Multilayer ceramic capacitor

Abstract

The present disclosure provides a multilayer ceramic capacitor including: a capacitor body including a dielectric layer and an inner electrode layer; and an external electrode disposed on an outer surface of the capacitor body. The dielectric layer includes a plurality of dielectric grains, at least one of the plurality of dielectric grains having a core-shell structure including a core portion and a shell portion surrounding at least a portion of the core portion. The dielectric grains having the core-shell structure include barium (Ba), titanium (Ti), and a rare earth element including lanthanum (La). In a measurement region extending from an interface between the core portion and the shell portion to a depth of about 5 nm from into the shell portion, an absolute value of a concentration gradient of lanthanum (La) is about 0.12 to 0.58 mole parts per nanometer based on 100 mole parts of titanium (Ti).

Description

Technical Field

[0001] This disclosure relates to a multilayer ceramic capacitor. Background Technology

[0002] Ceramic electronic components that utilize ceramic materials include capacitors, inductors, piezoelectric elements, varistors, and thermistors. Among ceramic electronic components, multilayer ceramic capacitors (MLCCs) are used in various electronic devices due to their advantages such as small size, high capacitance, and ease of installation.

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

[0004] Recently, a technique has been proposed to reduce the thickness of the dielectric layer and the inner electrode layer to achieve ultra-high capacitance in ultra-miniature multilayer ceramic capacitors. Furthermore, design research is underway to achieve uniform resistance distribution by controlling the grain size and distribution within the dielectric layer. Summary of the Invention

[0005] The embodiment provides a multilayer ceramic capacitor with excellent DC bias characteristics.

[0006] An embodiment provides a multilayer ceramic capacitor, the multilayer ceramic capacitor comprising: a capacitor body including a dielectric layer and an inner electrode layer; and an outer electrode disposed on the outer surface of the capacitor body, wherein the dielectric layer includes a plurality of dielectric grains, at least one of the plurality of dielectric grains having a core-shell structure, the core-shell structure including a core and a shell surrounding at least a portion of the core, the dielectric grain having the core-shell structure including barium (Ba), titanium (Ti) and a rare earth element including lanthanum (La), and in a measurement region from the interface between the core and the shell to a depth of about 5 nm from the interface toward the shell, when measured from the interface toward the shell, the absolute value of the concentration gradient of lanthanum (La) based on 100 moles of titanium (Ti) is about 0.12 moles / nm to about 0.58 moles / nm.

[0007] In TEM-EDS (Transmission Electron Microscopy-Energy Dispersive Spectroscopy) line analysis of the long axis straight segment passing through the center of the dielectric grain having the core-shell structure, the core can be a region based on 100 moles of titanium (Ti) and less than 0.8 moles of lanthanum (La), and the shell can be a region based on 100 moles of titanium (Ti) and greater than or equal to 0.8 moles of lanthanum (La).

[0008] The molar content of lanthanum (La) in the shell may be higher than the molar content of lanthanum (La) in the core.

[0009] In the shell, based on 100 molar parts of titanium (Ti), the content of lanthanum (La) may be greater than or equal to 0.8 molar parts and less than or equal to about 2.0 molar parts.

[0010] The rare earth elements may also include at least one auxiliary element 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 rare earth elements may also include auxiliary elements containing yttrium (Y), terbium (Tb), and dysprosium (Dy).

[0012] The capacitor body may include an effective region in which the dielectric layer and the inner electrode layer are alternately arranged in the stacking direction, and in the central region of the effective region, the average size of the dielectric grains having the core-shell structure is greater than or equal to about 10 nm and less than about 130 nm. The central region is a region in which the horizontal length from the center of the effective region along a direction perpendicular to the stacking direction to the two vertical edges of the central region corresponds to about 1 / 6 of the total horizontal length of the effective region, and the vertical length from the center of the effective region along the stacking direction to the two horizontal edges of the central region corresponds to about 1 / 6 of the total vertical length of the effective region.

[0013] In the central region, the average size of the core may be about 35% to about 67.3% of the average size of the dielectric grain having the core-shell structure.

[0014] Another embodiment provides a multilayer ceramic capacitor, the multilayer ceramic capacitor comprising: a capacitor body including a dielectric layer and an inner electrode layer; and an outer electrode disposed on the outer surface of the capacitor body, wherein the dielectric layer includes a plurality of dielectric grains, at least one of the plurality of dielectric grains having a core-shell structure, the core-shell structure including a core and a shell surrounding at least a portion of the core, the dielectric grain having the core-shell structure including barium (Ba), titanium (Ti) and rare earth elements, and the rare earth elements including lanthanum (La); and selected The rare earth element has at least one auxiliary element 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), and in a measurement region extending from the interface between the core and the shell to a depth of approximately 5 nm from the interface toward the shell, when measured from the interface toward the shell, the absolute value of the total concentration gradient of the rare earth element is approximately 0.12 mol / nm to approximately 0.58 mol / nm based on 100 mol parts of titanium (Ti).

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

[0016] In the shell, based on 100 moles of titanium (Ti), the total content of the rare earth elements may be greater than or equal to about 1.2 moles and less than or equal to about 5.5 moles.

[0017] In the dielectric grain having the core-shell structure, the rare earth elements may include La, Y, Tb, and Dy.

[0018] The total molar content of La, Y, Tb and Dy in the shell may be higher than the total molar content of La, Y, Tb and Dy in the core.

[0019] In the shell, based on 100 molar parts of titanium (Ti), the total content of La, Y, Tb and Dy may be greater than or equal to about 1.2 molar parts and less than or equal to about 5.5 molar parts.

[0020] The multilayer ceramic capacitor according to the embodiment can have excellent DC bias characteristics. Attached Figure Description

[0021] Figure 1 This is a perspective view showing a multilayer ceramic capacitor according to an embodiment.

[0022] Figure 2 It is along Figure 1 A cross-sectional view of a multilayer ceramic capacitor taken by line I-I'.

[0023] Figure 3 It is along Figure 1 A cross-sectional view of a multilayer ceramic capacitor taken from line II-II'.

[0024] Figure 4 By splitting Figure 1 The capacitor body is shown in an exploded perspective view of the stacked structure.

[0025] Figure 5 This is a schematic diagram illustrating the dielectric layer according to an embodiment.

[0026] Figure 6 This is a schematic diagram showing the dielectric grains according to an embodiment.

[0027] Figure 7 yes Figure 2 An enlarged view of region A in the image.

[0028] Figure 8A and Figure 8B The image is based on the TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) mapping analysis of the dielectric layer in Example 1.

[0029] Figure 9A and Figure 9B The image is based on the TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis image of the dielectric layer in Example 1.

[0030] Figure 9C This is a graph showing the content of lanthanum (La) in TEM-EDS line analysis.

[0031] Figure 10A and Figure 10B The image is based on the TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis image of the dielectric layer in Example 1.

[0032] Figure 10C This is a graph showing the total content of rare earth elements in TEM-EDS line analysis.

[0033] Figure 11 This is a graph showing the average size of the dielectric grains according to Example 1 and Comparative Example 2. Detailed Implementation

[0034] The present disclosure will now be described in detail with reference to the accompanying drawings, in which embodiments of the disclosure are illustrated. The drawings and description are to be considered illustrative rather than restrictive in nature. Throughout the specification, the same reference numerals denote the same elements. In the drawings, some components are exaggerated, omitted, or shown schematically, and the dimensions of each component do not perfectly reflect their actual dimensions.

[0035] The accompanying drawings are intended only to facilitate understanding of the embodiments disclosed in this specification, and it should be understood that the technical concepts disclosed herein are not limited to the drawings, and all variations, equivalents or alternatives within the scope of the technical concepts disclosed herein are included within the scope of this disclosure.

[0036] Although terms such as "first," "second," etc., are used to describe various components, the components are not limited by these terms. These terms are only used to distinguish one component from another.

[0037] Furthermore, it should be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it may be directly on the other element, or there may be an intermediate element present. In contrast, when an element is referred to as being "directly on" another element, there is no intermediate element present. Additionally, when an element is referred to as being "on" or "above" a reference element, it may be located "above" or "below" the reference element, and it is not necessarily located "above" or "above" in a direction opposite to the direction of gravity.

[0038] Throughout this specification, the terms “comprising” or “having” are intended to specify the presence of the said features, quantities, steps, operations, components, parts, or combinations thereof, but do not exclude the presence or addition of one or more other features, quantities, steps, operations, components, parts, and / or combinations thereof. Therefore, unless explicitly stated otherwise, the words “comprising” and variations such as “including” or “having” will be understood to imply the inclusion of the said elements but not the exclusion of any other elements.

