Multilayer ceramic capacitor and method of manufacturing the same

Abstract

A multilayer ceramic capacitor according to one aspect of the present invention comprises 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 chip. On the terminal-electrode-facing part of the cover layer, in an element distribution map created by measuring the nickel concentration distribution within any cross-section parallel to the layering direction, there are nickel segregation regions recognized as regions having a maximum dimension of 0.4 µm or greater in which the concentration of nickel is higher than that in surrounding regions, and among the nickel segregation regions, the density of those having a maximum dimension of 0.5 µm or greater is at least 0.015 locations / µm2. Additionally, on the terminal-electrode-non-facing part of the cover layer, in the element distribution map created by measuring the nickel concentration distribution within any cross-section parallel to the layering direction, the density of the nickel segregation regions having a maximum dimension of 0.5 µm or greater is no greater than 0.008 locations / µm2.

Description

Multilayer ceramic capacitors

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

[0002] A known multilayer ceramic capacitor is one that includes a laminated chip in which dielectric layers made of dielectric porcelain and internal electrodes primarily composed of metal are alternately stacked, and which has cover layers made of dielectric porcelain at both ends in the stacking direction; a pair of connecting conductors formed inside or on the surface of the laminated chip and connecting the internal electrodes alternately in the stacking direction; and a pair of terminal electrodes formed on one surface of the cover layer and electrically connected to the pair of connecting conductors.

[0003] Among multilayer ceramic capacitors having such a structure, those containing a conductive metal or an oxide thereof in the cover layer have been reported.

[0004] Patent Document 1 discloses that in a multilayer ceramic capacitor, a plurality of diffusion metal portions formed of the same type of metal as the metal contained in the internal electrode are arranged in a first main surface side outer layer portion and a second main surface side outer layer portion corresponding to a cover layer.

[0005] Patent Document 2 discloses that when manufacturing a multilayer ceramic capacitor, by incorporating peroxidized metal particles into a green sheet for forming an outer cover corresponding to a cover layer, a multilayer ceramic capacitor can be obtained in which the metal particles formed by reduction are contained in the cover layer.

[0006] Patent Document 3 discloses that, when manufacturing a multilayer ceramic capacitor, ceramic green sheets for forming outer layer portions corresponding to cover layers are pre-impregnated with an oxide of the conductive metal powder contained in the internal electrodes.

[0007] JP 2019-106443 A JP 2015-226053 A JP 2003-173925 A

[0008] A multilayer ceramic capacitor having the above-described structure is mounted on a circuit board by connecting the terminal electrodes to the circuit board. In a multilayer ceramic capacitor mounted on a circuit board in this manner, stress is concentrated on the terminal electrodes and the cover layer in contact with them due to bending of the circuit board. Therefore, when mounted on a circuit board that is expected to be significantly bent during use, a multilayer ceramic capacitor having the above-described structure is required to prevent cracks from occurring in the cover layer and short-circuit failures caused by the cracks reaching the internal electrodes.

[0009] However, Patent Documents 1 to 3 do not disclose a multilayer ceramic capacitor in which the occurrence of cracks in the cover layer due to the concentration of external stress is suppressed.

[0010] Furthermore, in recent years, multilayer ceramic capacitors have been becoming smaller in size, and as a result, the cover layers have tended to become thinner and the distance between the terminal electrodes has tended to become narrower. In the multilayer ceramic capacitors disclosed in Patent Documents 1 to 3, the thinner cover layers cause conductive metal to precipitate on the surface of the cover layers, and the narrower distance between the terminal electrodes may cause a short circuit between the terminal electrodes via the precipitated conductive metal.

[0011] Therefore, an object of the present invention is to provide a multilayer ceramic capacitor that can suppress the occurrence of cracks in the cover layer due to the concentration of external stress, and can also suppress short circuits between terminal electrodes.

[0012] The present inventors have conducted various studies to solve the above-mentioned problems, and have found that when manufacturing a multilayer ceramic capacitor, forming a terminal electrode or its underlayer containing a metal containing nickel as a main component by physical vapor deposition (PVD) or thermal spraying, and then firing the resulting capacitor, generates segregated portions of the metal elements contained in the terminal electrode or its underlayer in the cover layer facing the terminal electrode, thereby suppressing the occurrence of cracks in the cover layer, and have completed the present invention.

[0013] That is, a first aspect of the present invention for solving the above-mentioned problems provides a laminated chip in which dielectric layers formed of dielectric ceramic and internal electrodes mainly composed of metal are alternately laminated, and which includes cover layers formed of dielectric ceramic at both ends in a stacking direction; connection conductors formed inside or on the surface of the laminated chip and electrically connecting the internal electrodes to each other; and a plurality of terminal electrodes formed on at least one surface of the cover layers at intervals from each other, which are electrically connected to the connection conductors and at least the portions in contact with the cover layers contain a metal containing nickel as a main element, wherein, in the cover layer having the terminal electrodes on its surface, portions that overlap with the terminal electrodes when viewed from the stacking direction are defined as terminal electrode facing portions and portions that do not overlap with the terminal electrodes when viewed from the stacking direction are defined as terminal electrode non-facing portions, and in each of the terminal electrode facing portions, an element distribution map created by measuring the nickel concentration distribution in an arbitrary cross section parallel to the stacking direction has nickel segregation regions that are recognized as regions where the nickel concentration is higher than the surroundings and have a maximum dimension of 0.4 μm or more, and the density of the nickel segregation regions, which have a maximum dimension of 0.5 μm or more, is 1 μm or more. ２ In the non-terminal electrode facing portion, in an element distribution map created by measuring the nickel concentration distribution in an arbitrary cross section parallel to the lamination direction, the density of the nickel segregation regions having a maximum dimension of 0.5 μm or more is 1 μm or more. ２ This is a multilayer ceramic capacitor with a density of 0.008 or less per unit area.

[0014] A second aspect of the present invention for solving the above-mentioned problems is a laminated chip in which dielectric layers made of dielectric ceramic and internal electrodes mainly composed of metal are alternately laminated, and which is provided with cover layers made of dielectric ceramic at both ends in a stacking direction; connection conductors formed inside or on the surface of the laminated chip and electrically connecting the internal electrodes; and a plurality of terminal electrodes formed on at least one surface of the cover layers at intervals from each other, electrically connected to the connection conductors, and at least portions in contact with the cover layers containing a metal mainly composed of nickel, in which portions of the cover layers having the terminal electrodes on their surfaces that overlap with the terminal electrodes when viewed from the stacking direction are terminal electrode opposing portions, and when viewed from the stacking direction, When the portions that do not overlap with the terminal electrodes are defined as terminal electrode non-facing portions, in the terminal electrode facing portions, when an element distribution map created 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, which are recognized as regions with a maximum dimension of 0.4 μm or more where the nickel concentration is higher than the surrounding areas, are confirmed is 50% or more of the total number of cells, and in the terminal electrode non-facing portions, when an element distribution map created 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 the nickel segregation regions are confirmed is 5% or less of the total number of cells.

[0015] a green sheet having an internal electrode pattern containing a metal on the green sheet; stacking a predetermined number of the green sheets on which the internal pattern has been formed, disposing green sheets for cover layers at both ends in the stacking direction, and then pressing the stacked sheets together to obtain a green laminate; singulating the green laminate to obtain a pre-fired laminated chip; removing the binder from the pre-fired laminated chip; forming a plurality of metal layers containing nickel as a main component by physical vapor deposition or thermal spraying, the metal layers being spaced apart from each other on the surface of at least one of the green sheets for cover layers in the pre-fired laminated chip after the binder has been removed; and firing the green formed body on which the plurality of metal layers have been formed to obtain a sintered body.

[0016] According to the present invention, it is possible to provide a multilayer ceramic capacitor that can suppress the occurrence of cracks in the cover layer due to the concentration of external stress and also suppress short circuits between terminal electrodes.

