JP7237787B2 - capacitor - Google Patents

Description

The present disclosure relates to stacked capacitors.

2. Description of the Related Art In recent years, multilayer capacitors (hereinafter referred to as capacitors) are becoming smaller and higher in capacity. On the other hand, capacitors are required to have a characteristic that the decrease in capacitance is small when a DC voltage is applied (hereinafter sometimes referred to as DC bias characteristics) (see, for example, Patent Documents 1 and 2). ).

JP 2011-132056 A JP 2019-021927 A

The capacitor of the present disclosure includes a capacitor body in which a plurality of dielectric layers and internal electrode layers are alternately laminated, and the dielectric layers include a plurality of first crystal grains containing barium titanate as a main component. , and a plurality of second crystal grains containing at least one of calcium titanate and strontium titanate as a main component, the plurality of first crystal grains forming a matrix of the dielectric layer. A plurality of the second crystal grains are present in the matrix phase forming an agglomerate.

1 is an external perspective view of a capacitor shown as an example of an embodiment; FIG. FIG. 2 is a cross-sectional view taken along line ii-ii of FIG. 1; 3 is an enlarged view of a portion P1 in FIG. 2; FIG. 4 is an enlarged view of a P2 portion in FIG. 3; FIG. 5 is an enlarged view of a P3 portion in FIG. 4; FIG. 5 is an enlarged view of a P4 portion in FIG. 4; FIG.

Conventionally, a dielectric material containing barium titanate as a main component has been used for a dielectric layer constituting a capacitor. A dielectric material containing barium titanate as a main component exhibits ferroelectricity, and thus can have a high dielectric constant. 2. Description of the Related Art In recent years, capacitors are required to exhibit a higher capacitance when a DC voltage is applied.

A capacitor according to an embodiment will be described below with reference to FIGS. 1 to 6. FIG. It should be noted that the invention is not limited to the specific embodiments described below. The present invention comprises various aspects consistent with the spirit or scope of the general inventive concept defined by the appended claims.

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

The dielectric layer 5 has a plurality of first crystal grains 5a and a plurality of second crystal grains 5b, as shown in FIG. The first crystal grains 5a are crystal grains containing barium titanate as a main component. The first crystal grains 5 a form the mother phase 5 A of the dielectric layer 5 . The second crystal grains 5b are crystal grains 5b containing at least one of calcium titanate and strontium titanate as a main component. The plurality of second crystal grains 5b form aggregated portions 5B in the mother phase 5A.

In the capacitor of the embodiment, the electric field concentrates on the agglomerate portion 5B formed by gathering a plurality of the second crystal grains 5b mainly composed of at least one of calcium titanate and strontium titanate in the dielectric layer 5. 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 agglomerate portion 5B is the electric field strength of That is, in the dielectric layer 5, the electric field strength on the side of the conglomerate portion 5B is increased, and the electric field strength on the side of the parent phase 5A is decreased. This can improve the DC bias characteristics of the capacitor.

Also, from the viewpoint of the dielectric material, it can be explained that the DC bias characteristic of the capacitor is enhanced when the dielectric layer 5 has the conglomerates 5B. In general, dielectric materials have a constant CR product. where C is the capacitance of the dielectric material. R is the resistance of the dielectric material. Calcium titanate has a lower dielectric constant than barium titanate. Strontium titanate also has a lower dielectric constant than barium titanate. Therefore, the crystal grains (second crystal grains 5b) containing calcium titanate as a main component have a higher specific resistance than the crystal grains (first crystal grains 5a) containing barium titanate as a main component. The crystal grains (second crystal grains 5b) containing strontium titanate as a main component also have a higher specific resistance than the crystal grains (first crystal grains 5a) containing barium titanate as a main component. Therefore, in the agglomerated portion 5B where the second crystal grains 5b containing at least one of calcium titanate and strontium titanate as a main component are agglomerated, the second crystal grains 5b are mixed with the first crystal grains in the matrix 5A. The electric field is more likely to be concentrated compared to the case where each of them exists between 5a. That is, in the dielectric layer 5, the electric field strength in the parent phase 5A is reduced by the amount that the electric field strength in the conglomerate portion 5B is higher than that in the parent phase 5A. As a result, a capacitor with a dielectric layer 5 having conglomerates 5B will have enhanced DC bias characteristics.

