Multilayer ceramic capacitor

Abstract

To provide a multilayer ceramic capacitor in which an area where internal electrodes are overlapped with each other in a lamination direction is increased by forming an end surface of a ceramic body in an outwardly protruding shape, and a portion where a thickness is locally thin in an external electrode formed on the ceramic body is eliminated to improve a covering property by the external electrode.SOLUTION: In the laminated ceramic capacitor, a plurality of internal electrodes are laminated through a dielectric layer, and the ceramic body 1 has a substantially hexahedral shape having an upper surface and a lower surface opposed to each other in a lamination direction, a pair of end surfaces opposed to each other in the lamination direction and to which a plurality of internal electrodes are led out, and a pair of side surfaces orthogonally opposed to each of the upper surface, the lower surface and the end surfaces, and the end surface of the ceramic body is formed in a shape having a curved surface.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a multilayer ceramic capacitor, and more particularly to the shape of an end face of a ceramic body included in a multilayer ceramic capacitor. [Background technology]

[0002] A conventional multilayer ceramic capacitor comprises a ceramic body in which multiple internal electrodes are laminated via dielectric layers whose main component is ceramic, and a pair of external electrodes with opposite polarities formed at both ends of the ceramic body in the longitudinal direction, with portions of the external electrodes extending around the top and bottom surfaces and both side surfaces of the ceramic body.

[0003] 2. Description of the Related Art In recent years, as digital electronic devices such as mobile phones have become smaller and thinner, the size of multilayer ceramic capacitors mounted on electronic circuit boards and the like has also been reduced. Generally, when the size of a multilayer ceramic capacitor is reduced, the area where the internal electrodes overlap in the lamination direction becomes smaller, resulting in a decrease in capacitance. Therefore, in order to maintain capacitance while miniaturizing multilayer ceramic electronic components, efforts are being made to reduce the thickness of the dielectric layers and internal electrodes, as well as to narrow the width of marginal portions. However, there is a limit to how thin the dielectric layers and internal electrodes can be and how narrow the margins can be.

[0004] On the other hand, by reducing the thickness of the external electrodes, it becomes possible to increase the number of layers and increase the margin required for insulation, etc. Therefore, thinning the external electrodes makes it possible to design an internal structure that achieves even higher capacity and improved reliability despite the limited size of electronic components.

[0005] Furthermore, when the end faces of the ceramic body are shaped to protrude outward, as in the ceramic capacitors described in Patent Documents 1 and 2, the area where the internal electrodes overlap in the stacking direction can be made larger by the amount of protrusion, leading to an increase in capacitance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-164451 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-51425 Summary of the Invention [Problem to be solved by the invention]

[0007] In the multilayer ceramic capacitor, the external electrodes are typically formed by immersing the end faces of the ceramic body in a bath of conductive paste, then lifting the ceramic body to allow the conductive paste to adhere, and then drying and baking the resulting material. In conventional multilayer ceramic capacitors, the pair of opposing end faces of the ceramic body are flat, which makes it easy for bubbles to form when the end faces of the ceramic body come into contact with the surface of the conductive paste.These bubbles, influenced by the viscosity of the conductive paste, tend to remain on the end faces of the ceramic body and cause pinholes in the external electrodes.

[0008] In contrast, in the ceramic capacitor described in Patent Document 1, the cross-sectional shape of a pair of opposing end faces of the ceramic body is made arc-shaped, which makes it possible to prevent air from being entrained when the end faces of the ceramic body come into contact with the surface of the conductive paste, thereby suppressing the occurrence of pinholes and improving the quality of the external electrodes. Furthermore, in the multilayer ceramic capacitor described in Patent Document 2, by forming a pair of opposing end faces of the ceramic body into a pyramidal shape, it is said that the quality of the external electrodes is improved by reducing pinholes for the same reason as in the multilayer ceramic capacitor described in Patent Document 1.

[0009] In addition to electrically connecting the internal electrodes to each other, the external electrodes also serve to prevent the infiltration of plating solution, moisture, etc. from the outside, and therefore must reliably cover the ceramic body. For this reason, it is preferable for the external electrodes to have as few locally thin areas as possible. In particular, if the external electrodes are made thin in order to ensure the size of the ceramic body for miniaturization and increased capacity, the locally thin portions of the external electrodes will lose their density, reducing their coverage and leading to reduced long-term reliability due to the infiltration of plating solution and moisture.

