JPH0536562A - Ceramic multilayer capacitor - Google Patents

Abstract

PURPOSE:To provide a ceramic multilayer capacitor having small temperature dependency of a capacity and large capacity. CONSTITUTION:Ceramic dielectrics having different temperature characteristics of permittivities of layers, are laminated to form one multilayer capacitor. Since the capacity of the multilayer capacitor is the total sum of capacities of respective layers, a ceramic multilayer capacitor having small temperature dependency of the capacity can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic multilayer capacitor which is small in size and has a large capacity.

[0002]

2. Description of the Related Art A conventional ceramic multilayer capacitor is shown in FIG.
The internal electrode layer 2 having the structure shown in Fig.
And ceramic dielectric layers of 10 to several tens of microns are alternately stacked in layers to form a structure that is small in size and has a large capacity.

Since the capacitance of a capacitor is proportional to the dielectric constant and area of the material used and is semi-proportional to the thickness of the material used, the ceramic capacitor having the structure shown in FIG. 7 is small and has a large capacity. As the ceramic dielectric, a high dielectric constant ceramic dielectric represented by barium titanate, lead zirconate titanate, lead magnesium niobate, or the like is used. Further, in order to reduce the temperature dependence of the dielectric constant, that is, the temperature dependence of the capacitance of the ceramic multilayer capacitor, a ceramic dielectric to which an additive element called shifter or depressor is added is often used as a material.

Conventionally, there is only one type of material used for one laminated body, but regarding a laminated body in which different materials are laminated in each layer, as described in JP-A-63-188905, there are two or more materials. The only purpose was to realize the functions with a single laminated body.

[0005]

Conventionally, since only one type of ceramic dielectric material was used for one ceramic multilayer capacitor, in order to manufacture a ceramic multilayer capacitor having a small temperature dependence of capacitance, the dielectric constant should be reduced. It was necessary to use a ceramic dielectric material having a low temperature dependence of. Here, since the ceramic dielectric having a small temperature dependence of the dielectric constant has a small dielectric constant, the ceramic laminated capacitor having a small temperature dependence of the capacity has a drawback that the capacity is small. On the contrary, a ceramic multilayer capacitor using a material having a large relative dielectric constant has a large capacity, but has a drawback that the temperature dependence of the capacity is large.

For example, in the case of the composite perovskite of lead magnesium niobate, as shown in FIG. 8, the dielectric constant at the temperature at which the dielectric constant is highest is larger than that of barium titanate, but the temperature dependence is large.

[0007] Therefore, an object of the present invention is to provide a ceramic laminated capacitor having a small capacity temperature dependency and a large capacity.

[0008]

In order to achieve the above object, the present invention is a ceramic multilayer capacitor in which ceramic dielectric layers having different constituents are laminated in each layer. As the ceramic dielectric material used for the above-mentioned ceramic multilayer capacitor, if the temperature at which the maximum dielectric constant is used is within the temperature range in which the capacitor is used and several types of materials having high dielectric constants at the temperature at which the maximum dielectric constant is used are combined, Good. In addition, in order to reduce the temperature dependence of the capacitance of the ceramic multilayer capacitor over the entire operating temperature range, several types of materials are selected so that the maximum dielectric constant temperature is uniform within the operating temperature range. It is preferable to stack a number proportional to the reciprocal of the dielectric constant at the temperature at which the dielectric constant is highest.

As an example, a ceramic multilayer capacitor of the present invention (capacity n, operating temperature T ₁ -T ₂ [ ° C]) is considered. First, A, B, and C shown below are selected as the three types of materials.

A: The dielectric constant reaches its maximum at temperature T ₁ , and T ₁
Dielectric permittivity of epsilon _A in B: temperature _{(T 1 + T 2) /} 2 in the dielectric constant is highest and
Dielectric C having an inductivity of ε _B at (T ₁ + T ₂ ) / 2: Dielectric having the highest permittivity at temperature T ₂ and having an ε _C at T ₂ of these A, B, C The number of dielectric layers using is as follows. The number of layers using the material A is n × (1 / ε _A ) / (1 / ε _A + 1 / ε _B + 1 / ε _C ). The number of layers using the material B is n × (1 / ε _B ) / (1 / ε _A + 1 / ε _B + 1 / ε _C ) The number of layers using the material C is n × (1 / ε _C ) / (1 / ε _A + 1 / ε _B + 1 / ε _C ).

When a composite perovskite of lead magnesium niobate and lead titanate is used, FIG. 8 (Electronic Ceramics Vol. 18, No. 88 p. 10)
As shown in FIG. 5, the temperature at which the maximum induction rate varies depending on the content of lead titanate changes from −10 ° C. to 100 ° C. It suffices to stack lead composite perovskites. In this case, it is desirable to make the number of laminated layers of each component proportional to the reciprocal of the dielectric constant at the temperature at which the dielectric constant is highest.

[0012]

The capacitance of the ceramic multilayer capacitor constructed as described above at each temperature is the sum of the capacitance of each layer at that temperature, so that the temperature dependence of the capacitance is small within the operating temperature range, and It becomes a large ceramic laminated capacitor.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. First, in manufacturing the ceramic multilayer capacitor shown in FIG. 1 which is an embodiment of the present invention,
(That is, the dielectric layer 50 layer, the external dummy layer 10)
Layers, 8 mm long, 6 mm wide, 6.5 mm high) were used, and the following three types were prepared by changing the dielectric material using a ceramic laminated capacitor.

