JPH07283684A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To obtain a surface acoustic wave device which is capable of attaining sufficient extent of attenuation and in which a balanced connection is secured with a mechanically stable structure. CONSTITUTION:A surface acoustic wave element 10 is composed by forming an electrode structure column 20 composed of IDTs21, 22 and 23, and an electrode structure column 30 composed of IDTs31, 32 and 33 on a piezoelectric substrate 12. This surface acoustic wave element 10 is stored in a package 40. In the package 40, an electrically conductive layer 45 for connection which is independent of electrically conductive layers 41, 42, 43 and 44 for input/output is formed, the IDT23 for connection of the electrode structure column 20 and the IDT32 for connection of the electrode structure column 30 are connected by using the electrically conductive layer 45 for connection on the package 40, and a balance connection is performed for the electrode structure column 20 and the electrode structure column 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention contains a surface acoustic wave device in which a plurality of electrode structure rows having a plurality of IDTs (interdigital transducers, also called comb-shaped electrodes) are formed on a piezoelectric substrate. The present invention relates to a surface acoustic wave device.

[0002]

2. Description of the Related Art Surface acoustic wave resonator filters are widely used in mobile communication and the like because of their low insertion loss and small size. As a basic structure of the surface acoustic wave resonator filter, an electrode structure array in which a plurality of IDTs are sandwiched by a pair of reflectors is formed on a piezoelectric substrate. Of the plurality of IDTs in the electrode structure array, one IDT is used for input and the other IDT is used for output to form a surface acoustic wave resonator filter with low insertion loss.

However, in recent years, it has been required to further attenuate the out-of-band attenuation of the surface acoustic wave resonator filter. In order to further improve the out-of-band attenuation of the surface acoustic wave resonator filter, a plurality of electrode structure rows may be formed on the piezoelectric substrate and these electrode structure rows may be connected in cascade. When the electrode structure columns are connected in cascade, each electrode structure column is considered to be equivalently a four-terminal circuit, and a connection method such as the equivalent circuit shown in FIG. 10 can be considered. That is, the connection method shown in FIG. 10A is a connection method called unbalanced connection, in which one of the connection lines that cascade-connects the electrode structure rows 2 and 4 is connected to the input side and / or the output side. Side is connected to a common ground wire. In addition, the connection method shown in FIG. 10B is a connection method called balanced connection, and neither of the connection lines that cascade-connect the electrode structure rows 2 and 4 is grounded.

[0004]

In the case of unbalanced connection, it is sufficient to connect only one of the connection lines to be cascaded and the other is grounded, which is advantageous in that the connection is simple, but the amount of attenuation is small. There was a problem that did not grow. On the other hand, in the case of the balanced connection, although sufficient damping characteristics can be obtained, there is a problem that it is difficult to connect because all of the connection lines connected in cascade must be connected without being grounded.

For example, when the electrode structure rows are connected in series by wiring on the piezoelectric substrate, the area of the piezoelectric substrate becomes large due to the wiring, which makes it difficult to downsize the surface acoustic wave element. there were. Further, there is a problem that it is difficult to apply the sound absorbing agent on the piezoelectric substrate due to the wiring. Further, there is a problem that the surface acoustic wave is reflected by the wiring formed on the piezoelectric substrate and the device characteristics are deteriorated.

Further, when the electrode structure rows are cascade-connected by the bonding wires, since the bonding wires cross each other in the space inside the package, the bonding wires may come into contact with each other and are mechanically unstable. There was a problem. An object of the present invention is to provide a surface acoustic wave device that can obtain a sufficient amount of attenuation and is balanced-connected with a mechanically stable structure.

[0007]

[Means for Solving the Problems] The above object is to provide a plurality of IDs.
In a surface acoustic wave device comprising a surface acoustic wave element having a plurality of electrode structure rows each having T formed on a piezoelectric substrate and a package accommodating the surface acoustic wave element, the package is independent of input / output terminals. The connection wiring is formed, and the connection wiring is used for at least one of the connection lines that connect the IDT of one electrode structure row and the IDT of the other electrode structure row that are cascade-connected. This is achieved by a surface acoustic wave device.

In the above-described surface acoustic wave device, a wiring formed on the piezoelectric substrate is used as a connection line connecting the IDT of one electrode structure row and the IDT of the other electrode structure row connected in cascade. Is desirable.

