JP5010256B2 - Surface acoustic wave device and communication device including the same - Google Patents

Description

The present invention relates to a communication apparatus having a wave device and which elastic surface. The surface acoustic wave device of the present invention includes surface acoustic wave elements such as surface acoustic wave filter elements and surface acoustic wave resonators, and is used in mobile communication devices such as mobile phones.

  2. Description of the Related Art Conventionally, a surface acoustic wave filter has been widely used as a frequency selection (band pass) filter used in an RF (Radio Frequency) stage of a mobile communication device such as a mobile phone or a car phone. In addition to downsizing, the surface acoustic wave filter is required to cope with a wide band, to cope with a higher frequency of a communication carrier, to improve the attenuation outside the pass band, and to improve the insertion loss of the pass band.

Recently, in order to reduce the size, weight, and cost of mobile communication devices, the number of parts used has been reduced, and a new function has been required for the surface acoustic wave filter.
For example, there is a demand for an unbalanced-balanced conversion function such that the surface acoustic wave filter can be configured as an unbalanced input-balanced output type or a balanced input-unbalanced output type.
Here, the balanced input or the balanced output means that a signal is input or output as a potential difference between two signal lines, and the signals in each signal line have the same amplitude and the opposite phase. On the other hand, unbalanced input or unbalanced output means that a signal is input or output as the potential of one signal line with respect to the ground potential.

  Many conventional surface acoustic wave filters are unbalanced input-unbalanced output type surface acoustic wave filters (hereinafter also simply referred to as “unbalanced surface acoustic wave filters”). For this reason, when a circuit or an electronic component connected to the subsequent stage of the unbalanced surface acoustic wave filter is a balanced input type, an unbalanced-balanced state is present between the unbalanced surface acoustic wave filter and the subsequent stage. A converter (hereinafter referred to simply as “balun”) is required. Further, when the circuit or electronic component in the previous stage of the unbalanced surface acoustic wave filter is a balanced output type, a balun is required between the previous stage and the unbalanced surface acoustic wave filter.

  Therefore, in order to add a balun function to the unbalanced surface acoustic wave filter itself, this unbalanced surface acoustic wave filter is provided with an unbalanced-balance conversion function. Further, a balanced input-unbalanced output type surface acoustic wave filter having a balanced-unbalanced conversion function (hereinafter also referred to as “balanced type surface acoustic wave filter”) has been put into practical use. In addition, it has been proposed to improve the balance of the balanced surface acoustic wave filter.

For example, a multi-electrode surface acoustic wave filter 900 shown in FIG. 32 has three IDT (Inter Digital Transducer) electrodes 901, 902, and 903 on a piezoelectric substrate along the propagation direction of the surface acoustic wave. It is arranged. In addition, reflector electrodes 904 and 905 are disposed at positions where the three IDT electrodes 901, 902 and 903 are sandwiched (see Patent Document 1).
The IDT electrode 902 excites a surface acoustic wave by applying an electric field from the unbalanced input terminal 906 to one of a pair of comb-like electrodes arranged to face each other. The excited surface acoustic wave is propagated to the IDT electrodes 901 and 903 located on both sides of the IDT electrode 902. A signal is output from an output signal terminal 907 connected to one of the comb-like electrodes of the IDT electrode 901, and a signal is output from an output signal terminal 908 connected to one of the comb-like electrodes of the IDT electrode 903. Thus, the surface acoustic wave filter 900 can output a balanced signal.

With this structure, the surface acoustic wave filter 900 can have an unbalanced input-balanced output conversion function as a balun.
The surface acoustic wave filter 910 shown in FIG. 33 has three IDT electrodes 911, 912, and 913 arranged close to each other along the propagation direction of the surface acoustic wave, and reflector electrodes 914 and 914 are disposed at positions sandwiching these IDT electrodes. 915 is disposed (see Patent Document 2).

In the IDT electrode 912, one of a pair of comb-like electrodes forming the IDT electrode 912 is divided into two. The comb-shaped electrodes divided into two are respectively connected to the balanced signal terminals 916 and 917 so that they are acoustically connected in cascade and electrically connected in series.
Each of the IDT electrodes 911 and 913 has a shape whose polarity is reversed with respect to the IDT electrode 912 and is connected to one unbalanced signal terminal 918.

With such a configuration, the surface acoustic wave filter 910 can have an unbalance-balance conversion function as a balun. Further, the impedance (about 200Ω) on the balanced signal terminals 916, 917 side can have about four times the impedance (about 50Ω) on the unbalanced signal terminal 918 side.
In the longitudinally coupled resonator type surface acoustic wave filter described in Patent Document 3, among the three IDT electrodes arranged in the propagation direction of the surface acoustic wave, the IDT electrodes arranged at the center are made into an even pair, thereby achieving a balance. The structure which improves is proposed.

In the surface acoustic wave filter 920 shown in FIG. 34, three IDT electrodes 921, 922, and 923 are arranged close to each other along the propagation direction of the surface acoustic wave, and reflector electrodes 924 are disposed at positions sandwiching these IDT electrodes. An electrode pattern 941 of a surface acoustic wave element provided with 925 is provided.
In the IDT electrode 922, one of a pair of comb-like electrodes forming the IDT electrode 922 is divided into two. The comb-shaped electrodes divided into two are respectively connected to the balanced signal terminals 926 and 927 so as to be acoustically connected in cascade and electrically connected in series.

Each of the IDT electrodes 921 and 923 has a shape whose polarity is reversed with respect to the IDT electrode 922, and both the IDT electrodes 921 and 923 are connected to the unbalanced signal terminal 928.
A reactance (capacitance) component 929 is connected to the wiring connecting the IDT electrode 922 and the balanced signal terminal 926.

  In addition, the surface acoustic wave filter 930 shown in FIG. 35 has IDT electrodes 931, 932, and 933 arranged close to each other between the IDT electrodes 921, 923 and the unbalanced signal terminal 928 of the surface acoustic wave filter 920 described above. An electrode pattern 942 of a surface acoustic wave element in which reflector electrodes 934 and 935 are disposed so as to sandwich these IDT electrodes is provided. The electrode pattern 942 of the surface acoustic wave element and the electrode pattern 941 of the surface acoustic wave element are connected in cascade (see Patent Document 4).

The IDT electrode 932 is connected to the unbalanced signal terminal 928, the IDT electrode 931 is connected to the IDT electrode 921 via a connection wiring, and the IDT electrode 933 is connected to the IDT electrode 923 via a connection wiring. .
In this way, the surface acoustic wave filter 930 can further increase the attenuation outside the passband as compared with the surface acoustic wave filter 920.

In addition to the above, an example in which an IDT electrode is formed to be asymmetric with a virtual axis in the center perpendicular to the propagation direction of the surface acoustic wave sandwiched as in Patent Document 5 is also known.
JP-A-6-204781 JP 11-97966 A JP 2002-84164 A JP 2004-96244 A JP 2003-46369 A

  The surface acoustic wave filter as described above has been proposed. Recently, however, improvement of the amplitude balance and the phase balance within the passband has been demanded. Alternatively, it is measured as a potential difference between two output signal lines. Here, “amplitude balance” is a value that represents the degree of equality of the amplitudes of the signals flowing in each signal line, and is unnecessary because the amplitudes are approximated as the amplitudes are equal. The signal is canceled and approaches 0 dB, and the amplitude balance is improved. The phase balance is a value indicating the degree to which the phase between two input or output signal lines is inverted by 180 degrees. The closer the phase difference is to 180 degrees, the more the phase balance is , Close to 0 degrees, the phase balance is improved.

  Incidentally, the surface acoustic wave element (surface acoustic wave filter) 900 (see FIG. 32) disclosed in Patent Document 1 is formed so that the phases of the signals output from the IDT electrodes 901 and 903 are opposite to each other. ing. In the IDT electrodes 901 to 903, the balance in the surface acoustic wave device 900 can be adjusted by changing the electrode finger pitch or changing the arrangement interval between these IDT electrodes.

However, such a structure has a problem that the degree of balance tends to deteriorate.
In the surface acoustic wave element (surface acoustic wave filter) 910 (see FIG. 33) disclosed in Patent Document 2, the polarities of the electrode fingers adjacent to the IDT electrode 912 and the IDT electrode 911, the IDT electrode 912, and the IDT The polarity of the electrode finger adjacent to the electrode 913 is different. For this reason, since the parasitic capacitances generated at the balanced signal terminals 916 and 917 are different, there is a problem that the balance of the surface acoustic wave element 910 is deteriorated.

Furthermore, in the surface acoustic wave element disclosed in Patent Document 3, for example, when a LiTaO ₃ single crystal substrate is used as the piezoelectric substrate, the amplitude balance is about 1.2 dB and the phase balance is about 11 degrees. Can only be obtained. Therefore, this surface acoustic wave device cannot obtain a sufficient balance.
Further, the effect of the surface acoustic wave element (surface acoustic wave filter) 930 (see FIG. 35) disclosed in Patent Document 4 was verified.

FIG. 36 is a graph showing the relationship between the insertion loss and the frequency of the surface acoustic wave element 930 and the surface acoustic wave element 930 ′.
Here, as the surface acoustic wave element 930 ′ as a comparative example, as shown in FIG. 37, a surface acoustic wave element 930 ′ that does not add the reactance (capacitance) component 929 in the surface acoustic wave element 930 in FIG.

