JPH1127090A - Surface wave resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface wave resonator which can be miniaturized and also can prevent the generated surface waves from being scattered and absorbed by forming a vibration part consisting of two interdigital parts opposite to each other on one of main face sides of a piezoelectric substrate with a pair of terminal parts continuous to the interdigital parts on the other main face side respectively and accordingly using an almost entire surface of one of both main face sides of the substrate as a vibration part. SOLUTION: A pair of electrodes 2 consisting of interdigital parts 21 and terminal parts 22 are formed on the surface of a piezoelectric substrate 1. Only the parts 21 opposite to each other are formed on one (side 1a) of both main face sides of the substrate 1, and both parts 21 are continuous up to the other main face side (rear side) 1b via the side faces of the substrate 1. A part of each part 21 continuous up to the side la and a pair of parts 22 bundling the parts 21 are formed on the side 1b. When a high frequency signal 4 is applied between a pair of parts 22 on the side 1b, the surface waves are generated at the parts 21 on the side 1a. Thus, the function of a surface wave resonator is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface acoustic wave resonator that generates a surface acoustic wave by applying a high-frequency signal to a piezoelectric substrate.

[0002]

2. Description of the Related Art A schematic structure of a conventional surface acoustic wave resonator is as shown in FIG. This surface acoustic wave resonator includes a pair of opposing comb-shaped electrodes 2 and 2 on one main surface of a piezoelectric substrate 1 made of a piezoelectric material such as quartz or LiNbO ₃ .

The electrode 2 is composed of opposing comb teeth 21 and a terminal 22 for bundling them, and the vicinator 3 is located near the comb teeth 21. When the high-frequency signal 4 is applied to the terminal portion 22, distortions of opposite phases are generated between the adjacent comb-tooth portions 21 due to the piezoelectric effect, and surface waves are excited in the vibrating portion 3 to serve as a surface wave resonator (resonator). Can work.

Although not shown, two pairs of electrodes 2 and 2 are formed on the piezoelectric substrate 1 and one of the electrodes 2 and 2 is formed.
An input terminal can be formed on the second electrode 2 and an output terminal can be formed on the other electrodes 2 and 2 to provide a surface acoustic wave filter.

When such a surface acoustic wave resonator is enclosed in a package, as shown in FIG. 7, an electrode 2 is provided on a base 11 having a lead electrode 13 and a lead terminal 14.
A piezoelectric substrate 1 provided with
After connecting between the lead electrode 13 and the lead electrode 13 by wire bonding 16, the lead electrode 13 is covered with a cap 12 and sealed.

[0006]

However, in the surface acoustic wave resonator shown in FIG. 6, since all the electrodes 2 are formed on one main surface of the piezoelectric substrate 1, only a part of the piezoelectric substrate 1 vibrates. Could not be used.

Therefore, a piezoelectric substrate 1 larger than the size of the vibrating section 3 is required, and it has been difficult to reduce the size. Also,
Since the surface wave generated in the vibrating section 3 is diffused and absorbed by the surrounding portion, there is a problem that the generation efficiency of the surface wave is low. In addition, when a protective film is formed to increase the durability of the vibrating portion 3, it is difficult to form the protective film so as to cover only the vibrating portion 3 without covering the terminal portion 22.

Further, when the surface acoustic wave resonator is sealed in a package, it is necessary to perform wire bonding as shown in FIG. 7, and there is a problem that the manufacturing process becomes complicated.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a surface acoustic wave resonator having a pair of electrodes, each having a comb-teeth portion and a terminal portion, opposed to each other on the surface of a piezoelectric substrate. A vibrating portion comprising a comb tooth portion facing each other, and a pair of terminal portions continuous with the comb tooth portion are formed on the other main surface.

That is, by using both sides of the piezoelectric substrate and making one main surface a vibrating portion comprising a comb tooth portion, almost the entire main surface can be used as a vibrating portion. It is possible to prevent the generated surface wave from being diffused and absorbed in the surrounding area.

Further, by forming a pair of terminals on the other main surface (back surface) of the piezoelectric substrate, it is not necessary to perform wire bonding when enclosing the piezoelectric substrate in a package. And so on.

