Multilayer capacitor

Abstract

The present disclosure provides a multilayer capacitor. The multilayer capacitor includes a main body including a plurality of dielectric layers and a plurality of internal electrodes stacked in a first direction, and an external electrode. The main body includes an effective portion in which the plurality of internal electrodes are provided to form a capacitance, a cover portion covering the effective portion in the first direction, and a side edge portion covering the effective portion in a second direction perpendicular to the first direction, and 1.49 < A1 / A2 < 2.50, where A1 is an average grain size of the dielectric layers in a central region of the effective portion, and A2 is an average grain size of the dielectric layers in an effective-cover boundary portion of the effective portion adjacent to the cover portion.

Description

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2020-0186436, filed on December 29, 2020, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] This disclosure relates to a multilayer capacitor. Background Technology

[0003] A capacitor is a device that stores electrical charge. In a capacitor, when a voltage is applied, charge typically accumulates in each of the two opposing electrodes. When a direct current (DC) voltage is applied, current flows in the capacitor, and charge accumulates. When the accumulation is complete, no current flows. On the other hand, when an alternating current (AC) voltage is applied, AC current flows, and the polarity of the electrodes changes.

[0004] Various types of capacitors can exist, depending on the material of the electrodes or the type of insulating material disposed between the electrodes. These include aluminum electrolytic capacitors (comprising aluminum electrodes and a thin oxide film disposed between the aluminum electrodes), tantalum capacitors using tantalum as the electrode material, ceramic capacitors using a dielectric material with a high dielectric constant (such as barium titanate) between the electrodes, multilayer ceramic capacitors (MLCCs) using a ceramic material with a high dielectric constant as the dielectric material disposed between the electrodes in a multilayer structure, and thin film capacitors using polystyrene film as the dielectric material disposed between the electrodes.

[0005] Among these capacitors, multilayer ceramic capacitors offer excellent temperature and frequency characteristics and can be manufactured in small sizes, making them increasingly popular in devices across various fields, such as radio frequency (RF) circuits. Recently, efforts have been made to achieve smaller multilayer ceramic capacitors. To this end, the dielectric layer and internal electrodes have been designed with reduced thickness. However, as the component size decreases, it may be difficult to improve electrical and structural reliability. Summary of the Invention

[0006] One aspect of this disclosure is to provide a multilayer capacitor that has improved reliability, such as withstand voltage characteristics and capacitance characteristics, by adjusting the average grain size of the dielectric layer in each region.

[0007] According to an aspect of the present disclosure, a multilayer capacitor includes: a main body including a plurality of dielectric layers and a plurality of internal electrodes, the plurality of internal electrodes being stacked in a first direction with respective dielectric layers interposed therebetween; and an external electrode formed on an outer surface of the main body and connected to the internal electrodes. The main body includes an active portion, a cover portion, and a side margin portion, wherein the plurality of internal electrodes are disposed in the active portion to form a capacitance, the active portion corresponds to a region between the internal electrodes disposed at an outermost side in the first direction among the plurality of internal electrodes, the cover portion covers the active portion in the first direction, the side margin portion covers the active portion in a second direction perpendicular to the first direction, and 1.49<A1 / A2<2.50, wherein A1 is an average crystal grain size of the dielectric layers in a central region of the active portion, and A2 is an average crystal grain size of the dielectric layers in an active-cover boundary portion of the active portion adjacent to the cover portion.

[0008] A1 may be an average size of crystal grains present in an A1 rectangle on a cut surface of the main body, the A1 rectangle may have a horizontal length of WA / 3 and a vertical length of TA / 3, and the A1 rectangle may be symmetrical with respect to a center line along the first direction and a center line along the second direction of the active portion, wherein based on the cut surface of the main body, TA is a length of the active portion in the first direction, and WA is a length of the active portion in the second direction, and the cut surface of the main body is perpendicular to a third direction, the third direction being perpendicular to the first direction and the second direction.

[0009] A2 may be an average size of crystal grains present in an A2 rectangle on the cut surface, the A2 rectangle may have a horizontal length of WA / 3 and a vertical length of TA / 6, and the A2 rectangle may be symmetrical with respect to the center line along the first direction of the active portion and may be in contact with the internal electrode disposed at the outermost side in the first direction among the plurality of internal electrodes.

[0010] C1<M1, wherein C1 is an average crystal grain size of the dielectric layers in a central region of the cover portion, and M1 is an average crystal grain size of the dielectric layers in a central region of the side margin portion.

[0011] C1 may be an average size of crystal grains present in a C1 rectangle on a cut surface of the main body, the C1 rectangle may have a horizontal length of WA / 3 and a vertical length of TC / 3, and the C1 rectangle may be symmetrical with respect to a centerline of the covering portion along a first direction and a centerline along a second direction, wherein, based on the cut surface of the main body, TC is a length of the covering portion in the first direction, WA is a length of the active portion in the second direction, the cut surface of the main body is perpendicular to a third direction, and the third direction is perpendicular to the first direction and the second direction.

