Multilayer ceramic electronic component and manufacturing method for the same

Abstract

To improve the dielectric constant of a dielectric layer in multilayer ceramic electronic components while enhancing the temperature characteristics and reliability of the multilayer ceramic electronic components.SOLUTION: The multilayer ceramic electronic component includes a body formed by alternately stacking internal electrode layers and dielectric layers. The dielectric layer includes particles having a rectangular shape in a cross-section taken along the stacking direction between the internal electrode layer and the dielectric layer of the body. The particles have a rectangular prism shape or a cubic shape. The particles also have a hexahedral shape with six faces, including opposing first and second faces. The first face and the second face each face the internal electrode layer and are parallel to the internal electrode layer.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a multilayer ceramic electronic component and a method for manufacturing the same. [Background technology]

[0002] BACKGROUND ART Various proposals have been made to improve the dielectric constant of materials forming dielectric layers of multilayer ceramic electronic components such as multilayer ceramic capacitors (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-011221 Summary of the Invention [Problem to be solved by the invention]

[0004] As multilayer ceramic electronic components continue to become smaller and have larger capacitances, materials that form dielectric layers are required to have higher dielectric constants, and there is also a demand for improved temperature characteristics and reliability in multilayer ceramic electronic components.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to improve the dielectric constant of the dielectric layers in a multilayer ceramic electronic component, as well as the temperature characteristics and reliability of the multilayer ceramic electronic component. [Means for solving the problem]

[0006] To achieve the above object, the multilayer ceramic electronic component includes an element body formed by alternately stacking internal electrode layers and dielectric layers, and the dielectric layers include multiple layers of rectangular particles in a cross section along the stacking direction of the internal electrode layers and the dielectric layers of the element body.

[0007] In the multilayer ceramic electronic component having the above configuration, the particles may have a rectangular parallelepiped or cubic shape.

[0008] In the multilayer ceramic electronic component having the above configuration, the particles may have a hexahedral shape having six faces including a first face and a second face that are opposed to each other.

[0009] In the multilayer ceramic electronic component having the above configuration, the particles may have first and second surfaces that face each other, and the first and second surfaces may face the internal electrode layers, respectively.

[0010] Furthermore, in the multilayer ceramic electronic component having the above configuration, the particles may have first and second surfaces that face each other, and the first and second surfaces may be parallel to the internal electrode layers.

[0011] In addition, to achieve the above object, a method for manufacturing a multilayer ceramic electronic component includes the steps of: preparing a raw material powder containing particles having a hexahedral shape with six faces including a first face and a second face opposite to each other; forming a laminate that serves as a capacitance forming portion by alternately stacking first internal electrode layers and second internal electrode layers with a dielectric layer containing the raw material powder sandwiched therebetween; and firing the laminate.

[0012] In the method for manufacturing a multilayer ceramic electronic component having the above-described configuration, the step of preparing the raw material powder can include a step of applying a dielectric material to a smooth surface of a support member and preparing a plate-like body containing the dielectric material on the support member, and a step of removing the plate-like body from the support member and crushing the plate-like body to prepare the particles.

[0013] In the method for producing a monolithic ceramic electronic component having the above configuration, the step of preparing the raw material powder may include a step of sorting the fragments obtained by crushing the plate-like body by shape to extract the particles.

[0014] In the method for producing a monolithic ceramic electronic component having the above configuration, the step of producing the raw material powder may include a step of producing the particles by hydrothermal synthesis using at least titanium oxide for 20 hours or more.

[0015] In the method for producing a multilayer ceramic electronic component having the above configuration, the hydrothermal synthesis may be carried out for 24 hours or more.

[0016] In the method for manufacturing a multilayer ceramic electronic component having the above configuration, the step of preparing the raw material powder may include a step of preparing the particles by hydrothermal synthesis using at least titanium oxide and polyvinylpyrrolidone.

[0017] In the method for manufacturing a monolithic ceramic electronic component having the above configuration, the step of preparing the raw material powder may include a step of sorting the resultant obtained in the step of performing hydrothermal synthesis by shape to extract the particles.

[0018] In the method for manufacturing a multilayer ceramic electronic component having the above-described configuration, the step of forming the laminate can include a pressing step of supplying the raw material powder, which contains the particles and has been made into a slurry, onto a support member and pressing the slurried raw material powder against the support member, and a step of producing a ceramic sheet by performing the pressing step multiple times.

[0019] In the method for manufacturing a multilayer ceramic electronic component having the above-described configuration, the step of forming the laminate can include a step of supplying the raw material powder, which contains the particles and has been made into a slurry, onto a support member, and driving a roller on the slurried raw material powder to produce a ceramic sheet. [Effects of the Invention]

[0020] According to the present invention, it is possible to improve the dielectric constant of the dielectric layers in a multilayer ceramic electronic component, and also improve the temperature characteristics and reliability of the multilayer ceramic electronic component. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view of a multilayer ceramic capacitor according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor taken along line AA′ in FIG. [Figure 3] Fig. 3(A) is a cross-sectional view of the multilayer ceramic capacitor taken along line BB' in Fig. 1. Fig. 3(B) is a cross-sectional view of the multilayer ceramic capacitor taken along line CC' in Fig. 1. [Figure 4] Fig. 4(A) is a diagram schematically illustrating the state of particles forming a dielectric layer in one embodiment, and Fig. 4(B) is a diagram schematically illustrating the state of particles forming a dielectric layer in a comparative example. [Figure 5] 5(A) to 5(C) are diagrams illustrating rectangles (rectangular parallelepiped and cubic shapes). [Figure 6] FIG. 6 is a diagram illustrating that the core area of ​​a particle having a rectangular parallelepiped or cubic shape is larger than that of a particle having a spherical shape. [Figure 7] FIG. 7 is an explanatory diagram showing the difference in temperature characteristics caused by the difference in core area. [Figure 8] FIG. 8 is a flowchart showing an example of a method for manufacturing the multilayer ceramic capacitor according to an embodiment. [Figure 9] 9(A-1) to 9(A-4) are diagrams showing a schematic diagram of a manufacturing process for particles having a rectangular parallelepiped shape, and Fig. 9(B) is a perspective view of a particle having a rectangular parallelepiped shape. [Figure 10] 10(A) to 10(G) are diagrams showing the steps of manufacturing a ceramic sheet using particles having a rectangular parallelepiped shape. [Figure 11] Fig. 11(A) is a flow chart showing an example of a method for producing particles having a cubic shape, and Fig. 11(B) is a perspective view of particles having a cubic shape. [Figure 12] 12(A) and 12(B) are diagrams schematically showing the washing step and the drying step in the method for producing cubic particles. [Figure 13] FIG. 13 shows a modified example of the manufacturing process for a ceramic sheet using particles having a rectangular parallelepiped shape. DETAILED DESCRIPTION OF THE INVENTION

