes a plurality of dielectric grains, and at least one of the plurality of dielectric grains is 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. In the results of TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis of the dielectric grain from the center of the dielectric grain to any one of the grain boundaries, the first point having the maximum atomic percentage of hafnium (Hf) or the first transition metal is different from the position of the second point having the maximum atomic percentage of the rare earth element or the second transition metal. The first transition metal does not include hafnium (Hf), and the first transition metal and the second transition metal provide different multilayer ceramic capacitors.

[0008] In the TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis of the dielectric grain, among the results from the center of the dielectric grain to any one of the grain boundaries, the second point having the maximum atomic percentage of the rare earth element or the second transition metal can be located more outside from the center of the dielectric grain than the first point having the maximum atomic percentage of hafnium (Hf) or the first transition metal.

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

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

[0011] In the TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis for the dielectric crystal grains, among the results from the center of the dielectric crystal grains to any one of the grain boundaries, the first shell may be a region including a peak having the maximum atomic percentage of hafnium (Hf) or a first transition metal, and the second shell may be a region including a peak having the maximum atomic percentage of a rare earth element or a second transition metal, and the first shell and the second shell can have different regions from each other.

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

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

[0014] The rare earth element can include dysprosium (Dy), terbium (Tb), yttrium (Y), lanthanum (La), cerium (Ce), samarium (Sm), gadolinium (Gd), holmium (Ho), erbium (Er), or a combination thereof.

[0015] The second transition metal can include manganese (Mn), vanadium (V), or a combination thereof.

[0016] The hafnium (Hf) or the first transition metal can be doped in an amount of 0.1 atomic % to 5 atomic % with respect to the total amount of the dielectric composite.

[0017] The sub-component is contained in an amount of 0.1 atomic % to 2 atomic % with respect to the total amount of the components of the second shell.

[0018] The length of the core measured along the major axis passing through the center of the dielectric crystal grains may be 50 nm to 150 nm.

[0019] The average length of the first shell measured along the major axis passing through the center of the dielectric crystal grains may be 10 nm to 50 nm.

[0020] The average length of the second shell measured along the major axis passing through the center of the dielectric crystal grains may be 40 nm to 240 nm.

[0021] The average diameter of the dielectric crystal grains may be 100 nm or more and less than 266 nm. Among the plurality of dielectric crystal grains, the ratio of the number of dielectric crystal grains having the core-double shell structure may be 50% or more and 100% or less.

[0022] Another embodiment includes the steps of manufacturing 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; laminating the dielectric green sheets having 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 an internal electrode layer; and forming an external electrode on one surface of the capacitor body, wherein the dielectric layer includes a plurality of dielectric crystallites (grains), and at least one of the plurality of dielectric crystallites is 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, and in a TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis for the dielectric crystallite, among the results from the center of the dielectric crystallite to any one of the grain boundaries, a first point having the maximum atomic percentage of hafnium (Hf) or the first transition metal is different from the position of a second point having the maximum atomic percentage of the rare earth element or the second transition metal, the first transition metal does not include hafnium (Hf), and the first transition metal and the second transition metal are different from each other, and a method for manufacturing a multilayer ceramic capacitor is provided.

[0023] The dielectric composite powder in which the barium titanate-based compound is doped with hafnium (Hf) or a first transition metal (TM) includes a core portion including a barium titanate-based compound, and a shell portion surrounding at least a part of the core portion, and Ba(Ti, Hf)O 3 or Ba(Ti, TM)O 3 and may include a shell portion including the same.

[0024] The dielectric composite powder can be manufactured by including a step of producing barium titanate seed containing barium (Ba) and titanium (Ti) through hydrothermal synthesis; and a step of mixing the barium titanate seed with a hafnium (Hf)-containing compound or a first transition metal-containing compound.

[0025] The hafnium (Hf)-containing compound or the first transition metal-containing compound can be mixed in an amount of 0.1 to 3 mole parts with respect to 100 mole parts of the titanium (Ti).

[0026] The first transition metal-containing compound can include a zirconium (Zr)-containing compound, a yttrium (Y)-containing compound, a tantalum (Ta)-containing compound, a niobium (Nb)-containing compound, or a combination thereof.

[0027] The sub-component powder can include a rare earth element-containing compound, a second transition metal-containing compound, or a combination thereof.

[0028] The rare earth element-containing compound can include 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, an erbium (Er)-containing compound, or a combination thereof.

[0029] The second transition metal-containing compound can include a manganese (Mn)-containing compound, a vanadium (V)-containing compound, or a combination thereof.

Advantages of the Invention

[0030] A multilayer ceramic capacitor according to an embodiment can improve DC-bias characteristics and reliability.

Brief Description of the Drawings

[0031]

Figure 1

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Figure 4

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Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0032] 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 order to clearly explain the present invention in the drawings, parts that are unnecessary for the description are omitted, and the same reference numerals are given to the same or similar components throughout the specification. Also, in the accompanying drawings, some components are exaggerated, omitted, or shown schematically, and the sizes of the components do not fully reflect the actual sizes.

[0033] The attached drawings are provided to facilitate an easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings. It should be understood that the attached drawings include all modifications, equivalents, and alternatives included in the spirit and technical scope of the present invention.

[0034] Terms including ordinal numbers such as first, second, etc. can be used to describe various components, but the components are not limited by these terms. These terms are used only for the purpose of distinguishing one component from another.

[0035] Also, when a part such as a layer, film, region, plate, etc. is "on" or "above" another part, this includes not only the case where it is "directly above" the other part, but also the case where there are other parts in between. Conversely, when a part is "directly above" another part, it means that there are no other parts in between. Also, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" or "above" in the direction opposite to gravity.

[0036] 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 be understood not to preclude in advance the possibility of 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, unless otherwise stated to the contrary, it can further include other components rather than excluding other components.

[0037] Also, throughout the specification, when referring to "on a plane", this means when looking at the target part from above, and when referring to "in a cross-section", this means when looking at the cross-section obtained by vertically cutting the target part from the side.

[0038] Also, throughout the specification, when referring to "connected", this does not only mean that two or more components are directly connected, but also that two or more components are indirectly connected through other components, not only physically connected, but also electrically connected, or can mean that they are integrated although referred to by different names depending on their position and function.

[0039] Hereinafter, a multilayer ceramic capacitor according to an embodiment will be described with reference to FIGS. 1 to 3.

[0040] FIG. 1 is a perspective view showing a multilayer ceramic capacitor according to an embodiment, FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor cut along the line I-I' of FIG. 1, and FIG. 3 is a cross-sectional view of the multilayer ceramic capacitor cut along the line II-II' of FIG. 1.

[0041] The L-axis, W-axis, and T-axis shown in FIGS. 1 to 3 indicate the length direction, width direction, and thickness direction of the capacitor body 110, respectively. Here, the thickness direction (T-axis direction) is a direction perpendicular to the wide surface (main surface) of the sheet-shaped component, and for example, can be used in the same concept as the stacking direction in which the dielectric layer 111 is stacked. The length direction (L-axis direction) is a direction extending parallel to the wide surface (main surface) of the sheet-shaped component and is substantially perpendicular to the thickness direction (T-axis direction). For example, it may 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) is a direction extending parallel to the wide surface (main surface) of the sheet-shaped component and is substantially perpendicular to the thickness direction (T-axis direction) and the length direction (L-axis direction). The length of the sheet-shaped component in the length direction (L-axis direction) may be longer than the length in the width direction (W-axis direction).