[0012] M1 may be an average size of crystal grains present in an M1 rectangle on a cut surface of the main body, the M1 rectangle may have a horizontal length of WM / 3 and a vertical length of TA / 3, and the M1 rectangle may be symmetrical with respect to a centerline of the side edge portion along the first direction and a centerline along the second direction, wherein, based on the cut surface of the main body, WM is a length of the side edge portion in the second direction, TA is a length of the active portion in the first direction, the cut surface of the main body is perpendicular to a third direction, and the third direction is perpendicular to the first direction and the second direction.

[0013] 0.9 < C2 / M1 < 1.1, wherein C2 is an average crystal grain size of a dielectric layer in a covering-active boundary portion of the covering portion adjacent to the active portion.

[0014] C2 may be an average size of crystal grains present in a C2 rectangle on a cut surface of the main body, the C2 rectangle may have a horizontal length of WA / 3 and a vertical length of TC / 6, and the C2 rectangle may be symmetrical with respect to the centerline of the covering portion along the first direction and may be in contact with an innermost electrode disposed at an outermost position in the first direction among the plurality of internal electrodes, wherein, based on the cut surface of the main body, TC is a length of the covering portion in the first direction, WA is a length of the active portion in the second direction, the cut surface of the main body is perpendicular to a third direction, and the third direction is perpendicular to the first direction and the second direction.

[0015] The plurality of dielectric layers may include a barium titanate component, and a molar ratio of barium (Ba) to titanium (Ti) of the dielectric layer in a central region of the active portion is smaller than a molar ratio of Ba to Ti of the dielectric layer in a central region of the covering portion.

[0016] A molar ratio of Ba to Ti of the dielectric layer in a central region of the side edge portion may be smaller than a molar ratio of Ba to Ti of the dielectric layer in the central region of the covering portion, and may be larger than a molar ratio of Ba to Ti of the dielectric layer in the central region of the active portion.

[0017] At least one of the plurality of dielectric layers may have an average thickness of less than 0.4 μm.

[0018] According to another aspect of the present disclosure, a multilayer capacitor includes: a main body including a plurality of dielectric layers and a plurality of internal electrodes, the plurality of internal electrodes being stacked in a first direction with respective dielectric layers interposed therebetween, and an external electrode formed on an outer surface of the main body and connected to the internal electrodes. The main body includes an effective portion, in which the plurality of internal electrodes are disposed to form a capacitance, the effective portion corresponding to a region between the internal electrodes disposed at the outermost side in the first direction among the plurality of internal electrodes, a covering portion covering the effective portion in the first direction, and a side edge portion covering the effective portion in a second direction perpendicular to the first direction, and 1.14≤A1 / A3<1.50, where A1 is an average grain size of dielectric layers in a central region of the effective portion, and A3 is an average grain size of dielectric layers in an effective-side boundary portion of the effective portion adjacent to the side edge portion.

[0019] According to another aspect of the present disclosure, a multilayer capacitor includes: a capacitance forming portion including internal electrodes stacked in a thickness direction and dielectric layers disposed between the internal electrodes, wherein an average grain size of dielectric grains of the dielectric layers in a central region of the capacitance forming portion is A1; a dielectric covering portion disposed above and below the capacitance forming portion in the thickness direction, wherein an average grain size of dielectric grains in a boundary region of the capacitance forming portion adjacent to the dielectric covering portion is A2; and an external electrode disposed on opposite surfaces of the capacitance forming portion in a length direction, wherein 1.49<A1 / A2<2.50, and wherein the internal electrodes are disposed in a length-width plane perpendicular to the thickness direction, and the width direction is perpendicular to the thickness direction. Brief Description of the Drawings

[0020] The above and other aspects, features and advantages of the present disclosure will be more clearly understood through the following detailed description taken in conjunction with the accompanying drawings.

[0021] Figure 1 is a schematic perspective view showing the appearance of a multilayer capacitor according to an exemplary embodiment of the present disclosure.

[0022] Figure 2 is taken along Figure 1 along line I-I'.

[0023] Figure 3 is an enlarged cross-sectional view taken along Figure 1 along line II-II'.

[0024] Figure 4 It shows Figure 3 The main body is divided into various sub-regions.

[0025] Figures 5 to 9 The shape of the dielectric grains in each region of the body is shown. Detailed Implementation

[0026] In the following description, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0027] However, this disclosure may be exemplified in many different forms and should not be construed as being limited to the specific embodiments set forth herein. Rather, these embodiments are 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. Therefore, for clarity of description, the shape and size of the elements in the drawings may be exaggerated. Furthermore, the same reference numerals will be used to describe elements having the same function within the scope of the same concepts represented in the drawings of each exemplary embodiment.

[0028] In the accompanying drawings, the same elements will be represented by the same reference numerals. Furthermore, redundant and detailed descriptions of known functions and elements that may unnecessarily obscure the essential points of the invention will be omitted. In the drawings, some elements may be exaggerated, omitted, or briefly shown, and the dimensions of the elements do not necessarily reflect their actual dimensions. Moreover, it should be understood that, unless otherwise stated, when a portion “includes” an element, that portion may also include other elements, without excluding other elements.

