JPH0323261A - multilayer ceramic capacitor - Google Patents

Abstract

PURPOSE:To enhance the insulation resistance, dielectric breakdown strength, etc., of the title compsn. by specifying X, y and z when the principal component is represented by a general formula xBaO.y[(TiO2)(1-m)(ZrO2)m].z(Re(1-n)Men)O3/2 and by adding a specified amt. (expressed in terms of V2O5) of vanadium oxide. CONSTITUTION:This dielectric porcelain compsn. contains 100 pts.wt. principal component represented by the above-mentioned general formula (where x, y and z show a molar ratio within the ranges each defined by points a-f in the table, X+y+z=1.00, 0.001<=m<=0.200, 0.01<=n<=0.20, Re is one or more kinds of rare earth elements selected among La, Pr, Nd and Sm, and Me is one or more kinds of rare earth elements other than Re) and 0.005-1.000 pt.wt. (expressed in terms of V2O5) vanadium oxide as a secondary component. ZrO2 enhances dielectric breakdown strength and V2O5 enhances insulation resistance, dielectric breakdown strength, satisfaction Q, etc.

Description

[Detailed description of the invention] Industrial application field The present invention has high dielectric constant, insulation resistance, and dielectric breakdown voltage, greatly improves the quality Q, and has a small capacitance temperature coefficient, and is suitable for multilayer ceramic capacitors. In terms of usage, the present invention relates to a dielectric magnetic composition that can prevent a decrease in capacitance and quality Q when the thickness of internal electrodes is reduced, and can reduce variations in capacitance and quality Q.

Conventional technology Conventionally, the dielectric constant and insulation resistance are high, and the quality Q is excellent.
The following systems are known as dielectric-magnetic combinations with small capacitance temperature coefficients.

・BaO-TiO2-Nd203 system ・BaO-TiO2-Sm203 system Problems to be solved by the invention However, these compositions, for example, 0.09BaO-0.
56T i 02-A dielectric material having a composition ratio of 0.35NdOz/2 is used, and the palladium internal electrode thickness is 4.
μm, dielectric thickness 12 μm, internal electrode overlap dimension 1.
When a multilayer ceramic capacitor with a laminated structure of 2w×0.7mm and 19 dielectric layers is manufactured, the average value of capacitance: 742pF, the average value of goodness Q: 8700, and the average value of capacitance temperature coefficient: N35ppm/ 'C, average value of insulation resistance: 6. OX1012Ω, average value of dielectric breakdown strength: 117 kv/III1, which is not a satisfactory value in terms of insulation resistance. In addition, the crystal grain size is 1 to 5 μm.
As a result, the porosity in the element body increases, the electric field strength applied to each crystal grain increases, and the dielectric breakdown strength also does not have a satisfactory value.

Furthermore, in order to reduce the cost of multilayer ceramic capacitors and to prevent the occurrence of delamination, which is a structural defect inside the element body, the thickness of the palladium internal electrode was increased by 4.
When thinning from μm to 2 μm, a dielectric material with the above composition ratio is used, the dielectric thickness is the above, the internal electrode overlap dimension is
The average value of capacitance of a multilayer ceramic capacitor having a laminated structure with a number of dielectric layers is as small as 610 pF, and the variation in capacitance is large as 256 to 713 pF. Furthermore, there was a problem in that the average value of the quality level Q was as low as 4,000, and the variation in the quality level Q was large, ranging from 600 to 8,800.

Means for Solving the Problems In order to solve these problems, the present invention provides a formula xBa
O−y[(TiO2)t+−m>(ZrO2)sl
When expressed as z(R e (I-n)M en) 03/2 (>(+y+z=1.00.0.001
≦m≦0.200.0.01≦n≦0.20. Re is L
a, Pr. One or more rare earth elements selected from Nd and Sm, Me is La. Pr. One or more rare earth elements selected from rare earth elements excluding Nd and Sm. ), X, y+
For each point a.z represented below: b, c, d, e. For the 100th weight part of the main component having a molar ratio range surrounded by f, vanadium oxide is added as a subcomponent to V,,0.0 in terms of OS.
The present invention proposes a dielectric ceramic composition characterized by containing 0.005 to 1.000 parts by weight.