[0022] (First embodiment) A first embodiment of the present invention will be described below with reference to the drawings. In the drawings, X-axis, Y-axis, and Z-axis, which are mutually orthogonal, are shown as appropriate, and are common to all the drawings.

[0023] [Overall Configuration of Multilayer Ceramic Capacitor 10] 1 to 3(B) are diagrams showing an example of a multilayer ceramic capacitor 10 according to an embodiment of the present invention. Fig. 1 is a perspective view of the multilayer ceramic capacitor 10. Fig. 2 is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line AA' in Fig. 1. Fig. 3(A) is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line BB' in Fig. 1. Fig. 3(B) is a cross-sectional view of the multilayer ceramic capacitor 10 taken along line CC' in Fig. 1.

[0024] The multilayer ceramic capacitor 10 includes a ceramic body 11 having a substantially rectangular parallelepiped shape. Of the six faces of the ceramic body 11, the opposing main faces are referred to as the upper and lower faces, and the remaining four faces are referred to as side faces. Generally, the main faces have the largest area. The ceramic body 11 has a first external electrode 14a and a second external electrode 14b provided on its surface, spaced apart from each other. In the example shown in FIGS. 1 to 3(B), the first external electrode 14a and the second external electrode 14b are provided on two opposing side faces (the first side face and the second side face), respectively. The first external electrode 14a extends from the first side face to four adjacent faces. The second external electrode 14b extends from the second side face to four adjacent faces. However, the first external electrode 14a and the second external electrode 14b are spaced apart from each other.

[0025] As long as the first external electrode 14a and the second external electrode 14b are spaced apart, they can be provided at any position on the surface of the ceramic body 11. For example, the first external electrode 14a and the second external electrode 14b may be spaced apart on the same surface of the ceramic body 11, or the first external electrode 14a and the second external electrode 14b may be spaced apart on two adjacent surfaces or two opposing surfaces of the ceramic body 11.

[0026] As long as the first external electrode 14a and the second external electrode 14b are spaced apart from each other, they may extend from the surface of the ceramic body 11 on which they are provided to any other surface. For example, they may extend to an adjacent surface, or may extend further from the surface on which they are provided.

[0027] The multilayer ceramic component has a first direction, which is the stacking direction; a second direction, which is perpendicular to the stacking direction and where two opposing surfaces intersect; and a third direction, which is perpendicular to the stacking direction and also perpendicular to the second direction and where two opposing surfaces intersect. The first, second, and third directions are mutually orthogonal. The stacking direction can be set in any of the length, width, and height directions of the ceramic body 11.

[0028] 1 to 3(B), the stacking direction, i.e., the first direction, is the Z-axis direction, which is the height direction of the ceramic body 11 and the direction in which the internal electrode layers face each other. In FIGS. 1 to 3(B), the second direction perpendicular to the stacking direction is the X-axis direction, which is the length direction of the ceramic body 11, the direction in which the first side surface and the second side surface of the ceramic body 11 face each other, and the direction in which the first external electrode 14a and the second external electrode 14b face each other. In FIGS. 1 to 3(B), the third direction perpendicular to the stacking direction and perpendicular to the second direction is the Y-axis direction, which is the width direction of the internal electrode layers and the direction in which two of the four side surfaces of the ceramic body 11 other than the first and second side surfaces (the third and fourth side surfaces) face each other. The X-axis direction, the Y-axis direction, and the Z-axis direction are orthogonal to each other.

[0029] The ceramic body 11 has a configuration in which dielectric layers 15 containing a ceramic material that functions as a dielectric and internal electrode layers are alternately stacked. The internal electrode layers include a plurality of first internal electrode layers 12 and a plurality of second internal electrode layers 13. The first internal electrode layers 12 and the second internal electrode layers 13 are alternately stacked. Edges of the first internal electrode layers 12 are extended to the surface of the ceramic body 11 on which the first external electrode 14a is provided. Edges of the second internal electrode layers 13 are extended to the surface of the ceramic body 11 on which the second external electrode 14b is provided. Note that it is sufficient that the first internal electrode layers 12 and the second internal electrode layers 13 are exposed in different regions on the surface of the laminate and are electrically connected to different external electrodes. The different regions on the surface of the laminate may be respective surface regions on opposing surfaces of the laminate, respective surface regions on adjacent surfaces of the laminate, or different surface regions on the same surface of the laminate. As long as the different external electrodes are spaced apart from each other, the first internal electrode layer 12 and the second internal electrode layer 13 may extend from the surface exposed in the surface region of the laminate to the other surface.

[0030] In the example shown in FIGS. 1 to 3(B), the edges of the first internal electrode layers 12 extend to the first side surface of the ceramic body 11 on which the first external electrode 14a is provided. The edges of the second internal electrode layers 13 extend to the second side surface of the ceramic body 11 on which the second external electrode 14b is provided. This allows the first internal electrode layers 12 and the second internal electrode layers 13 to be alternately electrically connected to the first external electrode 14a and the second external electrode 14b. As a result, the multilayer ceramic capacitor 10 has a configuration in which capacitor units are stacked. In addition, in a laminate of dielectric layers 15 and internal electrode layers, the internal electrode layers are arranged as the outermost layers in the stacking direction, and the upper and lower surfaces of the laminate are covered with a cover 18. The cover 18 is mainly composed of a ceramic material.

