JPH03238708A - Dielectric porcelain composition and condenser - Google Patents

Abstract

PURPOSE:To obtain a dielectric porcelain composition for which a short-time baking is possible without sacrificing a high dielectric constant by adding a specific mol% of lead oxide (PbO) and nitrogen oxide (NiO) to a tentatively baked powder of a primary component dielectric porcelain composition formed out of the values within a specific region. CONSTITUTION:Referring to an expression I in which a dielectric porcelain composition has a perovskite structure, (a) is in a range of 0.001<=a<=0.250, and to the value of (a) within this range, 1.0-25.0 mol% of lead oxide (PbO) as well as 1.0-15.0mol% of nitrogen oxide (NiO) or 1.0-15.0mol% of tungsten trioxide WO3 are added to a tentatively baked powder of a primary component dielectric porcelain composition formed out of the values in the region formed in a pentagon with tops of compositions A-E expressed by the values in the parenthesis of an expression V, in trigonometric coordinates with tops of expressions II-IV. In the expression I, (x)-(z) express x+y+z=1. A ceramic condenser can thus be obtained which has a dielectric constant high enough for baking even in a neutral or reducing atmosphere, for a short period of time at a temperature of 800-1000 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a dielectric ceramic composition that can be fired at a firing temperature of 800 to 1000°C in a short time in a neutral atmosphere or a reducing atmosphere, and has a high resistivity. Concerning objects and capacitors.

Conventional Technology Materials containing barium titanate as a main component have been used as high dielectric constant materials for ceramic capacitors, which are becoming smaller and larger in capacity. However, in order to sinter this material, it is necessary to use high-temperature firing temperatures of around 1,300°C in the atmosphere, so when manufacturing multilayer ceramic capacitors, expensive noble metals such as platinum or palladium are used as electrode materials. In particular, as capacity increases, the internal electrode material becomes a factor pushing up raw material costs.

In contrast, in recent years, methods have been developed to make barium titanate-based materials more resistant to reduction, using inexpensive base metals as electrode materials and firing them in an atmosphere with low oxygen partial pressure, and using lead-based dielectric materials and inexpensive silver. By using a method of firing at a low temperature of around 1000°C using an electrode material mainly made of silver-palladium alloy,
Efforts are being made to reduce the cost of multilayer ceramic capacitors.

On the other hand, in electronic devices where miniaturization and high reliability are desired, hybrid ICs with high packaging density are being used, and there is an increasing demand for thick film capacitors in place of conventional chip capacitors.

In order to manufacture this thick film capacitor, a dielectric material that can be fired at low temperatures and for a short period of time is required, and lead-based dielectric materials are mainly used as the material for this purpose. Therefore, lead-based dielectrics are being actively developed as a material that can be fired at low temperatures and can be used to increase the capacity of multilayer ceramic capacitors or to increase the thickness of capacitors.

Problems to be Solved by the Invention Now, (Pb+, ooSra)(Mg+/3Nb2/
3)03+a.

(Pb+, ooSra)TiO:++a, (Pb
+,ooSra)(Ni+/zW+/2)0
3+ll type dielectric composition is disclosed in Japanese Patent Application Laid-Open No. 62-123060.
As is known from the publication, the dielectric constant ceramic composition is fired in a low oxygen atmosphere at 1100°C or less, but in order to increase the dielectric constant and obtain a sufficiently dense fired body, the firing temperature must be adjusted several times. Need to keep time.

On the other hand, when producing thick film capacitors for hybrid ICs, low-temperature and short-time firing is essential, and under such conditions the dielectric material becomes unfired, so there is a problem that the desired characteristics cannot be obtained. Ta.

In view of this problem, in the present invention, (Pb1.ooSra)(Mg+/3Nb2/3)03
+a r(Pb1.00Sr, >TiO3+a, (Pt
)+ ,ooSra)(Ni+/2W+/2)03+a
A dielectric ceramic composition that can be fired for a short period of time at 800 to 1000°C in a neutral or reducing atmosphere without impairing the high dielectric constant of a solid medium, and a ceramic capacitor or thick film using the same. The purpose is to provide capacitors.