[0042] Referring to FIGS. 1 to 3, a multilayer ceramic capacitor 100 according to an embodiment includes a capacitor body 110, and external electrodes 131 and 132 disposed outside the capacitor body 110. The external electrodes 131 and 132 can include a first external electrode 131 and a second external electrode 132 disposed at both ends facing each other in the length direction (L-axis direction) of the capacitor body 110.

[0043] The capacitor body 110 has, for example, a substantially hexahedral shape.

[0044] For the sake of convenience in explaining an embodiment, in the capacitor body 110, both surfaces facing each other in the thickness direction (T-axis direction) are defined as a first surface and a second surface, both surfaces connected to the first surface and the second surface and facing each other in the length direction (L-axis direction) are defined as a third surface and a fourth surface, and both surfaces connected to the first surface and the second surface and connected to the third surface and the fourth surface and facing each other in the width direction (W-axis direction) are defined as a fifth surface and a sixth surface.

[0045] For example, the first surface, which is the lower surface, becomes the surface facing the mounting direction. Also, the first surface to the sixth surface are flat, but an embodiment is not limited thereto. For example, the first surface to the sixth surface may be convex curved surfaces at the central portions, and the corner portions, which are the boundaries of each surface, may be rounded.

[0046] The shape, dimensions, and number of stacked dielectric layers 111 of the capacitor body 110 are not limited to those shown in the drawings of this embodiment.

[0047] The capacitor body 110 includes a plurality of dielectric layers 111 and internal electrode layers 121 and 122. Specifically, the capacitor body 110 includes a plurality of dielectric layers 111 and a first internal electrode 121 and a second internal electrode 122 alternately arranged in the thickness direction (T-axis direction) with the dielectric layers 111 therebetween.

[0048] At this time, the boundaries between the respective dielectric layers 111 of the capacitor body 110 adjacent to each other are integrated to such an extent that it is difficult to confirm without using a scanning electron microscope (SEM).

[0049] The capacitor body 110 can have an active region. The active region is a region where the dielectric layers 111 and the internal electrode layers 121 and 122 are alternately arranged, and is a part that contributes to the capacitance formation of the multilayer ceramic capacitor 100. Specifically, the active region may be a region where the first internal electrode 121 or the second internal electrode 122 laminated along the thickness direction (T-axis direction) overlaps.

[0050] Also, the capacitor body 110 can further include a cover portion and side margin portions.

[0051] The cover portion is a margin portion in the thickness direction and can be located on the first surface and the second surface sides of the active region in the thickness direction (T-axis direction). Such a cover portion may be a single dielectric layer 111 or a laminate of two or more dielectric layers 111 laminated on the upper surface and the lower surface of the active region, respectively.

[0052] The side margin portions can be regarded as side cover portions and can be located on both side ends of the active region facing each other in the width direction (W-axis direction), that is, on the fifth surface and the sixth surface sides. The side margin portions can be formed by applying a conductive paste layer for the internal electrode layer only to a partial region of the surface of the dielectric green sheet when applying the conductive paste layer to the surface of the 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, but the formation method is not limited to this.

[0053] The cover portion and the side margin portions serve to prevent damage to the first internal electrode 121 and the second internal electrode 122 due to physical or chemical stress.

[0054] The dielectric layer 111 includes a plurality of dielectric crystallites (grains).

[0055] At least one of the plurality of dielectric crystallites 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. The first transition metal can correspond to all transition metals except 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.

[0056] According to one embodiment, in the TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis for the dielectric crystallite, among the results from the center of the dielectric crystallite to any one of the grain boundaries, the first point having the maximum atomic percentage of hafnium (Hf) or the first transition metal is different from the position of the second point having the maximum atomic percentage of the rare earth element or the second transition metal. That is, the positions of the first point and the second point in the dielectric crystallite are different. Thus, the dielectric crystallite having a structure in which the positions of the first point and the second point are different can increase the crystallinity by suppressing defects near the center of the dielectric crystallite. Thereby, it is possible to realize fine dielectric crystallites, and the DC bias characteristics of the multilayer ceramic capacitor can be improved. Here, the improvement of the DC-bias characteristics means that the DC effective capacitance is improved, and the degree of capacitance reduction when a DC voltage is applied becomes smaller.

[0057] Specifically, the second point having the maximum atomic percentage of the rare earth element or the second transition metal can be located more outside from the center of the dielectric crystallite than the first point having the maximum atomic percentage of hafnium (Hf) or the first transition metal. Thus, the dielectric crystallite having a structure in which the first point is located inside from the center of the dielectric crystallite 10 and the second point is located more outside can realize fine dielectric crystallites by increasing the crystallinity, and the DC bias characteristics of the multilayer ceramic capacitor can be improved.

[0058] For example, at least one of the plurality of dielectric crystallites can have a core-double shell structure. The dielectric crystallite having the core-double shell structure will be described with reference to FIG. 4.

[0059] FIG. 4 is a schematic diagram showing a dielectric crystallite according to an embodiment.

[0060] Referring to FIG. 4, a dielectric crystallite 10 according to an embodiment can have a core-double shell structure including 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.

[0061] The core 20 can include a barium titanate-based compound.

[0062] The barium titanate-based compound is a dielectric base material, has a high dielectric constant, and contributes to the formation of the dielectric constant of the multilayer ceramic capacitor 100.

[0063] The barium titanate-based compound is a compound containing barium (Ba) and titanium (Ti), and for example, 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 , (Ba, Sr)(Ti, Sn)O 3 , or a combination thereof.

[0064] The first shell 30 can include a barium titanate-based compound and hafnium (Hf) or a first transition metal.

[0065] Specifically, the first shell 30 can include the dielectric composite, that is, a dielectric composite in which a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal.

[0066] All transition metals except hafnium (Hf) can correspond to the first transition metal. The first transition metal can include, for example, zirconium (Zr), yttrium (Y), tantalum (Ta), niobium (Nb), or a combination thereof.

[0067] The second shell 40 can include a barium titanate-based compound as a main component and a sub-component. The sub-component can include a rare earth element, a second transition metal, or a combination thereof.

[0068] The rare earth element can include, for example, dysprosium (Dy), terbium (Tb), yttrium (Y), lanthanum (La), cerium (Ce), samarium (Sm), gadolinium (Gd), holmium (Ho), erbium (Er), or a combination thereof.

[0069] The second transition metal is different from the first transition metal and can include, for example, manganese (Mn), vanadium (V), or a combination thereof.

[0070] According to one embodiment, the dielectric crystal grains 10 have a core-double shell structure, and the first shell 30 has a structure including 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. During firing that progresses 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. As a result, defects in the core 20 are suppressed, the crystallinity of the core 20 is increased, it is possible to realize fine-grained dielectric crystal grains, and the DC bias characteristics of the multilayer ceramic capacitor can be improved.

[0071] The core-double shell structure of the dielectric crystal grains 10 can be confirmed by TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis. That is, in the TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis for the dielectric crystal grains 10, among the results from the center of the dielectric crystal grains to any one of the grain boundaries, the first shell 30 can be defined as the region including the peak with the maximum atomic percentage of hafnium (Hf) or the first transition metal. Also, the second shell 40 can be defined as the region including the peak with the maximum atomic percentage of the rare earth element or the second transition metal. At this time, the first shell 30 and the second shell 40 have different regions from each other.

[0072] Specifically, in the first shell 30, the atomic percentage content of hafnium (Hf) or the first transition metal may be more than the atomic percentage content of the rare earth element or the second transition metal. Also, in the second shell 40, the atomic percentage content of hafnium (Hf) or the first transition metal may be less than the atomic percentage content of the rare earth element or the second transition metal.