[0031] The size of the multilayer ceramic capacitor 10 may be, for example, 0.25 mm in length, 0.125 mm in width, and 0.125 mm in height, or 0.4 mm in length, 0.2 mm in width, and 0.2 mm in height, or 0.6 mm in length, 0.3 mm in width, and 0.3 mm in height, or 1.0 mm in length, 0.5 mm in width, and 0.5 mm in height, or 3.2 mm in length, 1.6 mm in width, and 1.6 mm in height, or 4.5 mm in length, 3.2 mm in width, and 2.5 mm in height, but is not limited to these sizes. The size of the multilayer ceramic capacitor 10 may be, for example, length > width ≥ height, width > length ≥ height, height > length ≥ width, or height > width ≥ length.

[0032] In detail, the protective portion 17 has a cover portion 18 located outside the stacking direction of the capacitance forming portion 16, i.e., outside the Z-axis direction of the capacitance forming portion 16 in the examples of Figures 1 to 3; a side margin portion 19 located outside the stacking direction of the capacitance forming portion 16 perpendicular to the stacking direction as a region that does not include edge portions of the first internal electrode layer 12 and the second internal electrode layer 13 that are drawn to the surface of the ceramic body 11 in a direction perpendicular to the stacking direction, i.e., outside the Y-axis direction of the capacitance forming portion 16 in the examples of Figures 1 to 3; and an end margin portion 20 located outside the stacking direction of the capacitance forming portion 16 perpendicular to the stacking direction as a region that includes edge portions of the first internal electrode layer 12 and the second internal electrode layer 13 that are drawn to the surface of the ceramic body 11 in a direction perpendicular to the stacking direction, i.e., outside the X-axis direction of the capacitance forming portion 16 in the examples of Figures 1 to 3.

[0033] The side margins 19 are regions consisting only of the dielectric layers. The end margins 20 are regions including the dielectric layers and the edge portions of the first internal electrode layers 12 and the second internal electrode layers 13 that are drawn to the surface of the ceramic body 11.

[0034] The capacitance forming portion 16 is disposed inside the protective portion 17 and constitutes a functional portion. The capacitance forming portion 16 is formed by laminating a plurality of first internal electrode layers 12 and a plurality of second internal electrode layers 13 in the Z-axis direction via dielectric layers 15 (see FIG. 2). In the example of FIGS. 1 to 3(B), the internal electrode layers 12, 13 are both sheet-shaped extending along a plane perpendicular to the lamination direction and are alternately arranged in the lamination direction. In the example of FIGS. 1 to 3(B), they are sheet-shaped extending along the XY plane and are alternately arranged along the Z-axis direction. The configuration of the dielectric layers 15 will be described in detail later.

[0035] The first internal electrode layers 12 and the second internal electrode layers 13 are mainly composed of base metals such as nickel (Ni), copper (Cu), tin (Sn), etc., or alloys containing these. Noble metals such as platinum (Pt), palladium (Pd), silver (Ag), gold (Au), etc., or alloys containing these may also be used as the main component of the first internal electrode layers 12 and the second internal electrode layers 13. The main component of the first internal electrode layers 12 and the second internal electrode layers 13 may be the same or different.

[0036] The dielectric layer 15 has a main phase made of a ceramic material having a perovskite structure represented by the general formula ABO3. 3-α (0≦α≦1: α represents the amount that deviates from the stoichiometric composition; hereinafter, α will be omitted.) For example, the ceramic material in question is barium titanate (BaTiO3), calcium zirconate (CaZrO3), calcium titanate (CaTiO3), strontium titanate (SrTiO3), magnesium titanate (MgTiO3), BaTiO3, which forms a perovskite structure, 1-x-y Ca x Sr y Ti 1-z Zr z At least one of the following can be selected and used: O3 (0≦x≦1, 0≦y≦1, 0≦z≦1). 1-x-y Ca x Sr y Ti 1-z Zr zO3 includes barium strontium titanate, barium calcium titanate, barium zirconate, barium titanate zirconate, calcium titanate zirconate, and barium calcium titanate zirconate. For example, the dielectric layer 15 contains 50 at% or more of the main component ceramic, e.g., 90 at% or more. The thickness of the dielectric layer 15 is, for example, 5.0 μm or less, 3.0 μm or less, 1.0 μm or less, 0.5 μm or less, 0.4 μm or less, 0.3 μm or less, or 0.2 μm or less. The thickness of the dielectric layer 15 can be measured by observing the cross section of the multilayer ceramic capacitor 10 with a scanning electron microscope (SEM), measuring the thickness at 10 points on each of 10 different dielectric layers 15, and deriving the average value of all the measurement points.

[0037] An additive may be added to the dielectric layer 15. Examples of additives to the dielectric layer 15 include oxides of zirconium (Zr), magnesium (Mg), manganese (Mn), molybdenum (Mo), vanadium (V), chromium (Cr), rare earth elements (scandium (Sc), cerium (Ce), neodymium (Nd), yttrium (Y), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb)), oxides containing cobalt (Co), nickel (Ni), lithium (Li), boron (B), sodium (Na), potassium (K), or silicon (Si), or glasses containing cobalt, nickel, lithium, boron, sodium, potassium, or silicon.

[0038] The protective portion 17 is also made of a dielectric ceramic. In terms of suppressing internal stress, it is preferable that the end margin portion 20 of the protective portion 17 has the same main component composition as the dielectric layer 15. In this embodiment, the cover portion 18 also has the same main component composition as the dielectric layer 15. This improves manufacturing efficiency.

[0039] The external electrodes 14a, 14b each have a base film 21 formed to cover the lead portions of the internal electrode layers 12, 13 and part of the surface of the ceramic body 11, and a plating film 22 formed on the base film 21. The base film 21 is formed, for example, by firing a conductive paste or by sputtering. The plating film 22 is formed by electrolytic plating. Each film of the external electrodes 14a, 14b is formed of a metal or alloy containing, for example, nickel (Ni), copper (Cu), tin (Sn), palladium (Pd), platinum (Pt), silver (Ag), gold (Au), or aluminum (Al) as a main component. Alternatively, the external electrodes 14a, 14b can be formed by printing and drying a conductive paste containing a curable resin, such as Ag, and a conductive metal.

