JPH06215981A - Ceramic electronic component - Google Patents

Abstract

PURPOSE:To provide a ceramic electronic component having an external electrode which is excellent in solder wettability and has a large adhesive strength. CONSTITUTION:The electronic part consists of a ceramic base 2 and external electrodes 4. The external electrode 4, based on ceramic powder 41 and glass, is formed on the ceramic base 2. The surface of the ceramic powder 41 is covered with a metal film 42, which composed of a first metal film 421 and second metal film 422. The first metal film 421, composed of a metallic material excellent in heat resistance, covers the surface of the ceramic powder 41; the second metal film 422, composed of a metallic material excellent in solder wettability, covers the first metal film 421.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ceramic electronic components, and more particularly to the structure of external electrodes.

[0002]

2. Description of the Related Art Most of the external electrodes of conventional ceramic electronic parts are those prepared by mixing glass frit with silver or silver-palladium alloy powder, forming a paste, and baking the mixture, and are not necessarily excellent in solderability. I could not say. Therefore, in the case of chip-type electronic components, which have been frequently used with the recent miniaturization, most of them have been plated with nickel, tin, or the like on the baked electrode to improve the solderability. .

[0003]

However, in the case of a ceramic electronic component having improved solderability by plating nickel or tin on the baked electrode, the ceramic element body is Since the plating solution penetrates into and remains inside, there is a problem in that the characteristics of electronic components are sometimes deteriorated. As a means for solving this problem, recently, it has been proposed to use an adhesive conductive paste as an external electrode.
However, in the case of such a conductive paste, the adhesiveness with the ceramic body is insufficient, and in the case of a laminated ceramic electronic component having an internal electrode, the contactability between the internal electrode and the external electrode is not good. , There is a problem in practice.

Therefore, an object of the present invention is to provide a ceramic electronic component having an external electrode which is excellent in solderability and has a large adhesive strength.

[0005]

To solve the above problems, the present invention is a ceramic electronic component having a ceramic body and external electrodes, wherein the external electrodes include ceramic powder and glass. The main component is formed on the ceramic body, the surface of the ceramic powder is covered with a metal film, and the metal film includes a first metal film and a second metal film.
A metal film, the first metal film is made of a metal material having excellent solder heat resistance and covers the surface of the ceramic powder, and the second metal film is made of a metal material having excellent solder wettability. It covers the metal film.

The preferred embodiment of the present invention is as follows. First, the ceramic powder is alumina, zirconia, titania, barium titanate, ferrite,
The main component is at least one selected from silica and lead zirconate titanium.

The first metal film preferably contains at least one selected from palladium, nickel and copper as a main component.

The second metal film preferably contains at least one selected from silver, platinum and silver solder as a main component.

The outer electrode may further have a second layer. The second layer is mainly composed of solder or tin and constitutes an outermost layer.

[0010]

The external electrode has a ceramic powder as a main component and is formed on the ceramic body, the surface of the ceramic powder is covered with a metal film, and the metal film has a first metal film. Since the first metal film is made of a metal material having excellent solder heat resistance and covers the surface of the ceramic powder, high solder heat resistance can be ensured by the first metal film.

The metal film further includes a second metal film, and since the second metal film is made of a metal material having excellent solder wettability and covers the first metal film, the second metal film provides good solder wettability. Become. By sharing the roles of the first metal film and the second metal film, a ceramic electronic component having excellent solderability can be obtained.

The external electrode is composed mainly of ceramic powder, and the surface of the ceramic powder is covered with a metal film. Therefore, the ceramic powder is bonded only by sintering the metal films on the surface. Therefore, the voids between the powders are large, and when soldering the external electrodes, the voids between the ceramic powders are filled with the solder, and they are firmly bonded,
High adhesion strength can be obtained. Since the external electrode contains glass, the adhesion strength to the ceramic body can be increased by the glass.

The external electrode is mainly composed of ceramic powder,
Since the surface of the ceramic powder is covered with the metal film having excellent solderability, the amount of expensive metal material used can be small and the electrode cost can be reduced.

The ceramic powder is alumina, zirconia,
In a preferred embodiment containing at least one selected from titania, barium titanate, ferrite, silica and lead titan zirconate (PZT) as a main component, a powder having the same quality as the ceramic body can be selected. By making the coefficient of thermal expansion close to that of the body, the thermal shock resistance is improved. For this reason, it is possible to suppress the occurrence of element cracks that are likely to occur due to thermal shock, such as soldering.

In the embodiment in which the first metal film contains at least one selected from palladium, nickel and copper as the main component, the sinterability of the first metal film becomes easy and the adhesive strength is further improved. In the example in which the second metal film contains at least one selected from silver, platinum and silver brazing as the main component, the solderability becomes good.

In the embodiment in which the external electrode has the second layer, and the second layer is composed mainly of solder or tin and is formed on the second metal film, the solderability becomes better.

