JP2006333024A - Surface acoustic wave element piece, surface acoustic wave device and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave element piece which makes lateral mode spuriousness small and puts it away from a reference frequency, and decreases impedance, a surface acoustic wave device, and electronic equipment. <P>SOLUTION: The surface acoustic wave element piece 10 is constituted by providing an inter-digital electrode 12 and reflectors 30 arranged on both sides of the inter-digital electrode 12 on a piezoelectric substrate 18, providing a plurality of linear portions 24 and 26 to electrode fingers 20 of the inter-digital electrode 12 and electrode fingers 32 of the reflectors 30, and providing connection portions 22 and 34 which are obliquely bent between the linear portions 24 and 36, the linear portions 24 provided to the inter-digital electrode 12 and the linear portions 36 provided to the reflectors 30 corresponding to each other in a propagation direction of a surface acoustic wave being related so that the linear portions 24 of the inter-digital electrode 12 are longer than the linear portions 36 of the reflectors 30. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface acoustic wave element, a surface acoustic wave device, and an electronic apparatus.

  A SAW element piece 1 used for a surface acoustic wave (hereinafter referred to as SAW) filter or a SAW resonator includes, as shown in FIG. 7, an interdigital electrode 2 (Interdigital Transducer: hereinafter referred to as IDT) and In this configuration, the reflector 3 is provided on the piezoelectric substrate 4. The IDT 2 is formed by short-circuiting the base ends of a plurality of electrode fingers 5 to form comb teeth, and meshing two comb-teeth electrode fingers 5 with each other. The reflector 3 is disposed at a position sandwiching the IDT 2 in the SAW propagation direction, and is formed by short-circuiting both ends of the plurality of electrode fingers 6 disposed along the electrode fingers 5 of the IDT 2. The electrode finger 5 of the IDT 2 and the electrode finger 6 of the reflector 3 have a linear shape.

  Such a SAW element piece 1 has a high impedance when a piezoelectric substrate 4 having a small electromechanical coupling coefficient, such as a quartz substrate, is used, and it is not easy to perform impedance matching with a circuit. For this reason, the SAW element piece 1 is required to have a low impedance. As a method for lowering the impedance of the SAW element piece 1, there is known a method of widening the crossing width W of the electrode fingers of the IDT 2, but when this crossing width W is widened, a transverse mode in the direction perpendicular to the SAW propagation direction is obtained. Spurious is generated and the filter characteristics are deteriorated. This lateral mode spurious appears in a position closer to the center frequency in the filter characteristics as the crossing width W is increased, and degrades the filter characteristics.

FIG. 8 is a diagram showing the filter characteristics of a SAW filter according to the prior art. The vertical axis in FIG. 8 indicates the amount of attenuation (Att), and the horizontal axis indicates the frequency deviation (ΔF) based on the center frequency of the filter characteristics. Then, as indicated by arrows A ₁ and A ₂ in FIG. 8, the transverse mode spurious appears at a position close to the center frequency.

By the way, Patent Document 1 is cited as a document that discloses a SAW element piece that suppresses transverse mode spurious. The SAW element piece (SAW device) disclosed in Patent Document 1 has a configuration in which reflectors are provided on both sides of the IDT, and the length of the electrode fingers of the reflector is 70% or less with respect to the IDT intersection width. In terms of ratio, transverse mode spurious is suppressed.
JP-A-7-86869

  When the length of the electrode fingers of the reflector is narrower than the crossing width of the IDT, even if the transverse mode spurious can be suppressed, it cannot be moved away from the center frequency. For this reason, even if the IDT crossing width is increased in order to reduce the impedance, only the transverse mode spurs are reduced, and the transverse mode spurs remain near the center frequency, and the filter characteristics remain deteriorated.

  Further, when the length of the electrode fingers of the reflector is set to a ratio of 70% or less with respect to the intersection width of the electrode fingers of the IDT, it is considered that the filter characteristics, particularly the attenuation amount, deteriorates as the ratio is reduced. .