[0073] For example, the first shell 30 can include a dielectric composite in which a barium titanate-based compound is doped with hafnium (Hf).

[0074] Hafnium (Hf) has a high melting temperature, and the ionic radius of Hf 4+ is 0.71 nm, which is larger than that of Ti with an ionic radius of 0.61 nm 4+ . Therefore, hafnium (Hf) itself has slow diffusion inside barium titanate (BaTiO 3 ), and it can suppress the diffusion of secondary components such as rare earth elements of the additive into the core. Thereby, when hafnium (Hf) is doped into barium titanate (BaTiO 3 ) and applied to the dielectric layer, it can suppress the diffusion of the additive into the core during firing, resulting in having a fine particle size (fine grains), and the DC bias characteristics can be improved.

[0075] A dielectric composite in which a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal can be used in powder form having a core-shell structure during the manufacture of a dielectric layer. Specifically, the core contains a barium titanate-based compound. When the first transition metal is designated as TM, the shell can contain Ba(Ti, Hf)O 3 or Ba(Ti, TM)O 3 and can include.

[0076] Generally, a dielectric of a core-shell structure is manufactured by adding an additive to barium titanate powder and then adjusting the firing conditions. By adjusting the firing conditions, the formation of a core-shell structure is possible. However, since the grain growth behavior changes depending on the firing conditions, it is difficult to have fine-grained crystal grains and at the same time form a core-shell structure. Also, some of the additives present in the shell diffuse into the core and form defects in the core.

[0077] According to one embodiment, in the synthesis step of barium titanate powder, a dielectric composite powder having a core-shell structure is synthesized to manufacture a dielectric. Therefore, the dielectric layer 111 according to one embodiment can improve DC bias characteristics and reliability by having dielectric crystal grains 10 of a core-double shell structure manufactured in such a manner.

[0078] The core-double shell structure of the dielectric crystal grains 10, and the components and their contents present in the core 20, the first shell 30, and the second shell 40 respectively can be confirmed by TEM-EDS (transmission electron microscope-energy dispersive spectroscopy) analysis.

[0079] Specifically, after placing the multilayer ceramic capacitor 100 in an epoxy mixture and curing it, the W-axis and T-axis direction surfaces (WT surfaces) of the capacitor body 110 are polished to a depth of 1 / 2 in the L-axis direction, maintained in a vacuum atmosphere chamber after fixing, and a cross-sectional sample can be obtained so that the active region where the dielectric layer 111 and the internal electrode layers 121 and 122 intersect can be observed. Subsequently, it can be measured with a transmission electron microscope (TEM) so that at least one layer, for example, 1 to 5 layers of the dielectric layer 111 can be seen with respect to the active region of the cross-sectional sample. For example, the TEM can be measured under the condition of an acceleration voltage of 200 kV using Xe-FIB (focused ion beam) in a region of about 800 nm × 800 nm where at least one layer of the dielectric layer 111 can be seen in the active region. Subsequently, in the TEM image of the measured cross-sectional sample, EDS (energy dispersive spectroscopy) line analysis can be performed for a straight line section from one point on the outermost contour of any dielectric grain to the center and then across to another point on the outermost contour. By EDS line analysis, the core-double shell structure and the component composition present in each region can be confirmed.

[0080] The hafnium (Hf) or the first transition metal contained in the first shell 30 is doped into the barium titanate-based compound at 0.1 atomic % to 5 atomic % with respect to the total amount of the dielectric composite, and can be doped, for example, at 0.5 atomic % to 4 atomic %. When hafnium (Hf) or the first transition metal is doped into the barium titanate-based compound within the above content range, diffusion of sub-components such as rare earth elements into the core 20 during firing can be prevented, and the crystallinity of the core increases. Thereby, it is possible to realize fine-grained dielectric grains, and the DC bias characteristics and reliability of the multilayer ceramic capacitor are improved.

[0081] The secondary components such as rare earth elements contained in the second shell 40 are contained in an amount of 0.1 atomic % to 2 atomic % with respect to the total amount of components of the second shell 40, and are contained, for example, in an amount of 0.5 atomic % to 1.5 atomic %. When the secondary components are contained within the above content range in the second shell 40, a multilayer ceramic capacitor with excellent reliability can be ensured.

[0082] Referring to FIG. 4, the length (L1) of the core 20 measured along the major axis passing through the center of the dielectric crystal grains 10 is 50 nm to 150 nm, and is, for example, 60 nm to 140 nm, 70 nm to 130 nm.

[0083] Further, the average lengths (L2, L2') of the first shell 30 measured along the major axis passing through the center of the dielectric crystal grains 10 are 10 nm to 50 nm, and are, for example, 15 nm to 45 nm, 20 nm to 40 nm. Here, L2 and L2' are different from each other, and the average length of the first shell 30 may be the average value of L2 and L2'.

[0084] Further, the average lengths (L3, L3') of the second shell 40 measured along the major axis passing through the center of the dielectric crystal grains 10 are 40 nm to 240 nm, and are, for example, 50 nm to 230 nm, 60 nm to 220 nm. Here, L3 and L3' are different from each other, and the average length of the second shell 40 may be the average value of L3 and L3'.

[0085] When the core 20, the first shell 30, and the second shell 40 each have a length within the above range and the core-double shell structure of the dielectric crystal grains 10 is ensured, the DC bias characteristics and reliability of the multilayer ceramic capacitor can be improved.

[0086] The lengths of the core 20, the first shell 30, and the second shell 40 can be obtained by TEM-EDS (transmission electron microscope-energy dispersive spectroscopy) analysis. The TEM-EDS analysis method is as described above.

[0087] The average diameter of the dielectric crystal grains is 100 nm or more and less than 266 nm, for example, 120 nm to 250 nm. This is an average value measured for a plurality of, for example, 2 to 200, 5 to 150 dielectric crystal grains, and the average diameter is the average value with respect to the sum of the major axis of the dielectric crystal grains and the axis intersecting perpendicularly thereto. When the average diameter of the dielectric crystal grains is within the above range, by having fine dielectric crystal grains, the DC bias characteristics of the multilayer ceramic capacitor can be improved.

[0088] The average diameter of the dielectric crystal grains can be obtained by SEM (scanning electron microscope) analysis.

[0089] Specifically, after the multilayer ceramic capacitor 100 is put into an epoxy mixture and cured, the W-axis and T-axis direction surfaces (WT surfaces) of the capacitor body 110 are polished to a depth of 1 / 2 in the L-axis direction, fixed, and maintained in a vacuum atmosphere chamber, and a cross-sectional sample can be obtained so that the active region where the dielectric layer 111 intersects the internal electrode layers 121 and 122 can be observed. Subsequently, it can be measured with a scanning electron microscope (SEM) so that at least 1 layer, for example, 2 to 5 layers of the dielectric layer 111 can be seen with respect to the active region of the cross-sectional sample. For example, the SEM is measured under the condition of 10 kV in a region of about 2.5 μm × 2.5 μm where 3 layers of the dielectric layer 111 can be seen in the active region using the Verios G4 product of Thermo Fisher Scientific. The average value with respect to the sum of the major axis and the axis intersecting perpendicularly thereto can be calculated for 100 or more dielectric crystal grains in the SEM image of the cross-sectional sample.

[0090] According to one embodiment, the ratio of the number of dielectric crystal grains having the core-double shell structure among the plurality of dielectric crystal grains is 50% or more and 100% or less, and may be, for example, 60% to 100%. When the ratio of the dielectric crystal grains having the core-double shell structure is within the above range, a multilayer ceramic capacitor with improved DC bias characteristics and reliability can be ensured.

