JPH1116765A - Internal electrode paste and laminated ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide internal electrode paste which can prevent the occurrence of delamination, when the paste is baked, and a laminated ceramic capacitor. SOLUTION: Internal electrode paste contains powder of at least one kind of noble metal selected from among Pt, Pd, Au, and Ag, the powder of a lead- based pervoskite type oxide, and Al2 O3 powder, with the mixing ratios of the oxide powder and Al2 O3 powder in the paste respectively being adjusted to 9-22 pts.vol. and 2-16 pts.vol. against 100 pts.vol. noble metal powder. It is desirable to use Pb(Mg1/3 Nb2/3 )O3 as the lead-based pervoskite oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable telephone, a VT
The present invention relates to an internal electrode paste and a multilayer ceramic capacitor used for electronic devices such as a camera, a camera, and a personal computer.

[0002]

2. Description of the Related Art In general, a multilayer ceramic capacitor is
First, an internal electrode paste is printed by a screen printing method on a ceramic green sheet obtained by a doctor blade method or the like. Next, after laminating and pressing, a pressed body composed of the ceramic green sheet and the internal electrode paste layer is simultaneously fired, and thereafter, an external electrode is formed.

The internal electrode paste is P
Noble metal powders such as t, Pd, Au, and Ag are added to and dispersed in an organic vehicle containing a binder such as ethyl cellulose resin and a solvent.

[0004] However, the internal electrode paste has a lower firing shrink temperature than ceramic powder (ceramic green sheet). Further, the firing shrinkage is higher than that of ceramic powder (ceramic green sheet). Therefore, when a multilayer ceramic capacitor is obtained by simultaneously firing the internal electrode paste layer and the ceramic green sheet, there is a problem that during firing, distortion occurs between the internal electrode layer and the dielectric layer, and delamination easily occurs. I was

Therefore, conventionally, in order to alleviate the distortion generated when the internal electrode paste layer and the ceramic green sheet are simultaneously fired, ceramic powder of the same material as the ceramic green sheet is added to the internal electrode paste. Thus, an attempt has been made to eliminate the difference in the shrinkage ratio between materials (Japanese Patent Application Laid-Open No. 8-78267).

[0006]

However, due to recent miniaturization and large capacity of multilayer ceramic capacitors,
As the thickness of the dielectric layer of the multilayer ceramic capacitor is reduced and the number of layers is increased, the stress due to the difference in firing shrinkage tends to increase, and ceramic powder of the same material as the ceramic green sheet is contained in the internal electrode paste. Even the method described above was insufficient to prevent the occurrence of delamination.

An object of the present invention is to provide an internal electrode paste and a multilayer ceramic capacitor which can prevent the occurrence of delamination during firing.

[0008]

The internal electrode paste of the present invention comprises at least one of Pt, Pd, Au and Ag.
Seed noble metal powder, 9 to 22 parts by volume of a lead-based perovskite oxide powder with respect to 100 parts by volume of the noble metal powder,
It contains 2 to 16 parts by volume of Al ₂ O ₃ powder based on 100 parts by volume of the noble metal powder. Here, the lead-based perovskite oxide powder is composed of Pb (Mg _1/3 N
b _2/3 ) O ₃ powder is desirable.

Further, the multilayer ceramic capacitor of the present invention is a multilayer ceramic capacitor in which a plurality of dielectric layers and a plurality of internal electrode layers are alternately laminated, wherein the dielectric layer is made of a lead-based perovskite oxide. With
The internal electrode layer includes at least one noble metal of Pt, Pd, Au, and Ag, and 9 to 22 parts by volume of a lead-based perovskite oxide with respect to 100 parts by volume of the noble metal.
Al ₂ O ₃ is added in an amount of 2 to 16 based on 100 parts by volume of the noble metal.
Volume part, and the lead-based perovskite oxide in the internal electrode layer is Pb (Mg _1/3 Nb _2/3 ) O ₃
It is desirable that

[0010]

In the internal electrode paste of the present invention, a lead-based perovskite oxide powder, for example, Pb (Mg _1/3 Nb _2/2 )
By adding the O ₃ powder, the firing shrinkage temperature of the internal electrode layer during firing can be made closer to the firing shrinkage temperature of ceramics (dielectric layer). Also, by adding Al ₂ O ₃ powder to the internal electrode paste, the firing shrinkage of the internal electrode is reduced, and the ceramic (dielectric layer)
Can be approached.