All 50 dielectric layers are layers containing lead magnesium niobate as a component All 50 dielectric layers are lead magnesium niobate composite perovskite containing lead titanate in a 6 mole fraction A layer containing 50% of the dielectric layer as a layer containing a composite perovskite containing lead magnesium niobate and lead titanate in a 17 mole fraction

The results of measuring the temperature dependence of the capacitance of these three types of ceramic multilayer capacitors are shown in FIGS. 4, 5 and 6, respectively.

As a result of the above, the temperature at which the capacity of the lead magnesium niobate prepared only becomes maximum is -10 ° C.
And the capacitance was 2.18 [μF] at this time.
Further, the temperature at which the maximum capacity of the composite perovskite containing lead magnesium niobate and lead titanate at 6 mol fraction is 20 ° C., and the capacity at this time is 3.
It was 00 [μF].

1 lead titanate to lead magnesium niobate
The temperature at which the capacity of the composite perovskite containing 7 mole fractions became maximum was 80 ° C., and the capacity at this time was 4.76 [μF].

From these results, when the number of layers of each material was calculated so that the number of layers of each material was proportional to the reciprocal of the dielectric constant at the temperature where the maximum dielectric constant was obtained, the total number of layers was 50 layers. In this case, 23 layers containing lead magnesium niobate as a component, 16 layers containing lead titanate in a 6 mole fraction,
There are 11 layers containing 17 mol% of lead titanate.

Based on the above results, FIG. 1 shows an embodiment of the present invention. 50 dielectric layers, 10 external dummy layers,
A ceramic laminated capacitor having a length of 8 mm, a width of 6 mm, and a height of 6.5 mm is manufactured. 23 out of 50 dielectric layers
The layer is a layer containing lead magnesium niobate as a component, the 16 layer is a layer containing composite perovskite containing lead magnesium niobate in a lead titanate content of 6 mole fractions, and the 11th layer is lead magnesium niobate in lead titanate. A layer containing a composite perovskite containing 17 mole fraction was prepared.

FIG. 2 shows the results of measuring the temperature dependence of the capacitance of the ceramic multilayer capacitor shown in FIG. In the case of a ceramic multilayer capacitor composed of a single material, the maximum capacitance is large as shown in FIGS. 4, 5 and 6, but the temperature dependence is also large. On the other hand, according to the present invention, as shown in FIG. 2, the ceramic laminated capacitor has a large capacitance and a small temperature dependence of the capacitance.

[0021]

As described above, according to the present invention, as shown in FIG. 4, a ceramic laminated capacitor having a large capacitance and a small temperature dependency is obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of a ceramic multilayer capacitor of the present example manufactured using a composite perovskite of lead magnesium niobate and lead titanate.

FIG. 2 is a measurement result of capacitance-temperature dependence of the ceramic multilayer capacitor shown in FIG.

FIG. 3 is a schematic diagram of a prototype ceramic multilayer capacitor for manufacturing the ceramic multilayer capacitor shown in FIG.

FIG. 4 is a measurement result of the capacitance temperature dependency of the ceramic multilayer capacitor shown in FIG. 3 in which all 50 dielectric layers are layers containing lead magnesium niobate as a component.

FIG. 5: Measurement of the capacitance-temperature dependence of the ceramic multilayer capacitor shown in FIG. 3 in which all 50 dielectric layers were layers containing a composite perovskite containing lead magnesium titanate and lead titanate in a 6 mole fraction The result.

FIG. 6 is a measurement of the capacitance-temperature dependence of the ceramic multilayer capacitor shown in FIG. 3, in which all 50 dielectric layers are layers containing a composite perovskite containing lead magnesium titanate and lead titanate in a mole fraction of 17 The result.

FIG. 7 is a schematic view of a conventional ceramic multilayer capacitor.

FIG. 8 is a dielectric constant temperature characteristic of a composite perovskite of lead magnesium niobate.

[Explanation of symbols]

1 Ceramic dielectric 2 Internal electrode layer 3 external electrodes

Claims (5)

[Claims] 1. A ceramic multilayer capacitor in which ceramic dielectric layers having constituent components different from each other are laminated in each layer. 2. The ceramic multilayer capacitor according to claim 1, wherein ceramic dielectric layers having different maximum dielectric constant temperatures are laminated in each layer. 3. Several kinds of materials are selected so that the temperature at which the maximum permittivity is constant becomes uniform within the temperature range of use of the capacitor, and the number of laminated layers of each material is defined as the maximum permittivity. The ceramic multilayer capacitor according to claim 2, wherein the number is proportional to the reciprocal number. 4. A ceramic dielectric layer having different constituents from each other is laminated in each layer.
2. The ceramic multilayer capacitor according to claim 1, wherein composite perovskites of lead magnesium niobate and lead titanate having different lead titanate contents are laminated in each ceramic dielectric layer. 5. The ceramic multilayer capacitor according to claim 4, wherein the content of lead titanate in each ceramic dielectric layer is 0 to 20 mole fraction.