Capacitor

The present invention relates to a capacitor composed of crystal particles containing barium titanate as a main component and capable of thinning.

Conventionally, barium titanate has been used as the dielectric material of the multilayer ceramic capacitor because of its high relative permittivity, and an inexpensive base metal (Ni, etc.) is used for the internal electrode layer of the multilayer ceramic capacitor. It is used. When the dielectric layer containing barium titanate as the main component and the internal electrode layer are fired at the same time, it is necessary to lower the oxygen partial pressure (for example, 0.03 Pa or less at 1300 ° C) so as not to oxidize Ni. In this case, there is a problem that the dielectric layer is reduced, the insulating property is lowered, and practical characteristics cannot be obtained.

Therefore, for example, in the case of a multilayer ceramic capacitor that satisfies the X5R characteristics (or JIS standard B characteristics) of the EIA standard, the dielectric material is, for example, barium titanate as the main component, and oxides of rare earth elements and Mn. , V, Cr, Mo, Fe, Ni, Cu, Co and other acceptor-type and donor-type element compounds are added to a reduction-resistant dielectric ceramic (see, for example, Patent Document 1). Crystal particles in which a plurality of such additive components are solid-solved in barium titanate have a core part having a tetragonal crystal structure (usually pure BaTiO).₃) And a shell part that surrounds the core part and has a solid solution of additive components.

In addition, rare earth elements such as vanadium, magnesium, and yttrium and manganese are added to barium titanate as a dielectric porcelain in which crystal particles containing barium titanate as the main component have a core-shell structure and satisfy the X5R characteristics of the EIA standard. Has also been proposed (see, for example, Patent Document 2).

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2001-230150</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2008-239407</text></patcit></p>

<p> In recent years, electronic devices such as mobile phones have been miniaturized and mounted at higher densities, and multilayer ceramic capacitors used in such small electronic devices also satisfy the EIA standard X5R characteristics. However, further increase in capacity is required.</p><p> Therefore, an object of the present invention is to provide a capacitor having a high dielectric constant while satisfying the X5R characteristics of the EIA standard.</p>

<p> In the capacitor of the present invention, the dielectric layer is mainly composed of barium titanate, the crystal structure is a tetragonal core part, and the crystal structure is a cubic system.<u style="single">And the vanadium melted</u>It is composed of crystal particles having a shell portion, and the thickness of the shell portion is 11.8 to 2<u style="single">4</u>It is characterized by being composed of a dielectric porcelain having an average particle size of .5 nm and an average particle size of 0.15 to 0.35 μm.</p><p> Further, in the capacitor of the present invention, the dielectric porcelain contains vanadium, magnesium, at least one rare earth element (RE) selected from yttrium, dysprosium, holmium, terbium and ytterbium, and manganese, and is a titanium acid. Vanadium is V for 100 mol of barium₂O₅0.04 to 0.10 mol in terms of conversion, 0.4 to 1.2 mol of magnesium in terms of MgO, RE of the rare earth element (RE)₂O₃It is desirable to consist of dielectric porcelain containing 0.12 to 0.48 mol of manganese and 0.05 to 0.35 mol of manganese in terms of MnO.</p><p> Further, in the capacitor of the present invention, the dielectric porcelain contains vanadium, magnesium, at least one rare earth element (RE) selected from yttrium, dysprosium, holmium, terbium and ytterbium, and manganese, and is a titanium acid. Vanadium is added to 100 mol of barium.₂O₅0.04 to 0.10 mol in terms of conversion, 0.4 to 1.2 mol of magnesium in terms of MgO, RE of the rare earth element (RE)₂O₃It is desirable to contain 0.30 to 0.48 mol in terms of conversion and 0.05 to 0.35 mol of the manganese in terms of MnO.</p><p> Further, in the capacitor of the present invention, the dielectric porcelain has a grain boundary phase between the crystal grains, and the grain boundary phase is a two-sided grain boundary phase formed by a plurality of the crystal grains and a triple point grain boundary. It is composed of a phase and contains the rare earth element, the magnesium and silicon, and the respective concentrations of the rare earth element, the magnesium and the silicon in the two-sided intergranular phase are C1, and the triple-point grain boundary phase. It is desirable that the concentration ratio C2 / C1 of two of the respective elements is 0.8 to 1.2 when the respective concentrations of the rare earth element, the magnesium and the silicon are C2.</p><p> Further, in the capacitor of the present invention, the dielectric porcelain has a grain boundary phase between the crystal grains, and the grain boundary phase is a two-sided grain boundary phase formed by a plurality of the crystal grains and a triple point grain boundary. It is composed of a phase and contains the rare earth element, magnesium and silicon, and the concentrations of the rare earth element, magnesium and silicon in the two-sided intergranular phase are C1 and the triple-point grain boundary phase. It is desirable that the concentration ratio C2 / C1 of each element is 0.8 to 1.2 when the respective concentrations of the rare earth element, the magnesium and the silicon in the above are C2.</p>

<p> According to the present invention, a capacitor having a high dielectric constant can be obtained while satisfying the X5R characteristics of the EIA standard.</p>

<figref num="1">(a) is a schematic cross-sectional view showing an example of the capacitor of the present invention, and (b) is an enlarged view of the inside.</figref><figref num="2">It is sectional drawing which shows the internal structure of the crystal particle containing barium titanate as a main component in the dielectric porcelain which is the dielectric layer which constitutes the capacitor of this embodiment.</figref><figref num="3">In the dielectric porcelain which is the dielectric layer constituting the capacitor of the present embodiment, the two-sided grain boundary phase and the triple point formed by a plurality of crystal grains for measuring the concentration ratios of rare earth elements, magnesium and silicon. It is sectional drawing which shows the measurement position of the grain boundary phase.</figref>

The capacitor of this embodiment will be described in detail with reference to a schematic cross-sectional view of the multilayer ceramic capacitor shown in FIG. FIG. 1 (a) is a schematic cross-sectional view showing an example of the capacitor of the present invention, and FIG. 1 (b) is an enlarged view of the inside. FIG. 2 is a schematic cross-sectional view showing the internal structure of crystal particles containing barium titanate as a main component in the dielectric porcelain which is the dielectric layer constituting the capacitor of the present embodiment.

