Multilayer ceramic capacitor

Abstract

A multilayer ceramic capacitor 1 comprises: an element body 10 that includes a plurality of internal electrode layers 30 and a plurality of dielectric ceramic layers 20 which are laminated in the lamination direction T; and external electrodes 11, 12 that are provided to a surface of the element body 10 and that are electrically connected to the internal electrode layers 30. The internal electrode layers 30 contain nickel (Ni) and a first rare earth element. The first rare earth element includes at least one rare earth element (Re) selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), yttrium (Y), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). In a range of 10 nm or less toward an internal electrode layer 30 from the interface between that internal electrode layer 30 and a dielectric ceramic layer 20, the element ratio of Re with to the total of Ni and Re satisfies 0.001≤Re / (Ni+Re)≤0.060.

Description

Multilayer ceramic capacitor

[0001] This invention relates to a multilayer ceramic capacitor.

[0002] Patent Document 1 discloses a stacked electronic component comprising a body including a dielectric layer and internal electrodes arranged alternately with the dielectric layer in a first direction, and external electrodes arranged on the body and connected to the internal electrodes, wherein the internal electrodes contain Ni and Dy, and when C0 is the atomic ratio of the Dy content to the sum of the Ni and Dy contents, the condition 0.02 at% ≤ C0 ≤ 5 at% is satisfied.

[0003] Japanese Patent Publication No. 2022-93251

[0004] According to Patent Document 1, the reliability of multilayer electronic components such as multilayer ceramic capacitors can be improved by including dysprosium (Dy) in the internal electrodes.

[0005] Patent Document 1 includes, for example, nickel (Ni) powder and dysprosium oxide (Dy ２ O ３ An internal electrode can be formed using an internal electrode paste containing the powder, and Dy relative to Ni powder ２ O ３ It is stated that the amount of Dy contained in the internal electrodes after firing can be controlled by adjusting the atomic ratio of the powder.

[0006] On the other hand, our own investigations have revealed that in multilayer ceramic capacitors containing Dy in the internal electrodes containing Ni, the equivalent series resistance may increase. Equivalent series resistance, like capacitance, is one of the important parameters that indicate capacitor performance, and it becomes impossible to ignore as the frequency of use increases.

[0007] This invention was made to solve the above problems and aims to provide a multilayer ceramic capacitor that can suppress the increase in equivalent series resistance while maintaining reliability.

[0008] The multilayer ceramic capacitor of the present invention comprises a base body including a plurality of dielectric ceramic layers and a plurality of internal electrode layers stacked in the stacking direction, and an external electrode provided on the surface of the base body and electrically connected to the internal electrode layer. The internal electrode layer includes nickel (Ni) and a first rare earth element. The first rare earth element includes at least one rare earth element (Re) selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), yttrium (Y), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Within a range of 10 nm from the interface between the internal electrode layer and the dielectric ceramic layer toward the internal electrode layer, the elemental ratio of Re to the sum of Ni and Re satisfies 0.001 ≤ Re / (Ni + Re) ≤ 0.060.

[0009] According to the present invention, it is possible to provide a multilayer ceramic capacitor that can suppress the increase in equivalent series resistance while maintaining reliability.

[0010] Figure 1 is a schematic perspective view showing an example of a multilayer ceramic capacitor of the present invention. Figure 2 is an example of an LT cross-sectional view of the multilayer ceramic capacitor shown in Figure 1, including the length direction L along the line II-II and the stacking direction T. Figure 3 is an example of a WT cross-sectional view of the multilayer ceramic capacitor shown in Figure 1, including the width direction W along the line III-III and the stacking direction T. Figure 4 is an example of a cross-sectional view for illustrating the point analysis of the internal electrode layer. Figure 5 is another example of a cross-sectional view for illustrating the point analysis of the internal electrode layer.

[0011] The multilayer ceramic capacitor of the present invention will be described below. However, the present invention is not limited to the following embodiments and may be modified as appropriate without altering the essence of the invention. Furthermore, a combination of several preferred configurations described in the following embodiments also constitutes the present invention.

[0012] In this specification, terms describing relationships between elements (e.g., "perpendicular," "parallel," "orthogonal," etc.) and terms describing the shapes of elements do not represent only strict meanings, but also include a range of substantially equivalent terms, such as differences of a few percent.

[0013] The following diagrams are schematic representations, and their dimensions, aspect ratios, and scales may differ from those of the actual product. The same reference numerals are used for identical or equivalent parts in the diagrams. Furthermore, identical elements are denoted by the same reference numerals in each diagram, and redundant explanations are omitted.

[0014] Figure 1 is a schematic perspective view showing an example of the multilayer ceramic capacitor of the present invention.

[0015] The multilayer ceramic capacitor 1 shown in Figure 1 comprises a base body 10 and external electrodes 11 and 12 provided on the surface of the base body 10. In the base body 10, the length direction, width direction, and stacking direction are defined by double arrows L, W, and T, respectively.

[0016] The base body 10 is, for example, a rectangular parallelepiped. In this case, the base body 10 has a first main surface 10a and a second main surface 10b facing the stacking direction T, a first side surface 10c and a second side surface 10d facing the width direction W perpendicular to the stacking direction T, and a first end surface 10e and a second end surface 10f facing the length direction L perpendicular to the stacking direction T and the width direction W.

