JP2895056B1 - Porcelain composition and multilayer ceramic capacitor - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To be capable of sintering at 950 ° C. or lower and at room temperature to 70 ° C.
Provided are a porcelain composition having a relative dielectric constant of 00 or more and a highly reliable multilayer ceramic capacitor, and a low-cost and highly reliable multilayer ceramic capacitor. A magnesium tungstate, lead nickel niobate, lead zinc niobate, includes four types of complex perovskite compounds of lead titanate as the main component in a specific composition range, it expressed the complex perovskite compound ABO ₃ Sometimes A / B ratio A / B is 0.9
A porcelain composition which is in the range of 75 to 0.998 and further contains the manganese lead-containing composite perovskite compound in the range of 0.05 to 2.0 mol% with respect to the composition of the main component is used for the multilayer ceramic capacitor. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porcelain composition and a laminated ceramic capacitor, and more particularly to a highly reliable laminated ceramic capacitor which can be sintered at 950.degree. C. or less and has a relative dielectric constant of 7000 or more at room temperature. The present invention relates to a porcelain composition for obtaining the same, and a low-cost and highly reliable multilayer ceramic capacitor manufactured using the porcelain composition.

[0002]

2. Description of the Related Art Conventionally, a porcelain composition used for a multilayer ceramic capacitor has been mainly composed of barium titanate (hereinafter referred to as "barium titanate-based composition").
Is widely used. This barium titanate-based composition has a Y5V characteristic (-30 ° C. to 85
° C: ΔC / C (20 ° C): + 22% to -82%) and X7R characteristics (-55 ° C to 125 ° C: ΔC / C (20
C): ± 15%) is widely used as a porcelain composition for multilayer ceramic capacitors. The relative permittivity of these compositions is about 3000 to 3500 for X7R characteristics and about 12000 to 15000 for Y5V characteristics.

However, since the barium titanate-based composition has a high firing temperature of 1300 ° C. or higher, expensive platinum, palladium or the like must be used for the internal electrodes of the multilayer ceramic capacitor, which has increased the cost. Therefore, in recent years, multilayer ceramic capacitors using inexpensive nickel for the internal electrodes have been developed and are being spread on the market.

On the other hand, composite perovskite compounds based on lead titanate have been widely studied as porcelain compositions for multilayer ceramic capacitors other than barium titanate-based compositions, and some of them have been put to practical use. Since the firing temperature of the composite perovskite compound is 1100 ° C. or lower, a feature is that a silver-palladium alloy or the like, which is cheaper than palladium, can be used for the internal electrodes of the multilayer ceramic capacitor. Furthermore, by combining a plurality of lead-based perovskite compounds, the relative dielectric constant at room
A wide range of materials can be designed from materials having a high dielectric constant of 0000 or more to materials having a small change in relative dielectric constant with temperature so as to satisfy X7R characteristics of the EIA standard. Examples of such a composition having a high relative dielectric constant include, for example, JP-A-58-1983.
No. 161972, lead magnesium tungstate (Pb (Mg _1/2 W _1/2 ) O ₃ : PMW), lead titanate (PbTiO ₃ : PT), lead nickel niobate (Pb (Ni _{1 / 3} Nb _2/3) O _3: composition of three kinds of complex perovskite compound of PNN) can be mentioned.

Japanese Patent Application Laid-Open No. 62-113755 discloses a technique in which lead zinc niobate is added in an amount of 20 mol% or less to a main component in order to increase the relative dielectric constant at room temperature. JP-A-58-176177 and JP-A-58-176178 disclose a technique of adding a Mn-containing composite perovskite compound for improving insulation resistance and temperature characteristics (TCC). Each of these porcelain compositions can be sintered at 1050 ° C. or less.

