JPH03173211A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To increase the trap attenuation at a high band by providing an absorber to a main cross part of interdigital electrodes. CONSTITUTION:Leadout electrodes 2,3, interdigital electrodes 4,5 and a ground electrode 6 made of a metal such as Al are provided to a polished face of a piezoelectric substrate 13. The absorber 14 coated with an epoxy resin or an acrylic resin is provided to a part below 1/3 from the leadout electrode 3 toward the center among the parts where the interdigital electrodes 5 are crossed with each other to attenuate the vibration of a bulk wave thereby reducing the level of the signal converted into an electric signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to surfaces used in video equipment such as television receivers and video tape recorders, communication equipment such as pagers, and oscillation circuits for security-related transmitters. It concerns wave devices.

BACKGROUND OF THE INVENTION A conventional surface wave device will be described below. 6th
The figure is a plan view showing the configuration of a piezoelectric body of a conventional surface wave device. In FIG. 5, aluminum is deposited on the entire main plane of a single crystal piezoelectric substrate 1, and then lead electrodes 2 and 3, comb-shaped electrodes 4 and 6, and a ground electrode 6 are provided by photolithography, and both ends of the piezoelectric substrate 1 are The absorber 7 is provided by applying epoxy resin or acrylic resin. Second
The figure is a plan view showing the structure of the surface wave device, and FIG. 3 is a plan cross-sectional view thereof. In FIGS. 2 and 3, the piezoelectric substrate 1 is placed on the stem 8 with the electrode surface facing up, and the epoxy resin 9
The lead electrodes 2 and 3 and the terminal 1o of the metal stem 8 are connected using an aluminum wire 11. The earth electrode 6 is also grounded to the stem 7 with an aluminum wire 11, a cap 12 is placed over the stem 7, and the stem 7 and the cap 12 are welded to form an airtight seal.

Problems to be Solved by the Invention However, the conventional configuration described above has a problem in that the bulk wave propagated in the thickness direction of the piezoelectric substrate overlaps the high band trap portion, resulting in a small attenuation amount of the high band trap. Was.

The present invention solves the above-mentioned conventional problems and aims to provide a surface wave device having a large amount of trap attenuation in a high band.

Means for Solving the Problems To achieve this object, the surface wave device of the present invention provides a surface wave device of the present invention in which, at the main intersection of the comb-shaped electrodes, from the extraction electrode toward the center of the intersection, one-third of the intersection width is It has a structure in which the following parts are coated with epoxy resin or acrylic resin.

Effect: With this configuration, it is possible to attenuate the vibration of the bulk wave propagating in the thickness direction of the piezoelectric substrate, and it is possible to increase the amount of trap attenuation of the frequency characteristic.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing the structure of a piezoelectric body of a surface wave device in an embodiment of the present invention.

In FIG. 1, the main plane of a single-crystal piezoelectric substrate 13 is polished, and aluminum is deposited on the polished surface.

The vapor-deposited aluminum is etched by photolithography to provide extraction electrodes 2, 3, interdigitated electrodes 4.5, and ground electrode 6. Then, as shown in FIG.
The absorber 14 is formed by coating the following parts. The absorber 7 is formed by applying the same resin as above to the piezoelectric substrate 13 on the opposite side to the part subjected to the above treatment so as not to cover the comb-shaped electrodes 4.

The piezoelectric substrate 13 subjected to the above treatment is assembled in the same manner as a conventional surface wave device as explained in FIGS. 2 and 3.

In the surface wave device, an electrical signal applied to the comb-shaped electrode 4 via the external lead terminal 10 is converted into mechanical vibration due to the piezoelectric effect of the piezoelectric substrate 13, and this mechanical vibration is transmitted over the main plane of the piezoelectric substrate 13. It propagates toward one of the comb-shaped electrodes 6. The mechanical vibrations that reach the comb-shaped electrodes 6 are converted into electrical vibrations due to the piezoelectric effect.

In the conventional surface wave device, in FIG. 5, among the signal waves converted from electrical signals to mechanical vibrations by the comb-shaped electrode 4, waves (bulk waves) propagated in the thickness direction of the piezoelectric substrate 13 are generated.
is reflected from the surface of the piezoelectric substrate 1 opposite to the surface on which the comb-shaped electrodes 4 are formed, and reaches the comb-shaped electrodes 6. When this bulk wave is converted into an electric signal, as shown in waveform A shown in FIG. 4, the bulk wave overlaps exactly with the trap portion of Takagi, and the amount of trap attenuation becomes smaller than the designed value.

In the present invention, in FIG. 1, among the parts where the electrodes of the comb-shaped electrode 6 intersect, three
By attenuating the vibration of the bulk wave using the absorber 14 whose portion is coated with epoxy resin or acrylic resin, the signal level converted into an electrical signal can be lowered.

In this way, the influence of bulk waves can be eliminated and the waveform opening shown in FIG. 4 can be obtained.

In addition, if the intersecting width of the electrodes 4 and 6 of the comb-shaped electrodes is different,
Since phenomena such as an increase in insertion loss occur, the width of the intersection of the comb-shaped electrodes 6 is preferably made larger than the width of the intersection of the comb-shaped electrodes 4. What are the dimensions to increase?

The dimensions are such that the absorber covers the intersection of the comb-shaped electrodes when the above process is carried out.

Effects of the Invention As described above, the present invention realizes an excellent surface wave device in which the effects of bulk waves can be removed and the mounting circuit can be simplified by providing an absorber at the main intersection of the comb-shaped electrodes. It is possible.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the structure of a piezoelectric body of a surface wave device according to an embodiment of the present invention, FIG. 2 is a plan view showing the structure of the surface wave device, FIG. 3 is a plan cross-sectional view thereof, and FIG. 6 is a graph showing the amount of trap attenuation of the frequency characteristics of the conventional surface wave device and the present embodiment, and FIG. 6 is a plan view showing the structure of the piezoelectric body of the conventional surface wave device.

Claims (1)

[Claims] A comb-shaped electrode made of metal such as aluminum is provided on the piezoelectric substrate, and at the main intersection of the comb-shaped electrode, epoxy is applied to a portion of one-third or less of the intersection width from the extraction electrode toward the center of the intersection. A surface wave device coated with resin or acrylic resin to increase trap attenuation in frequency characteristics.