WO2020158461A1

WO2020158461A1 - Multilayered ceramic capacitor

Info

Publication number: WO2020158461A1
Application number: PCT/JP2020/001565
Authority: WO
Inventors: 勝義山口
Original assignee: 京セラ株式会社
Priority date: 2019-01-29
Filing date: 2020-01-17
Publication date: 2020-08-06
Also published as: JP2020123619A

Abstract

This multilayered ceramic capacitor is provided with a stack in which dielectric layers and internal electrode layers are alternately stacked. The stack includes a capacitive region in which internal electrode layers adjacent to each other are opposed to each other, and a margin region disposed around the capacitive region. In the margin region, heterophase particles having a high rare-earth element concentration are present.

Description

Monolithic ceramic capacitors

The present disclosure relates to a laminated ceramic capacitor.

Conventionally, there is known a multilayer ceramic capacitor that is manufactured by alternately stacking a plurality of dielectric layers and a plurality of internal electrode layers and then firing them integrally (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 2015-88550

The monolithic ceramic capacitor of the present disclosure includes a laminated body in which dielectric layers and internal electrode layers are alternately laminated. The stacked body has a capacitance region in which the adjacent internal electrode layers face each other, and a margin region arranged around the capacitance region. Heterogeneous particles having a high rare earth element concentration are present in the margin region.

FIG. 1 is a partial cross-sectional perspective view showing a monolithic ceramic capacitor according to an embodiment of the present disclosure. FIG. 2 is a sectional view taken along the line AA of FIG. 1. FIG. 2 is a sectional view taken along line BB of FIG. 1.

FIG. 1 is a partial cross-sectional perspective view showing a monolithic ceramic capacitor 100 according to an embodiment of the present disclosure. FIG. 2 is a sectional view taken along the line AA of FIG. FIG. 3 is a sectional view taken along line BB of FIG. As shown in FIGS. 1 to 3, the laminated ceramic capacitor 100 includes a laminated body 10 in which dielectric layers 11 and internal electrode layers 12 are alternately laminated. 1 to 3, a laminated body 10 having a rectangular parallelepiped shape is shown. However, the laminated body 10 is not limited to such a shape. For example, each surface of the laminated body 10 may be a curved surface, and the laminated body 10 may have a rounded shape as a whole. The size is not particularly limited, and may be an appropriate size depending on the application. The number of stacked dielectric layers 11 and internal electrode layers 12 is not particularly limited and may be 20 or more.

The monolithic ceramic capacitor 100 may include a pair of

external electrodes

20a and 20b, which are separated from each other, on the surface of the laminated body 10. In this case, the edge of each internal electrode layer 12 in the laminated body 10 is alternately connected to the external electrode 20a and the external electrode 20b. The monolithic ceramic capacitor 100 may include two or more pairs of external electrodes.

The dielectric layer 11 is a dielectric material such as BaTiO ₃ (barium titanate)-based material, CaZrO ₃ (calcium zirconate)-based material, CaTiO ₃ (calcium titanate)-based material, SrTiO ₃ (strontium titanate)-based material, or the like as a main component. Contains. Here, the main component is a compound having the highest content concentration (mol%) in the dielectric layer 11. The main component of the dielectric layer 11 is not limited to the above dielectric material.

A high dielectric constant material may be used as the main component of the dielectric layer 11 from the viewpoint of increasing the capacitance of the multilayer ceramic capacitor 100. As an example of the high dielectric constant material, a perovskite type ferroelectric material containing the above-mentioned dielectric material may be used.

The dielectric layer 11 contains at least one rare earth element in addition to the main component. The rare earth element is selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. The dielectric layer 11 may contain two or more kinds of rare earth elements. The rare earth element may be at least one selected from the group consisting of Y, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. In this case, it is possible to increase the number ratio of different phase particles described later.

The concentration of the rare earth element in the dielectric layer 11 is not particularly limited. The rare earth element (Re) may be contained in an amount of 2.5 mol or more in terms of oxide (compositional formula Re ₂ O ₃ ) based on 100 mol of the main component. With such a configuration, it is possible to increase the number ratio of heterogeneous particles described later. The dielectric layer 11 may contain various components such as Si and Mg in addition to the above components. The composition of the dielectric layer 11 can be confirmed by inductively coupled plasma (ICP) emission spectroscopy. The thickness of the dielectric layer 11 is not particularly limited, and may be about 0.5 to 20 μm per layer.

Various metal materials can be applied to the internal electrode layer 12. For example, base metals such as Ni (nickel), Cu (copper) and Sn (tin), noble metals such as Pt (platinum), Pd (palladium), Ag (silver) and Au (gold) and alloys containing these are used. May be. The thickness of the internal electrode layer 12 may be appropriately determined depending on the application and may be about 0.1 to 3.0 μm.

