JPH0646620B2 - Method for manufacturing multilayer capacitor element - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer capacitor element, and more particularly to a multilayer capacitor element using lead perovskite oxide as a dielectric and using copper or an alloy containing copper as a main component as an internal electrode. Manufacturing method.

2. Description of the Related Art In recent years, as a ceramic capacitor, a multilayer ceramic capacitor is rapidly becoming popular due to demands for smaller size and larger capacity of the element. Further, as the frequency of the circuit becomes higher, it is necessary to use a multilayer ceramic capacitor element in a region where an electrolytic capacitor has been conventionally used. Multilayer ceramic capacitors are usually manufactured by a process of integrally firing internal electrodes and ceramics. Conventionally, barium titanate-based materials have been used for high dielectric constant ceramic capacitor materials, but since the firing temperature is as high as about 1300 ° C,
It was necessary to use expensive metals such as Pt and Pd as the internal electrode material. For this reason, attempts have been made to use inexpensive base metals for the internal electrodes.

On the other hand, the inventors have proposed a multilayer capacitor element in which lead perovskite oxide is used as a dielectric and copper or an alloy containing copper as a main component is used as an internal electrode.

Separately from this, a multilayer capacitor element using a barium titanate-based dielectric and using Ni as an internal electrode has been proposed, and its manufacturing method is known from the method described in JP-A-60-178611. ing. In these conventional techniques, metal powder is used as a starting material for the internal electrodes.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In a method for manufacturing a multilayer capacitor element having a base metal as an internal electrode, when a metal powder is used as a starting material for the internal electrode, a dielectric green sheet and a burnout of a binder component of the internal electrode paste are used. Occasionally, oxidation of the internal electrodes occurs, which causes problems such as a decrease in capacitance and an increase in dielectric loss at high frequencies due to the characteristics of the multilayer capacitor element after firing. Also, when burnout is performed in a low oxygen partial pressure atmosphere where oxidation of the internal electrodes does not occur, the carbonization phenomenon of the binder component is likely to occur, and the dielectric substance is reduced by carbon remaining after firing and the insulation resistance of the element is reduced. And the sintered density is likely to decrease.

Further, in order to use it as a starting material for the internal electrode, a metal powder having a small particle diameter is required, and the cost required for crushing at the time of manufacturing and the cost required for rust-proofing treatment of the metal powder, etc. There was a problem that the advantage could not be fully utilized.

Means for Solving Problems After using a raw material containing Cu ₂ O, CuO or a mixture thereof as a starting material for the copper internal electrode, the internal electrode pattern is printed on the dielectric green sheet and laminated. The binder component is burned out in air, and then the internal electrode is reduced to metallize at a temperature lower than the firing temperature.

Effect In the method for manufacturing a multilayer capacitor element according to the present invention, burnout can be performed in air, carbon can be prevented from remaining, and reduction in insulation resistance and reduction in firing density due to reduction of the dielectric ceramic during firing can be prevented. it can. In addition, copper has a higher equilibrium oxygen partial pressure than other base metals such as Ni, Fe, and Al, and does not form a passivation film. Therefore, Cu ₂ O, CuO, or a mixture thereof, is superior to other base metal oxides. Since it is completely reduced at low temperature and relatively high oxygen partial pressure, the electrode is reduced with almost no reduction in the dielectric, the dielectric after firing is dense and has a high insulation resistance, and the electrode is intercalated with oxide. Since it becomes a complete metal layer without any loss, a multilayer capacitor element with a small dielectric loss at high frequencies can be obtained. Further, by adopting such a manufacturing method, it is possible to use oxide powder, which is cheaper than metal powder, as a starting material for the internal electrodes.

Example 1 A material represented by the following composition formula was used as a dielectric.

(Pb _1.00 Ca _0.025 ) (Mg _1/3 Nb _2/3 ) _0.70 Ti _0.25 (Ni _1/2 W _1/2 )
_{The 0.05} O _3.025 dielectric powder was manufactured according to the usual ceramic manufacturing method. The calcination condition was 800 ° C. for 2 hours. The pulverized calcined powder was mixed in a ball mill with 5 wt% of polyvinyl butyral resin and 50 wt% of the calcined powder, and a sheet having a thickness of 35 μm was formed using a doctor blade. Purity average particle diameter 0.8μm of Cu ₂ O (Cu ₂ O as an internal electrode 9
9%) as a starting material, and kneaded with 0.5 wt% ethyl cellulose and 25 wt% solvent in Cu ₂ O by a three-roll mill to make an electrode paste, and print the internal electrode pattern on the dielectric green sheet using the screen printing method. did. This was laminated and cut so that the electrodes could be drawn out alternately to the left and right.

The above-mentioned electrode paste was applied to the end faces from which the electrodes were alternately drawn out to form external electrodes.

The laminate thus prepared was prepared by placing coarse-grained zirconia on a porcelain board and placing the zirconia on it to burn out the binder at 450 ° C. in air.

As shown in FIG. 1, burned-out laminated material 14
The porcelain board 12 on which is placed is placed inside the core tube 11 having an inner diameter of 50 mm in a tubular furnace, and nitrogen gas bubbling 20 wt.
The internal electrode was reduced by maintaining the temperature for 8 hours.

