Multilayer ceramic capacitor

Abstract

This invention provides a multilayer ceramic capacitor with excellent DC bias characteristics. [Solution] A multilayer ceramic capacitor is provided, comprising a capacitor body including a dielectric layer and an internal electrode layer, and an external electrode disposed on the outside of the capacitor body, wherein the dielectric layer includes a plurality of dielectric crystal grains, at least one of the plurality of dielectric crystal grains has a core-shell structure including a core portion and a shell portion surrounding at least a part of the core portion, the dielectric crystal grain having the core-shell structure includes rare earth elements including barium (Ba), titanium (Ti), and lanthanum (La), and when measured in the direction from the interface to the shell portion in a measurement area from the interface between the core portion and the shell portion to a depth of 5 nm from the interface toward the shell portion, the absolute value of the concentration gradient of lanthanum (La) is 0.12 mol parts / nm to 0.58 mol parts / nm with reference to 100 mol parts of titanium (Ti).

Description

Technical Field

[0001] The present disclosure relates to multilayer ceramic capacitors.

Background Art

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

[0003] For example, multilayer ceramic capacitors (MLCC) can be used as chip capacitors mounted on the substrates of various electronic products such as video devices such as liquid crystal displays (LCD), plasma display panels (PDP), and organic light-emitting diodes (OLED), computers, personal mobile terminals, and smartphones, and play a role in charging and discharging electricity.

[0004] Recently, in order to achieve ultra-high capacitance with ultra-small multilayer ceramic capacitors, technologies for thinning the thickness of dielectric layers and internal electrode layers have been presented. Also, design studies have been conducted to control the size and dispersion of crystal grains in the dielectric layer and have a uniform resistance distribution.

Summary of the Invention

Problems to be Solved by the Invention

[0005] One embodiment provides a multilayer ceramic capacitor having excellent DC bias characteristics.

Means for Solving the Problems

[0006] One embodiment provides a multilayer ceramic capacitor comprising a capacitor body including a dielectric layer and an internal electrode layer, and an external electrode disposed on the outside of the capacitor body, wherein the dielectric layer comprises a plurality of dielectric crystal grains, and at least one of the plurality of dielectric crystal grains has a core-shell structure comprising a core portion and a shell portion surrounding at least a part of the core portion, the dielectric crystal grain having the core-shell structure comprises rare earth elements including barium (Ba), titanium (Ti), and lanthanum (La), and when measured in the direction from the interface to the shell portion in a measurement area from the interface between the core portion and the shell portion to a depth of 5 nm from the interface toward the shell portion, the absolute value of the lanthanum (La) concentration gradient is 0.12 mol parts / nm to 0.58 mol parts / nm with reference to 100 mol parts of titanium (Ti).

[0007] When performing TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis on a linear section of the long axis passing through the center of a dielectric crystal grain having the core-shell structure, the core portion may be a region where the lanthanum (La) is less than 0.8 moles per 100 moles of titanium (Ti), and the shell portion may be a region where the lanthanum (La) is 0.8 moles or more per 100 moles of titanium (Ti).

[0008] The lanthanum (La) can have a higher molar content in the shell portion than in the core portion.

[0009] The lanthanum (La) content in the shell portion can be 0.8 moles or more and 2.0 moles or less per 100 moles of titanium (Ti).

[0010] The rare earth elements may further include one or more auxiliary elements selected from scandium (Sc), yttrium (Y), neodymium (Nd), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), ytterbium (Yb), and lutetium (Lu).

[0011] The aforementioned rare earth elements may further include auxiliary elements such as yttrium (Y), terbium (Tb), and dysprosium (Dy).

[0012] The capacitor body includes an active region in which the dielectric layer and the internal electrode layer are arranged alternately, and the central region has a horizontal length corresponding to 1 / 6 of the total horizontal length of the active region in a direction perpendicular to the stacking direction, and a vertical length corresponding to 1 / 6 of the total vertical length of the active region in a direction perpendicular to the stacking direction, and the average size of the dielectric crystal grains having the core-shell structure can be 10 nm or more and less than 130 nm.

[0013] In the central region, the average size of the core portion may be 35% to 67.3% of the average size of the dielectric crystal grains.

[0014] Another embodiment includes a capacitor body comprising a dielectric layer and an internal electrode layer, and an external electrode disposed outside the capacitor body, wherein the dielectric layer comprises a plurality of dielectric crystal grains, and at least one of the plurality of dielectric crystal grains has a core-shell structure comprising a core portion and a shell portion surrounding at least a part of the core portion, and the dielectric crystal grain having the core-shell structure comprises barium (Ba), titanium (Ti), and rare earth elements, wherein the rare earth elements are lanthanum (La), scandium (Sc), yttrium (Y), neodymium (Nd), europi The present invention provides a multilayer ceramic capacitor comprising one or more auxiliary elements selected from um (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), ytterbium (Yb), and lutetium (Lu), wherein when measured in the direction from the interface to the shell portion within a measurement area from the interface to a depth of 5 nm toward the shell portion, the absolute value of the total concentration gradient of the rare earth elements is 0.12 mol parts / nm to 0.58 mol parts / nm with reference to 100 mol parts of titanium (Ti).

[0015] The total content of the rare earth elements can have a higher molar content in the shell portion than in the core portion.

[0016] The total content of the rare earth elements in the shell portion can be 1.2 mol parts or more and 5.5 mol parts or less with respect to 100 mol parts of the titanium (Ti).

[0017] The rare earth elements can include La, Y, Tb, and Dy.

[0018] The total content of La, Y, Tb, and Dy can have a higher molar content in the shell portion than in the core portion.

[0019] The total content of La, Y, Tb, and Dy in the shell portion can be 1.2 mol parts or more and 5.5 mol parts or less with respect to 100 mol parts of the titanium (Ti).

Advantages of the Invention

[0020] The DC bias characteristics of the multilayer ceramic can be improved.

Brief Description of the Drawings

[0021] [Figure 1] It is a perspective view showing a multilayer ceramic capacitor according to an embodiment. [Figure 2] It is a cross-sectional view of the multilayer ceramic capacitor cut along the line I-I' of FIG. 1. [Figure 3] It is a cross-sectional view of the multilayer ceramic capacitor cut along the line II-II' of FIG. 1. [Figure 4] It is an exploded perspective view showing the laminated structure by disassembling the capacitor body of FIG. 1. [Figure 5] It is a schematic view showing a dielectric layer according to an embodiment. [Figure 6] It is a schematic view showing dielectric crystallites according to an embodiment. [Figure 7]It is an enlarged view in which the A region in FIG. 2 is enlarged. [Figure 8] It is a TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) mapping analysis image of the dielectric layer according to Example 1. [Figure 9] It is an image showing the content of lanthanum (La) during TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis of the dielectric layer according to Example 1. [Figure 10] It is an image showing the total content of rare earth elements during TEM-EDS (transmission electron microscope - energy dispersive spectroscopy) line analysis of the dielectric layer according to Example 1. [Figure 11] It is a graph showing the average size of the dielectric crystal grains according to Example 1 and Comparative Example 2.

Embodiments for Carrying Out the Invention

[0022] Hereinafter, referring 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 not related to the explanation 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 schematically illustrated, and the sizes of each component do not fully reflect the actual sizes.

[0023] The attached drawings are for facilitating the understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, or alternatives included in the idea and technical scope of the present invention.

[0024] Terms including ordinal numbers such as first, second, etc. can be used to explain various components, but the components are not limited by the terms. These terms are only used for the purpose of distinguishing one component from another.

[0025] Furthermore, when a layer, membrane, region, plate, or other part is said to be "on top of" or "above" another part, it includes not only cases where it is "directly above" the other part, but also cases where there is another part in between. Conversely, when one part is said to be "directly above" another part, it means that there is no other part in between. Also, when a part is said to be "on top of" or "above" a reference part, it means that it is located above or below the reference part, and does not necessarily mean that it is located "above" or "on top of" in the opposite direction of gravity.

[0026] Throughout the specification, terms such as “includes” or “has” should be understood to indicate the presence of features, figures, steps, actions, components, parts, or combinations thereof described in the specification, and not to pre-exist the presence or possibility of adding one or more other features, figures, steps, actions, components, parts, or combinations thereof. Therefore, when a part “includes” a component, this means, unless otherwise stated, that it may include other components rather than excluding them.