As shown in FIG. 2, in the laminated body 10 in which the dielectric layers 11 and the internal electrode layers 12 are alternately laminated, a region where the adjacent internal electrode layers 12 face each other is a region where an electric capacitance is generated. Therefore, the area is referred to as “capacity area 13”. On the other hand, in the region of the stacked body 10 arranged around the capacitance region 13, almost no electric capacitance is generated. The area is referred to as "margin area 14". In the laminated body 10, the margin region 14 forms the surface of the laminated body 10.

As shown in FIG. 3, when the monolithic ceramic capacitor 100 includes the

external electrodes

20a and 20b, a 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 provided. , The capacity region 13.

The capacity area 13 and the margin area 14 may be integrally formed. That is, the structure may be such that there is no interface such as an adhesive surface between the capacitance region 13 and the margin region 14. With such a structure, it is possible to reduce the occurrence of cracks that cause dielectric breakdown in the multilayer body 10 and obtain the monolithic ceramic capacitor 100 having a high dielectric breakdown voltage (BDV). In the monolithic ceramic capacitor 100 according to the embodiment, particles having a high rare earth element concentration are present in the margin region 14. The particles are called heterophase particles. The heterophasic particles may contain two or more kinds of rare earth elements.

Here, “particles having a high concentration of rare earth elements”, that is, “heterogeneous particles” have a higher concentration of rare earth elements than main phase particles of the dielectric layer 11 (particles whose main component is the same as the dielectric layer 11). It is a particle. The main component of the different phase particles is different from the main component of the main phase particles. The concentration (mol%) of the rare earth element in the heterophase particles is, for example, 1.5 times or more the concentration (mol%) of the rare earth element in the main phase particles. In this case, the concentration of the rare earth element means the concentration (mol%) of all the contained rare earth elements, and summed.

The concentration of the rare earth element in the particles is determined by subjecting the laminate 10 to polishing treatment to expose the cross section of the laminate 10, and then using a SEM-EDX apparatus (scanning electron microscope and energy dispersion method) for the particles present in the cross section. It can be measured by performing point analysis using a type X-ray analyzer. At this time, 10 or more main phase particles are arbitrarily selected, the concentration (mol%) of the rare earth element is measured, and then the average concentration (mol%) is calculated. Particles in which the concentration (mol%) of the rare earth element is, for example, 1.5 times or more the average concentration (mol%) may be used as the heterophase particles.

When the heterogeneous particles are present in the margin area 14, the margin area 14 is densified and the hardness of the margin area 14 is increased. As a result, since the surface strength of the laminated body 10 is improved, it is possible to reduce the occurrence of cracks on the surface of the laminated body 10 due to the force acting from the outside. The force acting from the outside may be, but is not limited to, a thermal force at the time of mounting the board, a mechanical force due to the bending of the board after the board is mounted, and the like.

When a crack occurs on the surface of the laminated body 10, the crack may extend to the capacity region 13 from the crack. However, the above-described configuration can reduce the cracks generated in the capacitance region 13. As a result, a monolithic ceramic capacitor 100 having a high dielectric breakdown voltage (BDV) can be obtained.

The existence of heterogeneous particles in the margin area 14 may be verified as follows. First, the laminate 10 is subjected to a polishing treatment to expose the cross section of the laminate 10. The cross-section exposed at this time may be the cross-section of only the margin region 14 or the cross-section including the margin region 14 and the capacitance region 13. Next, using the SEM-EDX apparatus (scanning electron microscope and energy dispersive X-ray analysis apparatus) on the exposed cross section, the presence or absence of foreign phase particles in the margin region 14 is confirmed. At this time, if heterogeneous particles having a particle diameter of 0.1 μm or more are confirmed, it may be determined that the heterogeneous particles are present in the margin region 14. The particle size of the heterogeneous particles may be measured from the SEM image using image analysis software. The particle size is defined as the tangential diameter of the tangential direction that is the distance between two parallel tangents that sandwich the particle. If the particle to be measured has a polygonal shape, the average value of the tangential diameters measured in about 3 directions is the particle size. Good.

The number ratio of different phase particles in the margin region 14 is not particularly limited, and the number of different phase particles existing in a predetermined area (10 μm×10 μm) of the margin region 14 in the cross-sectional view of the laminate 10 is 15 or more. Good. With such a configuration, the hardness of the margin region 14 is sufficiently improved, and the monolithic ceramic capacitor 100 having a high dielectric breakdown voltage (BDV) can be obtained. The number ratio of the different phase particles may be calculated by counting the number of the different phase particles in the margin region 14 from the above-described SEM image and then converting the number into a predetermined area (10 μm×10 μm). The particle size of the different phase particles to be counted is 0.1 μm or more.

The above-described effects are realized even when the heterogeneous particles exist in the capacity region 13 in addition to the margin region 14. That is, the heterogeneous particles may exist only in the margin region 14, or may exist in both the margin region 14 and the capacitance region 13. When the different-phase particles are present in the capacitance region 13 that is a region where an electric capacitance is generated, the electrostatic capacitance of the monolithic ceramic capacitor 100 may decrease. This is because the heterophase particles are low dielectric constant particles. On the other hand, the different phase particles existing in the margin region 14 have almost no influence on the capacitance of the monolithic ceramic capacitor 100. This is because the margin region 14 is a region in the stacked body 10 that hardly generates an electric capacity.

