Multilayer ceramic capacitor

Abstract

An aspect of the present disclosure may provide a multilayer ceramic capacitor capable of increasing a breakdown voltage and a mean time to failure (MTTF).SOLUTION: According to an aspect of the present invention, there is provided a multilayer ceramic capacitor including: a ceramic body in which a dielectric layer and first and second internal electrodes opposing each other with the dielectric layer interposed therebetween are positioned, wherein the ceramic body satisfies the following conditional expression: [Conditional Expression] 0 ≤ (a-b) / a ≤ 0.1 Here, a: fired hardness of the lower portion of the ceramic body b: fired hardness of the upper portion of the ceramic body SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a multilayer ceramic capacitor. [Background technology]

[0002] Multi-layered ceramic capacitors (MLCCs), a type of multilayer electronic component, are chip-type capacitors that are mounted on printed circuit boards of various electronic products such as video equipment (OLED, LED), computers, smartphones, and mobile phones to store and release electrical charges when needed.

[0003] Such multilayer ceramic capacitors can be used as components in various electronic devices due to their advantages of being small, having high capacitance, and being easy to mount. As various electronic devices such as computers and mobile devices become smaller and have higher output, there is an increasing demand for multilayer ceramic capacitors with higher capacitance and smaller size.

[0004] As multilayer ceramic capacitors become smaller, their breakdown voltage (BDV) and mean time to failure (MTTF) become shorter, which may lead to a deterioration in the reliability of the multilayer ceramic capacitors. Therefore, a solution to this problem is needed. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of one aspect of the embodiment is to provide a multilayer ceramic capacitor capable of extending the breakdown voltage and the mean time to failure. [Means for solving the problem]

[0006] According to one embodiment, the multilayer ceramic capacitor includes a ceramic body having a dielectric layer therein and a first internal electrode and a second internal electrode facing each other with the dielectric layer therebetween, and the ceramic body satisfies the following conditional formula:

[0007] [Conditional Expression] 0≦(ab) / a≦0.1 where: a: Firing hardness of the lower part of the ceramic body b: Firing hardness of the upper part of the ceramic body

[0008] When the ceramic body is divided into two equal parts based on the distance from the top surface to the bottom surface, the lower part of the ceramic body may be the part of the ceramic body closest to the bottom surface, and the upper part of the ceramic body may be the part of the ceramic body closest to the top surface.

[0009] When the ceramic body is divided into four equal parts based on the distance from the top surface to the bottom surface, the lower part of the ceramic body may be the part of the ceramic body closest to the bottom surface, and the upper part of the ceramic body may be the part of the ceramic body closest to the top surface.

[0010] When the ceramic body is divided into three equal parts based on the distance from the top surface to the bottom surface, the lower part of the ceramic body may be the part of the ceramic body closest to the bottom surface, and the upper part of the ceramic body may be the part of the ceramic body closest to the top surface.

[0011] The ceramic body may have an upper surface which is an upper surface of the ceramic body and a lower surface which is a lower surface of the ceramic body, and the upper surface may be a portion to which pressure is applied when the ceramic body is fired.

[0012] The semiconductor device may further include a first external electrode connected to the first internal electrode and a second external electrode connected to the second internal electrode. [Effects of the Invention]

[0013] According to at least one of the embodiments, a multilayer ceramic capacitor having a small difference in firing hardness between the top and bottom portions can be provided, thereby improving breakdown voltage (BDV) and mean time to failure (MTTF). [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view showing a multilayer ceramic capacitor according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view showing a bisecting line on a ceramic body separated from a multilayer ceramic capacitor. [Figure 3] 2 is a perspective view showing a ceramic body separated from the multilayer ceramic capacitor of FIG. 1 with a quadrant line indicating the ceramic body. [Figure 4] 4 is a perspective view showing the ceramic body of the multilayer ceramic capacitor of FIG. 1 from a side different from that shown in FIGS. 2 and 3. FIG. [Figure 5] 2 is a cross-sectional view taken along line VV' in FIG. [Figure 6] 6 is an enlarged view of a portion A1 of FIG. 5. [Figure 7] 1 is a diagram showing a plurality of dielectric green sheets. [Figure 8] 8 is a diagram showing a laminated structure of a ceramic body using the dielectric green sheets of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. In the drawings, parts that are not relevant to the description are omitted in order to clearly explain the present invention, and the same reference numerals are used throughout the specification to refer to the same or similar components. In addition, in the accompanying drawings, some components are exaggerated, omitted, or illustrated schematically, and the size of each component does not completely reflect the actual size.

[0016] The attached drawings are provided to facilitate understanding of the embodiments disclosed in this specification, and should not be construed as limiting the technical ideas disclosed in this specification, but should be understood to include all modifications, equivalents, and alternatives included within the spirit and technical scope of the present invention.

[0017] Terms including ordinal numbers such as first, second, etc. may be used to describe various components, but the components are not limited by the terms. These terms are used only to distinguish one component from another.

[0018] Furthermore, when a layer, film, region, plate, or other part is said to be "on" or "above" another part, this includes the case where it is "directly above" the other part, and the case where there is another part between them. Conversely, when a part is said to be "on" another part, it means that there is no other part in between. Furthermore, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "above" or "above" the direction opposite to gravity.

[0019] Throughout the specification, terms such as "comprise" or "have" should be understood to specify the presence of a stated feature, number, step, operation, component, part, or combination thereof, but not to preclude the possible presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof. Thus, when a part is said to "comprise" a certain component, this means that it can further include other components, rather than excluding other components, unless specifically stated to the contrary.