[0010] As described above, when external electrodes are formed by immersing the end faces of a ceramic body in a bath of conductive paste and then pulling the ceramic body out (hereinafter referred to as the "dip method"), droplets of conductive paste wrap around and adhere to the end faces, upper and lower faces, and portions of both side faces of the ceramic body. As a result, the shape of the external electrodes formed on the end faces, upper and lower faces, and portions of both side faces of the ceramic body is approximately elliptical in a cross section of the ceramic body cut along a plane parallel to a pair of side faces (hereinafter referred to as a "vertical plane") and in a cross section of the ceramic body cut along a plane parallel to the upper and lower faces (hereinafter referred to as a "horizontal plane").

[0011] FIG. 1 is a perspective view of the appearance of a ceramic body having a pair of opposing end faces with an arc-shaped cross section, and a cross-sectional view schematically showing the shape of external electrodes formed on the ceramic body by a dipping method. The upper part shows a cross section of the ceramic body cut along a vertical plane, and the lower part shows a cross section of the ceramic body cut along a horizontal plane. As shown in these figures, a multilayer ceramic capacitor having a ceramic element body with an end face cross-sectional shape that is arc-shaped has a problem in that the thickness of the external electrodes at the corners (R portions) of the ceramic element body is significantly thinner in the cross section on the horizontal plane than in the cross section on the vertical plane.

[0012] 2 is a perspective view of the appearance of a ceramic body having a pair of opposing end faces formed in a pyramidal shape, and a cross-sectional view schematically showing the shape of external electrodes formed on the ceramic body by a dipping method. The cross section shown is a cross section of the ceramic body cut horizontally at a position two-thirds of the way up from the bottom. 2, in a multilayer ceramic capacitor having a ceramic element body with a pair of opposing end faces formed in a pyramidal shape, the end faces of the ceramic element body are pyramidal, eliminating the difference between the horizontal and vertical cross sections at the corners (R portions) of a multilayer ceramic capacitor having a ceramic element body with the end faces having an arc-shaped cross section. However, there is a problem in that the thickness of the external electrodes becomes thin at the corners of the pyramidal portions.

[0013] The present invention has been made in consideration of the above-mentioned problems in the conventional technology, and aims to provide a multilayer ceramic capacitor in which the area where internal electrodes overlap in the stacking direction is increased by making both end faces of the ceramic body protrude outward, and in which the external electrodes formed on the ceramic body do not have locally thin portions, thereby improving the covering ability of the external electrodes. [Means for solving the problem]

[0014] As a result of research into solving the above-mentioned problems, the inventors discovered that by making the end faces of the ceramic body protrude in a convex shape consisting of a curved surface, it is possible to make the thickness of the external electrodes at the central part of the end faces of the ceramic body thinner than when the end faces of the ceramic body have a conventional flat shape, while maintaining the thickness of the external electrodes at the corners of the ceramic body the same as when the end faces of the ceramic body have a conventional flat shape, and thus completed the present invention.

[0015] That is, one aspect of the present invention for solving the above problem is: a ceramic element body having a substantially hexahedral shape, in which a plurality of internal electrodes are stacked via dielectric layers, the ceramic element body having an upper surface and a lower surface opposed to each other in a stacking direction, a pair of end surfaces opposed to each other in parallel with the stacking direction and from which the plurality of internal electrodes are drawn out, and a pair of side surfaces opposed to each other and perpendicular to the upper surface, the lower surface and the end surfaces, respectively; a pair of external electrodes provided on the pair of end faces, respectively, and extending around parts of the upper and lower faces and both side faces; Equipped with The end faces of the ceramic body have a convex shape formed by a curved surface, and the ceramic body is a multilayer ceramic capacitor. [Effects of the Invention]

