JPH0997734A - Laminated capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the durability of a laminated capacitor enhance under a high temperature and a high pressure by a method wherein dielectric layers, which contain a barium titanate-zirconate as their main component and contain a specified amount of Li, Si and B, are provided in such a way that the thickness of the layers and the rate of segragation phases in the layers are specified. SOLUTION: A capacitor is constituted by laminating alternately dielectric layers 1, which contain a barium titanate-zirconate as their main component and contain 0.4 to 1.2 pts.wt. of Li, Si and B in total amount in the case where the Li, the Si and the B are respectively converted into Li2 O, SiO2 and B2 O3 to 100 pts.wt. of this titanium zirconic acid barium, and internal electrode layers 2, which consist of a base metal layer. The layers 1 are formed so that they have a thickness of 3 to 10μm and at the same time, segragation phases 4, which consist of a composite oxide containing at least two kinds of elements out of Li, Si and B, exist in an area ratio of 4 to 12% on each breaking surface of the layers 1 in the layers 1. In such a way, the phases 4 exist at a constant rate, whereby even in the case where an electron mobility in grain boundary phases in the layers 1 is lessened and the layers 1 are formed into a thin form, a function to be brought out as a dielectric material is fully ensured and the life of the capacitor can be prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention alternately comprises a dielectric layer containing barium titanium zirconate as a main component and containing at least one of Li, Si and B, and an internal electrode layer made of a base metal such as nickel. The present invention relates to a laminated type multilayer capacitor.

[0002]

2. Description of the Related Art Conventionally, in obtaining a multilayer capacitor, a sintered body obtained by alternately laminating electrode layers constituting internal electrodes and dielectric layers and then firing them integrally is used.

By the way, when a multilayer capacitor is manufactured, a conventional dielectric material containing BaTiO ₃ as a main component is fired at 1300 to 1500 ° C., and therefore Pt which does not melt at such a temperature is used as an internal electrode material. Noble metals such as Pd have been used.

[0004] However, these noble metals are expensive, and there has been a problem that when the number of internal electrodes is increased in order to increase the capacity, the cost is significantly increased. Therefore, in recent years, inexpensive base metals such as nickel have been used as internal electrode materials.

However, when an internal electrode made of a base metal such as nickel is used, the internal electrode material must be fired in a reducing atmosphere in order to prevent the oxidation of the internal electrode material. There is a problem that the body ceramics are reduced and the insulating property is lost.

In recent years, therefore, basic oxides such as (Ba, Ca, Sr) which do not reduce dielectric ceramics even when fired in a reducing atmosphere.
Barium titanate solid solution (Ba, Ca, S) in which O is added in excess of stoichiometric ratio to TiO ₂ as an acidic oxide
r) a basic component composed of (Ti, Zr) O ₃ and Li ₂ O
A dielectric porcelain composition consisting of and an additive component containing Si ₂ O has been proposed (see, for example, Japanese Patent Publication No. 60-20851).

[0007]

However, the multilayer capacitor using the above-mentioned conventional composition has a problem that the product life is short when used in a high temperature and high voltage environment. That is, in the above-described conventional composition, in a high-temperature, high-voltage environment, the electric conductivity of the dielectric porcelain itself increases, the function as a dielectric decreases, and the life as a dielectric decreases. Was. In particular, in recent years, there has been a tendency to reduce the thickness of the dielectric layer in order to increase the capacity. However, as the dielectric layer becomes thinner, the electrical conductivity tends to increase under high temperature and high voltage environments. There is a problem that the function of the device is easily deteriorated.

[0008]

OBJECTS OF THE INVENTION The present invention provides a dielectric layer having a thickness of 3 to 10 .mu.m.
An object of the present invention is to provide a multilayer capacitor that can improve the life under high temperature and high voltage environment even when the thickness is as thin as m.

