JP4634861B2 - Surface acoustic wave device and communication device - Google Patents

Description

  The present invention relates to a surface acoustic wave device that is preferably used for a filter element, a duplexer, and the like, and includes a plurality of surface acoustic wave elements having passbands of different frequencies, and a communication device including the surface acoustic wave device. This communication device is used for mobile communication devices such as mobile phones.

In a communication device such as a cellular phone, a surface acoustic wave device using a surface acoustic wave element including an IDT electrode (Inter Digital Transducer) is used as a duplexer for separating a transmission signal and a reception signal. The surface acoustic wave device is small, has steep filter element characteristics, and has excellent features such as excellent mass productivity.
Japanese National Patent Publication No. 11-510666 Special Table 2002-504773

Recently, in order to reduce the size and weight of communication equipment, there is a demand for a small surface acoustic wave device in which a transmission filter element and a reception filter element are integrated in a surface acoustic wave device. . In addition to a low insertion loss as a filter element, an even greater attenuation is required for out-of-band attenuation characteristics.
If the out-of-band attenuation of the transmission filter element and the reception filter element deteriorates, an unnecessary radio signal is transmitted or received, and the quality of the received radio signal is reduced, Problems such as interference with other wireless communication devices may occur.

To meet the above requirements, the out-of-band attenuation characteristics of the conventional surface acoustic wave device cannot sufficiently meet the demand, and further improvement is desired.
The present invention has been devised in view of the above demands, and the object thereof is to provide a high-pass filter element and a low-pass filter element, and these filter elements have excellent out-of-band attenuation characteristics. Another object of the present invention is to provide a surface acoustic wave device that can be miniaturized and has high reliability.

The surface acoustic wave device of the present invention includes a first filter element including a first input / output electrode, a first ground electrode, and a first IDT electrode formed on one main surface of a piezoelectric substrate, and the piezoelectric substrate. same surface formed on the second input-output electrodes, viewed including the second ground electrode and the second IDT electrode, the passing frequency band is the second higher than the pass band of the first filter element A filter element; and a circuit board for mounting the surface of the piezoelectric substrate on which the first and second filter elements are formed, wherein the first and second filter elements of the piezoelectric substrate are formed. In the surface, the first ground electrode and the second ground electrode are formed to be electrically separated, and the first ground electrode is connected to the surface of the circuit board on which the piezoelectric substrate is mounted. The first grounding conductor terminal and the second grounding electrode A second grounding conductor terminal to be connected is formed separately from the surface of the circuit board opposite to the surface on which the piezoelectric substrate is mounted or an inner layer surface of the circuit board. First and second penetrations that are provided with electrodes and are connected to the first grounding conductor terminal and the second grounding conductor terminal and penetrate the circuit board to the position of the third grounding electrode, respectively. A conductor is provided.

  According to this configuration, since the two filter elements can be formed on the same piezoelectric substrate, the surface acoustic wave device can be reduced in size as compared with the case where they are formed on separate piezoelectric substrates, and mounted on the circuit board. The area can be reduced. Further, by providing the first and second through conductors for grounding each filter element, the out-of-band attenuation characteristics of the first filter element and the second filter element can be lowered to desired values, respectively. Therefore, a highly reliable surface acoustic wave device can be provided.

Further, the surface acoustic wave device of the present invention having the above structure, before Symbol first ground electrode, the series inductance of the first grounding conductor terminal and the first through-conductor, the second ground electrode, It is higher than the series inductance of the second grounding conductor terminal and the second through conductor.
In the surface acoustic wave device of the present invention, (1) the area of the first ground electrode on the piezoelectric substrate is smaller than the area of the second ground electrode on the piezoelectric substrate. (2) the first through conductor Is less than the number of the second through conductors, (3) the first through conductor has a crank shape, and (4) the cross-sectional area of the first through conductor is that of the second through conductor. Any of the configurations that are smaller than the cross-sectional area is adopted.

Each of the first filter element and the second filter element includes a series IDT electrode connected between the input and output electrodes, and a parallel IDT electrode connected between the signal line and the ground. May be .
Hereinafter, the effect by this structure is demonstrated.
FIG. 1 is a diagram showing an equivalent circuit of an IDT electrode. The impedance of this IDT electrode is represented by a complex number Z1.

A series inductance formed by the first ground electrode, the first ground conductor terminal, and the first through conductor is represented by Lg1, and the second ground electrode, the second ground conductor terminal, and the second ground conductor are represented by Lg1. The series inductance formed by the through conductors is represented by Lg2. Lg1 and Lg2 are collectively referred to as “Lg”.
FIG. 2 shows a circuit in which a series inductance Lg is connected in series to the circuit of FIG. The impedance of the circuit of FIG. 2 is represented by the sum of Z1 and Lg, and this is expressed as “Z”. Then, the reactance component of Z is X, and the resistance component is R.

FIG. 3 is a graph with the reactance X on the vertical axis and the frequency on the horizontal axis. The parameter of each curve in the graph is Lg.
The reactance X has a resonance point at a certain frequency fr0 and an anti-resonance point at a higher frequency fa0.
As can be seen from the graph, the larger the value of Lg, the higher the curve rises and the lower both the resonance frequency fr0 and the antiresonance frequency fa0.

FIG. 4 shows the absolute value | Z | of each impedance of the parallel IDT electrode, the serial IDT electrode, and the parallel IDT electrode and the serial IDT electrode of the second filter element on the vertical axis. The graph and the graph which represented the attenuation amount of the said 1st filter element and the 2nd filter element on the vertical axis | shaft are shown. The horizontal axis shows a common frequency.
From this combined graph, if the impedance of the parallel IDT electrode of the first filter element is lowered near the anti-resonance frequency, as shown by an arrow b , a high frequency outside the pass band of the first filter element is obtained. The attenuation on the band side can be increased (see arrow d ). Further, as shown by the arrow a , if the impedance of the parallel IDT electrode of the second filter element is lowered near the resonance frequency, the attenuation amount on the low frequency side outside the pass band of the second filter element is reduced. It can be enlarged (see arrow c ).

In order to reduce the impedance of the parallel IDT electrode of the first filter element in the vicinity of the anti-resonance frequency, it is only necessary to increase the series inductance Lg1 of the first filter element as shown by the arrow e in FIG. In order to lower the impedance of the parallel IDT electrode of the second filter element in the vicinity of the resonance frequency, it is understood that the series inductance Lg2 of the second filter element may be reduced as shown by the arrow f .