[0016] According to the present invention, by forming the end faces of the ceramic body into a convex shape consisting of curved surfaces, it is possible to make the ceramic body relatively larger while maintaining the size of the multilayer ceramic capacitor, and to increase the area where the internal electrodes overlap in the stacking direction, thereby achieving a higher capacitance. Furthermore, it is possible to eliminate locally thin portions of the external electrodes, improving the covering ability of the external electrodes and ensuring long-term reliability. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view of a ceramic body having a pair of opposing end faces each having an arc-shaped cross section, and a cross-sectional view schematically showing the shape of an external electrode formed on the ceramic body by a dipping method. [Figure 2] FIG. 1 is a perspective view of the appearance of a ceramic body having a pair of opposing end faces formed in a pyramidal shape, and a cross-sectional view schematically showing the shape of external electrodes formed on the ceramic body by a dipping method. [Figure 3] FIG. 1 is an external perspective view showing an example of a ceramic body having a convex shape made up of curved surfaces in a multilayer ceramic capacitor according to an embodiment of the present invention. [Figure 4]4 is a cross-sectional view of one end face taken along a horizontal plane at a position two-thirds of the height from the bottom, schematically illustrating a multilayer ceramic capacitor (upper row) according to this embodiment that includes the ceramic element body shown in FIG. 3, and a conventional multilayer ceramic capacitor (lower row) that includes a ceramic element body whose end faces have a flat shape. [Figure 5(A)] FIG. 1 is a vertical cross-sectional view of one end surface of a multilayer ceramic capacitor, showing that the apex of a convex protrusion in the ceramic body is located at the center in the height direction of the ceramic body. [Figure 5(B)] FIG. 1 is a horizontal cross-sectional view of one end surface of a multilayer ceramic capacitor, showing that the apex of a convex protrusion on the ceramic body is located at the center in the width direction of the ceramic body. [Figure 5(C)] 5(A) or 5(B) is a vertical cross-sectional view of one end surface of the multilayer ceramic capacitor, showing the horizontal position of the apex of the protrusion. [Figure 6(A)] FIG. 1 is a vertical cross-sectional view of one end face schematically showing an example of a multilayer ceramic capacitor in which the apex of a convex protrusion in the ceramic body is not positioned at the center in the height direction of the ceramic body. [Figure 6(B)] FIG. 10 is a horizontal cross-sectional view of one end face schematically showing an example of a multilayer ceramic capacitor in which the apex of a convex protrusion in the ceramic body is not positioned at the center in the width direction of the ceramic body. [Figure 6(C)] 6(A) or 6(B) is a vertical cross-sectional view of one end surface of the multilayer ceramic capacitor, showing the horizontal position of the apex of the protrusion. [Figure 7] 5(A) is a partial cross-sectional view showing a state in which the multilayer ceramic capacitor shown in FIG. 5(A) is correctly mounted on a mounting board. [Figure 8] FIG. 5(B) is a partial cross-sectional view showing a state in which the multilayer ceramic capacitor shown in FIG. 5(A) is not properly mounted on a mounting board. [Figure 9] FIG. 6(B) is a partial cross-sectional view showing a state in which the multilayer ceramic capacitor shown in FIG. 6(A) is mounted on a mounting substrate. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described with reference to the drawings. However, the present invention is not limited to this embodiment, and various other embodiments are included as long as they are within the scope of the technical idea described in the claims. When a numerical range is expressed using "to," it means that the numerical values ​​stated as the lower and upper limits are included.

[0019] The multilayer ceramic capacitor of this embodiment has: a ceramic element body having a substantially hexahedral shape, in which a plurality of internal electrodes are stacked via dielectric layers, the ceramic element body having an upper surface and a lower surface opposed to each other in a stacking direction, a pair of end surfaces opposed to each other in parallel with the stacking direction and from which the plurality of internal electrodes are drawn out, and a pair of side surfaces opposed to each other and perpendicular to the upper surface, the lower surface and the end surfaces, respectively; a pair of external electrodes provided on the pair of end faces, respectively, and extending around parts of the upper and lower faces and both side faces; Equipped with The end face of the ceramic body has a convex shape composed of a curved surface. Here, the term "convex shape consisting of a curved surface" means that the convex shape is smooth without any corners. Furthermore, in this specification, the term "approximately hexahedral shape" is not limited to a mathematically defined hexahedron, but refers to any shape consisting of six distinct faces, including, for example, shapes with rounded edges and corners, and shapes with curved edges.