[0040] [Detailed configuration of dielectric layer 15] Fig. 3(B) is a cross-sectional view taken along line CC' of the multilayer ceramic capacitor in Fig. 1. Fig. 4(A) is a diagram schematically showing the state of particles forming the dielectric layer in the embodiment. Fig. 4(B) is a diagram schematically showing the state of particles forming the dielectric layer in the comparative example. Note that hatching of the external electrodes 14a and 14b in Fig. 3(B) is omitted.

[0041] FIG. 4(A) shows a dielectric layer 15 formed by molding ceramic material particles 151 into a sheet, laminating and pressing the sheet between the first internal electrode layer 12 and the second internal electrode layer 13, and then sintering the sheet. FIG. 4(A) shows a cross section along the lamination direction of the first internal electrode layer 12, the second internal electrode layer 13, and the dielectric layer 15. That is, FIG. 4(A) shows an enlarged view of one layer of the dielectric layer 15 in FIG. 2, and the first internal electrode layer 12 and the second internal electrode layer 13 sandwiching the dielectric layer 15. In this cross section, the particle 151 is generally rectangular. The particle 151 has a first surface 151a. The particle 151 also has a second surface 151b facing the first surface 151a. The first surface 151a and the second surface 151b face the first internal electrode layer 12 or the second internal electrode layer 13, respectively. The first surface 151a and the second surface 151b are provided so as to be parallel to the first internal electrode layer 12 or the second internal electrode layer 13. For convenience, one of the pair of opposing surfaces of the particle 151 is referred to as the first surface 151a and the other as the second surface 151b. Therefore, the first surface 151a and the second surface 151b are not fixed to either one side of the pair of surfaces.

[0042] Both the first surface 151a and the second surface 151b are generally smooth surfaces. The particles 151 are stacked in the Z direction. This makes it difficult for gaps to form between the first internal electrode layer 12 and the second internal electrode layer 13 in the dielectric layer 15. Furthermore, as shown in FIG. 4(B), rectangular particles 151 are more likely to produce large-diameter cores than particles 351 that are circular in cross section. Obtaining a large-diameter core is expected to improve the dielectric constant and temperature characteristics. These will be explained in detail later.

[0043] Here, a comparative example shown in FIG. 4(B) will be described. The particle 351 of the comparative example is circular in the cross section shown in FIG. 4(B). That is, the particle 351 has a cross section of, for example, a roughly circular or roughly elliptical shape, and these will be described using a circular cross section. With circular particles like the particle 351, components of the first internal electrode layer 12 and the second internal electrode layer 13 tend to infiltrate into the gaps formed between the particles 351. Furthermore, the components of the first internal electrode layer 12 and the second internal electrode layer 13 tend to infiltrate into the gaps formed between the particles 351, which tends to make the thickness of the dielectric layer 35 uneven. If the distance between the first internal electrode layer 12 and the second internal electrode layer 13 is the thickness of the dielectric layer 35, the thickness of the dielectric layer 35 can be thickness t[35a] or thickness t[35b]. The electric field strength is stronger in the portion with thickness t[35b] than in the portion with thickness t[35a]. The portion with strong electric field strength has a lower withstand voltage and is more susceptible to dielectric breakdown. Furthermore, migration and other problems are more likely to occur. Such protruding deterioration in parts shortens the life of the multilayer ceramic capacitor. It is believed that variations in the thickness of the dielectric layer 35 in this way are more likely to cause variations in the life of the multilayer ceramic capacitor.

[0044] In contrast, the thickness t

[15] of the dielectric layer 15 in this embodiment is generally consistent throughout the entire region in the X direction, as shown in Fig. 4(A). This makes the electric field strength in the dielectric layer 15 uniform, and is expected to improve the lifespan evaluated by, for example, a HALT (Highly Accelerated Limit Test) test.

[0045] Furthermore, by using the particles 151, the unevenness of the surfaces of the dielectric layers 15 that contact the first internal electrode layers 12 and the second internal electrode layers 13 is reduced, improving smoothness. This is expected to improve the continuity ratio of the first internal electrode layers 12 and the second internal electrode layers 13. By improving the continuity ratio of the first internal electrode layers 12 and the second internal electrode layers 13, it is also expected to improve the capacitance.

[0046] Although the particles 151 are rectangular when viewed in a cross section along the stacking direction, each particle 151 has a hexahedral shape with six faces, including a first face 151a and a second face 151b. Such a hexahedral shape may be a rectangular parallelepiped or a cubic shape. That is, the particles may be cube-shaped or plate-shaped. The hexahedral shape has three pairs of opposing faces. However, the opposing faces do not have to be strictly parallel. Furthermore, each face is not required to be completely smooth; each face may be concave or convex. Furthermore, a single face may have an uneven surface. Furthermore, the hexahedral shape has six vertices formed where the three faces and three sides meet. However, the angle formed by two sides at each vertex does not have to be strictly 90 degrees. Furthermore, each side is not required to be a perfectly straight line; it is sufficient that it can be recognized as a boundary between adjacent faces.

[0047] Here, with reference to Figs. 5(A) to 5(C), the rectangular shape of the particle 151 in this embodiment will be described in more detail. For example, a cross-sectional image as shown schematically in Fig. 5(A) is taken by a TEM (transmission electron microscope). Then, four line segments S1, S2, S3, and S4 forming one particle 151 are extracted. A plurality of measurement points p are set at arbitrary equal intervals on each of the line segments S1 to S4. It is preferable that one particle 151 is a proper rectangle, but in reality, it is sufficient that each line segment approximates the concave and convex shapes to form a rectangle. Then, an approximation line is obtained from the measurement points p for each line segment as shown in Fig. 5(B), and the coefficient of determination R of the approximation line is calculated. 2 The approximate line for the line segment S1 is expressed as y=ax+b, and its coefficient of determination is R s1 2 The approximate line for the line segment S2 is expressed as y=cx+d, and its coefficient of determination is R s2 2 The approximate line for the line segment S3 is expressed as y = ex + f, and its coefficient of determination is R s3 2The approximate line for the line segment S4 can be expressed as y = gx + h, and its coefficient of determination is R s4 2 And the coefficient of determination R s1 2 , R s2 2 , R s3 2 and R s4 2 If all of the line segments S1 to S4 are equal to or greater than a predetermined value, then all of the line segments S1 to S4 are considered to be straight lines. The predetermined value can be set arbitrarily, but can be, for example, 0.92, or 0.95 for a more straight line, or 0.98 for an even more straight line. The fact that all of the line segments S1 to S4 are straight lines is the first condition for the particle 151 to be rectangular.