In this way, when the parasitic inductance generated in the grounding conductor terminal of the second filter element is reduced, the impedance Z in the band overlapping the frequency band of the first filter element is obtained for the parallel IDT electrode of the second filter element. Can be small.
As a result, it is possible to effectively block signals that pass through a band that overlaps the frequency band, and it is possible to improve the out-of-band attenuation characteristics on the low frequency side of the second filter element.

Further, when the parasitic inductance generated at the grounding conductor terminal of the first filter element is increased, the impedance Z in the band overlapping the frequency band of the second filter element is reduced for the parallel IDT electrode of the first filter element. Can do.
As a result, it is possible to effectively block signals that pass through a band that overlaps the frequency band, and it is possible to improve the out-of-band attenuation characteristics on the high frequency side of the first filter element.

  In order to realize the reduction and increase of the parasitic inductance as described above, the area of the first ground electrode on the piezoelectric substrate is made smaller than the area of the second ground electrode on the piezoelectric substrate, The number of first through conductors may be less than the number of the second through conductors, the first through conductors may be crank-shaped, the second through conductors may be linear, It is conceivable that the cross-sectional area of the through conductor is made smaller than the cross-sectional area of the second through conductor. These configurations for reducing and increasing the parasitic inductance may be used alone or in combination.

  In the surface acoustic wave device configured as described above, if the pass frequency band of the reception filter element is higher than the pass frequency band of the transmission filter element, the parasitic inductance generated in the grounding conductor terminal of the reception filter element By increasing the parasitic inductance generated at the grounding conductor terminal of the transmission filter element, it is possible to improve the desired out-of-band attenuation characteristics, which is good when used for a duplexer of communication equipment Communication quality can be obtained.

  In the surface acoustic wave device according to the present invention, in each of the above structures, the first and second filter elements are formed on the surface of the piezoelectric substrate on which the first and second filter elements are formed. And an annular conductor connected to the annular electrode is formed on the surface of the circuit board on which the piezoelectric substrate is mounted. In this structure, the surface acoustic wave element can be hermetically sealed and protected from the outside air by the piezoelectric substrate, the circuit board, the annular electrode, and the annular conductor, so that the surface acoustic wave element can be stably operated over a long period of time. Therefore, a highly reliable surface acoustic wave device can be obtained.

The annular conductor may be configured to individually surround each filter element. Since each annular electrode serves as an electromagnetic shield for each filter element, the electromagnetic coupling of each filter element can be eliminated, and interference between the filter elements can be suppressed.
In the surface acoustic wave device according to the present invention, the second ground electrode of the second filter element is connected to the annular electrode, and the annular conductor as the second grounding conductor terminal is connected to the plurality of second through conductors. In this case, a structure for connecting to the third ground electrode is adopted.

This structure uses an annular electrode and an annular conductor to reduce the inductance of the ground electrode.
The surface acoustic wave device of the present invention employs a structure in which a second grounding conductor terminal is connected to the annular conductor, and the annular conductor is connected to the third grounding electrode by a plurality of third through conductors. To do.

This structure uses an annular conductor to reduce the inductance of the grounding conductor terminal.
According to these structures, the parasitic inductance can be reduced without newly creating a large-area ground electrode or grounding conductor terminal in the second filter element, and the smaller surface acoustic wave of the present invention can be obtained. An apparatus can be realized.

The communication device of the present invention includes the surface acoustic wave device and a reception circuit and / or transmission circuit that uses the surface acoustic wave device as a circuit element.
Since this communication device does not require a large dielectric filter element as in the prior art and can be significantly reduced in size, a communication device having a small size and excellent communication quality can be provided.
By using a high-pass filter element having good out-of-band attenuation characteristics, for example, as a reception filter element, unnecessary out-of-band signals can be sufficiently removed, and the quality of the received signal can be improved. It becomes. Further, by using a low-pass filter element having good out-of-band attenuation characteristics, for example, as a transmission filter element, it is possible to transmit a communication signal with excellent quality without transmitting an unnecessary out-of-band signal. A communication device with excellent power durability can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 5 is a diagram showing an embodiment of the surface acoustic wave device according to the present invention, and is a plan view of one surface side of the surface acoustic wave element 100. FIG. 6 is a plan view of the upper surface of the circuit board 200 on which the surface acoustic wave element 100 is mounted.
The surface acoustic wave element 100 is formed on the piezoelectric substrate 300 and forms two types of filter elements having different pass frequency bands.

In the embodiment of the present invention, the low frequency band filter element is used for the transmission filter element TX, and the high frequency band filter element is used for the reception filter element RX.
5, the IDT electrode 110, the ground electrode 312 and the signal input / output electrode 311 of the transmission filter element TX are formed on one main surface of the piezoelectric substrate 300. The IDT electrode 120 and the ground electrode 322 of the reception filter element RX are formed. In addition, signal input / output electrodes 321 are formed.

The IDT electrode 110 of the transmission filter element TX includes a series IDT electrode connected between the input / output electrodes 311 and a parallel IDT electrode connected between the signal line and the ground.
The IDT electrode 120 of the receiving filter element RX includes a series IDT electrode connected between the input / output electrodes 321 and a parallel IDT electrode connected between the signal line and the ground.
Furthermore, a substantially rectangular annular electrode 330 is formed on one main surface of the piezoelectric substrate 300 so as to surround the IDT electrode 110, the IDT electrode 120, and the like.

By providing such an annular electrode 330 along the outer edge of the piezoelectric substrate 300, the IDT electrode 110, the IDT electrode 120, and the like can be effectively arranged on the inner side using a wide area.
The annular electrode 330 may be formed so as to individually surround the transmission filter element TX and the reception filter element RX. When the annular electrode 330 is formed so as to individually surround the transmission filter element TX and the reception filter element RX, the annular electrode 330 serves as an electromagnetic shield for each filter element. The electromagnetic coupling of the filter elements can be eliminated, and interference between the filter elements can be suppressed.

FIG. 6 shows a circuit board 200 for mounting the piezoelectric substrate 300. On the upper surface of the circuit board 200, a signal input / output conductor terminal 411 of the transmission filter element TX, a grounding conductor terminal 412 of the transmission filter element TX, a signal input / output conductor terminal 421 of the reception filter element RX, a reception filter A plurality of grounding conductor terminals 422 of the element RX are respectively formed.
The signal input / output conductor terminal 411 corresponds to the signal input / output terminal 311 of the piezoelectric substrate 300, the grounding conductor terminal 412 corresponds to the ground electrode 312 of the piezoelectric substrate 300, and the signal input / output conductor terminal 421 corresponds to the piezoelectric substrate 300. The grounding conductor terminal 422 is formed to correspond to the ground electrode 322 of the piezoelectric substrate 300. An annular conductor 430 is formed corresponding to the annular electrode 330 of the piezoelectric substrate 300 so as to surround these terminals.