Therefore, the number ratio of different phase particles in the margin region 14 may be higher than the number ratio of different phase particles in the capacity region 13. In other words, the number ratio of different phase particles in the capacity region 13 may be lower than the number ratio of different phase particles in the margin region 14. By increasing the number ratio of different phase particles in the margin region 14 to be higher than the number ratio of different phase particles in the capacitance region 13, the dielectric breakdown voltage (BDV) of the multilayer ceramic capacitor 100 is improved while reducing the decrease in capacitance. Can be made. As a result, it is possible to obtain the monolithic ceramic capacitor 100 having a high capacitance and a high dielectric breakdown voltage (BDV).

The fact that the number ratio of different phase particles in the margin area 14 is higher than the number ratio of different phase particles in the capacity area 13 may be verified as follows. First, the laminated body 10 is subjected to a polishing treatment to expose a cross section including the margin region 14 and the capacitance region 13. Next, using the SEM-EDX apparatus (scanning electron microscope and energy dispersive X-ray analyzer) for the exposed cross section, the number of different phase particles in the margin region 14 and the capacitance region 13 is counted. When capturing the SEM image, one SEM image of each of the capacitance region 13 and the margin region 14 may be captured along one direction from the center portion of the cross section to be observed toward the outer peripheral portion. In this case, the two SEM images should be taken at a predetermined interval. The different-phase particles to be counted have a particle size of 0.1 μm or more. Then, the number ratio may be calculated by converting the number into a predetermined area (10 μm×10 μm). The cross section is observed on three or more sides. As a result, it may be determined that, in a majority of the observed cross sections, the number ratio of different phase particles in the margin region 14 is higher than the number ratio of different phase particles in the capacity region 13.

The number ratio of different phase particles in the capacity region 13 is not particularly limited, and the number of different phase particles existing in a predetermined area (10 μm×10 μm) may be less than 20. With such a configuration, the capacitance of the monolithic ceramic capacitor 100 is unlikely to decrease.

By the way, when a voltage is applied to the monolithic ceramic capacitor 100, an electric field acts on the capacitance region 13, and mechanical strain called electrostriction occurs in the capacitance region 13. This electrostriction appears as an extension of the laminated body 10 in the laminating direction and causes cracks in the laminated ceramic capacitor 100. In particular, the electric field acting on the capacitance region 13 tends to be remarkable in the outer peripheral portion of the capacitance region 13. Therefore, the amount of electrostriction increases in the outer peripheral portion of the capacitance region 13, and cracks are likely to occur in the outer peripheral portion of the capacitance region 13.

On the other hand, when the heterogeneous particles are present in the capacitance region 13, the electric field acting on the capacitance region 13 concentrates on the heterogeneous particles. This is because the heterophasic particles are high-resistance particles, but at the same time, the heterophasic particles are low-dielectric constant particles, so that electrostriction is unlikely to occur. As a result, electrostriction of the capacitance region 13 is reduced.

On the other hand, as described above, when the different phase particles exist in the capacitance region 13, the capacitance of the monolithic ceramic capacitor 100 may decrease. In addition, the margin region 14 existing so as to cover the outer periphery of the capacitance region 13 has a role of suppressing electrostriction of the capacitance region 13 extending in the stacking direction. Therefore, when the heterogeneous particles are present in the margin region 14, the hardness of the margin region 14 increases as described above, and the electrostriction of the capacitance region 13 is further reduced. Furthermore, as described above, the heterogeneous particles existing in the margin region 14 have almost no influence on the capacitance of the monolithic ceramic capacitor 100. Considering the above, the number ratio of the different phase particles may be gradually increased from the central portion of the laminated body 10 toward the outer peripheral portion of the laminated body 10.

"The state in which the number ratio of the different phase particles gradually increases from the central portion of the laminated body 10 toward the outer peripheral portion of the laminated body 10" means that the central portion 13a of the capacitance region 13 and the outer peripheral portion 13b of the capacitance region 13, This means that the number ratio of different phase particles increases in the order of the margin region 14. The capacitance region 13 is divided into two so that the distance from the center of gravity of the volume of the capacitance region 13 to the outer periphery of the capacitance region 13 is divided into two equal parts. Of the two divided regions, the center side may be the center part 13a of the capacitance region 13 and the outer circumference side may be the outer circumference part 13b of the capacitance region 13. Therefore, there may be a region where the number ratio of the different phase particles is locally reversed between the center side and the outer peripheral side of the laminate 10.

