JP2000143337A - Dielectric ceramic composition and thick film capacitor produced by using the composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric ceramic composition having high dielectric constant and low dielectric loss and producible in a short time by baking at a temperature as low as <=900 deg.C. SOLUTION: The objective ceramic composition is composed mainly of a component expressed by compositional formula of xPb(Mg1/3Nb2/3)O3.yPb(Fe1/2 Nb1/2)O3.zPbTiO3 ((x), (y) and (z) are each a molar ratio; x+y+z=1; 0.80<=x<=0.92; 0.02<=y<=0.19; 0.005<=z<=0.06). The composition further contains 0.5-5.0 mol% of MgO based on the main component and 3-10 wt.% of a flux expressed by the compositional formula of a (PbO).b(ZnO).c (BiO3/2)1-n(GeO2)n} ((a), (b) and (c) are each a molar ratio; a+b+c=1; 0.30<=a<=0.80; 0.15<=c<=0.50; 0<n<=0.75) based on the sum of the main component and MgO.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition having a high dielectric constant used for electronic parts. Further, the present invention relates to a thick film capacitor using the composition.

[0002]

2. Description of the Related Art In electronic equipment for which miniaturization and high reliability are desired, a hybrid IC having a high mounting density is being promoted, and a demand for a thick film capacitor is increasing instead of a conventional multilayer chip capacitor. I have. Also, the demand for CR chip electronic components combining a thick film resistor and a thick film capacitor is increasing. Thick film capacitors are made by forming a dielectric thick film on a lower electrode on a ceramic substrate and forming an upper electrode thereon. If a dielectric material for a thick film capacitor used for a hybrid IC or a CR chip can be fired at a temperature of about 850 ° C. for firing a resistor paste for a thick film resistor in a short time, the thick film resistor is manufactured. It can be produced with high efficiency using a belt furnace.

However, in order to sinter barium titanate (BaTiO ₃ ) or lead relaxer-based dielectric materials used in multilayer chip capacitors, a 100
It must be kept at a high firing temperature of 0 ° C. or more for several hours, and when this dielectric material is fired at a low temperature and in a short time, the dielectric material becomes unfired (unsintered), and in any case, a thick film Not suitable for dielectric material for capacitors. Conventionally, as a material suitable for a dielectric material for a thick film capacitor, PbTiO ₃
-Pb (Mg _1/3 Nb _2/3 ) O ₃ -PbZrO ₃ system with MnO
₂ discloses a dielectric porcelain composition (JP-A-5-314816). This dielectric porcelain composition does not impair the dielectric constant, is characterized in that it can be fired in air, a neutral atmosphere, or a reducing atmosphere at 800 to 1000 ° C. for a short time and has a small dielectric loss.

[0004]

However, the above-mentioned Japanese Patent Application Laid-Open
The dielectric porcelain composition disclosed in -314816 is
As is clear from the example, the dielectric constant is about 200 to 465, not so high, and the dielectric loss is 0.5 to 0.9.
About 5%, not so small. Therefore, a dielectric porcelain composition having more excellent dielectric properties has been desired. An object of the present invention is to provide a dielectric material having a large dielectric constant and a small dielectric loss,
An object of the present invention is to provide a dielectric porcelain composition that can be fired at a low temperature of not more than ℃ for a short time. Another object of the present invention is to provide a thick film capacitor using the dielectric ceramic composition.

[0005]

The invention according to claim 1 is
Pb (Mg _1/3 Nb _2/3 ) O ₃ , Pb (Fe _1/2 Nb _1/2 )
A main component of a composition composed of three components of O ₃ and PbTiO ₃ and represented by the following formula (1), MgO, PbO, ZnO,
Bi ₂ O ₃ and Bi ₂ O ₃ consists of four components of GeO ₂ Bi
A dielectric porcelain composition containing a flux represented by the following formula (2) when converted to O _3/2 , comprising 0.5 to 5.0 mol% of MgO based on the main component, and A dielectric porcelain composition characterized by containing 3 to 10% by weight based on the total of the main component and MgO. xPb (Mg _1/3 Nb _2/3 ) O ₃ .yPb (Fe _1/2 Nb _1/2 ) O ₃ .zPbTiO ₃ (1) (where x, y and z are x + y + z = 1, 0.8
0 ≦ x ≦ 0.92, 0.02 ≦ y ≦ 0.19, 0.00
5 ≦ z ≦ 0.06) a (PbO) · b (ZnO) · c {(BiO _3/2 ) _1-n (GeO ₂ ) _n } (2) (where a, b, and c are A + b + c = 1, 0.3 in molar ratio
0 ≦ a ≦ 0.80, 0.15 ≦ c ≦ 0.50, 0 <n ≦
0.75) By using a composition in which a specific ratio of MgO and a specific composition of flux are added to the above-mentioned main component of the specific composition, low-temperature firing becomes possible, and a ceramic composition having a high dielectric constant and a small dielectric loss. Can be realized.

