Multilayer ceramic capacitor

Abstract

Provided is a multilayer ceramic capacitor 1 comprising a layered body 10 including a dielectric ceramic layer 20 and internal electrode layers (21, 22) layered in a layering direction T, wherein: the layered body 10 has a substantially rectangular parallelepiped shape having a first main surface 11 and a second main surface 12 that face each other in a layering direction T, a first side surface 13 and a second side surface 14 that face each other in a width direction W orthogonal to the layering direction T, and a first end surface 15 and a second end surface 16 that face each other in a length direction L orthogonal to the layering direction T and the width direction W; a WT cross section that is a cross section of the layered body 10 taken along the width direction W and the layering direction T has Ni non-segregation parts (41, 43) that are present in a region at a prescribed thickness from at least one surface of the layered body 10 toward the interior of the layered body 10, and Ni segregation parts (42, 44) that are present farther into the layered body than the Ni non-segregation parts (41, 43) and contain Ni segregated in the dielectric ceramic layer 20; and a boundary (d) between the Ni non-segregation parts (41, 43) and the Ni segregation parts (42, 44) is positioned in a region of 5-20 μm from the surface of the layered body 10 toward the interior of the layered body 10.

Description

Multilayer ceramic capacitors

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

[0002] Patent Document 1 discloses a multilayer ceramic capacitor as a multilayer ceramic electronic component, which is characterized in that it includes an inner layer portion in which dielectric layers and internal electrode layers containing Ni as a main component are alternately stacked, and a pair of dielectric outer layer portions sandwiching the inner layer portion, and Ni particles are segregated in the dielectric outer layer portions.

[0003] JP 2013-102123 A

[0004] The dielectric outer layer portions in Patent Document 1 are regions where internal electrode layers are not alternately laminated and are portions (ineffective portions) that do not exhibit capacitance. Patent Document 1 claims that a multilayer ceramic capacitor with high moisture resistance can be obtained by segregating Ni particles in the ineffective portions.

[0005] Here, the present inventors have investigated the properties of a multilayer ceramic capacitor in which Ni particles are segregated in the ineffective portions, and have found that the bending strength becomes insufficient.

[0006] The present invention has been made to solve the above problems, and an object of the present invention is to provide a multilayer ceramic capacitor that is excellent in moisture resistance and flexural strength.

[0007] The multilayer ceramic capacitor of the present invention is a multilayer ceramic capacitor comprising a laminate including dielectric ceramic layers and internal electrode layers laminated in a lamination direction, wherein the laminate has a substantially rectangular parallelepiped shape having first and second main surfaces opposing each other in the lamination direction, first and second side surfaces opposing each other in a width direction perpendicular to the lamination direction, and first and second end faces opposing each other in a length direction perpendicular to the lamination direction and the width direction, and in a WT cross section which is a cross section of the laminate taken along the width direction and the lamination direction, the multilayer ceramic capacitor has a Ni-segregation-free portion which is present in a region of a predetermined thickness from at least one surface of the laminate toward the interior of the laminate, and a Ni-segregation portion which is present more inside the laminate than the Ni-segregation-free portion and contains Ni segregated in the dielectric ceramic layers, and the boundary between the Ni-segregation-free portion and the Ni-segregation portion is located in a region of 5 μm or more and 20 μm or less from the surface of the laminate toward the interior of the laminate.

[0008] According to the present invention, it is possible to provide a multilayer ceramic capacitor having excellent moisture resistance and bending strength.

[0009] FIG. 1 is a perspective view schematically showing an example of a multilayer ceramic capacitor of the present invention. FIG. 2 is a perspective view schematically showing an example of a laminate constituting the multilayer ceramic capacitor shown in FIG. 1. FIG. 3 is a cross-sectional view (WT cross-sectional view) of the laminate shown in FIG. 2 taken along line A-A. FIG. 4 is an enlarged view of a region indicated by region B in FIG. 3, including an outer layer portion in contact with the second main surface of the laminate. FIG. 5 is a Ni mapping image obtained by WDX of an electron microscope photograph taken at a position corresponding to FIG. 4. FIG. 6 is an enlarged view of a region indicated by region C in FIG. 3, including an outer layer portion in contact with the second side surface of the laminate. FIG. 7 is a Ni mapping image obtained by WDX of an electron microscope photograph taken at a position corresponding to FIG. 6.

[0010] The multilayer ceramic capacitor of the present invention will be described below. However, the present invention is not limited to the following configurations, and can be appropriately modified and applied within the scope of the present invention. Note that a combination of two or more of the individual preferred configurations described below also falls within the scope of the present invention.

[0011] [Multilayer Ceramic Capacitor] Fig. 1 is a perspective view schematically showing an example of a multilayer ceramic capacitor of the present invention. Fig. 2 is a perspective view schematically showing an example of a laminate constituting the multilayer ceramic capacitor shown in Fig. 1. Fig. 3 is a cross-sectional view (WT cross-sectional view) taken along line A-A of the laminate shown in Fig. 2.

[0012] In this specification, the lamination direction, width direction, and length direction of the multilayer ceramic capacitor and laminate are defined by arrows T, W, and L, respectively, in the multilayer ceramic capacitor 1 shown in Fig. 1 and the laminate 10 shown in Fig. 2. Here, the lamination direction T, the width direction W, and the length direction L are perpendicular to one another. The lamination direction T is the direction in which the plurality of dielectric ceramic layers 20 and the plurality of internal electrode layers (first internal electrode layers 21 and second internal electrode layers 22) are stacked up.