[0017] At least one of the corners and edges of the base body 10 may be rounded. Here, the corners are the parts where the three faces of the base body 10 intersect, and the edges are the parts where the two faces of the base body 10 intersect.

[0018] The external electrode 11 is provided on the first end face 10e of the base body 10. The external electrode 11 may wrap around to a part of the first main surface 10a, the second main surface 10b, the first side surface 10c, and the second side surface 10d of the base body 10.

[0019] The external electrode 12 is provided on the second end face 10f of the base body 10. The external electrode 12 may wrap around to a part of the first main surface 10a, the second main surface 10b, the first side surface 10c, and the second side surface 10d of the base body 10.

[0020] The dimensions of the multilayer ceramic capacitor 1 are not particularly limited. For example, the dimension of the body 10 in the length direction L is 0.35 mm or more and 3.6 mm or less, the dimension of the body 10 in the width direction W is 0.15 mm or more and 2.9 mm or less, and the dimension of the body 10 in the stacking direction T is 0.15 mm or more and 2.9 mm or less.

[0021] FIG. 2 is an example of an LT cross-sectional view including the length direction L and the stacking direction T along the line II-II of the multilayer ceramic capacitor shown in FIG. 1. FIG. 3 is an example of a WT cross-sectional view including the width direction W and the stacking direction T along the line III-III of the multilayer ceramic capacitor shown in FIG. 1.

[0022] The body 10 includes a plurality of dielectric ceramic layers 20 and a plurality of internal electrode layers 30 stacked in the stacking direction T.

[0023] The internal electrode layer 30 includes, for example, a first internal electrode layer 31 and a second internal electrode layer 32 alternately arranged in the stacking direction T.

[0024] The first internal electrode layer 31 extends to the first end face 10e of the body 10 and is electrically connected to the external electrode 11 there.

[0025] The second internal electrode layer 32 extends to the second end face 10f of the body 10 and is electrically connected to the external electrode 12 there.

[0026] The first internal electrode layer 31 and the second internal electrode layer 32 facing each other with the dielectric ceramic layer 20 interposed therebetween are not electrically connected. Therefore, when a voltage is applied between the first internal electrode layer 31 and the second internal electrode layer 32 via the external electrodes 11 and 12, charges are accumulated. Capacitance is generated by the accumulated charges, and thereby the function as a capacitive element is exhibited.

[0027] An outer layer portion 25 formed by stacking only the dielectric ceramic layers 20 may be provided outside the plurality of dielectric ceramic layers 20 and the plurality of internal electrode layers 30 stacked in the stacking direction T. The outer layer portion 25 is located on both main surface sides of the body 10 and is a dielectric ceramic layer located between each main surface and the internal electrode layer 30 closest to that main surface. On the other hand, the region sandwiched between both outer layer portions 25 can also be referred to as an inner layer portion.

[0028] The internal electrode layer 30 contains nickel (Ni) and a first rare earth element.

[0029] Nickel (Ni) is the main component of the internal electrode layer 30. The internal electrode layer 30 may contain nickel as a conductive metal, or it may contain a nickel alloy.

[0030] The first rare earth element includes at least one rare earth element (Re) selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), yttrium (Y), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0031] In the multilayer ceramic capacitor 1, within a range of 10 nm from the interface between the internal electrode layer 30 and the dielectric ceramic layer 20 toward the internal electrode layer 30, the elemental ratio of Re to the sum of Ni and Re satisfies 0.001 ≤ Re / (Ni + Re) ≤ 0.060.

[0032] Actual capacitors have, in addition to their capacitance component, resistive components due to losses in the dielectric or electrodes, and parasitic inductance components due to electrodes or lead wires. Therefore, the frequency characteristics of the impedance |Z| are V-shaped, and the equivalent series resistance (ESR) also shows frequency characteristics corresponding to the loss. As described above, the inventors have discovered that in multilayer ceramic capacitors containing rare earth elements such as Dy in the internal electrode layer containing Ni, the rare earth elements such as Dy increase the electrode resistance, leading to an increase in ESR and a problem of heat generation.

[0033] In the multilayer ceramic capacitor 1, the ESR can be lowered by controlling the elemental ratio of Re to the sum of Ni and Re within the above range of the internal electrode layer 30 to 0.001 ≤ Re / (Ni + Re) ≤ 0.060. As a result, the effect of suppressing heat generation in the multilayer ceramic capacitor 1 is obtained.

[0034] In the above range of the internal electrode layer 30, there is no particular limit to the method for controlling the elemental ratio of Re to the sum of Ni and Re to 0.001 ≤ Re / (Ni + Re) ≤ 0.060. For example, the elemental ratio of Re / (Ni + Re) can be reduced by setting the firing temperature during manufacturing to a relatively high temperature. This is because the co-material contained in the conductive paste is discharged to the dielectric ceramic layer 20 side during firing, and it is thought that increasing the firing temperature reduces the elemental ratio of Re / (Ni + Re).

[0035] Furthermore, using a relatively low firing temperature also has the effect of suppressing a decrease in the coverage of the internal electrode layer 30. The coverage of the internal electrode layer 30 refers to the ratio of the area of ​​the internal electrode layer 30 to the area of ​​the dielectric ceramic layer 20 (coverage rate).

