JP3252552B2 - Dielectric porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric porcelain composition, and more particularly to a dielectric porcelain composition used as a material for a laminated ceramic capacitor.

[0002]

2. Description of the Related Art Conventionally, as a dielectric ceramic composition having a small voltage dependency, a high strength of a ceramic, and a flat dielectric temperature characteristic, for example, BaTiO ₃ as a main component and Bi ₂ O _{3 -TiO 2, Bi 2 O 3} -SnO
₂ , Bismuth compounds such as Bi ₂ O ₃ —ZrO ₂ and those in which a rare earth element is added as an auxiliary component are widely known.

On the other hand, separately from the dielectric ceramic composition having the above composition, BaTiO ₃ is used as a main component, and Nb ₂ O ₅ , a rare earth oxide, and a transition metal oxide such as Cr, Mn, Fe, Co, and Ni are used. It has been reported that, even when a substance is added as a subcomponent, a flat permittivity-temperature characteristic can be obtained while having a high permittivity of 3000 or more.

The temperature characteristics of these dielectric ceramic compositions are as follows:
X7R characteristics of EIA standard, that is, -55 ° C to +125
In the temperature range of ° C., the capacitance change rate based on the capacitance at + 25 ° C. was within ± 15%.

[0005]

In recent years, a porcelain multilayer capacitor has been used for an EEC module (electronic control unit for an engine) mounted in an engine room of an automobile. Since this device is used to stably control the engine, it is desirable that the temperature characteristics of the capacitor used satisfy the R characteristic (capacity change rate within ± 15%) from the viewpoint of the temperature stability of the circuit. .

On the other hand, the temperature in the engine room of a car drops to about -20 ° C. in winter in a cold region.
When the engine is started, it is expected that the temperature will rise to about + 130 ° C. in summer. In particular, when the engine is overheated, it can be considered that the temperature rises to about + 150 ° C. Therefore,
The conventional dielectric ceramic composition having the X7R characteristic cannot cope with the case where the temperature in the engine room becomes high.

Further, since this multilayer capacitor is mounted on an automobile, if it is broken during mounting on a substrate, the EEC module cannot function sufficiently, and in the worst case, it may lead to an accident. No. Further, it is conceivable that vibrations and stresses are constantly applied while the automobile is running, and the strength of the porcelain must be sufficiently high so as not to be destroyed by these vibrations and stresses.

Further, if the dielectric ceramic composition has a large voltage dependency, it cannot cope with the thinning of the dielectric material, making it impossible to manufacture a small-sized and large-capacity ceramic multilayer capacitor. It is not preferable from the viewpoint.

By the way, BaTiO ₃ is used as a main component, and Nb ₂ O ₅ , a rare earth oxide and Cr, Mn, F
A dielectric porcelain composition to which a transition metal oxide such as e, Co, Ni, or the like is added as a sub-component has a low porcelain strength, and thus may be broken during mounting on a substrate. In addition, these dielectric ceramic compositions having a large dielectric constant have a large voltage dependency, so that they cannot cope with recent thinning, and a small-sized, large-capacity ceramic multilayer capacitor cannot be manufactured.

On the other hand, as described above, a dielectric ceramic composition containing BaTiO ₃ as a main component and a bismuth compound added thereto has a small voltage dependency and a high ceramic strength. The rate of temperature change of the rate increases.
Further, when the firing temperature is increased to 1160 ° C. or higher, in the case of a porcelain multilayer capacitor, 30% by weight or more of Pd must be contained in the internal electrodes. Therefore, the reaction between Pd and Bi ₂ O ₃ in the internal electrode is likely to occur, and the cost for the internal electrode increases.