In the capacitor of this embodiment, external electrodes 3 are formed at both ends of the capacitor body 1. The external electrode 3 is formed by baking, for example, Cu or an alloy paste of Cu and Ni.

The capacitor body 1 is configured by alternately stacking a dielectric layer 5 made of dielectric porcelain and an internal electrode layer 7. Although FIG. 1 shows the laminated state of the dielectric layer 5 and the internal electrode layer 7 in a simplified manner, the capacitor of this embodiment is a laminated body in which the dielectric layer 5 and the internal electrode layer 7 extend to several hundred layers. It has become.

The dielectric layer 5 made of dielectric porcelain is composed of crystal particles 9 and grain boundary phases 11, and its thickness is preferably 3 μm or less, particularly 2 μm or less, thereby increasing the size and capacity of the multilayer ceramic capacitor. It becomes possible to do. When the thickness of the dielectric layer 5 is 0.5 μm or more, it is possible to stabilize the temperature characteristics of the capacitance.

Nickel (Ni) is preferable for the internal electrode layer 7 because the manufacturing cost can be suppressed even if the internal electrode layer 7 is highly laminated and simultaneous firing with the dielectric layer 5 can be achieved.

In the capacitor of this embodiment, the dielectric layer is mainly composed of barium titanate, the crystal structure is a tetragonal core portion, and the crystal structure is a cubic crystal system.<u style="single">And the vanadium melted</u>It is composed of crystal particles having a shell portion, and the thickness of the shell portion is 11.8 to 2<u style="single">4</u>It is made of dielectric porcelain having a diameter of .5 nm and an average particle size of 0.15 to 0.35 μm.

The dielectric layer 5 constituting the multilayer ceramic capacitor has crystal particles in the above average particle size range, and the crystal structure of the crystal particles 9 is a cubic core portion 9a and a cubic shell portion 9b. It has a core-shell structure, and when the thickness t of the shell portion 9b is within the above range, the relative permittivity of the dielectric layer 5 constituting the capacitor at room temperature (25 ° C) is 3950 or more, and the temperature of the capacitance is high. A monolithic ceramic capacitor whose characteristics satisfy the EIA standard X5R characteristics (in the temperature range of -55 to 85 ° C, the rate of change in capacitance with respect to 25 ° C is within ± 15%). can do.

The EIA standard X5R characteristics indicate that the rate of change in capacitance is within ± 15% when 25 ° C is used as a reference in the temperature range of -55 to 85 ° C.

In the capacitor of this embodiment, the thickness of the shell portion 9b of the crystal particles 9 having a core-shell structure is 11.8 to 26.5 nm. When the thickness of the shell part 9b is thinner than 11.8 nm, the temperature characteristic of the capacitance becomes difficult to satisfy the X5R characteristic, while when the thickness of the shell part 9b is thicker than 26.5 nm, the relative permittivity is lower than 3950. Become.

Further, in the capacitor of this embodiment, the average particle size of the crystal particles 9 constituting the dielectric porcelain which is the dielectric layer 5 is 0.15 to 0.35 μm. If the average particle size of the crystal particles 9 is smaller than 0.15 μm, it becomes difficult to form a core-shell structure in the crystal particles 9, and the structure changes to a structure in which the additive component is solid-solved even in the center of the crystal particles 9. Therefore, the temperature change rate of the capacitance becomes larger than ± 15%, which does not satisfy the X5R characteristics of the EIA standard. On the other hand, if the average particle size of the crystal particles 9 is larger than 0.35 μm, the temperature change rate of the capacitance becomes larger than ± 15%, which does not satisfy the X5R characteristics of the EIA standard.

Further, in the capacitor of the present embodiment, the dielectric porcelain constituting the dielectric layer 5 is composed of vanadium, magnesium, at least one rare earth element (RE) selected from yttrium, dysprosium, holmium, terbium and ytterbium. Vanadium is added to 100 mol of barium titanate, which contains manganese.₂O₅0.04 to 0.10 mol of magnesium, 0.4 to 1.2 mol of magnesium in terms of MgO, and RE of at least one rare earth element (RE) selected from yttrium, dysprosium, holmium, terbium and ytterbium.₂O₃It is desirable to consist of a dielectric porcelain containing 0.12 to 0.48 mol of manganese and 0.05 to 0.35 mol of manganese in terms of MnO.

When the composition of the dielectric porcelain constituting the dielectric layer 5 is within the above range, the relative permittivity can be set to 4500 or more and the AC bias characteristic is 30% or less while the temperature characteristic of the capacitance satisfies the X5R characteristic. It is possible to obtain a monolithic ceramic capacitor having a dielectric loss of 5% or less. Here, the AC bias characteristic is the ratio of the amount of change in the permittivity when AC 1 V / um is applied to the permittivity when AC 0.01 V / um is applied.

