JPS62254310A - High dielectric constant porcelain compound - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a high dielectric constant ceramic composition, particularly Pb (Zn
Dielectric constant basis coefficient (T, C
, C) is small and has excellent reliability.

[Technical background of the invention and its problems] Conventionally, the dielectric constant exceeds 3000! 12
As the S material, barium titanate (BaT103)
These materials are mainly used.

Today, using this material, the dielectric thickness is 20 to 30 μm.
m1 Multilayer ceramic condenser with 20 to 80 layers # (
MLC) has been put into practical use. However, when a multilayer ceramic capacitor is manufactured using this material, various problems have emerged. As the thickness of the dielectric becomes thinner, the voltage per dielectric thickness increases, resulting in a significant decrease in the DC bias dependence of the dielectric, that is, the effective capacitance when a rated voltage is applied. For example, in an MLC with an EVA rating of 25V and a 1.0μF(7)F characteristic, the M electric rate is 10000. If the dielectric thickness is 25 μm, the capacitance decreases by about 70% when the rated voltage is applied, and the resulting capacitance is only 0.3 μF. Furthermore, the temperature coefficient of dielectric constant (
Considering T, C, C), a circuit that requires a capacitance of at least 1.0 μF when the rated voltage is applied must use an MLC of 3.3 μF or more.

Further, in reducing the thickness of the dielectric, the large crystal grain size poses a problem. The crystal grain size of BaTiO3 by normal solid phase reaction is 4 to 10 μm.

If the dielectric thickness is reduced to 20 μm or less in order to increase the capacity, the number of particles between layers will decrease, causing a decrease in withstand voltage. Furthermore, the firing temperature of barium titanate material is 130
The internal electrode material, which is simultaneously fired at a high temperature of 0 to 1400° C., must necessarily be an expensive true metal material such as palladium Pd or platinum Pt, which is not oxidized at high temperatures, which causes high costs. In order to solve the problems of barium titanate-based materials, research on composite perovskite compounds containing lead is being widely conducted. For example, lead iron niobate Pb
Mainly composed of (Fe Nb)03 and 1/2
1/Matamono (Japanese Unexamined Patent Publication No. 57-57204), Magnesium lead niobate Pb (MQ Nb )O as main component (Japanese Unexamined Patent Application No. 55-51758) Magnesium lead tungstate Pb (Mc+ W1/2) 03 (Japanese Unexamined Patent Publication No. 52-21699) is known. Products made mainly of lead iron niobate have a large change in crystal particle size and insulation resistance depending on the firing temperature, and a large drop in insulation resistance at temperatures above 85°C, resulting in problems with reliability at high temperatures. However, the firing temperature is relatively high and it is difficult to obtain a perovskite single phase. Further, materials mainly made of magnesium lead tungstate have the problem that if the insulation resistance is large, the dielectric constant is small, and if the dielectric constant is large, the insulation resistance is small. Furthermore, the results of a humidity load test on multilayer ceramic capacitors made using these materials were insufficient compared to those using barium titanate.

[Purpose of the Invention] The present invention has been made in consideration of the above points, and has a large dielectric constant, a small temperature coefficient, and can be fired at a low temperature of 1100°C or less, and is suitable for humidity resistance load tests when made into a multilayer ceramic capacitor. The purpose is to provide an excellent high dielectric constant ceramic composition.

[Summary of the Invention] The present invention provides a general formula % formula % ( , when a (x
=0.50. y=o, oo, z=0.50> b (x=1.oO, y=o, oo, z=0.0
0) C(X=0.20.'/=0.80.Z=
0.00) d (x=0.05. y=0.90.
z = 0, 05) A part of the pb of the composition within the line connecting each point indicated by 1 to 3
ff1f for a high dielectric constant ceramic composition characterized by substitution with at least one of Ba and Sr at 5 mo1%
Bio 4 with fi ratio of 0.05-1.0mff1%
0-60wt%, SiO5-15wt%, 8010-3
3wt%.

