WO2024135566A1 - 積層セラミックコンデンサ - Google Patents

積層セラミックコンデンサ Download PDF

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Publication number
WO2024135566A1
WO2024135566A1 PCT/JP2023/045072 JP2023045072W WO2024135566A1 WO 2024135566 A1 WO2024135566 A1 WO 2024135566A1 JP 2023045072 W JP2023045072 W JP 2023045072W WO 2024135566 A1 WO2024135566 A1 WO 2024135566A1
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Prior art keywords
rare earth
ratio
concentration region
thickness direction
less
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PCT/JP2023/045072
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English (en)
French (fr)
Japanese (ja)
Inventor
直人 衡田
博之 和田
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Murata Manufacturing Co Ltd
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Murata Manufacturing Co Ltd
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Priority to CN202380086829.5A priority Critical patent/CN120303756A/zh
Priority to JP2024565882A priority patent/JPWO2024135566A1/ja
Publication of WO2024135566A1 publication Critical patent/WO2024135566A1/ja
Priority to US19/171,464 priority patent/US20250259790A1/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G4/00—Fixed capacitors; Processes of their manufacture
    • H01G4/002—Details
    • H01G4/005—Electrodes
    • H01G4/008—Selection of materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B18/00—Layered products essentially comprising ceramics, e.g. refractory products
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/46—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
    • C04B35/462—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates
    • C04B35/465—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates
    • C04B35/468—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates based on barium titanates
    • C04B35/4682—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates based on barium titanates based on BaTiO3 perovskite phase
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Definitions

  • the present invention relates to a multilayer ceramic capacitor.
  • Multilayer ceramic capacitors have a structure in which dielectric layers and internal electrode layers are alternately laminated, and due to the thinned high-permittivity dielectric layers, they have a large capacitance despite their small size.
  • those using barium titanate (BaTiO 3 )-based compounds for the dielectric layers and nickel (Ni) or other base metals for the internal electrode layers are widely used because they are inexpensive and exhibit high characteristics.
  • Patent Document 1 discloses a dielectric ceramic composition that contains barium titanate, at least one selected from europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, and ytterbium oxide, barium zirconate, magnesium oxide, and manganese oxide, and contains a main component expressed by a specific composition formula (claim 1 of Patent Document 1).
  • Patent Document 1 also describes that the ceramic composition is applied to the dielectric ceramic layer of a multilayer ceramic capacitor whose internal electrodes are composed of nickel or a nickel alloy, and that when used at high electric field strength, the product of insulation resistance and capacitance (CR product) is high, dielectric strength is high, and weather resistance performance such as high temperature load and moisture load is excellent (claims 4 and [0007] of Patent Document 1).
  • the inventors conducted extensive research in light of these problems. As a result, they discovered that by controlling the region containing rare earth elements in the dielectric ceramic layer, it is possible to significantly improve the reliability of multilayer ceramic capacitors.
  • the present invention was completed based on these findings, and its objective is to provide a highly reliable multilayer ceramic capacitor.
  • the present invention encompasses the following aspects.
  • the expression "-" includes both ends of the expression.
  • X-Y is synonymous with "X or more and Y or less.”
  • a piezoelectric vibrator has a first main surface and a second main surface opposed to each other in a thickness direction, a first side surface and a second side surface opposed to each other in a width direction, and a first end surface and a second end surface opposed to each other in a length direction, a multilayer ceramic capacitor comprising: a body portion including a plurality of dielectric ceramic layers and a plurality of internal electrode layers stacked in the thickness direction; and a pair of external electrodes provided on the first end face and the second end face, respectively, and electrically connected to the plurality of internal electrode layers,
  • the dielectric ceramic layer contains, as a main component, crystal grains constituted of a perovskite-type composite oxide containing barium (Ba) and titanium (Ti), and further contains a rare earth element (Re); the dielectric ceramic layer includes a rare earth high concentration region having a molar ratio of rare earth element (Re) to titanium (Ti) (Re/Ti ratio) of 0.04 or more
  • the present invention provides a highly reliable multilayer ceramic capacitor.
  • FIG. 2 is a perspective view showing the outer shape of the multilayer ceramic capacitor.
  • 1 is a cross-sectional view that typically illustrates an internal structure of a multilayer ceramic capacitor.
  • 1 is a cross-sectional view that typically illustrates an internal structure of a multilayer ceramic capacitor.
  • 1 is a diagram for explaining a thickness direction line segment ratio of a rare earth high concentration region and its CV value.
  • 1 is a schematic cross-sectional view showing a microstructure of a multilayer ceramic capacitor.
  • present embodiment A specific embodiment of the present invention (hereinafter referred to as the "present embodiment") will be described. Note that the present invention is not limited to the following embodiment, and various modifications are possible without departing from the gist of the present invention.
  • the multilayer ceramic capacitor of this embodiment has a first main surface and a second main surface facing each other in the thickness direction, a first side surface and a second side surface facing each other in the width direction, and a first end surface and a second end surface facing each other in the length direction, and includes a body portion including a plurality of dielectric ceramic layers and a plurality of internal electrode layers stacked in the thickness direction, and a pair of external electrodes provided on each of the first end surface and the second end surface and electrically connected to the plurality of internal electrode layers.