[0017] 1 is a schematic diagram (longitudinal cross-sectional view) showing the structure of a multilayer ceramic capacitor according to a first embodiment of the present invention; FIG. 2 is a schematic diagram (width-direction cross-sectional view) showing the structure of a multilayer ceramic capacitor according to a first embodiment of the present invention; FIG. 3 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 a multilayer ceramic capacitor according to a first embodiment of the present invention; FIG. 4 is an example of an element distribution map obtained for a cross section parallel to the stacking direction of a terminal electrode non-opposing portion in a multilayer ceramic capacitor according to a second embodiment of the present invention; FIG. 5 is a diagram showing a state in which a square cell S with a side length of 5 μm is drawn in an element distribution map obtained for a cross section parallel to the stacking direction of a terminal electrode opposing portion in a multilayer ceramic capacitor according to a second embodiment of the present invention; FIG. 6 is a diagram showing a state in which a square cell S with a side length of 5 μm is drawn in an element distribution map obtained for a cross section parallel to the stacking direction of a terminal electrode non-opposing portion in a multilayer ceramic capacitor according to a second embodiment of the present invention; FIG. 1 is a schematic view (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; FIG. 2 is a schematic view (longitudinal cross-sectional view) showing the structure of a third modified example of the multilayer ceramic capacitor according to the first and second aspects; FIG. 3 is a schematic view (longitudinal cross-sectional view) showing the structure of a third modified example of the multilayer ceramic capacitor according to the first and second aspects; FIG. 4 is a schematic view (overall perspective view) showing the structure of a fourth modified example of the multilayer ceramic capacitor according to the first and second aspects.

[0018] The configuration and effects of the present invention will be described below, along with the technical concept, with reference to the drawings. However, the mechanism of action includes assumptions, and the correctness of such assumptions does not limit the present invention.

[0019] [Multilayer Ceramic Capacitor] <First Embodiment> FIG. 1 shows a first embodiment of a multilayer ceramic capacitor according to a first aspect of the present invention. The multilayer ceramic capacitor 100 according to the first embodiment has a rectangular parallelepiped shape and includes a pair of faces perpendicular to each of three mutually perpendicular axes: the L axis, which is the length direction, the W axis, which is the width direction, and the T axis, which is the height direction. The rectangular parallelepiped is not limited to a mathematically defined rectangular parallelepiped; any shape can be recognized as a rectangular parallelepiped when observed as a whole. Therefore, a rectangular parallelepiped in the present disclosure also includes a capacitor with rounded edges or corners, a capacitor with curved edges, and a capacitor with small curved surfaces. The length (L), width (W), and height (T) dimensions of the ceramic capacitor 100 can each independently take any value, and the relative sizes among them are not limited. For example, (L direction dimension) > (W direction dimension) ≥ (T direction dimension), or (W direction dimension) > (L direction dimension), or (T direction dimension) > (W direction dimension).

[0020] As shown in the cross-sectional views of FIG. 1 (LT cross section) and FIG. 2 (WT cross section), the multilayer ceramic capacitor 100 according to the first embodiment includes a laminated chip 30 in which dielectric layers 10 made of dielectric ceramic and internal electrodes 20 made primarily of metal are alternately stacked in the T direction. The laminated chip 30 includes cover layers 50 made of dielectric ceramic at both ends in the stacking direction (T direction). The laminated chip 30 also has a pair of lead-out surfaces 40a and 40b facing each other in the longitudinal direction (L direction) and from which every other internal electrode 20 is drawn. That is, the laminated chip 30 has the lead-out surface 40a from which the internal electrode 20a is drawn in the L direction and the lead-out surface 40b from which the internal electrode 20b is drawn in the L direction. The laminated chip 30 may have side margins 60 formed on a pair of side surfaces facing in the W direction, i.e., on the lead-out surfaces 40a and 40b and on side surfaces perpendicular to the respective cover layers 50. The multilayer ceramic capacitor 100 according to the first embodiment includes connection conductors 71a and 71b that electrically connect the internal electrodes drawn out onto the lead-out surfaces 40a and 40b of the multilayer chip 30, and a pair of terminal electrodes 72a and 72b that are formed at a distance from each other on the surface of one of the cover layers 50 and are electrically connected to the connection conductors 71a and 71b. In the multilayer ceramic capacitor 100 according to the first embodiment, the connection conductor 71a and the terminal electrode 72a, and the connection conductor 71b and the terminal electrode 72b are integrally formed, respectively, to form external electrodes 70a and 70b.

[0021] Hereinafter, each part constituting the multilayer ceramic capacitor 100 according to the first embodiment will be described in detail.

[0022] (Dielectric Layer) The dielectric layer 10 is made of a dielectric ceramic. The composition of the dielectric ceramic is not particularly limited and may be appropriately selected depending on the characteristics required for the multilayer ceramic capacitor. A preferred composition of the dielectric ceramic is barium titanate (BaTiO ３) as a main component. The dielectric layer 10 may contain the following additive elements. Examples of the additive elements include Mo, Nb, Ta, W, Mg, Mn, V, Cr, and rare earth elements (Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb), as well as at least one selected from Co, Ni, Li, B, Na, K, and Si. The additive elements may be contained as simple elements or in the form of compounds such as oxides, nitrides, and carbides. Furthermore, the additive elements may exist in a state of solid solution in the main component, barium titanate, or may form a different phase from the elements constituting the main component or other additive elements.

[0023] (Internal Electrode) The internal electrode 20 is mainly composed of a metal. The type of metal is not particularly limited, but nickel (Ni) is preferably used as the main component element because it can be co-fired with the dielectric layer 10 and is inexpensive. Here, the term "main component element" in this specification refers to the element with the highest content expressed in atomic percentage (atomic %).

[0024] The internal electrodes 20 may contain, in addition to metal, a dielectric powder having the same composition as the dielectric ceramic that constitutes the dielectric layers 10, or a glass component.

[0025] (Cover Layer) The cover layer 50 functions as a protective portion that protects the dielectric layer 10 and the internal electrode 20 .

[0026] The material of the main phase of the cover layer 50 is not limited as long as it has high electrical insulation and low permeability to deterioration factors such as moisture. From the viewpoints of making the shrinkage during firing when manufacturing the multilayer ceramic capacitor 100 uniform and alleviating internal stress within the multilayer ceramic capacitor 100, it is preferable that the main phase of the cover layer 50 be the same as the dielectric ceramic that forms the dielectric layer 10.

[0027] At least one of the cover layers 50 has terminal electrodes 72a and 72b, which will be described later, on its surface. The cover layer 50 having the terminal electrodes 72a and 72b on its surface has terminal electrode facing portions 51a and 51b that overlap with the terminal electrodes 72a and 72b, respectively, when viewed from the stacking direction, and a terminal electrode non-facing portion 52 that does not overlap with the terminal electrodes 72a and 72b when viewed from the stacking direction.

[0028] As shown in FIG. 3, the terminal electrode opposing portions 51a and 51b have nickel segregation regions 53 recognized as regions with a maximum dimension of 0.4 μm or more in which the nickel concentration is higher than the surrounding area in element distribution maps Ma and Mb created by measuring the nickel concentration distribution in any cross section parallel to the lamination direction. ２ The density is 0.015 or more per 1 μm. This makes it possible to suppress the occurrence of cracks in the cover layer 50 due to external forces when the capacitor is mounted on a circuit board. This is presumably because the terminal electrode opposing portions 51 a and 51 b, where stress tends to concentrate due to the structure of the multilayer ceramic capacitor 100, have a large number of relatively large nickel segregation regions 53 with a high Young's modulus, which absorb and relieve the stress. A density of nickel segregation regions 53 with a maximum dimension of 0.5 μm or more in the terminal electrode opposing portions 51 a and 51 b is considered to be 1 μm or less, in that the effect of suppressing cracks in the cover layer 50 is significant. ２ It is preferable that the number of particles is 0.020 or more per 1 μm ２ More preferably, the number is 0.025 or more per unit area.

[0029] The terminal electrode opposing portions 51 a and 51 b preferably have nickel segregation regions 53 with a maximum dimension of 0.7 μm or more in the element distribution maps Ma and Mb, thereby enhancing the stress relaxation effect described above and more effectively suppressing the occurrence of cracks in the cover layer 50 due to external forces.

