JP2906530B2 - Dielectric porcelain composition and capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a dielectric ceramic composition having a high resistivity, which can be fired in a short time in a neutral atmosphere or a reducing atmosphere at a firing temperature of 800 to 1000 ° C. It relates to an object and a capacitor.

2. Description of the Related Art Barium titanate-based materials have been used as high dielectric constant materials for ceramic capacitors, which are being miniaturized and increased in capacity. However, firing this material requires a high temperature of about 1300 ° C in the air and a firing temperature.Therefore, when manufacturing a multilayer ceramic capacitor, an expensive noble metal such as platinum or palladium is used as an electrode material. It is indispensable to use the material, and in particular, the internal electrode material has increased the raw material cost with the increase in capacity.

On the other hand, in recent years, barium titanate-based materials have been given reduction resistance, and inexpensive base metals have been used as electrode materials and fired in an atmosphere with a low oxygen partial pressure, or lead-based dielectric materials and inexpensive silver have been used. The cost of the multilayer ceramic capacitor is reduced by a method of firing at a low temperature of about 1000 ° C. using a silver-palladium alloy electrode material as a main component.

On the other hand, in electronic devices for which miniaturization and high reliability are desired, hybrid ICs having a high mounting density are being promoted, and demand for thick film capacitors in place of conventional chip capacitors is increasing. To manufacture this thick film capacitor, a dielectric that can be fired at a low temperature for a short time is required, and a lead-based dielectric is mainly used as a material for this purpose. Accordingly, lead-based dielectrics have been actively developed as a material capable of being fired at a low temperature, which can be used for both increasing the capacity of a multilayer ceramic capacitor and increasing the thickness of a capacitor.

Problems to be Solved by the Invention Now, (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) O _{3 + a} , (Pb _1.00 Ba _a ) TiO _{3 + a} , (Pb _1.00 Ba _a ) (Ni _{1 / 2} W _1/2 ) O
_{The 3 + a-} based dielectric composition is _a dielectric ceramic composition that is fired in a low oxygen atmosphere at 1100 ° C. or lower, as is known from Japanese Patent Application Laid-Open No. 62-123061. In order to obtain a high and sufficiently dense fired body, it is necessary to hold at a firing temperature for several hours. On the other hand, when manufacturing a thick film capacitor for a hybrid IC, low-temperature and short-time firing is indispensable, and under such conditions, the dielectric material is not fired, so that there is a problem that desired characteristics cannot be obtained. Was.

In view of this problem, in the present invention, (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) O _{3 + a} , (Pb _1.00 Ba _a ) TiO _{3 + a} , (Pb _1.00 Ba _a ) (Ni _{1 / 2} W _1/2) O
Dielectric ceramic composition that can be fired at 800-1000 ° C in a neutral atmosphere or reducing atmosphere for a short time without impairing the high dielectric constant of the _{3 + a-} based solid volume, and a ceramic capacitor using the same Another object is to provide a thick film capacitor.

Means for Solving the Problems To solve the above problems, the dielectric porcelain composition of the present invention comprises (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) _x Ti _y (Ni _1/2 W _1/2 ) In the porcelain composition represented by _z O _{3 + a} (where x + y + z = 1), it is in the range of 0.001 ≦ a ≦ 0.250, and for the value of a in this range, (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) O _{3 + a} , (Pb _1.00 Ba _a ) TiO _{3 + a} , (Pb _1.00 Ba _a ) (Ni _1/2 W _1/2 ) O
_In the triangular coordinates with _{3 + a} as the apex, the composition of the main component dielectric porcelain composition consisting of a pentagonal region with the vertices of the compositions A, B, C, D, and E represented by numerical values in [] below PbO 1.0 against calcined powder
~ 25.0 mol%, and 1.0 ~ 15.0 mol% of NiO or WO
₃ is added in an amount of 1.0 to 15.0 mol%.

Action That is, in the composition of the present invention, (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) O _{3 + a} − (Pb _1.00 Ba _a ) TiO ₃₊ having a perovskite structure _a − (Pb _1.00 Ba _a ) (Ni _1/2 W _1/2 ) O
By adding PbO, NiO or WO ₃ to the _{3 + a-} based calcined powder, a liquid phase is generated at a low temperature by utilizing the eutectic composition of PbO and NiO or WO ₃ , and these additives are used. Simultaneous solid solution at both A and B sites facilitates diffusion into the dielectric, suppresses the formation of grain boundary layers due to additives, prevents a decrease in the dielectric constant, and is used in a neutral atmosphere or a reducing atmosphere. It is possible to obtain a large-capacity ceramic capacitor or a thick-film capacitor having a high firing rate and a high density at a low firing temperature of 1000 ° C. or less.

Examples Hereinafter, examples of the present invention will be described.