  • the dielectric ceramic layer contains, as a main component, crystal grains composed of a perovskite-type complex oxide containing barium (Ba) and titanium (Ti), and further contains a rare earth element (Re).
  • the dielectric ceramic layer includes, in a cross section including the thickness direction, a rare earth high concentration region having a molar ratio (Re/Ti ratio) of the rare earth element (Re) to titanium (Ti) of 0.04 or more and 0.30 or less at an area ratio of 50% or more.
  • the CV value of the thickness direction line segment ratio of the rare earth high concentration region is 25% or less.
  • FIG. 1 is a perspective view showing the external shape of a multilayer ceramic capacitor.
  • Figures 2 and 3 are cross-sectional views showing the inside of the multilayer ceramic capacitor.
  • the multilayer ceramic capacitor (100) comprises a body portion (6) including a plurality of laminated dielectric ceramic layers (2) and a plurality of internal electrode layers (4), and a pair of external electrodes (8a, 8b) provided on both end faces (14a, 14b) of the body portion (6).
  • the multilayer ceramic capacitor (100) and the body portion (6) have an approximately rectangular parallelepiped shape.
  • An approximately rectangular parallelepiped includes not only a rectangular parallelepiped but also a rectangular parallelepiped with rounded corners and/or edges.
  • the multilayer ceramic capacitor (100) and the element part (6) have a first main surface (10a) and a second main surface (10b) facing the thickness direction T, a first side surface (12a) and a second side surface (12b) facing the width direction W, and a first end surface (14a) and a second end surface (14b) facing the length direction L.
  • the thickness direction T refers to the direction in which the multiple dielectric ceramic layers (2) and the multiple internal electrode layers (4) are stacked.
  • the length direction L refers to a direction perpendicular to the thickness direction T and perpendicular to the end surfaces (14a, 14b) on which the external electrodes (8a, 8b) are provided.
  • the width direction W is a direction perpendicular to the thickness direction T and the length direction L.
  • a surface including the thickness direction T and the width direction W is defined as a WT surface
  • a surface including the width direction W and the length direction L is defined as an LW surface
  • a surface including the length direction L and the thickness direction T is defined as an LT surface.
  • the external electrodes (8a, 8b) are composed of a first external electrode (8a) provided on the first end face (14a) and a second external electrode (8b) provided on the second end face (14b).
  • the first external electrode (8a) may extend not only to the first end face (14a) but also to parts of the first main face (10a), second main face (10b), first side face (12a) and second side face (12b).
  • the second external electrode (8b) may extend not only to the second end face (14b) but also to parts of the first main face (10a), second main face (10b), first side face (12a) and second side face (12b).
  • the first external electrode (8a) and the second external electrode (8b) are not in contact with each other and are electrically separated from each other.
  • the internal electrode layer (4) is composed of a plurality of first internal electrode layers (4a) and a plurality of second internal electrode layers (4b).
  • the plurality of first internal electrode layers (4a) extend to the first end face (14a) and are electrically connected to the first external electrode (8a) at that point.
  • the plurality of second internal electrode layers (4b) extend to the second end face (14b) and are electrically connected to the second external electrode (8b) at that point.
  • the first internal electrode layer (4a) and the second internal electrode layer (4b) which face each other across the dielectric ceramic layer (2), are not electrically connected. Therefore, when a voltage is applied between the first internal electrode layer (4a) and the second internal electrode layer (4b) via the external electrodes (8a, 8b), electric charges are accumulated. The accumulated electric charges generate electrostatic capacitance, which allows the device to function as a capacitive element.
  • the dimensions of the multilayer ceramic capacitor (100) are not particularly limited. However, it is preferable that the length direction L dimension is 0.4 mm or more and 5.7 mm or less, the width direction W dimension is 0.2 mm or more and 5.0 mm or less, and the stacking direction T dimension is 0.125 mm or more and 5.0 mm or less.
  • the dielectric ceramic layer is made of ceramic.
  • the dielectric ceramic layer contains, as a main component, crystal grains made of a perovskite-type complex oxide containing barium (Ba) and titanium (Ti). That is, the main crystal grains are made of a perovskite-type complex oxide.
  • the main crystal grains are made of a barium titanate (BaTiO 3 )-based compound. Therefore, it can be said that the dielectric ceramic layer is made of a sintered body of a BaTiO 3 -based compound.
  • BaTiO 3 is a perovskite-type oxide represented by the general formula: ABO 3.
  • BaTiO 3 is a ferroelectric that exhibits a tetragonal crystal structure at room temperature and has a high dielectric constant. Therefore, by using a BaTiO 3 -based compound as the main component, the dielectric constant of the dielectric ceramic can be increased, and the capacitance of the capacitor can be increased.
  • the main component refers to the component that is contained in the ceramic at the highest ratio. The content of the main component may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more.
  • the barium titanate (BaTiO 3 ) based compound is not particularly limited as long as it is a perovskite type composite oxide mainly containing barium (Ba) and titanium (Ti). That is, this compound may be BaTiO 3 , or a part of Ba and/or Ti contained in BaTiO 3 may be replaced with other elements. Specifically, a part of barium (Ba) may be replaced with other elements such as strontium (Sr) and calcium (Ca), and a part of titanium (Ti) may be replaced with other elements such as zirconium (Zr) and hafnium (Hf).
