JP2001110665A - Dielectric component and ceramic capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric component excellent in anti-reducing characteristic on baking with comparatively high permittivity after baking, and excellent in capacitive temperature characteristic. SOLUTION: The dielectric component at least contains barium titanate and calcium titanate. The molar ratio of these two materials is 0.5>X>0.3 with respect to the barium titanate X, and Y=1-X as the calcium titanate Y.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric composition and a ceramic capacitor using the same, and more particularly to a dielectric composition which has excellent resistance to reduction during firing and a relatively high dielectric constant (for example, 500 or more) after firing. ) And has excellent capacitance-temperature characteristics (for example, satisfies JIS standard SL characteristics), low-temperature sinterable dielectric composition, and high insulation resistance and relatively high capacitance (for example, a dielectric constant of 500 or more).
The present invention also relates to a ceramic capacitor having a flat capacitance-temperature characteristic (for example, satisfying the SL characteristic of JIS standard) and capable of using a base metal such as nickel or a nickel alloy for an internal electrode.

[0002]

2. Description of the Related Art As a dielectric composition used for a ceramic capacitor or the like, barium titanate (BaTiO) is used.
High dielectric constant systems such as ₃ ) are known. In this type of composition, the relative dielectric constant εr can be increased, but the capacitance temperature change rate is large.

[0003] Zirconic acid is used as a dielectric composition.
Calcium (CaZrO)₃), Stront zirconate
Um (SrZrO₃), Calcium titanate (CaT
iO ₃), Strontium titanate (SrTi
O₃), Strontium calcium zirconate (Ca
SrZrO₃) Are also known. This
The main composition has a very small capacity temperature change rate,
Used for pulling circuits, audio circuits, image processing circuits, etc.
Can be

However, since it is a paraelectric substance, the relative dielectric constant εr is as low as 30 to 200, and it is difficult to obtain a high-capacity capacitor.

Therefore, as a ceramic dielectric composition for temperature compensation having a dielectric constant of 300 or more and a small capacity temperature coefficient, calcium titanate (CaTiO ₃ ) -barium titanate (BaTiO ₃ ) -strontium titanate (SrT)
An iO ₃ ) -based composition has been proposed (for example, see JP-A-54-96800).

[0006]

By the way, conventionally, platinum (Pt),
Although a noble metal such as gold (Au) or silver (Ag) is used, it is preferable to use a base metal such as nickel (Ni) from the viewpoint of cost.

The dielectric composition described in Japanese Patent Application Laid-Open No. 54-96800 is inferior in reduction resistance, so that it is necessary to fire it in an oxidizing atmosphere.

However, when firing in an oxidizing atmosphere,
When a low-cost base metal such as Ni is used for the internal electrode, Ni is oxidized, and eventually the P
Noble metals such as t, Au or Ag had to be used.

On the other hand, as a dielectric composition having reduction resistance and capable of using a base metal as an internal electrode, calcium titanate (CaTiO ₃ ) -strontium zirconate (SrZrO ₃ ) -silicon oxide (SiO ₂₎ )-
A manganese oxide (MnO ₂ ) -based composition (see, for example, JP-A-62-180905) or (SrCa)
TiO ₃ -based compositions (for example, see JP-A-8-2955)
No. 60 gazette) has been proposed.

However, all of the compositions described in these publications have a low relative dielectric constant εr of about 130 to 230, making it difficult to secure sufficient capacity (electrical characteristics).

A first object of the present invention is to solve the problems of the prior art, and to provide a dielectric material having excellent resistance to reduction during firing, a relatively high dielectric constant after firing, and excellent capacitance temperature characteristics. It is to provide a body composition.

A second object of the present invention is to provide a ceramic capacitor which has a high insulation resistance and a relatively high dielectric constant, has a flat capacitance-temperature characteristic, and can use a base metal for an internal electrode. is there.

[0013]

[Means for Solving the Problems] In order to achieve the above object, a dielectric composition according to the first aspect of the present invention is a dielectric composition containing at least barium titanate and calcium titanate. The composition molar ratio (X) of barium titanate is 0.3 <X <0.5, and the composition molar ratio (Y) of calcium titanate is 1-X.

Since it is considered that the composition molar ratio of barium titanate and calcium titanate does not change before and after firing, the term dielectric composition in the present specification includes both before and after firing. .

According to the present invention, a ferroelectric barium titanate is added to a paraelectric calcium titanate at a specific ratio, so that the paraelectric phase and the ferroelectric phase are balanced, and firing is performed. Sometimes it has excellent reduction resistance, shows a relatively high dielectric constant (for example, a relative dielectric constant εr is preferably 500 or more) after firing, and also has excellent capacity temperature characteristics (for example, preferably SL characteristics according to JIS standards). Is satisfied) can be provided. In addition,
In the present invention, satisfying the SL characteristic of the JIS standard means that
The rate of change of capacitance with respect to temperature (ΔC) is at least 2
Within a temperature range of 0 to 85 ° C, -1000 to 350
ppm / ° C (however, the reference temperature of the capacitance C is 20 ° C)
Is the case.

2. The dielectric composition according to the first aspect of the present invention may contain an additive.

[0017]Sintering aid Such additives include, for example, SiO 2₂, Al
₂O₃And (Ba, Ca)_xSiO_{2 + x},
B₂O₃, Li₂O, Na₂O, K₂ O, Ba
Sintering aids such as O, CaO and SrO can be mentioned.
You. Among them, adopt any of the following combinations
Is preferred.

First, SiO₂, Al₂O₃And
And (Ba, Ca)_xSiO_{2 + x} Selected from the group consisting of
Preferably, at least one of them is used. Composite oxide
(Ba, Ca)_xSiO_{2 + x}Has a low melting point
Therefore, at least barium titanate and calcium titanate
Good reactivity with basic components containing
In the present invention, BaO and / or CaO are combined with the above composite.
More preferably, it is added as an oxide.

_{X in} (Ba, Ca) _x SiO _{2 +} x is preferably 0.8 to 1.2, and more preferably 0.9 to 1.1. If x is too small, that is, if there is too much SiO _2, it reacts with barium titanate to deteriorate the dielectric properties. On the other hand, if x is too large, the melting point becomes high and the sinterability deteriorates, which is not preferable. The ratio between Ba and Ca is arbitrary, and may contain only one of them.