[0030] In the terminal electrode non-opposing portion 52, as shown in FIG. 4, in an element distribution map Mm created by measuring the nickel concentration distribution in an arbitrary cross section parallel to the lamination direction, the density of nickel segregation regions 53 having a maximum dimension of 0.5 μm or more is 1 μm or more. ２ In this way, since there are not many large highly conductive nickel segregation regions 53 between the terminal electrodes 72a and 72b, electrical insulation between the terminal electrodes 71a and 71b is ensured, and short circuits can be suppressed. A density of nickel segregation regions 53 with a maximum dimension of 0.5 μm or more in the non-opposing portion 52 of the terminal electrodes is preferably 1 μm or less, in terms of obtaining better electrical insulation. ２ It is preferable that the number of locations is 0.005 or less per 1 μm. ２ In the terminal electrode non-facing portion 52, it is more preferable that there are no nickel segregation regions 53 having a maximum dimension of 0.5 μm or more in an element distribution map created by measuring the nickel concentration distribution in any cross section parallel to the stacking direction.

[0031] The element distribution maps Ma, Mb, and Mm of the cross sections parallel to the stacking direction of the terminal electrode facing portions 51a and 51b and the non-terminal electrode facing portion 52 are created using the following procedure. First, the multilayer ceramic capacitor is cut near the center in the W direction along a plane passing through the terminal electrodes 72a and 72b and parallel to the stacking direction. Next, the cut multilayer ceramic capacitor is embedded in resin so that the cut surfaces are exposed, and the resin is cured. Next, the cut surfaces exposed from the cured resin are mirror-polished. Next, carbon is vapor-deposited on the polished cut surfaces to impart conductivity, creating a measurement sample. Next, the nickel concentration distribution is measured for each of the terminal electrode facing portions 51a and 51b and the non-terminal electrode facing portion 52 in the cover layer 50 of the measurement sample using a field emission electron probe microanalyzer (FE-EPMA). The measurement conditions are an acceleration voltage of 15 kV, a probe current of 50 nA, and a measurement time per measurement point of 50 milliseconds. Next, an element distribution map is displayed based on the measurement results obtained. This element distribution map is calculated by calculating the relative value of the Ni-Kα ray intensity at each measurement point, with the maximum Ni-Kα ray intensity obtained in the measurement area being set at 100, and displaying these values ​​in different colors according to intensity.

[0032] The determination of the nickel segregation regions 53 in the element distribution maps Ma, Mb, and Mm, the measurement of their maximum dimensions, and the calculation of the density of the nickel segregation regions 53 having a maximum dimension of 0.5 μm or more are performed in the following procedure. First, in the element distribution map to be analyzed, a region in which the relative intensity of Ni-Kα radiation is 25 or more and which is separated by a region in which the relative intensity is less than 25 is set as a candidate for one nickel segregation region 53. Next, for each candidate nickel segregation region 53, the line segment connecting any two points on its periphery that has the longest length is determined, and the line segment having a maximum dimension of 0.4 μm or more is determined as the nickel segregation region 53. The maximum dimension obtained for each nickel segregation region 53 is then taken as the maximum dimension of each nickel segregation region 53. Next, the number of nickel segregation regions 53 having a maximum dimension of 0.5 μm or more confirmed in the element distribution map is multiplied by the area (μm) of the element distribution map. ２) to calculate the density of the nickel segregation region 53. When the terminal electrode 72a (72b) and the internal electrode 20 are confirmed in the element distribution map Ma (Mb) as shown in FIG. 3, and when the internal electrode 20 is confirmed in the element distribution map Mm as shown in FIG. 4, the area of ​​the portion corresponding to the cover layer 50 is measured and calculated, and the obtained value (μm ２ The density of the nickel segregated regions 53 is calculated by dividing the number of the nickel segregated regions 53 by the number of nickel segregated regions 53.

[0033] The terminal electrode opposing portions 51a and 51b preferably have nickel-diffused regions near the interfaces with the respective terminal electrodes 72a and 72b, in which the nickel concentration decreases with distance from the terminal electrodes. The presence of nickel-diffused regions in the terminal electrode opposing portions 51a and 51b suggests that the nickel segregation regions 53 are formed by nickel diffusion from the terminal electrodes 72a and 72b. The nickel segregation regions 53 thus formed form a better interface with the surrounding ceramic particles than those formed by incorporating nickel or nickel oxide particles into the green sheet for forming the cover layer, thereby exhibiting an excellent crack suppression effect.

[0034] (Side Margin) The side margin 60 functions as a protective portion that protects the dielectric layer 10 and the internal electrode 20 .

[0035] There are no limitations on the material of the side margin portion 60, as long as it has high electrical insulation and low permeability to deterioration factors such as moisture. From the viewpoints of making shrinkage during firing uniform when manufacturing the multilayer ceramic capacitor 100 and mitigating internal stress within the multilayer ceramic capacitor 100, it is preferable that the material of the cover layer 50 and the side margin portion 60 be the same as the dielectric ceramic that forms the dielectric layer 10.

[0036] (Connection Conductor) The connection conductor 71a electrically connects the internal electrodes 20a drawn onto the drawing surface 40a of the laminated chip 30, and the connection conductor 71b electrically connects the internal electrodes 20b drawn onto the drawing surface 40b of the laminated chip 30. The connection conductors 71a and 71b may be formed so as to wrap around the cover layer 50 and the surface of the side margin portion 60 on which the terminal electrodes 72a and 72b are not formed, as shown in Figures 1 and 2 .

[0037] The material of the connection conductors 71a and 71b is not particularly limited as long as it is conductive. Examples of 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 the main component, and conductive resins. However, when the connection conductors 71a and 71b are formed by co-firing with the stacked chip 30, in addition to conductivity, thermal stability and chemical stability that prevent melting or oxidation during firing are also required, so Ni, Pd, Pt, etc. are preferably used.

[0038] (Terminal Electrodes) The terminal electrodes 72a and 72b are formed on the surface of one of the cover layers 50 at intervals from each other, and are electrically connected to the connection conductors 71a and 71b, respectively.

[0039] At least the portions of the terminal electrodes 72a and 72b that contact the cover layer 50 contain a metal primarily composed of nickel. This is necessary because, as will be described later, when manufacturing a multilayer ceramic capacitor, the laminated chip 30 and at least portions of the terminal electrodes 72a and 72b are simultaneously fired to form nickel segregation regions 53 in the terminal electrode facing portions 51a and 51b of the cover layer 50. Examples of metals primarily composed of nickel include nickel and nickel alloys. In FIG. 1 , the region containing the metal primarily composed of nickel is indicated as 73.

[0040] The thickness of the region 73 containing a metal having nickel as a main component is preferably 0.1 μm or more and 1.5 μm or less. A metal layer of such a thickness can be suitably formed by physical vapor deposition (PVD) or thermal spraying. As will be described later, by forming the portions of the terminal electrodes 72a and 72b that contact the cover layer 50 by physical vapor deposition (PVD) or thermal spraying and then firing the formed portions, the nickel segregation region 53 can be effectively formed in the terminal electrode facing portions 51a and 51b of the cover layer 50. The thickness of the region 73 containing a metal having nickel as a main component is more preferably 0.2 μm or more and 1.0 μm or less.

[0041] Here, the determination of whether the terminal electrodes 72a and 72b contain a metal containing nickel as a primary component in the portions in contact with the cover layer 50 and the measurement of the thickness of the region 73 containing the metal containing nickel as a primary component are performed using the following procedure. First, the multilayer ceramic capacitor is cut near the center in the W direction along a plane that passes through the terminal electrodes 72a and 72b and is parallel to the stacking direction. Next, the cut multilayer ceramic capacitor is embedded in resin so that the cut surface is exposed, and the resin is cured. Next, the cut surface exposed from the cured resin is mirror-polished to prepare a measurement sample. Next, the measurement sample is observed using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscopy (EDS) detector or a wavelength dispersive X-ray spectroscopy (WDS) detector to identify the positions of the terminal electrodes 72a and 72b. Then, line analysis is performed using EDS or WDS measurement in the thickness direction of the terminal electrodes 72a and 72b. Next, from the obtained analysis results, the concentration of each element detected at each measurement point is calculated in atomic percentage (atomic %). If the atomic percentage of nickel is highest among the detected elements 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 its main element. 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 elements other than nickel is highest is measured, and the obtained value is defined as the thickness of the region 73 containing a metal containing nickel as its main element.