  • the ratio of A-site elements (Ba, Sr, Ca, etc.) and B-site elements (Ti, Zr, Hf, etc.) of the BaTiO 3 based compound is not strictly limited to 1:1. As long as the perovskite type crystal structure is maintained, a deviation in the ratio of A-site elements and B-site elements is allowed.
  • the dielectric ceramic layer further contains a rare earth element (Re) in addition to barium (Ba) and titanium (Ti).
  • the rare earth element (Re) is a general term for elements constituting a group consisting of scandium (Sc) with atomic number 21, yttrium (Y) with atomic number 39, and lanthanum (La) with atomic number 57 to lutetium (Lu) with atomic number 71 in the periodic table.
  • the dielectric ceramic layer may contain one type of rare earth element, or may contain a combination of multiple types of rare earth elements.
  • the rare earth element may be contained only in the BaTiO 3 -based compound that is the main crystal grain, or may be contained together with the main crystal grain at the grain boundary or triple point. When contained in the main crystal grain, it may occupy the Ba site (A site) of the BaTiO 3 -based compound, may occupy the Ti site (B site), or may occupy both sites.
  • the reliability of the multilayer ceramic capacitor and various other characteristics such as the temperature characteristic of the dielectric constant can be improved.
  • the BaTiO 3 -based compound which is the main component, may contain many oxygen vacancies generated during the firing process. These oxygen vacancies tend to reduce the insulation resistance when accompanied by electronic compensation, and also tend to move under an electric field, causing a decrease in the insulation resistance over time.
  • a rare earth element When a rare earth element is added to the dielectric ceramic layer, it tends to be solid-dissolved in the Ba site or Ti site of the BaTiO 3 -based compound. The solid-dissolved rare earth element acts as a donor or acceptor, preventing the movement of oxygen vacancies or suppressing the generation of conduction electrons.
  • the BaTiO 3 -based compound has a large temperature dependency of the dielectric constant near the Curie temperature Tc. By solid-dissolving the rare earth element, it is possible to make the temperature change of the dielectric constant flatter in a wide range including the Curie temperature Tc.
  • the type of rare earth element (Re) contained in the dielectric ceramic layer is not particularly limited. However, it is preferable to include at least one selected from the group consisting of yttrium (Y), 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), and lutetium (Lu), and it is particularly preferable to include dysprosium (Dy).
  • Y yttrium
  • La lanthanum
  • Ce cerium
  • Pr praseodymium
  • Nd neodymium
  • Sm samarium
  • Eu europium
  • Gd gadolinium
  • Tb terbium
  • Dy dyspros
  • Dy is an element located near the middle of the lanthanoid group in the periodic table, and its ion radius is also about medium. Therefore, it can be dissolved in both the Ba site (A site) and the Ti site (B site) of the BaTiO 3 -based compound, which is effective in improving reliability.
  • the dielectric ceramic layer may contain only Dy as a rare earth element, or may contain other rare earth elements in addition to Dy.
  • the dielectric ceramic layer preferably contains 0.1 to 35.0 moles of rare earth element (Re) per 100 moles of titanium (Ti), more preferably 0.5 to 30.0 moles, and even more preferably 3.5 to 25.0 moles. Note that these mole numbers are the mole numbers of the raw material.
  • the dielectric ceramic layer may contain additive components other than rare earth elements (Re).
  • additive components include manganese (Mn), magnesium (Mg), silicon (Si), aluminum (Al), vanadium (V), lithium (Li), boron (B), copper (Cu), and/or molybdenum (Mo).
  • Mn manganese
  • Mg magnesium
  • Si silicon
  • Al aluminum
  • V vanadium
  • V lithium
  • B boron
  • Cu copper
  • Mo molybdenum
  • the form in which the additive components are present is not limited. They may be present in any of the main crystal grains, grain boundaries, and triple points.
  • the thickness of the dielectric ceramic layer is 0.5 ⁇ m or more and 7.0 ⁇ m or less.
  • the thickness of the dielectric ceramic layer 0.5 ⁇ m or more, deterioration of the insulation characteristics can be prevented, leading to improved reliability.
  • the thickness 7.0 ⁇ m or less the dielectric ceramic layer is made thinner, making it possible to improve the capacity.
  • the number of layers of the dielectric ceramic layer is preferably 50 layers or more and 1000 layers or less.
  • the dielectric ceramic layer contains a rare earth high concentration region with an area ratio of 50% or more in a cross section including the thickness direction.
  • the thickness direction is the stacking direction of the dielectric ceramic layers and internal electrode layers. Therefore, a cross section including the thickness direction is a plane passing through the inside of the multilayer ceramic capacitor, the perpendicular of which is perpendicular to the thickness direction, for example, the LT plane or WT plane.
  • the rare earth high concentration region is a region in which the molar ratio of rare earth element (Re) to titanium (Ti) (Re/Ti ratio) is 0.04 or more and 0.30 or less.