Second, M1 (where M1 is SiO
₂ and at least one of Al ₂ O ₃ ), M2
(Where M2 is at least one selected from BaO, CaO and SrO) and M3 (where M3 is
Li ₂ O, Na ₂ O, K ₂ O, and B ₂ O ₃ ).

When the sintering temperature is increased, a dense sintered body can be obtained.
The capacity-temperature characteristics tend to deteriorate due to the diffusion of the internal electrode material. On the other hand, if the sintering temperature is lowered, such a disadvantage does not occur, but a dense sintered body cannot be obtained. Therefore, it is desired to obtain a dense sintered body while preventing interruption of the internal electrode and deterioration of the capacitance temperature characteristic. By adding the first and second sintering aids described above, it is possible to suitably obtain a dense sintered body while preventing interruption of the internal electrode and deterioration of the capacitance temperature characteristics.

This type of sintering aid has the function of lowering the sintering temperature. Also, the capacitance-temperature characteristics are not significantly affected. However, if the addition amount is too large, the sinterability tends to deteriorate, and the insulation resistance (IR) tends to decrease,
If the addition amount is too small, the sinterability is further reduced,
Insulation resistance (IR) tends to deteriorate. Therefore,
The amount of these sintering aids added is at least 100% of the basic component containing barium titanate and calcium titanate.
The range of 0.2 to 6 mol% is preferable to the mol%.

When the first sintering aid is used, 120
Sintering can be performed at a low temperature of 0 ° C., and when the second sintering aid is used, sintering can be performed at a temperature lower than 1200 ° C. If the amount added is too large or too small,
The sinterability at a low temperature of about 0 ° C. is poor, and a dense sintered body tends not to be obtained.

3. In order to achieve the above object, a particularly preferred embodiment is a dielectric composition according to the following second to third aspects.

The dielectric composition according to the second aspect of the present invention comprises a basic component containing at least barium titanate and calcium titanate, SiO ₂ , Al ₂ O ₃ and (Ba, Ca) _x SiO _{2 + x} (where , X =
0.8 to 1.2), wherein the composition molar ratio (X) of barium titanate is 0 with respect to the composition molar ratio of the basic components. 0.3 <X <0.5, the composition molar ratio (Y) of calcium titanate is 1-X, and the amount of the additional component to be added is 0.1 to 100 mol% of the basic component.
2 to 6 mol%.

According to a third aspect of the present invention, there is provided a dielectric composition comprising a basic component containing at least barium titanate and calcium titanate, and M1 (where M1 is SiO 2).
₂ and at least one of Al ₂ O ₃ ), M2
(Where M2 is at least one selected from BaO, CaO and SrO) and M3 (where M3 is
Li ₂ O, Na ₂ O, K ₂ O and B ₂ O ₃
Wherein the compositional molar ratio (X) of barium titanate is 0.3 to 0.3.
<X <0.5, composition molar ratio of calcium titanate (Y)
Is 1-X, and when the composition molar ratio of the additive component is represented by a triangular diagram (M1, M2, M3), the composition molar ratio of the additive component is within a region surrounded by the following points a to f. Yes (Fig. 6
Outside shaded area. However, it is not included on the boundary line), and the addition amount of the additional component is 0.2 to 6 mol% with respect to 100 mol% of the basic component. a: (0.1, 0, 0.9) b: (0.5, 0, 0.5) c: (0.7, 0.2, 0.1) d: (0.2, 0. 7, 0.1) e: (0, 0.5, 0.5) f: (0, 0.1, 0.9)

Preferably, the composition molar ratio of the additional component in the dielectric composition according to the third aspect is a triangular diagram (M1, M
When expressed by (2, M3), the composition molar ratio of the additive component is within a region surrounded by the following points k, b, c, l, and m (the inside hatched portion in FIG. 6; Is not included). k: (0.2, 0, 0.8) b: (0.5, 0, 0.5) c: (0.7, 0.2, 0.1) l: (0.35, 0. 55, 0.1) m: (0, 0.2, 0.8)

If the sintering temperature is increased, a dense sintered body can be obtained.
The capacity-temperature characteristics tend to deteriorate due to the diffusion of the internal electrode material. On the other hand, if the sintering temperature is lowered, such a disadvantage does not occur, but a dense sintered body cannot be obtained. Therefore, it is desired to obtain a dense sintered body while preventing interruption of the internal electrode and deterioration of the capacitance temperature characteristic. In the dielectric composition according to the above-described viewpoint, by adding a glass component having a specific composition, a dense sintered body can be suitably obtained even when firing at a low temperature of about 1200 ° C.

In particular, the additive component in the dielectric composition according to the third aspect has an effect of further lowering the sintering temperature. The amount of the glass component added is 100 mol% of the basic component containing the barium titanate and calcium titanate.
Is preferably in the range of 0.2 to 6 mol%. If the amount is too large or too small, the sinterability at a low temperature of about 1100 ° C. is poor, and a dense sintered body tends not to be obtained.

According to the above-described dielectric composition according to the third aspect, since it can be fired at a low temperature of about 1100 ° C.,
Grain growth during sintering can be suppressed, and abnormal expansion such as expansion of the substrate can be effectively prevented.

4. As described above, in the dielectric compositions of the first to third aspects, the composition molar ratio of barium titanate and calcium titanate is such that the composition molar ratio (X) of barium titanate is 0.3 <X <0. And the composition molar ratio (Y) of calcium titanate is 1-X. However, when the composition molar ratio (X) of barium titanate increases, the dielectric constant increases, but the capacitance-temperature characteristics tend to not satisfy the SL characteristics.

On the other hand, when the composition molar ratio (Y) of calcium titanate increases, the capacity-temperature characteristics are not satisfied, and the dielectric constant tends to decrease.

Therefore, in order to better balance the dielectric constant and the capacitance-temperature characteristic, the composition molar ratio (X) of barium titanate is 0.35 or more and 0.48 or less, and the composition molar ratio of calcium titanate (X) is Y) is preferably 1-X, particularly preferably X is 0.35 or more and 0.4 or more.
Where Y is 1-X.

