JPH0831394B2 - 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 which uses lead or perovskite oxide as a dielectric and uses 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 laminated ceramic capacitor element in a region where an electric field 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 as high-dielectric-constant ceramic capacitor materials, but since the firing temperature is as high as 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, and a manufacturing method thereof. Among them, the method for manufacturing a multilayer capacitor element using copper oxide as a starting material for the internal electrodes has an advantage that a binder can be burned out easily and an inexpensive material can be used. In this manufacturing method, nitrogen gas containing 0.1% to 1% H ₂ or nitrogen gas bubbling ammonia water is used as an atmospheric gas in the step of reducing the internal electrode before firing.

Problems to be Solved by the Invention 0.1% to atmosphere gas that reduces internal electrodes before firing
When nitrogen gas containing 1% H ₂ is used, there is a problem in mass productivity because some of the samples placed in the container at the time of reduction have their dielectrics reduced too much in the samples placed in the periphery. It was Further, when nitrogen gas bubbling ammonia water is used, the reduction state varies depending on the temperature of the ammonia water, and the ammonia water concentration gradually decreases, making it difficult to manage the ammonia water. SUMMARY OF THE INVENTION It is an object of the present invention to solve these problems and provide a method for manufacturing a multilayer capacitor element which is stable and easily obtains an optimal reduced state of an internal electrode and which is rich in mass productivity.

Means for Solving Problems The holding temperature of the internal electrode during reduction is 450 ° C or higher and 650 ° C or lower, and the atmosphere gas at that time is element gas, water vapor gas, and oxygen gas including oxygen gas, and is reduced at room temperature. When the volume percentages of hydrogen gas, water vapor gas, and oxygen gas are respectively x%, y%, and z% before being put into the furnace, 2z + 0.01 ≤ x ≤ 2z + 0.16 0.4 ≤ y ≤ 3.00 0 <z ≤ 2.00 Within the range of.

Action The reduction treatment of the internal electrodes requires complete reduction of the internal electrodes, but not reduction of the dielectric. When the reduction treatment is performed under the condition of strong reducing power, the dielectric substance may be reduced. With H ₂ —N ₂ system gas, the reducing power rapidly increases near room temperature when the hydrogen gas concentration before charging into the reduction furnace exceeds twice the oxygen gas concentration. In the region where the hydrogen gas concentration exceeds twice the oxygen gas concentration, the reducing power becomes weaker as the water vapor concentration becomes higher. Atmospheric gas does not contain water vapor H ₂ −
When N ₂ gas is used, the atmosphere gas is often supplied, and the steam gas generated by the reduction of copper oxide, which is a self-made atmosphere, tends to scatter, and samples placed around the container may undergo strong reduction. There is a nature. According to the present invention, by mixing water vapor gas in the atmosphere gas in advance and setting the hydrogen gas concentration to a limited range that is more than twice the oxygen gas concentration, the water vapor gas which is a self-made atmosphere scatters. However, since the reducing power does not become so large, the dielectric does not reduce. Therefore, it is possible to stably obtain a sample in which only the electrode portion is reduced.

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

(Ph _1.00 Ca _0.025 ) (Mg _1/3 Nb _2/3 ) _0.70 Ti _0.25 (Ni _1/2 W
_1/2 ) _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 calcinated powder is 5 wt% of polyvinyl butyral resin, 5%
The mixture was mixed with a 0 wt% solvent in a ball mill and formed into a sheet having a thickness of 35 μm using a doctor blade. For the internal electrode, Cu ₂ O with an average particle size of 0.8 μm (purity 99% as Cu ₂ O) was used as the starting material, and 0.5 wt% of ethyl cellulose to Cu ₂ O, 25w
An internal electrode pattern was printed on the dielectric green sheet using a screen printing method by kneading with a t% solvent using a three-roll mill to form an electrode paste. 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 laminated body created in this way is a porcelain boat (50 mm ×
Coarse-grained magnesia was laid in 120 mm, depth 15 mm), and about 400 pieces were placed on it, and the binder was burned out at 550 ° C in the air.

As shown in FIG. 1, the reduction treatment of the internal electrodes was performed by placing a porcelain boat 12 on which a burned-out laminated body sample 14 was placed inside a core tube 11 having an inner diameter of 70 mm in a tubular furnace, and using nitrogen containing 0.001% oxygen gas. Gas and nitrogen gas containing 1.0% hydrogen gas are mixed after measuring the flow rate using a floating flow meter 15 and then mixed with pure water 16
Was bubbled three times, and 1 liter / min of this gas was flowed into the furnace core tube to maintain it at a predetermined temperature to reduce the internal electrode. The water vapor concentration was controlled by adjusting the temperature of pure water to be bubbled, and measured by a magnesia-chromia temperature sensor 17.