  • the ratio of the area occupied by the high rare earth concentration region to the total area of the ultra-high rare earth concentration region, the high rare earth concentration region, and the low rare earth concentration region is 50% or more.
  • a high rare earth concentration means that the average distance between the positions where rare earths are present is shorter.
  • Rare earth elements have the effect of preventing the movement of oxygen vacancies.
  • the effect of suppressing the movement of oxygen vacancies is increased, resulting in improved reliability. From the viewpoint of improving reliability, the higher the area ratio of the rare earth high concentration region, the more preferable it is.
  • the area ratio may be 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, 95% or more, or it may be 100%. However, if the area ratio is excessively high, the dielectric constant may decrease. From the viewpoint of improving the dielectric constant, the area ratio may be 95% or less, 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, 65% or less, or 60% or less.
  • the CV value of the Re/Ti ratio in the rare earth high concentration region is 35% or less.
  • the CV value is an index of variation. The smaller the CV value of the Re/Ti ratio, the smaller the variation in the Re/Ti ratio for each location in the rare earth high concentration region.
  • the CV value of the Re/Ti ratio is 35% or less, the variation in reliability can be suppressed. The details of the reason are unknown, but it is speculated as follows. Even if the average Re/Ti ratio is the same, a large CV value may mean that there is a region where the Re/Ti ratio is extremely lower than the average, or that the total size of the low Re/Ti ratio regions that are distributed is large.
  • the low Re/Ti ratio region may reduce reliability. Therefore, if the CV value of the Re/Ti ratio is small, the reliability variation can be reduced in the sense that the reliability is less likely to decrease. From the viewpoint of suppressing the reliability variation, the smaller the CV value, the more preferable it is.
  • the CV value may be 30% or less, 25% or less, 20% or less, 15% or less, or 10% or less.
  • the CV value of the Re/Ti ratio can be calculated by dividing the rare earth high concentration region into minute regions, measuring the Re/Ti ratio of each region using a method such as transmission electron microscope (TEM)-energy dispersive X-ray spectroscopy (EDX), and using the average value and standard deviation ⁇ according to the following formula (1).
  • TEM transmission electron microscope
  • EDX energy dispersive X-ray spectroscopy
  • the CV value of the thickness direction line ratio of the rare earth high concentration region is 25% or less.
  • the thickness direction line ratio of the rare earth high concentration region refers to the ratio of the area occupied by the rare earth high concentration region on a line facing the thickness direction inside the dielectric ceramic layer. Therefore, the CV value of the thickness direction line ratio is an index of the variation in distribution of the rare earth high concentration region and other regions inside the dielectric ceramic layer.
  • Figures 4(a) and (b) show schematic diagrams of low rare earth concentration regions scattered among high rare earth concentration regions in the cross section of a dielectric ceramic layer.
  • the ratio of the area occupied by the high rare earth concentration regions (X in the figure) thickness direction line segment ratio of the high rare earth concentration regions
  • the CV value of the thickness direction line segment ratio becomes large.
  • the value of the thickness direction line segment ratio is almost constant regardless of the line. Therefore, the CV value of the thickness direction line segment ratio becomes small.
  • a small CV value of the thickness direction line ratio means that the rare earth high concentration region and other regions are more uniformly distributed within the ceramic layer. If these distributions become more uniform, local electric field concentration is alleviated, which leads to further improvement in reliability. From the viewpoint of improving reliability and reducing variation, it is more preferable that the CV value of the thickness direction line ratio of the rare earth high concentration region is 15% or less.
  • the CV value of the thickness direction line segment ratio of the rare earth high concentration region is obtained as follows. First, a line parallel to the thickness direction is virtually drawn in a cross section including the thickness direction. Next, the length Lc of the part where this line crosses the dielectric ceramic layer is obtained. Lc can also be said to be the length of the line segment on the line partitioned by the dielectric ceramic layer. In addition, the total length Lhigh -Re of the part where this line crosses the rare earth high concentration region is obtained. Lhigh-Re can also be said to be the total length of the line segment on the line partitioned by the rare earth high concentration region.
  • the ratio of Lhigh -Re to Lc ( Lhigh-Re / Lc ) is calculated as the thickness direction line segment ratio of the rare earth high concentration region.
  • the thickness direction line segment ratio is calculated for a plurality of (e.g., 256) lines that are spaced apart, and the CV value is calculated according to the following formula (2) using the average value and standard deviation ⁇ .
  • the reliability and variation of multilayer ceramic capacitors can be evaluated by examining their high-temperature load life.
  • High-temperature load life can be evaluated by subjecting a capacitor to a high-temperature load test and using the resulting mean time to failure (MTTF) and B1 life. Specifically, high-temperature load tests are performed on multiple capacitors, and the time at which the insulation resistance drops drastically is defined as the failure time.
  • a Weibull analysis is performed on the failure time of each capacitor to determine the failure time at which the cumulative failure rate is 63.2% and the shape parameter m, from which the mean time to failure (MTTF) is determined.
  • the failure time at which the cumulative failure rate is 1% is defined as the B1 life.
  • the longer the MTTF the higher the reliability can be determined.
  • the larger the B1 life/MTTF the smaller the variation in reliability can be determined.
  • the distribution of the rare earth high concentration regions contained in the dielectric ceramic layer is not particularly limited.