[0029] Figure 1 This is a schematic perspective view showing the appearance of a multilayer capacitor according to an exemplary embodiment of the present disclosure. Figure 2 It is along Figure 1 The cross-sectional view taken from line I-I'. Figure 3 It is along Figure 1 An enlarged view of the cross-section taken from line II-II', and Figure 4 It shows Figure 3 The main body is divided into various sub-regions. Figures 5 to 9 The shape of the dielectric grains in each region of the body is shown.

[0030] Reference Figures 1 to 3 According to an exemplary embodiment, the multilayer capacitor 100 may include a body 110 and external electrodes 131 and 132. The body 110 includes a dielectric layer 111 and a plurality of internal electrodes 121 and 122, which are stacked in a first direction (X direction, thickness direction) and the dielectric layer 111 is located between the plurality of internal electrodes 121 and 122. The average grain size of the dielectric layer 111 can be adjusted for each region of the body 110.

[0031] The main body 110 may have a stacked structure in which multiple dielectric layers 111 are stacked in a first direction (X direction), and can be obtained, for example, by stacking multiple green sheets and sintering the stacked green sheets. Due to this sintering process, the multiple dielectric layers 111 can be in a monolithic form. Figure 1 As shown, the body 110 may have a shape similar to a cuboid. The dielectric layer 111 included in the body 110 may include a ceramic material with a high dielectric constant, such as barium titanate (BaTiO3)-based ceramic, but other materials known in the art may be used, provided that sufficient capacitance can be obtained. Depending on the need, in addition to the ceramic material as a main component, the dielectric layer 111 may also include additives, organic solvents, plasticizers, binders, and dispersants. Additives may include metallic components, and during the manufacturing process, additives may be added in the form of metal oxides. Examples of metal oxide additives include at least one of MnO2, Dy2O3, BaO, MgO, Al2O3, and Cr2O3. Additives may also include SiO2 and CaCO3.

[0032] Multiple internal electrodes 121 and 122 can be obtained by printing a paste containing a conductive metal to a predetermined thickness on one surface of a ceramic green sheet and sintering the printed paste. For example... Figure 2 As shown, the plurality of internal electrodes 121 and 122 may include a first internal electrode 121 and a second internal electrode 122, the first internal electrode 121 and the second internal electrode 122 being exposed to one surface and another surface of the body 110 that are opposite to each other in the third direction (Z direction), respectively. Figure 3 As shown, multiple inner electrodes 121 and 122 may be exposed on the first surface S1 and the second surface S2 of the effective portion 112 of the body 110, which are opposite to each other in a second direction (Y direction, width direction). When the direction in which the first surface S1 and the second surface S2 of the effective portion 112 of the body 110 are opposite to each other is referred to as the second direction (Y direction), the third direction (Z direction) may be a direction perpendicular to the first direction (X direction) and the second direction (Y direction). The first inner electrode 121 and the second inner electrode 122 may be connected to different outer electrodes 131 and 132 to have opposite polarities when driven, and the first inner electrode 121 and the second inner electrode 122 may be electrically isolated from each other by a dielectric layer 111 disposed therebetween. The number of outer electrodes 131 and 132 or the method of connecting the outer electrodes 131 and 132 to the inner electrodes 121 and 122 may be varied according to exemplary embodiments. The main material of the inner electrodes 121 and 122 may be nickel (Ni), copper (Cu), palladium (Pd), silver (Ag), or alloys thereof.

[0033] The outer electrodes 131 and 132 may be formed on the outer surface of the body 110, and may be connected to the inner electrodes 121 and 122. For example, the outer electrodes 131 and 132 may include a first outer electrode 131 and a second outer electrode 132 that are respectively connected to the first inner electrode 121 and the second inner electrode 122. In this case, the first outer electrode 131 and the second outer electrode 132 may be disposed opposite to each other in the third direction (Z direction). The outer electrodes may be formed by: preparing a material containing conductive metal into a paste, and applying the prepared paste to the body 110. Examples of the conductive metal may include nickel (Ni), copper (Cu), palladium (Pd), gold (Au), or alloys thereof. The outer electrodes 131 and 132 may further include a plating layer containing nickel (Ni), tin (Sn), or the like.

[0034] Reference Figure 3 In the present embodiment, the body 110 may include: an effective portion 112, in which a plurality of inner electrodes 121 and 122 are disposed to form a capacitance, the effective portion 112 corresponds to a region between the inner electrodes disposed at the outermost side in the first direction (X direction) among the plurality of inner electrodes 121 and 122; a covering portion 114 covering the effective portion 112 in the first direction (X direction); and a side edge portion 113 covering the effective portion 112 in the second direction (Y direction). The characteristics of the dielectric layers included in the side edge portion 113 and the covering portion 114 (for example, average grain size, Ba / Ti ratio, etc.) may be different from the characteristics of the dielectric layer 111 included in the effective portion 112. This is designed by analyzing factors that affect withstand voltage characteristics and the like in each region of the body 110. For example, the average grain size of the dielectric layer may be varied for each region of the body 110, which is adjusted in consideration of characteristics such as withstand voltage and high-temperature reliability.