FIG. 2 shows a cross section of the magnesia porcelain container in which the laminated body at the time of firing is put, and FIG. 3 shows a cross section of the firing furnace core tube. The size of the magnesia porcelain container 21 is the same as the porcelain boat used for burnout and internal electrode reduction treatment (50 mm × 120 mm, depth 15 mm), and the above-mentioned calcined powder 22 is spread about 1/3 of the volume in the container. Coarse-grained Magnesia 23 is laid on top of it for about 1 mm, and the above-mentioned burn-out and reduction-processed laminate 25 is fully
I put 400 pieces. The lid 24 of the magnesia porcelain, inserted into tubular electric furnace core tube 26 of, and replaced with N ₂ -H ₂ -H ₂ O gas mixture After degassing the reactor core tube in a rotary pump, the oxygen partial pressure is 1x10 ^The mixed gas was caused to flow while adjusting the mixing ratio of N ₂ and H ₂ gas to be ⁻⁸ , the temperature was raised to 980 ° C. at 400 ° C./hr, and the temperature was kept for 2 hours, and then lowered at 400 ° C./hr. Po ₂ in the furnace core tube was obtained from the following formula from the voltage E (V) between the electrodes drawn from the platinum electrodes formed on the atmosphere side and inside the furnace of the stabilized zirconia oxygen sensor 27 inserted.

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

The outer 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. A layer and two ineffective layers were provided above and below. The multilayer capacitor element has a capacity and tanδ of 1KHz when an AC voltage of 1V is applied.
Was measured at the following frequency. The resistance value was calculated from the value of 1 minute after applying a voltage of 50 V / mm. Electrical measurement is performed on all samples, capacity is 140 nF or less, tan δ is 5.0% or more, and resistance is 1 × 10
Those satisfying any of the conditions of ⁺⁹ Ω or less were regarded as defective, and the others were regarded as good.

Table 1 shows the hydrogen gas and water vapor gas concentrations during the reduction treatment of the internal electrodes, the temperature, the time, the capacity of good products, tan δ, the average resistance value, and the number of defects.

As is clear from Table 1, the hydrogen gas concentration is 0.011%
If it is smaller, the reduction process will take longer, the reduction of the internal electrode will be insufficient, and the electrode that is still oxidizing will react with the dielectric during firing, resulting in a decrease in the electrode area, resulting in a decrease in capacity and a decrease in resistance value. However, the number of defects also increases. When the hydrogen gas concentration exceeds 0.161%, reduction of the dielectric occurs, the dielectric does not sinter, and the capacity is significantly reduced. When the water vapor concentration is less than 0.4%, the sample placed around the container during the reduction process has a defect that the dielectric substance is not reduced and does not sinter. When the water vapor concentration was more than 3%, the reduction was insufficient and many defects occurred. If the holding temperature during electrode reduction is lower than 250 ° C, the electrode will not be sufficiently reduced and will remain oxidized, and will diffuse into the dielectric layer during firing, which will lower the insulation resistance value and reduce the electrode layer to completely metal. Since it does not form a layer, the dielectric loss at high frequencies is reduced. Further, the reduction requires a long holding time. Above 650 ° C,
The dielectric is reduced and does not function as a multilayer capacitor element after firing.

Example 2 As the dielectric, a material represented by the following composition formula was used.

(Pb _1.00 Sr _0.025 ) (Ni _1/3 Nb _2/3 ) _0.50 Ti _0.400 (Ni _1/2
W _1/2 ) _0.10 O _3.025 The same method as in Example 1 was used for _{forming the} dielectric material into a sheet. CuO with an average particle size of 1.2 μm for the internal electrodes
(Purity of 97% as CuO) is used as a starting material, and 0.5w is used for CuO.
An internal electrode pattern was printed on the dielectric green sheet by using a screen printing method by kneading with 3% rolls together with t% ethyl cellulose and 25 wt% solvent to form an electrode paste. This was laminated and cut so that the electrodes could be drawn out alternately to the left and right.

The laminated body created in this way is made of porcelain boat (50 mm
Coarse-grained magnesia was laid in 120 mm, depth 15 mm), and about 400 pieces were placed on it, and the binder was burned out at 600 ° C in the air.

As shown in FIG. 4, the reduction treatment of the internal electrodes was carried out by placing a porcelain boat 42 on which a burned-out laminated body sample 44 was placed inside a core tube 41 having an inner diameter of 70 mm in a tubular furnace, and using nitrogen containing 0.001% oxygen gas. Gas and 1.0% nitrogen gas containing 1.0% hydrogen gas
Nitrogen gas containing oxygen gas was mixed after measuring the flow rate using a floating flow meter 45, and after mixing, pure water 46 was bubbled three times to flow 1 liter / min of this gas into the core tube and hold it at a predetermined temperature. Was reduced. The water vapor concentration was measured by a magnesia-chromia humidity sensor 47, which was controlled by adjusting the temperature of pure water to be bubbled.

