JP2001240467A - Porcelain of dielectrics, process of producing the same and laminated ceramic condenser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a porcelain of dielectrics and its production process capable of enhancing specific dielectric constant, and to provide a laminated ceramic condenser capable of enhancing capacitance without thinning layer of dielectrics to achieve high fidelity. SOLUTION: This porcelain of dielectrics comprises BaTiO3, as the main component, Mg, Mn and rare earth elements having specific dielectric constant at 25 deg.C of 4300 or more. Variation in specific dielectric constant in the range of -25 to 85 deg.C based on that at 20 deg.C is within ±15%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic, a method for producing the same, and a multilayer ceramic capacitor.
The present invention relates to a dielectric porcelain optimal for a multilayer ceramic capacitor, a method for producing the same, and a multilayer ceramic capacitor.

[0002]

2. Description of the Related Art In a conventional multilayer ceramic capacitor, an upper end face ceramic layer and a lower end face ceramic layer are formed on the upper and lower surfaces of a laminate formed by alternately stacking a plurality of ceramic layers and a plurality of rectangular internal electrodes. Thus, a capacitor body is formed, and external electrodes are provided at both ends of the capacitor body.

[0003] Such a multilayer ceramic capacitor includes:
For example, first, ceramic powder on a PET film,
A ceramic slurry containing an organic binder and a solvent is applied, dried, and then separated from the PET film to form a plurality of ceramic green sheets, and a plurality of these are laminated to form lower and upper end face ceramic green sheets. . This lower end face ceramic green sheet is arranged on a base plate, and is bonded by pressing with a press machine.

On the other hand, the same ceramic slurry as described above is applied to a PET film, and after drying, an internal electrode paste containing, for example, one of Ni, Cu, and Ag-Pd is applied to the ceramic green sheet. After forming a plurality of rectangular internal electrode patterns on the ceramic green sheet, the green sheet on which the internal electrode patterns are formed is peeled from the PET film.

[0005] Thereafter, a green sheet on which an internal electrode pattern is formed is laminated on the lower end face ceramic green sheet, and a step of pressing and temporarily fixing the green sheet on which the internal electrode pattern is formed is repeated by a press. A predetermined number of sheets are stacked, and then an upper end face ceramic green sheet is stacked, and a plurality of ceramic green sheets and a plurality of rectangular internal electrode patterns are alternately stacked. A molded body of a capacitor body on which a ceramic green sheet layer is laminated is produced.

Next, the capacitor body molded body in which the ceramic green sheets and the internal electrode patterns are alternately stacked is heated at a time to a temperature at which the ceramic green sheets and the internal electrode patterns are softened, and are pressed by a press machine in the stacking direction. Then, a rubber mold is placed on the upper part of the molded body of the capacitor, and then subjected to hydrostatic pressure molding while being heated to the same temperature as described above.

After that, the chip is cut into a predetermined chip shape,
Calcination is performed at 1100 to 1300 ° C. at an oxygen partial pressure of × 10 ⁻⁹ Pa or less.
At ℃, the oxygen partial pressure is set to 1 × 10 ⁻⁷ Pa or more, and the oxidation treatment is performed, and the capacitor body is manufactured.

Thereafter, external electrode paste is applied to both end surfaces of the capacitor body and baked to form a multilayer ceramic capacitor.

[0009]

Generally, in order to increase the capacitance per volume of a multilayer ceramic capacitor, it is necessary to reduce the thickness of the dielectric layer or to increase the dielectric constant of the dielectric layer. However, if the thickness of the dielectric layer is reduced to, for example, 3 μm or less, the ceramic green sheet expands according to the pressing force of the press machine, the layer thickness becomes thinner, and the occurrence rate of short circuit increases. There was a problem.
In particular, there has been a problem that the thinner the ceramic green sheet, the higher the short-circuit occurrence rate and the lower the reliability.

