JPH0548381A - Surface acoustic wave circuit - Google Patents

Abstract

PURPOSE:To prevent interference with a surface acoustic fundamental wave and to attain tight fixing by using an adhesives so as to adhere a metallic plate thereby fixing a piezoelectric substrate to a base substrate and absorbing the surface acoustic wave. CONSTITUTION:A part of a metallic plate 5 corresponding to input output side interdigital electrodes 1a, 1b provided on a piezoelectric substrate 2 is cut off and the plate 5 covers only the edges of the substrate 2. An adhesive sheet 4 is applied to coat a lower face of the metallic plate 5 and fixed to a base substrate 3 so as to keep the substrate 2 between them. An input radio wave is given to the electrode 1a, from which a surface acoustic wave is generated and propagates on the substrate 2 in two directions toward the electrode 1b and the substrate 2. The surface acoustic wave propagating in the direction of the end is absorbed by the sheet 4 to prevent interference with the fundamental wave. Furthermore, since the substrate 2 is fitted to the substrate 3 via the metallic plate 5, the substrate 2 is fitted strongly thereto. Moreover, since the adhesive sheet 4 is coated to the metallic plate 5 and adhered to the substrate 3 so as to keep the substrate 2 with the metallic plate 5 and the substrate 3 inbetween, the fitting man-hour is reduced, the job time is decreased and the reliability is improved.

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 circuit utilizing surface acoustic waves generated on the surface of a substrate.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional surface acoustic wave circuit disclosed in, for example, Japanese Utility Model Laid-Open No. 57-45690.
In FIG. 4, reference numerals 1a and 1b are input side comb-teeth electrodes, output side comb-teeth electrodes 3 provided on both sides of the surface of the piezoelectric substrate 2, 3 is a base substrate, and 4 is an adhesive for fixing the piezoelectric substrate 2 to the substrate 3. It is a sheet.

Next, the operation will be described. A surface acoustic wave is generated by the comb electrode 1a on the input side in accordance with the input radio wave. This surface acoustic wave propagates on the piezoelectric substrate in the two directions of the output side comb-teeth electrode 1b and the end of the piezoelectric substrate 2, and the surface wave propagating in the direction of the end is reflected at the end. Propagate in the direction of.
Then, it interferes with the fundamental wave and causes ripples in the pass band. Therefore, it is necessary to prevent reflection at the end of the piezoelectric substrate and absorb the surface wave at the end. Therefore, the piezoelectric substrate 2 is fixed to the substrate 3 by using the adhesive sheet 4 in which the portions corresponding to the comb-shaped electrodes 1a and 1b on the input / output side are cut out so that only the ends of the piezoelectric substrate 2 can be covered. With this configuration, it is possible to absorb the surface wave at the end portion of the piezoelectric substrate by simply attaching the adhesive sheet 4 and prevent interference with the fundamental wave, and at the same time, attach the piezoelectric substrate 2 to the substrate 3. Therefore, it is possible to reduce the man-hours and the working time.

[0004]

Since the conventional surface acoustic wave circuit is constructed as described above, the adhesive sheet 4 for fixing the piezoelectric substrate 2 to the substrate 3 has a contact corner portion A between the two and 3.
There is a problem that the piezoelectric substrate 2 cannot be firmly fixed because the piezoelectric substrate 2 is lifted from the substrate 3 because it may be broken due to an increase in tensile strength.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a surface acoustic wave circuit capable of firmly fixing substrates to each other and absorbing unnecessary surface acoustic waves.

[0006]

According to the surface acoustic wave circuit of the present invention, a peripheral portion of the piezoelectric substrate is cut out by cutting out a portion corresponding to the comb-teeth electrode on the input / output side provided on the piezoelectric substrate. It is provided with a metal plate capable of covering only the portion, and a substrate for fixing the metal plate and the piezoelectric substrate with an adhesive material applied to the lower surface of the metal plate.

In the surface acoustic wave circuit according to the second aspect of the present invention, a portion corresponding to the comb-teeth electrode on the input / output side provided on the piezoelectric substrate can be cut out to cover only the peripheral portion of the piezoelectric substrate. And a metal plate integrally formed with a shield plate located between the input and output, and a substrate for fixing the metal plate and the piezoelectric substrate with an adhesive applied to the lower surface of the metal plate. is there.

[0008]

In the piezoelectric substrate according to the present invention, since the piezoelectric substrate is bonded and fixed to the base substrate through the metal plate that covers only the end portion of the piezoelectric substrate, the piezoelectric substrate can be firmly fixed and unnecessary surface acoustic waves. To prevent reflection.

