Multilayer ceramic capacitor

Abstract

A multilayer ceramic capacitor according to one aspect of the present invention has a plurality of terminal electrodes containing a metal having nickel as a main component element on the surface of at least one cover layer of a multilayer sheet, and a plurality of terminal electrodes are formed on terminal electrode facing portions of the cover layer. In an element distribution map generated by measuring the nickel concentration distribution in an arbitrary cross-section parallel to the stacking direction, there is a nickel segregation region identified as a region having a higher nickel concentration than the surroundings and having a maximum size of 0.4 [mu] m or more. The density of a nickel segregation region having a maximum size of 0.5 [mu] m or more among the nickel segregation regions is 0.015 / [mu] m2 or more, and in an element distribution pattern generated by measuring the nickel concentration distribution in an arbitrary cross-section parallel to the lamination direction in the terminal electrode non-facing portion of the coating layer, the nickel concentration distribution is less than or equal to 0.015 / [mu] m2. The density of the nickel segregation region having a maximum size of 0.5 [mu] m or more is 0.008 / [mu] m2 or less.

Description

Technical Field

[0001] The present invention relates to a laminated ceramic capacitor. Background Art

[0002] A known structure of a multilayer ceramic capacitor includes: a multilayer sheet in which dielectric layers formed of dielectric ceramic and internal electrodes composed mainly of metal are alternately stacked, and a cover layer formed of dielectric ceramic is provided at both ends in the stacking direction; a pair of connecting conductors formed within or on the surface of the multilayer sheet, which alternately connect the internal electrodes to each other in the stacking direction; and a pair of terminal electrodes formed on the surface of one of the cover layers, which are electrically connected to the pair of connecting conductors.

[0003] In a multilayer ceramic capacitor having such a structure, a structure in which a conductive metal or an oxide thereof is contained in a cover layer has been reported.

[0004] Patent Document 1 discloses a multilayer ceramic capacitor in which a plurality of diffusion metal portions formed of the same metal as that contained in internal electrodes are arranged on first and second principal surface side outer layer portions corresponding to cover layers.

[0005] Patent Document 2 discloses that, when manufacturing a multilayer ceramic capacitor, overoxidized metal particles are contained in a green sheet forming an outer cover corresponding to a cover layer, thereby obtaining a multilayer ceramic capacitor having reduced metal particles contained in the cover layer.

[0006] Patent Document 3 discloses that, when manufacturing a multilayer ceramic capacitor, a ceramic green sheet used to form an outer layer portion corresponding to a cover layer is preliminarily provided with an oxide of a conductive metal powder included in an internal electrode.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2019-106443

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2015-226053

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2003-173925 Summary of the Invention

[0012] Technical problem to be solved by the invention

[0013] A multilayer ceramic capacitor having the above-described structure can be mounted on a circuit board by connecting the terminal electrodes to the circuit board. In such a multilayer ceramic capacitor mounted on a circuit board, stress concentrates on the terminal electrodes and the cover layer in contact therewith due to the flexure of the circuit board. Therefore, when mounted on a circuit board that is expected to experience significant flexural deformation during use, multilayer ceramic capacitors having the above-described structure must be able to suppress cracks in the cover layer and prevent short-circuit failures caused by cracks reaching the internal electrodes.

[0014] However, Patent Documents 1 to 3 do not disclose a multilayer ceramic capacitor capable of suppressing cracking in the cover layer due to external stress concentration.

[0015] Furthermore, in recent years, the miniaturization of multilayer ceramic capacitors has been progressing, and with this, the cover layer has been thinning, and the distance between terminal electrodes has been narrowing. In the multilayer ceramic capacitors disclosed in Patent Documents 1 to 3, the thinning of the cover layer may cause conductive metal to precipitate on the surface of the cover layer. As the distance between the terminal electrodes is narrowed, the terminal electrodes may short-circuit through the precipitated conductive metal.

[0016] Therefore, an object of the present invention is to provide a multilayer ceramic capacitor that can suppress cracking in a cover layer due to external stress concentration and can also suppress short circuiting between terminal electrodes.

[0017] Means for solving technical problems

[0018] The inventors have conducted various studies to solve the above-mentioned problems and have discovered that, when manufacturing a multilayer ceramic capacitor, by forming a terminal electrode or its base layer containing a metal having nickel as a main component element by using a physical vapor deposition (PVD) method or a spraying method and then firing it, a segregation portion of the metal element contained in the terminal electrode or its base layer can be generated in the covering layer opposite to the terminal electrode, thereby suppressing the occurrence of cracks in the covering layer, thereby completing the present invention.

[0019] That is, a first aspect of the present invention for solving the above-mentioned technical problems is a multilayer ceramic capacitor characterized by comprising: a laminated sheet in which dielectric layers formed of dielectric ceramic and internal electrodes composed mainly of metal are alternately laminated, and a cover layer composed of dielectric ceramic is provided at both ends in the lamination direction; a connecting conductor formed inside or on the surface of the laminated sheet, which electrically connects the internal electrodes to each other; and a plurality of terminal electrodes formed on the surface of at least one of the cover layers at intervals, which are electrically connected to the connecting conductor and contain a metal composed mainly of nickel at least in a portion in contact with the cover layer, when provided on the surface When the portion of the covering layer having the terminal electrode that overlaps with each terminal electrode when viewed from the stacking direction is a terminal electrode opposing portion, and the portion of the covering layer having the terminal electrode on the surface that does not overlap with each terminal electrode when viewed from the stacking direction is a terminal electrode non-opposing portion, in each of the terminal electrode opposing portions, in an element distribution map generated by measuring the nickel concentration distribution in an arbitrary cross-section parallel to the stacking direction, there is a nickel segregation region identified as a region with a maximum size of 0.4 μm or more in which the nickel concentration is higher than that of the surrounding area, and the density of the nickel segregation regions with a maximum size of 0.5 μm or more in the nickel segregation region is 0.015 places / μm or more. 2 In the element distribution map generated by measuring the nickel concentration distribution in any cross section parallel to the stacking direction in the non-opposing portion of the terminal electrodes, the density of the nickel segregation area with a maximum size of 0.5 μm or more is less than 0.008 places / μm 2 .

[0020] In addition, a second aspect of the present invention for solving the above-mentioned technical problems is a multilayer ceramic capacitor, characterized in that it includes: a laminated sheet in which dielectric layers formed of dielectric ceramic and internal electrodes mainly composed of metal are alternately laminated, and has a cover layer formed of dielectric ceramic at both ends in the stacking direction; a connecting conductor formed inside or on the surface of the laminated sheet, which electrically connects the internal electrodes to each other; and a plurality of terminal electrodes formed on the surface of at least one of the cover layers at intervals, which are electrically connected to the connecting conductor and contain a metal mainly composed of nickel at least in the portion contacting the cover layer, when the cover layer having the terminal electrodes provided on the surface overlaps with each terminal electrode when viewed in the stacking direction as a terminal electrode facing portion, and the cover layer having the terminal electrodes provided on the surface is provided with the terminal electrodes. When the portion of the covering layer of the terminal electrode that does not overlap with the terminal electrodes when viewed in the stacking direction is the non-opposite portion of the terminal electrode, in each of the terminal electrode opposing portions, when the element distribution map generated by measuring the nickel concentration distribution in an arbitrary cross-section parallel to the stacking direction is divided into square cells with one side of 5 μm, it can be internally confirmed that the number of cells of the nickel segregation area identified as an area with a maximum size of 0.4 μm or more and having a nickel concentration higher than the surrounding area is more than 50% of the total number of cells, and in the non-opposite portion of the terminal electrode, when the element distribution map generated by measuring the nickel concentration distribution in an arbitrary cross-section parallel to the stacking direction is divided into square cells with one side of 5 μm, it can be internally confirmed that the number of cells of the nickel segregation area is less than 5% of the total number of cells.

[0021] A third aspect of the present invention for solving the above-mentioned technical problems is a method for manufacturing a multilayer ceramic capacitor, which is the method for manufacturing a multilayer ceramic capacitor according to the first or second aspect, and comprises: preparing a powder of a dielectric ceramic composition; mixing the powder of the dielectric ceramic composition with a binder and forming the mixture into a sheet to obtain a green sheet; forming an internal electrode pattern comprising metal on the green sheet; laminating a predetermined number of green sheets having the internal pattern formed thereon, placing cover layer green sheets at both ends in the lamination direction, and then press-bonding the sheets to obtain a green laminate; singulating the green laminate to obtain pre-fired laminates; removing the binder from the pre-fired laminates; forming a plurality of metal layers having nickel as a main component element by physical vapor deposition or sputtering so as to be spaced apart from each other on the surface of at least one cover layer green sheet in the pre-fired laminate after the binder has been removed; and firing the resulting body having the plurality of metal layers formed thereon to obtain a sintered body.