[0011] Therefore, the main object of the present invention is to provide:
It can be fired at 160 ° C. or less, and satisfies the X8R characteristic while having a high dielectric constant of 1000 or more.
The temperature change rate of the capacitance (hereinafter, referred to as “TC”) is flat within ± 15% over a wide temperature range of
When the mechanical strength of the porcelain is high and the thickness of the dielectric porcelain layer is reduced to 10 μm to 15 μm, the JIS
According to the standard of RB characteristic of C6429, the rated voltage of 50
% When the DC voltage is applied (hereinafter referred to as “bias TC”) is + 15% to −4.
An object of the present invention is to provide a dielectric ceramic composition as small as 0% or less.

[0012]

Means for Solving the Problems The present invention has a general formula:
{100- (a + b + c + d + e + f)} BaTiO ₃
+ AZnO + bBi ₂ O ₃ + cNb ₂ O ₅ + dMaO +
eMbO ₂ + fRe ₂ O ₃ (However, Ma is Pb, Ca
Mb is Ti, Z
at least one selected from r and Sn, and Re is L
at least one selected from a, Pr, Nd, Sm, Dy, and Er; a, b, c, d, e, and f are mol%), and the main component represented by 97.5 to 99.95% by weight. %,
However, a, b, c, d, e and f in the above general formulas are respectively in the following ranges: 0.5 ≦ a ≦ 4.5 2.0 ≦ b ≦ 6.0 0.5 ≦ c ≦ 4. 50 <d ≦ 4.0 6.5 ≦ e ≦ 10.0 0.5 ≦ f ≦ 5.5 0.05 to 2.5% by weight of the first subcomponent composed of glass containing SiO ₂ as a main component. And a dielectric porcelain composition comprising:

Further, the present invention provides a compound represented by the general formula:
(A + b + c + d + e + f)｝ BaTiO ₃ + aZnO
+ BBi ₂ O ₃ + cNb ₂ O ₅ + dMaO + eMbO ₂
+ FRe ₂ O ₃ (where Ma is at least one selected from Pb and Ca, Mb is at least one selected from Ti, Zr and Sn, and Re is La, Pr and N
at least one selected from d, Sm, Dy, and Er; a, b, c, d, e, and f are mol%, and 0.5 ≦ a
≦ 4.5, 2.0 ≦ b ≦ 6.0, 0.5 ≦ c ≦ 4.5,
0 <d ≦ 4.0, 6.5 ≦ e ≦ 10.0, 0.5 ≦ f ≦
5.5) The main component represented by 5.5) is 97.0 to 99.94% by weight, the first subcomponent composed of glass mainly containing SiO ₂ is 0.05 to 2.5% by weight, Cr, Mn, A dielectric porcelain composition comprising 0.01 to 0.5% by weight of at least one second subcomponent selected from oxides of Fe, Co and Ni.

Here, as the glass mainly composed of SiO ₂ as the first subcomponent, for example, BaO—SrO—C
there is _{aO-Li 2 O-SiO 2} . This glass is a sintering aid for lowering the sintering temperature to 1160 ° C. or lower, and is not limited thereto. For example, BaO—Li ₂ O—B ₂
An oxide glass containing boron oxide such as an O ₃ —SiO ₂ system may be used. Further, a system containing a non-oxide such as a SiO ₂ -B ₄ C system may be used. In the case where the glass contains boron oxide, when an aqueous binder is used as a molding binder for the ceramic raw material, it is preferable to use water-stable B ₄ C as the boron oxide raw material.

[0015]

Industrial Applicability The dielectric porcelain composition according to the present invention comprises:
Can be fired at a low temperature of 1160 ° C or less, from -55 ° C to +15
TC satisfies the R characteristic over a wide temperature range up to 0 ° C. and has a flat temperature characteristic. Therefore, the ceramic laminated capacitor using this dielectric ceramic composition can be used for all electrical equipment located in a place where the temperature changes greatly under various conditions.

In addition, since the porcelain has a high mechanical strength, when it is used as a porcelain multilayer capacitor, breakage such as cracking or chipping does not occur when mounted on a substrate. Therefore, accidents such as short-circuit failure and burning due to heat generation can be prevented.

