JPH06224682A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To provide the surface acoustic wave device where the electrostatic breakdown is prevented to preclude the loss of a surface wave exciting part by providing a sacrificial electrode for electrostatic breakdown in at least one of input and output electrodes. CONSTITUTION:An input electrode 7 and an output electrode 8 are provided on the upper face of a piezoelectric substrate 6 made of a lithium tantalate, and two surface wave exciting parts 9 and 10 are provided in parallel between the input electrode 7 and the output electrode 8. Surface wave exciting parts 9 and 10 consist of exciting parts 9a and 10a, where comb-shaped electrodes face each other, and grating reflectors 9b and 10b provided on both sides of these exciting parts. Input and output electrodes 7 and 8 are provided with electrodes 7a and 8a for sacrifice to electrostatic breakdown where comb-shaped electrodes face each other. When static electricity is applied to input and output electrodes 7 and 8, electrostatic breakdown is first brought about in parts of the sacrificial electrodes 7a and 8a for electrostatic breakdown where electrode fingers and their intervals are narrow, and these parts are lost, and as the result, electrostatic breakdown of exciting parts 9a and 10a does not occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device used for filters, oscillators and the like.

[0002]

2. Description of the Related Art FIG. 3 shows a filter used as a filter, and 1 is a piezoelectric substrate. An input electrode 2 and an output electrode 3 are provided on the upper surface of the piezoelectric substrate 1.
, Two surface wave excitation units 4 and 5 are provided between the input and output electrodes 2 and 3. These surface wave excitation units 4 and 5 are composed of excitation units 4a and 5a and reflectors 4b and 5b provided on both sides thereof, respectively. That is, the surface waves generated in the exciting portions 4a and 5a are reflected by the reflectors 4b and 5b on both sides of the exciting portions 4a and 5a to cause resonance, and the resonance characteristic is used to obtain the filter characteristic.

That is, of the signals input to the input electrode 2, only the signals selected by the filter characteristics of the surface wave excitation units 4 and 5 are taken out from the output electrode 3 as an output.

[0004]

However, the exciting portions 4a and 5a cause the excitation of the surface wave, and the distance between the electrode fingers is extremely small, about 1 μm.
If, for example, static electricity is applied to at least one of the input and output electrodes 2 and 3 at the time of manufacturing, electrostatic breakdown may occur in the excitation parts 4a and 5a, and the electrodes may disappear. Then, this invention aims at preventing this electrostatic breakdown.

[0005]

To achieve this object, the present invention provides an electrostatic discharge sacrifice electrode on at least one of the input and output electrodes.

[0006]

With the above construction, even when static electricity is applied to the input and output electrodes, the electrostatic breakdown occurs first at the electrostatic breakdown sacrifice electrode, so that the excitation portion does not disappear. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 6 is a piezoelectric substrate made of lithium tantalate and having a thickness of 0.5 mm and a length of 2 mm and a width of 4 mm. An input electrode 7 and an output electrode 8 are provided on the upper surface of the piezoelectric substrate 6. Two surface wave excitation units 9 and 10 are provided in parallel between the input electrode 7 and the output electrode 8. These surface wave excitation portions 9 and 10 are respectively formed by excitation portions 9a and 10a formed by facing comb-shaped electrodes and grating reflectors 9b and 10b provided on both sides thereof.
Further, the input / output electrodes 7 and 8 are provided with electrostatic breakdown sacrificial electrodes 7a and 8a formed by facing comb-shaped electrodes.

In the above structure, the electrode fingers of the comb-shaped electrodes of the excitation parts 9a and 10a have a width of 1 μm and the intervals are also 1 μm, while the electrodes 7a and 8a for sacrificing electrostatic discharge are the electrode fingers of the comb-shaped electrodes. Is 0.5 μm and the spacing is 0.5 μm. Therefore, when static electricity is applied to the input and output electrodes 7 and 8, first, electrostatic breakdown occurs in the electrodes 7a and 8a for electrostatic breakdown sacrifice with a narrow electrode finger width and a narrow interval, and the portions disappear, As a result, electrostatic breakdown of the excitation parts 9a and 10a does not occur. In this embodiment, the electrodes 7a and 8a for sacrificing electrostatic discharge are the grating reflectors 9b and 10b.
Since it is provided in a direction orthogonal to, the vibration generated in this portion does not hinder the vibration generated in the excitation parts 9a and 10a. FIG. 2 shows another embodiment of the present invention. In this embodiment, the electrodes 7a and 8a for sacrificing electrostatic discharge are constructed by facing electrodes having sharp points. That is, if the pointed electrodes are made to face each other in close proximity to each other, electrostatic breakdown occurs more smoothly, and the effect as the electrode for sacrificing electrostatic breakdown is enhanced.

[0009]

As described above, according to the present invention, the electrostatic destruction sacrificial electrode is provided on at least one of the input and output electrodes.
Even when static electricity is applied to the input and output electrodes, the electrostatic breakdown first occurs at the electrode for sacrificing electrostatic breakdown, thus providing an excellent surface acoustic wave device in which the excitation part of the surface wave does not disappear. Is something that can be done.

[Brief description of drawings]

FIG. 1 is a plan view of a surface acoustic wave device according to an embodiment of the present invention.

FIG. 2 is a plan view of a surface acoustic wave device according to another embodiment of the present invention.

FIG. 3 is a plan view of a conventional surface acoustic wave device.

[Explanation of symbols]

 6 Piezoelectric Substrate 7 Input Electrodes 7a and 8a Electrodes for Electrostatic Damage 8 Output Electrodes 9 Surface Wave Excitation Section 10 Surface Wave Excitation Section

Claims (2)

[Claims] 1. A piezoelectric substrate, an input / output electrode provided on the surface of the piezoelectric substrate, and a surface wave excitation portion provided between the input / output electrodes of the surface of the piezoelectric substrate. A surface acoustic wave device in which an electrode for sacrificing electrostatic discharge is provided on at least a part of the surface. 2. The surface acoustic wave device according to claim 1, wherein the electrode for sacrificing electrostatic discharge is formed by facing two electrodes having sharp points.