JPH11234081A - Surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave device having a superior suppression characteristic out of a band by means of reducing the number of wires. SOLUTION: A surface acoustic wave device is provided with a piezoelectric substrate 1, where first input/output transducers 2-1 and 3-1 and second input/ output transducers 2-2 and 3-2 are formed on a surface and the output transducer 3-1 is electrically connected to the input transducer 2-2, a package 5 where the piezoelectric substrate 1 is mounted and a wire 10 which electrically connects the respective input/output transducers 2-1, 3-1, 2-2 and 3-2 with the terminal of the package 5. The ground terminal of the package is divided into a ground terminal 8, where the respective ground electrodes of the input transducer 2-1 and the second output transducer 3-1 are connected and a ground terminal 9 where the respective ground electrodes of the output transducer 3-1 and the input transducer 2-2 are connected. The respective ground electrodes and the ground terminals 8 and 9 are connected by the ground wire 10.

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, and more particularly to a high-performance and small-sized S
The present invention relates to a surface acoustic wave device such as an AW filter and a resonator.

[0002]

2. Description of the Related Art Conventional surface acoustic wave devices have been mainly used for optimizing aperture lengths of input and output transducers and improving package grounding in order to realize desired frequency characteristics. In particular, in a surface acoustic wave device having band-pass characteristics, it is important to improve out-of-band suppression characteristics in order to suppress unnecessary signals. Regarding the improvement of this characteristic, for example, Japanese Patent Publication No.
-116377, Japanese Utility Model Publication No. 64-1788,
There is a proposal described in Japanese Utility Model Publication No. 1-2977.

FIG. 6 is a plan view of a conventional surface acoustic wave device. In the figure, 1 is a piezoelectric substrate, 2-1 is a first input transducer, 2-2 is a second input transducer, 3
-1 is the first output transducer, 3-2 is the second output transducer, 4 is the grating reflector, 5 is the package, 6 is the input terminal of the package, 7 is the output terminal of the package, 10 is the wire, 12 is ground. Terminal.

[0004]

Generally, a SAW filter used in a wireless device or the like is required to have low insertion loss and excellent out-of-band suppression characteristics. In order to realize such characteristics, a multi-electrode transducer is required. Or a surface acoustic wave device combining these transducers and a grating reflector.

In particular, the out-of-band suppression characteristic has been conventionally improved by increasing the number of wires or improving the package. However, the production cost is increased, and as shown in FIG. Input and output transducer 2-
1,2-2,3-1,3-2 and grating reflector 4
However, the surface acoustic wave device formed with the above has a defect such as an insufficient out-of-band suppression characteristic.

That is, as shown in FIG. 6, a first output transducer cascade-connected to respective ground electrodes of a first input transducer 2-1 and a second output transducer 3-2 for inputting and outputting electric signals. 3-1
The ground electrode of each of the first and second input transducers 2-2 was connected to the same ground terminal 12 of the package 5 by a wire 10. In the surface acoustic wave device provided with the grating reflector 4, the grating reflector 4 is also connected to the same ground terminal 12 of the package 5.

Therefore, the first input transducer 2-
The ground electrodes of the first and second output transducers 3-2 and the ground electrode of the first output transducer 3-1 and the second input transducer 2-2 or the ground electrode of the grating reflector 4 are connected to the ground terminal of the package 5. Since they are electrically coupled by the ground 12, the ground current of the package 5 increases, and the current flowing on the ground surface of the circuit board decreases, so that the desired out-of-band suppression characteristics cannot be obtained.

An object of the present invention is to provide a surface acoustic wave device which has the above disadvantages of the prior art, reduces the number of wires, and has excellent out-of-band suppression characteristics.

[0009]

According to a first aspect of the present invention, a first input / output transducer and a second input / output transducer are formed on a surface.
A piezoelectric substrate on which the first output transducer and the second input transducer are electrically connected, a package on which the piezoelectric substrate is mounted, each of the first and second input and output transducers and terminals of the package It is intended for a surface acoustic wave device provided with wires for electrically connecting between them.

The ground terminal of the package includes a first ground terminal to which ground electrodes of the first input transducer and the second output transducer are connected, a first output transducer and a second input. Each ground electrode of the transducer is separated into a second ground terminal to be connected, and each ground electrode and the ground terminal are connected by a ground wire.

According to a second aspect of the present invention, a first input / output transducer, a second input / output transducer, and a grading reflector are formed on a surface, and the first output transducer and a grading reflector are formed. A piezoelectric substrate to which two input transducers are electrically connected; a package on which the piezoelectric substrate is mounted;
The present invention is directed to a surface acoustic wave device having wires for electrically connecting input / output transducers, grading reflectors, and terminals of a package.