Further, since the bias TC is excellent,
The thickness of the dielectric ceramic layer can be reduced to 10 μm to 15 μm, and the size and the capacity of the multilayer ceramic capacitor can be reduced.

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

[0019]

First, a method for preparing the main components of the dielectric ceramic composition will be described. BaT which is an industrial material as a starting material
iO ₃ , ZnO, Bi ₂ O ₃ , Nb ₂ O ₅ , MaO (M
a is Pb, Ca), MbO ₂ (Mb is Ti, Zr, S
n), Re ₂ O ₃ (Re is La, Pr, Nd, Sm, D
y, Er) was prepared. These starting materials were weighed so as to have the composition ratios shown in Table 1, wet-mixed and pulverized with a ball mill for 16 hours, and then dried by evaporation to obtain a mixed powder. The obtained mixed powder is placed in a zirconia box, calcined in a natural atmosphere at 1000 ° C. for 2 hours, and then coarsely pulverized so as to pass through a 200-mesh sieve. Powder.

Next, a method for preparing the first subcomponent of the dielectric ceramic composition will be described. In this embodiment, the firing temperature is set to 116.
As a first subcomponent to be 0 ° C. or lower, the composition is 8BaO-6.
An oxide glass represented by _{SrO-6CaO-30Li 2 O-} 50SiO 2 ( mol%). BaCO ₃ , SrCO ₃ , CaC which are industrial raw materials as starting materials
O ₃ , Li ₂ O, and SiO ₂ were prepared. These starting materials were weighed so as to have the above composition, wet-mixed and pulverized for 16 hours with a ball mill, and then evaporated to dryness to obtain a mixed powder. The obtained mixed powder was placed in an alumina crucible, left at a temperature of 1300 ° C. for 1 hour, and then rapidly cooled to vitrify. This was pulverized so as to pass through a 200-mesh sieve to obtain a raw material powder of the first subcomponent of the porcelain composition.

The raw material powder of the first subcomponent of the porcelain composition thus obtained was added to the raw material powder of the main component of the porcelain composition so as to have a weight ratio shown in Table 1.

The second subcomponent is Cr ₂ O ₃ , MnO ₂ , Fe ₂ O _3, Co ₂ O ₃ and N ₂ which are industrial raw materials.
iO was prepared. The main component composition is 88.5BaTiO ₃ −
_{1.5ZnO-3.0Bi 2 O 3 -1.0Nb 2} O 5 -
2.0 PbO-1.0 TiO ₂ -0.5 SnO ₂ -0.
5ZrO ₂ -2.0Nd ₂ O ₃ (mol%), to which the above-mentioned first sub-component was added in an amount of 1.0% by weight, the second sub-component was added so as to have a composition ratio shown in Table 2. did.

A polyvinyl butyral-based binder and an organic solvent such as toluene and ethyl alcohol were added thereto, and the mixture was wet-mixed with a ball mill for 16 hours.
A sheet was formed by a blade method to obtain a green sheet. The thickness of the green sheet was 19 μm. The internal electrode pattern is made of Ag / P on this green sheet.
After printing using a paste of d = 70/30 (% by weight), 6 layers of green sheets were stacked and thermocompression bonded together with a dummy sheet to obtain a compression body. A molded body having a length of 5.5 mm, a width of 4.5 mm, and a thickness of 1 mm was cut out from the pressed body. Thereafter, the molded body was fired at the firing temperatures shown in Tables 3 and 4 for 2 hours to obtain a sintered body. The dielectric thickness after sintering was 13 μm.

Then, a silver electrode was baked on the end face of the obtained sintered body, and the dielectric constant (ε), dielectric loss (tan δ), TC and bias TC at room temperature were measured as a measurement sample (multilayer capacitor). .