[0022] Effects of the Invention

[0023] According to the present invention, it is possible to provide a multilayer ceramic capacitor capable of suppressing cracks in a cover layer due to external stress concentration and suppressing short circuits between terminal electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram (longitudinal cross-sectional view) showing the structure of a multilayer ceramic capacitor according to the first embodiment of the present invention.

[0025] Figure 2 Schematic diagram (cross-sectional view in the width direction) showing the structure of a multilayer ceramic capacitor according to the first embodiment of the present invention.

[0026] Figure 3 This is an example of an element distribution map obtained for a cross section parallel to the stacking direction of a terminal electrode opposing portion in the multilayer ceramic capacitor according to the first embodiment of the present invention.

[0027] Figure 4 This is an example of an element distribution diagram obtained for a cross section parallel to the stacking direction of a portion where the terminal electrodes do not face each other in the multilayer ceramic capacitor according to the first embodiment of the present invention.

[0028] Figure 5 This figure shows a state where a square unit cell S with a side of 5 μm is plotted in an element distribution map obtained on a cross section parallel to the stacking direction of a terminal electrode opposing portion of a multilayer ceramic capacitor according to a second embodiment of the present invention.

[0029] Figure 6 This figure shows a state where a square unit cell S with a side of 5 μm is plotted in an element distribution map obtained on a cross section parallel to the stacking direction of a portion where the terminal electrodes do not face each other in the multilayer ceramic capacitor according to the second embodiment of the present invention.

[0030] Figure 7 It is a schematic diagram (longitudinal cross-sectional view) showing the structure of a first modified example of the multilayer ceramic capacitor according to the first and second aspects of the present invention.

[0031] Figure 8 It is a schematic diagram (longitudinal cross-sectional view) showing a preferred structure of a first modified example of the multilayer ceramic capacitor according to the first and second aspects of the present invention.

[0032] Figure 9 It is a schematic diagram (longitudinal cross-sectional view) showing the structure of a second modified example of the multilayer ceramic capacitor according to the first and second aspects of the present invention.

[0033] Figure 10a 1 is a schematic diagram (longitudinal cross-sectional view) showing the structure of a third modified example of the multilayer ceramic capacitor according to the first and second aspects.

[0034] Figure 10b 1 is a schematic diagram (longitudinal cross-sectional view) showing the structure of a third modified example of the multilayer ceramic capacitor according to the first and second aspects.

[0035] Figure 10c 1 is a schematic diagram (longitudinal cross-sectional view) showing the structure of a third modified example of the multilayer ceramic capacitor according to the first and second aspects.

[0036] Figure 11 It is a schematic diagram (overall perspective view) showing the structure of a fourth modified example of the multilayer ceramic capacitor according to the first and second aspects. DETAILED DESCRIPTION

[0037] The following describes the technical solutions and effects of the present invention with reference to the accompanying drawings and in combination with the technical concept. However, the mechanism of action includes speculation, and its accuracy does not limit the present invention.

[0038] [Multilayer Ceramic Capacitors]

[0039] <First embodiment>

[0040] An embodiment of the multilayer ceramic capacitor according to the first aspect of the present invention is shown as a first embodiment. Figure 1 . The multilayer ceramic capacitor 100 of the first embodiment is in the shape of a rectangular parallelepiped, and includes a pair of faces that are orthogonal to three axes that are orthogonal to each other, namely, the L axis in the length direction, the W axis in the width direction, and the T axis in the height direction. The rectangular parallelepiped is not limited to the mathematically defined rectangular parallelepiped, as long as it is a shape that can be identified as a rectangular parallelepiped when observing the overall shape. Therefore, the case where the edges or corners have rounded corners, the case where the edges are curved, and the case where the formed surface is a curved surface with a small curvature also belongs to the rectangular parallelepiped in the present invention. The dimensions of the ceramic capacitor 100 in the length (L) direction, the dimensions in the width (W) direction, and the dimensions in the height (T) direction can each independently take any value, and the relationship between their sizes is not limited. For example, it can be (dimension in the L direction)>(dimension in the W direction)≥(dimension in the T direction), and it can also be (dimension in the W direction)>(dimension in the L direction), and it can also be (dimension in the T direction)>(dimension in the W direction).

[0041] The multilayer ceramic capacitor 100 of the first embodiment is as shown in Figure 1 (LT section) and Figure 2As schematically shown in the cross-sectional view (WT cross section), the laminate 30 includes a laminate 30 in which dielectric layers 10 formed of dielectric ceramic and internal electrodes 20 composed primarily of metal are alternately stacked in the T direction. The laminate 30 includes cover layers 50 formed of dielectric ceramic at both ends in the stacking direction (T direction). Furthermore, the laminate 30 has a pair of lead surfaces 40a and 40b that oppose each other in the longitudinal direction (L direction), and the internal electrodes 20 are led out to these lead surfaces 40a and 40b at alternate layers. Specifically, the laminate 30 has lead surfaces 40a and 40b, with the internal electrodes 20a leading out to the lead surfaces 40a in the L direction and the internal electrodes 20b leading out to the lead surfaces 40b in the L direction. The laminated sheet 30 may also have side edges 60 formed on a pair of side surfaces opposing each other in the W direction, i.e., on the side surfaces perpendicular to the lead surfaces 40a and 40b and each cover layer 50. The multilayer ceramic capacitor 100 of the first embodiment includes connecting conductors 71a and 71b that electrically connect the internal electrodes extending to the lead surfaces 40a and 40b of the laminated sheet 30, and a pair of terminal electrodes 72a and 72b that are spaced apart from each other and electrically connected to the connecting conductors 71a and 71b on the surface of one cover layer 50. Furthermore, in the multilayer ceramic capacitor 100 of the first embodiment, the connecting conductor 71a and the terminal electrode 72a are integrally formed, and the connecting conductor 71b and the terminal electrode 72b are integrally formed, thereby forming the external electrodes 70a and 70b.

[0042] Next, each component constituting the multilayer ceramic capacitor 100 according to the first embodiment will be described in detail.

[0043] (Dielectric layer)

[0044] The dielectric layer 10 is formed of a dielectric ceramic. The composition of the dielectric ceramic is not particularly limited and can be appropriately selected according to the characteristics required of the multilayer ceramic capacitor. As a preferred composition of the dielectric ceramic, a dielectric ceramic having barium titanate (BaTiO3) as a main component can be exemplified. The dielectric layer 10 can contain the following additive elements. As additive elements, at least one element selected from the group consisting of Mo, Nb, Ta, W, Mg, Mn, V, Cr and rare earth elements (Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb), and Co, Ni, Li, B, Na, K and Si can be exemplified. The additive element can be included in the form of a simple element or in the form of a compound such as an oxide, nitride or carbide. In addition, the additive element can be present in a state of solid solution in the main component barium titanate or can form a different phase with the element constituting the main component or other additive elements.

[0045] (Internal Electrode)

[0046] Internal electrode 20 is primarily composed of metal. The type of metal is not particularly limited, but a metal primarily composed of nickel (Ni) is preferred because it can be co-fired with dielectric layer 10 and is inexpensive. As used herein, "primary component element" refers to the element with the highest content expressed in atomic percentage (atom %).

[0047] The internal electrode 20 may contain, in addition to metal, dielectric powder having the same composition as that of the dielectric ceramic constituting the dielectric layer 10 , or a glass component.

[0048] (covering layer)

[0049] The cover layer 50 functions as a protection portion that protects the dielectric layer 10 and the internal electrode 20 .

[0050] The material of the main phase of cover layer 50 is not limited as long as it has high electrical insulation properties and low permeability to degrading factors such as moisture. From the perspectives of uniform shrinkage during firing during the manufacture of multilayer ceramic capacitor 100 and mitigating internal stress within multilayer ceramic capacitor 100, it is preferred that the main phase of cover layer 50 be the same as the dielectric ceramic forming dielectric layer 10.

[0051] At least one covering layer 50 has terminal electrodes 72a and 72b described later on its surface, and the covering layer 50 having terminal electrodes 72a and 72b on its surface has: terminal electrode relative portions 51a and 51b that overlap with the terminal electrodes 72a and 72b, respectively, when viewed from the stacking direction; and terminal electrode non-relative portions 52 that do not overlap with the terminal electrodes 72a and 72b when viewed from the stacking direction.

