JPH0734419B2 - 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, due to the higher frequency of the circuit, it has become necessary to use a multilayer 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 for high-dielectric-constant ceramic capacitor materials, but since the firing temperature is as high as 1300 ° C, expensive metals such as Pt and Pd are used as internal electrode materials. There was a need. 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.

The above-mentioned manufacturing method is a method of burning out the binder of the laminated body element in air, reducing the internal electrodes at a temperature lower than the baking temperature, and then baking, which is an excellent manufacturing method rich in mass productivity. In the technology of, the reduction of the internal electrode, laying coarse-grained magnesia or coarse-grained zirconia in a porcelain container,
The laminated body element was placed on it.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In a method for manufacturing a multilayer capacitor element using copper or an alloy containing copper as a main component for an internal electrode, at the time of reducing the internal electrode, a reduction of a dielectric substance occurs in the element on the reducing gas inlet side. It tends to occur, metallization of internal electrodes tends to be insufficient on the outlet side, and there are variations in the values of insulation resistance, capacitance, etc. of the multilayer capacitor elements obtained after firing, which causes a high failure rate and poses a problem in mass productivity. was there.

An object of the present invention is to provide a method for manufacturing a multilayer capacitor element that solves the above problems.

Means to solve the problem After printing the internal electrode pattern on the dielectric green sheet and stacking it, burn out the binder component in the air,
Then, in the method of manufacturing a multilayer capacitor element in which the internal electrode is reduced at a temperature lower than the firing temperature and fired, the internal electrode of the element is reduced by embedding the element in an inorganic compound powder.

Action In the method for manufacturing a multilayer capacitor element of the present invention, reduction of the internal electrodes of the element is performed by embedding the element in the powder of the inorganic compound, while the reducing gas passes between the powder particles,
The gas is brought into uniform contact with a large number of elements, and the internal electrodes of the elements can be reduced with good mass productivity.

Example 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 ) _0.75 Ti _0.20 (Ni _1/2 W _1/2 ) _0.05 O _{3.025 The} dielectric powder was manufactured according to the usual ceramic manufacturing method. The calcination conditions were 800 ° C. and 2 hours. The pulverized calcinated powder was mixed with 5% by weight of polyvinyl butyral resin and 50% by weight of the calcinated powder in a ball mill and formed into a sheet having a thickness of 35 μm using a doctor blade. Cu ₂ O with an average particle size of 0.8 μm as an internal electrode (99% purity as Cu ₂ O)
Was used as a starting material, and was kneaded with 0.5 wt% ethyl cellulose and 25 wt% solvent with respect to Cu ₂ O by a three-roll mill to form an electrode paste, and an internal electrode pattern was printed on the dielectric green sheet by a screen printing 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.

In the laminated body thus prepared, coarse-grained magnesia was laid in a porcelain boat and placed thereon, and the binder was burned out at 450 ° C. in air.

FIG. 1 shows a cross-sectional view of a magnesia porcelain container in which the laminated body is placed when the internal electrodes are reduced, and FIG. 2 shows a cross-sectional view of a reduction device for the internal electrodes. In the magnesia porcelain container 11, about 3/4 of the powder 12 of the inorganic compound was spread, and the burned out laminated body element 13 was placed thereon, and the coarse powder was sprinkled to fill the laminated body. A magnesia porcelain container was placed inside a furnace core tube 14 having an inner diameter of 70 mm in a tubular furnace, and nitrogen gas bubbling 20 wt.
The internal electrode was reduced by holding it at 550 ° C for 6 hours.

FIG. 3 shows a cross section of the magnesia porcelain container in which the laminated body at the time of firing is put, and FIG. 4 shows a cross section of the firing furnace core tube. In the magnesia porcelain container 21, about 1/3 of the volume of the above-mentioned calcined powder 22 was spread, and about 1 mm of coarse-grained magnesia 23 was spread thereon, and the burned-out laminated body 25 was placed thereon. The lid 24 of the magnesia porcelain is put on, the tube is inserted into the core tube 26 of the tubular electric furnace, the inside of the core tube is degassed by a rotary pump, and then replaced with a N ₂ -H ₂ mixed gas, and the oxygen partial pressure is 1 × 10 _−. Flow the mixed gas while adjusting the mixing ratio of N ₂ and H ₂ gas to be ₈ Pa, and 400 ° C up to 980 ° C.
The temperature was raised at / hr, the temperature was held for 2 hours, and then the temperature was lowered at 400 ° C / hr. The P _o2 in the core tube was obtained from the following equation from the voltage E (V) between the electrodes drawn from the platinum electrode formed on the atmosphere side of the inserted stabilized zirconia oxygen sensor 27 and the inside of the furnace.

