JP2021052149A - Capacitor - Google Patents

Abstract

To provide a multilayer capacitor with improved DC bias characteristics.SOLUTION: A multilayer capacitor comprises a capacitor main body in which a plurality of dielectric layers 5 and internal electrode layers 7 are alternately laminated, and the dielectric layers each has a plurality of first crystal grains that form a parent phase 5A and contain barium titanate as a main component, and a plurality of second crystal grains that form agglomerate parts 5B present in the parent phase and contain calcium titanate or strontium titanate as a main component.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to multilayer capacitors.

In recent years, multilayer capacitors (hereinafter referred to as capacitors) have been made smaller and have higher capacities. On the other hand, the capacitor is required to have a characteristic that the decrease in capacitance is small when a DC voltage is applied (hereinafter, may be referred to as a DC bias characteristic) (see, for example, Patent Documents 1 and 2). ).

Japanese Unexamined Patent Publication No. 2011-132056 Japanese Unexamined Patent Publication No. 2019-021927

The capacitor of the present disclosure includes a dielectric body in which a plurality of layers of dielectric layers and internal electrode layers are alternately laminated, and the dielectric layer is composed of a plurality of first crystal particles containing barium titanate as a main component. , Calcium titanate and a plurality of second crystal particles containing at least one of strontium titanate as a main component, and the plurality of the first crystal particles form a matrix of the dielectric layer. The plurality of the second crystal particles are present in the matrix in the agglomerated portion.

It is external perspective view of the capacitor which shows as an example of embodiment. FIG. 1 is a cross-sectional view taken along the line ii-ii of FIG. It is an enlarged view of P1 part in FIG. It is an enlarged view of the P2 part in FIG. It is an enlarged view of the P3 part in FIG. It is an enlarged view of the P4 part in FIG.

Conventionally, a dielectric material containing barium titanate as a main component has been used for the dielectric layer constituting the capacitor. Since the dielectric material containing barium titanate as a main component is a material exhibiting ferroelectricity, a high relative permittivity can be obtained. In recent years, a capacitor is required to exhibit a higher capacitance when a DC voltage is applied.

Hereinafter, the capacitor of the embodiment will be described with reference to FIGS. 1 to 6. The present invention is not limited to the specific embodiments described below. The present invention includes various aspects as long as it is in line with the spirit or scope of the general concept of the invention as defined by the appended claims.

As shown in FIG. 1, the capacitor shown as an example of the embodiment has a capacitor main body 1 and an external electrode 3 provided on an end surface thereof. As shown in FIG. 2, the capacitor body 1 has a dielectric layer 5 and an internal electrode layer 7. A plurality of layers of the dielectric layer 5 and the internal electrode layer 7 are alternately laminated. In FIG. 2, the number of layers of the dielectric layer 5 and the internal electrode layer 7 is simplified to several layers, but the number of layers of the dielectric layer 5 and the internal electrode layer 7 is actually several hundred layers. It also extends to. The external electrode 3 is electrically connected to the internal electrode layer 7.

As shown in FIG. 3, the dielectric layer 5 has a plurality of first crystal particles 5a and a plurality of second crystal particles 5b. The first crystal particles 5a are crystal particles containing barium titanate as a main component. The first crystal particles 5a form the matrix 5A of the dielectric layer 5. The second crystal particle 5b is a crystal particle 5b containing at least one of calcium titanate and strontium titanate as a main component. The plurality of second crystal particles 5b form an agglomerate portion 5B in the matrix 5A.

In the capacitor of the embodiment, the electric field is concentrated on the agglomerated portion 5B formed by a plurality of second crystal particles 5b containing at least one of calcium titanate and strontium titanate as main components in the dielectric layer 5. It will be easier. In the configuration shown in FIG. 3, when a DC voltage is applied to the two internal electrode layers 7 sandwiching the dielectric layer 5, in the dielectric layer 5, the agglomerated portion 5B is compared with the matrix 5A. The electric field strength of is increased. That is, in the dielectric layer 5, the electric field strength on the matrix 5A side is lowered by the amount that the electric field strength is increased on the agglomerated portion 5B side. As a result, the DC bias characteristic of the capacitor can be improved.