[0036] In the multilayer ceramic capacitor 1, it is preferable that the elemental ratio of Re to the sum of Ni and Re in the range of 10 nm or less from the interface between the internal electrode layer 30 and the dielectric ceramic layer 20 toward the internal electrode layer 30 satisfies 0.008 ≤ Re / (Ni + Re) ≤ 0.060.

[0037] As described above, the co-material contained in the conductive paste for forming the internal electrode layer 30 is discharged to the dielectric ceramic layer 20 side during firing. Therefore, in the multilayer ceramic capacitor 1, it is preferable that the content of the first rare earth element in the range of 10 nm or less from the interface between the internal electrode layer 30 and the dielectric ceramic layer 20 toward the internal electrode layer 30 is greater than the content of the first rare earth element in the center of the internal electrode layer 30.

[0038] The internal electrode layer 30 preferably contains first dielectric particles in which a first rare earth element is solid-dissolved in at least the central region of particles composed of a first perovskite-type composite oxide. In this case, the first perovskite-type composite oxide preferably contains at least one of barium (Ba), calcium (Ca), and strontium (Sr), and at least one of titanium (Ti) and zirconium (Zr).

[0039] On the other hand, it is preferable that the dielectric ceramic layer 20 includes second dielectric particles in which a second rare earth element is solid-dissolved in at least the central region of particles composed of a second perovskite-type composite oxide. In that case, the second perovskite-type composite oxide preferably contains at least one of barium (Ba), calcium (Ca), and strontium (Sr), and at least one of titanium (Ti) and zirconium (Zr), and the second rare earth element preferably contains at least one rare earth element (Re) selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), yttrium (Y), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0040] The first perovskite-type composite oxide and the second perovskite-type composite oxide may have the same composition or different compositions. The first perovskite-type composite oxide and the second perovskite-type composite oxide may contain only the same elements, or they may contain some or all different elements. Furthermore, the first rare earth element and the second rare earth element may be the same or different. The number of first rare earth elements and the number of second rare earth elements may be different.

[0041] The first perovskite-type composite oxide and the second perovskite-type composite oxide each preferably contain Ba and at least one of Ca and Sr.

[0042] For example, the first perovskite-type composite oxide and the second perovskite-type composite oxide are each barium titanate (BaTiO2). ３ It is a compound of the ) system. BaTiO ３ It is a ferroelectric material that exhibits a tetragonal crystal structure at room temperature and has a high dielectric constant. Therefore, BaTiO ３ By using the compound system as the main component of the dielectric ceramic layer 20, the dielectric constant of the dielectric ceramic layer 20 can be increased, making it possible to increase the capacitance of the capacitor.

[0043] For example, when the first perovskite-type composite oxide and the second perovskite-type composite oxide are BaTiO ３ -based compounds, the BaTiO ３ -based compound may be a compound in which part of Ba and / or Ti contained in BaTiO ３ is substituted with other elements. For example, part of Ba may be substituted with an alkaline earth metal element such as Ca or Sr, and part of Ti may be substituted with a transition metal element such as Zr or hafnium (Hf). Furthermore, the molar ratio of the A-site element (Ba, Ca, Sr, etc.) to the B-site element (Ti, Zr, Hf, etc.) of the BaTiO ３ -based compound (hereinafter also referred to as the A / B ratio) is not strictly limited to 1:1, and as long as the perovskite-type crystal structure is maintained, a deviation in the molar ratio of the A-site element to the B-site element is allowed.

[0044] When the dielectric ceramic layer 20 contains a rare earth element (Re), various properties such as the reliability of the multilayer ceramic capacitor 1 and the temperature characteristics of the dielectric constant can be improved. Perovskite-type composite oxides such as BaTiO ３ -based compounds may contain many oxygen vacancies generated in the firing process. These oxygen vacancies tend to reduce the insulation resistance when accompanied by electron compensation, and also tend to move under an electric field and cause a decrease in the insulation resistance over time.

[0045] Therefore, when the dielectric ceramic layer 20 contains a rare earth element (Re), BaTiO ３Rare earth elements (Re) tend to solid-solve in the A site (e.g., Ba site) or B site (e.g., Ti site) of perovskite-type composite oxides such as compound systems. In particular, in structures in which rare earth elements (Re) are solid-solved in at least the central region of particles composed of perovskite-type composite oxides, the solid-solved rare earth elements (Re) are more likely to act as donors or acceptors compared to structures in which rare earth elements (Re) are solid-solved in the peripheral region (shell region) of the particles, so-called core-shell structures, which do not solid-solve in the central region (core region) of the particles composed of perovskite-type composite oxides. This makes it easier to hinder the movement of oxygen vacancies or to suppress the generation of conduction electrons. As a result, the degradation of insulation resistance is reduced and the high-temperature load life is improved.

[0046] The first and second rare earth elements are preferably Dy. Dy is an element located near the middle of the lanthanide group in the periodic table, and its ionic radius is also of an intermediate size. Therefore, BaTiO ３ It can be dissolved in both the A site (e.g., the Ba site) and the B site (e.g., the Ti site) of perovskite-type complex oxides such as system compounds, and is effective in improving reliability.

[0047] Figure 4 is an example of a cross-sectional view illustrating the point analysis of the internal electrode layer. Figure 5 is another example of a cross-sectional view illustrating the point analysis of the internal electrode layer.

