JP3389947B2 - Dielectric ceramic composition and thick film capacitor using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In electronic devices that are required to be compact and highly reliable, hybrid ICs with a high packaging density are being promoted, and there is an increasing demand for thick film capacitors in place of conventional multilayer chip capacitors. There is. Demand for CR chip electronic components that combine thick film resistors and thick film capacitors is also increasing. A thick film capacitor is manufactured by forming a thick film of a dielectric material on a lower electrode on a ceramic substrate and then forming an upper electrode on the thick film. If the dielectric material for the thick film capacitor used for the hybrid IC or the CR chip can be fired at the temperature of about 850 ° C. for firing the resistance paste for the thick film resistor in a short time, this thick film resistor is manufactured. It can be produced with high efficiency using a belt furnace.

However, in order to fire the barium titanate (BaTiO ₃ ) or lead relaxor dielectric materials used in multilayer chip capacitors, it is necessary to use 100
It must be held at a high firing temperature of 0 ° C. or higher for several hours, and if this dielectric material is fired at a low temperature for a short time, the dielectric material becomes unfired (unsintered), and both are thick films. Not suitable as a dielectric material for capacitors. Conventionally, PbTiO _{3 has been} used as a material suitable for a dielectric material for thick film capacitors.
-Pb MnO in _{(Mg 1/3 Nb 2/3) O 3} -PbZrO 3 series
₂ dielectric ceramic composition obtained by adding a has been disclosed (JP-A-5-314816). This dielectric ceramic composition is characterized in that it does not impair the permittivity, can be fired in the 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 Unexamined Patent Application Publication No.
The dielectric ceramic composition disclosed in Japanese Patent Publication No. 314816-
As is clear from the example, the dielectric constant is about 200 to 465, which is not so high, and the dielectric loss is 0.5 to 0.9.
It is about 5%, which is not so small. Therefore, a dielectric ceramic composition having further excellent dielectric properties has been desired. It is an object of the present invention that the dielectric constant is large and the dielectric loss is small.
An object of the present invention is to provide a dielectric ceramic composition that can be fired at a low temperature of ℃ or less for a short time. Another object of the present invention is to provide a thick film capacitor using this 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 )
The main component of the composition represented by the following formula (1) consisting of three components of O ₃ and PbTiO ₃ , MgO, PbO, ZnO,
Bi ₂ O ₃ and GeO ₂ composed of 4 components Bi ₂ O ₃
A dielectric ceramic composition containing a flux represented by the following (2) when converted to O _3/2 , containing 0.5 to 5.0 mol% of MgO with respect to the main component and containing the flux. The dielectric ceramic composition is characterized by containing 3 to 10% by weight with respect to 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 molar ratios 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 Molar ratio a + b + c = 1, 0.3
0 ≦ a ≦ 0.80, 0.15 ≦ c ≦ 0.50, 0 <n ≦
0.75) A porcelain composition with a high dielectric constant and a small dielectric loss that enables low temperature firing by adding MgO in a specific ratio and a flux of a specific composition to the main component of the specific composition described above. Can be realized.

The invention according to claim 2 relates to a lower electrode 12 provided on a ceramic substrate 11 as shown in FIG. 2, and a dielectric ceramic composition according to claim 1 provided on the lower electrode 12. A thick film capacitor having 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 represented by the above formula (1) of the dielectric ceramic composition of the present invention is 3 as shown in FIG.
In the composition chart of the component system, it is within the range of the diagonal line surrounded by the points A to E. That is, A, B, in FIG.
The composition (u, v, w) at each point of C, D and E is Pb (Mg
_1/3 Nb _2/3 ) O ₃ in u mol%, 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, when x is less than 0.80, the dielectric loss becomes large, and when x exceeds 0.92, the firing temperature becomes high. Therefore, the range of x is determined to be 0.80 ≦ x ≦ 0.92. Preferably 0.83 ≦ x ≦ 0.91. See y
Is less than 0.02, the firing temperature is high, and y is 0.
If it exceeds 19, the specific resistance decreases. 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 becomes small, and when z exceeds 0.06, the dielectric loss becomes large. Therefore, the range of z is 0.00
It is determined that 5 ≦ z ≦ 0.06. Preferably 0.005
≦ x ≦ 0.04. MgO for the main component of the present invention
Is contained in an amount of 0.5 to 5.0 mol%. When MgO is less than 0.5 mol%, it hardly contributes to the improvement of the dielectric constant, and when it exceeds 5.0 mol%, the dielectric constant becomes low. It is preferably 1.0 to 3.0 mol%.

With respect to the total of the main component of the present invention and MgO,
The flux (fluxing agent) consisting of four components of PbO, ZnO, Bi ₂ O ₃ and GeO ₂ is 3 to 10% by weight, preferably 4
~ 7% by weight. If the added amount of the flux is less than 3% by weight, it is difficult to perform firing at a low temperature for a short time, and if it exceeds 10% by weight, the dielectric constant lowers. In addition, the flux of a (PbO) · b (Zn in the above formula (2) is
In _{O) · c {(BiO 3/2} ) 1-n (GeO 2) n},
When a is less than 0.30, it becomes difficult to perform firing at a low temperature for a short time, and when it exceeds 0.80, dielectric loss increases. c
Is less than 0.15, it becomes difficult to fire at low temperature for a short time, and if it exceeds 0.50, the crystal grains become large. Also n
Is 0, the GeO ₂ component is not contained, and low temperature firing becomes more difficult, and when it exceeds 0.75, the dielectric constant becomes low. Regarding b, a + b + c = 1, and it is optional in a range determined from the above range of a and the range of c.