[0035] The above content will be described in more detail with reference to Figure 4 below. In Figure 4 , each region of the body is subdivided, and the inner electrodes are not shown. In the present embodiment, A1 and A2 satisfy the condition of 1.49<A1 / A2<2.50, where A1 is the average grain size of the dielectric layer 111 in the central region of the effective portion 112, and A2 is the average grain size of the dielectric layer in the effective-covering boundary portion of the effective portion 112 adjacent to the covering portion 114. As described above, in the body 110, the effective portion 112 may be defined as a region between the inner electrodes 121 and 122 disposed at the outermost side in the first direction (X direction), and the covering portion 114 may be defined as a region extending outward in the first direction (X direction) from a region in contact with the inner electrodes 121 and 122 disposed at the outermost side to the surface of the body 110.

[0036] When A1 and A2 satisfy the condition of 1.49 < A1 / A2 < 2.50, the capacitance can be sufficiently ensured and the withstand voltage characteristics can be improved. For this reason, in the central region of the active portion 112 and the active-covering boundary portion, the grain growth rate can be changed so that the average grain size can be different, to ensure sufficient capacitance in the active portion 112 and improve the withstand voltage characteristics in the active-covering boundary portion through relatively fine and uniform grains. It can be seen from the experimental results described later that compared with the case where A1 / A2 is less than or equal to 1.49, when A1 / A2 is greater than 1.49, the capacitance or withstand voltage reliability can be improved. However, when A1 / A2 increases to 2.50 or more and the deviation of the average grain size in each region thus increases significantly, the capacitance characteristics and the like will deteriorate.

[0037] In addition to the condition of 1.49 < A1 / A2 < 2.50, A3 satisfies the condition of 1.14 ≤ A1 / A3 < 1.50, wherein A3 is the average grain size of the dielectric layer 111 in the active-side boundary portion adjacent to the side edge portion 113 of the active portion 112. It can be seen from the experimental results described later that compared with the case where A1 / A3 is less than 1.14, when A1 / A3 is 1.14 or more, the capacitance or withstand voltage reliability can be improved. However, when A1 / A3 increases to 1.50 or more and the deviation of the average grain size in each region thus increases significantly, the capacitance characteristics and the like will deteriorate. As described above, in this embodiment, in the central region of the active portion 112, the grains of the dielectric layer 111 can fully grow, so that the average grain size is relatively large, and thus the capacitance characteristics can be improved. Furthermore, in the side edge portion 113 and the covering portion 114, grain growth can be relatively suppressed, so that the average grain size can be smaller. In this case, the average grain size of the dielectric layer in the active-covering boundary portion and the active-side boundary portion of the active portion 112 can also be smaller, and A1, A2 and A3 can satisfy both the condition of 1.49 < A1 / A2 < 2.50 and the condition of 1.14 ≤ A1 / A3 < 1.50.

[0038] Reference Figures 5 to 9 and Figure 4 , as an example of a method for measuring the average grain size, the average grain size of the dielectric layer 111 can be measured based on a cut surface (for example, a cut surface of the main body 110 perpendicular to the third direction (Z direction), which is formed by cutting the main body 110 along the first direction (X direction) and the second direction (Y direction)). In this case, a cut surface formed by cutting the center of the main body 110 in the third direction (Z direction) can be used. For example, the average grain size can be measured using an image obtained by photographing the cut surface with an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0039] A1 (the average grain size of the dielectric layer 111 in the central region of the effective portion 112) can be a rectangular A1 region R existing on the cut surface. A1 The average size of grain G1 in the structure. In this case, A1 rectangle R A1 The horizontal length can be WA / 3 and the vertical length can be TA / 3 (where TA is the length of the effective part 112 in the first direction (X direction), and WA is the length of the effective part 112 in the second direction (Y direction), and A1 rectangle R A1 It can be symmetrical with respect to the centerline L1 along the first direction (X direction) and the centerline L2 along the second direction (Y direction) of the effective portion 112. A2 (the average grain size of the dielectric layer 111 in the effective-cover boundary portion of the effective portion 112 adjacent to the cover portion 114) can be a rectangle R of A2 existing on the cut surface. A2 The average size of grain G2 in A2 rectangle. A2 The horizontal length can be WA / 3 and the vertical length can be TA / 6, and rectangle R of size A2 A2 It can be symmetrical with respect to the centerline L1 of the effective part 112 along the first direction (X direction) and can contact the inner electrode of the plurality of inner electrodes 121 and 122 located at the outermost position in the first direction (X direction). A3 can be a rectangle R existing on the cut surface. A3 The average size of grain G3 in A3 rectangle. A3 The horizontal length can be WA / 4 and the vertical length can be TA / 3, and the A3 rectangle R A3 It can be symmetrical with respect to the centerline L2 of the effective part 112 and can contact the side edge part 113. When measuring the dimensions of grains G1, G2, and G3, the following methods can be used: measuring the area of ​​grains G1, G2, and G3 and converting the measured area into the equivalent diameter of a circle, measuring the length of the major axis and the length of the minor axis to calculate their average value, etc. Furthermore, only the rectangle R of A1 as a reference can be selected. A1 A2 rectangle R A2 and A3 rectangle R A3 The entire region of grains G1, G2, and G3 is surrounded by grain boundaries to improve measurement accuracy. This measurement method can be applied to other grains G4 and G6.