Further, from the aspect of the dielectric material, it can be explained that the DC bias characteristic of the capacitor becomes high when the dielectric layer 5 has the agglomerated portion 5B. Generally, the CR product of the dielectric material is constant. Here, C is the capacitance of the dielectric material. R is the resistance of the dielectric material. Calcium titanate has a lower relative permittivity than barium titanate. Also, strontium titanate has a lower relative permittivity than barium titanate. Therefore, the crystal particles containing calcium titanate as a main component (second crystal particles 5b) have a higher resistivity than the crystal particles containing barium titanate as a main component (first crystal particles 5a). Crystal particles containing strontium titanate as a main component (second crystal particles 5b) also have higher resistivity than crystal particles containing barium titanate as a main component (first crystal particles 5a). Therefore, in the agglomerated portion 5B in which the second crystal particles 5b containing at least one of calcium titanate and strontium titanate as main components are aggregated, the second crystal particles 5b are the first crystal particles in the matrix 5A. The electric field is more likely to be concentrated than when it exists individually between 5a. That is, in the dielectric layer 5, the electric field strength in the matrix 5A is lowered by the amount that the electric field strength in the agglomerated portion 5B is higher than that in the matrix 5A. As a result, the DC bias characteristic of the capacitor provided with the dielectric layer 5 having the agglomerated portion 5B is enhanced.

Here, the main component is a component contained most in the crystal particles. The term "barium titanate as a main component" means that the crystal particles contain a larger amount of titanium and barium than other components. The term "calcium titanate as a main component" means that the crystal particles contain a larger amount of titanium and calcium than other components. The term "strontium titanate as a main component" means that the crystal particles contain a larger amount of titanium and strontium than other components. The matrix 5A is a phase formed by crystal particles having the largest volume ratio in the dielectric layer 5. The ratio is a volume ratio or an area ratio in the cross section of the dielectric layer 5.

According to the capacitor of the embodiment, it is possible to obtain a capacitor in which cracks are less likely to occur even in a deflection test and the electrical characteristics are less deteriorated. This is a second crystal particle containing at least one of calcium titanate and strontium titanate as a main component in the dielectric layer 5 having the first crystal particle 5a containing barium titanate as the main component and the parent phase 5A. This is because the mechanical strength of the dielectric layer 5 is increased by including the agglomerated portion 5B mainly composed of 5b.

As for the ratio of the second crystal particles 5b contained in the dielectric layer 5, the result of X-ray diffraction of the powder obtained by pulverizing the dielectric layer 5 or the capacitor body 1 is used for convenience. Specifically, determining the ratio between the diffraction intensity I _ST of the diffraction intensity I _CT or strontium titanate calcium titanate constituting the agglomerate portion 5B for diffraction intensity I _BT barium titanate constituting the matrix phase 5A. In this case, the ratio I _CT / I _BT is preferably 0.01 or more and 0.12 or less.

In the capacitor of the embodiment, as shown in FIG. 4, the agglomerate portion 5B may have a main body portion 5Ba and auxiliary particles 5Bb. In this case, the main body portion 5Ba corresponds to a portion occupying the central region of the agglomeration portion 5B. The main body portion 5Bb is a portion in which at least three second crystal particles 5b are bonded to each other at a two-sided grain boundary bo. A portion in which at least three second crystal particles 5b are bonded to each other at a two-sided grain boundary bo is defined as a particle group 5bm. In this case, the main body portion 5Bb preferably has a structure having a plurality of particle groups 5bm. Further, it is preferable that the particle groups 5 bm are in a state of being bonded (sintered) via the interplaneal grain boundary bo. When the particle groups 5bm are bonded to each other via the two-sided grain boundary bo, the structure is such that the plurality of particle groups 5bm are bonded to each other via the void po and the two-sided grain boundary bo. The area becomes even larger. On the other hand, the sub-particle 5Bb corresponds to a portion located on the peripheral edge of the main body portion 5Ba.