[0039] Furthermore, throughout the specification, the phrase "in plan view" or "on a plane" indicates the target portion as viewed from the top, and the phrase "in section view" or "on a section" indicates the section formed by vertically cutting the target portion as viewed from the side.

[0040] Throughout the specification, the term "connection" may mean not only that two or more constituent components are directly connected, but also that two or more constituent components are indirectly connected through another constituent component, that two or more constituent components are electrically connected and physically connected, or that two or more constituent components are referred to by different names according to their location and / or function, but are integrated with each other.

[0041] In the following text, reference will be made to Figures 1 to 4 A multilayer ceramic capacitor according to an embodiment is described.

[0042] Figure 1 This is a perspective view showing a multilayer ceramic capacitor according to an embodiment. Figure 2 It is along Figure 1 A cross-sectional view of a multilayer ceramic capacitor taken by line I-I'. Figure 3 It is along Figure 1A cross-sectional view of a multilayer ceramic capacitor taken from line II-II', and Figure 4 By splitting Figure 1 The capacitor body is shown in an exploded perspective view of the stacked structure.

[0043] Figures 1 to 4 The L-axis, W-axis, and T-axis shown represent the length, width, and thickness directions of the capacitor body 110, respectively. Here, the thickness direction (T-axis direction) can be perpendicular to the wide surface (main surface) of the sheet assembly, and can be used, for example, as the same concept as the stacking direction of the stacked dielectric layers 111. The length direction (L-axis direction) can be a direction extending parallel to the wide surface (main surface) of the sheet assembly, and can be substantially perpendicular to the thickness direction (T-axis direction). For example, the length direction (L-axis direction) can be the direction in which the first external electrode 131 and the second external electrode 132 are opposite each other. The width direction (W-axis direction) can be a direction extending parallel to the wide surface (main surface) of the sheet assembly, and can be substantially perpendicular to both the thickness direction (T-axis direction) and the length direction (L-axis direction). The length of the sheet assembly in the length direction (L-axis direction) can be longer than its length in the width direction (W-axis direction).

[0044] Reference Figures 1 to 4 According to an embodiment, the multilayer ceramic capacitor 100 includes a capacitor body 110 and external electrodes 131 and 132 disposed on the outer surface of 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 opposite ends of the capacitor body 110 in the longitudinal direction (L-axis direction).

[0045] For example, the capacitor body 110 may have a generally hexahedral shape.

[0046] For ease of description of the embodiments, the two surfaces of the capacitor body 110 that are opposite to each other in the thickness direction (T-axis direction) are referred to as the first surface and the second surface, the two surfaces of the capacitor body 110 that are connected to the first surface and the second surface and are opposite to each other in the length direction (L-axis direction) are referred to as the third surface and the fourth surface, and the two surfaces of the capacitor body 110 that are connected to the first surface and the second surface, connected to the third surface and the fourth surface, and are opposite to each other in the width direction (W-axis direction) are referred to as the fifth surface and the sixth surface.

[0047] As an example, the first surface, which serves as the lower surface, can be a mounting surface. Furthermore, the first to sixth surfaces can be flat, but the embodiments are not limited to this. For example, the first to sixth surfaces can be curved surfaces with a convex central portion, and the edges of each surface (the boundaries between the surfaces) can be rounded.

[0048] The shape and size of the capacitor body 110 and the number of stacked dielectric layers 111 are not limited to the shape and size of the capacitor body and the number of stacked dielectric layers shown in the accompanying drawings of the embodiment.

[0049] The capacitor body 110 includes a plurality of dielectric layers 111 and a plurality of internal electrode layers 121 and 122. Specifically, the capacitor body 110 includes a plurality of dielectric layers 111, a plurality of first internal electrode layers 121 and a plurality of second internal electrode layers 122, wherein the first internal electrode layers 121 and the second internal electrode layers 122 are alternately arranged in the thickness direction (T-axis direction) and the dielectric layer 111 is located between the first internal electrode layers 121 and the second internal electrode layers 122.

[0050] At this point, the dielectric layer 111 of the capacitor body 110 can be integrated to such an extent that the boundaries between adjacent dielectric layers 111 are difficult to distinguish without the use of a scanning electron microscope (SEM).

[0051] The capacitor body 110 may include an effective area A and coverage areas 112 and 113.

[0052] The effective region A is the area where dielectric layer 111 and inner electrode layers 121 and 122 are stacked alternately, which contributes to the capacitance of the multilayer ceramic capacitor 100. Specifically, the effective region A may be the area where the first inner electrode layer 121 and the second inner electrode layer 122 are stacked along the thickness direction (T-axis direction).

[0053] Cover regions 112 and 113 are thickness-direction edges and can be positioned on the upper and lower surfaces of the effective region A in the thickness direction (T-axis direction), respectively. Cover regions 112 and 113 can be a single dielectric layer or two or more dielectric layers stacked on the upper and lower surfaces of the effective region A, respectively.

[0054] In addition, the capacitor body 110 may also include a side edge region.

[0055] The side edge region may be located on the opposite side surfaces (i.e., the side surfaces corresponding to the fifth and sixth surfaces) of the effective region A in the width direction (W-axis direction). The side edge region may be formed by stacking dielectric green sheets and then firing the dielectric green sheets, wherein the dielectric green sheets are coated with conductive paste only in a portion of the surface of the dielectric green sheets and are not coated with conductive paste in the two side regions of the surface of the dielectric green sheets, but the formation method is not limited to this.

[0056] Coverage areas 112 and 113, as well as side edge areas, are used to prevent damage to the first inner electrode layer 121 and the second inner electrode layer 122 due to physical stress and / or chemical stress.

[0057] dielectric layer Reference Figures 5 to 7 Describes dielectric layer 111 according to an embodiment.

[0058] Figure 5 This is a schematic diagram illustrating the dielectric layer according to an embodiment.

[0059] Reference Figure 5 According to an embodiment, the dielectric layer 111 includes a plurality of dielectric grains 10, and at least one of the plurality of dielectric grains 10 has a core-shell structure, the core-shell structure including a core portion 12 and a shell portion 14 surrounding at least a portion of the core portion 12.

[0060] The dielectric grains 10 with a core-shell structure include barium (Ba), titanium (Ti), and rare earth elements, among which lanthanum (La) is included.

[0061] Specifically, barium (Ba) and titanium (Ti) may be derived from barium titanate-based compounds used as dielectric matrix materials and may be primarily included in the core portion 12 of the dielectric grain 10. Rare earth elements, including lanthanum (La), may be derived from additives added to the dielectric matrix material and may be primarily included in the shell portion 14 of the dielectric grain 10.

[0062] Barium titanate-based compounds have high dielectric constants and contribute to the capacitance of the multilayer ceramic capacitor 100.

[0063] For example, barium titanate-based compounds may include at least one selected from BaTiO3, Ba(Ti, Zr)O3, Ba(Ti, Sn)O3, (Ba, Ca)TiO3, (Ba, Ca)(Ti, Ca)O3, (Ba, Ca)(Ti, Zr)O3, (Ba, Ca)(Ti, Sn)O3, (Ba, Sr)TiO3, (Ba, Sr)(Ti, Zr)O3, and (Ba, Sr)(Ti, Sn)O3.

[0064] The dielectric properties of dielectric materials can be explained primarily through four polarization mechanisms. These mechanisms include: ionic polarization, which occurs when the equilibrium positions of electrons change under the influence of an electric field applied to ionicly bonded materials fixed in a crystal lattice; electronic polarization, which occurs due to charge asymmetry caused by the movement of atomic nuclei; dipole polarization, which occurs from materials with self-polarization; and space charge polarization, which occurs when charge carriers within the material move under an applied electric field.

[0065] According to an embodiment, when the dielectric grains 10 with a core-shell structure within the dielectric layer 111 include lanthanum (La), ionic polarization can occur, resulting in a high permittivity. That is, when lanthanum (La) replaces the barium (Ba) sites in the dielectric matrix material and changes from a tetragonal structure to a cubic structure, the temperature at which the resistance decreases (i.e., the Curie temperature) decreases, thereby achieving a high dielectric constant at room temperature.

[0066] Figure 6 This is a schematic diagram showing the dielectric grains according to an embodiment.