[0013] The multilayer ceramic capacitor 1 shown in FIG. 1 includes a laminate 10, and a first external electrode 51 and a second external electrode 52 provided on both end surfaces of the laminate 10, respectively.

[0014] As shown in FIG. 2 , the laminate 10 has a rectangular or approximately rectangular parallelepiped shape, and has a first main surface 11 and a second main surface 12 that face each other in a stacking direction T, a first side surface 13 and a second side surface 14 that face each other in a width direction W that is perpendicular to the stacking direction T, and a first end surface 15 and a second end surface 16 that face each other in a length direction L that is perpendicular to the stacking direction T and the width direction W.

[0015] Methods for distinguishing between the width direction W and the length direction L include a method in which the surface from which the internal electrode layers are drawn out is defined as the end face of the laminate, and the direction in which the end faces of the laminate face each other is defined as the length direction L, or a method in which the length direction L is defined as the longitudinal direction in which the dimensions of the laminate increase among directions other than the stacking direction of the laminate.

[0016] In this specification, a cross section of the multilayer ceramic capacitor 1 or laminate 10 that is orthogonal to the first end face 15 and the second end face 16 and parallel to the stacking direction T is referred to as an LT cross section, which is a cross section along the length direction L and the stacking direction T. A cross section of the multilayer ceramic capacitor 1 or laminate 10 that is orthogonal to the first side face 13 and the second side face 14 and parallel to the stacking direction T is referred to as a WT cross section, which is a cross section along the width direction W and the stacking direction T. A cross section of the multilayer ceramic capacitor 1 or laminate 10 that is orthogonal to the first side face 13, the second side face 14, the first end face 15, and the second end face 16 and perpendicular to the stacking direction T is referred to as an LW cross section, which is a cross section along the length direction L and the width direction W. Therefore, FIG. 3 shows a WT cross section of the laminate 10. The WT surface is a surface where the internal electrode layers are drawn to the surface (end face) of the laminate.

[0017] The corners and ridges of the laminate 10 are preferably rounded. A corner is a portion where three surfaces of the laminate intersect, and a ridge is a portion where two surfaces of the laminate intersect.

[0018] 2 and 3 , the laminate 10 has a laminated structure including a plurality of dielectric ceramic layers 20 laminated in a lamination direction T, and a plurality of pairs of first internal electrode layers 21 and second internal electrode layers 22 formed along the interfaces between the dielectric ceramic layers 20. The dielectric ceramic layers 20 extend along the width direction W and the length direction L, and each of the first internal electrode layers 21 and the second internal electrode layers 22 extends in a flat plate shape along the dielectric ceramic layers 20.

[0019] The first internal electrode layer 21 is extended to a first end face 15 of the laminate 10 , while the second internal electrode layer 22 is extended to a second end face 16 of the laminate 10 .

[0020] The first internal electrode layers 21 and the second internal electrode layers 22 face each other in the stacking direction T via the dielectric ceramic layers 20. Electrostatic capacitance is generated by the portions where the first internal electrode layers 21 and the second internal electrode layers 22 face each other via the dielectric ceramic layers 20. Note that in the multilayer ceramic capacitor of the present invention, the positions where the internal electrode layers are drawn out are not limited to the first end face and the second end face.

[0021] Each of the internal electrode layers (first internal electrode layer 21 and second internal electrode layer 22) preferably contains a metal as a conductive material, and preferably contains Ni. Furthermore, the internal electrode layers may contain the same dielectric ceramic material as the dielectric ceramic layer 20 in addition to the metal.

[0022] The thickness of each of the internal electrode layers (first internal electrode layer 21 and second internal electrode layer 22) is preferably 1.5 μm or less, and the thickness of each of the internal electrode layers is preferably 0.4 μm or more.

[0023] The dielectric ceramic layer is made of a ceramic material, for example, BaTiO ３ It is preferable that the internal electrode layer is made of a dielectric ceramic material containing, as a main component, Ni, etc. Furthermore, elements such as Ni contained in the internal electrode layer may be diffused into the dielectric ceramic layer.

[0024] The thickness of the dielectric ceramic layers is preferably 10 μm or less. Also, the thickness of each dielectric ceramic layer is preferably 0.5 μm or more. The thickness of the dielectric ceramic layers here refers to the thickness of the dielectric ceramic layers between the internal electrode layers, i.e., the thickness of the dielectric ceramic layers in the inner layer portion.

[0025] The first external electrode 51 is provided on the first end face 15 of the laminate 10, and in Fig. 1 has a portion that extends around to each of the first main face 11, the second main face 12, the first side face 13, and the second side face 14. The first external electrode 51 is connected to the first internal electrode layer 21 at the first end face 15.

[0026] The second external electrode 52 is provided on the second end face 16 of the laminate 10, and in Fig. 1 has a portion that extends around to each of the first main face 11, the second main face 12, the first side face 13, and the second side face 14. The second external electrode 52 is connected to the second internal electrode layer 22 at the second end face 16.

[0027] The first external electrode 51 and the second external electrode 52 may each contain Ni. The first external electrode 51 and the second external electrode 52 may each include a Ni layer containing Ni and a ceramic material. The Ni layer is a base electrode layer. Such a Ni layer may be formed by a so-called co-firing method in which the Ni layer is fired simultaneously with the first internal electrode layer 21 and the second internal electrode layer 22.