Although not shown, the annular conductor 430 is connected to a grounding conductor formed inside or on the lower surface of the circuit board 200 through a through conductor. Thereby, the heat generated in the IDT electrode of the transmission filter element can be diffused through the grounding annular electrode 430 formed so as to surround the IDT electrode.
In addition, on the back surface of the circuit board 200, as indicated by broken line hatching in FIG. 6, the back surface signal conductor 212 connected to the signal input / output conductor terminal 411 and the back surface connected to the signal input / output conductor terminal 421 through the via conductors, respectively. A back surface grounding conductor terminal 220 connected to the signal conductor 222 and the grounding conductor terminals 412 and 422 is formed.

The back surface grounding conductor terminal 220 is formed in a large area on the back surface of the circuit board 200 and is common to the grounding conductor terminal 412 of the transmission filter element TX and the grounding conductor terminal 422 of the reception filter element RX. This is the ground terminal. This ground electrode functions as a third ground electrode.
In the surface acoustic wave device of the present invention using the piezoelectric substrate 300 and the circuit substrate 200 as described above, each electrode of the piezoelectric substrate 300 is connected to each conductor terminal of the circuit substrate 200 via a conductor bump, and this ring An electrode 330 is connected to an annular conductor 430 formed on the upper surface of the circuit board 200 so as to be annularly sealed using a brazing material such as solder.

In this way, the surface acoustic wave element 100 in which the transmission filter element TX and the reception filter element RX are formed on one main surface of the piezoelectric substrate can be mounted with the one main surface facing the upper surface of the circuit board 200. it can.
The annular sealing can maintain the airtightness on the operation surface side of the piezoelectric substrate 300, so that the surface acoustic wave element 100 can be stably operated without being affected by the exterior protective material 500 or the like, and its operation Can be stably performed over a long period of time, and a highly reliable surface acoustic wave device can be obtained.

In addition, the inside of the annular electrode 330 and the annular conductor 430 that are hermetically sealed in an annular shape is sealed with, for example, nitrogen gas, which is an inert gas, to effectively deteriorate each electrode and each conductor terminal due to oxidation or the like. Therefore, it is possible to further improve the reliability.
The width of the annular electrode 330 is preferably formed within a range of, for example, 0.05 mm to 0.15 mm in consideration of sealing performance by brazing material such as solder and alignment accuracy. When the width is smaller than 0.05 mm, it becomes difficult to satisfy the sealing performance by solder and the reliability by mechanical stress. In addition, providing the annular electrode 330 with an unnecessarily large width makes it difficult to effectively dispose the transmitting filter element TX and the receiving filter element RX using a large area on the inside thereof. What is necessary is just to set suitably according to the characteristic and specification which are required for a surface acoustic wave apparatus.

In this example, the transmission filter element TX and the reception filter element RX are formed one by one and one annular electrode 330 is formed so as to surround them. However, the transmission electrode disposed inside the annular electrode 330 is formed. A plurality of trust filter elements TX and a plurality of reception filter elements RX may be provided.
Further, as described above, one main surface of the piezoelectric substrate 300 is divided into a plurality of regions, and the transmitting filter element TX and the receiving filter element RX are formed in each region so as to surround them. Also good. In such a case, it is possible to greatly reduce the mutual interference of the transmission signal or the reception signal between the surface acoustic wave device portions surrounded by the annular electrodes 330.

  The IDT electrode 110, the ground electrode 312 and the signal input / output electrode 311 of the transmission filter element TX, and the IDT electrode 120, the ground electrode 322 and the signal input / output electrode 321 of the reception filter element RX are made of a piezoelectric substrate such as lithium tantalate. On the other hand, a metal film such as aluminum is formed on the main surface by a vacuum film formation technique such as sputtering, and then a desired resist pattern is formed using means such as photolithography, and unnecessary portions are etched using the mask as a mask. It is formed by removing.

  For example, 36 ° ± 3 ° Y-cut X-propagation lithium tantalate single crystal, 42 ° ± 3 ° Y-cut X-propagation lithium tantalate single crystal, 64 ° ± 3 ° Y-cut X-propagation niobate A lithium single crystal, a 41 ° ± 3 ° Y-cut X-propagation lithium niobate single crystal, and a 45 ° ± 3 ° X-cut Z-propagation lithium tetraborate single crystal each have a large electromechanical coupling coefficient and a frequency temperature coefficient. Can be suitably used because of its small size.

The thickness of the piezoelectric substrate is preferably about 0.1 mm to 0.5 mm. If the thickness is less than 0.1 mm, the piezoelectric substrate is likely to be cracked, and if it exceeds 0.5 mm, the component size becomes large and it is difficult to achieve miniaturization.
The IDT electrode 110 and the IDT electrode 120 constitute a ladder-type filter element connected in a ladder shape in series and in parallel, thereby realizing a steep and low-loss filter element characteristic.

7 is a sectional view of the surface acoustic wave device formed by joining the surface acoustic wave element on the piezoelectric substrate 300 of FIG. 5 and the circuit substrate 200 of FIG. It is.
The circuit board 200 is manufactured by laminating a plurality of insulating layers, in this example, three insulating layers.
Reference numeral 412 denotes a grounding conductor terminal of the transmission filter element TX formed on the upper surface of the circuit board 200, and reference numeral 211 denotes a transmission-side through conductor formed inside the circuit board 200.

The transmission-side through conductor 211 is formed by connecting a plurality of through conductors 211a in the vertical direction from the upper surface to the lower surface of the circuit board 200 with a conductor layer 211b formed between insulating layers. The transmission side through conductor 211 is connected to the grounding conductor terminal 412 on the upper surface of the circuit board 200, and is connected to the rear surface grounding conductor terminal 220 on the back surface of the circuit board 200.
Reference numeral 422 denotes a grounding conductor terminal of the reception filter element RX formed on the upper surface of the circuit board 200, and reference numeral 221 denotes a reception-side through conductor formed linearly from the upper surface to the back surface of the circuit board 200.

The reception-side through conductor 221 is formed by connecting a plurality of through conductors 221a in the vertical direction from the upper surface to the lower surface of the circuit board 200 with a conductor layer 221b formed between insulating layers. The upper surface of the circuit board 200 is connected to the grounding conductor terminal 422, and the back surface of the circuit board 200 is connected to the rear surface grounding conductor terminal 220.
112 and 122 are conductor bumps, 112 is a transmission filter element TX connection bump, and 122 is a reception filter element RX connection bump.