<Example 1> First, as a starting material, PbO, BaCO ₃ ,
MgO, Nb ₂ O ₅ , TiO ₂ , NiO, WO ₃ were used. After correcting the purity, a predetermined amount was weighed, pure water was added, and the mixture was mixed with a ball made of agate using a ball mill for 17 hours. This is suction-filtered to separate most of the water, dried and then charged and crushed with a raikai machine.
It was molded into a cylindrical shape having a height of about 50 mm and a molding pressure of 500 kg / cm ² . Put this in an aluminum crucible, cover with the same quality, 750
Calcination was performed at ~ 1000 ° C for 2 hours. Next, the calcined product was roughly crushed in an alumina mortar, further crushed in a ball mill for 17 hours, suction-filtered, and dried. The above calcination, pulverization, and drying were repeated several times. The powder was analyzed by X-ray analysis to confirm that it was a perovskite phase.

PbO and NiO or WO ₃
Was added and mixed in a chaser mill, a polyvinyl alcohol 6 wt% aqueous solution was added 6 wt% of the powder weight, it was granulated through a 32 mesh sieve, diameter 13mm at a molding pressure of 500 kg / cm ^2, a disc of height of about 5mm It was molded into a shape. Then, after holding the molded product at 600 ° C. in the air for 1 hour to remove the binder, put it in a magnesia porcelain container, cover it with the same quality, and use the atmosphere belt furnace in a neutral atmosphere or in a reducing atmosphere. Raise the temperature to 2400 ° C / hrs, hold at the maximum temperature for 10 minutes,
The temperature dropped at 00 ° C / hrs.

The fired product obtained as described above was processed into a disk shape having a thickness of 1 mm, and Cr-Ag was deposited on both surfaces as electrodes, and the dielectric constant, t
anδ was measured under an electric field of 1 KHz and 1 V / mm. In addition, the resistivity was determined as a value of one minute after applying a voltage of 30 V to the sample.

Table 1 below shows the material composition of the present invention and the dielectric properties and resistivity of the fired product in a neutral atmosphere of nitrogen as the firing atmosphere. The dielectric properties and resistivity of the fired product when the firing atmosphere was a nitrogen-hydrogen mixed gas having an oxygen partial pressure of 10 ^-8 atm or more are shown in Table 2 below.

As shown in the above <Table 1> and <Table 2>, the fired product according to the material composition of the present invention has a high dielectric constant despite firing at 800 to 1000 ° C. for a short time and firing in various atmospheres. A dense fired body is obtained, and by adding barium,
A fired body having high resistivity was obtained even in firing in a neutral atmosphere or a reducing atmosphere.

FIG. 1 shows the composition ranges of the main components of the present invention: (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) O _{3 + a} , (Pb _1.00 Ba _a ) TiO _{3 + a} , (Pb _1.00 Ba _a ) (Ni _1/2 W _1/2 ) O
_This is shown in the triangular composition diagram containing _{3 + a} as a main component.

Here, in the present invention, the claims are expressed as (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) _x Ti _y (Ni _1/2 W _1/2 ) _z O _{3 + a.} In the porcelain composition (however, x + y + z = 1), it is in the range of 0.001 ≦ a ≦ 0.250, and for the value of a in this range, (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) O _{3 + a} , (Pb _1.00 Ba _a ) TiO _{3 + a} , (Pb _1.00 Ba _a ) (Ni _1/2 W _1/2 ) O
_In the triangular coordinates with _{3 + a} as the apex, the composition of the main component dielectric porcelain composition consisting of a pentagonal region with the vertices of the compositions A, B, C, D, and E represented by numerical values in [] below PbO 1.0 against calcined powder
~ 25.0 mol%, and 1.0 ~ 15.0 mol% of NiO or WO
₃ , a dielectric ceramic composition characterized by adding 1.0 to 15.0 mol%, Specifically, as shown in Comparative Examples of <Table 1> and <Table 2>, in the compositions outside the scope of the invention, the composition in which the amount of the auxiliary agent was small and the calcination temperature lower than 800 ° C. At the temperature, firing becomes insufficient, a dense fired body cannot be obtained, and 1000
At a sintering temperature higher than ℃, the dielectric constant is greatly reduced due to the reaction of the auxiliary with the dielectric. Also, a is 0.
When it is smaller than 001, the resistivity of the fired body is low, and when a exceeds 0.250, the dielectric constant is greatly reduced, and
This is because a composition in which x, y, and z are out of the limited range has a problem that a high dielectric constant cannot be obtained.

Then, in the composition outside the limited range, the following permittivity of the sintered body of the present sintering conditions specifically 3000, or the resistivity of the sintered body becomes less 10 ¹⁰ cm · Omega, to obtain desired characteristics as a capacitor Absent.

