Multilayer capacitors and plate assemblies in which multilayer capacitors are mounted

Abstract

This disclosure provides a multilayer capacitor and a plate assembly in which the multilayer capacitor is mounted. The multilayer capacitor includes: a capacitor body including an effective region and an upper cover and a lower cover, the effective region having dielectric layers and internal electrodes alternately stacked therein, the upper cover and lower cover being disposed on an upper surface and a lower surface of the effective region, respectively; and an external electrode disposed on an outer surface of the capacitor body. In at least one of the upper cover and the lower cover, a portion of the at least one of the upper cover and the lower cover located between the boundary surface of the effective region and the boundary surface of the capacitor body is divided into a first cover region and a second cover region, the first cover region being adjacent to the effective region, the second cover region being adjacent to the boundary surface of the capacitor body, and the first cover region including grains having a Sn-doped core-shell structure. Compared to the total number of grains in the first cover region, the first cover region includes 20% or more of the Sn-doped core-shell structure grains.

Description

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2020-0180613, filed on December 22, 2020, with the Korean Intellectual Property Office, and Korean Patent Application No. 10-2021-0170635, filed on December 2, 2021, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field

[0002] This disclosure relates to a multilayer capacitor and a plate assembly in which the multilayer capacitor is mounted. Background Technology

[0003] Recently, as electronic devices have become smaller, chip assemblies are also being miniaturized, and multilayer capacitors also need to be reduced in size and have greater capacitance and superior reliability.

[0004] Specifically, to ensure the reliability of ultra-small multilayer capacitors, more precise control is needed in material selection and manufacturing.

[0005] Therefore, due to the miniaturization of multilayer capacitors and the thinning of dielectric layers, the properties of the required materials and sintering conditions are changing.

[0006] Specifically, due to the thinning of the dielectric layer, reliability issues are becoming a significant concern. Furthermore, as the plasticizing conditions at high temperatures decrease, the surface diffusion of the grains is reduced. Therefore, ensuring the densification of the sintered body is crucial.

[0007] Furthermore, as the density of the capacitor body's cap decreases, its moisture resistance deteriorates. Therefore, the need for technological development to address the sintering behavior of the cap is increasing.

[0008] However, current caps are formed simply by changing the number of identical sheets stacked together, and have the following characteristics: the density of the outside of the cap is significantly lower than the density of the inside of the cap.

[0009] Therefore, there is a need for a method to improve and properly control the density of the cover exposed to the outside based on the characteristics of the sheet (such as moisture resistance, toughness, and hardness). Summary of the Invention

[0010] This summary is provided to introduce selected concepts in a simplified form, which will be further described in the detailed description below. This summary is not intended to limit the key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter.

[0011] One aspect of this disclosure is to provide a multilayer capacitor and a plate assembly in which the multilayer capacitor is mounted, wherein properties of the cap, such as moisture resistance, toughness and hardness, as well as densification, are ensured at a certain level or higher in the multilayer capacitor.

[0012] According to an embodiment, a multilayer capacitor includes: a capacitor body including an effective region and an upper cover and a lower cover, the effective region having dielectric layers and internal electrodes alternately stacked therein, the upper cover and the lower cover being disposed on an upper surface and a lower surface of the effective region, respectively; and an external electrode disposed on an outer surface of the capacitor body. In at least one of the upper cover and the lower cover, a portion of the upper cover and the lower cover located between the boundary surface of the effective region and the boundary surface of the capacitor body is divided into a first cover region and a second cover region, the first cover region being adjacent to the effective region, the second cover region being adjacent to the boundary surface of the capacitor body, and the first cover region comprising grains with a Sn-doped core-shell structure. The first cover region comprises 20% or more Sn-doped core-shell structure grains compared to the total number of grains in the first cover region.

[0013] In the core-shell structured grains with Sn doping, the molar ratio of Sn in the Sn-doped portion of a grain to Ba in the grain is called the coverage, and the coverage can be 30% or greater.

[0014] The grains included in the second capping region may not include Sn.

[0015] The grain size of the second capping region can be larger than the grain size of the first capping region.

[0016] The thickness of the first cover area can be 40% to 80% of the sum of the thicknesses of the first cover area and the second cover area.

[0017] The grain size of the second capping region can be larger than that of the grain size of the first capping region, and the thickness of the first capping region can be 40% to 80% of the sum of the thicknesses of the first capping region and the second capping region.

[0018] The grain size of the first capping region can be from 100 nm to 180 nm.

[0019] The grain size of the second capping region can be 200 nm or larger.

[0020] The grain size of the first capping region can be from 100 nm to 180 nm, and the grain size of the second capping region can be 200 nm or larger.

[0021] The molar ratio of Ba to Ti in the grains of the first cap region may be higher than that in the grains of the effective region.