5. The dielectric composition according to the present invention according to the first to third aspects has at least two kinds of crystal structures, and at least one of the crystal structures is a tetragonal containing barium titanate. Cubic, orthorhombic containing calcium titanate
Alternatively, it is preferably a tetragonal crystal. It is preferable that the composition after firing has at least two types of crystal structures because, when the solid solution of barium titanate and calcium titanate progresses to have only one crystal structure, the relative dielectric constant This is because (εr) tends to decrease and the dielectric loss (tan δ) at high temperatures tends to deteriorate.

6. The dielectric composition according to the first to third aspects of the present invention has a double value (2θ) of the Bragg angle (θ) of 44 to 46 deg. In X-ray diffraction analysis (Kα ray of Cu).
Within the range, barium titanate as a main component (00
2) It preferably has a pseudo cubic peak including a crystal plane peak and a (200) crystal plane peak. The pseudo cubic peak referred to here has no difference in lattice constant between the peak of the (002) crystal plane containing barium titanate as a main component and the peak of the (200) crystal plane, and is difficult to separate by X-ray diffraction analysis. Means the peak which became. It has been found that by adopting a structure having this pseudo cubic peak, the capacity-temperature characteristics can be improved.

7. The dielectric composition according to the first to third aspects of the present invention has a double value (2θ) of the Bragg angle (θ) of 44 to 48 deg. In X-ray diffraction analysis (Kα ray of Cu).
Within the range of (4), calcium titanate as a main component (04
0) It preferably has an orthorhombic peak in the crystal plane.

8. In the dielectric composition according to the present invention according to the first to third aspects, the barium titanate includes calcium, around a core portion substantially made of barium titanate.
A shell portion made of a layer in which at least one selected from the group consisting of magnesium, aluminum, vanadium, molybdenum, tungsten, cobalt, silicon, barium and calcium titanate is dissolved in barium titanate, or substantially calcium titanate. Surrounded by
It preferably has a core-shell structure.

The term "substantially composed of barium titanate" as used in the present invention means that the substance is composed entirely of barium titanate and contains impurities to such an extent that the effects of the present invention can be obtained. It is intended to include those that include, and "consist substantially of calcium titanate"
This is intended to include, in addition to those composed entirely of calcium titanate, those containing impurities to such an extent that the effects of the present invention can be exerted. Less than,
The same is true. By having barium titanate having such a structure, the capacitance-temperature characteristics of the dielectric composition can be made flatter.

9. In the dielectric composition according to the first to third aspects of the present invention, the calcium titanate is formed around calcium, magnesium, aluminum, vanadium, molybdenum, tungsten, and cobalt around a core portion substantially composed of calcium titanate. A layer in which at least one selected from the group consisting of silicon, barium and barium titanate is solid-dissolved in calcium titanate, or substantially barium titanate,
It preferably has a core-shell structure.

With the calcium titanate having such a structure, the capacitance-temperature characteristics of the dielectric composition can be made flatter.

Particularly, in the above-described dielectric composition of the present invention, the barium titanate has the core-shell structure, and the calcium titanate also has the core-shell structure.
It is particularly preferred to have a shell structure. By having barium titanate and calcium titanate having such a structure, the capacitance-temperature characteristics of the dielectric composition can be further flattened.

10. The dielectric composition according to the first to third aspects described above may contain various additives other than the sintering aid (limited to the composition according to the first aspect).

Reduction-Resistant Aids Such additives include, for example, Mg, Mn, C
at least one oxide (eg, MgO or MnO) selected from the group consisting of r, Co, Zn, and Al, and / or a compound (eg, MnCO ₃ or MgCO ₃ ) that becomes an oxide of Mg and / or Mn when fired
₃ ) reduction aids such as carbonates.

Among them, it is preferable to employ one of the following (1) and (2), and (1) and (2)
Is more preferably used in combination.

(1) An oxide of Mn and / or a compound which becomes an oxide of Mn by firing is preferable, and MnO is more preferable. This kind of reduction resistance auxiliary mainly has an effect of accelerating sintering and an effect of improving insulation resistance (IR). However, if the addition amount is too large, the insulation resistance (IR) is reduced.
, And the dielectric loss (tan δ) tends to increase. Therefore, the amount of addition should be at least 100 mol% of the basic component containing at least barium titanate and calcium titanate.
Is preferably in the range of 0.1 to 1 mol%.

(2) An oxide of Mg and / or a compound which becomes an oxide of Mg by firing is also preferable, and MgO is more preferable. This kind of reduction resistance aid has an effect of mainly flattening the capacity-temperature characteristic, but if the addition amount is too large, the sinterability deteriorates and the relative permittivity (εr) tends to decrease. Therefore, the addition amount is preferably 4 mol% or less based on 100 mol% of the basic component containing at least barium titanate and calcium titanate.

Other Additives Other additives include V ₂ O ₅ , MoO
₃ , at least one oxide selected from the group consisting of WO ₃ and Co ₃ O ₄ .
Among them, V ₂ O ₅ is preferable. This type of oxide is
It has the effect of lowering the sintering temperature, but if the amount is too large, the insulation resistance (IR) and dielectric loss (tan)
δ) tends to be significantly deteriorated,
0.01 to 100 mol% of the basic component containing at least barium titanate and calcium titanate
It is preferably in the range of 0.5 mol%.

11. The dielectric composition according to the first to third aspects of the present invention can be preferably used as a material for the dielectric layer of a ceramic capacitor having an internal electrode and a dielectric layer.

In this case, the internal electrode is made of nickel (N
More preferably, it is composed of i) or a Ni alloy. Since the dielectric composition according to the present invention is excellent in reduction resistance during firing, sintering in a reducing atmosphere becomes possible,
Ni or a Ni alloy can be used as the internal electrode, and the cost can be reduced.

The structure of the ceramic capacitor is not particularly limited, and includes a single-plate capacitor in addition to a multilayer capacitor.

Such a capacitor comprises the above-described dielectric composition of the present invention and a base metal (eg, Cu, Cu alloy, N
i or a Ni alloy) and by firing them simultaneously.

The lamination method is not particularly limited, and includes a printing method and a sheet method. It can also be manufactured by the injection method.