Therefore, when the internal electrode layer of the multilayer ceramic capacitor is formed by using the above-mentioned internal electrode paste, it is possible to suppress the shrinkage distortion of firing generated between the internal electrode layer and the ceramic (dielectric layer). it can.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The internal electrode paste of the present invention is
t, Pd, and at least one noble metal powder of Au and Ag, and lead-based perovskite-type oxide powder, Al ₂
O ₃ powder. At least one noble metal powder of Pt, Pd, Au and Ag is a concept including two or more noble metal powders and a concept including alloy powders of these noble metals. As the noble metal powder, a noble metal powder composed of Ag and Pd is desirable from the viewpoint of cost reduction.

The lead-based perovskite oxide powder is preferably Pb (Mg _1/3 Nb _2/3 ) O ₃ powder, but is not necessarily limited thereto. For example, Pb (Fe _1/2 Nb _1/2 ) O ₃ , Pb (Mg _1/3
Nb _2/3 ) O ₃ . As the lead-based perovskite-type oxide powder, the constituent material of the dielectric layer of the capacitor is most desirable from the viewpoint of preventing delamination.

The lead-based perovskite oxide powder needs to be contained in an amount of 9 to 22 parts by volume with respect to 100 parts by volume of the noble metal. This is because when the amount of the lead-based perovskite oxide powder is less than 9 parts by volume, the effect of bringing the firing shrinkage temperature of the internal electrode layer close to the firing shrinkage temperature of the ceramic (dielectric layer) is small, and delamination occurs. If the amount is more than 22 parts by volume, the connection between the noble metal particles is interrupted, the designed capacity cannot be obtained, and the capacity variation increases when the capacitor is manufactured.

The lead-based perovskite-type oxide powder is desirably contained in an amount of 9 to 16 parts by volume with respect to 100 parts by volume of the noble metal from the viewpoint of preventing delamination and suppressing variation in capacity.

The alumina powder must be contained in an amount of 2 to 16 parts by volume based on 100 parts by volume of the noble metal. This is because when the alumina powder is less than 2 parts by volume, the effect of reducing the firing shrinkage of the internal electrode is small, and delamination is likely to occur. Is reduced. Alumina powder is used in an amount of 5 parts per volume of noble metal from the viewpoint of preventing delamination and improving CR product.
It is desirable to contain 含有 13 parts by volume.

Further, the multilayer ceramic capacitor of the present invention is a multilayer ceramic capacitor in which a plurality of dielectric layers and a plurality of internal electrode layers are alternately laminated, wherein the dielectric layer is made of a lead-based perovskite oxide. With
The internal electrode layer contains at least one noble metal of Pt, Pd, Au, and Ag, a lead-based perovskite oxide, and Al ₂ O ₃ , and the lead is contained in 100 parts by volume of the noble metal. -Based perovskite oxide
22 parts by volume, containing 2 to 16 parts by volume of the Al ₂ O ₃ . The reason for limiting each numerical value is the same as above.

The dielectric layer in the multilayer ceramic capacitor according to the present invention is made of a lead-based perovskite oxide, for example, Pb (Mg _1/3 Nb _2/3 ) O ₃ , P ₃
b (Mg _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ , Pb (M
g _1/3 Nb _2/3 ) O ₃ —PbTiO ₃ —CuO, Pb
(Mg _1/3 Nb _2/3 ) O ₃ -Pb (Zn _1/3 Nb _2/3 )
O ₃ —Pb (Sm _1/3 Nb _2/3 ) O ₃ —CuO and the like.