This is a high dielectric constant ceramic composition characterized by adding a glass component consisting of Aq2015 to 25 wt%.

Various composite perovskite compounds have been studied as dielectric materials, but zinc lead niobate is difficult to form a porcelain O-buskite structure and was thought to be unsuitable as a dielectric material (NECRe5earch).
&oeve+opment NQ 29 A
I) ri+1973 p, 15-21). According to research related to the present invention, it has been found that a stable perovskite structure can be formed in porcelain by appropriately replacing a portion of lead in zinc niobate with barium or strontium. Furthermore, it has been found that such a ceramic composition exhibits extremely high dielectric constant and insulation resistance, and also has extremely good temperature characteristics. As a result of further research, it was discovered that by combining this zinc lead niobate with magnesium lead niobate and lead titanate, a high dielectric constant porcelain composition with even higher dielectric constant and insulation resistance could be obtained. It was. This material contains B1040-60wt%, 5ho
25-15wt%, 820310-30wt%, Aa2
0 0.05 to 25 wt% glass component
It has been found that by containing 1.0 wt%, the results of the humidity load test of multilayer ceramic capacitors can be significantly improved.

The composition range of the composition of the present invention will be explained below. M
e-Ba and 3r are necessary elements for forming the perovskite structure of the above-mentioned general formula, and if the content is less than 1m01%, a pyrochlore structure will be present and high dielectric constant and high insulation resistance will not be exhibited. At 35mo1% or more, the dielectric constant is 100.
It may become small to about 0 or less, or the firing temperature may be 11
The temperature may rise to 00°C or higher. Therefore, the Me acid component substitution amount is o, o when expressed as (Pb1.Me8).
It is assumed that i≦a≦0.35.

In order to increase the capacitance of dielectric materials at room temperature, the Curie temperature at which the dielectric constant becomes maximum is around room temperature (0 to 3
0℃). The Me acid component of the present invention is an essential component for forming a perovskite structure as described above, but it also functions as a shifter to lower the Curie temperature of the porcelain composition of the present invention. Furthermore, it significantly increases insulation resistance and improves mechanical strength.

The substitution position of pb by the Me acid component can be appropriately selected taking into consideration the Curie temperature, etc., but it is important to note that the substitution position of pb by the Me acid component can be appropriately selected in consideration of the Curie temperature, etc. 1)
Therefore, 10+o1% or more is preferable, and in areas with a large amount of lead magnesium niobate (y>0.6.z<0.05), 1 m
At 0.01% or more, the substitution effect is sufficiently exhibited.

FIG. 1 shows the composition range of the ceramic composition of the present invention.

Outside the line segment ad, the firing temperature becomes as high as 1100° C. or higher, and the insulation resistance also decreases, making it impossible to obtain high reliability.

Furthermore, since the Curie temperature outside the line segment cd is originally near normal temperature, the substitution with the Me acid component significantly shifts the Curie temperature to the lower temperature side, resulting in a significant decrease in the dielectric constant at room temperature. In addition, the additive B1040~60wt
%, Si, 025~15wt%, 8010~30w
t%.

0.0 glass component consisting of 802015~25wt%
If the content is less than 0.05% by weight, it will hardly be expected to significantly improve the moisture resistance load test results when used as a multilayer ceramic capacitor, and if it is more than 1% by weight, the dielectric constant will increase significantly. This is because it decreases to .

Next, a method for producing the composition of the present invention will be explained.

Pb, Ba, Sr, Zn as starting materials.

Oxides of Nb, Ti, and MO, or salts such as carbonates and oxalates that become oxides upon firing, hydroxides, organic compounds, and the like are weighed out in predetermined proportions, thoroughly mixed, and then calcined. This calcination is performed at about 700 to 850°C. If the calcination temperature is too low, the sintered density will decrease, and if it is too high, the sintered density will also decrease and the insulation resistance will decrease.

