Multilayer ceramic electronic components

Abstract

To provide multilayer ceramic electronic components that can improve reliability. [Solution] The multilayer ceramic electronic component has a plurality of internal electrode layers facing each other in a predetermined direction, a plurality of dielectric layers laminated between the plurality of internal electrode layers, and an external electrode electrically connected to the internal electrode layers. The dielectric layer includes first crystalline particles of a main component ceramic having a perovskite structure represented by the general formula ABO3, and second crystalline particles mainly composed of a barium titanate-based composite oxide in which the elemental ratio of barium to titanium is 0.70 or less, and the second crystalline particles are in contact with at least one of a pair of internal electrode layers sandwiching the dielectric layer.

Description

[Technical Field]

[0001] This invention relates to multilayer ceramic electronic components. [Background technology]

[0002] Regarding multilayer ceramic electronic components, for example, Patent Document 1 describes a multilayer ceramic capacitor. In recent years, in response to the demand for higher capacitance in multilayer ceramic electronic components, the number of layers has been increased, and the dielectric layers between internal electrodes in the ceramic body have been thinned. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-50033 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, as the dielectric layer becomes thinner, there is a risk that its resistance to electrostriction, for example, may decrease. Furthermore, the insulation resistance (IR) may decrease due to voids in the dielectric layer created during the binder removal process in manufacturing. This could potentially reduce the reliability of multilayer ceramic electronic components.

[0005] This invention has been made in view of the above-mentioned problems, and aims to provide a multilayer ceramic electronic component that can improve reliability. [Means for solving the problem]

[0006] The multilayer ceramic electronic component of the present invention has a plurality of internal electrode layers facing each other in a predetermined direction, a plurality of dielectric layers laminated between the plurality of internal electrode layers, and external electrodes electrically connected to the internal electrode layers. The dielectric layer includes first crystal particles of a main component ceramic having a perovskite structure represented by the general formula ABO3 and second crystal particles mainly composed of a barium titanate-based composite oxide having an elemental ratio of barium to titanium of 0.70 or less. The second crystal particles contact at least one of the pair of internal electrode layers sandwiching the dielectric layer.

[0007] In the above multilayer ceramic electronic component, the second crystal particles have a size of 80% or more with respect to the thickness of the cross section of the dielectric layer along the predetermined direction.

[0008] In the above multilayer ceramic electronic component, the second crystal particles are BaTi2O5, BaTi4O9, BaTi5O 11 、BaTi6O 13 、Ba4Ti 11 O 26 、Ba4Ti 12 O 27 、Ba4Ti 13 O 30 、and Ba6Ti 17 O 40 and may be at least one selected from them.

[0009] In the above multilayer ceramic electronic component, the first crystal particles may be barium titanate.

[0010] In the above multilayer ceramic electronic component, the second crystal particles may contact both of the pair of internal electrode layers sandwiching the dielectric layer.

[0011] In the above multilayer ceramic electronic component, in a direction substantially orthogonal to the predetermined direction, the width of the contact region of the second crystal particles with respect to the internal electrode layer may be 50 to 500 μm.

[0012] In the above multilayer ceramic electronic component, the thickness of the cross-section of the dielectric layer may be 0.4 μm or less.

Advantages of the Invention

[0013] According to the present invention, the reliability of the multilayer ceramic electronic component can be improved.

Brief Description of the Drawings

[0014] [Figure 1] FIG. 1 is a partial cross-sectional perspective view of a multilayer ceramic capacitor. [Figure 2] FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. [Figure 3] FIG. 3 is a cross-sectional view taken along line B-B of FIG. 1. [Figure 4] FIG. 4(A) is an enlarged cross-sectional view near one of the external electrodes. FIG. 4(B) is an enlarged cross-sectional view near the other external electrode. [Figure 5] FIG. 5 is an enlarged cross-sectional view of a part of the dielectric layer. [Figure 6] FIG. 6 is a diagram showing an example of a unit cell of the perovskite-type structure of the first crystal particles. [Figure 7] FIG. 7 is a diagram illustrating the flow of a method for manufacturing a multilayer ceramic capacitor. [Figure 8] FIGS. 8(A) and 8(B) are diagrams illustrating the internal electrode forming process. [Figure 9] FIG. 9 is a diagram illustrating the lamination and pressing process. [Figure 10] FIG. 10 is a diagram illustrating the side margin part. [Figure 11] FIG. 11(A) is a cross-sectional view illustrating the internal electrode pattern and the dielectric pattern before the firing process. FIG. 11(B) is a cross-sectional view illustrating the internal electrode pattern and the dielectric pattern after baking of the metal paste after the first step of the firing process. FIG. 11(C) is a cross-sectional view illustrating the dielectric layer after the second step of the firing process. FIG. 11(D) is a cross-sectional view illustrating the dielectric layer in which the second crystal particles do not exist. [Modes for carrying out the invention]

[0015] [Embodiment] (Configuration of multilayer ceramic capacitors) Figure 1 is a partial cross-sectional perspective view of a multilayer ceramic capacitor 100 according to an embodiment. Figure 2 is a cross-sectional view taken along line AA in Figure 1. Figure 3 is a cross-sectional view taken along line BB in Figure 1. As illustrated in Figures 1 to 3, the multilayer ceramic capacitor 100 comprises a base body 10 having a substantially rectangular parallelepiped shape and external electrodes 20a and 20b provided on two opposing end faces of either the base body 10. Of the four faces of the base body 10 other than the two end faces, the two faces other than the top and bottom faces in the stacking direction are referred to as side faces. The external electrodes 20a and 20b extend to the top, bottom, and two side faces of the base body 10 in the stacking direction. However, the external electrodes 20a and 20b are spaced apart from each other.

