JP3246104B2 - 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 that is added bismuth compounds such -ZrO ₂ and a rare earth element as an auxiliary component is widely known.

On the other hand, apart from the dielectric ceramic composition having the above composition, BaTiO ₃ is mainly used, and Nb ₂ O ₅ ,
In some cases, rare earth oxides and transition metal oxides such as Cr, Mn, Fe, Co, and Ni are added as subcomponents.
It has been reported that a flat dielectric-temperature characteristic can be obtained while having a high dielectric constant of 00 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 ECC 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.

[0007] Further, since this multilayer capacitor is mounted on an automobile, if it is broken during mounting on a board, the ECC module cannot be functioned 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, so that it may be broken at the time of mounting on a substrate, which may be a problem.

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 it is not possible to produce a small and large-capacity ceramic multilayer capacitor. .

On the other hand, 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 as described above. The rate of temperature change of the rate increases.
Further, when the firing temperature is increased to 1160 ° C. or more, 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 Pb and Bi ₂ O ₃ in the internal electrode is likely to occur, and the cost for the internal electrode increases.

[0012] 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, that is, −55 ° C. to + 150 ° C. based on the capacitance at + 25 ° C.
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 RB characteristic standard of C6429, the temperature change rate of the capacitance when a DC voltage of 25 V (50% of the rated voltage of 50 V) is applied (hereinafter, referred to as “bias TC”).
Is as small as + 15% to -40% or less.

[0013]

Means for Solving the Problems The present invention has a general formula:
{100- (a + b + c + d)} (Ba 100-x Pb x)
TiO ₃ + aZnO + bBi ₂ O ₃ + cNb ₂ O ₅ + d
Re ₂ O ₃ (where Re is La, Pr, Nd, Sm,
At least one selected from Dy and Er, a,
where b, c, d and x are mol%)
7.5 to 99.95% by weight, provided that a,
b, c, d and x are respectively in the following ranges: 0.5 ≦ a ≦ 4.5 0.5 ≦ b ≦ 4.5 0.5 ≦ c ≦ 4.5 0.5 ≦ d ≦ 5.5 0 <x ≦ 6.0 first auxiliary component composed of an SiO ₂ glass whose main component is 0.05 to 2.5 wt%, a dielectric ceramic composition comprising a. Further, the present invention provides a method of $ 100- (a + b + c +
d)｝ (Ba _100-x Pb _x ) TiO ₃ + aZnO + bB
i ₂ O ₃ + cNb ₂ O ₅ + dRe ₂ O ₃ (However, Re
Is at least one selected from La, Pr, Nd, Sm, Dy, and Er, and a, b, c, d, and x are mol%.) The main component represented by 97.0 to 99.94% by weight. ,
However, a, b, c, d and x in the above general formula are respectively in the following ranges: 0.5 ≦ a ≦ 4.5 0.5 ≦ b ≦ 4.5 0.5 ≦ c ≦ 4.50 0.5 ≦ d ≦ 5.50 <x ≦ 6.0 0.05 to 2.5% by weight of a first subcomponent composed of glass mainly composed of SiO ₂ , Cr, Mn, Fe, Co, and Ni Is a dielectric porcelain composition comprising 0.01 to 0.5% by weight of at least one second subcomponent selected from oxides of the following.

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 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. The SiO ₂ —B ₄ C-based glass is particularly useful when the forming binder of the ceramic raw material is an aqueous binder.

[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 the dielectric ceramic composition can be used for various electric devices in a place where the temperature changes greatly under various conditions.

Further, since the mechanical strength of the porcelain is high, when the porcelain is used as a porcelain multilayer capacitor, breakage such as cracking or chipping does not occur at the time of mounting 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 small, the thickness of the dielectric ceramic layer can be reduced to 10 μm to 15 μm, and the size and the capacitance 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]

EXAMPLES First, a method for adjusting the main components of the dielectric ceramic composition will be described. As a starting material, an industrial raw material Ba
TiO ₃ , PbO, TiO ₂ , ZnO, Bi ₂ O ₃ , N
b ₂ O ₅ , Re ₂ O ₃ (Re is La, Pr, Nd, S
m, Dy, Er) were prepared. Table 1 shows these starting materials.
Was weighed so as to have the composition ratio shown in Table 1, and wet-mixed and pulverized by a ball mill for 16 hours, and then evaporated to dryness to obtain a mixed powder. The obtained mixed powder was put in a zirconia box and calcined at 1000 ° C. for 2 hours in a natural atmosphere.
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 dielectric ceramic composition.

[0020]

[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 dielectric ceramic composition obtained as described above is adjusted to have the weight ratio shown in Table 1 with respect to the raw material powder of the main component of the dielectric ceramic composition. Was added.

The second subcomponents are 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 93.0 (Ba ₉₇ Pb
₃ ) TiO ₃ -1.5ZnO-1.5Bi ₂ O ₃ -2.
0 Nb ₂ O ₅ -2.0 Nd ₂ O ₃ (mol%) and 1.0 wt% of the first subcomponent were added to Table 2
The second subcomponent was added so as to have the composition ratio shown in FIG.

