Multilayer capacitor

Abstract

To provide a multilayer capacitor.SOLUTION: A multilayer ceramic capacitor in one embodiment of the present invention includes a main body including a plurality of dielectric layers and a plurality of internal electrodes stacked in a first direction with the dielectric layers held therebetween, and an external electrode formed outside the main body and connected to the internal electrode. The main body includes an active part including the internal electrodes and forming electrostatic capacitance, a side margin part covering at least one surface of a first surface and a second surface of the active part facing each other in a second direction, and a cover part covering the active part in the first direction. The dielectric layers contain a barium titanate based composition. The dielectric layer in the side margin part contains a Sn component in a different Sn content from the dielectric layer in the active part. The dielectric layer in the side margin part contains grains with a core-shell structure at least partially.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] A capacitor is a device that can store electricity. Generally, when two electrodes are placed facing each other and a voltage is applied, electricity accumulates in each electrode. When a DC voltage is applied, current flows inside the capacitor as electricity is stored, but once the storage is complete, the current stops flowing. On the other hand, when an AC voltage is applied, the polarity of the electrodes alternates, resulting in an AC current flow.

[0003] Such capacitors can be classified into various types depending on the type of insulator provided between the electrodes, such as aluminum electrolytic capacitors in which the electrodes are made of aluminum and a thin oxide film is provided between the aluminum electrodes, tantalum capacitors that use tantalum as the electrode material, ceramic capacitors that use a high dielectric constant dielectric such as barium titanate between the electrodes, multi-layer ceramic capacitors (MLCCs) that use a multi-layer structure of high dielectric constant ceramic as the dielectric provided between the electrodes, and film capacitors that use a polystyrene film as the dielectric between the electrodes.

[0004] Among these, multilayer ceramic capacitors have the advantages of excellent temperature and frequency characteristics and being small in size, and have therefore been widely applied in various fields in recent years, such as high-frequency circuits. In recent years, attempts have been made to form thinner dielectric layers and internal electrodes in order to further reduce the size of multilayer ceramic capacitors.

[0005] To increase capacitance while miniaturizing multilayer capacitors, a process has been used in which the internal electrodes are exposed across the width of the body, thereby maximizing the area of ​​the internal electrodes across the width through a margin-free design. After fabricating the chip, side margins are then attached to the exposed electrode surfaces across the chip before firing. However, this method results in a reduced thickness and area of ​​the side margins, increasing the risk of breakage and cracking due to external impact. Therefore, there is a need for a dielectric material that can improve the impact resistance and crack resistance of the side margins in ultra-small and high-capacity products. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a multilayer capacitor having improved electrical and mechanical properties by using a highly reliable dielectric material. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the present invention proposes a new structure of a multilayer capacitor, as an example. Specifically, the multilayer capacitor includes a body including a plurality of dielectric layers and a plurality of internal electrodes stacked in a first direction with the dielectric layers sandwiched therebetween, and external electrodes formed outside the body and connected to the internal electrodes. The body includes an active section where the internal electrodes are located to form capacitance, a side margin section covering at least one of a first side and a second side of the active section facing in a second direction, and a cover section covering the active section in the first direction. The plurality of dielectric layers include a barium titanate-based composition, and the dielectric layers in the side margin section include a Sn component having a different Sn content from the dielectric layers in the active section. The dielectric layers in the side margin section at least partially include grains having a core-shell structure.

[0008] In one embodiment, the shell portion of the core-shell structure may have a higher Sn content than the core portion.

[0009] In one embodiment, in the shell portion of the core-shell structure, a portion of Ti may be substituted with Sn.

[0010] In an embodiment, the Sn content of the dielectric layer of the side margin portion may be higher than the Sn content of the dielectric layer of the active portion.

[0011] In one embodiment, the shell portion can cover 30% or more of the surface of the core.

[0012] In one embodiment, the grains in which the shell portion in the dielectric layer of the side margin portion covers 30% or more of the core surface may be 10% or more of the total grains.

[0013] In one embodiment, the dielectric layer of the side margin portion can contain 0.1 to 10 moles of Sn per 100 moles of barium titanate.

[0014] In an embodiment, the dielectric layer in the side margin portion may have an average grain size smaller than that of the dielectric layer in the active portion.

[0015] In one embodiment, the dielectric layer of the cover part at least partially includes grains having a core-shell structure, and the shell part of the core-shell structure may have a higher Sn content than the core part.