  • the dielectric ceramic layer may have a sea-island structure in cross section, with the rare earth high concentration regions and other regions constituting a sea portion and an island portion, respectively.
  • the rare earth high concentration regions may have other regions, such as rare earth low concentration regions, dispersedly arranged within the rare earth high concentration regions.
  • the rare earth high concentration regions and other regions may extend in layers, and each layer of the dielectric ceramic layer may have a laminated structure of the layered rare earth high concentration regions and other regions.
  • the dielectric ceramic layer includes a low rare earth concentration region, and the low rare earth concentration region is composed of a plurality of sub-regions surrounded by a high concentration region.
  • the average value of the circle equivalent diameter of each of the sub-regions in the cross section is 130 nm or more. That is, it is preferable that the dielectric ceramic layer has a sea-island structure in its cross section, the high rare earth concentration region constitutes the sea portion, the low rare earth concentration region constitutes the island portion, and the average circle equivalent diameter of the island portion is a predetermined value or more.
  • the Curie temperature Tc of the high rare earth concentration region may be lower than room temperature depending on the Re/Ti ratio, and in this case, the dielectric constant will decrease.
  • the dielectric constant is accompanied by a size effect, a higher dielectric constant can be obtained by increasing the average circle equivalent diameter of the rare earth low concentration region to a predetermined value or more.
  • the average circle equivalent diameter of the sub-regions may be 140 nm or more, 150 nm or more, 160 nm or more, 170 nm or more, 180 nm or more, 190 nm or more, 200 nm or more, 210 nm or more, or 220 nm or more.
  • the size of the rare earth low concentration region is suppressed to a certain size.
  • the average circle equivalent diameter of the sub-regions may be 300 nm or less, 290 nm or less, 280 nm or less, 270 nm or less, 260 nm or less, 250 nm or less, 240 nm or less, 230 nm or less, 220 nm or less, 210 nm or less, 200 nm or less, 190 nm or less, 180 nm or less, 170 nm or less, or 160 nm or less.
  • the average equivalent circle diameter (D50) is the diameter of a circle that has the same area as the cumulative 50% area.
  • the cumulative 50% area is the area of a sub-area when the total area of each sub-area is taken as 100%, and the areas of the sub-areas are added up in ascending order against that total area to reach a cumulative 50%.
  • the average equivalent circle diameter can be calculated using the cumulative 50% area according to the following formula (3).
  • the average circularity (average circularity) of each of the sub-regions constituting the rare earth low concentration region is 0.70 or more.
  • the circularity is an index that indicates the complexity of the region shape, and is 1 for a perfect circle, and the more complex the shape, the smaller the circularity.
  • the average circularity of the sub-regions may be 0.75 or more, 0.80 or more, or 0.85 or more.
  • the average circularity can be calculated by using the area and perimeter of each sub-region determined by TEM observation or the like to calculate the circularity according to the following formula (4), and then calculating the average value.
  • the internal electrode layer includes a conductive metal.
  • a conductive metal known electrode materials such as nickel (Ni), copper (Cu), silver (Ag), palladium (Pd), and alloys thereof may be used.
  • the internal electrode layer may also include other components besides the conductive metal.
  • ceramic components acting as co-materials may be mentioned.
  • BaTiO3 -based compounds included in the dielectric ceramic layer may be mentioned.
  • the thickness of the internal electrode layer is 0.3 ⁇ m or more and 0.7 ⁇ m or less.
  • the thickness of the internal electrode layer 0.3 ⁇ m or more, defects such as electrode discontinuities are suppressed.
  • the thickness of the internal electrode layer 0.7 ⁇ m or less it is possible to suppress a decrease in the proportion of the electrically functional dielectric ceramic layer in the capacitor, and the resulting decrease in capacity.
  • a known configuration can be adopted as the external electrode.
  • a laminate structure consisting of an underlayer, a first plating layer, and a second plating layer can be used from the end face side of the multilayer ceramic capacitor.
  • the underlayer contains metals such as nickel (Ni) and copper (Cu).
  • ceramic powder may be included as a common material.
  • the first plating layer is, for example, a nickel (Ni) plating layer.
  • the second plating layer is, for example, a tin (Sn) plating layer.
  • a conductive resin layer may be provided between the underlayer and the first plating layer.
  • the conductive resin layer is a layer containing conductive metal particles such as copper (Cu), silver (Ag), and nickel (Ni), and a resin.
  • the external electrode is not limited in its form as long as it is electrically connected to the internal electrode layer and functions as an external input/output terminal.
  • An exemplary manufacturing method includes the following steps: a step of preparing a green sheet containing at least barium (Ba), titanium (Ti), and a rare earth element (Re) (green sheet preparation step), a step of applying a conductive paste to the surface of the green sheet to obtain a green sheet with an internal electrode pattern (electrode pattern formation step), a step of stacking and pressing a plurality of green sheets to obtain a laminated block (stacking step), a step of cutting the obtained laminated block to obtain a laminated chip (cutting step), a step of performing a binder removal process and a firing process on the obtained laminated chip to obtain an element part (firing step), and a step of forming an external electrode on the obtained element part (external electrode formation step). Details of each step are described below.