Here, the agglomerate portion 5B will be described in detail with reference to FIG. In this case, the agglomerate portion 5B is an area surrounded by a frame line F (solid line). That is, the agglomerate portion 5B is a region in which a plurality of sub-particles 5Bb arranged around the main body portion 5Ba are connected by a frame line F. The frame line F is arranged with the outer surface of the sub-particle 5Bb as a contact point when viewed from the position of the center of the main body portion 5Ba. In this case, the frame line F may be linear as long as it connects the sub-particles 5Bb.

As shown below, the sub-particles 5Bb have hump-like particles 5Bbt. When the agglomerated portion 5B contained in the dielectric layer 5 further has hump-shaped particles 5Bbt on its peripheral edge, the range surrounded by the frame line F (solid line) becomes larger as shown in FIG. When the agglomerated portion 5B expands to the range having the hump-shaped particles 5Bbt, it includes the first crystal particles 5a together with the void po adjacent to the hump-shaped particles 5Bbt. The agglomerated portion 5B has a larger area. In this way, in the dielectric layer 5, the region where the electric field strength is high is further expanded, and the DC bias characteristic of the capacitor can be further enhanced.

As shown in FIGS. 4 and 6, the sub-particles 5Bb may further include isolated particles 5Bbs existing at positions away from the main body 5Ba. The isolated particles 5Bbs are preferably arranged at a distance from the main body portion 5Ba so that at least one of the void po and the first crystal particles 5a is present. Here, the existence of the first crystal particles 5a between the isolated particles 5Bbs and the main body 5Ba means that the first crystal particles 5a are within the particle size range of the isolated particles 5Bbs indicated by the reference numeral w, as shown in FIG. It means that it may be in a state where a part of is applied. In other words, when the isolated particles 5Bbs and the main body 5Bb face each other, a part of the first crystal particles 5a exists within the width w of the isolated particles 5Bb in the direction substantially parallel to the surface of the main body 5Bb. It means that you are doing it. When the agglomerated portion 5B has a structure including not only the hump-shaped particles 5Bbt but also the isolated particles 5Bbs, the apparent region of the agglomerating portion 5B becomes larger. As a result, it becomes possible to further enhance the DC bias characteristic of the capacitor having the dielectric layer 5 mainly composed of the matrix 5A.

In the capacitor of the embodiment, it is preferable that the capacitor body 1 contains two or more dielectric layers 5 having the above-mentioned agglomerated portion 5. In this case, the dielectric layer 5 having the agglomerated portion 5 is preferably arranged on all layers in that the DC bias characteristic of the capacitor can be enhanced. On the other hand, the dielectric layer 5 having the agglomerated portion 5 may be locally arranged for the reason of maintaining a high capacitance of the capacitor. In this case, the end of the capacitor body 1 in the stacking direction is preferable as the place where the dielectric layer 5 having the agglomerated portion 5 is arranged. As shown in FIG. 2, the ends of the capacitor body 1 in the stacking direction are the upper end 1up and the lower end 1ud in the stacking direction in the region where the dielectric layer 5 contributing to the capacitance is laminated. That is. This is because the upper end portion 1up and the lower end portion 1ud in the stacking direction of the capacitor main body 1 tend to have higher electric field strength than the middle portion in the stacking direction when a DC voltage is applied to the capacitor. The dielectric layer 5 having the agglomerated portion 5 is preferably arranged in the same number or the same number of layers at the upper end portion 1up and the lower end portion 1ud in the stacking direction in the capacitor main body 1.

In the capacitor of the embodiment, the area ratio of the agglomerated portion 5B in the dielectric layer 5 of one layer is preferably 3% or more and 10% or less. In this case, the capacitor main body 1 preferably has two or more dielectric layers 5 in which the area ratio of the agglomerated portion 5B is 3% or more and 10% or less. When the capacitor body 1 has two or more dielectric layers 5 in which the area ratio of the agglomerated portion 5B is 3% or more and 10% or less, the dielectric layer 5 having the agglomerated portion 5B increases. Also, the capacitance per layer can be maintained in a high state. Further, even if the DC voltage applied to the capacitor is increased, the decrease in capacitance can be reduced.

