JPH0537288A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To absorb the mechanical distortion due to the variance of temperature and the mechanical shock and vibration of an external body by providing an elastic sheet which is provided between a piezoelectric substrate and the external body and is partially fixed to the piezoelectric substrate and the external body. CONSTITUTION:An elastic sheet 10 is provided between a piezoelectric substrate 1 and a package 8 with adhesives 9 and 11 for partial adhesion between them. A thin conductive sheet (elastic sheet) like a copper foil is used as this sheet 10, and an adhesive to fix the piezoelectric substrate 1 and the conductor sheet 10 in the same manner as a conventional example is used as this adhesive 9. At this time, they are not overall but partially adhered by adhesives 9 and 11 for the purpose of giving a margin as play for distortion absorption to the conductor sheet 10. Consequently, the mechanical distortion due to the difference of thermal expansion coefficient between the piezoelectric substrate 1 and the package 8 at the time of the variance of temperature is absorbed by the conductor sheet 10, and the mechanical shock and vibration from the external body are absorbed also.

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 as a filter, a resonator, a delay line or the like.

[0002]

2. Description of the Related Art FIGS. 2 and 3 are block diagrams showing a conventional surface acoustic wave device shown on page 138 of, for example, a surface wave device and its application, edited by Japan Society of Electronic Materials, published by Nikkan Kogyo Shimbun. Is. In the figure, 1 is lithium niobate (Li
A piezoelectric substrate such as a NbO ₃ ) YZ substrate. Reference numeral 2 denotes a surface-wave-excited interdigital transducer that is arranged on the piezoelectric substrate 1 and excites a surface acoustic wave. 3 is arranged on the piezoelectric substrate 1 so as to face the IDT 2 for exciting the surface acoustic wave, and the IDT 3 receives the surface acoustic wave excited by the IDT 2 for exciting the surface acoustic wave. It is an electrode.

Reference numeral 4 denotes strip-shaped electrode fingers arranged in parallel with each other, and reference numeral 5 denotes a pad for connecting the electrode fingers 4 at one end in a comb shape. Each of the interdigital transducer 2 for exciting surface acoustic waves and the interdigital transducer 3 for receiving surface acoustic waves is formed by arranging two sets of electrode fingers 4 connected in a comb shape by the pads 5 in an interdigitated shape. There is.

Reference numerals 6a and 6b are input terminals to which electric signals are input by being connected to the pads 5 of the interdigital transducer 2 for exciting surface acoustic waves, and 7a and 7b are the interdigital electrodes 3 for receiving surface acoustic waves. The output terminal is connected to each pad 5 and outputs an electric signal.

Next, the operation will be described. Input terminal 6
The electric signal input between a and 6b is applied to each pad 5 of the interdigital transducer 2 for exciting surface acoustic waves on the piezoelectric substrate 1. The interdigital transducer 2 for surface acoustic wave excitation to which the electric signal is applied excites the surface acoustic wave in accordance with the electric signal and sends it to the piezoelectric substrate 1.

The surface acoustic wave transmitted from the interdigital transducer 2 for exciting surface acoustic waves propagates on the piezoelectric substrate 1 at the propagation velocity of the free propagation path and reaches the interdigital electrode 3 for receiving surface acoustic waves. Upon receiving the surface acoustic wave, the interdigital transducer 3 for receiving the surface acoustic wave converts the surface acoustic wave into an electric signal and outputs the electric signal from the output terminals 7a and 7b.

Reference numeral 8 is a package for accommodating a so-called surface acoustic wave element composed of the piezoelectric substrate 1, the interdigital transducer 2 for exciting the surface acoustic wave, the interdigital transducer 3 for receiving the surface acoustic wave, and the like. This is an adhesive for fixing the piezoelectric substrate 1.

[0008]

Since the conventional surface acoustic wave device is constructed as described above, mechanical strain and mechanical shock due to the difference in thermal expansion coefficient between the piezoelectric substrate and the package during temperature fluctuations. As a result, vibrations are transmitted directly to the surface acoustic wave element through the package, causing cracks in the piezoelectric substrate, which causes problems such as performance degradation.

The present invention has been made to solve the above problems, and it is an object of the present invention to prevent the piezoelectric substrate from cracking and improve the reliability of the surface acoustic wave device.

[0010]

The surface acoustic wave device according to the present invention absorbs mechanical strain due to the difference in thermal expansion coefficient between the piezoelectric substrate and the external body and mechanical shock or vibration from the external body. The elastic sheet provided between the piezoelectric substrate and the external body is partially fixed to the piezoelectric substrate and the external body.

[0011]

In the surface acoustic wave device according to the present invention, since the elastic sheet is provided between the external body and the piezoelectric substrate, the mechanical strain and the external force due to the difference in the thermal expansion coefficient between the piezoelectric substrate and the external body are generated. A highly reliable surface acoustic wave device capable of absorbing mechanical shock and vibration from the body can be obtained.

[0012]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a piezoelectric substrate, 5 is a pad, 6a is an input terminal, and 7a is an output terminal.
Detailed description is omitted because it is the same as or equivalent to the conventional one denoted by the same reference numeral in FIG.

10 is a thin conductor sheet (elastic sheet) such as copper foil, 9 is an adhesive for fixing the piezoelectric substrate 1 and the conductor sheet 10 as in the conventional example,
Reference numeral 11 is an adhesive for fixing the conductor sheet 10 and the package 8 together. At this time, both the adhesives 9 and 11 are provided on the entire surface in order to allow the conductive sheet 10 a play for absorbing the strain. No partial bonding.

Next, the operation will be described. Since the electrical operation is the same as the conventional example, detailed description will be omitted. Since the conductor sheet 10 is provided between the piezoelectric substrate 1 and the package 8, mechanical strain due to a difference in thermal expansion coefficient between the piezoelectric substrate 1 and the package 8 during temperature fluctuation is absorbed by the conductor sheet 10 and externally. Mechanical shocks and vibrations from the body are also absorbed. Therefore, there is an effect of improving the reliability of the surface acoustic wave device.

Example 2. Although the thin conductor sheet is provided between the piezoelectric substrate 1 and the package 8 in the above embodiment, a film-like insulating sheet is provided between the piezoelectric substrate 1 and the package 8. The same effect as that of the above embodiment can be obtained.

[0016]

As described above, according to the present invention, the elastic sheet provided between the piezoelectric substrate and the external body and partially fixed to the piezoelectric substrate and the external body is provided. It is possible to absorb mechanical strain and mechanical shock and vibration of an external body, and to obtain a highly reliable surface acoustic wave device.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional side view showing a conventional surface acoustic wave device.

FIG. 3 is a perspective view showing a conventional surface acoustic wave device.

[Explanation of symbols]

1 piezoelectric substrate 2 interdigital transducer for surface acoustic wave excitation 3 interdigital transducer for surface acoustic wave reception 8 package (outer body) 10 conductive sheet or insulating sheet (elastic sheet)

Claims (1)

Claim: What is claimed is: 1. A piezoelectric substrate, a surface acoustic wave excitation interdigital electrode that is disposed on the piezoelectric substrate and excites a surface acoustic wave, and the surface acoustic wave excitation is provided on the piezoelectric substrate. Between the piezoelectric substrate and the external body, between the piezoelectric substrate and the external body, the interdigital transducer is disposed so as to face the interdigital transducer, and receives the surface acoustic wave excited by the interdigital electrode for exciting the surface acoustic wave. A surface acoustic wave device provided with an elastic sheet that is provided, is partially fixed to the piezoelectric substrate, and is partially fixed to the external body.