[0020] The product dimensions of the multilayer ceramic capacitor of this embodiment are not limited, but examples of capacitors with the same height and width include a length of 0.6±0.05 mm, and width and height of 0.3±0.05 mm, a length of 0.4±0.02 mm, and width and height of 0.2±0.02 mm, and a length of 0.25±0.013 mm, and width and height of 0.125±0.013 mm. Furthermore, examples of products whose height is greater than their width (tall products) include products whose length is 1.0±0.05 mm, whose width is 0.5±0.05 mm, and whose height is 0.8±0.05 mm. Furthermore, examples of products whose height is smaller than their width (low-profile products) include products whose length is 1.0±0.05 mm, whose width is 0.5±0.05 mm, and whose height is 0.13±0.02 mm.

[0021] [Ceramic element end face shape] FIG. 3 is an external perspective view showing an example of a ceramic body 1 in the multilayer ceramic capacitor of this embodiment, in which the end faces have a convex shape made up of curved surfaces. In the figure, a indicates a position two-thirds of the height from the bottom. FIG. 4 is a cross-sectional view of one end face taken along a horizontal plane at a position two-thirds of the height from the bottom, schematically showing a multilayer ceramic capacitor (upper row) according to this embodiment that includes the ceramic body 1, and a multilayer ceramic capacitor (lower row) that includes a conventional ceramic body whose end faces have a planar shape.

[0022] In the multilayer ceramic capacitor of this embodiment, the end faces of the ceramic body are formed into a convex shape composed of curved surfaces. As a result, as shown in FIG. 4, the external electrodes formed on the ceramic body do not have locally thin portions, as in the multilayer ceramic capacitors described in the above-mentioned Patent Documents 1 and 2. Furthermore, in the multilayer ceramic capacitor of this embodiment, by making the end faces of the ceramic body convex and curved, the thickness of the external electrodes at the corners of the ceramic body can be kept the same as in conventional cases where the end faces have a flat shape, while the thickness of the external electrodes at the central parts of the end faces of the ceramic body can be made thinner than in conventional cases where the end faces have a flat shape.

[0023] Furthermore, the shape of the external electrode, which is achieved by making the end faces of the ceramic body convex and curved, i.e., a shape in which there are no locally thin portions, the corners of the ceramic body are kept sufficiently thick, and the thickness is thin in the central portion of the end faces of the ceramic body, is obtained not only in the cross section shown in Figure 4 above, but also in the entire external electrode.

[0024] Furthermore, in the multilayer ceramic capacitor of this embodiment, the end faces of the ceramic body have a convex shape composed of curved surfaces, which makes it possible to suppress the entrapment of air when forming the external electrodes by the dipping method, and thus makes it possible to suppress the occurrence of pinholes in the external electrodes. Furthermore, in the multilayer ceramic capacitor of this embodiment, by making the end faces of the ceramic body convex and curved, the area of ​​the end faces is larger than when the end faces are flat, thereby improving the adhesion strength between the ceramic body and the external electrodes and enabling improved mounting reliability.

[0025] The apex of the convex protrusion formed by the curved surface of the end face of the ceramic body in the multilayer ceramic capacitor of this embodiment will be described in detail below using a cross-sectional view (hereinafter referred to as a "vertical cross-sectional view") that schematically shows only one end face of the multilayer ceramic capacitor of this embodiment, cut along a plane that passes through the apex of the protrusion and is parallel to a pair of side faces, and a cross-sectional view (hereinafter referred to as a "horizontal cross-sectional view") that schematically shows only one end face of the multilayer ceramic capacitor of this embodiment, cut along a plane that passes through the apex of the protrusion and is parallel to the top and bottom faces.

[0026] In the example of the ceramic body 1 in the multilayer ceramic capacitor of this embodiment shown in FIG. 3, the apex of the convex protrusion formed by the curved surface of the end face of the ceramic body is located at the center in both the height direction and the width direction of the ceramic body, but the position of the apex of the protrusion is not limited to this example. That is, in the ceramic capacitor of this embodiment, the apex of the convex protrusion consisting of the curved surface of the end face of the ceramic body 1 does not have to be located in the center of both the height and width of the ceramic body 1; for example, it may be shifted from the center of the height of the ceramic body 1 or the center of the width of the ceramic body 1.

[0027] 5(A) and 5(B) are diagrams of one end face of a multilayer ceramic capacitor according to this embodiment, in which the apex P of the convex protrusion in the ceramic body 1 is located at the center of both the height and width directions of the ceramic body, with FIG. 5(A) being a vertical cross-sectional view through which the apex P of the protrusion passes, and FIG. 5(B) being a horizontal cross-sectional view through which the apex P of the protrusion passes. In addition, internal electrodes are omitted from all figures, and in the figures, 1 represents the ceramic body and 2 represents the external electrodes.

