KR900002529B1 - Eielectric ceramic composition - Google Patents

Abstract

A dielectric ceramic compsn. comprises 91.6-95.5 wt.% barium titanate, 0.18-0.31 wt.% cobalt oxide, 1.04-1.87 wt.% bismuth trioxide, 0.68-1.23 wt.% titanium dioxide, 0.67-1.20 wt.% lead oxide, 0.26-0.46 wt.% boron oxide, 0.82-1.49 wt.% zinc oxide and 0-0.11 wt.% manganese dioxide. The compsn. has dielectric constant of no less than 2400 and electrostatic capacity variation of less than 15% to room temparature at -125-35 deg.C.

Description

Insulation ceramic composition

The present invention relates to an insulating ceramic composition fired at a low temperature and having a dielectric constant that does not change by more than 15% over its default value over a wide temperature range. In particular, the present invention relates to insulating ceramic compositions having a dielectric constant of at least 2400 formed by suing a base ceramic blend consisting of a mixture of insulating oxide and ceramic flux at a temperature not exceeding about 1150 ° C.

The multilayer ceramic capacitor typically forms an insulating layer made of an insulated ceramic powder, on which a conductive metal electrode layer, usually in the form of a metal paste, is coated, and the insulating layer provided with the conductive metal electrode layer is stacked to form a multilayer ceramic capacitor. It is made by calcining the product to densify and form a solid solution of the insulating oxide constituting.

Barium titanate is one of insulating oxides which are frequently used for forming an insulating ceramic layer.

However, due to the high Curie temperature of barium titanate, other oxides usually react with barium titanate to form a solid solution, resulting in a reduced curie temperature of the resulting ceramic material.

Since the dielectric constant is the highest at the Curie temperature of the material, the Curie temperature of the material used as the capacitor is preferably about room temperature.

Any other oxide, such as manganese dioxide, may be added to act as a particle growth controller to improve insulation resistance and to control the dielectric constant of the product. It is also important in practice that the dielectric constant of the ceramic composition to be used in the multilayer capacitor varies with temperature.

Many insulating ceramic compositions, including barium titanate, have a dielectric constant that varies substantially with temperature. Insulating ceramic compositions for multilayer capacitors that are used for applications requiring a stable dielectric constant over a wide temperature range preferably have a dielectric constant vary within ± 15% from the default value at 25 ° C (room temperature).

As with the adjustment of the Curie temperature, reacting the selected oxide with barium titanate is necessary to obtain a dielectric constant that does not change significantly with temperature.

Materials commonly used to produce capacitors with dielectric constants above 2000 and temperature stable are generally fired and aged in an atmosphere at temperatures above 1500 ° C.

At such temperatures, the metal electrode layer should be made of so-called alloys of precious metals, such as palladium and silver alloys, alloys of palladium and silver with poor melting points and alloys of palladium and gold, and other similar expensive alloys well known in the art.

This is necessary to prevent the phenomenon in which the insulating ceramic layer and the electrode react or to prevent the phenomenon of melting causing discontinuity of the conductive layer.

The method of preparing a ceramic composition that can be suited at temperatures below 1150 ° C., has desirable temperature characteristics and has a dielectric constant of 2000 or more will enable the use of inexpensive electrode materials without sacrificing capacitor performance.

Insulating ceramic compositions previously used to make multilayer capacitors at temperatures below 1150 [deg.] C. have dielectric defects of 2000 or less and are not suitable in many cases.

It is an object of the present invention to prepare a ceramic composition having a stable dielectric constant over a wide temperature range.

Yet another object of the present invention is to produce a ceramic composition fired at low temperature, having a dielectric constant of 2400 or more, the dielectric constant of which rarely changes with temperature.

The above-mentioned objects of the present invention are provided by the present invention for producing a low-temperature fired insulating ceramic composition formed from two components, namely, a main component constituting the base ceramic blend and a glass frit, i.e., a subcomponent constituting the ceramic flux. Can be performed.

In particular, in forming the insulating ceramic composition of the present invention, the main component is comprised of 93.5-96.5% by weight of the insulated ceramic composition and the minor component is comprised of 3.5-6.5% by weight of the composition.