[0017]

1 is a sectional view showing a model of a structure of a ceramic electronic component according to the present invention. The ceramic electronic component 1 shown in the embodiment is a laminated chip inductor. The ceramic electronic component 1 includes a ceramic body 2 made of a Cu—Zn—Co ferrite material or the like, and an internal electrode 3 made of silver or the like laminated inside the ceramic body 2.
The internal electrode 3 and the external electrode 4 that is electrically connected are included.

The external electrodes 4 are formed on both ends of the ceramic body 2. FIG. 2 is an enlarged cross-sectional view showing the structure of the external electrode 4. The external electrodes 4 are mainly composed of ceramic powder 41 and glass (not shown), and are formed by coating and baking the surfaces of both ends of the ceramic body 2. The external electrode 4 includes ceramic powder 41, and the surface of the ceramic powder 41 is covered with a metal film 42, as shown in an enlarged view in FIG. 3. Such an external electrode 4 is
The conductive paste containing the ceramic powder 41 as a main component coated with the metal film 42 is applied onto the ceramic body 2 and baked at a low temperature to form it. The particle size of the ceramic powder 41 is preferably a size convenient for use as a paste, for example, 0.5 to 10 μm.

As shown in FIG. 3, the metal film 42 has a two-layer structure in which the first metal film 421 covers the surface of the ceramic powder 41 and the second metal film 422 covers the first metal film 421. ing. The first metal film 421 is made of a metal material having excellent solder heat resistance, and the second metal film 422 is made of a metal material having excellent solder wettability. Preferably, the first metal film 421 contains at least one selected from palladium, nickel and copper as a main component, and the second metal film 422 contains at least one selected from silver, platinum and silver braze. .

As described above, the external electrode 4 is mainly composed of the ceramic powder 41 and is formed on the ceramic body 2. The surface of the ceramic powder 41 is covered with the metal film 42. The metal film 42 has a first metal film 421, and the first metal film 421 is made of a metal material having excellent solder heat resistance and covers the surface of the ceramic powder 41.
The metal film 421 can ensure high soldering heat resistance.

The metal film 42 further includes a second metal film 422. Since the second metal film 422 is made of a metal material having excellent solder wettability and covers the first metal film 421, the second metal film 422 is formed. This improves solderability. By sharing the roles of the first metal film 421 and the second metal film 422, a ceramic electronic component having excellent solderability can be obtained.

In the external electrode 4, the ceramic powder 41 is the main component and the surface of the ceramic powder 41 is covered with the metal film 42. Therefore, the ceramic powder 41 is bonded only by sintering the metal films 42 on the surface. It Therefore, the voids between the ceramic powders 41, 41 are large, and when soldering the external electrode 4, as shown in FIG. Buried. Thereby, high adhesion strength can be obtained. The penetration of the solder 51 is caused by the ceramic powder 41 on the surface of the metal film 4.
This is due to the large gap between the ceramic powders 41-41 because the two surfaces are bonded only by sintering. Moreover, since the external electrode 4 contains glass, the adhesion strength to the ceramic body 2 can be increased by the glass.

FIG. 5 is an enlarged sectional view showing another embodiment of the ceramic electronic component according to the present invention. In this example,
The external electrode 4 includes a second layer 43. Second layer 43
Is mainly composed of solder or tin, and contains ceramic powder 41
It is formed on the metal film 42 formed above. This improves the solderability.

Next, the method of forming the external electrodes 4 will be described more specifically.

A base (for example, 2.0 × 1.2 × 0.9 mm) composed of a Cu—Zn—Co ferrite material forming the ceramic body 2 and silver forming the internal electrode 3 is prepared. , The first metal film 421 as the external electrode 4
Is coated with a nickel powder, the second metal film 422 is a silver powder, the ceramic powder 41, lead borosilicate glass, and a conductive paste made of an organic vehicle are applied and baked at 650 ° C. for 1 hour.

According to the ceramic electronic component 1 thus formed, the ceramic powder 4 is formed on the surface of the external electrode 4.
Since the silver layer is formed as the first second metal film 422, the solder wettability is 1 second or less at 215 ° C., and the nickel layer is formed as the first metal film 421 on the silver base. Therefore, the solder heat resistance was 280 ° C. for 10 seconds or more, and good solderability was obtained.

Further, since the external electrode 4 contains glass frit and is baked at a low temperature,
Since there are many voids between the powders, the solder is firmly bonded while filling the voids of the powder during soldering. As a result,
The tensile strength was 5 kg or more and the bending strength was 3 mm or more, and good adhesion between the external electrode 4 and the ceramic body 2 was obtained.

As described above, according to the present embodiment, the ceramic electronic component 1 having a high practical value, which is provided with the external electrode 4 which is excellent in solderability and has a good adhesive strength with the ceramic body 2, is provided. be able to.