On the other hand, JP-A-57-67209 discloses a porcelain composition which can be sintered at a temperature of 1000 ° C. or less, has a high dielectric constant and a small dielectric loss, and has a high specific resistance. Lead (Pb (Fe _1/2 Nb _1/2 )
O ₃ ), lead magnesium tungstate (Pb (Mg _1/2
W _1/2 ) O ₃ ), lead zinc niobate (Pb (Zn _1/3 N
A ternary porcelain composition comprising b _2/3 ) O ₃ ) is disclosed.

[0007]

From the viewpoint of reducing the cost of a multilayer ceramic capacitor, attention is paid to the ratio of silver in a silver-palladium alloy used for an internal electrode.

For example, assuming that a porcelain composition having a sintering temperature of 1000 ° C. is used, the liquidus line in the phase diagram exceeds approximately 1200 ° C. in consideration of a margin of about 200 ° C. for the internal electrodes of the multilayer ceramic capacitor. Such, ie, a silver-palladium alloy with at least 30% palladium is used. Here, in order to further reduce the manufacturing cost, it is necessary to further increase the ratio of silver. Therefore, if the silver 70% -palladium 30% alloy or the silver 90% -10% palladium alloy is used for the internal electrode instead of the silver 65% -palladium 35% alloy, the cost of the internal electrode is about 13% and about 63%, respectively. %.

However, the liquidus line in the phase diagram of the alloy is changed from about 1220 ° C. to 1190 ° C.
° C respectively. Therefore, for example, in order to use a silver palladium alloy having a silver ratio of 90%, which is very effective in terms of cost, for the internal electrode, considering the same margin, the sintering temperature of the composite perovskite compound is at least 950 ° C. or lower. Need to be. In addition, when the ratio of silver in the internal electrode is high, migration of silver is likely to occur, so that there is a problem that reliability is reduced.

Although the above-mentioned conventional composite perovskite-based compound is disclosed which can be sintered at 1050 ° C. or lower, it is not sufficient in terms of the sintering temperature and the decrease in reliability due to silver migration. Things. Regarding the sintering temperature, there is also disclosed a porcelain composition that can be fired at a temperature of 1000 ° C. or less. However, since this contains iron as a component, the insulating property decreases at a high temperature of about 100 ° C. or more. The associated reliability problems have recently become apparent.

An object of the present invention is to provide a ceramic composition which can be sintered at a temperature of 950 ° C. or less, has a relative dielectric constant of 7000 or more at room temperature, and can provide a highly reliable multilayer ceramic capacitor. An object of the present invention is to provide a low-cost and highly reliable multilayer ceramic capacitor manufactured using a product.

[0012]

The present invention provides lead magnesium tungstate (Pb (Mg _1/2 W _1/2 ) O ₃ ) and nickel nickel niobate (Pb (Ni _1/3 Nb _2/3 ) O. ₃ ), lead zinc niobate (Pb (Zn _1/3 Nb _2/3 ) O ₃ ), and four kinds of composite perovskite compounds of lead titanate (PbTiO ₃ ) as main components, and the composition of the main components is as follows: The constituent ratios (molar ratios) of the composite perovskite compound are x, y,
z, u (where x + y + z + u = 1), and the composition range of the main component is (x, y, z, u) = (1, 0, 0, 0),
(0.1,0,0), (0,0,1,0), (0,0,
When represented by a regular tetrahedron having the four points of (0, 1) as vertices, z
= 0.08 on a plane (x, y,
u) = A: (0.20, 0.44, 0.28), B:
(0.20, 0.35, 0.37), C: (0.45,
0.12, 0.35), D: (0.45, 0.04,
0.43) and the four points E on the plane at z = 0.40
To H is (x, y, u) = E: (0.20, 0.29,
0.11), F: (0.20, 0.21, 0.19),
G: (0.45, 0.01, 0.14), H: (0.3
5,0.01,0.24) and ABCD-GE
When the complex perovskite compound is expressed as ABO ₃ on and inside the surface of a hexahedron surrounded by FH, A
The ratio A / B of the site (Pb ion) to the B site (ion other than Pb and O) is in the range of 0.975 to 0.998, and the manganese lead-containing composite perovskite compound is further added to the composition of the main component. It relates to a porcelain composition characterized by being contained in the range of 0.05 to 2.0 mol%.

