JPH05242730A - Dielectric porcelain composition and laminated ceramic capacitor using it - Google Patents

Abstract

PURPOSE:To provide a dielectric porcelain composition which provides a high dielectric constant without becoming a semiconductor even when baked in a reducing atmosphere and notwithstanding the crystal particle diameter being small. CONSTITUTION:This is a dielectric ceramic composition which contains a glass oxide of 0.05 to 5.0 parts by weight including a main component of BaO-SrO- Li2O-SiO2 in proportion to the following main component of 100 parts by weight: When each oxide of Mn and Ni is represented by MnO2 and NiO for a sub- component, at least one kind of the respective oxides of Mn and Ni is added to contain 0.02 to 2.0mol in proportion to 100mol of the main component which satisfies the following general formula: (Ba1-x-y-zSrxReyMgz)m (Ti1-oCoo)O3 where (x), (y), (z), (o) and (m) are to be 0.05<=x<=0.35, 0.0005<=y <=0.03, 0.0005<=z<=0.05, 0.0005<=o<=0.03, 1.00<=m<=1.04.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition and a laminated ceramic capacitor using the same, and more particularly to a dielectric ceramic composition used for a laminated ceramic capacitor including internal electrodes made of Ni or Ni alloy and the same. Relates to a monolithic ceramic capacitor.

[0002]

2. Description of the Related Art Generally, in a manufacturing process of a monolithic ceramic capacitor, first, a sheet-shaped dielectric material having an electrode material applied to its surface is prepared. As the dielectric material, for example, a material containing BaTiO ₃ as a main component is used. Sheet-shaped dielectric materials coated with this electrode material are laminated, thermocompression-bonded, and integrated to be fired at 1250 to 1350 ° C. in a natural atmosphere to obtain a dielectric ceramic having internal electrodes. Then, an external electrode that is electrically connected to the internal electrode is printed on the end surface of this dielectric porcelain to obtain a monolithic ceramic capacitor. Also, with the recent development of electronics, miniaturization of electronic parts has rapidly progressed, and the trend toward miniaturization of monolithic ceramic capacitors has become remarkable.

[0003]

The materials for the internal electrodes used in such a monolithic ceramic capacitor are as follows:
The following conditions must be met.

(A) Since the dielectric porcelain and the internal electrodes are fired at the same time, the dielectric porcelain must have a melting point equal to or higher than the firing temperature.

(B) It should not be oxidized even in an oxidizing high temperature atmosphere and should not react with the dielectric.

Noble metals such as platinum, gold, palladium or alloys thereof have been used as electrode materials which satisfy such conditions.

However, while these electrode materials have excellent characteristics, they are expensive. Therefore, the ratio of the electrode material cost to the monolithic ceramic capacitor is 30 to 7
It was as high as 0%, which was the biggest factor in raising the manufacturing cost.

N having a high melting point other than noble metal
Although there are base metals such as i, Fe, Co, W, and Mo, these base metals are easily oxidized in a high-temperature oxidizing atmosphere and do not serve as electrodes. Therefore, in order to use these base metals as the internal electrodes of the monolithic ceramic capacitor, it is necessary to fire them together with the dielectric ceramic in a neutral or reducing atmosphere. However, the conventional dielectric ceramic material has a drawback that it is remarkably reduced when it is fired in such a reducing atmosphere and becomes a semiconductor.

As a method of miniaturizing the monolithic ceramic capacitor, it is generally known to use a material having a large dielectric constant or to thin the dielectric layer. However, a material having a large dielectric constant has a large number of crystal grains, and in the case of a thin film having a thickness of 10 μm or less, the number of crystal grains present in one layer is reduced and reliability is deteriorated.

On the other hand, JP-A-58-135507 discloses
JP-A-58-223669 and JP-A-59-861
As disclosed in Japanese Patent Laid-Open No. 03-2003, there is known a dielectric ceramic having a small crystal grain size, which is obtained by adding cerium oxide or neodymium oxide to a barium titanate solid solution. By reducing the crystal grain size in this way, the number of crystal grains present in one layer can be increased, and a decrease in reliability can be prevented.