[0009]

Means for Solving the Problems As a result of intensive studies made by the present inventors on the above problems, Li, Si and B were added to Li ₂ for 100 parts by weight of barium titanium zirconate, respectively.
The thickness of the dielectric layer contained in a total amount of 0.4 to 1.2 parts by weight in terms of O, SiO ₂ , B ₂ O _{3 is set to 3} to 10 μm, and segregated from a composite oxide containing Li, Si, and B. The ratio of the area of the phase to the area of the fracture surface of the dielectric layer is 4
It has been found out that the life can be improved under the environment of high temperature and high voltage even if the dielectric layer is a thin layer by setting the content to ˜12%, and the present invention has been completed.

That is, the multilayer capacitor of the present invention contains barium titanium zirconate as a main component, and Li, Si, and B are added to Li ₂ O, SiO ₂ , and B ₂ O with respect to 100 parts by weight of barium titanium zirconate, respectively. 0.4 in total of ₃
A multilayer capacitor, wherein a dielectric layer containing 1.2 to 1.2 parts by weight and an internal electrode layer made of a base metal are alternately laminated, wherein the dielectric layer has a thickness of 3 to 10 μm, and In the body layer, a segregation phase composed of a composite oxide containing at least two kinds of Li, Si and B,
It exists in an area ratio of 4 to 12% on the fracture surface of the dielectric layer.

[0011]

In the multilayer capacitor of the present invention, even when the thickness of the dielectric layer is thinned to 3 to 10 μm, the multilayer capacitor has a sufficient function as a dielectric and is capable of operating under high temperature and high voltage environments. The life can be extended.

That is, it is considered that the life under high temperature and high voltage environment is affected by the mobility of electrons moving in the grain boundary phase in the dielectric ceramic, but the segregation of the composition containing Li, Si and B This is because the mobility of electrons in the grain boundary phase can be reduced by the existence of the phases at a constant ratio.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The multilayer capacitor of the present invention contains barium titanium zirconate as a main component, and Li, Si and B are added to Li ₂ O, SiO ₂ and B to 100 parts by weight of barium titanium zirconate, respectively. ₂ O ₃ total amount in terms of 0.
The dielectric layer used in the present invention is, for example, Ba (T).
i, Zr) O ₃ and a component containing 1.0 to 8.0 parts by mole of CaTiO ₃ with respect to 100 parts by mole,
0.3 to 0.8 parts by weight of Nd ₂ O _{3 based} on parts by weight,
The main component is constituted by containing 0.1 to 0.2 parts by weight of MnO ₂ .

On the other hand, in the triangular diagram represented by the molar ratio of Li ₂ O, SiO ₂ and B ₂ O ₃ , (Li ₂ O, Si
A (20, 80, 0), B, which is represented by O ₂ , B ₂ O ₃ ).
(70, 30, 0), C (80, 0, 20), D (4
(0, 20, 40), the grain boundary phase component in the composition range surrounded by four points is calcined at a temperature of 900 ° C. or higher to produce a composite oxide containing at least two kinds of Li, Si, and B. .
The composite oxide containing Li, Si, B is added in a total amount of 0.4 to 1.2 parts by weight with respect to 100 parts by weight of the main component. Al ₂ O ₃ , Fe ₂ O ₃ , ZrO _{2 and the} like may be mixed as impurities in the dielectric layer.

In the present invention, the grain boundary phase components added are Li ₂ Si, B, Li ₂ O, SiO ₂ and B, respectively.
_It suffices that the total amount is 0.4 to 1.2 parts by weight in terms of ₂ O ₃ , and the three types of components are not essential components, and two types may be used. Of these, a combination of Li and Si is particularly desirable from the viewpoint of improving the dielectric constant.

The internal electrode layer made of a base metal is made of, for example, Ni, Co, Cu or the like.