[0013] The present invention also relates to a multilayer ceramic capacitor manufactured using the above porcelain composition.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS For the understanding of the present invention, FIG. 1 shows a tetrahedral composition diagram for explaining the range of the main component composition of the porcelain composition of the present invention. FIGS. 2 and 3 show ternary composition diagrams at mol% and 40 mol%, respectively.
Are shown below. In the figure, PMW, PN
N, PZN, and PT are lead magnesium tungstate (Pb (Mg _1/2 W _1/2 ) O ₃ ), lead nickel niobate (Pb (Ni _1/3 Nb _2/3 ) O ₃ ), and zinc niobate, respectively. Lead (Pb (Zn _1/3 Nb _2/3 ) O ₃ ), lead titanate (PbT
iO ₃ ).

In the porcelain composition of the present invention, the manganese lead-containing composite perovskite compound is composed of lead manganese niobate (Pb (Mn _1/3 Nb _2/3 ) O ₃ ) and lead manganese tantalate (Pb (Mn _{1 / 3} Ta _2/3 ) O ₃ ), lead manganese antimonate (Pb (Mn _1/3 Sb _2/3 ) O ₃ ), lead manganese tungstate (Pb (Mn _1/2 W _1/2 ) O ₃ ) Preferably, it is either one. Further, the manganese lead-containing composite perovskite compound is 0.1% with respect to the composition of the main component.
It is preferably added in the range of 1.0 mol% to 1.0 mol%.

The composition ratios x and z of the main components are 0.30 ≦ x ≦ 0.40 and 0.10 ≦ z ≦ 0.20, respectively.
It is preferred that If the composition ratio z is within this range, the relative dielectric constant can be further increased.

Further, the ratio A / B between the A site and the B site
(A / B site ratio) is preferably in the range of 0.980 to 0.995, and more preferably in the range of 0.990 to 0.995.

In the multilayer ceramic capacitor of the present invention, the internal electrodes are preferably made of a silver-palladium alloy. The ratio of silver and palladium is 70% silver.
It is preferably in the range of 30% palladium to 90% silver to 10% palladium, and 75% silver to 25% palladium.
More preferably, it is in the range of 85% silver and 15% palladium.

Hereinafter, the present invention will be described in detail with reference to examples. For comparison, the case where the present invention is out of the scope is also described.

Example 1 As a starting material, lead oxide (P
bO), magnesium oxide (MgO), tungsten trioxide (WO ₃ ), nickel oxide (NiO), niobium pentoxide (Nb ₂ O ₅ ), zinc oxide (ZnO), titanium dioxide (TiO ₂ ), and manganese carbonate ( MnCO ₃ ) was weighed so that each sample had the composition shown in Table 1.

Next, the weighed raw materials are wet-mixed in a resin ball mill, pre-fired at 725 ° C. to 800 ° C., wet-ground in a resin ball mill, filtered,
After drying, a dielectric powder was obtained.

The obtained dielectric powder is made to have a diameter of about 15 mm,
Press-formed into a disc with a thickness of about 1.5mm, 850 ℃
The firing was performed at 1050 ° C.

The sintered density of the fired disk sample was determined by the Archimedes method. The temperature at which 95% of the theoretical density was reached was taken as the densification temperature.

Next, an electrode is formed by applying and baking a silver paste on both surfaces of the fired disk sample, and then using an LCR meter at room temperature and at -30 ° C to 85 ° C.
Was measured at each temperature, and the Curie point (Tc) was determined from the temperature at which the capacitance C was maximized.

Table 1 shows each composition, densification temperature, Curie point of the sample fired at the densification temperature, and relative dielectric constant at 20 ° C.
It was shown to. Note that those marked with * in the sample numbers in Table 1 are out of the scope of the present invention.