[0027] Furthermore, throughout the specification, "on a plane" means when the subject is viewed from above, and "on a cross-section" means when the subject is viewed from the side of a cross-section cut perpendicularly into it.

[0028] Furthermore, throughout the specification, "connected" does not only mean that two or more components are directly connected, but can also mean that two or more components are indirectly connected through other components, that they are not only physically connected but also electrically connected, or that they are a single entity due to their location or function, even though they were previously referred to by different names.

[0029] Furthermore, throughout this specification, "contains as a major component" means that among the at least one component present in a given region, one component has the highest content relative to the total amount of components.

[0030] A multilayer ceramic capacitor according to one embodiment will be described below with reference to Figures 1 to 4.

[0031] Figure 1 is a perspective view showing a multilayer ceramic capacitor according to one embodiment; Figure 2 is a cross-sectional view of the multilayer ceramic capacitor cut along the line I-I' in Figure 1; Figure 3 is a cross-sectional view of the multilayer ceramic capacitor cut along the line II-II' in Figure 1; and Figure 4 is an exploded perspective view showing the multilayer structure when the capacitor body of Figure 1 is disassembled.

[0032] The L-axis, W-axis, and T-axis shown in Figures 1 to 4 represent the length, width, and thickness directions of the capacitor body 110, respectively. Here, the thickness direction (T-axis direction) is perpendicular to the broad surface (main surface) of the sheet-shaped component, and can be used, for example, with the same concept as the stacking direction in which the dielectric layers 111 are stacked. The length direction (L-axis direction) is the direction extending parallel to the broad surface (main surface) of the sheet-shaped component, and can be approximately perpendicular to the thickness direction (T-axis direction). For example, it can be the direction in which the first external electrode 131 and the second external electrode 132 are located on both sides. The width direction (W-axis direction) is the direction extending parallel to the broad surface (main surface) of the sheet-shaped component, and can be approximately perpendicular to the thickness direction (T-axis direction) and the length direction (L-axis direction). The length in the length direction (L-axis direction) of the sheet-shaped component may be longer than the length in the width direction (W-axis direction).

[0033] Referring to Figures 1 to 4, a multilayer ceramic capacitor 100 according to one embodiment includes a capacitor body 110 and external electrodes 131 and 132 disposed outside the capacitor body 110. The external electrodes 131 and 132 may include a first external electrode 131 and a second external electrode 132 disposed at opposing ends of the capacitor body 110 in the longitudinal direction (L-axis direction).

[0034] The capacitor body 110 may, for example, have a roughly hexahedral shape.

[0035] For the convenience of describing one embodiment, in the capacitor body 110, the two surfaces facing each other in the thickness direction (T-axis direction) are defined as the first and second surfaces, the two surfaces connected to the first and second surfaces are defined as the third and fourth surfaces, the two surfaces facing each other in the length direction (L-axis direction) are defined as the first and second surfaces, the two surfaces connected to the third and fourth surfaces are defined as the fifth and sixth surfaces, and the two surfaces facing each other in the width direction (W-axis direction) are defined as the fifth and sixth surfaces.

[0036] For example, the first surface, which is the bottom surface, can be the surface facing the mounting direction. Also, the first to sixth surfaces may be flat, but this is not the only embodiment. For example, the first to sixth surfaces may be curved surfaces with a convex central portion, and the corners that form the boundaries of each surface may be rounded.

[0037] The shape, size, and number of dielectric layers 111 of the capacitor body 110 are not limited to those shown in the drawings of this embodiment.

[0038] 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 layer 121 and a second internal electrode layer 122 that are alternately arranged in the thickness direction (T-axis direction) between the dielectric layers 111.

[0039] At this time, the boundaries between adjacent dielectric layers 111 of the capacitor body 110 may be so integrated that they are difficult to confirm without using a scanning electron microscope (SEM).

[0040] The capacitor body 110 may include an active region (A) and cover regions 112 and 113.

[0041] The active region is a region in which the dielectric layer 111 and the internal electrode layers 121 and 122 are arranged alternately, and is the part that contributes to the formation of capacitance in the multilayer ceramic capacitor 100. Specifically, the active region (A) may be a region in which the first internal electrode layer 121 or the second internal electrode layer 122, which are stacked along the thickness direction (T-axis direction), overlap.

[0042] The cover regions 112 and 113 are thickness-direction margins and can be located on the first and second surfaces of the active region, respectively, in the thickness direction (T-axis direction). Such cover regions 112 and 113 may be formed by a single dielectric layer 111 or by two or more dielectric layers 111 being laminated on the upper and lower surfaces of the active region, respectively.

[0043] Furthermore, the capacitor body 110 may also include a side margin region.

[0044] The side margin region is a widthwise margin portion and can be located on both opposite ends of the active region in the widthwise direction (W-axis direction), i.e., on the fifth and sixth surfaces, respectively. The side margin region can be formed by applying a conductive paste layer for the internal electrode layer to the surface of the dielectric green sheet, applying the conductive paste layer only to a portion of the surface of the dielectric green sheet, and not applying the conductive paste layer to both sides of the dielectric green sheet surface, then laminating the dielectric green sheet and firing it, but the method of formation is not limited to this.

[0045] The cover regions 112, 113 and the side margin regions serve to prevent damage to the first internal electrode layer 121 and the second internal electrode layer 122 due to physical or chemical stress.

[0046] Dielectric layer A dielectric layer 111 according to one embodiment will be described with reference to Figures 5 to 7.

[0047] Figure 5 is a schematic diagram showing a dielectric layer according to one embodiment.

[0048] Referring to Figure 5, the dielectric layer 111 according to one embodiment includes a plurality of dielectric crystal grains 10, and at least one of the plurality of dielectric crystal grains 10 has a core-shell structure including a core portion 12 and a shell portion 14 surrounding at least a part of the core portion 12.

[0049] The dielectric crystal grains 10 having a core-shell structure contain barium (Ba), titanium (Ti), and rare earth elements, the rare earth element being lanthanum (La).

[0050] Specifically, barium (Ba) and titanium (Ti) can be derived from barium titanate-based compounds, which are the dielectric matrix, and can be mainly contained in the core portion 12 of the dielectric crystal grains 10. Rare earth elements, including lanthanum (La), can be derived from additives added to the dielectric matrix, and can be mainly contained in the shell portion 14 of the dielectric crystal grains 10.

[0051] Barium titanate compounds have a high dielectric constant and contribute to the formation of the dielectric constant of the multilayer ceramic capacitor 100.

[0052] As an example, barium titanate compounds may include one or more selected from BaTiO3, Ba(Ti,Zr)O3, Ba(Ti,Sn)O3, (Ba,Ca)TiO3, (Ba,Ca)(Ti,Zr)O3, (Ba,Ca)(Ti,Sn)O3, (Ba,Sr)TiO3, (Ba,Sr)(Ti,Zr)O3, and (Ba,Sr)(Ti,Sn)O3.

[0053] The dielectric properties of dielectric materials can be explained by four main polarization mechanisms. These mechanisms include ionic polarization, which occurs when an electric field is applied to ionic bonded material fixed within a lattice, causing a change in the equilibrium position of electrons; electronic polarization, which occurs asymmetrically due to the movement of atomic nuclei; dipole polarization, which arises from materials with self-polarization; and space charge polarization, which appears when charge carriers within the material move while the electric field is maintained.

[0054] According to one embodiment, when dielectric crystal grains 10 having a core-shell structure within the dielectric layer 111 contain lanthanum (La), ionic polarization occurs, potentially resulting in a huge dielectric constant. That is, lanthanum (La) is substituted at the barium (Ba) sites of the dielectric matrix, changing the crystal structure from tetragonality to cubic, thereby lowering the temperature at which resistance decreases, i.e., the Curie temperature, and enabling a high dielectric constant at room temperature.

[0055] Figure 6 is a schematic diagram showing dielectric crystal grains according to one embodiment.