[0048] For the multilayer ceramic capacitor 1, the various elemental ratios (atomic concentration ratios) in the internal electrode layer 30 can be determined by analyzing the cross-section of the internal electrode layer 30 with a scanning transmission electron microscope (STEM)-energy dispersive X-ray spectrometer (EDX), as shown in Figure 4 or Figure 5, and performing point analysis on the obtained cross-sectional EDX image. The number of measurement points is not particularly limited; for example, by performing point analysis on cross-sectional EDX images at different locations, the average value of point analyses at 20 locations can be obtained. For example, Figure 4 shows an example of point analysis within a range of 10 nm from the interface between the internal electrode layer 30 and the dielectric ceramic layer 20 towards the internal electrode layer 30. On the other hand, Figure 5 shows an example of point analysis at the center of the internal electrode layer 30.

[0049] Specifically, the central part of the multilayer ceramic capacitor 1 is polished to obtain an LT cross-section, exposing the internal electrode layer 30. STEM observation is performed on particles in a predetermined range of the exposed internal electrode layer 30, and a mapping image showing the elemental distribution is obtained using EDX.

[0050] In the dielectric ceramic layer 20 and the internal electrode layer 30, the rare earth element (Re) only needs to be solid-dissolved in at least the central region of the particles composed of the perovskite-type composite oxide. Specifically, the rare earth element (Re) may be solid-dissolved only in the central region of the particle, or it may be solid-dissolved in the central region as well as in regions other than the central region. Among these, it is preferable that the rare earth element (Re) is solid-dissolved throughout the entire particle, and more preferably that it is uniformly solid-dissolved throughout the entire particle.

[0051] For the multilayer ceramic capacitor 1, the distribution of rare earth elements (Re) in the particles of the dielectric ceramic layer 20 and the internal electrode layer 30 can be confirmed from the mapping image showing the elemental distribution described above. If the mapping image confirms that rare earth elements (Re) are distributed in at least the central region of the particles, this state is considered to be that the rare earth elements (Re) are solid-dissolved in at least the central region of the particles.

[0052] The internal electrode layer 30 may include, in the case where the internal electrode layer 30 includes first dielectric particles in which the first rare earth element is solid-dissolved in at least the central region of the particles composed of the first perovskite-type composite oxide, it may also include dielectric particles in which the first rare earth element is not solid-dissolved in the central region of the particles composed of the first perovskite-type composite oxide. For example, the internal electrode layer 30 may include dielectric particles in which the first rare earth element is not solid-dissolved throughout the entire particles composed of the first perovskite-type composite oxide, or it may include dielectric particles in which the first rare earth element is solid-dissolved only in the outer peripheral region of the particles composed of the first perovskite-type composite oxide.

[0053] The dielectric ceramic layer 20 may include dielectric particles in which the second rare earth element is dissolved in at least the central region of the particles composed of the second perovskite-type composite oxide, or it may include dielectric particles in which the second rare earth element is not dissolved in the central region of the particles composed of the second perovskite-type composite oxide. For example, the dielectric ceramic layer 20 may include dielectric particles in which the second rare earth element is not dissolved throughout the entire particles composed of the second perovskite-type composite oxide, or it may include dielectric particles in which the second rare earth element is dissolved only in the outer peripheral region of the particles composed of the second perovskite-type composite oxide.

[0054] The dielectric ceramic layer 20 may further contain elements other than the barium (Ba), calcium (Ca), strontium (Sr), titanium (Ti), zirconium (Zr), and rare earth elements (Re) mentioned above. Examples of other elements include alloying elements such as magnesium (Mg), manganese (Mn), and silicon (Si).

[0055] The internal electrode layer 30 may further contain elements other than the aforementioned nickel (Ni), barium (Ba), calcium (Ca), strontium (Sr), titanium (Ti), zirconium (Zr), and rare earth elements (Re). However, it is preferable that the internal electrode layer 30 does not contain additive elements such as magnesium (Mg), manganese (Mn), and silicon (Si).

[0056] The thickness of the dielectric ceramic layer 20 is not particularly limited, and is, for example, 0.55 μm or more and 1.6 μm or less. If the thickness of the dielectric ceramic layer 20 is within the above range, deterioration of the insulating properties can be prevented. Furthermore, if the thickness of the dielectric ceramic layer 20 is within the above range, the dielectric ceramic layer 20 can be made thinner, and the capacitance can be improved.

[0057] The number of dielectric ceramic layers 20 is, for example, 50 or more and 1000 or less.

[0058] The average particle size of the ceramic grains contained in the dielectric ceramic layer 20 is not particularly limited, but is preferably 100 nm or more and 400 nm or less, and more preferably 150 nm or more and 300 nm or less.

[0059] The thickness of the internal electrode layer 30 is not particularly limited, and is, for example, 0.45 μm or more and 0.70 μm or less. When the thickness of the internal electrode layer 30 is within the above range, defects such as electrode breaks are suppressed. Furthermore, when the thickness of the internal electrode layer 30 is within the above range, the decrease in the proportion of the electrically functional dielectric ceramic layer 20 in the capacitor is suppressed, making it possible to suppress a decrease in capacitance.

[0060] The thickness of the dielectric ceramic layer 20 and the internal electrode layer 30 is determined by observing the WT cross-section of the exposed substrate 10 by polishing using a scanning electron microscope (SEM). The thickness is measured along a center line passing through the center of the WT cross-section along the stacking direction T, and along a total of five lines drawn at equal intervals on both sides of this center line. The average of these five measured values ​​is then used.