  As shown in FIG. 7, one main surface of the piezoelectric substrate 300 is arranged to face the upper surface of the circuit board 200, and the ground electrode 312 of the transmission filter element TX and the ground conductor terminal 412 of the circuit board 200 are for transmission. The filter element TX connection bump 112 is connected, and the ground electrode 322 of the reception filter element RX and the ground conductor terminal 422 of the circuit board 200 are electrically connected by the reception filter element RX connection bump 122, respectively. Thus, the surface acoustic wave element 100 is mounted on the upper surface of the circuit board 200.

  Although not shown in FIG. 7, the signal input / output terminal 311 of the transmission filter element TX and the signal input / output conductor terminal of the transmission filter element TX formed on the upper surface of the circuit board 200 are similarly conductor bumps. It is connected. Similarly, the signal input / output terminals of the reception filter element RX and the signal input / output conductor terminals of the reception filter element RX formed on the upper surface of the circuit board 200 are also connected by conductor bumps.

  In this way, the ground electrode 322 of the reception filter element RX is used for grounding the back surface via the reception filter element RX connection bump 122 and the plurality of through conductors 221 formed linearly on the circuit board 200 from the upper surface to the lower surface. The ground electrode 312 of the transmission filter element TX connected to the conductor terminal 220 is connected to the back surface grounding conductor terminal 220 via the transmission filter element TX connection bump 112 and the through conductor 211 formed on the circuit board 200 from the upper surface to the lower surface. Connected to.

  In the example of FIGS. 6 and 7, the back-surface grounding conductor terminal 220 that electrically connects the ground electrode 322 of the reception filter element RX and the ground electrode 312 of the transmission filter element TX on the back surface of the circuit board 200 is provided. However, as shown in FIGS. 17 and 18, in the surface acoustic wave device 1, the ground electrode 322 of the reception filter element RX and the ground electrode 312 of the transmission filter element TX are electrically connected. Alternatively, a plurality of back-surface grounding conductor terminals 220 'may be provided and connected by a ground electrode 230 of a PCB (Printed Circuit Board) of a communication device on which the surface acoustic wave device 1 is mounted.

  The through conductors 211a and 221a can be formed with a diameter of about 0.03 mm to 0.2 mm per one. If the diameter of the through conductor is smaller than 0.03 mm, the connection reliability may be lowered due to a positional deviation with respect to the conductor layers 211b and 221b formed between the insulating layers of the circuit board 200. When the diameter exceeds 0.2 mm, the difference in thermal expansion coefficient between the material of the insulating layer of the circuit board 200, for example, ceramics and the metal through conductor increases, and cracks such as cracks occur in the insulating layer near the through conductor. This may cause a decrease in connection reliability.

Further, when a plurality of linear through conductors 221 are formed and connected to the ground electrode 322 of the reception filter element RX, the plurality of linear through conductors 221 have an interval of about 0.02 mm to 0.2 mm, for example. A small inductance can be achieved with a small area.
For the insulating layer of the circuit board 200, for example, ceramics mainly composed of alumina, glass ceramics that can be sintered at a low temperature, or glass epoxy resins mainly composed of organic materials are used. When ceramics or glass ceramics are used, a green sheet is produced by molding a slurry in which a metal oxide such as ceramics and an organic binder are homogeneously kneaded with an organic solvent, etc., into a sheet shape, for connecting desired wiring patterns and internal conductors. After the via hole (penetrating conductor) pattern is formed, these green sheets are laminated and pressure-bonded so as to be integrally formed and fired.

The conductor pattern formed on each of the insulating layers is formed by combining a metal conductor such as Au, Cu, Ag, Ag-Pd, and W with screen printing or a film forming method such as vapor deposition or sputtering and etching. Each conductor pattern may be plated with Ni, Au, or the like if necessary for good bonding with the surface acoustic wave element 100.
The transmission filter element TX connection bump 112 and the reception filter element RX connection bump 122 are formed of a conductive material such as solder or Au. In the case of forming with solder, for example, by applying cream solder to the ground electrodes 312 and 322 and the input / output electrodes 311 and 321 by screen printing, the conductor bumps can be formed by melting the solder. Further, when gold is formed, for example, a gold bump can be wire-bonded to the ground electrodes 312 and 322 and the input / output electrodes 311, 321 and cut into a short length to form a conductor bump.

Also, the soldering is performed on the grounding conductor terminals 412 and 422 and the signal input / output conductor terminals 411 and 421 of the circuit board 200, and this is used as a conductor bump to connect the ground electrodes 312 and 322 and the signal input / output terminals 311 and 321. Is possible. Alternatively, when connecting with the conductor bumps, crimping may be performed while applying heat or ultrasonic waves, and a reliable and good connection is possible.
Further, in FIG. 7, reference numeral 500 denotes an exterior protective material for protecting the surface acoustic wave element 100 mounted on the circuit board 200. In this example, the surface protective wave element 500 wraps around the side surface of the piezoelectric substrate 300. It is formed to hold 100. The exterior protective material 500 is made of an epoxy resin, a biphenol resin, a polyimide resin, or a resin in which a filler such as alumina, aluminum nitride, or silicon nitride is mixed as a solid filler. Alternatively, it may be Au, Ag, Cu, Sn, Al, Pb, or a metal film such as an alloy containing at least one of them as a main component. The exterior protective material 500 can protect the piezoelectric substrate 300 from mechanical impacts, moisture, chemicals, and the like, so that the highly reliable surface acoustic wave device 1 can be obtained. The exterior protective material 500 may cover all surfaces other than the surface on which the IDT electrodes and the like of the piezoelectric substrate 300 are formed so that the piezoelectric substrate 300 is not exposed. By doing in this way, the tolerance with respect to a mechanical impact is further securable.

FIG. 8 is a circuit diagram of a surface acoustic wave device configured by bonding the surface acoustic wave element on the piezoelectric substrate 300 of FIG. 5 and the circuit board 200 of FIG. The upper half of FIG. 8 shows a circuit constituting the transmission filter element TX, and the lower half shows a circuit constituting the reception filter element RX. Both circuits are grounded by a common back-surface grounding conductor terminal 220.
According to the surface acoustic wave device 1 of the present invention, the ground electrode 322 of the reception filter element RX is connected to the plurality of through conductors 221 provided on the circuit board 200 from the upper surface to the lower surface. Since the ground electrode 312 of the transmission filter element TX is connected to one through conductor 211 provided on the circuit board 200 from the upper surface to the lower surface, a parasitic inductance generated at the ground conductor terminal of the transmission filter element TX. Can be increased.