Further, in the capacitor of the present embodiment, the dielectric porcelain constituting the dielectric layer 5 contains vanadium V with respect to 100 mol of barium titanate.₂O₅0.04 to 0.10 mol in terms of conversion, 0.5 to 1.2 mol of magnesium in terms of MgO, RE rare earth element (RE)₂O₃It is desirable to consist of a dielectric porcelain containing 0.30 to 0.48 mol of manganese and 0.05 to 0.35 mol of manganese in terms of MnO. When the dielectric porcelain constituting the dielectric layer 5 has the above composition, the AC bias characteristic can be further reduced.

In the capacitor of this embodiment, a glass component and other additive components are contained in the dielectric porcelain at a ratio of 4% by mass or less as an auxiliary agent for improving the sinterability as long as the desired dielectric properties can be maintained. You may.

In the capacitor of the present embodiment, the shell portion 9b has a structure surrounding the core portion 9a, but the crystal particles 9 in which the shell portion 9a surrounds the core portion 9a are a transmission electron microscope equipped with an elemental analyzer (EDS). Confirm by analysis using. As a sample to be analyzed, 10 to 20 crystal particles 9 having an average particle size in the range of ± 30% are extracted from a sample prepared by processing a multilayer ceramic capacitor. The spot size of the electron beam when performing elemental analysis shall be 1 to 3 nm, and the analysis location shall be the region from the grain boundary to the central part, which is the surface of the crystal particles 9. In this case, the concentration of the element (magnesium or rare earth element) is obtained every 5 to 10 nm from the grain boundary on the surface of the crystal particle 9 to the central part, and a graph is created with the horizontal axis as the distance and the vertical axis as the element concentration. .. Here, in the graph, three points are taken in order from the measurement point closest to the grain boundary side, an approximate straight line is drawn using these three points, and the slope of the straight line is used as the concentration gradient of the element on the surface layer side, and the crystal. Take three points in order from the measurement point on the center side of the crystal particle 9 among the measurement points within the range of 30 to 100 nm from the grain boundary of the particle 9, draw an approximate straight line from these three points, and calculate the slope of the straight line. The concentration gradient of the element on the central side. When the concentration gradient of the element on the surface layer side is 0.15 atomic% / nm or more and the concentration gradient of the element on the central portion side is 0.5 atomic% / nm or less, the core-shell structure is assumed.

Next, the crystal structures of the core portion 9a and the shell portion 9b constituting the crystal particles 9 are determined by an X-ray diffraction method. First, from the X-ray diffraction pattern of the dielectric layer 5, the (004) plane ((004) plane) showing the cubic system of barium titanate appearing between the (004) plane and the (400) plane showing the tetragonal system of barium titanate. The diffraction intensity of the 040) plane and the (400) plane overlap.) Is equal to or equal to the diffraction intensity of either the (400) plane or the (004) plane showing the tetragonal system of barium titanate. It is assumed that the crystal particles 9 have tetragonal and cubic crystal structures when they are larger than that.

Then, the analysis result by a transmission electron microscope confirming that the crystal particles 9 have a core portion 9a and a shell portion 9b surrounding the core portion 9a, and the crystal particles 9 have a tetragonal system and a cubic crystal system. From the result of the fact that the crystal particles 9 have a tetragonal core portion 9a and a cubic shell portion 9b surrounding the core portion 9a, it is determined that the crystal particles 9 have a tetragonal core portion 9a.

Next, the thickness of the shell portion of the crystal particles 9 is determined for those in which the crystal particles 9 are determined to consist of the tetragonal core portion 9a and the cubic shell portion 9b surrounding the core portion 9a. For the thickness of the shell portion 9b of the crystal particles 9, the X-ray diffraction method shown in JP-A-2006-137647 and J. Am. Ceram. Soc., 90 [4] 1107-1111 (2007) was used. Based on the evaluation method, it is calculated from the following formula.

The crystal structure of the crystal particles 9 of interest is such that in the measured X-ray diffraction pattern, the selected X-ray diffraction pattern is compared to the reflection of pure tetragonal (hkl) or cubic (h'k'l'). It is broad and includes reflections of tetragonal (hkl) and cubic (h'k'l') from the identification of peak positions.

The target diffraction data are the reflections of tetragonal (hkl) and cubic (h'k'l'), from the diffraction peak to the peak intensity (= integrated intensity), the 2θ position of the peak top, and the full width at half maximum. , Obtain parameters such as peak shape function. At that time, peak separation is performed as necessary. In this case, the conditions for peak separation are background function: 0th order polynomial, synchrotron radiation: Kα1, profile function: the psedo-Voigt function, half width: different half width for all reflections, profile objectivity: target, And data resolution: sharp (minimum half width: about 0.1 °). Commercially available software (for example, PROFIT) can be used for peak separation, and the tool for peak separation is not particularly limited.

<maths num="1"><img file="JP5496331B2_D0001.tif" /></maths>

<maths num="2"><img file="JP5496331B2_D0002.tif" /></maths>

The average particle size of the crystal particles 9 is measured by the following procedure. First, the fracture surface of the sample, which is the capacitor body 1 after firing, is polished. After that, take a picture of the internal structure of the polished sample using a scanning electron microscope, draw a circle containing 50 to 100 crystal particles on the picture, and select the crystal particles in and around the circle. .. Next, the contour of each crystal particle is image-processed to obtain the area of each crystal particle, the diameter when replaced with a circle having the same area is calculated, and the diameter is calculated from the average value.