[0061] Furthermore, the average particle size of the ceramic grains contained in the dielectric ceramic layer 20 can be measured by analyzing cross-sectional images scanned with a SEM. For example, the average particle size of the ceramic grains can be measured using software that measures the average particle size in accordance with the JIS G 0551:2013 standard.

[0062] The configuration of the external electrodes 11 and 12 is not particularly limited. The external electrodes 11 and 12 may have a laminated structure consisting of a base layer, a first plating layer, and a second plating layer, starting from the end face side of the multilayer ceramic capacitor 1. The base layer contains a metal such as nickel (Ni) or copper (Cu). The base layer may also contain ceramic powder as a co-material in addition to the metal. The first plating layer is, for example, a nickel (Ni) plating layer. The second plating layer is, for example, a tin (Sn) plating layer. A conductive resin layer may be provided between the base layer and the first plating layer. The conductive resin layer is a layer containing conductive metal particles made of copper (Cu), silver (Ag), nickel (Ni), or an alloy containing at least one of these metals, and a resin. The external electrodes 11 and 12 are not limited in their form as long as they are electrically connected to the internal electrode layer 30 and function as external input / output terminals.

[0063] The manufacturing method of the multilayer ceramic capacitor of the present invention is not limited, as long as the above-mentioned requirements are satisfied.

[0064] The present invention relates to a method for manufacturing a multilayer ceramic capacitor, comprising: a step of manufacturing a green sheet containing, for example, at least one of barium (Ba), calcium (Ca), and strontium (Sr), at least one of titanium (Ti) and zirconium (Zr), and at least one of rare earth elements (Re) (green sheet manufacturing step); and a step of manufacturing nickel (Ni), at least one of barium (Ba), calcium (Ca), and strontium (Sr), at least one of titanium (Ti) and zirconium (Zr), and rare earth elements The process comprises the steps of: applying a conductive paste containing at least one element (Re) to the surface of the green sheet to obtain a green sheet with an internal electrode pattern formed on it (electrode pattern formation step); stacking and pressing a plurality of green sheets to obtain a stacked block (stacking step); cutting the obtained stacked block to obtain a stacked chip (cutting step); subjecting the obtained stacked chip to a binder removal process and a firing process to obtain a base body (firing step); and forming external electrodes on the obtained base body (external electrode formation step). Details of each step are described below.

[0065] <Green Sheet Manufacturing Process> In the green sheet manufacturing process, a green sheet is manufactured containing, for example, at least one of barium (Ba), calcium (Ca), and strontium (Sr), at least one of titanium (Ti) and zirconium (Zr), and at least one of rare earth elements (Re). The green sheet is a precursor of the dielectric ceramic layer and contains the main component raw material and additive raw material of the dielectric ceramic layer. The method for manufacturing the green sheet is not particularly limited. For example, a dielectric raw material can be manufactured by mixing the main component raw material with the additive raw material, a binder and a solvent can be added and mixed to the obtained dielectric raw material to form a slurry, and a green sheet can be formed from the obtained slurry.

[0066] For example, BaTiO ３ A powder of the compound is used. BaTiO ３ The compound can be synthesized using known ceramic synthesis methods such as solid-phase reaction, hydrothermal synthesis, or alkoxide synthesis, with known ceramic raw materials such as oxides, carbonates, hydroxides, nitrates, organic acid salts, alkoxides, and / or chelate compounds.

[0067] BaTiO ３ When synthesizing compound iontochemistry, for example, in addition to Ba, Ti, and Re raw materials, Ca, Sr, Zr, etc., as needed, are wet-mixed in a ball mill, dried, and then heated. At this time, in order to facilitate the solid solution of the element Re, the Re raw material may be pre-milled (also called fine powdering). Furthermore, in order to facilitate the solid solution of elements such as Re, Ca, Sr, and Zr, the wet-mixing and heating process may be repeated after heating.

[0068] As the Ba raw material, known ceramic raw materials such as Ba oxides, carbonates, acetates, hydroxides, and chlorides can be used.

[0069] As the Ti raw material, known ceramic raw materials such as Ti oxides, acetates, and chlorides can be used.

[0070] As the Re raw material, known ceramic raw materials such as Re oxides, carbonates, acetates, and hydroxides can be used.

[0071] As the Ca raw material, known ceramic raw materials such as Ca oxides and carbonates are used.

[0072] As the Sr raw material, known ceramic raw materials such as Sr oxides and carbonates are used.

[0073] As the Zr raw material, known ceramic raw materials such as Zr oxides, acetates, and chlorides can be used.

[0074] The additive raw materials may also include raw materials for other additive components such as Mn, Mg, Si, Al, and V. Furthermore, the main component is BaTiO ３ To adjust the composition of the compound system, barium carbonate (BaCO3) is used. ３ ) and titanium dioxide (TiO ２ Ba raw materials and Ti raw materials such as ) may be added to the additive raw materials.

[0075] Slurry formation can be carried out by known methods; for example, by mixing an organic binder and an organic solvent with the dielectric material. As the organic binder, known binders such as polyvinyl butyral-based binders can be used. As the organic solvent, known solvents such as toluene and ethanol can be used. Additives such as plasticizers may be added to the slurry as needed. Furthermore, the green sheet can be formed by known methods such as the doctor blade method or the lip method.