FIG. 6 is a sectional view showing another embodiment of the ceramic electronic component according to the present invention. In this embodiment, a multilayer chip capacitor is used as the ceramic electronic component 1. A ceramic electronic component 1 which is a multilayer chip capacitor includes a ceramic body 2 made of a barium titanate-based ceramic material, an internal electrode 3 made of palladium or the like laminated inside the ceramic body 2, and an internal electrode 3 It is composed of a pair of external electrodes 4 formed at both ends of the ceramic body 2 for energizing the. The external electrode 4 has the structure shown in FIGS. Also in the case of this embodiment, it is possible to obtain the same effects as those of the embodiment shown in FIGS.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. For example, the ceramic powder may be not only ferrite but also alumina or zirconia. In the embodiment, the second metal film made of ceramic powder with the silver layer formed is used.
The same effect can be obtained by using silver solder for the second metal film.
Although illustration is omitted, the present invention can be widely applied to varistor, thermistor, resistor, or composite parts thereof having an external electrode for external connection.

[0031]

According to the present invention described in detail above, the following effects can be obtained. (A) The external electrode has a ceramic powder as a main component and is formed on a ceramic body, the surface of the ceramic powder is covered with a metal film, and the metal film has a first metal film. Since the first metal film is made of a metal material having excellent solder heat resistance and covers the surface of the ceramic powder, it is possible to provide a ceramic electronic component capable of ensuring high solder heat resistance by the first metal film. it can. (B) The metal film further includes a second metal film, and the second metal film is made of a metal material having excellent solder wettability and covers the first metal film. Become. By sharing the roles of the first metal film and the second metal film described above, it is possible to provide a ceramic electronic component having excellent solderability. (C) Since the external electrode has the ceramic powder as a main component and the surface of the ceramic powder is covered with the metal film, high adhesion strength can be obtained in soldering the external electrode. Moreover, since the external electrode contains glass, the adhesion strength to the ceramic body can be increased by the glass. (D) Since the external electrode is mainly composed of ceramic powder and the surface of the ceramic powder is covered with a metal film having excellent solderability, the amount of expensive metal material used can be small.
Electrode cost is low. (E) In a preferred embodiment in which the ceramic powder contains at least one selected from alumina, zirconia, titania, barium titanate, ferrite, silica and lead titan zirconate (PZT) as a main component, thermal shock, for example, It is possible to suppress the occurrence of element cracks that are likely to occur during soldering. (F) In the example in which the first metal film contains at least one selected from palladium, nickel and copper, the sinterability of the first metal film becomes easy and the adhesive strength is further improved. In the example in which the second metal film contains at least one selected from silver, platinum and silver brazing as the main component, the solderability becomes good. (G) In the example in which the external electrode has the second layer, and the second layer has solder or tin as a main component and is formed on the second metal film, the solderability becomes better.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a ceramic electronic component according to the present invention.

FIG. 2 is an enlarged cross-sectional view of the ceramic electronic component shown in FIG.

FIG. 3 is a diagram showing a modeled structure of a ceramic powder for external electrodes of the ceramic electronic component shown in FIGS. 1 and 2.

FIG. 4 is an enlarged cross-sectional view showing a model of an external electrode structure of a ceramic electronic component according to the present invention.

FIG. 5 is an enlarged sectional view showing another embodiment of the ceramic electronic component according to the present invention.

FIG. 6 is a cross-sectional view showing another embodiment of the ceramic electronic component according to the present invention.

[Explanation of symbols]

 1 Ceramic Electronic Component 2 Ceramic Element 3 Internal Electrode 4 External Electrode 41 First Metal Film 42 Second Metal Film

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[Procedure amendment]

[Submission date] March 3, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 3

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 4

[Correction method] Change

[Correction content]

Claims (5)

[Claims] 1. A ceramic electronic component having a ceramic body and an external electrode, wherein the external electrode contains ceramic powder and glass as main components and is formed on the ceramic body. The surface of the ceramic powder is covered with a metal film, the metal film has a first metal film and a second metal film, and the first metal film is made of a metal material having excellent solder heat resistance. A ceramic electronic component that covers the surface of the ceramic powder, and the second metal film is made of a metal material having excellent solder wettability and covers the first metal film. 2. The ceramic powder is at least one selected from alumina, zirconia, titania, barium titanate, ferrite, silica and lead titanium zirconate.
The ceramic electronic component according to claim 1, wherein the seed is a main component. 3. The ceramic electronic component according to claim 4, wherein the first metal film contains at least one selected from palladium, nickel, and copper as a main component. 4. The ceramic electronic component according to claim 4, wherein the second metal film contains at least one selected from silver, platinum and silver solder as a main component. 5. The ceramic according to claim 1, wherein the outer electrode has a second layer, and the second layer is mainly composed of solder or tin and constitutes an outermost layer. Electronic components.