JP5473784B2 - Surface acoustic wave device - Google Patents

Description

  The present invention relates to a surface acoustic wave device such as a surface acoustic wave (SAW) filter and a duplexer.

  Conventionally, a piezoelectric substrate is housed in a package made of ceramic or the like, and a SAW device (for example, see Patent Document 1) sealed with a metal lid or the like, or a piezoelectric substrate is flip-chip mounted on a flat ceramic substrate. A CSP (Chip Size Package) type SAW device is known (for example, see Patent Document 2).

  In recent years, a so-called WLP (Wafer Level size Package) type SAW device in which a protective cover made of resin or the like is formed on a piezoelectric substrate by build-up has been proposed as a structure that further reduces the overall structure of the SAW device. Yes. Such a WLP-type SAW device has a piezoelectric substrate, a filter portion provided on the piezoelectric substrate, and a protective cover formed so as to provide a vibration space of the filter portion (see, for example, Patent Document 3). ).

  By the way, in a SAW device having a filtering function that allows only a signal in a specific frequency band to pass, an inductor pattern may be provided to adjust the characteristics of the filter. For example, in the SAW device of Patent Document 1, it is disclosed that an attenuation pattern outside the passband of a filter is increased by providing an inductor pattern between a parallel resonator constituting a ladder-type SAW filter and a reference potential portion. Yes. Such an inductor pattern needs to draw a long and narrow pattern relatively long in order to ensure an inductance of a predetermined size, and is usually provided in a package or the like on which a piezoelectric substrate is mounted.

JP 2004-7250 A JP 2003-78389 A JP 2007-208665 A

  However, in the case of a WLP type SAW device, there is no longer a package on which a piezoelectric substrate is mounted, and the entire structure is very small, so that there is almost no space for forming an inductor pattern. That is, in the WLP type SAW device, it is difficult to form an inductor pattern having a sufficiently large inductance, and it is difficult to increase the attenuation outside the passband of the ladder type SAW filter. In other words, a WLP-type SAW device that can increase the attenuation outside the passband is desired.

  Accordingly, an object of the present invention is to provide a WLP type SAW device capable of increasing the attenuation outside the passband.

  A surface acoustic wave device according to an aspect of the present invention includes a piezoelectric substrate, a ladder-type filter unit including a plurality of parallel resonators provided on the piezoelectric substrate, and surrounding the plurality of parallel resonators. A protective cover having a frame portion disposed on a main surface of the substrate and a lid portion that closes an opening of the frame portion; a first region provided on the piezoelectric substrate and commonly connected to the plurality of parallel resonators; and A reference potential wiring having a second region extending from the first region; a first reference potential terminal provided standing in the first region of the reference potential wiring and penetrating through the frame portion and the lid portion; A second reference potential terminal provided upright in the second region of the reference potential wiring, penetrating the frame and the lid, and provided on a main surface of the lid, connected to the second reference potential terminal And connected to the first reference potential terminal. And have the metal layer, those comprising a.

  According to the SAW device having the above structure, the reference potential wiring provided on the piezoelectric substrate and having a first region commonly connected to the plurality of parallel resonators and a second region extending from the first region; A first reference potential terminal provided in the first region of the reference potential wiring and penetrating the frame portion and the lid portion; and provided in a second region of the reference potential wiring; And a second reference potential terminal penetrating through the lid portion and a metal layer provided on the main surface of the lid portion and connected to the second reference potential terminal and not connected to the first reference potential terminal Since the configuration is provided, the inductor formed in the second region of the reference potential wiring can be used effectively, so that the attenuation outside the passband can be increased.