[0048] Next, the conditions for the angle formed by line segment S1 and line segment S4 will be explained. As shown in FIG. 5(C), the angle formed by line segment S1 and line segment S2 is ∠A, the angle formed by line segment S2 and line segment S3 is ∠B, the angle formed by line segment S3 and line segment S4 is ∠C, and the angle formed by line segment S4 and line segment S1 is ∠D. The second condition for particle 151 to be rectangular is that ∠A = 90° ± α, ∠B = 90° ± α, ∠C = 90° ± α, and ∠D = 90° ± α. Here, α can be set arbitrarily, for example, to α = 10°. It is also preferably set to 5°. It is assumed that the corners in the cross section have a chamfered shape or a curved, rounded shape. In such a case, if the angle formed by extending the two line segments is within the range of 90°±α, it can be determined that the second condition above is met.

[0049] When the particle 151 satisfies the first and second conditions, it can be said that its cross section is rectangular.

[0050] A cubic particle 251 (see FIG. 17(B)) described later is also a type of hexahedron, and the same conditions as those for the rectangular particle 151 are applied to its rectangular cross section.

[0051] Next, referring to Figure 6, it will be explained that by using particles with a rectangular parallelepiped (cubic) cross section, it is easier to obtain a large-diameter core compared to spherical particles with a circular cross section. In the following explanation, particle 151 is drawn as a cube for ease of understanding.

[0052] FIG. 6 shows a region Ar of the same area set within the dielectric layer 15 (35), with cubic particles 151 with a rectangular cross section and spherical particles 351 with a circular cross section spread throughout the region Ar. Particles 151 and 351 are each arranged so that they are most densely packed within the region Ar. For ease of understanding, hypothetical values ​​are given to the dimensions of each part of particle 151 and particle 351. Units are omitted here, as only the ratio of the dimensions of particle 151 and particle 351 is required. If one side of particle 151 is 1.5, the radius of particle 351 is 0.775. Assume that the shell thickness of particle 151 and the shell thickness of particle 351 are both 0.25. In this case, the length of one side of the core of particle 151 is 1.0. The radius of the spherical core of particle 351 is 0.525. Therefore, the cross-sectional area of ​​the core of particle 151 is 1.0×1.0=1.0, whereas the cross-sectional area of ​​the core of particle 351 is 0.525×0.525×π=0.87.

[0053] In this way, when particles are densely packed in an area Ar of the same area, it can be seen that the cross-sectional area of ​​the core of the cubic particle 151 is larger than that of the spherical particle 351.

[0054] Next, referring to FIG. 7, the difference in temperature characteristics due to the difference in the area of the core part will be described. In FIG. 7, graphs showing temperature characteristics and graphs showing capacitance change rates are drawn for particles with a thin shell and a large core area, and particles with a thick shell and a small core area. The temperature characteristics indicate how the dielectric constant ε (or capacitance) changes when an AC voltage of a certain frequency is applied to the multilayer ceramic capacitor 10 and the temperature is changed. The particles shown in FIG. 7 are all particles having a core-shell structure with a core part of BaTiO3 and a shell containing BaTiO3 and additives arranged around it. Although the cross-sectional shape of the particles 151 in the present embodiment is rectangular, in FIG. 7, since it is for a general explanation of temperature characteristics, the shape of the particles is shown as hexagonal. That is, the following explanation of temperature characteristics is not limited to particles of a specific shape, but widely applies to particles having a core-shell structure.

[0055] In FIG. 7, temperatures t 1 to t 4 are shown, and their magnitude relationship is t 1 < t 2 < t 3 < t 4. Temperature t 2 is approximately room temperature. Temperature t 1 is the lower limit temperature at which the use of the multilayer ceramic capacitor 10 is assumed. Temperature t 3 is the temperature at which the dielectric constant ε becomes maximum in particles with a thick shell and a small core area. Temperature t 4 is the temperature (Curie point) at which the dielectric constant ε becomes maximum in particles with a thin shell and a large core area.

[0056] The graph showing the capacitance change rate is expressed as a ratio to this reference capacitance with the capacitance at temperature t 2 as the reference capacitance. The numerical value a% in the graph showing the capacitance change rate indicates the upper limit value that needs to be compensated in the temperature environment assumed for the use of the multilayer ceramic capacitor 10. The numerical value b% in the graph showing the capacitance change rate indicates the lower limit value that needs to be compensated in the temperature environment assumed for the use of the multilayer ceramic capacitor 10.

[0057] In particles with a thin shell and a large core area, a peak originating from BaTiO3 appears around temperature t4. On the other hand, in particles with a thick shell and a small core area, a peak appears around temperature t3. At temperature t3, the influence of the shell becomes dominant. In particles with a thick shell and a small core area, the peak originating from the BaTiO3 core around temperature t4 is greatly reduced.

[0058] When these temperature characteristics are converted into the rate of capacitance change, it is expected that particles with thick shells and small core areas will experience a large drop in the rate of capacitance change near temperature t4, falling below the required lower limit of b%.In contrast, particles with thin shells and large core areas will not experience a drop at temperature t4, and will be able to keep the rate of capacitance change between the upper limit of a% and the lower limit of b%.

[0059] In this way, by increasing the area of ​​the core portion, it becomes easier to compensate for the rate of change in capacitance. In this embodiment, by using particles with a rectangular parallelepiped shape having a rectangular cross section, the core area can be increased and temperature characteristics can be improved.

[0060] [Method of manufacturing the multilayer ceramic capacitor 10] Next, a description will be given of a method for manufacturing the multilayer ceramic capacitor 10. FIG.