[0040] The present invention has found that when each region of the dielectric layer 111 satisfies at least one of the above average crystal grain size conditions (for example, the condition of 1.49 < A1 / A2 < 2.5 and the condition of 1.14 ≤ A1 / A3 < 1.50), characteristics related to the reliability standards of multilayer capacitors, such as voltage withstand characteristics, can be improved. In addition, the present invention confirms that the average crystal grain size relationship among the central region of the active portion 112, the active-coverage boundary portion and the active-side boundary portion is an important parameter affecting the above characteristics. This will be described in more detail later.

[0041] As a more detailed average crystal grain size condition, C1 and M1 may satisfy the condition of C1 < M1, wherein C1 is the average crystal grain size of the dielectric layer in the central region of the coverage portion 114, and M1 is the average crystal grain size of the dielectric layer in the central region of the side edge portion 113. For example, the present embodiment adopts the following structure: the average crystal grain size of the dielectric layer in the central region of the coverage portion 114 is smaller than that in the central region of the side edge portion 113. Therefore, the moisture resistance reliability of the coverage portion 114 can also be improved. In this case, C2 may satisfy the condition of 0.9 < C2 / M1 < 1.1, wherein C2 is the average crystal grain size of the dielectric layer in the coverage-active boundary portion of the coverage portion 114 adjacent to the active portion 112. This means that the microstructure of the dielectric layer is generally uniform in the central region of the side edge portion 113 and the coverage-active boundary portion of the coverage portion 114 adjacent to the active portion 112.

[0042] As an example of measurement standards for C1, C2 and M1, C1 may be a C1 rectangle R present on a cut surface C1 wherein the average size of the crystal grains G4 in. The horizontal length of the C1 rectangle R C1 may be WA / 3 and the vertical length may be TC / 3, wherein TC is the length of the coverage portion 114 in the first direction (X direction), and the C1 rectangle R C1 may be symmetrical with respect to the center line L1 along the first direction of the coverage portion 114 (here, the coverage portion 114 and the active portion 112 share the center line L1, but the present invention is not limited thereto) and the center line L3 along the second direction. Furthermore, M1 may be the average size of crystal grains G5 present in the M1 rectangle R M1 on the cut surface. The horizontal length of the M1 rectangle R M1 may be WM / 3 and the vertical length may be TA / 3, wherein WM is the length of the side edge portion 113 in the second direction (Y direction), and the M1 rectangle R M1 may be symmetrical with respect to the center line L4 along the first direction and the center line L2 along the second direction of the side edge portion 113 (here, the side edge portion 113 and the active portion 112 share the center line L2, but the present invention is not limited thereto). In addition, C2 may be a C2 rectangle R present on the cut surface C2The average size of grain G6 in C2 rectangle R. C2 The horizontal length can be WA / 3 and the vertical length can be TC / 6, and the C2 rectangle R C2 It can be symmetrical with respect to the center line L1 of the cover 114 along the first direction and can contact the inner electrode of the plurality of inner electrodes 121 and 122 located at the outermost position in the first direction (X direction). In this case, M1 and C2 can have similar levels and exist in the rectangle R of M1. M1 The size of the grains in the C2 rectangle R can be compared with that in the C2 rectangle R C2 The grain sizes in G6 are similar. However, M1 and C2 have similar levels, but not necessarily the same level. Additionally, as... Figure 9 As shown, G5 and G6 do not have to have the same shape.

[0043] To achieve the aforementioned dielectric grain size conditions, the following method can be used as an example. For instance, when preparing a ceramic green sheet to form the body 110 by mixing ceramic powder, binder, and solvent, methods such as adjusting the ceramic particle size distribution, binder content, and Ba / Ti value (e.g., the molar ratio of Ba to Ti) in the respective sheets can be used for the sheets used to form the effective portion 112, the side edge portion 113, or the cover portion 114. When the binder content in the sheet used to form the side edge portion 113 and the cover portion 114 is lower than the binder content in the sheet used to form the effective portion 112, or when the Ba / Ti value in the sheet used to form the side edge portion 113 and the cover portion 114 is greater than the Ba / Ti value in the sheet used to form the effective portion 112, the sheet used to form the side edge portion 113 and the cover portion 114 shrinks first. In this case, the shrinkage rate of the side edge portion 113 and the cover portion 114 may be higher than the shrinkage rate of the boundary portion of the effective portion 112. In contrast, the shrinkage rate in the central region of the effective portion 112 can be higher than the shrinkage rate in the boundary portion of the effective portion 112. Therefore, the average grain size in the dielectric layer of the side edge portion 113 and the cover portion 114 can be relatively small. Since little binder is detected in the effective portion 112, the side edge portion 113, and the cover portion 114 after the sintering process, the binder content cannot be compared, but the Ba / Ti value conditions can be the same as the Ba / Ti value conditions in the manufacturing process. For example, the molar ratio of Ba to Ti in the dielectric layer 111 in the central region of the effective portion 112 can be less than the molar ratio of Ba to Ti in the dielectric layer in the central region of the cover portion 114. In addition, the molar ratio of Ba to Ti in the dielectric layer in the central region of the side edge portion 113 can be less than the molar ratio of Ba to Ti in the dielectric layer in the central region of the cover portion 114, and can be greater than the molar ratio of Ba to Ti in the dielectric layer 111 in the central region of the effective portion 112.