  An object of the present invention is to provide a surface acoustic wave element, a surface acoustic wave device, and an electronic apparatus that reduce the transverse mode spurious and away from the reference frequency and reduce the impedance.

  In order to achieve the above object, a surface acoustic wave element according to the present invention includes an interdigital electrode and reflectors disposed on both sides of the interdigital electrode on a piezoelectric substrate. Provided on the interdigital electrode corresponding to the propagation direction of the surface acoustic wave by providing a plurality of straight portions on the electrode fingers and the electrode fingers of the reflector, and providing connecting portions that bend diagonally between the straight portions. In addition, the relationship between the linear portion and the linear portion provided in the reflector is characterized in that the length of the linear portion of the interdigital electrode is made longer than that of the linear portion of the reflector.

  The surface acoustic wave element piece can cancel the transverse mode energy of the second or higher order, and can reduce the transverse mode spurious. Further, the interdigital electrode fingers are divided into a plurality of straight portions by the connecting portions, so that the crossing width can be reduced. Therefore, the transverse mode spurious can be kept away from the reference frequency. Further, since the crossing width of the entire interdigital electrode is the sum of the straight portions, the crossing width of the entire interdigital electrode remains wide. Therefore, the impedance of the surface acoustic wave element piece can be reduced.

  Further, the surface acoustic wave element piece is provided with a comb-like electrode and reflectors disposed on both sides of the comb-like electrode on a piezoelectric substrate, and is formed by bending the electrode finger of the comb-like electrode. A plurality of linear portions at both ends of the connecting portion, and at both ends of the electrode fingers of the interdigital electrode, a refracting portion formed by bending following the connecting portion of the interdigital electrode is provided, A connection part formed by bending in the middle of the electrode finger of the reflector is provided, and a plurality of linear parts are provided at both ends of the connection part, and the connection of the reflector is provided at both ends of the electrode finger of the reflector. The relationship between the linear portion provided in the interdigital electrode and the linear portion provided in the reflector corresponding to the propagation direction of the surface acoustic wave is provided by providing a refracting portion formed by bending along the portion. , The straight of the interdigital electrode The length of the section is made longer than the straight line portion of the reflector, it is characterized in that.

  Since the refracting portions are provided at both ends of the electrode finger, the electrode shape of the interdigital electrode and the reflector is symmetrical with respect to the center line of each track along the propagation direction of the surface acoustic wave. Thereby, the propagation of the surface acoustic wave can be made uniform. Further, since the length of the straight portion of the reflector is made shorter than that of the interdigital electrode, the energy of the second-order or higher transverse mode can be canceled and the transverse mode spurious can be reduced. Furthermore, since the interdigital transducer electrode fingers are divided into a plurality of straight portions by the connecting portions, the crossing width can be reduced. Therefore, the transverse mode spurious can be kept away from the reference frequency. Furthermore, since the crossing width of the entire interdigital electrode is the sum of the straight portions, the crossing width of the entire interdigital electrode remains wide. Therefore, the impedance of the surface acoustic wave element piece can be reduced.

  A plurality of the interdigital electrodes are provided between the reflectors. If any one of the plurality of interdigital electrodes is used as an input electrode and the other one is used as an output electrode, a surface acoustic wave resonator filter can be configured.

  The midpoint of the straight line portion provided on the interdigital electrode and the midpoint of the straight line portion provided on the reflector are disposed on the same line along the propagation direction of the surface acoustic wave. It is characterized by. The straight line portion provided in the reflector is shorter than the straight line portion provided in the interdigital electrode and is located inside the both ends of the straight line portion provided in the interdigital electrode. The reflector can reflect the surface acoustic wave propagated from the central portion of the straight portion of the interdigital electrode toward the interdigital electrode, and the surface acoustic wave propagated from the end of each linear portion of the interdigital electrode can be reflected. There is no reflection toward the interdigital electrode. Therefore, the surface acoustic wave element piece can cancel the energy of the second or higher transverse mode and can reduce the transverse mode spurious.