[0091] The average thickness (average length in the T-axis direction) of the dielectric layer 111 is 0.1 μm to 8.0 μm, and may be, for example, 0.1 μm to 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 excellent.

[0092] The average thickness of the dielectric layer 111 can be measured by putting the multilayer ceramic capacitor 100 into an epoxy mixture, curing it, polishing it, then ion milling it, and performing scanning electron microscope (SEM) analysis. The scanning electron microscope can use, for example, the Verios G4 product of Thermo Fisher Scientific. The measurement conditions are 10 kV and 0.2 nA, the analysis magnification is 100 times, and the measurement can be performed so that at least one layer, three layers, five layers, or ten or more layers of the dielectric layer 111 can be seen. In the scanning electron microscope (SEM) image, taking the central point in the length direction (L-axis direction) or width direction (W-axis direction) of the dielectric layer 111 as the reference point, it may be the arithmetic mean value of the thickness of the dielectric layer 111 at 10 points separated from the reference point by a predetermined interval. The interval between the 10 points is adjusted according to the scale of the scanning electron microscope (SEM) image, and may be, for example, an interval of 1 μm to 100 μm, 1 μm to 50 μm, or 1 μm to 10 μm. At this time, all 10 points must be located within the dielectric layer 111. 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.

[0093] The first internal electrode 121 and the second internal electrode 122 are electrodes having different polarities from each other, and are alternately arranged so as to face each other along the T-axis direction with the dielectric layer 111 interposed therebetween, and one end of each is exposed through the third and fourth surfaces of the capacitor body 110.

[0094] The first internal electrode 121 and the second internal electrode 122 are electrically insulated from each other by the dielectric layer 111 disposed in the middle.

[0095] The ends of the first internal electrode 121 and the second internal electrode 122 that are alternately exposed through the third and fourth surfaces of the capacitor body 110 are electrically connected to the first external electrode 131 and the second external electrode 132, respectively.

[0096] The first internal electrode 121 and the second internal electrode 122 may contain a conductive metal, such as a metal like Ni, Cu, Ag, Pd, Au, or an alloy thereof, such as an Ag-Pd alloy.

[0097] Also, the first internal electrode 121 and the second internal electrode 122 may contain dielectric particles of the same composition system as the ceramic material contained in the dielectric layer 111.

[0098] The first internal electrode 121 and the second internal electrode 122 can be formed using a conductive paste containing a conductive metal. As the printing method of the conductive paste, a screen printing method or a gravure printing method can be used.

[0099] The average thickness of the first internal electrode 121 and the second internal electrode 122 may be 0.1 μm to 2 μm. The average thickness of the first internal electrode 121 and the second internal electrode 122 is measured by scanning electron microscope (SEM) analysis. Here, since the scanning electron microscope (SEM) analysis is the same as the method for measuring the average thickness of the dielectric layer 111 described above, its description is omitted.

[0100] The capacitor body 110 can be formed by firing a laminate in which a plurality of dielectric layers 111 and internal electrode layers 121, 122 are laminated.

[0101] The first external electrode 131 and the second external electrode 132 are provided with voltages of different polarities and are electrically connected to the exposed portions of the first internal electrode 121 and the second internal electrode 122, respectively.

[0102] With the above-described configuration, when a predetermined voltage is applied to the first external electrode 131 and the second external electrode 132, charges are accumulated between the first internal electrode 121 and the second internal electrode 122 that face each other. At this time, the capacitance of the multilayer ceramic capacitor 100 becomes proportional to the overlapping area of the first internal electrode 121 and the second internal electrode 122 that overlap each other along the T-axis direction in the active region.

[0103] The first external electrode 131 and the second external electrode 132 are respectively disposed on the third and fourth surfaces of the capacitor body 110, and include first and second connection portions connected to the first internal electrode 121 and the second internal electrode 122, and the third and fourth surfaces of the capacitor body 110, and first and second band portions disposed at corners where the first and second surfaces, or the fifth and sixth surfaces are in contact.

[0104] The first and second band portions can respectively extend to a part of the first and second surfaces, or the fifth and sixth surfaces of the capacitor body 110 at the first and second connection portions. The first and second band portions serve to improve the adhesion strength of the first external electrode 131 and the second external electrode 132.

[0105] The first external electrode 131 and the second external electrode 132 can each include a sintered metal layer in contact with the capacitor body 110, a conductive resin layer disposed to cover the sintered metal layer, and a plating layer disposed to cover the conductive resin layer.

[0106] The sintered metal layer can include a conductive metal and glass.

[0107] The conductive metal can include copper (Cu), nickel (Ni), silver (Ag), palladium (Pd), gold (Au), platinum (Pt), tin (Sn), tungsten (W), titanium (Ti), lead (Pb), alloys thereof, or combinations thereof. For example, copper (Cu) can include a copper (Cu) alloy. When the conductive metal includes copper, the metal other than copper is included in an amount of 5 mol parts or less with respect to 100 mol parts of copper.

[0108] The glass can include a composition in which oxides are mixed, and may be, for example, one or more selected from the group consisting of silicon oxide, boron oxide, aluminum oxide, transition metal oxide, alkali metal oxide, and alkaline earth metal oxide. The transition metal is selected from the group consisting of zinc (Zn), titanium (Ti), copper (Cu), vanadium (V), manganese (Mn), iron (Fe), and nickel (Ni), the alkali metal is selected from the group consisting of lithium (Li), sodium (Na), and potassium (K), and the alkaline earth metal may be one or more selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

[0109] Optionally, the conductive resin layer is formed on the sintered metal layer and can be formed, for example, in a form that completely covers the sintered metal layer. On the other hand, the first external electrode 131 and the second external electrode 132 may not include the sintered metal layer, and in this case, the conductive resin layer can be in direct contact with the capacitor body 110.

[0110] The conductive resin layer extends to the first and second surfaces, or the fifth and sixth surfaces of the capacitor body 110, and the length of the region (i.e., the band portion) where the conductive resin layer extends and is disposed on the first and second surfaces, or the fifth and sixth surfaces of the capacitor body 110 may be longer than the length of the region (i.e., the band portion) where the sintered metal layer extends and is disposed on the first and second surfaces, or the fifth and sixth surfaces of the capacitor body 110. That is, the conductive resin layer can be formed on the sintered metal layer and in a form that completely covers the sintered metal layer.

[0111] The conductive resin layer includes a resin and a conductive metal.

[0112] The resin contained in the conductive resin layer is not particularly limited as long as it has bonding properties and shock absorption properties and can be mixed with the conductive metal powder to form a paste, and can include, for example, a phenol resin, an acrylic resin, a silicone resin, an epoxy resin, or a polyimide resin.

[0113] The conductive metal contained in the conductive resin layer serves to be electrically connected to the first internal electrode 121 and the second internal electrode 122 or the sintered metal layer.

[0114] The conductive metal contained in the conductive resin layer can have a spherical, flaky, or a combination of these forms. That is, the conductive metal may consist only of flakes, only of spheres, or a form in which flakes and spheres are mixed.

[0115] Here, the spherical shape can include a form that is not a perfect sphere. For example, it can include a form in which the ratio of the length of the major axis to the minor axis (major axis / minor axis) is 1.45 or less. The flaky powder means a powder having a flat and elongated form and is not particularly limited. For example, the ratio of the length of the major axis to the minor axis (major axis / minor axis) may be 1.95 or more.