[0020] Throughout the specification, "in a plane" means a portion viewed from above, and "in cross section" means a portion viewed from the side across a vertical cross section.

[0021] Throughout this specification, the term "connected" does not only mean that two or more components are directly connected, but also means that two or more components are indirectly connected by other components, that two or more components are not only physically connected but also electrically connected, or that two or more components are referred to by different names depending on their position or function but are still one.

[0022] In describing multilayer ceramic capacitors in this specification, the direction in which the main components of the multilayer ceramic capacitor are stacked is defined as the "stacking direction," but this may also be the "thickness direction." Also, the direction parallel to a plane perpendicular to the stacking direction can be defined as the "planar direction."

[0023] FIG. 1 is a perspective view schematically illustrating a multilayer ceramic capacitor 10 according to an embodiment. FIG. 2 is a perspective view in which a bisector is indicated on the ceramic body 100 separated from the multilayer ceramic capacitor 10 of FIG. 1. FIG. 3 is a perspective view in which a quarter line is indicated on the ceramic body 100 separated from the multilayer ceramic capacitor 10 of FIG. 1. FIG. 4 is a perspective view showing the multilayer ceramic capacitor 10 of FIG. 1 from a side different from that shown in FIGS. 2 and 3. FIG. 5 is a cross-sectional view taken along line V-V' of FIG. 1.

[0024] 1, 2, 3, 4, and 5, the multilayer ceramic capacitor according to the present embodiment includes a ceramic body 100, a first external electrode 200, and a second external electrode 300.

[0025] First, to clearly explain this embodiment, the directions will be defined. The L axis, W axis, and T axis shown in the drawings indicate the length direction, width direction, and thickness direction of the ceramic body 100, respectively.

[0026] The thickness direction (T-axis direction) may be a direction perpendicular to the broad surface (main surface) of a sheet-shaped component. For example, the thickness direction (T-axis direction) may be used in the same concept as the direction in which the components of the ceramic body 100 are stacked.

[0027] The length direction (L-axis direction) is a direction parallel to the wide surface (main surface) of the sheet-shaped component and may be a direction intersecting (or perpendicular to) the thickness direction (T-axis direction). For example, the length direction (L-axis direction) may be a direction in which the first external electrode 200 and the second external electrode 300 face each other.

[0028] The width direction (W axis direction) is a direction parallel to the wide surface (main surface) of a sheet-shaped component, and can be a direction that simultaneously intersects (or is perpendicular to) the thickness direction (T axis direction) and the length direction (L axis direction).

[0029] The ceramic body 100 may have an approximately hexahedral shape, but this embodiment is not limited thereto. Due to shrinkage during sintering, the ceramic body 100 may have a substantially hexahedral shape, but not a perfect hexahedral shape. For example, the ceramic body 100 may have an approximately rectangular hexahedral shape, but the corners and vertices may be rounded, and the outer portion of the upper part may be sloped downward.

[0030] In this embodiment, for convenience of explanation, the surfaces facing each other in the length direction (L-axis direction) are defined as the first surface (S1) and the second surface (S2), the surfaces facing each other in the width direction (W-axis direction) and connecting the first surface (S1) and the second surface (S2) are defined as the third surface (S3) and the fourth surface (S4), and the surfaces facing each other in the thickness direction (T-axis direction) and connecting the first surface (S1) and the second surface (S2) are defined as the fifth surface (S5) and the sixth surface (S6). Hereinafter, the fifth surface (S5) and the sixth surface (S6) will be referred to as the upper surface (S5) and the lower surface (S6), respectively. The upper surface (S5) may be a portion to which pressure is applied during sintering of the ceramic body 100.

[0031] Therefore, the first direction in which the first surface (S1) and the second surface (S2) face each other may be the length direction (L-axis direction), and the second and third directions that are perpendicular to the first direction and perpendicular to each other may be the thickness direction (T-axis direction) and the width direction (W-axis direction), respectively. In another example, the first direction in which the first surface (S1) and the second surface (S2) face each other may be the length direction (L-axis direction), and the second and third directions that are perpendicular to the first direction and perpendicular to each other may be the width direction (W-axis direction) and the thickness direction (T-axis direction), respectively.

[0032] The length of the ceramic body 100 may refer to the maximum length of a plurality of line segments parallel to the length direction (L axis direction) of the ceramic body 100 while connecting two outermost boundary lines facing each other in the length direction (L axis direction) of the ceramic body 100 shown in the cross-section photograph taken with an optical microscope or a scanning electron microscope (SEM) of a cross-section in the length direction (L axis direction) and thickness direction (T axis direction) at the center of the width direction (W axis direction) of the ceramic body 100. The length of the ceramic body 100 may refer to the minimum length of a plurality of line segments parallel to the length direction (L axis direction) of the ceramic body 100 while connecting two outermost boundary lines facing each other in the length direction (L axis direction) of the ceramic body 100 shown in the cross-section photograph. The length of the ceramic body 100 may refer to the arithmetic average length of at least two line segments parallel to the length direction (L axis direction) of the ceramic body 100 while connecting two outermost boundary lines facing each other in the length direction (L axis direction) of the ceramic body 100 shown in the cross-section photograph.