Further, the straight portions provided on the same electrode finger in the interdigital electrode are separated by a distance L1 along the propagation direction of the surface acoustic wave, and are provided on the same electrode finger in the reflector. The straight portions are separated by a distance L2 along the propagation direction of the surface acoustic wave, and the distances L1 and L2 are
3λ / 8 ≦ L1 ≦ 5λ / 8 (where λ is the wavelength of the surface acoustic wave)
3λ / 8 ≦ L2 ≦ 5λ / 8
It is characterized by satisfying the relationship. As a result, the transverse mode spurious can be moved away from the reference frequency, and the impedance can be reduced.

  Further, the straight portions provided on the same electrode finger of the interdigital electrode are characterized by having different lengths. Since the length of each straight line portion is different, the position of spurious generated at each straight line portion can be changed. Since the spurious appearing in the filter characteristics is a combination of spurious generated at each linear portion, the spurious after combining can be reduced if the position of the spurious generated at each linear portion is different.

  In the following, the best embodiments of a surface acoustic wave (SAW) element piece, a SAW device, and an electronic apparatus according to the present invention will be described. First, the first embodiment will be described. In the first embodiment, a mode in which a SAW filter is formed of SAW element pieces will be described. FIG. 1 is a schematic plan view of a SAW element piece according to the first embodiment and vibration energy distribution diagrams of first to third transverse modes. In the SAW element piece 10 according to the first embodiment, an input electrode 14 and an output electrode 16 composed of interdigital electrodes (IDT) 12 are disposed on a piezoelectric substrate 18, and the input electrode 14 and the output electrode 16 are sandwiched between them. It is the structure by which the reflector 30 was arrange | positioned.

The IDT 12 is composed of a pair of comb teeth 17 that mesh with each other. The comb teeth 17 have a plurality of electrode fingers 20 and their base ends are short-circuited. Each electrode finger 20 is provided with a connecting portion 22 bent obliquely in the middle thereof, and each electrode finger 20 is divided into a plurality of linear portions 24. That is, each electrode finger 20 includes a connection portion 22 and a straight portion 24 connected to both ends of the connection portion 22. The connecting portion 22, it is preferred that the length c ₁ is short.

  Further, at both ends of each electrode finger 20, a refracting portion 26 that is bent along the connecting portion 22 is provided. That is, the connecting portion 22 and the refracting portion 26 are bent at the same or substantially the same angle with respect to the straight portion 24. The length of the refracting portion 26 provided at the proximal end of the electrode finger 20 is longer than that of the refracting portion 26 provided at the distal end of the electrode finger 20. Accordingly, the refracting portion 26 provided at one comb tooth 17 and provided at the base end of each electrode finger 20 is short-circuited, and the refracting portion 26 provided at the tip end of the electrode finger 20 is short-circuited with the other comb tooth 17. There is nothing.

Further, the straight portions 24 provided on one electrode finger 20 are separated in the SAW propagation direction, and the distance L1 satisfies the relationship of 3λ / 8 ≦ L1 ≦ 5λ / 8. Here, λ represents the wavelength of SAW. The intersection width of the IDT ₁₂ is the sum of the intersection width b _{1 of one} straight line portion 24 and the intersection width b ₁ of the other straight line portion 24.

