JP2003119076A - Dielectric ceramic composition and ceramic electronic parts using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave dielectric ceramic composition having high insulation resistance and excellent electric characteristics for microwaves and sintered at low temperature, and to provide ceramic electronic parts which use the composition. SOLUTION: The dielectric ceramic composition contains <=2 wt.% of a glass composition as a sub component to the main component containing bismuth oxide, calcium oxide and niobium oxide in specified proportions and further preferably contains copper oxide by <=0.2 wt.% in terms of CuO.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a resonator, a filter, an antenna, especially in a high frequency band such as a microwave and a millimeter wave.
The present invention relates to a dielectric ceramic composition useful for devices used as capacitors, inductors, circuit boards and the like, and a ceramic electronic component using the same.

[0002]

2. Description of the Related Art With the recent development of mobile communication equipment, a laminated dielectric ceramic device in which a dielectric ceramic and an internal electrode are laminated to form a circuit has been widely used. To get a small, high-performance device,
The characteristics of dielectric ceramics are high relative permittivity (εr) in the microwave region and dielectric loss (tan δ).
Is low, that is, the reciprocal Q value is high, and the absolute value of the temperature coefficient (TCF) of the resonance frequency is small. In addition, the conductor of the internal electrode has high conductivity of gold,
Since it is necessary to use a metal containing silver and copper as the main components, and the conductor and the dielectric ceramic are co-fired together, the temperature at which these metals do not melt by firing, that is, 8
It should be a dielectric ceramic that is densely fired at relatively low temperatures of 50 ° C to 1050 ° C.

As a dielectric ceramic composition satisfying the above requirements, Japanese Patent No. 2798105 discloses BiO _{3 /} 2-.
The CaO—NbO _5/2 based materials have been proposed by the present inventors. This material system has a high relative permittivity of 50 or more, 3 to
It has a high Q value of 300 or more at 5 GHz and a small resonance frequency temperature coefficient of 50 ppm / ° C. or less. Again 10
Since it is densely fired at a low temperature of 50 ° C. or less, a laminated dielectric ceramic device using a metal having a high conductivity such as gold, silver or copper can be obtained, which is an extremely useful material system.

[0004]

However, this BiO
The inventors of the present invention have found that the _{3 / 2-} CaO-NbO5 _{/ 2-} based material has a low insulation resistance value at high temperatures. In a high-frequency resonator or filter, no DC voltage is applied to the dielectric ceramic, so there is no problem, but when a high-frequency circuit module that includes a multilayer ceramic capacitor or a capacitor is made of this material system, dielectric breakdown occurs due to a DC bias voltage. There is a possibility that it may occur, and there may be a problem in reliability.

The present invention has been made in view of the above circumstances, and is a low temperature sintering microwave dielectric ceramic composition having a high insulation resistance value and excellent microwave electric characteristics, and a ceramic electronic component using the same. The purpose is to provide.

[0006]

In order to achieve the above object, the present invention has the following constitution.

According to a first aspect of the present invention, a composition comprising bismuth oxide, calcium oxide and niobium oxide is added to xBiO _3/2 -yCaO-zNbO _5/2 (x, y,
In the three-component composition diagram, where z is a molar ratio, x + y + z = 1.0), x, y and z are the following A, B,
It contains 2% by weight or less of a glass composition containing at least SiO ₂ as a sub-component with respect to the main component in the pentagonal region having C, D and E as vertices, and has a high insulation resistance value at high temperature, A dielectric ceramic composition having excellent microwave electric characteristics can be obtained.

A: (x, y, z) = (0.55, 0.1
6, 0.29) B: (x, y, z) = (0.50, 0.21, 0.2)
9) C: (x, y, z) = (0.44, 0.24, 0.3
2) D: (x, y, z) = (0.44, 0.20, 0.3
6) E: (x, y, z) = (0.50, 0.175, 0.3
25) In the invention according to claim 2 of the present invention, the glass composition as an accessory component is prepared by adding 35 to 60% by weight of SiO ₂ , 0 to 30% by weight of B ₂ O ₃ , and 0 to 20% by weight of Al _2. O ₃ is limited to 0 to 50% by weight of MO (where M is at least one element selected from Ca, Sr, and Ba), has a high insulation resistance value at high temperature, and has extremely excellent microwave electric characteristics. A dielectric ceramic composition can be obtained.