In FIG. 36, the horizontal axis represents frequency (unit: MHz), and the vertical axis represents insertion loss (unit: dB). Further, the broken line in the figure shows the characteristic curve of the insertion loss of the surface acoustic wave element 930 shown in FIG. 35, and the solid line in the figure shows the insertion loss of the surface acoustic wave element 930 ′ shown in FIG. A characteristic curve is shown.
According to the characteristic curve (dashed line) of the surface acoustic wave element 930, the ripple in the passband is increased as compared with the surface acoustic wave element 930 ′. This is because, in the surface acoustic wave device 930, the capacitance component is connected in parallel as the reactance component 929 to the balanced signal terminal 926, and the capacitance component is added in parallel to one of the balanced signals. It is thought that it was because of.

FIG. 38 is a graph showing the relationship between the frequency of the surface acoustic wave element 930 and the surface acoustic wave element 930 ′ and VSWR (Voltage Standing Wave Ratio).
In FIG. 38, the horizontal axis represents frequency (unit: MHz), and the vertical axis represents VSWR. Further, the broken line in the figure shows the characteristic curve in the surface acoustic wave element 930 shown in FIG. 35, and the solid line in the figure shows the characteristic curve in the surface acoustic wave element 930 ′ shown in FIG. .

According to the characteristic curve (dashed line) of the surface acoustic wave element 930, it can be seen that the VSWR is degraded as compared with the surface acoustic wave element 930 ′. This is presumably because the reflection characteristic of the surface acoustic wave has changed because a capacitance component (reactance component 929) is added in parallel to one of the balanced signals.
FIG. 39 (a) is a graph showing the amplitude balance in the vicinity of the passband of the surface acoustic wave element 930 and the surface acoustic wave element 930 ′, and FIG. 39 (b) shows the surface acoustic wave element 930 and the surface acoustic wave. 6 is a graph showing the degree of phase balance in the vicinity of the pass band of the wave element 930 ′.

  In FIG. 39A, the horizontal axis represents frequency (unit: MHz), and the vertical axis represents amplitude balance (unit: dB). In FIG. 39 (b), the horizontal axis represents frequency (unit: MHz), and the vertical axis represents phase balance (unit: degree). Also, the broken line in the figure shows the characteristic curve of the surface acoustic wave element 930 shown in FIG. 35 (the upper and lower broken lines are due to the fact that the reactance component 929 is swung at two levels), and the solid line in the figure is 37 shows a measurement result obtained by the surface acoustic wave element 930 ′ shown in FIG.

According to FIG. 39A, the surface acoustic wave element 930 has a value far from the value of 0 dB as compared with the surface acoustic wave element 930 ′, and the amplitude balance is not good. This is presumably because in the surface acoustic wave element 930, even when a capacitance component (reactance component 929) is added in parallel to the balanced signal, the deviation in amplitude cannot be corrected.
Further, according to FIG. 39B, the surface acoustic wave element 930 has a value far from the value of 0 degrees as compared with the surface acoustic wave element 930 ′, and the phase balance is not good. This is presumably because in the surface acoustic wave element 930, even if a capacitance component is added in parallel to the balanced signal, the phase shift cannot be corrected.

As shown in FIGS. 36, 38 and 39, the surface acoustic wave element 930 can be inserted loss, VSWR, amplitude balanced even if a capacitance component as a reactance component 929 is connected in parallel to one balanced signal terminal 926. There is no significant improvement in degree and phase balance, but rather some characteristics are worse.
Therefore, the present invention uses a surface acoustic wave element that functions as a high-quality surface acoustic wave filter that reduces the deterioration of the amplitude balance and the phase balance of the surface acoustic wave element and reduces the insertion loss and VSWR . It is an object of the present invention to provide a surface acoustic wave device and a communication device using the same.

In order to achieve the above object, a surface acoustic wave device of the present invention includes a surface acoustic wave element that excites a surface acoustic wave by an IDT electrode formed on a piezoelectric substrate, and a mounting substrate on which the surface acoustic wave element is mounted. The surface acoustic wave element includes a piezoelectric substrate and three or more pairs of comb-like electrodes formed along the propagation direction of the surface acoustic wave propagating on the piezoelectric substrate. One comb of a pair of comb-like electrodes constituting an IDT electrode disposed on both sides of the IDT electrode formed in the center among the odd number of IDT electrodes. A pair of first and second reference potential terminals is connected to the tooth-like electrode, and a pair of IDT electrodes disposed on both sides of the IDT electrode formed in the center among the odd number of IDT electrodes. Of the other comb-like electrode , It is connected to the unbalanced signal terminal, among the odd number of IDT electrode, the IDT electrode formed on the center, one of the pair of comb-shaped electrodes with being divided into two parts, being the two divided A first balanced signal terminal is connected to one of the comb-like electrodes, and a second balanced signal terminal is connected to the other, and the first and second reference potential terminals are IDTs formed in the center. It is formed asymmetrically with respect to a virtual central axis that passes through the center of the electrode and is orthogonal to the propagation direction, and the mounting substrate faces the first and second reference potential terminals. And first and second grounding conductors, and first and second through-grounding conductors connected so as to penetrate the mounting substrate from the first and second grounding conductors. The first and second grounding conductors are connected to the virtual central axis. The first and second through grounding conductors are formed symmetrically, and are formed differently in at least one of diameter, cross-sectional shape and number so as to be formed asymmetrically with respect to the virtual central axis. is there.

According to this configuration, by arranging the first and second reference potential terminals asymmetrically, an inductance component is connected to the reference potential terminal of the surface acoustic wave element. For this reason, the same effect as when the matching circuit is connected to the connection terminal is produced, and the insertion loss and VSWR of the surface acoustic wave element can be reduced.
Of the odd number of IDT electrodes, one of the pair of comb-like electrodes constituting the IDT electrode formed at the center is divided into at least two and connected to each of the divided comb-like electrodes. When the terminals are connected, the surface acoustic wave device in which the surface acoustic wave element is mounted on the mounting substrate can have a function of an unbalance-balance converter. Further, since the parasitic capacitance is not added to the connection terminal side of the surface acoustic wave device, the amplitude balance and the phase balance of the surface acoustic wave element are hardly deteriorated.

  At least one surface acoustic wave resonator may be connected between the connection terminal and the odd number of IDT electrodes. As a result, the surface acoustic wave device has a structure in which a plurality of surface acoustic wave elements are connected in cascade, so that signals outside the desired passband can be further attenuated. As a result, the surface acoustic wave device having these surface acoustic wave elements can favorably extract a signal in a desired pass band.

In addition, it is preferable that at least one of the position, shape, and area of the reference potential terminal is different so as to be formed asymmetrically with respect to the virtual central axis.
In addition, it is preferable that the magnitude of the inductance component generated in each of the first and second reference potential terminals is 0.1 to 0.3 nH.
Moreover, it is preferable that the difference in the magnitude of the inductance component generated in each of the first and second reference potential terminals is 0.1 to 0.2 nH.

Further, the surface acoustic wave device, wherein arranged on both sides of the odd number of IDT electrodes, be those having a reflector electrode having a plurality of electrode fingers formed in a direction perpendicular to the propagation direction May be.
The surface acoustic wave device of the present invention includes the surface acoustic wave element having the above-described configuration and a mounting substrate on which the surface acoustic wave element is mounted. The mounting substrate includes the first and second references. The first and second grounding conductors arranged opposite to the potential terminal are arranged.

It said first and second grounding conductors, Ru der those formed asymmetrically with respect to the imaginary central axis.

  According to this configuration, in the surface acoustic wave device in which the surface acoustic wave element is mounted on the mounting substrate, the matching circuit is connected to the connection terminal by arranging the first and second grounding conductors asymmetrically. It produces almost the same effect as the state that is being done. As a result, the amplitude balance and the phase balance of the surface acoustic wave device are less deteriorated, and as a result, the insertion loss and VSWR of the surface acoustic wave device can be reduced.

Further, Oite the configuration of the surface acoustic wave device of the present invention has first and second through ground conductors connected so as to penetrate the mounting substrate from said first and second grounding conductor the first and second through grounding conductor, to so that is formed asymmetrically with respect to the imaginary central axis, the diameter, at least one of the cross-sectional shape and number are formed differently.
The communication device of the present invention includes at least one of a reception circuit and a transmission circuit including the surface acoustic wave device described above. According to this communication device, the surface acoustic wave device of the present invention can be suitably applied to a high-frequency circuit such as a mobile communication device.

  For example, a high-frequency signal transmitted from a mobile phone has an unnecessary signal removed by a surface acoustic wave filter, is amplified by a power amplifier, passes through a duplexer including the isolator and the surface acoustic wave device of the present invention, and then from the antenna. Radiated. On the other hand, the high-frequency signal received by the antenna is separated by the branching filter, amplified by the low-noise amplifier, the unnecessary signal is removed by the surface acoustic wave filter, and then re-amplified by the amplifier and converted to a low-frequency signal by the mixer. Converted.

  As described above, by applying the surface acoustic wave device of the present invention to a duplexer of a communication device, a communication device having good high frequency characteristics can be provided.

In the following drawings, the size of each electrode, the distance between the electrodes, the number of electrode fingers, the interval, and the like are schematically drawn for explanation.
FIG. 1 is a plan view showing a first embodiment of a surface acoustic wave device according to the present invention. FIG. 2 is a plan view showing each layer in the mounting substrate on which the surface acoustic wave element is mounted, and FIG. 3 is a cross-sectional view of the stacked mounting substrate.