  Thereby, for the parallel IDT electrodes of the transmission filter element TX, the impedance in the frequency band of the high-frequency filter element, that is, the band overlapping the reception frequency band of the reception filter element RX can be reduced. It is possible to effectively block signals passing through overlapping bands. Therefore, the out-of-band attenuation characteristics on the high frequency side of the transmission filter element TX can be greatly improved.

Further, according to the surface acoustic wave device 1 of the present invention, the ground electrode 322 of the reception filter element RX is connected to the plurality of linear through conductors 221 formed linearly on the circuit board 200 from the upper surface to the lower surface. Therefore, the parasitic inductance generated at the grounding conductor terminal of the reception filter element RX can be reduced.
As a result, for the parallel IDT electrodes of the reception filter element RX, the impedance in the frequency band of the low-pass filter element, that is, the band overlapping the transmission frequency band of the transmission filter element TX can be reduced. It is possible to effectively block signals passing through overlapping bands. Therefore, it is possible to satisfactorily improve the low frequency side out-of-band attenuation characteristic of the reception filter element RX.

  In the above embodiment, the number of ground through conductors of the transmission filter element TX is made smaller than the number of ground through conductors of the reception filter element RX (in the example of FIG. 5, the through conductors of the reception filter element RX). However, the number of through conductors of the transmission filter element TX is one), and the parasitic inductance generated at the grounding conductor terminal of the transmission filter element TX is increased.

However, there is a method in which the shape of the grounding through conductor of the transmission filter element TX is bent into a crank shape along with this or other methods.
FIG. 9 shows an example in which the shape of the grounding through conductor of the transmission filter element TX is changed.
Reference numeral 211 ′ denotes a transmission side through conductor formed inside the circuit board 200. The through conductor 211 ′ is formed by connecting a plurality of through conductors 211a ′ formed by shifting the vertical position from the upper surface to the lower surface of the insulating layer by the conductor layer 211b ′ formed between the insulating layers in the circuit board 200. The upper surface of the circuit board 200 is connected to the grounding conductor terminal 412.

422 is a grounding conductor terminal of the receiving filter element RX formed on the upper surface of the circuit board 200, and 221 'is a plurality of linear through conductors formed linearly from the upper surface to the lower surface of the circuit board 200.
In this manner, the ground electrode 322 of the reception filter element RX is connected to the plurality of linear through conductors 221 ′ formed linearly on the circuit board 200 from the upper surface to the lower surface via the bumps 122, and for transmission. The ground electrode 312 of the filter element TX is a conductor layer 211b formed between the insulating layers in the circuit board 200 with a through conductor 211a 'provided by shifting the vertical position from the upper surface to the lower surface of the circuit board 200 via the bump 112. The surface acoustic wave device 1 shown in FIG. 9 is configured by being connected to a crank-shaped through conductor 211 ′ formed by being connected at a line.

  Since the crank-shaped through conductor 211 'is provided, the parasitic inductance generated in the grounding conductor terminal 312 of the transmission filter element TX can be increased, and thereby the parallel IDT electrodes of the transmission filter element TX can be increased. The impedance in the band overlapping the reception frequency band of the reception filter element RX can be reduced. Therefore, it is possible to effectively block a signal passing through a band that overlaps the reception frequency band, so that the high frequency side out-of-band attenuation characteristic of the transmission filter element TX can be greatly improved.

  In addition, since a plurality of linear through conductors 221 'are provided on the circuit board 200 from the upper surface to the lower surface and connected in parallel, the inductance value can be further reduced, and therefore parasitics generated at the grounding conductor terminal of the reception filter element RX. The inductance can be further reduced, and the out-of-band attenuation characteristics of the reception filter element RX can be further greatly improved.

In the above embodiment, the impedance is increased by increasing the number of the linear through conductors 221 'of the reception filter element RX by increasing the impedance by making the through conductor 211' of the transmission filter element TX into a crank shape. It was. However, as other methods, there are a method of changing the diameter of the grounding through conductor and a method of changing the length of the grounding through conductor.
FIG. 10 is a cross-sectional view showing an example in which the length of the grounding through conductor of the receiving filter element RX is shortened. It is assumed that the circuit board 200 is a module circuit board 200 on which elements other than the piezoelectric substrate 300 are mounted.

211 ″ denotes one transmission-side through conductor formed inside the circuit board 200. The through conductor 211 ″ has the same structure as that shown in FIG.
Reference numeral 221a ″ denotes a short through conductor formed from the grounding conductor terminal of the reception filter element RX formed on the upper surface of the circuit board 200 to the inner layer ground electrode 221c ″.
In this example, a solid inner layer ground electrode 221c ″ is provided on the inner surface of the multilayer circuit board 200, for example, the XX ′ surface shown in FIG. 10, and this inner layer ground electrode 221c ″ is set to a common ground potential anywhere outside this drawing. Connected.

The inner layer ground electrode 221c ″ needs to have a hole at a location where the through conductor 211 ″ passes so as not to contact the through conductor 211 ″ of the transmission filter element TX.
Thus, by connecting the through conductor 221a ″ to the inner layer ground electrode 221c ″, the length thereof can be made shorter than the thickness of the circuit board 200, and the inductance Lg due to the through conductor 221a ″ can be reduced by the transmission filter element. The inductance of the through conductor 211 ″ of TX can be made smaller.

Although not illustrated and described, the diameter of the through conductor of the transmission filter element TX is set to be relatively larger than the diameter of the through conductor of the reception filter element RX within the allowable range of the diameter of the through conductor described above. It is also effective to make it smaller. Specifically, for the purpose of reducing the inductance of the linear through conductor, the through conductor may have a diameter of 0.1 mm or more.
Next, another embodiment of the surface acoustic wave device of the present invention will be described.

FIG. 14 is a plan view showing one principal surface side of the surface acoustic wave element. FIG. 15 is a plan view showing an upper surface of the circuit board 200 on which the surface acoustic wave element is mounted. 16 is a cross-sectional view of the circuit board 200 of FIG. 15 taken along line BB.
In this example, the same members as those shown in FIGS. 5 to 7 are denoted by the same reference numerals, and redundant description will be omitted.

  The difference between this configuration and the configuration shown in FIGS. 5 to 7 is that the ground electrode of the reception filter element RX is formed as a conductor pattern 330 a on the piezoelectric substrate 300, and this conductor pattern 330 a is formed on the annular electrode 330. Is connected. Then, an annular conductor 430 formed on the upper surface of the circuit board 200 and connected to the annular electrode 330 is formed on the back surface of the circuit board 200 via a plurality of through conductors 231 provided on the four sides of the circuit board 200. It is connected to the grounding conductor terminal 220.