[0009]

According to the present invention, the connection wiring independent of the input / output terminals is formed in the package, and the connection line connecting the IDT of one electrode structure row and the IDT of the other electrode structure row connected in cascade is formed. Since the connection wiring of the package is used for at least one of them, it is possible to perform the balanced connection that can obtain a sufficient attenuation amount without using the wiring on the piezoelectric substrate or the bonding wire.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface acoustic wave device according to a first embodiment of the present invention will be described with reference to FIGS. 1 shows a surface acoustic wave element, FIG. 2 shows a package, and FIG. 3 shows a state in which the surface acoustic wave element is housed in a package. As shown in FIG. 1, the surface acoustic wave element 10 in the surface acoustic wave device according to the present embodiment has a two-electrode structure composed of three IDTs on a piezoelectric substrate 12 made of a 43 ° cut lithium tetraborate substrate. Rows 20 and 30 are formed.

As the electrode structure array 20, an input IDT 21 having a plurality of pairs of interdigital electrodes is formed at the center, and a plurality of pairs of interdigital electrodes are provided on both sides of the input IDT 21 for cascade connection. I for connection
DTs 22 and 23 are formed. A bonding pad 21 is provided on each interdigital electrode of the input IDT 21.
a and 21b are provided. The bonding pad 23 is provided on one of the interdigital electrodes of the connection IDT 23.
a is provided, and the bonding pad 23a and the interdigital electrode of the other connection IDT 22 are connected by a connection line 24.

As the electrode structure array 30, an output IDT 31 having a plurality of pairs of interdigital electrodes is formed at the center, and a plurality of pairs of interdigital electrodes are provided on both sides of the output IDT 31 for cascade connection. I for connection
DTs 32 and 33 are formed. A bonding pad 31 is provided on each interdigital electrode of the output IDT 31.
a and 31b are provided. The bonding pad 32 is provided on one of the interdigital electrodes of the connection IDT 32.
a is provided, and the bonding pad 32a and the interdigital electrode of another connection IDT 33 are connected by a connection line 34.

The interdigital electrodes of the connecting IDT 22 of the electrode structure column 20 and the connecting IDT of the electrode structure column 30.
32 is connected to the interdigital electrode 32 by the connection line 25, and the interdigital electrode of the connection IDT 23 of the electrode structure column 20 and the connection ID of the electrode structure column 30 are connected.
The interdigital electrode of T33 is connected to the connection line 35.
Connected by. The connection lines 25, 35 are provided between the electrode structure rows 20, 30, and the connection lines 24, 3
4 is provided outside the electrode structure rows 20 and 30.

A package of the surface acoustic wave device of this embodiment is shown in FIG. 2A is a top view.
2B is a sectional view taken along the line AA, and FIG. 2C is a bottom view. The package 40 of this embodiment has a structure in which a plurality of ceramic plates are laminated. The input conductive layer 41 is formed on the upper left side of FIG.
An input grounding conductive layer 42 is formed so as to surround the. An output conductive layer 43 is formed on the lower right side of FIG. 2A, and an output grounding conductive layer 44 is formed so as to surround the output conductive layer 43. As shown in FIGS. 2B and 2C, the output conductive layer 43 extends to the back surface of the package 40, and the output grounding conductive layer 44 also surrounds the output conductive layer 43 on the back surface. It extends to the back side. As shown in FIG. 2A, at the bottom of the package 40, the conductive layer 4 for connection is provided from the upper right portion to the lower left portion.
5 is formed.

FIG. 3 shows a surface acoustic wave device in which the surface acoustic wave element 10 shown in FIG. 1 is housed in the package 40 shown in FIG. 3A is a plan view and FIG. 3B is A
FIG. In the surface acoustic wave device of this embodiment, the surface acoustic wave element 10 is mounted on the bottom of the package 40, and the bonding pad of the surface acoustic wave element 10 and the package 4 are mounted.
The conductive layer 0 is connected by a bonding wire.

The input conductive layer 41 of the package 40 is the input IDT 21 of the electrode structure array 20 of the surface acoustic wave device 10.
Bonding wire 50 on the bonding pad 21a of
And the conductive layer 4 for input grounding of the package 40
2 is an input I of the electrode structure array 20 of the surface acoustic wave element 10.
The bonding wire 21 is connected to the bonding pad 21b of the DT 21.