The main component of the ceramic composition is a base ceramic of insulating oxide composed of barium titanate (BaTiO ₃ ), niobium pentoxide, and cobalt oxide, or an oxide of these components, that is, an oxide precursor.

Preferably, TAM ceramics TICON HPB, product number 52901, high purity barium titanate is used for manufacturing the base ceramic.

The component range of the base ceramic blend component represented by the oxide is 98.0-99.0 wt% barium titanate, 0.97-1.54 wt% niobium pentoxide, and 0.19-0.32 wt% cobalt oxide.

The minor components of the ceramic flux consist of bismuth titanate, lead titanate (PbTiO ₃ ), zinc oxide and boron oxide or their component oxides, ie oxide precursors.

Bismuth titanate mentioned herein is an oxide of its component, ie an oxide precursor, in an amount capable of forming Bi ₂ Ti ₂ O ₇ or Bi ₂ Ti ₂ O ₇ .

The content ratio of the grass frit is 16-60 weight% of bismuth titanate, 8-52 weight% of lead titanate, 18-35 weight% of zinc oxide, and 5-11 weight% of boron oxide.

Manganese dioxide can also be added to the mixture of base ceramics and ceramic fluxes in the form of precursors such as oxides themselves or solutions containing manganese carbonate or manganese ions. The composition ratio of manganese dioxide is contained at 0.114% by weight or less, preferably 0.05% by weight, of the combined weight of the ceramic flux and the base ceramic compound.

In a preferred specific embodiment, the base ceramic formulation is comprised of 93.5-96.5 wt% of the total weight of the insulation composition and the grass frit is preferably comprised of 3.5-6.5 wt% of the total weight of the insulation composition, the composition ratio being particularly It is more preferable that 95 weight% and glass frit consist of 5 weight%.

In a preferred specific implementation, the weight ratio of bismuth titanate to lead titanate in the ceramic flux is 7.33: 1 to 0.33: 1 to 1.24: 1. The preferred amount of zinc oxide for the base ceramic blend is 1.22-1.6 wt%, the preferred amount of boron oxide for the base ceramic blend is 0.38-0.50 wt%, boron oxide 0.26-0.46 wt%, cobalt oxide 0.18-0.31 wt%, 0.11% or less by weight of manganese dioxide, 0.82-1.49% by weight of zinc oxide, 1.04-1.87% by weight of bismuth oxide, 0.68-1.23% by weight of titanium dioxide, 0.67-1.20% by weight of lead oxide, and 0.91-1.49% by weight of niobium oxide It is good to be%.

The dielectric constant of the preferred ceramic composition of the present invention formed of a multilayer capacitor is typically at least 2400, the dissipation coefficient is 1.4% at 1 Vrms, and the dielectric constant varies only by ± 15% in the temperature range of -55 ° C to 125 ° C. The capacitor is preferably formed by firing at a temperature of 1100 ℃ to 1150 ℃.

In a preferred specific implementation, the ceramic insulation composition comprises 95.24% by weight of a base ceramic blend consisting of 98.31% BaTiO ₃ , 1.40% Nb ₂ O ₅ and 0.29% CoO; A mixture of 4.76% by weight of ceramic flux consisting of 27.98% by weight of Bi ₂ Ti ₂ O ₇ , 40.02% by weight of PbTiO ₃ , 24.4% by weight of ZnO and 7.6% by weight of B ₂ O _3, and the combined total weight of the base ceramic blend and ceramic flux. It can be formed from manganese dioxide in an amount of 0.05%.

As will be described below, the insulating ceramic composition of the present invention has several advantages that can result in substantial cost savings without sacrificing the desired physical and electrical properties.

The present invention provides a novel insulating ceramic composition having improved temperature properties that can be prepared by firing component oxides or precursors thereof at temperatures not exceeding 1150 ° C.

Such compositions differ from prior art insulating ceramic compositions where desired physical properties such as high dielectric constants are sacrificed to obtain a material that can be produced at such low temperatures. Since the ceramic composition of the prior art has a dielectric constant that is too low to be practically used, it has previously been necessary to use a calcined material at a temperature of 1150 ° C or higher.

At such high temperatures, an electrode containing a lot of precious metals such as palladium or platinum should be used.