The composition of the dielectric porcelain is determined by using ICP (Inductively Coupled Plasma) analysis and atomic absorption spectrometry on a solution of a multilayer ceramic capacitor dissolved in acid. In this case, the amount of oxygen is obtained by using the valence of each element as the valence shown in the periodic table.

Further, in the capacitor of the present embodiment, the grain boundary phase 11 forming the dielectric porcelain which is the dielectric layer 5 is a two-sided grain boundary phase and a triple point grain boundary phase formed by a plurality of crystal particles 9. The rare earth elements, magnesium and silicon contained in the dielectric porcelain are between the two-sided intergranular phase and the triple-point grain boundary phase, and the rare earth elements, magnesium and silicon in the two-sided intergranular phase. When the respective concentrations are C1 and the respective concentrations of rare earth elements, magnesium and silicon in the triple-point grain boundary phase are C2, the C2 / C1 of two of the rare earth elements, magnesium and silicon are 0.8 to 1.2. Is desirable. When C2 / C1 of two of the rare earth elements, magnesium and silicon is 0.8 to 1.2, the capacitance variation of the capacitor (for example, 85 ° C) is higher than room temperature (25 ° C) (for example, 85 ° C). CV) can be reduced. Furthermore, when C2 / C1 of all rare earth elements, magnesium and silicon is 0.8 to 1.2, the capacitance of the capacitor at a temperature higher than room temperature (25 ° C) (for example, 85 ° C) The variation (CV) can be further reduced.

FIG. 3 shows an interplanetary structure formed by a plurality of crystal grains 9 for measuring the concentration ratios of rare earth elements, magnesium and silicon in a dielectric porcelain which is a dielectric layer 5 constituting the capacitor of the present embodiment. It is sectional drawing which shows the measurement position of the grain boundary phase 11a and the triple point grain boundary phase 11b.

The concentrations of rare earth elements, magnesium and silicon in the two-sided intergranular phase 11a and the triple-point grain boundary 11b are determined by the X-ray microanalyzer (XMA) attached to the transmission electron microscope. In this case, the sample used for the analysis is a thin plate-shaped dielectric porcelain cut out from the dielectric layer 5 of the capacitor and subjected to ion milling processing. In the region to be analyzed, the maximum diameter of at least three crystal particles 9 is the average particle size when the two-sided grain boundary phase 11a and the triple-point grain boundary phase 11b formed of the plurality of crystal particles 9 are viewed in cross section. The location consists of 9 groups of crystal particles within ± 20% of. Then, using an X-ray microanalyzer (XMA), as shown in FIG. 3, the rare earth elements, magnesium and silicon, respectively, at the position S1 of the interfacial grain boundary phase 11a and the position S2 of the triple point grain boundary phase 11b, respectively. The concentration is obtained, and the ratio C2 / C1 of the concentration C1 of each element in the interfacial grain boundary phase 11a and the concentration C2 of each element in the triple point grain boundary phase 11b is obtained. At this time, the position S1 of the two-sided grain boundary phase 11a to be analyzed is approximately the center of the width of the grain boundary phase 11, and the position S2 of the triple point grain boundary phase 11b is the center of the triple point grain boundary phase 11b. Further, the position S1 of the interfacial grain boundary phase 11a is set to a position 50 nm or more away from the position where the position S2 of the triple point grain boundary phase 11b is defined.

Next, a method of manufacturing the capacitor of the present embodiment will be described.

First, a ceramic slurry is prepared by using an organic resin such as polyvinyl butyral resin and a solvent such as toluene and alcohol with a dielectric powder using a ball mill or the like, and then the ceramic slurry is prepared by using a sheet forming method such as a doctor blade method or a die coater method. To form a ceramic green sheet on the substrate. The thickness of the ceramic green sheet is preferably 1 to 5 μm in terms of thinning the dielectric layer 5 for increasing the capacity and maintaining high insulation.

As the dielectric powder used in the manufacturing method of the multilayer ceramic capacitor of the present embodiment, barium titanate powder (hereinafter referred to as BT powder; Ba / Ti molar ratio is 1.001 to 1.009) is used. The average particle size of the BT powder is preferably 0.21 to 0.30 μm. In the method for manufacturing the multilayer ceramic capacitor of the present embodiment, the average particle size of the BT powder for forming the crystal particles 9 constituting the dielectric porcelain to be the dielectric layer 5 is in the range of 0.21 to 0.30 μm. By using the material, it is possible to suppress the solid dissolution of the additive component including the rare earth element (RE) in the BT powder and to form a shell portion having a thickness described later. This facilitates the thinning of the dielectric layer 5, and makes it possible to obtain crystal particles 9 as BT powder, which have a high dielectric constant under firing conditions described later and satisfy the X5R characteristics of the EIA standard.

The dielectric powder used in manufacturing the capacitor of this embodiment contains barium titanate, which will be described later, as a main component, and contains, for example, vanadium, magnesium, a rare earth element, manganese, and all the components of a sintering aid in a predetermined amount. It is better to use a coated one.

In this case, the dielectric powder to be used is prepared, for example, as follows. First, ammonia as a pH adjuster is added to a suspension of barium titanate powder (BT powder) having a purity of 99.9% or more, a Ba / Ti molar ratio of 1.001 to 1.09, and an average particle size of 0.21 to 0.30 μm. Using water, set the pH to the range of 6 to 8, and add lithium aqueous solution, silica sol, barium carbonate aqueous solution, magnesium hydroxide aqueous solution, calcium hydroxide aqueous solution, ammonium vanadate aqueous solution, manganese acetate aqueous solution, and itrium, displosium, formium. , An aqueous solution of at least one rare earth element selected from terbium and itterbium is added and mixed in this order to prepare a ceramics rally. The purity of these raw material reagents is preferably 99.5% or more because it suppresses the mixing of impurities into the obtained dielectric porcelain and obtains high dielectric properties.