[0056] Referring to Figure 6, in a dielectric crystal grain 10 having a core-shell structure, when measuring in the direction from the interface to the shell portion 14 in a measurement region (X) from the interface between the core portion 12 and the shell portion 14 to a depth of 5 nm toward the shell portion 14, the absolute value of the La concentration gradient may be 0.12 mol / nm to 0.58 mol / nm relative to 100 mol parts of Ti, for example, 0.12 mol / nm to 0.55 mol / nm, or 0.12 mol / nm to 0.50 mol / nm. When the absolute value of the La concentration gradient in the measurement region (X) is within this range, it not only has a high dielectric constant but also improves the structural fraction of the core portion and shell portion, thereby improving the DC bias characteristics of the multilayer ceramic capacitor. That is, if the absolute value of the La concentration gradient is less than 0.12 mol / nm or greater than 0.58 mol / nm relative to 100 mol parts of Ti, the DC bias characteristics of the multilayer ceramic capacitor may deteriorate.

[0057] Furthermore, in one embodiment, the rare earth element may further include, in addition to lanthanum (La), one or more auxiliary elements selected from scandium (Sc), yttrium (Y), neodymium (Nd), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), ytterbium (Yb), and lutetium (Lu). As an example, the rare earth element may include lanthanum (La), yttrium (Y), terbium (Tb), and dysprosium (Dy).

[0058] When the rare earth elements include La and the aforementioned auxiliary elements, when measuring in the measurement region (X) from the interface between the core portion 12 and the shell portion 14 toward the shell portion 14, the absolute value of the total concentration gradient of the rare earth elements may be 0.12 mol / nm to 0.58 mol / nm with respect to 100 mol / nm of Ti, for example, 0.12 mol / nm to 0.55 mol / nm, or 0.12 mol / nm to 0.50 mol / nm. Here, the total concentration of the rare earth elements means the sum of the content of La and the aforementioned auxiliary elements, for example, the sum of the content of La, Y, Tb, and Dy. When the absolute value of the total concentration gradient of the rare earth elements in the measurement region (X) is within the above range, it is possible to not only have a high dielectric constant but also improve the structural fraction of the core portion and shell portion, thereby improving the DC bias characteristics of the multilayer ceramic capacitor. In other words, if the absolute value of the total concentration gradient of rare earth elements is less than 0.12 mol / nm but greater than 0.58 mol / nm per 100 mol / nm of Ti, the DC bias characteristics of the multilayer ceramic capacitor may deteriorate.

[0059] In the measurement region (X) for the absolute value of the La concentration gradient and the absolute value of the total concentration gradient of rare earth elements, the interface between the core portion 12 and the shell portion 14 can be a point where, when performing TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis on a linear section of the long axis passing through the center (α) of the dielectric crystal grain 10 having a core-shell structure, La is approximately 0.8 moles per 100 moles of Ti. That is, the measurement region (X) for the absolute value of the La concentration gradient may be a region from the point where La is 0.8 moles per 100 moles of Ti to a depth of 5 nm towards the shell portion 14.

[0060] The absolute value of the concentration gradient of La and the absolute value of the total concentration gradient of the rare earth elements, i.e., La and the auxiliary elements, can be measured by TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis.

[0061] Specifically, after curing the multilayer ceramic capacitor 100 in an epoxy mixture, the L-axis and T-axis planes (LT planes) of the capacitor body 110 are polished in the W-axis direction to a depth of 1 / 2 to obtain a cross-sectional sample so that the active region (A) where the dielectric layer 111 and the internal electrode layers 121 and 122 intersect can be observed. For example, when the active region (A) is divided into three equal parts in the T-axis direction, i.e., the stacking direction, into an upper region, a central region, and a lower region, a cross-sectional sample is obtained so that at least one dielectric layer and one internal electrode layer are visible in each region. Subsequently, the obtained cross-sectional sample is measured using a TEM (transmission electron microscope). The TEM can be measured, for example, using a FIB (focused ion beam) under conditions of an acceleration voltage of 200kV and a magnification of 225k. The TEM image of the measured cross-sectional sample is analyzed by EDS (energy dispersive spectroscopy) to confirm dielectric crystal grains 10 having a core-shell structure within the dielectric layer 111.

[0062] Furthermore, using the TEM image, EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis can be performed on a linear section of the long axis passing through the center (α) of the dielectric crystal grain 10 having a core-shell structure, and the absolute value of the La concentration gradient and the absolute value of the total concentration gradient of rare earth elements in the measurement region (X) can be measured. For example, two dielectric layers 111 can be selected from the upper region, central region, and lower region within the active region (A), and five dielectric crystal grains 10 having a core-shell structure can be arbitrarily selected from each dielectric layer 111, so that the average value of the absolute value of the La concentration gradient and the average value of the absolute value of the total concentration gradient of rare earth elements in the measurement region (X) can be determined for a total of 30 dielectric crystal grains having a core-shell structure. In this case, the measurement region (X) may be the region from the interface between the core portion 12 and the shell portion 14 to a depth of 5 nm from the interface toward the shell portion 14, and the measurement is performed in the measurement region (X) toward the shell portion 14. Furthermore, the absolute value of the La concentration gradient can be measured by the absolute value of the slope of a straight line passing through two values: the La content at point (P1) at the interface between the core portion 12 and the shell portion 14, and the La content at point (P2) at a depth of 5 nm from the interface toward the shell portion 14. Similarly, the absolute value of the total concentration gradient of rare earth elements can be measured by the absolute value of the slope of a straight line passing through two values: the total rare earth content at point (P1) and the total rare earth content at point (P2). The measurement is also performed on dielectric crystal grains 10 having a core-shell structure, where point (P2) at a depth of 5 nm is located within the shell portion 14.

[0063] As an example, when performing TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis on a linear section of the long axis passing through the center (α) of a dielectric crystal grain 10 having a core-shell structure, the interface between the core portion 12 and the shell portion 14 may be a point where La is 0.8 moles per 100 moles of Ti. That is, the core portion 12 and the shell portion 14 can be divided based on the point where La is 0.8 moles per 100 moles of Ti. For example, the core portion 12 may be a region where La is less than 0.8 moles per 100 moles of Ti, and the shell portion 14 may be a region where La is 0.8 moles or more per 100 moles of Ti.

[0064] As an example, during the TEM-EDS line analysis, the molar content of La can be higher in the shell portion 14 than in the core portion 12. For example, the La content in the shell portion 14 may be between 0.8 moles and 2.0 moles per 100 moles of Ti, or for example, between 1.0 and 2.0 moles. When the La content in the shell portion is within this range, it not only has a high dielectric constant but also improves the structural fraction between the core portion and the shell portion, thereby improving the DC bias characteristics of the multilayer ceramic capacitor.

[0065] Furthermore, during the TEM-EDS line analysis, the total content of rare earth elements can be higher in the shell portion 14 than in the core portion 12. For example, the total content of rare earth elements in the shell portion 14 may be between 1.2 moles and 5.5 moles per 100 moles of Ti, or for example, between 1.3 moles and 5.0 moles.

[0066] For example, the total content of La, Y, Tb, and Dy can be higher in the shell portion 14 than in the core portion 12. For instance, the total content of La, Y, Tb, and Dy in the shell portion 14 may be between 1.2 moles and 5.5 moles per 100 moles of Ti, for example, between 1.3 moles and 5.0 moles.

[0067] When the total content of rare earth elements in the shell portion, for example, the total content of La, Y, Tb, and Dy, is within the aforementioned range, it not only has a high dielectric constant but also improves the structural fraction of the core portion and the shell portion, thereby improving the DC bias characteristics of the multilayer ceramic capacitor.

[0068] The absolute values ​​of the La concentration gradient and the total concentration gradient of rare earth elements can be obtained by controlling various process conditions during dielectric slurry production, such as adjusting the amount of rare earth elements including La added and adjusting firing conditions such as firing temperature.

[0069] According to one embodiment, when the absolute value of the La concentration gradient is within the range described above, the dielectric crystal grains 10 having a core-shell structure in the central region within the active region (A) can have a small average size. This can be explained with reference to Figure 8.

[0070] Figure 7 is an enlarged view of area A in Figure 2.