The surface acoustic wave device S1 has a structure in which the surface acoustic wave element 1 shown in FIG. 1 is mounted on a mounting substrate 100 shown in FIG.
In addition, the “main surface” in this specification refers to the surface of the piezoelectric substrate 19 formed in a plate shape and an electrode formation surface on which an electrode pattern or the like is formed.
On the piezoelectric substrate 19, the direction axis in which the surface acoustic wave propagates is defined as the X axis, and the direction axis perpendicular to the X axis is defined as the Y axis.

As shown in FIG. 1, the surface acoustic wave element 1 includes an electrode pattern N of the surface acoustic wave element, connection terminals 11, 12, and 13 for signal input / output on the main surface of the piezoelectric substrate 19. , Second reference potential terminals 14 and 15 (hereinafter, the connection terminals 11 to 13 and the reference potential terminals 14 and 15 are collectively referred to as “terminals 11 to 15”).
The first and second reference potential terminals 14 and 15 to which a reference potential serving as a reference for driving is applied to the surface acoustic wave element 1 uses a ground potential as the reference potential in the following description of the embodiment. Therefore, the first and second reference potential terminals 14 and 15 are referred to as “first and second ground terminals 14 and 15”.

  In the electrode pattern N of the surface acoustic wave element, three electrodes 3, 4 and 5 (referred to as IDT (Inter Digital Transducer) electrodes) having a pair of comb shaped electrodes are arranged in the X-axis direction. It is arranged by. Each comb-like electrode has a plurality of electrode fingers formed along the Y-axis direction. The IDT electrode is configured by engaging electrode fingers of a pair of comb-like electrodes. Reflector electrodes (hereinafter also referred to as “reflectors”) 6 and 7 having a plurality of electrode fingers formed along the Y-axis direction are disposed on both sides of the three IDT electrodes 3 to 5. Yes.

Among the IDT electrodes 3 to 5, in the IDT electrode 4 disposed in the center, one of the pair of comb-like electrodes is divided into two. Each of the two divided comb-like electrodes of the IDT electrode 4 is connected to connection terminals 12 and 13 as balanced signal terminals.
In the IDT electrodes 3 and 5 arranged on both sides, one of the pair of comb-like electrodes is connected to a connection terminal 11 as an unbalanced signal terminal. The other of the pair of comb-like electrodes of the IDT electrode 3 and the reflector 6 are connected to the grounding terminal 14, and the other of the pair of comb-like electrodes of the IDT electrode 5 and the reflector 7 are connected to the grounding terminal 15. Has been.

The piezoelectric substrate 19 is formed of a material having a large piezoelectric property such as a lithium tantalate single crystal, a lithium niobate single crystal, or a lithium tetraborate single crystal. By using this material, the electromechanical coupling coefficient of the piezoelectric substrate 19 can be increased, and the group delay time temperature coefficient can be decreased.
In addition, if these materials having piezoelectricity are subjected to a treatment for generating oxygen defects or a solid solution treatment of Fe or the like, the pyroelectric effect generated in the piezoelectric substrate 19 can be remarkably reduced. As a result, electrostatic breakdown that occurs in the process of forming the electrode fingers of the IDT electrodes 3 to 5 on the main surface of the piezoelectric substrate 19 can be prevented, and the reliability of the surface acoustic wave device 1 can be kept good. .

The thickness of the piezoelectric substrate 19 is preferably about 0.1 to 0.5 mm. For this reason, the piezoelectric substrate 19 does not become brittle as when the thickness is less than 0.1 mm, and conversely, when the thickness is greater than 0.5 mm. The material cost does not increase and the surface acoustic wave element 1 does not increase in size.
The electrode patterns N and terminal patterns (hereinafter referred to as various electrode patterns and terminal patterns formed on the main surface of the piezoelectric substrate 19) of the surface acoustic wave element formed on the piezoelectric substrate 19 are simply referred to as “various electrodes. The pattern is also referred to as Al or Al alloy (for example, Al—Cu system, Al—Cu) using a thin film forming method such as vapor deposition, sputtering, or CVD (Chemical Vapor Deposition method). It is manufactured by forming a metal such as (Ti-based).

Further, on various electrode patterns, Si, SiO _2, SiNx, protective film for a semiconductor or an insulator of Al ₂ O ₃ or the like as a material (not shown) covers. This protective film can prevent electrical short-circuiting caused by conductive foreign substances adhering to various electrode patterns, and can improve power resistance. This protective film can be formed using a method of forming a thin film such as a vapor deposition method or a sputtering method after the IDT electrodes 3 to 5 and the reflectors 6 and 7 are formed.

The IDT electrodes 3 to 5 can suitably excite surface acoustic waves by setting the electrode thickness to about 0.1 μm to 0.5 μm.
On the other hand, the mounting substrate 100 on which the surface acoustic wave element 1 is mounted includes an upper surface layer 101 on the surface to be joined to face the surface acoustic wave element 1 and through holes as via holes, as shown in FIGS. The first through conductor layer 102 in which the conductor 120 is formed, the internal electrode pattern layer 103, the second through conductor layer 104 in which the through conductor 140 is formed, the lower electrode pattern layer 105, and the lower dielectric layer 106 It has a laminated structure.

  On the upper surface layer 101, the connection pad conductors 111, 112, 113 formed at positions facing the connection terminals 11, 12, 13 and the positions facing the ground terminals 14, 15, respectively. Grounding conductors 114 and 115 are disposed (hereinafter, the connecting pad conductors 111 to 113 and the grounding conductors 114 and 115 are collectively referred to as “conductors 111 to 115”).

The first through conductor layer 102 includes a through conductor 120 connected to the connection pad conductors 111 to 113 and through ground conductors 124 and 125 respectively connected to the ground conductors 114 and 115 (hereinafter collectively referred to as generic names). In this case, a through conductor 120 is provided.
An internal electrode pattern 130 connected to the through conductor 120 is formed on the internal electrode pattern layer 103.

A through conductor 140 connected to the internal electrode pattern 130 is formed in the second through conductor layer 104.
On the lower electrode pattern layer 105, a lower electrode pattern 150 connected to the through conductor 140 is formed.
The mounting substrate 100 is configured by laminating a plurality of insulating layers formed of an insulating material. Specifically, each of the layers 101 to 106 of the mounting substrate 100 is formed of an insulating material such as ceramics or glass ceramics. And the green sheet which shape | molded the slurry which homogeneously knead | mixed metal oxides, such as ceramics, and the organic binder with the organic solvent etc. in the sheet form is produced, and patterns, such as a penetration conductor, are formed. These green sheets are stacked, pressure-bonded, integrally formed and fired, whereby the mounting substrate 100 is manufactured.

The conductors 111 to 115, the internal electrode pattern 130, and the bottom electrode pattern 150 are conductive materials such as Au, Cu, Ag, Ag-Pd, and W, and use a film forming method such as screen printing or etching, or a conductive layer. The material is laminated in order from the lower layer using an electrolytic plating method or an electroless plating method, and formed into a desired pattern.
The through conductors 120 and 140 are made of a conductive material such as Ag, and penetrate through a predetermined position of the green sheet using a method such as micro drilling, punching, laser processing, die punching, or photolithography. A hole is formed. The through conductors 120 and 140 are formed by filling these through holes with a conductive paste such as Ag.

On the conductors 111 to 115, for mounting (bonding) the surface acoustic wave element 1 to the mounting substrate 100, a melting method such as solder paste, Au—Sn paste, or the like using a printing method such as screen printing or a dispenser. A joining layer is formed of a conductor.
The bonding layer is formed on the conductors 111 to 115 of the mounting substrate 100, but may be formed on the terminals 11 to 15 of the surface acoustic wave element 1. At this time, the bonding layer can be formed on the terminals 11 to 15 in the same manner as described above.

Hereinafter, a method for mounting the surface acoustic wave element 1 on the mounting substrate 100 will be described.
In the surface acoustic wave element 1, a rectangular frame-shaped annular electrode (not shown) is formed so as to surround various electrode patterns such as the IDT electrodes 3 to 5 and the reflectors 6 and 7 on the main surface of the piezoelectric substrate 19. Has been.
On the other hand, an annular conductor (not shown) is continuously formed on the mounting substrate 100 for mounting the surface acoustic wave element 1 at a position facing the annular electrode on the surface acoustic wave element 1. .

  When the surface acoustic wave element 1 is mounted on the mounting substrate 100, the main surface side of the piezoelectric substrate 19 in the surface acoustic wave element 1 is mounted face-down on the upper surface layer 101 of the mounting substrate 100. That is, the main surface of the piezoelectric substrate 19 in the surface acoustic wave element 1 and the upper surface layer 101 of the mounting substrate 100 are arranged to face each other. Then, the connection terminals 11 to 13 and the ground terminals 14 and 15 are bonded to the connection pad conductors 111 to 113 and the ground conductors 114 and 115, respectively, by the bonding layer, so that the surface acoustic wave device 1 is mounted. Mounting on the circuit board 100 is completed. With this structure, the surface acoustic wave element 1 mounted on the mounting substrate 100 can be electrically connected to other circuit members connected to the mounting substrate 100.

Further, the annular electrode on the surface acoustic wave element 1 is bonded to the annular conductor on the mounting substrate 100 by the bonding layer. As a result, the IDT electrodes 3 to 5 and the reflectors 6 and 7 are sealed in the space surrounded by the main surface of the piezoelectric substrate 19, the upper surface layer 101 of the mounting substrate 100 and the annular electrode.
Next, the outer periphery of the surface acoustic wave element 1 that has been mounted on the mounting substrate 100 is sealed with resin. This is provided in order to prevent high-humidity air from entering the sealed space and to increase the mechanical strength of the surface acoustic wave device S1. The resin used here is a material such as a thermosetting resin such as an epoxy resin or a polyimide resin, a thermoplastic resin such as a polyphenylene sulfide resin, an ultraviolet curable resin, or a low-melting glass. And this sealing resin is hardened after apply | coating on the surface acoustic wave element 1 using the potting method or the printing method.