FIG. 1 is a ternary diagram showing the composition range of the main components of the composition according to the present invention, and the reason for limiting the composition range of the main components will be explained with reference to FIG. That is, sintering is extremely difficult in region A. Further, in the BfiJi region, the quality Q decreases, making it impractical. Furthermore, C. In region D, the capacitance temperature coefficient becomes too large on the negative side, making it impractical. In region E, the temperature coefficient of capacitance shifts to a positive direction, but the dielectric constant is too small to be practical. Also, Re is La. By selecting from Pr, Nd, and Sm, L a r P r , N d r S m
It is possible to shift the capacitance temperature coefficient in the positive direction without significantly lowering the dielectric constant in the order of La, P
r. The temperature coefficient of capacitance can be adjusted by selecting one type or a combination of Nd and Sm. Furthermore, La, Pr. Nd
, Sm - Some of the rare earth elements of W1 or higher are selected from
By replacing with one or more rare earth elements selected from rare earth elements excluding La, Pr, Nd, and Sm, the quality Q
It has the effect of significantly improving . If the amount of substitution is less than 0.01, there is no substitution effect. When it exceeds 0.20, the dielectric constant decreases and becomes impractical.

By replacing TiO2 with ZrO2, it is possible to reduce the crystal grain size and increase dielectric breakdown strength without significantly changing the dielectric constant, quality factor Q, temperature coefficient of capacitance, and insulation resistance. However, if the substitution rate m is less than 0.001, there is no substitution effect, and if it exceeds 0.200, the dielectric constant and good quality Q. Insulation resistance decreases.

Figures 2 (a) to (e) are graphs showing the effect of the addition of the minor component V2O5 on the characteristics of multilayer ceramic capacitors with respect to the main components of the composition according to the present invention. The reason will be explained with reference to the graph. As shown in Figure 2, the inclusion of v205 improves I, insulation resistance, and dielectric breakdown strength, increases capacitance and quality Q, and reduces variations in capacitance and quality Q. have an effect. Insulation resistance and dielectric breakdown strength are improved by the inclusion of V20,, but when the content of V,OS is less than 0.005 parts by weight per 100 parts by weight of the main component, the capacitance and good quality Q was excluded from the scope of the present invention because the capacitance and quality Q varied greatly. On the other hand, the content of V205 is 1.00% of the main precept.
If it exceeds 0 parts by weight, the quality Q and insulation resistance will decrease, and the temperature coefficient of capacitance will become large on the negative side, making it impractical.

Example The present invention will be explained below using specific examples.

(Example 1) Chemically high purity BaCO3T i 02 was used as the starting material.
．． Zr 02. L a2oz, Pz+o++, Nd
203, Sm203. Ce02. Gd203, Dy20
3 and v205 powders were weighed to have the composition ratios shown in Table 1 below, put into a rubber-lined ball mill equipped with agate balls together with pure water, wet mixed, and then dehydrated and dried. This dry powder was placed in a high alumina crucible and calcined in air at 1100°C for 2 hours. This calcined powder,
The mixture was placed in a rubber-lined ball mill equipped with agate balls together with pure water, wet-milled, and then dehydrated and dried. After adding an organic binder to the pulverized powder and making it homogeneous, the powder is sized through a 32-mesh sieve and molded using a mold and a hydraulic press at a molding pressure of 1 ton/cj to a diameter of 15n+n and a thickness of 0.
It was molded to 4 mm. Next, the molded disk was placed in an alumina pod covered with zirconia powder, and burned in the air at the salinity shown in Table 1 below for 2 hours to produce dielectric porcelain having the composition ratio shown in Table 1. Obtained.