  The reflector 30 has a configuration in which a plurality of electrode fingers 32 are arranged at a predetermined pitch in the SAW propagation direction, and both ends of the electrode fingers 32 are short-circuited. Each electrode finger 32 is provided with a connecting portion 34 that is bent obliquely, and each electrode finger 32 is divided into a plurality of linear portions 36. That is, each electrode finger 32 includes a connection portion 34 and straight portions 36 connected to both ends of the connection portion 34. The straight line portion 36 is formed with a length shorter than that of the straight line portion 24 of the IDT 12 in the straight line portion 24 of the IDT 12 corresponding to the SAW propagation direction and the straight line portion 36 provided in the reflector 30. It is arrange | positioned inside the both ends of the linear part 24 of IDT12. In addition, it is preferable that the midpoint of each linear part 36 provided in the reflector 30 is located on a line passing through the midpoint of each linear part 24 of the IDT 12 along the SAW propagation direction. That is, it is preferable that the straight line portion 24 of the IDT 12 and the straight line portion 36 of the reflector 30 have a line-symmetric shape along the SAW propagation direction in each track described later.

  Further, at both ends of each electrode finger 32, a refracting portion 38 formed by bending along the connecting portion 34 is provided. That is, the connecting portion 34 and the refracting portion 38 are bent at the same or substantially the same angle with respect to the straight portion 36. And the connection part 22 provided in IDT12 and the connection part 34 provided in the reflector 30 are arrange | positioned along the propagation direction of SAW.

Further, each linear portion 36 provided on one electrode finger 32 of the reflector 30 is separated in the SAW propagation direction, and the distance L2 satisfies the relationship of 3λ / 8 ≦ L2 ≦ 5λ / 8. ing. The cross width of the reflector 30 has a cross width a ₁ of one of the straight portion 36 consists of a cross width a ₁ Metropolitan of the other linear portion 36.

  In such a SAW element piece 10, the overlapping portion of each straight line portion 24 in the IDT 12 and each straight line portion 36 in the reflector 30 in the SAW propagation direction becomes a track, and in FIG. 1, track 1 and track 2 are formed. Yes.

  Next, the operation of the SAW element piece 10 will be described. First, when an electric signal is applied to the input electrode 14, the SAW is excited by the piezoelectric substrate 18 and propagates to the reflector 30. At this time, the primary transverse mode of each straight line portion 24 in the input electrode 14 (IDT 12) becomes the main response, and the secondary transverse mode or more becomes spurious. Of the SAW propagated from the IDT 12 to the reflector 30, the SAW propagated to the linear portion 36 of the reflector 30 is reflected and returned toward the IDT 12, and a standing wave is generated between the reflectors 30 sandwiching the IDT 12. . In the case of FIG. 1, among the SAWs propagated from the IDT 12 to the reflector 30, the SAW propagated from the vicinity of the center of each linear portion 24 in the IDT 12 is reflected by the reflector 30 and returned toward the IDT 12. A standing wave is generated between the sandwiching reflectors 30. At this time, in the SAW element piece 10, the linear part 24 of the IDT 12 and the linear part 36 of the reflector 30 are symmetrical with respect to the center line of each track. It cancels out and spurious is suppressed. The SAW reflected by the reflector 30 and returned to the IDT 12 has its vibration energy confined between the reflectors 30. When this SAW reaches the output electrode 16, it is converted into an electrical signal and output. In such a SAW element piece 10, the SAWs propagating in the track 1 and the track 2 are coupled to excite one wave as a whole.

FIG. 2 is a diagram showing filter characteristics of the SAW element piece according to the first embodiment. Here, the vertical axis in FIG. 2 indicates the attenuation (Att), and the horizontal axis indicates the frequency deviation (ΔF) with respect to the center frequency (reference frequency) of the filter characteristics. The filter characteristics of the SAW element piece 10 operated as described above are as shown in FIG. 2, and the transverse mode spurious becomes smaller as shown by arrows B ₁ and B ₂ in FIG. 2, and moves away from the center frequency.