In this manner, the surface acoustic wave device S1 is manufactured by mounting the surface acoustic wave element 1 on the mounting substrate 100.
The mounting structure of the surface acoustic wave device of the present invention is not limited to the above-described embodiment. For example, a surface acoustic wave device that does not have a sealing structure surrounded by an annular electrode as described above may be used.

By the way, as shown in FIG. 1, the grounding terminal 14 and the grounding terminal 15 of the surface acoustic wave element 1 pass through the center of the IDT electrode 4 provided in the center and are in the Y-axis direction orthogonal to the propagation direction. Are arranged asymmetrically with respect to a virtual central axis A (hereinafter also simply referred to as the A axis) provided in
Further, the grounding conductor 114 and the grounding conductor 115 of the mounting substrate 100 corresponding to the grounding terminal 14 and the grounding terminal 15 are also arranged asymmetrically with respect to the A ′ axis, as shown in FIG. The through-grounding conductor 124 and the through-grounding conductor 125 corresponding to the grounding terminal 14 and the grounding terminal 15 are also arranged asymmetrically with respect to the A ′ axis.

The A ′ axis of the mounting substrate 100 shown in FIG. 2 coincides with the A axis of the surface acoustic wave element 1 shown in FIG. 1 when the surface acoustic wave element 1 is mounted on the mounting board 100. It is an axis to do.
The surface acoustic wave device S1 formed by mounting the surface acoustic wave element 1 on the mounting substrate 100 has a function of an unbalance-balance converter.
Further, the grounding terminals 14 and 15 are arranged asymmetrically with respect to the A axis, and the grounding conductors 114 and 115 and the through-grounding conductors 124 and 125 are arranged asymmetrically with respect to the A ′ axis. With this arrangement, as shown in the equivalent circuit diagram of FIG. 4, inductance components L <b> 1 and L <b> 2 are added to the grounding terminals 14 and 15 of the surface acoustic wave element 1. The value of L1 is preferably from 0.1 nH to 0.3 nH, and the value of L2 is also preferably from 0.1 nH to 0.3 nH. The absolute value | L1-L2 | of the difference between L1 and L2 is preferably 0.1 nH or more and 0.2 nH or less. When the absolute value | L1-L2 | of the difference is smaller than 0.1 nH, an inductance component is connected to the grounding terminal of the surface acoustic wave element, and a matching circuit is connected to the connecting terminal. The same effect is produced, and the effect that the insertion loss and VSWR of the surface acoustic wave element can be reduced becomes insufficient. If the absolute value of the difference | L1-L2 | is greater than 0.2 nH, the inductance component connected to the grounding terminal of the surface acoustic wave element becomes too large, and the degree of balance deteriorates.

This circuit configuration produces the same effect as when a matching circuit is connected to the connection terminals 12 and 13. That is, the insertion loss of the surface acoustic wave element 1 can be reduced and the VSWR can be made close to 1.
Since the parasitic capacitance is not added to the connection terminals 12 and 13 side, the amplitude balance and the phase balance of the surface acoustic wave device 1 are not deteriorated.

FIG. 5 is a plan view showing a first modification of the surface acoustic wave element according to the first embodiment.
In the surface acoustic wave element 1a according to this modification, the grounding terminal 14a connected to the IDT electrode 3 and the reflector 6 is connected to the IDT electrode 5 and the reflector 7 as compared with the surface acoustic wave element 1 shown in FIG. Compared to the grounding terminal 15 connected, it has a larger area.
The surface acoustic wave device mounted with the surface acoustic wave element 1a is further different in size in the wiring paths of the grounding terminals 14a and 15 by increasing the ratio of the areas of the grounding terminals 14a and 15. An inductance component can be added. Thereby, the degree of balance of the surface acoustic wave device having the surface acoustic wave element 1a is hardly deteriorated, and as a result, the insertion loss and VSWR of the surface acoustic wave device can be reduced.

FIG. 6 is a plan view showing a second modification of the surface acoustic wave element according to the first embodiment.
The surface acoustic wave element 1b has a shape in which a surface acoustic wave resonator B is connected between the connection terminal 11 and the electrode pattern N of the surface acoustic wave element in the surface acoustic wave element 1 shown in FIG. ing.
The surface acoustic wave resonator B is formed along one or more IDT electrodes provided with a plurality of electrode fingers formed along the Y-axis direction and on both sides of the IDT electrode, and formed along the Y-axis direction. And a reflector electrode having a plurality of electrode fingers. With this shape, the surface acoustic wave resonator B generates one or more mode resonances.

  By connecting the surface acoustic wave resonator B in series with the electrode pattern N, the anti-resonance frequency of the surface acoustic wave resonator B matches the anti-resonance frequency of the surface acoustic wave element 1b. Since the degree of matching is improved, the insertion loss in the passband is greatly reduced. Further, by making the anti-resonance frequency of the surface acoustic wave resonator B substantially coincide with the cutoff frequency on the high frequency side of the surface acoustic wave element 1b, the frequency characteristics of the surface acoustic wave element 1b are caused by the surface acoustic wave resonator B. Since an attenuation pole is generated, the amount of attenuation outside the passband can be further increased.

Therefore, the surface acoustic wave device having the surface acoustic wave element 1b can further reduce the deterioration of the balance within the pass band, and can further reduce the insertion loss and the VSWR.
In the embodiment shown in FIG. 6, the surface acoustic wave resonator B is connected in series to the electrode pattern N, but may be connected in parallel.
FIG. 7 is a plan view showing a third modification of the surface acoustic wave element according to the first embodiment.

In the surface acoustic wave element 1c, surface acoustic wave resonators C1 and C2 are provided between the electrode pattern N of the surface acoustic wave element and the connection terminals 12 and 13 in the surface acoustic wave element 1 shown in FIG. It has a connected shape.
The surface acoustic wave resonators C1 and C2 are respectively arranged on one or more IDT electrodes each having a plurality of electrode fingers formed along the Y-axis direction, and on both sides of the IDT electrodes, and along the Y-axis direction. And a reflector electrode having a plurality of formed electrode fingers.

With this configuration, the surface acoustic wave device 1c can reduce the deterioration of the balance within the pass band, and can further reduce the insertion loss and the VSWR.
In the embodiment shown in FIG. 7, the surface acoustic wave resonators C1 and C2 are connected in series to the electrode pattern N. However, the surface acoustic wave resonators C1 and C2 are connected to the electrode pattern N. May be connected in parallel.

FIG. 8 is a plan view showing a fourth modification of the surface acoustic wave element according to the first embodiment.
A surface acoustic wave element 1d according to this modification has an electrode pattern D of a surface acoustic wave element in which insertion reflectors 8d and 9d are inserted in the configuration of the electrode pattern N of the surface acoustic wave element shown in FIG. Yes.
The electrode pattern D of the surface acoustic wave element is between the IDT electrodes (between the IDT electrodes 3 and 4 and between the IDT electrodes 4 and 5) of the electrode pattern N of the surface acoustic wave element shown in FIG. The insertion reflectors 8d and 9d having a plurality of electrode fingers that are long in the Y-axis direction are arranged. The insertion reflectors 8d and 9d are formed such that the distance between the centers of adjacent electrode fingers is gradually narrowed from both ends toward the center.

  This surface acoustic wave element 1d adjusts the period of the multi-coupled standing wave mode generated from the surface acoustic wave excited by the IDT electrode 4 by changing the electrode finger pitch of the insertion reflectors 8d and 9d. The frequency to be filtered can be controlled. For this reason, the surface acoustic wave device having the surface acoustic wave element 1d can obtain excellent electrical characteristics with a wider band and lower loss.

FIG. 9 is a plan view showing a fifth modification of the surface acoustic wave element according to the first embodiment.
The surface acoustic wave element 1e according to this modification includes ground terminals 16e and 17e connected to the IDT electrodes 3 and 5 as compared with the surface acoustic wave element 1 shown in FIG. Is formed at a symmetrical position.
On the other hand, the ground terminals 14e and 15e connected to the reflector electrodes 6 and 7 are formed at asymmetric positions with respect to the A axis.

In the surface acoustic wave element 1e, electrode patterns other than the ground terminals 14e and 15e are arranged symmetrically with respect to the A axis.
The inductance component is connected to the grounding terminals 14e and 15e of the surface acoustic wave element 1e. As in the case described above with reference to FIG. 4, the same operation as when the matching circuit is connected to the connection terminals 12 and 13 is produced on the equivalent circuit of the surface acoustic wave element 1 e. For this reason, the insertion loss and VSWR of the surface acoustic wave element can be reduced. Further, since the parasitic capacitance is not added to the connection terminals 12 and 13, the amplitude balance and the phase balance of the surface acoustic wave device 1e are not deteriorated. Therefore, the balance of the surface acoustic wave device having the surface acoustic wave element 1e can be further improved.

Below, the structure of the modification of the mounting board | substrate 100 shown in FIG. 2 is demonstrated.
FIG. 10 is a plan view showing each layer according to the first modification of the mounting substrate shown in FIG.
In the mounting substrate 100a according to this modification, the area of the grounding conductor 114a is formed larger than that of the mounting substrate 100 shown in FIG. The through-ground conductor 124a connected to the ground conductor 114a is also formed with a larger diameter (that is, a cross-sectional area) than the through-ground conductor 124 in FIG.