Here, the main component is the component contained most in the crystal grains. Having barium titanate as a main component means that the content of titanium and barium in crystal grains is higher than that of other components. Having calcium titanate as a main component means that the crystal particles contain more titanium and calcium than other components. Having strontium titanate as a main component means that the content of titanium and strontium in crystal particles is higher than that of other components. The parent phase 5A is a phase formed by crystal grains having the largest volume ratio in the dielectric layer 5 . A 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 with less occurrence of cracks in the deflection test and less deterioration in electrical characteristics. This is because second crystal grains containing at least one of calcium titanate and strontium titanate as a main component are contained in dielectric layer 5 having first crystal grains 5a containing barium titanate as a main component as base phase 5A. This is because the mechanical strength of the dielectric layer 5 is increased by including the agglomerates 5B mainly composed of 5b.

For the ratio of the second crystal grains 5b contained in the dielectric layer 5, the result of X-ray diffraction of powder obtained by pulverizing the dielectric layer 5 or the capacitor body 1 is used for convenience. Specifically, the ratio of the _{diffraction intensity ICT of calcium titanate or the diffraction intensity IST of} strontium titanate forming the agglomerated portion 5B to the diffraction intensity _IBT of barium titanate forming the matrix 5A is obtained. 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 structure including a main body portion 5Ba and sub-particles 5Bb. In this case, the body portion 5Ba corresponds to a portion that occupies the central region of the conglomerate portion 5B. The main body portion 5Bb is a portion where at least three second crystal grains 5b are bonded to each other at the grain boundaries bo between the two surfaces. A portion where at least three second crystal grains 5b are bonded to each other at a two-plane grain boundary bo is defined as a grain group 5bm. In this case, the main body portion 5Bb preferably has a structure having a plurality of particle groups 5bm. Moreover, the particle groups 5bm are preferably in a state of being bonded (sintered) via the interfacial grain boundary bo. When the particle groups 5bm are bonded to each other via the interfacial grain boundaries bo, a plurality of the particle groups 5bm are bonded via the gaps po and the interfacial grain boundaries bo. area becomes even larger. On the other hand, the sub-particles 5Bb correspond to the portion located at the periphery 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 a region surrounded by a frame line F (solid line). In other words, the agglomerate portion 5B is a region where a frame line F connects the plurality of sub-particles 5Bb arranged around the main body portion 5Ba. The frame line F is arranged with the outer surface of the sub-particle 5Bb as a point of contact when viewed from the center position of the main body 5Ba. In this case, the frame line F may be linear within the range connecting the sub-particles 5Bb.

As shown below, sub-particles 5Bb have nodular particles 5Bbt. When the agglomerate portion 5B included in the dielectric layer 5 further has bump-like particles 5Bbt around its periphery, the range surrounded by the frame line F (solid line) becomes even larger, as shown in FIG. When the agglomerate portion 5B expands to the range having the nodular grains 5Bbt, it comes to include the first crystal grains 5a together with the voids po adjacent to the nodular grains 5Bbt. The area of the agglomerate portion 5B becomes even larger. In this way, the region of high electric field strength is further expanded in the dielectric layer 5, and the DC bias characteristic of the capacitor can be further improved.

As shown in FIGS. 4 and 6, the sub-particles 5Bb may further include isolated particles 5Bbs located at a distance from the main body 5Ba. The isolated grains 5Bbs are preferably spaced apart from the main body portion 5Ba such that at least one of the voids po and the first crystal grains 5a exists. Here, the presence of the first crystal grains 5a between the isolated grains 5Bbs and the main body portion 5Ba means that the first crystal grains 5a are present in the range of the grain size of the isolated grains 5Bbs indicated by the symbol w, as shown in FIG. This means that it is acceptable even if a part of the In other words, when the isolated particle 5Bbs faces the main body 5Bb, part of the first crystal grain 5a exists within the range of the width w of the isolated particle 5Bb in the direction substantially parallel to the surface of the main body 5Bb. It means that you are If the agglomerate portion 5B has a structure including isolated particles 5Bbs in addition to the nodular particles 5Bbt, the apparent area of the agglomerate portion 5B is further increased. As a result, it is possible to further improve the DC bias characteristics of the capacitor having the dielectric layer 5 mainly composed of the mother phase 5A.