[0028] In the multilayer ceramic capacitor of the present invention, a WT cross section, which is a cross section of the laminate, has a Ni-segregation-free portion that exists in a region of a predetermined thickness from at least one surface of the laminate toward the interior of the laminate, and a Ni-segregation portion that exists more inward of the laminate than the Ni-segregation portion and contains Ni segregated in the dielectric ceramic layer. Furthermore, the boundary between the Ni-segregation-free portion and the Ni-segregation portion is located in a region of 5 μm or more and 20 μm or less from the surface of the laminate toward the interior of the laminate. The WT cross section, which is a cross section of the laminate, is taken at a position that does not contact the external electrodes. Since external electrodes are often provided on both end surfaces of the laminate, it is preferable that the WT cross section be taken near the center of the laminate in the longitudinal direction L.

[0029] Fig. 3 is a cross-sectional view (WT cross-sectional view) taken along line A-A of the laminate shown in Fig. 2. The laminate 10 shown in Fig. 3 has an inner layer portion 30 in which first internal electrode layers 21 and second internal electrode layers 22 face each other with the dielectric ceramic layer 20 interposed therebetween, and outer layer portions 31 and 32 arranged to sandwich the inner layer portion 30 in the stacking direction T. The outer layer portion 31 is an outer layer portion in contact with the first main surface 11, and the outer layer portion 32 is an outer layer portion in contact with the second main surface 12. The laminate 10 also has an inner layer portion 33 in which the first internal electrode layers 21 and second internal electrode layers 22 extend in the width direction W, and outer layer portions 34 and 35 arranged to sandwich the inner layer portion 33 in the width direction W. The outer layer portion 34 is an outer layer portion in contact with the first side surface 13, and the outer layer portion 35 is an outer layer portion in contact with the second side surface 14. Each outer layer is made of a dielectric ceramic layer, and is usually a layer in which a plurality of dielectric ceramic layers are laminated.

[0030] Fig. 4 is an enlarged view of a region including an outer layer portion in contact with the second main surface of the laminate, which is indicated by region B in Fig. 3. Fig. 4 shows a Ni-segregation-free portion 41 that exists in a region of a predetermined thickness from the second main surface 12 of the laminate, which is one surface of the laminate 10, toward the interior of the laminate 10 (upward in the drawing), and a Ni-segregation portion 42 that exists further inside the laminate 10 than the Ni-segregation-free portion 41 and contains Ni segregated in the dielectric ceramic layer. The Ni-segregation-free portion 41 and the Ni-segregation portion 42 together form the outer layer portion 32.

[0031] The presence of Ni-segregated and Ni-non-segregated portions can be confirmed by polishing the cross section of the laminate so that the WT cross section is exposed, and detecting Ni through composition analysis using a wavelength dispersive X-ray analyzer (WDX). An FE-WDX (Field-Emission WDX) may be used as the WDX.

[0032] Figure 5 is a Ni mapping image by WDX of an electron microscope photograph taken at a position corresponding to that of Figure 4. The Ni segregated area is where a large amount of Ni particle light is observed when Ni element mapping is performed in WDX analysis. The state of light emitted by Ni particles can be understood from the Ni mapping image by WDX.

[0033] The Ni-segregation-free portion is a portion where Ni is not present or where Ni is present but is dissolved in the crystals of the dielectric ceramic, and does not appear to glow as particles in a Ni mapping image obtained by WDX. The Ni-segregation-free portion does not mean a region where Ni is completely absent, nor does it mean a region where no light from Ni particles is observed. In the Ni-segregation-free portion, light from Ni particles may be observed to a lesser extent than in the Ni-segregation portion.

[0034] As a method for defining the Ni segregation-free portion, a region in which the number of Ni particles is 20% or less of the number of Ni particles observed in a region sufficiently inward from the surface of the laminate (75 μm inward from the surface of the laminate) (the number of Ni particles that appear to shine per unit area) may be defined as the Ni segregation-free portion.

[0035] Furthermore, if the boundary between the Ni-segregated and Ni-non-segregated regions can be determined by visual observation without counting the number of Ni particles, the Ni-segregated and Ni-non-segregated regions may be determined by visual observation of a Ni mapping image obtained by WDX. In particular, when the thickness of the outer layer portion is less than 75 μm, it may be difficult to determine the location of the "region sufficiently inside from the surface of the laminate" that serves as the standard for comparing the number of Ni particles. Therefore, the boundary between the Ni-segregated and Ni-non-segregated regions may be determined by visual observation.

[0036] In the Ni mapping image obtained by WDX, there are areas where a lot of Ni particle light is observed and areas where almost no particle light is observed. If the boundary line between these areas can be visually identified, the boundary between the Ni-segregated and Ni-nonsegregated areas can be determined.

[0037] The boundary between the Ni-segregation-free portion 41 and the Ni-segregation portion 42 is the line indicated by the dotted line d in Fig. 4 and Fig. 5. This boundary is located in a region extending from the second main surface 12 of the laminate, which is the surface of the laminate 10, toward the inside of the laminate, and is 5 µm or more and 20 µm or less.