[0067] Reference Figure 6 In the dielectric grain 10 with a core-shell structure, in a measurement region X extending from the interface between the core 12 and the shell 14 to a depth of approximately 5 nm from the interface toward the shell 14, when measurements are taken from this interface toward the shell 14, the absolute value of the lanthanum (La) concentration gradient is approximately 0.12 mol / nm to approximately 0.58 mol / nm (based on 100 mol of titanium (Ti)), for example, approximately 0.12 mol / nm to approximately 0.55 mol / nm or approximately 0.12 mol / nm to approximately 0.50 mol / nm. When the absolute value of the La concentration gradient in the aforementioned measurement region X is within the above range, not only does the multilayer ceramic capacitor exhibit a high dielectric constant, but the structural fraction of the core and shell (the respective volume percentages of the core and shell) is also improved, thereby improving the DC bias characteristics of the multilayer ceramic capacitor. In other words, the DC bias characteristics of multilayer ceramic capacitors may deteriorate when the absolute value of the concentration gradient of Ti and La based on 100 moles is less than about 0.12 moles / nm and greater than about 0.58 moles / nm.

[0068] In addition to lanthanum (La), the rare earth elements according to the embodiments may also 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). For example, the rare earth elements may include lanthanum (La), yttrium (Y), terbium (Tb), and dysprosium (Dy).

[0069] When the rare earth elements include La and auxiliary elements, when the measurement is performed in the measurement region X from the interface between the core 12 and the shell 14 toward the shell 14, the absolute value of the total concentration gradient of the rare earth elements is about 0.12 mol / nm to about 0.58 mol / nm (based on 100 mol of titanium (Ti)), for example, about 0.12 mol / nm to about 0.55 mol / nm or about 0.12 mol / nm to about 0.50 mol / nm. Here, the total concentration of rare earth elements represents the sum of the contents of La and auxiliary elements, and can be, for example, the sum of the contents of La, Y, Tb and Dy. When the absolute value of the total concentration gradient of rare earth elements in the measurement region X is within the above range, not only does the multilayer ceramic capacitor have a high dielectric constant, but the structural fraction of the core and shell is also improved, thereby improving the DC bias characteristics of the multilayer ceramic capacitor. In other words, when the absolute value of the total concentration gradient of rare earth elements based on 100 moles of Ti is less than about 0.12 moles / nm and greater than about 0.58 moles / nm, the DC bias characteristics of multilayer ceramic capacitors may deteriorate.

[0070] In the measurement region X for the absolute values ​​of the La concentration gradient and the total rare earth element concentration gradient, when performing TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis along a straight line segment passing through the long axis of the center α of the core-shell dielectric grain 10, the interface between the core 12 and the shell 14 can be the point where La is 0.8 moles (based on 100 moles of Ti). That is, the measurement region X for the absolute values ​​of the La concentration gradient can be the area from the point where La is 0.8 moles (based on 100 moles of Ti) to a depth of approximately 5 nm from that point toward the shell 14.

[0071] The absolute values ​​of the concentration gradient of La and the absolute values ​​of the total concentration gradient of rare earth elements (i.e., rare earth elements including La and auxiliary elements) can be measured by TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis.

[0072] Specifically, a multilayer ceramic capacitor 100 is immersed in an epoxy resin mixture and cured. Then, the L-axis and T-axis surfaces (LT surfaces) of the capacitor body 110 are polished to a depth of half the W-axis, obtaining a cross-sectional sample of the effective region A where the dielectric layer 111 and the inner electrode layers 121 and 122 are visible. For example, the effective region A is divided into three parts (upper part, central part, and lower part) along the T-axis (i.e., the stacking direction) to obtain a cross-sectional sample where at least one dielectric layer and at least one inner electrode layer are visible in each part. The obtained cross-sectional sample is then measured using a transmission electron microscope (TEM). For example, TEM can be performed using a focused ion beam (FIB) at an accelerating voltage of 200 kV and a magnification of 225 k. The TEM images of the obtained cross-sectional sample are subjected to EDS (energy-dispersive spectroscopy) analysis to confirm the presence of core-shell structured dielectric grains 10 within the dielectric layer 111.

[0073] Furthermore, by performing EDS (energy-dispersive spectroscopy) line analysis on the straight line segment passing through the long axis of the center α of the core-shell structured dielectric grain 10 in the TEM image, the absolute values ​​of the La concentration gradient and the total rare earth element concentration gradient in the measurement region X can be measured separately. For example, by selecting two dielectric layers 111 from each of the upper, central, and lower portions within the effective region A, and randomly selecting five core-shell structured dielectric grains 10 from each dielectric layer 111, the average absolute values ​​of the La concentration gradient and the average absolute values ​​of the total rare earth element concentration gradient in the measurement region X can be obtained for a total of 30 core-shell structured dielectric grains. In this case, the measurement region X can be a region extending from the interface between the core 12 and the shell 14 to a depth of 5 nm from the interface toward the shell 14, and measurements are performed in the measurement region X from the interface toward the shell 14. Furthermore, the absolute value of the La concentration gradient can be measured as the absolute value of the change in La content along a straight line passing through two points: point P1 at the interface between the core 12 and the shell 14; and point P2 at a depth of 5 nm from the interface toward the shell 14. Similarly, the absolute value of the total rare earth element concentration gradient can be measured as the absolute value of the change in the total rare earth element content along a straight line passing through points P1 and P2. Moreover, in the dielectric grain 10 with the core-shell structure, point P2 at a depth of approximately 5 nm within the shell 14 is the measurement target for the dielectric grain 10.

[0074] For example, when performing TEM-EDS (Transmission Electron Microscopy-Energy Dispersive Spectroscopy) line analysis on a straight line segment passing through the center α of the dielectric grain 10 with a core-shell structure, the interface between the core 12 and the shell 14 can be a point where La is 0.8 moles (based on 100 moles of Ti). That is, the core 12 and the shell 14 can be distinguished based on the point where La is 0.8 moles (based on 100 moles of Ti). For example, the core 12 can be a region where La is less than 0.8 moles based on 100 moles of Ti, and the shell 14 can be a region where La is greater than or equal to 0.8 moles based on 100 moles of Ti.

[0075] For example, in TEM-EDS line analysis, the molar content of La in the shell 14 can be higher than that in the core 12. For instance, the La content in the shell 14 can be greater than or equal to 0.8 moles and less than or equal to about 2.0 moles (based on 100 moles of Ti), for example, about 1.0 moles to about 2.0 moles. When the La content in the shell is within the above range, not only does the multilayer ceramic capacitor exhibit a high dielectric constant, but the structural fraction of the core and shell is also improved, thereby improving the DC bias characteristics of the multilayer ceramic capacitor.

[0076] Furthermore, during TEM-EDS line analysis, the total molar content of rare earth elements in the shell 14 can be higher than that in the core 12. For example, the total content of rare earth elements in the shell 14 can be greater than or equal to about 1.2 molar parts and less than or equal to about 5.5 molar parts (based on 100 molar parts of Ti), for example, about 1.3 molar parts to about 5.0 molar parts.

[0077] For example, the total molar content of La, Y, Tb, and Dy in the shell 14 may be higher than the total molar content of La, Y, Tb, and Dy in the core 12. For example, the total content of La, Y, Tb, and Dy in the shell 14 may be greater than or equal to about 1.2 molar parts and less than or equal to about 5.5 molar parts (based on 100 molar parts of Ti), for example, about 1.3 molar parts to about 5.0 molar parts.

[0078] When the total content of rare earth elements in the shell (e.g., the total content of La, Y, Tb and Dy) is within the above range, not only does the multilayer ceramic capacitor have a high dielectric constant, but the structural fraction of the core and shell is also improved, thereby improving the DC bias characteristics of the multilayer ceramic capacitor.

[0079] The total content of rare earth elements in shell 14 can be the average value of the total content of rare earth elements in shell 14.

[0080] For example, by selecting two dielectric layers 111 in each of the upper, central, and lower portions within the effective region A, and randomly selecting five dielectric grains 10 with a core-shell structure from each dielectric layer 111, the average total content of rare earth elements in the shell portion 14 can be obtained for a total of 30 dielectric grains with a core-shell structure. In this case, the total content of rare earth elements in the shell portion 14 of a single dielectric grain 10 can be obtained, for example, as the average total content of rare earth elements at five equally spaced points within the shell portion 14.

[0081] The content of La in shell 14 can also be the average value of the content obtained using the same method.

[0082] The absolute values ​​of the La concentration gradient and the absolute values ​​of the total rare earth element concentration gradient can be obtained by controlling various process conditions (such as controlling the amount of rare earth elements, including La, added when preparing the dielectric paste, or controlling the firing conditions (such as firing temperature)).

[0083] According to the embodiment, when the absolute value of the concentration gradient of La is within the above-mentioned range, the dielectric grain 10 with a core-shell structure in the central region of the effective region A can have a small average size. This can be specifically described with reference to FIG8.

[0084] Figure 7 yes Figure 2 An enlarged view of region A in the image.