[0022] The material of the grains in the second capping region can be the same as the material of the grains in the effective region.

[0023] The average grain size of the grains in the second capping region can be greater than the average grain size of the grains in the first capping region.

[0024] The average grain size of the grains in the first capping region can be from 100 nm to 180 nm.

[0025] The average grain size of the grains in the second capping region can be 200 nm or larger.

[0026] The average grain size of the first capping region can be from 100 nm to 180 nm, and the average grain size of the second capping region can be 200 nm or larger.

[0027] According to an embodiment, a board assembly in which a multilayer capacitor is mounted includes: a substrate having a plurality of electrode pads disposed on an upper surface of the substrate; and the multilayer capacitor mounted on the substrate such that the external electrode of the multilayer capacitor is mounted on the plurality of electrode pads. The multilayer capacitor includes: a capacitor body including an effective region and an upper cover and a lower cover, the effective region having dielectric layers and internal electrodes alternately stacked therein, the upper cover and the lower cover being disposed on the upper surface and lower surface of the effective region, respectively; and an external electrode disposed on the outer surface of the capacitor body. In the upper cover and the lower cover, the portion of the upper cover and the lower cover located between the boundary surface of the effective region and the boundary surface of the capacitor body includes two cover regions, and in the two cover regions, a first cover region adjacent to the effective region includes grains with a Sn-doped core-shell structure. The first cover region includes 20% or more Sn-doped core-shell structure grains compared to the total number of grains in the first cover region.

[0028] According to an embodiment, a multilayer capacitor includes: a capacitor body including an effective region and an upper cover and a lower cover, the effective region having dielectric layers and internal electrodes alternately stacked therein, the upper cover and the lower cover being disposed on an upper surface and a lower surface of the effective region, respectively; and an external electrode disposed on an outer surface of the capacitor body. At least one of the upper cover and the lower cover includes a first region and a second region, the first region being adjacent to the effective region and the second region being adjacent to a boundary surface of the capacitor body. The first region includes grains with a core-shell structure, the core-shell grains being doped with more Sn than the grains in the second region. The average grain size of the grains in the second region is larger than the average grain size of the grains in the first region.

[0029] The grains contained in the second region may not contain Sn.

[0030] The molar ratio of Ba to Ti in the grains of the first region may be higher than that in the grains of the effective region.

[0031] The material of the grains in the second region may be the same as the material of the grains in the effective region.

[0032] The average particle size of the first region can be from 100 nm to 180 nm, and the average particle size of the second region can be 200 nm or larger. Attached Figure Description

[0033] The above and other aspects, features, and advantages of this disclosure will be more clearly understood from the following detailed embodiments, taken in conjunction with the accompanying drawings, in which:

[0034] Figure 1 This is a perspective view schematically showing a portion of a multilayer capacitor according to an exemplary embodiment;

[0035] Figure 2 It is along Figure 1 A cross-sectional view taken from line I-I';

[0036] Figure 3 It is along Figure 1 A cross-sectional view taken from line II-II′;

[0037] Figure 4 yes Figure 1 Enlarged view of region A;

[0038] Figure 5 This is a perspective view schematically showing a plate assembly in which a multilayer capacitor is mounted according to an exemplary embodiment, and is a view showing a portion of the multilayer capacitor being cut off;

[0039] Figure 6 It is along Figure 5 A cross-sectional view taken from line III-III′;

[0040] Figure 7 and Figure 8 The image is an analytical transmission electron microscope-energy dispersive spectroscopy (TEM-EDS) image at the boundary between the effective area and the top cover;

[0041] Figure 9 This is an enlarged scanning electron microscope (SEM) image showing the grain structure in the first cap region;

[0042] Figure 10 This is a magnified SEM image showing the grain structure in the second cap region;

[0043] Figure 11 It is a graph showing the grain size in the first and second capping regions;

[0044] Figure 12 This is a graph showing the moisture resistance of a comparative example when the ratio of the number of Sn-doped core-shell grains in the first cap region to the total number of grains in the first cap region is 18%; and

[0045] Figure 13 This is a graph illustrating the moisture resistance when the ratio of the number of Sn-doped core-shell structured grains in the first cap region to the total number of grains in the first cap region is 20%, according to an exemplary embodiment. Detailed Implementation

[0046] The following detailed embodiments are provided to aid the reader in gaining a comprehensive understanding of the methods, apparatus, and / or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatus, and / or systems described herein will be readily understood by those skilled in the art. The order of operations described herein is merely illustrative and is not limited to the order presented; changes that will be readily understood by those skilled in the art may be made, except for operations that must occur in a specific order. Furthermore, for clarity and brevity, descriptions of functions and constructions well-known to those skilled in the art may be omitted.