[0052] At the terminal electrode opposing portions 51a and 51b, respectively, Figure 3 As shown, in the element distribution maps Ma and Mb generated by measuring the nickel concentration distribution in an arbitrary cross section parallel to the stacking direction, there is a nickel segregation region 53 identified as a region with a maximum size of 0.4 μm or more, where the nickel concentration is higher than that of the surrounding area, and the density of the nickel segregation region 53 with a maximum size of 0.5 μm or more in the nickel segregation region 53 is 0.015 or more / μm. 2 . As a result, cracks in the covering layer 50 caused by external forces when mounted on a circuit board can be suppressed. It is speculated that this is because, in the terminal electrode opposing portions 51a and 51b where stress concentration is likely to occur in the structure of the multilayer ceramic capacitor 100, a large number of nickel segregation regions 53 with a high Young's modulus are present in a relatively large size, thereby absorbing and alleviating stress. Regarding the density of the nickel segregation regions 53 with a maximum size of 0.5 μm or more in the terminal electrode opposing portions 51a and 51b, from the viewpoint of making the effect of suppressing cracks in the covering layer 50 significant, it is preferably 0.020 or more / μm. 2, more preferably 0.025 or more / μm 2 .

[0053] The terminal electrode facing portions 51a and 51b preferably have nickel segregation regions 53 with a maximum size of 0.7 μm or more in the element distribution patterns Ma and Mb. This enhances the stress relaxation effect and more effectively suppresses cracking of the cover layer 50 due to external forces.

[0054] In the terminal electrode non-opposing portion 52, as shown Figure 4 As shown, in the element distribution map Mm generated by measuring the nickel concentration distribution in an arbitrary cross section parallel to the stacking direction, the density of nickel segregation regions 53 with a maximum size of 0.5 μm or more is 0.008 or less / μm. 2 In this way, there is no large amount of nickel segregation region 53 with high conductivity between the terminal electrode 72a and the terminal electrode 72b, thereby ensuring the electrical insulation between the terminal electrode 71a and the terminal electrode 71b and suppressing short circuits. Regarding the density of the nickel segregation region 53 with a maximum size of 0.5 μm or more in the terminal electrode non-opposite portion 52, from the viewpoint of obtaining better electrical insulation, it is preferably 0.005 or less / μm. 2 , more preferably less than 0.003 / μm 2 More preferably, in the terminal electrode non-opposing portion 52 , the nickel segregation region 53 having a maximum size of 0.5 μm or more does not exist in an element map generated by measuring the nickel concentration distribution in an arbitrary cross section parallel to the stacking direction.

[0055] Here, the element distribution maps Ma, Mb, and Mm of the cross-sections parallel to the stacking direction of the terminal electrode opposing portions 51a and 51b and the terminal electrode non-opposing portion 52 are generated according to the following process. First, the center portion of the multilayer ceramic capacitor in the W direction is cut using a plane parallel to the stacking direction, passing through the terminal electrodes 72a and 72b. Next, the cut multilayer ceramic capacitor is embedded in resin with the cut surface exposed, and the resin is cured. Next, the cut surface exposed from the cured resin is mirror-polished. Next, carbon is vapor-deposited to impart conductivity to the polished cut surface, forming a measurement sample. Next, the nickel concentration distribution of the terminal electrode opposing portions 51a and 51b and the terminal electrode non-opposing portion 52 in the cover layer 50 of the measurement sample is measured using a field emission electron probe microanalyzer (FE-EPMA). The measurement conditions are an acceleration voltage of 15 kV, an irradiation current of 50 nA, and a measurement time of 50 milliseconds per measurement point. Next, an elemental distribution map is displayed based on the obtained measurement results. In this elemental distribution map, the relative value of the Ni-Kα line intensity at each measurement point is calculated when the maximum Ni-Kα line intensity obtained in the measured area is set to 100, and the relative value is displayed in different colors according to the intensity.

[0056] In addition, the determination of the nickel segregation area 53 in the above-mentioned element distribution diagrams Ma, Mb and Mm, the measurement of its maximum size, and the calculation of the density of the nickel segregation area 53 with a maximum size of 0.5 μm or more are carried out according to the following process. First, in the element distribution diagram as the analysis object, the area with a relative intensity of the Ni-Kα line of less than 25 is separated and the area with the relative intensity of the Ni-Kα line is taken as a candidate for one nickel segregation area 53. Then, for each candidate nickel segregation area 53, the line segment with the longest length among the line segments connecting any two points on its periphery is determined, and the candidate nickel segregation area 53 whose length, i.e., the maximum size is 0.4 μm or more is determined as the nickel segregation area 53. And, the maximum size obtained for each nickel segregation area 53 is taken as the maximum size of each nickel segregation area 53. Then, the number of nickel segregation areas 53 with a maximum size of 0.5 μm or more confirmed in the element distribution diagram is divided by the area (μm) of the element distribution diagram. 2 ), to calculate the density of the nickel segregation region 53. Figure 3 As shown in the element distribution diagram Ma (Mb), when the terminal electrode 72a (72b) and the internal electrode 20 are confirmed, and when Figure 4 As shown, when the internal electrode 20 is confirmed in the element distribution map Mm, the area of ​​the portion corresponding to the cover layer 50 is measured and calculated, and the obtained value (μm 2 ) Remove the number of nickel segregation areas 53 and calculate their density.

[0057] The terminal electrode facing portions 51a and 51b preferably have a nickel diffusion region near the interface with the terminal electrodes 72a and 72b, where the nickel concentration decreases with increasing distance from the terminal electrodes. The presence of the nickel diffusion region in the terminal electrode facing portions 51a and 51b indicates that the nickel segregation region 53 is formed by nickel diffusion from the terminal electrodes 72a and 72b. Compared to nickel segregation regions formed by incorporating nickel or nickel oxide particles into the green sheet used to form the overlay layer, the nickel segregation region 53 thus formed forms a better interface with the surrounding ceramic particles, thereby exhibiting superior crack suppression.

[0058] (Side edge)

[0059] The side edge portion 60 functions as a protection portion that protects the dielectric layer 10 and the internal electrode 20 .

[0060] The material of side edge portion 60 is not limited as long as it has high electrical insulation and low permeability to degrading factors such as moisture. From the perspectives of achieving uniform shrinkage during firing and alleviating internal stress within multilayer ceramic capacitor 100 during manufacturing, it is preferred that cover layer 50 and side edge portion 60 be made of the same material as the dielectric ceramic forming dielectric layer 10.

[0061] (Connecting conductor)

[0062] The connection conductor 71a electrically connects the internal electrodes 20a led out to the lead surface 40a of the laminate 30, and the connection conductor 71b electrically connects the internal electrodes 20b led out to the lead surface 40b of the laminate 30. The connection conductors 71a and 71b may be as follows: Figure 1 and Figure 2 As shown, the electrode is formed so as to go around to the surface of the cover layer 50 and the side edge portion 60 where the terminal electrodes 72 a and 72 b are not formed.

[0063] The material of the connecting conductors 71a and 71b is not particularly limited as long as it is conductive. Examples of such materials include metals such as nickel (Ni), copper (Cu), tin (Sn), palladium (Pd), platinum (Pt), silver (Ag), and gold (Au), alloys containing any of these as main components, and conductive resins. However, when the connecting conductors 71a and 71b are formed by simultaneous firing with the laminate 30, in addition to conductivity, they are also required to have thermal and chemical stability to prevent melting or oxidation during firing. Therefore, Ni, Pd, and Pt are preferably used.

[0064] (Terminal electrode)

[0065] Terminal electrodes 72a and 72b are formed on the surface of one cover layer 50 at a distance from each other and are electrically connected to connection conductors 71a and 71b, respectively.

[0066] At least the portion of the terminal electrodes 72a and 72b that contacts the cover layer 50 contains a metal having nickel as a main component element. As will be described later, this is necessary to simultaneously fire the laminate 30 and at least a portion of the terminal electrodes 72a and 72b when manufacturing the multilayer ceramic capacitor, thereby forming a nickel segregation region 53 in the terminal electrode facing portions 51a and 51b of the cover layer 50. Examples of the metal having nickel as a main component element include nickel and nickel alloys. Figure 1 , a region containing a metal having nickel as a main component element is indicated by 73 .

[0067] The thickness of the region 73 containing the metal having nickel as the main component element is preferably not less than 0.1 μm and not more than 1.5 μm. A metal layer of such thickness can be appropriately formed by physical vapor deposition (PVD) or spraying. As described later, by forming the portions of the terminal electrodes 72a and 72b in contact with the covering layer 50 by physical vapor deposition (PVD) or spraying and then firing, a nickel segregation region 53 can be effectively formed in the terminal electrode opposing portions 51a and 51b of the covering layer 50. A more preferred thickness of the region 73 containing the metal having nickel as the main component element is not less than 0.2 μm and not more than 1.0 μm.