[0085] Reference Figure 7 The average size of the core-shell structured dielectric grains 10 in the central region R within the effective region A can be greater than or equal to about 10 nm and less than about 130 nm, for example, about 20 nm to about 129 nm, about 30 nm to about 128 nm, or about 40 nm to about 127 nm. In this case, the central region R can be a region where the horizontal length from the center Cp of the effective region A along a direction perpendicular to the stacking direction to the two vertical edges of the central region R corresponds to about 1 / 6 of the total horizontal length l of the effective region A, and the vertical length from the center Cp of the effective region A along the stacking direction to the two horizontal edges of the central region R corresponds to about 1 / 6 of the total vertical length t of the effective region A. When the average size of the core-shell structured dielectric grains 10 is within the above range, not only does the multilayer ceramic capacitor have a high dielectric constant, but the structural fraction of the core and shell is also improved, thereby improving the DC bias characteristics of the multilayer ceramic capacitor.

[0086] Furthermore, in the central region R, the average size of the core 12 can be approximately 35% to approximately 67.3% of the average size of the dielectric grains 10, for example, approximately 36% to approximately 67.3% or approximately 37% to approximately 67.3% of the average size of the dielectric grains 10. When the average size of the core 12 is within the above range, not only does the multilayer ceramic capacitor have a high dielectric constant, but the structural fraction of the core and the shell can also be improved, thereby improving the DC bias characteristics of the multilayer ceramic capacitor.

[0087] The average size of the dielectric grain 10 and the average size of the core 12 can be measured by the following methods.

[0088] A multilayer ceramic capacitor 100 is immersed in an epoxy resin mixture and cured. Then, the L-axis and T-axis surfaces (LT surfaces) of the capacitor body 110 are polished to a depth of half the W-axis, obtaining a cross-sectional sample in which the effective region A, where the dielectric layer 111 and the inner electrode layers 121 and 122 are stacked, is observable. For example, the effective region A is divided into three parts (upper part, central part, and lower part) in the T-axis direction (i.e., the stacking direction) to obtain a cross-sectional sample in which at least one dielectric layer and at least one inner electrode layer are visible in the central part. Next, the central region R within the central portion of the obtained cross-sectional sample is measured using transmission electron microscopy (TEM). Specifically, the central region R is defined as follows: the horizontal length from the center Cp of the effective region A along a direction perpendicular to the stacking direction to the two vertical edges of the central region R corresponds to approximately 1 / 6 of the total horizontal length l of the effective region A; and the vertical length from the center Cp of the effective region A along the stacking direction to the two horizontal edges of the central region R corresponds to approximately 1 / 6 of the total vertical length t of the effective region A. For example, TEM can be performed using a focused ion beam (FIB) at an accelerating voltage of 200 kV and a magnification of 225 k. By performing EDS (energy-dispersive spectroscopy) analysis on the TEM image of the obtained cross-sectional sample, the presence of dielectric grains 10 with a core-shell structure within the central region R of the effective region A can be confirmed. The average size of the dielectric grains 10 and the average size of the core 12 can then be measured.

[0089] Here, the average size of the dielectric grain 10 can be calculated as the average size of at least two (e.g., five) dielectric grains 10 present in the central region R, and the average size of the core 12 can be calculated as the average size of the core 12 within, for example, the five identical dielectric grains 10.

[0090] At this time, as Figure 6As shown, the size of the dielectric grain 10 can be obtained as the average of the length of the major axis with the largest diameter and the length of the minor axis with the smallest diameter passing through the center α of the dielectric grain 10. Furthermore, the average size of the core 12 can be obtained as the average of the size of the core 12 obtained along the length of the major axis with the largest diameter passing through the center α of the dielectric grain 10 and the size of the core 12 obtained along the length of the minor axis with the smallest diameter passing through the center α of the dielectric grain 10.

[0091] The average thickness (average length in the T-axis direction) of the dielectric layer 111 can be from about 0.1 μm to about 8 μm, and for example, from about 0.1 μm to about 6.0 μm. When the average thickness of the dielectric layer 111 is within the above range, the reliability of the multilayer ceramic capacitor can be improved.

[0092] The average thickness of dielectric layer 111 can be measured by immersing the multilayer ceramic capacitor 100 in an epoxy resin mixture, curing it, polishing it, then ion-milling it, and then analyzing it using a scanning electron microscope (SEM). The SEM can be performed under conditions such as an accelerating voltage of 10 kV and a magnification of 100x, and can be measured such that at least one, three, five, or ten layers of dielectric layer 111 are visible in the effective region where dielectric layer 111 is stacked with inner electrode layers 121 and 122. In the SEM image, the average thickness of the dielectric layer can be obtained by taking the center point of the dielectric layer 111 along its length (L-axis direction) or width (W-axis direction) as a reference point, and taking the average thickness of the dielectric layer 111 at 10 points spaced at predetermined intervals from the reference point. The spacing between the 10 points can be adjusted according to the scale of the SEM image, and can be, for example, approximately 1 μm to approximately 100 μm, approximately 1 μm to approximately 50 μm, or approximately 1 μm to approximately 10 μm. In this case, all 10 points must be located within the dielectric layer 111, and if all 10 points are not located within the dielectric layer 111, the position of the reference point can be changed, or the spacing between the 10 points can be adjusted. Here, the spacing can refer to the spacing between two adjacent points. Furthermore, by extending this average measurement to 10 dielectric layers, the average thickness of the dielectric layer can be more generalized.

[0093] Inner electrode layer The inner electrode layers 121 and 122 (i.e., the first inner electrode layer 121 and the second inner electrode layer 122) are electrodes with different polarities and are alternately arranged to face each other along the T-axis direction. The dielectric layer 111 is located between the inner electrode layers 121 and 122, and one end of the first inner electrode layer 121 and one end of the second inner electrode layer 122 can be exposed through the third surface and the fourth surface of the capacitor body 110, respectively.

[0094] The first inner electrode layer 121 and the second inner electrode layer 122 are electrically insulated from each other by a dielectric layer 111 disposed therebetween.

[0095] The ends of the first inner electrode layer 121 and the second inner electrode layer 122, which are alternately exposed through the third and fourth surfaces of the capacitor body 110, can be electrically connected to the first outer electrode 131 and the second outer electrode 132, respectively.

[0096] The inner electrode layers 121 and 122 comprise conductive metals and may include at least one metal selected from Ni, Cu, Ag, Pd, Au, and alloys thereof.

[0097] In addition, inner electrode layers 121 and 122 may include dielectric particles having the same composition as the ceramic material included in dielectric layer 111.

[0098] The inner electrode layers 121 and 122 can be formed using a conductive paste comprising a conductive metal. The printing method for the conductive paste can be screen printing or gravure printing.

[0099] The average thickness of each of the first inner electrode layer 121 and the second inner electrode layer 122 may be from about 0.1 μm to about 2 μm.

[0100] The average thickness of the first inner electrode layer 121 and the second inner electrode layer 122 can be measured by scanning electron microscopy (SEM) analysis. Specifically, in an SEM image of a cross-sectional sample obtained by the same method used to measure the average thickness of the dielectric layer 111, the average thickness of the inner electrode layers can be obtained by taking the center point of each of the inner electrode layers 121 and 122 in the length direction (L-axis direction) or width direction (W-axis direction) as a reference point, and taking the average thickness of each of the inner electrode layers 121 and 122 at 10 points spaced at predetermined intervals from the reference point. The interval of the 10 points can be adjusted according to the scale of the SEM image, and can be, for example, about 1 μm to about 100 μm, about 1 μm to about 50 μm, or about 1 μm to about 10 μm. At this point, all 10 points must be located within each of the inner electrode layers 121 and 122. If not all 10 points are located within each of the inner electrode layers 121 and 122, the position of the reference point can be changed, or the spacing between the 10 points can be adjusted. Here, the spacing can refer to the spacing between two adjacent points. Furthermore, by extending this average measurement to all 10 inner electrode layers, the average thickness of the inner electrode layers can be more generalized.

[0101] The capacitor body 110 can be formed by firing a stacked structure in which multiple dielectric layers 111 and multiple internal electrode layers 121 and 122 are stacked.

[0102] external electrode The external electrodes 131 and 132 (i.e., the first external electrode 131 and the second external electrode 132) are provided with voltages of different polarities and can be electrically connected to the exposed portions of the first inner electrode layer 121 and the second inner electrode layer 122, respectively.

[0103] According to the above structure, when a predetermined voltage is applied to the first external electrode 131 and the second external electrode 132, charge accumulates between the first inner electrode layer 121 and the second inner electrode layer 122 facing each other. At this time, the capacitance of the multilayer ceramic capacitor 100 is proportional to the stacked area of ​​the first inner electrode layer 121 and the second inner electrode layer 122 stacked together along the T-axis in the effective region.