In the capacitor of the embodiment, it is preferable that two or more layers of the dielectric layer 5 having the agglomerates 5 are included in the capacitor body 1 . In this case, the dielectric layer 5 having the conglomerates 5 is preferably arranged over the entire layer in that the DC bias characteristics of the capacitor can be enhanced. On the other hand, for reasons of keeping the capacitance of the capacitor high, the dielectric layer 5 with the conglomerates 5 may be placed locally. In this case, the end of the capacitor body 1 in the stacking direction is preferable as the location for disposing the dielectric layer 5 having the conglomerates 5 . As shown in FIG. 2, the ends of the capacitor body 1 in the lamination direction are the upper end portion 1up and the lower end portion 1ud in the lamination direction in the region where the dielectric layers 5 that contribute to the capacitance are laminated. It's about. This is because the upper end portion 1up and the lower end portion 1ud in the stacking direction of the capacitor body 1 tend to have a higher electric field strength than the middle portion in the stacking direction when a DC voltage is applied to the capacitor. Dielectric layers 5 having agglomerated portions 5 are preferably arranged in the same number or approximately the same number of layers at upper end portion 1up and lower end portion 1ud in the lamination direction of capacitor body 1 .

In the capacitor according to the embodiment, the area ratio of the conglomerates 5B in one dielectric layer 5 is preferably 3% or more and 10% or less. In this case, the capacitor body 1 preferably has two or more dielectric layers 5 in which the area ratio of the conglomerates 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 conglomerates 5B is 3% or more and 10% or less, the number of dielectric layers 5 having the conglomerates 5B increases. It is also possible to maintain a high capacitance per layer. Also, even if the DC voltage applied to the capacitor is increased, the decrease in capacitance can be reduced.

Here, the area ratio of the agglomerate portion 5B can be explained as follows. First, as indicated by symbol Acs in FIG. 2, one dielectric layer 5 is selected from the cross section of the capacitor body 1 . Next, let 1 be the total area A0 of the cross section of the selected dielectric layer 5 . Next, the total area A1 including the areas of the conglomerates 5B seen in the cross section of the selected dielectric layer 5 is obtained. The area ratio of the conglomerates 5B is the ratio (A1 /A0). As a cross section of the capacitor body 1 for determining the area ratio of the agglomerate portion 5B, FIG. However, the cross section of the capacitor body 1 for determining the area ratio of the agglomerate portion 5B is not limited to the L cross section, and may be a cross section in the direction in which the two external electrodes 3 of the capacitor face each other (W cross section).

In the capacitor of the embodiment, the ratio D1/D0 is preferably 0.019 or more and 0.093 or less, where D1 is the average particle diameter of the sub-particles 5Bb and D0 is the average diameter of the agglomerate portion 5B. 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. It is a value that represents the ratio of (C1-C0)/C0 in %. As described above, according to the capacitor of the embodiment, even when a DC voltage is applied to the capacitor, the amount of attenuation of the capacitance can be reduced. In this case, the average particle diameter D1 of the sub-particles 5Bb is preferably 0.13 μm or more and 0.68 μm or less. Also, the average diameter D0 of the conglomerates 5B is preferably 5 μm or more and 10 μm or less, particularly 7 μm or more and 7.8 μm or less. Furthermore, the average grain size D2 of the first crystal grains 5a is preferably 0.047 μm or more and 0.22 μm or less.

Here, the average particle diameter D1 of the sub-particles 5Bb is the average value of the maximum diameter of the nodular particles 5Bbt and the maximum diameter of the isolated particles 5Bbs. The maximum diameter of the nodular particles 5Bbt is in the range of D3 shown in FIG. The maximum diameter of isolated particles 5Bbs is in the range of D4 shown in FIG. The average diameter D0 of the agglomerates 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 conglomerate 5B are obtained as follows. In this case, first, the area of the region of the frame line F is obtained by image analysis. Next, the area of the area of the frame line F is obtained once as a circle. If necessary, determine the diameter from the area of the circle. When a plurality of conglomerates 5B exist in one dielectric layer 5, the diameters of the conglomerates 5B are obtained individually, and an average value is obtained. Let this average value be the average diameter D0 of the agglomerate portion 5B.