[0047] The features described herein may be implemented in different forms and are not to be construed as being limited to the examples described herein. Rather, the examples described herein have been provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0048] Note here that the use of the term "may" in relation to an embodiment or example (e.g., what an embodiment or example may include or implement) means that there exists at least one embodiment or example that includes or implements such a feature, and is not limited to all embodiments or examples including or implementing such a feature.

[0049] Throughout the specification, when an element (such as a layer, region, or substrate) is described as being "on" another element, "connected to" another element, or "bonded to" another element, that element may be directly "on" that other element, directly "connected to" that other element, or directly "bonded to" that other element, or there may be one or more other elements in between. In contrast, when an element is described as being "directly on" another element, "directly connected to" another element, or "directly bonded to" another element, there are no other elements in between.

[0050] As used herein, the term “and / or” includes any one or any combination of any two or more of the relevant listed items.

[0051] Although terms such as “first,” “second,” and “third” may be used herein to describe various components, assemblies, regions, layers, or parts, these components, assemblies, regions, layers, or parts are not limited by these terms. Rather, these terms are used only to distinguish one component, assembly, region, layer, or part from another. Therefore, without departing from the teachings of the examples described herein, the first component, first assembly, first region, first layer, or first part mentioned in the examples may also be referred to as a second component, second assembly, second region, second layer, or second part.

[0052] For ease of description, spatial relative terms such as “above,” “up,” “below,” and “down” are used herein to describe the relationship between one element and another, as shown in the accompanying drawings. Such spatial relative terms are intended to encompass not only the orientation depicted in the drawings but also different orientations of the device during use or operation. For example, if the device in the drawings is flipped, the element described as being “above” or “up” relative to another element will then be “below” or “down” relative to that other element. Therefore, the term “above” encompasses both “above” and “below” orientations depending on the spatial orientation of the device. The device may also be positioned in other ways (e.g., rotated 90 degrees or in other orientations), and the spatial relative terms used herein will be interpreted accordingly.

[0053] The terminology used herein is for the purpose of describing various examples only and is not intended to limit this disclosure. Unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. The terms “comprising,” “including,” and “having” enumerate the presence of the stated features, quantities, operations, components, elements, and / or combinations thereof, but do not exclude the presence or addition of one or more other features, quantities, operations, components, elements, and / or combinations thereof.

[0054] The shapes shown in the accompanying drawings may vary due to manufacturing techniques and / or tolerances. Therefore, the examples described herein are not limited to the specific shapes shown in the drawings, but include changes in shape that occur during manufacturing.

[0055] The features of the examples described herein can be combined in a variety of ways that will be readily understood after an understanding of the disclosure of this application. Furthermore, although the examples described herein have various configurations, other configurations that will be readily understood after an understanding of the disclosure of this application are possible.

[0056] For clarity, illustration and convenience, the accompanying drawings may not be drawn to scale, and the relative sizes, proportions and depictions of elements in the drawings may be exaggerated.

[0057] Figure 1 This is a schematic perspective view showing a portion of a multilayer capacitor obtained by cutting a multilayer capacitor according to an embodiment. Figure 2 It is along Figure 1 The cross-sectional view taken by line I-I', and Figure 3 It is along Figure 1 The cross-sectional view taken from line II-II'.

[0058] Reference Figures 1 to 3 According to an embodiment, the multilayer capacitor 100 includes a capacitor body 110, a first external electrode 131, and a second external electrode 132.

[0059] According to the embodiment, the Z direction shown in the figure represents the thickness direction of the capacitor body 110, the X direction represents the length direction of the capacitor body 110, and the Y direction represents the width direction of the capacitor body 110.

[0060] In this case, the Z direction can refer to the stacking direction of the inner electrode and the dielectric layer.

[0061] The capacitor body 110 may have a first surface 1 and a second surface 2 that are opposite to each other in the Z direction, a third surface 3 and a fourth surface 4 that are opposite to each other in the X direction, and a fifth surface 5 and a sixth surface 6 that are opposite to each other in the Y direction.

[0062] There are no particular restrictions on the shape of the capacitor body 110. For example, the capacitor body 110 may not have a perfectly straight hexahedral shape, but may have an approximate hexahedral shape.

[0063] The capacitor body 110 includes an effective area 115, an upper cover 140, and a lower cover 150, with the upper cover 140 and the lower cover 150 respectively disposed above and below the effective area 115.

[0064] The effective region 115 includes multiple dielectric layers 111, multiple first internal electrodes 121, and multiple second internal electrodes 122.

[0065] According to an embodiment, the effective region 115 can be formed by alternately stacking the first inner electrode 121 and the second inner electrode 122 and the dielectric layer 111 in the Z direction.