[0016] In Figures 1 to 3, the Z-axis direction (first direction) is the stacking direction, and is the direction in which each internal electrode layer faces another. The X-axis direction (second direction) is the length direction of the base body 10, and is the direction in which the two end faces of the base body 10 face each other, and is the direction in which the external electrode 20a and external electrode 20b face each other. The Y-axis direction (third direction) is the width direction of the internal electrode layer, and is the direction in which the two sides of the base body 10 (excluding the two end faces) face each other. The X-axis direction, the Y-axis direction, and the Z-axis direction are mutually orthogonal.

[0017] The base body 10 has a structure in which dielectric layers 11 containing a ceramic material that functions as a dielectric and internal electrode layers 12 are alternately stacked. The edges of each internal electrode layer 12 are alternately exposed to the end face of the base body 10 where the external electrode 20a is provided and the end face where the external electrode 20b is provided. As a result, each internal electrode layer 12 is alternately electrically connected to the external electrode 20a and the external electrode 20b. Consequently, the multilayer ceramic capacitor 100 has a structure in which multiple dielectric layers 11 are stacked via internal electrode layers 12. Furthermore, in the laminate of dielectric layers 11 and internal electrode layers 12, the outermost layer in the stacking direction is the internal electrode layer 12, and the top and bottom surfaces of the laminate are covered by a cover layer 13. The cover layer 13 mainly consists of a ceramic material. For example, the cover layer 13 may have the same composition as the dielectric layer 11 or a different composition. Furthermore, the configuration is not limited to that shown in Figures 1 to 3, as long as the internal electrode layer 12 is exposed on two different surfaces and is electrically connected to different external electrodes.

[0018] The dimensions of the multilayer ceramic capacitor 100 are, 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 are not limited to these dimensions.

[0019] The internal electrode layer 12 is mainly composed of base metals such as nickel (Ni), copper (Cu), tin (Sn), or alloys containing these. Precious metals such as platinum (Pt), palladium (Pd), silver (Ag), and gold (Au), or alloys containing these, may also be used as the internal electrode layer 12. The average thickness per layer of the internal electrode layer 12 in the Z-axis direction is, for example, 0.3 μm to 8.0 μm, 0.4 μm to 7.0 μm, or 0.5 μm to 6.0 μm. The thickness of the internal electrode layer 12 can be measured by observing the cross-section of the multilayer ceramic capacitor 100 with an SEM (Scanning Electron Microscope), measuring the thickness at 10 points for each of 10 different internal electrode layers 12, and deriving the average value of all measurement points.

[0020] The dielectric layer 11 mainly consists of a ceramic material having a perovskite structure represented by the general formula ABO3. Note that this perovskite structure is an ABO3 structure that deviates from the stoichiometric composition. 3-α This includes the following. In this embodiment, barium titanate (BaTiO3) is used as the main ceramic component of the dielectric layer 11. The dielectric layer 11 contains, for example, 90 at% or more of barium titanate.

[0021] As illustrated in Figure 2, the region where the internal electrode layer 12 connected to the external electrode 20a and the internal electrode layer 12 connected to the external electrode 20b face each other is a region in the multilayer ceramic capacitor 100 where capacitance is generated. Therefore, this region where capacitance is generated is referred to as the capacitance region 14. In other words, the capacitance region 14 is the region where adjacent internal electrode layers 12 connected to different external electrodes 20a and 20b face each other.

[0022] The region where internal electrode layers 12 connected to external electrode 20a face each other without being connected to an internal electrode layer 12 connected to external electrode 20b is called the end margin 15. Similarly, the region where internal electrode layers 12 connected to external electrode 20b face each other without being connected to an internal electrode layer 12 connected to external electrode 20a is also called the end margin 15. In other words, the end margin 15 is the region where internal electrode layers 12 connected to the same external electrode face each other without being connected to an internal electrode layer 12 connected to a different external electrode. The end margin 15 is a region where no capacitance is generated.

[0023] As illustrated in Figure 3, in the element 10, the side margin 16 is a region provided to cover the two side edges (the edges in the Y-axis direction) of the dielectric layer 11 and the internal electrode layer 12. In other words, the side margin 16 is a region provided outside the capacitance portion 14 in the Y-axis direction. The side margin 16 is also a region that does not generate capacitance.

[0024] Figure 4(A) is an enlarged cross-sectional view of the vicinity of one external electrode 20a. Figure 4(B) is an enlarged cross-sectional view of the vicinity of the other external electrode 20b. In Figures 4(A) and 4(B), hatches representing cross-sections are omitted. As illustrated in Figures 4(A) and 4(B), the external electrodes 20a and 20b have a structure in which a plating layer 22 is provided on a base layer 21. The base layer 21 mainly consists of nickel, copper, etc. The base layer 21 may also contain ceramic particles as a co-material, or it may contain glass components. The plating layer 22 mainly consists of metals such as nickel, copper, aluminum, zinc, tin, or alloys of two or more of these. The plating layer 22 may be a plating layer of a single metal component, or it may be multiple plating layers of different metal components. For example, the plating layer 22 has a structure in which a first plating layer 23, a second plating layer 24, and a third plating layer 25 are formed in order from the base layer 21 side. The first plating layer 23 is, for example, a copper plating layer. The second plating layer 24 is, for example, a nickel plating layer. The third plating layer 25 is, for example, a tin plating layer.