[0026]

[Table 1]

(Embodiment 2) Composite Perro used for Dielectric Material
The main component composition of the buskite compound is 35 Pb (Mg
_{1 / Two}W_1/2) O_Three-17Pb (Ni_1/3Nb_2/3) O_Three-15
Pb (Zn_1/3Nb_2/3) O _Three-33PbTiO_ThreeAnd vice
Lead manganese niobate Pb (Mn_1/3Nb_2/3) O_Three
Content of 0.1 mol% to 1 mol of main component composition
And A / of the composite perovskite compound as the main component
Three types of invitations with B site ratios of 1, 0.998 and 0.995
An electric conductor powder was prepared. These dielectric powders were used in Example 1.
Synthesized in the same manner as indicated. Particle size of dielectric powder
Is used to make the green sheet thinner and stronger.
3 μm or less is desirable.

The obtained dielectric powder is dispersed together with an organic binder in an organic solvent to form a slurry, and the slurry is formed on a carrier film by a doctor blade method in a thickness of 10 to 12 μm.
Thus, a ceramic green sheet having a thickness of m was prepared.

A silver-palladium alloy paste having a predetermined silver-palladium ratio was printed as an internal electrode on the green sheet by a screen printing method. After drying, the green sheet was peeled from the carrier film, cut, laminated, and thermocompressed. Thereafter, the resultant was cut into a predetermined chip shape to obtain a green laminate of a multilayer ceramic capacitor. The silver-palladium ratio of the internal electrodes used was 85% silver-15% palladium, and the number of stacked sheets on which the internal electrodes were printed was 100.

After the binder was decomposed at 450 to 500 ° C., the green laminate was fired at 875 to 925 ° C. Next, terminal electrodes were formed by baking silver paste on both ends of the fired chip capacitor to produce a multilayer ceramic capacitor.

In order to evaluate the reliability of the manufactured multilayer ceramic capacitor, an accelerated life test was performed at 150 ° C. and 32 V. The number of samples subjected to the test was 50 for each level, and the capacities and insulation resistances of all the samples were measured at 100 hours, 500 hours, 1000 hours, and 3000 hours after the start of the test. At this time, those having an insulation resistance of less than 100 MΩ were regarded as failures. FIG. 4 shows the cumulative failure rate of each sample.

Example 3 The main component composition used for the dielectric material was the same as that in Example 2, and the A / B site ratio of the composite perovskite compound was 0.995. Here, a lead component of manganese niobate (Pb (Mn)
_1/3 Nb _2/3 ) O ₃ ) was prepared by mixing two kinds of dielectric powders of 0 mol% and 0.05 mol% with respect to 1 mol of the main component composition in the same manner as the method shown in Example 1. And a multilayer ceramic capacitor was manufactured by the method described in Example 2.

The reliability of the manufactured sample was tested in the same manner as in Example 2. FIG. 5 shows the results.

Example 4 The main component composition used in the dielectric material was the same as that in Example 2, the A / B site ratio of the composite perovskite compound was 0.995, and the main component was lead manganese niobate as an auxiliary component. 0.1 mol% to 1 mol
Was prepared as a dielectric powder. Powder production was carried out in the same manner as described in Example 1.

Next, a multilayer ceramic capacitor was manufactured according to the method described in the second embodiment. At this time, the silver / palladium ratio used for the internal electrode was 65 / silver / palladium.
Three types were selected: 35, 70/30 and 85/15.

For each level, the sample 100 after the formation of the terminal electrode was used.
Each piece was examined for the presence of internal defects by an ultrasonic flaw detector. FIG. 6 is a diagram showing the abundance of internal defects with respect to the ratio of silver occupying the internal electrodes.

From the above results, the porcelain composition of the present invention is limited to the above range for the following reasons.