To produce 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 of O ₃ ), titanium oxide (TiO ₂ ), or a complex oxide of these are weighed so as to have a predetermined ratio, pure water is added, and sufficiently mixed by a wet ball mill or the like. The mixture is then dried and, if necessary, 7
Calcination is performed in the range of 00 to 900 ° C for several hours. 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 this flux is added to the calcined powder and mixed.

When making a thick film capacitor from this dielectric material, the above-mentioned flux-added mixture is dried and pulverized to make a dielectric powder. An organic vehicle is added to this dielectric powder and kneaded to prepare a dielectric paste. Figure 2
As shown in FIG. 3, an electrode paste containing a metal powder of Cu, Ag, or Ag—Pd, a glass powder, and an organic vehicle is screen-printed on an insulating ceramic substrate 11 such as an alumina substrate, dried, and then baked. Then 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.
3 is formed. Next, Cu, A on the dielectric layer 13
The lower electrode 14 is formed by screen-printing an electrode paste containing a metal powder of g or Ag-Pd, a glass powder, and an organic vehicle, drying the paste, and then firing the paste. It is also possible to make a ceramic capacitor from this dielectric material. When a disk-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 above flux-added mixture, and the mixture is granulated. After press-forming into a cylindrical or cylindrical shape, it is fired. When making a monolithic ceramic capacitor from this dielectric material, an organic binder whose main component is polyvinyl butyral is added to the above-mentioned flux-added mixture to make a ceramic green sheet, and the green sheet and the electrodes are alternated. After laminating a large number of sheets, they are fired. The dielectric porcelain composition of the present invention is fired in a temperature range of 700 to 900 ° C. for 5 to 15 minutes in making a capacitor of any form.

[0012]

EXAMPLES 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 the thick film capacitor in order to easily investigate the electrical characteristics. PbO, MgNb ₂ O ₆ , F as starting materials
The main components of eNbO ₄ and TiO ₂ and MgO were used, these were 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, this mixture was dehydrated, dried, and then calcined at 750 ° C. for 2 hours.
The calcined product was again wet mixed with pure water in a ball mill for 23 hours, dehydrated and dried. Next, PbO and Bi
₂ O ₃ , ZnO and GeO ₂ were weighed so that the compounding ratio shown in Table 1 was obtained, thoroughly mixed with a mortar, and then 600
It was calcined at ℃ for 4 hours. This calcined product was thoroughly crushed again using a mortar to obtain a flux.

The above flux was added to the dried product containing the above main component and MgO in the 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, then dried and pulverized. Polyvinyl butyral as an organic binder was added to this dry powder, and the mixture was dried at 120 ° C. for 1 hour and pressure-molded at a pressure of 2 ton / cm ² to produce a disk-shaped molded body. This molded body was placed in the atmosphere for 10
The temperature was raised at a rate of 0 ° C./hour, and the temperature was kept at about 700 to 900 ° C. for 10 minutes for firing. The Ag paste was applied to each of the upper surface and the lower surface of the disk-shaped porcelain body having a diameter of 12 mm and a thickness of 0.8 mm thus obtained.
An upper electrode and a lower electrode were formed by baking at 50 ° C. to obtain a disk-shaped ceramic capacitor. The electrical characteristics of this ceramic capacitor were investigated. The results are shown in Table 2. Note that the dielectric constant and dielectric loss (tan δ) of the electrical characteristics are YH
Using a P digital LCR meter model 4274A, measurement was performed 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, in Examples 1 to 17 in which the main component composition ratio, the amount of MgO added, the flux composition ratio and the amount of flux added were within the scope of the present invention, 8
It can be seen that the density of the dielectric ceramic composition fired at a low temperature of 50 to 900 ° C. is high. 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 amount of MgO added, the flux composition ratio, and the amount of flux added were outside the scope of the present invention, good results were obtained as compared with Examples 1 to 17. There wasn't.

[0018]

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

[Brief description of drawings]

FIG. 1 is a P showing a 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. 2A is a top view of the thick film capacitor of the present invention. (B) The sectional view on the AA line of FIG.

[Explanation of symbols]

11 Ceramic substrate 12 Lower electrode 13 Dielectric layer 14 Upper electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-8-31233 (JP, A) JP-A-6-263517 (JP, A) JP-A-5-330909 (JP, A) JP-A-2- 263761 (JP, A) JP 60-200513 (JP, A) JP 5-190376 (JP, A) JP 6-191941 (JP, A) JP 54-110500 (JP, A) JP-A-8-259324 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04B 35/42-35/50 H01B 3/12 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. Pb (Mg _1/3 Nb _2/3 ) O ₃ , Pb (F
e _1/2 Nb _1/2 ) O ₃ and PbTiO _{3 which} are the three main components of the composition represented by the following formula (1), MgO, and P
It consists of four components of bO, ZnO, Bi ₂ O ₃ and GeO ₂ , and by converting Bi ₂ O ₃ to BiO _3/2 , the following (2)
A dielectric porcelain composition including a flux represented by the following: 0.5 to 5.0 mol% of MgO with respect to the main component, and the flux with respect to the total of the main component and the MgO. A dielectric ceramic 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 molar ratios 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 Molar ratio a + b + c = 1, 0.3
0 ≦ a ≦ 0.80, 0.15 ≦ c ≦ 0.50, 0 <n ≦
0.75) 2. The lower electrode (12) provided on a ceramic substrate (11), and the 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).