JPH07131284A - Thin film electrode of piezoelectric oscillator - Google Patents

Abstract

PURPOSE:To obtain the thin film electrode of the piezoelectric oscillate which is large in contacting force to a piezoelectric substrate, small in internal stress, and excellent in solderability. CONSTITUTION:The piezoelectric oscillate 10 includes the piezoelectric substrate 12. On the piezoelectric substrate 12, the thin film electrode 14 is formed. The thin film electrode 14 is formed of a 1st metallic layer 16 and a 2nd metallic layer 18. The 1st metallic layer 16 is formed of alloy of metal which comes into good contact with the piezoelectric substrate 12 and metal which is large in ductility and extensibility. The 2nd metallic layer 18 is formed of the metal which is included in the 1st metallic layer 16 and large in ductility and extensibility.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film electrode of a piezoelectric vibrator, and more particularly to a thin film electrode of a piezoelectric vibrator which is formed on a piezoelectric substrate and drives the piezoelectric vibrator by giving a signal. .

[0002]

2. Description of the Related Art FIG. 7 is a perspective view showing an example of a conventional piezoelectric vibrator using a thin film electrode. The piezoelectric vibrator 1 includes a piezoelectric substrate 2. The piezoelectric substrate 2 is made of, for example, piezoelectric ceramic. Thin film electrodes 3 are formed on both surfaces of the piezoelectric substrate 2. As the material of the thin film electrode 3, for example, a material having good solderability such as Ag, Cu or Au is used.

However, these materials are used for the piezoelectric substrate 2
A thin film electrode having a two-layer structure as shown in FIG. 8 is used because of its low adhesion strength to. The two-layer structure thin film electrode 3 includes a first metal layer 4 and a second metal layer 5. As the first metal layer 4, for example, a material such as Cr, Ni, Ti, W having a large rigidity and having a good adhesion to the piezoelectric substrate 2 is used. Further, as the second metal layer, Ag, C
A material having good solderability and high ductility and malleability, such as u or Au, is used. By using the thin film electrode 3 having such a two-layer structure, it is possible to obtain a thin film electrode which has good adhesion to the piezoelectric substrate 2 and good solderability. As shown in FIG. 9, the piezoelectric vibrator 1 is adhered to the vibrating body 7 with an adhesive 6. Then, by applying a drive signal to the thin film electrode 3, the vibrating body 7 can be vibrated.

[0004]

However, the thin-film electrode of such a two-layer structure piezoelectric vibrator has a large internal stress although it has good adhesion to the piezoelectric substrate, and the internal stress of the thin-film electrode causes piezoelectric vibration. There were inconveniences such as warping of the child. When the piezoelectric vibrator warps,
As shown in FIGS. 10 and 11, when the piezoelectric vibrator is attached to the vibrating body, the adhesion with the vibrating body becomes unstable, and the workability is poor. Moreover, as the piezoelectric vibrator becomes smaller, the piezoelectric substrate also becomes thinner, so it is considered that the warp of the piezoelectric vibrator due to the internal stress of the thin-film electrode will become even larger.

Materials having a small internal stress include Ag and C.
Materials with high ductility and malleability such as u and Au are considered. However, since these materials have low adhesion strength to the piezoelectric substrate, when these are used alone as a thin film electrode, the thin film electrode peels off in a process such as dicing.

Therefore, a main object of the present invention is to provide a thin film electrode of a piezoelectric vibrator having a large adhesion to a piezoelectric substrate, a small internal stress, and good solderability.

[0007]

The present invention relates to a thin film electrode of a piezoelectric vibrator formed on a piezoelectric substrate, which is formed of an alloy of a metal having high adhesion and a metal having high ductility and malleability. A first metal layer disposed on the piezoelectric substrate,
A thin film electrode of a piezoelectric vibrator, comprising: a second metal layer formed on a first metal layer and formed of a material having high ductility and malleability contained in the first metal layer. As the alloy used for the thin film electrode of this piezoelectric vibrator, it is desirable that the content of the metal having high adhesion is in the range of 20 to 40%. Further, the thickness of the first metal layer is preferably in the range of 10 to 30% of the total thickness of the first metal layer and the second metal layer.

[0008]

Since the alloy used for the first metal layer contains a metal having high adhesion, the adhesion between the piezoelectric substrate and the first metal layer can be increased. Further, since the alloy used for the first metal layer contains a metal having high ductility and malleability, internal stress due to the metal having high adhesion is relaxed.