[0028] As shown in Figure 5(A), the protrusion apex P is on a line segment L1 equidistant from the upper and lower surfaces in a vertical cross section through which the protrusion apex P passes, and at the same time, as shown in Figure 5(B), the protrusion apex P is on a line segment L2 equidistant from each side surface in a horizontal cross section through which the protrusion apex P passes.

[0029] FIG. 5C is a vertical cross-sectional view showing the position of the apex P of the protrusion shown in FIG. 5A or 5B, through which the apex P of the protrusion passes. As shown in the figure, in a vertical cross section through which the apex P of the protrusion passes, the distance L from the line segment connecting the intersection (P1) of the top surface and the end surface of the ceramic body 1 and the intersection (P2) of the bottom surface and the end surface of the ceramic body 1 to the apex P of the protrusion of the convex shape is p (hereinafter, also referred to as "length of the protrusion") is preferably 5 μm or more. Said L p By setting the thickness to 5 μm or more, it is possible to eliminate locally thin portions of the external electrodes, and the effect of reducing the thickness of the external electrodes in the central portion of the end face of the ceramic body while maintaining the thickness of the external electrodes in the corners of the ceramic body is remarkable.

[0030] Figures 6(A) and 6(B) are diagrams that schematically show that in the multilayer ceramic capacitor of this embodiment, the apex P of the convex protrusion in the ceramic body 1 may be offset from the center of the ceramic body 1 in the height direction or the center of the ceramic body 1 in the width direction, and in both figures, the internal electrodes are omitted.

[0031] Figure 6(A) is a vertical cross-sectional view showing an example in which the protrusion apex P is offset from the center in the height direction of the ceramic body 1. In this example, in the vertical cross-section through which the protrusion apex P passes, the protrusion apex P is not on the line segment L1 but is offset toward the lower surface. When the apex P of the protrusion is not on the line segment L1, and the distance between the upper and lower surfaces of the ceramic body 1 is T, the position of the apex of the protrusion is determined by the distance t between the apex P and the closest of the upper and lower surfaces. p However, 0.35T≦t p It is preferable that the T is <0.50T. distance t p If is in this range, the same effect can be obtained as when the apex P of the curved convex projection of the external electrode formed on the ceramic body is on the line segment L1.

[0032] Moreover, Figure 6(B) is a horizontal cross-sectional view showing an example in which the protrusion apex P is offset from the center in the width direction of the ceramic body 1. In this example, in the horizontal cross-section through which the protrusion apex P passes, the protrusion apex P is not on the line segment L2 but is offset to one side. When the apex P of the convex projection is not on the line segment L2, and the distance between both side surfaces of the ceramic body 1 is W, the position of the apex P of the convex projection is determined by the distance w between the apex P and the nearest one of the side surfaces. p However, 0.35W≦w p It is preferable to meet <0.50W. Distance w pIf is in this range, the same effect can be obtained as when the apex P of the curved convex protrusion of the external electrode formed on the ceramic body is on the line segment L2.

[0033] FIG. 6C is a vertical cross-sectional view showing the position of the apex P of the protrusion of the convex shape in FIG. 6A or 6B, and passing through the apex P of the protrusion. As shown in the figure, in FIG. 6(A) or FIG. 6(B), in the same manner as described in the previous paragraph

[0029] , in a vertical cross section through which the protrusion apex P passes, the distance L from the line segment connecting the intersection point (P1) of the protrusion apex P with the end face of the upper surface of the ceramic body 1 and the intersection point (P2) of the protrusion apex P with the end face of the lower surface of the ceramic body 1 is p However, it is preferable that the thickness is 5 μm or more.

[0034] Furthermore, as will be described below with reference to FIGS. 7 to 9, when the multilayer ceramic capacitor of this embodiment is soldered onto a mounting board, the distance t between the top P of the protrusion and the bottom surface of the ceramic body is p , 0.35T≦t p By setting it to <0.50T, the height of the solder wetting can be kept low and placed in the optimal position.