Firing the ceramic composition of the present invention at low temperature makes it possible to use silver-palladium electrodes having a composition of 70% silver and 30% palladium as the conductive layer in the multilayer capacitor.

This is very desirable because the precious metal palladium is considerably more expensive than silver. Therefore, the use of the ceramic composition according to the invention in a multilayer capacitor is a significant economic savings.

The calcined ceramic body of the present invention is a base ceramic compound containing barium oxide, titanium dioxide, cobalt oxide and niobium pentoxide, bismuth trioxide, titanium dioxide, Prepared by reacting a small amount of grass frit containing lead oxide, zinc oxide and boron oxide. Oxides of the base ceramic blend and the ceramic flux may be included as titanate or other combinations.

For example, barium titanate may be formed by reacting barium oxide with titanium dioxide. Similarly, bismuth oxide and titanium dioxide may react to form bismuth titanate and Bi ₂ Ti ₂ O ₇ . Bound oxides may be formed from the reaction of oxide precursors such as carbonates or nitrides with other component oxides or precursors thereof.

As is well known in the art, commercial production of barium titanate, lead titanate, bismuth titanate, etc., has several grades, so the ratio of the base ceramic blend to the ceramic flux components is finely tuned using well-known experimental methods to achieve the desired properties. Should be done.

Alternatively, the calcined ceramic body of the present invention reacts with a master mix prepared by calcining cobalt oxide, niobium pentoxide, zinc oxide, boric acid, and manganese carbonate during firing, and barium titanate, bismuth titanate, and lead titanate. Are prepared. In the present invention, the proportions and particle sizes of the constituent oxides of the base ceramic formulation are selected to maximize the desired physical and electrical properties. When niobium pentoxide is added to barium titanate, it shifts the sharp dielectric constant peak that occurs at the curie temperature of barium titanate to room temperature.

It is believed that the proper distribution of constituent oxides results in a nonuniform solid solution of niobium pentoxide along the barium titanate particles and calcined ceramic grain boundaries, resulting in a wide range of Curie temperatures. This keeps the constant temperature constant of the capacitance while suppressing the dielectric constant. Cobalt oxide in the base ceramic blend acts as a flux and also as a charge compensator for pentavalent niobium. The constituents of the ceramic flux are selected to obtain a non-homogeneous solution of barium titanate particles and grain boundaries at the lower firing temperature conditions and with a lower dielectric constant of the base ceramic formulation, as in the base ceramic formulation. Zinc oxide boric acid produces a low viscosity eutectic mixture during the firing process. Zinc bromide also inhibits the dielectric constant, so the amount of these compositions should be kept as low as possible. Bismuth titanate and lead titanate act as high viscosity fluxes to increase the viscosity of the zinc bromide formed during firing. Bismuth titanate and lead titanate act as fluxing agents because of their very high dielectric constant and Curie temperature, minimizing the suppression of the dielectric constant.

The ratio of zinc oxide to boric acid and bismuth titanate to lead titanate is also chosen to balance charge compensation and the overall stoichiometric amount of calcined ceramic, which is important in the art. Manganese oxide components are very effective in balancing receptor-donor ions due to their multivalent valences. With this ability, manganese oxide improves the insulation resistance of fired ceramics.

In the preparation of the base ceramic blend used in the present invention, the component oxides in the proportions described above can be slurried together in water. After drying, the mixture can be mixed with the ceramic flux composition and manganese oxide. The ceramic flux composition may consist of a mixture of component oxides, and the flux component oxides may be dissolved together, quenched and pulverized to form a single component frit. The combined mixture of base ceramic blend, ceramic flux composition, and manganese oxide is cast into a sheet which is typically used using standard methods, 70% is formed of a multilayer capacitor having a structure of -30% palladium electrode, and 1110 for 3 hours. It is baked at a temperature of ℃ -1150 ℃.

-F(오옴-파라데이)보다 크고, 125℃와 50V_DC/mil에서 2,000

-F보다 큰 절연저항-정전 용량적(RC)을 갖는다. 유전상수는 전형적으로 1KHz와 1Volt rms에서 약 2500±200이고 소산계수는 1KHz 와 1 Volt rms에서 약 1.8±0.2%이다.The insulating composition fired at a low temperature of the present invention is 10,000 at 25 ℃ and 50V _DC / mil

Greater than -F (Ohm Faraday), 2,000 at 125 ° C and 50V _DC / mil

Has insulation resistance-capacitance (RC) greater than -F. The dielectric constant is typically about 2500 ± 200 at 1KHz and 1Volt rms and the dissipation factor is about 1.8 ± 0.2% at 1KHz and 1 Volt rms.

