JPH05299967A - Interdigital electrode for surface acoustic wave device - Google Patents

Abstract

PURPOSE:To prevent a part of ab interdigital electrode from being fused by currents generated due to the generation of a static electricity or an inside potential difference without generating the fluctuation of an amplitude character istic due to the increase of an electrostatic capacity or an unnecessary wave. CONSTITUTION:This electrode is equipped with the same potential exciting finger group 4 periodically provided, and the different potential exciting finger group 14 of a different potential disposed so as to be periodically adjacent to the exciting finger group 4. Also, the end top parts of the first adjacent fingers 4a1 and 14a1 of one driving finger group (4 or 14) adjacent to the other driving finger group (14 or 4), are electrically connected with the end top parts of the second adjacent fingers 4a2 and 14a2 adjacent to the first adjacent fingers 4a1 and 14a1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a comb-shaped electrode for a surface acoustic wave device, and more particularly, to prevent the comb-shaped electrode from being broken (broken) due to a current generated due to static electricity or an internal potential difference. And a comb-shaped electrode for a surface acoustic wave device.

[0002]

2. Description of the Related Art A surface acoustic wave device has a comb-shaped electrode 22, 23 and a comb-shaped electrode 2 on a main surface of a surface acoustic wave substrate 21, as shown in FIG.
It is formed by arranging extraction electrodes 22a, 23a, etc. connected to 2, 23. And the comb-shaped electrode 2
2, 23 are formed by disposing a plurality of finger groups such as an excitation finger group and a dummy finger group (not shown) at predetermined positions on the main surface of the surface acoustic wave substrate 21. .. However, each of the fingers forming the comb-shaped electrodes 22 and 23 is minute, and an electrostatic charge is supplied from the outside, or a potential difference is generated due to a temperature change based on pyroelectricity which is an original property of the surface acoustic wave substrate 21. If there is such a problem, there is a problem in that the current partially flows at once and the fingers are fused.

In order to solve such a problem, therefore, as shown in FIG. 3, a comb shape in which the tips of the excitation finger group 24 and the dummy finger group 25 are short-circuited by the horizontal fingers (short-circuit electrodes) 26, 27. Electrodes have been proposed. However, this comb-shaped electrode is
Although it is possible to suppress the melting of a, the provision of the horizontal fingers 26 and 27 causes an increase in capacitance and the generation of unwanted waves, resulting in a large increase in bandwidth and compatibility with conventional products. There is a problem that is damaged.

Further, in order to solve these problems, as shown in FIG. 4, the horizontal fingers 26 and 27 are respectively excited by the excitation fingers 24a and the dummy fingers 2.
There has been proposed a comb-shaped electrode arranged so as to be displaced from the front end of 5a at a position retracted. However, also in this comb-shaped electrode, if the distances from the tips of the excitation fingers 24a and the dummy fingers 25a to the horizontal fingers 26 and 27 are small, the effect of suppressing the electrostatic capacitance becomes insufficient, and the distances are also reduced. If it becomes too large, there is a problem that the effect of preventing fusing is diminished.

The present invention is intended to solve the above-mentioned problems, and a part of the comb-shaped electrode can be prevented from generating static electricity or an internal potential difference without causing an increase in electrostatic capacitance or a change in amplitude characteristic due to an unnecessary wave. It is an object of the present invention to provide a comb-shaped electrode for a surface acoustic wave device, which can prevent melting due to a current generated thereby, has excellent stability of characteristics, and has high reliability.

[0006]

In order to achieve the above object, the inventors of the present invention have, for example, a 2nd I of DBS in Japan.
128 ° Y-cut X-propagation LiNbO as a surface acoustic wave substrate with a center frequency of about 402 MHz used for F
_For a surface acoustic wave filter using _three substrates and using fingers as split fingers to reduce the TTE (finger width is about 1 μm), the fusing mechanism of the fingers was investigated and studied. As a result, of the fingers for excitation of one potential, the fingers adjacent to the group of fingers for excitation of different potentials (the fingers closest to the group of excitation fingers of different potentials (first adjacent finger)),
Moreover, the tip portion is a source of a current generated by static electricity or an internal potential difference. For example, in the case of a comb-shaped electrode as shown in FIG. all right. Therefore, by electrically connecting the first adjacent finger and the tip of the adjacent finger (second adjacent finger) with a lateral finger to form a bypass, and reducing the current flowing through the first adjacent finger, A comb-shaped electrode was completed so as to prevent the first adjacent finger from generating heat to a temperature at which it melts.