  • Green sheet production process a green sheet containing at least barium (Ba), titanium (Ti), and rare earth elements (Re) is prepared.
  • the green sheet is a precursor of the dielectric ceramic layer of the capacitor, and contains the main component raw material and the additive raw material of the dielectric ceramic layer.
  • the preparation of the green sheet may be performed by a known method, and is not particularly limited.
  • the main component raw material is mixed with the additive raw material to prepare a dielectric raw material, and a binder and a solvent are added and mixed to the obtained dielectric raw material to form a slurry, and the obtained slurry is molded into a green sheet.
  • a powder of a BaTiO 3 -based compound is used as the main component raw material.
  • the BaTiO 3 -based compound may be synthesized by using a known ceramic raw material such as an oxide, carbonate, hydroxide, nitrate, organic acid salt, alkoxide, and/or chelate compound, and by using a known ceramic synthesis method such as a solid-phase reaction method, a hydrothermal synthesis method, or an alkoxide method.
  • the additive raw material includes at least a rare earth element (Re) raw material.
  • Re raw material a known ceramic raw material such as an oxide, carbonate, hydroxide, nitrate, organic acid salt, alkoxide, and/or chelate compound of Re may be used.
  • the additive raw material may include raw materials of other additive components such as Mn, Mg, Si, Al, V, Li, B, Cu, and/or Mo. Furthermore, in order to adjust the composition of the BaTiO 3 -based compound, which is the main component, a Ba raw material or a Ti raw material such as barium carbonate (BaCO 3 ) or titanium oxide (TiO 2 ) may be added to the additive raw material.
  • a Ba raw material or a Ti raw material such as barium carbonate (BaCO 3 ) or titanium oxide (TiO 2 ) may be added to the additive raw material.
  • the raw materials may be mixed by a known method, for example, by wet mixing and grinding the weighed main component raw materials, additive raw materials, and water together with grinding media using a ball mill. When wet mixing is performed, the resulting mixture may be dried. If necessary, the dielectric raw materials obtained after drying may be calcined.
  • the slurry may also be made by a known method, and an organic binder and an organic solvent may be mixed into the dielectric raw materials.
  • the organic binder a known binder such as a polyvinyl butyral-based binder may be used.
  • the organic solvent a known solvent such as toluene or ethanol may be used.
  • an additive such as a plasticizer may be added to the slurry.
  • the green sheet may be formed by a known method such as a doctor blade method or a lip method.
  • a conductive paste is applied to the surface of the green sheet to obtain a green sheet on which an internal electrode pattern is formed.
  • the internal electrode pattern becomes an internal electrode layer after firing.
  • a conductive material such as nickel (Ni), copper (Cu), silver (Ag), palladium (Pd), and alloys containing these may be used.
  • a ceramic component acting as a co-material may also be added to the conductive paste.
  • the ceramic component the main component raw material of the dielectric ceramic layer may be used.
  • the conductive paste may be applied by a known method such as screen printing or gravure printing.
  • ⁇ Lamination process> In the lamination process, a plurality of green sheets are laminated and pressed to obtain a laminated block. Green sheets having internal electrode patterns are used as the green sheets, but green sheets having no internal electrode patterns may also be used. The lamination and pressing may be performed by a known method.
  • the obtained laminated block is cut to obtain laminated chips.
  • the cutting may be performed so that chips of a predetermined size are obtained and at least a part of the internal electrode pattern is exposed on an end face of the laminated chip.
  • the obtained laminated chip is subjected to a binder removal process and a firing process to obtain an element part.
  • the green sheet and the internal electrode pattern are co-sintered by the firing process to become a dielectric ceramic layer and an internal electrode layer, respectively.
  • the conditions of the binder removal process may be determined according to the type of organic binder contained in the green sheet and the internal electrode pattern.
  • the firing process may be performed at a temperature at which the laminated chip is sufficiently densified. For example, the firing process may be performed under conditions of holding the temperature at 1100°C or higher and 1200°C or lower for 1 hour or longer and 10 hours or shorter.
  • the firing process may be performed in an atmosphere in which the BaTiO 3 -based compound, which is the main component, is not reduced and the oxidation of the conductive metal is suppressed.
  • the firing process may be performed in an N 2 -H 2 -H 2 O air flow with an oxygen partial pressure of 1.9 x 10 -11 MPa or higher and 6.4 x 10 -9 MPa or lower.
  • an annealing process may be performed after the firing process.
  • external electrodes are formed on the obtained element body.
  • the external electrodes may be formed by a known method. For example, silver ( The conductive paste may be applied and baked to the both end surfaces of the laminated chip before firing.
  • the electrodes may be formed as a base layer, and a plating film of nickel (Ni) or tin (Sn) may be formed thereon.
  • a capacitor is fabricated.
  • BaTiO 3 powder with a BET diameter of 190 nm and a tetragonality of 1.0099 was prepared as BT-A powder.
  • the tetragonality is an index of the degree of tetragonality in a tetragonal crystal structure, and is expressed as the ratio of the c-axis length to the a-axis length in the tetragonal crystal (c/a axis ratio).
  • the tetragonality can be determined by powder X-ray diffraction (XRD).