Here, the area ratio of the agglomerated portion 5B can be explained as follows. First, as shown by the reference numeral Acs in FIG. 2, one dielectric layer 5 is selected from the cross section of the capacitor body 1. Next, the total area A0 of the cross section of the selected dielectric layer 5 is set to 1. Next, the total area A1 including the areas of the agglomerated portion 5B found in the cross section of the selected dielectric layer 5 is obtained. The area ratio of the agglomerated portion 5B is a ratio (A1) obtained by dividing the total area A1 of the agglomerated portion 5B found in the cross section of the specific dielectric layer 5 by the total area A0 of the cross section of the dielectric layer 5. / A0). As a cross section of the capacitor main body 1 for obtaining the area ratio of the agglomerated portion 5B, FIG. 2 shows a cross section (L cross section) of the capacitor main body 1 perpendicular to the direction in which the two external electrodes 3 face each other. However, the cross section of the capacitor body 1 for obtaining the area ratio of the agglomerated portion 5B is not limited to the L cross section, but may be a cross section (W cross section) in the direction in which the two external electrodes 3 of the capacitor face each other.

In the capacitor of the embodiment, when the average particle size of the sub-particles 5Bb is D1 and the average diameter of the agglomerated portion 5B is D0, the ratio D1 / D0 is preferably 0.019 or more and 0.093 or less. When the ratio D1 / D0 is 0.019 or more and 0.093 or less, the DC bias characteristic can be made smaller than −23.9%. In this case, the DC bias characteristic of -23.9% means that the capacitance at zero bias (when no DC voltage is applied) is C0, and the capacitance obtained when a specific DC voltage is applied is C1. Is the value obtained by displaying the ratio of (C1-C0) / C0 in%. As described above, according to the capacitor of the embodiment, the amount of attenuation of the capacitance can be reduced even when a DC voltage is applied to the capacitor. In this case, the average particle size D1 of the sub-particles 5Bb is preferably 0.13 μm or more and 0.68 μm or less. Further, the average diameter D0 of the agglomerated portion 5B is preferably 5 μm or more and 10 μm or less, and particularly preferably 7 μm or more and 7.8 μm or less. Furthermore, the average particle size D2 of the first crystal particles 5a is preferably 0.047 μm or more and 0.22 μm or less.

Here, the average particle size D1 of the sub-particles 5Bb is an average value obtained by combining the maximum diameters of the hump-shaped particles 5Bbt and the maximum diameters of the isolated particles 5Bbs. The maximum diameter of the hump-shaped particles 5Bbt is in the range of D3 shown in FIG. The maximum diameter of the isolated particles 5Bbs is in the range of D4 shown in FIG. The average diameter D0 of the agglomerated portion is within the range of the frame line F shown in FIG. From the range of the frame line F, the area and diameter of the agglomerated portion 5B are obtained as follows. In this case, first, the area of the area of the frame line F is obtained by image analysis. Next, the area of the area of the frame line F is once determined as an area as a circle. If necessary, find the diameter from the area of the circle. When a plurality of agglomerated portions 5B are present in the dielectric layer 5 of one layer, the average value including the diameters of the agglomerated portions 5B is calculated individually. This average value is defined as the average diameter D0 of the agglomerate portion 5B.

The average particle size D2 of the first crystal particles 5a is obtained as follows. As the sample for obtaining the average particle size D2 of the first crystal particles 5a, for example, the same sample prepared for obtaining the average diameter D0 of the agglomerated portion 5B may be used. In the cross section of the sample prepared for obtaining the average diameter D0 of the agglomerate portion 5B, first, a region excluding the agglomerate portion 5B is selected. The region to be selected is a region in which 20 to 30 first crystal particles 5a are contained. All of the first crystal particles 5a found in the region containing 20 to 30 first crystal particles 5a are contoured. Next, the area as a circle is individually obtained from the contour of the first crystal particle 5a. Next, the diameter is calculated from the area of each circle. Finally, the average value of the diameters corresponding to each of the first crystal particles 5a is obtained. This average value is defined as the average particle size D2 of the first crystal particles 5a.