[0016] Another aspect of the present invention provides a multilayer capacitor including: a main body including a plurality of dielectric layers and a plurality of internal electrodes stacked in a first direction with the dielectric layers sandwiched therebetween; and external electrodes formed outside the main body and connected to the internal electrodes, the main body including an active section in which the plurality of internal electrodes are located to form capacitance; side margin sections covering first and second sides of the active section facing in a second direction; and a cover section covering the active section in the first direction, the plurality of dielectric layers including a barium titanate-based composition, the dielectric layer of the cover section including a Sn component having a different Sn content from the dielectric layer of the active section, and the dielectric layer of the cover section including at least a portion of grains having a core-shell structure. [Effects of the Invention]

[0017] In the case of a multilayer capacitor according to an embodiment of the present invention, electrical and mechanical properties can be improved. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a perspective view schematically illustrating an appearance of a multilayer capacitor according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view taken along line II' in the multilayer capacitor of FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along line II-II' in the multilayer capacitor of FIG. [Figure 4] FIG. 2 is an enlarged schematic view showing grains of a dielectric layer. [Figure 5] This shows the main body region in FIG. 3 subdivided. [Figure 6] 1 shows the morphology of dielectric grains in different regions of the body. [Figure 7] 1 shows the morphology of dielectric grains in different regions of the body. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to specific embodiments and the accompanying drawings. However, the embodiments of the present invention may be modified into several other forms, and the scope of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Therefore, the shapes and sizes of elements in the drawings may be enlarged or reduced (or highlighted or simplified) for clearer explanation, and elements designated by the same reference numerals in the drawings are the same elements.

[0020] In the drawings, parts not relevant to the description are omitted in order to clearly explain the present invention, thicknesses are exaggerated to clearly depict multiple layers and regions, and components having the same function within the same concept are referred to by the same reference numerals. Furthermore, throughout the specification, when a part "comprises" a certain element, it does not mean that it excludes other elements, but that it may further include other elements, unless otherwise specified.

[0021] Fig. 1 is a perspective view schematically illustrating the appearance of a multilayer capacitor according to one embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line II' in the multilayer capacitor of Fig. 1. Fig. 3 is a cross-sectional view taken along line II' in the multilayer capacitor of Fig. 1. Fig. 4 is a schematic diagram showing an enlarged view of the grains of a dielectric layer. Fig. 5 is a fragmented view of the main body region of Fig. 3.

[0022] 1 to 3, a multilayer capacitor 100 according to an embodiment of the present invention includes a body 110 including a dielectric layer 111 and a plurality of internal electrodes 121 and 122 stacked in a first direction (X direction) across the dielectric layer 111, and external electrodes 131 and 132. The body 110 includes an active portion 112, a side margin portion 113, and a cover portion 114. The dielectric layer 111 of the side margin portion 113 contains a Sn component, and has a different Sn content from the dielectric layer 112 of the active portion 112. The dielectric layer 111 of the side margin portion 113 also includes at least a portion of grains having a core-shell structure.

[0023] The body 110 has a laminated structure in which a plurality of dielectric layers 111 are stacked in a first direction (X direction). For example, the body 110 may be obtained by stacking a plurality of green sheets and then sintering them. The sintering process may result in an integrated configuration of the plurality of dielectric layers 111. As shown in FIG. 1, the body 110 may have a shape similar to a rectangular parallelepiped. The dielectric layer 111 included in the body 110 may include a ceramic material having a high dielectric constant, such as a barium titanate (BaTiO3)-based composition. Specifically, the dielectric layer 111 may include a matrix main component including Ba and Ti. Here, the matrix main component may include BaTiO3 or a main component partially solid-solubilized with Ca, Zr, Sn, etc., expressed as (Ba,Ca)(Ti,Ca)O3, (Ba,Ca)(Ti,Zr)O3, Ba(Ti,Zr)O3, or (Ba,Ca)(Ti,Sn)O3. In addition to the ceramic material as the main component, the dielectric layer 111 may further include additives, organic solvents, plasticizers, binders, dispersants, etc., as needed. The additives may include metal components, which may be added in the form of metal oxides during the manufacturing process. Examples of such metal oxide additives include at least one of MnO2, Dy2O3, BaO, MgO, Al2O3, SiO2, Cr2O3, and CaCO3.