Also, the average grain size D2 of the first crystal grains 5a is obtained as follows. As a sample for obtaining the average grain size D2 of the first crystal grains 5a, for example, the same sample prepared for obtaining the average grain size D0 of the agglomerate portion 5B may be used. In the cross section of the sample prepared for obtaining the average diameter D0 of the conglomerate portion 5B, first, a region excluding the conglomerate portion 5B is selected. The selected region is a region containing 20 to 30 first crystal grains 5a. The contours of all the first crystal grains 5a found in the region containing 20 to 30 first crystal grains 5a are taken. Next, the area of each circle is obtained from the outline of the first crystal grain 5a. Next, determine the diameter from the area of each circle. Finally, the average value of the diameters corresponding to each of the first crystal grains 5a is obtained. This average value is defined as the average grain size D2 of the first crystal grains 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 agglomerate portion 5B in the same direction as the thickness direction of the dielectric layer 5 is D0, Moreover, 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 obtained by the following procedure. First, the dielectric layer 5 to be used for thickness measurement is selected. As the dielectric layer 5 to be selected, for example, the dielectric layer 5 selected for analyzing the conglomerate portion 5B may be selected. In the selected dielectric layer 5, a plurality of locations are specified evenly in the width direction. The number of points where the thickness is measured should be 3 to 10 points. Next, the thickness of each designated portion is obtained. Next, the average value of the obtained thicknesses is obtained. The average value of the thickness of the dielectric layer 5 obtained in this way is defined as the thickness t of the dielectric layer 5 . The area ratio of the agglomerated portion 5B, the average diameter D0 of the agglomerated portion 5B, the average particle diameter d1 of the sub-particles 5Bb, the maximum diameter D3 of the nodular particles 5Bbt constituting the sub-particles 5Bb, the maximum diameter D4 of the isolated particles 5Bbs, the dielectric The thickness t of the body layer 5 is determined from a photograph of the cross section of the capacitor body 1 . A scanning electron microscope is preferably used to photograph the cross section of the capacitor body 1 . Also in this case, the scanning electron microscope preferably has an analyzer. If the scanning electron microscope is equipped with an analyzer, the crystal grains to be imaged can be identified by composition. Note that, even when included in the dielectric layer 5, crystal grains having a maximum diameter of less than 0.03 μm may be excluded.

Next, a method for manufacturing the capacitor of the embodiment will be described. In the capacitor of the embodiment, a raw material powder containing barium titanate as a main component is added to a ceramic green sheet for forming the dielectric layer 5, and calcium carbonate powder is slurried in advance using an amine-based dispersant. and strontium carbonate powder slurried with an amine-based dispersant are added in a predetermined ratio, and the capacitor can be manufactured by a conventional manufacturing method. When calcium carbonate powder, which has been slurried in advance using 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 grains containing barium titanate as a main component are formed. In the dielectric layer 5 as the phase 5A, the agglomerate portion 5B in which the crystal grains containing calcium titanate as a main component are aggregated is likely to be formed. Similarly, when strontium carbonate powder slurried with an amine-based dispersant is added in advance, conglomerate portions 5B are formed in the dielectric layer 5 in which crystal particles having strontium titanate as a main component are aggregated. easier to be The ratio of the agglomerates 5B present in the dielectric layer 5 is adjusted by the amount of calcium carbonate powder, strontium carbonate powder, and amine-based dispersant added and the firing temperature.

Hereinafter, capacitors were specifically manufactured and their characteristics were evaluated. Here, first, an example of manufacturing a capacitor by adding calcium carbonate powder to dielectric powder will be described. First, as raw material powders for preparing dielectric powders, barium titanate powder (BaTiO ₃ ), calcium carbonate powder (CaCO ₃ ), magnesium carbonate powder (Mg ₂ CO ₃ ), dysprosium 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 %)) were prepared. In this case, barium titanate powder having an average particle size of 0.05 μm was used as the barium titanate powder. Dielectric powders are 0.8 mol of magnesium oxide powder (MgO) converted to MgO, 0.8 mol of dysprosium oxide powder ( _Dy2O3 ), and _MnCO3 powder with respect to ₁₀₀ mol of barium titanate powder. was added in an amount of 0.3 mol in terms of MnO, and a glass component (SiO ₂ —BaO—CaO-based glass powder) was added in an amount of 1 part by mass with respect to 100 parts by mass of the barium titanate powder. Table 1 shows the amount of calcium carbonate added. 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 amounts of the amine-based dispersant and the carboxylic acid-based dispersant shown in Table 1 are percentages relative to the amount of calcium carbonate powder added.

Next, a ceramic green sheet having an average thickness of 20 μm was produced by a doctor blade method using a slurry prepared by mixing the prepared dielectric powder with an organic vehicle. A butyral-based resin was used as the resin contained in the organic vehicle when preparing the ceramic green sheets. The amount of the butyral resin added was 10 parts by mass with respect to 100 parts by mass of the dielectric powder. A 1:1 mixture of ethyl alcohol and toluene was used as the solvent. Nickel powder was used as a metal for conductive paste for forming internal electrode patterns. 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 the nickel powder. As a solvent, a mixture of dihydroterpineol solvent and butyl cellosolve was used.