The output conductive layer 43 of the package 40 is the output IDT 31 of the electrode structure array 30 of the surface acoustic wave device 10.
Bonding wire 52 to bonding pad 31b of
And the conductive layer 4 for output grounding of the package 40
Reference numeral 4 denotes an output I of the electrode structure array 30 of the surface acoustic wave element 10.
The bonding wire 31 is connected to the bonding pad 31 a of the DT 31.

The upper right end of the connecting conductive layer 45 of the package 40 is connected to the bonding pad 23a of the connecting IDT 23 of the electrode structure column 20 of the surface acoustic wave device 10 by the bonding wire 54, and the connecting conductive layer of the package 40 is connected. The lower left end of 45 is the bonding pad 32a of the connecting IDT 32 of the electrode structure row 30 of the surface acoustic wave element 10.
To a bonding wire 55. The conductive layer 45 for connection is not connected to the outside of the package,
With the conductive layer 45 for connection and the connection lines 25 and 35,
The electrode structure row 20 and the electrode structure row 30 are balance-connected.

In order to protect the surface acoustic wave device 10 housed in the package 40, the upper portion of the package 40 is covered with a lid 47. As described above, according to this embodiment, the two electrode structure rows are connected in series by the connection conductive layer formed on the package and the connection line on the piezoelectric substrate, and thus the surface acoustic wave device can be downsized. Balanced connection can be achieved with a mechanically stable structure. As shown in FIG. 4, the surface acoustic wave device according to the present embodiment has an out-of-band attenuation reduced by about 20 dB and a sufficient out-of-band attenuation of about 60 dB or more as compared with the surface acoustic wave device with unbalanced connection. We were able to secure the quantity.

A surface acoustic wave device according to a second embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. 5 shows a surface acoustic wave element, and FIG. 6 shows a state where the surface acoustic wave element is housed in a package. The same or similar components as those of the surface acoustic wave device according to the first embodiment shown in FIGS. 1 to 3 are designated by the same reference numerals to omit or simplify the description. In the present embodiment, the surface acoustic wave element 10 in which the electrode structure array 20 is composed of two IDTs 21 and 22 and the electrode structure array 30 is composed of two IDTs 31 and 32 is used. It is housed in the same package 40 as in the first embodiment.

In the surface acoustic wave device 10 of the surface acoustic wave device of this embodiment, an input IDT 21 having a plurality of pairs of interdigital electrodes is formed as the electrode structure array 20, and a plurality of input IDTs 21 are provided on the right side of the input IDT 21. A connection IDT 22 having a pair of interdigital electrodes is formed. Bonding pads 21a and 21b are provided on each interdigital electrode of the input IDT 21. A bonding pad 22a is provided on one of the interdigital electrodes of the connection IDT 22.

As the electrode structure array 30, an output IDT 31 having a plurality of pairs of interdigital electrodes is formed.
On the left side of the output IDT 31, a connection IDT 32 having a plurality of pairs of interdigital electrodes is formed.
Bonding pads 31a and 31b are provided on each interdigital electrode of the output IDT 31. A bonding pad 32a is provided on one of the interdigital electrodes of the connecting IDT 32.

The interdigital electrodes of the connecting IDT 22 of the electrode structure row 20 and the connecting IDT of the electrode structure row 30.
One of the interdigital electrodes 32 is connected by a connection line 25 between the electrode structure rows 20 and 30.
FIG. 6 shows a surface acoustic wave device in which the surface acoustic wave element 10 shown in FIG. 5 is housed in the package 40 shown in FIG.

In the surface acoustic wave device of this embodiment, the surface acoustic wave element 10 is placed on the bottom of the package 40, and the bonding pad of the surface acoustic wave element 10 and the conductive layer of the package 40 are connected by a bonding wire. There is. The input conductive layer 41 of the package 40 is connected to the bonding pad 21a of the input IDT 21 of the electrode structure array 20 of the surface acoustic wave device 10 by the bonding wire 50, and the input grounding conductive layer 42 of the package 40 is a surface acoustic wave. The bonding wire 51 is connected to the bonding pad 21b of the input IDT 21 of the electrode structure array 20 of the element 10.