Next, the calcined product is pulverized and the above-mentioned glass component is added to produce a raw material powder. The average particle diameter is preferably about 0.5 to 2 μm; if it is too large, the sintered density will decrease, and if it is too small, the moldability will decrease. A high dielectric constant porcelain is obtained by molding such raw material powder into a desired shape and firing it. By using the composition of the present invention, firing is possible at 1100°C.
Hereinafter, it can be carried out at a relatively low temperature of about 930 to 1080°C.

When manufacturing a laminated type element, a binder, a solvent, etc. are added to the raw material powder mentioned above to form a slurry, a green sheet is formed, internal electrodes are printed on this green sheet, and a predetermined number of sheets are printed as a Vi layer.

Manufactured by pressing and firing. At this point, since the dielectric material of the present invention can be fired at a low temperature, an inexpensive, low-resistivity material mainly composed of silver, for example, can be used as the internal electrode material.

Furthermore, since it can be fired at such a low temperature, it is also effective as a material for thick film dielectric pastes printed and fired on circuit boards and the like.

The ceramic composition of the present invention has excellent moisture resistance load tests when used as a multilayer ceramic capacitor, which had been a drawback of conventional lead perovskite composite compounds, and has high insulation resistance and
Low dielectric loss and good DC bias characteristics. Also C
It also has a large R value, which is sufficient even at high temperatures, and has excellent reliability at high temperatures.

Small T, C, and C are major features of the present invention,
This is particularly noticeable for large dielectric constants such as K≧10,000. When the dielectric constant is as large as this, it is required that (permittivity)/(absolute value of temperature change rate) be large. The present invention is also very superior in this respect.

Furthermore, the dependence of the dielectric constant on electric field is also superior to that of conventional lead titanate-based materials, and it is possible to obtain a material with a dielectric constant change rate of 10% or less even when the rate of change is 4/#.

Therefore, it is effective as a material for high pressure. Furthermore, it has low dielectric loss and is effective for AC and high frequency applications.

Furthermore, since <T, C, C, as described above, is small, even when applied to an electrostrictive element, an element with small temperature change at displacement can be obtained.

Furthermore, since the grain size during firing is made uniform to 1 to 3 μm, it also has excellent pressure resistance.

Although the electrical properties have been described above, the mechanical strength is also sufficiently excellent.

[Effect of the invention] As explained above, according to the present invention, the weight ratio is 0.05
~1.0mm% Bi20340~60wt%, sto
5-15wt%, B2O310-30wt%, A
020 By adding a glass component of 15 to 25 wt%, it has excellent moisture resistance load test when made into a multilayer ceramic capacitor, and has high insulation resistance, low dielectric loss, and good fg T, C, C, and DC bias characteristics. A high dielectric constant ceramic composition can be obtained. In particular, since ceramic compositions with such excellent properties can be obtained by firing at low temperatures, they are suitable for application to multilayer ceramic elements such as low-cost multilayer ceramic capacitors and multilayer ceramic displacement generating elements. .

[Embodiments of the invention] The present invention will be explained in detail below.

Starting materials such as oxides of Pb, Ba, Sr, Zn, Nb, Ti, and Mq are mixed in a ball mill etc.
Calculate at 0℃. Next, a predetermined amount of Bi2O is added to this calcined body.
3,5i02,8203°Ag2O is heated in a platinum crucible, poured into the vitrified solution in water, and then a glass component crushed to 0.5 to 10 μm with a ball mill etc. is added, crushed with a ball mill etc., and after drying, A binder was added, granulated, and pressed to form a disc-shaped element with a diameter of 17 m+ and a thickness of about 2 m. As balls for mixing and grinding, it is preferable to use balls with high hardness and high toughness, such as partially stabilized zirconia balls, in order to prevent contamination of impurities.

