JPH0734418B2 - 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 manufacturing method is a method suitable for mass-producing an inexpensive multilayer capacitor element, in which the binder of the multilayer element is burned out in air, and the internal electrodes are reduced at a temperature lower than the firing temperature, and then fired. However, in the conventional technique, the firing of the element is spread by laying out the calcined powder of the dielectric in a porcelain container, and laying coarse zirconia or coarse magnesia on it.
It was done by mounting a multilayer capacitor element.

Problems to be Solved by the Invention In a method for manufacturing a multilayer capacitor element using lead perovskite oxide as a dielectric, at the time of firing the element,
There was a difference in the PbO vapor pressure between the lee side and the lee side of the atmospheric gas in the porcelain container, and the characteristics of the obtained device, especially the insulation resistance value, varied, and the rate of occurrence of defects was high.

Means to solve the problem Lead perovskite oxide was used as a dielectric, copper oxide was used as the starting material for the copper internal electrode, and the internal electrode pattern was printed on the dielectric green sheet and laminated. After that, burn out the binder component in the air,
In a method of manufacturing a multilayer capacitor element, in which an internal electrode is reduced at a temperature lower than a firing temperature and then fired, the element is embedded in a mixture of a calcined powder of a dielectric material and coarse powder magnesia and fired.

Action In the firing step of the method for manufacturing a multilayer capacitor element of the present invention, by burying the element in a mixture of a calcined powder of a dielectric and coarse-grained magnesia, the inside of the porcelain container containing the element is uniformly saturated with PbO vapor. In addition, the element can be easily exposed to the atmosphere gas to suppress the evaporation of lead from the element, and the firing can be performed in an atmosphere in which the internal electrodes are not oxidized and the dielectric is not reduced. Through the above-described element firing process, an element having a dense dielectric layer having a high insulation resistance value is stably produced, and the rate of occurrence of defects is reduced.

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 ) _0.70 Ti _0.25 (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. 0.5 wt% of ethyl cellulose relative to Cu ₂ O used as the starting material (purity of 99% as Cu ₂ O) Cu ₂ O having an average particle diameter of 0.8μm as the internal electrodes, kneaded electrode with a three-roll with 25 wt% of the solvent An internal electrode pattern was printed on the dielectric green sheet by using a screen printing method as a 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 produced as described above was laid with coarse-grained magnesia in a porcelain boat and placed on it, and the binder was burned out at 450 ° C. in the air.

The burned out laminated body was laid in a porcelain boat on which coarse-grained magnesia was laid, and pure water was bubbled on it. 0.08vol% H
Nitrogen gas containing ₂ was flown at 1 liter per minute and maintained at 450 ° C. for 8 hours to reduce the internal electrodes.

FIG. 1 shows a cross section of a magnesia porcelain container in which the laminate is put during firing, and FIG. 2 shows a cross section of a firing furnace core tube. In the magnesia porcelain container 1, the mixture 2 of the above-mentioned calcined powder of dielectric material and coarse-grained magnesia is spread over about 1/3 of the volume, and the laminated body 3 is placed thereon, and the laminated body 3 is filled to the extent that the dielectric body 3 is filled. The mixture 2 of calcined powder and coarse-grained magnesia was sprinkled. After covering the lid 4 of the magnesia porcelain and inserting it into the core tube 5 of the tubular electric furnace shown in FIG. 2, the inside of the core tube was degassed with a rotary pump.
Replace with N ₂ -H ₂ mixed gas and let the mixed gas flow while adjusting the mixing ratio of N ₂ and H ₂ gas so that the oxygen partial pressure is 1 × 10 ^-8 Pa at 400 ° C / hr up to 980 ° C. The temperature was raised and maintained for 2 hours, and then the temperature was lowered at 400 ° C / hr. The P _o2 in the core tube was _calculated from the voltage E (V) between the electrodes of the stabilized zirconia oxygen sensor 6 inserted in the atmosphere and the platinum electrode formed on the inside of the furnace, according to the following equation.

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. The capacity is 100 when 300 elements are fired.
Those satisfying any of nF or less, tan δ of 2% or more, and resistance of 1.0 × 10 ⁺¹⁰ Ω or less were regarded as defective.

Table 1 shows the weight ratio x of the calcined dielectric powder in the mixture filling the device and the defect occurrence rate.

As shown in Table 1, when the weight ratio of the calcined dielectric powder in the mixture filling the device was less than 0.15 during firing of the device, the evaporation of PbO from the device was severe and many defects occurred. If the weight ratio of the calcined dielectric powder is more than 0.85, the amount of coarse-grained magnesia will be too small and the atmosphere gas will be difficult to touch the element, the electrode will not be sufficiently reduced and will remain as an oxide and diffuse during firing. , Causing a decrease in insulation resistance and increasing the defect occurrence rate.

As is clear from the above examples, a lead perovskite-based oxide dielectric was used, starting materials containing copper oxide as the main component were used for the internal electrodes, and internal electrode patterns were applied to the dielectric green sheets to form a laminate. After that, the binder component is burned out in the air, the internal electrodes are reduced at a temperature lower than the firing temperature, and then fired in a method of manufacturing a multilayer capacitor element, where the element is in a mixture of a calcined powder of dielectric material and coarse-grained magnesia. The rate of occurrence of defects was reduced by burying in and baking. In the firing process of the device, when the device is embedded in a mixture of a calcined powder of a dielectric and coarse magnesia, the weight ratio of the calcined powder of the dielectric and the coarse magnesia is respectively x,
When y is set, it is desirable to spread a mixture in the range of x + y = 1 0.15 ≦ x ≦ 0.85 under the device and further sprinkle the device so as to fill the device.

EFFECTS OF THE INVENTION According to the method for manufacturing a multilayer capacitor element of the present invention, the failure occurrence rate is reduced in the multilayer capacitor element using lead perovskite as a dielectric and copper as an internal electrode.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnesia porcelain container used for firing an element in an embodiment of the present invention, and FIG. 2 is a sectional view of a firing furnace core tube. 11 ...... Magnesia porcelain container, 12 …… Coarse-grain mixture of magnesia and dielectric calcined powder, 13 …… Layered sample, 14 …… Magnesia porcelain container lid, 15 …… Core tube, 16 …… Zirconia oxygen sensor

Claims (2)

[Claims] 1. A lead perovskite oxide is used as a dielectric, a starting material containing copper oxide as a main component is used for an internal electrode, an internal electrode pattern is printed on a dielectric green sheet and laminated, and then in air. In a method of manufacturing a multilayer capacitor element in which a binder component is burned out and the internal electrodes are reduced and then fired at a temperature lower than the firing temperature, the firing is performed by embedding the element in a mixture of a calcined powder of a dielectric and coarse-grained magnesia. A method for manufacturing a multilayer capacitor element, which is carried out. 2. A weight ratio of a calcined powder of a dielectric material and a mixture of coarse-grained magnesia for filling a device, where x and y are respectively, x + y = 1 0.15 ≦ x ≦ 0.85 The method for producing a multilayer capacitor element according to claim 1, wherein the mixture is spread under the element and further sprinkled to fill the element.