[0068] Here, the determination of whether the terminal electrodes 72a and 72b contain a metal with nickel as the main component element in the portion in contact with the covering layer 50, and the measurement of the thickness of the region 73 containing the metal with nickel as the main component element, are performed according to the following process. First, the center portion of the multilayer ceramic capacitor in the W direction is cut through the terminal electrodes 72a and 72b using a surface parallel to the stacking direction. Next, the cut multilayer ceramic capacitor is buried in a resin in such a way that the cut surface is exposed, and the resin is cured. Next, the cut surface exposed from the cured resin is mirror-polished to form a measurement sample. Next, the measurement sample is observed using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) detector or a wavelength dispersive X-ray spectrometer (WDS) detector, and after determining the positions of the terminal electrodes 72a and 72b, a line analysis of the thickness direction of the terminal electrodes 72a and 72b is performed by EDS measurement or WDS measurement. Next, based on the obtained analysis results, the concentration of the element detected at each measurement point is calculated in atomic percentage (atom %). Then, based on the fact that the atomic percentage of nickel is the highest among the elements detected at the measurement point closest to the cover layer 50, it is determined that the portion in contact with the cover layer 50 contains a metal containing nickel as the main component element. Furthermore, for the terminal electrode for which this determination has been made, the distance between the measurement point closest to the cover layer 50 and the measurement point immediately preceding the first measurement point at which the atomic percentage of an element other than nickel is the highest is measured, and the resulting value is used as the thickness of the region 73 containing the metal containing nickel as the main component element.

[0069] The terminal electrodes 72a and 72b may be formed of other conductive materials except for the portions in contact with the cover layer 50. Examples of materials include, in addition to Ni, metals such as copper (Cu), tin (Sn), palladium (Pd), platinum (Pt), silver (Ag), and gold (Au), alloys containing any of these as main components, and conductive resins. Figure 1 In the multilayer ceramic capacitor 100 of the first embodiment shown, the external electrodes 70a and 70b formed by the terminal electrodes 72a and 72b and the connecting conductors 71a and 71b have a stacked structure in which a Cu layer 74, a Ni layer 75, and a Sn layer 76 are sequentially formed on the surface of a metal layer containing nickel as a main component element.

[0070] <Second embodiment>

[0071] Next, an embodiment of a multilayer ceramic capacitor according to the second aspect of the present invention will be described as a second embodiment.

[0072] The basic structure of the multilayer ceramic capacitor of the second embodiment is the same as Figure 1 and Figure 2 The multilayer ceramic capacitor of the first embodiment shown is the same as that of the first embodiment, and differs only in the distribution of the nickel segregation region 53 in the cover layer 50. Therefore, using Figure 1 and Figure 2 The reference numerals shown indicate the characteristic parts thereof. In the multilayer ceramic capacitor of the second embodiment, the aspects other than the distribution of the nickel segregation regions 53 in the cover layer 50 are the same as those of the first embodiment, and therefore the description thereof will be omitted.

[0073] In the cover layer 50 of the ceramic capacitor of the second embodiment, as shown in FIG. Figure 5 As shown, in the terminal electrode facing portions 51a and 51b, when elemental distribution maps Ma and Mb, generated by measuring the nickel concentration distribution within arbitrary cross sections parallel to the stacking direction, are divided into square cells S with a side of 5μm, the number of cells containing nickel segregation regions 53, identified as regions with a maximum dimension of 0.4μm or greater and with a nickel concentration higher than that of the surrounding area, accounts for more than 50% of the total number of cells. This indicates that nickel segregation regions 53 are distributed over a wide area of ​​the terminal electrode facing portions 51a and 51b. This widespread distribution of nickel segregation regions 53 can suppress cracking in the cover layer 50 due to external forces during mounting on a circuit board. This is presumably because the high Young's modulus nickel segregation regions 53 are widely present in the terminal electrode facing portions 51a and 51b, where stress concentration is likely to occur due to the structure of the multilayer ceramic capacitor 100, thereby absorbing and alleviating stress over the entire area. The percentage of the number of cells in which the nickel segregation region 53 can be confirmed is preferably 60% or more, and more preferably 70% or more, from the viewpoint of achieving a significant effect of suppressing cracks in the coating layer 50 .

[0074] For the same reasons as in the first embodiment, the terminal electrode opposing portions 51a and 51b preferably have nickel segregation regions 53 with a maximum size of 0.7 μm or greater in the element distribution patterns Ma and Mb. Furthermore, from the perspective of enhancing the aforementioned stress relaxation effect and more effectively suppressing cracking in the cover layer 50 due to external forces, it is more preferable that nickel segregation regions 53 with a maximum size of 0.7 μm or greater be confirmed in at least 10% of the aforementioned square cells S in the element distribution patterns Ma and Mb in each of the terminal electrode opposing portions 51a and 51b. The percentage of the aforementioned square cells S in which nickel segregation regions 53 with a maximum size of 0.7 μm or greater are confirmed is further preferably 15% or greater, and particularly preferably 20% or greater.

[0075] The cover layer 50 of the multilayer ceramic capacitor of the second embodiment is as follows: Figure 6As shown, in the terminal electrode non-opposing portion 52, when the element distribution map Mm generated by measuring the nickel concentration distribution in an arbitrary cross-section parallel to the stacking direction is divided into square cells S with a side of 5 μm, the number of cells in which the above-mentioned nickel segregation region can be confirmed is less than 5% of the total number of cells. In this way, even if a highly conductive nickel segregation region 53 exists between the terminal electrode 72a and the terminal electrode 72b, as long as its distribution is concentrated in a specific location or there is sufficient spacing between them, electrical insulation between the terminal electrode 72a and the terminal electrode 72b can be ensured, and short circuits can be suppressed. From the perspective of obtaining better electrical insulation, the percentage of the number of cells in the terminal electrode non-opposing portion 52 in which the nickel segregation region 53 can be confirmed is preferably less than 3%, and more preferably less than 1%.

[0076] Here, the element distribution maps Ma, Mb, and Mm in the multilayer ceramic capacitor of the second embodiment are generated using the same process as the element distribution map for the ceramic capacitor of the first embodiment described above. Furthermore, the nickel segregation region 53 in the element distribution map is identified and its maximum size is measured using the same process as that used in the multilayer ceramic capacitor of the first embodiment described above.

[0077] The method of dividing each element distribution map Ma, Mb and Mm into square cells S with a side of 5 μm is as follows. For Ma and Mb, first, as Figure 5 As shown, the shortest distance between the areas where the nickel concentration is extremely high (the relative intensity of the Ni-Kα line is 95 or more) at the position across the terminal electrode opposing portion 51a (51b) is measured. In addition, the areas with extremely high nickel concentration correspond to the terminal electrode 72a (72b) and the internal electrode 20, respectively. Therefore, in the following description, this element name is used when distinguishing between the two. Next, a line segment is drawn as the baseline H0, passing through the points on the terminal electrode 72a (72b) among the points where the above shortest distance is obtained, and parallel to the upper and lower sides of the element distribution diagram Ma (Mb). Next, the above shortest distance is divided by the length corresponding to 5μm in the element distribution diagram Ma (Mb) and the remainder r1 is divided by 2. At a position that is r1 / 2 away from the baseline H0 toward the internal electrode side, a line segment H1 is drawn parallel to the baseline. The two ends of the length of the line segment H1 reach the ends of the element distribution diagram Ma (Mb). Next, from the line segment H1 to the vicinity of the internal electrode 20, line segments H2, H3, ..., Hb are drawn parallel to the line segment H1 at intervals corresponding to 5 μm in the element distribution map Ma (Mb). m In addition, Figure 5In this example, m=4. These line segments, like line segment H1, have both ends reaching the ends of the element distribution diagram Ma (Mb). Next, measure the length of line segment H1, divide this length by the length corresponding to 5 μm in the element distribution diagram Ma (Mb), and divide the remainder r2 by 2 to calculate the resulting value, namely r2 / 2. Next, from point A on line segment H1 at a distance of r2 / 2 from one end of line segment H1, draw a line segment perpendicular to line segment H1 toward the internal electrode 20, and refer to it as line segment V1. Next, draw a line segment perpendicular to line segment H1 from line segment V1 to the opposite point on line segment H1 (at Figure 5 On the side of point B), line segments V2, V3, ..., V2 parallel to line segment V1 are drawn at intervals corresponding to 5 μm in the element distribution map Ma (Mb). n In addition, Figure 5 In the example, n=7. Then, the line segments H1, H2, ..., H m and V1, V2, ..., V n Each divided region is defined as a square cell S. The element distribution map Mm may be drawn in the same manner except that the terminal electrode 72 a ( 72 b ) is replaced with the surface of the cover layer 50 .