It is particularly important that the dielectric constant of the ceramic composition of the present invention hardly change with temperature and predictably change with temperature. In a preferred insulating ceramic composition in which a multilayer capacitor whose temperature stability is important is used, the temperature coefficient of the capacitance is such that the dielectric constant does not increase or decrease by more than 15 percent in the temperature range of -55 ° C to 125 ° C from the reference value at 25 ° C. This figure represents a reference in the ceramic industry known as the X7R temperature characteristic.

The temperature coefficient of capacitance in the insulating ceramic composition of the present invention meets this criterion.

The invention is further illustrated by the following examples, but is not necessarily limited thereto.

The numerical values in the following examples can be varied based on factors known in the art.

For example, in Examples 1-31, the dielectric constant may be significantly increased and the acid coefficient may be significantly reduced by grinding, milling and uniformly dispersing the starting material into fine particles. Such a particle treatment process normally performed in the manufacture of ceramic capacitors is not fully shown in the method of Examples 1-31. In addition, variations in firing temperature, sample thickness and formulation, and measurement errors cause differences in measurements for the same composition.

Depending on the manufacturing technique and irrespective of the particle size, the properties of the ceramic composition produced using the proportions given in the preparation method according to Examples 1-31 can vary from the given values.

For example, the dielectric constant may vary by ± 200, the dissipation factor may vary by ± 0.2%, and the change in capacitance with temperature at a capacitance at 25 ° C. may vary by ± 1.5%.

Example 1-7

Effect of Changes in the Ratio of Ceramic Flux on Base Ceramic Compounds

The base ceramic formulation is prepared by slurrying TAM ceramic TICON HPB high purity barium titanate 49.15 grams, technical grade fine particle size niobium pentoxide 0.70 grams, and cobalt oxide fine particles 0.15 grams in water.

A mixture of 0-5 grams of ceramic flux consisting of 41.2 wt% of bismuth titanate (Bi ₂ Ti ₂ O ₇ ), 26.8 wt% of lead titanate (PbTiO ₃ ), and 24.4 wt% of zinc oxide (ZnO) is mixed with 7.6 grams Boron oxide (B ₂ O ₃ ) of is added in the form of boric acid (H ₃ BO ₃ ).

The ratio of the base ceramic formulation and the ceramic flux of Examples 1-7 is shown in Table 1.

For each sample manganese carbonate is added to the resulting mixed powder of base ceramic blend and ceramic flux in an amount of 0.057% by weight of the total powder. The ceramic powder mixture is added to 25 ml of distilled water and mixed thoroughly in a high speed specex paint mixer for 10 minutes.

The resulting slurry is then dried into cakes and ground into pestle. 4 ml of a binder solution containing 26% by weight of water, 26% by weight of propylene glycol and 48% by weight of coon syrup are mixed with ceramic powder in mortar and pestle and placed through a 40 mesh nylon screen. Discs of the resulting mixture, 0.1-0.15 cm thick and 1.27 cm in diameter, are compressed to a pressure of 38,000 pounds per square inch in a stainless steel die.

The resulting disk is placed on a stabilized zirconia setter and subjected to a temperature of 1110 ° C.-1150 ° C. for 3 hours. After cooling the product, the thickness and diameter of the sintered ceramic discs were measured with micro meta and vernier calipers. The silver electrode was painted on the main surface and fired at 850 ° C. on the electrode to sinter it on the electrode. Capacitance, dissipation factor (DF) and temperature-dependent capacitance change (TC) for capacitance at 25 ° C were measured with an Electro Scientific Industry Model 2100A bridge at 1KH _Z 1Vrms.

At least three disks were measured from each example. The measurement and temperature change programs were controlled by both computer and microcomputer, and the measuring steps were carried out in accordance with accepted industrial practice.