[0066] In this embodiment, unless otherwise stated, the upper cover 140 and the lower cover 150 are not separately distinguished from each other in the capacitor body, and it is understood that the upper cover 140 and the lower cover 150 are respectively the regions between the effective area 115 and the second surface 2 and the first surface 1 of the capacitor body 110 that are opposite each other in the Z direction.

[0067] The dielectric layer 111 may include a ceramic material with a high dielectric constant, and may include, for example, barium titanate (BaTiO3) based powder or strontium titanate (SrTiO3) based powder, but there are no particular limitations on the material of the dielectric layer 111, as long as sufficient capacitance can be obtained.

[0068] In addition, if desired, ceramic additives, organic solvents, plasticizers, binders and dispersants may be used together with ceramic powder as materials for forming dielectric layer 111.

[0069] Transition metal oxides, transition metal carbides, rare earth elements, magnesium (Mg), aluminum (Al), etc., can be used as ceramic additives, but this disclosure is not limited thereto.

[0070] In this case, the thickness of dielectric layer 111 can be arbitrarily changed according to the capacitance design of multilayer capacitor 100.

[0071] The first inner electrode 121 and the second inner electrode 122 may be alternately arranged in the Z direction, and the dielectric layer 111 is located between the first inner electrode 121 and the second inner electrode 122.

[0072] The first inner electrode 121 and the second inner electrode 122 can be electrically insulated from each other by a dielectric layer 111 disposed between the first inner electrode 121 and the second inner electrode 122.

[0073] In addition, the first inner electrode 121 and the second inner electrode 122 are electrodes to which voltages of different polarities are applied, and the first inner electrode 121 and the second inner electrode 122 can be formed by printing a conductive paste containing conductive metal of a predetermined thickness on one surface of the dielectric layer 111.

[0074] The first internal electrode 121 may be exposed through the third surface 3 of the capacitor body 110 (or in contact with or extending from the third surface 3 of the capacitor body 110), and the second internal electrode 122 may be exposed through the fourth surface 4 of the capacitor body 110 (or in contact with or extending from the fourth surface 4 of the capacitor body 110).

[0075] The first inner electrode 121 and the second inner electrode 122 can be connected to the first outer electrode 131 and the second outer electrode 132 respectively through the portions of the first inner electrode 121 and the second inner electrode 122 exposed on the outer surface of the capacitor body 110.

[0076] Therefore, when a voltage is applied to the first external electrode 131 and the second external electrode 132, charge accumulates between the first internal electrode 121 and the second internal electrode 122 facing each other, and in this case, the capacitance of the multilayer capacitor 100 is proportional to the area of ​​the overlapping region of the first internal electrode 121 and the second internal electrode 122 in the effective region 115.

[0077] In addition, the conductive metal contained in the conductive paste forming the first inner electrode 121 and the second inner electrode 122 may be nickel (Ni), copper (Cu), palladium (Pd) or alloys thereof, and this disclosure is not limited thereto.

[0078] The first external electrode 131 and the second external electrode 132 can be disposed at both ends of the capacitor body 110 in the X direction to be connected to the first internal electrode 121 and the second internal electrode 122, respectively.

[0079] In this case, the first external electrode 131 and the second external electrode 132 include conductive layers formed on the third surface 3 and the fourth surface 4 of the capacitor body 110, respectively, and if necessary, the first external electrode 131 and the second external electrode 132 may also include plating formed on the conductive layers.

[0080] The coating may include a nickel (Ni) coating formed on a conductive layer and a tin (Sn) coating formed on a nickel (Ni) coating.

[0081] The first external electrode 131 may include a first connecting portion 131a and a first strip portion 131b.

[0082] The first connecting portion 131a is formed on the third surface 3 of the capacitor body 110 and connected to the exposed portion of the first internal electrode 121, and the first strip portion 131b is a portion extending from the first connecting portion 131a to a portion of the first surface 1 of the capacitor body 110.

[0083] In this case, the first strip 131b may also extend to a portion of the fifth surface 5, a portion of the sixth surface 6, and a portion of the second surface 2 of the capacitor body 110 to improve the fixing strength.

[0084] The second external electrode 132 may include a second connecting portion 132a and a second strip portion 132b.

[0085] The second connecting portion 132a is formed on the fourth surface 4 of the capacitor body 110 and is connected to the exposed portion of the second inner electrode 122, and the second strip portion 132b is a portion extending from the second connecting portion 132a to a portion of the first surface 1 of the capacitor body 110.

[0086] In this case, the second strip 132b may also extend to a portion of the fifth surface 5 and a portion of the sixth surface 6 of the capacitor body 110 as well as a portion of the second surface 2 to improve the fixing strength.