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

Next, the molded body of the capacitor body was sintered to produce a capacitor body. The firing was carried out in hydrogen-nitrogen under the conditions of a temperature increase rate of 900°C/h and a maximum temperature of 1190°C. A resistance heating type firing furnace was used for this firing. Subsequently, the capacitor main body was subjected to re-oxidation treatment. The conditions for the reoxidation treatment were a nitrogen atmosphere, a maximum temperature of 1000° C., and a holding time of 5 hours. The size of the capacitor body was 3.2 mm x 1.6 mm x 1.6 mm. The average thickness of the dielectric layer was 15 μm. The average thickness of the internal electrode layers 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 external electrodes. The external electrode paste used was one to which Cu powder and glass were added. Then, using an electrolytic barrel machine, the surfaces of the external electrodes were sequentially plated with Ni and Sn to obtain a capacitor.

Next, the produced capacitors were evaluated as follows. First, several of the obtained capacitors were selected and pulverized using a mortar to prepare samples for X-ray diffraction. Among the manufactured capacitors, in the capacitor manufactured by adding calcium carbonate powder to the dielectric powder, diffraction peaks of calcium titanate were observed together with barium titanate in the X-ray diffraction pattern of the dielectric layer. Subsequently, from the X-ray diffraction pattern, the ratio of the diffraction intensity ICT of the main peak of calcium titanate to the diffraction intensity _IBT of _the main peak of barium titanate was determined. The diffraction peak with index (111) was selected as the main peak of barium titanate. The diffraction peak with index (121) was selected as the main peak of calcium titanate. The diffraction intensity ratio is shown in Table 1 as the ratio of calcium titanate contained in the dielectric layer.

Next, the parent phase and agglomerates constituting the dielectric layer were analyzed. For this analysis, capacitor samples processed as follows were used. First, the cross section of the capacitor was polished to prepare a sample with the cross section exposed as shown in FIG. Next, thermal etching was performed on the sample whose cross section was exposed. By performing thermal etching on the sample with the cross section exposed, the contours of the crystal grains and the grain boundaries were made clearly visible in the cross section of the dielectric layer. Next, the obtained samples were subjected to the following analysis and evaluation using a scanning electron microscope equipped with an analyzer. First, from a photograph obtained by observation with a scanning electron microscope, a cross-section was selected that contained one dielectric layer as shown in FIG. A region defined as a unit area is a W cross section of one 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 part to be analyzed was the central part in the width direction of the selected dielectric layer. Next, the components (compounds) of the parent phase and the components (compounds) of the agglomerates existing in the selected one dielectric layer were identified. As a result of analysis, it was found that the main component of the mother phase was barium titanate. All of the capacitors prepared using an amine-based dispersant had conglomerates formed in the dielectric layer. In addition, the agglomerates were formed of crystal grains containing calcium titanate as a main component. In addition, all of the agglomerates had a main body located in the central region and sub-particles located at the periphery of the main body. Furthermore, the main body occupying the central part of the agglomerate had a structure in which at least three crystal grains containing calcium titanate as a main component were in contact with each other at the grain boundaries between two surfaces. Further, in the agglomerated part, nodular particles connected with the main part through the neck part were found. In addition, the agglomerates contained isolated particles that were distant from the main body. In this case, as the isolated particles, those existing in a range equal to or less than the maximum diameter of adjacent nodular particles were selected.

Next, by analyzing the photographed photograph, the average diameter D0 of the agglomerate, the area ratio of the agglomerate (A1/A0), the average thickness t of the selected dielectric layer, and the average thickness t of the dielectric layer Ratio of average diameter D0 of agglomerates (D0/t), average diameter D1 of sub-particles, ratio of average diameter D1 of sub-particles to average diameter D0 of agglomerates (D1/D0), first crystal grains and the ratio (D2/D1) of the average grain size D2 of the first crystal grains to the average grain size D1 of the secondary grains. At this time, the average particle size of the nodular particles was determined from the average value of the maximum diameters determined for a plurality of nodular particles. All the nodular particles existing on the periphery of the main body constituting the agglomerated part were targeted. The average particle diameter of the isolated particles was obtained from the average value of the maximum diameters obtained for a plurality of isolated particles. In this case as well, all the isolated particles present on the periphery of the main body constituting the agglomerate were targeted. Among the manufactured samples, the capacitor manufactured by adding calcium carbonate powder containing an amine-based dispersant to the ceramic green sheet showed agglomeration in the dielectric layer constituting the capacitor body in all samples. department was formed. In this case, the agglomerates had nodular particles and isolated particles along with the body.