[0053]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a partially cutaway perspective view showing an embodiment of the multilayer ceramic capacitor of the present invention, and FIG. 2 shows the fine structure of the dielectric composition in Example (Sample 3) of the present invention.
M, FIG. 3 schematically shows the photograph of FIG. 2, and FIG. 4 shows capacitance-temperature characteristics (SL characteristics) of Examples (Sample 3) and Comparative Examples (Sample 8, Sample 0) of the present invention. FIG. 5 is a graph showing the measurement results of X-ray diffraction of the dielectric compositions in Example (Sample 3) and Comparative Example (Sample 0) of the present invention (where the horizontal axis represents the Bragg angle θ of 2). Double value (2θ, unit is deg.), Vertical axis is intensity (I, unit is c)
ps)), and FIG. 6 is a ternary composition diagram of a glass component in the dielectric composition according to the third aspect of the present invention.

In this embodiment, first, the structure of the multilayer ceramic capacitor will be described, and then a method of manufacturing the multilayer ceramic capacitor will be described.

[0056] As shown in ceramic capacitors Figure 1, the multilayer ceramic capacitor 1 of the present embodiment, the internal electrode 11 and the dielectric layer 12 are laminated alternately, a pair of connecting to the internal electrodes outside It has an electrode 13.

In the present embodiment, the internal electrode 11 is formed of Ni or a Ni alloy, and is not particularly limited.
The i-alloy is preferably 95% by weight or more of Ni and one or more alloys such as manganese (Mn), chromium (Cr), cobalt (Co), and aluminum (Al). Also, Ni or Ni alloy may contain 0.1% by weight or less of phosphorus (P) or the like as a trace component.

Various conditions such as the thickness of the internal electrode 11 may be appropriately determined according to the purpose and application.
It is 5 μm, preferably 2-3 μm.

The material of the dielectric layer 12 is composed of a dielectric composition containing at least barium titanate and calcium titanate. The molar ratio of these two components is as described above. It is preferable that a reduction resistance assistant and a sintering assistant are added to the dielectric composition.

The external electrode 13 is usually made of copper (C
u), a Cu alloy, Ni or a Ni alloy, or the like, but gold (Au), an alloy of silver (Ag) and palladium (Pd), or the like can also be used. The thickness of the external electrode 13 is arbitrary, and may be appropriately determined according to the purpose and application.
0 to 50 μm.

The shape and size of such a multilayer ceramic capacitor 1 may be appropriately determined according to the purpose and application. For example, in the case of a rectangular parallelepiped, usually 1 to 1.
It is about 6 mm × 0.5 to 0.8 mm × 0.3 to 0.6 mm.

Next, a method of manufacturing the above-mentioned multilayer ceramic capacitor 1 will be described. First, a paste for a dielectric layer, a paste for an internal electrode, and a paste for an external electrode are manufactured.

The dielectric layer paste is produced by kneading a dielectric material and an organic vehicle according to the composition of the above-described dielectric composition, or as a water-based paint. As the dielectric material, any of the above-described composite oxides and various compounds that become oxides, for example, carbonates, nitrates, hydroxides, organometallic compounds, and the like can be appropriately selected and used.
The content of each compound in the dielectric material may be determined so as to have the above-described composition of the dielectric layer after firing. The dielectric material is usually used as a powder having an average particle diameter of about 0.1 to 3.0 μm.

The organic vehicle is obtained by dissolving a binder in an organic solvent, and the binder used for the organic vehicle is not particularly limited, and may be appropriately selected from ordinary various binders such as ethyl cellulose and polyvinyl butyral. In addition, the organic solvent used at this time is not particularly limited, and may be appropriately selected from organic solvents such as terpineol, butyl carbitol, acetone, and toluene depending on a method such as a printing method or a sheet method.

The water-based paint is obtained by dissolving a water-soluble binder, a dispersant, and the like in water. The water-soluble binder is not particularly limited, and may be polyvinyl alcohol, cellulose, water-soluble acrylic resin, emulsion, or the like. May be selected as appropriate.

The paste for an internal electrode is obtained by kneading the above-mentioned organic vehicle with the above-mentioned conductive material comprising various conductive metals or alloys or various oxides, organometallic compounds, resinates, etc. which become the above-mentioned conductive materials after firing. It is prepared by The external electrode paste is also prepared in the same manner as the internal electrode paste.

The content of the organic vehicle in each of the above-mentioned pastes is not particularly limited, and may be a usual content, for example, about 1 to 5% by weight of a binder and about 10 to 50% by weight of a solvent. Each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, and the like, as necessary.

When a printing method is used, a dielectric chip and an internal electrode paste are laminated and printed on a substrate such as polyethylene terephthalate, cut into a predetermined shape, and then peeled off from the substrate to form a green chip. On the other hand, when the sheet method is used, a green sheet is formed using a dielectric paste, an internal electrode paste is printed thereon, and these are laminated to form a green chip.

Next, the green chip is subjected to binder removal processing and firing. The binder removal process is performed before firing,
It may be performed under normal conditions, but particularly when a base metal such as Ni or a Ni alloy is used as the conductive material of the internal electrode layer, the temperature is increased at a rate of 5 to 300 ° C./hour, more preferably 10 to 300 ° C./hour in an air atmosphere. 100 ° C / hour, holding temperature 180 ~
400 ° C., more preferably 200 to 300 ° C., and the temperature holding time is 0.5 to 24 hours, more preferably 5 to 20 hours.

The firing atmosphere of the green chip may be appropriately determined according to the type of the conductive material in the internal electrode layer paste. However, when a base metal such as Ni or a Ni alloy is used as the conductive material, the firing atmosphere may be different. Oxygen partial pressure is preferably 10
^-10 to 10 ^-3 Pa. If the oxygen partial pressure is too low, the conductive material of the internal electrode will be abnormally sintered and be interrupted, and if the oxygen partial pressure is too high, the internal electrode will be oxidized. The holding temperature for firing is preferably 11
00 to 1400 ° C, more preferably 1200 to 1380
° C. If the holding temperature is too low, the densification becomes insufficient, and if the holding temperature is too high, the capacitance-temperature characteristics deteriorate due to the interruption of the electrodes due to abnormal sintering of the internal electrodes or the diffusion of the internal electrode material. However, if the dielectric composition according to the above-described second to third aspects is used, even at a low temperature of about 1100 ° C., a dense sintered body can be obtained while preventing interruption of the internal electrodes and deterioration of the capacitance temperature characteristic. .