Means for Solving the Problems In order to solve the above problems, the dielectric ceramic composition of the present invention is composed of (Pb + , QOSra ) (Mg + /3Nb2
/3)xT 1y(N i + /2WI/2)ZO
Porcelain composition represented by 3+Q (x+y+21)
is in the range of o, ooi≦a≦0.225, and for the value of a within this range, (Pb+
, ooSra) (Mg+/3Nb2/3)03+a.

(Pb + , ooSra) Ti03+3, (
Pb+, ooSra) (N i I /2WI/
2) In the triangular coordinates with 03+a as the vertex, the composition is within the composition range expressed by the numerical value in [1] below, and the calcined powder of the main component dielectric ceramic composition is within the area of a within this range. On the other hand, PbO is 1.0 to 25.0 mol%, and PbO is 1.0 to 25.0 mol%.
bO 1.0 to 15.0 mol% or WO2 1.0
It has a configuration in which ~15.0 mol % of the metal is added.

In other words, the composition according to the claims of the present invention has a perovskite structure (Pb+, ooSra
)(Mg+/3Nb2/3)03+a-(Pb+,
ooSra ) Ti03+a-(Pb+ , ooSr
a) By adding PbO or WOs to PbO1 and PbO1 to the calcined powder of (N i +/2Wl/2)Oi+ self-system, the eutectic composition of PbO and NiO or WO3 can be used to reduce the temperature By generating a liquid phase at the A and 8 sites simultaneously, these additives can diffuse smoothly into the dielectric, and by suppressing the formation of a grain boundary layer due to the additives, the dielectric A large capacity ceramic capacitor or thick film capacitor with high resistivity can be obtained by preventing a decrease in capacitance and firing in a short time and densely at a low firing temperature of 1000°C or less in a neutral or reducing atmosphere. That will happen.

Example Examples of the present invention will be shown below.

<Example 1> First, chemically highly purified Pbo, S
rCOs, MgO, Nb2O5, T i 021Ni
O, WO3 was used. After correcting the purity of these, a predetermined amount was weighed, pure water was added, and the mixture was mixed for 17 hours in a ball mill using agate stones. This is filtered by suction to remove most of the moisture, dried, and then thoroughly crushed using a Raikai machine. 5wt% of the crushed amount of pure water is added to form a cylinder with a diameter of 60mm and a height of about 50mm. Molding was carried out at a molding pressure of 500 kg/-. Place this in an aluminum pot and cover it with a homogeneous lid.75
Calcining was performed at 0 to 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, filtered under suction, and then dried. The above steps of calcination, crushing, and drying were repeated several times. This powder was analyzed by X-ray analysis and confirmed to be a perovskite phase.

PbO and NiO or WOs were added as subcomponents to this dielectric powder, and after mixing in a Raikai machine, a 6 wt% aqueous solution of polyvinyl alcohol was added to the powder amount of 6 wt%.
%, granulated through a 32-mesh sieve, and molded into a disk shape with a diameter of 13 m and a height of about 5 cm at a molding pressure of 500 b/c+j. Next, this molded product was heated in the atmosphere at 600°C for 1
After holding for a time to remove the binder, the container is placed in a magnesia porcelain container with a homogeneous lid, and heated to a specified temperature of 2400℃ in a neutral or reducing atmosphere using an atmospheric belt furnace.
/hrs and held at the maximum temperature for 10 minutes, then 240
The temperature was lowered at 0°C/hrs.

The fired product obtained as described above was processed into a disk shape with a thickness of 1 μm, Cr-Ag was deposited as an electrode on both sides, and the dielectric constant, tan δ, was adjusted under an electric field of I KHz and IV/m. It was measured. In addition, the resistivity is measured after applying a voltage of 30V to the sample.
The value of A was determined.

