JPH06224680A - Chip type electronic parts - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a structure of an external electrode that can secure good solderability while avoiding a problem due to soldering in a chip-type piezoelectric resonator and that has low electric resistance. A first layer 17a made of a first metal having a relatively small electric resistance and a good solder wettability, and a second layer 17b made of a second metal having an effect of preventing solder shaving are formed on the external electrode 17.
And the first layer 17a is formed directly on the outer surface of the piezoelectric resonator body 11 so as to be in contact with the terminal electrodes therein, and the second layer 17b is formed on the first layer 17a.
Is formed so as to cover both sides of the first layer 17a while exposing the central portion in the width direction. [Effect] Since the electric resistance of the external electrode connected to the ground is reduced, deterioration of the out-of-band attenuation characteristic is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip type electronic component, and more particularly to improvement of the structure of its external electrode.

[0002]

2. Description of the Related Art A background art interesting to the present invention will be described with reference to FIGS. In Figure 3,
The external appearance of the chip-type piezoelectric resonator 1 is shown in a perspective view. The piezoelectric resonator 1 is provided with a piezoelectric substrate 2 made of, for example, ceramic as shown alone in FIG.

Referring to FIG. 4, divided vibrating electrodes 3 and 4 are formed on one main surface of piezoelectric substrate 2, and vibrating electrodes 3 and 4 are formed on the other main surface as indicated by a broken line. Opposing vibrating electrodes 5 are formed. Terminal electrodes 6, 7 and 8 are connected to the vibrating electrodes 3, 4 and 5, respectively, and the terminal electrodes 6 to 8 are located at the edges of the piezoelectric substrate 2.

The piezoelectric resonator 1 constitutes an energy trap type dual mode piezoelectric filter utilizing a thickness longitudinal vibration mode, which has divided vibrating electrodes 3 and 4 and a vibrating electrode 5 facing the vibrating electrodes 3. .

As shown in FIG. 5, exterior resins 9 and 10 are applied to both surfaces of the piezoelectric substrate 2 as described above.
A cavity is formed in a specific region of the interface between the exterior resins 9 and 10 and the piezoelectric substrate 2 so as not to disturb the vibration in the vibration region provided by the vibrating electrodes 3 to 5 on the piezoelectric substrate 2. To be done. Also, the exterior resins 9 and 10
Is a thermosetting resin, and these exterior resins 9 and 1
For giving 0, for example, pouring into a mold or a frame, or a dip method is adopted. Usually piezoelectric substrate 2
Is prepared in a state of a mother substrate that provides a plurality of piezoelectric substrates 2 by cutting, and the application of the exterior resins 9 and 10 described above is performed at the stage of such a mother substrate, and the exterior resin 9 and 10 is cut. In the piezoelectric resonator body 11 shown in FIG. 5, the above-mentioned terminal electrodes 6 to 8 are exposed on the side surfaces thereof, respectively.

On the outer surface of the piezoelectric resonator body 11, FIG.
As shown in, external electrodes 12, 13 and 14 are formed, and these external electrodes 12, 13 and 14 are electrically connected to terminal electrodes 6, 7 and 8, respectively.

The external electrodes 12 to 14 described above are usually formed by vacuum vapor deposition or sputtering. More specifically, a layer of NiCu alloy (Monel) or chromium is formed by vapor deposition or sputtering on the base to prevent solder nicks, and then silver or copper is used to improve solder wettability. The layer to be formed is formed by vapor deposition or sputtering.

[0008]

However, according to the external electrodes 12 to 14 having the above-mentioned structure, the electric resistance of monel or chrome is higher than that of silver or copper, so that the out-of-band attenuation characteristic of the filter is obtained. Encounter the problem of deterioration. This will be described in more detail with reference to FIGS. 6 and 7.

FIG. 6 is a circuit diagram showing a state in which the piezoelectric resonator 1 is used as a filter. In FIG. 6, r
_{1 2} , r _{1 3} and r _{1 4} are the external electrodes 1 respectively.
It shows the electrical resistance provided by 2, 13 and 14. Further, R ₁ and R ₂ are impedance matching resistors, when the piezoelectric resonator 1 is 330Ω For example, R ₁
And R ₂ are both 330Ω.