[0042] The terminal electrodes 72a and 72b may be formed of other conductive materials except for the portions that contact 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 a main component, and conductive resins. In the multilayer ceramic capacitor 100 according to the first embodiment shown in FIG. 1 , the entire external electrodes 70a and 70b formed by the terminal electrodes 72a and 72b and the connecting conductors 71a and 71b have a laminated structure in which a Cu layer 74, a Ni layer 75, and a Sn layer 76 are formed in this order on the surface of a metal layer containing nickel as a main component.

[0043] Second Embodiment A multilayer ceramic capacitor according to a second aspect of the present invention will be described below as a second embodiment.

[0044] The multilayer ceramic capacitor according to the second embodiment has a basic structure in common with the multilayer ceramic capacitor according to the first embodiment shown in Figures 1 and 2, and differs only in the distribution of the nickel segregation regions 53 in the cover layer 50. Therefore, the characteristic features will be described using the reference numerals shown in Figures 1 and 2. Note that the multilayer ceramic capacitor according to the second embodiment is common to the first embodiment in all respects except for the distribution of the nickel segregation regions 53 in the cover layer 50, and therefore description thereof will be omitted.

[0045] In the cover layer 50 of the ceramic capacitor according to the second embodiment, as shown in FIG. 5 , when element distribution maps Ma and Mb, created by measuring the nickel concentration distribution in any cross section parallel to the lamination direction in the terminal electrode facing portions 51a and 51b, are divided into square cells S with sides of 5 μm, the number of cells in which nickel segregation regions 53, recognized as regions with a maximum dimension of 0.4 μm or more and where the nickel concentration is higher than that of the surrounding area, are confirmed is 50% or more of the total number of cells. This means that the nickel segregation regions 53 are distributed over a wide area in the terminal electrode facing portions 51a and 51b. The wide distribution of the nickel segregation regions 53 can suppress the occurrence of cracks in the cover layer 50 due to external forces when the capacitor is mounted on a circuit board. This is presumably because the nickel segregation regions 53, which have a high Young's modulus, are evenly distributed throughout the terminal electrode facing portions 51a and 51b, where stress tends to concentrate due to the structure of the multilayer ceramic capacitor, and therefore, stress absorption and relaxation effects are exhibited throughout the entire area. The percentage of the number of cells in which the nickel segregation region 53 is confirmed is preferably 60% or more, and more preferably 70% or more, in that the effect of suppressing cracking in the cover layer 50 is significant.

[0046] For the same reasons as in the first embodiment, the terminal electrode opposing portions 51a and 51b preferably have nickel segregation regions 53 having a maximum dimension of 0.7 μm or more in the element distribution maps Ma and Mb. Furthermore, in order to enhance the stress relaxation effect and more effectively suppress the occurrence of cracks in the cover layer 50 due to external forces, it is more preferable that the terminal electrode opposing portions 51a and 51b have nickel segregation regions 53 having a maximum dimension of 0.7 μm or more confirmed in 10% or more of the square cells S in the element distribution maps Ma and Mb. The percentage of the square cells S in which nickel segregation regions 53 having a maximum dimension of 0.7 μm or more confirmed is more preferably 15% or more, and particularly preferably 20% or more.

[0047] 6 , in the cover layer 50 of the multilayer ceramic capacitor according to the second embodiment, when an element distribution map Mm, created by measuring the nickel concentration distribution in any cross section parallel to the stacking direction in the non-electrode facing portion 52, is divided into square cells with sides of 5 μm, the number of cells in which the nickel segregation region is confirmed is 5% or less of the total number of cells. Thus, even if a highly conductive nickel segregation region 53 exists between the terminal electrodes 72 a and 72 b, as long as the distribution is concentrated in a specific location or is sufficiently spaced apart, electrical insulation between the terminal electrodes 72 a and 72 b can be ensured and short circuits can be suppressed. To obtain better electrical insulation, the percentage of cells in which the nickel segregation region 53 is confirmed in the non-electrode facing portion 52 is preferably 3% or less, and more preferably 1% or less.

[0048] The element distribution maps Ma, Mb, and Mm for the multilayer ceramic capacitor according to the second embodiment are created using the same procedures as those for the ceramic capacitor according to the first embodiment described above. Furthermore, the nickel segregation region 53 in the element distribution maps is determined and its maximum dimension is measured using the same procedures as those for the multilayer ceramic capacitor according to the first embodiment described above.

[0049] The method for dividing each element distribution map Ma, Mb, and Mm into square cells S with sides of 5 μm is as follows. For Ma and Mb, first, as shown in FIG. 5, the shortest distance between regions with extremely high nickel concentration (where the relative intensity of Ni-Kα radiation is 95 or more) located on either side of the terminal electrode opposing portion 51a (51b) is measured. Note that since these regions with extremely high nickel concentration correspond to the terminal electrode 72a (72b) and the internal electrode 20, respectively, these element names will be used to distinguish between them in the following explanation. Next, a line segment that passes through the points located on the terminal electrode 72a (72b) among the points for which the shortest distance was obtained and that is parallel to the top and bottom sides of the element distribution map Ma (Mb) is defined as the baseline H. ０Next, the remainder r obtained by dividing the shortest distance by the length corresponding to 5 μm in the element distribution map Ma (Mb) is １ Divide by 2 and get the value r １ / 2 only, baseline H ０ A line segment H parallel to the baseline is drawn at a position away from the center of the internal electrode. １ Construct the line segment H １ The length of the line segment H is such that both ends of the line segment H reach the ends of the element distribution map Ma (Mb). １ From the line segment H to the vicinity of the internal electrode 20 at intervals corresponding to 5 μm in the element distribution map Ma (Mb). １ A line segment H parallel to ２ , H ３ , ..., H ｍ In FIG. 5, m=4. For these line segments, the line segment H １ Similarly, both ends of the line segment H reach the ends of the element distribution map Ma (Mb). １ The length is measured, and the remainder r is obtained by dividing the length by the length corresponding to 5 μm in the element distribution map Ma (Mb). ２ is the value obtained by dividing by 2 ２ Next, calculate the line segment H １ The distance from one end of ２ Line segment H at / 2 １ From the upper point A toward the internal electrode 20 side, a line segment H １ Draw a line segment perpendicular to the line V １ Next, the line segment V １ From the line segment H １ Towards the opposing point (point B in FIG. 5) on the upper side, a line segment V is drawn at an interval corresponding to 5 μm in the element distribution map Ma (Mb). １ A line segment V is parallel to ２ , V ３ , …, V ｎ In FIG. 5, n=7. Then, each of the drawn line segments H １ , H ２ , ..., H ｍ , and V １ , V ２ , …, V ｎEach of the regions separated by the squares is defined as one square cell S. The element distribution map Mm can be similarly drawn by replacing the terminal electrode 72a (72b) with the surface of the cover layer 50.

[0050] In the terminal electrode facing portions 51a and 51b, the element distribution maps Ma and Mb are divided into square cells S, which are surface layer cells S located on the surface side of the center portion in the thickness direction of the cover layer 50. ｓ and an internal cell S located inside the center of the cover layer in the thickness direction. ｉ When the cells are divided into the surface and inner cells, it is preferable that the percentage of the number of cells in which the nickel segregation region is confirmed is higher in the surface cells than in the inner cells, which enhances the stress relaxation effect near the surface where stress is more likely to concentrate and cracks are more likely to occur, resulting in a significant crack suppression effect.