This element body was sintered in air at 930 to 1080°C for 2 hours, silver electrodes were baked on both main surfaces, and various characteristics were measured. The dielectric loss and weight were measured using a digital LCR meter under conditions of 1kl-1z, 1Vrms, and 25°C, and the dielectric constant was calculated from these values. In addition, the insulation resistance is 100
It was calculated from the value measured using an insulation resistance meter after applying a voltage of 0 V for 2 minutes. In addition, T, C, C, are 25℃
Based on the value of , it was expressed as a rate of change at -25°C and 85°C. The capacitance-resistance product was determined from (dielectric constant at 25° C. and 125° C.)×(insulation resistance)×(dielectric constant in vacuum). Insulation resistance measurements were performed in silicone oil to eliminate the effect of atmospheric moisture. The results are shown in Table 1.

The blank space below The multilayer ceramic capacitor was created using the following method. First, a binder and an organic solvent were added to calcined powder having such a composition to form a slurry, and then a 45 μm green sheet was created using a doctor blade type caster.

1514 of 70AQ/30Pd on this green sheet
The paste was printed in a predetermined pattern, and 20 sheets having such an electrode pattern were laminated and pressure-bonded. Thereafter, it was cut into a predetermined shape, degreased, and fired at 1040° C. for 2 hours. After sintering, AQ paste was baked as an external electrode to produce a multilayer ceramic capacitor. FIG. 2 shows a multilayer ceramic capacitor obtained by the above method, and Table 2 shows the electrical characteristics of a multilayer ceramic capacitor constructed as shown in FIG. 2 using the composition of Example 4 shown in Table 1. It shows the characteristics of 1 in Figure 2
is a dielectric, 2 is an internal electrode, and 3 is an external electrode.

Tables 2 and 3 show the results of the humidity load test of the insulation resistance (ΩF) of the multilayer ceramic capacitors prepared using the compositions of Examples 1 and 2.4 and Reference Examples 1 and 3.

Table 3 Test conditions were 40°C, 95% RH, and 50V applied.

It took 2000 hours. The quantity is 100 pieces for each lot. In the judgment, those whose resistance was 500 ΩF or less after the test were judged as defective. As is clear from Table 3, 5 to 6/100 of 'M4M ceramic capacitors using materials that do not contain glass components show a decrease in insulation resistance after the test, whereas the present invention A multilayer ceramic capacitor fabricated using a material containing 0.05 to 1 wt% of the glass component having the above structure shows no decrease in insulation resistance in a humidity load test.

As described above, the high dielectric constant ceramic composition according to the present invention has excellent various properties and is particularly effective as a material for V4 layer ceramic capacitors.

In the above explanation, the glass component as an additive was added to the roasted powder, but it is clear that the same characteristics can be obtained even if it is added at the time of preparation, and such methods are also included in the scope of the present invention.

[Brief explanation of drawings]

FIG. 1 is a composition diagram showing the composition range of the present invention, and FIG. 2 is a composition diagram showing the composition range of the present invention.
FIG. 2 is a partially cutaway perspective view showing a multilayer ceramic capacitor. 1...Dielectric 2...Inner electrode 3...Outer electrode Patent application Marcon Electronics Co., Ltd. Composition diagram showing the composition range of the present invention Figure 1 1M electric Partially cutaway perspective view of a multilayer ceramic capacitor Figure 2

Claims (1)

[Claims] General formula xPb(Zn_1_/_3Nb_2_/_3)O_3-
yPb(Mg_1_/_3Nb_2_/_3)O_3-
When expressed as zPbTiO_3, the ternary diagram a(x=0.50, y=0.00, z=0.50)b(
x=1.00, y=0.00, z=0.00)c(x=
0.20, y=0.80, z=0.00) d(x=0.
1 to 35 mol% of Ba
and Bi_2O_340 to 60 for a high dielectric constant ceramic composition characterized by substitution with at least one of Sr.
wt%, SiO_25-15wt%, B_2O_310
A high dielectric constant ceramic composition characterized by adding 0.05 to 1.0 wt% of a glass component consisting of ~30 wt% and 15 to 25 wt% of Ag_2O.