However, this material containing a rare earth oxide is reduced by firing in a reducing atmosphere, and it is impossible to manufacture a monolithic ceramic capacitor using a base metal such as Ni as an internal electrode.

Therefore, a main object of the present invention is to obtain a dielectric ceramic composition which does not become a semiconductor even when fired in a reducing atmosphere and has a large dielectric constant despite its small crystal grain size. It is an object of the present invention to provide a small-sized and large-capacity monolithic ceramic capacitor with low cost and high reliability.

[0013]

[Means for Solving the Problems] The first invention is Ba, S
r, Mg, Ti, Co and Re (Re is Tb, Dy,
At least one kind selected from Ho and Er) and has the following general formula: (Ba _1-xyz Sr _x
Re _y Mg _z ) _m (Ti _1-o Co _o ) O ₃ ,
x, y, z, o and m are 0.05 ≦ x ≦ 0.35,
0.0005 ≦ y ≦ 0.03, 0.0005 ≦ z ≦ 0.
05, 0.0005 ≦ o ≦ 0.03, 1.00 ≦ m ≦
For 100 moles of the main component satisfying the relationship of 1.04,
When each oxide of Mn and Ni is expressed as MnO ₂ and NiO as an accessory component, 0.02 to 2.0 mol of at least one oxide of each oxide of Mn and Ni is added and contained.
BaO-SrO-L containing 100 parts by weight of the main component
Oxide glass containing i ₂ O-SiO ₂ as the main component is 0.0
A dielectric ceramic composition containing 5 to 5.0 parts by weight.

A second invention is a multilayer ceramic capacitor including a dielectric layer made of the above dielectric ceramic composition and an internal electrode made of one kind of Ni and a Ni alloy.

[0015]

Function: Ba, Sr, Mg, Ti, Co and Re (R
e is the composition ratio of each oxide of at least one kind of rare earth element selected from Tb, Dy, Ho and Er, and each oxide of Mn and Ni and BaO—SrO—Li are adjusted.
By adding an oxide glass containing ₂ O-SiO ₂ as a main component, it is possible to perform firing even in a reducing atmosphere without deteriorating its characteristics. Furthermore, T
The rare earth oxides and Co oxides of b ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ and Er ₂ O _{3 have} the effect of suppressing grain growth of the dielectric. Since the crystal grain size is small, 1
Since it is possible to increase the number of crystal grains existing in one dielectric layer, it is possible to prevent deterioration of reliability even if the thickness of the dielectric layer is reduced.

[0016]

According to the present invention, it is possible to obtain a dielectric ceramic composition which is not reduced even when fired in a reducing atmosphere and does not become a semiconductor. Therefore, if a monolithic ceramic capacitor is manufactured using this dielectric ceramic composition, a base metal can be used as an electrode material, and firing can be performed at a relatively low temperature of 1270 ° C. or lower, which reduces the cost of the monolithic ceramic capacitor. Can be planned.

Further, the laminated ceramic capacitor using this dielectric ceramic composition has a dielectric constant of 10,000 or more, and has a high dielectric constant as described above.
The crystal grains are as small as 3 μm or less. Therefore, even if the dielectric layer is thinned, the amount of crystal grains existing in the layer does not decrease unlike the conventional multilayer ceramic capacitor. Therefore, it is possible to obtain a highly reliable, small-sized, large-capacity monolithic ceramic capacitor.

The above and other objects, features and advantages of the present invention will become more apparent from the detailed description of the embodiments below.

[0019]

EXAMPLE First, as a raw material, B having a purity of 99.8% or more was used.
_{aCO 3, SrCO 3, MgCO 3} , Tb 2 O 3, Dy
₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , TiO ₂ , CoO,
MnO ₂ and NiO were prepared. These raw materials (Ba
_{1-xyz Sr x Re y Mg} z) m (Ti 1-o Co o) O
_It was represented by the compositional formula of ₃ and was blended so that x, y, z, o, and m were in the ratios shown in Table 1 to obtain a blended raw material. here,
Re is at least one selected from Tb, Dy, Ho and Er. The blended raw materials were wet mixed in a ball mill, pulverized, dried, and calcined in air at 1100 ° C. for 2 hours to obtain a calcined product. The calcined product was crushed by a dry crusher to obtain a crushed product having a particle size of 1 μm or less. BaO-S having a particle size of 1 μm or less prepared in advance was added to this pulverized product.
The rO-Li ₂ O-SiO ₂ were weighed oxide glass mainly, by adding an organic solvent such as polyvinyl butyral binder and ethanol were wet mixed by a ball mill to prepare a ceramic slurry. After that, the ceramic slurry was formed into a sheet by a doctor blade method to obtain a rectangular green sheet having a thickness of 26 μm.