[0044] The ceramic particle size distribution can also affect the average grain size of the dielectric layer 111 in the effective portion 112, the dielectric layer in the side edge portion 113, and the dielectric layer in the cover portion 114 after the sintering process. However, according to the research of the present invention, the influence of the ceramic particle size distribution is less than the influence of the binder content or the Ba / Ti value. Therefore, it is not necessary to use ceramic particles with a smaller particle size than the ceramic particles of the sheet used to form the side edge portion 113 or the cover portion 114 to obtain the above-mentioned average grain size conditions of this embodiment.

[0045] Furthermore, in this embodiment, at least one of the plurality of dielectric layers 111 may have an average thickness of less than 0.4 μm. The thickness of the dielectric layer 111 can be measured by an image of the cut surface, and the average thickness of the dielectric layer 111 can be obtained by calculating the average of the thicknesses measured at a plurality of points (e.g., ten points) arranged at regular intervals. When the dielectric layer 111 is implemented as a thin film with a thickness of less than 0.4 μm, the size of the multilayer capacitor 100 can be appropriately reduced and the capacitance increased, but there is a possibility that the withstand voltage characteristics of the dielectric layer 111 may deteriorate. However, when the average grain size condition proposed in this embodiment is met, the average grain size can be adjusted for each region to ensure that the withstand voltage characteristics are improved.

[0046] This invention uses samples with different average grain sizes in the effective portion, side edge portion, and cover portion. The average grain size in each of the effective portion, side edge portion, and cover portion was measured and their ratios were calculated. Capacitance and breakdown voltage (BDV) tests were performed on each sample. The test results are listed in Table 1, and the unit of average grain size is nanometers (nm). In the samples, samples 1 and 2 correspond to examples of this disclosure, and samples 3* to 11* correspond to comparative examples where neither condition A1 / A2 nor condition A1 / A3 is satisfied.

[0047] Table 1

[0048]

[0049]

[0050] SMP: Sample Number

[0051] C(μF): Capacitance (μF)

[0052] *: Comparison example

[0053] According to the above test results, when the condition of 1.49<A1 / A2<2.50 is satisfied, the capacitance is as high as greater than 4.7μF, and the withstand voltage characteristic is relatively improved. In addition, even when the condition of 1.14≤A1 / A3<1.50 is satisfied, the capacitance characteristic and the withstand voltage characteristic are also improved. This may be because the crystal grains of the dielectric layer in the active portion grow sufficiently, thereby ensuring sufficient capacitance, and meanwhile the dielectric layer in the active portion has a relatively dense structure (with a uniform average grain size), thereby improving reliability. In addition to these conditions, when the condition of 0.9<C2 / M1<1.1 is satisfied and thus the difference between the average grain size in the coverage-effective boundary portion and the average grain size in the side edge portion is not large, it is advantageous in terms of capacitance characteristics and withstand voltage characteristics. Although the resulting value of C1 is not presented, the condition of C1<M1 is satisfied in the exemplary embodiments. This means that the average grain size of the dielectric layer in the central region of the side edge portion is larger than the average grain size of the dielectric layer in the central region of the coverage portion.

[0054] As described above, in terms of the multilayer capacitor according to the exemplary embodiment, the withstand voltage characteristic, the capacitance characteristic, etc. can be improved.

[0055] While the exemplary embodiments have been shown and described above, it will be readily appreciated by those skilled in the art that modifications and variations can be made without departing from the scope of the present disclosure defined by the appended claims.

Claims

1. A multilayer capacitor, comprising: The main body includes multiple dielectric layers and multiple internal electrodes, wherein the multiple internal electrodes are stacked in a first direction and the corresponding dielectric layers are located between the multiple internal electrodes; as well as An outer electrode is formed on the outer surface of the body and connected to the inner electrode. The main body includes an effective portion, a covering portion, and a side edge portion. The effective portion contains the plurality of inner electrodes to form a capacitor. The effective portion corresponds to the region between the outermost inner electrodes located in the first direction. The covering portion covers the effective portion in the first direction, and the side edge portion covers the effective portion in a second direction perpendicular to the first direction. Among them, 1.49 <A1 / A2<2.50, Wherein, A1 is the average grain size of the dielectric layer in the central region of the effective portion, and A2 is the average grain size of the dielectric layer in the effective-cover boundary portion of the effective portion adjacent to the cover portion. Among them, C1 <M1, Wherein, C1 is the average grain size of the dielectric layer in the central region of the cover portion, and M1 is the average grain size of the dielectric layer in the central region of the side edge portion.

2. The multilayer capacitor according to claim 1, wherein, A1 is the average size of the grains present in the A1 rectangle on the cut surface of the main body, and the horizontal length of the A1 rectangle is WA / 3 and the vertical length is TA / 3, and the A1 rectangle is symmetrical with respect to the center line of the effective portion along the first direction and the center line along the second direction. Wherein, based on the cutting surface of the main body, TA is the length of the effective part in the first direction, and WA is the length of the effective part in the second direction, the cutting surface of the main body is perpendicular to a third direction, and the third direction is perpendicular to the first direction and the second direction.

