JPH0244609A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To prevent dispersion from occurring due to lowered insulation resistance or low breakdown voltage by using 2CaO.3B2O3 as one component of additive. CONSTITUTION:This is constituted by adding SiO2 by 1.0-3.0weight%, and ZnO by 0.5-3.0weight% to the main components in the range of compositions which contains BaTiO3 by 18.0-27.0weight%, Nd2O3 by 31.6-36.3weight%, TiO3 by 27.6-35.5weight%, Bi2O3 by 2.5-8.1weight%, and Pb3O4 by 5.6-9.0weight%, 2CaO.3 B2O3 by 0.15-2.0weight%. With this, the dielectric porcelain composition is capable of being baked in the low temperature range of 1000-1050 deg.C, hereby even in the case that it is used as a laminated type porcelain capacitor using Ag-Pd for an internal electrode, the reaction between the internal electrode and Bi2O3 is reduced, and inductive characteristics can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention has a temperature coefficient of capacity in the range of ±30 ppm/'C in the temperature range of -155 to +125 °C, and
The present invention relates to a dielectric ceramic composition for a temperature-compensating ceramic capacitor that uses a g-Pd alloy as an internal electrode.

(Background Art) In general, high dielectric constant/temperature compensation ceramic capacitors, especially commercially available multilayer ceramic capacitors, are made by laminating multiple layers of thin dielectrics with internal electrodes formed on the surface, and alternating the internal electrodes. They are simultaneously fired in parallel to external connection electrodes. This type of multilayer capacitor requires a relatively high firing temperature (1240° C.) in order to sufficiently densify the capacitor to have a high dielectric constant.

Therefore, the metal used for this electrode must be an expensive noble metal (platinum or palladium) whose melting point is higher than the firing temperature of the dielectric, and the cost of such metal materials increases the total cost of this type of capacitor. is increasing.

Therefore, the firing temperature of the dielectric and the internal electrodes was lowered, and the cheap Ag--P was used instead of the expensive noble metals as the internal electrodes.
Attempts have been made to increase the content of d-alloy, particularly A-g, to obtain inexpensive multilayer ceramic capacitors. However,
It is generally known that lowering the firing temperature of a dielectric material lowers its crystallinity and therefore its relative dielectric constant. physical and temperature characteristics cannot be obtained.

[Description of prior art]

As a prior art, Japanese Patent Application Laid-Open No. 57-170405 describes N
d2Tie, , BaTiO3, Tie2, Bi2O, and pb3o.

By adding appropriate amounts of ZnO and SiO2 to the main components of the composition, the firing temperature can be adjusted to 1050-1100.
To use an inexpensive Ag-Pd alloy with a low melting point as the internal electrode in manufacturing a multilayer capacitor that can obtain a sintered body in the temperature range of °C and requires firing of the internal electrode at the same time as the firing of the porcelain. It is stated that this can be done.

[Problem to be solved by the invention]

However, the present inventors previously discovered that when an Ag-Pd alloy was used as an internal electrode for a system containing Bi, 03 in the dielectric, Ag-Pd and B
i, O, react directly with each other to form a PdO solid solution containing Bi as a solid solution, resulting in a rapid increase in the electrical resistance of the Ag-Pd internal electrode and rapid changes in the dielectric properties of the dielectric, especially the Q value and insulation resistance. The result was that it decreased to . Therefore, Bi,
It was concluded that when sintering O and O in contact with each other at the same time, it is necessary to sinter at a temperature of 1050° C. or lower.

On the other hand, according to the above-mentioned conventional technology, the firing temperature is 1050 to 1100°C, and the above-mentioned Ag-Pd and Bi
The suppression of the reaction with 2O has not been substantially solved, and the capacitance temperature coefficient is +30 to -300 ppm in terms of characteristics.
/'C, it has been applied to a relatively wide range, and has fatal drawbacks for practical use, such as a decrease in insulation resistance, a low breakdown voltage, and large variations.