A ground electrode of each of the first output transducer and the second input transducer is electrically connected to a grading reflector, and a ground terminal of the package is connected to the first input transducer and the second output transducer. The grounding electrode for the transducer to which each ground electrode of the transducer is connected and the grounding terminal for the grading reflector to which the grading reflector is connected are separated. It is characterized by being connected.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, in the first invention,
A ground terminal of the package has a first ground terminal to which a ground electrode of each of the first input transducer and the second output transducer is connected, and a ground electrode of each of the first output transducer and the second input transducer. The second ground terminal to be connected is provided separately.

According to the second aspect of the present invention, the ground terminal of the package is connected to the ground terminal for the transducer to which the ground electrodes of the first input transducer and the second output transducer are connected, and the grading reflector is connected. The grading reflector is provided separately for the ground terminal.

By separately providing the ground terminals of the package in this manner, the electrical connection between the ground wires can be reduced, the number of wires can be reduced, and the out-of-band suppression characteristics can be improved.

Next, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. FIG. 1 is a plan view of a surface acoustic wave device according to a first embodiment, FIG. 2 is a schematic diagram for explaining electrical coupling of an input / output transducer and a grating reflector in the surface acoustic wave device of the present invention, FIG. 3 is a plan view of a surface acoustic wave device according to a second embodiment, and FIG.
FIG. 3 is a plan view of the surface acoustic wave device according to the embodiment.

In these figures, 1 is a piezoelectric substrate, 2-
1 is a first input transducer, 2-2 is a second input transducer, 3-1 is a first output transducer, 3-2 is a second output transducer, 4 is a grating reflector, 5 is a package, 6 is Input terminals of the package, 7 is an output terminal of the package, 8 and 9 are ground terminals, 10 is a wire, and 11 is a bonding pad for relay.

In the surface acoustic wave device of the present invention, a multi-electrode transducer is cascaded in two stages. An input transducer 2 and an output transducer 3 are formed on a piezoelectric substrate 1 by a thin film of aluminum or the like. The substrate 1 is housed in a ceramic package 5.

Between the input transducer 2-1 and the input terminal 6 of the package 5, between the output transducer 3-2 and the output terminal 7 of the package 5, the input and output transducers 2-1, 2-2, 3-1, 3. The -2 ground electrode and the ground terminal 8 of the package 5 are connected by a ground wire 10 made of aluminum.

In the case of the embodiment shown in FIG. 1, ground terminals 8 and 9 are provided at positions away from the four corners of the package 5, respectively.
A first ground terminal 8 to which respective ground electrodes of the first input transducer 2-1 and the second output transducer 3-2 are connected, and a first output transducer 3
-1 and a second ground terminal 9 to which the respective ground electrodes of the second input transducer 2-2 are connected,
Ground wires 10 from the input and output transducers 2-1, 2-2, 3-1 and 3-2 are individually connected to the ground terminals 8 and 9, respectively.

FIG. 2 is a diagram showing the electrical connection between the input and output transducers of this surface acoustic wave device and the ground terminal. As shown in the drawing, most of the ground current flows to the ground surface of the circuit board having a large ground effect, and the first output transducer cascaded to the first input transducer and the second output transducer is connected to the first output transducer. Since it becomes difficult for the second input transducers to be electrically coupled to each other via the ground plane of the package, the out-of-band suppression characteristics can be improved.

Conventionally, as many earth wires as possible have been provided in order to obtain a sufficient grounding effect. However, according to the present invention, a large grounding effect can be obtained with a smaller number of wires than in the prior art. it can.

FIG. 3 is a plan view of a surface acoustic wave device according to a second embodiment of the present invention. In this example, in order to further reduce the loss, the input and output transducers 2-1 and 2-1 are used.
Grating reflectors 4 are provided at both ends of 2-2, 3-1 and 3-2. The ground electrodes of the first output transducer 3-1 and the second input transducer 2-2 connected in cascade are connected to the grating reflector 4, and the ground electrode and the grating reflector 4 are connected by one wire 10. It is configured so that it can be grounded.
As shown in the figure, the ground terminal of the package 5 is a transducer ground terminal 8 to which the respective ground electrodes of the first input transducer 2-1 and the second output transducer 3-2 are connected, and the grading reflector 4
Are connected to a grounding terminal 9 for the grading reflector to be connected, and a ground wire 1 is provided between each grounding electrode and the grading reflector 4 and the grounding terminals 8, 9.
0 is connected. In the case of this example, since the ground electrode of the grading reflector 4 is also separated, the electrical coupling can be weakened as in the first embodiment.