[0116] The first external electrode 131 and the second external electrode 132 can further include a plating layer disposed outside the conductive resin layer.

[0117] The plating layer can include nickel (Ni), copper (Cu), tin (Sn), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), tungsten (W), titanium (Ti), or lead (Pb) alone, or an alloy thereof. For example, the plating layer may be a nickel (Ni) plating layer or a tin (Sn) plating layer, or may be a form in which a nickel (Ni) plating layer and a tin (Sn) plating layer are sequentially laminated, or may be a form in which a tin (Sn) plating layer, a nickel (Ni) plating layer, and a tin (Sn) plating layer are sequentially laminated. Also, the plating layer may include a plurality of nickel (Ni) plating layers and / or a plurality of tin (Sn) plating layers.

[0118] The plating layer can improve the mountability with the substrate of the multilayer capacitor 100, structural reliability, durability against the outside, heat resistance, and equivalent series resistance (ESR).

[0119] Hereinafter, a method for manufacturing a multilayer ceramic capacitor 100 according to an embodiment will be described.

[0120] The multilayer ceramic capacitor 100 according to an embodiment can be manufactured through steps of: manufacturing 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 containing the dielectric composite powder and a sub-component powder, and forming a conductive paste layer on the surface of the dielectric green sheet; laminating the dielectric green sheets on which the conductive paste layer is formed to manufacture a dielectric green sheet laminate; firing the dielectric green sheet laminate to manufacture a capacitor body including a dielectric layer and an internal electrode layer; and forming an external electrode on one surface of the capacitor body.

[0121] First, a dielectric composite powder in which a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal is manufactured.

[0122] The first transition metal may be all transition metals except hafnium (Hf), and may include, for example, zirconium (Zr), yttrium (Y), tantalum (Ta), niobium (Nb), or combinations thereof.

[0123] The dielectric composite powder will be described with reference to FIG. 5.

[0124] FIG. 5 is a schematic diagram showing a dielectric composite powder according to an embodiment.

[0125] Referring to FIG. 5, the dielectric composite powder 50 can have a core-shell structure including a core portion 60 and a shell portion 70 surrounding at least a part of the core portion 60. The core portion 60 can contain a barium titanate-based compound. When the first transition metal is TM, the shell portion 70 can contain Ba(Ti, Hf)O 3 or Ba(Ti, TM)O 3 and can be included.

[0126] The dielectric composite powder 50 can be produced by hydrothermal synthesis. After producing barium titanate seeds containing barium (Ba) and titanium (Ti), the produced barium titanate seeds are mixed with a hafnium (Hf)-containing compound or a first transition metal-containing compound.

[0127] The temperature of the hydrothermal synthesis may be 180 °C or higher, for example, it may be 180 °C to 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.

[0128] The hafnium (Hf)-containing compound and the first transition metal-containing compound may each be an oxide, a nitride, or a salt compound, or they can also be used in the form of a sol dispersed in an organic solvent.

[0129] The hafnium (Hf)-containing compound or the first transition metal-containing compound is mixed in an amount of 0.1 part by mole to 3 parts by mole with respect to 100 parts by mole of titanium (Ti), and for example, it can be mixed in an amount of 0.5 part by mole to 2.5 parts by mole. When the hafnium (Hf)-containing compound or the first transition metal-containing compound is contained within the above content range, by doping the barium titanate-based compound at an appropriate level, it is possible to prevent secondary components such as rare earth elements of the additive from diffusing into the core 20. Thereby, the crystallinity of the core 20 increases, it is possible to realize a fine-grained dielectric composite powder, and a multilayer ceramic capacitor excellent in DC bias characteristics and reliability can be manufactured.

[0130] Subsequently, the produced dielectric composite powder and the secondary component powder are mixed to produce a dielectric slurry.

[0131] The secondary component powder can include a rare earth element-containing compound, a second transition metal-containing compound, or a combination thereof.

[0132] The rare earth element-containing compound can include 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, an erbium (Er)-containing compound, or a combination thereof.

[0133] The second transition metal-containing compound can include a manganese (Mn)-containing compound, a vanadium (V)-containing compound, or a combination thereof.

[0134] When an additive such as a rare earth element-containing compound is added to the dielectric composite powder described above, hafnium (Hf) that already occupies the lattice in the manufacturing step of the dielectric composite powder forms a first shell without diffusion, and then a second shell composed of an additive such as a rare earth element is formed. As a result, hafnium (Hf) suppresses the diffusion of additives such as rare earth elements into the core, and defects in the core are reduced.

[0135] The sub-component powder may be contained in an amount of 0.01 to 5 mol parts, or 0.1 to 4 mol parts, per 100 mol parts of titanium (Ti). When the sub-component powder is contained within the above content range, a multilayer ceramic capacitor with excellent reliability can be manufactured.

[0136] As an example, the rare earth element-containing compound can include a dysprosium (Dy)-containing compound. The dysprosium (Dy)-containing compound is contained in an amount of 0.5 to 1.5 mol parts, for example, 0.7 to 1.3 mol parts, per 100 mol parts of titanium (Ti). When the dysprosium (Dy)-containing compound is contained within the above content range, a multilayer ceramic capacitor with excellent reliability can be manufactured.

[0137] The dielectric slurry can be manufactured by additionally mixing additives such as a dispersant, a binder, a plasticizer, a lubricant, an antistatic agent, and a solvent.

[0138] The dispersant can include, for example, a phosphate ester-based dispersant, a polycarboxylic acid-based dispersant, or a combination thereof. The dispersant is mixed in an amount of 0.1 to 5 parts by weight, for example 0.3 to 3 parts by weight, per 100 parts by weight of the barium titanate-based compound. When the dispersant is mixed within the above content range, the dispersibility of the dielectric slurry is excellent, and the amount of impurities contained in the produced dielectric layer can be reduced.

[0139] The binder may be, for example, an acrylic resin, a polyvinyl butyl resin, a polyvinyl acetal resin, an ethyl cellulose resin, etc. The binder is added in an amount of 0.1 to 50 parts by weight, for example 3 to 30 parts by weight, per 100 parts by weight of the barium titanate-based compound. When the binder is mixed within the above content range, the dispersibility of the dielectric slurry is excellent, and the amount of impurities contained in the produced dielectric layer can be reduced.

[0140] The plasticizer may be, for example, phthalic acid-based compounds such as dioctyl phthalate, benzyl butyl phthalate, dibutyl phthalate, dihexyl phthalate, di(2-ethylhexyl) phthalate, di(2-ethylbutyl) phthalate; adipic acid-based compounds such as dihexyl adipate, di(2-ethylhexyl) adipate; glycol-based compounds such as ethylene glycol, diethylene glycol, triethylene glycol; glycol ester-based compounds such as triethylene glycol dibutyrate, triethylene glycol di(2-ethylbutyrate), triethylene glycol di(2-ethylhexanoate), etc. The plasticizer is added in an amount of 0.1 to 20 parts by weight, for example 1 to 10 parts by weight, per 100 parts by weight of the barium titanate-based compound. When the plasticizer is mixed within the above content range, the dispersibility of the dielectric slurry is excellent, and the amount of impurities contained in the produced dielectric layer can be reduced.

