JP3303453B2 - 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, Bi ₂ O ₃ obtained by adding a bismuth compound and a rare earth element such -ZrO ₂ as an auxiliary component is widely known porcelain composition.

On the other hand, apart from the dielectric ceramic composition having the above composition, BaTiO ₃ is mainly used, and Nb ₂ O ₅ ,
Rare earth oxides and oxides to which transition metal oxides such as Cr, Mn, Fe, Co, and Ni are added as subcomponents have a high dielectric constant of 3000 or more, yet have a flat dielectric temperature characteristic. Has been reported to be

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]

Problems to be Solved by the Invention However, Ba
The dielectric ceramic composition containing TiO ₃ as a main component and a bismuth compound added thereto had a low dielectric constant of about 1,000. Further, when the dielectric constant is increased, the rate of temperature change of the capacitance is increased. In addition, when firing at high temperature, B
There has been a problem that i ₂ O ₃ evaporates, causing distortion in the porcelain, a change in the composition ratio, a failure in obtaining necessary electrical characteristics and mechanical strength, and variations.

On the other hand, BaTiO ₃ is used as a main component, and Nb ₂ O ₅ , a rare earth oxide and Cr, Mn, Fe, C
A dielectric porcelain composition to which a transition metal oxide such as o or Ni is added as a subcomponent has a dielectric constant of 3000 or more and has flat temperature characteristics. However, the firing temperature of this dielectric porcelain composition was as high as 1200 ° C. or higher.

Further, recent ceramic capacitors tend to be miniaturized. In particular, in a multilayer ceramic capacitor, the thickness of the ceramic dielectric layer is 5 μm to 15 μm in order to reduce the size and increase the capacity.
m. Therefore, it is desired that the dielectric ceramic composition has low voltage dependency.

However, the above-mentioned dielectric ceramic composition having a large dielectric constant has a large voltage dependency, so that it cannot cope with recent thinning, and a small-sized large-capacity ceramic multilayer capacitor cannot be produced. . In addition, since the strength of the porcelain is low, the porcelain may be broken during mounting, which has been a problem.

[0009] Therefore, the main object of the present invention is to provide:
Can be fired at 160 ° C or less, and the thickness of the dielectric ceramic layer is 5 μm
DC, so as to be able to cope with
Even when a bias electric field of 2 kV / mm is applied, the rate of change of the capacitance is as small as ± 20% or less, and the mechanical strength of the porcelain is high.
Based on the capacitance at 25 ° C., −55 ° C.
An object of the present invention is to provide a dielectric porcelain composition having stable characteristics under various conditions, in which the temperature change rate of capacitance is flat within ± 15% over a wide temperature range of + 125 ° C.

[0010]

Means for Solving the Problems The present invention has a general formula:
{100- (a + b + c + d)} BaTiO 3 + aZn
O + bBi ₂ O ₃ + cNb ₂ O ₅ + dRe ₂ O ₃ (where Re is at least one selected from La, Pr, Nd, Sm, Dy, and Er; a, b, c, and d are mol%, 0 0.5 ≦ a ≦ 4.5, 0.5 ≦ b ≦ 4.5,
0.5 ≦ c ≦ 4.5,0.5 ≦ d ≦ 5.5) the main component is 97.5-99.5% by weight represented by the first sub made of glass whose main component is SiO ₂ A dielectric ceramic composition comprising 0.05 to 2.5% by weight of a component.

Further, the present invention provides a compound represented by the general formula:
(A + b + c + d)｝ BaTiO ₃ + aZnO + bBi
₂ O ₃ + cNb ₂ O ₅ + dRe ₂ O ₃ (where Re is at least one selected from La, Pr, Nd, Sm, Dy, and Er; a, b, c, and d are mol%;
0.5 ≦ a ≦ 4.5, 0.5 ≦ b ≦ 4.5, 0.5 ≦ c
≦ 4.5, 0.5 ≦ d ≦ 5.5)
7.0 to 99.94% by weight, the first subcomponent composed of glass mainly composed of SiO ₂ is 0.05 to 2.5% by weight,
r, Mn, Fe, Co, and at least one second subcomponent selected from oxides of Ni is 0.01% or less.
~ 0.5% by weight of the dielectric porcelain composition.

Here, as the glass mainly containing SiO ₂ as a sub-component, for example, BaO—SrO—Ca
There is an _{O-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 O ₃
Oxide glass containing boron oxide such as SiO ₂ 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.