3. The multilayer capacitor according to claim 2, wherein, A2 is the average size of the grains present in the A2 rectangle on the cut surface, and the horizontal length of the A2 rectangle is WA / 3 and the vertical length is TA / 6. The A2 rectangle is symmetrical with respect to the center line of the effective portion along the first direction and is in contact with the inner electrode of the plurality of inner electrodes located at the outermost position in the first direction.

4. The multilayer capacitor according to claim 1, wherein, The average grain size or Ba / Ti molar ratio of the dielectric layer included in the side edge portion is different from that of the dielectric layer included in the effective portion, and the average grain size or Ba / Ti molar ratio of the dielectric layer included in the cover portion is different from that of the dielectric layer included in the effective portion.

5. The multilayer capacitor according to claim 4, wherein, C1 is the average size of the grains present in the C1 rectangle on the cut surface of the main body, and the horizontal length of the C1 rectangle is WA / 3 and the vertical length is TC / 3, and the C1 rectangle is symmetrical with respect to the center line of the cover portion along the first direction and the center line along the second direction. Wherein, based on the cutting surface of the main body, TC is the length of the covering portion in the first direction, and WA is the length of the effective portion in the second direction, the cutting surface of the main body is perpendicular to a third direction, and the third direction is perpendicular to both the first and second directions.

6. The multilayer capacitor according to claim 4, wherein, M1 is the average size of the grains present in the M1 rectangle on the cut surface of the body, and the horizontal length of the M1 rectangle is WM / 3 and the vertical length is TA / 3, and the M1 rectangle is symmetrical with respect to the center line of the side edge along the first direction and the center line along the second direction. Wherein, based on the cutting surface of the main body, WM is the length of the side edge portion in the second direction, and TA is the length of the effective portion in the first direction, the cutting surface of the main body is perpendicular to a third direction, and the third direction is perpendicular to both the first and second directions.

7. The multilayer capacitor according to claim 1, wherein, 0.9 <C2 / M1<1.1, Wherein, C2 is the average grain size of the dielectric layer in the cover-effective boundary portion adjacent to the effective portion of the cover portion.

8. The multilayer capacitor according to claim 7, wherein, C2 is the average size of the grains present in the C2 rectangle on the cut surface of the main body, and the horizontal length of the C2 rectangle is WA / 3 and the vertical length is TC / 6. The C2 rectangle is symmetrical with respect to the center line of the cover portion along the first direction and contacts the outermost inner electrode of the plurality of inner electrodes located in the first direction. Wherein, based on the cutting surface of the main body, TC is the length of the covering portion in the first direction, and WA is the length of the effective portion in the second direction, the cutting surface of the main body is perpendicular to a third direction, and the third direction is perpendicular to both the first and second directions.

9. The multilayer capacitor according to claim 1, wherein, The plurality of dielectric layers include barium titanate, and The molar ratio of barium to titanium in the dielectric layer of the central region of the effective portion is less than the molar ratio of barium to titanium in the dielectric layer of the central region of the covering portion.

10. The multilayer capacitor according to claim 9, wherein, The molar ratio of barium to titanium in the dielectric layer in the central region of the side edge portion is less than the molar ratio of barium to titanium in the dielectric layer in the central region of the cover portion, and greater than the molar ratio of barium to titanium in the dielectric layer in the central region of the effective portion.

11. The multilayer capacitor according to claim 1, wherein, At least one of the plurality of dielectric layers has an average thickness of less than 0.4 μm.

12. A multilayer capacitor, comprising: The main body includes multiple dielectric layers and multiple internal electrodes, wherein the multiple internal electrodes are stacked in a first direction and corresponding dielectric layers are interposed between the multiple internal electrodes. An outer electrode is formed on the outer surface of the body and connected to the inner electrode. The main body includes an effective portion, a covering portion, and a side edge portion. The effective portion contains the plurality of inner electrodes to form a capacitor. The effective portion corresponds to the region between the outermost inner electrodes located in the first direction. The covering portion covers the effective portion in the first direction, and the side edge portion covers the effective portion in a second direction perpendicular to the first direction. Where 1.14 ≤ A1 / A3 < 1.50, Wherein, A1 is the average grain size of the dielectric layer in the central region of the effective portion, and A3 is the average grain size of the dielectric layer in the effective-side boundary portion adjacent to the side edge portion of the effective portion. The plurality of dielectric layers include barium titanate, and the molar ratio of barium to titanium in the dielectric layer in the central region of the effective portion is less than the molar ratio of barium to titanium in the dielectric layer in the central region of the side edge portion.

13. The multilayer capacitor according to claim 12, wherein, A1 is the average size of the grains present in the A1 rectangle on the cut surface of the main body, and the horizontal length of the A1 rectangle is WA / 3 and the vertical length is TA / 3, and the A1 rectangle is symmetrical with respect to the center line of the effective portion along the first direction and the center line along the second direction. Wherein, based on the cutting surface of the main body, TA is the length of the effective part in the first direction, and WA is the length of the effective part in the second direction, the cutting surface of the main body is perpendicular to a third direction, and the third direction is perpendicular to the first direction and the second direction.