  By increasing the ratio of the areas (cross-sectional areas) of the grounding conductors 114a and 115 and the through-grounding conductors 124a and 125, the ratio of inductances generated in the grounding conductors 114a and 115 can be increased. Accordingly, since the parasitic capacitance is prevented from being added to the connection terminals 12 and 13 of the surface acoustic wave device, the balance can be kept good. Therefore, the surface acoustic wave device having the mounting substrate 100a can further reduce the insertion loss and the VSWR.

FIG. 11 is a plan view showing each layer according to the second modification of the mounting substrate shown in FIG.
In the second modification, like the mounting substrate 100b shown in FIG. 11, the portion corresponding to the grounding conductor 124a in the mounting substrate 100a shown in FIG. In the form, it is formed as two).

In this mounting substrate 100b, as a result, the through-grounding conductor 124b and the through-grounding conductor 125 are formed with different numbers (and consequently, cross-sectional areas) with respect to the A axis. The substantially same effect as the mounting substrate 100a shown can be obtained.
As shown in FIG. 11, one of the plurality of through grounding conductors 124 b may be arranged at a position symmetrical to the through grounding conductor 125 with respect to the A ′ axis.

  As described above, in the mounting substrates 100, 100a, and 100b shown in FIGS. 2, 10, and 11, the grounding conductors 114, 114a, and 114b with respect to the grounding conductor 115, and the through-grounding with respect to the A ′ axis. The surface acoustic wave device having the mounting substrate 100 (100a, 100b) is inserted as a result of making the arrangement of the through-grounding conductors 124, 124a, 124b with respect to the conductor 125 asymmetrical or providing a difference in cross-sectional area. Loss and VSWR can be reduced.

FIG. 12 is a plan view showing a second embodiment of the surface acoustic wave element included in the surface acoustic wave device of the present invention. FIG. 13 is a plan view showing each layer in the mounting substrate used in the surface acoustic wave device.
The surface acoustic wave element 2 has an electrode pattern N of the surface acoustic wave element of the surface acoustic wave element 1 and an electrode pattern F of the surface acoustic wave element connected in cascade.

  The electrode pattern F of the surface acoustic wave element is arranged on the main surface of the piezoelectric substrate 19 along the X-axis direction, and includes three IDTs having a plurality of electrode fingers formed along the Y-axis direction. Electrodes 21, 22, and 23 are provided. The electrode pattern F is provided with reflectors 24 and 25 each having a plurality of electrode fingers formed on the both sides of the IDT electrodes 21 to 23 and formed along the Y-axis direction.

In the electrode pattern F of the surface acoustic wave element, the IDT electrode 21 and the reflector 24 are connected to the grounding terminal 26, and the IDT electrode 23 and the reflector 25 are connected to the grounding terminal 27.
On the other hand, as shown in FIG. 13, the mounting substrate 200 on which the surface acoustic wave element 2 is mounted has an upper surface layer 101 on the surface to be bonded to the surface acoustic wave element 2 and a through conductor 120 as a via hole. The formed first through conductor layer 102, the internal electrode pattern layer 103, the second through conductor layer 104 in which the through conductor 140 is formed, the lower electrode pattern layer 105, and the lower dielectric layer 106 are laminated. It has a structure.

  On the upper surface layer 101 of the mounting substrate 200, connection pad conductors 111, 112, 113 are arranged at positions facing the connection terminals 11, 12, 13, and at positions facing the ground terminals 14, 15. The grounding conductors 114 and 115 are disposed. The grounding conductors 116 and 117 are arranged at positions facing the grounding terminals 26 and 27. The grounding conductors 114 to 117 are joined to the through conductors 124 to 127 formed through the first through conductor layer 102 of the mounting substrate 200.

With this structure, the surface acoustic wave element 2 can be electrically connected to other circuit members via the mounting substrate 200.
By the way, as shown in FIG. 12, the grounding terminals 14 and 15 of the surface acoustic wave element 2 are disposed asymmetrically with respect to the A axis passing through the center of the IDT electrode 4 provided at the center.
Further, as shown in FIG. 13, the grounding conductors 114 and 115 of the mounting substrate 200 corresponding to the grounding terminals 14 and 15 are also arranged asymmetrically with respect to the A ′ axis. The through-ground conductors 124 and 125 corresponding to 14 and 15 are also arranged asymmetrically with respect to the A ′ axis.

The surface acoustic wave device S2 in which the surface acoustic wave element 2 is mounted on the mounting substrate 200 has a function of an unbalance-balance converter.
Further, by arranging the grounding terminals 14 and 15, the grounding conductors 114 and 115, and the through-grounding conductors 124 and 125 asymmetrically, different inductance components are provided to the grounding terminals 14 and 15 of the surface acoustic wave device 2. Will be connected.

For this reason, the insertion loss and VSWR of the surface acoustic wave element 2 can be reduced as described with reference to FIG. Further, since the parasitic capacitance is not added to the connection terminals 12 and 13 side, the amplitude balance and the phase balance of the surface acoustic wave element 2 are not deteriorated. Therefore, the characteristics of the surface acoustic wave device S2 can be improved.
In addition to the above, the surface acoustic wave element 2 has a structure in which the electrode pattern N and the electrode pattern F of the surface acoustic wave element are connected in cascade, so that a signal outside a desired pass band can be further attenuated. As a result, the surface acoustic wave device having the surface acoustic wave element 2 can separate and extract signals in a desired pass band satisfactorily.

FIG. 14 is a plan view showing a first modification of the surface acoustic wave element according to the second embodiment.
In the surface acoustic wave element 2g according to this modification, the grounding terminal 14g connected to the IDT electrode 3 and the reflector 6 is connected to the IDT electrode 5 and the reflector 7 as compared with the electrode pattern N of the surface acoustic wave element of FIG. Compared with the grounding terminal 15 connected to, the area is very large.
The surface acoustic wave device mounted with the surface acoustic wave element 2g further increases the area ratio of the grounding terminals 14g and 15 that are asymmetric with respect to the A axis, thereby further increasing the wiring path of the grounding terminals 14g and 15 to the wiring path. Largely different inductance components can be added. As a result, the degree of balance of the surface acoustic wave device having the surface acoustic wave element 2g is less deteriorated, and as a result, the insertion loss and VSWR of the surface acoustic wave device can be reduced.

FIG. 15 is a plan view showing a second modification of the surface acoustic wave element according to the second embodiment.
The surface acoustic wave element 2h has a shape in which a surface acoustic wave resonator H is connected between the connection terminal 11 and the electrode pattern F of the surface acoustic wave element in the surface acoustic wave element 2 shown in FIG. ing.
The surface acoustic wave resonator H is formed along one or more IDT electrodes provided with a plurality of electrode fingers formed along the Y-axis direction and on both sides of the IDT electrode, and formed along the Y-axis direction. And a reflector electrode having a plurality of electrode fingers. With this structure, the surface acoustic wave resonator H generates one or more mode resonances.

Since this surface acoustic wave element 2h has a shape in which a surface acoustic wave resonator H is connected, connection terminals 11, 12, 13 for input signals (or output signals) and input / output electrodes of IDT electrodes Can be easily matched in impedance.
Further, in the frequency characteristics of the surface acoustic wave element 2h, an attenuation pole is generated by the surface acoustic wave resonator H, so that the amount of attenuation outside the passband can be further improved.

Therefore, the surface acoustic wave device having the surface acoustic wave element 2h can further reduce the deterioration of the balance within the pass band, and can further reduce the insertion loss and the VSWR.
The surface acoustic wave resonator H is connected in series to the electrode pattern F in the embodiment shown in FIG. 15, but may be connected in parallel to the electrode pattern F.
FIG. 16 is a plan view showing a third modification of the surface acoustic wave element according to the second embodiment.

The surface acoustic wave element 2i according to this modification has a shape in which surface acoustic wave resonators I1 and I2 are connected between the electrode pattern N and the connection terminals 12 and 13, respectively.
Each of the surface acoustic wave resonators I1 and I2 is arranged on one or more IDT electrodes each having a plurality of electrode fingers formed along the Y-axis direction and on both sides of the IDT electrode, and along the Y-axis direction. And a reflector electrode having a plurality of formed electrode fingers.

With this configuration, the surface acoustic wave element 2i can reduce the deterioration of the balance within the passband, and can further reduce the insertion loss and the VSWR.
In the embodiment shown in FIG. 16, the surface acoustic wave resonators I1 and I2 are connected in series to the electrode pattern N. However, the surface acoustic wave resonator I1 is connected to the electrode pattern N. , I2 may be connected in parallel.

FIG. 17 is a plan view showing a fourth modification of the surface acoustic wave element according to the second embodiment.
The surface acoustic wave element 2j includes an electrode pattern J1 of a surface acoustic wave element in which insertion reflectors 8j and 9j are inserted into the configuration of the electrode pattern N of the surface acoustic wave element shown in FIG. The pattern F includes a surface acoustic wave element electrode pattern J2 having a shape in which insertion reflectors 28j and 29j are inserted.

  The electrode pattern J1 of the surface acoustic wave element is formed between the IDT electrodes (between the IDT electrodes 3 and 4 and between the IDT electrodes 4 and 5) of the electrode pattern N of the surface acoustic wave element shown in FIG. Insertion reflectors 8j and 9j each having a plurality of electrode fingers formed along the direction are arranged. The insertion reflectors 8j and 9j are formed such that the distance between the centers of the adjacent electrode fingers is gradually narrowed from both ends toward the center.

