JP3470285B2 - Manufacturing method of multilayer ceramic capacitor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer ceramic capacitor. More specifically, the present invention relates to N
The present invention relates to a multilayer ceramic capacitor using a base metal such as i for an internal electrode and having a high insulation resistance value. 2. Description of the Related Art A multilayer ceramic capacitor using a high dielectric constant ceramic material mainly composed of a titanate such as barium titanate as a dielectric and using Pt, Pd or an alloy thereof as an internal electrode is small in size. However, since it has a large capacitance, it is widely used in various electronic circuits requiring high reliability. When manufacturing a multilayer ceramic capacitor, first, a ceramic green sheet having a predetermined film thickness is prepared by a usual method, and Pt, Pd or an alloy powder paste of these alloys serving as internal electrodes is printed on the ceramic green sheet. Alternatively, a large number of these may be laminated, press-bonded while heating, and integrated. 1300 ° C in air
It is fired at the temperature before and after to produce a sintered body. An external electrode that is electrically connected to the internal electrode of the sintered body is formed by baking on the side surface of the sintered body. In the conventional manufacturing method as described above, Pt, Pd or an alloy thereof is used as a material for forming an internal electrode, because the metal is formed of ceramic even if the ceramic dielectric and the internal electrode are fired simultaneously. This is because it has a melting point not lower than the firing temperature of the dielectric, does not melt, is not oxidized even in an oxidizing atmosphere, and does not react with the ceramic dielectric. [0005] However, Pt, Pd or alloys thereof are very expensive, and have been a major cause for increasing the cost of the multilayer ceramic capacitor. For this reason, use of Ni as an internal electrode material has been attempted. However, Ni printed as an electrode is in the form of a powder having a high surface activity, is easily oxidized in a high-temperature oxidizing atmosphere, loses conductivity, and thus does not function as an electrode. Therefore, in order to use Ni as an internal electrode, at least until the powdered Ni becomes plate-like by sintering and the surface activity is reduced, the Ni internal electrode is placed in a reducing atmosphere together with the ceramic dielectric. Must be fired. However, on the other hand, when ceramic dielectric materials are fired in a reducing atmosphere, these materials are excessively reduced and may be converted into semiconductors. Since the oxidation of the internal electrode proceeds simultaneously with the oxidation reaction of the dielectric, there is a limit in improving the insulating property of the dielectric within a range where the conductivity of the internal electrode is not lost. Accordingly, an object of the present invention is to provide a method of manufacturing a multilayer ceramic capacitor having a high insulation resistance value using a base metal such as Ni as an internal electrode. An object of the present invention is to provide a multilayer ceramic sintered body comprising a plurality of dielectric ceramic layers and a plurality of base metal internal electrodes alternately laminated via the dielectric ceramic layers. Is prepared, and the sintered body is prepared in a range of 600 to 1200.
The problem can be solved by performing the oxidation treatment in an atmosphere having an oxygen partial pressure of 0.1 MPa or more at a temperature in the range of ° C. According to the present invention, by utilizing the difference between the oxidation reaction of Ni and the oxidation reaction of a dielectric, only the dielectric is selectively oxidized and the insulation resistance value is reduced. Can be improved. In the case of Ni, the rate of the oxidation reaction in the sintered body is determined by the diffusion of oxygen, and is independent of the surrounding oxygen partial pressure. On the other hand, in the case of a dielectric, since the rate is determined by a chemical bonding reaction with oxygen, the reaction rate is proportional to the surrounding oxygen partial pressure. Therefore, by increasing the oxygen partial pressure in the atmosphere during the oxidation treatment of the sintered body, only the oxidation of the dielectric can be promoted, and the insulation resistance value of the dielectric can be increased. When the sintered body is oxidized by the method of the present invention, it is preferable to use a sealable pressure vessel and maintain the oxygen partial pressure in the vessel at 0.1 MPa or more. When the oxygen partial pressure is less than 0.1 MPa, a pressure vessel is unnecessary, but the effect of selectively oxidizing only the dielectric is small. When the sintered body is oxidized by the method of the present invention, the temperature is preferably in the range of 600 to 1200 ° C. When the temperature is lower than 600 ° C., the processing time becomes too long, and the throughput is reduced. On the other hand, the temperature is 1200 ° C
If it is longer than the above, the processing time is shortened. However, if it is too close to the firing temperature of the dielectric, it is not preferable because the electrical properties of the dielectric are adversely affected. The dielectric ceramic on which the method of the present invention is practiced is generally preferably a barium titanate-based ceramic. The specific composition of the barium titanate-based ceramic is not particularly limited. For example, the following general _{formula, {Ba (1-x)} Ca x} A {Ti (1-y) Zr y} B O 3 ( where, in the formula, with 1.00 <A / B <1.02 Yes, 0.05 ≦ x ≦ 0.15, 0.01 ≦ y ≦
Together with a main component represented by 0.25), and L, mM and nG (wherein L is at least one compound among lanthanide compounds except Pm, and M is M
G is an oxide containing n as a main component, G is a glass-forming oxide containing Si as a main component, and 0 <l <5.0 mol%,
0.1 <m ≦ 1.0 mol% and 0 <n <3.0 wt%) can be preferably used. However, it is needless to say that the composition is not limited to this. As the internal electrode material, in addition to Ni, base metals such as Fe and Co can be equally used. However, Ni is most preferable in terms of cost, suitability for use, and the like. The effects of the present invention will now be illustrated by examples. Example 1 (Ba _0.950 Ca _0.050 ) _1.01 (Ti _0.78 Zr _0.22 ) O ₃
+0.5 mol% Gd ₂ O ₃ +0.3 mol% MnCO ₃ +0.