[0078] In each of the terminal electrode facing portions 51a and 51b, the square cells S obtained by dividing the element distribution patterns Ma and Mb are divided into surface layer cells S located on the surface side relative to the center portion in the thickness direction of the cover layer 50. s , and an inner cell S located inside the center of the thickness direction of the cover layer i In the case of the above-mentioned nickel segregation region, the percentage of the number of cells in which the nickel segregation region can be confirmed is preferably higher in the above-mentioned surface cells than in the above-mentioned internal cells. As a result, the stress relaxation effect near the surface where stress is more likely to concentrate and cracks are likely to occur is enhanced, and the crack suppression effect becomes more significant.

[0079] Here, in the element distribution diagrams Ma and Mb in which the above-mentioned square cells are drawn, the surface layer cell Ss is drawn between the base line H0 and the line segment H0 parallel to the base line and closest to the internal electrode 20. m Equidistant line segments H b When the line segment H b On the other hand, the inner cell S i is located at a position greater than the above line segment H b Therefore, when the number of cells S arranged in the thickness direction of the cover layer 50 is an even number, all the cells S are classified as surface layer cells S. s and the inner cell S iIn any case, when the number of cells S arranged in the thickness direction of the cover layer 50 is an odd number, the cells S located in the center of the thickness direction are not classified as surface layer cells S. s and the inner cell S i Any of .

[0080] Modification (1)

[0081] As a first modification of the multilayer ceramic capacitor according to the first and second aspects, the following can be cited. Figure 7 In the illustrated multilayer ceramic capacitor 200, external electrodes 70a and 70b are arranged in an L-shaped cross section on the surface of the laminate 30. The multilayer ceramic capacitor 200 having such a structure has the advantage of being able to reduce its height because the connecting conductors 71a and 71b do not extend to the upper cover layer.

[0082] In addition, the first modification example may also be as follows Figure 8 In the illustrated multilayer ceramic capacitor 200', the portion of the connecting conductors 71a and 71b that contacts the laminate 30 lacks a region 73 containing a metal primarily composed of nickel. These connecting conductors 71a and 71b are formed by plating. This structure of the multilayer ceramic capacitor 200' reduces the total thickness of the connecting conductors 71a and 71b, thereby offering the advantage of reducing the height and dimension in the L direction.

[0083] Modification (2)

[0084] As a second modification of the multilayer ceramic capacitor according to the first and second aspects, the following can be cited: Figure 9 In the illustrated multilayer ceramic capacitor 300, connecting conductors 71a and 71b are formed inside the laminate 30 and extended to a cover layer. This structure of the multilayer ceramic capacitor 300 has the advantage of being miniaturized because connecting conductors 71a and 71b are not present on the surface of the laminate 30.

[0085] Modification (3)

[0086] As a third modification of the multilayer ceramic capacitor according to the first and second aspects, the following can be cited: Figure 10a and Figure 10b The laminated ceramic capacitor 400 and the Figure 10cThe illustrated multilayer ceramic capacitor 400' includes an additional electrode 21, which does not contribute to capacitance formation, disposed within the cover layer 50. Furthermore, the cover layer 50 includes an oxide layer 22 of the metal contained in the internal electrode 20. In multilayer ceramic capacitors 400 and 400' with such structures, when terminal electrodes 72a and 72b and connecting conductors 71a and 71b formed by wrapping around the cover layer surface are fired simultaneously with the laminate 30, the additional electrode 21 and the oxide layer 22 each act as a barrier to nickel diffusion, thereby suppressing leakage current between the external electrodes 70a and 70b and the internal electrode 20 that might otherwise occur due to the inclusion of nickel throughout the thickness of the cover layer 50.

[0087] Modification (4)

[0088] As a fourth modification of the multilayer ceramic capacitor according to the first and second aspects, the following can be cited: Figure 11 The illustrated multilayer ceramic capacitor 500 has four external electrodes 70. Even with such a structure, the effects of the present invention can be achieved, namely, cracking in the cover layer due to external stress concentration can be suppressed, and short circuiting between terminal electrodes can be suppressed.

[0089] [Method for Manufacturing Multilayer Ceramic Capacitor]

[0090] <Third embodiment>

[0091] Next, an embodiment of a method for manufacturing a multilayer ceramic capacitor according to a third aspect of the present invention will be described as a third embodiment.

[0092] The third embodiment of the method for manufacturing a multilayer ceramic capacitor is used to manufacture the first and second embodiments described above, and includes: a step of preparing a powder of a dielectric ceramic composition; a step of mixing the powder of the dielectric ceramic composition with a binder and forming the mixture into a sheet to obtain a green sheet; a step of forming an internal electrode pattern containing a metal on the green sheet; a step of stacking a predetermined number of green sheets having the internal pattern formed thereon, arranging green sheets for covering layers at both ends in the stacking direction, and then pressing them together to obtain a green laminate; a step of singulating (singling) the green laminate to obtain a pre-fired laminate having a lead surface; a step of removing the binder from the pre-fired laminate; a step of forming a plurality of metal layers having nickel as a main component element by physical vapor deposition or sputtering so as to be spaced apart from each other on the surface of at least one green sheet for covering layers in the pre-fired laminate after the binder is removed; and a step of firing the resulting body having the plurality of metal layers formed thereon to obtain a sintered body. Figure 1 and Figure 2 or Figure 7 Each operation in the case of the multilayer ceramic capacitor with the structure shown will be described in detail.

[0093] (Preparation of Dielectric Ceramic Composition Powder)

[0094] Dielectric ceramic composition powder can be obtained by mixing various raw material powders containing the constituent elements thereof in predetermined proportions and pre-firing (temporarily firing). When the various raw material powders are mixed in predetermined proportions, various additives such as the aforementioned additional elements and sintering aids may be added, and these various additives may also be added to the pre-fired powder.

[0095] The method for mixing the raw material powders is not particularly limited, as long as the powders can be uniformly mixed while suppressing the incorporation of impurities. Either dry mixing or wet mixing can be employed. In the case of wet mixing using a ball mill, for example, partially stabilized zirconia (PSZ) balls can be used, and stirring can be performed in a ball mill using an organic solvent such as ethanol or water as a dispersion medium for approximately 8 to 60 hours, followed by evaporation of the dispersion medium to dryness.

[0096] The conditions for calcining the raw material mixed powder are not particularly limited, as long as the various raw material powders described above react to produce the desired dielectric ceramic composition. For example, calcining in air at a temperature of 800°C to 1100°C for 1 to 10 hours is exemplified. The calcined powder can be processed into green sheets as is, but pulverization using a ball mill or stamp mill is preferred to obtain smooth green sheets from a uniform slurry and improve sinterability.

[0097] When commercially available dielectric ceramic composition powder is available, the above-mentioned mixing and pre-firing of the raw material powders may not be performed, and the powder may be subjected to subsequent operations.

[0098] (Production of Green Sheet)

[0099] The green sheet is obtained by mixing the above-mentioned dielectric ceramic composition powder with a binder and a dispersion medium to prepare a slurry, and forming the slurry into a sheet.

[0100] The binder used should maintain the shape of the green sheet and volatilize without leaving any residual carbon or the like during the binder removal process before firing. Examples of usable binders include polyvinyl alcohol, polyvinyl butyral, cellulose, urethane, and vinyl acetate-based binders. The amount of binder used is not particularly limited, but since it must be removed in subsequent steps, it is preferably minimized to achieve the desired formability and shape retention to reduce raw material costs.

[0101] The dispersion medium used is one that does not cause aggregation of the calcined powder and the binder and can be easily removed by volatilization after forming the green sheet described below. Examples of usable dispersion media include water and alcoholic solvents.

[0102] Components such as a dispersant, a plasticizer, and a thickener may be added to the slurry to adjust the properties of the slurry.

[0103] The method for mixing the mixed powder, the binder, and the dispersion medium is not particularly limited, as long as the components can be uniformly mixed while preventing the incorporation of impurities. For example, ball mill mixing can be used.

[0104] As a method of forming the prepared slurry into a sheet shape to obtain a green sheet, a conventional method such as a doctor blade method can be used.

[0105] (Formation of Internal Electrode Pattern)

[0106] The metal-containing internal electrode pattern on the green sheet can be formed by printing or applying an internal electrode paste in a predetermined pattern on the green sheet, or by forming a metal film in a predetermined pattern on the green sheet by vapor deposition or sputtering.

[0107] When using an internal electrode paste to form the internal electrode pattern, the internal electrode paste can be obtained by mixing metal particles forming the internal electrode with a carrier using a three-roll mill. In addition to the aforementioned components, the internal electrode paste may also contain glass powder or dielectric ceramic composition powder.

[0108] The type and amount of the binder and solvent contained in the vehicle used are not limited and may be appropriately selected in consideration of the viscosity of the internal electrode paste, ease of handling, compatibility with the green sheet, and the like.

[0109] The internal electrode paste can be printed on the green sheet using, for example, a screen mask having a predetermined internal electrode pattern formed thereon. During printing, the internal electrode paste can be printed while isolating the space that will become the side edge portion when the multilayer ceramic capacitor is manufactured.