[0071] Referring to Figure 7, the average size of the dielectric crystal grains 10 having a core-shell structure in the central region (R) within the active region (A) may be 10 nm or more and less than 130 nm, for example, 20 nm to 129 nm, 30 nm to 128 nm, or 40 nm to 127 nm. In this case, the central region (R) may have a horizontal length corresponding to 1 / 6 of the total horizontal length (l) of the active region (A) facing in directions perpendicular to the stacking direction from the midline (Cp) of the active region (A), and a vertical length corresponding to 1 / 6 of the total vertical length (t) of the active region (A) facing in the stacking direction from the midline (Cp) of the active region (A). When the average size of the dielectric crystal grains 10 having a core-shell structure is within the above range, it is possible to not only have a high dielectric constant but also improve the structural fraction of the core and shell parts, thereby improving the DC bias characteristics of the multilayer ceramic capacitor.

[0072] Furthermore, in the central region (R), the average size of the core portion 12 may be 35% to 67.3% of the average size of the dielectric crystal grains 10, for example, 36% to 67.3% or 37% to 67.3% of the average size of the dielectric crystal grains 10. When the average size of the core portion 12 is within this range, it not only has a high dielectric constant but also improves the structural fraction of the core portion and the shell portion, thereby improving the DC bias characteristics of the multilayer ceramic capacitor.

[0073] The average size of the dielectric crystal grains 10 and the average size of the core portion 12 can be measured by the following method.

[0074] After curing the multilayer ceramic capacitor 100 in an epoxy mixture, the L-axis and T-axis planes (LT planes) of the capacitor body 110 are polished to a depth of 1 / 2 in the W-axis direction to obtain a cross-sectional sample that allows observation of the active region (A) where the dielectric layer 111 and the internal electrode layers 121 and 122 intersect. For example, when the active region (A) is divided into three equal parts in the T-axis direction, i.e., the stacking direction, into an upper region, a central region, and a lower region, a cross-sectional sample is obtained such that at least one dielectric layer and one internal electrode layer are visible in the central region. Subsequently, the central region (R) within the central region of the obtained cross-sectional sample, i.e., the central region (R) having a horizontal length corresponding to 1 / 6 of the total horizontal length (l) of the active region (A) opposite the direction perpendicular to the stacking direction, and a vertical length corresponding to 1 / 6 of the total vertical length (t) of the active region (A) opposite the stacking direction, is measured using a TEM (transmission electron microscope). TEM can be used, for example, with a focused ion beam (FIB) under conditions of an acceleration voltage of 200 kV and a magnification of 225 k. After analyzing the TEM image of the measured cross-sectional sample using energy-dispersive spectroscopy (EDS) to confirm the presence of dielectric crystal grains 10 with a core-shell structure in the central region (R) within the active region (A), the average size of the dielectric crystal grains 10 and the average size of the core portion 12 can be measured.

[0075] Here, the average size of the dielectric crystal grains 10 can be calculated by the average value of the sizes of at least two, for example, five dielectric crystal grains 10 present in the central region (R), and the average size of the core portion 12 can be calculated, for example, by the average value of the sizes of the core portion 12 within the same five dielectric crystal grains 10.

[0076] In this case, the size of the dielectric crystal grain 10 can be obtained by the average value of the long axis length having the maximum diameter passing through the center (α) of the dielectric crystal grain 10 and the short axis length having the minimum diameter, as shown in Figure 6. Furthermore, the average size of the core portion 12 can be obtained by the average value of the size of the core portion 12 obtained along the long axis length having the maximum diameter passing through the center (α) of the dielectric crystal grain 10 and the size of the core portion 12 obtained along the short axis length having the minimum diameter.

[0077] The average thickness (average length in the T-axis direction) of the dielectric layer 111 may be between 0.1 μm and 8.0 μm, for example, between 0.1 μm and 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.

[0078] The average thickness of the dielectric layer 111 can be measured by scanning electron microscopy (SEM) analysis after the multilayer ceramic capacitor 100 has been cured in an epoxy mixture, polished, ion milled, and then analyzed. The SEM can be used, for example, at 10kV and 100x magnification, and can be used to measure so that at least one, three, five, or ten layers of the dielectric layer 111 are visible in the active region where the dielectric layer 111 and the internal electrode layers 121 and 122 intersect. In the SEM image, the center point of the dielectric layer 111 in the length direction (L-axis direction) or width direction (W-axis direction) is used as the reference point, and the average thickness of the dielectric layer 111 at 10 points spaced at predetermined intervals from the reference point can be determined. The interval of the 10 points can be adjusted according to the scale of the SEM image, for example, between 1μm and 100μm, between 1μm and 50μm, or between 1μm and 10μm. In this case, 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 spacing between the 10 points can be adjusted. Furthermore, by extending this average value measurement to 10 dielectric layers and measuring the average value, the average thickness of the dielectric layer can be more generalized.

[0079] internal electrode layer The internal electrode layers 121 and 122, namely the first internal electrode layer 121 and the second internal electrode layer 122, are electrodes having opposite polarities and are alternately arranged facing each other along the T-axis direction with the dielectric layer 111 in between, with one end of each electrode being exposed through the third and fourth surfaces of the capacitor body 110.

[0080] The first internal electrode layer 121 and the second internal electrode layer 122 can be electrically insulated from each other by the dielectric layer 111 placed in between them.

[0081] The ends of the first internal electrode layer 121 and the second internal electrode layer 122, which are alternately exposed through the third and fourth surfaces of the capacitor body 110, are connected to the first external electrode 131 and the second external electrode 132, respectively, and can be electrically connected.

[0082] The internal electrode layers 121 and 122 contain a conductive metal, and may include one or more metals and alloys thereof, such as Ni, Cu, Ag, Pd, Au.

[0083] Furthermore, the internal electrode layers 121 and 122 may also contain dielectric particles with the same composition as the ceramic material contained in the dielectric layer 111.

[0084] The internal electrode layers 121 and 122 can be formed using a conductive paste containing a conductive metal. The conductive paste can be printed using screen printing or gravure printing.

[0085] The average thickness of the internal electrode layers 121 and 122 may be 0.1 μm to 2 μm.

[0086] The average thickness of the internal electrode layers 121 and 122 can be measured by scanning electron microscopy (SEM) analysis. Specifically, using an SEM image of a cross-sectional sample obtained in the same manner as the method for measuring the average thickness of the dielectric layer 111, the average thickness of the internal electrode layers 121 and 122 can be determined from 10 points separated by a predetermined interval from the reference point, with the center point in the length direction (L-axis direction) or width direction (W-axis direction) of the internal electrode layers 121 and 122 being used as the reference point. The interval of the 10 points can be adjusted according to the scale of the SEM image, for example, between 1 μm and 100 μm, 1 μm and 50 μm, or 1 μm and 10 μm. In this case, all 10 points must be located within the internal electrode layers 121 and 122. If all 10 points are not located within the internal electrode layers 121 and 122, the position of the reference point can be changed or the interval between the 10 points can be adjusted. Furthermore, by extending this average value measurement to 10 internal electrode layers and measuring the average value, the average thickness of the internal electrode layers can be more generalized.

[0087] The capacitor body 110 can be formed by firing a laminate in which multiple dielectric layers 111 and internal electrode layers 121 and 122 are stacked.

[0088] external electrode The external electrodes 131 and 132, namely the first external electrode 131 and the second external electrode 132, are supplied with voltages of different polarities from each other and can be electrically connected to the exposed portions of the first internal electrode layer 121 and the second internal electrode layer 122, respectively.

[0089] With the above configuration, when a predetermined voltage is applied to the first external electrode 131 and the second external electrode 132, charge is accumulated between the first internal electrode layer 121 and the second internal electrode layer 122, which face each other. At this time, the capacitance of the multilayer ceramic capacitor 100 will be proportional to the overlapping area of ​​the first internal electrode layer 121 and the second internal electrode layer 122, which overlap each other along the T-axis in the active region.

[0090] The first external electrode 131 and the second external electrode 132 are arranged on the third and fourth surfaces of the capacitor body 110, respectively, and may include first and second connecting portions that connect to the first internal electrode layer 121 and the second internal electrode layer 122, as well as first and second band portions arranged at the corners where the third and fourth surfaces of the capacitor body 110 meet the first and second surfaces or the fifth and sixth surfaces.