[0035] FIG. 7 is a partial view schematically illustrating a state in which a plating layer 3 is formed on the external electrode 2 of the multilayer ceramic capacitor in which the apex P of the protrusion is at the center in the height direction of the ceramic body, as shown in FIG. 5(A), and the multilayer ceramic capacitor is then mounted on a mounting substrate 6 via an electrode pad 5 using solder 4. Although FIG. 7 shows a state where the soldering is performed correctly, there are cases where the solder 4 wets up through the plating layer 3. FIG. 8 shows a state where the soldering has not been performed correctly and the solder 4 has wetted upward. If the solder 4 wets up too quickly, the rigidity increases and the deflection strength against stress decreases, which may cause problems in mounting the multilayer ceramic capacitor.

[0036] 7, FIG. 9 is a partial view schematically illustrating a state in which a plating layer 3 is formed on the external electrode 2 of the multilayer ceramic capacitor in which the protrusion apex P is located closer to the underside of the ceramic body as shown in FIG. 6(A), and then the multilayer ceramic capacitor is mounted on a mounting substrate 6. As shown in the figure, the height of the wetting and rising of the solder 4 can be kept low by displacing the apex P of the protrusion from the center in the height direction of the ceramic body toward the mounting surface side. However, if the wetting of the solder 4 is too low, the adhesive strength of the solder 4 will decrease, so the distance t p is preferably 0.35T or more.

[0037] [Internal electrode] In the multilayer ceramic capacitor according to this embodiment, the conductive material forming the internal electrodes is not particularly limited, and may be at least one metal material selected from the group consisting of nickel (Ni), copper (Cu), palladium (Pd), platinum (Pt), silver (Ag), and gold (Au). A base metal material such as Ni or Cu is preferably used as the main component in order to reduce manufacturing costs, and Ni is particularly preferred in terms of its ability to be co-fired with the dielectric layers. When Ni is used as the main component of the metal material, tin (Sn) or gold (Au) may be added.

[0038] [Dielectric layer] In the multilayer ceramic capacitor according to this embodiment, the dielectric layers are made of a dielectric ceramic obtained by firing ceramic raw material powder. Dielectric ceramics with a high dielectric constant are used to increase the capacitance of the dielectric layer. Examples of high dielectric constant dielectric ceramics include perovskite-structured materials containing barium (Ba) and titanium (Ti), such as barium titanate (BaTiO). The dielectric layer 12 may contain strontium titanate (SrTiO3), calcium titanate (CaTiO3), magnesium titanate (MgTiO3), calcium zirconate (CaZrO3), calcium titanate zirconate (Ca(Ti,Zr)O3), barium calcium titanate zirconate ((Ba,Ca)(Zr,Ti)O3), barium zirconate (BaZrO3), titanium oxide (TiO2), or the like. The dielectric layer may also contain a glass phase other than the dielectric ceramic.

[0039] [External electrode] In the multilayer ceramic capacitor of this embodiment, the external electrodes are provided on each of a pair of end faces of the ceramic body by a dipping method using a conductive paste, and portions of the external electrodes extend around the top face, the bottom face, and both side faces. The average thickness of the external electrodes in contact with the end faces of the ceramic body is preferably 8 μm to 30 μm, and more preferably 12 μm to 20 μm.

[0040] The external electrodes can be baked electrodes formed by using a conductive paste made by mixing a conductive material with a glass component, an organic binder, and an organic solvent, applying the paste to the ceramic body, drying it, and then baking it. The conductive material used in the conductive paste may be mainly composed of nickel (Ni), copper (Cu), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), etc., but from the viewpoint of cost, Ni or Cu metal is preferably used. Alternatively, the external electrodes may be formed by applying a conductive paste made by dispersing particles of the conductive material in a thermosetting resin such as an epoxy resin and an organic solvent to the ceramic body, drying the paste, and then subjecting the paste to a curing treatment. When a conductive resin electrode is used, it may be formed on the baked electrode after the baked electrode has been formed, rather than being formed directly on the ceramic body. Furthermore, by forming a plating layer on the surface of the external electrodes by plating with a metal such as Ni, Cu, or Sn, it is possible to improve the solder wettability.