In such a SAW element piece 10, the length of the straight portion 36 of the reflector 30 is shorter than the straight portion 24 of the IDT 12 in each track, and the straight portion 36 of the reflector 30 is connected to both ends of the straight portion 24 of the IDT 12. Of the SAW propagated from the IDT 12 to the reflector 30, the SAW propagated to the straight portion 36 of the reflector 30 is reflected toward the IDT 12 to generate a standing wave, and the connection of the reflector 30 is performed. In the SAW propagated to the part 34 and the refracting part 38, no standing wave is generated. Therefore, the SAW element piece 10 can cancel the energy in the transverse mode of the second or higher order, and the transverse mode spurious can be reduced as shown in FIG. Such an effect can be obtained regardless of the ratio between the length of the straight portion 24 provided in the IDT 12 and the length of the straight portion 36 provided in the reflector 30. That is, the above-described effect can be obtained regardless of the ratio between the intersection width b ₁ of each linear portion 24 in the IDT ₁₂ and the intersection width a ₁ of each linear portion 36 in the reflector 30.

  Further, since the electrode fingers 20 of the IDT 12 are divided into the straight portions 24 by the connecting portions 22, each cross width can be narrowed. However, since the cross width of the entire IDT 12 is the sum of the lengths of the respective straight portions 24, The width is not narrowed. Therefore, since the crossing width of each linear part 24 is narrow, as shown in FIG. 2, the transverse mode spurious can be kept away from the center frequency (reference frequency). Moreover, since the crossing width of the entire IDT 12 remains wide, the impedance can be reduced.

  In the first embodiment described above, the two linear portions 24 and 36 are provided by providing one connection portion 22 and 34 on the electrode finger 20 of the IDT 12 and the electrode finger 32 of the reflector 30. It is not limited to this form. That is, the SAW element piece 10 may have a configuration in which three or more straight portions 24 and 36 are provided by providing a plurality of connection portions 22 and 34 on the electrode finger 20 of the IDT 12 and the electrode finger 32 of the reflector 30. Good. FIG. 3 is a schematic plan view of a SAW element piece according to this modification. As shown in FIG. 3, the SAW element piece 10 is provided with three straight portions 24 and 36 by providing two connection portions 22 and 34 on the electrode finger 20 of the IDT 12 and the electrode finger 32 of the reflector 30. be able to. In this case, the connecting portions 22 and 34 may be bent to the left or right with respect to the straight portions 24 and 36. That is, the electrode fingers 20 and 32 may have connecting portions 22 and 34 that are bent in either the right direction or the left direction, and are bent in the right direction or the left direction as shown in FIG. The connecting portions 22 and 34 may be provided. The refracting portions 26 and 38 provided at both ends of the electrode fingers 20 and 32 are in the same direction as the connecting portions 22 and 34 connected to the opposite side of the straight portions 24 and 36 to which the refracting portions 26 and 38 are connected. It only needs to be bent.

  Next, a second embodiment will be described. In the second embodiment, a SAW element piece in which the lengths of the straight portions provided on the electrode fingers are different will be described. Therefore, in 2nd Embodiment, the same number is attached | subjected to the component similar to 1st Embodiment, and the description is abbreviate | omitted or simplified. FIG. 4 is a schematic plan view of a SAW element piece according to the second embodiment. The SAW element piece 40 according to the second embodiment has a configuration in which the input electrode 14 and the output electrode 16 made of the IDT 12 and the reflectors 30 arranged on both sides of the IDT 12 are provided on the piezoelectric substrate 18. The electrode finger 20 of the IDT 12 has a connecting portion 22 that is bent in the middle thereof, and a linear portion 24 having a different length. The electrode fingers 20 of the IDT 12 are provided with refracting portions 26 at both ends thereof.

  By the way, in the SAW element piece 40, when the length of the linear portion 24 of the IDT 12 is changed, the position of the center frequency of the filter characteristic is moved and the position of the spurious is also moved. In the filter characteristics of the SAW element piece 40, a combination of spurious generated in each linear portion 24 appears. Accordingly, the length of each straight line portion 24 may be set as appropriate by previously obtaining a position where spurious generated in each straight line portion 24 does not overlap by calculation or experiment. Further, in each straight line portion 24, if the length of the straight line portion 24 is changed, the center frequency of the filter characteristic changes. Therefore, the wavelength of the propagated SAW is changed for each straight line portion 24, and the center frequency of the passband is changed. Just add.