According to a third aspect of the present invention, copper oxide is used as the second subcomponent, and CuO is added to 100% by weight of the main component.
It is contained at 0.2% by weight or less in terms of
A dielectric ceramic composition that can be fired at a low temperature of 0 ° C. or less can be obtained.

The invention according to claim 4 of the present invention comprises a dielectric layer comprising the dielectric ceramic composition according to any one of claims 1 to 3 and a conductor layer containing at least silver or copper. Since they are laminated, a ceramic electronic component having a high insulation resistance value and extremely excellent microwave electric characteristics can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) Specific embodiments of the present invention will be described below. In the first embodiment, a method for producing a dielectric ceramic composition and an evaluation method will be described.

As a starting material for producing the dielectric ceramic composition of the present invention, oxides, carbonates, nitrates, organic metal salts and the like of each constituent element are used. The purity is preferably 99% or more, but is not particularly limited.

First, a method for producing a glass composition as an accessory component will be described. Table 1 shows the first embodiment of the present invention.
It is the weight ratio of the constituent elements of the glass composition used in. The respective starting materials were weighed so that the weight ratio shown in Table 1 was obtained, and they were mixed for 24 hours by a ball mill method using ethyl alcohol as a solvent. The mixed slurry is dried, put in a platinum crucible and melted by heat treatment at 1400 ° C. to 1600 ° C. for 1 hour, and the melt is dropped on a metal plate and rapidly cooled. The obtained heat-treated product is pulverized by the same method as in the above mixing to obtain a glass composition powder as an accessory component.

[0014]

[Table 1]

The composition of the main component is 0.46 BiO _3/2 − in terms of molar ratio which is superior to the electrical characteristics in Japanese Patent No. 2798105.
0.215CaO-0.325NbO _5/2 was selected.
The respective starting materials were weighed so as to have this molar ratio, and mixed with water as a solvent by a ball mill method for 24 hours. The mixed slurry is dried and put in an alumina crucible at 800 ° C.
It was calcined for 2 hours. After crushing the calcined powder, an arbitrary amount of the glass composition powder prepared above is added, and these are mixed and pulverized by the same method as described above and dried to obtain the target raw material powder.

Next, a method for evaluating the characteristics of the sintered body of the present composition will be described. After adding 10% by weight of a 5% aqueous solution of polyvinyl alcohol as a binder to the raw material powder and mixing, 3
The mixture was granulated through a 2-mesh sieve and press-molded at 100 MPa into a cylindrical body having a diameter of 13 mm and a thickness of about 8 mm, and a disk body having a diameter of 13 mm and a thickness of about 1 mm. Molded body 600
After the binder was incinerated by heating at 0 ° C for 2 hours, it was put in a magnesia container, covered with a lid, and held at 850 to 1100 ° C in the atmosphere for 2 hours for firing.

Each characteristic was measured on a sintered body which was fired at a temperature at which the density was maximized. Commercially available silver conductor paste was applied to the front and back surfaces of the sintered disc body, and baked by using a belt furnace at 850 ° C. for 10 minutes to form an electrode. Applied voltage was 500 V, time was 60 seconds, and measurement temperature was 120 ° C. The insulation resistance value under high temperature was measured. In addition, the resonant frequency and the unloaded Q value in the microwave were obtained by the dielectric resonator method using the sintered cylindrical body. The relative permittivity was calculated from the dimensions of the sintered body and the resonance frequency. The resonance frequency is 3 ~
It was 5 GHz. The Qf product was calculated by multiplying the unloaded Q value and the resonance frequency f, and this was used as an index representing the loss of the dielectric ceramic composition. This method is a method commonly used by those skilled in the art. Furthermore, -25 ℃, 20
The resonance frequency at ° C and 85 ° C was measured, and the temperature coefficient (TCF) was calculated by the least square method.

(Second Embodiment) In the second embodiment, Bi
O _{3 / 2-} CaO-NbO _{5 / 2-} based material as the main component,
The effect of adding the glass composition was examined. The results are shown in (Table 2).

[0019]

[Table 2]

When glass was not added as in Sample No. 1, the insulation resistance value at high temperature was 5 × 10 ⁸ Ω. This value is a low value for using the dielectric ceramic composition as a capacitor and may cause a problem in reliability. On the other hand, when the glass composition a is added in the range of 2.0% by weight or less as in Sample Nos. 2 to 5, the microwave resistance has almost no change and the insulation resistance value at high temperature is 1 × 10 ¹⁰ Ω or more. It was confirmed that it would be high. However, when the addition amount of the glass composition a is as large as 3% by weight as in Sample No. 6, the Qf product suddenly becomes small, resulting in a large dielectric loss, which is not desirable as a microwave dielectric ceramic.