[0024]

[Table 2]

To these additives, a polyvinyl butyral-based binder and an organic solvent such as toluene and ethyl alcohol were added, and the mixture was wet-mixed by a ball mill for 16 hours, and then formed into a sheet by a doctor blade method.
I got a green sheet. The thickness of this green sheet is 1
It was 9 μm. After printing an internal electrode pattern on this green sheet using a paste of Ag / Pd = 70/30 (% by weight), six green sheets were stacked,
Thermocompression bonding was performed together with the dummy sheet to obtain a compression-bonded body. 5.5 mm long, 4.5 mm wide, 1 mm thick from this crimped body
Was cut out. 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.

[0026]

[Table 3]

[0027]

[Table 4]

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 under the conditions of a temperature of 25 ° C., 1 kHz, and 1 Vrms. As for TC, the value at which the rate of temperature change 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 voltage of 0 V is used as a reference. The maximum change rate (Δ
C _maxB ) was determined.

The flexural strength of the porcelain was measured by three-point bending. First, sheet-shaped materials of 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. Thus, for each composition, 20
The transverse rupture strength of this sample was measured, and the average was taken as the transverse rupture strength of the porcelain 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 main component amount, the first subcomponent amount and the second subcomponent amount are limited in the present invention will be described.

First, the reason for limiting the main component composition will be described.

With respect to the value of a, that is, ZnO, the range is set to 0.5 to 4.5 mol%.
_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. Further, as in Sample No. 10, when the content exceeds 4.5 mol%, the TC exceeds the maximum change rate (ΔC _max ) of −15%, and the bias TC also becomes −
The change exceeds 40%, which is not preferable.

The reason why the value of b, that is, Bi ₂ O ₃ , is set to 0.5 to 4.5 mol% is that TC is less than 0.5 mol% as in Sample No. 11. The rate of change (ΔC _max ) exceeds -15%, and the transverse rupture strength is undesirably a low value of 1500 kg / cm ² or less. Also, as in Sample No. 12, when the content exceeds 4.5 mol%, 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 exceeds -15% at the maximum rate of change (ΔC _max ), and bias TC also becomes −
The change exceeds 40%, which is not preferable.

The reason why the value of d, that is, Re ₂ O ₃ , is set to 0.5 to 5.5 mol% is that TC is less than 0.5 mol% as in Sample No. 15. The rate of change (ΔC _max ) exceeds -15%, and the bias T
C also changes more than -40%, which is not preferable. Also,
As in Sample No. 16, when the content exceeds 5.5 mol%, TC
Exceeds the maximum change rate (ΔC _max ) of −15%, which is not preferable.

For the value of x, ie PbTiO ₃ ,
As shown in Sample No. 17, when it exceeds 6.0 mol%, TC
In the maximum change rate (ΔC _max ) exceeds −15%, and the bias TC also changes more than −40%, which is not preferable.

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 is as shown in Sample No. 18,
If it is less than 0.05% by weight, the firing temperature exceeds 1160 ° C., which is not preferable. If the content exceeds 2.5% by weight as in Sample No. 21, 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 that the second subcomponent is used. If the component amount is less than 0.01% by weight, there is no effect of preventing reduction,
When the content exceeds 0.5% by weight as in sample No. 31, the dielectric loss (tan δ) becomes a large value exceeding 2.5%, which is not preferable.

In the above-described embodiment, the auxiliary component 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 front page (56) References JP-A-4-89353 (JP, A) JP-A-5-36308 (JP, A) JP-A-5-109319 (JP, A) JP-A-7- 37428 (JP, A) (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)} (Ba _100−x Pb _x )
TiO ₃ + aZnO + bBi ₂ O ₃ + cNb ₂ O ₅ + d
Re ₂ O ₃ (where Re is La, Pr, Nd, Sm,
At least one selected from Dy and Er, a,
where b, c, d and x are mol%)
7.5 to 99.95% by weight, provided that a, b, c, d and x 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 ≦ 5.50 <x ≦ 6.0 0.05 to 2.5% by weight of a first subcomponent composed of glass containing SiO ₂ as a main component; A dielectric ceramic composition comprising: 2. The following general formula: {100− (a + b + c + d)} (Ba _100−x Pb _x )
TiO ₃ + aZnO + bBi ₂ O ₃ + cNb ₂ O ₅ + d
Re ₂ O ₃ (where Re is La, Pr, Nd, Sm,
At least one selected from Dy and Er, a,
where b, c, d and x are mol%)
7.0 to 99.94% by weight, provided that a, b, c, d and x 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 ≦ 5.50 <x ≦ 6.0 0.05 to 2.5% by weight of a first subcomponent composed of glass containing SiO ₂ as a main component; A dielectric ceramic composition comprising 0.01 to 0.5% by weight of at least one second subcomponent selected from oxides of Cr, Mn, Fe, Co, and Ni.