According to the present invention, in the above-mentioned surface acoustic wave resonator, an insulating protective film is formed on the main surface on which the vibrating portion is formed.

That is, since the terminal portion is formed on the back surface, the entire main surface on which the vibrating portion is formed can be covered with the protective film, and the protective film can be easily formed.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

The surface acoustic wave resonator shown in FIG. 1 has a structure in which a pair of electrodes 2 each having a comb portion 21 and a terminal portion 22 are formed on the surface of a piezoelectric substrate 1.

As shown in FIG. 1A, only opposing comb teeth 21, 21 are formed on one main surface 1a of the piezoelectric substrate 1, and each comb tooth 21, 21 has a side surface. Via the other main surface (back surface) 1b. Also,
As shown in FIG. 1B, the other main surface (back surface) 1b is formed by bundling a part of the comb teeth 21 continuous with the main surface 1a and the comb teeth 21 on the main surface 1b. A pair of terminal portions 22, 22 are formed.

If a high-frequency signal 4 is applied between the pair of terminal portions 22 provided on the main surface 1b, a surface wave can be generated at the comb teeth 21 on the main surface 1a. , Can act as a surface wave resonator.

At this time, since the entire surface of the main surface 1a of the piezoelectric substrate 1 can be the vibrating portion 3, the dimensions of the piezoelectric substrate 1 can be effectively used, and the size of the surface acoustic wave resonator can be reduced. it can. Further, since the generated surface wave is not diffused and absorbed in the surrounding portion, the surface wave generation efficiency can be increased.

Next, another embodiment of the surface acoustic wave resonator of the present invention is shown in FIG.
A part of the comb tooth part 21 and the terminal part 22 may be formed in a, and only the terminal part 22 may be formed on the other main surface 1b.

Further, as shown in FIG. 3A, a through hole 23 is formed in the substrate 1 and a comb tooth portion 21 formed on the main surface 1a and a through hole 23 formed on the main surface 1b side. The terminal portions 22 may be connected by a conductive material filled in the through holes 23.

Further, as shown in another embodiment in FIG. 3B, an insulating protective film 5 is formed on the main surface 1a on the vibrating portion 3 side to improve the durability of the comb teeth portion 21 of the electrode 2. It can also be done. That is, in the surface acoustic wave resonator of the present invention, the vibrating section 3
Since the protective film 5 described above may be formed on the entire main surface 1a of the piezoelectric substrate 1, it can be easily formed.

The above-described surface acoustic wave resonator of the present invention comprises:
Since a surface acoustic wave can be generated by applying the high-frequency signal 4, it can be used for a piezoelectric actuator using a surface wave, an oscillator, a filter, a duplexer, and the like.

In addition, as shown in FIG. 4, two pairs of electrodes 2 and 2 formed on the piezoelectric substrate 1 are provided, and one of the electrodes 2 and 2 has an input terminal, and the other has a pair of electrodes 2 and 2. Can be used as a surface acoustic wave filter by connecting the output terminals to the filter.

When the above-described surface acoustic wave resonator is encapsulated in a package, as shown in FIG.
After mounting the piezoelectric substrate 1 provided with the above and connecting the terminal portion 22 and the lead electrode 13 formed on the one main surface 1b of the piezoelectric substrate 1 with the solder 15, it may be covered with the cap 12 and sealed. .

As described above, in the surface acoustic wave resonator according to the present invention, since the terminal portion 22 exists on the main surface (back surface) 1b opposite to the vibrating portion 3, the terminal portion 22 is easily formed by solder reflow or the like as in normal surface mounting. Since the connection can be made by the solder 15, there is no need for wire bonding or the like, and the manufacturing process can be simplified.

The piezoelectric substrate 1 is made of quartz, LiTaO ₃ ,
LiNbO ₃ , Bi ₁₂ GeO ₂₀ , Li ₂ B ₄ O ₇ , PZ
It is made of a piezoelectric material such as T, ZnO, AlN, etc.
Each of them is manufactured by a known method, cut into a product size, and then subjected to vapor deposition or sputter processing.