In the capacitor of the embodiment, as shown in FIG. 3, when the thickness of one layer of the dielectric layer 5 is t and the average diameter of the agglomerated portion 5B in the same direction as the thickness of the dielectric layer 5 is D0. In addition, the ratio D0 / t is preferably 0.47 or more and 0.52 or less. Here, the thickness t of the dielectric layer 5 is the average thickness of the dielectric layer 5. The average thickness t of the dielectric layer 5 is determined by the following procedure. First, the dielectric layer 5 used for measuring the thickness is selected. As the dielectric layer 5 to be selected, for example, the dielectric layer 5 selected for analyzing the agglomerated portion 5B may be selected. In the selected dielectric layer 5, a plurality of locations are evenly designated in the width direction. The number of points for measuring the thickness is preferably 3 to 10. Next, the thickness of each designated portion is obtained. Next, the average value of the obtained thickness is obtained. The average value of the thicknesses of the dielectric layer 5 thus obtained is defined as the thickness t of the dielectric layer 5. Area ratio of agglomerated portion 5B, average diameter D0 of agglomerated portion 5B, average particle size d1 of subparticles 5Bb, maximum diameter D3 of hump-shaped particles 5Bbt constituting subparticles 5Bb, maximum diameter D4 of isolated particles 5Bbs, dielectric The thickness t of the body layer 5 is obtained from a photograph of a cross section of the capacitor body 1 taken. A scanning electron microscope is preferably used to photograph the cross section of the capacitor body 1. In this case as well, the scanning electron microscope preferably has an analyzer. When the scanning electron microscope is equipped with an analyzer, the crystal particles to be photographed can be specified by the composition. Even when it is contained in the dielectric layer 5, crystal particles having a maximum diameter smaller than 0.03 μm may be excluded from the target.

Next, a method of manufacturing the capacitor of the embodiment will be described. The capacitor of the embodiment is a calcium carbonate powder obtained by preliminarily slurping a raw material powder containing barium titanate as a main component on a ceramic green sheet for forming the dielectric layer 5 with an amine-based dispersant. It can be produced by a conventional method for producing a capacitor, except that at least one of the strontium carbonate powder slurried with an amine-based dispersant is added at a predetermined ratio. When calcium carbonate powder slurried in advance with an amine-based dispersant is added to a ceramic green sheet mainly containing a raw material powder containing barium titanate as a main component, crystal particles containing barium titanate as a main component become a mother. In the dielectric layer 5 as the phase 5A, an agglomerated portion 5B in which crystal particles containing calcium titanate as a main component are aggregated is likely to be formed. Similarly, when strontium titanate powder slurried with an amine-based dispersant is added in advance, the agglomerated portion 5B in which crystal particles containing strontium titanate as a main component are aggregated is similarly formed in the dielectric layer 5. It becomes easy to be formed. The proportion of the agglomerated portion 5B present in the dielectric layer 5 is adjusted by the amount of calcium carbonate powder, strontium carbonate powder, amine-based dispersant added, and the firing temperature.

Hereinafter, a capacitor was specifically manufactured and its characteristics were evaluated. Here, first, an example in which a capacitor is manufactured by adding calcium carbonate powder to a dielectric powder will be described. First, as raw material powders for preparing dielectric powder, barium titanate powder (BaTIO ₃ ), calcium carbonate powder (CaCO ₃ ), magnesium carbonate powder (Mg ₂ CO ₃ ), and disprosium oxide powder (Dy ₂ O ₃₎ ), Manganese carbonate powder (MnCO ₃ ) and glass powder (SiO ₂ = 55, BaO = 20, CaO = 15, Li ₂ O ₃ = 10 (mol%)) and prepared. In this case, barium titanate powder having an average particle size of 0.05 μm was used as the barium titanate powder. As for the dielectric powder, for 100 mol of barium titanate powder, 0.8 mol of magnesium oxide powder (MgO) in terms of MgO, 0.8 mol of disprosium oxide powder (Dy ₂ O ₃ ), and MnCO ₃ powder. Was added in an amount of 0.3 mol in terms of MnO, and _{1 part by mass of a glass component (SiO 2-} BaO-CaO-based glass powder) was added to 100 parts by mass of barium titanate powder. The amount of calcium carbonate added is shown in Table 1. The amount of calcium carbonate powder added shown in Table 1 is a ratio to 100 parts by mass of barium titanate powder. The calcium carbonate powder used was previously dispersed in an amine-based dispersant or a carboxylic acid-based dispersant to form a slurry. The amount of the amine-based dispersant and the carboxylic acid-based dispersant shown in Table 1 is the ratio to the amount of the calcium carbonate powder added.