Other firing conditions include a heating rate of 50 to 500 ° C./hour, more preferably 200 to 300 ° C.
° C / hour, the temperature holding time is 0.5-8 hours, more preferably 1-3 hours, the cooling rate is 50-500 ° C / hour, more preferably 200-300 ° C / hour, and the firing atmosphere is a reducing atmosphere. It is desirable to use, for example, a wet mixed gas of nitrogen gas and hydrogen gas as the atmosphere gas.

When firing in a reducing atmosphere, it is desirable to anneal the sintered body of the capacitor chip. Annealing is a process for reoxidizing the dielectric layer, which can increase the insulation resistance. The oxygen partial pressure of the annealing atmosphere is preferably 10 ⁻⁴ Pa or more, more preferably 10 ⁻⁴ to 10 Pa. If the oxygen partial pressure is too low, reoxidation of the dielectric layer becomes difficult, and if the oxygen partial pressure is too high, the internal electrodes may be oxidized. The holding temperature at the time of annealing is 1100 ° C. or less, more preferably 50 ° C.
0 to 1100 ° C. If the holding temperature is too low, the reoxidation of the dielectric layer becomes insufficient, the insulation resistance is deteriorated, and the accelerated life is shortened. On the other hand, if the holding temperature is too high, not only is the internal electrode oxidized to lower the capacity, but also reacts with the dielectric substrate, which deteriorates the capacity temperature characteristic, insulation resistance and accelerated life thereof. Note that the annealing may be constituted by only the temperature raising step and the temperature lowering step. In this case,
The temperature holding time is zero, and the holding temperature is synonymous with the maximum temperature.

Other annealing conditions include a temperature holding time of 0 to 20 hours, more preferably 6 to 10 hours,
The cooling rate is 50 to 500 ° C./hour, more preferably 10 to 500 ° C./hour.
The temperature is set to 0 to 300 ° C./hour, and as an atmosphere gas for annealing, for example, it is desirable to use a wetted nitrogen gas.

Incidentally, in the above-described binder removal treatment, firing and annealing steps, for example, a wetter or the like can be used to humidify the nitrogen gas or the mixed gas. The water temperature in this case is desirably 5 to 75 ° C.

The binder removal, firing and annealing may be performed continuously or independently of each other. In the case where these steps are continuously performed, the atmosphere is changed without cooling after the binder removal processing, the temperature is raised to the holding temperature at the time of firing, and firing is performed. When the temperature reaches the above, it is more preferable to change the atmosphere and perform the annealing treatment.

On the other hand, when these steps are performed independently, the firing is performed by raising the temperature in a nitrogen gas or humidified nitrogen gas atmosphere to the holding temperature during the binder removal treatment, and then changing the atmosphere. It is preferable to continue the temperature increase, and after cooling to the annealing holding temperature, it is preferable to change the atmosphere to a nitrogen gas or a humidified nitrogen gas atmosphere again and continue the cooling. Further, regarding the annealing, the atmosphere may be changed after the temperature is raised to the holding temperature in the nitrogen gas atmosphere, or the entire annealing process may be performed in a humidified nitrogen gas atmosphere.

The end surface of the fired capacitor body obtained as described above is subjected to, for example, barrel polishing or sand blasting, and the external electrode paste is printed or transferred and fired to form an external electrode. The firing conditions for the external electrode paste are preferably, for example, about 10 minutes to 1 hour at 600 to 800 ° C. in a humidified mixed gas of nitrogen gas and hydrogen gas. Then, if necessary, a coating layer is formed on the surface of the external electrode by plating or the like.

The ceramic capacitor 1 of the present embodiment manufactured as described above is mounted on a printed circuit board by soldering or the like, and is used for various electronic devices.

[0079]

Next, the present invention will be described in more detail by way of examples which embody the embodiments of the present invention. However,
The present invention is not limited to only these examples.

Hereinafter, the characteristics of the dielectric composition according to the present invention itself and the characteristics of the multilayer ceramic capacitor using the dielectric composition as a dielectric layer were evaluated.

Preparation of Dielectric Composition BaTiO ₃ (hereinafter referred to as BT) having an average particle size of 0.1 to 1 μm
), CaTiO ₃ (hereinafter, also referred to as CT),
MnCO ₃ , MgCO ₃ , (BaCa) Si
O ₃ , SiO ₂ , (Si, Ti) O ₂ , B ₂ O
₃ , BaO, CaO, SrO, Al ₂ O ₃ , Li
₂ O and V ₂ O ₅ (both industrial powders)
Were weighed so as to have the compounding ratios shown in the columns of Samples 0 to 49 in Tables 1 to 5, and these were respectively weighed by a ball mill.
The mixture was wet-mixed for about 16 hours and dried to obtain a dielectric composition.

By the way, the base materials BT and CT are:
BaCO ₃ , CaCO ₃ and TiO ₂ were each weighed and wet mixed using a ball mill for about 16 hours,
The same characteristics were obtained by using a material which was dried and then fired at a temperature of about 1150 ° C. in the air and wet-pulverized with a ball mill for about 50 hours. Similar characteristics were obtained even when BT and CT as base materials were prepared by using hydrothermal synthetic powder, oxalate method or the like.

Next, with respect to the obtained dielectric composition,
Polyvinyl alcohol as a binder was added so as to be 0.05% by weight, and the binder and the dielectric composition were mixed so as to be granulated. Then, 0.3 g of this granular dielectric composition was weighed, and 1.3 ton / cm ²
To obtain a disc-shaped molded body having a diameter of 12 mm and a thickness of 0.7 mm.

Next, the disc-shaped molded body was subjected to binder removal processing, firing and annealing to obtain a disk having a diameter of about 10 mm.
A disc-shaped fired body having a thickness of about 0.5 mm was obtained.