Table 1 below shows the material composition of the present invention and the dielectric properties and resistivity of the fired product when the firing atmosphere was nitrogen, which is a neutral atmosphere. Further, the dielectric properties and resistivity of the fired product are shown in Table 2 below when the firing atmosphere is a nitrogen-hydrogen mixed gas having an oxygen partial pressure of 110-8 at or more.

(Hereinafter, blank) As shown in Tables 1 and 2 above, the fired products according to the material composition of the present invention have good performance in firing at 800 to 1000°C for a short time and in various atmospheres. Also, a dense fired body with a high dielectric constant was obtained, and by adding strontium, a fired body with high resistivity was obtained even when fired in a neutral atmosphere or a reducing atmosphere.

Figure 1 shows the composition range of the main components of the present invention (Pb+,
ooSra ) (Mgt /3Nb2/3)Os+a
.

(Pb+,ooSrs)Ti03+s*(Pb+
, ooSra ) (N i +ytW+/2)03+
It is shown in a triangular composition diagram with a as the main component.

Here, in the present invention, the claims are defined as (Pb+
,ooSra)(Mg+/xNb+/z)xTiy(
In the porcelain composition represented by Ni+i2W+/2)zo3+a (where X+y+Z=1), it is in the range of 0.001≦a≦0.225, and for the value of a within this range, (Pb+
, ooSra) (Mgt/5Nb2/3)03+a.

(Pb+,005ra)Ti03+a+(Pb
+ ,ooSr, )(N it/2W+/2)03
In triangular coordinates with 1s as the vertex, the composition is within the range of the composition expressed by the numerical value in J below, and for the calcined powder of the main component dielectric ceramic composition consisting of the area a within this range. , PbO
1.0 to 25.0 mol% of PbO, and 1.0 to 25.0 mol% of PbO.
0 to 15.0 mol% or 1.0 to 15.0 mol% of W O3.
As shown in the comparative examples in Tables 1 and 2, the dielectric ceramic composition is characterized by the addition of 0 mol%. However, if the composition contains a small amount of additives and the firing temperature is lower than 800°C, the firing will be insufficient and a dense fired product will not be obtained.
This is because at a firing temperature higher than 000° C., the dielectric constant significantly decreases due to the reaction of the auxiliary agent to the dielectric material. Also, a
is less than 0.001, the resistivity of the fired body is low, and a
This is because if the value exceeds 0.225, the dielectric constant will drop significantly, and compositions in which x, y, and z are outside the specified ranges will not be able to obtain a high dielectric constant. .

If the composition is outside the limited range, specifically, under the main firing conditions, the dielectric constant of the fired body will be 3000 or less, or the resistivity of the fired body will be 10"ell・Ω or less, and the desired characteristics as a capacitor cannot be obtained. do not have.

<Example 2> PbO and NiO or WO2 are added as subcomponents to the dielectric powder calcined, crushed and dried in the same manner as in Example 1 above, wet mixed in a ball mill and then dried to obtain ethylcellulose as the main component. A vehicle in which the resin was dissolved in a solvent was added, and the mixture was kneaded using a three-stage roll to prepare a dielectric paste. On the other hand, in order to form a thick film capacitor having a 2×2×2 shape on an alumina substrate with a purity of 96%, a copper electrode was printed as a lower electrode and dried. Next, the dielectric paste was printed and dried twice to a thickness of 50 to 60 μm as a dielectric layer, and a copper electrode, which was the same as the lower electrode, was printed and dried as an upper electrode. A printed thick film with a three-layer structure of electrodes was formed and fired in nitrogen using a belt furnace at a maximum temperature of 800 to 1000°C for a holding time of 10 minutes. The dielectric constant, tan δ, of the thick film capacitor thus obtained was measured at IKHz under an electric field of IV/+s+. Further, the resistivity was determined as a value for 1 minute after applying a voltage of 30 V to the sample. 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.

(See Table 3 above.) As shown in Table 3 above, the fired product of the material composition of the present invention is a dense fired product with high resistivity and high capacity despite being fired at a low temperature and for a short time. A thick film capacitor was obtained.