Therefore, in Japanese Patent Application No. 58-231180 (Japanese Unexamined Patent Publication No. 60-124306), the applicant proposed
aTiO3, Nd2O3, Tie, , Bi2O3, Pb
SiO□ as an additive to the main component of the 3O4 composition system
, ZnO and B3O□ in a specific ratio, 100
It is possible to perform firing at a temperature of 0 to 1050°C, which suppresses the reaction between Ag-Pd and Bi2O, and provides stable temperature characteristics with a capacitance temperature coefficient in the range of ±30ppm/'C. A dielectric ceramic composition that is extremely excellent for use in temperature-compensating ceramic capacitors having Ag-Pd as internal electrodes, which has low insulation resistance, low breakdown voltage, and little variation. proposed.

The inventors of the present invention have discovered a new problem in putting this dielectric ceramic composition having excellent properties into practical use. That is, when such a dielectric ceramic composition is used in a capacitor, the raw material powder is first processed into a thin sheet-shaped compact, but in this forming process, the 82O3 in the composition is soluble in water, As a dispersion medium, it is necessary to use a dispersion medium other than water, that is, an organic solvent such as toluene. This is because when B2O3 dissolves in water, it becomes boric acid, which lowers the hydrogen ion concentration of the slurry and changes the viscosity of the slurry, making it impossible to obtain a sheet-like molded product with a stable thickness.

However, the use of organic solvents such as toluene is explosive in itself and has an impact on the human body, so for practical mass production, it is necessary to take complete explosion-proof measures in the molding and drying processes. This was a major cause of soaring product costs.

[Purpose of the invention]

As a result of intensive research into dielectric ceramic compositions that can solve the above problems while maintaining the above-mentioned excellent properties, the inventors of the present invention found that 2C, aO.3B was used instead of B2O3.

We have found that water can be used as a dispersion medium by using 0□, and we would like to propose this here.

[Means to solve problems]

In the present invention, B a T i O3 is 18.0 to 27.0
wt%, 31.6-36.3 wt% Nd2O3, Ti
27.6-35.5% by weight of O2, 2.5% of Bi3O3
~8.1 wt% and 5.6-9.0 wt% pb3O4
For the main components in the composition range including 2Ca0.3B2O
0.15 to 2.0% by weight of SiO2 and 1°0 to 3.0% of SiO2.
0% by weight and 0.5 to 3.0% by weight of ZnO, thereby obtaining a dielectric ceramic composition having excellent properties that can be fired at 1000 to 1050°C.

One major feature of the present invention is 1. The point is that 2Ca0.3B203 was selected as one of the additive components. That is, 2Ca0.3B, ○, is insoluble in water, and therefore,
Water can be used as a dispersion medium for slurry, and each raw material powder can be uniformly dispersed together with the emulsion organic binder, water-soluble dispersant, and surfactant, and a homogeneous green sheet with a stable thickness can be produced without the need for any special equipment. It can be produced at low cost and with good workability.

On the other hand, during calcination, 2Ca0.3B203 coexists with ZnO, and 1
Dense porcelain can be sintered at 000-1050°C.

FIG. 1 shows Zno and 8, which are one of the components in the composition of the present invention.
A binary phase diagram with 2O3 is shown. According to this diagram, in the coexistence with ZnO, when 82O3 is about 30 mol%, the liquidus line is 960.
℃, indicating that ZnO and B2O3 can effectively act as a sintering accelerator flux by using them in an appropriate composition.

Therefore, when ZnO and 2Ca0.3B, ○ are simultaneously added as additive components to the above-mentioned main component and fired, 2C
aO・3B2O3 reacts at a low temperature below 900℃, and B2
O3 forms a more stable compound with ZnO at low temperatures, and C
It is believed that aO reacts with BaTiO3, the main component, at high temperatures.