A conventionally known dielectric material containing barium titanate as a main component and containing magnesium, manganese, and a rare earth element has a flat temperature characteristic, but a relative dielectric constant of 4,200 or less. Further, higher dielectric constant has been required.

An object of the present invention is to provide a dielectric porcelain capable of increasing the relative permittivity and a method for producing the same, and further to increase the capacitance per unit volume without reducing the thickness of the dielectric layer. And to provide a highly reliable multilayer ceramic capacitor.

[0012]

According to the present invention, there is provided a dielectric porcelain comprising:
It is characterized by containing barium titanate as a main component, magnesium, manganese and a rare earth element as metal elements, and having a relative dielectric constant of 4300 or more at 25 ° C.

The relative dielectric constant at 25 ° C. is 43
After sintering a molded body containing barium titanate as a main component and containing magnesium oxide, manganese oxide, and a rare earth element oxide, the ceramic body was cooled from the sintering temperature to 700 ° C. or less, and then again. In the method of producing dielectric porcelain in which the temperature is increased to 900 ° C. or higher and heat-treated,
It can be obtained by setting the oxygen partial pressure in the temperature lowering process from 000 ° C. to 700 ° C. to 1 × 10 ⁻¹⁷ to 1 × 10 ⁻¹⁰ Pa.

Thus, after firing, the temperature is increased from 1000 ° C to 700 ° C.
The oxygen partial pressure in the process of cooling down to 1 ° C. is 1 × 10 ⁻¹⁷ to 1
By setting the pressure to 10 ^-10 Pa, the temperature is reduced from 1000 ° C to 70 ° C.
Reduction treatment is performed in the course of cooling to 0 ° C.
By performing the heat treatment at a temperature higher than or equal to ° C., the oxygen diffusion rate is increased and oxygen is efficiently supplied to the dielectric ceramic, and the relative dielectric constant is increased to 4300 while having a flat temperature characteristic.
I can do that.

Here, -25 with respect to the relative dielectric constant at 20 ° C.
It is desirable that the temperature change rate of the relative dielectric constant at -85 ° C be within ± 15%.

The dielectric porcelain of the present invention is made of BaTiO.
₃ 100 mol parts and 10 mol parts of BaTiO ₃ ,
Y is 0.4 to 3.0 mole parts in terms of Y ₂ O ₃ , and Mg is MgO
0.5 to 8.0 parts by mol in terms of Mn, and Mn is in the range of 0,0 in terms of MnO.
It is desirable that the glass component be contained in an amount of from 0.4 to 0.5 mol part and also contain Si, Ba and Ca as glass components.

A multilayer ceramic capacitor according to the present invention is a multilayer ceramic capacitor in which internal electrodes mainly composed of a base metal and dielectric layers are alternately laminated, wherein the dielectric layer comprises the above-mentioned dielectric ceramic. It is.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The dielectric porcelain of the present invention contains barium titanate as a main component, contains magnesium oxide, manganese oxide and rare earth oxide, and has a relative dielectric constant at 25 ° C. of 4300 or more, particularly 4500 or more. That's all. It is desirable that the rate of temperature change of the relative dielectric constant at −25 to 85 ° C. relative to the relative dielectric constant at 20 ° C. is within ± 15%.

As rare earth elements, Y, La, Ce, P
r, Nd, Sm, Dy, Ho, Er, Yb, etc.
Among them, Y, Ho, Er, and Yb are preferable from the viewpoint of extending the high temperature load life. Further, from the viewpoint of sintering properties, it is desirable that the dielectric ceramic of the present invention contains Si, Ba, and Ca as glass components, and further that it contains Li, and further, it is desirable that the glass component contains Li. K, B, etc. may be added from the viewpoint of improving the binding properties.