[0141] The solvent may be an aqueous solvent such as water; an alcohol solvent such as ethanol, methanol, benzyl alcohol, methoxyethanol; a glycol solvent such as ethylene glycol, diethylene glycol; a ketone solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone; an ester solvent such as butyl acetate, ethyl acetate, carbitol acetate, butyl carbitol acetate; an ether solvent such as methyl cellosolve, ethyl cellosolve, butyl ether, tetrahydrofuran; an aromatic solvent such as benzene, toluene, xylene, etc. The solvent can use an alcohol solvent or an aromatic solvent, for example, considering the solubility and dispersibility of various additives contained in the dielectric slurry. The solvent is mixed in an amount of 50 parts by weight to 1000 parts by weight, for example, 100 parts by weight to 500 parts by weight, based on 100 parts by weight of the barium titanate-based compound. When the solvent is mixed within the above content range, the dielectric slurry components are sufficiently mixed, and the subsequent removal of the solvent is also easy.

[0142] For the mixing of the dielectric slurry described above, a wet ball mill or a stirring mill can be used. When using zirconia balls in a wet ball mill, a large number of zirconia balls with a diameter of 0.1 mm to 10 mm can be used for wet mixing for 8 hours to 48 hours, or 10 hours to 24 hours.

[0143] The produced dielectric slurry is formed as a dielectric layer after firing.

[0144] As a method for forming the produced dielectric slurry into a sheet shape, tape forming methods such as the doctor blade method and the calendar roll method can be used. For example, an on-roll coater using a head discharge method can be used, and then the formed body is dried to obtain a dielectric green sheet.

[0145] After firing, a conductive paste can be produced by mixing conductive powder made of a conductive metal or its alloy, a binder, and a solvent to form a conductive paste layer that will become the internal electrode layer. Further, if necessary, barium titanate powder may be mixed together as a co-material. The co-material can act to suppress the sintering of the conductive powder during the firing process. A conductive paste layer is formed by applying the conductive paste in a predetermined pattern to the surface of the dielectric green sheet by various printing methods such as screen printing or transfer methods.

[0146] The conductive powder can include nickel (Ni) or a nickel (Ni) alloy.

[0147] Subsequently, a dielectric green sheet laminate is manufactured by laminating a plurality of dielectric green sheets with internal electrode patterns formed thereon and then pressing in the lamination direction. At this time, the dielectric green sheet and the internal electrode pattern can be laminated on the upper and lower surfaces in the lamination direction of the dielectric green sheet laminate so that the dielectric green sheet is located.

[0148] The step of selectively cutting the manufactured dielectric green sheet laminate into a predetermined size by dicing or the like can be performed.

[0149] In addition, the dielectric green sheet laminate can be solidified and dried to remove a plasticizer or the like if necessary, and can be barrel polished using a horizontal centrifugal barrel machine or the like after solidification and drying. In barrel polishing, the dielectric green sheet laminate is put into a barrel container together with media and a polishing liquid, and unnecessary parts such as burrs generated during cutting can be polished by applying rotational motion, vibration, or the like to the barrel container. Also, after barrel polishing, the dielectric green sheet laminate can be washed with a cleaning liquid such as water and dried.

[0150] Subsequently, the dielectric green sheet laminate can be debound and fired to manufacture a capacitor body.

[0151] The debinding treatment conditions can be appropriately adjusted according to the components of the dielectric layer and the internal electrode layer. For example, the heating rate during debinding treatment 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 atmosphere during debinding treatment may be air or a reducing atmosphere.

[0152] The firing treatment conditions 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, firing is carried out at a temperature of 1100 °C to 1400 °C, and may be carried out at a temperature of 1200 °C to 1350 °C, for example. Also, firing is carried out for 0.5 hour to 8 hours, for example 1 hour to 3 hours. Further, firing may be carried out in a reducing atmosphere, for example, an atmosphere in which a mixed gas of nitrogen and hydrogen 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 may be sufficient.

[0153] After the firing treatment, annealing can be carried out as necessary. Annealing is a treatment for re-oxidizing the dielectric layer, and can be carried out when firing is carried out in a reducing atmosphere. The conditions of the annealing treatment can also be appropriately adjusted according to the components of the dielectric layer. For example, the temperature during annealing may be 950 °C to 1150 °C, the time may be 0 hour 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 (N 2 ) atmosphere, and the oxygen partial pressure may be 1.0×10 -9 MPa to 1.0×10 -5 MPa may be sufficient.

[0154] In the debinding process, firing process, or annealing process, in order to humidify nitrogen gas, mixed gas, etc., for example, a wetter can be used. In this case, the water temperature may be 5°C to 75°C. The debinding process, firing process, and annealing process may be performed continuously or independently.

[0155] Optionally, surface treatments such as sandblasting, laser irradiation, and barrel polishing can be performed on the third and fourth surfaces of the manufactured capacitor body 110. By performing such surface treatments, the ends of the first internal electrode and the second internal electrode are exposed on the outermost surfaces 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 facilitating the formation of an alloy part.

[0156] Subsequently, an external electrode is formed on one surface of the manufactured capacitor body 110.

[0157] For example, after applying a paste for forming a sintered metal layer to the external electrode, it can be sintered to form a sintered metal layer.

[0158] The paste for forming a sintered metal layer can contain a conductive metal and glass. Since the description of the conductive metal and glass is the same as above, repeated description is omitted. Also, the paste for forming a sintered metal layer can optionally contain a binder, a solvent, a dispersant, a plasticizer, an oxide powder, etc. As the binder, for example, ethyl cellulose, acrylic, butyral, etc. can be used, and as the solvent, for example, organic solvents such as terpineol, butyl carbitol, alcohol, methyl ethyl ketone, acetone, toluene, or an aqueous solvent can be used.

[0159] As a method of applying the paste for forming a sintered metal layer onto the outer surface of the capacitor body 110, dipping method, various printing methods such as screen printing, coating methods using a dispenser or the like, spraying methods using a spray, etc. can be used. The paste for forming a sintered metal layer is applied at least to the third and fourth surfaces of the capacitor body 110, 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.

[0160] Thereafter, the capacitor body 110 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.

[0161] Optionally, after applying a paste for forming a conductive resin layer onto the outer surface of the obtained capacitor body 110, it can be cured to form a conductive resin layer.

[0162] The paste for forming a conductive resin layer can contain a resin and optionally a conductive metal or a non-conductive filler. Since the explanations of the conductive metal and the resin are the same as those described above, repeated explanations are omitted. Also, the paste for forming a conductive resin layer can optionally contain a binder, a solvent, a dispersant, a plasticizer, an oxide powder, etc. As the binder, for example, ethyl cellulose, acrylic, butyral, etc. can be used, and as the solvent, organic solvents such as terpineol, butyl carbitol, alcohol, methyl ethyl ketone, acetone, toluene, or aqueous solvents can be used.

[0163] For example, as a method of forming the conductive resin layer, it can 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 onto the surface of the capacitor body 110 by a screen printing method or a gravure printing method, or by applying the paste for forming a conductive resin layer onto the surface of the capacitor body 110 and then curing it.

[0164] Subsequently, a plating layer is formed on the outside of the conductive resin layer.

[0165] For example, the plating layer can be formed by a plating method, and can also be formed by sputtering or electroplating.

[0166] Hereinafter, through examples, the above-described embodiments will be described in more detail. However, the following examples are for illustrative purposes only and do not limit the scope of the rights.

[0167] (Manufacture of multilayer ceramic capacitor) [Example 1] Titanium dioxide (TiO 2 ) peptizing sol and barium hydroxide (BaOH) were hydrothermally synthesized at 260 °C to produce barium titanate (BaTiO 3 ) seed. After that, barium titanate (BaTiO 3 ) seed and hafnium oxide (HfO 2 ) were mixed to produce Hf-doped BaTiO 3 powder, that is, dielectric composite powder. The dielectric composite powder was manufactured in a core-shell structure composed of a BaTiO 3 core and a Ba(Ti, Hf)O 3 shell. At this time, hafnium oxide (HfO 2 ) was mixed in a ratio of 1 mol part to 100 mol parts of titanium (Ti).