[0041] [Ceramic capacitor manufacturing method] Generally, multilayer ceramic capacitors are (1) A process of printing an internal electrode pattern on the surface of a ceramic green sheet using a conductive paste for forming an internal electrode, and printing a dielectric pattern in the same thickness as the internal electrode pattern on the portions (end margin portion and side margin portion) where the internal electrode pattern is not printed using a dielectric paste. (2) A step of laminating a predetermined number of ceramic green sheets on which the internal electrode patterns are printed, and then laminating and pressing a ceramic green sheet having no internal electrode pattern on the uppermost surface and / or the lowermost surface in the lamination direction so as to cover the internal electrode pattern, to obtain a laminated sheet; (3) cutting the obtained laminated sheet into predetermined chip dimensions so that the internal electrode ends are alternately pulled out and exposed on both end surfaces of the laminate and side margins are formed on both side surfaces of the laminate to obtain unfired laminated chips; and (4) A step of firing the obtained green laminated chip and then forming external electrodes; It is manufactured through the following process.

[0042] In addition, in the method of post-installing the unfired side margin portion, in the step (1), only the end margin portion is provided and the internal electrode pattern is printed, and instead of the step (3), (3-1) A step of cutting the integrated laminate sheet to obtain an unfired laminate chip in which the ends of the internal electrode patterns are pulled out and exposed on both end surfaces and also on both side surfaces. (3-2) A step of attaching side margins to the sides of the obtained unfired laminated chip It is manufactured through the following process.

[0043] In this embodiment, the end faces of the ceramic body can be formed into a curved, convex shape by using any one of the following methods or a combination of these methods. (A) In the process of printing an internal electrode pattern and a dielectric pattern on a ceramic green sheet, a paste containing a dielectric that is resistant to shrinkage and a paste containing a dielectric that is apt to shrink are used for different parts. Specifically, by applying a paste containing a dielectric that is less likely to shrink to the end margin portion in the center of the stacking direction and applying a paste containing a dielectric that is more likely to shrink to all side margin portions, a convex shape consisting of a curved surface can be formed on the end face due to shrinkage during firing. Furthermore, by adjusting the application location, density, binder, sintering aid, etc. of the material that shrinks easily and / or the material that does not shrink easily, the position of the apex of the protruding part of the convex shape consisting of a curved surface can be changed as desired. (B) An unfired laminated chip is produced by forming the ceramic green sheet located in the center of the stacking direction from a material that is less likely to shrink, and then attaching the side margin portion made from a material that is more likely to shrink using a side margin attachment method. (C) In the process of printing internal electrode patterns and dielectric patterns on ceramic green sheets, a paste containing a dielectric that is resistant to shrinkage is applied to the end margins of the ceramic green sheets located in the center of the stacking direction, and an unfired laminated chip is produced using the ceramic green sheets. A side margin formed from a material that is resistant to shrinkage is attached using a side margin attachment method. [Example]

[0044] Example 1 The method (A) described above is to apply a material that is difficult to shrink to the end margin located in the center of the lamination direction, and a material that is easy to shrink to all side margins. pA ceramic body having a dielectric layer (main component BaTiO3) thickness after firing of less than 1.0 μm, internal electrode (main component Ni) thickness after firing of less than 1 μm, number of layers: 342) with a thermal conductivity of 0.50T was obtained. Baked electrodes (external electrodes) were formed on both end faces, portions of the top and bottom faces, and portions of both side faces (hereinafter referred to as "wraparound portions") of the obtained ceramic body by a dipping method using a conductive paste mainly composed of copper (Cu), and then a plating layer was formed on top of them to obtain a multilayer ceramic capacitor (Example 1). As a comparative example, a multilayer ceramic capacitor (conventional example) was obtained in the same manner as in Example 1, except that a ceramic element having flat end faces formed by a conventional method was used.

[0045] One side of the obtained multilayer ceramic capacitor was polished to half the distance between the side faces, and the polished surface was observed to determine the height position (tp) of the apex of the protrusion on the end face of the ceramic body, the length of the protrusion (L p ), the end faces of the external electrodes (baked electrodes), the maximum thickness of the R portion and the wraparound portion, the maximum dimensions of L, W, and T of the ceramic body, and the maximum dimensions of the length, width, and length of the product were confirmed. The results obtained are shown in Table 1 below.

[0046] [Table 1]

[0047] As shown in Table 1, the end face of the ceramic body obtained in Example 1 had a convex shape consisting of a curved surface with the horizontal position of the apex of the protrusion being 8.1 μm, and the radius of curvature was approximately 1620 μm. Furthermore, it was confirmed that the thickness of the external electrodes in the multilayer ceramic capacitor obtained in Example 1 was at the same level as that of the conventional example in the R portion and wraparound portion, but was reduced by approximately 5 μm at the end faces compared to the conventional example.