[0020]

[Table 1]

Next, a conductive paste containing Ni as a main component was printed on the ceramic green sheet to form a conductive paste layer for forming internal electrodes. A plurality of ceramic green sheets having a conductive paste layer formed thereon were laminated so that the sides from which the conductive paste was drawn out were staggered to obtain a laminate. The obtained laminated body was heated to a temperature of 350 ° C. in a N ₂ atmosphere to burn the binder, and then the H 2 having an oxygen partial pressure of 10 ⁻⁹ to 10 ⁻¹² MPa.
_It was fired at a temperature shown in Table 2 for 2 hours in a reducing atmosphere composed of _2- N ₂ -air gas to obtain a ceramic sintered body. The surface of the obtained ceramic sintered body was observed with a scanning electron microscope at a magnification of 1500 times to measure the grain size. The results are shown in Table 2.

[0022]

[Table 2]

After firing, Ag paste was applied to both end faces of the obtained sintered body and baked at a temperature of 600 ° C. in an N ₂ atmosphere to form external electrodes electrically connected to the internal electrodes. The outer dimensions of the monolithic ceramic capacitor thus obtained are 1.6 mm in width, 3.2 mm in length,
The thickness is 1.2 mm, and the thickness of the dielectric ceramic layer interposed between the internal electrodes is 16 μm. The total number of effective dielectric ceramic layers is 19, and the area of the counter electrode per layer is 2.1 mm ² .

Capacitance (C) and dielectric loss (tan)
δ) is a frequency of 1 kHz using an automatic bridge type measuring instrument
The measurement was performed at z, 1 V _rms and a temperature of 25 ° C., and the dielectric constant (ε) was calculated from the capacitance. Next, in order to measure the insulation resistance (R), a DC voltage of 25 V is applied for 2 minutes using an insulation resistance meter to measure the insulation resistance (R) at 25 ° C. and 85 ° C. The product of (C) and insulation resistance (R), that is, the CR product was obtained. In addition, the rate of change of capacitance with respect to temperature change was measured. Note that the rate of change in capacitance with respect to temperature change was based on the capacitance at 20 ° C.
Change rate (ΔC / C ₂₀ ) at 5 ° C and 85 ° C and -25 ° C
The value (| ΔC / C ₂₀ | _max ) at which the rate of change is the maximum as an absolute value is shown in the range from to 85 ° C. The results are shown in Table 2.

Next, the reasons for limiting each composition will be described.

(Ba _1-xyz Sr _x Re _y Mg _z ) _m (
In Ti _1-o Co _o ) O ₃ , like sample number 1,
When the Sr amount x is less than 0.05, the dielectric constant ε is 10,000
The dielectric loss tan δ exceeds 5.0%, which is not preferable. In addition, as in Sample No. 17, the Sr amount x
When the value exceeds 0.35, the sinterability of the porcelain deteriorates, the dielectric loss tan δ exceeds 5.0%, and the CR product is 10 at 25 ° C.
It is less than 00 MΩ · μF and less than 100 MΩ · μF at 85 ° C., which is not preferable because the insulation resistance decreases.

Further, when the Re amount y is less than 0.0005 as in the sample No. 2, the dielectric loss tan δ is 5.0.
%, And the crystal grain size becomes larger than 3 μm, the dielectric layer cannot be thinned, which is not preferable. On the other hand, when the Re amount y exceeds 0.03 as in Sample No. 18, the porcelain is reduced when it is fired in a reducing atmosphere to become a semiconductor, and the insulation resistance is significantly reduced, which is not preferable.