In the dielectric layer of the multilayer ceramic capacitor of the present invention, a pyrochlore phase or a metal phase may be precipitated in addition to a lead-based perovskite oxide crystal. Also,
As described above, the internal electrode layer contains Al ₂ O in the noble metal.
_Three particles and, for example, Pb (Mg _1/3 Nb _2/3 ) O ₃ particles are dispersed. The average crystal grain size of the Al ₂ O ₃ particles is 0.8 from the point that the average grain size of the noble metal particles is about 1 μm.
And the average crystal grain of the lead-based perovskite oxide crystal grains is preferably 0.8 to 1.2 μm.

[0020]

EXAMPLE First, a ceramic green sheet was produced. _{69.7Pb (Mg 1/3 Nb 2/3} ) O 3 -29.3
Pb (Zn _1/3 Nb _2/3 ) O ₃ -0.2 Pb (Sm _1/3
A slurry was obtained by mixing a lead-based perovskite oxide powder composed of Nb _2/3 ) O ₃ -0.8 CuO (unit: mol%) and an organic binder. This slurry was formed into a sheet by a doctor blade method to produce a ceramic green sheet having a thickness of 10 μm. Next, an internal electrode paste was prepared. Ag-Pd mixed powder having an average particle size of 1 μm (weight ratio 3: 7) and Pb having an average particle size of 1 μm
(Mg _1/3 Nb _2/3 ) O ₃ powder and Al ₂ O ₃ powder are dispersed in an organic vehicle using ethyl cellulose resin as a binder and α-terpineol as a solvent with a three-roll to prepare an internal electrode paste. did. Ag-Pd powder and Pb (Mg _1/3 N
Table 2 shows the ratio of the volume parts of b _2/3 ) O ₃ powder to Al ₂ O ₃ powder.

In sample No. 17, Pb (Mg _1/3 Nb _2/3 ) O ₃ powder was used instead of Pb (Mg _1/3 Nb _2/3 ) O ₃ powder in the internal electrode paste.
b (Fe _1/2 Nb _1/2 ) O ₃ powder was added. In sample No. 18, P was used as the noble metal in the internal electrode paste.
t, Au in sample No. 19 and P in sample No. 20
d was used.

Thereafter, a multilayer ceramic capacitor was manufactured using the obtained internal electrode paste and ceramic green sheets. That is, the internal electrode paste was printed on one surface of the ceramic green sheet by a screen printing method, and dried, and 50 ceramic green sheets each having an internal electrode paste layer formed thereon were laminated. Thereafter, they were integrated by hot pressing and cut into a predetermined size to produce a green chip.

The obtained green chip is placed in the air at 400
C. for 2 hours to completely decompose the binder and remove the binder, and then calcined at a temperature of 1020 C.
A laminated sintered body having a size of 1.6 mm in width, 3.2 mm in length, and 0.6 mm in thickness was obtained. The effective area of the electrode is 2.6m
m ² , and the thickness of the dielectric layer was 7 μm.

Thereafter, a conductive paste is applied and baked on the exposed end surface of the sintered body where the internal electrode is exposed,
External electrodes were formed to obtain a multilayer ceramic capacitor.

Next, the capacitance and insulation resistance of each of the 100 laminated ceramic capacitors were measured. The measurement is
Performed at a reference temperature of 25 ° C., with a capacitance of 1.0 kHz
z, under a measurement condition of a measurement voltage of 1.0 Vrms, and the insulation resistance was measured when a DC voltage of 1 V was applied for 1 minute. The product of the measured capacitance value and the insulation resistance value was calculated to be a CR product (ΩF). CR product is 20000Ω
Below F, the reliability cannot be satisfied and the size of the multilayer ceramic capacitor cannot be reduced.
F or higher was regarded as good.

From the average value and the standard deviation calculated from the measured capacitance values, the ratio of the standard deviation to the average value was defined as the capacitance variation (%). In addition, when the capacitance variation is 5% or more, the yield of the capacitance is reduced.

Each of these multilayer ceramic capacitors 100
The individual pieces were cut and polished on a plane perpendicular to the internal electrode layer, and the presence or absence of delamination between the internal electrode layer and the dielectric layer was checked with a microscope. If delamination occurs in the multilayer ceramic capacitor, the reliability cannot be satisfied.