[0038] When the boundary between the Ni-segregation-free portion and the Ni-segregation portion is located in a region 5 μm or more and 20 μm or less from the surface of the laminate toward the interior of the laminate, the Ni-segregation-free portion exists in a region 5 μm or more thick from the surface of the laminate. The presence of the Ni-segregation-free portion in this region can improve the flexural strength of the multilayer ceramic capacitor. In this case, it can also be said that the thickness of the Ni-segregation-free portion is 5 μm or more. Furthermore, when the boundary between the Ni-segregation-free portion and the Ni-segregation portion is located in a region less than 5 μm from the surface of the laminate toward the interior of the laminate, the thickness of the Ni-segregation-free portion is thin, less than 5 μm, and the flexural strength of the multilayer ceramic capacitor is insufficient.

[0039] When the boundary between the Ni-segregation-free portion and the Ni-segregation portion exists in a region extending from the surface of the laminate toward the interior of the laminate to a depth of more than 20 μm, the Ni-segregation-free portion exists in a region extending from the surface of the laminate to a thickness of more than 20 μm. In this case, the moisture resistance of the multilayer ceramic capacitor is reduced. In the Ni-segregation portion, the presence of Ni particles suppresses abnormal grain growth of dielectric ceramic particles, so the presence of the Ni-segregation portion in a predetermined region contributes to improved moisture resistance. When the thickness of the Ni-segregation-free portion exceeds 20 μm and becomes deep, the distance from the surface of the laminate to the Ni-segregation portion is long, resulting in reduced moisture resistance of the multilayer ceramic capacitor. By positioning the boundary between the Ni-segregation-free portion and the Ni-segregation portion within a region extending from the surface of the laminate toward the interior of the laminate to a depth of 20 μm or less, the provision of the Ni-segregation portion exhibits the effect of improving moisture resistance.

[0040] From the above, when the boundary between the Ni-segregated portion and the Ni-segregated portion is located in a region of 5 μm or more and 20 μm or less from the surface of the laminate toward the inside of the laminate, the effects of improving both the flexural strength and the moisture resistance of the multilayer ceramic capacitor are exerted.

[0041] FIG. 4 shows that in a region including an outer layer portion in contact with the second main surface of the laminate, a Ni-segregation-free portion and a Ni-segregation portion are present in a region of a predetermined thickness extending from the second main surface toward the interior of the laminate. However, in the multilayer ceramic capacitor of the present invention, a Ni-segregation-free portion and a Ni-segregation portion may be present in a region of a predetermined thickness extending from the surface of at least one of the first main surface and the second main surface toward the interior of the laminate in the WT cross section.

[0042] In a region including an outer layer portion in contact with the first main surface of the laminate, a Ni-segregated portion and a Ni-segregated portion may be present in a region of a predetermined thickness extending from the first main surface toward the interior of the laminate. Also, in each of a region including an outer layer portion in contact with the first main surface of the laminate and a region including an outer layer portion in contact with the second main surface of the laminate, a Ni-segregated portion and a Ni-segregated portion may be present in a region of a predetermined thickness extending from the first main surface and the second main surface toward the interior of the laminate.

[0043] Fig. 6 is an enlarged view of a region including an outer layer portion in contact with the second side surface of the laminate, which is indicated by region C in Fig. 3. Fig. 6 shows a Ni-segregation-free portion 43 that exists in a region of a predetermined thickness from the second side surface 14 of the laminate, which is one surface of the laminate 10, toward the interior of the laminate 10 (toward the left in the drawing), and a Ni-segregation portion 44 that exists further inside the laminate 10 than the Ni-segregation-free portion 43 and contains Ni segregated in the dielectric ceramic layer. The Ni-segregation-free portion 43 and the Ni-segregation portion 44 together form an outer layer portion 35.

[0044] Fig. 7 is a Ni mapping image obtained by WDX of an electron microscope photograph taken at a position corresponding to that of Fig. 6. Fig. 7 shows that there are Ni-segregation-free and Ni-segregation parts in the Ni mapping image obtained by WDX, as well as the boundary between the Ni-segregation-free and Ni-segregation parts.

[0045] The boundary between the Ni-segregation-free portion 43 and the Ni-segregation portion 44 is indicated by the dotted line d in Figures 6 and 7. This boundary is located in a region extending from 5 µm to 20 µm toward the inside of the laminate from the second side surface 14 of the laminate, which is the surface of the laminate 10. The boundary between the Ni-segregation-free portion 43 and the Ni-segregation portion 44 located in this region provides the effects of improving both the flexural strength and the moisture resistance of the multilayer ceramic capacitor.

[0046] FIG. 6 shows that in a region including an outer layer portion in contact with the second side surface of the laminate, a Ni-segregation-free portion and a Ni-segregation portion are present in a region of a predetermined thickness extending from the second side surface toward the interior of the laminate. However, in the multilayer ceramic capacitor of the present invention, a Ni-segregation-free portion and a Ni-segregation portion may be present in a region of a predetermined thickness extending from the surface of at least one of the first side surface and the second side surface toward the interior of the laminate in the WT cross section.

[0047] In a region including an outer layer portion in contact with a first side surface of the laminate, a Ni-segregated portion and a Ni-segregated portion may be present in a region of a predetermined thickness extending from the first side surface toward the interior of the laminate. Also, in each of a region including an outer layer portion in contact with the first side surface of the laminate and a region including an outer layer portion in contact with a second side surface of the laminate, a Ni-segregated portion and a Ni-segregated portion may be present in a region of a predetermined thickness extending from the first side surface and the second side surface toward the interior of the laminate.