[0104] The first external electrode 131 may include a first connecting portion and a first strip portion. The first connecting portion is disposed on the third surface of the capacitor body 110 and connected to the first inner electrode layer 121. The first strip portion is disposed on the edge where the third surface of the capacitor body 110 intersects with the first surface and the second surface and / or the fifth surface and the sixth surface. The second external electrode 132 may include a second connecting portion and a second strip portion. The second connecting portion is disposed on the fourth surface of the capacitor body 110 and connected to the second inner electrode layer 122. The second strip portion is disposed on the edge where the fourth surface of the capacitor body 110 intersects with the first surface and the second surface and / or the fifth surface and the sixth surface.

[0105] The first strip may extend from the first connecting portion to a portion of the first surface, a portion of the second surface, and / or a portion of the fifth surface and a portion of the sixth surface of the capacitor body 110. The second strip may extend from the second connecting portion to a portion of the first surface, a portion of the second surface, and / or a portion of the fifth surface and a portion of the sixth surface of the capacitor body 110. The first strip and the second strip can be used to improve the bonding strength between the first external electrode 131 and the second external electrode 132 and the capacitor body 110.

[0106] The external electrodes 131 and 132 may include a sintered metal layer in contact with the capacitor body 110, a conductive resin layer configured to cover the sintered metal layer, and a plating layer configured to cover the conductive resin layer.

[0107] The sintered metal layer may include conductive metals and glass.

[0108] The conductive metal may include one or more selected from copper (Cu), nickel (Ni), silver (Ag), palladium (Pd), gold (Au), platinum (Pt), tin (Sn), tungsten (W), titanium (Ti), lead (Pb), and alloys thereof, and for example, when the conductive metal includes copper (Cu), it may mean that the conductive metal may include copper (Cu) metal or copper (Cu) alloys. When the conductive metal includes copper (Cu), based on 100 molar parts of copper (Cu), metals other than copper (Cu) may be included in an amount of less than or equal to about 5 molar parts.

[0109] The glass may comprise a composition of oxides (e.g., one or more selected from the group consisting of silicon oxides, boron oxides, aluminum oxides, transition metal oxides, alkali metal oxides, and alkaline earth metal oxides). The transition metal may be at least one selected from the group consisting of zinc (Zn), titanium (Ti), copper (Cu), vanadium (V), manganese (Mn), iron (Fe), and nickel (Ni); the alkali metal may be at least one selected from the group consisting of lithium (Li), sodium (Na), and potassium (K); and the alkaline earth metal may be at least one selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

[0110] Alternatively, the conductive resin layer may be formed on the sintered metal layer, and for example, may be formed in a shape that completely covers the sintered metal layer. Additionally, the external electrodes 131 and 132 may not include the sintered metal layer, and in this case, the conductive resin layer may directly contact the capacitor body 110.

[0111] The conductive resin layer extends to the first and second surfaces and / or the fifth and sixth surfaces of the capacitor body 110, and the length of the region (i.e., the strip portion) where the conductive resin layer extends and is disposed on the first and second surfaces and / or the fifth and sixth surfaces of the capacitor body 110 may be longer than the length of the region (i.e., the strip portion) where the sintered metal layer extends and is disposed on the first and second surfaces and / or the fifth and sixth surfaces of the capacitor body 110. In other words, the conductive resin layer may be formed on the sintered metal layer and may be formed in a shape that completely covers the sintered metal layer.

[0112] The conductive resin layer may include resin and conductive metal.

[0113] The resin included in the conductive resin layer can be, but is not limited to, a material that has adhesive and damping properties and can form a paste when mixed with conductive metal powder. For example, the resin may include phenolic resin, acrylic resin, silicone resin, epoxy resin, or polyimide resin.

[0114] The conductive metal included in the conductive resin layer is used to electrically connect the inner electrode layers 121 and 122 or the sintered metal layer to the plating layer.

[0115] The conductive metal included in the conductive resin layer may have a spherical shape, a sheet shape, or a combination thereof. That is, the conductive metal may be formed only in a sheet shape, only in a spherical shape, or in a mixed form of sheet and spherical shapes.

[0116] Here, spherical shape can also include shapes that are not perfect spheres, such as shapes whose length ratio of major axis to minor axis (major axis / minor axis) is less than or equal to about 1.45. Sheet shape refers to a flat and elongated shape, and there are no particular restrictions, such as shapes whose length ratio of major axis to minor axis (major axis / minor axis) is greater than or equal to about 1.95.

[0117] The external electrodes 131 and 132 may also include a plating layer disposed on the outside of the conductive resin layer.

[0118] The coating may include individual nickel (Ni), copper (Cu), tin (Sn), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), tungsten (W), titanium (Ti), or lead (Pb), or alloys thereof. For example, the coating may be a nickel (Ni) coating or a tin (Sn) coating, which may be in the form of nickel (Ni) coatings and tin (Sn) coatings stacked sequentially, or in the form of tin (Sn) coatings, nickel (Ni) coatings, and tin (Sn) coatings stacked sequentially. Furthermore, the coating may include multiple nickel (Ni) coatings and / or multiple tin (Sn) coatings.

[0119] The coating can improve the mountability, structural reliability, external durability, heat resistance and equivalent series resistance (ESR) of the multilayer ceramic capacitor 100 on the substrate.

[0120] Methods for manufacturing multilayer ceramic capacitors Hereinafter, a method for manufacturing a multilayer ceramic capacitor 100 according to an embodiment will be described.

[0121] The multilayer ceramic capacitor 100 according to the embodiment can be manufactured by the following method: preparing a dielectric paste by mixing a barium titanate-based compound and a rare earth element compound including a lanthanum (La) compound; manufacturing a dielectric green sheet using the dielectric paste and forming a conductive paste layer on the surface of the dielectric green sheet; manufacturing a dielectric green sheet stack by stacking a plurality of dielectric green sheets on which the conductive paste layer is formed; manufacturing a capacitor body including a dielectric layer and an inner electrode layer by firing the dielectric green sheet stack; and forming an outer electrode on the surface of the capacitor body.

[0122] The rare earth element-containing compounds may also include one or more compounds containing auxiliary elements selected from scandium (Sc) compounds, yttrium (Y) compounds, neodymium (Nd) compounds, europium (Eu) compounds, gadolinium (Gd) compounds, terbium (Tb) compounds, dysprosium (Dy) compounds, holmium (Ho) compounds, erbium (Er) compounds, ytterbium (Yb) compounds, and lutetium (Lu) compounds. For example, rare earth element-containing compounds may include lanthanum (La) compounds, yttrium (Y) compounds, terbium (Tb) compounds, and dysprosium (Dy) compounds.

[0123] Based on 100 moles of barium titanate-based compound, a lanthanum (La)-containing compound can be mixed in amounts from about 0.1 moles to about 2 moles (e.g., from about 0.3 moles to about 1.8 moles). When the lanthanum (La)-containing compound is mixed within the above-mentioned content range, dielectric grains with improved core and shell structure fractions can be obtained, and multilayer ceramic capacitors with high dielectric constants and excellent DC bias characteristics can be obtained.

[0124] Furthermore, when mixing compounds containing auxiliary elements, based on 100 moles of barium titanate-based compound, the total amount of compounds containing auxiliary elements can be mixed in a total amount greater than or equal to about 1.2 moles and less than or equal to 5.5 moles. When compounds containing auxiliary elements are mixed within the above-mentioned content range, dielectric grains with improved core and shell structure fractions can be obtained, and multilayer ceramic capacitors with high dielectric constants and excellent DC bias characteristics can be obtained.

[0125] Lanthanum (La) compounds and compounds containing auxiliary elements can be in the form of oxides, nitrides, salts, or sols dispersed in organic solvents.

[0126] Dielectric pastes can be prepared by further mixing with additives such as dispersants, binders, plasticizers, lubricants, antistatic agents, and solvents.

[0127] The dispersant may include at least one selected from, for example, phosphate ester dispersants and polycarboxylic acid dispersants. Based on 100 parts by weight of the barium titanate-based compound, the dispersant can be mixed in amounts from about 0.1 parts by weight to about 5 parts by weight (e.g., from about 0.3 parts by weight to about 3 parts by weight). When the dispersant is mixed within the above-mentioned content range, the dielectric paste exhibits excellent dispersibility and reduces the amount of impurities included in the manufactured dielectric layer.

[0128] The binder can be, for example, acrylic resin, polyvinyl butyral resin, polyvinyl acetal resin, ethyl cellulose, etc. Based on 100 parts by weight of barium titanate compound, the binder can be added in amounts from about 0.1 parts by weight to about 50 parts by weight (e.g., from about 3 parts by weight to about 30 parts by weight). When the binder is mixed within the above content range, the dielectric paste exhibits excellent dispersibility and reduces the amount of impurities included in the manufactured dielectric layer.