  The electrode finger 32 of the reflector 30 has a connecting portion 34 formed by bending in the middle thereof, and a linear portion 36 having a different length is formed. The straight line portion 36 is formed shorter than the adjacent straight line portion 24 of the IDT 12 and is disposed on the inner side of both ends of the straight line portion 24 of the IDT 12. The electrode fingers 32 of the reflector 30 are provided with refracting portions 38 at both ends thereof.

In FIG. 4, the IDT 12 and the reflector 30 are provided with two straight portions 24 and 36, respectively. The length b ₂ of one straight portion 24 and the length b ₃ of the other straight portion 24 in the IDT 12 The relationship between the length a ₂ of the one straight line portion 36 and the length a ₃ of the other straight line portion 36 in the reflector 30 is b ₂ ≠ b ₃ , a ₂ ≠ a ₃ , b ₂ > a _2. , it is as shown in _{b 3> a} 3.

  Next, the operation of the SAW element piece 40 will be described. First, when an electric signal is applied to the input electrode 14, SAW is excited by the piezoelectric substrate 18 and propagates to the reflector 30. At this time, in the reflector 30, among the SAWs propagated from the IDT 12 to the reflector 30, the SAW propagated to the linear portion 36 of the reflector 30 is reflected and returned toward the IDT 12. In the SAW element piece 40, the straight line portion 24 of the IDT 12 and the straight line portion 36 of the reflector 30 are symmetrical with respect to the center line of each track. .

  Further, since the lengths of the straight portions 24 are different, the positions of spurious generated in the respective straight portions 24 (tracks) are different. For this reason, even if the spurious generated in each linear portion 24 is combined, no large spurious is generated in the filter characteristics. The vibration energy of the SAW returned to the IDT 12 is confined between the reflectors 30. When this SAW reaches the output electrode 16, it is converted into an electrical signal and output.

  In such a SAW element piece 40, since the length of each straight line portion 24 in the IDT 12 is changed, spurious is not increased even if the filter characteristics obtained in each straight line portion 24 are combined. Further, since the length of the straight line portion 36 of the reflector 30 is shorter than the straight line portion 24 of the IDT 12 and the straight line portion 36 of the reflector 30 is disposed inside the both ends of the straight line portion 24 of the IDT 12, Among the SAWs propagated to 30, the SAW propagated to the linear portion 36 of the reflector 30 is reflected toward the IDT 12, and a standing wave is generated between the reflectors 30 sandwiching the IDT 12. On the other hand, in the SAW propagated to the connecting portion 34 and the refracting portion 38 of the reflector 30, no standing wave is generated between the reflectors 30 sandwiching the IDT 12. Therefore, the SAW element piece 40 can further reduce the transverse mode spurious.

  Further, since the electrode fingers 20 of the IDT 12 are divided into the straight portions 24 by the connecting portions 22, each cross width can be narrowed. However, since the cross width of the entire IDT 12 is the sum of the lengths of the respective straight portions 24, The width is not narrowed. Accordingly, since the crossing width of each straight line portion 24 is narrow, the transverse mode spurious can be kept away from the center frequency (reference frequency). Moreover, since the crossing width of the entire IDT 12 remains wide, the impedance can be reduced.

  In the second embodiment described above, the two linear portions 24 and 36 are provided by providing one connection portion 22 and 34 on the electrode finger 20 of the IDT 12 and the electrode finger 32 of the reflector 30. It is not limited to this form. That is, the SAW element piece 40 has a configuration in which three or more linear portions 24 and 36 are provided by providing two or more connection portions 22 and 34 on the electrode finger 20 of the IDT 12 and the electrode finger 32 of the reflector 30. May be. In this case, the order of arranging the straight portions 24 and 36 having different lengths is arbitrary.