By setting the number ratio of different-phase particles in the outer peripheral portion 13b of the capacitance region 13 on which a higher electric field acts to be higher than the number ratio of different-phase particles in the central portion 13a of the capacitance region 13, the capacitance of the multilayer ceramic capacitor 100 can be reduced. It is possible to effectively reduce the electrostriction of the capacitance region 13 while reducing the decrease. Further, by setting the number ratio of the different phase particles in the margin region 14 to be the highest in the laminated body 10, the electrostriction of the capacitance region 13 can be reduced without lowering the capacitance of the laminated ceramic capacitor 100.

In this way, by making the number ratio of the different phase particles gradually increase from the central portion of the laminated body 10 toward the outer peripheral portion of the laminated body 10, reduction in the capacitance of the laminated ceramic capacitor 100 is reduced. However, the electrostriction of the capacitance region 13 can be effectively reduced. As a result, the occurrence of cracks is reduced, and thus it is possible to obtain the monolithic ceramic capacitor 100 having high capacitance and high dielectric breakdown voltage (BDV).

The fact that the number ratio of the different phase particles gradually increases from the central portion of the laminated body 10 toward the outer peripheral portion of the laminated body 10 may be verified as follows. First, the laminated body 10 is subjected to a polishing treatment to expose the cross section including the margin region 14 and the capacitance region 13. The exposed cross section is a cross section including the central portion 13 a of the capacitance region 13. Next, using the SEM-EDX apparatus (scanning electron microscope and energy dispersive X-ray analyzer) for the exposed cross section, the central portion 13a of the capacitance region 13, the outer peripheral portion 13b of the capacitance region 13 and the margin region are used. The number of different phase particles in 14 is counted (see FIG. 2). In capturing the SEM image, one SEM image of each of the central portion 13a of the capacitance region 13, the outer peripheral portion 13b of the capacitance region 13, and the margin region 14 is provided along one direction from the central portion of the cross section to be observed toward the outer peripheral portion. You may take pictures one by one. In this case, the three SEM images should be taken at a predetermined interval. The different-phase particles to be counted have a particle size of 0.1 μm or more. Then, the number ratio of each of the different phase particles is calculated by converting into the number of different phase particles per a predetermined area (10 μm×10 μm). Observation of the cross section is performed on three or more surfaces. As a result, in the majority of the observed cross-sections, when the number ratio of the different-phase particles increases in the order of the central portion 13a of the capacitance region 13, the outer peripheral portion 13b of the capacitance region 13, and the margin region 14, the different-phase particles It may be judged that the number ratio of the number gradually increases from the central portion of the laminated body 10 toward the outer peripheral portion of the laminated body 10.

At this time, the number of different phase particles per predetermined area (10 μm×10 μm) in the central portion 13a of the capacity region 13 is 5 or less and the number of different phase particles per predetermined area (10 μm×10 μm) in the outer peripheral portion 13b of the capacity region 13 is increased. It is preferable that the number is 10 or more and less than 20, and the number of different phase particles per predetermined area (10 μm×10 μm) of the margin region 14 is 20 or more. With such a configuration, it is possible to improve the dielectric breakdown voltage (BDV) of the monolithic ceramic capacitor 100 while reducing the decrease in capacitance. However, the number ratio of the different phase particles is not limited to this.

The heterophasic particles may contain a compound containing a rare earth element (Re) as a main component. The compound containing a rare earth element is not particularly limited. For example, an oxide of a rare earth element represented by a composition formula of Re ₂ O _3, a composite oxide of two or more kinds of rare earth elements, and the like can be given. When the heterophase particles contain a compound containing a rare earth element as a main component, the hardness of the margin region 14 is further increased and the electrostriction amount of the capacitance region 13 is further reduced. As a result, a monolithic ceramic capacitor 100 having a high dielectric breakdown voltage (BDV) can be obtained.

The average particle size of the heterogeneous particles is not particularly limited and may be about 0.1 to 3.0 μm. The average particle size of the heterophase particles may be smaller than the average particle size of the main phase particles. In this case, the densification of the margin region 14 is promoted, and the monolithic ceramic capacitor 100 having a high dielectric breakdown voltage (BDV) can be obtained. The average particle size of the main phase particles is about 0.1 to 5.0 μm.

The fact that the average particle size of the heterophasic particles is smaller than the average particle size of the main phase particles may be verified as follows. First, the laminate 10 is subjected to a polishing treatment to expose the cross section of the laminate 10. Next, using the SEM-EDX device (scanning electron microscope and energy dispersive X-ray analysis device) on the exposed cross section, the average particle diameter of the different phase particles and the main phase particles in the cross section of the laminate 10 is measured. To do. The particle size is measured from the SEM image using image analysis software. At this time, the magnification was adjusted so that one SEM image had about 50 particles, and a plurality of photographs were obtained so that the total was 300 particles or more, and the average of the particle diameters measured for all the particles on the photograph was obtained. The value may be the average particle size.