[0048] Furthermore, in the multilayer ceramic capacitor of the present invention, in the WT cross section, Ni-segregation-free portions and Ni-segregation portions may be present in regions of a predetermined thickness extending from each of the first main surface, the second main surface, the first side surface, and the second side surface toward the interior of the laminate. In this case, a Ni-segregation portion is present around the inner layer portion located at the center of the WT cross section, and a Ni-segregation-free portion is further present around the Ni-segregation portion. The presence of Ni-segregation-free portions and Ni-segregation portions in regions of a predetermined thickness extending from the surface of the laminate toward the interior of the laminate, regardless of the first main surface, the second main surface, the first side surface, and the second side surface, is preferable because this increases the flexural strength and moisture resistance regardless of the orientation of the multilayer ceramic capacitor and prevents the surface from having locally inferior flexural strength or moisture resistance.

[0049] Preferred dimensions of the multilayer ceramic capacitor of the present invention include the following: The lengthwise dimension of the laminate is 0.6 mm or more and 3.2 mm or less; The widthwise dimension of the laminate is 0.3 mm or more and 2.5 mm or less; The lamination direction dimension of the laminate is 0.3 mm or more and 2.5 mm or less. An example of the size of the multilayer ceramic capacitor is a 3216 size (length 3.2 mm × width 1.6 mm). In a relatively large multilayer ceramic capacitor such as the 3216 size, the presence of a Ni-segregation-free portion and a Ni-segregation portion in a region of a predetermined thickness from the surface of the laminate toward the interior of the laminate tends to provide the effect of increasing the bending strength and moisture resistance.

[0050] In addition, in the WT cross section, it is preferable that the distance from the surface of the laminate, where the Ni-segregation-free portion and the Ni-segregation portion exist in a region of a predetermined thickness from the surface toward the interior of the laminate, to the internal electrode layer is 80 μm or more and 250 μm or less. The distance from the surface of the laminate to the internal electrode layer as specified above means the thickness of the outer layer portion in which the Ni-segregation-free portion and the Ni-segregation portion exist. A multilayer ceramic capacitor having outer layer portions with the above dimensions is a multilayer ceramic capacitor with relatively thick outer layer portions, and in a multilayer ceramic capacitor with relatively thick outer layer portions, the presence of the Ni-segregation-free portion and the Ni-segregation portion in a region of a predetermined thickness from the surface of the laminate toward the interior of the laminate tends to achieve the effect of increasing the flexural strength and moisture resistance.

[0051] In addition, in the multilayer ceramic capacitor of the present invention, the boundary between the Ni-segregation-free portion and the Ni-segregation portion is located in a region of 5 μm or more and 20 μm or less from the surface of the laminate toward the interior of the laminate, but as long as this condition is satisfied, the thickness of the outer layer portion may be less than 20 μm. For example, a case in which the thickness of the outer layer portion is 15 μm and the boundary between the Ni-segregation-free portion and the Ni-segregation portion is located in a region of 10 μm from the surface of the laminate toward the interior of the laminate (an example in which the thickness of the Ni-segregation-free portion is 10 μm and the thickness of the Ni-segregation portion is 5 μm) is also included in the multilayer ceramic capacitor of the present invention.

[0052] [Method for Manufacturing Multilayer Ceramic Capacitor] The method for manufacturing the multilayer ceramic capacitor of the present invention is not particularly limited, but it can be manufactured, for example, by the following method. First, ceramic green sheets to become the dielectric ceramic layers are prepared. The ceramic green sheets contain ceramic raw materials including the above-mentioned dielectric ceramic material as well as binders, solvents, etc. The ceramic green sheets are formed on a carrier film using, for example, a die coater, gravure coater, microgravure coater, etc.

[0053] When the ceramic green sheet contains Ni, the portion of the ceramic green sheet containing Ni can become a Ni segregated portion.

[0054] Unsintered internal electrode layers are formed on the ceramic green sheets using a conductive paste, for example, by screen printing, gravure printing, or the like.

[0055] A mother block is produced by alternately stacking, in the stacking direction, first ceramic green sheets on which unsintered first internal electrode layers corresponding to the first internal electrode layers are formed and second ceramic green sheets on which unsintered second internal electrode layers corresponding to the second internal electrode layers are formed.

[0056] Ceramic green sheets without unsintered internal electrode layers are laminated on the top and bottom surfaces of the mother block to form outer layer portions arranged to sandwich the inner layer portions in the lamination direction. The thickness of the outer layer portions arranged to sandwich the inner layer portions in the lamination direction is adjusted by adjusting the thickness and number of laminated ceramic green sheets that form the outer layer portions.

[0057] As the ceramic green sheets that become the outer layer portions arranged so as to sandwich the inner layer portion in the stacking direction, one or more ceramic green sheets that do not contain Ni are arranged at positions that become the surfaces of the laminate, thereby providing a Ni-segregation-free portion up to a predetermined thickness from the surface (first main surface or second main surface) of the laminate toward the interior of the laminate.

[0058] As the ceramic green sheets that become outer layer portions arranged so as to sandwich the inner layer portion in the stacking direction, one or more Ni-containing ceramic green sheets are arranged at positions that are more internal to the laminate than the Ni-free ceramic green sheets, thereby providing a Ni-segregated portion that is located more internal to the laminate than the Ni-free portion.

