JPH05304042A - Layered ceramic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To solve a problem that the defective connection of internal electrode layers with external electrode layers is generated and required capacitance is not obtained, to improve the connectability of the internal electrode layers with the external electrode layers, to improve the reliability of a layered ceramic capacitor as well as to contrive a cost reduction of the layered ceramic capacitor, which is used as the circuit element of a microminiature, thin and lightweight electronic apparatus, and a method of manufacturing the capacitor. CONSTITUTION:Internal electrode layers 2 and dielectric layers 1 are alternately laminated and electrode layers 5 are respectively formed at connection parts 4, where the layers 2 and external electrode layers 3 are connected to each other, in such a way as to become thicker than the parts other than the parts 4 of the layers 2. Thereby, as the connectability between the layers 2 and the layers 3 is improved, a reduction in a capacitance due to the defective connection between the layers 2 and the layers 3 can be dissolved and the amount of internal electrodes can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated porcelain capacitor used in radios, microcassette recorders, electronic tuners, video cameras and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a method of manufacturing a laminated porcelain capacitor is as follows. A ceramic dielectric green sheet having a thickness of μm is produced, then a sheet having internal electrodes printed thereon is peeled off from the support, and a plurality of stacked sheets are stacked, and then a laminated molded article is produced by pressure bonding, and then formed into a chip shape. After cutting and firing, it is common to form an external electrode for fabrication.

[0003]

On the other hand, there are strong demands for miniaturization, large capacity, and low cost of laminated ceramic capacitors.
Higher stacking is required to achieve small size and large capacity.
As the number of layers increases, the amount of internal electrode material used also increases. At present, it is general to use a noble metal such as palladium as an internal electrode material of a laminated ceramic capacitor mainly containing barium titanate. Therefore, in order to realize the cost reduction of the laminated ceramic capacitor, it is indispensable to reduce the usage amount of the internal electrode which is a noble metal. However, in order to reduce the amount of electrode material used, even if the internal electrode thickness is made as thin as possible to manufacture a capacitor, the internal electrode material also undergoes metal sintering during sintering, so the internal electrode layer is pulled inside the sintered body. As a result, the state of connection with the external electrode becomes worse than when the internal electrode is thick, and the desired capacity cannot be obtained, and the capacity hit rate decreases.

The present invention is intended to solve the above problems,
It is an object of the present invention to provide a laminated ceramic capacitor having high productivity and low cost by improving the connectivity of the internal electrode layer and the external electrode layer to improve the capacity hit rate, and a manufacturing method thereof.

[0005]

In order to achieve the above object, the laminated ceramic capacitor of the present invention has the following structure. That is, in the laminated ceramic capacitor having a design in which the internal electrode layers and the dielectric layers are alternately laminated and the external electrodes are provided so that the internal electrode layers are connected in parallel, the internal electrode layers and the external electrode layers are connected to each other. The thickness of the internal electrode layer of a part is made thicker than the thickness of other internal electrode layers.

In order to have such a structure, after forming a dielectric sheet on a support, an internal electrode layer is formed on this dielectric sheet by a screen printing method so as to have a desired electrode shape. Next, an internal electrode layer is further formed only in advance on the internal electrode layer portion where the internal electrode layer and the external electrode layer are considered to be connected, and the thickness of the internal electrode at the connection portion with the external electrode is increased. Then, the dielectric layer and the internal electrode layer are peeled off from the support, and a plurality of laminated sheets are stacked and pressure-bonded to produce a laminated molded body. This is cut into chips and fired, and then external electrodes are formed to manufacture a laminated ceramic capacitor.

[0007]

Therefore, according to the present invention, since the thickness of the internal electrode layer at the portion connected to the external electrode is made thicker than other portions, the connectivity between the internal electrode layer and the external electrode layer is improved as compared with the conventional method. It becomes good, and the problem of capacity decrease due to poor connection can be solved. Even if most of the internal electrodes that are not connected to the external electrodes are thinned, as long as the electrodes are connected somewhere,
Even if the electrodes are interrupted, they can function as the original electrodes of the capacitor, and the amount of electrodes used can be reduced, leading to cost reduction of the capacitor.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings and in comparison with a conventional example.

FIG. 1 is a sectional view showing the structure of the laminated ceramic capacitor of the present invention, and FIG. 2 is an enlarged view of a connecting portion between an internal electrode layer and an external electrode layer. In FIG. 1, 1 is a dielectric layer, 2
Is an internal electrode layer, 3 is an external electrode layer, 4 is a connecting portion between the internal electrode layer 2 and the external electrode layer 3, 5 is an electrode layer formed near the connecting portion, and the electrode thickness is larger than that of the internal electrode 2 portion. Is becoming

FIG. 4 is an enlarged view of the connecting portion between the internal electrode layer and the external electrode layer of the laminated ceramic capacitor manufactured by the conventional method. 11 is a dielectric layer, 12 is an internal electrode layer, 13 is an external electrode layer, Reference numeral 14 indicates a connecting portion between the internal electrode layer and the external electrode layer.

As can be seen from FIGS. 2 and 4, the internal electrode layer 2
Alternatively, when the capacitor is manufactured by reducing the amount of use of 12, the discontinuity occurs in the internal electrode layers 2 or 12 due to metal sintering. However, even if the electrodes are interrupted, as long as the internal electrode layers 2 or 12 are connected as the electrode surface, they serve as the capacitor electrodes sandwiching the dielectric layer 1 or 11 and no particular problem occurs. However, regarding the connection with the external electrode layer 3 or 13, in the conventional method, the internal electrode layer 12 is not pulled in and connected inside, or even if it is connected, the contact area is small and a problem remains from the viewpoint of reliability. On the other hand, in the present invention, since the internal electrode layer 5 near the connecting portion between the internal electrode layer 2 and the external electrode layer 3 is thickened, the connection is not defective and the reliability is high.