In this case, the dielectric constant (ε) and the dielectric loss (tan δ) were measured at a temperature of 25 ° C., 1 kHz, and 1 Vrms. As for TC, a value at which the rate of change in capacitance between -55 ° C. and + 150 ° C. is the maximum, that is, the maximum rate of change (ΔC _max ) was determined based on the capacitance at 25 ° C. As for the bias TC, the capacitance is measured while superimposing a DC voltage of 25 V on the measurement sample in the above temperature range, and the TC at a temperature of 25 ° C. and an applied DC voltage of 0 V is used as a reference. The maximum change rate (ΔC
_maxB ) was determined.

The bending strength of the porcelain was measured by three-point bending. First, materials obtained by sheet molding the raw materials having the respective compositions shown in Tables 1 and 2 were compression molded, and a molded body having a length of 35 mm, a width of 7 mm, and a thickness of 1.2 mm was cut out from the compressed body. Thereafter, these compacts were fired at the firing temperatures shown in Tables 3 and 4 for 2 hours to obtain strip-shaped porcelain. In this way, the bending strength was measured for 20 samples of each composition, and the average was defined as the bending strength of each composition.

The results of the above tests are shown in Table 3 for the composition of Table 1, and Table 4 for the composition of Table 2.

The reason why the ranges of the amounts of the main component, the first subcomponent, and the second subcomponent are limited in the present invention will be described.

First, the reason for limiting the main component composition will be described. The reason for setting the value of a, that is, ZnO, to 0.5 to 4.5 mol% is that as shown in Sample No. 9, when the concentration is less than 0.5 mol%, TC has a maximum change rate (ΔC
_max ) exceeds -15%, and the bending strength is 1500 kg / c.
The value is as low as m ² or less, which is not preferable. On the other hand, when the amount exceeds 4.5 mol% as in Sample No. 10, the TC exceeds -15% at the maximum rate of change (ΔC _max ), and the bias TC also decreases
The change exceeds 40%, which is not preferable.

The reason why the value of b, that is, Bi ₂ O ₃ , is set in the range of 2.0 to 6.0 mol% is that TC is less than 2.0 mol% as in Sample No. 11. The rate of change (ΔC _max ) exceeds -15%, and the transverse rupture strength is 15
The value is as low as 00 kg / cm ² or less, which is not preferable. On the other hand, when the value of b exceeds 6.0 mol% as in sample No. 12, the dielectric constant (ε) is less than 1000, which is not preferable.

With respect to the value of c, that is, the range of 0.5 to 4.5 mol% for Nb ₂ O ₅ , sample number 13
When TC is less than 0.5 mol%, and when it exceeds 4.5 mol as in Sample No. 14, TC has a maximum change rate (ΔC
_max ) exceeds -15% and the bias TC is -40%
, Which is not preferable.

The reason why the range of the value of d, ie, MaO, is set to 4.0 mol% or less is that as shown in Sample No. 15, when the content exceeds 4.0 mol%, the TC changes at a maximum rate of change (ΔC _max). ) Changes more than -15%, which is not preferable.

With respect to the value of e, ie, MbO ₂ , the range was set to 6.5 to 10.0 mol% in the case of sample No. 16.
If it is less than 6.5 mol% as in the above, or if it exceeds 10.0 mol% as in the sample No. 17, the TC changes in maximum change rate (ΔC _max ) more than −15%, which is not preferable.

The reason why the value of f, that is, Re ₂ O ₃ , is set in the range of 0.5 to 5.5 mol% is that TC is less than 0.5 mol% as in Sample No. 18. The rate of change (ΔC _max ) exceeds 15% and the bias TC
Changes over -40%, which is not preferable. On the other hand, if the content exceeds 5.5 mol% as in sample No. 19, the TC changes by more than 15% at the maximum rate of change (ΔC _max ), which is not preferable.