The particle size is defined as the tangential diameter of the tangential direction that is the distance between two parallel tangents that sandwich the particle. If the particle to be measured has a polygonal shape, the average value of the tangential diameters measured in three directions is used as the particle size. Good. As a result, in the cross section of the laminate 10, when the average particle size of the different phase particles is smaller than the average particle size of the main phase particles, it is determined that the average particle size of the different phase particles is smaller than the average particle size of the main phase particles. Good.

Next, a specific example of a method of manufacturing the monolithic ceramic capacitor 100 according to the embodiment will be described. First, a dielectric material for forming the dielectric layer 11 is prepared and made into a paint to prepare a paste for the dielectric layer 11. As the dielectric material, a main component material and a rare earth element material are prepared.

Examples of the main component raw material include dielectric materials such as BaTiO ₃ (barium titanate)-based material, CaZrO ₃ (calcium zirconate)-based material, CaTiO ₃ (calcium titanate)-based material, SrTiO ₃ (strontium titanate)-based material, and the like. Mixtures of can be used. As the main component material, a high dielectric constant material may be used from the viewpoint of increasing the capacitance of the monolithic ceramic capacitor 100. As an example of the high dielectric constant material, a perovskite type ferroelectric material containing the above-mentioned dielectric material may be used.

As the rare earth element raw material, an oxide powder of a rare earth element having an average particle diameter of 20 nm or less is used, and preferably, an oxide powder of a rare earth element having an average particle diameter of 10 nm or less is used. The rare earth element is at least one selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, preferably Y, Gd. , Tb, Dy, Ho, Er, Tm, Yb, and Lu. When the rare earth element is selected from Y, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, the number ratio of different phase particles can be increased. As the rare earth element raw material, two or more kinds of powders containing different kinds of rare earth elements may be used. As the rare earth element raw material, a composite oxide powder of two or more kinds of rare earth elements may be used.

The rare earth oxide powder having an average particle diameter of 20 nm or 10 nm or less can be obtained by further classifying a commercially available rare earth oxide powder having a particle diameter of nm order. Examples of the classification method include liquid chromatography (SEC/HDC), flow field separation method (FFF), and electric mobility classifier (DMA) method.

The average particle size of the rare earth oxide powder can be measured from a scanning electron microscope (SEM) image using image analysis software. At this time, the magnification was adjusted so that one SEM image had about 50 particles, and a plurality of photographs were obtained so that the total was 300 particles or more, and the average of the particle diameters measured for all the particles on the photograph was obtained. The value may be the average particle size. The particle size is defined as the tangential diameter of the tangential direction that is the distance between two parallel tangents that sandwich the particle. If the particle to be measured has a polygonal shape, the average value of the tangential diameters measured in three directions is used as the particle size. Good.

2.5 mol or more of the rare earth element raw material may be added to 100 mol of the main component raw material. As a result, the number ratio of different phase particles can be increased. Various materials such as SiO ₂ and MgO may be added to the dielectric material in addition to the main component material and the rare earth element material.

Next, in order to prepare the dielectric raw material, the raw materials for each component are thoroughly mixed to obtain a mixed powder, which is heat-treated (calcined) to obtain a calcined raw material. The mixing of the raw materials is not particularly limited, and the materials are thoroughly mixed by a wet method for about 20 hours and then dried. The calcination temperature is 1000 to 1350° C., the holding time is 2 to 4 hours, and the temperature rising/falling rate is 100° C./hour to 200° C./hour.

The calcined raw material (raw material after the reaction) thus obtained is crushed if necessary. Then, if necessary, the calcination raw material and additional raw material components are mixed to obtain a dielectric raw material. Since some components may volatilize during calcination and firing and the composition may change, addition of components to the calcination raw material may be determined so that the desired composition is obtained after firing.

Next, the dielectric material is made into a coating material to prepare the dielectric layer 11 paste. The paste for the dielectric layer 11 may be an organic paint obtained by kneading a dielectric material and an organic vehicle, or may be an aqueous paint. The organic vehicle is a binder dissolved in an organic solvent. The binder used for the organic vehicle is not particularly limited and may be appropriately selected from various ordinary binders such as ethyl cellulose and polyvinyl butyral. The organic solvent used is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, and toluene according to the method to be used such as the printing method and the sheet method.

When the paste for the dielectric layer 11 is a water-based paint, the water-based vehicle in which a water-soluble binder or dispersant is dissolved may be kneaded with the dielectric material. The water-soluble binder used in the water-based vehicle is not particularly limited. Examples of the water-soluble binder include polyvinyl alcohol, cellulose, water-soluble acrylic resin and the like.

The internal electrode layer 12 paste may be a base metal such as Ni (nickel), Cu (copper) or Sn (tin), or a noble metal such as Pt (platinum), Pd (palladium), Ag (silver) or Au (gold). It is prepared by kneading an alloy containing these and the above organic vehicle. The external electrode paste may be prepared in the same manner as the internal electrode layer 12 paste.

There is no particular limitation on the content of the organic vehicle in each paste, and the usual content may be, for example, 1 to 5% by mass of the binder and 10 to 50% by mass of the solvent. Each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators and the like, if necessary. The total content of these is preferably 10% by mass or less.