[0087] Figure 7 and Figure 8 These are images analyzed by TEM-EDS at the boundary between the effective area and the top cover. Figure 9 This is a magnified SEM image showing the grain structure in the first cap region. Figure 10 This is a magnified SEM image showing the grain structure in the second cap region. Figure 11 It is a graph showing the grain size of the grains in the first and second capping regions. Figure 12 This is a graph showing the moisture resistance of a comparative example when the ratio of the number of Sn-doped core-shell structured grains in the first cap region to the total number of grains in the first cap region is 18%. Figure 13 This is a graph illustrating the moisture resistance of an exemplary embodiment when the ratio of the number of Sn-doped core-shell structure grains in the first cap region to the total number of grains in the first cap region is 20%.

[0088] Reference Figures 7 to 11 It can be seen that the grain size of the first cover region 141 (which will be described in detail later) of the upper cover 140 is smaller than the grain size of the second cover region 142 (which will be described in detail later) and the grain size of the effective region 115, and the density of the first cover region 141 is relatively high. Here, the grain size can be the average grain size, the maximum grain size, or the minimum grain size.

[0089] Figure 7 and Figure 8 The TEM-EDS mapping image is the result of applying a core-shell structure powder doped with 3 mol of Sn (relative to 100 mol of Ba) to the first cap region. The grains included in the second cap region do not contain Sn.

[0090] from Figure 7 and Figure 8 In this process, the shape of the grains formed by sintering Sn-doped powder can be determined, thus revealing the structural differences between the first cap region and the effective region. Figure 8 A diagram of a grain with a core-shell structure doped with Sn is shown. Here, C represents the core in the core-shell structure.

[0091] The method for analyzing Sn content is as follows.

[0092] A thinned analytical sample (i.e., a sheet sample) is prepared by thinning a sintered multilayer capacitor to the YZ section at the center of the multilayer capacitor in the X direction using a focused ion beam (FIB) device. The damaged layer on the surface of the sheet sample is then removed using argon (Ar) ion milling.

[0093] Then, using scanning transmission electron microscopy-energy-dissipative-X-ray detector (STEM-EDX), mapping and quantitative analysis of Ba and Sn were performed on the three dielectric layers located at the center of the YZ section. The number of Sn-doped core-shell grains was confirmed in the mapping images, and the ratio of Sn-doped core-shell grains to undoped Sn grains was obtained.

[0094] In addition, the ratio of Sn content to Ba content in a grain is calculated and expressed as the molar ratio of Sn in the Sn-doped portion of a grain to Ba in the grain (i.e., coverage).

[0095] Reference Figure 7 and Figure 8 In a core-shell structured grain doped with Sn in the first cap region, the molar ratio of Sn in the Sn-doped portion of a grain to Ba in the grain is defined as the coverage, and when analyzing a grain, the coverage is confirmed to be 30% or higher.

[0096] If the coverage in the first cap region is less than 30%, the doping effect of Sn is reduced. In this case, similar to using ordinary BT (e.g., BaTiO3), grain growth occurs during sintering, and there may be a problem of deterioration in the densification of the first cap region.

[0097] Unlike the edges in the capacitor body, if excessive abnormal grain growth occurs in the cap, the effect of abnormal grain growth will affect the effective region, and a portion of the effective region may not be properly sintered, leading to low capacitance.

[0098] This problem can be prevented by varying the Sn doping amount during cap stacking. As the Sn doping amount increases, the effect of aberrant grain growth during the sintering process becomes relatively stronger. Therefore, by reducing the Sn doping amount in the first cap region to 1 mol to 3 mol (relative to 100 mol Ba), after sintering, the occupancy rate of Sn-doped core-shell structured grains relative to the total grains in the entire first cap region is ensured to be 20% or greater, reducing the problem of unsintered grains in the effective region due to aberrant grain growth occurring at doping amounts greater than 3 mol (relative to 100 mol Ba). In one example, the grain occupancy rate can refer to the ratio, for example, the number of Sn-doped core-shell structured grains in a region of the first cap region (such as a length-thickness cross-section cut at the center in the width direction or a width-thickness cross-section cut at the center in the length direction) measured by, for example, STEM-EDX, to the total number of grains in said region of the first cap region. These effects and principles apply to the cap structure of this embodiment. (Refer to...) Figure 12 and Figure 13 The multilayer capacitors used in this test have a length × width of 0.4 mm × 0.2 mm (product tolerance ±0.1 mm), 267 stacked internal electrodes, and a capacitance of approximately 0.9 μF. The test aims to measure the insulation resistance (IR) using 20 such multilayer capacitors and thereby determine their moisture resistance reliability. Figure 12 and Figure 13 In the graph, the horizontal axis represents time, and the vertical axis represents insulation resistance (Ω). (Refer to...) Figure 12 Some multilayer capacitors in the comparative examples exhibit IR reduction issues. In contrast, the reference... Figure 13 In the case of the multilayer capacitor according to the exemplary embodiment, grains with a core-shell structure doped with Sn are applied. Due to the relatively small grain size and improved density, the IR shows almost no change. Therefore, it can be seen that the multilayer capacitor according to the exemplary embodiment has no problem in terms of moisture resistance.