The dielectric porcelain of the present invention is made of BaTiO ₃ 10
Y is 0.4 to 3.0 mol parts in terms of Y ₂ O ₃ , Mg is 0.5 to 8.0 mol parts in terms of MgO, and Mn is MnO with respect to 0 mol parts and 100 mol parts of BaTiO _3. 0.04 in conversion
０．５0.5 mol part and S as a glass component
It is desirable to contain i, Ba and Ca.

The dielectric porcelain of the present invention comprises a main crystal particle composed of a perovskite-type composite oxide containing at least Ba and Ti, and Y, Mg, Mn in the main crystal particle.
Is dissolved in the solid solution, and Y ₂ O ₃ , MgO, M
It may include an nO phase. In addition, Si, Ba
And a glass phase containing Ca is formed. It is desirable that the glass phase contains Li.

Further, the dielectric porcelain of the present invention includes Fe,
Inevitable impurities in the raw material such as Al may be mixed, or a ball component of the pulverized ball, for example, ZrO ₂ may be mixed during the manufacturing process.

In particular, the dielectric porcelain of the present invention is made of BaTiO.
_ThreeFor 100 mole parts, Y is Y_TwoO _Three0.4 ~
3.0 mol parts, 0.5 to 8.0 mol of Mg in terms of MgO
Parts, 0.04 to 0.5 mol parts of Mn in terms of MnO.
And the molar ratio of Si, Ba, Ca and Li
The composition formula is_Two+ BBaO + cCaO + dLi_Two
When represented by O, a, b, c, and d are 0.30 ≦ a
≦ 0.70, 0.10 ≦ b ≦ 0.40, 0.10 ≦ c ≦
0.40, 0.05 ≦ d ≦ 0.30, a + b + c + d =
1 is BaTiO._Three100 parts by weight
It is desirable to contain 1 to 4 parts by weight.

Here, the reason for containing 0.4 to 3.0 mole parts of Y ₂ O _{3 is} that if it is less than 0.4 mole parts, the insulation resistance tends to be low, and the CR product tends to be small. If the amount exceeds the molar part, the relative permittivity tends to decrease. From the viewpoint of the relative dielectric constant, Y ₂ O ₃ is made of BaTiO ₃ 10
It is preferably contained in an amount of 0.5 to 2.0 mol parts per 0 mol parts.

The reason for containing 0.5 to 8.0 mol parts of MgO is that if less than 0.5 mol part, the insulation resistance becomes low,
This is because the CR product tends to decrease, and when it exceeds 8.0 mole parts, the relative dielectric constant tends to decrease. Especially, MgO is 0.5 to 2.0 molar parts with respect to BaTiO ₃ 100 molar parts are preferred.

The reason that MnO is contained in an amount of 0.04 to 0.5 mol part is that if it is less than 0.04 mol part, the insulation resistance tends to be low and the CR product tends to be small. If it exceeds, the change with time of the capacity tends to increase. In particular, it is preferable that MnO be contained in an amount of 0.1 to 0.4 part by mol with respect to 100 parts by mol of BaTiO ₃ .

Further, the composition formula based on the molar ratio is aSiO
_The reason that the sub-component (glass component) represented by ₂ + bBaO + cCaO + dLi ₂ O was contained in an amount of 1 to 4 parts by weight based on 100 parts by weight of BaTiO ₃ is that when the sub-component is less than 1 part by weight, the sinterability deteriorates. This is because the insulation resistance tends to decrease and the CR product tends to decrease, and if it exceeds 4 parts by weight, the relative permittivity and the insulation resistance tend to decrease. The auxiliary component is 1 to 2.5 parts by weight based on 100 parts by weight of BaTiO _3.
Desirably, parts by weight are used.

A indicating the molar ratio of SiO ₂ among the subcomponents
Is set to 0.30 ≦ a ≦ 0.70 because the sinterability tends to decrease when the molar ratio a is less than 0.30,
If it exceeds 0.70, the relative permittivity tends to decrease. The molar ratio a of SiO ₂ is preferably 0.40 ≦ a ≦ 0.60 in order to obtain more effects.