For example, when the printing method is used, the dielectric layer 11 paste and the internal electrode layer 12 paste are printed and laminated on a substrate such as PET, cut into a predetermined shape, and then peeled from the substrate to obtain a green chip. .. When the sheet method is used, a green sheet is formed by using the paste for the dielectric layer 11, the paste for the internal electrode layer 12 is printed thereon, and then these are laminated and cut into a predetermined shape to obtain a green chip. ..

Before firing, the green chip is subjected to binder removal processing. As the binder removal conditions, the holding temperature is 180 to 900° C., the holding time is 2 to 4 hours, and the temperature rising/falling rate is 100° C./hour to 200° C./hour. The binder removal atmosphere is air or a reducing atmosphere. After removing the binder, the green chip is fired. The atmosphere during firing of the green chip may be appropriately determined according to the type of conductive material in the internal electrode layer 12 paste. For example, when a base metal such as Ni or Ni alloy is used as the conductive material, the oxygen partial pressure in the firing atmosphere may be 10 ⁻⁸ to 10 ⁻⁵ MPa.

As the firing conditions, the firing temperature is 1100 to 1250° C., the holding time is 1 to 3 hours, and the temperature rising/falling rate is 100° C./hour to 200° C./hour. Further, the firing atmosphere is preferably a reducing atmosphere, and as the atmosphere gas, for example, a mixed gas of N ₂ and H ₂ can be humidified and used. After firing, the laminated body 10 may be annealed.

The laminated body 10 thus obtained is subjected to end face polishing, for example, by barrel polishing, and the external electrode paste is applied and baked to form the external electrode 4. Then, if necessary, a coating layer is formed on the surface of the external electrode by plating or the like. The monolithic ceramic capacitor 100 of this embodiment manufactured in this manner is mounted on a printed circuit board or the like by soldering or the like, and is used for various electronic devices or the like.

Above, one embodiment of the multilayer ceramic capacitor according to the present disclosure has been described. However, the monolithic ceramic capacitor of the present disclosure is not limited to the above-described embodiment, and can be variously modified without departing from the scope of the present invention.

Hereinafter, the multilayer ceramic capacitor of the present disclosure will be described based on more detailed examples. However, the laminated ceramic capacitor of the present disclosure is not limited to these examples.

First, the sample No. 2 to 5 multilayer ceramic capacitors were produced. As a main component material, BaTiO ₃ (barium titanate) powder was prepared. Furthermore, Dy ₂ O ₃ powder, Y ₂ O ₃ powder, and Gd ₂ O ₃ powder were prepared as rare earth element raw materials. The concentration of Dy ₂ O ₃ was 6.0 mol with respect to 100 mol of BaTiO ₃ (barium titanate). The concentrations of Y ₂ O ₃ and Gd ₂ O ₃ were each 2.0 mol with respect to 100 mol of BaTiO ₃ (barium titanate). Dy ₂ O ₃ powder, Y ₂ O ₃ powder and Gd ₂ O ₃ powder are obtained by further classifying commercially available rare earth element oxide powder having a particle size of nm order by an electric mobility classifier (DMA) method. used. As a result, the average particle size of the powder used was 20 nm or less.

In addition to the main component raw material and the rare earth element raw material, SiO ₂ powder, MgO powder and MnCO ₃ powder were prepared. The concentration of each of these powders was 2.0 mol or less with respect to 100 mol of BaTiO ₃ (barium titanate).

Mixing was performed by wet mixing and stirring for 20 hours with a ball mill. The mixture after wet mixing and stirring was dehydrated and dried. After dehydration and drying, the temperature was raised from room temperature to 1100°C at 100°C/hour. It was calcined at 1100° C. for 5 hours and pulverized as needed to obtain a powder of calcination raw material (dielectric raw material).

Next, 100 parts by mass of the obtained dielectric material, 10 parts by mass of polyvinyl butyral resin, 5 parts by mass of dioctyl phthalate (DOP) as a plasticizer, and 100 parts by mass of alcohol as a solvent were mixed by a ball mill. It was made into a paste to obtain a dielectric layer paste.

Separately from the dielectric layer paste, 44.6 parts by mass of Ni particles, 52 parts by mass of terpineol, 3 parts by mass of ethyl cellulose, and 0.4 parts by mass of benzotriazole were kneaded with a three-roll to form a paste. Thus, an internal electrode layer paste was prepared.

Then, using the prepared dielectric layer paste, a green sheet was formed on the PET film so that the thickness after drying was 15 μm. Then, an internal electrode layer paste was used to print an internal electrode layer in a predetermined pattern thereon. After printing, the sheet was peeled from the PET film to produce a green sheet having an internal electrode layer. Next, a plurality of green sheets having internal electrode layers were laminated and pressure-bonded to obtain a green laminate. A green chip was obtained by cutting this green laminated body into a predetermined size.