Therefore, even if 2Ca0.3B2O3 is used instead of B2O3, the liquid phase component in the sintering process acts in the same way, and 10
It has the effect of sintering at 00 to 1050°C. In addition, Ca
O is BaTi0. However, since the amount of CaO is very small, it does not have any effect on the entire system.

Moreover, the effect of adding 2Ca0.3B203 is not limited to lowering the sintering temperature, but also improves the Q value when used as a capacitor as shown in Example 2, similar to when B2O3 is added alone. At the same time, it has the great effect of reducing variations in insulation resistance and increasing breakdown voltage.

The reason why each of the above compositions is set in the above composition range will be explained. If B a T i 03 is less than 18.0% by weight, a sufficiently dense porcelain cannot be obtained unless the firing temperature is relatively high; on the other hand, if it exceeds 27.0% by weight, the firing temperature will be similarly low. If it is not high, it will not be sufficiently dense, and in this case, the insulation resistance (IR) will become small. Nd2O, is 31
．． If it is less than 6% by weight, it will not be sufficiently densified unless the firing temperature is high, and the insulation resistance (IR) will tend to be low, and the quality factor (Q) will tend to be small; if it exceeds 36.3% by weight, The capacity temperature coefficient (ppm/''C) largely shifts to the (+) side, but this tendency decreases when BaTi○ is small.

On the other hand, if the firing temperature is not high, it will not become sufficiently dense.

If T i O, is less than 27.6% by weight, it will not be sufficiently densified unless the firing temperature is raised, and if it exceeds 35.5% by weight, the temperature coefficient of capacity (ppm/'C) will increase toward the (-) side. There is a tendency to If Bi and Ol are less than 2.5% by weight, the capacity temperature coefficient (ppm/"C) shifts to the (-) side, and sufficient densification cannot be achieved unless the firing temperature is raised, and the insulation resistance (I R ) and quality coefficient (Q value) become smaller,
If it exceeds 8.1% by weight, the capacity temperature coefficient (ppm/”C)
As the insulation resistance (I R) largely shifts to the (-) side,
becomes smaller. If pb3O4 is less than 5.6% by weight, the capacity temperature coefficient (pρm/℃) will largely shift to the (-) side, and the sintering temperature will not be sufficiently densified unless the firing temperature is increased.
．． When it exceeds 0% by weight, the capacity temperature coefficient (ρpm/''C) shifts to the (+) side.

In addition, if the additive component 2Ca○-38203 is less than 0.15% by weight, the above-mentioned addition effect cannot be obtained, and sufficient densification cannot be obtained unless the firing temperature is high, and the insulation resistance (I R)
This results in an increase in the variation in the voltage and an increase in the breakdown voltage. On the other hand 2.
If the weight exceeds 0.2, fusion with a setter such as alumina is likely to occur during firing. Furthermore, if SiO2 is less than 1.0% by weight or more than 3.0% by weight, sufficient densification will not occur unless the firing temperature is increased, and the insulation resistance (IR) and quality factor (Q value) will decrease.

Finally, if ZnO is less than 0.5% by weight, it will not be sufficiently densified unless the firing temperature is high, and the insulation resistance (IR) and quality factor (Q value) will be small; if it exceeds 3.0% by weight, As the quality factor (Q value) decreases, the capacity temperature coefficient (p
pm/”C) increases toward the (+) side.

As mentioned above, B a T i O,, Nd2O,, Ti
O2, Bi2O,, Pb, O,, 2Ca()3B203
, SIO, and ZnO are outside the scope of the present invention, the quality factor (Q value), insulation resistance (IR), and breakdown voltage are too low, or the sintering at low temperature (toso℃ or below) is insufficient, resulting in failure of the present invention. It does not meet the purpose of the invention. Preferably 2Ca0・3B3
It is preferable that 0.45 to 1.35% by weight of O3, 1.0 to 3.0% by weight of SiO2, and 1.0 to 2.5% by weight of ZnO are added to the main components.

