JPH088192B2 - Monolithic ceramic capacitors - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated ceramic capacitor having an improved electrode material.

[0002]

2. Description of the Related Art A monolithic ceramic capacitor of this type is
It is composed of a laminated chip formed by laminating a plurality of flat plate-shaped internal electrodes via ceramics, and a pair of external electrodes attached to opposing walls of the laminated chip. The internal electrodes in the chip are alternately connected to the external electrodes in opposite directions so that a predetermined capacitance obtained between the internal electrodes can be taken out from the external electrodes.

The internal electrodes and the external electrodes are generally formed of silver or a silver alloy such as silver-palladium in view of heat resistance and corrosion resistance. However, while these metals have excellent characteristics as electrodes, they have the drawback that the material cost is high and the cost of the capacitor itself is high, and in particular, 30 to 40% of the total cost depends on the internal electrodes.

In order to solve the price problem associated with the monolithic ceramic capacitor, attempts have been made to form the internal electrodes from an inexpensive base metal. However, when the internal electrodes are formed of a base metal such as nickel, if silver or a silver alloy is used for the external electrodes, there is a drawback that the two electrodes are not well-adapted to each other and a conduction failure easily occurs in both electrodes.

In order to solve the problem of mutual familiarity between the electrodes, the internal electrodes are made of a base metal, while the external electrodes are made of the same or alloyed metal as the internal electrodes.
Also proposed is one comprising a first layer connected to the internal electrode and a second layer formed of silver or a silver alloy and attached to the outer surface of the first layer (JP-A-59-59). 163
23). In other words, in this monolithic ceramic capacitor, the external electrode portion connected to the internal electrode is formed of the same metal as the internal electrode, so that the familiarity between both electrodes is improved and conduction is improved.

[0006]

However, in the above-mentioned multilayer ceramic capacitor, the familiarity between the internal electrode and the first layer of the external electrode can be improved, while the first layer made of a base metal and the first layer made of silver or a silver alloy are used. Due to the poor compatibility with the two layers, there are disadvantages that conduction failure occurs at the boundary between the two layers forming the external electrode, tan δ is deteriorated, and capacitance loss occurs due to temperature cycle.

The present invention has been made in view of the above problems, and it is an object of the present invention that the capacitor itself can be formed at low cost, and the tensile strength of the external electrode is maintained while the external electrode and the internal electrode are maintained. It is an object of the present invention to provide a monolithic ceramic capacitor which can secure high electrical conductivity between the electrodes and the first and second layers constituting the external electrodes, and which does not deteriorate characteristics such as capacitance and tan δ.

[0008]

In order to achieve the above object, the present invention comprises a plurality of internal electrodes laminated via ceramics, and a pair of external electrodes which are electrically connected to the internal electrodes in a predetermined connection relationship. In the multilayer ceramic capacitor described above, the internal electrode is formed of a base metal or an alloy of a base metal, and the external electrode is formed of a first layer made of a base metal or an alloy of a base metal and connected to the internal electrode, and a first layer made of copper or a copper alloy. It is formed from a second layer attached to the outer surface of one layer.

[0009]

In the laminated ceramic capacitor according to the present invention,
Since the first layer of the external electrode connected to the internal electrode is formed of the same base metal or base metal alloy as the internal electrode,
Both are familiar and high conductivity can be secured at the boundary. Moreover, since the second layer of the external electrode is formed of copper or a copper alloy, which is one of the base metals, it is more familiar to the first layer than when the second layer is formed of silver or a silver alloy, High conductivity can be secured at the boundary between the two.

[0010]

1 is a sectional view of a monolithic ceramic capacitor to which the present invention is applied.

This monolithic ceramic capacitor comprises a plurality of (five in the figure) internal electrodes 1 in the form of a flat plate and a ceramic 2
It is composed of a rectangular multilayer chip 3 formed by stacking via a via, and a pair of external electrodes 4 attached to opposing walls in the internal electrode direction of the multilayer chip 3.

The internal electrodes 1 are arranged parallel to each other with the positions thereof spaced apart from each other, and the three edges thereof are exposed from the opposing wall on the right side in the drawing, and the two edges are also exposed. Is exposed from the opposing wall on the left side in the figure.

The internal electrode 1 is made of one kind or an alloy thereof selected from base metals such as nickel, copper, lead, zinc, iron, tin, aluminum, cobalt and chromium, preferably nickel, copper, lead and these. Alloy is used.

Each of the external electrodes 4 has a first layer 4a attached to the wall surface of the laminated chip 3 so as to extend to the periphery thereof, and a second layer 4b attached so as to cover the outer surface of the first layer 4a. It consists of The first layer 4a of each outer electrode 4 is joined to the edge of the inner electrode 1 exposed from the respective opposing wall.