  • the BET diameter is the average primary particle diameter calculated by converting the BET specific surface area of the BaTiO 3 powder, assuming that the particles are spherical.
  • BaTiO 3 powder with a BET diameter of 100 nm and a tetragonality of 1.007 was prepared as BT-B powder, which was then wet-pulverized to obtain finely pulverized BT-B powder.
  • the finely pulverized BT-B powder had a BET specific surface area of 50 m 2 /g.
  • Dy2O3 powder, BaCO3 powder, and TiO2 powder were separately wet-milled to obtain finely ground Dy2O3 powder, finely ground BaCO3 powder, and finely ground TiO2 powder.
  • the BET specific surface areas of the finely ground Dy2O3 powder , finely ground BaCO3 powder, and finely ground TiO2 powder were in the range of 50 m2 /g to 56 m2 /g.
  • BT-A powder, finely pulverized BT-B powder, finely pulverized Dy2O3 powder, finely pulverized BaCO3 powder, and finely pulverized TiO2 powder were mixed using a wet mill to obtain the composition shown in Table 1 below, and then dried to obtain a mixed powder.
  • Table 1 also shows the A/B ratio, which is the molar ratio of A-site elements to B-site elements in perovskite-type oxide ( ABO3 ).
  • Dy was treated as being present in both the A and B sites in the compounded composition so that the A/B ratio shown in Table 1 was obtained.
  • the resulting mixed powder was heated in air at a rate of 600°C/hour up to 1100°C and then heat-treated for 2 hours to obtain a calcined powder.
  • a polybutyral binder and a plasticizer were added to the obtained dielectric powder, and then toluene and ethyl alcohol were added.
  • the mixture was made into a slurry using a wet mill, and the slurry was molded into a green sheet.
  • the obtained green sheet had a thickness of 1.7 ⁇ m after sintering and densification.
  • a conductive paste containing nickel as its main component was screen-printed onto the surface of the resulting green sheet to form a pattern of the conductive paste layer that would become the internal electrode layer.
  • the resulting laminated block was cut into green laminated chips. The cutting was done so that the size of the manufactured laminated ceramic capacitor would be 3.2 mm x 1.6 mm.
  • the obtained green laminated chip was heat treated in a N 2 gas flow at 280° C. to burn off the binder, followed by firing for 2 hours in a N 2 —H 2 —H 2 O gas flow at 1150° C. and an oxygen partial pressure of 1.6 ⁇ 10 ⁇ 9 MPa.
  • a conductive paste mainly composed of Cu was applied to the end surface of the fired laminated chip where the internal electrode layer was pulled out, and baked at 800°C to form an external electrode, and then a Ni-Sn plating layer was formed on the surface of the external electrode.
  • the resulting multilayer ceramic capacitor had an external dimension of 3.2 mm length x 1.6 mm width x 1.6 mm thickness.
  • the number of dielectric ceramic layers sandwiched between the internal electrode layers was 200, and the thickness of each dielectric ceramic layer was 1.7 ⁇ m.
  • Rare earth oxides (Gd 2 O 3 , Y 2 O 3 , Ho 2 O 3 , and Er 2 O 3 ) corresponding to the rare earth element (Re) species shown in Table 1 below were prepared. Then, these rare earth oxides were individually wet-pulverized until the BET specific surface area was within the range of 50 m 2 /g to 60 m 2 /g to obtain finely pulverized Re oxide powder.
  • Raw material powders (BT-A powder, finely pulverized BT-B powder, finely pulverized Re oxide powder, finely pulverized BaCO 3 powder, and finely pulverized TiO 2 powder) were mixed and dried to obtain a mixed powder with the composition shown in Table 1 below.
  • the rare earth element (Re) was treated as being present in both the A site and the B site, and the raw materials were compounded so as to obtain the A/B ratio shown in Table 1 below.
  • multilayer ceramic capacitors were produced in the same manner as in Examples 1 to 19.
  • Rare earth oxides ( Dy2O3 , La2O3 , Nd2O3 , Tb4O7 , Yb2O3 , Lu2O3 , Eu2O3 , Sm2O3 , CeO2 , Pr6O11 , and Tm2O3 ) corresponding to the rare earth element ( Re ) species shown in Table 1 below were prepared. Then, these rare earth oxides were individually wet - pulverized until the BET specific surface area was within the range of 50 m2 /g to 60 m2 / g to obtain finely pulverized Re oxide powder.
  • Raw material powders (BT-A powder, finely pulverized BT-B powder, finely pulverized Re oxide powder, finely pulverized BaCO3 powder, and finely pulverized TiO2 powder) were mixed and dried to obtain a mixed powder with the composition shown in Table 1 below.
  • the amount of each of the rare earth elements other than Dy was set to 0.1 parts by mole.
  • La, Nd, Eu, Sm, Ce, and Pr were treated as being in the A site in the mixed composition.
  • Tb, Yb, Lu, and Tm were treated as being in the B site in the mixed composition.
  • Dy was treated as being in both the A site and the B site in the mixed composition. Taking these factors into consideration, the raw materials were mixed so as to obtain the A/B ratio shown in Table 1 below.
  • the multilayer ceramic capacitors were fabricated in the same manner as in Examples 1 to 19.