Examples of the present invention will be described below.

(Example 1) B a T i O3 with a purity of 99.8% or more synthesized in advance from equimoles of BaC0 and TiO2 at 1200°C, Nd2O with a purity of 98% or more, and Nd2O with a purity of 99.5% or more. Titanium dioxide (anatase) and B with a purity of over 95%
Weigh i2O and Pb3O4 with a purity of 95% or more so that it has the composition of each material listed in the main component composition tank in Table 1,
The total weight was 500g each. Furthermore, 2Ca0.3 B2O3, S i O with a purity of 95% or more
2 and ZnO were weighed and added to the main component so as to have the composition of each sample listed in the subcomponent tank in Table 1. Content 11.
Bulk volume 0.8Q (1.5kg) in 6111 porcelain pot
) with alumina balls (17+nmφ), and further added emulsion acrylic resin and ion-exchanged water as a dispersion medium along with one dispersant and a surfactant, and rotated at a rotational speed of 72 ppm for 24 hours. A green sheet with a wall thickness of 25 μm was molded by the method. 25 sheets of this Green Sea 1- were stacked and hot pressed to create a green molded plate, approximately 10nn thick.
It was cut into a green square plate with a + corner and a thickness of 0.50 nn. A green square plate was baked at a temperature of 1000 to 1100°C for 2 hours, and silver electrodes were applied to the top and bottom surfaces of a square plate approximately 8 m square and 0.4 ml thick, and evaluated as a single-layer square plate capacitor. It was used as a sample.

The capacitance and quality factor (
After measuring the insulation resistance (IR) by applying a DC voltage of 50 V for 1 minute, the temperature coefficient of capacitance at -55°C and +125°C was measured at a frequency of IMHz. In addition, the vertical (L) and horizontal (W) dimensions of the sample were measured with an accuracy of ±5 μm, and the thickness (1) was measured with an accuracy of ±1 μm, respectively. 8.865 X 10-'PF/n++n
) was used to calculate the relative dielectric constant.

The measurement or calculation results of the electrical properties thus obtained are shown in Table 1 along with the chemical composition and firing temperature of each sample.

(Left below) Sample numbers 1.2.3.7.9, 11.12, 1 in Table 1
5, 16, 17, 21, 22. In Nos. 25, 26, and 29, any of the compositions does not meet the composition range of the present invention, and requires a firing temperature of 1100° C. or more, which does not meet the purpose of the present invention. Also, sample number 11.
12.21.25°26 and 29 have quality coefficients (Q values) of less than 1000, which are too small and do not meet the purpose of the present invention. Also, sample number 7.11.15.16.17.21.22.
25 and 26 have too low insulation resistance (IR) and are not suitable for the purpose of the present invention.

Furthermore, sample number 7.9.11.12.15.16.2
1.25 and 29 have a capacity temperature coefficient (ppm/℃) of ±3
It deviates from the range of 0 ppm/°C and does not meet the purpose of the present invention. In this example, the evaluation sample was a single-plate type capacitor in which a silver electrode was provided on a single plate of fired porcelain. However, when these are actually fired as a laminate type, the firing temperature is further lowered by about 20°C. Therefore, it has been confirmed that when the capacity temperature coefficient (ppm/°C) is especially large on the (-) side, it shifts to the (+) side of about 15 ppm/'C.

On the other hand, all of the samples other than those mentioned above were sufficiently sintered at a temperature of 1050°C or lower, and had an insulation resistance of 10'MΩ or higher (I
R), and the relative dielectric constant (εr) is as high as 50 or more (εr=67 even in the case of sample number 10, which is the lowest), and the quality factor (Q value) is also excellent, being 10°00 or more. Indicates electrical characteristics and also capacitance temperature coefficient (ppm/℃)
It can be seen that the temperature characteristics are constant within the range of ±30 ppm/'C.

