JP3245342B2 - Manufacturing method of multilayer capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method of alternately forming 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 method for manufacturing a multilayer capacitor formed by laminating the capacitors.

[0002]

2. Description of the Related Art Hitherto, a multilayer capacitor has been manufactured by alternately laminating electrode layers constituting an internal electrode and a dielectric layer and then firing them integrally.

By the way, when manufacturing a multilayer capacitor,
In a conventional dielectric material mainly composed of BaTiO ₃ , 1
Since firing is performed at 300 to 1500 ° C., noble metals such as Pt and Pd that do not melt at such a temperature have been used as the internal electrode material.

[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, it must be fired in a reducing atmosphere to prevent oxidation of the internal electrode. There is a problem that the ceramics are reduced and lose insulation.

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) (Ti, Zr) a basic component consisting of O _3, a dielectric ceramic composition comprising an additive component containing Li ₂ O and SiO ₂ have been proposed (e.g., see JP-B-60-20851, etc. ).

[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]

The object of the present invention is to provide a dielectric ceramic having a thickness of 3 to 10 μm.
It is an object of the present invention to provide a method of manufacturing a multilayer capacitor capable of improving the life under a high-temperature, high-voltage environment even when the thickness is as small as m.

[0009]

Means for Solving the Problems As a result of intensive studies on the above problem, the present inventor has found that barium titanium zirconate is used.
The main component to be contained , and L per 100 parts by weight of the main component
At least one of i, Si and B is Li ₂
O, the total amount in SiO _2, B ₂ O ₃ in terms of 0.4 to 1. 2 parts by weight
Forming film containing calcined grain boundary phase component
And an internal electrode film containing a base metal alternately laminated.
A layer molded body is produced, and in a non-reducing atmosphere,
Baking at 1300 ° C, temperature drop from maximum temperature to 800 ° C
It has been found that by setting the speed to 20 to 40 ° C./hr or less, it is possible to improve the life under a high-temperature and high-voltage environment even if the dielectric layer is a thin layer.

That is, in the method for manufacturing the multilayer capacitor of the present invention,
The multilayer capacitor manufactured by the above-described method is characterized in that at least one of Li, Si, and B is Li ₂ O, SiO ₂ , A multilayer capacitor comprising a dielectric layer having a segregated phase containing a total amount of 0.4 to 1.2 parts by weight in terms of B ₂ O ₃ and an internal electrode layer made of a base metal alternately laminated. The dielectric layer has a thickness of 3 to 10 μm, and 60% or more of the number of segregated phases existing on the fracture surface of the dielectric layer is crystalline. Here, it is desirable that the crystalline material in the segregated phase be composed of a composite oxide containing at least two of Li, Si and B.

[0011]

According to the method for manufacturing a multilayer capacitor of the present invention, even when the thickness of the dielectric layer is reduced to 3 to 10 μm, the capacitor has a sufficient function as a dielectric and can be used in a high-temperature, high-voltage environment. Can also extend the life.

That is, the life under high temperature and high voltage environment is considered to be affected by the mobility of electrons moving through the grain boundary phase in the dielectric porcelain, but the crystalline segregation phase is more amorphous. Since the mobility of electrons is smaller than in the case of the above, by making 60% or more of the total number of grain boundary phase components in the dielectric layer crystalline, the mobility of electrons in the grain boundary phase can be reduced. .

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a multilayer capacitor according to the present invention
Is a main component containing barium titanium zirconate,
For 100 parts by weight of the main component, a small amount of Li, Si, and B
At least one kind converted to Li ₂ O, SiO ₂ , B ₂ O ₃
At 0.4 to 1.2 parts by weight in total
-Containing dielectric-forming film and base metal-containing interior
Produce a laminated molded body in which electrode films are alternately laminated and perform non-reduction.
Baking at 1200-1300 ° C in a neutral atmosphere
The cooling rate from the temperature to 800 ° C is 20 to 40 ° C / hr.
Although, the dielectric layer used in the present invention,
For example, Ba (Ti, Zr) and component a CaTiO ₃ containing 0.05 to 8.0 parts by mol with respect to O ₃ 100 molar parts, relative to the component 100 parts by weight, the Nd ₂ O ₃ 0.3 ~
0.8% by weight and 0.1 to 0.2 part by weight of MnO ₂ are contained to form a main component.