Further, b representing the molar ratio of BaO is 0.10
The reason why ≦ b ≦ 0.40 is that when the molar ratio b is less than 0.10, the sinterability tends to decrease, and when the molar ratio b exceeds 0.40, the sinterability decreases. This is because the rate tends to decrease. In particular, b representing the molar ratio of BaO is preferably 0.10 ≦ b ≦ 0.25.

The molar ratio of CaO, c, is 0.10 ≦ c ≦
The reason for setting the ratio to 0.40 is that when the molar ratio c is less than 0.10, the sinterability tends to decrease, and when it exceeds 0.40, the sinterability decreases and the relative dielectric constant decreases. This is because there is a tendency to do so. In particular, c indicating the molar ratio of CaO is 0.1.
10 ≦ c ≦ 0.25 is preferred.

D representing the molar ratio of Li ₂ O is 0.05 ≦ d
≦ 0.30 because the sinterability tends to decrease when the molar ratio d is less than 0.05, and the insulation resistance tends to decrease when the molar ratio d exceeds 0.30. .

The dielectric ceramic having a relative dielectric constant of 4300 or more according to the present invention is obtained by sintering a compact containing barium titanate as a main component, magnesium oxide, manganese oxide and rare earth element oxide, and then sintering the compact. In the method for producing a dielectric ceramic in which the temperature is lowered from the temperature to 700 ° C. or less, and the temperature is raised again to 900 ° C. or more and the heat treatment is performed, the temperature is reduced from 1000 ° C. to 70 ° C. after sintering.
Oxygen partial pressure in the process of cooling down to 0 ° C. is 1 × 10 ⁻¹⁷ to
It can be obtained by setting it to 1 × 10 ⁻¹⁰ Pa.

The dielectric ceramic of the present invention, specifically, for example, a BaTiO ₃ powder, MnCO ₃ powder, Y ₂ O ₃ powder,
And MgO powder, glass components (SiO ₂ , BaO, C
aO, Li ₂ O), water and a dispersant are added to the powder, mixed and pulverized by a ball mill, mixed with an organic binder, and formed into a sheet having a predetermined thickness. 10 ^{-8 to} 3 × 10 ^-3 Pa, temperature 1100 to 1
Sinter at 300 ° C for 0.5-3 hours.

That is, as shown in FIG. 1, for example, the temperature is raised at a heating rate of 150 to 400 ° C./h, and the firing temperature is 1100 to 1100.
After firing at 1300 ° C. for 0.5 to 3 hours, the temperature is lowered from the sintering temperature to 700 ° C. or less, particularly to 600 to 300 ° C., and then 900 at an oxygen partial pressure of 1 × 10 ⁻² to 2 × 10 ⁴ Pa. ° C
As described above, in particular, the heat treatment is performed at a temperature of 900 to 1100 ° C. for 0.5 to 7 hours. ^Partial pressure of 1 × 10 ^-17 to 1 × 10 ^-10 Pa
And it is necessary to perform a reduction treatment.

The reason that the oxygen partial pressure at the time of temperature decrease from 1000 ° C. to 700 ° C. is 1 × 10 ⁻¹⁷ to 1 × 10 ⁻¹⁰ Pa is that the oxygen partial pressure at the time of temperature decrease from 1000 ° C. to 700 ° C. is 1 ×. If it is lower than 10 ^-17 , the strength of the porcelain decreases, and if it is higher than 1 × 10 ^-10 Pa, the dielectric constant decreases.

The oxygen partial pressure is set to 1 × 10 ⁻¹⁷ to 1 × 10
^The temperature for controlling to ^-10 Pa is set to 1000 to 700 ° C. because the reduction treatment can be performed while suppressing grain growth.

