JP3139130B2 - Surface acoustic wave device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a surface acoustic wave (Surface
Acoustic Wave (hereinafter, referred to as SAW) element
In particular, the present invention relates to a structure of a SAW element in which a plurality of resonators are arranged on a piezoelectric substrate.

[0002]

2. Description of the Related Art SAW is a wave that propagates with energy of 90% or more concentrated at a depth within one wavelength from the surface of a propagation medium (piezoelectric substrate). In recent years, SAW devices utilizing the same have been used for various purposes. This kind of SAW element is usually provided on a piezoelectric substrate by using an interdigital electrode (Inter Digita).
l Transducer). In this resonator, each electrode vibrates the piezoelectric substrate at the time of power supply and forms a SAW filter by itself. A filter can be formed. In some cases, a plurality of resonators are used as SAW delay elements or the like.

FIG. 2 is a front view of a main part of a SAW element according to a conventional example of the present invention. Five resonators 21 are juxtaposed on a piezoelectric substrate 20, and adjacent resonators 21 are electrically conductive members 22.
Are electrically connected. As a result, a five-stage coupled SAW filter is formed.

[0004]

In the conventional resonator type SAW filter having the structure shown in FIG. 2, a plurality of (five in FIG. 2) resonators 21 are arranged on one piezoelectric substrate 20. Therefore, there is a problem that the required area of the piezoelectric substrate 20 becomes large.

In a portion where the resonators 21 are electrically connected to each other, the characteristics of the filter, especially the frequency characteristics, are degraded when vibration coupling is involved. Must be secured. Therefore, the area of the piezoelectric substrate 20 cannot be reduced, and there has been a problem that the size of a device using the piezoelectric substrate 20 cannot be reduced.
SAW elements of other types and uses have similar problems, and improvements have been desired.

The present invention has been made in view of such a problem, and has an S-shaped structure having a structure for preventing vibration coupling between resonators at a short distance.
It is intended to provide an AW element.

[0007]

In order to achieve the above object, according to the present invention, a plurality of resonators are arranged side by side on a piezoelectric substrate and an adjacent resonator is electrically connected to each other.
In the case of a W element, in which vibration coupling occurs between adjacent resonators at the time of power supply, a plurality of recesses are formed in parallel on the piezoelectric substrate at predetermined intervals, and the resonators are provided on the bottom surfaces of the recesses. And a conductive member electrically connecting each resonator is disposed along the vibration shielding wall.

[0008]

The position of the conductive member along the vibration shielding wall is higher than the surface of the resonator, and the effect of vibration generated during power supply does not affect the electrical connection portion. Further, since the vibration generated by each resonator is shielded by the vibration shielding wall, mutual interference with other resonators does not occur. Therefore, there is no problem even if the distance between the resonators is reduced.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A shows an SA according to an embodiment of the present invention.
It is a principal part structure front view of W filter, (b) is A-
It is A sectional drawing. Referring to FIG. 1, the SAW of this embodiment
In the filter, five concave portions 1 are formed on a piezoelectric substrate 10 and partitioned by vibration shielding walls 2. Resonators 11 are provided on the bottom surfaces of these concave portions 1. These resonators 1
Numeral 1 is similar to the conventional resonator 22 shown in FIG. 2, and each is composed of a combination of interdigital electrodes. The resonators 11 are electrically connected to each other by a conductive member 12 disposed along the vibration shielding wall 2, and a five-stage coupled SAW filter is formed as in the related art.

In the SAW filter having such a structure, vibrations due to the propagation of the SAW occur in the resonators 11 at the time of power supply, but the resonators 11 are shielded by the vibration shielding wall 2.
They do not interfere with each other. In addition, since the height of the electrical connection part and the height of the vibration generation part are different, mutual influence of both is eliminated. Therefore, not only does the filter characteristic not deteriorate due to vibration coupling of the electrical connection portion, but also improves.

Further, since it is not necessary to consider the influence of vibration coupling, there is no problem even if the distance between the resonators 11 is reduced. Therefore, if the number of the resonators 11 is the same, the area of the piezoelectric substrate 10 can be made much smaller than that of the conventional structure, and the size of a device using the same can be reduced.

The SAW filter of this embodiment is manufactured by the following steps.

First, the portions where the respective resonators 11 are provided on the surface of the piezoelectric substrate 10 are dug by etching to form the concave portions 1.
To form As a result, convex portions are formed between the concave portions.
This convex portion serves as a vibration shielding wall 2. Next, interdigital electrodes (resonators 11) are formed on the bottom surface of each concave portion 1 by using, for example, a well-known lift-off method, and thereafter, a conductive member 12 is arranged along the vibration shielding wall 2, and a space between the resonators 11 is formed. Make electrical connections. At this time, it is preferable that the electrode surface of the resonator 11 be lower than the top of the vibration shielding wall 2.

In this embodiment, a five-stage coupled resonator type S
Although an example of the AW filter has been described, the number of resonators is not limited to this embodiment. Also, the present embodiment
The present invention can be applied to other SAW elements affected by vibration coupling.

[0016]

As described above, according to the present invention, a plurality of recesses which are shielded by a vibration shielding wall are formed in a piezoelectric substrate, resonators are provided on the bottom surfaces of the respective recesses, and the portions where the respective resonators are disposed are provided. Since the SAW element has a structure in which the generated vibration is shielded by the vibration shielding wall, not only does the frequency characteristic not deteriorate as in the conventional structure, but also has the effect of improving it.

Further, since the characteristics are not affected even if the distance between the individual resonators is shortened, the area of the piezoelectric substrate can be reduced. Therefore, the size of the device on which the SAW element is mounted can be reduced.

[Brief description of the drawings]

FIG. 1A shows a resonator SA according to an embodiment of the present invention.
It is a principal part structure front view of W filter, (b) is A-
It is A sectional drawing.

FIG. 2 is a front view of a main part structure of a conventional resonator type SAW filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Depressed part formed in the piezoelectric substrate 2 ... Vibration shielding wall (convex part formed in the piezoelectric substrate) 10, 20 ... Piezoelectric substrate 11, 21 ... Resonator 12, 22 ... Conductive member

Claims (1)

(57) [Claims] 1. A surface acoustic wave device comprising a plurality of resonators arranged side by side on a piezoelectric substrate and electrically connecting adjacent resonators. In the case where coupling occurs, a plurality of recesses are formed in parallel on the piezoelectric substrate at predetermined intervals to provide the resonator on the bottom surface of each recess, and the protrusion adjacent to each recess serves as a vibration shielding wall; A surface acoustic wave device, wherein a conductive member for electrically connecting the elements is disposed along the vibration shielding wall.