The metal plate according to the second aspect of the present invention can reduce the coupling of radio waves between the input and the output by integrally including the metal plate located between the comb-teeth electrodes on the input and output sides.

[0010]

EXAMPLES Example 1. Hereinafter, a first embodiment of the present invention will be described with reference to FIG.
Will be described. In FIG. 1 in which the same portions as those in FIG. 4 are denoted by the same reference numerals and duplicate description is omitted, reference numeral 5 is a piezoelectric substrate 2 cut out at a portion corresponding to an input / output side comb-teeth electrode. It is a metal plate capable of covering only the end portion of the. The lower surface of the metal plate 5 is coated with the adhesive sheet 4, and the piezoelectric substrate 2 is fixed to the substrate 3 so as to be held.

Next, the operation of the above embodiment will be described.
A surface acoustic wave is generated by the comb electrode 1a on the input side in accordance with the input radio wave. This surface acoustic wave propagates on the piezoelectric substrate in two directions of the output side comb-teeth electrode 1b and the end portion of the piezoelectric substrate 2, and the surface acoustic wave propagated in the end portion is absorbed by the adhesive sheet 4. . Therefore, the interference with the fundamental wave can be prevented, and the piezoelectric substrate 2 is attached to the substrate 3 via the metal plate 5, so that the attachment is strong. In addition, since the adhesive sheet 4 is applied to the lower surface of the metal plate 5 and the metal plate 5 is adhesively fixed to the substrate 3 so as to hold the piezoelectric substrate 2, the number of attachment steps and the working time are reduced. And reliability is improved.

Example 2. 2 and 3 show Embodiment 2 of the present invention. FIG. 2 is a plan view and FIG. 3 is a sectional view.
The metal plate 5 in this embodiment is integrally formed with a shield plate 6 located between the comb-teeth electrodes on the input and output sides, and the shield plate 6 couples the comb-teeth electrodes with the input side and the output side by radio waves. Can be reduced. However, since a sound wave propagates on the surface of the piezoelectric substrate 2 between the input and the output, the metal plate 6 has to be slightly separated from the piezoelectric substrate 2. However, it floats by the thickness of the sheet 4. As a result, the characteristics are improved and the influence of unnecessary waves such as spurious can be suppressed.

[0013]

As described above, according to the first aspect of the present invention, since the piezoelectric substrate is fixed to the base substrate by the metal plate with the adhesive sheet, the surface acoustic wave can be absorbed. Therefore, interference with the elastic fundamental wave is prevented, and since the piezoelectric substrate is attached to the substrate by the metal plate, the piezoelectric substrate becomes strong, and the number of attachment steps is reduced, the working time is shortened, and the reliability is improved.

Further, according to the second aspect of the invention, since the shield plate is positioned between the input and the output of the comb-teeth electrode, it is possible to reduce the radio wave coupling between the input and the output, so that spurious is not necessary. You can suppress the effects of waves.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a surface acoustic wave circuit according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a surface acoustic wave circuit according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a surface acoustic wave circuit according to an embodiment of the present invention.

FIG. 4 is a configuration diagram showing a conventional surface acoustic wave circuit.

[Explanation of symbols]

 1a Input-side comb-tooth electrode 1b Output-side comb-tooth electrode 2 Piezoelectric substrate 3 Substrate 4 Adhesive sheet 5 Metal plate 6 Shield plate

Claims (2)

[Claims] 1. A piezoelectric substrate serving as a surface acoustic wave propagation medium, and an input-side comb tooth electrode and an output-side comb provided on the piezoelectric substrate so as to convert an electric signal into a surface acoustic wave or vice versa. A metal plate in which a tooth electrode and a portion corresponding to the comb-shaped electrode on the input / output side are cut out so that only the peripheral edge of the piezoelectric substrate can be covered, and the metal plate is formed by an adhesive applied to the lower surface of the metal plate. A surface acoustic wave circuit comprising: a substrate for fixing the piezoelectric substrate. 2. A piezoelectric substrate serving as a propagation medium of a surface acoustic wave, and an input side comb tooth electrode and an output side comb provided on the piezoelectric substrate so as to convert an electric signal into a surface acoustic wave or vice versa. A metal plate integrally formed with a shield plate located between the input and output by cutting out a portion corresponding to the tooth electrode and the comb-teeth electrode on the input / output side so that only the peripheral portion of the piezoelectric substrate can be covered. A surface acoustic wave circuit comprising a metal plate and a substrate for fixing the piezoelectric substrate with an adhesive applied to the lower surface of the metal plate.