This binder removal treatment is carried out at a heating rate of 300 ° C.
/ Hour, holding temperature 800 ° C., holding time 2 hours, air and humidified nitrogen gas atmosphere (1 Pa).
The firing was performed at a heating rate of 200 ° C./hour and a holding temperature of 12 ° C.
00 to 1300 ° C. (However, samples 13 to 17 are 1200
° C, samples 22 to 49 are 1100 ° C), retention time 2 hours,
The cooling was performed at a cooling rate of 300 ° C./hour in a mixed gas atmosphere (10 ⁻⁴ Pa) of humidified nitrogen gas and hydrogen gas.
The annealing is performed at a holding temperature of 900 ° C., a holding time of 9 hours, a cooling rate of 300 ° C./hour, a humidified nitrogen gas atmosphere (1 P
Performed under the condition of a). Note that a wetter was used for humidification of each atmosphere gas, and the water temperature was 35 ° C.

On both sides of the disc-shaped fired body thus obtained,
An electrode having a diameter of 6 mm was formed by applying an In-Ga alloy, and a sample (hereinafter, also referred to as a disk-shaped sample) was manufactured.

Using this disc-shaped sample, the porcelain characteristics, relative permittivity (εr), dielectric loss (tan δ), insulation resistance (I
R), and the capacity-temperature characteristics were measured. Tables 1 to 5 show the results excluding the evaluation of the porcelain characteristics.

The fine structure of the dielectric composition in Sample 3 (Example) such as the structure of the dielectric composition
FIG. 2 shows a photograph observed by an EM (Scanning Electron Microscope), and FIG. 3 schematically shows the photograph.

According to this, in the dielectric composition of this example, BT, which is a ferroelectric substance, has calcium and magnesium solidified around barium titanate around core portion 2 substantially made of barium titanate. It was confirmed that it had a core-shell structure surrounded by a shell portion 22 composed of a melted layer. Also, CT, which is a paraelectric,
A core surrounded by a shell portion 32 made of a layer in which magnesium and barium are dissolved in calcium titanate, around a core portion 3 substantially made of calcium titanate.
It was confirmed that it had a shell structure. That is,
Both BT, a ferroelectric, and CT, a paraelectric,
It was confirmed that it had a core-shell structure. Since the luminance differs depending on the composition, the particles mainly containing BT are observed as white, and the particles mainly containing CT are observed as black.

The crystal structures of the dielectric compositions of Sample 3 (Example) and Sample 0 (Comparative Example) were measured by X-ray diffraction using a product number MXP3 manufactured by Mac Science. A high intensity Cu target X-ray tube operated at 40 kV and 40 mA was used as an irradiation source. The result is shown in FIG. In FIG. 5, the vertical axis indicates the scale of the intensity.

Looking at this, in the case of the dielectric composition in Sample 3 (Example), the BT has a double value (2θ _BT ) of the Bragg angle (θ _BT ) of the (002) crystal plane of 4
5.2 deg. At the time of, the maximum intensity _{I BT} is 617cp
s, and the double value (2θ _BT ) of the Bragg angle (θ _BT ) of the (200) crystal plane is 45.38 deg. When the maximum intensity _{I BT} showed 708Cps. For CT, the Bragg angle of the (040) crystal plane (θ _CT ) is 2
Double value (2θ _CT ) is 47.52 deg. When the maximum intensity _{I CT} showed 720 cps. That is, it can be seen that it has two types of crystal structures.

On the other hand, in sample 0 (comparative example), BT
Angle of solid solution of CT and CT (θ_BTCT) Double value
(2θ_BTCT) Is 47.4 deg. When the strongest
Degree I _BTCTShowed 1716 cps. That is, one
It can be seen that it has only one crystal structure.

Production of Multilayer Ceramic Capacitors For samples 0 to 49 in Tables 1 to 5, multilayer ceramic capacitors were also produced.

First, with respect to the dielectric layer paste, 100% by weight of each dielectric composition, 4.8% by weight of acrylic resin, 40% by weight of methylene chloride, 20% by weight of ethyl acetate,
6% by weight of mineral spirit and 4% by weight of acetone were mixed in a ball mill to form a paste.

For the internal electrode paste, 100% by weight of Ni particles having an average particle diameter of 0.2 to 0.8 μm and 40% by weight of an organic vehicle (8% by weight of ethyl cellulose resin dissolved in 92% by weight of butyl carbitol) % And 10% by weight of butyl carbitol were kneaded with a three-roll mill to form a paste.

For the external electrode paste, 100% by weight of Cu particles having an average particle diameter of 0.5 μm, 35% by weight of an organic vehicle (8% by weight of ethyl cellulose resin dissolved in 92% by weight of butyl carbitol), 7% by weight of carbitol was kneaded to form a paste.

Next, green sheets having a thickness of 4.5 μm and 15 μm were formed on the PET film using the above-mentioned paste for the dielectric layer, and the paste for the internal electrodes was printed thereon. The sheet was peeled off. Next, a plurality of the green sheets thus obtained were laminated and pressed and pressed to produce a green chip. The number of stacked green sheets having internal electrodes was four.

Next, the green chip is cut into a predetermined size, subjected to binder removal processing, firing and annealing,
A laminated ceramic fired body was obtained.

The binder removal treatment is performed at a heating time of 15 ° C. /
The test was performed under the conditions of a time, a holding temperature of 280 ° C., a holding time of 8 hours, and an air atmosphere. The firing was performed at a heating rate of 200 ° C./hour and a holding temperature of 1200 to 1380 ° C. (however, sample 13
17 to 1200 ° C, Samples 22 to 49 to 1100 ° C),
Holding time 2 hours, cooling rate 300 ° C./hour, mixed gas atmosphere of humidified nitrogen gas and hydrogen gas (10 ⁻⁶ Pa)
Was performed under the following conditions. Annealing was performed under the conditions of a holding temperature of 900 ° C., a holding time of 9 hours, a cooling rate of 300 ° C./hour, and a humidified nitrogen gas atmosphere (10 ⁻¹ Pa). Note that a wetter was used for humidifying the respective atmosphere gases, and the water temperature was 35 ° C.

Next, after polishing the end face of the laminated ceramic fired body by sandblasting, the paste for external electrodes was transferred to the end face, and fired at 800 ° C. for 10 minutes in a humidified nitrogen gas and hydrogen gas atmosphere. External electrodes were formed to obtain a sample of the multilayer ceramic capacitor (hereinafter, also referred to as “capacitor sample”). The size of each sample was 3.2 mm × 1.6 mm × 0.6 mm, the thickness of the dielectric layer was 10 μm and 3 μm, and the thickness of the internal electrode was 2 μm.