  Next, a third embodiment will be described. In the third embodiment, a mode in which a SAW resonance piece is formed of SAW element pieces will be described. And in 3rd Embodiment, the same number is attached | subjected to the component similar to 1st Embodiment, and the description is abbreviate | omitted or simplified. FIG. 5 is a schematic plan view of a SAW element piece according to the third embodiment. The SAW element piece 50 according to the third embodiment has a configuration in which an IDT 12 and reflectors 30 disposed on both sides of the IDT 12 are disposed on a piezoelectric substrate 18.

  The electrode finger 20 of the IDT 12 is provided with a connecting portion 22 that is bent in the middle thereof, and a plurality of linear portions 24 are formed. The electrode fingers 20 of the IDT 12 are provided with refracting portions 26 at both ends thereof. The electrode finger 32 of the reflector 30 is provided with a connecting portion 34 that is bent in the middle of the electrode finger 32 to form a plurality of linear portions 36. The electrode fingers 32 of the reflector 30 are provided with refracting portions 38 at both ends thereof. And the straight part 36 provided in the reflector 30 is formed shorter than the linear part 24 of IDT12 which adjoins the length, and is arrange | positioned inside the both ends of the linear part 24 of IDT12. .

  Next, the operation of the SAW element piece 50 will be described. First, when an electric signal is applied to the IDT 12, the SAW is excited by the piezoelectric substrate 18 and propagates to the reflector 30. At this time, in the reflector 30, among the SAW propagated from the IDT 12 to the reflector 30, the SAW propagated to the linear portion 36 of the reflector 30 is reflected and returned toward the IDT 12. In such a SAW element piece 50, the linear portion 24 of the IDT 12 and the linear portion 36 of the reflector 30 are symmetrical with respect to the center line of each track. It is offset. The vibration energy of the SAW returned to the IDT 12 is confined between the reflectors 30. When this SAW reaches the IDT 12, it is converted into an electrical signal and output.

  Such a SAW element piece 50 can reduce the transverse mode spurious and can be kept away from the resonance frequency (reference frequency). Further, the impedance can be reduced.

  Next, a fourth embodiment will be described. In the fourth embodiment, a SAW device including the SAW element piece described in the first to third embodiments will be described. And in 4th Embodiment, the same number is attached | subjected to the component similar to 1st-3rd embodiment, and the description is abbreviate | omitted or simplified. FIG. 6 is a schematic sectional view of a SAW device according to the fourth embodiment. The SAW device 60 according to the fourth embodiment has a configuration in which the SAW element pieces 10, 40, and 50 described in the first to third embodiments are mounted on a package 62.

  As shown in FIG. 6, the SAW device 60 has a configuration including a package base 64 in which a recessed portion 66 is formed. The package base 64 includes mounting terminals 68 on the back surface and wire electrodes 70 to which wire bonding is applied on the bottom surface of the recessed portion 66. The mounting terminal 68 and the wire electrode 70 are electrically connected. The SAW element pieces 10, 40, 50 are mounted face-up on the recess 66 via a bonding material 76, and the IDT 12 and the wire electrode 70 of the SAW element pieces 10, 40, 50 are electrically connected by the wire 72. It is connected to the. A lid 74 is joined to the upper surface of such a package base 64 to seal the recess 66. In the SAW device 60, the SAW element pieces 10, 40, and 50 can be mounted face-down by using flip chip bonding.

  The SAW device 60 configured as described above is, for example, a SAW filter or a SAW resonator. Further, if a circuit for resonating the SAW resonator is mounted in a package constituting the SAW resonator, and the SAW element pieces 10, 40, 50 and the circuit are electrically connected, a SAW resonator is obtained. be able to. Further, the SAW device 60 configured in this manner can be a mass sensor that detects the mass of a substance from a change in resonance frequency, an acceleration sensor that detects the magnitude of an acceleration or impact applied from the outside, and the like.

  Such a SAW device 60 can be mounted on various electronic devices. As an example, the SAW device 60 can be mounted on a communication device as a filter element in a transmission circuit, or can be mounted on an electronic device as a reference frequency signal source.