FIG. 2 shows a cross section of a magnesia porcelain container in which the laminated body during firing is put, and FIG. 3 shows a cross section of a firing furnace core tube. In the magnesia porcelain container 21, the above-mentioned calcined powder 22 was spread over about 1/3 of the volume, 200 mm of ZrO ₂ powder 23 was spread over about 1 mm, and the burned-out laminated body 25 was placed on it.
Cover the lid 24 of the magnesia porcelain, and the core tube 26 of the tubular electric furnace.
Inside, and degass the inside of the core tube with a rotary pump, then replace with N ₂ -H ₂ mixed gas, and mix while adjusting the mixing ratio of N ₂ and H ₂ gas so that the oxygen partial pressure becomes 1 × 10 ^−8. A gas was flown to raise the temperature to 980 ° C. at 400 ° C./hr, hold for 2 hours, and then lower the temperature at 400 ° C./hr. Po ₂ in the core tube is the voltage E between the electrodes extracted from the platinum electrode formed on the atmosphere side of the stabilized zirconia oxygen sensor 27 inserted and the inside of the furnace.
It was calculated from the following formula from (V).

Po ₂ = 0.2 · exp (4FE / RT) where F is the Faraday constant 96489 clone, R is the gas constant 8.3144 J / deg · mol, and T is the absolute temperature.

The external shape of the multilayer capacitor element is 2.8x1.4x0.9mm, the effective electrode area is 1.3125mm ² (1.75x0.75mm) per layer, the thickness of the electrode layer is 2.0μm, the dielectric layer is 25.0μm per layer and the effective layer is 30. Layers, two ineffective layers were provided above and below. The multilayer capacitor element has a capacitance, tan δ, applied with an AC voltage of 1V.
It was measured at a frequency of 0 Hz to 2 MHz. The resistivity is 50V
The value of 1 minute after applying a voltage of / mm was obtained.

Table 1 shows the capacity, tan δ, and resistance value.

Example 2 The same method as in Example 1 was used for the dielectric material and its sheet formation.

As the internal electrode, CuO with an average particle size of 1.2 μm (purity 97% as CuO) was used as a starting material, and it was kneaded with 0.5% by weight of ethylcellulose and 25% by weight of CuO in a three-roll roll to form an electrode paste, which was screen printed. The internal electrode pattern was printed on the dielectric green sheet using the method. This was laminated and cut so that the electrodes could be drawn out alternately to the left and right.

The above-mentioned electrode paste was applied to the end faces from which the electrodes were alternately drawn out to form external electrodes.

The laminate thus prepared was prepared by placing coarse-grained zirconia in a porcelain boat and placing it on the porcelain boat to burn out the binder in air at 500 ° C.

The porcelain board on which the burned-out laminated body was placed was put inside the core tube with an inner diameter of 50 mm in the tubular furnace shown in FIG.
Nitrogen gas containing 1% H ₂ was flown at a rate of 1 liter / min and the temperature was maintained at 400 ° C. for 5 hours.

This was fired in the same manner as in Example 1.

The outer shape of the multilayer capacitor element is 2.8 × 1.4 × 0.9 mm, the effective electrode area is 1.3125 mm ² (1.75 × 0.75 mm) per layer, the thickness of the electrode layer is 2.0 μm, the dielectric layer is 25.0 μm per layer, and the effective layer is 30. Layers, two ineffective layers were provided above and below. The capacitance and tan δ of the multilayer capacitor element were measured at a frequency of 100 Hz to 2 MHz by applying an AC voltage of 1V. The resistivity is 5
The value of 1 minute after applying a voltage of 0 V / mm was determined.

Table 2 shows the capacity, tan δ, and resistance value.

Example 3 The same method as in Example 1 was used for the dielectric material and its sheet formation.

As the internal electrode, the average particle size used in Examples 1 and 2 was 1.2.
A mixture of 50 wt% CuO 50 wt% and Cu ₂ O 50 wt% with an average particle size of 0.8 μm was used as a starting material, and was kneaded with 0.5 wt% ethyl cellulose and 25 wt% solvent in a three-roll roll to form an electrode paste, which was screen printed. The internal electrode pattern was printed on the dielectric green sheet using. This was laminated and cut so that the electrodes could be drawn out alternately to the left and right.

The above-mentioned electrode paste was applied to the end faces from which the electrodes were alternately drawn out to form external electrodes.

The laminate thus prepared was prepared by placing coarse-grained zirconia on a porcelain board and placing it on the porcelain board to burn out the binder at 500 ° C. in the air.

A porcelain board on which the burned-out laminated body was placed was placed in a core tube having an inner diameter of 50 mm in the tubular furnace shown in FIG. .

This was fired in the same manner as in Example 1.

The external shape of the multilayer capacitor element is 2.8x1.4x0.9mm, the effective electrode area is 1.3125mm ² (1.75x0.75mm) per layer, the thickness of the electrode layer is 2.0μm, the dielectric layer is 25.0μm per layer and the effective layer is 30. Layers, two ineffective layers were provided above and below. The multilayer capacitor element has a capacitance, tan δ, applied with an alternating voltage of 1 V
It was measured at a frequency of 0 Hz to 2 MHz. The resistivity is 50V
The value of 1 minute after applying a voltage of / mm was obtained.