(I) If the ratio of lead zinc niobate (PZN), one of the main components, is less than 8 mol%, a high dielectric constant can be obtained, but the densification temperature rises to 1000 ° C. (Sample No. 13) ). On the other hand, the ratio of lead zinc niobate is 40 mol%.
When the temperature exceeds 20 ° C., the relative dielectric constant at 20 ° C. falls below 7000 (sample No. 14). From these results, it is necessary that the ratio of lead zinc niobate be in the range of 8 to 40 mol%.

(Ii) If the ratio of lead magnesium tungstate (PMW), which is one of the main components, is less than 20 mol%, the densification temperature rises from 1000 ° C. to 1050 ° C. (sample numbers 24 and 26). On the other hand, when it exceeds 45 mol%, the relative dielectric constant at 20 ° C. decreases to 4000 or less (Sample No. 25). From these results, it is necessary that the ratio of lead magnesium tungstate be in the range of 20 to 45 mol%.

(Iii) Lead nickel niobate (PNN) /
When the lead titanate (PT) ratio (y / u ratio) is out of the composition range of the present invention and becomes rich in lead titanate, the Curie point exceeds 40 ° C. (sample No. 11), and conversely nickel In the case of lead niobate-rich, the Curie point is lower than −10 ° C. (Sample No. 12), so that the relative dielectric constant at room temperature does not become 7000 or more in any case.

(Iv) Composite perovskite compound ABO ₃
When the A / B site ratio exceeds 0.998, the failure occurrence rate in the accelerated life test sharply increases (FIG. 4). on the other hand,
If it is less than 0.975, the densification temperature exceeds 950 ° C. (Sample No. 19). From this result, the A / B site ratio needs to be in the range of 0.975 to 0.998.

(V) When the content of lead manganese niobate as an auxiliary component with respect to the main component composition is 0, the relative dielectric constant at 20 ° C. is increased (sample No. 20), but failure in the accelerated life test is the same as in (iv). The incidence increases (FIG. 5). 0.
When the content is 05 mol%, the failure occurrence rate is low even after a long time has elapsed (FIG. 5). On the other hand, if the content exceeds 2 mol%, 20
Although the relative dielectric constant at ℃ is maintained at 7000 or more, the densification temperature exceeds 950 ° C (Sample No. 23). From this result, the amount of lead manganese niobate added was 0.05 to
It needs to be in the range of 2.0 mol%.

(Vi) In the region where the ratio of silver in the silver-palladium alloy of the internal electrode used in the multilayer ceramic capacitor is less than 70%, internal defects are present (FIG. 6). On the other hand, 9
If it exceeds 0%, the liquidus line is lower than 1150 ° C., and when the sintering temperature (densification temperature) of the dielectric ceramic is 950 ° C., the temperature difference between the two is used as a measure for securing reliability. Lower than ° C. Therefore, the ratio of silver in the silver-palladium alloy is preferably in the range of 70 to 90%.

[0044]

As described above, by using the porcelain composition of the present invention, a dielectric material which can be sintered at 950 ° C. or lower and has a relative dielectric constant at room temperature (20 ° C.) exceeding 7000 is obtained. be able to.

Further, in the multilayer ceramic capacitor using the porcelain composition of the present invention, high reliability can be maintained even when the silver ratio of the silver-palladium alloy of the internal electrode is set to 70% to 90%. Further, since the firing temperature at the time of manufacturing can be lowered, it is advantageous in terms of energy. Therefore,
A multilayer ceramic capacitor having high reliability at low cost can be provided.

[Brief description of the drawings]

FIG. 1 is a tetrahedral (tetracomponent) composition diagram for explaining a main component composition of a porcelain composition of the present invention.

FIG. 2 is a ternary composition diagram for explaining the main component composition of the porcelain composition of the present invention.

FIG. 3 is a ternary composition diagram for explaining the main component composition of the porcelain composition of the present invention.