Next, the obtained green chip was subjected to binder removal processing, firing and annealing under the following conditions to obtain a sintered body to be a laminated body.
<Binder removal processing conditions>
Temperature rising rate: 25°C/hour Holding temperature: 260°C
Temperature holding time: 8 hours Atmosphere: In air <Firing conditions>
Temperature rising/falling rate: 100°C/hour to 200°C/hour Firing temperature: 1100 to 1250°C
Holding time: 1 to 3 hours Atmosphere: N ₂ +H ₂ mixed gas humidified by a wetter (oxygen partial pressure: about 10 ⁻¹³ MPa)
<Annealing conditions>
Temperature rising rate: 200°C/hour Holding temperature: 1050°C
Temperature holding time: 2 hours Temperature falling rate: 200° C./hour Atmosphere: N ₂ gas humidified by a wetter (oxygen partial pressure: about 10 ⁻⁶ MPa)

Next, the obtained sintered body was barrel-polished to fully expose the internal electrode layers on the end faces of the laminate. A Ni external electrode was formed as an external electrode, and the sample No. 2 to 5 multilayer ceramic capacitors were obtained. The size of the obtained capacitor sample was 3.2 mm×1.6 mm×0.6 mm, the thickness of the dielectric layer was 10 μm, the thickness of the internal electrode layer was 1.0 μm, and the thickness of the dielectric layer sandwiched between the internal electrode layers was 10 μm. The number was 147.

Next, the prepared sample No. The following evaluations were performed on the laminated ceramic capacitors of 2 to 5. First, the capacitance of a capacitor sample was measured at a temperature of 25° C. using a constant temperature bath and an LCR meter. At this time, the frequency was set to 1.0 kHz, the measurement voltage was set to 1 Vrms, and the average value was obtained.

Next, the dielectric breakdown voltage (BDV) was measured. First, the internal electrode layer was connected to a digital ultra-high resistance/micro ammeter, and voltage was applied at a step of 5 V/sec for measurement. Next, the voltage value when the initial resistance value decreased by two digits was read, and the value was taken as the breakdown voltage value (V) of the sample. Next, the Vickers hardness was measured using a predetermined method.

Next, the number ratio of different phase particles in the central part of the capacity region, the outer peripheral part of the capacity region and the margin region was measured. First, the laminated body was subjected to polishing treatment to expose a cross section including a margin region and a capacitance region. The exposed cross section was a cross section in the stacking direction of the stack. The polishing treatment was performed in the direction of the side surface (the surface where the internal electrode layers were not exposed) of the laminate, and the exposed cross section included the central portion of the laminate.

Next, using an SEM-EDX apparatus (scanning electron microscope and energy dispersive X-ray analyzer) on the exposed cross section, heterogeneous particles in the central portion of the capacitance region, the outer peripheral portion of the capacitance region and the margin region are Each number was counted. In counting, the capacitance region was divided into two so that the distance from the center of gravity of the capacitance region to the outer periphery of the capacitance region was equally divided into two. Then, of the two divided regions, the center side was set as the center part of the capacitance region, and the outer circumference side was set as the outer circumference part of the capacitance region. In capturing the SEM image, one SEM image of each of the central portion of the capacitance region, the outer peripheral portion of the capacitance region, and the margin region was photographed along one direction from the central portion of the cross section to be observed toward the outer peripheral portion. At this time, the three SEM images were taken at predetermined intervals. The field of view of the SEM image was 5 μm×5 μm. The different-phase particles to be counted had a particle size of 0.1 μm or more. The method of measuring the particle size will be described later. When one heterophasic particle was present across two regions, it was counted that the heterophasic particle was present in one of the larger existing areas (area).

After that, it was converted into the number per predetermined area (10 μm × 10 μm) and the ratio of each number was calculated. The number ratio of the different phase particles in the entire capacity region was calculated from the number ratio of the different phase particles in the central part of the capacity region and the outer peripheral part of the capacity region. The decimal point generated in the calculation was rounded down.

After that, two new cross-sections different from the previously-exposed cross-section were exposed, and the size relationship of the number ratio of different phase particles in the central part of the capacity region, the outer peripheral part of the capacity region and the margin region was confirmed. As a result, the size relationship of the number ratio of the different phase particles was the same in all the three observed cross sections. All three cross sections observed were intended to include the center of the stack.

Next, the average particle size of the different phase particles was measured from the SEM image using image analysis software. At this time, the magnification was adjusted so that one SEM image had about 50 particles, and a plurality of photographs were obtained so that the total was 300 particles or more, and the average of the particle diameters measured for all the particles on the photograph was obtained. The value was defined as the average particle size. The particle size is defined as the tangential diameter of the tangential direction, which is the distance between two parallel tangents that sandwich the particle. did. As a result of measuring the average particle size of the main phase particles, the average particle size of the different phase particles was smaller than the average particle size of the main phase particles in all the samples.