Further, since the metal having a high ductility and malleability contained in the first metal layer is used as the material of the second metal layer, the adhesion between the first metal layer and the second metal layer is improved. growing. Further, by using such a metal, the solderability of the second metal layer becomes good.

[0010]

According to the present invention, the adhesion between the piezoelectric substrate and the first metal layer is large, and the first metal layer and the second metal layer are
It is possible to obtain a thin film electrode having high adhesion to the metal layer. Therefore, it is possible to prevent the thin film electrode from peeling off from the piezoelectric substrate. Moreover, since the internal stress of the first metal layer is small, it is possible to prevent the warpage of the piezoelectric vibrator when the thin film electrode is formed on the piezoelectric substrate.
Furthermore, since the solderability of the second metal layer is good,
It is easy to connect a lead wire or the like to the thin film electrode.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0012]

1 is a perspective view of a piezoelectric vibrator using a thin film electrode according to the present invention. The piezoelectric vibrator 10 includes a piezoelectric substrate 12
including. The piezoelectric substrate 12 is formed of, for example, piezoelectric ceramic in a rectangular plate shape. Thin film electrodes 14 are formed on both surfaces of the piezoelectric substrate 12. The thin film electrode 14 is shown in FIG.
As shown in, it has a two-layer structure.

The thin film electrode 14 is formed of a first metal layer 16 and a second metal layer 18. The first metal layer 16 is
It is formed of an alloy of a metal having high adhesion to the piezoelectric substrate 12 and a metal having high ductility and malleability. Examples of metals having high adhesion are Ti, Ni, Cr, W, Mo,
A metal having a large rigidity, such as Ta, Fe or Zr, is used. As the metal having a high ductility and malleability, for example, a metal such as Ag, Cu or Au is used. Also,
As the material of the second metal layer 18, a material having a large ductility and malleability similar to that used for the first metal layer 16 is used. That is, as the material of the second metal layer 18,
Metals such as Ag, Cu and Au are used. These metals are materials having good solderability. First metal layer 1
6 can be formed on the piezoelectric substrate 12 by two kinds of metal materials by a binary vapor deposition method or sputtering of an alloy target.

As shown in FIG. 3, the piezoelectric vibrator 10 is attached to, for example, a vibrating body 20 and is used to vibrate the vibrating body 20. The vibrating body 20 is made of, for example, a material that causes mechanical vibration, such as Elinba. In FIG. 3, the vibrating body 20 has a triangular prism shape, but may have another shape such as a plate shape or a prism shape. Then, by applying a drive signal to the thin film electrode 14, the piezoelectric vibrator 10 vibrates, and the vibrating body 20 also vibrates accordingly.

The internal stress and the adhesion strength with the piezoelectric substrate of the piezoelectric vibrator having a thin film electrode having a two-layer structure were measured, and the results are shown in FIGS. 4 and 5. The materials shown in Table 1 were used as the material of the thin film electrode. As shown in Table 1, in the piezoelectric vibrator of the present invention, an alloy material is used as the first metal layer, and a metal having high ductility and malleability contained in the first metal layer is used as the second metal layer. did. Moreover, in the comparative example, a single metal material was used for each of the first metal layer and the second metal layer. Then, the internal stress and the adhesion strength were compared for those using the same metal material. 4 and 5, the white circles indicate the piezoelectric vibrator using the thin film electrode of the present invention, and the black circles indicate the piezoelectric vibrator using the thin film electrode of the comparative example.

[0016]

[Table 1]

As can be seen from FIG. 4, in the piezoelectric vibrator using the thin film electrode of the present invention, the internal stress of the thin film electrode is smaller than that of the comparative example. It is considered that this is because the material of the first metal layer contains a metal having high ductility and malleability such as Ag and Cu. Further, as can be seen from FIG. 5, the adhesion with the piezoelectric substrate tends to be slightly inferior to that of the comparative example, but the first metal layer is made of Cr—C.
When the u alloy was used, the adhesion was higher than that of the comparative example.