Next, this ceramics rally is put into a spray dryer equipped with a 4-fluid nozzle to generate droplets with a diameter of 10 μm or less from the 4-fluid nozzle, and dried at a temperature of around 200 ° C to form a dielectric powder. The precursor of the above is prepared, and then the precursor of the dielectric powder is prepared by heat treatment at a temperature higher than the temperature of the drying treatment.

As for the composition of the dielectric powder, when the BT powder is 100 mol, the aqueous solution of ammonium vanadate is V.₂O₅0.04 to 0.10 mol in terms of conversion, 0.5 to 1.2 mol of magnesium hydroxide aqueous solution in terms of MgO, 0.05 to 0.35 mol of manganese acetate aqueous solution in terms of MnO, at least one rare earth element selected from yttrium, dysprosium, holmium, terbium and ytterbium. RE the aqueous solution of (RE)₂O₃It is desirable to have a composition of 0.12 to 0.48 mol in terms of conversion, which makes it possible to obtain a monolithic ceramic capacitor with a high dielectric constant, a capacitance temperature characteristic satisfying the X5R characteristic, and an AC bias characteristic and a small dielectric loss. become.

The amount of the sintering aid added is adjusted to 0.5 to 2.0 parts by mass with respect to 100 parts by mass of the BT powder. This makes it possible to further improve the sinterability of the dielectric porcelain. Its composition is Li₂O = 1 ~ 15 mol%, SiO₂= 40-60 mol%, BaO = 15-35 mol%, and CaO = 5-25 mol% are preferred.

Next, a rectangular internal electrode pattern is printed and formed on the main surface of the obtained ceramic green sheet. The conductor paste to be the internal electrode pattern is prepared by using Ni or an alloy powder thereof as a main component metal, mixing it with a ceramic powder as a co-material, and adding an organic binder, a solvent and a dispersant. Further, in order to eliminate the step due to the internal electrode pattern on the ceramic green sheet, it is preferable to form the ceramic pattern around the internal electrode pattern with substantially the same thickness as the internal electrode pattern. In this case, it is preferable to use the dielectric powder used for the ceramic green sheet as the ceramic component constituting the ceramic pattern in that the firing shrinkage in the simultaneous firing is the same.

Next, a desired number of ceramic green sheets on which the internal electrode pattern is formed are stacked, and a plurality of ceramic green sheets on which the internal electrode pattern is not formed are stacked on top of each other so that the upper and lower layers are the same number, and temporarily laminated. Form the body. The internal electrode pattern in the temporary laminate is shifted by half a pattern in the longitudinal direction. By such a laminating method, the internal electrode patterns can be formed so as to be alternately exposed on the end faces of the laminated body after cutting.

In the capacitor of the present embodiment, in addition to the construction method in which the internal electrode pattern is formed in advance on the main surface of the ceramic green sheet and then laminated, the internal electrode pattern is formed after the ceramic green sheet is once brought into close contact with the equipment on the lower layer side. A method in which a ceramic green sheet on which the internal electrode pattern is not printed is placed on the printed, dried, printed, and dried internal electrode pattern and temporarily adhered, and the ceramic green sheet is adhered and the internal electrode pattern is printed in sequence. Can also be formed by.

Next, the temporary laminate is pressed under conditions of a temperature and pressure higher than the temperature and pressure at the time of the temporary laminate to form a laminate in which the ceramic green sheet and the internal electrode pattern are firmly adhered to each other.

Next, the laminated body is cut in a grid pattern to form a capacitor body molded body in which the end portion of the internal electrode pattern is exposed.

Next, the obtained capacitor body molded body is degreased and then fired. It is desirable that firing be performed in a hydrogen-nitrogen atmosphere with a maximum temperature of 1150 to 1230 ° C and a holding time of 0.1 to 4 hours. After that, the capacitor body 1 is obtained by performing a reoxidation treatment in a temperature range of 900 to 1100 ° C. After that, if necessary, the ridgeline portion of the capacitor body 1 may be chamfered, and barrel polishing may be performed to expose the internal electrode layer 7 exposed from the opposite end faces of the capacitor body 1. By performing the firing under such conditions, the average particle size of the crystal particles 9 constituting the dielectric layer 5 is set in the range of 0.15 to 0.35 μm, and the crystal structure of the crystal particles 9 is the tetragonal core portion 9a. It is composed of a cubic shell part 9b in which at least one of the vanadium, magnesium, rare earth element (RE) and manganese is dissolved in a solid solution surrounding the core part, and the thickness of the shell part 9b is 10 to 20 nm. The capacitor body 1 can be obtained.

Further, in the case of manufacturing the capacitor of the present embodiment, after degreasing the obtained capacitor body molded body, once before reaching the maximum temperature in a hydrogen-nitrogen atmosphere, 0.5 at a temperature of 900 to 1000 ° C. It is desirable to provide a heat treatment step that holds for about 3 hours. By providing such a heat treatment step, it is possible to reduce the difference in composition of rare earth elements, magnesium and glass components in the two-sided grain boundary phase 11a and the triple point grain boundary phase 11b of the crystal particles 9, whereby the difference in composition of the capacitor can be reduced. Capacitance variation (CV) at temperatures above room temperature (25 ° C) can be reduced. Here, the capacitance variation (CV) is expressed by the ratio (σ / x) of the mean value (x) and the standard deviation (σ) obtained by using the measured values of the capacitances of a plurality of samples as parameters. Is the value to be.