That is, the comb-shaped electrode according to the present invention is
In a comb-shaped electrode for a surface acoustic wave device comprising an excitation finger group including a plurality of fingers and a dummy finger group, the excitation finger groups of the same potential, which are periodically arranged, and the excitation finger group A first finger having an exciting finger group of different potential, which is disposed so as to be periodically adjacent to, and which is adjacent to the exciting finger group of the other potential of the exciting finger group of one potential It is characterized in that the tip end portion of the adjacent finger and the tip end portion of the second adjacent finger adjacent to the first adjacent finger are electrically connected by a lateral finger.

[0008]

[Function] In one excitation finger group, the tips of the fingers (first adjacent fingers) adjacent to the excitation finger group of different potentials and the tips (second adjacent fingers) adjacent to the first adjacent fingers are lateral. If the current is generated by static electricity or an internal potential difference, the current is not limited to the first adjacent finger,
Since it also flows through the lateral fingers to the second adjacent fingers, the current flowing through the first adjacent fingers is reduced, and it is possible to prevent heat generation up to a temperature at which fusing occurs.

Therefore, even when a current generated due to static electricity or pyroelectricity of the surface acoustic wave substrate flows,
It is possible to prevent the fingers from melting and to stably maintain the characteristics for a long period of time, thereby improving reliability.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a surface acoustic wave device (surface acoustic wave filter) in which a comb-shaped electrode according to an embodiment of the present invention is arranged.
It is a perspective view which shows typically. In this surface acoustic wave filter, a 128 ° Y-cut X-propagation LiNbO ₃ substrate is used as a surface acoustic wave substrate 1, and comb-shaped electrodes 2 and 3 are provided on its main surface.
(Details not shown) are arranged, and the comb-shaped electrodes 2,
It is formed by arranging the extraction electrodes 2a and 3a connected to 3.

In this surface acoustic wave filter, the comb-shaped electrodes 2 and 3 are, as shown in FIG. 1, a group of fingers 4 for exciting one of a plurality of fingers 4a.
And a group of fingers for excitation 14 of the other potential (different potential) composed of a plurality of fingers 14a are periodically arranged on the main surface of the surface acoustic wave substrate 1, and a group of fingers for a dummy also composed of a plurality of fingers 5a. It is formed by arranging 5 at a predetermined position.

Then, the finger 4a adjacent to the exciting finger group 14 of the different potential of the exciting finger group 4 of one potential (the first adjacent finger 4a ₁ which is closest to the exciting finger group 14 of the different potential) ) And the tip of the finger (second adjacent finger) 4a ₂ adjacent to the first adjacent finger 4a ₁ is a lateral finger (short-circuit electrode).
Shorted by 6. Further, the tip portions of the first adjacent fingers 14a ₁ and the second adjacent fingers 14a ₂ that constitute the different-potential excitation finger group 14 are similarly connected by the horizontal fingers 6. However, the lateral fingers 6 are not formed at positions other than the above.

Incidentally, this comb-shaped electrode is a DBS in Japan.
Is a surface acoustic wave filter having a center frequency of about 402 MHz for 2ndIF, and the width W _{1 of} each finger 4a, 14a, 5a is 1.2 μm, and the distance G between each finger 4a, 14a, 5a is G = 1.2 μm. W ₂ = 1.0 μm, and the distance D 2 between the excitation finger group 4 and the dummy finger group 5 is D 5 = 5.0 μm.