[0129] Plasticizers may be, for example: phthalic acid compounds, such as dioctyl phthalate, butyl benzyl phthalate, dibutyl phthalate, dihexyl phthalate, di(2-ethylhexyl) phthalate, and di(2-ethylbutyl) phthalate; adipate compounds, such as dihexyl adipate and di(2-ethylhexyl) adipate; glycol compounds, such as ethylene glycol, diethylene glycol, and triethylene glycol; glycol ester compounds, such as triethylene glycol dibutyrate, triethylene glycol di(2-ethylbutyrate), and triethylene glycol di(2-ethylhexanoate); and the like. Based on 100 parts by weight of a barium titanate-based compound, the plasticizer may be added in an amount of about 0.1 parts by weight to about 20 parts by weight (e.g., about 1 part by weight to about 10 parts by weight). When plasticizers are mixed within the above-mentioned content range, the dielectric paste exhibits excellent dispersibility and reduces the amount of impurities included in the manufactured dielectric layer.

[0130] Solvents may be: aqueous solvents, such as water; alcohol solvents, such as ethanol, methanol, benzyl alcohol, and methoxyethanol; glycol solvents, such as ethylene glycol and diethylene glycol; ketone solvents, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents, such as butyl acetate, ethyl acetate, carbitol acetate, and butyl carbitol acetate; ether solvents, such as methyl cellosolve, ethyl cellosolve, butyl ether, and tetrahydrofuran; aromatic solvents, such as benzene, toluene, and xylene, etc. Considering the solubility or dispersibility of various additives included in the dielectric paste, the solvent may be, for example, an alcohol solvent or an aromatic solvent. Based on 100 parts by weight of the barium titanate compound, the solvent can be mixed in amounts from about 50 parts by weight to about 1000 parts by weight (e.g., from about 100 parts by weight to about 500 parts by weight). When the solvent is mixed within the above-mentioned content range, the dielectric paste components can be sufficiently mixed, and subsequent solvent removal is easy.

[0131] The dielectric slurry described above can be mixed using a wet ball mill or a stirred mill. When using zirconia balls in a wet ball mill, multiple zirconia balls with a diameter of about 0.1 mm to about 10 mm can be used for wet mixing for about 8 hours to about 48 hours or about 10 hours to about 24 hours.

[0132] The prepared dielectric paste forms a dielectric layer after firing.

[0133] As a method for forming the prepared dielectric paste into a sheet, a strip forming method such as a doctor blade method or a calendering roll method can be used. For example, a coating head discharge type roller forming coating machine can be used, and the dielectric sheet can then be obtained by drying the formed body.

[0134] To form a conductive paste layer that becomes the inner electrode layer after firing, the conductive paste is prepared by mixing conductive powder made of conductive metals or alloys thereof, a binder, and a solvent. Additionally, barium titanate powder can be mixed in as a co-agent if desired. The co-agent can be used to inhibit the sintering of the conductive powder during the firing process. The conductive paste layer is formed by applying the conductive paste in a predetermined pattern to the surface of the dielectric green sheet using various printing methods (such as screen printing or transfer printing).

[0135] The conductive powder may include nickel (Ni) or nickel (Ni) alloys.

[0136] Next, a dielectric green sheet stack is prepared by stacking multiple dielectric green sheets on which an internal electrode pattern (i.e., a conductive paste layer) is formed, and then pressing the multiple dielectric green sheets in the stacking direction. At this time, dielectric green sheets without an internal electrode pattern can be stacked on top of the stack, such that the dielectric green sheets without an internal electrode pattern are positioned at the top and bottom of the dielectric green sheet stack in the stacking direction.

[0137] Optionally, the step of cutting the manufactured dielectric sheet stack into a predetermined size by cutting or the like can be performed.

[0138] Furthermore, if necessary, the dielectric green sheet stack can be cured and dried to remove plasticizers, etc., and after curing and drying, the dielectric green sheet stack can be tumble polished using a horizontal centrifugal tumbler or similar device. In tumble polishing, the dielectric green sheet stack is placed in a tumbler container containing a dielectric and polishing fluid, and rotational motion or vibration is applied to the tumbler container, thus polishing away unwanted parts (such as burrs generated during cutting). After tumble polishing, the dielectric green sheet stack can be washed with a cleaning solution such as water and dried.

[0139] Subsequently, the capacitor body can be obtained after adhesive removal (calcination) and firing treatment of the dielectric green sheet stack.

[0140] The conditions for adhesive removal can be appropriately adjusted according to the composition of the dielectric layer and / or the inner electrode layer. For example, the heating rate during adhesive removal can be from about 5°C / hour to about 300°C / hour, the holding temperature can be from about 180°C to about 400°C, and the temperature holding time can be from about 0.5 hours to about 24 hours. Adhesive removal can be performed in an air atmosphere or a reducing atmosphere.

[0141] Firing can be carried out at a temperature greater than about 1180°C and less than about 1400°C. Furthermore, firing can be carried out for about 0.5 hours to about 8 hours, for example, about 1 hour to about 3 hours. Additionally, firing can be carried out in a reducing atmosphere, for example, in an atmosphere wetted by a mixture of nitrogen and hydrogen, and for example, under conditions such as a hydrogen concentration less than or equal to about 1.0%. When the inner electrode layer comprises nickel (Ni) or a nickel (Ni) alloy, the oxygen partial pressure in the firing atmosphere can be about 1.0 × 10⁻⁶. -14 MPa to approximately 1.0 × 10 -10 MPa.

[0142] After firing, annealing can be performed as needed. Annealing is a process that re-oxidizes the dielectric layer. If firing is carried out in a reducing atmosphere, annealing can be performed. The annealing conditions can also be adjusted appropriately according to the composition of the dielectric layer. For example, the annealing temperature can be from about 950°C to about 1150°C, the time can be greater than about 0 hours and less than or equal to about 20 hours, and the heating rate can be from about 50°C / hour to about 500°C / hour. The annealing atmosphere can be a wetting nitrogen (N2) atmosphere, and the oxygen partial pressure can be about 1.0 × 10⁻⁶. -9 MPa to approximately 1.0 × 10 -5 MPa.

[0143] In the adhesive removal process, firing process, or annealing process, for example, a wetting agent may be used to wet the nitrogen or mixed gas. In this case, the wetting agent temperature (e.g., water temperature) may be from about 5°C to about 75°C. The adhesive removal process, firing process, and annealing process may be performed sequentially or independently.

[0144] Optionally, the third and fourth surfaces of the prepared capacitor body 110 may be subjected to surface treatments such as sandblasting, laser irradiation, or tumble polishing. By performing this surface treatment, the ends of the first inner electrode layer and the second inner electrode layer can be exposed to the third and fourth surfaces, respectively, thereby improving the electrical connection between the first inner electrode layer and the first outer electrode, as well as between the second inner electrode layer and the second outer electrode, and facilitating the formation of alloy portions.

[0145] Subsequently, an external electrode is formed on the surface of the manufactured capacitor body 110.

[0146] As an example, a paste for forming a sintered metal layer can be applied to the outer surface of the capacitor body 110 and then sintered to form a sintered metal layer.

[0147] The paste used to form the sintered metal layer may include conductive metals and glass. Since the descriptions of conductive metals and glass are the same as described above, repeated descriptions will be omitted. Furthermore, the paste used to form the sintered metal layer may optionally include binders, solvents, dispersants, plasticizers, oxide powders, etc. The binder may be, for example, ethyl cellulose, acrylic resin, butyral resin, etc., and the solvent may be, for example, an organic solvent or an aqueous solvent such as terpineol, butyl carbitol, ethanol, methyl ethyl ketone, acetone, toluene, etc.

[0148] Methods for applying paste for forming a sintered metal layer to the outer surface of the capacitor body 110 may include dipping, various printing methods (such as screen printing), coating using a dispenser, and spraying using a sprayer. The paste for forming the sintered metal layer may be applied to at least the third and fourth surfaces of the capacitor body 110, and optionally to portions of the first, second, fifth, and / or sixth surfaces on which the first and second external electrodes are formed.

[0149] Subsequently, the capacitor body 110 coated with paste for forming a sintered metal layer is dried and sintered at a temperature of about 700°C to about 1000°C for about 0.1 hours to about 3 hours to form a sintered metal layer.

[0150] Optionally, a paste for forming a conductive resin layer is applied to the outer surface of the obtained capacitor body 110 and then cured to form a conductive resin layer.