Further, as shown in sample numbers 7 to 15, even if the glass composition to be added is changed from b to h within the scope of claim 2, if the addition amount is 2% by weight or less, the tendency is generally the same. It was confirmed that it is possible to improve the high temperature insulation resistance value without significantly impairing the microwave electric characteristics.

Next, an example within the scope of claim 1 but not within the scope of claim 2 will be described.

When a glass composition i having a low SiO ₂ content of less than 35% by weight was added as in Sample No. 17, and B ₂ in the glass composition as in Sample No. 19 was added. When the glass composition k having a large O ₃ content of 30% by weight or more is added, it has the effect of improving the high-temperature insulation resistance, but the reduction rate of the Qf product is slightly large. In addition, when the glass composition j having a large SiO ₂ content of 60% by weight or more is added as in the case of sample number 18, and Al in the glass composition as in the case of sample number 20 is added.
_{When the} glass composition 1 having a large content of ₂ O ₃ of 20% by weight or more is added, the improvement rate of the high temperature insulation resistance is small. It is considered that this is because the softening point of the glass composition becomes high. Further, as in Sample No. 21, when the glass composition m having a large MO content in the glass composition of 50% by weight or more is added, the temperature characteristic (TCF) of the resonance frequency tends to shift to the positive side. To be

As described above, when the glass composition which does not fall within the composition range of claim 2 is added, the effect of improving the high-temperature insulation resistance, which is the main object of the present invention, is recognized, but it is difficult to mass-produce and practical use. It is more preferable to add a glass composition within the scope of claim 2 because there is a possibility that the above characteristics may be a problem. In the second embodiment,
The main component BiO3 _{/ 2-} CaO-NbO5 _{/ 2} composition is shown only as an example, but the main component BiO3 _/ 2- shown in claim 1 is shown.
It was confirmed that in the composition range of the CaO-NbO _5/2 system, microwave electric characteristics were secured within this range, and further, the high temperature insulation resistance value was improved.

(Third Embodiment) In the third embodiment, the second
The effect of the addition of the sub-component copper oxide was investigated. 0.46BiO _3/2 -0.215CaO- which is the main component
0.325NbO _5/2 as 100% by weight of copper oxide as C
In the form of uO, 0 to 3% by weight was added when the raw material powders of the main component were mixed. A dielectric ceramic composition is prepared by the same method as in the first embodiment, and the results of evaluating the electrical characteristics are shown in (Table 3).

[0026]

[Table 3]

When the amount of copper oxide contained in the range of claim 3 is added as an additive like sample numbers 23, 24, 27, 30 and 31, most of the high temperature insulation resistance and microwave electric characteristics are deteriorated. Without this, the firing temperature can be lowered by 25 ° C. or more, and simultaneous firing with a silver electrode having a low melting point can be stably performed. However, when the addition amount exceeds 0.2% by weight as in Sample Nos. 25 and 28, the high-temperature insulation resistance decreases, so the addition amount of copper oxide is converted to CuO and is 0.
It is preferably 2% by weight or less.

(Embodiment 4) In Embodiment 4, an example of a laminated ceramic electronic component using the dielectric ceramic of the present invention will be described.

As a laminated ceramic electronic component, a known laminated ceramic capacitor having a structure in which dielectric layers and electrode layers are alternately laminated was prepared. A sectional view is shown in FIG. Here, 1 is a dielectric layer, 2 is an internal electrode, and 3 is a terminal electrode. The manufacturing method will be described below.

An organic binder, a solvent and a plasticizer were added to the ceramic composition of Sample No. 23 in (Table 3), and the resulting slurry was mixed by a ball mill or the like to prepare a green sheet having a thickness of 40 μm by a known doctor blade method. To do. Silver (100%) was selected as the conductor metal and kneaded with a vehicle prepared by mixing ethyl cellulose and a solvent to prepare a conductor paste.