On the other hand, for example, Li ₂ O, SiO ₂ , B ₂ O ₃
In the triangular diagram represented by the molar ratio of (Li ₂ O, Si
A (20, 80, 0) and B (7, O ₂ , B ₂ O ₃ )
0, 30, 0), C (80, 0, 20), D (40, 2)
(0, 40) is 90%.
Calcination is performed at a temperature of 0 ° C. or higher to produce a composite oxide containing at least two of Li, Si, and B. Then, the composite oxide containing Li, Si, and B is mixed with the main component 1 described above.
The total amount is 0.4 to 1.2 parts by weight based on 00 parts by weight. In the dielectric layer, A
l ₂ O ₃ , Fe ₂ O ₃ , ZrO _{2 and the} like may be mixed.

At least one of Li, Si and B is added to 100 parts by weight of barium titanium zirconate in a total amount of 0.4 to 1.2 in terms of Li ₂ O, SiO ₂ and B ₂ O ₃ respectively.
The reason for the inclusion in parts by weight is that when the content of Li, Si, and B is less than 0.4 parts by weight, the life under a high-temperature and high-voltage environment is reduced.
If the amount is more than the weight part, the capacity is reduced.

In the present invention, the grain boundary phase components to be added are Li, Si and B, respectively, Li ₂ O, SiO ₂ and B _2.
O ₃ may be contained amount 0.4 to 1.2 parts by weight in terms of,
The three components are not essential components, but may be two. 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 if the thickness of the dielectric layer is smaller than 3 μm, it is difficult to manufacture the dielectric layer. If the thickness is larger than 10 μm, This is because high capacity cannot be achieved. 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.

Further, among the segregated phases in the dielectric layer, L
The segregated phase composed of the composite oxide containing i, Si, and B is
For _{example, (3Li 2 O · B 2} O 3 + Li 4 SiO 4), (L
i ₄ SiO _4), there are those as expressed as _{(Li 4 SiO 4 + Li 2} O), such segregation phase is crystalline, the number of the segregation phase existing in the dielectric layer Of these, by controlling the ratio of being crystalline to constant, the mobility of electrons in the grain boundary phase can be controlled as described above, and the product life in a high-temperature, high-voltage environment can be extended. is there.

It is necessary that 60% or more of the number of segregated phases existing in one cross section (fracture surface) of the dielectric layer is crystalline. When the proportion of the crystalline segregated phase is lower than 60%, the life under high temperature and high voltage is significantly shortened.

As described above, in order to make the proportion of the crystalline segregated phase 60% or more, the rate of temperature decrease from the maximum temperature to 800 ° C. during firing is 20 to 40 ° C./hr.
It is necessary to This means that the cooling rate is 20 to 4
By setting the temperature to 0 ° C./hr, the crystallization of the segregated phase is promoted, and the proportion of the crystalline segregated phase can be increased to 60% or more.

In the manufacturing method of the multilayer capacitor of the present invention , first, for example, a predetermined binder and a plasticizer are added to the above-mentioned dielectric porcelain composition to prepare a slip for a dielectric layer. The binder and the plasticizer are added to prepare a slip for the internal electrode. Then, a slip for a dielectric layer is applied a plurality of times on the base plate by a doctor blade method to form a dielectric molded film having a predetermined thickness, and a slip for an internal electrode is screen-printed on the surface of the dielectric molded film. To form an internal electrode film having a predetermined shape.

After repeating this process until a desired capacity is obtained, the laminate is subjected to an oxygen partial pressure of 3 × 10 ^-5 to 3 × 10 ⁵
1200 to 1300 ° C in a non-reducing atmosphere of ^-3 Pa
For 1 to 5 hours, and the rate of temperature decrease from this maximum temperature to 800 ° C. is 20 to 40 ° C./hr. Thereafter, heat treatment is performed at 900 to 1100 ° C. for 2 to 7 hours in a nitrogen atmosphere to obtain the multilayer capacitor of the present invention.

[0024]

EXAMPLES Using Ba (Ti, Zr) O ₃ powder having an average particle size of 0.5μm obtained by hydrothermal synthesis method as a starting material, the average for this Ba (Ti, Zr) O ₃ 100 molar parts A component was prepared by adding 0.05 mol part of CaTiO ₃ having a particle size of 1.0 μm.
0.5 parts by weight of d ₂ O ₃ and 0.2 parts by weight of MnO ₂ are added and mixed to prepare a main component. The molar ratio of Li ₂ O, SiO ₂ , and B ₂ O ₃ to 100 parts by weight of the main component is shown in Table 1.
The calcined grain boundary phase component having the ratio shown in Table 1 was added in an amount shown in Table 1, and mixed with a ZrO ₂ ball to form a binder.
A plasticizer was added to obtain a dielectric layer slip.