[0048] (Examples 2 and 3) By adjusting the position where the material that is difficult to shrink is applied to the end margin portion in Example 1 in the stacking direction, the position (t p ) was 0.46T, and a ceramic body was 0.35T. Using each of the obtained ceramic bodies, multilayer ceramic capacitors (Examples 2 and 3) were obtained in the same manner as in Example 1. The obtained multilayer ceramic capacitor was subjected to the same measurements as in Example 1, and the results are shown in Table 1 above. From Table 1, it can be seen that in Examples 2 and 3, in which the positions of the apex P of the protrusion are 0.46T and 0.35T, respectively, the same effect as in Example 1, in which the position of the apex P of the protrusion is 0.50T, is obtained. [Explanation of symbols]

[0049] 1: Ceramic body 2: External electrode 3: Plating layer 4: Solder 5: Electrode pads 6: Mounting board P: Apex of the protruding part of the convex shape

Claims

1. a ceramic element body having a substantially hexahedral shape, in which a plurality of internal electrodes are stacked via dielectric layers, the ceramic element body having an upper surface and a lower surface opposed to each other in a stacking direction, a pair of end surfaces opposed to each other in parallel with the stacking direction and from which the plurality of internal electrodes are drawn out, and a pair of side surfaces opposed to each other and perpendicular to the upper surface, the lower surface and the end surfaces, respectively; a pair of external electrodes provided on the pair of end faces, respectively, and extending around parts of the upper and lower faces and both side faces; Equipped with The multilayer ceramic capacitor has end faces of the ceramic body each having a convex shape formed by a curved surface.

2. 2. The multilayer ceramic capacitor according to claim 1, wherein in a vertical cross section of the ceramic body taken along a plane parallel to the side surface and passing through the apex of the convex-shaped protrusion, the distance of the apex of the convex-shaped protrusion from a line segment connecting an intersection of the upper surface and the end surface and an intersection of the lower surface and the end surface is 5 μm or more.

3. The end surface has a vertex of the convex projection, (a) the vertex is not on a line segment equidistant from the upper surface and the lower surface in a cross section cut by a plane that passes through the vertex and is parallel to each of the side surfaces; and (b) the vertex is not on a line segment equidistant from each of the side surfaces in a cross section cut by a plane passing through the vertex and parallel to the upper and lower surfaces; The multilayer ceramic capacitor according to claim 1 , wherein at least one of the above is satisfied.

4. When the distance between the upper and lower surfaces of the ceramic body is T and the distance between the side surfaces is W, When the position of the apex of the protrusion of the convex shape satisfies the condition (a), a distance tp between the apex and the nearest one of the upper surface and the lower surface satisfies 0.35T≦tp<0.5T, When the position of the apex of the protrusion of the convex shape satisfies (b) above, the distance wp between the apex and the nearest one of the side surfaces satisfies 0.35W≦wp<0.5W. The multilayer ceramic capacitor according to claim 3 .

5. 5. The multilayer ceramic capacitor according to claim 1, wherein the product dimensions are 0.6±0.05 mm in length, 0.3±0.05 mm in width, and 0.3±0.05 mm in height.

6. 5. The multilayer ceramic capacitor according to claim 1, wherein the product dimensions are 0.4±0.02 mm in length, 0.2±0.02 mm in width, and 0.2±0.02 mm in height.

7. 5. The multilayer ceramic capacitor according to claim 1, wherein the product dimensions are 0.25±0.013 mm in length, 0.125±0.013 mm in width, and 0.125±0.013 mm in height.

8. 5. The multilayer ceramic capacitor according to claim 1, wherein the height of the product is greater than the width.

9. 5. The multilayer ceramic capacitor according to claim 1, wherein the height of the product is smaller than the width.

10. 5. The multilayer ceramic capacitor according to claim 1, wherein the average thickness of the external electrodes in contact with the end faces of the ceramic body is 8 to 30 μm.

11. 5. The multilayer ceramic capacitor according to claim 1, wherein the external electrodes are baked electrodes or baked electrodes having conductive resin electrodes thereon.

12. 5. The multilayer ceramic capacitor according to claim 1, wherein the external electrodes are conductive resin electrodes.

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