[0061] (Step S01: Raw material powder preparation process) A dielectric material for forming the dielectric layer 15 is prepared. First, a ceramic powder of (Ba,Sr,Ca)(Zr,Ti)O3 is prepared. Various methods have been known for synthesizing the ceramic powder of (Ba,Sr,Ca)(Zr,Ti)O3, such as the solid-phase method, the sol-gel method, and the hydrothermal method, and any suitable method can be selected and used.

[0062] The raw material powder preparation process includes a process for producing particles 151. In this embodiment, as shown in FIGS. 9(A-1) and 9(A-2), a plate-like body 150 of barium titanate (BaTiO3) is prepared. To prepare the plate-like body 150, as shown in FIG. 9(A-1), a dielectric material is applied to the smooth surface of a film-like support member 60 to form a thin film. A material is selected for the support member 60 that is thin, flexible, and can withstand a certain degree of temperature and pressure. In this embodiment, a PET (polyethylene terephthalate) film is used. The dielectric material is mixed with a solvent, dispersant, and binder, and applied to the support member 60 in the form of a slurry.

[0063] After the BaTiO3 plate-like body 150 is formed on the support member 60, the plate-like body 150 is removed from the support member 60 as shown in Fig. 9(A-2). To remove the plate-like body 150, for example, the support member 60 can be burned off. The support member 60 can be burned off by, for example, exposing it to an atmosphere at 1200 to 1400°C for 1 to 4 hours.

[0064] The plate-like body 150 removed from the support member 60 is crushed as shown in Fig. 9(A-3). For example, one side of the plate-like body 150 is scored in a lattice pattern according to the desired particle shape, and the plate-like body 150 is crushed by pressing from the other side toward the one side. This allows rectangular parallelepiped particles 151 to be obtained.

[0065] When the plate-like body 150 is crushed, particles 151 having a plate-like shape, that is, a substantially rectangular parallelepiped shape, are formed. However, when the plate-like body 150 is crushed, particles 151 are formed, and in some cases, fine particles 152 that cannot become a rectangular parallelepiped shape are formed. Such fine particles 152 are removed by shape selection. In this embodiment, as shown in FIG. 9(A-4), the separator 61 having an inclined surface 61a is used to remove the fine particles 152 and only the particles 151 are taken out. Specifically, the particles 151 and the fine particles 152 that are the result after crushing the plate-like body 150 are supplied to the inclined surface 61a. Then, the fine particles 152 that do not have a rectangular parallelepiped shape roll down the inclined surface 61a. On the other hand, the particles 151 having a rectangular parallelepiped shape stay on the inclined surface 61a due to the frictional force acting between the two when any one of the six surfaces contacts the inclined surface 61a. Thereby, the particles 151 can be taken out. The inclined surface 61a can also be in a mode of ultrasonic vibration. By the inclined surface 61a vibrating ultrasonically, the particles 151 and the fine particles 152 can be separated more quickly.

[0066] Here, the shape of the particles 151 taken out will be described with reference to FIG. 9(B). The particles 151 have sides generally along three orthogonal directions, and the lengths of the sides along each direction are denoted as a, b, and c. The relationship of the lengths of the three sides can be, for example, a < b < c, b < a < c, or a = b < c. The particles 151 in the present embodiment are used such that the longest c is along the X-axis direction.

[0067] As described above, since the particles 151 have a rectangular parallelepiped shape, a rectangle is also observed in the C-C' cross-section shown in FIG. 3(B). In FIG. 3(B), the D part is shown enlarged, and the particles 151 are observed.

[0068] (Step S02: Lamination process) Next, the particles 151 are used to obtain a sheet 70, which is a ceramic sheet for forming an unsintered ceramic body. The extracted particles 151 are processed into the sheet 70 through the steps shown in FIGS. 10(A) to 10(G). To form the sheet 70, a slurry 160 is prepared using the particles 151. The slurry 160 is prepared by mixing and dispersing the particles 151 with an additive, a dispersant, and a plasticizer binder. The additive is, for example, an oxide of a rare earth element such as Nd, La, Sm, Eu, Gd, Dy, Ho, Y, or Er, or a compound such as Cr, V, Mn, Mg, Al, Co, Ni, Mo, Fe, Li, B, Na, K, or Si. The organic solvent is, for example, ethanol, toluene, or the like. The binder is, for example, PVB (polyvinyl butyral).

[0069] The produced slurry 160 is supplied onto a support plate 62 as shown in FIG. 10(A) and pressed by a pressing member 63. When the slurry 160 is pressed by the pressing member 63, the particles 151 contained in the slurry 160 are sandwiched between the support plate 62 and the pressing member 63 and aligned. This forms a first layer as shown in FIG. 10(B). During the pressing in FIG. 10(A), ultrasonic vibrations can be applied to one or both of the support plate 62 and the pressing member 63. This makes it easier to align the particles 151 in a desired orientation.

[0070] Next, as shown in Figure 10(C), slurry 160 is again supplied onto the first layer. Then, the slurry 160 is pressed by the pressing member 63. As a result, as shown in Figure 10(D), the particles 151 contained in the slurry 160 are aligned in large numbers, forming a second layer. When pressing in Figure 10(C), ultrasonic vibrations can be applied in the same way as in Figure 10(A).

[0071] Thereafter, as shown in FIG. 10(E), slurry 160 is again supplied onto the second layer. Then, the pressing member 63 presses the slurry 160. As a result, as shown in FIG. 10(E), the particles 151 contained in the slurry 160 are aligned, forming a third layer. During the pressing in FIG. 10(E), ultrasonic vibrations can be applied as in FIG. 10(A). Thereafter, as shown in FIG. 10(G), the pressing member 63 is retracted, thereby obtaining a sheet 70. The sheet 70 thus obtained is used in the process of producing a ceramic multilayer chip C.

[0072] In this embodiment, pressing by the pressing member 63 is repeated three times to produce three layers of sheet 70, but the number of layers can be set as appropriate. After forming each layer, the upper surface or the entire slurry 160 can be dried before forming the next layer. This drying strengthens the boundary with the next layer, making it difficult for the layers to mix with each other.