1 is an external perspective view of a SAW device according to an embodiment of the present invention. It is sectional drawing in the II-II line of FIG. It is a typical top view which shows the structure of the filter part in the SAW apparatus of FIG. It is a top view for demonstrating the positional relationship of the metal layer and vibration space in the SAW apparatus of FIG. 6 is a plan view of a SAW device of a comparative pattern F. FIG. (A) is a plan view of the SAW device of pattern A, and (b) is a graph by simulation showing the attenuation characteristics of the SAW devices according to pattern A and comparison pattern F. (A) is a plan view of the SAW device of pattern B, and (b) is a graph by simulation showing the attenuation characteristics of the SAW devices according to pattern B and comparative pattern F. (A) is a plan view of the SAW device of pattern C, and (b) is a graph by simulation showing the attenuation characteristics of the SAW device according to pattern C and comparison pattern F. (A) is a plan view of the SAW device of pattern D, and (b) is a graph by simulation showing the attenuation characteristics of the SAW device according to pattern D and comparison pattern F. (A) is an equivalent circuit diagram of the SAW device when all reference potential terminals are connected to the metal layer, and (b) is a diagram in which the predetermined reference potential terminal is separated from the metal layer and the predetermined reference potential terminal is It is an equivalent circuit diagram of a SAW device when connected to a metal layer. It is a top view which shows another example of a SAW apparatus. It is a top view which shows the model of the SAW apparatus used for simulation, (a) is a state in which the metal layer does not surround the terminal, (b) is a state in which the metal layer surrounds the terminal. It is a figure which shows the simulation result performed about the model of FIG. 12, (a) respond | corresponds to Fig.12 (a), (b) respond | corresponds to FIG.12 (b).

  Hereinafter, a surface acoustic wave device (SAW device) according to an embodiment of the present invention will be described with reference to the drawings. Note that the drawings used in the following description are schematic, and the dimensional ratios and the like on the drawings do not necessarily match the actual ones.

  1 is an external perspective view of a SAW device 1 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line II-II in FIG.

  The SAW device 1 is a so-called WLP type SAW device in which a vibration space is secured on a piezoelectric substrate 3 by a protective cover made of resin. The SAW device 1 includes a piezoelectric substrate 3, a protective cover 5 fixed to the piezoelectric substrate 3, a metal layer 14 provided on the main surface 17a of the protective cover 5, and a plurality of terminals (input signals) exposed from the protective cover 5. Terminal 6, output signal terminal 7, and first reference potential terminal 8).

  The SAW device 1 receives a signal from the input signal terminal 6. The input signal is filtered by the filter unit 12 provided on the piezoelectric substrate 3. Then, the SAW device 1 outputs the filtered signal from the output signal terminal 7.

  The SAW device 1 is, for example, a plurality of resin-sealed parts that are placed on the mounting surface with the surface on the protective cover 5 side facing a mounting surface such as an external circuit board (not shown). It is mounted in a state where the terminal of is connected to the terminal on the mounting surface.

  The piezoelectric substrate 3 is a rectangular parallelepiped single crystal substrate having piezoelectricity, such as a lithium tantalate single crystal or a lithium niobate single crystal. The piezoelectric substrate 3 has a main surface 3a and a main surface 3b on the back side. The planar shape of the piezoelectric substrate 3 may be appropriately set. For example, the piezoelectric substrate 3 is a rectangle having a predetermined direction (Y direction) as a longitudinal direction. The size of the piezoelectric substrate 3 may be set as appropriate. For example, the thickness is 0.2 mm to 0.5 mm, and the length of one side is 0.5 mm to 2 mm.

  FIG. 3 is a schematic plan view showing a wiring structure on the main surface 3 a of the piezoelectric substrate 3.

  The piezoelectric substrate 3 is provided with a filter unit 12 having a function of filtering a signal. A region surrounded by a broken line in FIG. The filter unit 12 includes first to fourth series resonators 19a to 19d (hereinafter, these may be collectively referred to as a series resonator 19) and first to third parallel resonators 21a to 21c (hereinafter, these are referred to as a series resonator 19). (Which may be collectively referred to as parallel resonators 21) is a ladder type filter. In the schematic diagram of FIG. 3, the series resonator 19 and the parallel resonator 21 are hatched for easy understanding.

  The series resonator 19 and the parallel resonator 21 are, for example, an IDT (InterDigital Transducer) electrode arranged such that a pair of comb-like electrodes having a plurality of electrode fingers mesh with each other, and an IDT electrode The surface acoustic wave propagation direction (X direction) is composed of two reflector electrodes. The IDT electrode of each resonator has its intersection width, electrode width, number of electrode fingers, pitch between electrode fingers, and the like based on the resonance characteristics required for each of the series resonator 19 and the parallel resonator 21.