[0076] <Electrode Pattern Formation Process> In the electrode pattern formation process, a conductive paste is applied to the surface of a green sheet to obtain a green sheet with an internal electrode pattern formed on it. The internal electrode pattern becomes the internal electrode layer after firing. Conductive materials such as nickel (Ni) or alloys containing Ni are used as the conductive metal in the conductive paste. It is also preferable to add a ceramic component that acts as a co-material to the conductive paste. As the ceramic component, for example, the main component raw material of a dielectric ceramic layer is used. The conductive paste can be applied by known methods such as screen printing or gravure printing.

[0077] <Lamination Process> In the lamination process, multiple green sheets are laminated and compressed to obtain a laminated block. Green sheets with internal electrode patterns are used as the green sheets, but some green sheets without internal electrode patterns may also be used. Lamination and compression can be carried out by known methods.

[0078] <Cutting Process> In the cutting process, the obtained laminated block is cut to obtain a laminated chip. The cutting should be performed in such a way that a chip of a predetermined size is obtained and at least a portion of the internal electrode pattern is exposed on the end face of the laminated chip.

[0079] <Firing Process> In the firing process, the obtained laminated chip is subjected to a binder removal process and a firing process to obtain a base material. The firing process causes the green sheet and the internal electrode pattern to co-sinter, forming the dielectric ceramic layer and the internal electrode layer, respectively. The conditions for the binder removal process should be determined according to the type of organic binder contained in the green sheet and the internal electrode pattern. The firing process should be performed at a temperature at which the laminated chip becomes sufficiently dense. The firing process is performed, for example, with the main component BaTiO ３ The process is carried out in an atmosphere that prevents the reduction of the compound and suppresses the oxidation of the conductive metal. Furthermore, additional heat treatment may be performed after firing at an appropriate temperature and atmosphere.

[0080] <External Electrode Formation Process> In the external electrode formation process, external electrodes are formed on the obtained base body. The external electrodes can be formed by known methods. For example, they can be formed by applying and baking a conductive paste containing a metal such as silver (Ag), copper (Cu), and / or nickel (Ni) onto the end face of the base body exposed after the internal electrode layer has been drawn out. Alternatively, they can be formed by applying a conductive paste to both end faces of the laminated chip before firing and then performing a firing process. Furthermore, the formed electrodes can be used as a base layer, and a plating film of nickel (Ni) or tin (Sn) can be formed on top of it.

[0081] Based on the above steps, a multilayer ceramic capacitor is fabricated.

[0082] This specification discloses the following:

[0083] <1> A substrate comprising a plurality of dielectric ceramic layers and a plurality of internal electrode layers stacked in the stacking direction, and an external electrode provided on the surface of the substrate and electrically connected to the internal electrode layer, wherein the internal electrode layer comprises nickel (Ni) and a first rare earth element, and the first rare earth element comprises at least one rare earth element (Re) selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), yttrium (Y), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), A multilayer ceramic capacitor in which, within a range of 10 nm from the interface between the internal electrode layer and the dielectric ceramic layer toward the internal electrode layer, the elemental ratio of Re to the sum of Ni and Re satisfies 0.001 ≤ Re / (Ni + Re) ≤ 0.060.

[0084] <2> The multilayer ceramic capacitor according to <1>, wherein, in a range of 10 nm or less from the interface between the internal electrode layer and the dielectric ceramic layer toward the internal electrode layer, the elemental ratio of Re to the sum of Ni and Re satisfies 0.008 ≤ Re / (Ni + Re) ≤ 0.060.

[0085] <3> The multilayer ceramic capacitor according to <1> or <2>, wherein the content of the first rare earth element in a range of 10 nm or less from the interface between the internal electrode layer and the dielectric ceramic layer toward the internal electrode layer is greater than the content of the first rare earth element in the center of the internal electrode layer.

[0086] <4> The multilayer ceramic capacitor according to any one of <1> to <3>, wherein the internal electrode layer includes first dielectric particles in which the first rare earth element is solid-dissolved in at least the central region of particles composed of the first perovskite-type composite oxide, and the first perovskite-type composite oxide includes at least one of barium (Ba), calcium (Ca), and strontium (Sr), and at least one of titanium (Ti) and zirconium (Zr).

[0087] <5> The dielectric ceramic layer comprises second dielectric particles in which a second rare earth element is solid-dissolved in at least the central region of particles composed of a second perovskite-type composite oxide, the second perovskite-type composite oxide comprises at least one of barium (Ba), calcium (Ca), and strontium (Sr), and at least one of titanium (Ti) and zirconium (Zr), The multilayer ceramic capacitor according to <4>, wherein the second rare earth element described above includes at least one rare earth element (Re) selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), yttrium (Y), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0088] <6> The multilayer ceramic capacitor described in <5>, wherein the first rare earth element and the second rare earth element are each Dy.

[0089] <7> The multilayer ceramic capacitor according to <5> or <6>, wherein the first perovskite-type composite oxide and the second perovskite-type composite oxide each contain Ba and at least one of Ca and Sr.

[0090] <8> A multilayer ceramic capacitor according to any one of <1> to <7>, wherein the thickness of the internal electrode layer is 0.45 μm or more and 0.70 μm or less.

[0091] <9> A multilayer ceramic capacitor according to any one of <1> to <8>, wherein the thickness of the dielectric ceramic layer is 0.55 μm or more and 1.6 μm or less.