[0151] The paste used to form the conductive resin layer may include conductive metals and resins, and optionally include non-conductive fillers. Since the descriptions of the conductive metals and resins are the same as described above, repeated descriptions will be omitted. Furthermore, the paste used to form the conductive resin layer may optionally include binders, solvents, dispersants, plasticizers, oxide powders, etc. The binders may be, for example, ethyl cellulose, acrylic resins, butyral resins, etc., and the solvents may be organic solvents or aqueous solvents such as terpineol, butyl carbitol, ethanol, methyl ethyl ketone, acetone, and toluene.

[0152] For example, the conductive resin layer can be formed by immersing the capacitor body 110 in a paste for forming the conductive resin layer and then curing it, or by printing the paste for forming the conductive resin layer onto the surface of the capacitor body 110 by screen printing or gravure printing and then curing it, or by applying the paste for forming the conductive resin layer onto the surface of the capacitor body 110 and then curing it.

[0153] Next, a plating layer is formed on the outer side of the conductive resin layer.

[0154] For example, the coating can be formed by plating (e.g., electroplating (electrodeposition)) or sputtering.

[0155] In the following description, embodiments are illustrated in more detail with reference to examples. However, these examples are exemplary, and the scope of the claims is not limited thereto.

[0156] (Manufacturing of multilayer ceramic capacitors) Examples 1 to 4 Dielectric paste was prepared by mixing barium titanate (BaTiO3), lanthanum nitrate (La(NO3)3), yttrium oxide (Y2O3), terbium oxide (Tb4O7), and dysprosium oxide (Dy2O3). Specifically, La(NO3)3 was mixed in an amount of 0.5 moles based on 100 moles of BaTiO3, and La(NO3)3, Y2O3, Tb4O7, and Dy2O3 were mixed in a total amount of 1.8 moles based on 100 moles of BaTiO3.

[0157] Dielectric paste was prepared by mechanical milling using zirconia balls (ZrO2 balls) after adding ethanol / toluene, a wetting and dispersing agent and polyvinyl butyral (PVB) as a binder.

[0158] Dielectric green sheets are manufactured using the prepared dielectric paste by using a coating head discharge roller forming coating machine.

[0159] A conductive paste layer including nickel (Ni) is printed on the surface of a dielectric green sheet, and dielectric green sheets with the conductive paste layer formed thereon are stacked and pressed to manufacture a dielectric green sheet stack.

[0160] The dielectric green sheet stack is calcined in a nitrogen atmosphere at a temperature of 400°C or lower, and then calcined at a specified temperature and with a hydrogen concentration of 1.0% or lower to obtain the capacitor body. In Examples 1 to 4, the dielectric green sheet stack is calcined at temperatures of 1190°C, 1195°C, 1200°C, and 1205°C, respectively.

[0161] Next, an external electrode is formed on the capacitor body using a process such as plating to obtain a multilayer ceramic capacitor.

[0162] Comparative Example 1 The multilayer ceramic capacitor was manufactured in the same manner as in Example 1, except that La(NO3)3 was mixed with 0.01 moles of BaTiO3 based on 100 moles.

[0163] Comparative Example 2 The multilayer ceramic capacitor was manufactured in the same manner as in Example 2, except that it was mixed with 0.01 moles of La(NO3)3 based on 100 moles of BaTiO3.

[0164] Comparative Example 3 The multilayer ceramic capacitor is manufactured in the same manner as in Example 1, except that it is fired at 1180°C.

[0165] Comparative Example 4 The multilayer ceramic capacitor is manufactured in the same manner as in Example 1, except that it is fired at 1210°C.

[0166] Comparative Example 5 The multilayer ceramic capacitor is manufactured in the same manner as in Example 1, except that it is fired at 1220°C.

[0167] Evaluation 1: TEM-EDS Analysis (1) Identification of the composition of dielectric grains The multilayer ceramic capacitors manufactured in Examples 1 to 4 and Comparative Examples 1 to 5 were subjected to TEM-EDS (Transmission Electron Microscopy-Energy Dispersive Spectroscopy) mapping analysis using the following methods.

[0168] Each multilayer ceramic capacitor was immersed in an epoxy resin mixture and cured. The L-axis and T-axis surfaces (LT surfaces) of the capacitor body were then polished to half the depth of the capacitor body in the W-axis direction to obtain a cross-sectional sample where the effective region of the dielectric layer and inner electrode layer stacking was observable. At this point, the T-axis direction (i.e., the stacking direction) was effectively divided into three parts (upper part, central part, and lower part) to obtain a cross-sectional sample where at least one dielectric layer and at least one inner electrode layer were visible in each part. Next, the obtained cross-sectional sample was measured using transmission electron microscopy (TEM) with a focused ion beam (FIB) at an accelerating voltage of 200 kV and a magnification of 225 k. Energy-dispersive spectroscopy (EDS) mapping analysis was performed on the TEM images of the obtained cross-sectional sample, and the results are presented below. Figure 8A and Figure 8B middle.

[0169] Figure 8A and Figure 8B The image is based on the TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) mapping analysis of the dielectric layer in Example 1.

[0170] Reference Figure 8A and Figure 8B EDS mapping analysis confirmed the presence of core-shell structured dielectric grains within the dielectric layer of Example 1, and confirmed that the core-shell structured dielectric grains include Ba, Ti, and La.

[0171] (2) Concentration gradient of La and total concentration gradient of rare earth elements In the TEM images of the obtained cross-sectional samples, EDS (energy-dispersive spectroscopy) line analysis was performed on the straight line segment passing through the center of the dielectric grain with a core-shell structure. The absolute values ​​of the La concentration gradient and the total rare earth element concentration gradient in the measurement region X were measured, and the results are presented below. Figures 9A to 10C And in Table 1 below.

[0172] At this point, by selecting two dielectric layers from each of the upper, central, and lower portions within the effective region, and randomly selecting five dielectric grains 10 with core-shell structures from each dielectric layer, for a total of 30 dielectric grains with core-shell structures, the average absolute value of the La concentration gradient and the average absolute value of the total rare earth element concentration gradient in the measurement region X are obtained. The measurement region X is defined as the area extending from the interface between the core and shell to a depth of 5 nm from the interface toward the shell, and measurements are taken in the measurement region X from the interface between the core and shell toward the shell. The absolute value of the La concentration gradient is measured as the absolute value of the change in La content along a straight line passing through two points: point P1 at the interface between the core and shell; and point P2 at a depth of 5 nm from the interface toward the shell. Similarly, the absolute value of the total rare earth element concentration gradient is measured as the absolute value of the change in the total rare earth element content along a straight line passing through points P1 and P2. Furthermore, in dielectric grains with a core-shell structure, point P2 at a depth of 5 nm, located within the shell of the dielectric grain, is the target for measurement.

[0173] Figure 9A and Figure 9B The image is based on the TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis of the dielectric layer in Example 1, and Figure 9C This is a graph showing the lanthanum (La) content in TEM-EDS line analysis, and Figure 10A and Figure 10B The image is based on the TEM-EDS (transmission electron microscopy-energy dispersive spectroscopy) line analysis of the dielectric layer in Example 1, and Figure 10C This is a graph showing the total content of rare earth elements in TEM-EDS line analysis.

[0174] Reference Figures 9A to 10C As shown in Table 1 below, in the cases of Examples 1 to 4, when measurements are taken in the measurement region X from the interface between the core and the shell toward the shell, the absolute value of the La concentration gradient in each of Examples 1 to 4 is in the range of 0.12 mol / nm to 0.58 mol / nm (based on 100 mol of Ti).

[0175] Reference Figures 10A to 10CAs shown in Table 1 below, in Examples 1 to 4, when measurements are taken in the measurement region X from the interface between the core and shell towards the shell, the absolute value of the total rare earth element concentration gradient for each of Examples 1 to 4 ranges from 0.12 mol / nm to 0.58 mol / nm (based on 100 mol of Ti). Here, the absolute value of the total rare earth element concentration gradient represents the absolute value of the total concentration gradients of La, Y, Tb, and Dy.

[0176] At this point, it can be seen that the interface between the core and the shell is the point where La is 0.8 moles (based on 100 moles of Ti).

[0177] 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 expressed based on 100 moles of Ti.

[0178] (Table 1)

[0179] As can be seen from Table 1 above, in Examples 1 to 4, the absolute value of the concentration gradient of La is in the range of about 0.12 mol / nm to about 0.58 mol / nm (based on 100 mol of Ti), and the absolute value of the total concentration gradient of rare earth elements including La, Y, Tb and Dy is in the range of about 0.12 mol / nm to about 0.58 mol / nm (based on 100 mol of Ti).