Also, Ni and terpineol are 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 is applied to the base plate a plurality of times by the doctor blade method, and a dielectric molded film is produced so that the thickness after firing becomes the thickness shown in Table 1. On the upper surface of the substrate, screen printing of the slip for the internal electrode layer is performed so as to form a comb-shaped structure, and the steps from the formation of the dielectric molded film to the formation of the electrode film are repeated 20 times, thereby forming a laminate having 20 dielectric molded films. 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 the rate shown in Table 1, the heat treatment was performed at 1000 ° C. for 5 hours in a nitrogen atmosphere. Thereafter, external electrodes made of Cu were formed on both end surfaces of the sintered body to obtain a multilayer capacitor of the present invention.

For the multilayer capacitor thus obtained, the thickness of the dielectric layer was measured by using a scanning electron microscope (SEM).
And the state of the grain boundary phase component in the dielectric layer was observed with a transmission electron microscope (TEM).
The confirmation of the crystalline state is performed by confirming whether an electron analysis image can be obtained for each segregated phase, and the crystalline segregation for 50 segregated phases in the arbitrarily selected dielectric layer is performed. The ratio (%) of the number of phases was determined.

The capacity is measured with an LCR meter at a measurement frequency of 1.
It was measured under the conditions of kHz and an input signal level of 1 Vrms, and was obtained by converting into a capacitance per one dielectric layer.

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

[0030]

[Table 1]

From the results in Table 1, it was found that the sample of the present invention
High capacity of 50 nF or more, and 150 ° C., 8 V /
Even when a voltage of μm is applied, the time until a short-circuit failure is as long as 185 hours or more, indicating that the device has high reliability and a long life even in a high temperature and high voltage environment.

FIG. 1 shows No. 1 of the present invention. 7 shows the result of enlarging the cross section of the multilayer capacitor No. 7 by 5000 times with a TEM. In the figure, reference numeral 1 denotes a dielectric layer, reference numeral 2 denotes an internal electrode layer, reference numeral 3 denotes ceramic particles made of (Ba, Ca) (Ti, Zr) O ₃ , and reference numeral 4 denotes a segregation phase. FIG. 2 shows the result of magnifying the cross section of the dielectric ceramic of this sample by 100,000 times by TEM. In the figure, reference numeral 3 indicates (Ba,
Ceramic particles composed of Ca) (Ti, Zr) O ₃ , reference numeral 4 denotes a segregated phase.

[0033]

【The invention's effect】In the manufacturing method of the multilayer capacitor of the present invention,
A main component containing barium titanium zirconate;
Per 100 parts by weight of Li, Si, B
And one kind each Li _Two O, SiO _Two , B _Two O _Three Total in conversion
A calcined grain boundary phase component in an amount of 0.4 to 1.2 parts by weight;
-Containing dielectric film and internal electrode containing base metal
A laminated molded body in which the film and the film are alternately laminated is manufactured, and a non-reducing atmosphere is formed.
Fired at 1200-1300 ° C in ambient atmosphere, maximum temperature
From 40 to 800 ° C / hr.
In the fracture surface of the dielectric layer, Li, Si and B
A composite oxide containing at least two of them,
Whether to generate a segregated phase having 0% or more of crystallinity
When the thickness of the dielectric is reduced to 3 to 10 μm,
Also have a sufficient function as a dielectric, and
The life can be prolonged even under a voltage environment.

[Brief description of the drawings]

FIG. The cross section of the multilayer capacitor of No. 7 is TE
It is the figure expanded 5000 times by M.

FIG. 7 is a diagram in which the cross section of the dielectric ceramic of the multilayer capacitor of No. 7 is magnified 100,000 times by TEM.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Dielectric layer 2 ... Internal electrode layer 3 ... Ceramic particles 4 ... Segregation phase

Claims (1)

(57) [Claims] A main component containing barium titanium zirconate.
And at least one of Li, Si and B with respect to 100 parts by weight of the main component , respectively, Li ₂ O, SiO ₂ , B
It is calcined a total 0.4 to 1.2 parts by weight ₂ O ₃ in terms of
Dielectric forming film containing grain boundary phase component and base metal
To produce a laminated molded body with alternately laminated internal electrode films
And fired at 1200-1300 ° C in a non-reducing atmosphere.
And the cooling rate from the maximum temperature to 800 ° C is 20 to 4
A method for producing a multilayer capacitor, wherein the temperature is set to 0 ° C./hr .