JP3321823B2 - Non-reducing 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 non-reducing dielectric porcelain composition, and more particularly to a non-reducing dielectric porcelain composition used for, for example, a multilayer ceramic capacitor.

[0002]

2. Description of the Related Art To manufacture a laminated ceramic capacitor, first, a sheet-shaped dielectric material having an electrode material to be an internal electrode applied to the surface thereof is prepared. As the dielectric material, for example, a material mainly containing BaTiO ₃ is used. The sheet-shaped dielectric material coated with the electrode material is laminated, thermocompression-bonded, and the integrated material is fired at 1250 to 1350 ° C. in a natural atmosphere to obtain a dielectric porcelain having internal electrodes. Then, an external electrode that is electrically connected to the internal electrode is baked on the end face of the dielectric ceramic to manufacture a multilayer ceramic capacitor.

Therefore, the material of the internal electrode must satisfy the following conditions.

(A) Since the dielectric porcelain and the internal electrodes are fired at the same time, the dielectric porcelain has a melting point higher than the temperature at which the dielectric porcelain is fired.

(B) It is not oxidized even in an oxidizing high-temperature atmosphere and does not react with a dielectric.

As an electrode material satisfying such conditions, noble metals such as platinum, gold, palladium and alloys thereof have been used.

However, these electrode materials have excellent characteristics, but are expensive. Therefore, the ratio of the electrode material cost to the multilayer ceramic capacitor is 30 to 7%.
It reached 0%, which was the biggest factor in increasing the manufacturing cost.

[0008] In addition to the noble metals, N
There are base metals such as i, Fe, Co, W, and Mo. However, these base metals are easily oxidized in a high-temperature oxidizing atmosphere, and do not serve as an electrode. Therefore, in order to use these base metals as the internal electrodes of the multilayer ceramic capacitor, they must be fired in a neutral or reducing atmosphere together with the dielectric porcelain. However, the conventional dielectric porcelain material has a drawback that when it is fired in such a reducing atmosphere, it is significantly reduced and becomes a semiconductor.

In order to overcome such a drawback, for example, as disclosed in Japanese Patent Publication No. 57-42588, in a barium titanate solid solution, the ratio of barium site / titanium site is set to be larger than the stoichiometric ratio. Body material has been devised. By using such a dielectric material, it is possible to obtain a dielectric ceramic that does not turn into a semiconductor even when fired in a reducing atmosphere, and it is possible to manufacture a multilayer ceramic capacitor using a base metal such as nickel as an internal electrode. It became.

[0010]

With the development of electronics in recent years, the miniaturization of electronic components has rapidly progressed, and the tendency of miniaturization of multilayer ceramic capacitors has also become remarkable. As a method of reducing the size of the multilayer ceramic capacitor, it is generally known to use a material having a large dielectric constant or to reduce the thickness of the dielectric layer. However, a material having a large dielectric constant has a large crystal grain, and when the material is formed into a thin film having a thickness of 10 μm or less, the number of crystal grains existing in one layer is reduced, and reliability is reduced.

On the other hand, JP-A-58-135507 discloses
JP-A-58-223669, JP-A-59-861
As disclosed in Japanese Patent Application Publication No. 03-2003, a dielectric porcelain having a small crystal grain size in which a rare earth oxide such as La, Nd, Sm, or Dy is added to a barium titanate solid solution is known. By reducing the crystal grain size in this way, the number of crystal grains existing in one layer can be increased, and a decrease in reliability can be prevented.

[0012] However, the material to which the rare earth oxide is added cannot obtain a large dielectric constant, and is easily reduced during firing, and has a problem in characteristics.

[0013] Therefore, a main object of the present invention is to obtain a large dielectric constant despite the fact that it does not turn into a semiconductor even when fired in a reducing atmosphere and has a small crystal grain size. An object of the present invention is to provide a non-reducing dielectric ceramic composition that can reduce the size of a multilayer ceramic capacitor.

[0014]

Means for Solving the Problems] This invention has a main component Ba, becomes Sr, Ca, Ti, from the oxides of Zr and Nb, the following general _{formula, {(Ba 1-xy Sr} x Ca y )
O} is represented by _{m (Ti 1-op Zr o} Nb p) O 2 + p / 2,
x, y, o, p and m are 0.05 ≦ x ≦ 0.35,
0.005 ≦ y ≦ 0.12, 0 <o ≦ 0.20, 0.0
005 ≦ p ≦ 0.010, 1.002 ≦ m ≦ 1.04, and Mn,
Fe, Cr, Co, and Ni oxides were converted to MnO ₂ , Fe ₂
When represented by O ₃ , Cr ₂ O ₃ , CoO, and NiO, at least one of the oxides is 0.02 in total amount of each oxide.
2.0 is moles added, the main component as 100 parts by _{weight, BaO-SrO-Li 2 O} -SiO 2 oxide glass only contains 0.05 part by weight to 5.0 parts by weight of a main component,
A non-reducing dielectric ceramic composition having a crystal grain size of 3 μm or less .