[0051] Here, the surface cell Ss is the element distribution map Ma and Mb in which the square cells are plotted as described above, and the baseline H ０ and a line segment H parallel to the line segment H and closest to the internal electrode 20 ｍ Line segment H that is equidistant from ｂ When drawing the line segment H ｂ On the other hand, the internal cell S ｉ is the line segment H ｂ Therefore, if the number of cells S arranged in the thickness direction of the cover layer 50 is even, all of the cells S are surface cells S ｓ or internal cell S ｉ If the number of cells S aligned in the thickness direction of the cover layer 50 is odd, the cells S located in the center in the thickness direction are classified as surface cells S ｓ and the internal cell S ｉ It will not be classified as either of the above.

[0052] 7 shows a multilayer ceramic capacitor 200 in which external electrodes 70 a and 70 b are arranged in an L-shaped cross section on the surface of the laminated chip 30. The multilayer ceramic capacitor 200 having such a structure has the advantage that it can be made low-profile because the connection conductors 71 a and 71 b do not extend around the upper cover layer.

[0053] 8, a multilayer ceramic capacitor 200' may be formed by plating, with no region 73 containing a metal primarily composed of nickel present in the portions of the connecting conductors 71a and 71b that come into contact with the laminated chip 30. The multilayer ceramic capacitor 200' having such a structure can reduce the total thickness of the connecting conductors 71a and 71b, thereby offering the advantage of being able to reduce the height as well as the dimension in the L direction.

[0054] <Modification (2)> A second modification of the multilayer ceramic capacitor according to the first and second aspects is a multilayer ceramic capacitor 300 in which the connection conductors 71 a and 71 b are formed inside the laminated chip 30 and extended to one of the cover layers, as shown in Fig. 9. The multilayer ceramic capacitor 300 having such a structure has the advantage that it can be made smaller, since the connection conductors 71 a and 71 b are not present on the surface of the laminated chip 30.

[0055] <Modification (3)> Examples of a third modification of the multilayer ceramic capacitor according to the first and second aspects include a multilayer ceramic capacitor 400 in which an additional electrode 21 that does not contribute to capacitance formation is disposed in the cover layer 50, as shown in Figures 10a and 10b, and a multilayer ceramic capacitor 400' in which an oxide layer 22 of the metal contained in the internal electrode 20 is disposed in the cover layer 50, as shown in Figure 10c. In the multilayer ceramic capacitors 400 and 400' having such a structure, when the terminal electrodes 72a and 72b and the connecting conductors 71a and 71b formed around the surface of the cover layer are co-fired with the laminated chip 30, the additional electrode 21 and the oxide layer 22 each function as a barrier against nickel diffusion, and it is possible to suppress leakage current between the external electrodes 70a and 70b and the internal electrode 20, which may occur when the cover layer 50 contains nickel throughout its thickness.

[0056] <Modification (4)> A fourth modification of the multilayer ceramic capacitor according to the first and second aspects is a multilayer ceramic capacitor 500 in which external electrodes 70 are arranged at four locations, as shown in Fig. 11. A multilayer ceramic capacitor having such a structure can also achieve the effects of the present invention, that is, it is possible to suppress the occurrence of cracks in the cover layer due to the concentration of external stress, and to suppress short-circuiting between terminal electrodes.

[0057] [Method for Manufacturing Multilayer Ceramic Capacitor] <Third Embodiment> A method for manufacturing a multilayer ceramic capacitor according to the third aspect of the present invention will be described below as a third embodiment.

[0058] A method for manufacturing a multilayer ceramic capacitor according to a third embodiment, which is similar to the method for manufacturing the multilayer ceramic capacitor according to the first or second embodiment, includes the steps of preparing a powder of a dielectric ceramic composition, mixing the powder of the dielectric ceramic composition with a binder and forming the powder into a green sheet, forming an internal electrode pattern containing a metal on the green sheet, stacking a predetermined number of the green sheets with the internal pattern formed thereon, placing green sheets for cover layers on both ends of the green sheets in the stacking direction, and then pressing the stack together to obtain a green laminate, dividing the green laminate into individual chips having lead-out surfaces, removing the binder from the pre-fired chips, forming a plurality of metal layers containing nickel as a main component on the surface of at least one of the green sheets for cover layers in the pre-fired chips after the binder removal by physical vapor deposition or thermal spraying, so as to be spaced apart from each other, and firing the green formed body with the plurality of metal layers formed thereon to obtain a sintered body. The following describes in detail the steps involved in manufacturing a multilayer ceramic capacitor having a structure as shown in FIGS. 1 and 2 or 7.

[0059] (Preparation of Dielectric Porcelain Composition Powder) The powder of the dielectric ceramic composition is obtained by mixing various raw material powders containing its constituent elements in a predetermined ratio and pre-firing (calcining). When mixing the various raw material powders in a predetermined ratio, various additives such as the above-mentioned additive elements and sintering aids may be further added, and these various additives may be further added to the powder after calcination.

[0060] The method for mixing the raw material powders is not particularly limited as long as the powders are mixed uniformly while preventing impurities from being mixed in, and either dry mixing or wet mixing may be employed. When wet mixing using a ball mill is employed as the mixing method, for example, partially stabilized zirconia (PSZ) balls may be used, and the mixture may be stirred for about 8 to 60 hours in a ball mill using an organic solvent such as ethanol or water as a dispersion medium, and then the dispersion medium may be evaporated and dried.

[0061] 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 obtain a predetermined dielectric ceramic composition. One example is calcining in air at a temperature of 800°C to 1100°C for 1 hour to 10 hours. The powder after calcination may be processed into a green sheet as is, but crushing using a ball mill, stamp mill, or the like is preferred because it allows for a smooth green sheet to be obtained through a uniform slurry and improves sinterability.

[0062] When a commercially available dielectric ceramic composition powder is available, the subsequent steps may be carried out on this powder without carrying out the above-mentioned mixing and pre-firing of the raw material powders.

[0063] (Preparation of Green Sheet) The green sheet is obtained by mixing the powder of the above-mentioned dielectric ceramic composition with a binder and a dispersion medium to prepare a slurry, and then forming the slurry into a sheet.

[0064] The binder used is one that can maintain the shape of the green sheet and volatilizes without leaving carbon or other residues during the binder removal process prior to firing. Examples of binders that can be used include polyvinyl alcohol, polyvinyl butyral, cellulose, urethane, and vinyl acetate binders. The amount of binder used is not particularly limited, but since it is removed in a later process, it is preferable to keep it as small as possible within a range that achieves the desired moldability and shape retention in order to reduce raw material costs.

[0065] The dispersion medium used is one that does not cause aggregation of the calcined powder and binder and can be easily removed by volatilization or the like after forming into a green sheet, as described below. Examples of the dispersion medium that can be used include water and alcohol-based solvents.

[0066] Components for adjusting the properties of the slurry, such as dispersants, plasticizers, and thickeners, may be added to the slurry.

[0067] The method for mixing the mixed powder with the binder and the dispersion medium is not particularly limited as long as the components are mixed uniformly while preventing the inclusion of impurities. One example is ball mill mixing.

[0068] The prepared slurry can be formed into a sheet to obtain a green sheet by a commonly used method such as a doctor blade method.

[0069] (Formation of internal electrode pattern) The formation of the internal electrode pattern containing a metal on the green sheet described above can be carried out by a method of printing or applying an internal electrode paste on the green sheet in a predetermined pattern, or by a method of forming a metal film on the green sheet in a predetermined pattern by vapor deposition or sputtering.

[0070] When forming an internal electrode pattern using an internal electrode paste, the internal electrode paste used is obtained by mixing metal particles forming the internal electrodes and a vehicle in a triple roll mill. The internal electrode paste may contain glass frit and dielectric ceramic composition powder in addition to the above-mentioned components.

[0071] The type and amount of binder and solvent contained in the vehicle to be used are not limited, and may be selected appropriately taking into consideration the viscosity of the internal electrode paste, ease of handling, compatibility with the green sheet, and the like.

[0072] The internal electrode paste can be printed on the green sheet using, for example, a screen mask on which a predetermined internal electrode pattern is formed. When printing, spaces that will become side margins when the multilayer ceramic capacitor is completed may be left.