[0099] In this embodiment, with the upper cover 140 and the lower cover 150, the portions of the upper cover 140 and the lower cover 150 located between the boundary surface of the effective region 115 and the boundary surface of the capacitor body 110 are each divided into two regions. The portions of the two regions adjacent to the effective region 115 are defined as first cover regions 141 and 151, and the portions of the two regions adjacent to the boundary surface of the capacitor body 110 are defined as second cover regions 142 and 152.

[0100] Figure 4 Area A is Figure 1 An enlarged view of a portion of the upper cover 140. The only difference between the upper cover 140 and the lower cover 150 is that the lower cover 150 is located on the first surface 1 side of the capacitor body 110. Since the upper cover 140 and the lower cover 150 are similar in construction, the description will be based on the upper cover 140, but it is thought that the description of the upper cover 140 can be applied to the lower cover 150.

[0101] In the first capping region 141 adjacent to the boundary surface of the effective region 115, 20% or more of the total number of grains in the entire first capping region 141 may contain grains with abnormal grain growth.

[0102] The grains grown by anomalous grain growth have a core-shell structure doped with Sn, wherein the shell portion, which serves as the B site, is doped with Sn.

[0103] Additionally, the second cover region 142, which is adjacent to the second surface 2 of the capacitor body 110 as a boundary surface, includes grains that do not contain Sn and are grown normally.

[0104] The molar ratio of Ba to Ti in the abnormal grain growth included in the first cap region 141 is higher than that of Ba to Ti in ordinary BT. Therefore, the molar ratio of Ba to Ti in the first cap region 141 can be higher than that of Ba to Ti in the effective region 115.

[0105] In addition, relative to the total number of grains in the first cap region 141, the first cap region 141 may include 20% or more of grains with a core-shell structure doped with Sn.

[0106] Therefore, as from Figures 9 to 11 As can be seen, when using grains with a core-shell structure doped with Sn, the grain size is relatively smaller and the density is improved compared to ordinary BT.

[0107] When rapid heating firing conditions are applied due to the recent miniaturization of MLCC wafers, relatively smaller grains can be formed, and excessive grain growth including in the first cap region 141 is suppressed, reducing the grain size to 180 nm or smaller (specifically, 100 nm to 180 nm), and the densification degree of the first cap region 141 can be increased compared to the densification degree of the second cap region 142. In one example, the average grain size of the grains in the first cap region 141 may refer to the arithmetic mean grain size of the grains in the first cap region 141, but this disclosure is not limited thereto, and the average grain size of the grains in the first cap region 141 may be 180 nm or smaller (specifically, 100 nm to 180 nm). For example, a scanning electron microscope (SEM) can be used to measure the average grain size. Other methods and / or tools understood by those skilled in the art may be used even if not described in this disclosure.

[0108] In this case, if the ratio of the number of Sn-doped core-shell structure grains in the first cap region 141 to the total number of grains in the first cap region 141 is less than 20%, the effect of abnormal grain growth of the Sn-doped core-shell structure powder is not significant. Therefore, there may be problems such as grain growth and relatively low densification characteristics as in the case of using a conventional BT cap.

[0109] In addition, the thickness of the first cover area 141 can be 40% to 80% of the sum of the thicknesses of the first cover area 141 and the second cover area 142.

[0110] If the thickness of the first capping region 141 is less than 40%, the densification effect of the Sn-doped powder and the abnormal grain growth are not significant. When the thickness of the first capping region 141 exceeds 80%, relatively small grains are formed due to the abnormal grain growth of the Sn-doped powder. The relatively small grains also affect the effective region 115. Therefore, it may be difficult to realize the capacitor due to the abnormal grain growth of the effective region 115.

[0111] Therefore, when the ratio (40% to 80%) is met, the first cover region 141 can significantly reduce the impact of firing behavior on the effective region 115 at a suitable firing temperature for achieving sheet characteristics, and can also improve the degree of densification.

[0112] In this embodiment, the second cap region 142 includes grains that grow normally without containing Sn, and does not include grains with a core-shell structure (where the shell portion is doped with Sn).

[0113] For example, the grains in the second cover region 142 may be formed using the same material as the grains included in the effective region 115, instead of using the same material as the grains included in the first cover region 141.

[0114] Therefore, as Figures 9 to 11 As shown, the grain size of the grains included in the second capping region 142 may be larger than the grain size of the grains in the first capping region 141, and specifically, the grain size of the grains included in the second capping region 142 may be 200 nm or larger. In one example, the average grain size of the grains in the second capping region 142 may refer to the arithmetic mean grain size of the grains in the second capping region 142, but this disclosure is not limited thereto, and the average grain size of the grains in the second capping region 142 may be 200 nm or larger, and larger than the average grain size of the first capping region 141.