P _o2 = 0.2 ・ exp (4FE / RT) where F is Faraday constant 96489 Coulomb, R is gas constant
8.3144 J / deg · mol, T is the absolute temperature.

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, and the dielectric layer is 25.0 μm per layer.
Then, 30 effective layers were provided, and two ineffective layers were provided above and below. The multilayer capacitor element has a capacity and tan δ of 1 V
It was measured at a frequency of kHz. The resistance value was calculated from the value of 1 minute after applying a voltage of 50 V / mm. 1000 devices were fired in a single experiment, and a device having a resistance value of 1.0 × 10 ⁺¹⁰ Ω or less was regarded as a defective product.

Table 1 shows the type of inorganic compound powder filling the device, its particle size, capacity, tan δ, resistance value, and defect occurrence rate.

As shown in Table 1, when the particle size of the inorganic compound filling the element is smaller than 0.05 mm during the reduction of the internal electrode, it becomes difficult for the reducing gas to come into contact with the element, and the internal electrode is not sufficiently reduced, resulting in defects. It happened a lot. Also, the particle size of the inorganic compound is 1.
If it is larger than 4 mm, the reducing gas does not evenly touch the element, and the characteristics of the obtained element vary as in the case where the element is not filled. The inorganic compound to be used may be of any type as long as it does not melt, pyrolyze, or chemically react with the dielectric of the element or the reducing gas below the reduction temperature of the internal electrode.

As is clear from the above examples, a lead perovskite oxide dielectric was used, copper or an alloy containing copper as a main component was used for the internal electrodes, and the internal electrode patterns were printed on the dielectric green sheet and laminated. In a method of manufacturing a multilayer capacitor element in which a binder component is burned out in air and then the internal electrode is reduced at a temperature lower than a firing temperature, reduction of the internal electrode of the element is performed by embedding the element in an inorganic compound powder. By doing so, the failure rate decreased. At this time, the particle size of the inorganic compound used is preferably about 0.05-1.4 mm.

EFFECT OF THE INVENTION According to the method for manufacturing a multilayer capacitor element of the present invention, in a multilayer capacitor element that uses a lead perovskite-based oxide dielectric and uses copper or an alloy containing copper as a main component for internal electrodes, the failure occurrence rate is Can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnesia porcelain container used for reducing internal electrodes in an embodiment of the present invention, FIG. 2 is a sectional view showing a reducing device for internal electrodes used in an embodiment, and FIG. 3 is magnesia during firing. FIG. 4 is a sectional view of the vessel, and FIG. 4 is a sectional view of the furnace core tube of the firing furnace. 11 …… Magnesia porcelain container, 12 …… Inorganic compound powder,
13 …… Laminated sample, 14 …… Reactor tube, 15 …… Ammonia water, 21 …… Magnesia porcelain container, 22 …… Dielectric calcined powder, 23 …… Coarse-grained magnesia, 24 …… Magnesia porcelain lid , 25 …… laminated sample, 26 …… core tube, 27 …… zirconia oxygen sensor.

Claims (3)

[Claims] 1. A lead perovskite oxide dielectric is used, and copper or an alloy containing copper as a main component is used for the internal electrodes.
After printing the internal electrode pattern on the dielectric green sheet and stacking it, burn out the binder component in the air, and then reduce the internal electrode at a temperature lower than the firing temperature,
A method of manufacturing a multilayer capacitor element, comprising: reducing an internal electrode of the element by burying the element in an inorganic compound powder. 2. The reduction of the internal electrode of the device is carried out by reducing the particle size to 0.05-1.4 m.
The method for producing a multilayer capacitor element according to claim 1, wherein the element is embedded in coarse particles of an inorganic compound of m. 3. The element is reduced by embedding the element in coarse particles of an inorganic compound containing at least one of magnesia, zirconia and alumina as a main component to reduce the internal electrode of the element. Item 1. A method for manufacturing a multilayer capacitor element according to item 1 or 2.