  Further, the electrode pattern J2 of the surface acoustic wave element is formed between the IDT electrodes (between the IDT electrodes 22 and 21 and between the IDT electrodes 22 and 23) of the electrode pattern F of the surface acoustic wave element shown in FIG. Insertion reflectors 28j and 29j each having a plurality of electrode fingers formed along the axial direction are arranged. The insertion reflectors 28j and 29j are formed such that the distance between the centers of adjacent electrode fingers is gradually narrowed from both ends toward the center.

  The surface acoustic wave element 2j adjusts the period of the multiple coupled standing wave mode generated from the surface acoustic wave excited by the IDT electrode 4 by changing the electrode finger pitch of the insertion reflectors 8j and 9j. Therefore, the filtering frequency can be controlled by the resonance phenomenon of the standing wave mode. For this reason, the surface acoustic wave device having the surface acoustic wave element 2j can obtain good electrical characteristics with a wider band and lower loss.

FIG. 18 is a plan view showing a fifth modification of the surface acoustic wave element according to the second embodiment.
In the surface acoustic wave element 2k according to this modification, the grounding terminal 14k is connected to the reflector 6 and the grounding terminal 16k is connected to the IDT electrode 3 as compared with the surface acoustic wave element 2 shown in FIG. The reflector 7 is connected to a ground terminal 15k, and the IDT electrode 5 is connected to a ground terminal 17k. The ground terminals 14k and 16k have a larger area than the ground terminals 15k and 17k.

The surface acoustic wave element 2k further improves the balance of the surface acoustic wave device having the surface acoustic wave element 2k by arranging electrode patterns other than the grounding terminals 14k to 17k symmetrically with respect to the A axis. can do.
Below, the structure of the modification of the mounting board | substrate 200 shown in FIG. 13 is demonstrated.
FIG. 19 is a plan view showing each layer of the first modified example on the mounting substrate of the second embodiment shown in FIG.

In the mounting board 200g according to this modification, the diameter (cross-sectional area) of the grounding conductor 114g is formed larger than that of the grounding conductor 114 of the mounting board 200 shown in FIG. The through-ground conductor 124g connected to the ground conductor 114g is also formed with a larger diameter (cross-sectional area) than the through-ground conductor 124.
That is, the ratio of the diameters (cross-sectional areas) of the grounding conductors 114g and 115 and the ratio of the diameters (cross-sectional areas) of the through-grounding conductors 124g and 125 are increased. Thereby, the inductance generated in the grounding conductor 114g and the through-grounding conductor 124g and the inductance generated in the grounding conductor 115 and the through-grounding conductor 125 can be easily controlled. As a result, it is possible to suppress the addition of parasitic capacitance to the connection terminals 12 and 13 of the surface acoustic wave device and maintain a good balance, and the surface acoustic wave device having the mounting substrate 200g is Insertion loss and VSWR can be reduced.

FIG. 20 is a plan view showing each layer of the second modified example on the mounting substrate of the second embodiment shown in FIG.
In the mounting board 200h shown in FIG. 20, a portion corresponding to the grounding conductor 124g in the mounting board 200g shown in FIG. 19 is formed as a plurality of through-grounding conductors 124h (two in this embodiment). Yes.

With this configuration, the mounting substrate 200h is formed so that the number of the through-grounding conductors 124h and the through-grounding conductors 125 are different from each other with respect to the A ′ axis. Similar effects can be obtained.
As shown in FIG. 20, one of the plurality of through-grounding conductors 124h is preferably arranged at a position symmetrical to the through-grounding conductor 125 with respect to the A ′ axis. .

  As described above, the mounting boards 200, 200g, and 200h as shown in FIGS. 13, 19, and 20 correspond to the grounding conductors 114, 114g, and 114h corresponding to the grounding conductor 115 and the through-grounding conductor 125. In the through-ground conductors 124, 124g, 124h, the arrangement is made asymmetric with respect to the A ′ axis and the difference in the cross-sectional area results in the elastic surface having the mounting substrate 200 (200g, 200h). The wave device can reduce insertion loss and VSWR.

In the surface acoustic wave elements 1, 1a to 1e, 2, 2g to 2k described above, the grounding terminals (14, 15), the grounding conductors (114, 115), and the through-grounding conductors provided for grounding are provided. The various electrode patterns except (124, 125) are preferably arranged symmetrically with respect to the A axis and the A ′ axis.
The surface acoustic wave device of the present invention including the surface acoustic wave element described above can be suitably applied to a high-frequency circuit such as a mobile communication device.

FIG. 21 is a block circuit diagram showing the high-frequency circuit 90 of the mobile phone.
The unnecessary signal is removed from the high frequency signal transmitted from the cellular phone by the surface acoustic wave filter 91, amplified by the power amplifier 92, and then the demultiplexer 94 equipped with the isolator 93 and the surface acoustic wave device of the present invention. And radiated from the antenna 99.
The high frequency signal received by the antenna 99 is separated by the branching filter 94, amplified by the low noise amplifier 95, the unnecessary signal is removed by the surface acoustic wave filter 96, and then re-amplified by the amplifier 97 to be mixed by the mixer. At 98, it is converted to a low frequency signal.

As described above, by applying the surface acoustic wave device of the present invention having the surface acoustic wave element described above to the duplexer 94, the insertion loss and the VSWR can be reduced without degrading the amplitude balance and the phase balance. A duplexer 94 that functions as a reduced high-quality surface acoustic wave filter can be provided. As a result, a high frequency circuit 90 having good characteristics can be obtained.
In addition, implementation of this invention is not limited to the said form. For example, referring to FIG. 1, the IDT electrode 4 in the center is divided into at least two of a pair of comb-like electrodes, and each of the divided comb-like electrodes has a connection terminal. 12 and 13 are connected, and each of the IDT electrodes 3 and 5 disposed on both sides of the central IDT electrode 4 is connected with a connection terminal 11 on one comb-like electrode. These connection terminals 11, 12, and 13 have various shapes such as a circular shape, an elliptical shape, a triangular shape, a quadrangular shape, a pentagonal shape or more that are formed larger than the wiring. The thing of a magnitude | size and a shape can be used. Also, use of various sizes and shapes such as circular, elliptical, triangular, quadrangular, and pentagonal or higher polygonal shapes that are approximately the same size as the wiring it can. Furthermore, it is also possible to use a cross formed in substantially the same width as the wiring.

Examples of the surface acoustic wave device of the present invention will be described below.
The surface acoustic wave device S1 in which the surface acoustic wave element 1 shown in FIG. 1 is mounted on the mounting substrate 100 shown in FIG. 2 will be specifically described.
Here, a surface acoustic wave device S1 of PCS (Personal Communication Service) specification having a center frequency in the 1800 MHz band used for a mobile communication device was produced.

First, a 38.7 ° Y-cut X-propagation LiTaO ₃ single crystal was used for the base substrate. The “base substrate” is a substrate before dicing (cutting) into each piezoelectric substrate 19.
Various electrode patterns such as IDT electrodes 3 to 5, reflector electrodes 6 and 7, connection wirings, terminals 11 to 15, etc. formed on each piezoelectric substrate 19 of the base substrate are formed as follows. It was formed by photolithography using a projection exposure machine (stepper) or RIE (Reactive Ion Etching) apparatus.

This base substrate was subjected to ultrasonic cleaning with acetone, IPA (isopropyl alcohol) or the like to remove organic components.
Next, the base substrate was sufficiently dried by a clean oven, and then metal films to be various electrode patterns were deposited. For the formation of the metal film, an Al (99 mass%)-Cu (1 mass%) alloy was used as the material of the metal film using a sputtering apparatus. The thickness of the metal film at this time was about 0.16 μm.

  Next, a photoresist layer having a thickness of about 0.5 μm was formed on the metal film by spin coating. Then, patterning into a desired shape is performed by a reduction projection exposure apparatus (Step and Repeat Exposure Systems) (stepper), and an unnecessary portion of the photoresist layer is dissolved with an alkaline developer by a developing apparatus to express a desired pattern. I let you. Thereafter, the metal film was etched by an RIE apparatus to complete the patterning. In this way, various electrode patterns of the surface acoustic wave device 1 of the present invention were obtained on the base substrate.

Next, a SiO ₂ film having a thickness of about 0.02 μm was formed as a protective film on a region where various electrode patterns were formed using a CVD (Chemical Vapor Deposition) apparatus.
Thereafter, a photoresist layer is formed on the surface of the base substrate on which various electrode patterns are formed, and patterning is performed by photolithography to form a flip-chip window opening in the photoresist layer, such as an RIE apparatus. The window opening was formed by etching. Thereafter, a metal film containing Al as a main component was formed on the photoresist layer on the lower surface of the base substrate using a sputtering apparatus. The thickness of the metal film at this time was about 1.0 μm. Thereafter, the photoresist layer and the unnecessary Al metal film were simultaneously removed by a lift-off method. Then, an electrode for forming a bonding layer for flip-chip mounting the surface acoustic wave element 1 on an external circuit board or the like was formed in the window opening portion.

Next, a flip-chip bonding layer made of an Au material was formed on the electrode pad using a bump bonding apparatus. The bonding layer had a diameter of about 80 μm and a thickness of about 30 μm.
Next, the base substrate was diced along the dividing line (dicing line), and divided into individual surface acoustic wave elements 1 as chips.