In the filter circuit described above, r _{1 2} ,
Even if r _{1 3} and r _{1 4} both show resistance values of 1 to 2Ω, since R ₁ and R ₂ are 330Ω, the effect on insertion loss can be almost ignored, but regarding the out-of-band attenuation,
Originally, by connecting to ground with 0Ω,
Since a predetermined amount of attenuation as shown in (a) is obtained, if the resistance of r ₁₄ is as small as possible, FIG.
As shown in (b), it causes an extreme lack of attenuation.

Therefore, it is desirable that the external electrode 14 to be grounded has a low electric resistance. In this way, in order to reduce the electric resistance, in the external electrode 14,
It is also conceivable to adopt an extremely thick electrode made of silver or copper in consideration of soldering without using monel or chromium having high electric resistance. In this case, the silver or copper electrode usually needs to have a thickness of about 10 μm, but forming such an electrode by vapor deposition or sputtering causes a significant increase in cost. This is because if such a thick electrode is to be formed by one-time vapor deposition or sputtering, a considerably high temperature must be applied, but the application of a high temperature causes the polarization in the piezoelectric substrate 2 to be erased, so that the desired thickness is obtained. This is because vapor deposition or sputtering must be repeated several times in order to obtain

It is to be noted that lowering the electric resistance of the external electrode as described above is not limited to the chip type piezoelectric resonator, and is also required for other chip type electronic parts such as a chip type solid inductor.

Therefore, an object of the present invention is to provide a structure of an external electrode in a chip-type electronic component, which can secure good solderability while avoiding a problem due to solder shaving, and have a low electric resistance. Is to

[0014]

SUMMARY OF THE INVENTION The present invention is directed to a chip type electronic component body, an electrical element located inside the electronic component body, and an electronic component so as to be electrically connected to the electrical element. The present invention is directed to a chip-type electronic component including a plurality of external electrodes formed on an outer surface of a main body, and at least one of the external electrodes has an electric resistance in order to solve the above-mentioned technical problem. The first layer comprises a first metal which is relatively small and has a good solder wettability, and a second layer which comprises a second metal having an effect of preventing solder nicks.
The second layer is formed directly on the outer surface of the electronic component body so as to be in contact with the electrical element, and the second layer is formed on the first layer while exposing a part of the first layer. It has a feature.

[0015]

In the present invention, since the first layer provided on the external electrode is exposed from the second layer in a part thereof, the exposed portion has a connection with low electric resistance while providing good solderability. To enable. Further, the second layer partially covers the first layer to suppress the progress of solder shaving that may occur in the first layer.

[0016]

As described above, according to the present invention, even when the external electrodes are formed by vacuum vapor deposition or sputtering, the cost is not significantly increased and the problem due to the solder shaving is avoided, and the good result is obtained. It is possible to obtain an external electrode having a low electric resistance, which can provide excellent solderability.

[0017]

1 is a perspective view showing the external appearance of a chip type electronic component according to an embodiment of the present invention. In order to facilitate comparison with the above-described conventional technique, FIG. 1 shows a piezoelectric resonator 1a having substantially the same structure as the piezoelectric resonator 1 shown in FIG. 3 except for external electrodes. . Therefore,
Reference numerals similar to those used in the above-mentioned prior art are used to indicate corresponding elements also in this embodiment, so that duplicate description is omitted. Figure 2
FIG. 2 is a partial perspective view showing an enlarged main part of FIG. 1.

External electrodes 15, 16 and 17 are formed on the outer surface of the piezoelectric resonator body 11 of the piezoelectric resonator 1a. These external electrodes 15, 16 and 17 are electrically connected to the terminal electrodes 6, 7 and 8 (see FIG. 4) located inside the piezoelectric resonator body 11, respectively.

In particular, paying attention to the external electrode 17, it is composed of a first layer 17a made of a first metal having a relatively small electric resistance and a good solder wettability, and a second metal having an effect of preventing solder shaving. And a second layer 17b. 1st layer 1
As shown in FIG. 2, 7a is provided directly on the outer surface of the piezoelectric resonator body 11 so as to be in contact with the terminal electrode 8.
It is formed. The second layer 17b is formed on the first layer 17a while exposing a part of the first layer 17a. In this embodiment, the second layer 17b is provided outside the piezoelectric resonator body 11 from the first layer 17a so as to cover both side portions of the first layer 17a while exposing the widthwise central portion of the first layer 17a. It is formed so as to extend onto the surface.