[0033] The thickness of the ceramic body 100 may refer to the maximum length of a plurality of line segments parallel to the thickness direction (T axis direction) of the ceramic body 100, connecting two outermost boundary lines facing each other in the thickness direction (T axis direction) of the ceramic body 100 shown in the cross-section photograph taken using an optical microscope or a scanning electron microscope (SEM) of the ceramic body 100 at the center of the width direction (W axis direction). The thickness of the ceramic body 100 may refer to the minimum length of a plurality of line segments parallel to the thickness direction (T axis direction) of the ceramic body 100, connecting two outermost boundary lines facing each other in the thickness direction (T axis direction) of the ceramic body 100 shown in the cross-section photograph. The thickness of the ceramic body 100 may refer to the arithmetic average length of at least two line segments parallel to the thickness direction (T axis direction) of the ceramic body 100, connecting two outermost boundary lines facing each other in the thickness direction (T axis direction) of the ceramic body 100 shown in the cross-section photograph.

[0034] The width of the ceramic body 100 may refer to the maximum length of a plurality of line segments parallel to the width direction (W axis direction) of the ceramic body 100, connecting two outermost boundary lines facing each other in the width direction (W axis direction) of the ceramic body 100 shown in the cross-section photograph taken using an optical microscope or a scanning electron microscope (SEM) of the ceramic body 100 at the center of the thickness direction (T axis direction). The width of the ceramic body 100 may refer to the minimum length of a plurality of line segments parallel to the width direction (W axis direction) of the ceramic body 100, connecting two outermost boundary lines facing each other in the width direction (W axis direction) of the ceramic body 100 shown in the cross-section photograph. The width of the ceramic body 100 may refer to the arithmetic average length of at least two line segments parallel to the width direction (W axis direction) of the ceramic body 100, connecting the outermost boundary lines facing each other in the width direction (W axis direction) of the ceramic body 100 shown in the cross-section photograph.

[0035] Meanwhile, the length, width, and thickness of the ceramic body 100 can also be measured using a micrometer measurement method. The micrometer measurement method can be performed by setting the zero point with a gauge R&R (Repeatability and Reproducibility) micrometer, inserting the ceramic body 100 according to this embodiment between the tips of the micrometer, and turning the measuring lever of the micrometer. Meanwhile, when measuring the length of the ceramic body 100 using the micrometer measurement method, the length of the ceramic body 100 can refer to a value measured once or the arithmetic average of values ​​measured multiple times. This can also be applied to measuring the width and thickness of the ceramic body 100.

[0036] The ceramic body 100 includes a dielectric layer 110 , a first internal electrode 120 , a second internal electrode 130 , a first cover layer 140 , and a second cover layer 150 .

[0037] The dielectric layers 110 may be stacked in the thickness direction (T-axis direction) of the ceramic body 100. The boundaries between the dielectric layers 110 may be unclear. That is, multiple dielectric layers 110 may be shown as an integrated structure. For example, the boundaries between the dielectric layers 110 may be so unclear that they are difficult to identify without the use of a scanning electron microscope (SEM).

[0038] The dielectric layer 110 may include a ceramic material with a high dielectric constant. For example, the ceramic material may include a dielectric ceramic containing components such as BaTiO3, CaTiO3, SrTiO3, or CaZrO3. These components may further include auxiliary components such as manganese (Mn) compounds, iron (Fe) compounds, chromium (Cr) compounds, cobalt (Co) compounds, and nickel (Ni) compounds. For example, the dielectric layer 110 may include a ceramic material in which calcium (Ca), zirconium (Zr), etc. are partially dissolved in BaTiO3 (BaTiO3). 1-x Ca x )TiO3, Ba(Ti 1-y Ca y )O3, (Ba 1-x Ca x )(Ti 1-y Zr y )O3 or Ba(Ti 1-y Zr y )O3, etc., but the present invention is not limited to these.

[0039] The dielectric layer 110 may further include one or more of a ceramic additive, an organic solvent, a plasticizer, a binder, and a dispersant. For example, the ceramic additive may include a transition metal oxide, a carbide, a rare earth element, magnesium (Mg), or aluminum (Al).

[0040] The slurry for forming the dielectric layer 110 may contain a binder. The binder is used to impart plasticity and shapeability. The binder is decomposed during the firing process, and may not remain in the dielectric layer 110 after firing.

[0041] The first internal electrodes 120 and the second internal electrodes 130 may be alternately stacked with the dielectric layers 110 interposed therebetween. That is, a first internal electrode 120 / dielectric layer 110 / second internal electrode 130 / dielectric layer 110 structure may be repeatedly arranged inside the ceramic body 100. As an example, the internal electrode closest to the fifth surface (S5) of the ceramic body 100 may be the first internal electrode 120, and the internal electrode closest to the sixth surface (S6) may be the second internal electrode 130. As another example, the internal electrode closest to the fifth surface (S5) of the ceramic body 100 may be the second internal electrode 130, and the internal electrode closest to the sixth surface (S6) may be the first internal electrode 120.

[0042] The first internal electrode 120 and the second internal electrode 130 have different polarities and can be electrically insulated from each other by the dielectric layer 110 located therebetween.

[0043] The first internal electrode 120 and the second internal electrode 130 may be arranged to be offset from each other in the length direction (L-axis direction) with the dielectric layer 110 therebetween. That is, the first internal electrode 120 and the second internal electrode 130 may be arranged to partially overlap each other in the thickness direction (T-axis direction) and not to partially overlap each other. One side end of the first internal electrode 120 may be exposed through the first surface (S1) of the ceramic body 100. One side end of the second internal electrode 130 may be exposed through the second surface (S2) of the ceramic body 100. The end of the first internal electrode 120 exposed from the first surface (S1) of the ceramic body 100 may be connected to the first external electrode 200. The end of the second internal electrode 130 exposed from the second surface (S2) of the ceramic body 100 may be connected to the second external electrode 300.