(Example 2) Sample number 14 within the scope of the present invention in Table 1,
2 Ca 0.3 B2 O
Each paste was printed by adding an organic binder and its solvent to an alloy of 70% by weight and 30% by weight of Pd. 58 of each green sheet provided with this metal printing film were laminated,
Eight green sheets without a printing film were added to the top and bottom and hot pressed.

Furthermore, it was cut into individual pieces with vertical dimensions of 5.2 mm and 4 m, respectively, to produce green chips of multilayer ceramic capacitors, and baked at the respective temperatures shown in Table 1 for 2 hours. Ag-Pd alloy electrodes were applied to both ends of both fired chips to create a multilayer ceramic capacitor.

Capacitance (nF) of the multilayer ceramic capacitor thus obtained
and the quality factor (Q value) were measured at a frequency of I MHz and an input voltage of IVrms, a DC voltage of 50 V was applied for 1 minute to measure the insulation resistance (IR), and then a DC voltage was applied and the voltage was gradually increased. The voltage at the time of breakdown (breakdown voltage) was measured. The results of each measurement are shown in Table 2. however,
The number of measurement samples was 20 each, and the capacitance (nF) and quality factor (Q value) were the average values, and the breakdown voltage was the average value x (
V) and the variation index σ/x (%), the insulation resistance (I
For R), numbers on the order of 106 MΩ, 105 and 104 MΩ are shown, respectively.

(Leaving space below) As shown in Table 2, the multilayer ceramic capacitor of sample number 17 that does not contain 2Ca0.3B, O, has an average breakdown voltage of 321 x (V) and a dispersion index of 22. 4σ/x (%), and the insulation resistance (IR) is on the order of 104 MΩ out of 20 and on the order of 105 MΩ out of 20, indicating that the insulation resistance is insufficient. On the other hand, sample number 14 containing 2Ca0・3B20°
The average breakdown voltage of the multilayer ceramic capacitor is 760x.
(V) is more than double that of the former, its dispersion index is small at 9.6σ8 (%), and the insulation resistance (I R
) is 106 MΩ or more for all 20 out of 20, which is sufficient.

〔Effect of the invention〕

As detailed above, the dielectric ceramic composition of the present invention has a
It is possible to sinter in the low temperature range of 00 to 1050℃, which reduces the reaction between the internal electrodes and Bi2O even when used for multilayer ceramic capacitors with Ag-Pd internal electrodes, improving dielectric properties. can be stabilized. In addition, the temperature coefficient of capacitance can be made within the range of ±30 ppm/'C in the temperature range of -55°C to 125°C, and the drop and variation in insulation resistance and breakdown voltage are reduced, making it suitable for temperature-compensated multilayer capacitors. It has sufficient practical characteristics. Furthermore, since an Ag-Pd alloy with a relatively low melting point and a high content of Ag can be used as the internal electrode, an inexpensive multilayer capacitor can be obtained.

The above-mentioned excellent effects maintain the effects of the prior application filed by the present applicant, which used B2O3 as an additive component, but the present invention provides 2Ca0.3B2O in place of B2O3.
By using 3, it is possible to use water as a binder during firing, which allows the use of a filter press in the dehydration and drying processes, dramatically improving mass productivity and significantly reducing production costs. It has the added advantage of being able to achieve

[Brief explanation of the drawing]

FIG. 1 is a binary phase diagram of ZnO and 8203. −1 or more

Claims (1)

[Claims] 1. 18.0-27.0% by weight of BaTiO_3, Nd
_2O_3 31.6-36.3% by weight, TiO_2 27.6-35.5% by weight, Bi_2O_3 2.5-36.3% by weight
8.1% by weight and 5.6-9.0% by weight of Pb_3O_4, 0.15-2.0% by weight of 2CaO・3B_2O_3,
1.0 to 3.0% by weight of SiO_2 and 0.5% of ZnO
A dielectric ceramic composition characterized in that it contains ~3.0% by weight.