Next, a ceramic green sheet having an average thickness of 20 μm was prepared by a doctor blade method using a slurry prepared by mixing an organic vehicle with the prepared dielectric powder. A butyral resin was used as the resin to be contained in the organic vehicle when preparing the ceramic green sheet. The amount of the butyral resin added was 10 parts by mass with respect to 100 parts by mass of the dielectric powder. As the solvent, a solvent in which ethyl alcohol and toluene were mixed at a ratio of 1: 1 was used. Nickel powder was used as the metal for the conductor paste to form the internal electrode pattern. Ethyl cellulose was used as the resin for preparing the conductor paste. The amount of ethyl cellulose added was 5 parts by mass with respect to 100 parts by mass of nickel powder. As the solvent, a dihydroterpineol solvent and a butyl cellosolve were mixed and used.

Next, a conductor paste was printed on the prepared ceramic green sheet to prepare a pattern sheet. Next, 100 layers of the produced pattern sheets were laminated to prepare a core laminate. Next, a ceramic green sheet was laminated as a cover layer on the upper surface side and the lower surface side of the core laminate to prepare a base laminate. After that, the base laminate was cut to prepare a molded body of the capacitor body. The molded body of the capacitor body is formed of a ceramic green sheet in which all layers thereof contain calcium carbonate powder or strontium carbonate powder in the dielectric powder.

Next, the molded body of the capacitor body was fired to prepare the capacitor body. This firing was carried out in hydrogen-nitrogen under the conditions that the temperature rising rate was 900 ° C./h and the maximum temperature was set to 1190 ° C. A resistance heating type firing furnace was used for this firing. Subsequently, the capacitor body was subjected to a reoxidation treatment. The conditions for the reoxidation treatment were that the maximum temperature was set to 1000 ° C. and the holding time was 5 hours in a nitrogen atmosphere. The size of the capacitor body was 3.2 mm × 1.6 mm × 1.6 mm. The average thickness of the dielectric layer was 15 μm. The average thickness of the internal electrode layer was 0.8 μm. The design value of the capacitance of the produced capacitor was set to 1 μF.

Next, after barrel polishing the capacitor body, external electrode paste was applied to both ends of the capacitor body and baked at a temperature of 800 ° C. to form an external electrode. As the external electrode paste, one to which Cu powder and glass were added was used. Then, using an electrolytic barrel machine, Ni plating and Sn plating were sequentially formed on the surface of the external electrode to obtain a capacitor.

Next, the following evaluation was performed on the produced capacitor. First, several of the obtained capacitors were selected and pulverized using a mortar to prepare a sample for X-ray diffraction. Among the manufactured capacitors, in the capacitor manufactured by adding calcium carbonate powder to the dielectric powder, a diffraction peak of calcium titanate was observed together with barium titanate in the X-ray diffraction pattern of the dielectric layer. Subsequently, the X-ray diffraction pattern was determined main peak ratio of the diffraction intensity I _CT of calcium titanate for diffraction intensity I _BT of the main peak of barium titanate. A diffraction peak with an index (111) was selected as the main peak of barium titanate. A diffraction peak with an index (121) was selected as the main peak of calcium titanate. The ratio of this diffraction intensity is shown in Table 1 as the ratio of calcium titanate contained in the dielectric layer.