Further, FIG. 6 shows the rate of change in internal stress and adhesion strength of the piezoelectric vibrator using the thin film electrode of the present invention with respect to the comparative example. In FIG. 6, white circles indicate the change rate of adhesion strength, and black circles indicate the change rate of internal stress. As can be seen from FIG. 6, in the piezoelectric vibrator using the thin film electrode of the present invention, the change rate of the adhesion strength was less than 10%, but the change rate of the internal stress was 20 to 30%. Thus, the present invention, compared to the comparative example, without significantly lowering the adhesion strength,
Internal stress can be reduced. When the thin film electrode of the present invention is used, the adhesion strength is slightly inferior to that of the comparative example, but the adhesion strength is higher than that of the one-layer structure thin film electrode using Ag, Cu or the like. It is considered that this is because the material of the first metal layer contains a material having high adhesiveness such as Ni, Ti, and Cr.

As described above, when the thin film electrode of the present invention is used, since the internal stress is small, it is possible to prevent the warpage of the piezoelectric vibrator. Therefore, when the piezoelectric vibrator is attached to the vibrating body or the like, the vibrating body and the piezoelectric vibrator are brought into stable contact with each other, and the workability of attaching the piezoelectric vibrator is improved. Further, since the adhesion between the vibrating body and the piezoelectric vibrator is improved, it is possible to improve vibration characteristics and reliability in a heat cycle test.

Further, since the second metal layer is made of the same metal material as that contained in the first metal layer, the adhesion between the first metal layer and the second metal layer is also good. . Therefore, it is possible to prevent the thin film electrode from peeling off from the piezoelectric substrate in a process such as dicing. Further, since the second metal layer is formed of a metal having high ductility and malleability such as Ag, Cu, Au, etc., the second metal layer has good solderability and is easy to connect a lead wire and the like.

The ratio of the metal having high adhesion contained in the first metal layer is preferably in the range of 20-40%. The thickness of the first metal layer is preferably in the range of 10 to 30% of the total thickness of the thin film electrode. First
By setting the ratio of the material of the metal layer and the ratio of the thickness to within this range, good adhesion and small internal stress can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a piezoelectric vibrator using a thin film electrode of the present invention.

2 is a partial cross-sectional view showing the vicinity of a thin film electrode of the piezoelectric vibrator shown in FIG.

3 is a perspective view showing a state in which the piezoelectric vibrator shown in FIG. 1 is attached to a vibrating body.

FIG. 4 is a graph showing the internal stress of the thin film electrode of the piezoelectric vibrator using the thin film electrode of the present invention and the piezoelectric vibrator using the thin film electrode of the comparative example.

FIG. 5 is a graph showing the adhesion strength between the piezoelectric vibrator using the thin film electrode of the present invention and the piezoelectric vibrator using the thin film electrode of the comparative example, with the piezoelectric substrate.

FIG. 6 is a graph showing the rate of change of the present invention with respect to a comparative example of internal stress and adhesion strength of the piezoelectric vibrator using the thin film electrode of the present invention and the piezoelectric vibrator using the thin film electrode of the comparative example.

FIG. 7 is a perspective view showing an example of a conventional piezoelectric vibrator using a thin film electrode.

8 is a partial cross-sectional view showing the vicinity of a thin film electrode of the conventional piezoelectric vibrator shown in FIG.

9 is an illustrative view showing a state in which the conventional piezoelectric vibrator shown in FIG. 7 is attached to a vibrating body.

FIG. 10 is an illustrative view when the conventional piezoelectric vibrator shown in FIG. 7 is attached to a vibrating body in a warped state.

FIG. 11 is another schematic view when the conventional piezoelectric vibrator shown in FIG. 7 is attached to a vibrating body in a state where the piezoelectric vibrator is warped.

[Explanation of symbols]

 10 Piezoelectric vibrator 12 Piezoelectric substrate 14 Thin film electrode 16 First metal layer 18 Second metal layer 20 Vibrating body

Claims (3)

[Claims] 1. A thin film electrode of a piezoelectric vibrator formed on a piezoelectric substrate, the thin film electrode being formed of an alloy of a metal having high adhesion and a metal having high ductility and malleability and arranged on the piezoelectric substrate. Vibration including a first metal layer formed on the first metal layer and a second metal layer formed on the first metal layer and formed of a highly ductile and malleable material contained in the first metal layer. Thin film electrode of the child. 2. The thin film electrode of the piezoelectric vibrator according to claim 1, wherein the first metal layer contains 20 to 40% of the metal having high adhesion. 3. The thickness of the first metal layer is 10 to the total thickness of the first metal layer and the second metal layer.
The thin film electrode of the piezoelectric vibrator according to claim 1 or 2, which is 30%.