The dielectric constant (K) of each disk was calculated by the following equation:

Where C ₂₅ is the capacitance value at 25 ° C., l is the thickness of the disk in inches and D is the diameter of the disk in inches.

The results are shown in Table 1 from which, as in Examples 1 and 2, when the weight ratio of the ceramic flux / base ceramic compound is less than 0.035, the insulating ceramic composition is not sintered to a sufficient density, and the TC at -55 ° C is 18 You can see that it is greater than%.

As in Examples 6 and 7, when the weight ratio of the ceramic flux / base ceramic blend is greater than 0.065, the dielectric constant is reduced to 2100 or less.

These compositions have practically no value, even with improved dissipation coefficients and stable TC properties.

TABLE 1

Effect of Changes in the Ratio of Ceramic Flux on Base Ceramic Compounds

Example 8-11

Amount of manganese

50 g of the base ceramic blend as described in Examples 1-7 were mixed with 2.65 g of ceramic flux as described in Examples 1-7. Manganese carbonate was added to the resulting mixed powder while varying the weight percent as shown in Example 8-11 in Table 2.

Ceramic discs were prepared and sintered in the same manner as described in Examples 1-7. Dielectric properties were measured and the results are shown in Table 2. The addition of manganese carbonate increased the dissipation factor and TC of the ceramic insulation composition.

However, when the manganese carbonate was added in an amount of 0.190% by weight or more as in Example 11, the dielectric constant was reduced to 2100 or less, and as a result, the material was not suitable for use in the multilayer capacitor.

TABLE 2

Effect of Manganese Sheep

Example 12-17

Non-change of Bismuth Titanate to Lead Titanate

50 g of the base ceramic blend powder as described in Examples 1-7 are mixed in 2.65 g of ceramic flux. In each example, the ceramic flux contained 68% by weight of bismuth titanate and lead titanate, as well as 24.4% by weight zinc oxide and 7.6% by weight boron oxide. The weight ratio of bismuth titanate to lead titanate is varied as shown in Table 3. Manganese carbonate is added to the base ceramic blend / ceramic flux powder in an amount of 0.057% by weight.

The ceramic disks were then prepared and sintered and the insulation properties were measured as described in Examples 1-7.

It can be seen from this example that when the bismuth titanate / lead titanate weight ratio was increased, the dielectric constant of the insulating ceramic composition decreased to 2000 when no lead titanate was included as in Example 12.

As in Example 17, when the ratio of bismuth titanate / lead titanate became zero as in Example 17, the dielectric constant was high and the dissipation coefficient was low, but the TC value at -55 ° C exceeded -15%. The compositions of Examples 16 and 17 having a bismuth titanate / lead titanate weight ratio of less than 0.333 are less preferred than the compositions of Example 4, for example, for comparative purposes, for the second time in the TC feature that lead titanate starts at about 45 ° C. This has the acceptor effect of introducing the peaks and makes TC at 125 ° C. worse than ceramic compositions with bismuth titanate / lead titanate weight ratios greater than 0.333.

Although not apparent from Table 3, the capacitance change in Example 16 is still within ± 15% between −55 ° C. and 125 ° C. and when applied to a multilayer capacitor design, the composition of Example 16 is a very common additional component in multilayer capacitor manufacturing. Because of the acceptor, it has a high potential to make a second peak at about 45 ° C., which exceeds + 20%.

TABLE 3

Non-change of Bismuth Titanate to Lead Titanate

*: The composition of Example 12 did not contain lead titanate.

Example 18-25

Non-change of Bismuth Titanate + Lead Titanate to Zinc Oxide + Boron Oxide

50 g of the base ceramic blend was mixed with 2.65 g of ceramic flux and the resulting mixed powder was mixed with 0.057% by weight of manganese carbonate as described in Examples 18-25 in Examples 1-25.

In the ceramic flux compositions of these examples, the amount of binding of bismuth titanate and lead titanate to the amount of zinc oxide and boron oxide was varied. A mixture of 60.4 g of bismuth titanate and 39.6 g of lead titanate was prepared as a mixture of 78.2 g of zinc oxide and 21.8 g of boron oxide was prepared. The weight ratio of bismuth titanate / lead titanate to the zinc oxide / boron oxide mixture was varied as shown in Table 4.