[0073] (Preparation of Green Laminate) The green laminate is obtained by stacking a predetermined number of green sheets on which internal electrode patterns have been formed and pressing the green sheets together. The stacking and pressing can be performed by a conventional method, such as pressing the stacked green sheets together in the stacking direction while heating them, and thermocompression bonding by the action of a binder.

[0074] During lamination and compression bonding, green sheets that will become cover layers when the multilayer ceramic capacitor is completed are added to both ends in the lamination direction. In this case, the green sheets to be added may have the same composition as the green sheets on which the internal electrode patterns are printed, or a different composition. From the viewpoint of making the shrinkage rate during firing uniform, it is preferable that the composition of the green sheets to be added is the same as or similar to the green sheets on which the above-mentioned internal electrode precursors are arranged.

[0075] (Preparation of Pre-fired Laminated Chips) Pre-fired laminated chips are obtained by dividing the green laminate into individual laminated chip shapes. Singulation results in the formation of a pair of opposing lead-out surfaces parallel to the lamination direction, from which the internal electrode patterns are drawn out every other layer. Conventional methods such as a dicing saw or a laser cutting machine can be used for the singulation.

[0076] (Removal of Binder) The obtained pre-fired laminated chip is heated to remove the binder by volatilization. The heating conditions may be appropriately set in consideration of the volatilization temperature and content of the binder. For example, nitrogen (N ２ ) atmosphere at a temperature of 200°C to 500°C for 5 to 20 hours.

[0077] (Metal Layer Formation) A metal layer containing nickel as the main component is formed on the surface of the green cover layer sheet in the pre-fired laminated chip from which the binder has been removed by physical vapor deposition (PVD) or thermal spraying. This facilitates the formation of nickel segregation regions in the cover layer. While the reason for this is unclear, it is believed that the metal layer formed by physical vapor deposition or thermal spraying is composed of extremely fine metal particles at the atomic level, and the surface energy of each metal particle is high. Therefore, when the metal diffuses into the cover layer during firing, as described below, the metal particles are likely to form clusters within the cover layer. Examples of usable PVD methods include vapor deposition, sputtering, and ion plating. Examples of usable thermal spraying methods include flame spraying, arc spraying, and plasma spraying.

[0078] The shape of the metal layer to be formed may be such that it corresponds to the shape of the terminal electrode on the surface of one of the cover layer green sheets, i.e., the plurality of metal layers are spaced apart from one another. The metal layer may be formed only on the surface of one of the cover layer green sheets, or may be formed on the lead-out surface of the pre-fired laminated chip, or may even be formed on the surface of the other cover layer green sheet.

[0079] (Firing of Pre-Fired Laminated Chip) The pre-fired laminated chip is fired by heating the pre-fired laminated chip on which the metal layer is formed to a predetermined temperature. The firing conditions are set taking into consideration the state of nickel diffusion into the cover layer, since nickel contained in the metal layer is diffused into the cover layer during firing to form a nickel segregation region. When setting the firing conditions, it is preferable to also consider the sinterability 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. Examples of firing conditions include nitrogen (N ２ ) and hydrogen (H ２ ) and water vapor (H ２ In a reducing atmosphere containing a mixture of nitrogen (N O), the mixture is heated to about 900°C, which is lower than the normal firing temperature, for about 3 hours, and then heated to 1000°C to 1350°C for 5 minutes to 2 hours. ２ ) A reoxidation treatment may be performed by holding the material at 600°C to 1000°C in a gas atmosphere or a low-oxygen atmosphere. By firing, the powder of the dielectric ceramic composition is sintered to form a dielectric layer, the internal electrode pattern is sintered to form an internal electrode, and the metal layer is sintered to form a terminal electrode or a connecting conductor. At this time, nickel diffuses from the metal layer into the cover layer, forming the nickel segregation region and nickel diffusion region described above.

[0080] The sintered body obtained by firing may be used as a multilayer ceramic capacitor as is, or may be used as a multilayer ceramic capacitor after forming an additional conductive layer on the surface of the metal layer formed on the cover layer by means of plating, vapor deposition, or the like. Alternatively, a multilayer ceramic capacitor may be used by forming connecting conductors that connect terminal electrodes formed on the cover layer with internal electrodes drawn out to the drawing surface. The multilayer ceramic capacitor obtained in this manner has the structure shown in Figures 1, 2, 7, or 8.

[0081] The method for manufacturing a multilayer ceramic capacitor according to the third embodiment also contributes to improving the sintered density of the terminal electrode facing portion by diffusing nickel into the cover layer during firing. The terminal electrode facing portion has fewer internal electrodes positioned in the stacking direction than the non-terminal electrode facing portion, making it difficult to apply press pressure when fabricating a green laminate. Cover layers with low green density tend to be slow to sinter during firing, making it difficult to improve sintered density. However, the diffusion of nickel described above allows the terminal electrode facing portion to have a high sintered density.

[0082] <Modification (1) of the Third Embodiment> In the third embodiment, in order to form a connection conductor pattern inside the laminated chip, through holes may be formed in the green sheet prior to the formation of the internal electrode pattern. Methods for forming the through holes in the green sheet include punching and laser processing. By forming the internal electrode pattern on the green sheet with the through holes formed therein, or by filling the through holes with a conductor separately from the internal electrode pattern, a green sheet with a conductor penetrating in the thickness direction can be obtained.

[0083] When green sheets having conductors penetrating therethrough in the thickness direction are stacked to form a green laminate, the conductors in the through holes are connected in the stacking direction and connected to internal electrode patterns formed on green sheets adjacent in the stacking direction, thereby forming precursors of connecting conductors. In this case, by forming through holes filled with conductors in one of the green sheets for the cover layer as well, part of the precursor of the connecting conductor is exposed on the surface of the cover layer.

[0084] <Variation (2) of the Third Embodiment> In the third embodiment, holes may be formed in the thickness direction (stacking direction) of the green laminate obtained by stacking and pressing green sheets, through which the internal electrode patterns are drawn out to the wall surfaces, and a conductor may be filled in the holes to form precursors of connecting conductors.

[0085] The multilayer ceramic capacitor obtained by each of the modifications of the third embodiment has the structure shown in FIG.

[0086] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0087] [Example] As a powder of a dielectric ceramic composition, a calcined barium titanate (BaTiO ３) powder, and powders of oxides of Mn, Ho, and Si as trace additive components were prepared. A polyvinyl butyral binder and an alcohol-based solvent were added to these powders and mixed using a wet ball mill. The resulting mixed slurry was formed using a doctor blade to obtain a green sheet. Nickel paste was screen-printed onto the green sheet as an internal electrode paste to form an internal electrode pattern, and 500 layers of the green sheet were then stacked. 20 green sheets for cover layers were then stacked on the top and bottom surfaces of the green sheet, and the green sheet was then pressed together under a pressure of approximately 190 MPa while heated to obtain a green laminate. This green laminate was then singulated to obtain a pre-fired laminated chip having a pair of opposing lead surfaces parallel to the stacking direction, from which the internal electrode patterns were drawn every other layer. The pre-fired laminated chip was then heated to 300°C in a nitrogen atmosphere to perform a binder removal treatment. A Ni layer, which would serve as a base layer for the external electrodes, was formed by sputtering on a portion of the cover layer and on the surface of the lead surface of the pre-fired laminated chip. After the Ni layer was formed, the unfired laminated chip was held at 900°C for 3 hours in a so-called reducing-steam atmosphere, where water vapor was introduced into a reducing gas containing hydrogen in nitrogen, and then the temperature was raised to 1200°C and held there for 2 hours for firing, and the temperature was lowered to around room temperature to obtain a sintered body. A Cu layer, a Ni layer, and a Sn layer were formed in that order by plating on the surface of the Ni layer of the obtained sintered body, thereby obtaining the multilayer ceramic capacitor according to Example 1. The obtained multilayer ceramic capacitor had a rectangular shape with a surface perpendicular to the stacking direction of the laminated chip measuring 1.0 mm x 0.5 mm, and the dielectric layer was 0.6 μm thick.