[0110] (Production of Green Laminated Body)

[0111] A green laminate can be obtained by stacking a predetermined number of green sheets with internal electrode patterns and then press-bonding the green sheets together. Lamination and press-bonding can be performed using conventional methods, such as heating the stacked green sheets while pressing them in the stacking direction and then thermally pressing them together with an adhesive.

[0112] During lamination and pressure bonding, green sheets are added to both ends of the stacking direction to serve as cover layers when the multilayer ceramic capacitor is manufactured. In this case, the additional green sheets may have the same composition as or a different composition from the green sheets printed with the internal electrode patterns. To ensure consistent shrinkage during firing, the composition of the additional green sheets is preferably the same as or similar to that of the green sheets with the internal electrode precursors.

[0113] (Preparation of laminated sheets before firing)

[0114] Before firing, the laminate can be obtained by singulating the raw laminate into individual sheets (singling). Singulation creates a pair of opposing lead surfaces parallel to the stacking direction, with internal electrode patterns extending to these lead surfaces for every other layer. Singulation can be performed using conventional methods such as a dicing saw or laser cutter.

[0115] (Removal of adhesive)

[0116] The obtained pre-fired laminate can be heated to volatilize and remove the binder. The heating conditions can be appropriately set taking into account the volatilization temperature and content of the binder. As an example, it can be cited that the temperature is maintained at 200°C to 500°C in a nitrogen (N2) atmosphere for 5 to 20 hours.

[0117] (Formation of Metal Layer)

[0118] The formation of the metal layer of the covering layer on the surface of the green sheet, with nickel as the main component element, in the laminated sheet before firing after removing the adhesive can be carried out by physical vapor deposition (PVD) method or spraying method.Thus, it is easy to form a nickel segregation region in the covering layer.The reason is still unclear, but it can be considered that the metal layer formed by physical vapor deposition method or spraying method is composed of the extremely fine metal particles of atomic level, and is in a state where the surface energy of each metal particle is high. Therefore, when the metal is diffused into the covering layer during firing described later, the metal particles are easily generated clusters in the inside of the covering layer.As the PVD method that can be used, evaporation method, sputtering method, ion plating method etc. can be enumerated.As the spraying method that can be used, flame spraying method, arc spraying method, plasma spraying method etc. can be enumerated.

[0119] The shape of the metal layer formed on the surface of one cover layer green sheet corresponds to the shape of the terminal electrodes, that is, a shape in which multiple metal layers are arranged at intervals. The metal layer may be formed on only one cover layer green sheet, or may be formed on the lead-out surface of the laminate before firing, or may be formed on another cover layer green sheet.

[0120] (Firing of laminated sheets before firing)

[0121] The firing of the pre-fired laminate can be performed by heating the pre-fired laminate with the metal layer formed thereon to a predetermined temperature. During firing, the nickel contained in the metal layer is diffused into the covering layer to form a nickel segregation region. Therefore, the firing conditions should be set in consideration of the diffusion state of nickel in the covering layer. When setting the firing conditions, it is preferred to also consider the sintering properties of the dielectric ceramic composition, as well as the heat resistance and oxidation resistance of the metals contained in the internal electrode paste and the metal layer, respectively. As an example of firing conditions, there can be cited a reducing atmosphere obtained by mixing nitrogen (N2), hydrogen (H2) and water vapor (H2O), after maintaining the temperature at about 900°C, which is lower than the usual firing temperature, for about 3 hours, then raising the temperature and maintaining it at 1000°C to 1350°C for 5 minutes to 2 hours. After firing, a reoxidation treatment can be performed in a nitrogen (N2) gas atmosphere or a low-oxygen atmosphere, maintaining the temperature at 600°C to 1000°C. During firing, the dielectric ceramic composition powder sinters to form the dielectric layer, the internal electrode pattern sinters to form the internal electrode, and the metal layer sinters to form the terminal electrode or connecting conductor. Furthermore, during this process, nickel diffuses from the metal layer into the cover layer, forming the aforementioned nickel segregation region and nickel diffusion region.

[0122] The sintered body obtained by firing can be directly made into a laminated ceramic capacitor, or it can be made into a laminated ceramic capacitor after a conductive layer is further formed on the surface of the metal layer formed on the cover layer by plating or evaporation. In addition, a connecting conductor that connects the terminal electrode formed on the cover layer to the internal electrode led out to the lead surface can be formed to make a laminated ceramic capacitor. The laminated ceramic capacitor thus obtained has Figure 1 and Figure 2 、 Figure 7 or Figure 8 The structure shown.

[0123] The manufacturing method of the multilayer ceramic capacitor of the third embodiment also helps to improve the sintering density of the terminal electrode opposing portion due to the diffusion of nickel into the covering layer during firing. Compared with the terminal electrode non-opposing portion, the terminal electrode opposing portion has fewer internal electrodes located in the stacking direction, making it less susceptible to the pressing pressure during the production of the green laminate, and therefore difficult to increase the green density. The covering layer in a state of low green density tends to delay sintering during firing, making it difficult to increase the sintering density. However, the above-mentioned nickel diffusion effect can achieve a high sintering density in the terminal electrode opposing portion.

[0124] <Modification (1) of the third embodiment>

[0125] In the third embodiment, to form a connecting conductor pattern within the laminate, through-holes can be formed in the green sheet before forming the internal electrode pattern. Punching or laser processing can be used to form the through-holes in the green sheet. By forming the internal electrode pattern on the green sheet with the through-holes formed, or by filling the through-holes with conductors separately from the internal electrode pattern, a green sheet with conductors extending through the thickness can be obtained.

[0126] When a green laminate is formed by stacking green sheets with conductors extending through them in the thickness direction, the conductors in the through-holes are connected to each other in the stacking direction and are connected to the internal electrode patterns formed on adjacent green sheets in the stacking direction, forming a precursor for the connecting conductor. In this case, by also forming a through-hole filled with a conductor in one of the cover layer green sheets, a portion of the connecting conductor precursor is exposed on the surface of the cover layer.

[0127] <Modification (2) of the third embodiment>

[0128] In the third embodiment, holes capable of leading out internal electrode patterns may be formed on the wall surface of a green laminate obtained by laminating and press-bonding green sheets in the thickness direction (lamination direction), and the holes may be filled with conductors to form a precursor of a connection conductor.

[0129] The multilayer ceramic capacitors obtained by the modifications of the third embodiment have Figure 9 The structure shown.

[0130] Example

[0131] The present invention will be further described in detail below with reference to examples, but the present invention is not limited to these examples.

[0132] [Example]

[0133] The dielectric ceramic composition powder consists of pre-fired barium titanate (BaTiO3) powder as the main raw material, and powders of the oxides of Mn, Ho, and Si as trace additives. A polyvinyl butyral-based binder and an alcohol-based solvent are added to these powders and mixed in a wet ball mill. The resulting mixed slurry is shaped using a doctor blade to produce green sheets. Nickel paste is screen-printed onto these green sheets to form internal electrode patterns. 500 layers of these green sheets are then stacked. Furthermore, 20 cover layer green sheets are stacked on each of the upper and lower surfaces, and then pressed at a pressure of approximately 190 MPa while heating to form a green laminate. This green laminate is then singulated to produce pre-fired laminates with a pair of opposing lead surfaces parallel to the stacking direction, with internal electrode patterns extending to each alternate layer. The pre-fired laminates are then heated to 300°C in a nitrogen atmosphere to remove the binder. A Ni layer, which will serve as a base layer for the external electrodes, is formed by sputtering on a portion of the cover layer and the surface of the lead surface of the pre-fired laminate. The pre-fired laminate, after forming the Ni layer, is held at 900°C for 3 hours in a so-called reducing-steam atmosphere, obtained by introducing water vapor into a reducing gas containing hydrogen in nitrogen. The temperature is then raised to 1200°C and held for 2 hours for firing, and the temperature is then lowered to near room temperature to obtain a sintered body. On the surface of the Ni layer of the resulting sintered body, a Cu layer, a Ni layer, and a Sn layer are sequentially formed by plating to obtain the multilayer ceramic capacitor of Example 1. The resulting multilayer ceramic capacitor has a rectangular shape of 1.0 mm x 0.5 mm on a surface perpendicular to the stacking direction of the laminate, and the thickness of the dielectric layer is 0.6 μm.

[0134] [Comparative Example]

[0135] A multilayer ceramic capacitor of a comparative example was produced by the same method as in the example except that the Ni layer was formed on the laminated sheet before firing by dipping in nickel paste instead of sputtering.