The ceramic disks were then prepared, sintered and the insulation properties measured as described in Examples 1-7, and the results for each example are shown in Table 4.

As can be seen from this result, when the weight ratio of the bismuth titanate / lead titanate component to the zinc oxide / boron oxide component is larger than 3.2 as in Example 18, the ceramic insulating composition could not be sintered to a sufficient density. Therefore, in this example, the dielectric constant was low, the dissipation factor was high, and the TC was large.

If the ratio was less than 1.24 as in Examples 22-25, the ceramic composition was semiconducting and the TC characteristics were very large.

Examples 24 and 25 most clearly demonstrate the need to add bismuth titanate and lead titanate components in order to obtain stable temperature characteristics of the present invention.

TABLE 4

Non-change of Bismuth Titanate + Lead Titanate to Zinc Oxide + Boron Oxide

* Total: 2%

Example 26-31

Changes in the amount of zinc oxide and boron oxide

50 g of the base ceramic compound powder was mixed with 1.03 g of bismuth titanate and 0.67 g of lead titanate as described in Examples 1-7 in each of Examples 26-31, and the weight ratio of zinc oxide and boron oxide to the total It was changed as shown in Table 5. Manganese carbonate was added to the total mixture of each example in an amount of 0.057% by weight.

Ceramic discs were then prepared and sintered to measure insulation as described in Examples 1-7 and the results are shown in Table 5.

As can be seen from Table 5, if the ratio of boron oxide to total powder is greater than 0.005 as in Example 27, the dielectric constant decreased to 2100 or less and became too low for practical use. If the ratio of zinc oxide to total powder was greater than 0.016 as in Examples 30 and 31, the resulting sample was semiconducting and exhibited widely varying TC properties.

As can be seen from Example 31, a composition with a zinc oxide to total powder ratio of 0.020 showed a second peak of at least 15% in TC, so that a composition containing a higher amount of zinc oxide was a multilayer according to the present invention. Not suitable for use in capacitors.

TABLE 5

Changes in the amount of zinc oxide and boron oxide

Example 32

474.6 g base ceramic formulation powder described in Examples 1-7 6.6 g bismuth titanate, 9.5 g lead titanate, 5.8 g zinc oxide 3.2 g, 0.3 g manganese carbonate with 5 g Nuodex V1444 surfactant, 20 g toluene, 5 g ethanol And 250 g of a binder solution prepared by uniformly mixing 27.5 g of Butvar B-76 vinyl resin, 5 g of Nuodex V1444, 13.8 g of dioctyl phthalate, 163 g of toluene, and 445.8 g of ethanol to disperse uniformly to prepare a ceramic powder slurry. It was.

The resulting slurry was milled for 16 hours and discharged and filtered through a 44 micron screen. To adjust the viscosity to 3360 cps, 360 g of the resulting slip with a viscosity of 4960 cps were mixed with 4.8 g of toluene and 1.2 g of ethanol. The slips are then degassed by vacuum and cast into strips or tapes of 2.4 mil thickness by techniques known in the art. The tape was converted to a multilayer ceramic capacitor with electrodes of 70% silver and palladium 30% by known methods. This capacitor was preheated to 260 ° C. for 48 hours and placed in stabilized zirconia or high density alumina setter and sintered at 1110-1140 ° C. for 3 hours. The sintered capacitor had 10 active insulation layers with an insulation thickness of 1.75 mils. In order to connect the alternating layers, the electrode of DuPont Silver Pate No. 4822 was attached to the opposite end of the multilayer capacitor, and the capacitor was fired at 815 ° C. at the tunnel furnace.

-F 보다 컸으며 125℃와 50V_DC/mil에서 1650 Ω-F보다 컸고, 한편 1120-1140℃ 사이에서 소성된 커패시터인 경우에는 25℃, 50V_DC/mil에서 10, 000 Ω-F 보다 컸으며 125℃, 50V_DC/mil에서 2000 Ω-F 보다 컸었다.Results of measuring a dielectric constant insulating characteristics of the resulting capacitors 1KH was 2600 ± 200 in the _Z and 1Vrms, dissipation factor was 1.4 ± 0.2% at 1 KH _Z and 1 Vrms, TC is -12.0 ± 1.5% at -55 ℃ -9.0 ± 1.5% at -30 ° C, -4.0 ± 1.5% at 85 ° C, -0.5 ± 1.5% at 125 ° C, and RC is 3000 at 25 ° C and 50V _DC / mil for capacitors fired at 1110 ° C.