[0025] (Dielectric layer structure) Figure 5 is an enlarged cross-sectional view of a portion of the dielectric layer 11. The cross-section is a cross-section of the capacitance region 14 along the stacking direction, as shown in Figures 2 and 3.

[0026] The dielectric layer 11 includes first crystalline particles 41 of a main component ceramic having a perovskite structure represented by the general formula ABO3, and second crystalline particles 42 mainly composed of a barium titanate-based composite oxide in which the elemental ratio of barium to titanium is 0.70 or less. The dielectric layer 11 has a structure in which a plurality of first crystalline particles 41 constituting the main phase and one or more second crystalline particles 42 are sintered. For example, the dielectric layer 11 may have one first crystalline particle 41 in the thickness direction, or it may have a structure in which a plurality of first crystalline particles 41 are continuous via grain boundaries, as shown in Figure 5. The second crystalline particles 42 fill the gaps 44 between the first crystalline particles 41.

[0027] The first crystalline grain 41 is, for example, barium titanate. Therefore, the dielectric layer 11 exhibits a favorable capacitance compared to other ceramic materials. The first crystalline grain 41 may also be barium titanate in which other elements are solid-solved.

[0028] Figure 6 shows an example of a unit cell of the perovskite structure of the first crystal grain 41. The first crystal grain 41 is a crystal grain of barium titanate (BaTiO3) having a perovskite structure. Crystal grains having a perovskite structure have a unit cell as illustrated in Figure 6. This unit cell has A sites located at the vertices of the lattice, O sites located at the center of the lattice faces, and B sites located in the octahedron with the O sites as vertices. In the perovskite structure, alkaline earth metals that can take divalent cations, such as barium (Ba), strontium (Sr), and calcium (Ca), are arranged at the A sites, and metal atoms that can take tetravalent cations, such as hafnium (Hf), zirconium (Zr), and titanium (Ti), are arranged at the B sites. In this embodiment, barium is arranged at the A sites, titanium is arranged at the B sites, and at least one of the A sites and B sites may be substituted by the added elements.

[0029] The perovskite structure allows for compositional formulas that deviate from stoichiometric compositions. That is, the ratio of the A-site element to the B-site element does not necessarily have to be 1:1, and defects may be generated as long as they maintain the perovskite structure. Defects may also be generated in the oxygen atom. For example, compositional formula A α BO 3-β In this case, compositions in the range of 0.98 ≤ α ≤ 1.01 and 0 ≤ β ≤ 0.20 are permissible.

[0030] However, the formation of oxygen vacancies, for example, can reduce resistivity or cause ionic conductivity, leading to a decrease in electrical lifespan and increased dielectric loss when used as a multilayer ceramic capacitor, making it impractical in some cases. For this reason, the first crystal grain 41 having a perovskite structure may optionally contain at least one of the first transition elements: scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn). This makes it possible to improve resistivity, increase electrical lifespan, and reduce dielectric loss relative to capacitance.

[0031] Furthermore, the first crystal grain 41 may optionally contain at least one of the second transition elements: yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), and silver (Ag). This makes it possible to improve resistivity, increase electrical lifetime, and reduce dielectric loss relative to capacitance.

[0032] Furthermore, the first crystal grain 41 may optionally contain at least one of the following third transition elements: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au). This makes it possible to improve resistivity, increase electrical lifetime, and reduce dielectric loss relative to capacitance.

[0033] The second crystal grain 42 is a barium titanate-based composite oxide produced when a titanium-based additive (e.g., titanium oxide) is used with barium titanate, and has an elemental ratio (ratio of the number of elements) of barium to titanium of 0.70 or less. Examples of the second crystal grain 42 include BaTi2O5, BaTi4O9, and BaTi5O 11 BaLi6O 13 Ba4Ru 11 O 26 Ba4Ru 12 O 27 Ba4Ru 13 O 30 Ba6Lo 17 O 40 These are some examples.

[0034] The second crystal particle 42 is Ba4Ti 11 O 26Preferably, the barium titanate composite oxide is monoclinic, with a space group of C2 / m, and lattice constants of a=15.160Å, b=3.893Å, c=9.093Å, and β=98.6°. This is because the ratio of barium to titanium in this barium titanate composite oxide is relatively close to 1, and it is easy to intentionally precipitate it without using a large amount of titanium-based additives. This barium titanate composite oxide is described, for example, in the non-patent literature Acta Cryst. (1979). B35, 1590-1593.

[0035] A more preferred example of the second crystal grain 42 is Ba4Ti 11 O 26 In contrast, it is desirable that manganese is dissolved in the defect site and occupies it, or that some of the titanium is replaced. As is clear from the above non-patent literature, Ba4Ti 11 O 26 This material has a crystal structure in which defects occur at some of the titanium sites. Therefore, at the defect locations, titanium is more likely to change from a tetravalent cation to a trivalent cation, resulting in a decrease in resistivity. The presence of manganese in solid solution is effective in compensating for this.

[0036] The second crystal grains 42 are formed to fill the voids 44 that occur during the firing process when manufacturing the multilayer ceramic capacitor 100. The second crystal grains 42 are in contact with at least one of the pair of internal electrode layers 12 that sandwich the dielectric layer 11.