[0091] The first band portion and the second band portion can extend from the first and second connection portions to the first and second surfaces, or to a portion of the fifth and sixth surfaces, of the capacitor body 110, respectively. The first band portion and the second band portion can serve to improve the adhesion strength of the first external electrode 131 and the second external electrode 132.

[0092] The external electrodes 131 and 132 may include a sintered metal layer in contact with the capacitor body 110, a conductive resin layer positioned to cover the sintered metal layer, and a plating layer positioned to cover the conductive resin layer.

[0093] The sintered metal layer may contain conductive metals and glass.

[0094] Conductive metals 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 copper (Cu) alloys. If the conductive metal contains copper, the amount of other metals may be 5 moles or less per 100 moles of copper.

[0095] The glass may contain a composition of mixed oxides, for example, one or more selected from the group consisting of silicon dioxide, boron dioxide, aluminum oxide, transition metal oxides, alkali metal oxides, and alkaline earth metal oxides. The transition metals may be selected from the group consisting of zinc (Zn), titanium (Ti), copper (Cu), vanadium (V), manganese (Mn), iron (Fe), and nickel (Ni); the alkali metals may be selected from the group consisting of lithium (Li), sodium (Na), and potassium (K); and the alkaline earth metals may be one or more selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

[0096] Selectively, the conductive resin layer can be formed on the sintered metal layer, 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 do not have to include the sintered metal layer, in which case the conductive resin layer can be in direct contact with the capacitor body 110.

[0097] 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) in which the conductive resin layer extends to the first and second surfaces, or the fifth and sixth surfaces, of the capacitor body 110 can be longer than the length of the region (i.e., the band portion) in which the sintered metal layer extends to the first and second surfaces, or the fifth and sixth surfaces, of the capacitor body 110. In other words, the conductive resin layer can be formed on the sintered metal layer and can be formed in a manner that completely covers the sintered metal layer.

[0098] The conductive resin layer contains a resin and a conductive metal.

[0099] The resin contained in the conductive resin layer is not particularly limited as long as it has bonding properties and shock absorption and can be mixed with conductive metal powder to form a paste, and may include, for example, phenolic resin, acrylic resin, silicone resin, epoxy resin, or polyimide resin.

[0100] The conductive metal contained in the conductive resin layer serves to electrically connect with the internal electrode layers 121, 122, or the sintered metal layer.

[0101] The conductive metal contained in the conductive resin layer may be spherical, flake-shaped, or a combination thereof. That is, the conductive metal may be solely flake-shaped, solely spherical, or a mixture of flake-shaped and spherical forms.

[0102] Here, "spherical" can include forms that are not perfectly spherical, for example, forms in which the ratio of the length of the long axis to the short axis (long axis / short axis) is 1.45 or less. "Flake-type powder" means powder that is flat but has an elongated shape, and is not particularly limited, for example, the ratio of the length of the long axis to the short axis (long axis / short axis) may be 1.95 or more.

[0103] The external electrodes 131 and 132 may further include a plating layer positioned outside the conductive resin layer.

[0104] The plating layer may include nickel (Ni), copper (Cu), tin (Sn), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), tungsten (W), titanium (Ti), or lead (Pb), either alone or in alloys thereof. For example, the plating layer may be a nickel (Ni) plating layer or a tin (Sn) plating layer, or a configuration in which nickel (Ni) and tin (Sn) plating layers are sequentially laminated, or a configuration in which tin (Sn) plating layers, nickel (Ni) plating layers, and tin (Sn) plating layers are sequentially laminated. The plating layer may also include multiple nickel (Ni) plating layers and / or multiple tin (Sn) plating layers.

[0105] The plating layer can improve the mountability of the multilayer ceramic capacitor 100 on the substrate, structural reliability, durability against external elements, heat resistance, and equivalent series resistance (ESR).

[0106] Manufacturing method for multilayer ceramic capacitors The following describes a method for manufacturing a multilayer ceramic capacitor 100 according to one embodiment.

[0107] A multilayer ceramic capacitor 100 according to one embodiment can be manufactured by the following steps: mixing a barium titanate-based compound and a rare earth element-containing compound including a lanthanum (La)-containing compound to produce a dielectric slurry; using the dielectric slurry to produce a dielectric green sheet and forming a conductive paste layer on the surface of the dielectric green sheet; stacking the dielectric green sheets on which the conductive paste layer is formed to produce a dielectric green sheet laminate; firing the dielectric green sheet laminate to produce a capacitor body including a dielectric layer and an internal electrode layer; and forming an external electrode on one surface of the capacitor body.

[0108] Rare earth element-containing compounds may further include one or more auxiliary element-containing compounds selected from scandium (Sc)-containing compounds, yttrium (Y)-containing compounds, neodymium (Nd)-containing compounds, europium (Eu)-containing compounds, gadolinium (Gd)-containing compounds, terbium (Tb)-containing compounds, dysprosium (Dy)-containing compounds, holmium (Ho)-containing compounds, erbium (Er)-containing compounds, ytterbium (Yb)-containing compounds, and lutetium (Lu)-containing compounds. For example, rare earth element-containing compounds may include lanthanum (La)-containing compounds, yttrium (Y)-containing compounds, terbium (Tb)-containing compounds, and dysprosium (Dy)-containing compounds.

[0109] The lanthanum (La)-containing compound can be mixed in an amount of 0.1 to 2 moles per 100 moles of the barium titanate-based compound, for example, 0.3 to 1.8 moles. When the lanthanum (La)-containing compound is mixed within this content range, dielectric crystal grains with improved structural fractions between the core and shell can be obtained, resulting in a multilayer ceramic capacitor with high dielectric constant and excellent DC bias characteristics.

[0110] Furthermore, when auxiliary element-containing compounds are mixed together, the total amount of auxiliary element-containing compounds can be mixed in an amount of 1.2 moles to 5.5 moles per 100 moles of barium titanate-based compound. When the total amount of auxiliary element-containing compounds is mixed within the above content range, dielectric crystal grains with improved structural fractions between the core and shell can be obtained, resulting in a multilayer ceramic capacitor with high dielectric constant and excellent DC bias characteristics.

[0111] Lanthanum (La)-containing compounds and auxiliary element-containing compounds can be oxides, nitrates, salt compounds, or compounds in sol form dispersed in organic solvents, respectively.

[0112] Dielectric slurry can be manufactured by adding and mixing solvents with additives such as dispersants, binders, plasticizers, lubricants, and antistatic agents.

[0113] The dispersant may include, for example, phosphate ester-based dispersants, polycarboxylic acid-based dispersants, or combinations thereof. The dispersant can be mixed in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the barium titanate compound, for example, 0.3 to 3 parts by weight. 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 manufactured dielectric layer can be reduced.

[0114] Examples of binders include acrylic resin, polyvinyl butyl resin, polyvinyl acetal resin, and ethylcellulose resin. The binder can be added in an amount of 0.1 to 50 parts by weight per 100 parts by weight of the barium titanate compound, for example, 3 to 30 parts by weight. 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 manufactured dielectric layer can be reduced.

[0115] Examples of plasticizers include phthalate compounds such as dioctyl phthalate, benzyl butyl phthalate, dibutyl phthalate, dihexyl phthalate, di(2-ethylhexyl) phthalate, and di(2-ethylbutyl) phthalate; adipic acid compounds such as dihexyl adipic acid and di(2-ethylhexyl) adipic acid; glycol compounds such as ethylene glycol, diethylene glycol, and triethylene glycol; and glycol ester compounds such as triethylene glycol dibutyrate, triethylene glycol di(2-ethylbutylate), and triethylene glycol di(2-ethylhexanoate). The plasticizer can be added in an amount of 0.1 to 20 parts by weight per 100 parts by weight of the barium titanate compound, for example, 1 to 10 parts by weight. When the plasticizer is mixed within the above content range, the dispersion of the dielectric slurry is excellent, and the amount of impurities contained in the manufactured dielectric layer can be reduced.