Further, the reason why the thickness of the dielectric layer is set to 3 to 10 μm is that it is difficult to manufacture the dielectric layer if the thickness of the dielectric layer is thinner than 3 μm, and if the thickness is thicker than 10 μm, This is because it is not possible to increase the capacity. The thickness of the dielectric layer of the present invention is desirably 5 to 8 μm from the viewpoint of increasing the capacity and facilitating the production of the dielectric layer.

The segregation phase composed of a complex oxide containing Li, Si, B in the dielectric layer is, for example, (3 L
i ₂ O.B ₂ O ₃ + Li ₄ SiO ₄ ), (Li ₄ SiO
₄ ) and (Li ₄ SiO ₄ + Li ₂ O), and by controlling the amount of such a segregation phase to a constant value, the movement of electrons in the grain boundary phase as described above. The product life can be extended under high temperature and high voltage environment by controlling the temperature.

It is necessary that the segregation phase has an area ratio of 4 to 12% in the area of one cross section (fracture surface) of the dielectric layer. When the area ratio of the segregation phase is smaller than 4%, the life time of reliability at high temperature and high voltage is remarkably shortened, while when it is larger than 12%, the relative dielectric constant is remarkably lowered. Is. The area ratio of the segregated phase is 6 to 6 from the viewpoint of reliability and high capacity under high temperature and high voltage.
Desirably, it is 10%. Thus, in order to set the area ratio of the segregation phase to 4 to 12%, the temperature lowering rate from the maximum temperature to 800 ° C during firing should be 50 ° C / hr or less, and particularly 20 to 40 ° C / hr. is necessary. This is because when the cooling rate is set to 50 ° C./hr or less, the generation of the segregation phase is promoted, and the segregation phase ratio is 4 to 12%.
It can be.

In the multilayer capacitor of the present invention, for example, first, a predetermined binder and a plasticizer are added to the above-mentioned dielectric ceramic composition to prepare a slip for a dielectric layer and, for example, a predetermined binder is added to Ni. , Add a plasticizer to make a slip for the internal electrode. And on the base plate,
The dielectric layer slip is applied multiple times by the doctor blade method to form a dielectric molding film having a thickness of 5 to 14 μm, and the internal electrode slip is screen-printed on the surface of the dielectric molding film to a predetermined size. A shaped internal electrode film is formed. After repeating this step until the desired capacity is obtained, the maximum temperature is 1200 to 1300 ° C. for 1 to 5 in a non-reducing atmosphere having an oxygen partial pressure of 3 × 10 ^{−5 to} 3 × 10 ⁻³ Pa.
Firing is performed for an hour, and the rate of temperature decrease from this maximum temperature to 800 ° C. is 20 to 50 ° C./hr. Then, heat treatment is performed in a nitrogen atmosphere at 900 to 1100 ° C. for 2 to 7 hours to obtain the multilayer capacitor of the present invention.

[0021]

EXAMPLE A Ba (Ti, Zr) O ₃ powder having an average particle size of 0.5 μm obtained by a hydrothermal synthesis method was used as a starting material, and 100 parts by mole of this Ba (Ti, Zr) O _{3 was} mixed with water. CaT having an average particle size of 1.0 μm obtained by a thermal synthesis method
A component was prepared by adding 0.05 mol part of iO ₃ , and 0.5 part by weight of Nd ₂ O ₃ and M were added to 100 parts by weight of this component.
0.2 parts by weight of nO ₂ is added and mixed to prepare the main component. For 100 parts by weight of this main component, Li ₂ O, Si
A calcined grain boundary phase component having a molar ratio of O ₂ and B ₂ O ₃ shown in Table 1 was added in an amount shown in Table 1, mixed with ZrO ₂ balls, and a binder and a plasticizer were added. A slip for a dielectric layer was obtained.

In addition, Ni and terpineol were added, and A
mixed by l ₂ O ₃ balls, a binder, a plasticizer is added to give a slip internal electrode layer.