Next, the matrix and the agglomerated portion constituting the dielectric layer were analyzed. For this analysis, a capacitor sample processed as follows was used. First, the cross section of the capacitor was polished to prepare a sample in which the cross section as shown in FIG. 2 was exposed. Next, thermal etching was performed on the sample whose cross section was exposed. By performing thermal etching on the sample with the exposed cross section, the contours of the crystal particles and the grain boundaries can be clearly seen in the cross section of the dielectric layer. Next, the following analysis and evaluation were performed on the obtained sample by using a scanning electron microscope equipped with an analyzer. First, from the photographs obtained by observation with a scanning electron microscope, a cross section was selected so as to contain one dielectric layer as shown in FIG. The region defined as the unit area is the W cross section of one layer of the dielectric layer. The selected dielectric layer is one layer at one end in the stacking direction in the cross section of the capacitor body. The site to be analyzed was the central portion in the width direction of the selected dielectric layer. Next, the components (compounds) of the parent phase and the components (compounds) of the agglomerate portion existing in the selected one-layer dielectric layer were identified. As a result of the analysis, the matrix was mainly composed of barium titanate. Among the prepared capacitors, in all the samples using the amine-based dispersant, agglomerates were formed in the dielectric layer. In addition, the agglomerated portion was formed by crystal particles containing calcium titanate as a main component. In addition, each of the agglomerated portions had a main body portion located in the central region and auxiliary particles located on the peripheral edge of the main body portion. Further, the main body portion occupying the central portion of the agglomerated portion has a structure in which at least three crystal particles containing calcium titanate as a main component are in contact with each other at the two-sided grain boundary. Further, in the agglomerated portion, hump-like particles bonded to the main body portion via the neck portion were observed. In addition, the agglomerates contained isolated particles that were located distant from the body. In this case, as the isolated particles, those existing in the range equal to or less than the maximum diameter of the adjacent hump-like particles were selected.

Next, by analyzing the photograph taken, the average diameter D0 of the agglomerated portion, the area ratio of the agglomerated portion (A1 / A0), the average thickness t of the selected dielectric layer, and the average thickness t of the dielectric layer are obtained. The ratio of the average diameter D0 of the agglomerated portion (D0 / t), the average particle size D1 of the auxiliary particles, the ratio of the average particle size D1 of the auxiliary particles to the average diameter D0 of the agglomerated portion (D1 / D0), the first crystal particles The ratio (D2 / D1) of the average particle size D2 of the first crystal particles to the average particle size D1 of the sub-particles and the average particle size D2 of the first crystal particles was determined. At this time, the average particle size of the hump-shaped particles was determined from the average value of the maximum diameters obtained for the plurality of hump-like particles. All the hump-like particles existing on the periphery of the main body constituting the agglomerate were targeted. The average particle size of the isolated particles was determined from the average value of the maximum diameters obtained for a plurality of isolated particles. In this case as well, all the isolated particles existing on the periphery of the main body constituting the agglomerate were targeted. Among the prepared samples, the capacitors prepared by adding calcium carbonate powder containing an amine-based dispersant to the ceramic green sheet were agglomerated in the dielectric layer constituting the capacitor body in all the samples. The part was formed. In this case, the agglomerated portion had hump-like particles and isolated particles together with the main body portion.

Next, regarding the dielectric characteristics, the capacitance was measured under the condition that no DC voltage was applied and the condition that the DC voltage was applied. The conditions under which no DC voltage is applied are an AC voltage of 1.0 V and a frequency of 1 kHz. The conditions under which the DC voltage is applied are (1) AC voltage 1.0 V, DC voltage 5 V, frequency 1 kHz, and (2) AC voltage 1.0 V, DC voltage 10 V, frequency 1 kHz. The number of samples was 30, and the average value was calculated. The capacitance of the sample whose capacitance could be measured at zero vise was 0.89 μF or more.

In addition, a deflection test was conducted on the produced capacitor to evaluate the mechanical strength. The deflection test was performed by the following method. A glass epoxy substrate (thickness: 1.6 mm) was used as the substrate. In the glass epoxy substrate, two conductor layers (copper foil) were formed on one surface at a predetermined interval. The external electrodes of the capacitor were bonded to each of the two conductor layers. Eutectic solder was used as the bonding material. An autograph was used to pressurize the deflection test. The deflection limit of the substrate was set to 12 mm. The number of samples was 33. In the evaluated capacitors, samples in which the rate of decrease in capacitance after the deflection test was greater than 5% or cracks were observed in appearance after the deflection test were counted as defective.