[0037] Therefore, the second crystal particles 42 can sufficiently reduce the voids 44 within the dielectric layer 11 while being connected to at least one of the internal electrode layers 12. This strengthens the base body 10 and improves the dielectric layer 11's resistance to electrostriction and the like. Consequently, the overall mechanical strength of the multilayer ceramic capacitor 100 is improved. When the second crystal particles 42 are in contact with both internal electrode layers 12, the second crystal particles 42 act as columnar members connecting the two internal electrodes 12, further improving the mechanical strength of the base body 10. Since the second crystal particles 42 contain more additive elements (Si, Al, Ca, Mn, Mg, Ho, Dy, etc.) than the first crystal particles 41, they have lower hardness compared to the first crystal particles 41, effectively suppressing crack formation even when stress is applied to the dielectric layer 11. The hardness of the first crystal particles 41 and the second crystal particles 42 can be measured, for example, by a nanoindenter.

[0038] Furthermore, the second crystal particles 42 can sufficiently reduce the voids 44 within the dielectric layer 11, thereby increasing the resistance of the dielectric layer 11 and increasing the insulation resistance between the internal electrode layers 12. In addition, the bonding of the second crystal particles 42 with the surrounding first crystal particles 41 suppresses the movement of the first crystal particles 41 during firing, reducing variations in the thickness of the dielectric layer 11. This reduces variations in the electric field strength when a voltage is applied between the internal electrode layers 12. Consequently, the reliability of the multilayer ceramic capacitor 100 is improved.

[0039] Here, it is preferable that the second crystal grains 42 have a size Hd of 80% or more of the thickness d of the cross-section of the dielectric layer 11 along the stacking direction (Hd / d≧80). With this configuration, the voids 44 in the dielectric layer 11 can be suitably filled by the second crystal grains 42, thereby further strengthening the base body 10 and further improving the durability and insulating properties of the dielectric layer 11.

[0040] Furthermore, in a direction substantially perpendicular to the stacking direction (the X direction in this example), the width Wp of the contact region of the second crystal grain 42 with respect to the internal electrode layer 12 is preferably, for example, 50 to 500 μm. This width Wp allows for further and favorable improvement of the dielectric layer 11's resistance to electrostriction and the like.

[0041] The lower limit of the width Wp is determined, for example, from the viewpoint of sufficiently relaxing the stress acting on the dielectric layer. The lower limit of the width Wp is not limited to 50 μm, but is preferably 40 μm, and more preferably 30 μm.

[0042] The upper limit of the width Wp is determined, for example, from the viewpoint of sufficiently relaxing the stress acting on the dielectric layer. The upper limit of the width Wp is not limited to 500 μm, but is preferably 400 μm, and more preferably 300 μm.

[0043] In this example, the width Wp of the multilayer ceramic capacitor 100 in the longitudinal direction was given, but the width Wp is not limited to the longitudinal direction; it can be any width in a direction perpendicular to the stacking direction. That is, the width Wp is the dimension in any direction of the contact area of ​​the second crystal grains 42 with respect to the internal electrode layer 12. The width Wp can be measured by, for example, the following method. The width Wp can be measured by observing the cross-section of the multilayer ceramic capacitor 100 with an SEM (scanning electron microscope), setting a reference line passing through the point where the thickness of the internal electrode layer 12 in the stacking direction is maximum along the longitudinal or width direction of the multilayer ceramic capacitor 100 using image analysis software, and deriving the length over which the reference line and the second crystal grains are in contact.

[0044] The effects described above become more pronounced as the dielectric layer 11 becomes thinner. From this viewpoint, for example, the thickness d of the cross-section of the dielectric layer 11 is preferably 0.4 μm or less. The upper limit of the thickness d is not limited to 0.4 μm, but is preferably 0.3 μm, and even more preferably 0.2 μm.

[0045] Furthermore, from the viewpoint of sufficiently relaxing the stress acting on the dielectric layer, for example, the thickness d of the cross-section of the dielectric layer 11 is preferably 0.3 μm or more. The lower limit of the thickness d is not limited to 0.3 μm, but is preferably 0.4 μm, and even more preferably 0.5 μm.

[0046] The thickness of the dielectric layer 11 can be measured by observing the cross-section of the multilayer ceramic capacitor 100 with an SEM (scanning electron microscope), measuring the thickness at 10 points for each of the 10 different dielectric layers 11, and deriving the average value of all measurement points.

[0047] Furthermore, the size Hd of the second crystal grains 42 along the stacking direction can be measured, for example, by the following method. The size Hd can be measured by observing the cross-section of the multilayer ceramic capacitor 100 with an SEM (scanning electron microscope) and detecting the second crystal grains 42 using image analysis software.

[0048] Furthermore, the ratio of the content of first crystal grains 41 and second crystal grains 42 within one dielectric layer 11 is as follows. For example, if S1 is the ratio of the area occupied by first crystal grains 41 to the area of ​​a cross-section along the stacking direction as shown in Figures 2 and 3, and S2 is the ratio of the area occupied by second crystal grains 42, then S1 is approximately 90% to 95%, and S2 is approximately 3% to 20%.

[0049] The presence of the second crystal grains 42 in the dielectric layer 11 can be confirmed by the following procedure. The presence or absence of contact between the second crystal grains 42 and the internal electrode layer 12 can be confirmed in the same way as the method for confirming the width Wp described above.

[0050] First, the diffraction line profile of the dielectric layer 11 to be examined, or the powder obtained by grinding the dielectric layer 11, is measured using an X-ray diffractometer (XRD) that uses Cu-Kα rays. The grinding method for obtaining the powder is not particularly limited, and a hand mill (mortar and pestle) can be used. When measuring the diffraction profile of the ceramics constituting the multilayer ceramic capacitor 100, the electrodes and coatings formed on the surface of the element, and parts of the multilayer ceramic capacitor 100 other than the dielectric layer 11 are removed to expose the surface of the dielectric layer 11. This exposure method is not particularly limited, and methods such as cutting or polishing the element can be employed. Furthermore, when measuring the diffraction profile of the powder of the dielectric layer 11 constituting the multilayer ceramic capacitor 100, it is more preferable to grind it after removing the external electrodes 20a, 20b and coatings formed on the element, and parts of the multilayer ceramic capacitor 100 other than the dielectric layer 11.