Further, the multilayer ceramic capacitor was mounted on an alumina substrate by soldering, and subjected to a wet and medium load test under the following conditions. In the test method, a voltage twice as high as the rated voltage was applied in an environment of 85 ° C.-85% RH, and after 48 hours of operation, the capacitance deterioration and the insulation resistance deterioration were measured for each of 1,000 capacitors. . During the test,
The capacitance was determined to be defective when the rate of decrease in capacitance after the test was ± 30% or more of the capacitance before the test. Insulation resistance is 1.0 ×
10 ⁹ Ω or less was regarded as defective. Table 1 shows the occurrence rates of these defects and the results of the above characteristics.

[0029]

[Table 1]

As apparent from Table 1, Sample No.
In 1, 2, 4, and 6, a failure occurred in the wet load test. Sample No. In No. 10, the capacity variation is 8.7%, which is out of the target value.

On the other hand, in each of the samples of the present invention, the CR product was as large as 20500 ΩF or more, the capacitance variation was 4.7% or less, there was no delamination, and the capacitance and insulation in the wet and medium load test were high. There is no resistance failure.

When the amount of Al ₂ O ₃ is increased, no delamination occurs, no capacitance and no insulation resistance occur in a wet and medium load test, but the CR product decreases, and the variation in capacitance decreases. It turns out that it becomes big.

Sample No. The firing shrinkage curves of the dried powders of the internal electrode pastes 2, 4, 5, and 7 were measured by a thermomechanical analyzer (TMA) in comparison with the raw material powder of the dielectric layer.
The measurement conditions were as follows.
The temperature was raised to 100 ° C., maintained at 1100 ° C. for 2 hours, and thereafter, the temperature was lowered at a rate of 5 (° C./min). The result is shown in FIG. As shown in FIG. 1, Pb (Mg _1/3 Nb
_2/3 ) By adding the O ₃ powder, the firing shrinkage temperature of the internal electrode layer during firing can be made closer to the firing shrinkage temperature of the ceramic. Further, by adding Al ₂ O ₃ powder to the internal electrode paste, the shrinkage rate of firing of the internal electrode layer can be reduced.

[0034]

According to the internal electrode paste and the multilayer ceramic capacitor of the present invention, by adding the lead-based perovskite-type oxide powder, the temperature at which the firing of the internal electrode layer shrinks can be made closer to the firing shrinkage temperature of the dielectric layer. Can,
Also, by adding Al ₂ O ₃ powder to the internal electrode paste, the firing shrinkage of the internal electrode layer can be reduced, and the firing shrinkage distortion generated between the internal electrode layer and the dielectric layer is suppressed. can do. Therefore, there is no delamination without deteriorating the electrical characteristics such as CR product,
A multilayer ceramic capacitor that does not deteriorate reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing firing shrinkage curves of an internal electrode powder and a ceramic powder.

Claims (4)

[Claims] 1. A noble metal powder of at least one of Pt, Pd, Au and Ag, 9 to 22 parts by volume of a lead-based perovskite-type oxide powder with respect to 100 parts by volume of the noble metal powder, Al ₂ O ₃
An internal electrode paste containing 2 to 16 parts by volume of a powder. 2. The lead-based perovskite oxide powder is Pb
2. The internal electrode paste according to claim 1, wherein the paste is (Mg _1/3 Nb _2/3 ) O ₃ powder. 3. A multilayer ceramic capacitor comprising a plurality of dielectric layers and a plurality of internal electrode layers alternately stacked,
The dielectric layer is made of a lead-based perovskite oxide, and the internal electrode layer is made of Pt, Pd, Au and A.
g of at least one noble metal, 9 to 22 parts by volume of a lead-based perovskite oxide with respect to 100 parts by volume of the noble metal, and 2 to 16 parts by volume of Al ₂ O ₃ with respect to 100 parts by volume of the noble metal. The multilayer ceramic capacitor characterized by containing. 4. A multilayer ceramic capacitor according to claim 3, wherein the lead-based perovskite-type oxide in the internal electrode layer is characterized in that it is a _{Pb (Mg 1/3 Nb 2/3} ) O 3.