[0116] Examples of solvents include aqueous solvents such as water; alcoholic solvents such as ethanol, methanol, benzyl alcohol, and 2-methoxyethanol; glycolic solvents such as ethylene glycol and diethylene glycol; ketoneic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esteric solvents such as butyl acetate, ethyl acetate, carbitol acetate, and butyl carbitol acetate; etheric solvents such as methyl cellosolve, ethyl cellosolve, butyl ether, and tetrahydrofuran; and aromatic solvents such as benzene, toluene, and xylene. The solvent can be an alcoholic or aromatic solvent, for example, considering the solubility and dispersibility of the various additives contained in the dielectric slurry. The solvent can be mixed in an amount of 50 to 1000 parts by weight per 100 parts by weight of the barium titanate compound, for example, 100 to 500 parts by weight. When the solvent is mixed within the above content range, the dielectric slurry components can be thoroughly mixed, and subsequent removal of the solvent is also easy.

[0117] The aforementioned dielectric slurry can be mixed using a wet ball mill or a stirring mill. When using zirconia balls in a wet ball mill, multiple zirconia balls with diameters from 0.1 mm to 10 mm can be used for wet mixing for 8 to 48 hours, or 10 to 24 hours.

[0118] The manufactured dielectric slurry is formed with a dielectric layer after firing.

[0119] Methods for forming the manufactured dielectric slurry into a sheet shape include tape molding methods such as the doctor blade method and the calender roll method, or, for example, an on-roll molding coater with a head discharge system. After that, the molded body is dried to obtain a dielectric green sheet.

[0120] After firing, a conductive paste layer that will become the internal electrode layer can be formed by mixing conductive powder made of a conductive metal or an alloy thereof, a binder, and a solvent to produce a conductive paste. Additionally, barium titanate powder can be mixed in as a co-material if necessary. The co-material can suppress the sintering of the conductive powder during the firing process. The conductive paste layer is then applied to the surface of the dielectric green sheet in a predetermined pattern using various printing methods such as screen printing or transfer methods.

[0121] The conductive powder may include nickel (Ni) or a nickel (Ni) alloy.

[0122] Next, a dielectric green sheet laminate is manufactured by stacking multiple dielectric green sheets with internal electrode patterns formed on them, and then pressing them in the stacking direction. At this time, dielectric green sheets and internal electrode layer patterns can be stacked such that dielectric green sheets are located on the upper and lower surfaces of the dielectric green sheet laminate in the stacking direction.

[0123] The step of cutting the manufactured dielectric green sheet laminate to a predetermined size by dicing or other means can be selectively performed.

[0124] Furthermore, the dielectric green sheet laminate can be solidified and dried as needed to remove plasticizers and other substances, and after solidification and drying, it can be barrel polished using a horizontal centrifugal barrel polishing machine or the like. In barrel polishing, the dielectric green sheet laminate is placed in a barrel container along with media and polishing fluid, and rotational motion or vibration is applied to the barrel container to polish away unwanted parts such as burrs generated during cutting. After barrel polishing, the dielectric green sheet laminate can be washed with a cleaning solution such as water and then dried.

[0125] Next, the dielectric green sheet laminate can be debindered (calcined) and fired to manufacture a capacitor body.

[0126] 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 may be 5°C / hour to 300°C / hour, the support temperature 180°C to 400°C, and the temperature maintenance time 0.5 hours to 24 hours. The atmosphere during debinding may be air or a reducing atmosphere.

[0127] Firing can be performed at a temperature exceeding 1180°C but below 1210°C. Firing can also be performed for 0.5 to 8 hours, for example, 1 to 3 hours. Furthermore, firing can be performed in a reducing atmosphere, for example, a humidified atmosphere of a nitrogen and hydrogen mixture, for example, under conditions of a hydrogen concentration of 1.0% or less. If the internal electrode layer contains nickel (Ni) or a nickel (Ni) alloy, the oxygen partial pressure in the firing atmosphere should be 1.0 × 10⁻⁶. -14 MPa ~ 1.0 × 10 -10 MPa is also acceptable.

[0128] After firing, annealing can be performed as needed. Annealing is a process to re-oxidize the dielectric layer, and it can be performed when firing is carried out in a reducing atmosphere. The conditions for the annealing process can also be appropriately adjusted according to the composition of the dielectric layer. For example, the temperature during annealing can be 950°C to 1150°C, the time can be 0 to 20 hours, and the heating rate can be 50°C / hour to 500°C / hour. The annealing atmosphere may be a humidified nitrogen gas (N2) atmosphere, and the oxygen partial pressure should be 1.0 × 10⁻⁶. -9 MPa ~ 1.0 × 10 -5 MPa is also acceptable.

[0129] In the debindering, calcining, or annealing processes, a wetter, for example, can be used to humidify nitrogen gas or a mixed gas, in which case the water temperature can be between 5°C and 75°C. The debindering, calcining, and annealing processes can be carried out continuously or independently.

[0130] Selectively, the third and fourth surfaces of the manufactured capacitor body 110 can be subjected to surface treatments such as sandblasting, laser irradiation, and barrel polishing. By performing such surface treatments, the edges of the first and second internal electrode layers can be exposed on the outermost surfaces of the third and fourth surfaces, thereby improving the electrical connection between the first and second external electrodes and the first and second internal electrode layers, and facilitating the formation of the alloy portion.

[0131] Next, an external electrode is formed on one surface of the manufactured capacitor body 110.

[0132] For example, a paste for forming a sintered metal layer can be applied to an external electrode, and then sintered to form a sintered metal layer.

[0133] The paste for forming a sintered metal layer may contain conductive metals and glass. The explanation of conductive metals and glass is the same as above, so a repeated explanation will be omitted. The paste for forming a sintered metal layer may also selectively contain binders, solvents, dispersants, plasticizers, oxide powders, etc. Binders can be, for example, ethyl cellulose, acrylic, butyral, etc., and solvents can be, for example, organic solvents such as terpineol, butyl carbitol, alcohol, methyl ethyl ketone, acetone, toluene, or aqueous solvents.

[0134] Methods for applying the sintered metal layer-forming paste to the outer surface of the capacitor body 110 include the dip method, various printing methods such as screen printing, application methods using dispensers, and spraying methods using sprayers. The sintered metal layer-forming paste is applied to at least the third and fourth surfaces of the capacitor body 110, and may also be applied to a portion of the first, second, fifth, or sixth surfaces where the band portions of the first and second external electrodes are selectively formed.

[0135] Subsequently, the capacitor body 110 coated with the paste for forming a sintered metal layer is dried and then fired at a temperature of 700°C to 1000°C for 0.1 to 3 hours to form a sintered metal layer.

[0136] Selectively, a conductive resin layer can be formed by applying a conductive resin layer-forming paste to the outer surface of the obtained capacitor body 110 and then curing it.

[0137] The paste for forming a conductive resin layer may contain a resin and, selectively, a conductive metal or a non-conductive filler. The explanation of conductive metals and resins is the same as above, so a repetition of the explanation is omitted. The paste for forming a conductive resin layer may also selectively contain a binder, solvent, dispersant, plasticizer, oxide powder, etc. Binders can be, for example, ethyl cellulose, acrylic, butyral, etc., and solvents can be organic solvents such as terpineol, butyl carbitol, alcohol, methyl ethyl ketone, acetone, toluene, or aqueous solvents.

[0138] For example, the conductive resin layer can be formed by dipping the capacitor body 110 into a conductive resin layer forming paste and then curing it, printing the conductive resin layer forming paste onto the surface of the capacitor body 110 using screen printing or gravure printing, or applying the conductive resin layer forming paste to the surface of the capacitor body 110 and then curing it.

[0139] Next, a plating layer is formed on the outside of the conductive resin layer.

[0140] For example, the plating layer can be formed by a plating method, and can also be formed by sputtering or electroplating (electric deposition).

[0141] The above-described embodiments will be explained in more detail below through the examples provided. However, the following embodiments are for illustrative purposes only and do not limit the scope of the rights.

[0142] (Manufacturing of multilayer ceramic capacitors) Examples 1-4 A dielectric slurry was prepared by mixing barium titanate (BaTiO3), lanthanum nitrate (La(NO3)3), yttrium oxide (Y2O3), terbium oxide (Tb4O7), and dysprosium oxide (Dy2O3). In this process, La(NO3)3 was mixed at a ratio of 0.5 moles per 100 moles of BaTiO3, and the total amount of La(NO3)3, Y2O3, Tb4O7, and Dy2O3 was 1.8 moles per 100 moles of BaTiO3.