As described above, the capacitor of the present embodiment contains barium titanate as a main component for forming the dielectric layer 5, and vanadium, magnesium, rare earth element (RE), manganese, and a sintering aid are added thereto. Crystal particles 9 having a small average thickness in the shell portion 9b can be obtained by firing the obtained raw capacitor body molded body in a predetermined amount coated with all the components under firing conditions at a high heating rate. ..

Next, the external electrode paste is applied to the opposing ends of the capacitor body 1 and baked to form the external electrode 3. Further, in some cases, a plating film is formed on the surface of the external electrode 3 in order to improve the mountability. In this way, the capacitor of the present invention can be obtained.

<p> First, as a raw material powder, barium titanate powder (hereinafter referred to as BT powder) having a purity of 99.9% and a Ba / Ti molar ratio of 1.005 was prepared.</p><p> Next, ammonia water was used as a pH adjuster in the suspension of BT powder so that the pH was in the range of 6 to 8. Next, at least one selected from lithium aqueous solution, silica sol, barium carbonate aqueous solution, magnesium hydroxide aqueous solution, calcium hydroxide aqueous solution, ammonium vanadate aqueous solution, manganese acetate aqueous solution and ittrium, disprosium, formium, terbium and itterbium. An aqueous solution of a rare earth element was added in this order and mixed to prepare a ceramics rally.</p><p> Next, this ceramics rally is put into a spray dryer equipped with a 4-fluid nozzle to generate droplets with a diameter of 10 μm or less from the 4-fluid nozzle, and dried at a temperature of around 200 ° C to obtain a dielectric powder. Then, the precursor of this dielectric powder was heat-treated at 400 ° C., and all the components of vanadium, magnesium, rare earth elements, manganese and sintering aid were found on the surface of the BT powder. A quantitatively coated dielectric powder was prepared. Sintering aid is SiO₂= 55, BaO = 20, CaO = 15, Li₂The composition was adjusted so that the composition was O = 10 (mol%), and the amount of the sintering aid added was adjusted to 1 part by mass with respect to 100 parts by mass of the BT powder. In addition, a sample was prepared by adding glass powder as a sintering aid to BT powder coated with vanadium, magnesium, rare earth elements and manganese in a predetermined amount (Sample No. 33).</p><p> Next, the obtained dielectric powder was put into a mixed solvent of polyvinyl butyral resin and toluene and alcohol, and wet-mixed using a zirconia ball having a diameter of 1 mm to prepare a ceramic rally, and the thickness was prepared by a doctor blade method. A 2 μm ceramic green sheet was prepared.</p><p> Next, a plurality of conductor pastes containing Ni as a main component were formed on the upper surface of the ceramic green sheet so as to form a rectangular internal electrode pattern. As the conductor paste for forming the internal electrode pattern, BT powder was added to 100 parts by mass of Ni powder having an average particle size of 0.3 μm.</p><p> Next, 200 ceramic green sheets printed with the internal electrode pattern were laminated, and 20 ceramic green sheets without the internal electrode pattern printed were laminated on the upper and lower surfaces thereof, and the temperature was 60 ° C. using a press machine. Pressure 10⁷A laminated body was produced by bringing them into close contact with each other under the conditions of Pa and 10 minutes, and then the laminated body was cut to a predetermined size to form a capacitor body molded body.</p><p> Next, after debindering the capacitor body molded body in the atmosphere, the temperature rise rate was set to 2000 ° C / h in hydrogen-nitrogen, and the capacitor body was fired at the temperatures shown in Table 1. This firing was carried out using a roller hers kiln. In addition, a sample with a temperature rise rate of 500 ° C / h was prepared (Sample No. 34).</p><p> The produced capacitor body was subsequently reoxidized at 1000 ° C. for 4 hours in a nitrogen atmosphere. The size of this capacitor body is 2.05 x 1.28 x 1.28 mm³, The thickness of the dielectric layer is 2.0 μm, and the effective area of one internal electrode layer is 1.78 mm.²Met. The effective area is the area of the overlapping portion of the internal electrode layers formed alternately in the stacking direction so as to be exposed on different end faces of the capacitor body.</p><p> Next, after barrel polishing the capacitor body, an external electrode paste containing Cu powder and glass was applied to both ends of the capacitor body and baked at 850 ° C. to form an external electrode. Then, using an electrolytic barrel machine, the surface of the external electrode was sequentially Ni-plated and Sn-plated to prepare a monolithic ceramic capacitor.</p><p> Next, the following evaluations were made on these multilayer ceramic capacitors. The relative permittivity at room temperature (25 ° C) is measured using an LCR meter (manufactured by Hulett Packard) at a temperature of 25 ° C, a frequency of 1.0 kHz, and an AC voltage of 1.0 V / μm. It was obtained from the thickness of the internal electrode layer and the effective area of the internal electrode layer.</p><p> The dielectric loss was also measured using the same LCR meter under the same conditions as the capacitance. As for the temperature characteristics of the capacitance, the capacitance was measured in the temperature range of -55 to 85 ° C.</p><p> The AC bias characteristics are C1, temperature 25 ° C, frequency when alternating current (AC) voltage 0.01V / μm is applied under the conditions of temperature 25 ° C, frequency 1.0kHz, and AC voltage 0.01 to 3.5V / μm. It was calculated from ((C2-C1) / C1) x 100 (%) when the capacitance when 1.0kHz and AC voltage 3.5V / μm was applied was C2.</p><p> For the average particle size of the crystal particles constituting the dielectric layer, after polishing the fracture surface of the sample which is the main body of the capacitor after firing, a photograph of the internal structure is taken using a scanning electron microscope, and the crystal particles are photographed on the photograph. Draw a circle containing 30 particles, select crystal particles within and around the circle, image the outline of each crystal particle, obtain the area of each particle, and replace it with a circle with the same area. Was calculated and calculated from the average value.