This configuration is characterized in that the area of the ground electrode 322 shown in FIG.
With this configuration, it is possible to set the ground inductance Lg2 of the reception filter element RX to a low value by using a large area of the annular electrode 330.
With such a configuration, a smaller surface acoustic wave device can be realized. Further, since the annular electrode 430 is grounded, interference from the outside can be further reduced.

  Instead of the configuration in which the conductor pattern 330a is connected to the annular electrode 330, the ground electrode 322 and the annular electrode 330 of the reception filter element RX are separately formed on the piezoelectric substrate as shown in FIG. A grounding conductor terminal 422 connected to the ground electrode of the receiving filter element RX is formed as a conductor pattern on the circuit board 200 as shown in FIG. 20, and this conductor pattern is connected to the annular conductor 430 on the circuit board 200. You may employ | adopt the structure to do. As shown in FIG. 21, the annular conductor 430 is connected to a ground conductor terminal 220 formed on the back surface of the circuit board 200 through a plurality of through conductors 231 provided on the four sides of the circuit board 200.

In this structure, by using a large area of the annular conductor 430, the ground inductance Lg2 of the reception filter element RX can be set to a low value. Therefore, a smaller surface acoustic wave device can be realized.
The surface acoustic wave device of the present invention having the above-described configuration is suitably used for communication equipment, particularly communication equipment that handles multiband. Such a communication device will be described with reference to FIG.

  FIG. 11 shows a transmission / reception demultiplexing circuit (hereinafter referred to as a duplexer) DPX that separates transmission / reception frequency bands to which the surface acoustic wave device 1 of the present invention including an antenna, a transmission filter element TX, and a reception filter element RX is applied. It is a block diagram which shows the communication apparatus comprised by power amplifier PA, the reception low noise amplifier LNA, the filter element TX 'for transmission between stages, and the filter element RX' for reception between stages. Note that the interstage transmission filter element TX ′ and the interstage reception filter element RX ′ may be fabricated on the same piezoelectric substrate to constitute the surface acoustic wave device 1 ′ of the present invention.

In this communication device, a transmission signal output from a transmission circuit (not shown) is put on a carrier frequency by a mixer, an unnecessary signal is attenuated by a transmission band-pass filter element TX ′, and then transmitted by a transmission power amplifier PA. The signal is amplified and transmitted from the antenna through the duplexer DPX.
In the duplexer DPX, the radio signal pass frequency band of the reception filter element RX is set higher than the radio signal pass frequency band of the transmission filter element TX.

The reception signal received by the antenna passes through the duplexer DPX and is then amplified by the reception low noise amplifier LNA. Thereafter, the unnecessary signal is attenuated by the reception bandpass filter element RX ′, and the carrier frequency is obtained by the mixer (not shown). The signal is separated from the signal and transmitted to a receiving circuit for extracting the signal.
By the configuration of the surface acoustic wave device of the present invention as described above, the parasitic inductance generated in the grounding conductor terminal of the reception filter element RX is reduced, and the parasitic inductance generated in the grounding conductor terminal of the transmission filter element TX is increased. As a result, it is possible to improve the target out-of-band attenuation characteristics, and it is possible to obtain good transmission / reception separation performance as a wireless communication device.

  Note that, in the communication device of the present invention, in order to sufficiently exert the effects of the surface acoustic wave device of the present invention, the surface acoustic wave device 1 includes the transmission filter element TX and the reception filter as in the configuration described so far. It is preferable that both the element RX and the element RX are mounted. As a result, unnecessary signals of the transmission signal and the reception signal can be sufficiently reduced to improve the communication quality, and the transmission filter element TX and the reception filter element RX are integrated to form a small filter. Since the element can be configured, a small and high-quality communication device can be obtained.

  In the surface acoustic wave device and the communication device of the present invention as described above, the low-pass filter element constituted by the low-pass IDT electrode is used as the transmission filter element TX, and the high-pass filter constituted by the high-pass IDT electrode is used. The case where the band-side filter element is used as the reception filter element RX has been described as an example. On the other hand, the low-band side filter element constituted by the low-band side IDT electrode is used as the reception filter element RX, and the high band side is used. A high-pass filter element constituted by IDT electrodes may be used as the transmission filter element TX. Even in this case, the surface acoustic wave device and the communication device exhibit the same effects as described above.

  As an example of a transmission frequency band and a reception frequency band applied to the surface acoustic wave device and the communication device of the present invention, for example, in the case of the CDMA system in the United States, the transmission frequency band is set to 824 MHz to 849 MHz in the Cellular band. The frequency band is set from 869 MHz to 894 MHz, the low-pass filter element is set to the transmit filter element TX, and the high-pass filter element is set to the receive filter element RX. This setting makes it possible to apply as a duplexer used for this communication method. In the PCS (Personal Communication Services) band, the transmission frequency band is changed from 1850 MHz to 1910 MHz, the reception frequency band is changed from 1930 MHz to 1990 MHz, and the low-pass filter element is also received by the transmit filter element TX and the high-pass filter element is received. The filter element RX may be set. In the case of the Japanese CDMA system, the transmission frequency band is set to 887 MHz to 925 MHz, the reception frequency band is set to 832 MHz to 870 MHz, the high-frequency filter element is set as the transmission filter element TX, and the low-frequency filter element is set. By setting the passband using the reception filter element RX, it is possible to apply the duplexer used in this communication method.

  The present invention is not limited to the embodiments described above, and various changes and improvements can be made without departing from the scope of the present invention. For example, the filter element may include a structure such as a DMS (Double Mode SAW) filter element or a lattice filter element. The filter element only needs to include at least one serial IDT electrode and one parallel IDT electrode.

Furthermore, the mounting form for mounting the surface acoustic wave device of the present invention on a mounting substrate such as an electronic circuit module may be arbitrary. Not only the above-mentioned CSP (Chip Size Package) method but also a wire bonding method and a flip chip method. Various forms such as these can be applied.
In addition, in order to improve the isolation between the reception filter element RX and the transmission filter element TX in the circuit board, it is also possible to arrange a matching circuit using meandering phase matching lines, inductors and capacitors. It is. They pass through the transmission filter element TX from the transmission terminal by making the impedance of the reception filter element RX as viewed from the antenna terminal approach infinitely in the band overlapping the transmission frequency band in the reception frequency band. The received filter element RX functions as if it is electrically opened from the phase matching line or the matching circuit composed of the inductor and the capacitor. As a result, the transmission signal can be output from the antenna terminal without increasing the loss.