[0115] In the prior art, the density of the cap is ensured by adjusting the molar ratio of Ba and Ti in the composition constituting the cap.

[0116] Specifically, the capacitor body is formed by stacking caps on the upper and lower parts of the effective region, the caps having a molar ratio of Ba and Ti that ensures densification at the sintering temperature for achieving the appropriate capacitance of a multilayer capacitor.

[0117] In this case, since the cap is formed by controlling only the number of stacked dielectric layers with a single matrix material, it is difficult to control the sintering behavior based on the location of the cap.

[0118] Therefore, the particle size decreases and the densification level drops from the inside to the outside of the cap. Thus, densification can be ensured inside the cap, but significantly reduced on the outside, thereby affecting the moisture resistance of the multilayer capacitor.

[0119] However, if the densification of the cap is improved by simply reducing the molar ratio of Ba and Ti, the cap may shrink excessively due to over-sintering compared to the effective region. Therefore, there may be problems with chip shape deformation or excessive grain growth in the effective region.

[0120] In this situation, due to excessive grain growth, electrode aggregation or breakdown voltage (BDV) degradation may occur.

[0121] In this embodiment, after the first cover region 141 is first formed on the effective region 115, the second cover region 142 is formed on the first cover region 141, and the second cover region 142 is formed using a material with a relatively higher sintering driving force compared to the first cover region 141, thereby reducing the frequency of holes appearing in the exterior of the upper cover 140 (i.e., the second cover region 142).

[0122] Furthermore, since a matrix material with a size larger than that of the dielectric matrix material used in the first cover region 141 (e.g., the grain size of the matrix material) is applied to the second cover region 142 to increase the grain growth driving force, the densification degree of the second cover region 142, which serves as the exterior of the top cover 140, is lower than that of the first cover region 141, which can improve properties such as toughness and hardness.

[0123] Therefore, the reliability of the multilayer capacitor 100 can be improved, and the cracking rate can be reduced.

[0124] Figure 5 This is a schematic perspective view of a plate assembly in which a multilayer capacitor is mounted according to an embodiment, and a partial cross-sectional view of the multilayer capacitor is shown. Figure 6 It is along Figure 5 The cross-sectional view taken from line III-III'.

[0125] Reference Figure 5 and Figure 6 According to this embodiment, the board assembly on which the multilayer capacitor is mounted includes a multilayer capacitor 100 and a substrate 210 on which the multilayer capacitor 100 is mounted.

[0126] In this case, the multilayer capacitor 100 is a multilayer capacitor according to an embodiment of the present disclosure, and its detailed description will be omitted to avoid repetition.

[0127] The substrate 210 includes a first electrode pad 221 and a second electrode pad 222 formed on the upper surface of the substrate 210.

[0128] The first electrode pad 221 and the second electrode pad 222 can be connected to the first external electrode 131 and the second external electrode 132 of the multilayer capacitor 100, respectively.

[0129] For example, when the first external electrode 131 and the second external electrode 132 of the multilayer capacitor 100 are positioned to contact the first electrode pad 221 and the second electrode pad 222 respectively, the first external electrode 131 and the second external electrode 132 can be mounted on the substrate 210 by solder 231 and 232 respectively.

[0130] As described above, according to the embodiments, in the cap of the capacitor body, the inner first cap region can have a relatively high degree of densification without affecting the realization of the sheet characteristics, and the outer second cap region is configured to induce grain growth, thereby ensuring the characteristics of the multilayer capacitor, such as toughness and hardness, at a certain level or higher.

[0131] While this disclosure includes specific examples, it will be readily understood by those skilled in the art that various changes in form and detail may be made to these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered descriptive only and not for limiting purposes. The description of features or aspects in each example is to be considered applicable to similar features or aspects in other examples. Suitable results may be achieved if the described techniques are performed in a different order, and / or if components in the described system, architecture, apparatus, or circuit are combined in a different manner, and / or if components in the described system, architecture, apparatus, or circuit are replaced or added by other components or their equivalents. Therefore, the scope of this disclosure is not limited by the specific embodiments but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents shall be construed as included in this disclosure.

Claims

1. A multilayer capacitor, comprising: A capacitor body includes an effective region and an upper cover and a lower cover, the effective region having dielectric layers and internal electrodes alternately stacked therein, the upper cover and the lower cover being disposed on the upper surface and lower surface of the effective region, respectively; as well as External electrodes are disposed on the outer surface of the capacitor body. In at least one of the upper cover and the lower cover, the portion of the upper cover and the lower cover located between the boundary surface of the effective region and the boundary surface of the capacitor body is divided into a first cover region and a second cover region. The first cover region is adjacent to the effective region, and the second cover region is adjacent to the boundary surface of the capacitor body. The first cover region includes grains with a core-shell structure doped with Sn. Compared to the total number of grains in the first cap region, the first cap region comprises 20% or more of grains with a core-shell structure doped with Sn.