A green sheet and a conductor layer are laminated so that the structure shown in FIG. 1 is obtained. The conductor layer is printed by a screen method with a conductor paste in a rectangular pattern (width: 0.2 mm). Figure 1
As described above, two conductor layers were laminated, and one green sheet having a thickness of 40 μm was laminated between the conductor layers. The total number of layers is 1
There are five. The laminate is pressed completely under pressure at 40 ° C. and 500 kg / cm ² . Individual element using a cutter (length 1.2 mm x width 0.6 mm)
After cutting into pieces, the organic components were scattered under the conditions of holding at 500 ° C. for 10 hours, and baked under the conditions of holding at 925 ° C. for 2 hours. As the terminal electrode 3, apply a commercially available silver paste as shown in the figure and bake under the condition of holding at 800 ° C. for 10 minutes,
A multilayer ceramic capacitor was obtained.

The size of the capacitor after firing is 1.
The thickness was 0 mm, the width was 0.5 mm, and the thickness was 0.5 mm. The thickness of the dielectric layer 1 between the internal electrodes 2 was 25 μm, and the thickness of the internal electrodes 2 was about 6 μm.

As a result of measuring the capacitance value and Q value of the capacitor at 1 GHz using a material analyzer, the capacitance value was 2.0 pF and the Q value was about 800. As a comparative example, a commercially available monolithic ceramic capacitor having substantially the same capacitance value and shape has a Q value of about 300. From this, the laminated ceramic capacitor according to the present invention exhibits extremely excellent electric characteristics.

The insulation resistance value of the manufactured monolithic ceramic capacitor was measured under the conditions of an applied voltage of 50 V and a measuring time of 1 minute. As a result, it was 3 × 10 ¹³ Ω at room temperature and 2 × 10 ¹¹ Ω even at a high temperature of 120 ° C. It was confirmed that it was sufficiently high and the reliability as a monolithic ceramic capacitor was also excellent.

As a conductor of the internal electrode 2, silver (100
%), The same effect can be obtained by using a silver-platinum alloy, a silver-palladium alloy, copper, or the like. However, when copper is used as the conductor, it is necessary to perform binder removal and firing in a reducing atmosphere.

[0036]

As described above, according to the present invention, it is possible to obtain a dielectric ceramic composition which has a high insulation resistance value at a high temperature and is excellent in microwave electric characteristics and which is fired at a low temperature of 1050 ° C. or lower. By using this dielectric ceramic composition, it becomes possible to provide a microwave module component having excellent microwave electric characteristics and excellent insulation reliability of the capacitor portion, which is of great industrial value.

[Brief description of drawings]

FIG. 1 is a sectional view of a ceramic electronic component according to a fourth embodiment of the present invention.

[Explanation of symbols]

1 Dielectric layer 2 internal electrodes 3 terminal electrode

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshi Kagada             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 4G030 AA08 AA09 AA10 AA20 AA31                       AA35 AA36 AA37 AA43 BA09                 5E001 AB03 AC09 AE00 AE04                 5G303 AA01 AA02 AA05 AB10 AB15                       BA12 CA03 CB01 CB02 CB03                       CB05 CB06 CB11 CB21 CB30                       CB32                 5J006 HC07

Claims (4)

[Claims] 1. A composition comprising bismuth oxide, calcium oxide and niobium oxide is xBiO _3/2 -yCaO-z.
NbO _5/2 (x, y, z are molar ratios, x + y + z = 1.
In the three-component composition diagram represented by 0), x, y and z are glass compositions as sub-components with respect to the main component in the pentagonal region having the following A, B, C, D and E as vertices. A dielectric ceramic composition containing 2% by weight or less of a substance. A: (x, y, z) = (0.55, 0.16, 0.2
9) B: (x, y, z) = (0.50, 0.21, 0.2)
9) C: (x, y, z) = (0.44, 0.24, 0.3
2) D: (x, y, z) = (0.44, 0.20, 0.3
6) E: (x, y, z) = (0.50, 0.175, 0.3
25) 2. The glass composition as an accessory component comprises 35 to 60% by weight of SiO ₂ , 0 to 30% by weight of B ₂ O ₃ , 0 to 20% by weight of Al ₂ O ₃ , and 0 to 50% by weight. MO (where M is C
The dielectric ceramic composition according to claim 1, which is composed of at least one of a, Sr, and Ba). 3. Copper oxide as a main component 10 as a second accessory component.
The dielectric ceramic composition according to claim 1, which is contained in an amount of 0.2% by weight or less in terms of CuO with respect to 0% by weight. 4. A ceramic comprising a laminate formed by laminating a dielectric layer comprising the dielectric ceramic composition according to claim 1 and a conductor layer containing at least silver or copper. Electronic components.