According to a second aspect of the present invention, as shown in FIG. 2, a lower electrode 12 provided on a ceramic substrate 11 and a dielectric ceramic composition according to the first aspect provided on the lower electrode 12 are provided. This is a thick film capacitor including a dielectric layer 13 and an upper electrode 14 provided on the dielectric layer 13.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The main component composition of the dielectric ceramic composition of the present invention represented by the above formula (1) is 3 as shown in FIG.
In the component system composition diagram, the components are within the range of hatched lines surrounded by points A to E. That is, A, B,
The composition (u, v, w) of each point of C, D and E is Pb (Mg
_1/3 Nb _2/3 ) O ₃ in umol%, Pb (Fe _1/2 Nb _1/2 )
When O ₃ is v mol% and PbTiO ₃ is w mol%, A
(80, 14, 6), B (92, 2, 6), C (92,
7,0.5), D (81,19,0.5) and E (8
0, 19, 1).

XPb (Mg _1/3 Nb) of the formula (1) of the main component
_2/3 ) O ₃ .yPb (Fe _1/2 Nb _1/2 ) O ₃ .zPbTiO ₃
In x, when x is less than 0.80, the dielectric loss increases, and when x exceeds 0.92, the firing temperature increases. Therefore, the range of x is determined to be 0.80 ≦ x ≦ 0.92. Preferably, 0.83 ≦ x ≦ 0.91. Also y
Is less than 0.02, the firing temperature becomes high, and
When it exceeds 19, the specific resistance becomes small. Therefore, the range of y is determined to be 0.02 ≦ y ≦ 0.19. Preferably, 0.07 ≦ y ≦ 0.16. Further, when z is less than 0.005, the dielectric constant decreases, and when z exceeds 0.06, the dielectric loss increases. Therefore, the range of z is 0.00
It is determined that 5 ≦ z ≦ 0.06. Preferably 0.005
≤ x ≤ 0.04. MgO to the main component of the present invention
Is contained in an amount of 0.5 to 5.0 mol%. If MgO is less than 0.5 mol%, it hardly contributes to the improvement of the dielectric constant, and if it exceeds 5.0 mol%, the dielectric constant becomes low. Preferably it is 1.0 to 3.0 mol%.

With respect to the total of the main component of the present invention and MgO,
PbO, ZnO, Bi ₂ O ₃ and flux consisting of four components of GeO ₂ (flux) from 3 to 10 wt%, preferably 4
-7% by weight. If the added amount of the flux is less than 3% by weight, it is difficult to bake at a low temperature for a short time, and if it is more than 10% by weight, the dielectric constant is disadvantageously lowered. The flux a (PbO) · b (Zn) in the above equation (2)
O) · c {(BiO _3/2 ) _1-n (GeO ₂ ) _n }
If a is less than 0.30, it becomes difficult to perform baking at a low temperature for a short time, and if it exceeds 0.80, the dielectric loss increases. c
If it is less than 0.15, it will be difficult to fire at a low temperature for a short time, and if it exceeds 0.50, the crystal grains will be large. And n
Is 0, the GeO ₂ component is not contained, and low-temperature baking becomes more difficult. If it exceeds 0.75, the dielectric constant becomes low. b is arbitrary in the range of a + b + c = 1, which is determined from the range of a and the range of c.