[0136] (Crack generation rate)

[0137] For each obtained multilayer ceramic capacitor, the crack generation rate was evaluated according to the following process. The multilayer ceramic capacitor was mounted on the central part of a glass epoxy substrate with a length of 100 mm, a width of 40 mm and a thickness of 0.8 mm in such a way that its longitudinal direction (L direction) was consistent with the longitudinal direction of the substrate. The mounting surface of the substrate was provided with a copper foil with a thickness of 0.035 mm in the entire width direction of the central part in the longitudinal direction. The substrate on which the multilayer ceramic capacitor was mounted was supported at two positions with a distance of 45±2 mm from the central part in the longitudinal direction with the mounting surface facing downward, and the central part in the longitudinal direction was pressurized to a downward displacement of 2 mm and maintained for 60 seconds. Then, the appearance of the multilayer ceramic capacitor was observed to confirm the presence or absence of cracks. The above operation was performed on 1000 multilayer ceramic capacitors, and the percentage of multilayer ceramic capacitors with cracks confirmed was taken as the crack generation rate. The results are shown in Table 1.

[0138] [Evaluation of Multilayer Ceramic Capacitors]

[0139] (Generation of element distribution map)

[0140] The nickel concentration distribution was measured using the aforementioned method for both the terminal electrode-facing portion and the terminal electrode-non-facing portion of the cover layer of each multilayer ceramic capacitor for which crack generation rates were evaluated, generating elemental distribution maps. In both the example and comparative example multilayer ceramic capacitors, the elemental distribution maps obtained for the terminal electrode-facing portion confirmed the presence of a nickel diffusion region near the interface with the terminal electrode.

[0141] (Nickel segregation area)

[0142] The element distribution map was plotted and analyzed using the above-mentioned method to determine the maximum size and density of the nickel segregation region and the number of cells in which nickel segregation regions could be confirmed. The results are shown in Table 1.

[0143] [Table 1]

[0144]

[0145] As shown in Table 1, in the element distribution diagram of the terminal electrode facing portion, the density of nickel segregation areas with a maximum size of 0.5 μm or more is 0.015 points / μm or more. 2 The laminated ceramic capacitor of the embodiment can suppress cracks in the cover layer due to external stress concentration, and the density of the nickel segregation area is less than 0.015 points / μm 2 In the multilayer ceramic capacitor of the comparative example, cracks are likely to occur in the cover layer.

[0146] In addition, as can be seen from Table 1, when the element distribution diagram of the terminal electrode opposing parts is divided into square cells with one side of 5μm, the laminated ceramic capacitor of the embodiment in which the number of cells in which nickel segregation areas can be confirmed internally is 50% or more of the total number of cells can suppress the occurrence of cracks in the cover layer due to stress concentration from the outside, while the laminated ceramic capacitor of the comparative example in which the number of the above-mentioned cells is less than 50% of the total number of cells is prone to cracks in the cover layer.

[0147] This specification also discloses the following technical solutions.

[0148] (Note 1)

[0149] A laminated ceramic capacitor, comprising:

[0150] A laminated sheet in which dielectric layers formed of dielectric ceramic and internal electrodes mainly composed of metal are alternately laminated and has cover layers formed of dielectric ceramic at both ends in the lamination direction;

[0151] a connecting conductor formed inside or on a surface of the laminated sheet, which electrically connects the internal electrodes to each other; and

[0152] A plurality of terminal electrodes are formed on the surface of at least one of the cover layers at intervals, are electrically connected to the connection conductor, and contain a metal having nickel as a main component element at least in a portion in contact with the cover layer.

[0153] When the portion of the covering layer having the terminal electrodes on its surface that overlaps with the terminal electrodes when viewed from the stacking direction is the terminal electrode opposing portion, and the portion of the covering layer having the terminal electrodes on its surface that does not overlap with the terminal electrodes when viewed from the stacking direction is the terminal electrode non-opposing portion,

[0154] In each of the terminal electrode opposing portions, in an element distribution map generated by measuring the nickel concentration distribution in an arbitrary cross section parallel to the stacking direction, there is a nickel segregation region identified as a region having a nickel concentration higher than that of the surrounding area and having a maximum size of 0.4 μm or more, and the density of nickel segregation regions having a maximum size of 0.5 μm or more in the nickel segregation region is 0.015 locations / μm or more 2 ,

[0155] In the non-opposing terminal electrode portion, in an element distribution map generated by measuring nickel concentration distribution in an arbitrary cross section parallel to the stacking direction, the density of nickel segregation regions having a maximum size of 0.5 μm or more is 0.008 or less / μm. 2 .

[0156] (Note 2)

[0157] The multilayer ceramic capacitor according to (Supplementary Note 1), wherein the terminal electrode opposing portion has the nickel segregation region having a maximum size of 0.7 μm or more in the element distribution map.

[0158] (Note 3)

[0159] The stacked ceramic capacitor according to (Note 1) or (Note 2) is characterized in that: in the non-opposing portion of the terminal electrodes, in the element distribution diagram generated by measuring the nickel concentration distribution in any cross-section parallel to the stacking direction, there is no nickel segregation area with a maximum size of more than 0.5 μm.

[0160] (Note 4)

[0161] The multilayer ceramic capacitor according to any one of (Supplement 1) to (Supplement 3) is characterized in that the terminal electrode opposing portion has a nickel diffusion region near the interface with the terminal electrode, in which the nickel concentration decreases as the distance from the terminal electrode increases.

[0162] (Note 5)

[0163] The multilayer ceramic capacitor according to any one of (Supplementary Note 1) to (Supplementary Note 4), wherein the thickness of the portion of the terminal electrode containing the metal containing nickel as a main component element is 0.2 μm or more and 1.5 μm or less.

[0164] (Note 6)

[0165] A laminated ceramic capacitor, comprising:

[0166] A laminated sheet in which dielectric layers formed of dielectric ceramic and internal electrodes mainly composed of metal are alternately laminated and has cover layers formed of dielectric ceramic at both ends in the lamination direction;

[0167] a connecting conductor formed inside or on a surface of the laminated sheet, which electrically connects the internal electrodes to each other; and

[0168] A plurality of terminal electrodes are formed on the surface of at least one of the cover layers at intervals, are electrically connected to the connection conductor, and contain a metal having nickel as a main component element at least in a portion in contact with the cover layer.

[0169] When the portion of the covering layer having the terminal electrodes on its surface that overlaps with the terminal electrodes when viewed from the stacking direction is the terminal electrode opposing portion, and the portion of the covering layer having the terminal electrodes on its surface that does not overlap with the terminal electrodes when viewed from the stacking direction is the terminal electrode non-opposing portion,

[0170] In each of the terminal electrode opposing portions, when an element distribution map generated by measuring the nickel concentration distribution in an arbitrary cross section parallel to the stacking direction is divided into square cells with a side of 5 μm, the number of cells in which nickel segregation regions identified as regions with a maximum size of 0.4 μm or more, where the nickel concentration is higher than that of the surrounding areas, is confirmed to be 50% or more of the total number of cells.

[0171] In the non-opposite portion of the terminal electrode, when the element distribution diagram generated by measuring the nickel concentration distribution in any cross-section parallel to the stacking direction is divided into square cells with one side being 5 μm, it can be confirmed internally that the number of cells in the nickel segregation area is less than 5% of the total number of cells.

[0172] (Note 7)

[0173] The multilayer ceramic capacitor according to (Supplementary Note 6), wherein each of the terminal electrode opposing portions has the nickel segregation region having a maximum size of 0.7 μm or more in the element distribution map.

[0174] (Note 8)

[0175] The multilayer ceramic capacitor according to (Supplementary Note 7) is characterized in that, in each of the terminal electrode opposing portions, the number of cells in which nickel segregation regions having a maximum size of 0.7 μm or more can be confirmed within the unit cells accounts for 10% or more of the total number of cells.

[0176] (Note 9)

[0177] The multilayer ceramic capacitor according to any one of (Supplementary Note 6) to (Supplementary Note 8) is characterized in that each of the terminal electrode opposing portions has a nickel diffusion region near the interface with the terminal electrode, in which the nickel concentration decreases as the distance from the terminal electrode increases.

[0178] (Note 10)

[0179] The multilayer ceramic capacitor according to any one of (Supplementary Note 6) to (Supplementary Note 9), wherein the thickness of the portion of the terminal electrode containing the metal containing nickel as a main component element is 0.2 μm or more and 1.5 μm or less.

[0180] (Note 11)

[0181] The multilayer ceramic capacitor according to any one of (Note 6) to (Note 10) is characterized in that: in each of the terminal electrode relative portions, when the cells are divided into surface cells located closer to the surface side than the center portion in the thickness direction of the covering layer, and internal cells located closer to the inside than the center portion in the thickness direction of the covering layer, the percentage of the number of cells in which the nickel segregation area can be confirmed is higher in the surface cells than in the internal cells.