[0088] Comparative Example A multilayer ceramic capacitor according to a comparative example was produced in the same manner as in the example, except that the Ni layer was formed on the pre-fired multilayer chip by dipping in nickel paste instead of by sputtering.

[0089] (Crack Occurrence Rate) The crack occurrence rate for each multilayer ceramic capacitor obtained was evaluated using the following procedure. A multilayer ceramic capacitor was mounted at the center of a glass epoxy substrate measuring 100 mm in length, 40 mm in width, and 0.8 mm in thickness, with its length (L direction) aligned with the length of the substrate. A 0.035 mm thick copper foil was placed across the entire width of the mounting surface of the substrate at the center of the length. The substrate with the mounted multilayer ceramic capacitor was supported with the mounting surface facing downward at two locations 45±2 mm from the center of the length, and pressure was applied to the center of the length until a downward displacement of 2 mm was achieved and maintained for 60 seconds. The appearance of the multilayer ceramic capacitor was then observed to determine whether or not there were any cracks. The above procedure was performed on 1,000 multilayer ceramic capacitors, and the percentage of capacitors with confirmed cracks was taken as the crack occurrence rate. The results are shown in Table 1.

[0090] [Evaluation of Multilayer Ceramic Capacitors] (Creation of Element Distribution Map) For each multilayer ceramic capacitor for which the crack incidence rate was evaluated, the nickel concentration distribution was measured by the method described above for the terminal electrode facing portion and the non-terminal electrode facing portion of the cover layer, and an element distribution map was created. In both the multilayer ceramic capacitors according to the examples and the comparative examples, it was confirmed that a nickel-diffused region was present near the interface with the terminal electrode in the element distribution map obtained for the terminal electrode facing portion.

[0091] (Nickel Segregation Region) The element distribution map was plotted and analyzed by the method described above to determine the maximum size and density of the nickel segregation region and the number of cells in which the nickel segregation region was confirmed. The results are shown in Table 1.

[0092]

[0093] From Table 1, in the element distribution map of the terminal electrode opposing portion, the density of nickel segregation regions with a maximum dimension of 0.5 μm or more is ２In the multilayer ceramic capacitor according to the embodiment, the density of the nickel segregation region is 0.015 or more per 1 μm, and the occurrence of cracks in the cover layer due to the concentration of external stress is suppressed. ２ It can be said that the multilayer ceramic capacitor according to the comparative example, in which the crack count was less than 0.015 per square inch, was prone to cracks occurring in the cover layer.

[0094] Furthermore, Table 1 shows that when the element distribution map of the terminal electrode opposing portion is divided into square cells with sides of 5 μm, the multilayer ceramic capacitors according to the examples in which the number of cells in which nickel segregation regions are confirmed is 50% or more of the total number of cells are suppressed from developing cracks in the cover layer due to the concentration of external stress, whereas the multilayer ceramic capacitors according to the comparative examples in which the number of such cells is less than 50% are prone to developing cracks in the cover layer.

[0095] This specification also discloses the following techniques.

[0096] (Note 1) A laminated chip comprising: dielectric layers made of dielectric ceramic and internal electrodes mainly composed of metal alternately laminated; and cover layers made of dielectric ceramic at both ends in a stacking direction; connection conductors formed inside or on the surface of the laminated chip and electrically connecting the internal electrodes; and a plurality of terminal electrodes formed at intervals on at least one surface of the cover layers, electrically connected to the connection conductors, and at least a portion in contact with the cover layer containing a metal mainly composed of nickel; wherein, in the cover layer having the terminal electrodes on its surface, portions overlapping with the terminal electrodes when viewed from the stacking direction are defined as terminal electrode facing portions, and portions not overlapping with the terminal electrodes when viewed from the stacking direction are defined as terminal electrode non-facing portions, the terminal electrode facing portions each have a nickel segregation region recognized as a region having a nickel concentration higher than the surrounding area and a maximum dimension of 0.4 μm or more in an element distribution map created by measuring the nickel concentration distribution in an arbitrary cross section parallel to the stacking direction, and the density of the nickel segregation regions having a maximum dimension of 0.5 μm or more is 1 μm or more. ２In the non-terminal electrode facing portion, in an element distribution map created by measuring the nickel concentration distribution in an arbitrary cross section parallel to the lamination direction, the density of the nickel segregation regions having a maximum dimension of 0.5 μm or more is 1 μm or more ２ A multilayer ceramic capacitor with a density of 0.008 or less points per capacitor.

[0097] (Supplementary Note 2) The multilayer ceramic capacitor according to (Supplementary Note 1), wherein the terminal electrode opposing portion has the nickel segregation region having a maximum dimension of 0.7 μm or more in the element distribution map.

[0098] (Supplementary Note 3) The multilayer ceramic capacitor according to (Supplementary Note 1) or (Supplementary Note 2), wherein in the non-terminal electrode facing portion, in an element distribution map created by measuring the nickel concentration distribution in any cross section parallel to the stacking direction, there is no nickel segregation region having a maximum dimension of 0.5 μm or more.

[0099] (Supplementary Note 4) The multilayer ceramic capacitor according to any one of (Supplementary Note 1) to (Supplementary Note 3), wherein the terminal electrode opposing portion has a nickel diffusion region in the vicinity of the interface with the terminal electrode, in which the nickel concentration decreases with increasing distance from the terminal electrode.

[0100] (Supplementary Note 5) 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 a metal mainly composed of nickel is 0.2 μm or more and 1.5 μm or less.

[0101] (Note 6) A laminated chip is provided with: dielectric layers made of dielectric ceramic and internal electrodes mainly composed of metal alternately laminated; and cover layers made of dielectric ceramic are provided at both ends in a stacking direction; connection conductors formed inside or on the surface of the laminated chip and electrically connecting the internal electrodes; and a plurality of terminal electrodes formed at intervals from each other on at least one surface of the cover layers, electrically connected to the connection conductors, and at least portions in contact with the cover layers contain a metal mainly composed of nickel; and when portions of the cover layers having the terminal electrodes on their surfaces that overlap with the terminal electrodes when viewed from the stacking direction are defined as terminal electrode facing portions and portions that do not overlap with the terminal electrodes when viewed from the stacking direction are defined as terminal electrode non-facing portions, In each of the terminal electrode facing portions, when an element distribution map prepared by measuring the nickel concentration distribution in an arbitrary cross section parallel to the stacking direction is divided into square cells with a side length of 5 μm, the number of cells in which nickel segregation regions, which are recognized as regions with a maximum dimension of 0.4 μm or more where the nickel concentration is higher than the surrounding area, are confirmed is 50% or more of the total number of cells; and in the terminal electrode non-facing portion, when an element distribution map prepared by measuring the nickel concentration distribution in an arbitrary cross section parallel to the stacking direction is divided into square cells with a side length of 5 μm, the number of cells in which the nickel segregation regions are confirmed is 5% or less of the total number of cells.

[0102] (Supplementary Note 7) The multilayer ceramic capacitor according to (Supplementary Note 6), wherein the terminal electrode opposing portions each have the nickel segregation region having a maximum dimension of 0.7 μm or more in the element distribution map.

[0103] (Appendix 8) The multilayer ceramic capacitor according to (Appendix 7), wherein, in each of the terminal electrode opposing portions, the number of cells in which nickel segregation regions having a maximum dimension of 0.7 μm or more are confirmed is 10% or more of the total number of cells.

[0104] (Supplementary Note 9) The multilayer ceramic capacitor according to any one of (Supplementary Note 6) to (Supplementary Note 8), wherein each of the terminal electrode opposing portions has a nickel diffusion region in the vicinity of an interface with the terminal electrode, in which the nickel concentration decreases with increasing distance from the terminal electrode.

[0105] (Supplementary Note 10) 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 a metal mainly composed of nickel is 0.2 μm or more and 1.5 μm or less.

[0106] (Supplementary Note 11) The multilayer ceramic capacitor according to any one of (Supplementary Note 6) to (Supplementary Note 10), wherein, in the terminal electrode opposing portion, when the cells are divided into surface cells located closer to the surface than a central portion of the cover layer in the thickness direction and internal cells located inside the central portion of the cover layer in the thickness direction, the percentage of cells in which the nickel segregation region is confirmed inside is higher in the surface cells than in the internal cells.