Next, a method of manufacturing a laminated ceramic capacitor according to an embodiment of the present invention will be described. FIG. 3 is a diagram showing a manufacturing process of a laminated ceramic capacitor according to an embodiment of the present invention, in which a dielectric powder containing barium titanate as a main component, a binder, a plasticizer and an organic solvent are provided on a support 6 such as a polyester film. A dielectric green sheet 7 having a thickness of 15 μm is formed by a doctor blade method using the slurry made of. A commercially available palladium internal electrode paste was printed on the dielectric green sheet 7 by a screen printing method, and then dried 0.2 μm.
The internal electrode layer 2 was formed to have a thickness of m. Next, an electrode layer 5 having an electrode thickness of 1.5 μm was further formed by screen printing on a portion which was considered in advance as the connection portion 4 between the internal electrode layer 2 and the external electrode layer 3. For comparison, a conventional method, that is, a method in which the internal electrode layer at the connecting portion between the internal electrode and the external electrode is not formed particularly thick, uses the same palladium electrode paste as described above on the dielectric green sheet 7, Internal electrode layers having electrode thicknesses of 2.0 μm and 3.5 μm were formed by screen printing. Next, the dielectric green sheet 7 on which the internal electrode layers 2 and the electrode layers 5 are formed is peeled off from the support 6, and then placed in a die die 8 and thermocompression bonded to form a laminated molded body 9 having 80 layers. Specially made. This laminated molded body 9 was cut with a cutting blade 10 to produce a chip-shaped molded body 11. The broken line 12 is a cutting point. Next, after the chip-shaped molded body 11 was baked at 1320 ° C. for 2 hours, a silver paste was applied to the connection portion 4 and baked to form the external electrode layer 3. The capacitance of these laminated ceramic capacitors was measured according to a usual method to determine whether or not the capacitance value was a desired value. The results are shown in (Table 1). The number of measurements is 1 for each of this example and the conventional example.
It was set to 00.

[0013]

[Table 1]

As is clear from (Table 1), the sample not having the electrode layer 5 according to the conventional method frequently suffers from poor connection at the connecting portion between the internal electrode and the external electrode, and a desired capacitance value is obtained. The result was a low so-called capacity hit rate. On the other hand, when the thickness of the internal electrode layer is large even in this example or the conventional method, it is understood that the capacity hit rate is high because the connectivity between the internal electrode and the external electrode is good. In the case of this embodiment,
Compared with the case where the internal electrode layer thickness by the conventional method is large,
Even if the amount of the internal electrode paste used is halved, the capacity hit rate is the same, so the cost of the multilayer ceramic capacitor of this embodiment can be greatly reduced. It goes without saying that this effect becomes even greater as the number of stacked layers increases.

[0015]

As is apparent from the above embodiments, in the present invention, the electrode layer is provided so that the thickness of the internal electrode at the connecting portion where the internal electrode layer and the external electrode layer are connected is thicker than the other portions. After forming a dielectric sheet on a support, an internal electrode layer is formed on the dielectric sheet by screen printing so as to have a desired electrode shape, and then an internal electrode layer and an external electrode layer are formed. After further forming an electrode layer in the portion of the internal electrode layer that is considered to be the connection part with, the dielectric sheet and the internal electrode layer are peeled from the support, and after stacking a plurality of sheets, a laminated molded body is produced by pressure bonding. After that, after being cut into chips and baked, the external electrode is formed, so that the thickness of the internal electrode layer at the part where the internal electrode layer and the external electrode layer are connected is smaller than that at other parts. The inner electrode layer is thicker as a result Without having enables good connectivity with the inner electrode layer and the outer electrode layer, thereby preventing that the capacity is reduced by a connection failure. Although the amount of electrode paste used increases as the number of layers increases, the present invention does not require thickening of the internal electrodes except for the connection between the internal electrodes and the external electrodes. It becomes possible and the industrial value is extremely high.

[Brief description of drawings]

FIG. 1 is a sectional view of a laminated ceramic capacitor according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of the same laminated ceramic capacitor.

FIG. 3 is a process sectional view illustrating a method for manufacturing a laminated ceramic capacitor according to an embodiment of the present invention.

FIG. 4 is a sectional view of a conventional laminated ceramic capacitor.

[Explanation of symbols]

 1 Dielectric Layer 2 Internal Electrode Layer 3 External Electrode Layer 4 Connection Section 5 Electrode Layer

Claims (2)

[Claims] 1. Internal electrode layers and dielectric layers are alternately laminated,
In a laminated ceramic capacitor in which an external electrode layer is provided so that the internal electrode layers are connected in parallel, the thickness of the internal electrode layer at the connecting portion at which the internal electrode layer and the external electrode layer are connected is larger than that at other portions. A laminated ceramic capacitor in which an electrode layer is provided so as to be thick. 2. After forming a dielectric sheet on a support, an internal electrode layer is formed on the dielectric sheet by a screen printing method so as to have a desired electrode shape, and then the internal electrode layer and the internal electrode layer are formed in advance. After forming an electrode layer further on the portion of the internal electrode layer that will be the connection portion with the external electrode layer, the dielectric sheet and the internal electrode layer are peeled from the support, and a plurality of sheets are stacked, and then pressure-bonded to produce a laminated molded body. A method for manufacturing a laminated ceramic capacitor, which comprises cutting the material into chips, firing, and then forming external electrodes.