  • ⁇ TEM observation/EDX analysis> The dielectric ceramic layers of the multilayer ceramic capacitor were observed using a field emission transmission electron microscope (FE-TEM), and the components of the microscopic regions were analyzed using an energy dispersive X-ray spectrometer (EDX) attached to the TEM.
  • the observation samples were prepared by processing the dielectric ceramic layer into thin pieces using the FIB lift-out method. Observation and analysis were performed under the following conditions.
  • the dielectric ceramic layer within the observation field was extracted, and the area with a Re/Ti ratio of 0.04 or more and 0.30 or less was defined as a rare earth high concentration area, and its area ratio was calculated according to the following formula (5). Furthermore, the Re/Ti ratio of each pixel in the rare earth high concentration area was measured, and the CV value was calculated from the average value and standard deviation ⁇ according to the following formula (1).
  • the CV value of the thickness direction line segment ratio of the rare earth high concentration region was calculated as follows. First, a line parallel to the thickness direction was virtually drawn in a cross section including the thickness direction. Next, the number of pixels of the dielectric ceramic layer on this line was calculated as a value corresponding to the length L c of the part crossing the dielectric ceramic layer. Furthermore, the number of pixels of the rare earth high concentration region on this line was calculated as a value corresponding to the total length L high-Re of the part crossing the rare earth high concentration region. Then, as shown in the following formula (6), the ratio of L high-Re to L c (L high-Re /L c ) was calculated as the thickness direction line segment ratio of the rare earth high concentration region. The thickness direction line segment ratio was calculated for 256 lines spaced apart, and the CV value was calculated according to the following formula (2) using the average value and standard deviation ⁇ .
  • the region where the Re/Ti ratio is less than 0.04 was defined as the rare earth low concentration region, and the circle equivalent diameter and circularity of the sub-regions constituting the rare earth low concentration region were obtained.
  • the boundary between the sub-regions constituting the rare earth low concentration region and the rare earth high concentration region was drawn with a touch pen.
  • the obtained data was then analyzed using image analysis software (Mitani Shoji Co., Ltd., WINROOF) to obtain the area and perimeter of each sub-region.
  • the total area of each sub-region was set to 100 (100%), and the areas of the sub-regions were added up in ascending order to obtain the area of the sub-region when the cumulative area reached 50 (50%) (cumulative 50% area).
  • the average circle equivalent diameter (D50) was calculated according to the following formula (3).
  • the circularity of each sub-region was also obtained according to the following formula (4), and the average value was calculated.
  • the capacitance (C) of the obtained multilayer ceramic capacitor was measured using an automatic bridge type measuring device under the condition of an AC voltage of 1 V and 1 kHz.
  • the relative dielectric constant ( ⁇ r ) was calculated using the opposing electrode area of the multilayer ceramic capacitor and the number and thickness of the dielectric ceramic layers. Measurements were performed on 72 samples produced under the same conditions, and the average value of the obtained values was calculated.
  • MTTF, B1 Life A highly accelerated life test (HALT) was performed on the multilayer ceramic capacitor to determine the mean time to failure (MTTF).
  • HALT highly accelerated life test
  • a high temperature load was applied to the sample under the conditions of a temperature of 175°C and a test voltage of 50V.
  • the time when the insulation resistance became 200 k ⁇ or less was defined as the failure time.
  • the failure time was measured for 72 samples produced under the same conditions.
  • the example samples (Examples 2 to 17, Examples 19 to 28) in which the area ratio of the rare earth-rich region was 50% or more had an MTTF of 71 hours or more.
  • the samples (Examples 9, 12, 14, and 16) in which the rare earth element (Re) was Dy and the area ratio was 60% or more had a long MTTF of 122 hours or more.
  • the comparative example samples (Examples 1 and 18) in which the area ratio was less than 50% had a short MTTF of 39 hours or less.
  • the CV value of the thickness direction linear ratio of the rare earth high concentration region was 25% or less.
  • the MTTF was 79 hours or more and the B1 life/MTTF was 23% or more. From these results, it was found that by reducing the CV value of the thickness direction linear ratio of the rare earth high concentration region, reliability and its variation can be suppressed.
  • Figure 5(a) is a diagram showing the cross-sectional microstructure, with points A and C in the figure indicating the internal electrode layer, and point B indicating the dielectric ceramic layer.
  • Figure 5(b) is an element distribution diagram showing the distribution of Dy.
  • areas of high Dy concentration in the dielectric ceramic layer are displayed brightly, and areas of low concentration are displayed darkly.
  • the dielectric ceramic layer is composed of many crystal grains.
  • the Dy distribution is non-uniform, with low Dy concentration areas distributed in island-like patterns within the high Dy concentration areas. In addition, there are crystal grains containing multiple independent low rare earth concentration areas.

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WO2026070749A1 (ja) * 2024-09-30 2026-04-02 株式会社村田製作所 積層セラミックコンデンサ
WO2026070751A1 (ja) * 2024-09-30 2026-04-02 株式会社村田製作所 積層セラミックコンデンサ
WO2026070745A1 (ja) * 2024-09-30 2026-04-02 株式会社村田製作所 積層セラミックコンデンサ
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