  Next, the mounting substrate 100 was produced. Each of the layers 101 to 106 of the mounting substrate 100 is configured by laminating a plurality of insulating layers formed of a material such as ceramics or glass ceramics as an insulating material. And the green sheet which shape | molded the slurry which homogeneously knead | mixed metal oxides, such as ceramics, and the organic binder with the organic solvent etc. in the sheet form was produced, and patterns, such as the penetration conductors 120 and 140, were formed. Then, these green sheets were laminated and pressure-bonded, integrally formed and baked to produce a mounting substrate 100.

Thereafter, each chip was placed and fixed on the mounting substrate 100 by a flip chip mounting apparatus with the formation surface of the terminals 11 to 15 as the lower surface. As the mounting substrate 100, a 2.5 × 2.0 mm square laminated structure in which ceramic layers were laminated in multiple layers was used. Next, baking was performed in an N ₂ atmosphere.
Thus, the surface acoustic wave device S1 including the surface acoustic wave element 1 shown in FIG. 1 and the mounting substrate 100 shown in FIG. 2 was produced.

Of course, the surface acoustic wave devices having the surface acoustic wave elements 1a to 1e, 2, 2g to 2k and the mounting substrates 100a, 100b, 200, 200g, and 200h can be manufactured by the same method as described above.
Next, various frequency characteristics of the surface acoustic wave device of the present invention were measured.
24 to 26 described below, the frequency characteristics of each surface acoustic wave device were measured under the following conditions.

  In the following measurement, the surface acoustic wave device S1 in which the surface acoustic wave element 1 (see FIG. 1) is mounted on the mounting substrate 100 (see FIG. 2) was used. The surface acoustic wave device S1 adjusts the positions where the grounding terminal 14, the grounding conductor 114 and the through-grounding conductor 124 are arranged, and the magnitude of the inductance component generated at the grounding terminals 14 and 15 of the surface acoustic wave device S1. Were adjusted to L1 and L2, respectively. Here, numerical values L1 = 0.1 nH and L2 = 0.18 nH were set. This numerical value satisfies 0.1 ≦ L1 ≦ 0.3 nH, 0.1 ≦ L2 ≦ 0.3 nH, and 0.1 ≦ | L1−L2 | ≦ 0.2 nH.

On the other hand, as a comparative example, a surface acoustic wave device P in which a surface acoustic wave element 1p (see FIG. 22) is mounted on a mounting substrate 100p (see FIG. 23) was used.
In the surface acoustic wave element 1p shown in FIG. 22, the grounding terminals 14p and 15 are arranged in a symmetrical position and shape with respect to the A axis as compared with the surface acoustic wave element 1.
In the mounting substrate 100p shown in FIG. 23, the grounding conductor 114p and the grounding conductor 115 are arranged in a symmetrical position and shape with respect to the A ′ axis as compared with the mounting substrate 100, and the through-grounding conductor 124p The through-ground conductor 125 is arranged in a symmetrical position and shape.

  In the following measurement, a multiport network analyzer (“E5071A” manufactured by Agilent Technologies) is used as a measuring device, a 0 dBm signal is input at a frequency of 1640 to 2140 MHz, and the surface acoustic wave device S1, The surface acoustic wave device P was measured. The number of samples of each surface acoustic wave device S1 and surface acoustic wave device P was 30.

In the graphs of FIGS. 24 to 26, the solid line indicates the filter characteristic of the surface acoustic wave device S1 of the present invention, and the broken line indicates the filter characteristic of the surface acoustic wave device P of the comparative example.
FIG. 24 is a graph showing the relationship between the frequency and the insertion loss of the surface acoustic wave devices S1, P.
According to FIG. 24, the surface acoustic wave device S1 of the present invention had an insertion loss of about 1.97 dB when the frequency was 1947 MHz. On the other hand, the surface acoustic wave device P of the comparative example had an insertion loss of about 1.99 dB when the frequency was 1947 MHz (and 1941 MHz).

Further, according to FIG. 24, the surface acoustic wave device S1 of the present invention has an average insertion loss improved by about 0.02 dB on average compared with the surface acoustic wave device P of the comparative example at a frequency of about 1930-1960 MHz. It was.
Therefore, it can be said that the surface acoustic wave device S1 of the present invention including this surface acoustic wave element 1 can improve the insertion loss in the pass band. This means that an inductance component is added to the grounding terminals 14 and 15 of the surface acoustic wave element 1 on the equivalent circuit of the surface acoustic wave element 1, and the matching circuit is connected to the connection terminals 12 and 13. This is thought to be due to the same effect as the case.

FIG. 25 is a graph showing the relationship between the frequency of the surface acoustic wave devices S1, P and the VSWR.
According to FIG. 25, in the surface acoustic wave device S1 of the present invention, compared with the surface acoustic wave device P of the comparative example, the VSWR in the pass band of the filter characteristics was reduced overall. In particular, between about 1915 MHz and 1955 MHz, the VSWR decreased by an average of about 0.1.

Therefore, it can be said that the surface acoustic wave device S1 of the present invention can reduce the VSWR in the passband by this configuration. This is considered to be because an inductance component was added to the grounding terminal of the surface acoustic wave device S1.
FIG. 26 (a) is a graph showing the relationship between the frequency and the degree of amplitude balance of the surface acoustic wave devices S1, P, and FIG. 26 (b) is a graph showing the relationship between the frequency and the degree of phase balance. is there.

According to FIG. 26 (a), the surface acoustic wave device S1 of the present invention brings the amplitude balance closer to "0 dB" when the frequency is between about 1900 MHz and 2000 MHz, compared to the surface acoustic wave device P of the comparative example. I was able to.
Further, according to FIG. 26 (b), the surface acoustic wave device S1 of the present invention has a phase balance of "0 degree" when the frequency is between about 1910 MHz and 2000 MHz as compared with the surface acoustic wave device P of the comparative example. I was able to approach.

Therefore, it can be said that the surface acoustic wave device S1 of the present invention was able to improve the amplitude balance and the phase balance in the pass band. This is because when a matching circuit is connected to the connection terminals 12 and 13 by adding an inductance component whose value is adjusted to the ground terminals 14 and 15 of the surface acoustic wave element 1. This is thought to be due to the same effect.
29 to 31 described below, the frequency characteristics of each surface acoustic wave device were measured under the following conditions.

  In the following measurement, the surface acoustic wave device S2 in which the surface acoustic wave element 2 (see FIG. 12) is mounted on the mounting substrate 200 (see FIG. 13) was used. The surface acoustic wave device S2 adjusts the positions where the grounding terminal 14, the grounding conductor 114 and the through-grounding conductor 124 are arranged, and the magnitude of the inductance component generated at the grounding terminals 14 and 15 of the surface acoustic wave device S2. Were adjusted to L1 and L2, respectively. Here, numerical values L1 = 0.1 nH and L2 = 0.18 nH were set.

On the other hand, as a comparative example, a surface acoustic wave device Q in which a surface acoustic wave element 2q (see FIG. 27) is mounted on a mounting substrate 200q (see FIG. 28) was used.
In the surface acoustic wave element 2q shown in FIG. 27, compared to the surface acoustic wave element 2, the ground terminals 14q and 15 are arranged in a symmetrical shape and position with respect to the A axis.
In the mounting board 200q shown in FIG. 28, the grounding conductor 114q and the grounding conductor 115 are arranged in a symmetrical shape and position with respect to the A axis as compared with the mounting board 200, and the through-grounding conductor 124q and the through-hole conductor The ground conductor 125 is arranged in a symmetrical shape and position.

In the following measurement, a multiport network analyzer (“E5071A” manufactured by Agilent Technologies) is used as a measuring device, a 0 dBm signal is input at a frequency of 780 to 960 MHz, and the measurement point is set to an elastic surface under the condition of 800 points. Wave devices S2 and Q were measured. The number of samples of each surface acoustic wave device S2, Q was 30.
In the graphs of FIGS. 29 to 31, the solid line indicates the filter characteristic of the surface acoustic wave device S2 of the present invention, and the broken line indicates the filter characteristic of the surface acoustic wave device Q of the comparative example.

FIG. 29 is a graph showing the relationship between the frequency and the insertion loss of the surface acoustic wave devices S2, Q.
According to FIG. 29, the surface acoustic wave device S2 of the present invention had an insertion loss of about 1.64 dB when the frequency was 887 MHz. On the other hand, the surface acoustic wave device Q of the comparative example had an insertion loss of about 1.65 dB when the frequency was 887 MHz.

Therefore, the surface acoustic wave device S2 of the present invention has an average insertion loss of about 0.01 dB lower than that of the surface acoustic wave device Q of the comparative example at a frequency of about 870 to 892 MHz.
Therefore, it can be said that the surface acoustic wave device S2 of the present invention including the surface acoustic wave element 2 can reduce the insertion loss in the pass band. This is because the matching circuit is connected to the connection terminals 12 and 13 because the inductance component whose value has been adjusted is additionally connected to the ground terminals 14 and 15 of the surface acoustic wave element 2. This is thought to be due to the same effect as the case.

FIG. 30 is a graph showing the relationship between the frequency of the surface acoustic wave devices S2, Q and the VSWR.
According to FIG. 30, in the surface acoustic wave device S2 of the present invention, the VSWR in the pass band of the filter characteristics is reduced as compared with the surface acoustic wave device Q of the comparative example. In particular, between about 870 MHz and 898 MHz, the average VSWR was reduced by about 0.03.

Therefore, it can be said that the surface acoustic wave device S2 of the present invention can reduce the VSWR in the passband by this configuration. This is considered to be because an inductance component is added to the grounding terminal of the surface acoustic wave device S2, and almost the same function as that in the state where the matching circuit is connected to the connection terminals 12 and 13 works. .
FIG. 31 (a) is a graph showing the relationship between the frequency and the degree of amplitude balance of the surface acoustic wave devices S2, Q, and FIG. 31 (b) is a graph showing the relationship between the frequency and the degree of phase balance. is there.