[0013]

Industrial Applicability The dielectric porcelain composition according to the present invention comprises:
It can be fired at a low temperature of 1160 ° C. or less. Even when a DC bias electric field is applied at 2 kV / mm, the rate of change of the capacitance is ±
Less than 20%. Therefore, the thickness of the dielectric ceramic layer can be reduced to 5 μm to 15 μm. And
The miniaturization and large capacity of the ceramic laminated capacitor can be promoted.

Further, since the mechanical strength of the porcelain is high, when it is used as a porcelain multilayer capacitor, breakage such as cracking, chipping or the like during mounting on a substrate does not occur. Therefore, accidents such as short shots and burnout due to heat generation can be prevented.

Further, when the capacitance at + 25 ° C. is taken as a reference while having a high dielectric constant of 1000 or more, −
Over a wide temperature range from 55 ° C. to + 125 ° C., the temperature change rate of the capacitance is flat with ± 15% or less, and the temperature is stable. From the above, it can be used over a wide range as a dielectric porcelain for the industrial market or the consumer market.

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

[0017]

EXAMPLES First, a method for preparing the main components of the dielectric ceramic composition will be described. As a starting material, an industrial material B
aTiO ₃ , ZnO, Bi ₂ O ₃ , Nb ₂ O ₅ , Re ₂
O ₃ , (Re is La, Pr, Nd, Sm, Dy, Er)
Was prepared. These starting materials were weighed so as to have the composition ratios shown in Table 1, and wet-mixed and pulverized by 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 and placed in a natural atmosphere for 10 minutes.
After calcining at 00 ° C. for 2 hours, the mixture was roughly pulverized so as to pass through a 200-mesh sieve to obtain a raw material powder as a main component of the porcelain composition.

[0018]

[Table 1]

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 obtained as described above was added to the raw material powder of the main component of the porcelain composition in 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 , N ₂
iO was prepared. The composition of the main component is 93.0BaTiO _{3
-1.5ZnO-1.5Bi 2 O 3 -2.0Nb 2} O 5
The second sub-component was added so as to have a composition ratio shown in Table 2 with respect to the addition of 1.0 wt% of the above-mentioned first sub-component at −2.0 Nd ₂ O ₃ (mol%).

[0022]

[Table 2] A vinyl acetate-based binder was added thereto, and the mixture was wet-mixed with a ball mill for 16 hours, and then dried by evaporation to obtain a dried product. The dried product was granulated through a 200-mesh sieve, and then dried at a pressure of 2000 kg / cm _{2 to} a diameter of 10 kg.
It was press-molded into a disk having a thickness of 1 mm and a thickness of 1 mm to obtain a molded body. After that, the molded bodies were respectively referred to in Tables 3 and 4
The sintering was performed for 2 hours at the sintering temperature shown in Table 2 to obtain a disk-shaped porcelain.

[0023]

[Table 3]

[0024]

[Table 4]

Then, silver electrodes are baked on both main surfaces of the obtained porcelain to obtain a dielectric constant (ε), a dielectric loss (tan δ) at room temperature, and a static capacitance when a DC voltage is applied. The rate of change of the capacitance (DC bias characteristics) and the rate of change of the capacitance with respect to temperature change (TCC) were measured.

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. For the DC bias characteristics, the capacitance was measured when the DC voltage was superimposed on the measurement sample under the above measurement conditions, and the rate of change was determined based on the capacitance when the applied voltage was 0 V. . Further, regarding TCC, based on the capacitance (C ₂₅ ) at 25 ° C.,
The absolute value of the value at which the rate of temperature change is maximum between −55 ° C. and + 125 ° C., the so-called maximum rate of change (| ΔC / C ₂₅ |
max).

The bending strength of the porcelain was measured by three-point bending. First, raw materials having the respective compositions shown in Tables 1 and 2 were press-molded into a length of 35 mm, a width of 7 mm, and a thickness of 1.2 mm to obtain a molded body. After that, it was 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.

For each of the above tests, the results for the compositions in Table 1 are shown in Table 3 and the results for the compositions in Table 2 are shown in Table 4.

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 reasons for limiting the main component composition will be described.

With respect to the value of a, that is, ZnO, the range was set to 0.5 to 4.5 mol%, as shown in Sample No. 9, when the value of a, that is, ZnO was less than 0.5 mol%. , TCC exceeds 15% in ΔCmax, and the transverse rupture strength is not preferred because it is a low value of 1500 kg / cm ₂ or less. On the other hand, as shown in Sample No. 10, when the value of a exceeds 4.5 mol%, the DC bias characteristic becomes 2 kV /
mm, the change exceeds -20% and the TCC
Is also not preferred because ΔCmax exceeds 15%.