In order to manufacture such a derivative ceramic composition of the present invention, for example, lead monoxide (PbO), magnesium oxide (MgO), niobium pentoxide (Nb ₂ O ₅ ), ferric oxide (Fe ₂₎ Powders such as O ₃ ), titanium oxide (TiO ₂ ), or a composite oxide thereof are weighed so as to have a predetermined ratio, and pure water is added thereto and sufficiently mixed by a wet ball mill or the like. The mixture is then dried and, if necessary,
It is calcined for several hours in the range of 00 to 900 ° C. The obtained calcined product is pulverized by a wet ball mill or the like, and the calcined powder is dried. On the other hand, lead monoxide (PbO), zinc oxide (ZnO),
Boron oxide (B ₂ O ₃ ) and germanium oxide (Ge
O ₂ ) is weighed so as to have a predetermined ratio, and sufficiently mixed by a wet ball mill or the like to prepare a flux. A predetermined amount of the flux is added to the calcined powder and mixed.

When a thick film capacitor is made from this dielectric material, the mixture to which the flux has been added is dried and pulverized to produce a dielectric powder. An organic vehicle is added to the dielectric powder and kneaded to prepare a dielectric paste. FIG.
As shown in FIG. 5, an electrode paste containing a metal powder of any of Cu, Ag, and Ag-Pd, a glass powder, and an organic vehicle is screen-printed and dried on an insulating ceramic substrate 11 such as an alumina substrate. And lower electrode 12
To form The dielectric paste is screen-printed on the lower electrode 12, dried and fired to form the dielectric layer 1.
Form 3 Next, on this dielectric layer 13, Cu, A
g, an electrode paste containing a metal powder of Ag-Pd, a glass powder, and an organic vehicle is screen-printed, dried, and fired to form the lower electrode 14. Note that a ceramic capacitor can be made from this dielectric material. When a disc-shaped or cylindrical ceramic capacitor is made from this dielectric material, an organic binder containing polyvinyl butyral (PVB) as a main component is added to the mixture to which the above flux is added, and the mixture is granulated. After press-forming into a shape or a cylinder, baking is performed. When a multilayer ceramic capacitor is made from this dielectric material, a ceramic green sheet is prepared by adding an organic binder containing polyvinyl butyral as a main component to the mixture to which the above flux has been added, and the green sheet and the electrodes are alternately formed. After laminating a large number of pieces, baking is performed. Regardless of the type of the capacitor, the firing of the dielectric ceramic composition of the present invention is performed in a temperature range of 700 to 900 ° C. for 5 to 15 minutes.

[0012]

Next, examples of the present invention will be described together with comparative examples. In this example, a disk-shaped ceramic capacitor was manufactured instead of a thick-film capacitor in order to easily examine electrical characteristics. PbO, MgNb ₂ O ₆ , F
The main components of eNbO ₄ and TiO ₂ and MgO were used, weighed so as to have the compounding ratio shown in Table 1, and wet-mixed with pure water in a ball mill for 23 hours. Next, the mixture was dehydrated and dried, and then calcined at 750 ° C. for 2 hours.
The calcined product was again wet-mixed with pure water by a ball mill for 23 hours, then dehydrated and dried. Next, PbO, Bi
₂ O ₃ , ZnO and GeO ₂ were weighed so as to have the compounding ratios shown in Table 1 and thoroughly mixed using a mortar.
Calcination was performed at ℃ for 4 hours. The calcined product was sufficiently pulverized again using a mortar to obtain a flux.

The above flux was added to a dried product containing the above main component and MgO at a ratio shown in Table 1 and mixed. Ethanol as a solvent was added to this mixture, and the mixture was mixed by a ball mill for 23 hours, and then dried and powdered. Polyvinyl butyral as an organic binder was added to the dried powder, dried at 120 ° C. for 1 hour, and then molded under pressure at a pressure of 2 ton / cm ² to produce a disk-shaped molded body. This molded body is placed in the atmosphere 10
The temperature was raised at a rate of 0 ° C./hour, and calcined at a temperature range of about 700 to 900 ° C. for 10 minutes. Ag paste was applied to the upper and lower surfaces of the disc-shaped porcelain body having a diameter of 12 mm and a thickness of 0.8 mm obtained in this way, and
By baking at 50 ° C., an upper electrode and a lower electrode were formed to obtain a disc-shaped ceramic capacitor. The electrical characteristics of this ceramic capacitor were examined. Table 2 shows the results. The dielectric constant and the dielectric loss (tan δ) of the electric characteristics are YH
The measurement was performed using a P digital LCR meter model 4274A at a measurement frequency of 1 kHz, a measurement voltage of 1.0 Vrms, and a temperature of 25 ° C. The density of the porcelain body is also shown.