The firing was performed in the same manner as in Example 1. In the fired laminate, an external electrode paste containing metallic copper and glass frit was applied to the end face where the internal electrode was exposed, and baked at 600 ° C. in nitrogen.

The outer 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. A layer and two ineffective layers were provided above and below. The multilayer capacitor element has a capacity and tanδ of 1KHz when an AC voltage of 1V is applied.
Was measured at the following frequency. The resistance value was calculated from the value of 1 minute after applying a voltage of 50 V / mm. Electrical measurement is performed on all samples, capacity is 50nF or less, tanδ is 5.0% or more, and resistance is 1 × 10 ^+9.
Those satisfying any of the conditions of Ω or less were regarded as defective, and the others were regarded as good products.

Table 2 shows hydrogen gas and water vapor gas concentrations during the reduction treatment of the internal electrodes, temperature, time, and capacity of good products, tan δ, average resistance value, and the number of defects.

As is clear from Table 2, when the hydrogen gas concentration is less than 2z + 0.01% when the oxygen gas concentration is z%, the reduction process takes time, the reduction of the internal electrode is insufficient, and it is still oxidized. Since the electrode reacts with the dielectric during firing, the area of the electrode is reduced, resulting in a decrease in capacity and a decrease in resistance, and the number of defects also increases. When the hydrogen gas concentration exceeds 2z + 0.16%, reduction of the dielectric occurs, the dielectric does not sinter, and the capacity is significantly reduced. If the oxygen concentration exceeds 2%, there is a risk of explosion, which is not preferable. When the water vapor concentration is less than 0.4%, the sample placed around the container during the reduction process has a defect that the dielectric substance is not reduced and does not sinter. When the water vapor concentration was more than 3%, the reduction was insufficient and many defects occurred.

As is clear from the above two examples, in a method for manufacturing a multilayer capacitor element using a lead perovskite oxide dielectric and using copper as an internal electrode, copper oxide is used as a starting material for the copper internal electrode. When the internal electrode pattern is printed on the dielectric green sheet using the raw material to be laminated and then laminated, the binder component is burned out in the air, and then the internal electrode is reduced to metallize and fired. In the reduction treatment of the internal electrodes, the holding temperature during reduction of the internal electrodes is 450 ° C or higher and 650 ° C or lower, and the atmosphere gas at that time is hydrogen gas, steam gas, nitrogen gas containing oxygen gas, Prior to charging, the volume percentage of hydrogen gas, water vapor gas, and oxygen gas should be x%, y%, z, respectively.
%, When within the range of 2Z + 0.01 ≦ x ≦ 2Z + 0.16 0.4 ≦ y ≦ 3.00 0 <z ≦ 2.00, a multilayer capacitor element with large insulation resistance and excellent characteristics can be stably obtained. The number of defects in mass production also occurs.

Advantageous Effects of Invention The method for manufacturing a multilayer capacitor element according to the present invention is a multilayer capacitor element using lead perovskite as a dielectric and copper as an internal electrode. It is an industrially useful manufacturing method based on mass productivity.

[Brief description of drawings]

1 and 4 are cross-sectional views showing a reduction device for internal electrodes in one embodiment of the present invention, FIG. 2 is a cross-sectional view of a magnesia container during firing, and FIG. 3 is a cross-sectional view of a firing furnace core tube. . 11 …… Reactor tube, 12 …… Porcelain boat, 13 …… Coarse-grained magnesia, 14 …… Laminated sample, 15 …… Floating flow meter, 16 …… Pure water. 7 ... Humidity sensor, 41 ... Core tube, 42 ... Porcelain boat, 43 ... Coarse-grained magnesia, 44 ... Laminated sample, 45 ...
… Floating flow meter, 46 …… Pure water. 47 ... Humidity sensor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hideki Kuramitsu 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Junichi Kato 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 72) Inventor Toshihiro Mihara 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A copper or copper-based main component, characterized in that a raw material containing copper oxide as a main component is used as a starting material for the internal electrode, and the internal electrode is reduced to metallize at a temperature lower than a firing temperature. In the method for manufacturing a multilayer capacitor element using the alloy as an internal electrode and a lead perovskite oxide as a dielectric, the holding temperature of the internal electrode during reduction is 45
The temperature is 0 ° C or higher and 650 ° C or lower, and the atmosphere gas at that time is composed of hydrogen gas, steam gas, and nitrogen gas containing oxygen gas, and hydrogen gas before charging into the reducing furnace at room temperature, steam gas,
When the volume percentages of oxygen gas are x%, y%, and z%, respectively, they are in the range of 2z + 0.01 ≦ x ≦ 2z + 0.16 0.4 ≦ y ≦ 3.00 0 <z ≦ 2.00. Device manufacturing method.