The capacitance-temperature characteristics of the capacitor samples thus obtained were measured. The results are shown in Tables 1 to 5.

Evaluation items and evaluation method As for the porcelain characteristics, the shrinkage ratio during firing and the porcelain density were calculated from the dimensions and mass of the disc-shaped sample, and the sinterability was evaluated from the results. There was no problem about.

For a disc-shaped sample, at 25 ° C., L
The capacitance and the dielectric loss (tan δ) under the conditions of 1 kHz and 1 Vrms were measured by a CR meter. The relative dielectric constant (εr) was calculated from the obtained capacitance, the electrode dimensions and the thickness of the sample.

The insulation resistance (IR) is DC at 25 ° C.
Specific resistance ρ after applying 50 V to the disc-shaped sample for 60 seconds
Was measured and calculated from the measured value and the electrode area and thickness of the sample (unit: “Ωcm”).

Regarding the capacitance-temperature characteristics, the capacitance of a disc-shaped sample and a capacitor sample at a voltage of 1 V was measured using an LCR meter, and the SL characteristics according to JIS standard (when the reference temperature was 20 ° C., 20 It was examined whether or not the capacity change rate satisfies -1000 to 350 ppm / ° C within a temperature range of ~ 85 ° C. Tables 1 to 5 show the case where the condition is satisfied and "X" when the condition is not satisfied. In addition, the value (unit:%) of the rate of change in capacity (ΔC85) at + 85 ° C. is also shown for the SL characteristics. Further, for Sample 3, which satisfied the SL characteristics, Sample 8, which did not satisfy the SL characteristics, and Sample 0, -50
The capacity change rate ΔC / C from −150 ° C. is graphed in FIG. The figure shows the rate of change based on the capacity at 20 ° C. As can be seen from the figure, it can be understood that only the sample 3 shows good temperature characteristics.

Tables 1 to 5 show the above results. Table 1
In the numerical values of the insulation resistance (IR), “mE +
“n” means “m × 10 ^{+ n} ”.

[0107]

[Table 1]

From the results in Table 1, the following is understood with respect to the composition molar ratio of BT and CT. All of Samples 3 to 5 have a good balance between the relative dielectric constant and the capacitance-temperature characteristic (SL characteristic). Above all, the balance of Samples 3 and 4 is particularly good. On the other hand, in Sample 0, the relative permittivity tends to be low, and the capacitance-temperature characteristic (SL characteristic) is deteriorated.
Samples 1 and 2 have good capacitance-temperature characteristics (SL characteristics) but tend to have low relative dielectric constants. Sample 6-7
No. 1 has a good relative dielectric constant, but has a deteriorated capacitance-temperature characteristic (SL characteristic). By the way, samples 3-5
Shows an example of the present invention, and samples 0 to 2, 6 to 7
-10 indicates a comparative example of the present invention.

[0109]

[Table 2]

From the results shown in Table 2, it is understood that the addition amount of the reduction resistance auxiliary is as follows. From the comparison between Samples 8 and 9, when MnCO ₃ is not added at all, the capacity-temperature characteristics tend to deteriorate. From the comparison of samples 11 and 12,
If the amount of MnCO ₃ exceeds 1 mol%, the capacity-temperature characteristics (SL characteristics) tend to deteriorate. By the way, M
MnO was added in place of nCO ₃ and evaluated under the same conditions as above, but the same result was obtained in each case. Incidentally, samples 9 to 11 show examples of the present invention, and samples 8 and 12 show reference examples of the present invention.

[0111]

[Table 3]

From the results shown in Table 3, it is understood that the followings are added with respect to the amount of the sintering aid added. From the comparison between Samples 13 and 14, if (BaCa) SiO ₃ is not added at all,
Unless the firing temperature is increased, the densification tends to be difficult. From the comparison of Samples 16 and 17, (BaCa) SiO
_If the addition amount of ₃ exceeds 6 mol%, the dielectric constant tends to decrease. Incidentally, samples 14 to 16 show examples of the present invention, and samples 13 and 17 show reference examples of the present invention.

[0113]

[Table 4]

From the results shown in Table 4, it is understood that the addition amount of the reduction resistance auxiliary is as follows. From the comparison between Samples 20 and 21, when the amount of MgCO ₃ added exceeds 4 mol%, densification tends to be difficult unless the firing temperature is increased. MgO was added in place of MgCO ₃ and evaluated under the same conditions as above, but the same result was obtained in each case. Incidentally, samples 18 to 20 show examples of the present invention, and sample 21 shows a reference example of the present invention.

[0115]

[Table 5]

From the results in Table 5, the following is understood regarding the composition of the glass component.

From the comparison between Samples 28 and 43, when the M1 component is 0.8 mol, the relative dielectric constant tends to decrease, tan δ increases, and IR tends to deteriorate. Even if the amount of the glass component is large as in sample 42, the M1 component is 0.05 mol, the M2 component is 0 mol, and the M2 component is 0.8 mol as in sample 45. The same applies to the case where the M3 component is 0.05 mol like the sample 44.
Incidentally, samples 22 to 41, 47 and 48 show examples of the present invention, and samples 42 to 46 and 49 show reference examples of the present invention.

From the results shown in Table 5 above, the following can be understood with respect to the added amount of the glass component. Sample 4
From the comparison of 6,47, if no glass component is added, a dense sintered body tends not to be obtained at a firing temperature of 1100 ° C. From the comparison of Samples 48 and 49, when the added amount of the glass component is 7 mol%, the dielectric constant tends to decrease.

Although the embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples in any way, and various modes are provided without departing from the gist of the present invention. Of course, it can be carried out.

[0120]

As described above, according to the present invention, a dielectric composition having excellent resistance to reduction during firing, a relatively high dielectric constant after firing, and excellent capacity temperature characteristics is provided. Can be provided.

Further, according to the present invention, it is possible to provide a ceramic capacitor which exhibits a high insulation resistance and a relatively high dielectric constant, has a flat capacitance-temperature characteristic, and can use a base metal for an internal electrode. .

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of a multilayer capacitor of the present invention.

FIG. 2 is a photograph obtained by observing a microstructure of a dielectric composition in an example (sample 3) of the present invention by SEM.