[0024] The plurality of internal electrodes 121, 122 may be obtained by printing a paste containing a conductive metal to a predetermined thickness on one surface of a ceramic green sheet and then sintering the printed paste. In this case, the plurality of internal electrodes 121, 122 may include first and second internal electrodes 121, 122 exposed in a third direction (Z direction) facing each other of the body 110, as shown in FIG. 2. Here, the third direction (Z direction) may be a direction perpendicular to the first direction (X direction) and the second direction (Y direction), where the direction in which the first surface S1 and the second surface S2 of the active part 112 of the body 110 face each other is defined as the second direction (Y direction). The first and second internal electrodes 121, 122 may be connected to different external electrodes 131, 132 and have different polarities when driven, and may be electrically isolated from each other by a dielectric layer 111 disposed therebetween. However, the number of external electrodes 131, 132 and the manner of connection to the internal electrodes 121, 122 may vary depending on the embodiment. Examples of main constituent materials of the internal electrodes 121 and 122 include nickel (Ni), copper (Cu), palladium (Pd), and silver (Ag), and alloys of these may also be used.

[0025] The external electrodes 131 and 132 are formed outside the main body 110 and may include first and second external electrodes 131 and 132 connected to the first and second internal electrodes 121 and 122, respectively. The external electrodes 131 and 132 may be formed by preparing a paste containing a conductive metal and then applying the paste to the main body 110. Examples of the conductive metal may include nickel (Ni), copper (Cu), palladium (Pd), gold (Au), or alloys thereof. Here, the external electrodes 131 and 132 may further include a plating layer containing Ni, Sn, etc.

[0026] 3, the active section 112 has a plurality of internal electrodes 121 and 122 positioned therein to form capacitance. The side margin section 113 covers at least one of the first and second surfaces S1 and S2 of the active section 112, which face each other in a second direction (Y direction). In this embodiment, the side margin section 113 covers both the first and second surfaces S1 and S2. In this case, the second direction (Y direction) may be perpendicular to the first direction (X direction). The cover section 114 covers the active section 112 in the first direction (X direction). In this embodiment, the cover section 114 is disposed on both the top and bottom of the active section 112 in the first direction (X direction).

[0027] In this embodiment, the moisture resistance and toughness are improved by adjusting the components and grain size of the dielectric layer 111 in the side margin portion 113, which has a significant effect on the reliability of the multilayer capacitor 100. Although the following description focuses on the side margin portion 113, the highly reliable dielectric layer 111 can be applied to the cover portion 114, and can also be applied to both the side margin portion 113 and the cover portion 114 simultaneously to maximize the improvement in characteristics.

[0028] In this embodiment, the dielectric layers 111 of the active portion 112 and the side margin portion 113 contain Sn, but the Sn content is different. According to research by the inventors, in the dielectric layer 111 containing a barium titanate composition, the grain growth characteristics and toughness vary depending on the Sn content, and by varying the Sn content in each region constituting the main body 110, the electrical and mechanical properties are improved. For example, the Sn content in the dielectric layer 111 of the side margin portion 112 may be higher than the Sn content in the dielectric layer 111 of the active portion 113, thereby improving the moisture resistance reliability and toughness of the main body 110.

[0029] The dielectric layer 111 of the side margin portion 113 contains Sn to improve moisture resistance reliability and provide impact resistance and crack resistance, and the Sn content is adjusted to be higher than that of the dielectric layer 111 of the active portion 112. In this case, the dielectric layer 111 of the active portion 112 may contain no Sn or may contain only a very small amount of Sn. If the Sn content of the side margin portion 113 is higher than that of the dielectric layer 111 of the active portion 112, the grain growth of the dielectric layer 111 of the side margin portion 113 is relatively small, and the average size of the grains contained therein can be adjusted to be smaller than the average size of the grains contained in the dielectric layer 111 of the active portion 112. As a result, the side margin portion 113 can have higher moisture resistance and toughness than the active portion 112. Therefore, cracks in the body 110, particularly the side margin portion 113, can be improved when the multilayer capacitor 100 is mounted on a substrate, etc.

[0030] The Sn content can be adjusted to achieve sufficiently improved characteristics in the side margin portion 113. In this case, the dielectric layer 111 of the side margin portion 113 can contain 0.1 to 10 moles of Sn per 100 moles of barium titanate. If the Sn content is less than 0.1 mole, the substantial effect of adding Sn is unlikely to be achieved, and if the Sn content exceeds 10 moles, the formation of a network between Sn may cause a problem of deterioration in impact resistance.