According to FIG. 31 (a), the surface acoustic wave device S2 of the present invention has an amplitude balance of "0 dB" when the frequency is between about 865 MHz and 910 MHz, almost similar to the surface acoustic wave device Q of the comparative example. I was able to get closer.
Further, according to FIG. 26 (b), the surface acoustic wave device S2 of the present invention has a phase balance of "0" when the frequency is between about 865 MHz and 910 MHz, almost similar to the surface acoustic wave device Q of the comparative example. It was close to “degree”.

Therefore, it can be said that the surface acoustic wave device S2 of the present invention can improve the amplitude balance and the phase balance in the pass band by this configuration. This is considered to be due to the fact that an inductance component is added to the grounding terminals 14 and 15 of the surface acoustic wave element 2 to produce the same effect as when the matching circuit is connected to the connection terminals 12 and 13.
In addition, when the magnitudes of the inductance components to be connected to the grounding terminal of the surface acoustic wave device were set to L1 and L2 of 0.5 nH, the degree of balance deteriorated from the conventional example. Therefore, in the present invention, the magnitudes of the inductance components L1 and L2 generated in the grounding terminals 14 and 15 are preferably in the range of about 0.1 to 0.3 nH, respectively. Moreover, it is preferable that 0.1 ≦ | L1−L2 | ≦ 0.2 nH is satisfied.

FIG. 1 is a plan view showing a first embodiment of a surface acoustic wave element included in a surface acoustic wave device according to an embodiment of the present invention. FIG. 2 is a plan view showing each layer of the first embodiment on the mounting substrate included in the surface acoustic wave device according to the embodiment of the present invention. FIG. 3 is a cross-sectional view of the stacked mounting substrate. FIG. 4 is an equivalent circuit diagram of the surface acoustic wave element 1 of FIG. FIG. 5 is a plan view showing a first modification of the surface acoustic wave element according to the first embodiment. FIG. 6 is a plan view showing a second modification of the surface acoustic wave element according to the first embodiment. FIG. 7 is a plan view showing a third modification of the surface acoustic wave element according to the first embodiment. FIG. 8 is a plan view showing a fourth modification of the surface acoustic wave element according to the first embodiment. FIG. 9 is a plan view showing a fifth modification of the surface acoustic wave element according to the first embodiment. FIG. 10 is a plan view showing each layer of the first modified example on the mounting substrate of the first embodiment shown in FIG. FIG. 11 is a plan view showing each layer of the second modified example on the mounting substrate of the first embodiment shown in FIG. FIG. 12 is a plan view showing a second embodiment of a surface acoustic wave element included in a surface acoustic wave device according to another embodiment of the present invention. FIG. 13 is a plan view showing each layer of the second embodiment on a mounting substrate included in a surface acoustic wave device according to another embodiment of the present invention. FIG. 14 is a plan view showing a first modification of the surface acoustic wave element according to the second embodiment. FIG. 15 is a plan view showing a second modification of the surface acoustic wave element according to the second embodiment. FIG. 16 is a plan view showing a third modification of the surface acoustic wave element according to the second embodiment. FIG. 17 is a plan view showing a fourth modification of the surface acoustic wave element according to the second embodiment. FIG. 18 is a plan view showing a fifth modification of the surface acoustic wave element according to the second embodiment. FIG. 19 is a plan view showing each layer of the first modified example on the mounting substrate of the second embodiment shown in FIG. FIG. 20 is a plan view showing each layer of the second modified example on the mounting substrate of the second embodiment shown in FIG. FIG. 21 is a block circuit diagram of a high-frequency circuit of a mobile phone. FIG. 22 is a plan view showing a surface acoustic wave element included in a surface acoustic wave device as a comparative example. FIG. 23 is a plan view showing each layer on a mounting substrate included in a surface acoustic wave device as a comparative example. FIG. 24 is a graph showing the relationship between the frequency and insertion loss of each surface acoustic wave device. FIG. 25 is a graph showing the relationship between the frequency of each surface acoustic wave device and VSWR. (A) is the graph which showed the relationship between the frequency and amplitude balance of each surface acoustic wave apparatus, (b) is the graph which showed the relationship between a frequency and a phase balance. FIG. 27 is a plan view showing a surface acoustic wave element included in a surface acoustic wave device as a comparative example. FIG. 28 is a plan view showing each layer on a mounting substrate included in a surface acoustic wave device as a comparative example. FIG. 29 is a graph showing the relationship between the frequency and insertion loss of each surface acoustic wave device. FIG. 30 is a graph showing the relationship between the frequency of each surface acoustic wave device and VSWR. (A) is the graph which showed the relationship between the frequency and amplitude balance of each surface acoustic wave apparatus, (b) is the graph which showed the relationship between a frequency and a phase balance. FIG. 32 is a plan view of a multi-electrode surface acoustic wave filter. FIG. 33 is a plan view of a conventional surface acoustic wave filter. FIG. 34 is a plan view of a conventional surface acoustic wave filter. FIG. 35 is a plan view of a conventional surface acoustic wave filter. FIG. 36 is a graph showing the relationship between the frequency and insertion loss of each surface acoustic wave element. FIG. 37 is a plan view of a surface acoustic wave element to which no reactance (capacitance) component is added in the surface acoustic wave element shown in FIG. FIG. 38 is a graph showing the relationship between the frequency of each surface acoustic wave element and VSWR (Voltage Standing Wave Ratio). (A) is a graph showing the amplitude balance in the vicinity of the passband of each surface acoustic wave element, and (b) is a graph showing the phase balance of each surface acoustic wave element.

Explanation of symbols

S ₁ , S ₂ surface acoustic wave devices 1, 1a to 1e, ₂ , 2g to 2k surface acoustic wave elements N, D, F, J ₁ , electrode patterns B, C ₁ , C _{2 of} J ₂ surface acoustic wave elements, E, H, I ₁ , I ₂ surface acoustic wave resonator 19 Piezoelectric substrate 3, 4, 5, 21, 22, 23 IDT electrodes 6, 7, 24, 25 Reflector electrodes 8d, 9d, 28j, 29j Insert reflector Electrode 11 Pad terminal for connection (for input)
12, 13 Pad terminal for connection (for output)
14, 14a to 14h, 15, 26, 27 Grounding terminals 100, 100a, 100b, 200, 200g, 200h Mounting substrate 101 Upper surface layer 102 First through conductor layers 111, 112, 113 Connecting pad conductors 114, 114a, 114b, 114g, 114h, 115 Grounding conductor 120 Through conductors 124, 124a, 124b, 124g, 124h, 125 Through grounding conductor A Virtual axis X Surface acoustic wave excitation direction Y Direction orthogonal to surface acoustic wave excitation direction

Claims (7)

A surface acoustic wave element that excites a surface acoustic wave by an IDT electrode formed on the piezoelectric substrate, and a mounting substrate on which the surface acoustic wave element is mounted.
The surface acoustic wave element includes a piezoelectric substrate and three or more odd-numbered IDT electrodes including a pair of comb-shaped electrodes formed along the propagation direction of the surface acoustic wave propagating on the piezoelectric substrate. Have
Of the odd number of IDT electrodes, one comb-shaped electrode of the pair of comb-shaped electrodes constituting the IDT electrode disposed on both sides of the IDT electrode formed in the center includes first and second comb-shaped electrodes. 2 reference potential terminals are respectively connected,
Of the odd number of IDT electrodes, the other comb-shaped electrode of the pair of comb-shaped electrodes constituting the IDT electrode disposed on both sides of the IDT electrode formed in the center has an unbalanced signal terminal. Is connected,
Of the odd number of IDT electrodes, the IDT electrode formed in the center is divided into two parts, and one of the pair of comb-like electrodes is divided into the first one of the two divided comb-like electrodes. Are connected to the other balanced signal terminal and the second balanced signal terminal to the other,
The first and second reference potential terminals are formed asymmetrically with respect to a virtual central axis provided in a direction perpendicular to the propagation direction through the center of the IDT electrode formed at the center,
The mounting substrate includes first and second grounding conductors disposed opposite to the first and second reference potential terminals, and the mounting substrate from the first and second grounding conductors. First and second through grounding conductors connected so as to pass through the first and second grounding conductors, the first and second grounding conductors being formed asymmetrically with respect to the virtual central axis, The surface acoustic wave device, wherein the second through-grounding conductor is formed different in at least one of a diameter, a cross-sectional shape, and the number so as to be formed asymmetrically with respect to the virtual central axis.   2. The surface acoustic wave device according to claim 1, wherein a magnitude of an inductance component generated in each of the first and second reference potential terminals is 0.1 to 0.3 nH.   3. The surface acoustic wave device according to claim 2, wherein a difference in magnitude of an inductance component generated in each of the first and second reference potential terminals is 0.1 or more and 0.2 nH or less.   The said surface acoustic wave element further has an insertion reflector provided with a plurality of electrode fingers disposed between adjacent IDT electrodes extending in a direction orthogonal to the propagation direction. The surface acoustic wave device according to any one of the above.   5. The surface acoustic wave device according to claim 4, wherein the insertion reflector is formed such that a distance between the centers of the adjacent electrode fingers gradually decreases from both ends of the insertion reflector toward the center. 6. .   A communication apparatus comprising a receiving circuit including the surface acoustic wave device according to claim 1.   A communication device comprising a transmission circuit including the surface acoustic wave device according to claim 1.

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