[0073] Next, a metal conductive paste containing an organic binder for forming internal electrodes is printed on the surface of the sheet 70 by screen printing, gravure printing, or the like, to arrange a pattern for the internal electrode layer. Ceramic particles may or may not be added to the metal conductive paste as a co-material. When ceramic particles are added as a co-material, the main component of the ceramic particles is not particularly limited, but is preferably the same as the main component ceramic of the dielectric layer 15.

[0074] After peeling the sheets 70 from the substrate, the sheets 70 are alternately stacked so that the internal electrode layers 12, 13 and the dielectric layers 15 alternate, and so that the edges of the internal electrode layers 12, 13 are alternately exposed at both longitudinal end faces of the dielectric layers 15 and alternately drawn out to pairs of external electrodes 14a, 14b with opposite polarities. For example, the total number of layers is 100 to 500. Then, multiple cover sheets that become the cover portions 18 are pressure-bonded to the top and bottom of the stack of the sheets 70, respectively, to obtain a ceramic laminate, i.e., an unfired ceramic element. The obtained unfired ceramic element is then cut to a predetermined chip size (for example, a chip size that takes into account shrinkage due to firing when the dimensions of the multilayer ceramic capacitor 10 are 0.6 mm × 0.3 mm × 0.3 mm).

[0075] (Step S03: Firing process) In step S03, the green ceramic laminate obtained in step S02 is fired to produce the ceramic body 11 of the multilayer ceramic capacitor 10 shown in FIG. 1. The firing temperature in step S03 can be determined based on the temperature at which the green ceramic body is sintered. The firing can be carried out by a conventionally known method, for example, in a reducing atmosphere or a low oxygen partial pressure atmosphere. For example, the firing can be carried out in a reducing atmosphere or a low oxygen partial pressure atmosphere. -5 ~10 -8 The mixture can be fired in a reducing atmosphere at 1,100 to 1,300°C for 10 minutes to 2 hours.

[0076] (Step S04: Reoxidation treatment process) Thereafter, a re-oxidation treatment may be performed at 600°C to 1000°C in an N2 gas atmosphere.

[0077] (Step S05: External electrode formation process) Thereafter, the base film 21 is formed. The base film 21 is formed by applying unfired electrode material to the end faces, side faces, and main surfaces. The application method is, for example, a dipping method, but other conventionally known methods such as printing and sputtering, or a combination of these, may also be used. Next, the unfired electrode material is baked. The baking can be performed, for example, in a reducing atmosphere or a low oxygen partial pressure atmosphere. After the base film 21 is formed, electrolytic plating is performed by immersing the substrate in a plating solution that forms the plating film 22. This forms the plating film 22, and the external electrodes 14a, 14b.

[0078] In this manner, the multilayer ceramic capacitor 10 shown in FIGS. 1 to 3 is manufactured.

[0079] (First Modification) 11(A) and 11(B), a method for producing cubic particles 251 will be described. The particles 251 are used in place of the particles 151.

[0080] To obtain the particles 251, first, in step S11, hydrothermal synthesis is performed. In hydrothermal synthesis, BaCl2·2H2O + TiO2 + PVP (poly(vinylpyrrolidone)) + KOH are added to pure water. The use of PVP suppresses the grain growth of BaTiO3. This allows the production of BaTiO3 with uniform size.

[0081] In this embodiment, BaCl2 is 0.3 to 4 mol / L, TiO2 is 0.15 to 0.25 mol / L, PVP is 50 to 150 g / L, and KOH is 2 to 3 mol / L.

[0082] The hydrothermal synthesis is performed in an environment with a temperature of 200 to 250°C and a pressure of 1 atmosphere or greater. The hydrothermal synthesis can be performed for 20 hours or longer, but in this embodiment, it was performed for 24 hours. Using TiO2 as the Ti source, cubic particles 251 can be obtained by performing the hydrothermal synthesis for 24 hours. It is believed that if the hydrothermal synthesis time is short, the particle shape will become closer to spherical, while if the synthesis is performed over a longer period, the particle shape will become closer to cubic. PVP is considered necessary to improve dispersibility at the start of the reaction, but to obtain cubic particles 251, the PVP must ultimately be decomposed. The particles are considered to become closer to cubic during the PVP decomposition process, but decomposition of PVP takes a certain amount of time. Therefore, the hydrothermal synthesis time is set to 20 hours or longer, preferably 24 hours or longer.

[0083] After the hydrothermal synthesis in step S11, the particles 251 are washed with water and ethanol in step S12. The washing removes unreacted materials and Cl derived from BaCl. - ion, K from KOH + This is done to separate particles from ions, etc. Referring to Fig. 12(A), a solution containing particles 251 is supplied together with water and ethanol onto filter paper 81 set in a suction filtration device 80 connected to a suction pump P. As a result, the washed particles 251 remain on the filter paper 81. Note that the washing method is not limited to this, and other methods may be used.

[0084] In step S13, which is performed following step S12, the particles 251 are dried as shown in Fig. 12(B). Drying is performed to remove water and ethanol from the filter paper 81 on which the particles 251 remain, and to extract the dried particles 251. Drying is performed, for example, in the atmosphere at 100°C for 24 hours. The drying environment may be a vacuum environment, and the temperature and duration of drying can also be changed as appropriate.

[0085] The result of hydrothermal synthesis may contain fine particles other than the particles 251. Therefore, as in the embodiment, a separator 61 (see FIG. 9(A-4)) is used to extract only the particles 251. This allows the particles 251 to be extracted.

[0086] Here, the shape of the produced particle 251 will be described with reference to Fig. 11(B). The particle 251 has sides that extend roughly along three orthogonal directions, and the lengths of the sides along these directions are designated a, b, and c. The relationship between the lengths of the three sides is roughly a = b = c.

[0087] The particles 251 thus taken out can be used to obtain a sheet through steps similar to those shown in FIGS. 10(A) to 10(G) in the embodiment.