It is the schematic plan view of the SAW element piece which concerns on 1st Embodiment, and the vibration energy distribution figure of a 1st-3rd order transverse mode. It is a figure which shows the filter characteristic of the SAW element piece which concerns on 1st Embodiment. It is a schematic plan view of the SAW element piece which concerns on the modification of 1st Embodiment. It is a schematic plan view of the SAW element piece according to the second embodiment. It is a schematic plan view of the SAW element piece which concerns on 3rd Embodiment. It is a schematic sectional drawing of the SAW device which concerns on 4th Embodiment. It is a schematic plan view of the SAW element piece which concerns on a prior art. It is a figure which shows the filter characteristic of the SAW filter which concerns on a prior art.

Explanation of symbols

10 ... SAW element piece, 12 ... IDT, 20 ... Electrode finger, 22 ... Connection section, 24 ... Linear section, 26 ... Refraction section, 30 ... Reflector, 32 ..... electrode finger, 34 ..... connection part, 36 ..... straight line part, 38 ....... refracting part, 40, 50 ...... SAW element piece, 60 ..... SAW device.

Claims (8)

An interdigital electrode and reflectors disposed on both sides of the interdigital electrode are provided on a piezoelectric substrate,
A plurality of straight portions are provided on the electrode fingers of the interdigital electrodes and the electrode fingers of the reflector, and connection portions that are bent obliquely are provided between the straight portions.
The relationship between the straight portion provided in the interdigital electrode corresponding to the propagation direction of the surface acoustic wave and the straight portion provided in the reflector is the length of the straight portion of the interdigital electrode. Longer than the straight portion of the reflector,
A surface acoustic wave element having the above structure. An interdigital electrode and reflectors disposed on both sides of the interdigital electrode are provided on a piezoelectric substrate,
A connecting portion formed by bending in the middle of the electrode finger of the interdigital electrode is provided, and a plurality of straight portions are provided at both ends of the connecting portion, and the interdigital electrode is provided at both ends of the electrode finger of the interdigital electrode. Provided with a refracting part formed by bending following the connecting part of
A connection part formed by bending in the middle of the electrode finger of the reflector is provided, and a plurality of linear parts are provided at both ends of the connection part, and the connection of the reflector is provided at both ends of the electrode finger of the reflector. Provide a refracted part bent along the part,
The relationship between the straight portion provided in the interdigital electrode corresponding to the propagation direction of the surface acoustic wave and the straight portion provided in the reflector is the length of the straight portion of the interdigital electrode. Longer than the straight portion of the reflector,
A surface acoustic wave element having the above structure.   The surface acoustic wave element piece according to claim 1, wherein a plurality of the interdigital electrodes are provided between the reflectors.   The midpoint of the straight line portion provided on the interdigital electrode and the midpoint of the straight line portion provided on the reflector are disposed on the same line along the propagation direction of the surface acoustic wave. The surface acoustic wave element piece according to claim 1, wherein the surface acoustic wave element piece is according to claim 1. Each linear portion provided on the same electrode finger in the interdigital electrode is separated by a distance L1 along the propagation direction of the surface acoustic wave,
The straight portions provided on the same electrode finger in the reflector are separated by a distance L2 along the propagation direction of the surface acoustic wave,
The distances L1 and L2 are
3λ / 8 ≦ L1 ≦ 5λ / 8 (where λ is the wavelength of the surface acoustic wave)
3λ / 8 ≦ L2 ≦ 5λ / 8
The surface acoustic wave element piece according to any one of claims 1 to 4, wherein the relationship is satisfied.   6. The surface acoustic wave element piece according to claim 1, wherein the straight portions provided on the same electrode finger of the interdigital electrode have different lengths.   A surface acoustic wave device comprising the surface acoustic wave element according to claim 1.   An electronic apparatus comprising the surface acoustic wave device according to claim 7.

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