[0051] Next, in the obtained diffraction profile, the percentage of the strongest diffraction line intensity from other structures relative to the strongest diffraction line intensity from the perovskite structure is calculated. If this percentage is 10% or less, it is determined that the dielectric layer 11 under investigation is composed of a main phase having a perovskite structure. Note that when the surface of the dielectric layer 11 of the multilayer ceramic capacitor 100 is exposed using the above method, or when XRD measurements are performed on the pulverized powder, peaks from the external electrodes 20a, 20b, the internal electrode layer 12, and the materials constituting the coating may also be detected. In such cases, these should be excluded before calculating the ratio of diffraction line intensities as described above.

[0052] Next, we focus on peaks other than those originating from the perovskite structure to identify the crystalline phase. Ideally, crystalline phase identification should be confirmed by searching the PDF (Powder Diffraction File) published by ICDD (International Centre for Diffraction Data; Pennsylvania, USA) to determine if crystalline grains are present. Ba4Ti is a suitable example. 11 O 26In this case, the generation can be evaluated by identifying it by referring to PDF-01-083-1459.

[0053] Next, it is determined that the crystal grains consist of a barium titanate-based composite oxide in which the elemental ratio of barium to titanium is 0.70 or less by the following method.

[0054] First, the surface of the dielectric layer 11 is exposed. The method of exposure is not particularly limited, and methods such as cutting or polishing the element can be employed. At this time, in order to observe the internal ceramic structure sufficiently, it is preferable to obtain a smooth surface that can be judged as a mirror surface by ultimately using a diamond paste of 2 μm or less.

[0055] Next, the composition of the second crystal grain 42 is identified using an energy-dispersive X-ray spectrometer (EDS) or wavelength-dispersive X-ray spectrometer (WDS) mounted on a scanning electron microscope (SEM) or transmission electron microscope (TEM), an electron probe microanalyzer (EPMA), and laser-irradiated inductively coupled plasma mass spectrometry (LA-ICP-MS).

[0056] For example, in EDS measurements, the titanium K-line intensity is simply determined by the K-line intensity relative to the barium K-line or L-line, or the manganese K-line. More specifically, corrections (ZAF correction) are performed on these intensities, taking into account atomic number effects, absorption effects, and fluorescence excitation effects, to calculate the ratio of each element to the titanium element content, and these are then used as the ratio of each element.

[0057] When performing EDS measurements, particularly with barium's Lα line and titanium's Kα line, the energy peaks are close together, making it difficult to adequately compare elemental content. Therefore, it is desirable to obtain sufficient intensity for barium's Lβ2 and LIIIab lines, which do not overlap peaks, during the measurement. Specifically, it is desirable that the intensity at these peaks be 10,000 counts or more. In this case, the intensity of the characteristic X-ray from barium can be identified, and the elemental content can be calculated. Even if the barium Lα line and the titanium Kα line overlap, the intensity of the titanium Kα line can be identified, and the elemental content can be evaluated with high accuracy.

[0058] When the elemental ratio of barium to titanium obtained by the above method is 0.70 or less, the crystal grain is determined to be the second crystal grain 42. In other words, it is determined to be one of the above barium titanate composite oxides when the elemental ratio of barium to titanium is small compared to the barium titanate present in the surrounding area. In this case, when using SEM during observation, the crystal grain is characterized by being observed as darker and having relatively lower brightness compared to barium titanate in the backscattered electron image (BSE image). Furthermore, a more preferable determination is made by identifying the crystal grain by evaluating the diffraction profile using XRD. Next, in more detail, the area determined to be a crystal grain is cut out as a sample for transmission electron microscopy (TEM) observation, and the diffraction pattern obtained using limited-field diffraction is compared with data from known literature to determine whether it is BaTi2O5, BaTi4O9, or BaTi5O 11 BaLi6O 13 Ba4Ru 11 O 26 Ba4Ru 12 O 27 Ba4Ru 13 O 30 , or Ba6Ti 17 O 40 This checks whether it can be determined as such. This extraction can be performed using a FIB device or similar equipment.

[0059] (Manufacturing method for multilayer ceramic capacitors) Figure 7 is a diagram illustrating the flow of the manufacturing method for the multilayer ceramic capacitor 100.

[0060] (Raw material powder preparation process St1) First, a dielectric ceramic composition for forming the dielectric layer 11 is prepared. The A-site and B-site elements contained in the dielectric layer 11 are usually present in the form of a sintered body of ABO3 particles. For example, barium titanate is a compound that has a perovskite structure and belongs to the tetragonal crystal system at around room temperature, exhibiting a high dielectric constant. Barium titanate can generally be synthesized by reacting a titanium raw material such as titanium dioxide with a barium raw material such as barium carbonate. Various methods have been conventionally known for synthesizing barium titanate, which is the main component of the dielectric layer 11, such as the solid-phase method, the sol-gel method, and the hydrothermal method. Any of these methods can be used in this embodiment.

[0061] Titanium is added to the obtained barium titanate powder. For example, titanium oxide (TiO2) can be added. In this embodiment, it is preferable to add titanium to the barium titanate powder such that the elemental ratio of barium to titanium is 0.900 or more and 0.995 or less. For example, 0.5 mol or more and 10 mol or less of titanium is added to 100 mol of barium titanate powder.