[0059] This method makes it possible to have Ni-segregated portions and Ni-segregated portions present in a region of a predetermined thickness extending from the first or second main surface, which serves as the surface of the laminate, toward the interior of the laminate.

[0060] The mother block thus obtained is cut lengthwise, i.e., in a direction exposing the LT cross section of the laminate, and then cut widthwise, i.e., in a direction exposing the WT cross section of the laminate, to obtain a laminate. Unfired ceramic green sheets not having internal electrode layers formed thereon are attached to the first and second side surfaces of the obtained laminate, thereby providing outer layer portions arranged to sandwich the inner layer portion in the width direction.

[0061] As the ceramic green sheets that become the outer layer portions arranged so as to sandwich the inner layer portion in the width direction, one or more ceramic green sheets that do not contain Ni are arranged at a position that becomes the surface of the laminate, thereby providing a Ni-segregation-free portion from the surface (first side surface or second side surface) of the laminate toward the interior of the laminate to a predetermined thickness.

[0062] As the ceramic green sheets that become outer layer portions arranged so as to sandwich the inner layer portion in the width direction, one or more Ni-containing ceramic green sheets are arranged at positions that are more internal to the laminate than the Ni-free ceramic green sheets, thereby providing a Ni-segregated portion that is located more internal to the laminate than the Ni-free portion.

[0063] This method makes it possible to have Ni-segregated portions and Ni-segregated portions in a region of a predetermined thickness extending from the first side surface or the second side surface serving as the surface of the laminate toward the interior of the laminate.

[0064] Furthermore, the following method can be used to ensure that Ni-segregated portions and Ni-segregated portions exist in a region of a predetermined thickness from the surface (first side surface or second side surface) of the laminate toward the interior of the laminate: By adjusting the relationship between the application region of the internal electrode layer in the width direction on the ceramic green sheet and the cutting position along the length direction of the mother block, a laminate can be obtained in which the internal electrode layer is not exposed on the first side surface and the second side surface of the laminate after cutting, and which has outer layer portions sandwiching the internal layer portions in the width direction.

[0065] When the ceramic green sheets for obtaining a laminate contain Ni, Ni-segregated portions are provided in the outer layer portions that sandwich the inner layer portion in the width direction. By arranging one or more Ni-free ceramic green sheets on the first or second side surface of such a laminate at positions that will become the surface of the laminate, a Ni-segregated portion is provided from the surface (first or second side surface) of the laminate toward the interior of the laminate to a predetermined thickness.

[0066] Even with this method, it is possible to make the Ni-segregated portion and the Ni-segregated portion exist in a region of a predetermined thickness extending from the first side surface or the second side surface as the surface of the laminate toward the interior of the laminate.

[0067] The green laminate obtained by these methods is preferably subjected to barrel polishing, etc. By polishing the green laminate, the corners and ridges of the laminate after firing are rounded.

[0068] The unfired laminate is fired to form a laminate, for example, at a firing temperature of 900° C. or higher and 1300° C. or lower.

[0069] Thereafter, a conductive paste for external electrodes is applied to the first end face and the second end face of the laminate to form a metal layer, and if necessary, the metal layer is subjected to a baking process, and further Ni plating and Sn plating are applied to form the first external electrode and the second external electrode.

[0070] Through the above steps, a multilayer ceramic capacitor can be manufactured.

[0071] In the above method, a Ni-segregation-free portion is provided by disposing one or more Ni-free ceramic green sheets at a position that will become the surface of the laminate. By setting the total thickness of the Ni-free ceramic green sheets to 5 μm or more and 20 μm or less, the boundary between the Ni-segregation-free portion and the Ni-segregation portion can be positioned in a region that is 5 μm or more and 20 μm or less from the surface of the laminate toward the interior of the laminate.

[0072] In addition, when a ceramic green sheet containing Ni is used to provide Ni segregation portions in the above method, BaTiO ３ The ratio of Ni to 100 parts by mol is preferably 0.3 parts by mol or more and 3.0 parts by mol or less.

[0073] Furthermore, the method for producing a multilayer ceramic capacitor of the present invention is not limited to adjusting the stacking positions of two types of ceramic green sheets, i.e., Ni-free and Ni-containing, and the use of Ni-free ceramic green sheets is not essential. By adjusting the firing conditions of the laminate, a Ni-segregation-free portion can be formed in a region of a predetermined thickness from the surface of the laminate toward the interior of the laminate, and a Ni-segregation portion can be formed at a predetermined position inside the laminate relative to the Ni-segregation-free portion. By adjusting the firing conditions of the laminate, the position of the boundary between the Ni-segregation-free portion and the Ni-segregation portion can be adjusted so that the boundary is located in a region of 5 μm or more and 20 μm or less from the surface of the laminate toward the interior of the laminate.

[0074] The present specification discloses the following:

[0075] The present disclosure (1) provides a multilayer ceramic capacitor including a laminate including dielectric ceramic layers and internal electrode layers stacked in a stacking direction, wherein the laminate has a substantially rectangular parallelepiped shape having a first main surface and a second main surface opposing each other in the stacking direction, a first side surface and a second side surface opposing each other in a width direction perpendicular to the stacking direction, and a first end surface and a second end surface opposing each other in a length direction perpendicular to the stacking direction and the width direction, and wherein a WT cross section, which is a cross section of the laminate along the width direction and the stacking direction, has a Ni-segregation-free portion that exists in a region of a predetermined thickness from at least one surface of the laminate toward the interior of the laminate, and a Ni-segregation portion that exists more in the laminate than the Ni-segregation-free portion and contains Ni segregated in the dielectric ceramic layers, and the boundary between the Ni-segregation-free portion and the Ni-segregation portion is located in a region of 5 μm or more and 20 μm or less from the surface of the laminate toward the interior of the laminate.