[0015]

According to the present invention, it is possible to obtain a non-reducing dielectric ceramic composition which is not reduced even when fired in a reducing atmosphere and does not turn into a semiconductor. Therefore, if a porcelain multilayer capacitor is manufactured using this non-reducing dielectric porcelain composition, a base metal can be used as an electrode material, and
Since firing can be performed at a relatively low temperature of 250 ° C. or less, the cost of the multilayer ceramic capacitor can be reduced.

Further, the porcelain using the non-reducing dielectric porcelain composition has a dielectric constant of 11,000 or more, and despite having such a high dielectric constant, has crystal grains of 3 μm.
m or less. Therefore, when manufacturing a multilayer ceramic capacitor, even if the dielectric layer is thinned, the amount of crystal grains present in the layer does not decrease as in the conventional multilayer ceramic capacitor. Therefore, a highly reliable, small-sized, large-capacity multilayer ceramic capacitor can be obtained.

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

[0018]

EXAMPLE First, as a raw material, B having a purity of 99.8% or more was used.
aCO ₃ , SrCO ₃ , CaCO ₃ , TiO ₂ , ZrO
_{2, Nb 2 O 5, MnO} 2, Fe 2 O 3, Cr 2 O 3,
CoO and NiO were prepared. These raw materials are converted to ｛(Ba
_{1-xy Sr x Ca y)} O} m (Ti 1-op Zr o Nb p)
It was represented by the composition formula of O _{2 + p / 2} , and was blended so that x, y, m, o, and p had the ratios shown in Table 1, to obtain a blended raw material.
The raw materials were wet-mixed in a ball mill, pulverized, dried, and calcined in air at 1100 ° C. for 2 hours to obtain a calcined product. This calcined product is pulverized by a dry pulverizer,
A pulverized product having a particle size of 1 μm or less was obtained. BaO—SrO—Li ₂ O— having a particle size of 1 μm or less prepared in advance is added to this pulverized material.
An oxide glass mainly composed of SiO ₂ was weighed, pure water and a vinyl acetate binder were added, and mixed with a ball mill for 16 hours to obtain a mixture.

[0019]

[Table 1]

After this mixture is dried and granulated,
g / cm ² under pressure, diameter 10mm, thickness 0.5
mm discs were obtained. The obtained disk is placed in air for 50 minutes.
After heating to 0 ° C. to burn the organic binder, H ₂ —N ₂ — with an oxygen partial pressure of 3 × 10 ^{−8 to} 3 × 10 ⁻¹⁰ atm.
It was fired in a reducing atmosphere furnace made of air gas at the temperature shown in Table 2 for 2 hours to obtain a disc-shaped porcelain. The surface of the obtained porcelain was observed with a scanning electron microscope at a magnification of 1500 times, and the grain size was measured.

[0021]

[Table 2]

Then, a silver electrode was baked on the main surface of the obtained porcelain to obtain a measurement sample (capacitor). About the obtained sample, the dielectric constant (ε) at room temperature, the dielectric loss (tan)
δ) and the rate of change of the capacitance (C) with respect to the temperature change. The dielectric constant and the dielectric loss were measured at a temperature
C., 1 kHz, 1 V _rms . The rate of change of the capacitance with respect to the temperature change is the rate of change (−ΔC at −25 ° C. and 85 ° C. based on the capacitance at 20 ° C.)
C / C ₂₀ ) and a value (│ΔC / C) at which the rate of change is maximum as an absolute value in the range of −25 ° C. to 85 ° C.
₂₀ | _max ).

[0023] Further, the insulation resistance is measured by 50.
The insulation resistance value was measured after applying a direct current of 0 V for 2 minutes. The insulation resistance was measured at 25 ° C. and 85 ° C., and the logarithm (log ρ) of each volume resistivity was calculated. Table 2 shows the measurement results.

Next, the reasons for limiting each composition will be described.

[0025] _{{(Ba 1-xy Sr x} Ca y) O} m (Ti 1-op Zr
_o Nb _p ) O _{2 + p / 2} , as shown in Sample No. 1, when the strontium content x is less than 0.05, the dielectric constant is 11
If it is less than 000, the dielectric loss exceeds 2.0%, and the temperature change rate of the capacitance becomes large, which is not preferable. When the strontium content x exceeds 0.35 as in sample No. 17, the sinterability of the porcelain is poor, the dielectric constant is less than 11,000,
The temperature change rate of the capacitance does not satisfy the JIS standard F characteristic, which is not preferable.