[0180] (3) Average size of dielectric grains Using a focused ion beam (FIB) at an accelerating voltage of 200 kV and a magnification of 225 k, transmission electron microscopy (TEM) was used to measure the central region R within the central portion of the obtained cross-sectional sample. Specifically, the central region R is defined as follows: the horizontal length from the center Cp of the effective region along the direction perpendicular to the stacking direction to both vertical edges of the central region R corresponds to 1 / 6 of the total horizontal length l of the effective region; and the vertical length from the center Cp of the effective region along the stacking direction to both horizontal edges of the central region R corresponds to 1 / 6 of the total vertical length t of the effective region. EDS (energy-dispersive spectroscopy) analysis of the obtained TEM images confirmed the presence of dielectric grains with a core-shell structure within the central region R of the effective region. The average size of the dielectric grains and the average size of the core were then measured, and the results are presented below. Figure 11 And in Table 2 below.

[0181] The average size of the dielectric grains is calculated as the average of the sizes of the five dielectric grains present in the central region R, and the average size of the core is calculated as the average of the sizes of the cores within the same five dielectric grains. Here, the size of the dielectric grains is obtained as the average of the length of the major axis with the largest diameter and the length of the minor axis with the smallest diameter passing through the center α of the dielectric grains, and the size of the core is obtained as the average of the size of the core obtained along the length of the major axis with the largest diameter passing through the center α of the dielectric grains and the size of the core obtained along the length of the minor axis with the smallest diameter passing through the center α of the dielectric grains.

[0182] Figure 11 This is a graph showing the average size of the dielectric grains according to Example 1 and Comparative Example 2.

[0183] In Table 2 below, the size of the core is expressed as a ratio to the average size of the dielectric grains.

[0184] (Table 2)

[0185] pass Figure 11 As can be seen from Table 2, 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 about 0.12 mol / nm to about 0.58 mol / nm (based on 100 mol of Ti), the average size of the dielectric grains is smaller compared to the cases of Comparative Examples 1 to 5 which are outside the above range.

[0186] Evaluation 2: DC bias characteristics The DC bias characteristics of the multilayer ceramic capacitors manufactured in Examples 1 to 4 and Comparative Examples 1 to 5 were evaluated using the following methods, and the results are shown in Table 3 below.

[0187] After measuring the nominal capacitance at 1 kHz and 0.5 Vrms, the effective capacitance was measured by applying 1 V DC and 3 V DC at 100 kHz and 0.01 Vrms, respectively, and the rate of change of the effective capacitance compared to the nominal capacitance (ΔCp) was calculated.

[0188] In Table 3 below, it is determined that the DC bias characteristics deteriorate when the absolute value of ΔCp at 1V DC is 22% or greater or the absolute value of ΔCp at 3V DC is 65% or greater.

[0189] (Table 3)

[0190] Table 3 above confirms that in Examples 1 to 4, where the absolute values ​​of the La concentration gradient or the total rare earth element concentration gradient are in the range of approximately 0.12 mol / nm to approximately 0.58 mol / nm (based on 100 mol of Ti), the DC bias characteristics are superior compared to those in Comparative Examples 1 to 5, which are outside the aforementioned range. In Comparative Examples 1-3, the absolute value of ΔCp at 1V DC is 22% or greater, thus deteriorating the DC bias characteristics; and in Comparative Examples 4-5, the absolute value of ΔCp at 3V DC is 65% or greater, thus deteriorating the DC bias characteristics.

[0191] Although this disclosure has been described in conjunction with embodiments now considered to be practical, it should be understood that this disclosure is not limited to the disclosed embodiments, but rather is intended to cover various variations and equivalents included within the spirit and scope of the appended claims.

Claims

1. A multilayer ceramic capacitor, comprising: The capacitor body includes a dielectric layer and an inner electrode layer; as well as External electrodes are disposed on the outer surface of the capacitor body. The dielectric layer comprises a plurality of dielectric grains. At least one of the plurality of dielectric grains has a core-shell structure, the core-shell structure comprising a core and a shell surrounding at least a portion of the core. The dielectric grains having the core-shell structure include Ba, Ti, and rare earth elements containing La. In a measurement region extending 5 nm from the interface between the core and the shell to the depth of the shell from the interface, the absolute value of the concentration gradient of Ti and La based on 100 moles ranges from 0.12 moles / nm to 0.58 moles / nm.

2. The multilayer ceramic capacitor according to claim 1, wherein, In transmission electron microscopy-energy dispersive spectroscopy line analysis of the long axis straight segment passing through the center of the dielectric grain having the core-shell structure, The core is based on a region of 100 moles of Ti and less than 0.8 moles of La, and The shell portion is a region based on 100 moles of Ti, with La at least 0.8 moles.

3. The multilayer ceramic capacitor according to claim 1, wherein, The molar content of La in the shell is higher than that in the core.

4. The multilayer ceramic capacitor according to claim 1, wherein, In the shell portion, the content of La is greater than or equal to 0.8 moles and less than or equal to 2.0 moles based on 100 moles of Ti.

5. The multilayer ceramic capacitor according to claim 1, wherein, The rare earth elements also include at least one auxiliary element selected from the group consisting of Sc, Y, Nd, Eu, Gd, Tb, Dy, Ho, Er, Yb and Lu.

6. The multilayer ceramic capacitor according to claim 1, wherein, The rare earth elements also include auxiliary elements containing Y, Tb, and Dy.

7. The multilayer ceramic capacitor according to claim 1, wherein, The capacitor body includes an effective region in which the dielectric layer and the inner electrode layer are alternately arranged in the stacking direction. In the central region of the effective region, the average size of the dielectric grains having the core-shell structure is greater than or equal to 10 nm and less than 130 nm. The central region is defined as follows: the horizontal length from the center of the effective region along a direction perpendicular to the stacking direction to the two vertical edges of the central region corresponds to 1 / 6 of the total horizontal length of the effective region, and the vertical length from the center of the effective region along the stacking direction to the two horizontal edges of the central region corresponds to 1 / 6 of the total vertical length of the effective region.

8. The multilayer ceramic capacitor according to claim 7, wherein, In the central region, the average size of the core is 35% to 67.3% of the average size of the dielectric grain having the core-shell structure.

9. A multilayer ceramic capacitor, comprising: The capacitor body includes a dielectric layer and an inner electrode layer; as well as External electrodes are disposed on the outer surface of the capacitor body. The dielectric layer comprises a plurality of dielectric grains. At least one of the plurality of dielectric grains has a core-shell structure, the core-shell structure comprising a core and a shell surrounding at least a portion of the core. The dielectric grains having the core-shell structure include Ba, Ti, and rare earth elements, wherein the rare earth elements include La; and at least one auxiliary element selected from the group consisting of Sc, Y, Nd, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu. In a measurement region extending 5 nm from the interface between the core and the shell to the depth of the shell from the interface, the absolute value of the total concentration gradient of the rare earth elements, based on 100 moles of Ti, is between 0.12 moles / nm and 0.58 moles / nm.

10. The multilayer ceramic capacitor according to claim 9, wherein, In transmission electron microscopy-energy dispersive spectroscopy line analysis of the long axis straight segment passing through the center of the dielectric grain having the core-shell structure, The core is based on a region of 100 moles of Ti and less than 0.8 moles of La, and The shell portion is a region based on 100 moles of Ti, with La at least 0.8 moles.

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

12. The multilayer ceramic capacitor according to claim 9, wherein, In the shell, based on 100 molar parts of Ti, the total content of the rare earth elements is greater than or equal to 1.2 molar parts and less than or equal to 5.5 molar parts.

13. The multilayer ceramic capacitor according to claim 9, wherein, The capacitor body includes an effective region in which the dielectric layer and the inner electrode layer are alternately arranged in the stacking direction. In the central region of the effective region, the average size of the dielectric grains having the core-shell structure is greater than or equal to 10 nm and less than 130 nm. The central region is defined as follows: the horizontal length from the center of the effective region along a direction perpendicular to the stacking direction to the two vertical edges of the central region corresponds to 1 / 6 of the total horizontal length of the effective region, and the vertical length from the center of the effective region along the stacking direction to the two horizontal edges of the central region corresponds to 1 / 6 of the total vertical length of the effective region.

14. The multilayer ceramic capacitor according to claim 13, wherein, In the central region, the average size of the core is 35% to 67.3% of the average size of the dielectric grain having the core-shell structure.

15. The multilayer ceramic capacitor according to claim 9, wherein, The rare earth elements include La, Y, Tb, and Dy.

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

17. The multilayer ceramic capacitor according to claim 15, wherein, In the shell, the total content of Ti, La, Y, Tb and Dy is greater than or equal to 1.2 moles and less than or equal to 5.5 moles per 100 moles.

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