The dielectric powder was calcined, pulverized and dried as <Example 2> Example 1, was added PbO, NiO or WO ₃ as a secondary component, and dried after wet mixing in a ball mill, a main ethylcellulose A vehicle in which a resin as a component is dissolved in a solvent is added,
The mixture was kneaded with a three-stage roll to prepare a dielectric paste. On the other hand, in order to form a thick film capacitor having a shape of 2 × 2 mm ² on an alumina substrate having a purity of 96%, a copper electrode was printed as a lower electrode and dried. Next, the above-mentioned dielectric paste is twice printed and dried as a dielectric layer so as to have a thickness of 50 to 60 μm, and the same copper electrode as the lower electrode is printed and dried as an upper electrode, thereby obtaining an electrode-dielectric- Form a printed thick film with a three-layer structure of electrodes and use a belt furnace to reach the maximum temperature.
Calcination was performed in nitrogen at 800 to 1000 ° C. for 10 minutes. The dielectric constant tanδ of the thick film capacitor thus obtained is 1 KH
The measurement was performed under an electric field of z, 1 V / mm. The resistivity is 30V for the sample.
1 minute after the voltage was applied. Table 3 below shows the material composition of the present invention and the dielectric properties of the fired product fired at 900 ° C. in nitrogen.

As shown in Table 3 above, in the fired product according to the material composition of the present invention, a high-capacity thick-film capacitor having a high resistivity and having a high resistivity made of a dense fired body can be obtained despite firing at a low temperature for a short time. Was.

The reason for limiting the scope of the claims is that, as in the case of Example 1, as shown in the comparative example of Table 3, with a composition outside the limited range, the dielectric constant of the fired body under the firing conditions is 2500 or less, or This is because the resistivity of the fired body becomes 10 ¹⁰ cm · Ω or less, and desired characteristics as a thick film capacitor cannot be obtained.

In this example, it was shown that firing was possible in nitrogen. However, it is easily presumed that firing is possible even in a neutral atmosphere such as argon or helium.

As the electrode used in the present invention, an electrode that can be fired at 800 to 1000 ° C. in a neutral atmosphere or a reducing atmosphere is appropriately selected and used.

Effect of the Invention As described above, the present invention is represented by (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) _x Ti _y (Ni _1/2 W _1/2 ) _z O _{3 + a.} In the porcelain composition (however, x + y + z = 1), it is in the range of 0.001 ≦ a ≦ 0.250, and for the value of a in this range, (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) O _{3 + a} , (Pb _1.00 Ba _a ) TiO _{3 + a} , (Pb _1.00 Ba _a ) (Ni _1/2 W _1/2 ) O
_In the triangular coordinates with _{3 + a} as the apex, the composition of the main component dielectric porcelain composition consisting of a pentagonal region with the vertices of the compositions A, B, C, D, and E represented by numerical values in [] below PbO 1.0 against calcined powder
~ 25.0 mol%, and 1.0 ~ 15.0 mol% of NiO or WO
₃ , a dielectric ceramic composition characterized by adding 1.0 to 15.0 mol%, By having a high dielectric constant that can be fired at a temperature of 800 to 1000 ° C. in a short time and also in a neutral atmosphere or a reducing atmosphere, and a multilayer ceramic capacitor and a thick film capacitor having a high resistivity, It has an excellent effect that it can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the composition range of the present invention (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) O _{3 + a} , (Pb _1.00 Ba _a ) TiO _{3 + a} , (Pb _1.00 Ba _a ) (Ni _1/2 W _1/2 ) O
_It is a triangular composition diagram containing _{3 + a} as a main component.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-223061 (JP, A) JP-A-63-319241 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01B 3/12 H01G 4/12 C04B 35/00

Claims (3)

(57) [Claims] (1) (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) _x Ti _y (Ni _1/2
W _1/2 ) _z O _{3 + a} porcelain composition (where x + y +
z = 1), it is in the range of 0.001 ≦ a ≦ 0.250, and for the value of a in this range, (Pb _1.00 Ba _a ) (Mg _1/3 Nb _2/3 ) O _{3 + a} , (Pb _{1.00 Ba a) TiO 3 + a,} (Pb 1.00 Ba a) (Ni 1/2 W 1/2) O 3 + a triangular coordinate whose vertices, the composition a represented by numerical values in the following [], B, C, D, E
A dielectric material characterized by adding 1.0 to 25.0 mol% of PbO and 1.0 to 15.0 mol% of NiO to a calcined powder of a main component dielectric porcelain composition comprising a pentagonal region having vertexes Porcelain composition. 2. Use of the dielectric porcelain composition according to claim 1,
A ceramic capacitor comprising: an electrode that can be fired at 800 to 1000 ° C. in a neutral atmosphere or a reducing atmosphere. 3. A thick film capacitor comprising: a ceramic substrate; and a dielectric layer comprising the dielectric ceramic composition according to claim 1 and an electrode which can be fired at 800 to 1000 ° C. .