[0092] <10> The base body has a first main surface and a second main surface facing the stacking direction, a first side surface and a second side surface facing the width direction perpendicular to the stacking direction, and a first end surface and a second end surface facing the length direction perpendicular to the stacking direction and the width direction, the length dimension of the base body is 0.35 mm or more and 3.6 mm or less, the width dimension of the base body is 0.15 mm or more and 2.9 mm or less, and the stacking dimension of the base body is 0.15 mm or more and 2.9 mm or less, as described in any one of <1> to <9>.

[0093] The following are examples that more specifically disclose the multilayer ceramic capacitor of the present invention. However, the present invention is not limited to these examples.

[0094] [Fabrication of Multilayer Ceramic Capacitors] BaCO ３ powder, CaCO ３ Powder, TiO ２ Powder and D ２ O ３ Powders were prepared. These powders were weighed in predetermined proportions, and ZrO ２ A wet ball mill was performed using balls for 24 hours. The prepared slurry was dried into a powder, which was heated in air at a rate of 600°C / hour to 1300°C, held for 2 hours, and then cooled to obtain calcined powder. This calcined powder was then processed again with ZrO ２ A wet ball mill was performed using balls for 24 hours to produce a dry powder, which was then subjected to heat treatment at 1300°C as before. The heat treatment at 1300°C and the subsequent wet ball milling were repeated a total of three times to obtain the final calcined powder.

[0095] The resulting calcined powder was treated with BaCO3 ３ Powder, MgCO ３ Powder, MnCO ３ Powder and SiO ２ By adding a sol, followed by wet mixing and drying, a dielectric powder for a dielectric ceramic layer was obtained.

[0096] Next, BaCO ３ powder, CaCO ３ Powder, TiO ２ Powder and D ２ O３ Powders were prepared. These powders were weighed in predetermined proportions, and ZrO ２ A wet ball mill was performed using balls for 24 hours. The prepared slurry was dried into a powder, which was heated in air at a rate of 600°C / hour to 1300°C, held for 2 hours, and then cooled to obtain calcined powder. This calcined powder was then processed again with ZrO ２ A wet ball mill was performed using balls for 24 hours to produce a dry powder, which was then subjected to heat treatment at 1300°C as before. The heat treatment at 1300°C and the subsequent wet ball milling were repeated a total of three times to obtain an oxide material to be added to the conductive paste for the internal electrode layer.

[0097] A polybutyral-based binder and a plasticizer are added to the dielectric powder for the dielectric ceramic layer obtained, and then toluene and ethyl alcohol are added, and ZrO ２ The material was slurryed using a wet ball mill with balls, and this slurry was molded to obtain a green sheet. The thickness of the green sheet was adjusted to 1.7 μm after sintering and densification.

[0098] A conductive paste mainly composed of nickel, to which the above oxide co-material was added, was screen printed onto the surface of the obtained green sheet to form a pattern of conductive paste layers that would serve as the internal electrode layer.

[0099] Subsequently, 201 green sheets, each with a conductive paste layer formed on its surface, were stacked so that the sides with the conductive paste layer extended were alternating. Then, green sheets without a conductive paste layer were placed above and below them, and the entire assembly was pressed together to create a laminated block.

[0100] The resulting multilayer blocks were cut to produce green multilayer chips. The multilayer blocks were cut so that the length of the manufactured multilayer ceramic capacitors would be 3.2 mm and the width 1.6 mm.

[0101] The obtained green multilayer chips are N ２ The binder was removed by burning off the heat treatment at 280°C in an airflow. Subsequently, N was used at the firing temperatures shown in Table 1. ２ -H ２ -H ２ In an O-flow, the partial pressure of oxygen is 1.6 × 10⁻⁶.－９ The firing process was carried out for 2 hours under MPa conditions.

[0102] In the fired laminated chip, a conductive paste mainly composed of Cu was applied to the end face where the internal electrode layer was drawn out, and baked at 800°C to form the base layer for the external electrode. Furthermore, the external electrode was formed by forming a Ni plating layer and a Sn plating layer on the surface of the base layer.

[0103] A multilayer ceramic capacitor was fabricated using the above process. The resulting multilayer ceramic capacitor had external dimensions of 3.2 mm in length, 1.6 mm in width, and 1.6 mm in thickness. The number of dielectric ceramic layers sandwiched between the internal electrode layers was 200, and the thickness of each dielectric ceramic layer was 1.6 μm. The thickness of the internal electrode layer was 0.7 μm.

[0104] The multilayer ceramic capacitors were solidified with resin after firing and then polished. Table 1 shows the compositional analysis values ​​of the internal electrode layer within a range of 10 nm from the interface between the internal electrode layer and the dielectric ceramic layer toward the internal electrode layer.

[0105] [STEM-EDS Analysis] The internal electrode layer, located approximately halfway through the length, width, and height of the multilayer ceramic capacitor, was observed using a scanning transmission electron microscope (STEM), and component analysis of the fine region was performed using the attached energy-dispersive X-ray spectrometer (EDS). The observation samples were prepared by thinning the internal electrode layer using the FIB lift-out method. Observation and analysis were performed under the following conditions. • Equipment: JEOL Ltd., FE-TEM / EDX (JEOL JEM-F200 / Noran system 7) • STEM image observation, EDX point analysis • Field of view: n=1 • Magnification: 100,000x • Acceleration voltage: 200kV • Focusing lens aperture: #3 (40μm) • Camera length (cm): 300mm • EDX measurement conditions • Focusing lens aperture: #3 • Spot diameter: 5 • Number of pixels: 256×256 • Measurement seconds / frame: 10sec / frame • Number of integrations: 100 times The characteristic X-rays used for quantitative analysis of the internal electrode layer were K-rays for Ca and Ti, and L-rays for other elements.