2. The multilayer capacitor according to claim 1, wherein, In the core-shell structured grains with Sn doping, the molar ratio of Sn in the Sn-doped portion of a grain to Ba in the grain is called the coverage, and the coverage is 30% or greater.

3. The multilayer capacitor according to claim 1, wherein, The grains included in the second capping region do not include Sn.

4. The multilayer capacitor according to claim 1, wherein, The grain size of the second capping region is larger than that of the grain size of the first capping region.

5. The multilayer capacitor according to claim 1, wherein, The thickness of the first cover area is 40% to 80% of the sum of the thicknesses of the first cover area and the second cover area.

6. The multilayer capacitor according to claim 1, wherein, The grain size of the second capping region is larger than the grain size of the first capping region, and The thickness of the first cover area is 40% to 80% of the sum of the thicknesses of the first cover area and the second cover area.

7. The multilayer capacitor according to claim 1, wherein, The grain size of the first capping region is 100 nm to 180 nm.

8. The multilayer capacitor according to claim 1, wherein, The grain size of the second capping region is 200 nm or larger.

9. The multilayer capacitor according to claim 1, wherein, The grain size of the first cap region is 100 nm to 180 nm, and The grain size of the second capping region is 200 nm or larger.

10. The multilayer capacitor according to claim 1, wherein, The molar ratio of Ba to Ti in the grains of the first cap region is higher than that in the grains of the effective region.

11. The multilayer capacitor according to claim 1, wherein, The material of the grains in the second capping region is the same as the material of the grains in the effective region.

12. The multilayer capacitor according to claim 1, wherein, The average grain size of the grains in the second capping region is greater than the average grain size of the grains in the first capping region.

13. The multilayer capacitor according to claim 1, wherein, The average grain size of the grains in the first capping region is 100 nm to 180 nm.

14. The multilayer capacitor according to claim 1, wherein, The average grain size of the grains in the second capping region is 200 nm or larger.

15. The multilayer capacitor according to claim 1, wherein, The average grain size of the grains in the first capping region is 100 nm to 180 nm, and The average particle size of the second capping region is 200 nm or larger.

16. A plate assembly in which a multilayer capacitor is mounted, the plate assembly comprising: A substrate having a plurality of electrode pads disposed on the upper surface of the substrate; as well as The multilayer capacitor is mounted on the substrate such that its external electrodes are mounted on the plurality of electrode pads. The multilayer capacitor includes: A capacitor body includes an effective region and an upper cover and a lower cover. The effective region has dielectric layers and internal electrodes alternately stacked therein. The upper cover and the lower cover are respectively disposed on an upper surface and a lower surface of the effective region. External electrodes are disposed on the outer surface of the capacitor body. In at least one of the upper cover and the lower cover, the portion of the upper cover and the lower cover located between the boundary surface of the effective region and the boundary surface of the capacitor body includes two cover regions, and in the two cover regions, the first cover region adjacent to the effective region includes grains with a core-shell structure doped with Sn. Compared to the total number of grains in the first cap region, the first cap region comprises 20% or more of grains with a core-shell structure doped with Sn.

17. The plate assembly of claim 16, wherein, Of the two capping regions, the second capping region adjacent to the boundary surface of the capacitor body does not include Sn-containing grains.

18. A multilayer capacitor, comprising: A capacitor body includes an effective region and an upper cover and a lower cover, the effective region having dielectric layers and internal electrodes alternately stacked therein, the upper cover and the lower cover being disposed on the upper surface and lower surface of the effective region, respectively; as well as External electrodes are disposed on the outer surface of the capacitor body. Wherein, at least one of the upper cover and the lower cover includes a first region and a second region, the first region being adjacent to the effective region, and the second region being adjacent to the boundary surface of the capacitor body. The first region includes grains with a core-shell structure, wherein the grains with the core-shell structure are doped with more Sn than the grains in the second region, and The average grain size of the grains in the second region is greater than that of the grains in the first region.

19. The multilayer capacitor according to claim 18, wherein, The grains contained in the second region do not contain Sn.

20. The multilayer capacitor according to claim 18, wherein, The molar ratio of Ba to Ti in the grains of the first region is higher than that in the grains of the effective region.

21. The multilayer capacitor according to claim 18, wherein, The material of the grains in the second region is the same as the material of the grains in the effective region.

22. The multilayer capacitor according to claim 18, wherein, The average grain size of the grains in the first region is 100 nm to 180 nm, and The average grain size of the grains in the second region is 200 nm or larger.

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