JPH05226180A - Laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To eliminate improper tan delta and capacitance of a capacitor by forming a first terminal electrode layer made of silver or silver-palladium alloy and glass, forming a second terminal electrode layer made of organic solvent containing copper powder or copper alloy powder thereon and further forming a third terminal electrode of solder layer. CONSTITUTION:A part corresponding to a desired capacitance of a dielectric sheet 3 is so laminated as to dispose edges of the sheet 3 in which inner electrodes 2 are alternately opposed, and baked to manufacture a capacitor element 4. First terminal electrode layers 5 are provided at both ends of the element 4 by coating and baking the first layer made of silver-palladium alloy and glass. Second layer terminal electrodes 8 are formed on the first layer by applying and baking the first layer made of silver coated copper powder and phenol resin adhesive. Further, third layer terminal electrodes 9 are formed on the second layer by plating melted solder to form a capacitor 10.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a monolithic ceramic capacitor. In particular, it relates to the structure of the terminal electrode of the capacitor.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional monolithic ceramic capacitor has a dielectric sheet 3 coated with a paste-like ink 2 made of a silver-palladium alloy and an organic binder as internal electrodes on a ceramic green sheet 1. A plurality of layers are laminated and fired to form a capacitor element 4. This element 4
The terminal electrodes 5 made of silver-palladium alloy and glass are formed on both ends of the.

In addition, the structure of the terminal electrode is such that, as shown in FIG. 3, a second layer terminal of a nickel plating layer is provided on the first layer terminal electrode 5 made of silver palladium and glass shown in FIG. The electrode 6 and the terminal electrode 7 of the third layer of the solder plating layer have a three-layer structure, and as another one, as shown in FIG.
Two-layer structure of a second electrode layer 9 made of a molten solder plating layer on a first electrode layer 8 made of copper or copper alloy spherical powder and an organic adhesive (Japanese Patent Laid-Open No. 3-266404) Is known.

[0004]

The terminal electrode of the conventional capacitor is generally the terminal electrode 5 of the composition material composed of silver-palladium alloy and glass shown in FIG. When the capacitor 11 is mounted on a substrate by soldering, the terminal electrode 5 may be melted in the molten solder and the element 4 may be exposed.

The capacitor 12 shown in FIG. 3 is provided with a nickel plating layer 6 on the second layer to take measures against this. However, the plating solution during nickel plating remains and the insulation resistance during movement is increased. It cannot be applied to high withstand voltage products because it has the drawback of decreasing.

The capacitor 13 shown in FIG. 4 uses the material consisting of the spherical powder of copper or copper alloy and the organic adhesive for the first electrode layer 8, so that there is no soldering, moisture resistance and insulation resistance. There is no problem with the decrease of. However, since the organic adhesive is used, the baking temperature is as low as 200 ° C or lower, which is different from the case where the conventional electrode (glass) is baked at 800 ° C.
A structure in which the internal electrode 2 and the terminal electrode 8 diffuse into each other to form a complete alloy and are not connected to each other and further contact the spherical copper or copper alloy and the thin layered internal electrode 2 is point contact. Therefore, the smaller the number of layers of the internal electrodes 2, the smaller the capacity, the more the tan δ and the capacity defect tended to increase.

[0007]

SUMMARY OF THE INVENTION The present invention is to improve the terminal structure of a monolithic ceramic capacitor, which is a first terminal electrode layer 5 made of silver or silver-palladium alloy and glass.
And then a second terminal electrode layer 8 made of copper powder or copper alloy powder and an organic solvent is provided on the first electrode layer 5 and further the second electrode layer 8 is formed. Provided is a multilayer ceramic capacitor 10 having a third terminal electrode layer 9 of a solder layer 9 formed thereon.

[0008]

In the capacitor of the present invention, the layer 5 made of silver or silver palladium and glass is baked on the first layer of the terminal electrode at a high temperature of about 800 ° C., so that the mutual diffusion with the internal electrode 2 is sufficiently performed, and Are formed and connected. Since these contacts are made as line contacts, the contacts are surely made. By forming a layer made of copper or copper alloy powder and an organic solvent as a second layer thereon, the occurrence of tan δ defects and capacity defects can be prevented.

[0009]

EXAMPLE An example of the monolithic ceramic capacitor 10 of the present invention will be described with reference to FIG. A dielectric sheet is formed by forming an internal electrode 2 having a thickness of 1 to 3 μm on a surface of a green sheet 1 having a thickness of 30 μm made of a barium titanate-based ferroelectric ceramic and using a paste ink in which an organic binder is added to silver palladium. Produce 3. The dielectric sheets 3 are laminated by the amount corresponding to the desired capacitance so that the internal electrodes 2 of the dielectric sheet 3 are alternately located at the opposite edge portions. After this, the capacitor element 4 is manufactured by firing and integrating.

Terminal electrodes are formed on both ends of the capacitor element 4. As the first layer of the terminal electrode, a material composed of silver-palladium alloy and glass is applied and baked at 800 ° C. to form the first terminal electrode layer 5. A second terminal electrode layer 8 is formed by coating a silver-coated copper powder having an average particle size of 10 μm and a phenol resin adhesive on the first layer and baking at 200 ° C. Furthermore, the terminal electrode 9 of the third layer is formed on the second layer by hot-dip soldering to obtain the capacitor 10.

Table 1 shows the failure rate of tan δ in the unit of capacitance of a laminated ceramic capacitor having a rated voltage of 630 VDC in comparison with the conventional example (4th) and the example of the present invention. As the capacity of the conventional example decreases, tan δ
It can be seen that while the defect rate of No. 1 is large, the product of the example of the present invention is stabilized at a low value of tan δ regardless of the capacity. The margin below.

[0012]

[Table 1]

[0013]

According to the capacitor of the present invention, a layer of silver-palladium alloy and glass is formed on the first terminal electrode layer 5 as a layer.
Since baking is performed at a high temperature of 0 ° C., the internal electrode 2 and the terminal electrode 5 mutually diffuse to form an alloy and are connected. By forming the second terminal electrode layer 8 composed of the copper alloy powder and the organic solvent on this, tan δ and the capacity defect as the capacitor 10 can be eliminated.

[0014]

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view of a conventional capacitor.

FIG. 3 is a cross-sectional view of a conventional capacitor.

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

[Explanation of symbols]

2 ... internal electrode, 3 ... dielectric sheet, 4 ... element, 5
... first terminal electrode layer, 8 ... second terminal electrode layer, 9
... The third terminal electrode layer, 10 ... Capacitor.

Claims (1)

[Claims] 1. A monolithic ceramic capacitor comprising a dielectric sheet for forming internal electrodes on a ceramic dielectric, wherein a plurality of internal electrodes are led out from both ends of the dielectric sheet. First electrode composed of silver or a silver-palladium alloy and glass as an electrode
A terminal electrode of a layer is formed, and a second terminal electrode layer 8 made of copper powder or copper alloy powder and an organic solvent is provided on the first layer,
Furthermore, the third terminal electrode layer 9 of the solder layer is formed on the second layer.
Forming a laminated ceramic capacitor.