[0062] The obtained ceramic powder is then mixed with predetermined additives. As an example, oxides or glass containing Zr (zirconium), V (vanadium), Cr (chromium), Co (cobalt), Ni (nickel), Li (lithium), B (boron), Na (sodium), and K (potassium) may be used. Additionally, if necessary, oxides of rare earth elements such as Gd (gadolinium), Sc (scandium), Y (yttrium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Y (ytterbium), and Lu (lutetium) may be added.

[0063] For example, a ceramic material containing barium titanate powder and an additive compound is wet-mixed, dried, and pulverized to prepare the mixture of barium titanate powder and the additive compound. For example, the ceramic material obtained as described above may be pulverized as needed to adjust the particle size, or the particle size may be adjusted by combining this with a classification process. Specifically, the particle size can be adjusted by stirring the ceramic material together with beads made of yttrium-stabilized zirconia, alumina, or silicon nitride, with a diameter of 0.1 mm to 3 mm, for 10 to 100 hours. A dielectric ceramic composition is obtained through the above process.

[0064] (Coating process St2) Next, a binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer are added to the obtained dielectric ceramic composition and wet-mixed. Using the resulting slurry, a ceramic green sheet 51 is coated onto a substrate by, for example, a die coater or doctor blade method and then dried. The substrate is, for example, polyethylene terephthalate (PET) film. A diagram illustrating the coating process has been omitted.

[0065] (Internal electrode formation process St3) Figures 8(A) and 8(B) illustrate the internal electrode formation process St3. After the coating process St2, a metal conductive paste for forming internal electrodes, containing an organic binder, is printed onto the surface of the ceramic green sheet 51 by screen printing, gravure printing, etc., thereby arranging an internal electrode pattern 52 that is alternately drawn out to a pair of external electrodes with different polarities. Ceramic particles are added to the metal conductive paste as a co-material. The main component of the ceramic particles is not particularly limited, but it is preferable that it is the same as the main component ceramic of the dielectric layer 11. For example, barium titanate with an average particle diameter of 50 nm or less may be uniformly dispersed.

[0066] Next, a binder such as ethylcellulose and an organic solvent such as terpineol are added to the dielectric ceramic composition obtained in the raw material powder preparation process, and the mixture is kneaded in a roll mill to obtain a dielectric pattern paste for the reverse pattern layer. As illustrated in Figure 8(A), the dielectric pattern 53 is placed on the ceramic green sheet 51 by printing the dielectric pattern paste in the peripheral area where the internal electrode pattern 52 is not printed, thereby filling the step between it and the internal electrode pattern 52. The ceramic green sheet 51 with the internal electrode pattern 52 and dielectric pattern 53 printed on it is called a laminated unit.

[0067] Subsequently, as illustrated in Figure 8(B), stacking units are carried out so that the internal electrode layer 12 and the dielectric layer 11 are staggered, and the edges of the internal electrode layer 12 are alternately exposed on both ends of the dielectric layer 11 in the longitudinal direction, alternately leading to a pair of external electrodes 20a and 20b with different polarities. For example, the number of stacked internal electrode patterns 52 is 100 to 1000.

[0068] (Lamination and crimping process St4) Figure 9 illustrates the lamination and compression process St4. A predetermined number of cover sheets 54 (e.g., 2 to 10 layers) are laminated and heat-pressed onto the top and bottom of the laminated body, which is made up of laminated units. As an example of the ceramic material for the cover sheets 54, the dielectric ceramic composition described above can be used. After that, it is cut to a predetermined chip size (e.g., 1.0 mm × 0.5 mm). The side margins may be attached or coated to the sides of the laminated portion.

[0069] Figure 10 illustrates a side margin portion 55. For example, a laminate is obtained by alternately stacking a ceramic green sheet 51 and an internal electrode pattern 52 with the same width as the ceramic green sheet 51. Next, a sheet formed from dielectric pattern paste may be attached to the side surface of the laminate as the side margin portion 55.

[0070] (Binder removal process St5) Next, the debinding process St5 is performed. In the debinding process St5, the laminate is debinding in an N2 atmosphere at 250-500°C. The debinding process generates a liquid phase component, including glass, within the dielectric pattern 53. After the debinding process, the liquid phase component becomes solid as the laminate cools, but it becomes liquid again when heated in the subsequent firing process St7.

[0071] (External electrode formation process St6) Next, the external electrode formation process St6 is performed. In the external electrode formation process St6, a metal paste containing, for example, metal powder, glass frit, binder, and solvent is applied to each end face, top surface, bottom surface, and each side surface of the laminate by the dipping method. After the application of the metal paste, the metal paste is baked through the following firing process St7.

[0072] (Firing process St7) The firing process St7 is carried out in two stages, for example, a first step and a second step. In the first step, the laminate is fired at 1000°C for 15 to 60 minutes in an atmosphere with a hydrogen concentration of 0.05 to 1.0%. In the first step, the first crystal grains 41, which form the main phase of the dielectric layer 11, are necked together. Also, as will be described later, the liquid phase component generated in the debindering process St5 enters the gaps 44 between the bonded first crystal grains 41. This liquid phase component mainly contains second crystal grains 42 produced from the additive titanium. The heating rate to reach 1000°C is, for example, 1000°C / h. This makes it possible to appropriately control the size Hd of the second crystal grains 42 relative to the thickness d of the dielectric layer 11.