[0143] During the manufacturing of the dielectric slurry, zirconia balls (ZrO2 balls) were used as the dispersion medium. These balls were added together with ethanol / toluene, a wetting dispersant, and polyvinyl butyral (PVB) resin as a binder, followed by mechanical milling.

[0144] Dielectric green sheets were manufactured using a head-dispensing type on-roll molding coater with the manufactured dielectric slurry.

[0145] A dielectric green sheet laminate was manufactured by printing a conductive paste layer containing nickel (Ni) onto the surface of a dielectric green sheet, and then laminating and pressing the dielectric green sheets with the conductive paste layer formed on them.

[0146] The dielectric green sheet laminate was subjected to a calcination process at a temperature of 400°C or lower and in a nitrogen atmosphere, followed by firing at a predetermined temperature and a hydrogen concentration of 1.0% H2 or lower. Examples 1 to 4 were fired at temperatures of 1190°C, 1195°C, 1200°C, and 1205°C, respectively.

[0147] Next, the multilayer ceramic capacitor was manufactured through processes such as the formation of external electrodes and plating.

[0148] Comparative Example 1 A multilayer ceramic capacitor was manufactured in the same manner as in Example 1, except that La(NO3)3 was mixed in an amount of 0.01 moles per 100 moles of BaTiO3.

[0149] Comparative Example 2 A multilayer ceramic capacitor was manufactured in the same manner as in Example 2, except that La(NO3)3 was mixed in an amount of 0.01 moles per 100 moles of BaTiO3.

[0150] Comparative Example 3 A multilayer ceramic capacitor was manufactured in the same manner as in Example 1, except that it was fired at 1180°C.

[0151] Comparative Example 4 A multilayer ceramic capacitor was manufactured in the same manner as in Example 1, except that it was fired at 1210°C.

[0152] Comparative Example 5 A multilayer ceramic capacitor was manufactured in the same manner as in Example 1, except that it was fired at 1220°C.

[0153] Evaluation 1: TEM-EDS analysis (1) Confirmation of the composition of dielectric crystal grains TEM-EDS (transmission electron microscope-energy dispersive spectroscopy) mapping analysis was performed on the multilayer ceramic capacitors manufactured in Examples 1-4 and Comparative Examples 1-5 using the following method.

[0154] After curing each multilayer ceramic capacitor in an epoxy mixture, the L-axis and T-axis planes (LT planes) of the capacitor body were polished to a depth of 1 / 2 in the W-axis direction to obtain cross-sectional samples that allowed observation of the active region where the dielectric layer and internal electrode layer intersected. At this time, the active region was divided into three equal parts in the T-axis direction, i.e., the stacking direction, into upper, middle, and lower regions, and cross-sectional samples were obtained so that at least one dielectric layer and one internal electrode layer were visible in each region. Subsequently, the obtained cross-sectional samples were measured using a TEM (transmission electron microscope) with a focused ion beam (FIB) under conditions of an acceleration voltage of 200 kV and a magnification of 225 k. EDS (energy-dispersive spectroscopy) mapping analysis was performed on the TEM images of the measured cross-sectional samples, and the results are shown in Figure 8.

[0155] Figure 8 shows the TEM-EDS (transmission electron microscope-energy dispersive spectroscopy) mapping analysis image of the dielectric layer according to Example 1.

[0156] Referring to Figure 8, the EDS mapping analysis results confirm the presence of dielectric crystal grains with a core-shell structure within the dielectric layer of Example 1, and it can be confirmed that these dielectric crystal grains with a core-shell structure contain Ba, Ti, and La.

[0157] (2) Concentration gradient of La and total concentration gradient of rare earth elements EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis was performed on the TEM image of the measured cross-sectional sample for the linear section of the long axis passing through the center of the dielectric crystal grain having a core-shell structure. The absolute values ​​of the La concentration gradient and the total concentration gradient of rare earth elements in the measurement region (X) were measured, and the results are shown in Figures 9 and 10 and Table 1 below.

[0158] In this case, the absolute value of each concentration gradient was determined by selecting two dielectric layers from the upper, central, and lower regions within the active region, arbitrarily selecting five dielectric crystal grains having a core-shell structure from each dielectric layer, and then calculating the average value of the absolute value of the La concentration gradient and the average value of the total concentration gradient of rare earth elements for a total of 30 dielectric crystal grains having a core-shell structure in the measurement region (X). In this case, the measurement region (X) was the region from the interface between the core and shell to a depth of 5 nm toward the shell from the interface, and measurements were taken in the direction toward the shell from the interface between the core and shell in the measurement region (X). The absolute value of the La concentration gradient was measured as the absolute value of the slope of the line passing through two values: the content value at point (P1), which is the interface between the core and shell, and the content value at point (P2), which is 5 nm toward the shell from the interface. Similarly, the absolute value of the total concentration gradient of rare earth elements was measured as the absolute value of the slope of the straight line passing through the total content of rare earth elements at point (P1) and the total content of rare earth elements at point (P2). The measurement was also performed on dielectric crystal grains having a core-shell structure, where the point at a depth of 5 nm is located within the shell portion.

[0159] Figure 9 is an image showing the lanthanum (La) content in the dielectric layer according to Example 1 during TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis, and Figure 10 is an image showing the total content of rare earth elements in the dielectric layer according to Example 1 during TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis.

[0160] Referring to Figure 9 and Table 1 below, it can be seen that in Examples 1 to 4, when measuring in the measurement region (X) from the interface between the core and the shell towards the shell, the absolute value of the La concentration gradient is in the range of 0.12 mol / nm to 0.58 mol / nm, based on 100 mol / nm of Ti.

[0161] Furthermore, referring to Figure 10 and Table 1 below, it can be seen that in Examples 1 to 4, when measuring from the interface between the core and shell in the measurement region (X) towards the shell, the absolute value of the total concentration gradient of rare earth elements is in the range of 0.12 mol / nm to 0.58 mol / nm, based on 100 mol / nm of Ti. At this time, the absolute value of the total concentration gradient of rare earth elements represents the absolute value of the total concentration gradient of La, Y, Tb, and Dy.

[0162] At this point, it can be seen that the interface between the core and the shell is located at a point where La is approximately 0.8 moles relative to 100 moles of Ti.

[0163] In Table 1 below, the absolute values ​​of the La concentration gradient and the absolute values ​​of the total rare earth element concentration gradient are shown based on 100 moles of Ti.

[0164] [Table 1]

[0165] From Table 1 above, it can be seen that in Examples 1 to 4, the absolute value of the concentration gradient of La is in the range of 0.12 mol / nm to 0.58 mol / nm with respect to 100 mol parts of Ti, or the absolute value of the total concentration gradient of rare earth elements including La, Y, Tb, and Dy is in the range of 0.12 mol / nm to 0.58 mol / nm with respect to 100 mol parts of Ti.

[0166] (3) Average size of dielectric crystal grains The central region (R) within the central region of the cross-sectional sample obtained above, that is, the central region (R) having a horizontal length corresponding to 1 / 6 of the total horizontal length (l) of the active region facing perpendicular to the stacking direction from the midline (Cp) of the active region, and a vertical length corresponding to 1 / 6 of the total vertical length (t) of the active region facing perpendicular to the stacking direction from the midline (Cp) of the active region, was measured using a focused ion beam (FIB) with an acceleration voltage of 200 kV and a magnification of 225 k using a transmission electron microscope (TEM). After analyzing the measured TEM image using energy dispersive spectroscopy (EDS) to confirm dielectric crystal grains with a core-shell structure present in the central region (R) within the active region, the average size of the dielectric crystal grains and the average size of the core were measured, and the results are shown in Figure 11 and Table 2 below.