Greater than -F and greater than 1650 Ω-F at 125 ° C and 50V _DC / mil, whereas greater than 1, 000 Ω-F at 25 ° C and 50V _DC / mil for capacitors fired between 1120-1140 ° C. Greater than 2000 Ω-F at 125 ° C., 50V _DC / mil.

The isolation blocking voltage of the multilayer capacitor manufactured according to this embodiment was greater than 680 V _DC / mil.

Example 33

3.73 kg of cobalt oxide, 17.27 kg of niobium pentoxide, 15.16 kg of zinc oxide, 8.45 kg of boric acid, and 0.747 kg of manganese carbonate were mixed and blended in a large-scale conical blender for 2 hours to prepare a ceramic master mix.

The powder mixture was calcined in a tunnel kiln at a temperature of 815-825 ° C. for 3 hours.

The calcined material is then ground and placed in a vibratory energy mill with alumina medium in deionized water at about 55% by weight powder. The slurry was milled for 10 and a half hours, discharged, dried, and ground to a surface area of 4.97 M ² / g and a particle size of 1.4 microns.

As described above, the ceramic mixture was prepared by dry mixing and blending 424.7 kg of TAM ceramic TICON HPB high purity barium titanate, 6.05 kg of bismuth titanate, 8.636 kg of lead titanate, and 14.22 kg of master mix in a large-scale conical mixer for 2 hours. The resulting powder mixture had an average particle size of 1.3 microns and a surface area of 2.5 M ² / g.

400 g of the resulting insulating composition was mixed with 24 g of Butvar B-76 vinyl resin, 40.4 g of Nuodex V1444, 12 g of dioctyl phthalate, 142 g of toluene, and 35.5 g of ethanol. Place in a pebble mill with media. The slurry was milled for 16 hours and discharged and filtered through a 44 micron screen.

The slip having a viscosity of 1880 cps was degassed and cast into a tape of 1.5 mils in thickness by known techniques.

The tape was converted to a multilayer ceramic capacitor with electrodes of 70% silver and palladium 30% and sintered according to the known art to provide a silver electrode as described in Example 31.

The sintered ceramic capacitor of this example had ten active insulating layers with an insulating layer thickness of 1.0 mil.

The dielectric properties of the capacitor in this example were 2600 ± 200 at 1KHz and 1Vrms, the dissipation factor was 1.8 ± 0.2% at 1KHz and 1Vrms, and the temperature characteristic TC was -8.0 ± 1.5% at -55 ℃ and -30 ℃. At -5.5 ± 1.5 at -2.0 ± 1.5% at 85 ° C and 3.0 ± 1.5% at 125 ° C. Insulation-Capacitance The resulting RC was greater than 10,000 Ω-F at 25 ° C, 50V _DC / mil, and greater than 2,000 Ω-F at 125 ° C, 50V _DC / mil.

With 50V _DC bias voltage at 1KHz and 1Vrms, the capacitance change was -19.0 ± 2.0% at 25 ℃, -24.0 ± 2.0% at -55 ℃, and -24.0 ± 2.4% at 125 ℃.

The isolation cut-off voltage for the multilayer capacitor of this example was greater than 900V _DC / mil.

Claims (2)

91.6-95.5 wt% barium titanate, 0.91-1.49 wt% niobium pentoxide, 0.18-0.31 wt% cobalt oxide, 1.04-1.87 wt% bismuth oxide, 0.68-1.23 wt% titanium dioxide, 0.67-1.20 wt% lead oxide, oxidation Insulating ceramic composition, characterized in that consisting of 0.26-0.46% by weight of boron, 0.82-1.49% by weight of zinc oxide and 0.11% by weight of manganese dioxide. The insulating ceramic composition according to claim 1, wherein the dielectric constant of the composition changes within 15% at a temperature between −55 ° C. and −125 ° C. with respect to the capacitance when the dielectric constant is 2400 or more and the capacitance is 25 ° C. 3.