[0073] In the next step, the ceramic laminate is subjected to an oxygen partial pressure of 10 -12 ~10 -9 The laminate is fired at 1200-1300°C for 2-6 hours in a reducing atmosphere of atm. In the second step, second crystal particles 42 precipitate from the liquid phase component present in the gaps 44 between the first crystal particles 41, filling the gaps 44. As a result, the dielectric layer 11 is densified by the phase of the precipitated second crystal particles 42. In this way, a multilayer ceramic capacitor 100 is obtained. After that, a process for forming plating layers 22-25 on the external electrodes 20a and 20b (plating process) or a re-oxidation process may be performed.

[0074] (Formation of dielectric layer) Next, we will explain the process by which the dielectric layer 11 is formed in the firing process St7 described above.

[0075] Figure 11(A) is a cross-sectional view illustrating the internal electrode pattern 52 and dielectric pattern 53 before the firing process St7. The internal electrode pattern 52 contains, for example, a large number of nickel particles 520. The dielectric pattern 53 contains, for example, a ceramic main component 510 containing barium titanate, and a liquid phase component 511 and voids B generated by the debindering process St5. The liquid phase component 511 mainly contains second crystal particles 42, and also contains SiO2 and aluminum, among other things.

[0076] Figure 11(B) is a cross-sectional view illustrating the internal electrode pattern 52 and dielectric pattern 53 after the first step of the firing process St7. In the first step, firing is performed at 1000°C for 15 to 60 minutes. As a result, the organic matter in the metal paste volatilizes, and the nickel particles 520 in the internal electrode pattern 52 combine to form metallic nickel. Also, the first crystal particles 41 in the dielectric pattern 53 neck together, forming new gaps 44 between the first crystal particles 41. Liquid phase components 512, mainly composed of second crystal particles 42, enter these gaps 44. Liquid phase components 512 are the liquid phase components 511 that have changed after the first step, and exist as glass containing, for example, 70% titanium. When the firing temperature exceeds the softening point of the glass, the liquid phase components 512 soften and enter the voids 44. Note that the liquid phase components 512 also contain titanium and rare earth elements in addition to the second crystal particles 42. As the temperature rises, the liquid phase component 512 penetrates into the voids 44, aggregates through the grain boundaries, and segregates.

[0077] Figure 11(C) is a cross-sectional view illustrating the dielectric layer 11 after the second step of the firing process St7. In the second step, the oxygen partial pressure 10 -12 ~10 -9The laminate is fired at 1200-1300°C for 2-6 hours in a reducing atmosphere of atm. At this time, the liquid phase component 512 remains in the voids 44 between the first crystal particles 41, and second crystal particles 42 precipitate from the liquid phase component 512, filling the voids 44. As a result, the dielectric layer 11 is densified by the phase of the precipitated second crystal particles 42. This improves the strength of the dielectric layer 11, resulting in good resistance to electrostriction. In addition, the electrical resistance of the dielectric layer 11 is also improved by filling the voids 44 with second crystal particles 42.

[0078] Figure 11(D) is a cross-sectional view illustrating a dielectric layer 11 in which the second crystal grains 42 are absent. When a voltage is applied between the internal electrode layers 12, a large current flows through the low-resistance voids 44 compared to the areas where the first crystal grains 41 are present. Therefore, the resistance of the dielectric layer 11 is lower compared to the case where the second crystal grains 42 are present. [Examples]

[0079] Next, an embodiment of the multilayer ceramic capacitor 100 will be described.

[0080] (Examples 1-4 and Comparative Example 1) Barium titanate powder with an average particle size of 150 nm was prepared. To 100 moles of barium titanate powder, 0.75 moles of Gd2O3, 0.5 moles of TiO2, 1.5 moles of MnCO3, and 1.0 moles of SiO2 were added to obtain a dielectric ceramic composition. The Ba / Ti elemental ratio was 0.995.

[0081] A dielectric slurry was prepared by mixing a dielectric ceramic composition with ethanol, toluene, and PVB (polyvinyl butyral) resin. This slurry was molded into a ceramic green sheet using a die coater. After drying the ceramic green sheet, nickel paste was printed to form the internal electrode pattern. The resulting laminated units were stacked and pressed together with thick layers of ceramic green sheets without internal electrode patterns on the top and bottom, and then cut into small pieces. Subsequently, Ni paste was dipped into two end faces as a metal paste for the external electrodes, and the binder was removed in nitrogen gas. The small pieces were then fired and sintered in a reducing atmosphere controlled to ensure that the partial pressure of oxygen did not oxidize the nickel, thereby producing a multilayer ceramic capacitor 100.

[0082] The firing process was carried out in two steps, the first and second steps described above. In the first step, the firing temperature was raised to 1000°C, and in the second step, the firing temperature was raised from 1000°C to 1300°C. For each of Examples 1-4 and Comparative Example 1, the firing temperature was maintained at 1000°C for a predetermined time. This time is referred to as the "1000°C hold time".

[0083] The 1000°C holding time for Comparative Example 1 was 0 minutes. The 1000°C holding time for Example 1 was 15 minutes. The 1000°C holding time for Example 2 was 30 minutes. The 1000°C holding time for Example 3 was 45 minutes. The 1000°C holding time for Example 4 was 60 minutes.

[0084] (Comparative Examples 2-8) Barium titanate powder with an average particle size of 150 nm was prepared and mixed with ethanol, toluene, and PVB (polyvinyl butyral) resin to create a dielectric slurry. Unlike Examples 1-4 and Comparative Example 1, no additive compounds were added to the barium titanate powder. A multilayer ceramic capacitor 100 was fabricated from this slurry using the same method as in Examples 1-4 and Comparative Example 1.