[0168] The manufactured dielectric composite powder, and dysprosium oxide (Dy 2 O 3 ), manganese oxide (MnO), and vanadium oxide (V 2 O 5 ) as sub-component powders were mixed in ratios of 1 mol part, 0.24 mol part, and 0.46 mol part, respectively, to 100 mol parts of titanium (Ti) to produce a dielectric slurry.

[0169] The mixing during the production of the dielectric slurry was carried out using zirconia balls (ZrO 2Using (ball) as the dispersion medium, after adding ethanol / toluene, a wetting dispersant, and polyvinyl butyral (PVB) resin as a binder, mechanical milling was performed.

[0170] The manufactured dielectric slurry was used to produce a dielectric green sheet using an on-roll coater with a head discharge method.

[0171] A conductive paste layer containing nickel (Ni) was printed on the surface of the dielectric green sheet, and a dielectric green sheet laminate was manufactured by laminating and pressing the dielectric green sheet (width × length × height = 3.2 mm × 2.5 mm × 2.5 mm) with the conductive paste layer formed.

[0172] The dielectric green sheet laminate was subjected to a plasticizing process in a nitrogen atmosphere at 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 under the following conditions.

[0173] Subsequently, a multilayer ceramic capacitor was manufactured through processes such as external electrode and plating.

[0174] [Comparative Example 1] BaCO 3 powder and TiO 2 powder were mixed to produce barium titanate (BaTiO 3 )-based main component powder, and dysprosium oxide (Dy 2 O 3 ), manganese oxide (MnO), and vanadium oxide (V 2 O 5 ) were mixed in amounts of 1 mol part, 0.24 mol part, and 0.46 mol part, respectively, with respect to 100 mol parts of titanium (Ti) to produce a dielectric slurry. A multilayer ceramic capacitor was manufactured in the same manner as in Example 1, except for this.

[0175] Evaluation 1: TEM-EDS analysis For the multilayer ceramic capacitor manufactured in Example 1, TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) analysis was performed, and the results are shown in FIGS. 6 and 7.

[0176] Specifically, after the multilayer ceramic capacitor manufactured in Example 1 was put into an epoxy mixture and cured, the W-axis and T-axis direction surfaces (WT surfaces) of the capacitor body were polished to a depth of 1 / 2 in the L-axis direction. After fixing, it was maintained in a vacuum atmosphere chamber to obtain a cross-sectional sample so that the active region where the dielectric layer and the internal electrode layer intersect could be observed. Subsequently, the cross-sectional sample was measured with a transmission electron microscope (TEM) so that at least one layer of the dielectric layer could be seen in the active region. The TEM was measured under the conditions of an acceleration voltage of 200 kV using Xe-FIB (focused ion beam) in an area of about 800 nm × 800 nm where at least one layer of the dielectric layer could be seen in the active region. Subsequently, in the TEM image of the measured cross-sectional sample, EDS (energy dispersive spectroscopy) line analysis was performed on a straight line section from one point on the outermost contour of an arbitrary dielectric grain across the center to another point on the outermost contour to confirm the structure and component content of the dielectric grain.

[0177] FIG. 6 is a TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis diagram for the dielectric grains according to Example 1, and FIG. 7 is a TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) analysis image for the dielectric layer according to Example 1.

[0178] Referring to FIG. 6, in the TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis of the dielectric crystal grains, among the results from the center of the dielectric crystal grains to one of the grain boundaries, the positions of the first point with the maximum atomic percentage of hafnium (Hf) and the second point with the maximum atomic percentage of dysprosium (Dy) are different. It can be seen that the second point with the maximum atomic percentage of dysprosium (Dy) is located more outside from the center of the dielectric crystal grains than the first point with the maximum atomic percentage of hafnium (Hf). From this, it can be understood that the dielectric crystal grains according to Example 1 have a core-double shell structure, and the first shell contains a dielectric composite in which barium titanate is doped with hafnium (Hf).

[0179] Referring to FIG. 7, it can be seen that the dielectric crystal grains in the dielectric layer according to Example 1 contain hafnium (Hf) in the first shell and dysprosium (Dy) in the second shell.

[0180] Evaluation 2: SEM analysis For the multilayer ceramic capacitors manufactured in Example 1 and Comparative Example 1, SEM (scanning electron microscope) analysis was performed, and the average diameter of the dielectric crystal grains (grains) was measured, and the results are shown in FIGS. 8 and 9.

[0181] Specifically, after putting the multilayer ceramic capacitor into the epoxy mixture and curing it, the W-axis and T-axis direction surfaces (WT surfaces) of the capacitor body were polished to a depth of 1 / 2 in the L-axis direction, and after fixing, it was maintained in a vacuum atmosphere chamber to obtain a cross-sectional sample so that the active region where the dielectric layer and the internal electrode layer intersect could be observed. Subsequently, the active region of the cross-sectional sample was measured with a scanning electron microscope (SEM) so that three dielectric layers could be seen. The SEM used the Verios G4 product of Thermo Fisher Scientific and was measured under the condition of 10 kV in an area of about 2.5 μm × 2.5 μm where three dielectric layers could be seen in the active region. For more than 100 dielectric crystallites (grains) in the SEM image of the cross-sectional sample, the average value of the sum of the major axis and the axis perpendicular to it was calculated.

[0182] FIG. 8 is an SEM (scanning electron microscope) analysis image of the active region of the multilayer ceramic capacitor according to Example 1, and FIG. 9 is an SEM (scanning electron microscope) analysis image of the active region of the multilayer ceramic capacitor according to Comparative Example 1.

[0183] Referring to FIGS. 8 and 9, it can be seen that the average diameter of the dielectric crystallites in Example 1 is 229 nm, while the average diameter of the dielectric crystallites in Comparative Example 1 is 266 nm. This is considered to be because hafnium (Hf) with high thermal stability suppresses grain growth due to heat. From this, it can be seen that the dielectric crystallites according to one embodiment, that is, the dielectric crystallites having a core-double shell structure and containing a dielectric composite in which barium titanate is doped with hafnium (Hf) in the first shell, are refined to suppress defects in the core.

[0184] Evaluation 3: DC bias characteristics For the multilayer ceramic capacitors manufactured in Example 1 and Comparative Example 1, the DC bias characteristics were measured by the following method, and the results are shown in FIG. 10.

[0185] After maintaining a DC bias of 1 V and 3 V for 60 seconds respectively under the conditions of 1 kHz and AC 0.5 V, the effective capacitance was measured.

[0186] Figure 10 is a graph showing the DC bias characteristics of the multilayer ceramic capacitors according to Example 1 and Comparative Example 1.

[0187] Referring to Figure 10, in the case of Example 1, it can be seen that the DC bias characteristics are superior compared to Comparative Example 1. From this, it can be understood that the multilayer ceramic capacitor according to one embodiment, that is, the dielectric crystal grains having a core-double shell structure and including a dielectric composite in which barium titanate is doped with hafnium (Hf) in the first shell, has improved DC bias characteristics.

[0188] As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited thereto, and various modifications can be made and implemented within the scope of the claims, the description of the invention, and the appended drawings, and it is natural that these also belong to the scope of the present invention.