The surface acoustic wave device shown in FIGS. 7 and 8 was manufactured.
The surface acoustic wave device uses a 38.7 ° Y-cut X-propagation lithium tantalate single crystal substrate as a piezoelectric substrate, and an Al (99% by mass) -Cu (1% by mass) Al alloy is formed on this main surface. The IDT electrodes 110 and 120, the ground electrodes 312 and 322, the input / output electrodes 311 and 321, the wiring electrode that electrically connects them, and the grounding annular electrode 330 were formed.

These electrodes are produced by forming an Al alloy thin film by a sputtering method, performing photolithography using a stepper and coater / developer apparatus, etc., and etching with a RIE (reactive ion etching) apparatus or the like to obtain predetermined patterns. went.
The circuit board is manufactured by laminating a plurality of insulating layers. These insulating layers are made of ceramics whose main component is alumina (dielectric constant 9), and green sheets such as ceramics are prepared. After providing the desired wiring pattern and through conductors, these green sheets are laminated and crimped. This was produced by integrally forming and firing.

Conductor terminals or annular conductors corresponding to the electrodes on the piezoelectric substrate were formed on the upper surface of the circuit board, solder was formed on the conductor terminals and the annular conductor, and the electrodes on the piezoelectric substrate were joined.
The frequency characteristics of the signal attenuation amount of the transmission filter element TX and the signal attenuation amount of the reception filter element RX of the surface acoustic wave device thus manufactured were measured.

The results are shown in the graphs of FIGS. The horizontal axis of the graph represents frequency, and the vertical axis represents attenuation.
FIG. 12 shows frequency characteristics in the comparative example in which Lg1 of the transmission filter element TX and Lg2 of the reception filter element RX are both 0.2 nH by setting the same number of ground through conductors. According to FIG. 12, the signal attenuation amount of the transmission filter element TX in the reception band is 41.2 dB at 893 MHz.

FIG. 13 shows frequency characteristics when Lg1 of the transmission filter element TX is 1.2 nH and Lg2 of the reception filter element RX is 0.2 nH. According to FIG. 13, the signal attenuation amount of the transmission filter element TX in the reception band is 45.9 dB at 893 MHz, and the difference in attenuation amount is greatly improved to 4.7 dB compared to the case of FIG. ing.
The above measurement results show that a transmission filter element and a reception filter element having low loss and sufficient attenuation characteristics outside the band can be realized on one piezoelectric substrate.

It is a figure which shows the equivalent circuit of an IDT electrode. It is a circuit diagram which connected the serial inductance Lg in series with the IDT electrode. 3 is a graph in which the reactance component X of the impedance Z of the circuit of FIG. 2 is plotted on the vertical axis and the frequency is plotted on the horizontal axis. A graph representing the absolute value of each impedance of the parallel IDT electrode and the serial IDT electrode of the first filter element and the parallel IDT electrode and the serial IDT electrode of the second filter element on the vertical axis, the first filter element, It is the figure which synthesize | combined the graph which represented the passage attenuation characteristic of the 2nd filter element on the vertical axis | shaft. 1 is a diagram showing an embodiment of a surface acoustic wave device according to the present invention, and is a plan view of one main surface side of a surface acoustic wave element 100. FIG. 3 is a plan view of the upper surface of a circuit board 200 on which the surface acoustic wave element 100 is mounted. FIG. 6 is a cross-sectional view showing a surface acoustic wave device configured by bonding a surface acoustic wave element on a piezoelectric substrate 300 in FIG. 5 and a circuit board 200 in FIG. 6. 6 is a circuit diagram of a surface acoustic wave device configured by bonding a surface acoustic wave element on a piezoelectric substrate 300 of FIG. 5 and a circuit board 200 of FIG. It is sectional drawing which shows the example which made the shape of the grounding penetration conductor of the filter element TX for transmission into the shape of a crank. It is sectional drawing which shows the example which shortened the length of the grounding penetration conductor of the filter element RX for reception. Communication equipment including antenna, duplexer DPX1 using surface acoustic wave device of the present invention, transmission power amplifier PA, reception low noise amplifier LNA, and interstage surface acoustic wave device 1 'using surface acoustic wave device of the present invention FIG. It is the graph which measured the signal attenuation amount of the filter element TX for transmission, and the signal attenuation amount of the filter element RX for reception. It is the graph which measured the signal attenuation amount of the filter element TX for transmission, and the signal attenuation amount of the filter element RX for reception. FIG. 5 is a diagram showing another embodiment of the surface acoustic wave device of the present invention, and is a plan view of one main surface side of a piezoelectric substrate 300. FIG. 2 is a plan view of the top surface of a circuit board 200 on which a surface acoustic wave element is mounted. FIG. It is sectional drawing in BB of FIG. 3 is a plan view of the upper surface of a circuit board 200 on which the surface acoustic wave element 100 is mounted. FIG. It is sectional drawing in CC of FIG. FIG. 5 is a diagram showing another embodiment of the surface acoustic wave device of the present invention, and is a plan view of one main surface side of a piezoelectric substrate 300. FIG. 1 is a plan view of an upper surface of a circuit board 200 on which a surface acoustic wave device of the present invention is mounted. It is sectional drawing in DD of FIG.

Explanation of symbols

1 Surface acoustic wave device
110 First IDT electrode
120 Second IDT electrode
200 circuit board
211 First through conductor
220 Third ground electrode
221 Second through conductor
300 piezoelectric substrate,
311 First input / output electrode
312 First ground electrode
321 Second input / output electrode
322 Second ground electrode
330 annular electrode is formed,
412 First grounding conductor terminal
422 Second grounding conductor terminal
430 ring conductor
TX first filter element
RX second filter element

Claims (12)