[0076] The present disclosure (2) is the multilayer ceramic capacitor according to the present disclosure (1), wherein the Ni-segregation-free portion and the Ni-segregation portion are present in a region of a predetermined thickness extending from at least one of the first principal surface and the second principal surface toward the inside of the laminate in the WT cross section.

[0077] The present disclosure (3) is the multilayer ceramic capacitor according to the present disclosure (1) or (2), wherein the Ni-segregation-free portion and the Ni-segregation portion are present in a region of a predetermined thickness from a surface of at least one of the first side surface and the second side surface toward the inside of the laminate in the WT cross section.

[0078] The present disclosure (4) is the multilayer ceramic capacitor according to the present disclosure (1), wherein the Ni-segregation-free portion and the Ni-segregation portion are present in regions of a predetermined thickness from each of the first main surface, the second main surface, the first side surface, and the second side surface toward the inside of the laminate in the WT cross section.

[0079] The present disclosure (5) is the multilayer ceramic capacitor according to any one of the present disclosures (1) to (4), in which the internal electrode layers contain Ni.

[0080] The present disclosure (6) is a method for manufacturing a dielectric ceramic layer comprising: ３ The multilayer ceramic capacitor according to any one of the present disclosures (1) to (5), comprising:

[0081] The present disclosure (7) is a multilayer ceramic capacitor according to any one of the present disclosures (1) to (6), wherein the length of the laminate is 0.6 mm or more and 3.2 mm or less, the width of the laminate is 0.3 mm or more and 2.5 mm or less, and the stacking direction of the laminate is 0.3 mm or more and 2.5 mm or less.

[0082] The present disclosure (8) is a multilayer ceramic capacitor according to any one of the present disclosures (1) to (7), wherein, in the WT cross section, the Ni-segregation-free portion and the Ni-segregation portion are present in a region of a predetermined thickness from the surface of the laminate toward the interior of the laminate, and the distance from the surface to the internal electrode layer is 80 μm or more and 250 μm or less.

[0083] EXAMPLES Hereinafter, examples will be given that more specifically disclose the multilayer ceramic capacitor of the present invention, but the present invention is not limited to these examples.

[0084] <Ceramic green sheet> As a ceramic green sheet not containing Ni, a ceramic green sheet containing BaTiO as the main component ３ A ceramic green sheet (A) was prepared having a composition of 2.0 molar parts of Dy, 0.3 molar parts of Mg, 0.3 molar parts of Mn, and 1.0 molar parts of Si as the subcomponents, based on 100 molar parts of BaTiO. ３ Ceramic green sheets (B) each having a composition of 100 mol parts of the above, 2.0 mol parts of Dy, 0.3 mol parts of Mg, 0.3 mol parts of Mn, 1.0 mol part of Si, and 2.0 mol parts of Ni as auxiliary components were prepared. The thickness of each ceramic green sheet was 5 μm.

[0085] <Preparation of Samples> Internal electrode layers were formed on ceramic green sheets (B), and a plurality of ceramic green sheets on which the internal electrode layers were formed were stacked and cut to obtain a laminate before firing. At this time, the number of stacked sheets and the cutting position were adjusted so that the final chip size was 3216 size (length 3.2 mm × width 1.6 mm).

[0086] Ceramic green sheets (A) were attached to the first main surface, the second main surface, the first side surface, and the second side surface of the laminate before firing. The number of attached ceramic green sheets (A) was adjusted to produce each sample such that the thickness of the Ni-segregation-free portion formed from each surface toward the inside of the laminate was adjusted to different thicknesses. Note that in sample number 1, no ceramic green sheets (A) were attached, so that no Ni-segregation-free portion was provided. The thickness of all outer layer portions in contact with each surface of the laminate of each sample was 150 μm.

[0087] This laminate was ２ The binder was burned by heating at a temperature of 350°C in an atmosphere, and then the mixture was heated in a H atmosphere with an oxygen partial pressure of 10-10 to 10-12 MPa. ２ -N ２ -H ２ A laminate was obtained by firing in a reducing atmosphere of O gas at 1200° C. for 20 minutes. External electrodes were formed on the first end face and the second end face of the laminate to obtain a multilayer ceramic capacitor.

[0088] <Method for identifying Ni segregation-free and Ni segregation areas> (1) The laminate of each sample is polished lengthwise from the end face, and a Ni mapping image is obtained using FE-WDX for the WT cross section when the lengthwise dimension is halved. (2) The number of brightly shining points in the Ni mapping image (the number of Ni segregations) is counted for each distance from the surface of the laminate. (3) The Ni segregation-free area is defined as the area where the number of Ni segregations is 20% or less of the number of Ni segregations in a region sufficiently inward from the surface of the laminate (75 μm inward from the surface of the laminate).