With respect to the value of b, that is, Bi ₂ O ₃ , the range was set to 0.5 to 4.5 mol%, as shown in Sample No. 11 of Table 1, the value of b, that is, Bi ₂ O _3. Is less than 0.5 mol%, the TCC becomes 15% in ΔCmax.
And the bending strength also becomes a low value of 1500 kg / cm ₂ or less, which is not preferable. On the other hand, as shown in Sample No. 12, when the value of b exceeds 4.5 mol%, the dielectric constant (ε) becomes less than 1000, which is not preferable.

With respect to the value of c, ie, Nb ₂ O ₅ , the range was set to 0.5 to 4.5 mol%, as shown in Sample No. 13 of Table 1, the value of c, ie, Nb ₂ O ₅ Is less than 0.5 mol%, or as shown in Sample No. 14, when the value of c exceeds 4.5 mol%, the TCC exceeds 15% in ΔCmax, which is not preferable.

With respect to the value of d, ie, Re ₂ O ₃ , the range was set to 0.5 to 5.5 mol%, as shown in Sample No. 15 of Table 1, the value of d, ie, Re ₂ O _3. Is less than 0.5 mol%, the DC bias characteristic becomes 2 kV
/ -20% at the time of / mm application and TCC is ΔCmax
Is more than 15%. On the other hand, sample number 1
As shown in FIG. 6, when the value of d exceeds 5.5 mol%, TC
C is not preferred because ΔCmax exceeds 15%.

Next, the reason why the amount of the first subcomponent is limited will be described.

The range of the first subcomponent amount is set to 0.0
The reason for setting the content to 5 to 2.5% by weight, as shown in sample No. 17 in Table 1, is that it is not preferable if the amount of the first subcomponent is less than 0.05% by weight because the firing temperature exceeds 1160 ° C.
On the other hand, as shown in Sample No. 20, the amount of the first subcomponent was 2.5
If the content is more than 100% by weight, 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 subcomponent is for preventing the reduction of the dielectric porcelain. The reason why the range of the second subcomponent is set to 0.01 to 0.5% by weight is as follows. If the component amount is less than 0.01% by weight, there is no effect of preventing reduction,
As shown in Sample No. 30 in Table 2, when the content exceeds 0.5% by weight, tan δ becomes a large value exceeding 2.5%, which is not preferable.

In the above-described embodiment, a subcomponent which was prepared in advance at 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 of adding the first auxiliary component,
Heated to the extent that it is not melted by mixing it in a predetermined ratio in advance and adding a modified starting material or adding each constituent element of the first subcomponent to the main component in an arbitrary state such as a metal alkoxide, for example. May be added individually, 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. An oxide that becomes an oxide at the stage may be used.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-51-69200 (JP, A) JP-A-52-69200 (JP, A) JP-A-4-114496 (JP, A) JP-A-5-69 12918 (JP, A) JP-A-7-37427 (JP, A) JP-A-7-37428 (JP, A) (58) Fields investigated (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)} BaTiO ₃ + aZn
O + bBi ₂ O ₃ + cNb ₂ O ₅ + dRe ₂ O ₃ (where Re is at least one selected from La, Pr, Nd, Sm, Dy and Er, and a, b, c and d are mol%) The main component represented by 97.5 to 99.95% by weight, provided that a, b, c and d in the above general formula are in the following ranges: 0.5 ≦ a ≦ 4.5 0.5 ≦ b ≦ 4.5 0.5 ≦ c ≦ 4.5 0.5 ≦ d ≦ 5.5 first auxiliary component composed of an SiO ₂ glass whose main component is 0.05 to 2.5 wt%, the dielectric consisting of Body porcelain composition. 2. The following general formula: {100− (a + b + c + d)} BaTiO ₃ + aZn
O + bBi ₂ O ₃ + cNb ₂ O ₅ + dRe ₂ O ₃ (where Re is at least one selected from La, Pr, Nd, Sm, Dy and Er, and a, b, c and d are mol%) The main component represented is 97.0 to 99.94% by weight, provided that a, b, c and d in the above general formula are in the following ranges: 0.5 ≦ a ≦ 4.5 0.5 ≦ b ≦ 4.5 0.5 ≦ c ≦ 4.5 0.5 ≦ d ≦ 5.5 first subcomponent of SiO ₂ made of glass whose main component is 0.05 to 2.5 wt%, Cr, Mn , Fe, Co,
A dielectric porcelain composition comprising 0.01 to 0.5% by weight of at least one second subcomponent selected from Ni and Ni oxides.