[0044] The first internal electrode 120 and the second internal electrode may be formed by printing a conductive paste on the surface of the dielectric layer 110. In this case, the conductive paste may contain a conductive metal. For example, the internal electrodes may be formed by printing a conductive paste containing nickel (Ni) or a nickel (Ni) alloy on the surface of the dielectric green sheet 500 by screen printing or gravure printing. However, this embodiment is not limited thereto.

[0045] For example, the average thickness of the first internal electrode 120 and the second internal electrode 130 may be approximately 0.1 μm or more and 2 μm or less.

[0046] Here, the thickness of the internal electrode may refer to the average thickness of one internal electrode disposed between two dielectric layers 110. The average thickness of the internal electrode may be an arithmetic average value of thicknesses of one internal electrode shown in a scanning electron microscope (SEM) photograph taken at a magnification of 10,000 times on a cross section in the length direction (L axis direction) and thickness direction (T axis direction) at the center of the width direction (W axis direction) of the ceramic body 100, measured at 30 equally spaced points in the length direction (L axis direction).

[0047] When a voltage is applied to the first external electrode 200 and the second external electrode 300, a charge is accumulated between the first internal electrode 120 and the second internal electrode 130, which are adjacent to each other. That is, a capacitance can be obtained between the first internal electrode 120 electrically connected to the first external electrode 200 and the second internal electrode 130 electrically connected to the second external electrode 300. The capacitance of the multilayer ceramic capacitor 10 is proportional to the overlapping area of ​​the first internal electrode 120 and the second internal electrode 130 that overlap each other along the thickness direction (T-axis direction).

[0048] The ceramic body 100 of the present embodiment may have a small difference in indentation hardness (HIT) depending on the position in the thickness direction (T-axis direction). That is, the difference in firing hardness between the upper and lower parts of the ceramic body 100 may be small.

[0049] Sintered hardness is a value measuring the resistance of a material to deformation or indentation due to an applied force, and may refer to the resistance to permanent deformation and damage. Sintered hardness can be measured using a Brinell hardness test, a Rockwell hardness test, a Vickers hardness test, a Knoop hardness test, or the like. For example, sintered hardness can be measured using a nanoindenter. Generally, during the ceramic green sheet lamination process, the ceramic body 100 is stacked from the bottom, so the applied pressure accumulates. As a result, the sintered hardness increases toward the bottom of the ceramic body 100. This difference in accumulated pressure results in a significant difference in sintered hardness between the top and bottom of the ceramic body 100. The ceramic body 100 of this embodiment may have a small difference in sintered hardness between the top and bottom. Specifically, the ceramic body 100 may have a difference in firing hardness of 10% or less between the upper and lower parts. That is, the following conditional expression may be satisfied.

[0050] [Conditional Expression] 0≦(ab) / a≦0.1 where: a: Firing hardness of the lower part of the ceramic body b: Firing hardness of the upper part of the ceramic body Here, the lower ceramic body and the upper ceramic body may refer to portions of the ceramic body 100 .

[0051] 2, the lower and upper portions of the ceramic body can be divided based on a bisection plane (BS) that divides the ceramic body 100 in half based on the distance from the upper surface (S5) to the lower surface (S6). When the ceramic body 100 is divided in half as described above, the lower portion of the ceramic body is the portion (BP1) closest to the lower surface (S6), and the upper portion of the ceramic body is the portion (BP2) closest to the upper surface (S5). In other words, the lower portion of the ceramic body is the portion located between the bisection plane (BS) and the lower surface (S6), and the upper portion of the ceramic body is the portion located between the bisection plane (BS) and the upper surface (S5).

[0052] 3, the lower and upper portions of the ceramic body 100 may be defined as the bottom and top portions, respectively, when the ceramic body 100 is divided into four equal parts based on the distance from the top surface (S5) to the bottom surface (S6) of the ceramic body 100. When divided into four equal parts, the ceramic body 100 may be divided into a first portion (QP1) located at the bottom, a second portion (QP2) located at the top, and a third portion (QP3) and a fourth portion (QP4) located between the first portion (QP1) and the second portion (QP2). In this case, the lower portion of the ceramic body is the first portion (QP1), and the lower portion of the ceramic body is the second portion (QP2). In other words, when the ceramic body 100 is divided into four equal parts, the lower portion of the ceramic body is the portion (QP1) closest to the bottom surface (S6), and the upper portion of the ceramic body is the portion (QP2) closest to the top surface (S5). When viewed from the cross section, the ceramic body 100 can be divided into four equal parts based on the first cross section (QS1) located at the bottom, the second cross section (QS2) located at the top, and the third cross section (QS3) located between the first cross section (QS1) and the second cross section (QS2). In this case, the lower part of the ceramic body is the part located between the first cross section (QS1) and the lower surface (S6), and the upper part of the ceramic body is the part located between the second cross section (QS2) and the upper surface (S5).

[0053] 4, the lower and upper portions of the ceramic body 100 may be defined as the bottom and top portions, respectively, when the ceramic body 100 is divided into thirds based on the distance from the top surface (S5) to the bottom surface (S6) of the ceramic body 100. When divided into thirds, the ceramic body 100 may be divided into a first portion (TP1) located at the bottom, a second portion (TP2) located at the top, and a third portion located between the first portion (TP1) and the second portion (TP2). In this case, the lower portion of the ceramic body is the first portion (TP1), and the upper portion of the ceramic body is the second portion (TP2). In other words, when the ceramic body 100 is divided into thirds, the lower portion of the ceramic body is the portion (TP1) closest to the bottom surface (S6), and the upper portion of the ceramic body is the portion (TP2) closest to the top surface (S5). When viewed from the cross section, the ceramic body 100 can be divided into three equal parts based on the first cross section (TS1) located at the bottom and the second cross section (TS2) located at the top. In this case, the lower part of the ceramic body is the part located between the first cross section (TS1) and the bottom surface (S6), and the upper part of the ceramic body is the part located between the second cross section (TS2) and the top surface (S5).