</p><p> Next, whether or not the crystal particles having the core portion and the shell portion surround the core portion was confirmed by analysis using a transmission electron microscope equipped with an elemental analyzer (EDS). As the sample analyzed, 10 to 20 crystal particles in the range of ± 30% of the average particle size were extracted from the sample for TEM prepared by processing a multilayer ceramic capacitor. The spot size of the electron beam when performing elemental analysis was 1 to 3 nm, and the analysis location was the region from the grain boundary to the center, which is the surface of the crystal particles. In this case, the concentration of rare earth elements was obtained every 5 to 10 nm from the grain boundary, which is the surface of the crystal particles, to the central part, and a graph was created with the horizontal axis as the distance and the vertical axis as the element concentration. Here, in the graph, three points were taken in order from the measurement point closest to the grain boundary side, and an approximate straight line was drawn using these three points, and the slope of the straight line was taken as the concentration gradient of the element on the surface layer side. In addition, three measurement points within the range of 30 to 100 nm from the grain boundary of the crystal particle are taken in order from the measurement point closest to the center of the crystal particle, and an approximate straight line is drawn from these three points, and the slope of the straight line is drawn. Was taken as the concentration gradient of the element on the central side. In this case, when the concentration gradient of the element on the grain boundary side is 0.15 atomic% / nm or more and the concentration gradient of the element on the central part side is 0.5 atomic% / nm or less, the core-shell structure is assumed. ..</p><p> Next, the crystal structures of the core portion and the shell portion constituting the crystal particles were determined by X-ray diffraction. First, from the X-ray diffraction pattern of the sample obtained by crushing the dielectric layer, the cubic system of barium titanate appearing between the (004) plane and the (400) plane showing the tetragonal system of barium titanate is shown (004). The diffraction intensity of the plane ((040) plane and (400) plane overlap) is the diffraction intensity of either the (400) plane or the (004) plane showing the tetragonal system of barium titanate. It was assumed that the crystal particles had tetragonal and cubic crystal structures when they were equal to or larger than that.</p><p> Then, the analysis result by a transmission electron microscope confirming that the crystal particles have a core portion and a shell portion surrounding the core portion, and that the crystal particles have tetragonal and cubic crystal structures. From the results, it was determined that the crystal particles had a tetragonal core portion and a cubic shell portion surrounding the core portion.</p><p> Next, the thickness of the shell portion of the crystal particles was determined by the following method for those in which the crystal particles 9 were determined to have a tetragonal core portion and a cubic shell portion surrounding the core portion.</p><p> The shell thickness of the crystal particles was determined using the above-mentioned formulas 1 and 2. At this time, an X'Pertpro manufactured by PANalytical was used as the X-ray diffractometer. At this time, the crystal structure of the target crystal particles is compared with the reflection of the selected X-ray diffraction pattern of pure tetragonal (hkl) or cubic (h'k'l') in the measured X-ray diffraction pattern. The ones that are broad and contain the reflections of tetragonal (hkl) and cubic (h'k'l') from the identification of the peak position were selected.</p><p> Then, as the diffraction peak, the tetragonal crystals (002) and (200) and the cubic crystal (200) were measured. The size of the beam was 0.5 mm in the vertical direction and 5 mm in the horizontal direction. The wavelength was 1.54982 Å. For the measurement of dielectric porcelain, the step width was 0.02 ° and the counting time per point was 5.0 seconds. In addition, the number of repetitions was set to 10 times, and the integration of 10 times was defined as the diffraction intensity. In the evaluation, tetragonal (002) and (200) and cubic (200) were peak-separated from the diffraction peak using peak separation software (PROFIT) under the following conditions. The conditions for peak separation are background function: 0th order polynomial, synchrotron radiation: Kα1, profile function: the psedo-Voigt function, half width: different half width for all reflections, profile objectivity: target, data resolution: Sharp (minimum half width: about 0.1 °) and analysis range: 44 ° &lt;2θ &lt;47 °.</p><p> The composition of the obtained sintered sample was analyzed by ICP (Inductively Coupled Plasma) analysis and atomic absorption spectrometry. In this case, the obtained dielectric porcelain is mixed with boric acid and sodium carbonate, melted, and dissolved in hydrochloric acid. First, qualitative analysis of the elements contained in the dielectric porcelain is performed by atomic absorption spectrometry, and then identification is performed. Each element was quantified by ICP emission spectroscopic analysis using a diluted standard solution as a standard sample. In addition, the amount of oxygen was calculated by using the valence of each element as the valence shown in the periodic table. The composition of the dielectric layer constituting the obtained multilayer ceramic capacitor was in agreement with the composition shown in Table 1.</p><p> Table 1 shows the composition and firing conditions, and the average particle size and dielectric properties (relative permittivity, capacitance temperature characteristics, AC bias characteristics, dielectric loss) of the crystal particles that make up the dielectric layer in the obtained multilayer ceramic capacitor. ) Are shown in Table 2.<u style="single">Samples No. I-5, I-11, I-14, I-20, I-25, I-30, I-34 and I-35 in Tables 1 and 2 are reference samples.</u></p><p><tables num="1"><img file="JP5496331B2_D0003.tif" /></tables></p><p><tables num="2"><img file="JP5496331B2_D0004.tif" /></tables></p><p> As is clear from the results in Tables 1 and 2, Sample No. I-1 ~ 4, I-6 ~ 10, I-12, I-13, I-15 ~ 19, I-21 ~ 24, I-26 In ~ 29 and I-31 ~ 34, the relative permittivity at room temperature (25 ° C) was 3950 or more, and the temperature characteristics of the capacitance satisfied the X5R characteristics.</p><p> In addition, sample No. I-2 ~ 4, I-6 ~ 10, I-12, I-13, I-16 ~ 19, I-22 ~ 24, I-27 ~ 29, I-31 and I-32 The relative permittivity at room temperature (25 ° C) is 4500 or more, the temperature characteristic of capacitance satisfies the X5R characteristic, the AC bias characteristic is 30% or less, and the dielectric loss is 5% or less. Met.</p><p> In particular, the vanadium is added to 100 mol of barium titanate.₂O₅0.04 to 0.1 mol in terms of conversion, 0.5 to 1.2 mol of magnesium in terms of MgO, RE of the rare earth element (RE)₂O₃Sample No. No. I-2 to 3, I-6 to 10, I-12, I using a dielectric porcelain containing 0.3 to 0.48 mol of the converted manganese and 0.05 to 0.35 mol of the manganese in terms of MnO as a dielectric layer. -13, I-16 ~ 19, I-22 ~ 24, I-27 ~ 29, I-31 and I-32 have a relative permittivity of 4500 or more at room temperature (25 ° C) and capacitance temperature characteristics. Satisfied the X5R characteristics, the AC bias characteristics were 29.00% or less, and the dielectric loss was 5% or less.</p><p> On the other hand, samples No. I-5, I-11, I-14, I-20, I-25, I-30 and I-35 have a relative permittivity of 3950 or more at room temperature (25 ° C). And the temperature characteristic of the capacitance satisfies either of the characteristics of X5R.</p>

