JPH0734420B2 - 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.

In the above manufacturing method, the binder of the laminated body element is burned out in air, the internal electrodes are reduced at a temperature lower than the firing temperature, and then the firing is performed.

Problems to be Solved by the Invention According to this manufacturing method, after the burnout, the copper component of the internal electrode changes to copper oxide and causes volume expansion, so that cracks or the like occur in the laminated body element after the burnout. However, it is necessary to strictly control the heat treatment conditions in the reduction process of the internal electrodes, which complicates the manufacturing process and causes a high defect occurrence rate.

The present invention solves the above problems.

Means for Solving Problems In the method for manufacturing a multilayer capacitor element, in which the internal electrode pattern is printed on a dielectric green sheet and laminated, the binder component is burned out and then fired, the burnout of the binder component is O ₂ gas and H ₂ in the mixed gas flow to be used in the mixed gas flow containing ₂ gas and H ₂ gas
The gas concentration is in the range of 30≤X≤5000 0.3X≤Y≤4.5X, where the respective gas concentrations are Xppm and Yppm.

Action In the method for producing a multilayer capacitor element of the present invention, since the binder component is burned out in a mixed gas flow containing H ₂ gas and O ₂ gas, the binder component is decomposed and burned by the action of O ₂ gas. Oxidation of the metal component in the internal electrode that occurs is suppressed by the action of H ₂ gas. Therefore, an element without cracks can be stably obtained by a simple method without the reduction process of the internal electrodes, and the defect occurrence rate is reduced.

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 _0.225 (Ni _1/2 W _1/2 ) _0.075 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 calcined powder was mixed with 5% by weight of polyvinyl butyral resin as a binder and 50% by weight of solvent in a ball mill, and formed into a sheet having a thickness of 35 μm using a doctor blade. For the internal electrodes, a copper-nickel alloy with an average particle size of 0.5 μm (containing 10% nickel) was used as the starting material, and the mixture was kneaded with 0.5 wt% ethyl cellulose and 25 wt% solvent with respect to metallic copper with a three-roll mill to form an electrode paste and a screen. An internal electrode pattern was printed on the dielectric green sheet using a 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.

FIG. 1 shows a cross section of a magnesia porcelain container in which the laminate is put in when the binder component is burned out, and FIG. 2 shows a cross section of an apparatus used for burnout. In a magnesia porcelain container 11, 200-mesh coarse-grained magnesia 12 was spread, and a laminated material 13 was placed. Inner diameter of magnesia porcelain container in tubular furnace
It was put in a 110 mm core tube 14 and 2 liters of N ₂ gas containing various concentrations of O ₂ gas and H ₂ gas bubbling with pure water 15 was flowed and kept at 550 ° C. for 6 hours to burn the binder component. Went out.

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, the above-mentioned calcined powder 22 was spread over about 1/3 of the volume, and 200 mesh coarse-grained magnesia 23 was spread over about 1 mm, and the burned out laminated body 25 was placed on it. After covering the lid 24 of the magnesia porcelain and inserting it into the core tube 26 of the tubular electric furnace, deaerating the inside of the core tube with a rotary pump and then N ₂ -H
₂ Replace with mixed gas and adjust the oxygen partial pressure to 1x10 ^-8 Pa
980 ℃ by flowing the mixed gas while adjusting the mixing ratio of ₂ and H ₂ gas
Up to 400 ° C./hr, hold for 2 hours, and then lower 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 the Faraday constant 96489 coulomb, R is the gas constant 8.3144 J / deg · mol, and 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 electrode layer thickness is 2.0 μm, the dielectric layer is 21.0 μm per layer, and the effective layer is 3
0 layer and two ineffective layers were provided on the upper and lower sides. The capacitance and tan δ of the multilayer capacitor element were measured at a frequency of 1 kHz by applying an AC voltage of 1V. The resistance value was calculated from the value of 1 minute after applying a voltage of 50 V / mm. When 1000 elements were fired at the same time, the one with a capacity of 70% or less of the design capacity was regarded as a defective product, and each characteristic was an average value of non-defective products. (Design capacity is 320 nF) Table 1 shows the O ₂ gas concentration, H ₂ gas concentration, capacity, tan δ, insulation resistance, and non-defective rate in the atmosphere gas. As shown in Table 1, when the binder component is burned out, if the concentration of O ₂ gas in the mixed gas used is less than 30 ppm, carbon will be present in the dielectric layer in the laminated body after burnout. When remaining and firing, the dielectric was reduced, the insulation resistance of the obtained device was lowered, and the non-defective rate was lowered. On the other hand, if it is more than 500 ppm, the metal components in the internal electrode layers are oxidized at the time of burnout, diffused into the dielectric layer at the time of firing, and many capacitance defects occurred in the element obtained after firing. Further, when the concentration of H ₂ gas in the mixed gas used is less than 0.3 times the concentration of O ₂ gas, the metal components in the internal electrode layers are oxidized, and when it is more than 4.5 times, carbon remains in the dielectric layer. A lot of defects occurred for the same reason as above.