(Margin below) The thickness and diameter of the dielectric porcelain disk thus obtained were measured, and the dielectric constant, goodness Q, and capacitance temperature coefficient measurement samples were measured using the dielectric porcelain disk. Silver electrodes were baked on the entire surface of both sides, and a sample for measuring insulation resistance and dielectric breakdown strength was prepared by providing a portion with no silver electrodes with a width of IM inside the outer periphery of a dielectric ceramic disk, and baking silver electrodes on the dielectric ceramic disk. The rate, quality Q, and capacitance temperature coefficient were determined using a YHP digital LCR meter model 4275A at a measurement temperature of 20°C, a measurement voltage of 1.OVrms, and a measurement frequency of IMHz. The temperature coefficient of capacitance was determined by measuring capacitance at 20° C. and 85° C. using the following formula.

TC= (C-Co)/CoX1/65X106TC:
Temperature coefficient of capacitance (ppm/°C) Co: Capacitance at 20°C (pF) C: Capacitance at 85°C (pF) Further, the y1t ratio was determined from the following formula.

K=143.8XCoxt/D 2 K: Dielectric constant Co: Capacitance at 20°C (pF) D: Diameter of dielectric porcelain (mm) t: Thickness of dielectric porcelain (kaku) Furthermore, the insulation resistance is YHP HR meter model 4
329A, measuring voltage 50V. D. C. , was determined by measurement with a measurement time of 1 minute.

The dielectric breakdown strength was determined by using a high-voltage power supply PH835K-3 type manufactured by Kikusui Electronics Corporation, placing the sample in silicone oil, and dividing the dielectric breakdown voltage determined by a voltage increase rate of 50 V/see by the dielectric thickness. It was defined as dielectric breakdown strength per 1 mm. Further, the crystal grain size was determined by optical microscope observation at a magnification of 400.

The test results are shown in Table 2 below.

(Left below) (Example 2) Chemically high-purity BaCO3Ti02,Z was used as the starting material.
Using r02+Ndt03, Ce02 and V205 powder, composition ratio 0.09BaO-0.56Ti02
0.35[(NdO3/2)o9s(CeO2)o. o
V205 was added to 100 parts by weight of the main precept of sl.
001, 0.005, 0.010, 0.100, 1.0
Example 1 Calcined pulverized powder containing 0.00.2.000 parts by weight
Fabricate using the same method as . However, the v20s content is 0
．． 0.001.2.000 parts by weight is outside the scope of this invention; O05.0.010,0.100.1.0
00 parts by weight is within the scope of this invention.

An organic binder, plasticizer, dispersant, and organic solvent were added to this calcined and pulverized powder and mixed in a pot equipped with alumina balls to prepare a slurry. After mixing, the filtered slurry was processed into a green sheet having a dielectric thickness of 12 μm after sintering. 10 sheets of such green sheets were stacked on a support stand, and internal electrode palladium paste M L-3 7 2 4 manufactured by Shoei Chemical Co., Ltd. was screen printed so that the internal electrode thickness after sintering would be 2 μm. One green sheet was laminated on top of this, and the internal electrode overlap dimension after sintering was 1.2 w x 0.7.
rttps, print the internal electrode palladium paste by shifting the printing position, and after drying, print the green sheet 1.
The sheets were stacked. These operations were repeated until the number of dielectric layers reached 19. On top of this, 10 green sheets were laminated. After sintering this laminate, the internal electrode overlap dimension is 1. 2 m x 0. The capacitor was cut into a multilayer ceramic capacitor having a multilayer structure of 7 wm and 19 dielectric layers. The cut sample was placed in an alumina pod covered with zirconia powder, heated in air from room temperature to 350°C at a rate of 5°C/hr, and then heated for 10 minutes from 350°C.
After increasing the temperature at 0℃/hr and baking at 1270℃ for 2 hours,
The temperature was lowered to room temperature at a rate of 100°C/hr. Next, the test F1 side of the sample after burning was polished to fully expose the internal electrode part that will be connected to the external electrode, and a silver external electrode was baked on the exposed part of the internal electrode to make it conductive with the internal electrode, forming a multilayer ceramic capacitor. was created.