[0054] The ceramic body 100 of this embodiment can be manufactured using a dielectric paste containing 10 wt% to 30 wt% (weight percent) of a PVB (Polyvinyl Butyral) binder with a glass transition temperature (Tg) of 80°C to 90°C, both inclusive, based on the ceramic weight. This allows the ceramic body 100 to be manufactured with a small difference in firing hardness in the thickness direction (T-axis direction). Specifically, the ceramic body 100 can be manufactured with a difference in firing hardness of 10% or less between the upper and lower parts.

[0055] The breakdown voltage (BDV) and mean time to failure (MTTF) increase when there is no or a small difference in firing hardness between the upper and lower parts of the ceramic body 100. For example, when the difference in firing hardness between the upper and lower parts of the ceramic body 100 is 10% or less, the breakdown voltage (BDV) and mean time to failure (MTTF) can be significantly increased.

[0056] FIG. 6 is an enlarged view of the A1 portion of FIG.

[0057] Referring to Fig. 6, saddle portions (SD) are generally formed at the ends of the first internal electrode 120 and the second internal electrode 130 (although Fig. 6 only shows the saddle portion of the first internal electrode, a saddle portion is also formed at the end of the second internal electrode 130). The ceramic body 100 of this embodiment is formed so that the difference in firing hardness between the upper and lower portions is small, which allows the height of the saddle portions (SD) to be reduced. Therefore, deformation of the dielectric layer 110 caused by the formation of the saddle portions can be alleviated.

[0058] A first cover layer 140 and a second cover layer 150 may be disposed outside the active region (A) and the margin region (M) in the thickness direction (T-axis direction). The first cover layer 140 may be disposed between the fifth surface (S5) of the ceramic body 100 and the internal electrode closest thereto. The second cover layer 150 may be disposed between the sixth surface (S6) of the ceramic body 100 and the internal electrode closest thereto.

[0059] That is, the first cover layer 140 can be disposed over the internal electrode (hereinafter referred to as the "uppermost internal electrode") located at the top end in the thickness direction (T-axis direction) of the internal electrodes, and the second cover layer 150 can be disposed under the internal electrode (hereinafter referred to as the "lowermost internal electrode") located at the bottom end in the thickness direction (T-axis direction) of the internal electrodes.

[0060] The first cover layer 140 and the second cover layer 150 may have the same composition as the dielectric layer 110. The first cover layer 140 may be formed by laminating one or more dielectric layers on the topmost internal electrode and a dielectric layer parallel to the topmost internal electrode. The second cover layer 150 may be formed by laminating one or more dielectric layers under the bottommost internal electrode and a dielectric layer parallel to the bottommost internal electrode.

[0061] The first cover layer 140 and the second cover layer 150 may serve to prevent damage to the first internal electrode 120 and the second internal electrode 130 due to physical or chemical stress.

[0062] The first external electrode 200 and the second external electrode 300 are disposed on the outside of the ceramic body 100. The first external electrode 200 is disposed on the first surface (S1) of the ceramic body 100 and may extend to the third surface (S3), the fourth surface (S4), the fifth surface (S5), and the sixth surface (S6). The second external electrode 300 is disposed on the second surface (S2) of the ceramic body 100 and may extend to the third surface (S3), the fourth surface (S4), the fifth surface (S5), and the sixth surface (S6). In another embodiment, the first external electrode 200 and the second external electrode 300 may extend to a portion of at least one of the fifth surface (S5) and the sixth surface (S6).

[0063] The first external electrode 200 includes a first electrode layer 210 and a first conductive resin layer 230 , and the second external electrode 300 includes a second electrode layer 310 and a second conductive resin layer 330 .

[0064] The first electrode layer 210 and the second electrode layer 310 can include conductive metals and glasses.

[0065] For example, the first electrode layer 210 and the second electrode layer 310 may include, as a conductive metal, copper (Cu), a copper (Cu) alloy, nickel (Ni), silver (Ag), palladium (Pd), gold (Au), platinum (Pt), tin (Sn), tungsten (W), titanium (Ti), lead (Pb), an alloy thereof, or a combination thereof. For example, the first electrode layer 210 and the second electrode layer 310 may include glass, which may include a composition in which oxides are combined. For example, the oxide may be one or more selected from the group consisting of silicon oxide, boron oxide, aluminum oxide, transition metal oxide, alkali metal oxide, and alkaline earth metal oxide. The transition metal 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 metal may be selected from the group consisting of lithium (Li), sodium (Na) and potassium (K), and the alkaline earth metal may be one or more selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba).

[0066] The first conductive resin layer 230 and the second conductive resin layer 330 may contain a resin and a conductive metal.

[0067] The resin contained in the first conductive resin layer 230 and the second conductive resin layer 330 is not particularly limited as long as it has adhesiveness and shock absorbency and can be mixed with conductive metal powder to form a paste. For example, the resin contained in the first conductive resin layer 230 and the second conductive resin layer 330 can include phenol resin, acrylic resin, silicone resin, epoxy resin, or polyimide resin.

[0068] The conductive metal contained in the first conductive resin layer 230 and the second conductive resin layer 330 serves to electrically connect the first electrode layer 210 and the second electrode layer 310. The conductive metal contained in the first conductive resin layer 230 and the second conductive resin layer 330 may have a spherical shape, a flake shape, or a combination thereof.