14. The multilayer capacitor according to claim 13, wherein, A3 is the average size of the grains present in the A3 rectangle on the cut surface, and the A3 rectangle has a horizontal length of WA / 4 and a vertical length of TA / 3. The A3 rectangle is symmetrical with respect to the center line of the effective portion along the second direction and contacts the side edge portion.

15. The multilayer capacitor according to claim 12, wherein, C1 <M1, Wherein, C1 is the average grain size of the dielectric layer in the central region of the cover portion, and M1 is the average grain size of the dielectric layer in the central region of the side edge portion.

16. The multilayer capacitor according to claim 15, wherein, C1 is the average size of the grains present in the C1 rectangle on the cut surface of the main body, and the horizontal length of the C1 rectangle is WA / 3 and the vertical length is TC / 3, and the C1 rectangle is symmetrical with respect to the center line of the cover portion along the first direction and the center line along the second direction. Wherein, based on the cutting surface of the main body, TC is the length of the covering portion in the first direction, and WA is the length of the effective portion in the second direction, the cutting surface of the main body is perpendicular to a third direction, and the third direction is perpendicular to both the first and second directions.

17. The multilayer capacitor according to claim 15, wherein, M1 is the average size of the grains present in the M1 rectangle on the cut surface of the body, and the horizontal length of the M1 rectangle is WM / 3 and the vertical length is TA / 3, and the M1 rectangle is symmetrical with respect to the center line of the side edge along the first direction and the center line along the second direction. Wherein, based on the cutting surface of the main body, WM is the length of the side edge portion in the second direction, and TA is the length of the effective portion in the first direction, the cutting surface of the main body is perpendicular to a third direction, and the third direction is perpendicular to both the first and second directions.

18. The multilayer capacitor according to claim 15, wherein, 0.9 <C2 / M1<1.1, Wherein, C2 is the average grain size of the dielectric layer in the cover-effective boundary portion adjacent to the effective portion of the cover portion.

19. The multilayer capacitor according to claim 18, wherein, C2 is the average size of the grains present in the C2 rectangle on the cut surface of the body, and the horizontal length of the C2 rectangle is WA / 3 and the vertical length is TC / 6. The C2 rectangle is symmetrical with respect to the center line of the cover portion along the first direction and is in contact with the outermost inner electrode of the plurality of inner electrodes located in the first direction. Wherein, based on the cutting surface of the main body, TC is the length of the covering portion in the first direction, and WA is the length of the effective portion in the second direction, the cutting surface of the main body is perpendicular to a third direction, and the third direction is perpendicular to both the first and second directions.

20. The multilayer capacitor according to claim 12, wherein, At least one of the plurality of dielectric layers has an average thickness of less than 0.4 μm.

21. A multilayer capacitor, comprising: A capacitor forming section includes inner electrodes stacked in the thickness direction and a dielectric layer disposed between the inner electrodes, wherein the average grain size of the dielectric grains in the dielectric layer in the central region of the capacitor forming section is A1; A dielectric covering portion is disposed above and below the capacitor forming portion in the thickness direction, wherein the average grain size of the dielectric grains in the boundary region of the capacitor forming portion adjacent to the dielectric covering portion is A2; and External electrodes are disposed on surfaces opposite each other in the longitudinal direction of the capacitor forming portion. Among them, 1.49 <A1 / A2<2.50, The inner electrode is disposed in a length-width plane perpendicular to the thickness direction, and the width direction is perpendicular to the thickness direction. The dielectric layer and the dielectric covering portion include barium titanate, and the molar ratio of barium to titanium in the dielectric layer in the central region of the capacitor forming portion is less than the molar ratio of barium to titanium in the central region of the dielectric covering portion.

22. The multilayer capacitor according to claim 21, wherein, The central region of the capacitor forming portion is defined as a rectangle, which is symmetrical about the center line of the capacitor forming portion along the thickness direction and the center line of the capacitor forming portion along the width direction. The rectangle has a dimension of TA / 3 in the thickness direction and a dimension of WA / 3 in the width direction, where TA is the dimension of the capacitor forming portion in the thickness direction and WA is the dimension of the capacitor forming portion in the width direction.

23. The multilayer capacitor according to claim 21, wherein, The boundary region of the capacitor forming portion adjacent to the dielectric covering portion is defined as a rectangle, which is symmetrical about the center line of the capacitor forming portion along the thickness direction and contacts the outermost inner electrode of the capacitor forming portion in the thickness direction. The rectangle has a dimension of TA / 6 in the thickness direction and a dimension of WA / 3 in the width direction, where TA is the dimension of the capacitor forming portion in the thickness direction and WA is the dimension of the capacitor forming portion in the width direction.

24. The multilayer capacitor according to claim 21, further comprising: A dielectric-side edge portion is disposed on the side portion of the capacitor forming portion in the width direction, and the average grain size of the dielectric grains in the boundary region of the capacitor forming portion adjacent to the dielectric-side edge portion is A3. Among them, 1.14≤A1 / A3<1.50.

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