The electrode 2 is made of chromium, aluminum,
It is made of gold or the like and is formed on the piezoelectric substrate 1 by a thin film method such as vapor deposition. At this time, a predetermined-shaped mask is provided on each of the main surfaces 1a, 1b and side surfaces of the piezoelectric substrate 1, and the electrodes 2 having a predetermined shape can be formed by vapor deposition.

When the protective film 5 shown in FIG. 3 is formed, the material of the protective film 5 is a dielectric film such as alumina or an organic film such as a fluororesin, and is formed by sputtering or spraying. It is preferable that the thickness is 1 μm or less and as thin as possible.

[0029]

EXAMPLE A LiNbO ₃ was used as the piezoelectric substrate 1, chromium (Cr) was used as the electrode 2, and alumina was formed to a thickness of 5000 mm as the protective film 5 to produce the surface acoustic wave resonator according to the embodiment of the present invention shown in FIG. did. In addition, a surface acoustic wave resonator of a comparative example shown in FIG. 6 was manufactured using the same material.

In all of the comparative examples, the dimensions of the piezoelectric substrate 1 were 3 × 2.
In contrast, the size of the piezoelectric substrate 1 was 3 × 1 × 0.2 mm in the example of the present invention, which was × 0.5 mm.

Further, when the Q value was compared as the generation efficiency of the surface wave, it was confirmed that the example of the present invention was 2.5 times as large as that of the comparative example, and the generation efficiency was high.

Therefore, it can be seen that the surface acoustic wave resonator of the present invention can be downsized and the efficiency of generating surface acoustic waves can be improved.

[0033]

As described above, according to the present invention, in a surface acoustic wave resonator having a pair of electrodes each having a comb-teeth portion and a terminal portion opposed to each other on the surface of a piezoelectric substrate, one side of the piezoelectric substrate is provided. By forming a vibrating portion composed of comb teeth opposing each other on the main surface and forming a pair of terminal portions continuous with the comb tooth on the other main surface, almost the entire surface of one main surface vibrates. Since it can be used as a part, it is possible to reduce the size and prevent the generated surface wave from being diffused and absorbed in the surrounding part.

Further, by forming a pair of terminals on the other main surface (back surface) of the piezoelectric substrate, when encapsulating in a package, wire bonding is not required, and solder reflow is performed in the same manner as in normal surface mounting. And so on.

Further, according to the present invention, in the surface acoustic wave resonator described above, by forming an insulating protective film on the main surface on which the vibrating portion is formed, the entire surface of the main surface on which the vibrating portion is formed can be covered with the protective film. Thus, a protective film can be easily formed.

Therefore, according to the present invention, it is possible to easily manufacture a small surface acoustic wave resonator having high surface acoustic wave generation efficiency.

[Brief description of the drawings]

FIGS. 1A and 1B are perspective views showing a surface acoustic wave resonator of the present invention.

FIGS. 2A and 2B are perspective views showing another embodiment of the surface acoustic wave resonator of the present invention.

FIGS. 3A and 3B are cross-sectional views showing another embodiment of the surface acoustic wave resonator of the present invention.

FIG. 4 is a perspective view showing an embodiment in which the surface acoustic wave resonator of the present invention is applied to a filter.

FIG. 5 is a cross-sectional view showing a structure for housing the surface acoustic wave resonator of the present invention in a package.

FIG. 6 is a perspective view showing a conventional surface acoustic wave resonator.

FIG. 7 is a cross-sectional view showing a structure for accommodating a conventional surface acoustic wave resonator in a package.

[Explanation of symbols]

 1: Piezoelectric substrate 2: Electrode 21: Comb 22: Terminal 3: Vibration 4: High frequency signal 5: Protective film

Claims (1)

[Claims] 1. A surface acoustic wave resonator comprising a pair of electrodes each comprising a comb-shaped portion and a terminal portion provided on a surface of a piezoelectric substrate so as to face each other. A surface acoustic wave resonator comprising: a vibrating portion formed of a pair of terminals; and a pair of terminals connected to the comb tooth portion formed on the other main surface.