The rate of temperature decrease from 1000 ° C. to 700 ° C. is 50 to 500 ° C. /
h is desirable, and the oxygen partial pressure at this time is desirably 1 × 10 ^{−16 to} 3 × 10 ⁻¹¹ Pa from the viewpoint of improving reliability.
In particular, in order to obtain a high dielectric constant, 900 ° C. to 750 ° C.
The oxygen partial pressure is reduced from 1 × 10 ⁻¹⁵ to 1 × 10 ⁻ during the temperature lowering process.
It is desirable to control it between ¹¹ Pa.

The cooling rate at a cooling temperature of 700 ° C. or less is 20
0 to 300 ° C./h is desirable from the viewpoint of enhancing reliability. The rate of temperature rise from the temperature drop to the heat treatment temperature is 20
0 to 300 ° C./h is desirable from the viewpoint of improving reliability. The heat treatment condition is desirably 900 to 1050 ° C.

It should be noted that MnO ₂ powder was used instead of MnCO ₃ powder, and MgCO ₃ powder, BaO, C
Needless to say, carbonate powder may be used as aO and Li ₂ O.

The dielectric ceramic of the present invention is a multilayer ceramic capacitor in which a pair of external electrodes are formed on a laminate of the above-described dielectric ceramic and internal electrode layers mainly composed of a base metal, particularly Ni. It is preferably used.

BaTiO ₃ of dielectric porcelain in the present invention
The particles preferably have an average particle size of 0.2 to 1 μm from the viewpoint of reducing dielectric loss and improving dielectric constant.

[0042]

First, BaTiO ₃ was used as a main component, and Y ₂ O ₃ , MgO, MnCO _{3 was used with} respect to 100 mole parts of the main component.
The respective Y ₂ O _3, MgO, the dielectric powder added by an amount shown in Table 1 in terms of MnO, SiO ₂ powder, BaCO ₃
Powder, CaCO ₃ powder, Li ₂ CO ₃ powder is SiO ₂ , B
The subcomponents having the molar ratios shown in Table 1 in terms of aO, CaO, and Li ₂ O were added to 100 parts by weight of BaTiO ₃ in Table 1.
, And water and a dispersant were added thereto, mixed and pulverized with a ball mill, mixed and pulverized with a ball mill using ZrO _2, and mixed with an organic binder.
The obtained slurry was formed into a film-like sheet having a thickness of 5 μm.

A Ni paste obtained by adding an organic plasticizer to nickel powder is printed on this film-like sheet by a screen printing method, and then 100 layers of the Ni paste are laminated.
Laminate film-like sheets without printing paste,
After thermocompression bonding, it was cut.

This was heated in the atmosphere at a temperature of 300 ° C. for 4 hours to remove the binder.
The temperature was raised at 0 ° C / h, the temperature was 1260 ° C, and the oxygen partial pressure was 1
It was fired at × 10 ⁻⁶ Pa for 2 hours and sintered. After this, Table 1
The temperature was lowered at a rate of 300 ° C./h to the temperature shown in Table 1. At this time, the temperature was lowered in the temperature range shown in Table 1 with the oxygen partial pressure shown in Table 1,
Reduction treatment was performed.

Next, the temperature was increased to 300 ° C./h at a temperature shown in Table 1, and the mixture was heated at an oxygen partial pressure of 1 × 10 Pa for 2 hours, and the dimensions of the porcelain were 2.0 mm × 1.1 mm × 0.9 m.
m, a capacitor body having an effective electrode area of one layer of 1.05 mm ² and a dielectric layer thickness of 4 μm × 100 layers was obtained. Thereafter, a copper paste is applied to both end surfaces of the capacitor body,
It is baked at 0 ° C. to form an external electrode.
i-plating and Sn-plating were performed to obtain a multilayer ceramic capacitor of the present invention.

As a comparative example, a sample heat-treated at an oxygen partial pressure of 1 × 10 ⁻⁷ to 1 × 10 ⁻⁴ Pa in the process of decreasing the temperature from the sintering temperature was also prepared. In Table 2, the oxygen partial pressure of the heat treatment is shown in the column of the reduction treatment.