3.2 × 1.6 with 20 effective internal electrodes using a dielectric ceramic composition having a composition of 1 wt% SiO ₂
mm type green chips were produced. The thickness of the dielectric was 12 μm after sintering. Ni and Pd were used as internal electrodes. The green chip having Ni internal electrodes was fired at 1320 ° C. in a 3% H ₂ /97% N ₂ atmosphere. The green chip having a Pd internal electrode was fired at 1320 ° C. in air and used as a reference for the limit value of the dielectric oxidation treatment. The fired Ni internal electrode product was placed in N ₂ ,
1000 in air, 0.1 to 1 MPa oxygen atmosphere
An oxidation treatment was performed at 30 ° C. for 30 minutes. After the oxide layer on the surface of the Ni internal electrode exposed at the end face was removed by polishing, the Ag external electrode was baked. The Ag external electrode was baked on the Pd internal electrode product without performing the oxidation treatment.
The insulation resistance value of each of the obtained sintered bodies was measured. The results are shown in Table 1 below. [Table 1] As is apparent from the results shown in Table 1, the insulation resistance increases as the oxygen partial pressure during the oxidation treatment increases. Under the conditions of the first embodiment, the insulation resistance value becomes equal to that of the Pd internal electrode near 1 MPa, and the effect of the firing in the reducing atmosphere given to the dielectric is almost eliminated. Example 2 (Ba _0.950 Ca _0.050 ) _1.01 (Ti _0.78 Zr _0.22 ) O ₃
+0.5 mol% Gd ₂ O ₃ +0.3 mol% MnCO ₃ +0.
3.2 × 1.6 with 20 effective internal electrodes using a dielectric ceramic composition having a composition of 1 wt% SiO ₂
mm type green chips were produced. The thickness of the dielectric was 12 μm after sintering. Ni and Pd were used as internal electrodes. A green chip having Ni internal electrodes was fired at 1320 ° C. in a 3% H ₂ /97% N ₂ atmosphere. The green chip having a Pd internal electrode was fired at 1320 ° C. in air and used as a reference for the limit value of the dielectric oxidation treatment. Ag external electrodes were baked on the baked Ni and Pd internal electrode products. Then in air and 0.1
The oxidation treatment was performed at 800 ° C. for 2 hours in an oxygen atmosphere of １1 MPa. The insulation resistance value of each of the obtained sintered bodies was measured. The results are shown in Table 2 below. [Table 2] As is clear from the results shown in Table 2,
In the case of the Ni internal electrode product, the insulation resistance is about 10 times as large as that of the untreated one even if the oxidation treatment is performed at an oxygen partial pressure of 1.0 MPa. However, as compared with the Pd internal electrode product, the insulation resistance value of the Ni internal electrode product is not saturated even with the oxidation treatment at an oxygen partial pressure of 1.0 MPa.
It is expected that the insulation resistance value of the i internal electrode product will be even higher. As described above, according to the method of the present invention, a multilayer ceramic capacitor having a high insulation resistance can be obtained using a base metal such as Ni as an internal electrode.

Claims (1)

(57) [Claim 1] In a method of manufacturing a multilayer ceramic capacitor using a base metal as an internal electrode, (a) a plurality of dielectric ceramic layers and alternately laminated via the dielectric ceramic layers Preparing a multilayer ceramic sintered body comprising a plurality of base metal internal electrodes, and (b) subjecting the sintered body to a temperature in a range of 600 to 1200 ° C.
Oxidation treatment in an atmosphere with an oxygen partial pressure of 0.1 MPa or more
And wherein the dielectric ceramic layer contains barium titanate as a main component.
Wherein the internal electrode is made of Ni .