[0107] (Appendix 12) A method for manufacturing a multilayer ceramic capacitor according to any one of (Appendix 1) to (Appendix 11), comprising: preparing a powder of a dielectric ceramic composition; mixing the powder of the dielectric ceramic composition with a binder and forming the powder into a sheet to obtain a green sheet; forming an internal electrode pattern containing a metal on the green sheet; stacking a predetermined number of green sheets on which the internal pattern has been formed, arranging green sheets for cover layers at both ends in the stacking direction, and then pressing the green laminated body; singulating the green laminated body to obtain a pre-sintered laminated chip; removing the binder from the pre-sintered laminated chip; forming a plurality of metal layers containing nickel as a main component element by a physical vapor deposition method or a thermal spraying method so as to be positioned at intervals from each other on a surface of at least one green sheet for cover layer in the pre-sintered laminated chip after the binder has been removed; and firing a green formed body on which the plurality of metal layers have been formed to obtain a sintered body.

[0108] According to the present invention, it is possible to provide a multilayer ceramic capacitor that can suppress the occurrence of cracks in the cover layer due to the concentration of external stress and also suppress short circuits between terminal electrodes. Such a multilayer ceramic capacitor is useful in that it has high durability and a long life.

[0109] 100, 200, 200', 300, 400, 400', 500 Multilayer ceramic capacitor 10 Dielectric layer 20, 20a, 20b Internal electrode 21 Additional electrode 22 Oxide layer 30 Multilayer chip 40a, 40b Lead surface 50 Cover layer 51a, 51b Terminal electrode facing portion 52 Terminal electrode non-facing portion 53 Nickel segregation region 60 Side margin portion 70, 70a, 70b External electrode 71a, 71b Connecting conductor 72a, 72b Terminal electrode 73 Region containing metal having nickel as main element 74 Cu layer 75 Ni layer 76 Sn layer Ma, Mb Element distribution map (obtained for a cross section parallel to the stacking direction of the terminal electrode facing portion) Mm Element distribution map (obtained for a cross section parallel to the stacking direction of the terminal electrode non-facing portion) H ０ Baseline H １ , H ２ , ..., H ｍ Line segment V that vertically separates square cells １ , V ２ , …, V ｎ Line segment S that divides square cells horizontally Square cell S ｓ Surface cell S ｉ Interior Cell

Claims

1. A plurality of dielectric layers made of dielectric ceramic and a plurality of internal electrodes mainly made of metal are alternately laminated, and Multiple cover layers made of dielectric ceramic are provided at both ends in the stacking direction. stacked chips, a plurality of connection conductors formed inside or on the surface of the laminated chip, and electrically connecting the plurality of internal electrodes to each other; and are formed at intervals on at least one surface of the plurality of cover layers, The portions electrically connected to the plurality of connection conductors and in contact with the plurality of cover layers contain a metal containing nickel as a main component element. Multiple terminal electrodes Equipped with When portions of the plurality of cover layers that overlap with the plurality of terminal electrodes when viewed from the stacking direction are defined as a plurality of terminal electrode facing portions, and portions of the plurality of cover layers that do not overlap with the plurality of terminal electrodes when viewed from the stacking direction are defined as terminal electrode non-facing portions, In each of the plurality of terminal electrode opposing portions, an element distribution map created by measuring the nickel concentration distribution in any cross section parallel to the lamination direction has nickel segregation regions in which the nickel concentration is higher than the surrounding area and the maximum dimension is 0.4 μm or more, and the density of the nickel segregation regions having a maximum dimension of 0.5 μm or more is 1 μm or more. ２ 0.015 or more points per In the non-terminal electrode facing portion, in the element distribution map, the density of the nickel segregation region having a maximum dimension of 0.5 μm or more is 1 μm ２ 0.008 or less per Multilayer ceramic capacitor.

2. each of the plurality of terminal electrode opposing portions has a nickel segregation region having a maximum dimension of 0.7 μm or more in the element distribution map; The multilayer ceramic capacitor according to claim 1 .

3. In the non-terminal electrode facing portion, the nickel segregation region having a maximum dimension of 0.5 μm or more does not exist in the element distribution map. The multilayer ceramic capacitor according to claim 1 .

4. the terminal electrode facing portion has a nickel diffusion region in the vicinity of the interface with the terminal electrode, in which the nickel concentration decreases with increasing distance from the terminal electrode; The multilayer ceramic capacitor according to claim 1 .

5. a thickness of a portion of each of the plurality of terminal electrodes containing a metal containing nickel as a main component element is 0.2 μm or more and 1.5 μm or less; The multilayer ceramic capacitor according to claim 1 .

6. A plurality of dielectric layers made of dielectric ceramic and a plurality of internal electrodes mainly made of metal are alternately laminated, and Multiple cover layers made of dielectric ceramic are provided at both ends in the stacking direction. stacked chips, a plurality of connection conductors formed inside or on the surface of the laminated chip, and electrically connecting the plurality of internal electrodes to each other; and are formed at intervals on at least one surface of the plurality of cover layers, electrically connected to the connecting conductor; and The portion in contact with the plurality of cover layers contains a metal containing nickel as a main element. Multiple terminal electrodes Equipped with When portions of the plurality of cover layers that overlap with the plurality of terminal electrodes when viewed from the stacking direction are defined as a plurality of terminal electrode facing portions, and portions that do not overlap with the respective terminal electrodes when viewed from the stacking direction are defined as terminal electrode non-facing portions, In each of the plurality of terminal electrode opposing portions, when an element distribution map created by measuring the nickel concentration distribution in an arbitrary cross section parallel to the lamination direction is divided into square cells each having a side length of 5 μm, the number of cells containing nickel segregation regions having a nickel concentration higher than that of the surrounding area and a maximum dimension of 0.4 μm or more is 50% or more of the total number of cells; In the portion not facing the terminal electrode, when the element distribution map is divided into square cells each having a side length of 5 μm, the number of cells containing the nickel segregation region is 5% or less of the total number of cells. Multilayer ceramic capacitor.

7. each of the plurality of terminal electrode opposing portions has the nickel segregation region having a maximum dimension of 0.7 μm or more in the element distribution map; The multilayer ceramic capacitor according to claim 6.

8. In each of the plurality of terminal electrode opposing portions, the number of cells containing nickel segregation regions having a maximum dimension of 0.7 μm or more is 10% or more of the total number of cells. The multilayer ceramic capacitor according to claim 7.

9. Each of the plurality of terminal electrode facing portions has a nickel diffusion region in the vicinity of an interface with the plurality of terminal electrodes, in which the nickel concentration decreases with distance from the terminal electrodes. The multilayer ceramic capacitor according to claim 6.

10. a thickness of a portion of the plurality of terminal electrodes containing a metal containing nickel as a main component element is 0.2 μm or more and 1.5 μm or less; The multilayer ceramic capacitor according to claim 6.

11. In each of the plurality of terminal electrode opposing portions, when the cells are divided into surface cells located on the surface side of a central portion of the cover layer in the thickness direction and internal cells located on the inside of the central portion of the cover layer in the thickness direction, the percentage of the number of cells including the nickel segregation region inside is higher in the surface cells than in the internal cells. The multilayer ceramic capacitor according to claim 5 .

12. 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 a metal on the green sheet; a predetermined number of green sheets on which the internal pattern has been formed are stacked, green sheets for cover layers are disposed on both ends in the stacking direction, and then the green sheets are pressed together to obtain a green laminate; Slicing the green laminate into individual pieces to obtain pre-fired laminated chips; removing binder from the pre-fired laminated chips; forming a plurality of metal layers containing nickel as a main component by physical vapor deposition or thermal spraying on the surface of at least one green sheet for cover layer in the unfired laminated chip after binder removal, the metal layers being spaced apart from one another; Firing the green body on which the plurality of metal layers are formed to obtain a sintered body. Including, The method for manufacturing a multilayer ceramic capacitor according to any one of claims 1 to 11.

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