[0089] <Evaluation of Moisture Resistance> After a moisture resistance test was carried out on each sample of multilayer ceramic capacitor at a temperature of 125°C, a humidity of 95% RH, a DC voltage of 25 V, and a holding time of 144 hours, the insulation resistance was measured using an insulation resistance measuring device. A sample in which even one insulation resistance deterioration occurred, where the insulation resistance was below a predetermined value, was judged as x, and a sample in which no insulation resistance deterioration occurred was judged as ◯. The number of samples for each sample was 100, and the samples in which the insulation resistance was 10,000 Ω (10 ４ The samples in which the insulation resistance was below 1 / 2 Ω were judged to have deteriorated.

[0090] <Evaluation of Flexural Strength> The flexural strength of the multilayer ceramic capacitors was evaluated by a flexural test using three-point bending. The flexural test was performed under the following conditions: - Descending speed of the pressing jig: 0.1 (mm / sec) - Diameter of the tip of the pressing jig: 0.2 (mm) radius - Pressing position: Center where the length direction L and width direction W of the sample intersect (center of the LW surface) For each sample, the flexural strength of 20 multilayer ceramic capacitors was measured and the average value was calculated. Samples with a flexural strength of less than 500 N were rated as ×, and samples with a flexural strength of 500 N or more were rated as ○.

[0091] The specifications and evaluation results of each sample are summarized in Table 1.

[0092] Samples 2 to 5 are multilayer ceramic capacitors in which the boundary between the Ni-segregation-free portion and the Ni-segregation portion is located in a region of 5 μm or more and 20 μm or less from the surface of the laminate toward the interior of the laminate. By satisfying this condition, the effect of increasing the flexural strength and moisture resistance of the multilayer ceramic capacitor was obtained. Sample 1 did not have a Ni-segregation-free portion, and therefore the flexural strength of the multilayer ceramic capacitor was low. Samples 6 to 8 had a boundary between the Ni-segregation-free portion and the Ni-segregation portion located in a region more than 20 μm from the surface of the laminate toward the interior of the laminate, and the Ni-segregation-free portion was present in a region more than 20 μm thick from the surface of the laminate, resulting in low moisture resistance of the multilayer ceramic capacitor.

[0093] DESCRIPTION OF SYMBOLS 1 Multilayer ceramic capacitor 10 Laminate 11 First main surface of laminate 12 Second main surface of laminate 13 First side surface of laminate 14 Second side surface of laminate 15 First end surface of laminate 16 Second end surface of laminate 20 Dielectric ceramic layer 21 First internal electrode layer (internal electrode layer) 22 Second internal electrode layer (internal electrode layer) 30, 33 Internal layer portion 31, 32, 34, 35 External layer portion 41, 43 Ni-segregation-free portion 42, 44 Ni-segregation portion 51 First external electrode 52 Second external electrode T Stacking direction W Width direction L Length direction d Boundary between Ni-segregation-free portion and Ni-segregation portion

Claims

1. A multilayer ceramic capacitor comprising a laminate including dielectric ceramic layers and internal electrode layers laminated in a lamination direction, wherein the laminate has a substantially rectangular parallelepiped shape having first and second main surfaces opposing each other in the lamination direction, first and second side surfaces opposing each other in a width direction perpendicular to the lamination direction, and first and second end faces opposing each other in a length direction perpendicular to the lamination direction and the width direction, wherein in a WT cross section which is a cross section of the laminate along the width direction and the lamination direction, the laminate has a Ni-segregation-free portion which exists in a region of a predetermined thickness from at least one surface of the laminate toward the interior of the laminate, and a Ni-segregation portion which exists more in the laminate than the Ni-segregation-free portion and contains Ni segregated in the dielectric ceramic layers, and wherein the boundary between the Ni-segregation-free portion and the Ni-segregation portion is located in a region of 5 μm or more and 20 μm or less from the surface of the laminate toward the interior of the laminate.

2. The multilayer ceramic capacitor according to claim 1, wherein the Ni-segregation-free portion and the Ni-segregation portion are present in the WT cross section in a region of a predetermined thickness extending from at least one of the first and second main surfaces toward the interior of the laminate.

3. The multilayer ceramic capacitor according to claim 1 or 2, wherein the Ni-segregation-free portion and the Ni-segregation portion are present in the WT cross section in a region of a predetermined thickness extending from the surface of at least one of the first side surface and the second side surface toward the interior of the laminate.

4. The multilayer ceramic capacitor according to claim 1, wherein in the WT cross section, the Ni-segregation-free portion and the Ni-segregation portion are present in regions of a predetermined thickness extending from each of the first main surface, the second main surface, the first side surface, and the second side surface toward the interior of the laminate.

5. The multilayer ceramic capacitor according to any one of claims 1 to 4, wherein the internal electrode layers contain Ni.

6. The dielectric ceramic layer is BaTiO ３ The multilayer ceramic capacitor according to any one of claims 1 to 5, comprising:

7. The multilayer ceramic capacitor according to any one of claims 1 to 6, wherein the length of the laminate is 0.6 mm or more and 3.2 mm or less, the width of the laminate is 0.3 mm or more and 2.5 mm or less, and the length of the laminate in the lamination direction is 0.3 mm or more and 2.5 mm or less.

8. A multilayer ceramic capacitor according to any one of claims 1 to 7, wherein in the WT cross section, the Ni-segregation-free portion and the Ni-segregation portion are present in a region of a predetermined thickness from the surface of the laminate toward the interior of the laminate, and the distance from the surface to the internal electrode layer is 80 μm or more and 250 μm or less.

Images