Example 2 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 _0.225 (Ni _1/2 W _1/2 ) _0.075 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 calcined powder was mixed in a ball mill with 6 wt% acrylic resin and 40 wt% solvent as a binder for the calcined powder, and a sheet having a thickness of 35 μm was formed using a doctor blade. For the internal electrodes, metallic copper with an average particle size of 0.4 μm (purity 99%) was used as the starting material, and kneaded with 0.5 wt% ethyl cellulose and 25 wt% solvent with respect to metallic copper with a three-roll mill to form an electrode paste and screen printing method. An internal electrode pattern was printed on the used dielectric green sheet. This was laminated and cut so that the electrodes could be drawn out alternately to the left and right.

After coating the external electrode by the same method and apparatus as in Example 1, 2 liters of N ₂ gas containing various concentrations of O ₂ gas and H ₂ gas was made to flow at 2 liters per minute and held at 450 ° C. for 6 hours to remove the binder component. Burned out. After the burnout, firing of the device and evaluation of characteristics were performed by the same method as in Example 1.

Table 2 shows the O ₂ gas concentration, H ₂ gas concentration, capacity, tan δ, insulation resistance, and non-defective rate in the atmosphere gas.

As shown in Table 2, when acrylic resin is used as the binder of the dielectric green sheet, carbon is less likely to remain in the element after burnout because the acrylic resin has good thermal decomposability, and thus it is obtained after firing. The electrical characteristics of the
The quality rate has improved.

From the above examples, when manufacturing a multilayer capacitor element using a lead perovskite-based oxide dielectric and using copper or an alloy containing copper as a main component for the internal electrodes, an internal electrode pattern is printed on the dielectric green sheet. In the manufacturing method of the multilayer capacitor element, in which the binder component is burned out and then fired, the binder component is burned out in a mixed gas stream containing O ₂ gas and H ₂ gas, and the mixed gas is used. When the concentrations of O ₂ gas and H ₂ gas in the air stream are Xppm and Yppm, respectively, if the range is 30 ≦ X ≦ 5000 0.3X ≦ Y ≦ 4.5X, the reduction process of the internal electrode It can be seen that a crack-free element can be stably obtained by a simple method without passing through, and the defect occurrence rate is reduced.

At this time, the kind of the binder used for the dielectric green sheet is not limited, but the acrylic resin has good thermal decomposability and is effective.

It should be noted that H ₂ O gas or NH ₃ gas may be mixed to the extent that the effect is not impaired in the mixed gas flow used when the binder component is burned out.

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, the manufacturing process is simplified and the failure rate is reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a magnesia porcelain container used for binder component burnout in an embodiment of the present invention, FIG. 2 is a cross-sectional view showing an apparatus used for binder component burnout, and FIG. 3 is a magnesia container during firing. Sectional view of the fourth
The figure is a cross-sectional view of a firing furnace core tube. 11 …… Magnesia porcelain container, 12 …… Coarse-grained magnesia, 13
…… Laminated sample, 14 …… Reactor tube, 15 …… Pure water, 21 …… Magnesia porcelain container, 22 …… Dielectric calcined powder, 23 …… Coarse-grained magnesia, 24 …… Magnesia porcelain lid, 25 …… Laminated sample, 26 …… Core tube, 7 …… Zirconia oxygen sensor.

Claims (2)

[Claims] 1. When manufacturing a multilayer capacitor element using a lead perovskite oxide dielectric and using copper or an alloy containing copper as a main component for internal electrodes, an internal electrode pattern is printed on a dielectric green sheet. After lamination, burnout of the binder component is performed, and then in the method for manufacturing a multilayer capacitor element that is fired, the burnout of the binder component is performed in a mixed gas flow containing O ₂ gas and H ₂ gas, and the mixed gas used The concentration of O ₂ gas and H ₂ gas in the air flow is in the range of 30 ≦ X ≦ 5000 0.3X ≦ Y ≦ 4.5X when the respective gas concentrations are Xppm and Yppm. Device manufacturing method. 2. A binder for a dielectric green sheet,
The method for manufacturing a multilayer capacitor element according to claim 1, wherein an acrylic resin is used.