[0167] The average size of the dielectric crystal grains was calculated using the average size of five dielectric crystal grains located in the central region (R), and the average size of the core was calculated using the average size of the core within the five dielectric crystal grains. In this case, the size of the dielectric crystal grain was determined by the average value of the major axis length having the largest diameter and the minor axis length having the smallest diameter passing through the center (α) of the dielectric crystal grain, and the size of the core was determined by the average value of the core size obtained along the major axis length having the largest diameter passing through the center (α) of the dielectric crystal grain and the core size obtained along the minor axis length having the smallest diameter.

[0168] Figure 11 is a graph showing the average size of dielectric crystal grains for Example 1 and Comparative Example 2.

[0169] In Table 2 below, the size of the core is shown as a ratio to the average size of the dielectric crystal grains.

[0170] [Table 2]

[0171] As can be seen from Figure 11 and Table 2, in Examples 1 to 4, where the absolute value of the La concentration gradient or the absolute value of the total concentration gradient of rare earth elements is in the range of 0.12 mol / nm to 0.58 mol / nm based on 100 mol / nm of Ti, the average size of the dielectric crystal grains is smaller compared to Comparative Examples 1 to 5, where the range is exceeded.

[0172] Evaluation 2: DC Bias Characteristics The DC bias characteristics of the multilayer ceramic capacitors manufactured in Examples 1-4 and Comparative Examples 1-5 were evaluated using the following method, and the results are shown in Table 3 below.

[0173] After measuring the nominal capacitance under 1kHz and 0.5Vrms conditions, the effective capacitance was measured by applying 1V DC and 3V DC under 100kHz and 0.01Vrms conditions, respectively. The rate of change of the effective capacitance relative to the nominal capacitance (ΔCp) was then calculated.

[0174] In Table 3 below, if the ΔCp at 1V DC is -22% or higher, or if the ΔCp at 3V DC is -65% or higher, it was determined that the DC bias characteristics were degraded.

[0175] [Table 3]

[0176] As can be seen from Table 3 above, in Examples 1 to 4, where the absolute value of the concentration gradient of La or the absolute value of the total concentration gradient of rare earth elements is in the range of 0.12 mol / nm to 0.58 mol / nm based on 100 mol / nm of Ti, the DC bias characteristics are superior compared to Comparative Examples 1 to 5, which are outside this range.

[0177] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and can be implemented in various ways within the scope of the claims, description of the invention, and attached drawings, and these also naturally fall within the scope of the present invention. [Explanation of symbols]

[0178] 10 Dielectric crystal grains 12 Core section 14 Shell section 100 Multilayer Ceramic Capacitors 110 Capacitor Body 111 Dielectric layer 112 Coverage Area 113 Coverage Area 121 1st internal electrode layer 122 Second internal electrode layer 131 1st external electrode 132 2nd external electrode A Active Area R center area X measurement area P1 is the interface between the core and the shell. A point 5 nm deep from the P2 interface towards the shell. α Dielectric grain center l Total horizontal length t total vertical length

Claims

1. A capacitor body including a dielectric layer and an internal electrode layer, and Includes external electrodes positioned outside the capacitor body, The dielectric layer comprises a plurality of dielectric crystal grains. At least one of the plurality of dielectric crystal grains has a core-shell structure including a core portion and a shell portion surrounding at least a part of the core portion. The dielectric crystal grains having the core-shell structure contain rare earth elements including barium (Ba), titanium (Ti), and lanthanum (La). A multilayer ceramic capacitor, wherein when measuring from the interface to the shell portion in a measurement area extending 5 nm from the interface to the shell portion, the absolute value of the lanthanum (La) concentration gradient is between 0.12 mol parts / nm and 0.58 mol parts / nm, based on 100 mol parts of titanium (Ti).

2. When performing TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis on a linear section of the long axis passing through the center of a dielectric crystal grain having the core-shell structure, The core portion is a region in which the lanthanum (La) is less than 0.8 moles relative to 100 moles of titanium (Ti). The multilayer ceramic capacitor according to claim 1, wherein the shell portion is a region in which the lanthanum (La) is 0.8 moles or more relative to 100 moles of titanium (Ti).

3. The multilayer ceramic capacitor according to claim 1, wherein the lanthanum (La) has a higher molar content in the shell portion than in the core portion.

4. The multilayer ceramic capacitor according to claim 1, wherein the lanthanum (La) content in the shell portion is 0.8 moles or more and 2.0 moles or less per 100 moles of titanium (Ti).

5. The multilayer ceramic capacitor according to claim 1, wherein the rare earth element further comprises one or more auxiliary elements selected from scandium (Sc), yttrium (Y), neodymium (Nd), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), ytterbium (Yb), and lutetium (Lu).

6. The multilayer ceramic capacitor according to claim 1, wherein the rare earth element further comprises auxiliary elements including yttrium (Y), terbium (Tb), and dysprosium (Dy).

7. The capacitor body includes an active region in which the dielectric layer and the internal electrode layer are arranged alternately with respect to each other. The multilayer ceramic capacitor according to claim 1, wherein the central region has a horizontal length corresponding to 1 / 6 of the total horizontal length of the active region facing in a direction perpendicular to the stacking direction from the center of the active region, and a vertical length corresponding to 1 / 6 of the total vertical length of the active region facing in a direction perpendicular to the stacking direction from the center of the active region, and the average size of the dielectric crystal grains having the core-shell structure is 10 nm or more and less than 130 nm.

8. The multilayer ceramic capacitor according to claim 7, wherein in the central region, the average size of the core portion is 35% to 67.3% of the average size of the dielectric crystal grains.

9. A capacitor body including a dielectric layer and an internal electrode layer, and Includes external electrodes positioned outside the capacitor body, The dielectric layer comprises a plurality of dielectric crystal grains. At least one of the plurality of dielectric crystal grains has a core-shell structure including a core portion and a shell portion surrounding at least a part of the core portion. The dielectric crystal grain having the core-shell structure comprises barium (Ba), titanium (Ti), and rare earth elements, wherein the rare earth element comprises lanthanum (La) and one or more auxiliary elements selected from scandium (Sc), yttrium (Y), neodymium (Nd), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), ytterbium (Yb), and lutetium (Lu); A multilayer ceramic capacitor in which, when measured from the interface between the core portion and the shell portion in a measurement area extending 5 nm to a depth toward the shell portion, the absolute value of the total concentration gradient of the rare earth element is between 0.12 mol parts / nm and 0.58 mol parts / nm, based on 100 mol parts of titanium (Ti).

10. When performing TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis on a linear section of the long axis passing through the center of a dielectric crystal grain having the core-shell structure, The core portion is a region in which the lanthanum (La) is less than 0.8 moles relative to 100 moles of titanium (Ti). The multilayer ceramic capacitor according to claim 9, wherein the shell portion is in a region where the lanthanum (La) is 0.8 moles or more relative to 100 moles of titanium (Ti).

11. The multilayer ceramic capacitor according to claim 9, wherein the total content of the rare earth elements is higher in the shell portion than in the core portion.

12. The multilayer ceramic capacitor according to claim 9, wherein the total content of the rare earth element in the shell portion is 1.2 moles or more and 5.5 moles or less per 100 moles of titanium (Ti).

13. The capacitor body includes an active region in which the dielectric layer and the internal electrode layer are arranged alternately with respect to each other. The multilayer ceramic capacitor according to claim 9, wherein the central region has a horizontal length corresponding to 1 / 6 of the total horizontal length of the active region facing in a direction perpendicular to the stacking direction from the center of the active region, and a vertical length corresponding to 1 / 6 of the total vertical length of the active region facing in the stacking direction from the center of the active region, and the average size of the dielectric crystal grains having the core-shell structure is 10 nm or more and less than 130 nm.

14. The multilayer ceramic capacitor according to claim 13, wherein in the central region, the average size of the core portion is 35% to 67.3% of the average size of the dielectric crystal grains.

15. The multilayer ceramic capacitor according to claim 9, wherein the rare earth element comprises La, Y, Tb, and Dy.

16. The multilayer ceramic capacitor according to claim 15, wherein the total content of La, Y, Tb, and Dy has a higher molar content in the shell portion than in the core portion.

17. The multilayer ceramic capacitor according to claim 15, wherein the total content of La, Y, Tb, and Dy in the shell portion is 1.2 moles or more and 5.5 moles or less per 100 moles of titanium (Ti).

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