The capacitance, quality Q, temperature coefficient of capacitance, insulation resistance, and dielectric breakdown strength of these samples were determined by measurements under the same conditions as in Example 1. In addition, the laminated structure was confirmed by approximately 17' in the length and width directions of the laminated ceramic capacitor.
The internal electrode overlap dimension is a magnification of 100.
The dielectric thickness and internal electrode thickness were measured using an optical microscope Wl at a magnification of 400.
Obtained from mirror observation.

The measurement results are shown in FIGS. 2(a) to (e).

In addition, in the method for producing dielectric ceramic in the example, B
a CO3, T i 02, Z r 02. L
a203P rso11. Nd203, Sm203, C
Although e02Gd20a, Dy20:+ and v2o5 were used, the method is not limited to this method. Compounds such as BaTi03, carbonates, hydroxides, etc. can be heated in air to obtain the desired composition ratio. , Bad
, Ti02, Zr02, La203Prefer.
Nd203. Sm203. Ce02Gd203, Dy2
Even when compounds 03 and V205 are used, properties comparable to those of the examples can be obtained.

Further, even if the main component is calcined in advance and the subcomponents are added (IID), properties comparable to those of the examples can be obtained.

In addition, in the embodiment, I. , a, Pr, Nd. Although Ce, Dy, and Gd have been described as rare earth elements Me other than Sm, the same characteristics as those in the embodiment can be obtained even if other rare earth elements are used.

In addition to the basic composition described above, Si02Mn02. F
Salts and oxides that are generally considered blacks, such as e203 and ZnO, can also be added to the extent that they do not impair the properties.

Effects of the Invention According to the present invention, the crystal grain size is small, the dielectric constant, insulation resistance, and dielectric breakdown voltage are high, the quality Q is greatly improved, the temperature coefficient of capacitance is small, and the temperature coefficient of capacitance is small. In addition, when used in multilayer ceramic capacitors, it is possible to prevent a decrease in capacitance and quality Q when the thickness of the internal electrode is reduced, and to reduce variations in capacitance and quality Q. By making the capacitor thinner, the cost of the multilayer ceramic capacitor can be reduced, and delamination, which is an internal structural defect, can be prevented from occurring. In addition, because the dielectric breakdown voltage is high, the thickness of the dielectric layer is reduced, the size of the element is reduced,
Larger capacity is possible.

[Brief explanation of drawings]

FIG. 1 is a ternary diagram illustrating the main composition range of the composition according to the present invention, and FIG. 020.3
5 [(NdO 3/z)o. ss (C
e 02) O. Dielectric thickness: 12 μm
, internal electrode overlap dimension: 1. 2mm x O
．． 7 m+u. This is a graph showing the electrical characteristics of a multilayer ceramic capacitor having a multilayer structure with 19 dielectric layers.

Claims (1)

[Claims] General formula xBaO-y[(TiO_2)_(_1_-_m_)(
ZrO_2)_m]-z(Re_(_1_-_n_)M
e_n) When expressed as O_3_/_2 (however, x+y+
z=1.00,0.001≦m≦0.200,0.01
≦n≦0.20, Re is one or more rare earth elements selected from La, Pr, Nd, Sm, Me is La, Pr, Nd
, one or more rare earth elements selected from rare earth elements excluding Sm. ), x, y, z are the points a, b, c, d represented below
, e, f consisting of a range of molar ratios
V_2 of vanadium oxide as a subcomponent based on the weight part
A dielectric ceramic composition containing 0.005 to 1.000 parts by weight calculated as O_5. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