[0069] The first external electrode 200 may include a first plating layer 250 located outside the first conductive resin layer 230, and the second external electrode 300 may include a second plating layer 350 located outside the second conductive resin layer 330.

[0070] The first plating layer 250 and the second plating layer 350 may include nickel (Ni), copper (Cu), tin (Sn), palladium (Pd), platinum (Pt), gold (Au), silver (Ag), tungsten (W), titanium (Ti), lead (Pb), or the like, either alone or in alloys thereof. For example, the first plating layer 250 and the second plating layer 350 may be a nickel (Ni) plating layer or a tin (Sn) plating layer, or may be a nickel (Ni) plating layer and a tin (Sn) plating layer stacked sequentially, or a tin (Sn) plating layer, a nickel (Ni) plating layer, and a tin (Sn) plating layer stacked sequentially. The plating layer may also include multiple nickel (Ni) plating layers and / or multiple tin (Sn) plating layers.

[0071] The first plating layer 250 and the second plating layer 350 can improve the mountability of the multilayer ceramic capacitor 10 to a substrate, structural reliability, durability against external influences, heat resistance, and equivalent series resistance (ESR).

[0072] Hereinafter, a method for manufacturing the multilayer ceramic capacitor 10 according to one embodiment will be described with reference to FIGS.

[0073] Fig. 7 is a diagram showing a plurality of dielectric green sheets, and Fig. 8 is a diagram showing a laminated structure of a ceramic body using the dielectric green sheets of Fig. 7.

[0074] First, a dielectric paste is prepared for forming a plurality of dielectric green sheets 500. The dielectric paste may include ceramic powder, ceramic additives, an organic solvent, a plasticizer, a dispersant, and a binder.

[0075] For example, the ceramic powder may include a dielectric ceramic containing components such as BaTiO3, CaTiO3, SrTiO3, or CaZrO3. These components may further include auxiliary components such as Mn compounds, Fe compounds, Cr compounds, Co compounds, and Ni compounds. For example, BaTiO3-based dielectric ceramics in which Ca, Zr, etc. are partially dissolved (Ba 1-x Ca x )TiO3, Ba(Ti 1-y Ca y )O3, (Ba 1-x Ca x )(Ti 1-y Zr y )O3 or Ba(Ti 1-y Zr y )O3, etc.

[0076] By way of example, the ceramic additives may include transition metal oxides, transition metal carbides, rare earth elements, magnesium (Mg), aluminum (Al), and the like.

[0077] The organic solvent is not particularly limited, and examples thereof include butyl carbitol, acetone, toluene, and ethyl acetate.

[0078] The binder may be a PVB (Polyvinyl Butyral) binder having a glass transition temperature (Tg) of 80°C to 90°C. As an example, the binder may further include one of polyacrylic acid ester, polymethacrylic acid ester, polyvinyl alcohol, cellulose dielectric, polyalkylene oxide, polyurethane, polyvinyl acetate, polyethylene, ethylene-vinyl acetate copolymer, and polyvinyl chloride. The dielectric paste of this embodiment may include the binder in an amount of 10 wt% to 30 wt% based on the ceramic weight.

[0079] The dielectric paste can be prepared by a crushing process to ensure uniform powder particles in an organic solvent. For example, ceramic powder, ceramic additives, an organic solvent, a plasticizer, a dispersant, and a binder are filled into a hollow cylindrical crushing mill, and an impeller installed in the crushing mill is rotated at a constant speed to crush the powder by rotational force. A process for separating coarse particles can also be performed, and a filtering process for removing foreign matter can also be performed.

[0080] Referring to FIG. 7, the dielectric paste prepared as above is applied by a doctor blade, screen printing, or the like to form a plurality of dielectric green sheets 500 each having a thickness of several μm.

[0081] For example, the dielectric green sheet 500 can be manufactured by applying a dielectric paste to a film to a certain thickness, filtering and drying the paste, and then removing the film.

[0082] A conductive paste layer 600 is formed on a portion of the surface of the dielectric green sheet 500. After firing, the conductive paste layer 600 becomes the first internal electrode 120 and the second internal electrode 130. The conductive paste layer 600 can be formed by applying a conductive paste containing a conductive metal to the surface of the dielectric green sheet 500 using a doctor blade, screen printing, or other method. As an example, the conductive metal may include metals such as Ni, Cu, Ag, Pd, or Au, or alloys thereof.

[0083] For example, the conductive paste layer 600 may be applied in two patterns on the dielectric green sheet 500. The conductive paste may be applied in a first pattern on the surface of the first dielectric green sheet 510 to form the first conductive paste layer 610. The conductive paste may be applied in a second pattern on the surface of the second dielectric green sheet 520 to form the second conductive paste layer 620.

[0084] The dielectric green sheets 500 are laminated to produce a dielectric green sheet laminate.

[0085] The first and second patterns may be arranged such that the first conductive paste layer 610 and the second conductive paste layer 620 partially overlap and partially do not overlap when the first dielectric green sheet 510 and the second dielectric green sheet 520 are alternately laminated. The first conductive paste layer 610 may become the first internal electrode 120 after firing, and the second conductive paste layer 620 may become the second internal electrode 130 after firing.

[0086] 8, dielectric green sheets are laminated to manufacture a dielectric green sheet laminate. At this time, the first dielectric green sheet 510 and the second dielectric green sheet 520 are laminated so that the first conductive paste layer 610 and the second conductive paste layer overlap, but at least a portion of them do not overlap.

[0087] A third dielectric green sheet 530, on which no conductive paste layer is formed, is laminated on the first dielectric green sheet 510 and below the second dielectric green sheet 520.