[0106] [ESR Measurement] The frequency characteristics of the ESR were obtained for the fabricated multilayer ceramic capacitor using an impedance analyzer. The frequency range measured was from 0.01 to 1000 MHz. Table 1 shows the ESR value at 10 MHz.

[0107] [Coverage Measurement] Coverage was calculated by determining the ratio of the area where the internal electrode layer actually exists to the total area of ​​the field of view in an electron microscope image taken at a magnification of 2000x, including the central region of the internal electrode layer.

[0108]

[0109] As shown in Table 1, in Examples 1 to 10, where the elemental ratio of Re to the sum of Ni and Re satisfies 0.001 ≤ Re / (Ni + Re) ≤ 0.060 within a range of 10 nm from the interface between the internal electrode layer and the dielectric ceramic layer toward the internal electrode layer, the increase in ESR is suppressed.

[0110] Furthermore, in Examples 1 to 9, which satisfy 0.008 ≤ Re / (Ni + Re) ≤ 0.060, the decrease in coverage of the internal electrode layer is also suppressed.

[0111] The above evaluation focuses on the case where the rare earth element is Dy. However, similar evaluation results were confirmed for cases where the rare earth element is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb, Lu, or combinations thereof.

[0112] 1 Multilayer ceramic capacitor 10 Base body 10a First main surface 10b Second main surface 10c First side surface 10d Second side surface 10e First end surface 10f Second end surface 11, 12 External electrodes 20 Dielectric ceramic layer 25 Outer layer 30 Internal electrode layer 31 First internal electrode layer 32 Second internal electrode layer L Length direction W Width direction T Stacking direction

Claims

1. A substrate comprising a plurality of dielectric ceramic layers and a plurality of internal electrode layers stacked in the stacking direction, and an external electrode provided on the surface of the substrate and electrically connected to the internal electrode layer, wherein the internal electrode layer comprises nickel (Ni) and a first rare earth element, and the first rare earth element comprises at least one rare earth element (Re) selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), yttrium (Y), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), A multilayer ceramic capacitor in which, within a range of 10 nm from the interface between the internal electrode layer and the dielectric ceramic layer toward the internal electrode layer, the elemental ratio of Re to the sum of Ni and Re satisfies 0.001 ≤ Re / (Ni + Re) ≤ 0.

060.

2. The multilayer ceramic capacitor according to claim 1, wherein, in a range of 10 nm or less from the interface between the internal electrode layer and the dielectric ceramic layer toward the internal electrode layer, the elemental ratio of Re to the sum of Ni and Re satisfies 0.008 ≤ Re / (Ni + Re) ≤ 0.

060.

3. The multilayer ceramic capacitor according to claim 1 or 2, wherein the content of the first rare earth element in a range of 10 nm or less from the interface between the internal electrode layer and the dielectric ceramic layer toward the internal electrode layer is greater than the content of the first rare earth element in the center of the internal electrode layer.

4. The multilayer ceramic capacitor according to any one of claims 1 to 3, wherein the internal electrode layer includes first dielectric particles in which the first rare earth element is solid-dissolved in at least the central region of particles composed of a first perovskite-type composite oxide, and the first perovskite-type composite oxide includes at least one of barium (Ba), calcium (Ca), and strontium (Sr), and at least one of titanium (Ti) and zirconium (Zr).

5. The dielectric ceramic layer includes second dielectric particles in which a second rare earth element is solid-dissolved in at least the central region of particles composed of a second perovskite-type composite oxide, the second perovskite-type composite oxide includes at least one of barium (Ba), calcium (Ca), and strontium (Sr), and at least one of titanium (Ti) and zirconium (Zr), The multilayer ceramic capacitor according to claim 4, wherein the second rare earth element includes at least one rare earth element (Re) selected from the group consisting of lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), yttrium (Y), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

6. The multilayer ceramic capacitor according to claim 5, wherein the first rare earth element and the second rare earth element are each Dy.

7. The multilayer ceramic capacitor according to claim 5 or 6, wherein the first perovskite-type composite oxide and the second perovskite-type composite oxide each comprise Ba and at least one of Ca and Sr.

8. The multilayer ceramic capacitor according to any one of claims 1 to 7, wherein the thickness of the internal electrode layer is 0.45 μm or more and 0.70 μm or less.

9. The multilayer ceramic capacitor according to any one of claims 1 to 8, wherein the thickness of the dielectric ceramic layer is 0.55 μm or more and 1.6 μm or less.

10. The multilayer ceramic capacitor according to any one of claims 1 to 9, wherein the base body has a first main surface and a second main surface facing the stacking direction, a first side surface and a second side surface facing the width direction perpendicular to the stacking direction, and a first end surface and a second end surface facing the length direction perpendicular to the stacking direction and the width direction, the length dimension of the base body is 0.35 mm or more and 3.6 mm or less, the width dimension of the base body is 0.15 mm or more and 2.9 mm or less, and the stacking dimension of the base body is 0.15 mm or more and 2.9 mm or less.

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