FIG. 4 is a plan view of a surface acoustic wave device according to a third embodiment of the present invention. In this example, the ground wire 10 from the first input transducer 2-1 and the second output transducer 3-2 and the ground wire 10 from the grading reflector 4 are connected to dedicated ground terminals 8, 9 of the package 5, respectively. Have been. And the first
The ground wire 10 from the input transducer 2-1 and the second output transducer 3-2 is once connected to the relay bonding pad 11 provided on the piezoelectric substrate 1 and further connected to the ground terminal 8 by another wire. Have been.

With this configuration, a large grounding effect can be obtained as in the first embodiment, and it is not necessary to route the wire for a long time, and it is possible to prevent an electrical short circuit due to bending of the wire or mechanical vibration. it can.

In this embodiment, only the ground wire 10 from the input and output transducers 2-1 and 3-2 is connected to the ground terminal 8 via the relay bonding pad 11. The same effect can be obtained by connecting only the ground wire 10 to the ground terminal 9 via the relay bonding pad, or connecting both ground wires to the ground terminals 8 and 9 via the relay bonding pad, respectively.

[0027]

FIG. 5 is a diagram showing a comparison between the band characteristics of the product of the present invention (solid line) and the conventional product (chain line). As is clear from this figure, the present invention greatly enhances the out-of-band suppression characteristics. Can be improved.

As described above, in the first aspect of the present invention, the ground terminal of the package is connected to the first input transducer and the second input transducer.
A first ground terminal to which each ground electrode of each output transducer is connected, and a second ground terminal to which each ground electrode of each of the first output transducer and the second input transducer is connected.

In the second aspect of the present invention, the ground terminal of the package is connected to the ground terminal for the transducer to which the ground electrodes of the first input transducer and the second output transducer are connected, and the grading reflector is connected. The grading reflector is provided separately for the ground terminal.

By thus separately providing the ground terminals of the package, it is possible to reduce the electrical coupling between the ground wires, reduce the number of wires, and improve the out-of-band suppression characteristics.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram showing an electrical coupling relationship between an input / output transducer and a grating reflector in the surface acoustic wave device of the present invention.

FIG. 3 is a plan view of a surface acoustic wave device according to a second embodiment of the present invention.

FIG. 4 is a plan view of a surface acoustic wave device according to a third preferred embodiment of the present invention.

FIG. 5 is a frequency characteristic diagram of a product of the present invention and a conventional product.

FIG. 6 is a plan view of a conventional surface acoustic wave device.

[Explanation of symbols]

 Reference Signs List 1 piezoelectric substrate 2-1 first input transducer 2-2 second input transducer 3-1 first output transducer 3-2 second output transducer 4 grating reflector 5 package 6 package input terminal 7 package output Terminal 8, 9, 12 Ground terminal 10 Wire 11 Bonding pad for relay

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Norio Hosaka 1st Kitano, Makino, Mizusawa-shi, Iwate Prefecture Hitachi Media Electronics Co., Ltd.

Claims (3)

[Claims] A piezoelectric substrate having a first input / output transducer and a second input / output transducer formed on a surface thereof, wherein the first output transducer and the second input transducer are electrically connected; A surface acoustic wave device comprising: a package on which a piezoelectric substrate is mounted; and a wire for electrically connecting each of the first and second input and output transducers to a terminal of the package. A first ground terminal to which a ground electrode of each of the first input transducer and the second output transducer is connected;
The ground electrode of each of the output transducer and the second input transducer is separated into a second ground terminal to be connected, and a ground wire is connected between each ground electrode and the ground terminal. Surface wave device. 2. A piezoelectric element having a first input / output transducer and a second input / output transducer and a grading reflector formed on a surface thereof, wherein the first output transducer and the second input transducer are electrically connected. A surface acoustic wave device comprising: a substrate; a package on which the piezoelectric substrate is mounted; and wires for electrically connecting each of the first and second input / output transducers, the grading reflector, and a terminal of the package. A ground electrode of each of the first output transducer and the second input transducer is electrically connected to a grading reflector; and a ground terminal of the package is connected to each of the first input transducer and the second output transducer. Ground terminal for transducer to which the ground electrode is connected The separated grading reflecting dexterity ground terminal grading reflectors are connected, respectively earth electrode and grading reflector and the surface acoustic wave device, characterized in that is connected with the earth wire between the earth terminal. 3. The method according to claim 1, wherein
At least one of the ground electrode and the grading reflector of the input / output transducer is connected to a ground terminal of the package via a wire bonding pad formed on the piezoelectric substrate via a wire. Surface acoustic wave device.