Next, these evaluation samples were measured for capacitance and dielectric loss at −25 ° C., 20 ° C., 25 ° C. and 85 ° C. using an LCR meter 4284A at a frequency of 1.0 kHz and an input signal level of 1.0 Vrms. Is measured, and the relative permittivity is calculated.
The temperature change rate of the relative dielectric constant at 25 ° C. and 85 ° C. was calculated.

After applying DC 10 V for 60 seconds, the insulation resistance between the electrodes was measured using an insulation resistance meter DSM8103. These results are summarized in Table 1.

[0049]

[Table 1]

[0050]

[Table 2]

From Tables 1 and 2, it can be seen that in the comparative example in which the oxygen partial pressure was set to 1 × 10 ⁻⁷ to 1 × 10 ⁻⁴ Pa in the process of decreasing the temperature from the sintering temperature, the dielectric constant at + 25 ° C. was about 3500. On the other hand, the oxygen partial pressure was ^increased from 1 × 10 ⁻¹⁷ to 1 × 10 ⁻¹⁰ Pa in the temperature decreasing process from 1000 ° C. to 700 ° C.
In the sample of the present invention, which was reduced and controlled to
It was 300 or more.

[0052]

According to the dielectric porcelain of the present invention, after a compact containing barium titanate as a main component and containing magnesium, manganese and a rare earth element is sintered, it is once cooled to 700 ° C. or less, and then cooled again to 900 ° C. In the manufacturing method in which the temperature is increased to at least 100 ° C. and the heat treatment is performed, the oxygen partial pressure in the temperature decreasing process from 1000 ° C. to 700 ° C. is set to 1 × 10 ⁻¹⁷ to 1 ×.
By setting the pressure to 10 ⁻¹⁰ Pa, the relative dielectric constant at 25 ° C. can be 4300 or more. By manufacturing a multilayer ceramic capacitor using such a dielectric ceramic, the dielectric layer can be thinned. The capacitance per unit volume can be increased without the need.

[Brief description of the drawings]

FIG. 1 is a graph showing a firing pattern of the present invention.

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Claims (5)

[Claims] 1. A dielectric ceramic comprising barium titanate as a main component, magnesium, manganese, and a rare earth element as metal elements, and having a relative dielectric constant of 4300 or more at 25 ° C. 2. A relative dielectric constant of 20.degree.
2. The dielectric ceramic according to claim 1, wherein the temperature change rate of the relative dielectric constant at the time is within ± 15%. _3. 100 parts by mole of BaTiO ₃ ,
With respect to 100 mole parts of O ₃ , Y is 0.4 to 0.4 in terms of Y ₂ O _3.
3.0 mol parts, 0.5 to 8.0 mol parts of Mg in terms of MgO, 0.04 to 0.5 mol parts of Mn in terms of MnO, and Si, Ba and Ca as glass components. The dielectric porcelain according to claim 1, wherein: 4. After sintering a compact containing barium titanate as a main component and containing magnesium oxide, manganese oxide and a rare earth element oxide, the compact is cooled from a sintering temperature to 700 ° C. or lower and again to 900 ° C. or higher. In the method of producing dielectric porcelain which is heat-treated by raising the temperature, the temperature is raised from 1000 ° C. to 70 ° C. after sintering.
Oxygen partial pressure in the process of cooling down to 0 ° C. is 1 × 10 ⁻¹⁷ to
A method for producing a dielectric porcelain, wherein the pressure is 1 × 10 ⁻¹⁰ Pa. 5. A multilayer ceramic capacitor in which internal electrodes containing a base metal as a main component and dielectric layers are alternately laminated, wherein the dielectric layer is any one of claims 1 to 3. A multilayer ceramic capacitor comprising a dielectric porcelain.