The output conductive layer 43 of the package 40 is the output IDT 31 of the electrode structure array 30 of the surface acoustic wave device 10.
Bonding wire 52 to bonding pad 31b of
And the conductive layer 4 for output grounding of the package 40
Reference numeral 4 denotes an output I of the electrode structure array 30 of the surface acoustic wave element 10.
The bonding wire 31 is connected to the bonding pad 31 a of the DT 31.

The upper right end of the connecting conductive layer 45 of the package 40 is connected to the bonding pad 22a of the connecting IDT 22 of the electrode structure column 20 of the surface acoustic wave device 10 by the bonding wire 54, and the connecting conductive layer of the package 40 is connected. The lower left end of 45 is the bonding pad 32a of the connecting IDT 32 of the electrode structure row 30 of the surface acoustic wave element 10.
To a bonding wire 55.

As described above, according to this embodiment, the two electrode structure rows are connected in series by the connection conductive layer formed on the package and the connection line on the piezoelectric substrate, so that the surface acoustic wave device can be miniaturized. In addition, it is possible to achieve balanced connection with a mechanically stable structure. A surface acoustic wave device according to a third embodiment of the present invention will be described with reference to FIGS. 7 to 9. 7 shows a surface acoustic wave element, FIG. 8 shows a package, and FIG. 9 shows a state where the surface acoustic wave element is housed in the package. The same or similar components as those of the surface acoustic wave device according to the first embodiment shown in FIGS. 1 to 3 are designated by the same reference numerals to omit or simplify the description.

The surface acoustic wave element 10 in the surface acoustic wave device of this embodiment is composed of the connection IDTs 22 of the electrode structure array 20,
23 are provided with bonding pads 22a and 23a, respectively, and the connection IDTs 32 and 33 of the electrode structure column 30 are provided with bonding pads 32a and 33a, respectively. The interdigital electrodes of the connection IDTs 22 and 23 of the electrode structure column 20 are not connected by a connection line, and the interdigital electrodes of the connection IDTs 32 and 33 of the electrode structure column 30 are not connected by a connection line. .

The package of the surface acoustic wave device of this embodiment is shown in FIG. FIG. 8A is a top view.
(B) is the sectional view on the AA line. In the package 40 of this embodiment, the input conductive layer 41 is provided at the center of the upper portion of FIG.
And an input ground conductive layer 42 is formed so as to surround the input conductive layer 41. An output conductive layer 43 is formed in the center of the lower portion of FIG.
An output grounding conductive layer 44 is formed so as to surround 3. At the bottom of the package 40, as shown in FIG. 8A, two connecting conductive layers 45 and 46 are formed on the left and right.

FIG. 9 shows a surface acoustic wave device in which the surface acoustic wave element 10 shown in FIG. 7 is housed in the package 40 shown in FIG. 9A is a plan view, and FIG. 9B is A
FIG. Also in the surface acoustic wave device of this embodiment, the surface acoustic wave element 10 is placed on the bottom of the package 40, and the bonding pad of the surface acoustic wave element 10 and the package 4 are mounted.
The conductive layer 0 is connected by a bonding wire.

The input conductive layer 41 of the package 40 is the input IDT 21 of the electrode structure array 20 of the surface acoustic wave device 10.
Bonding wire 50 on the bonding pad 21a of
And the conductive layer 4 for input grounding of the package 40
2 is an input I of the electrode structure array 20 of the surface acoustic wave element 10.
The bonding wire 21 is connected to the bonding pad 21b of the DT 21.

The output conductive layer 43 of the package 40 is the output IDT 31 of the electrode structure array 30 of the surface acoustic wave device 10.
Bonding wire 52 to bonding pad 31b of
And the conductive layer 4 for output grounding of the package 40
Reference numeral 4 denotes an output I of the electrode structure array 30 of the surface acoustic wave element 10.
The bonding wire 31 is connected to the bonding pad 31 a of the DT 31.

The conductive layer 45 for connection on the left side of the package 40
Is connected to the bonding pad 22a of the connecting IDT 22 of the electrode structure row 20 of the surface acoustic wave device 10 by the bonding wire 54, and the lower end of the conductive layer 45 for connection on the left side of the package 40 is a surface acoustic wave device. The bonding wire 55 is connected to the bonding pad 32 a of the connection IDT 32 of the electrode structure column 30 of 10.