Next, regarding the dielectric properties, the capacitance was measured under the conditions in which no DC voltage was applied and in which a 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 was applied were (1) AC voltage of 1.0 V, DC voltage of 5 V, frequency of 1 kHz, and (2) AC voltage of 1.0 V, DC voltage of 10 V, and frequency of 1 kHz. The number of samples was 30, and the average value was obtained. All of the samples whose capacitance could be measured had a capacitance of 0.89 μF or more at zero bias.

Moreover, a deflection test was performed on the fabricated capacitors 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. Two conductor layers (copper foil) were formed on one surface of the glass epoxy substrate at a predetermined interval. The external electrodes of the capacitor were respectively joined to the two conductor layers. Eutectic solder was used as the bonding material. An autograph was used for pressurization in the deflection test. The board deflection limit was set at 12 mm. The number of samples was 33. In the evaluated capacitors, samples with a capacitance decrease rate of more than 5% after the flex test, or samples with visible cracks after the flex test were counted as defective.

Capacitors made by adding strontium carbonate powder to dielectric powder were also made in the same manner as in the case of using calcium carbonate powder, and were evaluated in the same manner. In the produced capacitor, conglomerates were formed in at least two dielectric layers at the ends in the stacking direction of the capacitor body. Also in this case, the agglomerated portion had nodular particles and isolated particles as well as the main portion.

As is clear from the results in Tables 1 and 2, except for the samples (Sample No. 1 and Sample No. 2) in which no agglomerates existed in the dielectric layer, all of Sample Nos. 3 to 13 and 15 to 25 had a DC bias characteristic of −13.3% or less when a DC voltage of 5 V was applied. Here, -13.3% or less means 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 was no defect in the deflection test.

In addition, capacitor samples (Samples No. 5 to 8 and Nos. 5 to 8 and 10 to 13, 17 to 20, and 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.

Furthermore, among these samples, a sample having a ratio D1/D0 of 0.019 or more and 0.093 or less, where D0 is the average diameter of the agglomerates and D1 is the average diameter of the sub-particles (No. 5 to 8, 10 to 12) had a DC bias characteristic of -23.9% or less when a DC voltage of 10 V was applied.

Separately, a capacitor was produced by adding equal amounts of calcium carbonate powder and strontium carbonate powder to dielectric powder, and the same evaluation was performed. The total addition amount of calcium carbonate powder and strontium carbonate powder was As with 7, it was set to 7 parts by mass. Also, the firing temperature was set to 1160°C. As for the characteristics of the capacitor thus produced, all the characteristics are similar to those of the sample No. A value equivalent to that of No. 19 was shown.

Reference numerals 1: Capacitor body 3: External electrode 5: Dielectric layer 5a: First crystal grains 5b Second crystal grains 5A Mother phase 5B Conglomerates 5Ba Main body portion 5Bb Sub-particle 5Bbt Nodular particle 5bbs Isolated particle 7 Internal electrode layer

Claims (5)

It comprises a capacitor body in which a plurality of dielectric layers and internal electrode layers are alternately laminated,
The dielectric layer has a plurality of first crystal grains containing barium titanate as a main component and a plurality of second crystal grains containing at least one of calcium titanate and strontium titanate as a main component. cage,
the plurality of first crystal grains form a matrix of the dielectric layer,
the plurality of second crystal grains are present in the matrix phase to form conglomerates;
capacitor. The agglomerate portion has a main body portion positioned in the central region and sub-grains positioned at the peripheral edge of the main body portion, and the main body portion has at least three of the second crystal grains interposed between two surfaces. 2. The capacitor of claim 1, having a grain boundary disposed structure, wherein said sub-grains comprise nodular grains connected to said body portion via neck portions. 3. The sub-particles further include isolated particles located away from the main body, and the isolated particles are present in a range equal to or less than the maximum diameter of the adjacent nodular particles. capacitors described in . 4. Among any of claims 1 to 3, wherein the capacitor body has at least two dielectric layers in which an area ratio of the agglomerate obtained when the dielectric layer is viewed in cross section is 3% or more and 10% or less. A capacitor according to any one of the preceding claims. 5. Any one of claims 1 to 4, wherein the ratio D1/D0 is 0.019 or more and 0.093 or less, where D0 is the average diameter of the agglomerates and D1 is the average diameter of the sub-particles. Capacitor as described.

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