A capacitor prepared by adding strontium carbonate powder to a dielectric powder was also produced by the same method as in the case of using the calcium carbonate powder described above, and the same evaluation was performed. In the produced capacitor, an agglomerated portion was formed in at least two dielectric layers at the end of the capacitor body in the stacking direction. Further, in this case as well, the agglomerated portion had hump-like particles and isolated particles together with the main body portion.

As is clear from the results in Tables 1 and 2, the sample No. 1 and the sample No. 2 were excluded, except for the samples (Sample No. 1 and Sample No. 2) in which no agglomerate was present in the dielectric layer. In 3 to 13, 15 to 25, the DC bias characteristic when a DC voltage of 5 V was applied was -13.3% or less. Here, -13.3% or less means that it is close to 0%. Further, all of these samples (Nos. 3 to 13, 15 to 25) had a capacitance of 0.89 μF or more. Furthermore, there were no defects in the deflection test.

Further, a sample of a capacitor having a dielectric layer in which the area ratio of the agglomerated portion obtained when the dielectric layer of the capacitor body is viewed in cross section is 3% or more and 10% or less (Sample Nos. 5 to 8 and 10 to 13, 17 to 20, 22 to 25) had a capacitance of 9.1 μF or more and a DC bias characteristic of -12.1% or less when a DC voltage of 5 V was applied.

Further, among these samples, when the average diameter of the agglomerated portion is D0 and the average particle size of the auxiliary particles is D1, the ratio D1 / D0 is 0.019 or more and 0.093 or less (No. In 5-8 and 10-12), the DC bias characteristic when a DC voltage of 10 V was applied was −23.9% or less.

Separately, a capacitor prepared by adding the same amount of calcium carbonate powder and strontium carbonate powder to the dielectric powder was prepared, and the same evaluation was performed. The total amount of calcium carbonate powder and strontium carbonate powder added is the sample No. It was 7 parts by mass as in 7. The firing temperature was set to 1160 ° C. The characteristics of the capacitors produced in this way are all the characteristics of the sample No. The value equivalent to the characteristic of 19 was shown.

1 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・First crystal particles 5b ・ ・ ・ ・ ・ ・ ・ ・ ・ Second crystal particles 5A ・ ・ ・ ・ ・ ・ ・ ・ Mother phase 5B ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・·····························································································································

Claims (5)

It is equipped with a capacitor body in which multiple layers of dielectric layers and internal electrode layers are alternately laminated.
The dielectric layer has a plurality of first crystal particles containing barium titanate as a main component and a plurality of second crystal particles containing at least one of calcium titanate and strontium titanate as a main component. Ori,
The plurality of the first crystal particles form a matrix of the dielectric layer.
The plurality of the second crystal particles are present in the matrix phase in an agglomerated portion.
Capacitor. The agglomerated portion has a main body portion located in the central region and auxiliary particles located on the peripheral edge of the main body portion, and the main body portion has at least three second crystal particles between two surfaces of each other. The capacitor according to claim 1, which has a structure arranged via grain boundaries, and the auxiliary particles include hump-like particles bonded to the main body portion via a neck portion. The sub-particle further contains an isolated particle existing at a position away from the main body portion, and the isolated particle exists in a range equal to or less than the maximum diameter of the adjacent hump-like particles. The capacitors listed in. Of claims 1 to 3, the capacitor body has at least two dielectric layers in which the area ratio of the agglomerated portion, which is obtained when the dielectric layer is viewed in cross section, is 3% or more and 10% or less. The capacitor described in either. Any one of claims 1 to 4, wherein the ratio D1 / D0 is 0.019 or more and 0.093 or less when the average diameter of the agglomerated portion is D0 and the average particle size of the subparticles is D1. Described capacitor.

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