FIG. 4 is a composite perovskite compound (general formula ABO ₃ )
FIG. 3 is a view showing a failure occurrence rate in an accelerated life test of a multilayer ceramic capacitor manufactured using a ceramic composition having different A / B site ratios.

FIG. 5 is a diagram showing a failure occurrence rate in an accelerated life test of multilayer ceramic capacitors manufactured using porcelain compositions having different contents of lead manganese niobate.

FIG. 6 is a graph showing the percentage of internal defects of a multilayer ceramic capacitor with respect to the silver ratio of silver-palladium internal electrodes.

Continuation of the front page (72) Inventor Tadahiko Horiguchi 231 Sukazawa, Yamazaki-cho, Shiso-gun, Hyogo Prefecture Hyogo Nippon Electric Co., Ltd. (56) References JP-A-62-254308 (JP, A) JP, A) JP-A-7-85723 (JP, A) JP-A-5-81929 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/46 C04B 35/49

Claims (6)

(57) [Claims] 1. A lead magnesium tungstate (Pb)
(Mg _1/2 W _1/2 ) O ₃ ), lead nickel niobate (Pb
(Ni _1/3 Nb _2/3 ) O ₃ ), lead zinc niobate (Pb (Z
n _1/3 Nb _2/3 ) O ₃ ) and four kinds of composite perovskite compounds of lead titanate (PbTiO ₃ ) as main components,
When the composition of the main component is such that each constituent ratio (molar ratio) of the composite perovskite compound is x, y, z, u (where x + y +
z + u = 1), and the composition range of the main component is (x, y,
z, u) = (1, 0, 0, 0), (0.1, 0, 0),
When represented by a regular tetrahedron having four points (0, 0, 1, 0) and (0, 0, 0, 1) as vertices, four points A to D on a plane at z = 0.08 are represented by ( x, y, u) = A: (0.20,
0.44, 0.28), B: (0.20, 0.35,
0.37), C: (0.45, 0.12, 0.35),
D: (0.45, 0.04, 0.43) and z = 0.
The four points E to H on the plane of 40 are represented by (x, y, u) =
E: (0.20, 0.29, 0.11), F: (0.2
0, 0.21, 0.19), G: (0.45, 0.0
1, 0.14), H: (0.35, 0.01, 0.2
4) On the surface and inside of the hexahedron surrounded by ABDC-GEFH when the compound perovskite compound is expressed as ABO ₃ , the A site (Pb ion)
And the ratio A / B of the B site (ion other than Pb and O) is in the range of 0.975 to 0.998, and the manganese lead-containing composite perovskite compound is contained in an amount of 0.05 to 2 with respect to the composition of the main component. A porcelain composition, which is contained in a range of 0.0 mol%. 2. The method according to claim 1, wherein the manganese lead-containing composite perovskite compound is made of lead manganese niobate (Pb (Mn _1/3 N).
b _2/3 ) O ₃ ), lead manganese tantalate (Pb (Mn _1/3
Ta _2/3 ) O ₃ ), lead manganese antimonate (Pb (Mn)
_1/3 Sb _2/3 ) O ₃ ), lead manganese tungstate (Pb
2. The porcelain composition according to claim 1, which is any one of (Mn _1/2 W _1/2 ) O ₃ ). 3. A multilayer ceramic capacitor produced using the porcelain composition according to claim 1. 4. The multilayer ceramic capacitor according to claim 3, wherein a silver palladium alloy is used for the internal electrodes. 5. A silver-palladium alloy is used for the internal electrode, and the ratio of silver to palladium in the silver-palladium alloy is 70% silver-30% palladium to 90% silver-palladium 10%.
The multilayer ceramic capacitor according to claim 3, which is in the range of%. 6. A silver-palladium alloy is used for an internal electrode, and a ratio of silver to palladium in the silver-palladium alloy is 75% silver-25% palladium to 85% silver-palladium 15%.
The multilayer ceramic capacitor according to claim 3, which is in the range of%.