Explanation of Reference Numerals

[0189] 10 Dielectric crystal grains (grain) 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 internal electrode 122 Second internal electrode 131 First external electrode 132 Second external electrode

Claims

1. a capacitor body including a dielectric layer and an internal electrode layer; and an external electrode disposed outside the capacitor body; the dielectric layer includes a plurality of dielectric grains; At least one of the plurality of dielectric crystal grains includes a dielectric composite in which a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal; and a minor component including a rare earth element, a second transition metal, or a combination thereof; In a TEM-EDS (Transmission Electron Microscopy-Energy Dispersive Spectroscopy) line analysis of the dielectric grains, a first point having a maximum atomic % of hafnium (Hf) or a first transition metal among results from a center of the dielectric grain to one of the grain boundaries is different from a second point having a maximum atomic % of a rare earth element or a second transition metal, The first transition metal does not include hafnium (Hf), and the first transition metal and the second transition metal are different from each other.

2. In a TEM-EDS (Transmission Electron Microscopy-Energy Dispersive Spectroscopy) line analysis of the dielectric crystal grains, the results from the center of the dielectric crystal grain to one of the grain boundaries are as follows:

2. The multilayer ceramic capacitor according to claim 1, wherein the second point having the maximum atomic % of the rare earth element or the second transition metal is located farther outward from the center of the dielectric crystal grain than the first point having the maximum atomic % of the hafnium (Hf) or the first transition metal.

3. 2. The multilayer ceramic capacitor according to claim 1, wherein at least one of the plurality of dielectric crystal 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 first shell includes a dielectric composite in which the barium titanate-based compound is doped with hafnium (Hf) or a first transition metal, The multilayer ceramic capacitor according to claim 3 , wherein the second shell includes a minor component including the rare earth element, the second transition metal, or a combination thereof.

5. In a TEM-EDS (Transmission Electron Microscopy-Energy Dispersive Spectroscopy) line analysis of the dielectric crystal grains, the results from the center of the dielectric crystal grain to one of the grain boundaries are as follows: The first shell is a region including a peak having a maximum atomic percentage of hafnium (Hf) or a first transition metal; the second shell is a region including a peak having a maximum atomic percentage of a rare earth element or a second transition metal; The multilayer ceramic capacitor of claim 4 , wherein the first shell and the second shell have different regions.

6. the atomic percent content of hafnium (Hf) or first transition metal is greater than the atomic percent content of rare earth elements or second transition metals in the first shell; 6. The multilayer ceramic capacitor of claim 5, wherein the atomic percent content of hafnium (Hf) or first transition metals in the second shell is less than the atomic percent content of rare earth elements or second transition metals.

7. 2. The multilayer ceramic capacitor of claim 1, wherein the first transition metal comprises zirconium (Zr), yttrium (Y), tantalum (Ta), niobium (Nb), or a combination thereof.

8. 2. The multilayer ceramic capacitor according to claim 1, wherein the rare earth element comprises dysprosium (Dy), terbium (Tb), yttrium (Y), lanthanum (La), cerium (Ce), samarium (Sm), gadolinium (Gd), holmium (Ho), erbium (Er), or a combination thereof.

9. The multilayer ceramic capacitor of claim 1 , wherein the second transition metal comprises manganese (Mn), vanadium (V), or a combination thereof.

10. 2. The multilayer ceramic capacitor according to claim 1, wherein the hafnium (Hf) or first transition metal is doped at 0.1 atomic % to 5 atomic % with respect to the total amount of the dielectric composite.

11. 5. The multilayer ceramic capacitor according to claim 4, wherein the subcomponent is contained in an amount of 0.1 atomic % to 2 atomic % based on a total amount of the components of the second shell.

12. 4. The multilayer ceramic capacitor according to claim 3, wherein the length of the core measured along the major axis passing through the center of the dielectric crystal grain is 50 nm to 150 nm.

13. 4. The multilayer ceramic capacitor according to claim 3, wherein an average length of the first shell measured along a major axis passing through a center of the dielectric crystal grain is 10 nm to 50 nm.

14. 4. The multilayer ceramic capacitor according to claim 3, wherein an average length of the second shell measured along a major axis passing through a center of the dielectric crystal grain is 40 nm to 240 nm.

15. 2. The multilayer ceramic capacitor according to claim 1, wherein an average diameter of the dielectric crystal grains is not less than 100 nm and less than 266 nm.

16. 4. The multilayer ceramic capacitor according to claim 3, wherein the ratio of the number of dielectric crystal grains having the core-double shell structure to the number of the dielectric crystal grains is 50% or more and 100% or less.

17. A step of preparing a dielectric composite powder in which a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal; preparing a dielectric green sheet using a dielectric slurry containing the dielectric composite powder and a subcomponent powder, and forming a conductive paste layer on a surface of the dielectric green sheet; manufacturing a dielectric green sheet laminate by stacking the dielectric green sheets on which the conductive paste layers are formed; Firing the dielectric green sheet laminate to manufacture a capacitor body including a dielectric layer and an internal electrode layer; and forming an external electrode on one surface of the capacitor body; the dielectric layer includes a plurality of dielectric grains; At least one of the plurality of dielectric crystal grains includes a dielectric composite in which a barium titanate-based compound is doped with hafnium (Hf) or a first transition metal; and a minor component including a rare earth element, a second transition metal, or a combination thereof; In a TEM-EDS (Transmission Electron Microscopy-Energy Dispersive Spectroscopy) line analysis of the dielectric grains, a first point having a maximum atomic % of hafnium (Hf) or a first transition metal among results from a center of the dielectric grain to one of the grain boundaries is different from a second point having a maximum atomic % of a rare earth element or a second transition metal, The first transition metal does not include hafnium (Hf), and the first transition metal and the second transition metal are different from each other.

18. The dielectric composite powder in which the barium titanate-based compound is doped with hafnium (Hf) or a first transition metal (TM) is A core portion including a barium titanate-based compound, and At least a part of the core is surrounded by Ba(Ti,Hf)O ３ Or Ba(Ti,TM)O ３ The method for producing a multilayer ceramic capacitor according to claim 17 , further comprising:

19. The dielectric composite powder comprises: Producing barium titanate seeds containing barium (Ba) and titanium (Ti) by hydrothermal synthesis; and The method for producing the multilayer ceramic capacitor according to claim 18, comprising the step of mixing the barium titanate seeds with a hafnium (Hf)-containing compound or a first transition metal-containing compound.

20. The method for producing a multilayer ceramic capacitor according to claim 19, wherein the hafnium (Hf)-containing compound or the first transition metal-containing compound is mixed in an amount of 0.1 to 3 parts by mol per 100 parts by mol of the titanium (Ti).

21. 20. The method for producing a multilayer ceramic capacitor according to claim 19, wherein the first transition metal-containing compound comprises a zirconium (Zr)-containing compound, an yttrium (Y)-containing compound, a tantalum (Ta)-containing compound, a niobium (Nb)-containing compound, or a combination thereof.

22. The method for producing a multilayer ceramic capacitor according to claim 17 , wherein the auxiliary component powder comprises a rare earth element-containing compound, a second transition metal-containing compound, or a combination thereof.

23. 23. The method for producing a multilayer ceramic capacitor according to claim 22, wherein the rare earth element-containing compound comprises a dysprosium (Dy)-containing compound, a terbium (Tb)-containing compound, an 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, an erbium (Er)-containing compound, or a combination thereof.

24. 23 . The method of claim 22 , wherein the second transition metal-containing compound comprises a manganese (Mn)-containing compound, a vanadium (V)-containing compound, or a combination thereof.

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