A piezoelectric substrate;
A first filter element including a first input / output electrode, a first ground electrode, and a first IDT electrode formed on one main surface of the piezoelectric substrate;
The formed on the same surface of the piezoelectric substrate, the second input-output electrodes, viewed including the second ground electrode and the second IDT electrode is higher than the passing frequency band pass frequency band of the first filter element A second filter element;
A circuit board for mounting the surface on which the first and second filter elements of the piezoelectric substrate are formed;
On the surface of the piezoelectric substrate on which the first and second filter elements are formed, the first ground electrode and the second ground electrode are formed by being electrically separated,
On the surface of the circuit board on which the piezoelectric substrate is mounted, a first ground conductor terminal to which the first ground electrode is connected, and a second ground conductor terminal to be connected to the second ground electrode Is formed separately,
A third ground electrode is provided on the surface of the circuit board opposite to the surface on which the piezoelectric substrate is mounted or on the inner layer surface of the circuit board,
First and second through conductors connected to the first ground conductor terminal and the second ground conductor terminal and penetrating the circuit board to the position of the third ground electrode, respectively, are provided ,
A series inductance of the first ground electrode, the first ground conductor terminal, and the first through conductor is equal to that of the second ground electrode, the second ground conductor terminal, and the second through conductor. Higher than the series inductance,
A surface acoustic wave device in which an area of the first ground electrode on the piezoelectric substrate is smaller than an area of the second ground electrode on the piezoelectric substrate . A piezoelectric substrate;
A first filter element including a first input / output electrode, a first ground electrode, and a first IDT electrode formed on one main surface of the piezoelectric substrate;
A second input / output electrode, a second ground electrode, and a second IDT electrode formed on the same surface of the piezoelectric substrate, the pass frequency band being higher than the pass frequency band of the first filter element. Two filter elements;
A circuit board for mounting the surface on which the first and second filter elements of the piezoelectric substrate are formed;
On the surface of the piezoelectric substrate on which the first and second filter elements are formed, the first ground electrode and the second ground electrode are formed by being electrically separated,
On the surface of the circuit board on which the piezoelectric substrate is mounted, a first ground conductor terminal to which the first ground electrode is connected, and a second ground conductor terminal to be connected to the second ground electrode Is formed separately,
A third ground electrode is provided on the surface of the circuit board opposite to the surface on which the piezoelectric substrate is mounted or on the inner layer surface of the circuit board,
First and second through conductors connected to the first ground conductor terminal and the second ground conductor terminal and penetrating the circuit board to the position of the third ground electrode, respectively, are provided,
A series inductance of the first ground electrode, the first ground conductor terminal, and the first through conductor is equal to that of the second ground electrode, the second ground conductor terminal, and the second through conductor. Higher than the series inductance,
A surface acoustic wave device in which the number of first through conductors is smaller than the number of second through conductors . A piezoelectric substrate;
A first filter element including a first input / output electrode, a first ground electrode, and a first IDT electrode formed on one main surface of the piezoelectric substrate;
A second input / output electrode, a second ground electrode, and a second IDT electrode formed on the same surface of the piezoelectric substrate, the pass frequency band being higher than the pass frequency band of the first filter element. Two filter elements;
A circuit board for mounting the surface on which the first and second filter elements of the piezoelectric substrate are formed;
On the surface of the piezoelectric substrate on which the first and second filter elements are formed, the first ground electrode and the second ground electrode are formed by being electrically separated,
On the surface of the circuit board on which the piezoelectric substrate is mounted, a first ground conductor terminal to which the first ground electrode is connected, and a second ground conductor terminal to be connected to the second ground electrode Is formed separately,
A third ground electrode is provided on the surface of the circuit board opposite to the surface on which the piezoelectric substrate is mounted or on the inner layer surface of the circuit board,
First and second through conductors connected to the first ground conductor terminal and the second ground conductor terminal and penetrating the circuit board to the position of the third ground electrode, respectively, are provided,
A series inductance of the first ground electrode, the first ground conductor terminal, and the first through conductor is equal to that of the second ground electrode, the second ground conductor terminal, and the second through conductor. Higher than the series inductance,
A surface acoustic wave device in which the first through conductor has a crank shape . The surface acoustic wave device according to claim 3, wherein the second through conductor has a linear shape . A piezoelectric substrate;
A first filter element including a first input / output electrode, a first ground electrode, and a first IDT electrode formed on one main surface of the piezoelectric substrate;
A second input / output electrode, a second ground electrode, and a second IDT electrode formed on the same surface of the piezoelectric substrate, the pass frequency band being higher than the pass frequency band of the first filter element. Two filter elements;
A circuit board for mounting the surface on which the first and second filter elements of the piezoelectric substrate are formed;
On the surface of the piezoelectric substrate on which the first and second filter elements are formed, the first ground electrode and the second ground electrode are formed by being electrically separated,
On the surface of the circuit board on which the piezoelectric substrate is mounted, a first ground conductor terminal to which the first ground electrode is connected, and a second ground conductor terminal to be connected to the second ground electrode Is formed separately,
A third ground electrode is provided on the surface of the circuit board opposite to the surface on which the piezoelectric substrate is mounted or on the inner layer surface of the circuit board,
First and second through conductors connected to the first ground conductor terminal and the second ground conductor terminal and penetrating the circuit board to the position of the third ground electrode, respectively, are provided,
A series inductance of the first ground electrode, the first ground conductor terminal, and the first through conductor is equal to that of the second ground electrode, the second ground conductor terminal, and the second through conductor. Higher than the series inductance,
A surface acoustic wave device in which a cross-sectional area of the first through conductor is smaller than a cross-sectional area of the second through conductor . The first IDT electrode includes a series IDT electrode connected between the first input / output electrodes, and a parallel IDT electrode connected between a signal line and ground,
The said 2nd IDT electrode has a parallel IDT electrode connected between the serial IDT electrode connected between the said 2nd input / output electrodes, and the signal track | line and the earth | ground. A surface acoustic wave device according to claim 1. An annular electrode surrounding the first and second filter elements is formed on the surface of the piezoelectric substrate on which the first and second filter elements are formed.
The surface acoustic wave device according to any one of claims 1 to 6, wherein an annular conductor connected to the annular electrode is formed on a surface of the circuit board on which the piezoelectric substrate is mounted . The annular electrodes are two annular electrodes respectively surrounding the first and second filter elements;
The surface acoustic wave device according to claim 7, wherein the annular conductor is connected to each of the two annular electrodes . The second ground electrode is connected to an annular electrode formed on the surface of the piezoelectric substrate on which the first and second filter elements are formed so as to surround the first and second filter elements. ,
The second grounding conductor terminal is an annular conductor formed so as to be connected to the annular electrode on a surface of the circuit board on which the piezoelectric substrate is mounted. The surface acoustic wave device described. An annular electrode surrounding the first and second filter elements is formed on the surface of the piezoelectric substrate on which the first and second filter elements are formed.
On the surface of the circuit board on which the piezoelectric substrate is mounted, an annular conductor formed to be connected to the annular electrode is provided,
The second grounding conductor terminal is connected to an annular conductor formed on a surface of the circuit board on which the piezoelectric substrate is mounted,
A third through conductor that is connected to the annular conductor instead of the second through conductor or together with the second through conductor and penetrates the circuit board to the position of the third ground electrode is provided. The surface acoustic wave device according to any one of claims 1 to 6 . A communication apparatus comprising the surface acoustic wave device according to any one of claims 1 to 10 and a transmission circuit including the surface acoustic wave device as a circuit element. 11. A communication device comprising the surface acoustic wave device according to claim 1 and a receiving circuit having the surface acoustic wave device as a circuit element.

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