[0014]

[Table 1]

In Table 1, * 1 indicates the amount added to the main component, and * 2 indicates the amount added to the total of the main component and MgO.

[0016]

[Table 2]

As is clear from Tables 1 and 2, the composition ratio of the main component, the added amount of MgO, the composition ratio of the flux and the added amount of the flux were 8% in Examples 1 to 17 within the scope of the present invention.
It can be seen that the density of each of the dielectric ceramic compositions fired at a low temperature of 50 to 900 ° C. is large. Further, it can be seen that the ceramic capacitors obtained from these dielectric ceramic compositions have a large dielectric constant (relative dielectric constant) and a small dielectric loss (tan δ). On the other hand, in Comparative Examples 1 to 14 in which the main component composition ratio, the added amount of MgO, the flux composition ratio and the added amount of flux were out of the range of the present invention, better results were obtained as compared with Examples 1 to 17. Did not.

[0018]

As described above, the dielectric ceramic composition of the present invention has a large dielectric constant and a small dielectric loss, and is therefore extremely useful as a dielectric material for a ceramic capacitor. Further, the dielectric ceramic composition of the present invention is fired at a low temperature and in a short time, and has a high density, so that it is suitable for a thick film capacitor used for a hybrid IC. For this reason,
Since a thick film capacitor can be manufactured in a belt furnace manufacturing line for manufacturing a thick film resistor of a hybrid IC circuit, a thick film capacitor can be produced with high efficiency and with a thick film resistor.

[Brief description of the drawings]

FIG. 1 shows the composition range of a dielectric ceramic composition of the present invention.
b (Mg _1/3 Nb _2/3 ) O ₃ .Pb (Fe _1/2 Nb _1/2 )
O ₃ · PbTiO ₃ ternary composition diagram.

FIG. 2 (a) is a top view of the thick film capacitor of the present invention. FIG. 2B is a sectional view taken along line AA of FIG.

[Explanation of symbols]

 Reference Signs List 11 ceramic substrate 12 lower electrode 13 dielectric layer 14 upper electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01G 4/12 415 H01G 4/06 102 F term (Reference) 4G031 AA03 AA10 AA11 AA21 AA32 BA09 5E001 AB03 AC09 AC10 AE00 AE03 AE04 AH01 AH09 AJ02 AZ00 5E082 AB03 BC30 BC40 EE04 EE23 EE26 EE35 FG22 FG26 FG27 FG46 FG54 KK01 LL02 MM22 MM24 PP03 5G303 AA01 AB05 AB15 BA03 CA01 CB13 CB17 CB21 CB25 CB25 CC

Claims (2)

[Claims] 1. Pb (Mg _1/3 Nb _2/3 ) O ₃ , Pb (F
e _1/2 Nb _1/2 ) O ₃ and PbTiO ₃ , a main component of a composition represented by the following formula (1), MgO, P
It is composed of four components of bO, ZnO, Bi ₂ O ₃ and GeO ₂ , and converts Bi ₂ O ₃ into BiO _3/2 to obtain the following (2)
A dielectric ceramic composition comprising: a flux represented by the following formula: wherein MgO is contained in an amount of 0.5 to 5.0 mol% with respect to the main component, and the flux is contained with respect to a total of the main component and the MgO. A dielectric porcelain composition comprising 3 to 10% by weight. xPb (Mg _1/3 Nb _2/3 ) O ₃ .yPb (Fe _1/2 Nb _1/2 ) O ₃ .zPbTiO ₃ (1) (where x, y and z are x + y + z = 1, 0.8
0 ≦ x ≦ 0.92, 0.02 ≦ y ≦ 0.19, 0.00
5 ≦ z ≦ 0.06) a (PbO) · b (ZnO) · c {(BiO _3/2 ) _1-n (GeO ₂ ) _n } (2) (where a, b, and c are A + b + c = 1, 0.3 in molar ratio
0 ≦ a ≦ 0.80, 0.15 ≦ c ≦ 0.50, 0 <n ≦
0.75) 2. A lower electrode (12) provided on a ceramic substrate (11), and a lower electrode (12) provided on the lower electrode (12).
A thick film capacitor comprising: a dielectric layer (13) made of the dielectric ceramic composition described above; and an upper electrode (14) provided on the dielectric layer (13).