Then, the dielectric layer slip was applied to the base plate a plurality of times by the doctor blade method to prepare a dielectric molded film so that the thickness after firing would be the thickness shown in Table 1, and this dielectric molded film was formed. The internal electrode layer slip is screen-printed on the upper surface of the so as to form a comb structure, and the steps from the formation of the dielectric molding film to the formation of the electrode film are repeated 20 times to form a laminated molding having 20 layers of the dielectric molding film. The body was made. After thermocompression bonding of the laminated molded body, the laminated molded body is fired at 1250 ° C. for 2 hours in a non-reducing atmosphere having an oxygen partial pressure of 3 × 10 ⁻⁴ Pa.
After cooling at a temperature falling rate of up to the rate shown in Table 1, heat treatment was performed at 1000 ° C. for 5 hours in a nitrogen atmosphere. Then, external electrodes made of Cu were formed on both end faces of the sintered body to obtain a multilayer capacitor of the present invention.

With respect to the multilayer capacitor thus obtained, the thickness of the dielectric layer was determined by scanning electron microscope (SEM).
And the state of segregation phase in the dielectric layer was observed with a transmission electron microscope (TEM). The proportion of the segregated phase was determined by calculating the area of the segregated portion of the SEM-observed photograph by image analysis. In addition, the capacity was measured with an LCR meter at a measurement frequency of 1 kHz and an input signal level of 1 Vrm.
It was measured under the condition of s and converted into the capacitance per one dielectric layer.

Further, a voltage (8 V / μm) was applied to the dielectric thickness in a measuring furnace at 150 ° C., and the time (life) until a short circuit failure was measured. The results are shown in Table 1.

[0026]

[Table 1]

From the results shown in Table 1, the sample of the present invention is 2
High capacity of 50 nF or more, and 150 ° C., 8 V /
Even when a voltage of μm is applied, it takes a long time to reach a short circuit failure of 185 hours or more, and it can be seen that the reliability is high and the life is long even in an environment of high temperature and high voltage.

FIG. 1 shows the results of enlarging the cross section of the laminated type capacitor No. 7 of the present invention by 5000 times with a TEM. In the figure, reference numeral 1 indicates a dielectric layer, reference numeral 2 indicates an internal electrode layer, reference numeral 3 indicates ceramic particles made of (Ba, Ca) (Ti, Zr) O ₃ , and reference numeral 4 indicates a segregation phase.

[0029]

In the multilayer capacitor of the present invention, 100 parts by weight of barium titanium zirconate is mixed with Li, Si,
The dielectric layer containing B in the total amount of 0.4 to 1.2 parts by weight in terms of Li ₂ O, SiO ₂ , and B ₂ O _{3 has} a thickness of ₃ to 1 respectively.
The area ratio of the segregation phase composed of a composite oxide containing at least two of Li, Si and B is 4 to 12% of the area of the fracture surface of the dielectric layer.
Therefore, even when the thickness of the dielectric layer is as thin as 3 to 10 μm, the life can be improved under the environment of high temperature and high voltage.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of Sample No. 7 of the present invention.

[Explanation of symbols]

 1 ... Dielectric layer 2 ... Internal electrode layer 3 ... Ceramic particle 4 ... Segregation phase

Claims (1)

[Claims] 1. A barium titanium zirconate as a main component,
L to 100 parts by weight of this barium titanium zirconate
i, Si and B are replaced with Li ₂ O, SiO ₂ and B ₂ O _{3 respectively.}
A dielectric layer containing a total amount of 0.4 to 1.2 parts by weight,
A multilayer capacitor, wherein internal electrode layers made of a base metal are alternately laminated, wherein the dielectric layer has a thickness of 3 to 10 μm, and Li, Si are contained in the dielectric layer.
And a segregation phase composed of a composite oxide containing at least two of B is 4 to 1 in the fracture surface of the dielectric layer.
A multilayer capacitor characterized by being present in an area ratio of 2%.