Next, the reason why the amount of the first subcomponent is limited will be described. Regarding the amount of the first subcomponent, the range is set to 0.0
The reason for setting the content to 5 to 2.5% by weight is as shown in Sample No. 20,
If the amount of the first subcomponent is less than 0.05% by weight, the firing temperature exceeds 1160 ° C., which is not preferable. On the other hand, when the amount of the first subcomponent exceeds 2.5% by weight as in Sample No. 22, the dielectric constant (ε) is less than 1000, which is not preferable.

Next, the reason why the amount of the second subcomponent is limited will be described. The second sub-component is for preventing the reduction of the dielectric porcelain. The reason why the range of the second sub-component is set to 0.01 to 0.5% by weight is that the amount of the second sub-component is If it is less than 0.01% by weight, there is no effect of preventing reduction,
On the other hand, when the content exceeds 0.5% by weight as in Sample No. 32,
Since the dielectric loss (tan δ) becomes a large value exceeding 2.5%, it is not preferable.

In the above-described embodiment, the first subcomponent which was previously prepared to have a predetermined composition ratio, heat-treated at a high temperature, melted, pulverized and vitrified, was added to the main component of the porcelain composition. However, as a method for adding the first sub-component, in addition to the above, the starting material is reformed by heating the mixture to such an extent that the first sub-component is not melted and added to the extent that the first sub-component is not melted. The constituent elements may be individually added to the main component in an arbitrary state, for example, a metal alkoxide, and may be vitrified by a melting reaction during firing.

In the above-mentioned embodiment, the second subcomponent was also added in the form of an oxide from the beginning. However, as a starting material at the time of preparing the raw material, a carbonate of each element or the like was used for calcination and firing. An oxide that becomes an oxide at the stage may be used.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

[Table 4]

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01B 3/12 303 C04B 35/46 H01G 4/12 358

Claims (2)

(57) [Claims] 1. The following general formula: {100− (a + b + c + d + e + f)} BaTiO ₃
+ AZnO + bBi ₂ O ₃ + cNb ₂ O ₅ + dMaO +
eMbO ₂ + fRe ₂ O ₃ (However, Ma is Pb, Ca
Mb is Ti, Z
at least one selected from r and Sn, and Re is L
at least one selected from a, Pr, Nd, Sm, Dy, and Er; a, b, c, d, e, and f are mol%), and the main component represented by 97.5 to 99.95% by weight. %, Wherein a, b, c, d, e and f in the above general formulas are respectively in the following ranges: 0.5 ≦ a ≦ 4.5 2.0 ≦ b ≦ 6.0 0.5 ≦ c ≦ 4.5 0 <a first auxiliary component composed of glass whose main component is d ≦ 4.0 6.5 ≦ e ≦ 10.0 0.5 ≦ f ≦ 5.5 SiO 2 is 0.05 to 2.5 % By weight of a dielectric porcelain composition. 2. The following general formula: {100− (a + b + c + d + e + f)} BaTiO ₃
+ AZnO + bBi ₂ O ₃ + cNb ₂ O ₅ + dMaO +
eMbO ₂ + fRe ₂ O ₃ (However, Ma is Pb, Ca
Mb is Ti, Z
at least one selected from r and Sn, and Re is L
at least one selected from a, Pr, Nd, Sm, Dy, and Er; a, b, c, d, e, and f are mol%), and the main component represented by 97.0 to 99.94% by weight. %, Wherein a, b, c, d, e and f in the above general formulas are respectively in the following ranges: 0.5 ≦ a ≦ 4.5 2.0 ≦ b ≦ 6.0 0.5 ≦ c ≦ 4.5 0 <a first auxiliary component composed of glass whose main component is d ≦ 4.0 6.5 ≦ e ≦ 10.0 0.5 ≦ f ≦ 5.5 SiO 2 is 0.05 to 2.5 A dielectric porcelain composition comprising 0.01% to 0.5% by weight of a second subcomponent composed of at least one selected from oxides of Cr, Mn, Fe, Co and Ni.