[0088] The dielectric green sheet laminate manufactured as described above is compressed. The pressure applied for compression may vary depending on the composition of the dielectric green sheets and conductive paste, the size of the ceramic body 100, and atmospheric conditions such as temperature. A simulation can be performed before the compression process to determine the appropriate pressure. That is, by compressing the laminate with a pre-calculated pressure, a ceramic body 100 with a small difference in firing hardness between the upper and lower portions can be manufactured from a dielectric paste containing 10 wt % to 30 wt % of a PVB (Polyvinyl Butyral) binder with a glass transition temperature (Tg) of 80°C to 90°C, based on the ceramic weight.

[0089] During the lamination or compression bonding of the dielectric green sheet laminate, flow of the dielectric green sheets may occur. Examples of such flow of the dielectric green sheets include pore collapse, binder flow, and particle rearrangement. The flow of the dielectric green sheets determines the firing hardness of the entire ceramic body 100. When the dielectric paste contains 10 wt% to 30 wt% of a PVB binder with a glass transition temperature (Tg) of 80°C to 90°C, based on the ceramic weight, as described above, the ceramic body 100 can be formed such that the difference in firing hardness between the top and bottom of the ceramic body 100 is within a range of 10% or less.

[0090] Optionally, the dielectric green sheet laminate may be cut so that the first conductive paste layer 610 and the second conductive paste layer 620 are exposed through both side end surfaces of the dielectric green sheet laminate.

[0091] The dielectric green sheet laminate is fired at a high temperature to produce the ceramic body 100. A first external electrode 200 is formed on the cross section of the ceramic body 100 where the first internal electrode 120 is exposed, and a second external electrode 300 is formed on the cross section of the ceramic body 100 where the second internal electrode 130 is exposed.

[0092] For example, the first external electrode 200 and the second external electrode 300 may be formed by applying a conductive paste onto the ceramic body 100 and firing the paste, or may be formed by plating. Alternatively, the first external electrode 200 and the second external electrode 300 may be formed by applying a conductive paste onto the dielectric green sheet laminate and then firing the conductive paste together with the dielectric green sheet laminate.

[0093] Specific examples of the invention will be described below.

[0094] [Manufacturing of multilayer ceramic capacitors] (Manufacturing method of Example 1) A dielectric paste containing barium titanate (BaTiO3) powder was applied to a carrier film and then dried to produce multiple dielectric green sheets with a thickness of 1.3 μm. The dielectric paste contained 22 wt% of a PVB binder with a glass transition temperature (Tg) of 85°C based on the ceramic weight.

[0095] A conductive paste containing nickel was applied onto the dielectric green sheet using a screen printing method.

[0096] Approximately 700 layers of dielectric green sheets coated with conductive paste were stacked, and 55 layers of dielectric green sheets not coated with conductive paste were stacked on top and bottom to manufacture a dielectric green sheet laminate.

[0097] The dielectric green sheet laminate was subjected to 1000 kgf / cm at 85°C. 2 The mixture was subjected to isostatic pressing under the pressure conditions.

[0098] The dielectric green sheet laminate after the compression bonding was cut into individual chips, and then the binder was removed by maintaining the chips at 230° C. for 60 hours in an air atmosphere.

[0099] Then, at 1200°C, the internal electrode was heated to 10°C, which is lower than the Ni / NiO equilibrium oxygen partial pressure, to prevent oxidation. -11 atm~10 -10 The powder was fired in a reducing atmosphere under an oxygen partial pressure of 1 atm.

[0100] Next, processes such as external electrode formation and plating were carried out to manufacture a multilayer capacitor (LxWxT=3.2mmx1.6mmx1.6mm).

[0101] (Manufacturing method of Example 2) In Example 1, a dielectric paste was prepared by adding 25 wt % of a PVB binder having a glass transition temperature (Tg) of 85° C. based on the ceramic weight. Except for this, a multilayer ceramic capacitor was prepared in the same manner as in Example 1.

[0102] (Manufacturing method of Example 3) In Example 1, a dielectric paste was prepared by adding 30 wt % of a PVB binder having a glass transition temperature (Tg) of 85° C. based on the ceramic weight. Except for this, a multilayer ceramic capacitor was prepared in the same manner as in Example 1.

[0103] (Manufacturing method of Example 4) In Example 1, a dielectric paste was prepared by adding 20 wt % of a PVB binder having a glass transition temperature (Tg) of 85° C. based on the ceramic weight. Except for this, a multilayer ceramic capacitor was prepared in the same manner as in Example 1.

[0104] (Manufacturing method of Example 5) In Example 1, a dielectric paste was prepared by adding 10 wt % of a PVB binder having a glass transition temperature (Tg) of 85° C. based on the ceramic weight. Except for this, a multilayer ceramic capacitor was prepared in the same manner as in Example 1.

[0105] (Manufacturing method of Comparative Example 1) In Example 1, a dielectric paste was prepared by adding 28 wt % of a PVB binder having a glass transition temperature (Tg) of 78° C. based on the ceramic weight. Except for this, a multilayer ceramic capacitor was prepared in the same manner as in Example 1.

[0106] (Manufacturing method of Comparative Example 2) In Example 1, a dielectric paste was prepared by adding 14 wt % of a PVB binder having a glass transition temperature (Tg) of 78° C. based on the ceramic weight. Except for this, a multilayer ceramic capacitor was prepared in the same manner as in Example 1.

[0107] (Production method of Comparative Example 3) In Example 1, a dielectric paste was prepared by adding 28 wt % of a PVB binder having a glass transition temperature (Tg) of 68° C. based on the ceramic weight. Except for this, a multilayer ceramic capacitor was prepared in the same manner as in Example 1.