If the Mg content z is less than 0.0005 as in sample No. 3, the CR product at 25 ° C. and 85 ° C. decreases, which is not preferable. On the other hand, like sample number 19,
When the amount z of Mg exceeds 0.05, the dielectric constant ε is 10,000.
It is not preferable because the insulating property is lowered as well as it is decreased to less than 1.

As in Sample No. 4, the Co amount o is 0.00
If it is less than 05, the dielectric loss tan δ exceeds 5.0%,
Further, since the crystal grain size is larger than 3 μm, the dielectric layer cannot be thinned, which is not preferable. On the other hand, when the Co amount o exceeds 0.03 as in Sample No. 20, the dielectric loss tan
δ becomes larger than 5.0% and CR product becomes 1 at 25 ℃
It is less than 000 MΩ · μF and less than 100 MΩ · μF at 85 ° C., which is not preferable because the insulation resistance decreases.

As shown in Sample No. 5, (Ba _1-xyz Sr
_{x Re y Mg z) m (} Ti 1-o Co o) the molar ratio of O ₃ m
Is less than 1.000, the porcelain is reduced when fired in a reducing atmosphere to become a semiconductor, and the insulation resistance is reduced, which is not preferable. On the other hand, when the molar ratio m exceeds 1.04 as in Sample No. 21, the sinterability is extremely deteriorated, which is not preferable.

Further, as shown in Sample No. 6, MnO ₂ ,
If the amount of NiO added is less than 0.02 mol, the CR product at 85 ° C. will be low, and the reliability of long-term use at high temperatures will be unfavorable. On the other hand, like sample number 22,
When the amounts of MnO ₂ and NiO exceed 2.0 mol, the dielectric loss tan δ exceeds 5.0% and increases, and at the same time, the insulation resistance decreases, which is not preferable.

Further, as in sample No. 7, BaO--Sr
When the amount of oxide glass for the O-Li ₂ O-SiO ₂ as the main component is less than 0.05 part by weight, the sintering property is deteriorated, the dielectric loss tanδ undesirably exceed 5.0%. On the other hand, like sample number 23, BaO-SrO-L
If the amount of the oxide glass containing i ₂ O—SiO ₂ as the main component exceeds 5.0 parts by weight, the dielectric constant decreases to less than 10,000 and the crystal grain size becomes larger than 3 μm, which is not preferable.

On the other hand, the multilayer ceramic capacitor using the dielectric ceramic composition of the present invention has a dielectric constant of 10
000 or more, the dielectric loss tan δ is 5.0% or less, and the rate of change in capacitance with temperature is -25 ° C to 85 ° C.
It is possible to obtain a dielectric porcelain satisfying the F characteristic standard defined in JIS standard in the range of ° C. Moreover, in this multilayer ceramic capacitor, the insulation resistance at 25 ° C. and 85 ° C. is 1000 MΩ ·
High values of μF or more and 100 MΩ · μF or more. Further, the dielectric ceramic composition of the present invention has a firing temperature of 127
It can be sintered at a relatively low temperature of 0 ° C. or less, and has a small particle size of 3 μm or less.

Claims (2)

[Claims] 1. Ba, Sr, Mg, Ti, Co and R
e (Re is Tb, Dy, at least one rare earth element selected from among Ho and Er) consists respective oxides of the following general formula _{(Ba 1-xyz Sr x Re} y Mg z) m (Ti 1 _-o Co _o ) O ₃ , and x, y, z, o and m are 0.05 ≦ x ≦ 0.35 0.0005 ≦ y ≦ 0.03 0.0005 ≦ z ≦ 0.05 0 0.0005 ≤ o ≤ 0.03 1.00 ≤ m ≤ 1.04 With respect to 100 mol of the main component, Mn and Ni oxides are added as MnO ₂ and Ni as auxiliary components.
When expressed as O, 0.02 to 2.0 mol of at least one kind of each oxide of Mn and Ni is added and contained, and the main component is 100 parts by weight, and BaO—SrO—Li ₂ O—
A dielectric ceramic composition containing 0.05 to 5.0 parts by weight of oxide glass containing SiO ₂ as a main component. 2. A laminated ceramic capacitor comprising a dielectric layer made of the dielectric ceramic composition of claim 1 and an internal electrode made of one of Ni and a Ni alloy.