[0031] In this embodiment, the dielectric layer 111 of the side margin portion 113 includes grains 11 having a shell structure, such as the core-shell structure shown in FIG. 4. In this case, the shell portion 11b of the core-shell structure may have a higher Sn content than the core 11a, and the shell portion 11b may have a form in which some of the Ti is substituted with Sn. The shell portion 11b may cover 30% or more of the surface of the core 11a. In the dielectric layer 111 of the side margin portion 113, the grains 12 in which the shell portion 11b covers 30% or more of the surface of the core 11a may account for 10% or more of the total grains 11 and 12. The thickness of the shell portion 11b is not particularly limited, but may be, for example, 2 to 50 nm.

[0032] Sn is an element with the same oxidation number as Ti but a different ionic radius. When Sn replaces a portion of Ti in the shell portion 11b, a structure generally having a cubic phase is transformed into a lattice structure, resulting in a phase with a dipole moment, thereby increasing the dielectric constant and ensuring a high dielectric constant. Furthermore, when a portion of Ti in the shell portion 11b is replaced with Sn, the ratio of Ba to Ti (Ba / Ti) can be increased, thereby suppressing the grain growth of the dielectric grains. In this case, the ratio of Ba to Ti (Ba / Ti) can be 1.0150 or more. When the molar ratio of Ba to Ti (Ba / Ti) is high, such as 1.0150 or more, the grain growth of the dielectric grains can be suppressed and densified during sintering, thereby improving electrical properties (voltage resistance characteristics), moisture resistance reliability, etc.

[0033] As described above, the grains (G2 in FIG. 7) included in the dielectric layer 111 of the side margin portion 113, which has a relatively higher Sn content, may have a smaller average grain size than the grains (G1 in FIG. 6) included in the dielectric layer 111 of the active portion 112. For example, the average grain size of the dielectric layer 111 of the side margin portion 112 may be 100 to 700 nm. The dielectric layer 111 of the active portion 113 may have a composition commonly used in the MLCC field, in which case the average grain size may be 300 to 900 nm. In this case, as the Sn content of the dielectric layer 111 of the side margin portion 113 increases, the grain size may decrease from the outer boundary surface of the side margin portion 113 to the inner region adjacent to the active portion 112. That is, Sn in the side margin portion 113 reduces the grain size of the dielectric grains, and the grain size of the dielectric grains further decreases inside adjacent to the active portion 112, so that the side margin portion 113 can have high toughness.

[0034] The average size of the grains included in the dielectric layer 111 can be determined by calculating the circle-equivalent diameter of the dielectric grains extracted from the corresponding region, or by measuring the major axis and shortened length and calculating the average size. Referring to Figures 6 and 7 in addition to Figure 5, as an example of a method for measuring the grain size, the average grain size of the dielectric layer 111 can be measured based on cross sections cut in the first direction (X direction) and the second direction (Y direction). In this case, a cross section cut at the middle of the length of the body 110 can be used for the third direction (Z direction).

[0035] When the length of the body 110 in the first direction (X direction) is T and the length of the active portion 112 in the second direction (Y direction) is WA, the average grain size in the dielectric layer 111 of the active portion 112 can be measured from the size of grains G1 present within a first rectangle R1 on the cross section of FIG. 5. The first rectangle R1 includes a central region CA of the active portion 112 and has a horizontal length of WA / 3 and a vertical length of T / 3. The active portion 112 is symmetrical with respect to center lines L1 and L2 in the first and second directions. The average grain size in the dielectric layer 111 of the side margin portion 113 can be measured from the size of grains G2 present within a second rectangle R2 including the central region CM. When the length of the side margin portion 113 in the second direction (Y direction) is WM, the second rectangle R2 has a horizontal length of WM / 3 and a vertical length of T / 3, and is symmetrical about the first and second direction center lines L3 and L2 in the side margin portion 113. In a similar manner, the average grain size in the dielectric layer 111 of the cover portion 114 can be determined by measuring the size of grains present in a third rectangle R3 including the center region CC, where the grains may have the same shape as in FIG. 7. The third rectangle R3 has a horizontal length of WA / 3 and a vertical length of t / 2 (where t is the thickness of the cover portion 114), and is symmetrical about the first and second direction center lines in the cover portion 114.

[0036] As described above, when measuring the size of the grains G1 and G2, methods that can be used include measuring the area of ​​the grains G1 and G2 and converting it into a circle-equivalent diameter, measuring the major axis and shortened length and calculating the average, etc. Also, to improve the accuracy of the measurement, only grains G1 and G2 whose entire area is surrounded by the grain boundary in the reference rectangular rectangles R1, R2, and R3 can be selected.