In the comb-shaped electrode of this embodiment configured as described above, when a current is generated due to static electricity or an internal potential difference, the current flows to the first adjacent fingers 4a ₁ and 14a _1.
Not only the current flows through the lateral fingers 6 but also through the second adjacent fingers 4a ₂ and 14a ₂ , so that the current flowing through the first adjacent fingers 4a ₁ and 14a ₁ can be reduced.
Therefore, it is possible to prevent the first adjacent fingers 4a ₁ and 14a ₁ from generating heat up to the temperature at which the first adjacent fingers 4a ₁ and 14a ₁ are melted by the current generated by the static electricity or the internal potential difference.
It is possible to reliably prevent disconnection of a ₁ and 14a ₁ .

Further, the horizontal fingers (short-circuit electrodes) 6 serve to connect the tip portions of the first adjacent fingers 4a ₁ and 14a _{1 and} the tip portions of the second adjacent fingers 4a ₂ and 14a ₂ as described above. Since it is formed only and not formed elsewhere, it is possible to effectively prevent variation in characteristics by suppressing increase in capacitance and generation of unnecessary waves.

As described above, in the comb-shaped electrode of the present invention, in order to suppress the increase of the electrostatic capacity and the generation of the unwanted wave as much as possible, the first adjacent fingers 4a ₁ and 14a ₁ and the second adjacent fingers 4a ₂ It is important not to form a horizontal finger other than the horizontal finger 6 connecting the tip of 14a ₂ .

Although the surface acoustic wave filter has been described in the above embodiment, the comb electrode of the present invention is not limited to the surface acoustic wave filter but can be applied to various surface acoustic wave device comb electrodes. is there.

Further, in the comb-shaped electrode for the surface acoustic wave device of the present invention, the specific shape, dimensions, or disposition position of the excitation finger group, the dummy finger group, the fingers constituting them, or the horizontal fingers. The above is not limited to the above embodiments, and various applications can be added within the scope of the present invention.

[0019]

As described above, the comb-shaped electrode for the surface acoustic wave device of the present invention is the first electrode adjacent to the excitation finger group of one potential and the excitation finger group of the other potential.
Since the tip portions of the adjacent fingers and the tip portions of the second adjacent fingers adjacent to the first adjacent fingers are electrically connected by the horizontal fingers to short-circuit, the fingers due to electrostatic breakdown or the like in the manufacturing process are It is possible to more reliably prevent disconnection and improve the yield of products, and to prevent a large increase in electrostatic capacitance due to the opposing horizontal fingers, and to ensure compatibility with conventional products.

Further, it is possible to prevent finger defects (breakage) that occur when an electric current is generated due to static electricity or the pyroelectric property of the surface acoustic wave substrate, and to maintain the characteristics stably for a long period of time. It is possible to improve reliability.

[Brief description of drawings]

FIG. 1 is a plan view showing a comb-shaped electrode for a surface acoustic wave device according to an embodiment of the present invention.

FIG. 2 is a perspective view schematically showing a surface acoustic wave filter having comb-shaped electrodes according to an embodiment of the present invention.

FIG. 3 is a plan view showing a conventional comb-shaped electrode for a surface acoustic wave device.

FIG. 4 is a plan view showing another conventional comb-shaped electrode for a surface acoustic wave device.

[Explanation of symbols]

1 SAW substrate 2 interdigital electrodes 4 and 14 excitation finger group 4a, finger 4a ₁ constituting the 14a excitation finger group, 14a ₁ first adjacent finger 4a _2, 14a ₂ second adjacent fingers 5 dummy finger Group 5a fingers 6 lateral fingers forming a dummy finger group

Claims (1)

[Claims] 1. A comb-shaped electrode for a surface acoustic wave device, comprising an exciting finger group including a plurality of fingers and a dummy finger group, wherein the exciting finger groups having the same potential are periodically arranged. A group of exciting fingers having different potentials, which are arranged so as to periodically adjoin the group of exciting fingers, and a group of exciting fingers of one potential, and a group of exciting fingers of the other potential. A comb-shaped electrode for a surface acoustic wave device, characterized in that a tip portion of a first adjacent finger adjacent to and a tip portion of a second adjacent finger adjacent to the first adjacent finger are electrically connected by a lateral finger.