Table 3 shows the capacity, tan δ, and resistance value.

Example 4 The same method as in Example 1 was used for the dielectric material and its sheet formation.

The internal electrode used in Example 1 has an average particle size of 0.8 μm.
Cu ₂ O is used as a starting material, and it is kneaded with 0.5 wt% ethyl cellulose and 25 wt% solvent with a three-roll mill to form an electrode paste, and an internal electrode pattern is printed on the dielectric green sheet by screen printing. did. This was laminated and cut so that the electrodes could be drawn out alternately to the left and right.

The above-mentioned electrode paste was applied to the end faces from which the electrodes were alternately drawn out to form external electrodes.

The laminate thus prepared was prepared by placing coarse-grained zirconia on a porcelain board and placing the zirconia on it to burn out the binder at 450 ° C. in air.

The porcelain board on which the burned-out laminated body was placed was put in the core tube with an inner diameter of 50 mm in the tubular furnace shown in FIG.
Nitrogen gas bubbling ammonia water or 1 vol%
Nitrogen gas containing H ₂ was flown at 1 liter per minute and maintained at a predetermined temperature for a predetermined time.

This was fired in the same manner as in Example 1.

The external shape of the multilayer capacitor element is 2.8x1.4x0.9mm, the effective electrode area is 1.3125mm ² (1.75x0.75mm) per layer, the thickness of the electrode layer is 2.0μm, the dielectric layer is 25.0μm per layer and the effective layer is 30. Layers, two ineffective layers were provided above and below. The multilayer capacitor element has a capacitance, tan δ, applied with an AC voltage of 1V.
It was measured at a frequency of 0 Hz to 2 MHz. The resistivity is 50V
The value of 1 minute after applying a voltage of / mm was obtained.

Table 4 shows the atmospheric gas, holding temperature, holding time, capacity, tan δ, and resistance value during electrode reduction.

As shown in Table 4, the holding temperature during electrode reduction is 250
If the temperature is lower than ℃, the electrode is not sufficiently reduced and remains oxidized, and diffuses into the dielectric layer during firing, which lowers the insulation resistance value and the electrode layer does not become a complete metal layer. Is reduced. Further, the reduction requires a long holding time. If it is higher than 650 ° C., the dielectric substance is reduced and it does not function as a laminated capacitor element after firing.

As is clear from the above four examples, in the method of manufacturing a multilayer capacitor element using a lead perovskite oxide dielectric and using copper as an internal electrode, Cu ₂ O, CuO, After printing the internal electrode pattern on the dielectric green sheet and stacking it using the raw material mainly containing the mixture, burnout of the binder component is performed in the air, and then the internal electrode is reduced at a temperature lower than the firing temperature. By adopting a manufacturing method in which metallization is performed and then firing is performed, a multilayer capacitor element having a large insulation resistance and a small dielectric loss at high frequencies can be obtained. Further, at this time, it is more desirable that the holding temperature of the internal electrode during reduction is 250 ° C. or higher and 650 ° C. or lower, and Cu is used as a starting material for the internal electrode.
_{If 2} O is used and a nitrogen gas in which ammonia water is bubbled is used as the reducing atmosphere, a multilayer capacitor element having further excellent characteristics can be obtained.

EFFECTS OF THE INVENTION According to the method for manufacturing a multilayer capacitor element of the present invention, in a multilayer capacitor element using lead perovskite as a dielectric and copper as an internal electrode, a multilayer capacitor element having a large insulation resistance value and a small high frequency dielectric loss can be obtained. In addition, the copper oxide powder, which is cheaper than the copper metal powder, can be used as a starting material for the internal electrode, and the electrode cost can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a reduction device for an internal electrode in one embodiment of the present invention, FIG. 2 is a sectional view of a magnesia container during firing, and FIG. 3 is a sectional view of a firing furnace core tube. 11 ... Reactor tube, 12 ... Porcelain boat, 13 ... Coarse-grained zirconia, 14 ... Laminated sample, 15 ... Ammonia water.

Claims (3)

[Claims] 1. A method of manufacturing a multilayer capacitor element, which uses a lead perovskite oxide dielectric and uses copper as an internal electrode, wherein Cu ₂ O, CuO or a mixture thereof is used as a starting material for the copper internal electrode. After printing the internal electrode pattern on the dielectric green sheet and stacking it using a raw material containing as a main component, burn out the binder component in air, and then reduce the internal electrode at a temperature lower than the firing temperature to metallize. A method of manufacturing a multilayer capacitor element, comprising: 2. The method for producing a multilayer capacitor element according to claim 1, wherein the holding temperature of the internal electrode during reduction is 250 ° C. or higher and 650 ° C. or lower. 3. A multilayer capacitor element according to claim 1, wherein Cu ₂ O is used as a starting material for the internal electrodes, and nitrogen gas with which ammonia water is bubbled is used as an atmosphere during reduction. Method.