FIG. 3 is a diagram schematically showing the photograph of FIG. 2;

FIG. 4 is a graph showing capacitance-temperature characteristics (SL characteristics) of an example (Sample 3) and a comparative example (Sample 8, Sample 0) of the present invention.

FIG. 5 is a graph showing the measurement results of X-ray diffraction of a dielectric composition in Examples (Sample 3) and Comparative Examples (Sample 0) of the present invention (where the horizontal axis is twice the Bragg angle θ). Value (2θ, unit is deg.), Vertical axis is intensity (I, unit is c)
ps).

FIG. 6 is a ternary composition diagram of a glass component in a dielectric composition according to a third aspect of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor 11 ... Internal electrode 12 ... Dielectric layer 13 ... External electrode 2 ... Core part which consists essentially of barium titanate 22 ... Shell part which consists of a solid solution layer 3 ... It consists essentially of calcium titanate Core part 32: Shell part composed of solid solution layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeki Sato 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation F-term (reference) 5E001 AB01 AB03 AC09 AE00 AE02 AE03 AE04

Claims (16)

[Claims] 1. A dielectric composition containing at least barium titanate and calcium titanate, wherein the composition molar ratio (X) of barium titanate is 0.3 <X <
A dielectric composition wherein the composition molar ratio (Y) of calcium titanate is 1-X. 2. The dielectric composition according to claim 1, further comprising a sintering aid. 3. A basic component containing at least barium titanate and calcium titanate, SiO ₂ , Al ₂ O ₃ and (Ba, Ca) _x.
A dielectric composition comprising at least one additive component selected from SiO _{2 + x} (where x = 0.8 to 1.2), wherein the composition molar ratio of the basic component is the composition mol of barium titanate When the ratio (X) is 0.3 <X <
0.5. A dielectric material in which the composition molar ratio (Y) of calcium titanate is 1-X, and the amount of the additional component is 0.2 to 6 mol% with respect to 100 mol% of the basic component. Composition. 4. A basic component containing at least barium titanate and calcium titanate, and M1 (where M1 is SiO ₂ and Al ₂ O)
₃ ), M2 (where M2 is Ba
O, CaO and at least one selected from SrO)
And M3 (where M3 is Li ₂ O, Na
₂ O, K ₂ O, and B ₂ O ₃ ), wherein the composition molar ratio of the basic component is barium titanate. (X) is 0.3 <X <
0.5, the composition molar ratio (Y) of calcium titanate is 1-X, and the composition molar ratio of the additive component is represented by a triangular diagram (M1, M2, M
When represented by 3), the compositional molar ratio of the additive component is within a region surrounded by the following points a to f (but not on the boundary line), and the additive component with respect to 100 mol% of the basic component. The dielectric composition wherein the amount of addition is 0.2 to 6 mol%. a: (0.1, 0, 0.9) b: (0.5, 0, 0.5) c: (0.7, 0.2, 0.1) d: (0.2, 0. 7, 0.1) e: (0, 0.5, 0.5) f: (0, 0.1, 0.9) 5. It has at least two crystal structures, at least one of which is a tetragonal crystal containing barium titanate, and the other is a cubic crystal, orthorhombic crystal containing calcium titanate or 5. The dielectric composition according to claim 1, which is tetragonal. 6. In X-ray diffraction analysis (Kα ray of Cu), a double value (2θ) of Bragg angle (θ) is 44 to 46d.
eg. The dielectric according to any one of claims 1 to 5, having a pseudo cubic peak including a peak of a (002) crystal plane and a peak of a (200) crystal plane mainly composed of barium titanate within the range. Composition. 7. In X-ray diffraction analysis (Kα ray of Cu), the double value (2θ) of the Bragg angle (θ) is 44 to 48 d.
eg. And having an orthorhombic peak of a (040) crystal plane containing calcium titanate as a main component in the range of 1 to 6.
The dielectric composition according to any one of the above. 8. The barium titanate is formed from a group consisting of calcium, magnesium, aluminum, vanadium, molybdenum, tungsten, cobalt, silicon, barium and calcium titanate around a core substantially consisting of barium titanate. A layer in which at least one selected is dissolved in barium titanate,
The dielectric composition according to any one of claims 1 to 7, having a core-shell structure surrounded by a shell portion substantially composed of calcium titanate. 9. The method according to claim 9, wherein the calcium titanate is formed around a core substantially consisting of calcium titanate, from a group consisting of calcium, magnesium, aluminum, vanadium, molybdenum, tungsten, cobalt, silicon, barium and barium titanate. A layer in which at least one selected is dissolved in calcium titanate,
The dielectric composition according to any one of claims 1 to 8, wherein the dielectric composition has a core-shell structure surrounded by a shell portion substantially made of barium titanate. 10. The dielectric composition according to claim 1, further comprising a reduction resistance auxiliary. 11. The reduction-resistant auxiliary agent is an oxide of Mn and / or a compound that becomes an oxide of Mn by firing, and the amount of the basic component containing at least barium titanate and calcium titanate is 100 mol%. On the other hand, 0.1
The dielectric composition according to claim 10, which is added in an amount of 1 mol% to 1 mol%. 12. The reduction-resistant auxiliary agent is a compound that becomes an oxide of Mg and / or an oxide of Mg by firing, based on 100 mol% of the basic component containing barium titanate and calcium titanate. 12. The dielectric composition according to claim 10, which is added in an amount of 4 mol% or less. 13. V₂O₅, MoO₃, WO₃
And Co₃O₄ At least selected from the group consisting of
One kind of oxide is prepared by using the barium titanate and the titanate described above.
For 100 mol% of the basic component containing calcium,
Claims to further contain in the range of 0.01 to 0.5 mol%
Item 13. The dielectric composition according to any one of Items 1 to 12. 14. A capacitance change rate with respect to temperature (ΔC)
Is at least within the temperature range of 20 to 85 ° C.,
The temperature is 1000 to 350 ppm / ° C. (the reference temperature of the capacitance C is 20 ° C.).
3. The dielectric composition according to any one of 3. 15. A ceramic capacitor having an internal electrode and a dielectric layer comprising the dielectric composition according to claim 1. 16. The ceramic capacitor according to claim 15, wherein said internal electrode is made of nickel or a nickel alloy.