<p> Next, in the firing step, after degreasing the produced capacitor molded body, before firing at the maximum temperature, heat treatment was once performed at the temperature shown in Table 3 for 1 hour, and all of the same as in Example 1. A sample was prepared by the same method, the same evaluation was performed, and the capacitance at 85 ° C was measured to determine the variation (CV). The variation in capacitance was determined from 32 samples each.</p><p> The concentrations of rare earth elements, magnesium and silicon in the two-sided grain boundary phase and the triple-point grain boundary phase in the dielectric porcelain were determined by an X-ray microanalyzer (XMA) attached to a transmission electron microscope. In this case, the sample used for the analysis was a thin plate-shaped dielectric porcelain cut out from the dielectric layer of the produced multilayer ceramic capacitor and subjected to ion milling. The region to be analyzed is from a group of crystal grains in which the maximum diameter of at least three crystal grains is within ± 20% of the average grain size when the two-sided grain boundary phase and the triple point grain boundary phase are viewed in cross section. I selected 5 places. Then, using an X-ray microanalyzer (XMA), as shown in FIG. 3, the concentrations of rare earth elements, magnesium and silicon at the positions S1 of the interfacial grain boundary phase and the position S2 of the triple point grain boundary phase were determined. The average value of the ratio C2 / C1 of the element concentration C1 in the two-sided grain boundary phase and the element concentration C2 in the triple point grain boundary phase was calculated. At this time, the position S1 of the interfacial grain boundary phase to be analyzed was set to be approximately the center of the width of the grain boundary phase, and the position S2 of the triple point grain boundary phase was set to the center of the triple point grain boundary phase. The position S1 of the interfacial grain boundary phase was set to a position about 50 nm away from the position where the position S2 of the triple point grain boundary phase was defined. Table 3 shows the fabrication conditions, and Table 4 shows the evaluation results such as dielectric properties. It was confirmed that all of Sample Nos. II-1 to 28 had a core-shell structure, the core part was tetragonal, and the shell part was cubic.</p><p><tables num="3"><img file="JP5496331B2_D0005.tif" /></tables></p><p><tables num="4"><img file="JP5496331B2_D0006.tif" /></tables></p><p> As is clear from the results in Tables 3 and 4, the prepared samples (Sample Nos. II-1 to 28) are all at room temperature (25 ° C) in the same manner as the samples prepared by the method of Example 1. The relative permittivity was 3950 or more, and the temperature characteristics of the capacitance satisfied the X5R characteristics. The AC bias characteristic was 30% or less, and the dielectric loss was 5% or less. Among these, a laminate produced by adding a heat treatment step of degreasing the obtained capacitor body molded body during production and then holding it at the temperature shown in Table 3 before reaching the maximum temperature in a hydrogen-nitrogen atmosphere. The ceramic capacitor samples (Sample Nos. II-1 to 23 and 25 to 28) have a variation in capacitance (CV) compared to the samples fired without a heat treatment step (Sample No. II-24). There both 2% and less, in particular, for the sample the temperature of the heat treatment step was 900 ~ 1000 ° C (sample No.II-1 ~ 21,25 ~ 28) , the variation in the capacitance (CV) is Both were less than 1.5%.</p>

1 Condenser body 3 External electrode 5 Dielectric layer 7 Internal electrode layer 9 Crystal particles 9a Core part 9b Shell part 11 Grain boundary phase 11a Two-sided grain boundary phase 11b Three-weight grain boundary phase