[0037] Furthermore, as described above, the description regarding the dielectric layer 111 of the side margin portion 113 can be applied to the cover portion 114 as well, and the Sn content characteristics and core-shell structure of the dielectric layer 111 described above can be applied only to the cover portion 114, not to the side margin portion 113. Furthermore, the Sn content characteristics and core-shell structure of the dielectric layer 111 described above can be applied to both the side margin portion 113 and the cover portion 114.

[0038] The present invention is not limited by the above-described embodiments and the accompanying drawings, but is limited by the scope of the accompanying claims. Therefore, it is obvious to those skilled in the art that various substitutions, modifications, and changes can be made without departing from the technical idea of ​​the present invention as set forth in the claims, and these also belong to the technical idea as set forth in the claims. [Explanation of symbols]

[0039] 100: Multilayer capacitor 110:Main body 111: Dielectric layer 112: Active section 113: Side margin 114: Cover part 121, 122: Internal electrode 131, 132: External electrode 11, 12: Grain 11a: Core 11b: Shell part

Claims

1. a main body including a plurality of dielectric layers and a plurality of internal electrodes stacked in a first direction with the plurality of dielectric layers sandwiched therebetween; an external electrode formed on the outside of the body and connected to the plurality of internal electrodes; the body includes an active portion where the plurality of internal electrodes are located to form capacitance, a side margin portion covering at least one of a first surface and a second surface facing a second direction of the active portion, and a cover portion covering the active portion in the first direction, the plurality of dielectric layers comprising a barium titanate-based composition; the dielectric layer of the side margin portion includes a Sn component, and the Sn content of the dielectric layer of the side margin portion is greater than the Sn content of the dielectric layer of the active portion; the dielectric layer in the side margin portion at least partially contains grains having a core-shell structure; The shell portion of the core-shell structure has a structure in which part of Ti is substituted with Sn. Multilayer capacitor.

2. 2. The multilayer capacitor of claim 1, wherein the shell of the core-shell structure has a higher Sn content than the core.

3. 3. The multilayer capacitor according to claim 1, wherein the shell portion of the core-shell structure covers 30% or more of the surface of the core.

4. 4. The multilayer capacitor according to claim 1, wherein the grains in the core-shell structure in the dielectric layer of the side margin portion, in which the shell portion covers 30% or more of the core surface, are 10% or more of the total grains.

5. 5. The multilayer capacitor according to claim 1, wherein the dielectric layer in the side margin portion contains 0.1 to 10 moles of Sn per 100 moles of barium titanate.

6. The multilayer capacitor according to claim 1 , wherein the dielectric layer in the side margin portion has an average grain size smaller than that of the dielectric layer in the active portion.

7. 7. The multilayer capacitor according to claim 1, wherein the dielectric layer of the cover portion at least partially includes grains having a core-shell structure, and the shell portion of the core-shell structure has a higher Sn content than the core.

8. a main body including a plurality of dielectric layers and a plurality of internal electrodes stacked in a first direction with the plurality of dielectric layers sandwiched therebetween; an external electrode formed on the outside of the body and connected to the plurality of internal electrodes; the body includes an active portion where the plurality of internal electrodes are located to form capacitance, a side margin portion covering first and second surfaces of the active portion facing each other in a second direction, and a cover portion covering the active portion in the first direction, the plurality of dielectric layers comprising a barium titanate-based composition; the dielectric layer of the cover portion includes a Sn component, and the Sn content of the dielectric layer of the cover portion is greater than the Sn content of the dielectric layer of the active portion; the dielectric layer of the cover portion at least partially contains grains having a core-shell structure; The shell portion of the core-shell structure has a structure in which part of Ti is substituted with Sn. Multilayer capacitor.

9. 9. The multilayer capacitor of claim 8, wherein the shell of the core-shell structure has a higher Sn content than the core.

10. 10. The multilayer capacitor according to claim 8, wherein the shell portion of the core-shell structure covers 30% or more of the surface of the core.

11. 11. The multilayer capacitor according to claim 8, wherein the grains of the shell portion in the core-shell structure in the dielectric layer of the cover portion covering 30% or more of the surface of the core are 10% or more of the total grains.

12. 12. The multilayer capacitor according to claim 8, wherein the dielectric layer of the cover contains 0.1 to 10 moles of Sn per 100 moles of barium titanate.

13. The multilayer capacitor according to claim 8 , wherein the dielectric layer of the cover section has an average grain size smaller than that of the dielectric layer of the active section.

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