[0085] During firing, the firing temperature was increased from 1000°C to 1300°C. The holding time at 1000°C for Comparative Example 2 was 0 minutes. The holding time at 1000°C for Comparative Example 3 was 15 minutes. The holding time at 1000°C for Comparative Example 4 was 30 minutes. The holding time at 1000°C for Comparative Example 5 was 45 minutes. The holding time at 1000°C for Comparative Example 6 was 60 minutes.

[0086] (Reliability testing) For Examples 1-4 and Comparative Examples 1-6, a HALT test was performed under test conditions of 125°C-15V as a reliability test to measure the lifespan of the multilayer ceramic capacitor 100.

[0087] [Table 1]

[0088] In Table 1, "Presence or Absence of Composite Oxide" indicates whether or not the second crystal grains 42 are present in the dielectric layer 11 of the multilayer ceramic capacitor 100. "1000°C Holding Time" indicates the holding time at 1000°C during the second step of firing, as described above. "Layer Thickness Occupancy" indicates the ratio (%) of the size Hd of the second crystal grains 42 to the thickness d of the dielectric layer 11 shown in Figure 4. "Lifetime" indicates the lifetime of the multilayer ceramic capacitor 100. "Judgment" indicates "○" (OK) if the HALT test result is 750 minutes or more, and "×" (NG) if the HALT test result is less than 450 minutes.

[0089] The film thickness occupancy rate was measured by cutting the multilayer ceramic capacitor 100 in the stacking direction and observing the cut surface with an electron microscope. The film thickness occupancy rate for Comparative Example 1 was 50%, for Example 1 it was 80%, for Example 2 it was 90%, and for Examples 3 and 4 it was 100%. The film thickness occupancy rate for Comparative Examples 2 to 6 was 0%. Thus, the longer the 1000°C holding time, the higher the layer thickness occupancy rate.

[0090] The results of the HALT test are as follows: The lifespan of Comparative Example 1 was 401 minutes, the lifespan of Example 1 was 850 minutes, the lifespan of Example 2 was 862 minutes, the lifespan of Example 3 was 882 minutes, and the lifespan of Example 4 was 885 minutes. In addition, the lifespan of Comparative Example 2 was 392 minutes, the lifespan of Comparative Example 3 was 400 minutes, the lifespan of Comparative Example 4 was 380 minutes, the lifespan of Comparative Example 5 was 386 minutes, and the lifespan of Comparative Example 6 was 412 minutes. As a result, Examples 1-4 were judged as "○" and Comparative Examples 1-6 were judged as "×".

[0091] Thus, the lifespan of Examples 1 to 4 exceeded that of Comparative Examples 1 to 6. This is because, as mentioned above, the durability and insulation properties of the dielectric layer 11 were improved due to the layer thickness occupancy rate of 80% or more in Examples 1 to 4. On the other hand, since the film thickness occupancy rate of Comparative Example 1 was 50%, the voids 44 in the dielectric layer 11 could not be sufficiently filled by the second crystal grains 42, and the durability and insulation properties of the dielectric layer 11 were not improved. Similarly, since the film thickness occupancy rate of Comparative Examples 2 to 6 was 0%, the durability and insulation properties of the dielectric layer 11 were not improved.

[0092] In this specification, a multilayer ceramic capacitor 100 is given as an example of a multilayer ceramic electronic component, but the multilayer ceramic electronic components to which the above configuration is applied are not limited to this. Other examples of multilayer ceramic electronic components include multilayer ceramic varistors and multilayer ceramic thermistors.

[0093] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0094] 11 Dielectric layer 12 Internal electrode layer 20a,20b external electrode 41. First crystal grain 42 Second Crystal Particle 44 void 100 Multilayer Ceramic Capacitors

Claims

1. Multiple internal electrode layers facing each other in a predetermined direction, A plurality of dielectric layers are stacked between each of the plurality of internal electrode layers, The internal electrode layer has an external electrode that is electrically connected to it, The dielectric layer is of the general formula ABO ３ It comprises first crystalline particles of a main component ceramic having a perovskite structure represented by and second crystalline particles mainly composed of a barium titanate-based composite oxide in which the elemental ratio of barium to titanium is 0.70 or less. The second crystal grain is in contact with at least one of the pair of internal electrode layers that sandwich the dielectric layer. Multilayer ceramic electronic components.

2. The second crystal grain has a size of 80% or more of the thickness of the cross-section of the dielectric layer along the predetermined direction. The multilayer ceramic electronic component according to claim 1.

3. The second crystal particles are BaTi ２ O ５ 、BaTi ４ O ９ 、BaTi ５ O １１ 、BaTi ６ O １３ 、Ba ４ Ti １１ O ２６ 、Ba ４ Ti １２ O ２７ 、Ba ４ Ti １３ O ３０ 、and Ba ６ Ti １７ O ４０ and are at least one selected from The multilayer ceramic electronic component according to claim 1.

4. The first crystal grain is barium titanate. The multilayer ceramic electronic component according to claim 1.

5. The second crystal grain is in contact with both of the pair of internal electrode layers that sandwich the dielectric layer. A multilayer ceramic electronic component according to any one of claims 1 to 4.

6. In a direction substantially perpendicular to the predetermined direction, the width of the contact region of the second crystal particles with respect to the internal electrode layer is 50 to 500 μm. A multilayer ceramic electronic component according to any one of claims 1 to 4.

7. The thickness of the cross-section of the dielectric layer is 0.4 μm or less. A multilayer ceramic electronic component according to any one of claims 1 to 4.

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