To form these external electrodes 15 to 17, more specifically, the following steps are carried out. First, silver or copper is vapor-deposited or sputtered through a mask so as to form the first layer 17a of the external electrode 17.
Then, Monel is vapor-deposited or sputtered through the mask so as to form the second layer 17b of the external electrode 17 and the external electrodes 15 and 16. Furthermore, preferably, these second layer 17b and external electrodes 15 and 1
On top of 6, silver is deposited or sputtered. In the latter second layer 17b and the external electrodes 15 and 16, monel has a function of preventing solder shaving, and silver has a function of enhancing conductivity and solderability. Note that chromium may be used instead of monel.

When the piezo-resonator 1 thus constructed is soldered to a printed circuit board (not shown), the solder crevice of the second layer 17a of the external electrode 17 is removed from the second layer 17b.
Is suppressed by the first layer 17a, and at least a part of the first layer 17a remains, and the solder adheres to the remaining first layer 17a in a state of low electric resistance. Further, even in the second layer 17b, although the electric resistance is large, the solder adheres to the second layer 17b, which serves to further enhance the reliability of electric conduction. Since the solder also adheres to the surface of the second layer 17b, the electric resistance of the entire second layer 17b including the solder on the surface is reduced. Further, particularly in this embodiment, the solder is attached while straddling between the second layers 17b on both sides of the first layer 17a. Therefore, if the second layer 1
In the portion exposed from 7b, even if the first layer 17a is lost due to solder shaving, it is possible to directly establish conduction between the solder and the terminal electrode 8 in a state of low electric resistance. Further, in this embodiment, since the second layer 17b is formed so as to cover both sides of the first layer 17a, when the second layer 17b is formed so as to cover only one side of the first layer 17a, Compared with this, it is possible to further suppress the solder crack in the first layer 17a.

In the above-described embodiment, the piezoelectric resonator 1a is used.
In particular, the characteristic configuration including the first layer 17a and the second layer 17b is adopted for the external electrode 17 to be grounded in particular, but the same configuration may be adopted for the other external electrodes 15 and 16. Good. Further, the present invention can be applied not only to the chip type piezoelectric resonator but also to other chip type electronic parts such as a chip type solid inductor.

[Brief description of drawings]

FIG. 1 is a perspective view showing an external appearance of a chip type piezoelectric resonator 1a according to an embodiment of the present invention.

2 is an enlarged perspective view showing a main part of the piezoelectric resonator 1a shown in FIG.

FIG. 3 Conventional piezoelectric resonator 1 of interest to the present invention
3 is a perspective view showing the external appearance of FIG.

FIG. 4 is a piezoelectric resonator 1 shown in FIGS. 1 and 3, respectively.
It is a perspective view which shows independently the piezoelectric substrate 2 contained in a and 1.

5 is a piezoelectric resonator 1 shown in FIGS. 1 and 3, respectively.
It is a perspective view which shows the piezoelectric resonator main body 11 provided in a and 1.

6 is a diagram showing a filter circuit configured by the piezoelectric resonator 1 shown in FIG.

7 is a diagram showing frequency characteristics given by the filter circuit shown in FIG. 6, where (a) shows frequency characteristics in a normal state, and (b) shows resistance r _{1 4} of FIG. The frequency characteristic when the resistance value is shown is shown.

[Explanation of symbols]

 1a Piezoelectric resonator (chip type electronic component) 3-5 Vibration electrode (electrical element) 6-8 Terminal electrode (electrical element) 11 Piezoelectric resonator main body (electronic component main body) 15, 16, 17 External electrode 17a 1st Layer 17b Second layer

Claims (1)

[Claims] 1. A chip-type electronic component body, an electrical element located inside the electronic component body, and an outer surface of the electronic component body that is electrically connected to the electrical element. In a chip-type electronic component including a plurality of external electrodes, at least one of the external electrodes has a first layer having a relatively low electric resistance and good solder wettability and a solder layer A second layer made of a second metal having a preventive effect, wherein the first layer is formed directly on the outer surface of the electronic component body so as to be in contact with the electrical element, and The chip-type electronic component, wherein the two layers are formed on the first layer while exposing a part of the first layer.