Then, the sample No. A monolithic ceramic capacitor No. 1 was produced. Sample No. In the laminated ceramic capacitor of No. 1, sample No. The same manufacturing method and evaluation method as in 2 to 5 were applied. However, the sample No. In the laminated ceramic capacitor of No. 1, the oxide powder of the rare earth elements (Dy ₂ O ₃ , Y ₂ O ₃ and Gd ₂ O ₃ ) was not classified. As a result, the average particle size of the rare earth oxide powder used was about 40 nm.

Prepared sample No. In the monolithic ceramic capacitor of No. 1, the different phase particles existed in the capacitance region, while the different phase particles did not exist in the margin region. That is, in the SEM image obtained by photographing the margin area in the visual field of 5 μm×5 μm, there were no heterophase particles having a particle size of 0.1 μm or more.

Table 1 shows the measurement results. Sample No. In Nos. 1 to 5, the applied firing conditions are different. Sample No. The firing conditions of 1 and 2 were a firing temperature of 1200° C., a holding time of 2 hours, and a temperature raising/lowering rate of 150° C./hour. Sample No. The firing conditions of No. 3 were such that the firing temperature was 1220° C., the holding time was 2 hours, and the temperature rising/falling rate was 150° C./hour. Sample No. The firing conditions of No. 4 were such that the firing temperature was 1240° C., the holding time was 2 hours, and the temperature rising/falling rate was 150° C./hour. Sample No. As for the firing conditions of No. 5, the firing temperature was 1200° C., the holding time was 1 hour, and the temperature rising/falling rate was 200° C./hour.

As shown in Table 1, the sample No. in which foreign phase particles exist in the margin area. Sample Nos. 2 to 5 in which no different phase particles exist in the margin area. It can be seen that the Vickers hardness is higher than 1 and the dielectric breakdown voltage (BDV) is improved. At this time, the sample No. In each of Nos. 2 to 4, the number of different phase particles per predetermined area (10 μm×10 μm) in the margin region was 15 or more.

Sample No. in which the number ratio of different phase particles in the volume area is higher than in the margin area It can be seen that in No. 5, the capacitance is lower than that of the other samples. On the other hand, the number ratio of the different phase particles in the margin area is higher than that in the capacity area. In Nos. 2 to 4, sample No. It can be seen that the breakdown voltage (BDV) is improved without substantially decreasing the capacitance as compared with 1.

Sample No. in a state where the number ratio of the different phase particles 9 gradually increases from the central portion of the laminated body 10 toward the outer peripheral portion of the laminated body 10. In Nos. 2 to 4, sample No. It can be seen that the breakdown voltage (BDV) is improved as compared with 1 without substantially decreasing the capacitance. At this time, the sample No. In all 2 to 4, the number of different phase particles per predetermined area (10 μm×10 μm) in the central portion of the capacity region 13 is 5 or less and the different phase per predetermined area (10 μm×10 μm) in the outer peripheral portion of the capacity region 13 The number of particles was 10 or more and less than 20, and the number of different-phase particles per predetermined area (10 μm×10 μm) of the margin region 14 was 20 or more.

100 Multilayer Ceramic Capacitor 10 Laminated Body 11 Dielectric Layer 12 Internal Electrode Layers 20a, 20b External Electrodes 13 Capacitance Region 13a Central Part of Capacitance Region 13b Peripheral Part of Capacitance Region 14 Margin Area

Claims

A laminated body in which dielectric layers and internal electrode layers are alternately laminated,
The stacked body has a capacitance region in which the adjacent internal electrode layers face each other, and a margin region arranged around the capacitance region,
A monolithic ceramic capacitor in which heterophase particles having a high rare earth element concentration are present in the margin region.
The multilayer ceramic capacitor according to claim 1, wherein the number ratio of the different phase particles in the margin region is higher than the number ratio of the different phase particles in the capacitance region.
The multilayer ceramic capacitor according to claim 1 or 2, wherein the number ratio of the different phase particles gradually increases from the central portion of the laminated body toward the outer peripheral portion of the laminated body.
The multilayer ceramic capacitor according to any one of claims 1 to 3, wherein, in the cross section of the multilayer body, the number ratio of the different phase particles existing in the margin region is 15 particles/100 µm 2 or more.
In the cross section of the laminate, the number ratio of the different phase particles existing in the central part of the capacity region is 5 particles/100 μm 2 or less, and the number ratio of the different phase particles existing in the outer peripheral part of the capacity region is 10. pieces / 100 [mu] m 2 or more 20/100 [mu] m is less than 2, and the ratio of the number of different phase particles is 20/100 [mu] m 2 or more, the multilayer ceramic capacitor according to claim 3 or 4 which is present in said margin area.
The monolithic ceramic capacitor according to any one of claims 1 to 5, wherein the average particle size of the different phase particles is smaller than the average particle size of the main phase particles of the dielectric layer.
The monolithic ceramic capacitor according to any one of claims 1 to 6, wherein the different phase particles contain a compound containing a rare earth element as a main component.