A conductive layer 46 for connection on the right side of the package 40
Is connected to the bonding pad 23a of the connecting IDT 23 of the electrode structure row 20 of the surface acoustic wave device 10 by the bonding wire 56, and the lower end of the connecting conductive layer 46 on the right side of the package 40 is a surface acoustic wave device. The bonding wire 57 is connected to the bonding pad 33a of the connection IDT 33 of the ten electrode structure columns 30.

The connecting conductive layers 45 and 46 are not connected to the outside of the package, and the connecting conductive layers 45 and 46 and the connecting lines 25 and 35 connect the electrode structure row 20 and the electrode structure row 30 in a balanced connection. Has been done. Thus, according to the present embodiment, the connection conductive layer formed on the package,
Since the two electrode structure rows are connected in series by the connection line on the piezoelectric substrate, the surface acoustic wave device can be downsized and balanced connection can be achieved with a mechanically stable structure. In particular, the out-of-band attenuation is improved by connecting the IDTs associated with the subordinate connection independently.

The present invention is not limited to the above embodiment, but various modifications can be made. For example, in the above-mentioned embodiment, the electrode structure array of the surface acoustic wave element is composed of two or three IDTs, but the electrode structure array may be composed of a larger number of IDTs, or both sides of the IDT. Insertion loss can also be reduced by providing a reflector in the.

Further, the conductive layer for connection formed in the package is not limited to the pattern shape and the number shown in the above embodiment.

[0038]

As described above, according to the present invention, an IDT of one electrode structure row and an IDT of the other electrode structure row, which are connected in cascade and have independent wiring from the input / output terminals, are formed in the package. Since at least one of the connecting lines to be connected is the wiring of the package, it is possible to perform the balanced connection that can obtain a sufficient amount of attenuation without using a complicated wiring or a bonding wire on the piezoelectric substrate.

[Brief description of drawings]

FIG. 1 is a diagram showing a surface acoustic wave element in a surface acoustic wave device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a package in the surface acoustic wave device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a surface acoustic wave device according to a first embodiment of the present invention.

FIG. 4 is a graph showing attenuation characteristics of the surface acoustic wave device according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a surface acoustic wave element in a surface acoustic wave device according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a surface acoustic wave device according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a surface acoustic wave element in a surface acoustic wave device according to a third embodiment of the present invention.

FIG. 8 is a diagram showing a package in a surface acoustic wave device according to a third embodiment of the present invention.

FIG. 9 is a diagram showing a surface acoustic wave device according to a third embodiment of the present invention.

FIG. 10 is an equivalent circuit diagram of a surface acoustic wave device in which a plurality of electrode structure rows are connected in cascade.

[Explanation of symbols]

2 ... Electrode structure sequence 4 ... Electrode structure sequence 10 ... Surface acoustic wave element 12 ... Piezoelectric substrate 20 ... Electrode structure sequence 21 ... Input IDTs 21a, 21b ... Bonding pads 22, 23 ... Connection IDTs 22a, 23a ... Bonding pad 30 ... Electrode structure column 31 ... Output IDTs 31a, 31b ... Bonding pads 32, 33 ... Connection IDTs 32a, 33a ... Bonding pads 24, 25, 34, 35 ... Connection lines 40 ... Package 41 ... Input conductive layer 42 ... Input Ground conductive layer 43 ... Output conductive layer 44 ... Output ground conductive layer 45, 46 ... Connection conductive layer 47 ... Lid 50, 51, 52, 53, 54, 55, 56, 57 ... Bonding wire

Claims (2)

[Claims] 1. A surface acoustic wave device comprising: a surface acoustic wave element having a plurality of electrode structure rows having a plurality of IDTs formed on a piezoelectric substrate; and a package accommodating the surface acoustic wave element. A connection wiring independent of the input / output terminal is formed on the connection electrode, and the connection wiring is used for at least one of the connection lines connecting the IDT of one electrode structure row and the IDT of the other electrode structure row connected in cascade. A surface acoustic wave device characterized in that 2. The surface acoustic wave device according to claim 1, wherein the connection line connecting the IDT of one electrode structure row and the IDT of the other electrode structure row connected in cascade is formed on the piezoelectric substrate. A surface acoustic wave device, characterized in that the wiring is used.