[0108] (Production method of Comparative Example 4) In Example 1, a dielectric paste was prepared by adding 11 wt % of a PVB binder having a glass transition temperature (Tg) of 78° C. to the ceramic weight. Except for this, a multilayer ceramic capacitor was prepared in the same manner as in Example 1.

[0109] (Production method of Comparative Example 5) In Example 1, a dielectric paste was prepared by adding 25 wt % of a PVB binder having a glass transition temperature (Tg) of 68° C. based on the ceramic weight. Except for this, a multilayer ceramic capacitor was prepared in the same manner as in Example 1.

[0110] (Production method of Comparative Example 6) In Example 1, a dielectric paste was prepared by adding 14 wt % of a PVB binder having a glass transition temperature (Tg) of 68° C. based on the ceramic weight. Except for this, a multilayer ceramic capacitor was prepared in the same manner as in Example 1.

[0111] (Production method of Comparative Example 7) In Example 1, a dielectric paste was prepared by adding 11 wt % of a PVB binder having a glass transition temperature (Tg) of 68° C. based on the ceramic weight. Except for this, a multilayer ceramic capacitor was prepared in the same manner as in Example 1.

[0112] [Breakdown voltage and mean time to failure measurements] After manufacturing 40 multilayer ceramic capacitors for each of Examples 1 to 5 and Comparative Examples 1 to 7, the breakdown voltage (BDV) and mean time to failure (MTTF) were measured.

[0113] The ratio to the dielectric thickness reduction width was also measured. The dielectric thickness reduction width was determined by measuring the thickness of the middle part (measured in the T-axis direction, Tc) and the thickness of the part where the saddle part is located (Ts) with respect to the uppermost dielectric layer (the dielectric layer between the first internal electrode and the second internal electrode located at the top), and calculating (Tc - Ts) / Tc.

[0114] Thereafter, the ceramic body 100 of the multilayer ceramic capacitor was separated into upper and lower halves, and the firing hardness of each of the upper and lower halves was measured.

[0115] Table 1 summarizes the measurement results.

[0116] [Table 1]

[0117] As shown in Table 1, it was confirmed that the average BDV, minimum BDV, and MTTF all increased as the firing hardness ratio increased. In particular, as the firing hardness ratio increased above 10, both BDV and MTTF increased significantly. Comparing Example 1 and Example 2, as the firing hardness ratio increased by 1.8% from 7.3 to 9.1, the average BDV, minimum BDV, and MTTF decreased by 4, 3, and 2, respectively. On the other hand, comparing Example 2 and Comparative Example 2, although the firing hardness ratio increased by 1.1% from 9.1 to 10.2, a relatively small decrease compared to the previous examples, the average BDV, minimum BDV, and MTTF decreased by 8, 10, and 5.5, respectively, confirming a relatively large decrease.

[0118] In conclusion, it can be seen that in the examples where the firing hardness ratio is 10% or less, the BDV and MTTF are significantly improved compared to the comparative examples.

[0119] In addition, it can be seen from Table 1 that as the firing hardness ratio increases, the dielectric thickness reduction also generally increases.

[0120] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited thereto, and various modifications can be made within the scope of the claims, the detailed description of the invention, and the accompanying drawings, and it is to be understood that these modifications also fall within the scope of the present disclosure. [Explanation of symbols]

[0121] 10 Multilayer ceramic capacitor 100 ceramic body 110 dielectric layer 120 1st internal electrode 130 2nd internal electrode 140 First Cover Layer 150 Second cover layer 200 1st external electrode 210 1st electrode layer 230 First conductive resin layer 250 First plating layer 300 2nd external electrode 310 Second electrode layer 330 Second conductive resin layer 350 Second plating layer 500 Dielectric Green Sheet

Claims

1. a ceramic body including a dielectric layer therein, and a first internal electrode and a second internal electrode positioned opposite each other with the dielectric layer therebetween; The ceramic body satisfies the following conditional formula: [Conditional Expression] 0≦(a-b) / a≦0.1 where: a: sintered hardness of the lower part of the ceramic body b: sintered hardness of the upper part of the ceramic body Multilayer ceramic capacitors meet these requirements.

2. When the ceramic body is divided into two equal parts based on the distance from the upper surface to the lower surface, the lower part of the ceramic body is the part of the ceramic body that is closest to the lower surface, and The multilayer ceramic capacitor according to claim 1 , wherein the upper portion of the ceramic body is a portion of the ceramic body closest to the top surface.

3. When the ceramic body is divided into four equal parts based on the distance from the top surface to the bottom surface, the lower part of the ceramic body is the part of the ceramic body that is closest to the bottom surface; and The multilayer ceramic capacitor according to claim 1 , wherein the upper portion of the ceramic body is a portion of the ceramic body closest to the top surface.

4. When the ceramic body is divided into three equal parts based on the distance from the top surface to the bottom surface, the lower part of the ceramic body is the part of the ceramic body that is closest to the bottom surface, and The multilayer ceramic capacitor according to claim 1 , wherein the upper portion of the ceramic body is a portion of the ceramic body closest to the top surface.

5. the ceramic body has an upper surface that is an upper surface of the ceramic body and a lower surface that is a lower surface of the ceramic body; The multilayer ceramic capacitor according to claim 1 , wherein the upper surface is a portion to which pressure is applied when the ceramic body is fired.

6. a first external electrode connected to the first internal electrode; The multilayer ceramic capacitor of claim 1 , further comprising: a second external electrode connected to the second internal electrode.

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