[0182] (Note 12)

[0183] A method for manufacturing a multilayer ceramic capacitor, the method for manufacturing a multilayer ceramic capacitor according to any one of (Supplementary Note 1) to (Supplementary Note 11), characterized by comprising:

[0184] a step of preparing a powder of a dielectric ceramic composition;

[0185] A step of mixing the powder of the dielectric ceramic composition with a binder and forming the mixture into a sheet to obtain a green sheet;

[0186] forming an internal electrode pattern including metal on the green sheet;

[0187] A step of laminating a predetermined number of green sheets having the internal pattern formed thereon, placing cover layer green sheets at both ends in the lamination direction, and then press-bonding the green sheets to obtain a green laminate;

[0188] The step of singulating the raw laminate to obtain pre-fired laminates;

[0189] a step of removing the binder from the laminate before firing;

[0190] A step of forming a plurality of metal layers having nickel as a main component element by physical vapor deposition or sputtering so as to be spaced apart from each other on the surface of at least one cover layer green sheet in the pre-fired laminate after the binder is removed; and

[0191] The step of firing the grown body on which the plurality of metal layers are formed to obtain a sintered body.

[0192] Industrial applicability

[0193] The present invention provides a multilayer ceramic capacitor that can suppress cracking in the cover layer due to external stress concentration and can also suppress short circuiting between terminal electrodes. Such a multilayer ceramic capacitor is useful in terms of high durability and long life.

[0194] Description of Reference Numerals

[0195] 100, 200, 200', 300, 400, 400', 500 multilayer ceramic capacitor, 10 dielectric layer, 20, 20a, 20b internal electrodes, 21 additional electrode, 22 oxide layer, 30 laminate, 40a, 40b lead surface, 50 cover layer, 51a, 51b terminal electrode opposing portion, 52 terminal electrode non-opposing portion, 53 nickel segregation region, 60 side edge portion, 70, 70a, 70b external electrodes, 71a, 71b connecting conductors, 72a, 72b terminal electrodes, 73 region containing metal having nickel as a main component element, 74 Cu layer, 75 Ni layer, 76 Sn layer, element distribution diagram of Ma and Mb (obtained for a cross section parallel to the stacking direction of the terminal electrode opposing portion), element distribution diagram of Mm (obtained for a cross section parallel to the stacking direction of the terminal electrode non-opposing portion), H0 baseline, H1, H2, ..., H m The line segments that divide each square unit cell in the vertical direction, V1, V2, ..., V n The line segments that divide each square unit cell in the horizontal direction, S square units, S s Surface cells, S i Internal cells.

Claims

1. A multilayer ceramic capacitor, characterized in that: include: A laminated sheet in which dielectric layers formed of dielectric ceramic and internal electrodes mainly composed of metal are alternately laminated and has cover layers formed of dielectric ceramic at both ends in the lamination direction; a connecting conductor formed inside or on the surface of the laminated sheet, which electrically connects the internal electrodes to each other; and A plurality of terminal electrodes are formed on the surface of at least one of the cover layers at intervals, are electrically connected to the connection conductor, and contain a metal having nickel as a main component element at least in a portion in contact with the cover layer. When the portion of the covering layer having the terminal electrodes on its surface that overlaps with the terminal electrodes when viewed from the stacking direction is the terminal electrode opposing portion, and the portion of the covering layer having the terminal electrodes on its surface that does not overlap with the terminal electrodes when viewed from the stacking direction is the terminal electrode non-opposing portion, In each of the terminal electrode opposing portions, in an element distribution map generated by measuring the nickel concentration distribution in an arbitrary cross section parallel to the stacking direction, there is a nickel segregation region identified as a region having a nickel concentration higher than that of the surrounding area and having a maximum size of 0.4 μm or more, and the density of nickel segregation regions having a maximum size of 0.5 μm or more in the nickel segregation region is 0.015 locations / μm or more 2 , In the non-opposing terminal electrode portion, in an element distribution map generated by measuring nickel concentration distribution in an arbitrary cross section parallel to the stacking direction, the density of nickel segregation regions having a maximum size of 0.5 μm or more is 0.008 or less / μm. 2 .

2. The multilayer ceramic capacitor according to claim 1, wherein: The terminal electrode facing portion includes the nickel segregation region having a maximum size of 0.7 μm or more in the element distribution map.

3. The multilayer ceramic capacitor according to claim 1, wherein: In the terminal electrode non-opposing portion, in an element map generated by measuring nickel concentration distribution in an arbitrary cross section parallel to the stacking direction, the nickel segregation region having a maximum size of 0.5 μm or more does not exist.

4. The multilayer ceramic capacitor according to claim 1, wherein: The terminal electrode facing portion includes a nickel diffusion region near an interface with the terminal electrode, wherein nickel concentration decreases as the distance from the terminal electrode increases.

5. The multilayer ceramic capacitor according to claim 1, wherein: The thickness of the portion of the terminal electrode containing the metal containing nickel as a main component element is 0.2 μm or more and 1.5 μm or less.

6. A multilayer ceramic capacitor, characterized in that: include: A laminated sheet in which dielectric layers formed of dielectric ceramic and internal electrodes mainly composed of metal are alternately laminated and has cover layers formed of dielectric ceramic at both ends in the lamination direction; a connecting conductor formed inside or on the surface of the laminated sheet, which electrically connects the internal electrodes to each other; and A plurality of terminal electrodes are formed on the surface of at least one of the cover layers at intervals, are electrically connected to the connection conductor, and contain a metal having nickel as a main component element at least in a portion in contact with the cover layer. When the portion of the covering layer having the terminal electrodes on its surface that overlaps with the terminal electrodes when viewed from the stacking direction is the terminal electrode opposing portion, and the portion of the covering layer having the terminal electrodes on its surface that does not overlap with the terminal electrodes when viewed from the stacking direction is the terminal electrode non-opposing portion, In each of the terminal electrode opposing portions, when an element distribution map generated by measuring the nickel concentration distribution in an arbitrary cross section parallel to the stacking direction is divided into square cells with a side of 5 μm, the number of cells in which nickel segregation regions identified as regions with a maximum size of 0.4 μm or more, where the nickel concentration is higher than that of the surrounding areas, is confirmed to be 50% or more of the total number of cells. In the non-opposite portion of the terminal electrode, when the element distribution diagram generated by measuring the nickel concentration distribution in any cross-section parallel to the stacking direction is divided into square cells with one side of 5 μm, it can be confirmed internally that the number of cells in the nickel segregation area is less than 5% of the total number of cells.

7. The multilayer ceramic capacitor according to claim 5, wherein: Each of the terminal electrode opposing portions has the nickel segregation region having a maximum size of 0.7 μm or more in the element distribution map.

8. The multilayer ceramic capacitor according to claim 6, wherein: In each of the terminal electrode facing portions, the number of cells in which nickel segregation regions having a maximum size of 0.7 μm or more can be confirmed within the cell accounts for 10% or more of the total number of cells.

9. The multilayer ceramic capacitor according to claim 5, wherein: Each of the terminal electrode facing portions has a nickel diffusion region near an interface with the terminal electrode, wherein the nickel concentration decreases as the distance from the terminal electrode increases.

10. The multilayer ceramic capacitor according to claim 5, wherein: The thickness of the portion of the terminal electrode containing the metal containing nickel as a main component element is 0.2 μm or more and 1.5 μm or less.

11. The multilayer ceramic capacitor according to claim 5, wherein: In each of the terminal electrode relative portions, when the cells are divided into surface cells located closer to the surface than the center portion in the thickness direction of the covering layer, and internal cells located closer to the inside than the center portion in the thickness direction of the covering layer, the percentage of the number of cells in which the nickel segregation area can be confirmed inside is higher in the surface cells than in the internal cells.

12. A method for manufacturing a multilayer ceramic capacitor, the method for manufacturing a multilayer ceramic capacitor according to any one of claims 1 to 11, characterized in that: include: a step of preparing a powder of a dielectric ceramic composition; A step of mixing the powder of the dielectric ceramic composition with a binder and forming the mixture into a sheet to obtain a green sheet; forming an internal electrode pattern including metal on the green sheet; A step of laminating a predetermined number of green sheets having the internal pattern formed thereon, placing cover layer green sheets at both ends in the lamination direction, and then press-bonding the green sheets to obtain a green laminate; The step of singulating the raw laminate to obtain pre-fired laminates; a step of removing the binder from the laminate before firing; A step of forming a plurality of metal layers having nickel as a main component element by physical vapor deposition or sputtering so as to be spaced apart from each other on the surface of at least one cover layer green sheet in the pre-fired laminate after the binder is removed; and The step of firing the grown body on which the plurality of metal layers are formed to obtain a sintered body.

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