The reason for limiting the scope of claims is as in Example 1,
As shown in the comparative example in Table 3, for compositions outside the limited range, the dielectric constant of the fired product is 2500 or less under the main firing conditions, or the resistivity of the fired product is 1010Ω or less, making it difficult to use as a thick film capacitor. This is because the desired characteristics cannot be obtained.

Although this example showed that firing is possible in nitrogen, it is easily inferred that firing is also possible in a neutral atmosphere such as argon or helium.

Note that 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.

Effects of the Invention As described above, the present invention provides (Pb+, ooSra)(Mg+/3Nbt/
3) xT 1cy(N i I/2W+ /2)z(
A porcelain composition represented by h+s (where x+y+z=1
) is in the range of 0.001≦a≦0.225, and for the value of a within this range, (Pb+
,ooSra) (Mg+/Jb2/3)Os+Sudden.

(Pb+, 0O5ra)Ti03+a, (Pb
+ , oosr, )(N i l/2'dl/2
) In the triangular coordinates with Os + a as the vertex, the composition range is within the composition range expressed by the numerical value in [J below, and for the calcined powder of the main component dielectric ceramic composition consisting of the area a within this range. hand,
1.0 to 25.0 mol% of PbO, and PbO
1.0 to 15.0 mol% or 1.0 to 15.0 mol% of W O3
A dielectric ceramic composition characterized by the addition of 15.0 mol%, which provides a high dielectric material that can be fired at a temperature of 800 to 1000°C in a short time and even in a neutral atmosphere or a reducing atmosphere. This exhibits the excellent effect of providing a multilayer ceramic capacitor and a thick film capacitor that have a high resistivity and a high resistivity.

[Brief explanation of drawings]

Figure 1 shows the composition range of the present invention (Pb+, ooSra)(Mg+/3Nb2/3)0
3+a+(Pb+, 005ra)Ti03+a
r (Pb+, 00Sra) (Ni wtWI/
2) It is a triangular composition diagram with 03+s as the main component.

Claims (4)

[Claims] (1) (Pb_1_._0_0Sr_a) (Mg_1_
/_3Nb_2_/_3)_xTi_y(Ni_1_/
In the porcelain composition represented by (_2W_1_/_2)_zO_3_+_a (where x+y+z=1), it is in the range of 0.001≦a≦0.225, and for the value of a within this range, (Pb_1
＿． _0_0Sr_a)(Mg_1_/_3Nb_2_
/_3)O_3_+_a, (Pb_1_._0_0Sr
_a) TiO_3_+a, (Pb_1_._0_0Sr
_a) (Ni_1_/_2W_1_/_2)O_3_+
Calcination of a main component dielectric porcelain composition consisting of a pentagonal area with compositions A, B, C, D, and E as vertices, represented by the numbers in brackets below in triangular coordinates with __a as the apex. A dielectric ceramic composition characterized in that 1.0 to 25.0 mol% of PbO and 1.0 to 15.0 mol% of NiO are added to the powder. A is x=0.950, y=0.049, z=0.001
, B is x=0.400, y=0.599, z=0.00
1, C is x=0.001, y=0.900, z=0.0
99, D is x=0.001, y=0.600, z=0.
399, E is x=0.700, y=0.100, z=0
．． 2000 (2) 1.0 to 25.0 mol% of PbO and W to the calcined powder of the main component dielectric ceramic composition according to claim 1;
A dielectric ceramic composition characterized in that 1.0 to 15.0 mol% of O_3 is added. (3) Using the dielectric ceramic composition according to claim 1 or 2, in a neutral atmosphere or a reducing atmosphere,
A ceramic capacitor comprising an electrode that can be fired at 00°C. (4) A dielectric layer made of the dielectric ceramic composition according to claim 1 or 2 on a ceramic substrate and heated at 800 to 1000°C.
A thick film capacitor characterized in that it is configured by providing an electrode that can be fired with.