The first layer 4a of the external electrode 4 is selected from a base metal or an alloy of a base metal similarly to the internal electrode 1, but does not necessarily have to be the same metal as the internal electrode 1.

The second layer 4b of the external electrode 4 is made of copper or a copper alloy, and the copper alloy is selectively used from brass alloys and bronze alloys.

A preferred specific example of the monolithic ceramic capacitor according to the present invention will be described below together with its manufacturing method.

First, a surface of a ceramic sheet made of a non-reducing ceramic composition and having a thickness of 10 to 60 .mu.m is coated with a paste of nickel powder as an internal electrode in a thickness of several .mu.m and a large number of rectangles. Print in regular rows.

Next, 20 to 100 sheets of the printed ceramic sheet are shifted in the plane direction to one sheet, and the sheets are cut in a predetermined size in the stacking direction to form a chip material. A nickel layer which will be an internal electrode is exposed on the opposing wall of the cut chip material.

Next, a paste of nickel powder, which is the first layer of the external electrode, is applied to each of the facing walls where the nickel layer of the chip material is exposed with a thickness of several μm to several tens of μm.

Next, the chip material after applying the paste is fired at a temperature of about 1300 ° C. in a neutral or reducing atmosphere. By this firing, a fired ceramic body is obtained, and at the same time, the paste of the inner electrode and the outer electrode first layer is fired.

Next, a paste of copper powder, which will be the second layer of the external electrode, is applied to the outer surface of the first layer of the external electrode with the same thickness as the first layer.

Next, the chip material coated with the paste is fired at a temperature of about 800 ° C. in a neutral or reducing atmosphere.
The baking of the external electrode second layer is performed by this baking.

As described above, the first of the inner electrode 1 and the outer electrode 4 is
The layer 4a is made of nickel, and the second layer 4 of the external electrode 4 is provided.
A monolithic ceramic capacitor as shown in FIG. 1, where b is made of copper, is manufactured.

In the above-mentioned laminated ceramic capacitor, since the first layer 4a of the external electrode 4 connected to the internal electrode 1 is made of the same nickel as the internal electrode 1, the two are well familiar to each other and have a high conductivity at the boundary portion. You can secure the sex. In addition, since the second layer 4b of the external electrode 4 is formed of copper, which is one of the base metals, it is more familiar to the first layer 4a than when the second layer 4b is formed of silver or a silver alloy. High conductivity can be secured at the boundary between the two.

By the way, according to the method described above, the first layer of the inner electrode and the outer electrode is made of nickel and the second layer is made of copper, and the length, width and height are 3.2 mm, 1.6 mm, 1.
An F characteristic multilayer ceramic capacitor (invention product) of 25 mm and a design capacity of 1.0 μF, and an F characteristic multilayer capacitor of the same size and having the same capacity as the first and second electrodes of the internal and external electrodes are nickel and silver. (Conventional product), each of which is manufactured for 100 units, and has a capacity of 0.9 μF or less among the products
When the number of products having δ of 5% or more was checked, and the same number was checked after each product was subjected to the temperature cycle test specified by JIS C5102, no defective products were found before and after the temperature cycle test. Although not seen, the conventional product had a capacity of 0.9 after the temperature cycle test.
Three of those with μF or less and eight with tan δ5% or more appeared.

When a base metal other than nickel or an alloy of a base metal is used as the first layer of the internal electrode and the external electrode, or when a copper alloy is used as the second layer of the external electrode, the same manufacturing method as above is applied to the laminated ceramic. A capacitor can be obtained, and the same effect can be obtained.

[0028]

As described above in detail, according to the present invention, the internal electrode and the external electrode are formed of a base metal or an alloy of a base metal having a low material cost, so that the capacitor itself can be formed at a lower cost. High electrical conductivity can be secured between the electrodes and the internal electrodes and between the first layer and the second layer forming the external electrodes.

[Brief description of drawings]

FIG. 1 is a sectional view of a monolithic ceramic capacitor to which the present invention is applied.

[Explanation of symbols]

1 ... Internal electrode, 2 ... Ceramic, 3 ... Layered chip, 4 ...
External electrodes, 4a ... 1st layer, 4b ... 2nd layer.

Claims (1)

[Claims] 1. A monolithic ceramic capacitor comprising a plurality of internal electrodes laminated via ceramics, and a pair of external electrodes conducting with a predetermined connection relationship with the internal electrodes, wherein the internal electrodes are a base metal or an alloy of a base metal. And the external electrode is formed of a first layer made of a base metal or an alloy of a base metal and connected to the internal electrode, and a second layer made of copper or a copper alloy and attached to the outer surface of the first layer. A multilayer ceramic capacitor characterized by the above.