[0088] The particle 251 has a first surface 251a and a second surface 251b similar to the first surface 151a and the second surface 151b of the particle 151. Therefore, the multilayer ceramic capacitor using the particle 251 can obtain the same effects as the multilayer ceramic capacitor 10 of the embodiment.

[0089] (Second Modification) Next, a modified example of the method for manufacturing the sheet 70 will be described. In the embodiment, the sheet 70 was obtained through the steps shown in FIGS. 10(A) to 10(G). In contrast, in a second modified example, the sheet 70 is produced on a support plate 64 that is movably provided as indicated by arrow 5 in FIG. 13. The support plate 64 is, for example, mounted on a conveyor (not shown) and moves in the direction indicated by arrow 5. First, a slurry 160 is supplied to the leftmost position in FIG. 13. Then, the slurry 160 is leveled by a roller 65 to align the particles 151. This forms a first layer. The distance between the roller 65 and the support plate 64 is set so that the long sides of the particles 151 in the slurry do not pass through but the short sides can pass through. Thereafter, a drying process is performed, and the slurry 160 is supplied on top of the first layer. The supplied slurry 160 is leveled by the roller 65. This forms a second layer. At this time, the distance between the roller 65 and the top surface of the first layer is set so that the long sides of the particles 151 in the slurry do not pass through but the short sides can pass. After that, a drying process is performed, and then the slurry 160 is supplied on top of the second layer. The supplied slurry 160 is leveled by the roller 65. This forms the third layer. The distance between the roller 65 and the second layer is set so that the long sides of the particles 151 in the slurry do not pass through but the short sides can pass through. This results in the sheet 70. The number of layers can be set as appropriate.

[0090] [effect] The multilayer ceramic capacitor 10 of this embodiment includes a dielectric layer 15 having rectangular grains 151 (251) in a cross section along the stacking direction of the internal electrode layers 12, 13 and the dielectric layer 15 of the ceramic body 11. Compared to a case where the dielectric is composed of grains with a nearly circular cross section, the dielectric grains having a rectangular cross section can increase the proportion of the dielectric grains in the same cross-sectional area. This allows for a larger grain cross-sectional area of ​​the dielectric, thereby increasing the cross-sectional area of ​​the core portion. This improves the dielectric constant of the dielectric layer 15 and the temperature characteristics, thereby improving the capacitance and temperature characteristics of the multilayer ceramic capacitor 10. Furthermore, since the cross-sections of the internal electrode layers 12, 13 are aligned with the cross-sectional shape of the grains in the dielectric layer 15, the two boundaries are not linear in the case of nearly circular grains, whereas the two boundaries are linear in the case of rectangular grains. This reduces the variation in the spacing between the internal electrodes, thereby improving the reliability of the multilayer ceramic capacitor 10.

[0091] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0092] In the above embodiment, the multilayer ceramic capacitor 10 has been described as an example of a multilayer ceramic electronic component, but the present invention is applicable to all multilayer ceramic electronic components in which dielectric layers and internal electrode layers are stacked. Examples of such multilayer ceramic electronic components include chip varistors, chip thermistors, and multilayer inductors. [Explanation of symbols]

[0093] 10...Multilayer ceramic capacitor 11...Ceramic body 12,13...Internal electrode layer 14a,14b...External electrode 151, 251…particles

Claims

1. The element body is formed by alternately laminating internal electrode layers and dielectric layers, the dielectric layer includes a plurality of layers of particles each having a rectangular shape in a cross section along a lamination direction of the internal electrode layer and the dielectric layer of the element body; Multilayer ceramic electronic components.

2. The particles have a rectangular or cubic shape. The multilayer ceramic electronic component according to claim 1 .

3. The particle has a hexahedral shape having six faces including a first face and a second face opposite to each other. The multilayer ceramic electronic component according to claim 1 .

4. the particles have opposing first and second surfaces, and the first and second surfaces face the internal electrode layers, respectively; The multilayer ceramic electronic component according to claim 1 .

5. The particles have opposing first and second surfaces, and the first and second surfaces are parallel to the internal electrode layers. The multilayer ceramic electronic component according to claim 1 .

6. A step of preparing a raw material powder including particles having a hexahedral shape with six faces including a first face and a second face opposite to each other; a step of forming a laminate that becomes a capacitance forming portion by alternately laminating first internal electrode layers and second internal electrode layers with dielectric layers containing the raw material powder sandwiched therebetween; and firing the laminate. Manufacturing method for multilayer ceramic electronic components.

7. The step of preparing the raw material powder includes a step of applying a dielectric material onto a smooth surface of a support member to prepare a plate-like body including the dielectric material on the support member; removing the plate-like body from the support member and crushing the plate-like body to produce the particles; The method for producing a multilayer ceramic electronic component according to claim 6.

8. The step of preparing the raw material powder includes a step of sorting the fragments obtained by crushing the plate-like body by shape and extracting the particles. The method for producing a multilayer ceramic electronic component according to claim 7.

9. the step of preparing the raw material powder includes a step of using at least titanium oxide and performing hydrothermal synthesis for 20 hours or more to prepare the particles; The method for producing a multilayer ceramic electronic component according to claim 6.

10. The hydrothermal synthesis is carried out for 24 hours or more. The method for producing a multilayer ceramic electronic component according to claim 9.

11. the step of preparing the raw material powder includes a step of performing hydrothermal synthesis using at least titanium oxide and polyvinylpyrrolidone to prepare the particles; The method for producing a multilayer ceramic electronic component according to claim 6.

12. The step of preparing the raw material powder includes a step of sorting the resultant obtained in the step of performing hydrothermal synthesis by shape and extracting the particles. The method for manufacturing the multilayer ceramic electronic component according to any one of claims 9 to 11.

13. The step of forming the laminate includes a step of supplying the slurried raw material powder containing the particles onto a support member, and pressing the slurried raw material powder against the support member, and a step of performing the pressing step multiple times to produce a ceramic sheet. The method for producing a multilayer ceramic electronic component according to claim 6.

14. The step of forming the laminate includes the steps of supplying the slurried raw material powder containing the particles onto a support member, and driving a roller on the slurried raw material powder to produce a ceramic sheet. The method for producing a multilayer ceramic electronic component according to claim 6.

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