Further, when the amount of calcium y is less than 0.005 as in sample No. 2, the sinterability of the porcelain is poor,
The dielectric loss exceeds 2.0%, and the insulation resistance is undesirably reduced. On the other hand, when the amount of calcium y exceeds 0.12 as in Sample No. 18, the sinterability deteriorates and the dielectric constant decreases, which is not preferable.

When the zirconium amount o is 0 as in Sample No. 3, the dielectric constant is less than 11,000, and the rate of change in capacitance with temperature is undesirably large. On the other hand, when the zirconium amount o exceeds 0.20 as in Sample No. 19, the sinterability decreases and the dielectric constant becomes less than 11,000, which is not preferable.

As shown in Sample No. 4, the niobium amount p is 0.0
If it is less than 005, the dielectric constant will be less than 11,000, and the crystal grain size will be larger than 3 μm. On the other hand, as in Sample No. 20, the niobium amount p is 0.0
If it exceeds 1, when sintered in a reducing atmosphere, the porcelain is reduced and turned into a semiconductor, resulting in a significant decrease in insulation resistance, which is not preferable.

As shown in sample No. 5, ｛(Ba _1-xy Sr
_{x Ca y) O} m (} Ti 1-op Zr o Nb p) O 2 + p / 2
If the molar ratio m is less than 1.002, the porcelain is reduced when fired in a reducing atmosphere and turned into a semiconductor, resulting in a decrease in insulation resistance. On the other hand, when the molar ratio m exceeds 1.04 as in Sample No. 21, the sinterability becomes extremely poor, which is not preferable.

Further, as shown in sample No. 6, MnO ₂ , Fe ₂ O ₃ , Cr ₂ O ₃ , C
When the addition amount of oO and NiO is less than 0.02 mol, 85
It is not preferable because the insulation resistance at a temperature of not less than ℃ is reduced, and the reliability of long-time use at high temperatures is lowered. On the other hand, when the amount of these additives exceeds 2.0 moles as in sample No. 22, the dielectric loss increases beyond 2.0%, and at the same time the insulation resistance deteriorates, which is not preferable.

Further, as shown in Sample No. 7, the additive (B)
When the addition amount of the oxide glass containing BaO—SrO—Li ₂ O—SiO ₂ as a main component is less than 0.05 part by weight, the sinterability deteriorates, and the dielectric loss exceeds 2.0%. Not preferred. On the other hand, as shown in Sample No. 23, BaO-S
If the amount of the oxide glass containing rO—Li ₂ O—SiO ₂ as a main component exceeds 5.0 parts by weight, the dielectric constant becomes 1100.
This is not preferable because the crystal grain size is reduced to less than 0 and the crystal grain size is larger than 3 μm.

On the other hand, when the non-reducing dielectric ceramic composition of the present invention is used, the dielectric constant is as high as 11,000 or more, the dielectric loss is 2.0% or less, and the rate of change of capacitance with temperature is It is possible to obtain a dielectric porcelain satisfying the F characteristic standard defined in the JIS standard in the range of -25 ° C to 85 ° C. Furthermore, in this dielectric porcelain, the insulation resistance at 25 ° C. and 85 ° C. is 1 when expressed in logarithm of volume resistivity.
It shows a high value of 2 or more. Further, the non-reducing dielectric ceramic composition of the present invention can be sintered at a relatively low temperature of 1250 ° C. or less, and has a small particle size of 3 μm or less.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-59-138003 (JP, A) JP-A-61-248304 (JP, A) JP-A-2-239152 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01B 3/12 303 C04B 35/46 H01G 4/12 358

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein the main components are Ba, Sr, Ca, Ti,
It made the oxides of Zr and Nb, represented by the following general formula _{{(Ba 1-xy Sr x} Ca y) O} m (Ti 1-op Zr o Nb p) O 2 + p / 2, x, When y, o, p and m are 0.05 ≦ x ≦ 0.35 0.005 ≦ y ≦ 0.120 0 <o ≦ 0.20 0.0005 ≦ p ≦ 0.010 1.002 ≦ m ≦ 1 .04, and 100 mol of the main component, M
The oxides of n, Fe, Cr, Co, and Ni were converted to MnO ₂ , F
When expressed as e ₂ O ₃ , Cr ₂ O ₃ , CoO, NiO,
At least one of the oxides has a total amount of 0.
02 to 2.0 is moles added, the 100 parts by weight of the main _{component, BaO-SrO-Li 2 O} -SiO 2 as main components oxide glass, and 0.05 part by weight to 5.0 parts by weight including
A non-reducing dielectric ceramic composition having a crystal grain size of 3 μm or less .