  In addition to the series resonator 19 and the parallel resonator 21, the main surface 3a of the piezoelectric substrate 3 includes an input signal pad 13a, an output signal pad 13b, a first reference potential pad 13c, a second reference potential pad 13d, and a third A reference potential pad 13e and a fourth reference potential pad 13f are provided, and these pads are electrically connected to either the series resonator 19 or the parallel resonator 21 by various wirings. Specifically, the input signal pad 13 a is connected to the first series resonator 19 a by the input signal wiring 22. The output signal pad 13b is connected to the fourth series resonator 19d by the output signal wiring 23. The first to fourth reference potential pads 13 c to 13 f are connected to the parallel resonator 13 by a reference potential wiring 24. In the present embodiment, the reference potential wiring 24 can be divided into two regions, a first region 24a and a second region 24b. The first region 24a is a region that is commonly connected to the first to third parallel resonators 21a to 21c in the reference potential wiring 24, and the second region 24b is from the first region 24a of the reference potential wiring. This is an extended area. A boundary between the first region 24a and the second region 24b is indicated by a one-dot chain line B. The second region 24 b of the reference potential wiring 24 is formed in a substantially C shape along the outer periphery of the main surface 3 a of the piezoelectric substrate 3. In other words, the entire second region 24b is formed along the outer periphery of the main surface 3a of the piezoelectric substrate 3, and has a gap so that both ends are not connected. By forming the second region 24b in this way, a relatively large inductance is formed in the second region.

  The first series resonator 19a, the second series resonator 19b, and the first parallel resonator 21a are connected to each other by a first intermediate wiring 25a. The second series resonator 19b, the third series resonator 19c, and the second parallel resonator 21b are connected to each other by a second intermediate wiring 25b. The third series resonator 19c, the fourth series resonator 19d, and the third parallel resonator 21c are connected to each other by a third intermediate wiring 25c.

  Various wirings, electrodes, and pads formed on the main surface 3a of the piezoelectric substrate 3 are made of, for example, an Al alloy such as an Al—Cu alloy, and the thickness thereof is, for example, 100 to 200 nm. These various wirings, electrodes, and pads may have a structure in which different metal materials are laminated. For example, the wiring, electrodes, and pads may be formed by laminating a metal made of a combination of Ti / Al, Cr / Ni / Au, Ni / Au. Also good.

The series resonator 19 and the parallel resonator 21 are covered with a protective layer 26 as shown in the cross-sectional view of FIG. The protective layer 26 mainly contributes to the oxidation prevention of the electrodes constituting the series resonator 19 and the parallel resonator 21. The protective layer 26 is formed of, for example, a material having an insulating property and a mass that is light enough not to affect the propagation of the SAW, such as silicon oxide (SiO ₂ or the like), silicon nitride, silicon, or the like. The thickness of the protective layer 26 is, for example, 10 to 50 nm.

  The protective cover 5 is provided so as to secure such a vibration space 51 of the series resonator 19 and the parallel resonator 21 of the filter unit 12. The planar shape of the protective cover 5 is the same as the planar shape of the piezoelectric substrate 3, for example. The protective cover 5 has, for example, a width approximately the same as that of the main surface 3a and covers substantially the entire surface of the main surface 3a.

  The protective cover 5 includes a frame portion 15 stacked on the main surface 3 a and a lid portion 17 stacked on the frame portion 15. An opening is formed in the frame portion 15, and the opening is closed by the lid portion 17, whereby a vibration space 51 is formed between the main surface 3 a and the protective cover 5.

  The frame portion 15 is configured by a layer having a substantially constant thickness. The thickness of the frame portion 15 is, for example, several μm to 30 μm. The lid portion 17 is composed of a layer having a substantially constant thickness. The thickness of the lid portion 17 is, for example, several μm to 30 μm.

  The frame portion 15 and the lid portion 17 are made of, for example, a photosensitive resin. The photosensitive resin is, for example, a urethane acrylate-based, polyester acrylate-based, or epoxy acrylate-based resin that is cured by radical polymerization of an acryl group or a methacryl group.

  The frame portion 15 and the lid portion 17 may be formed of the same material or may be formed of different materials. In the present application, for convenience of explanation, the boundary line between the frame portion 15 and the lid portion 17 is clearly shown. However, in an actual product, the frame portion 15 and the lid portion 17 are formed of the same material and are integrally formed. May be.

  A plurality of terminals are formed so as to penetrate the frame portion 15 and the lid portion 17. In the present embodiment, six terminals are formed. Specifically, the input signal terminal 6, the output signal terminal 7, the first reference potential terminal 8, the second reference potential terminal 9, the third reference potential terminal 10, and the fourth reference potential terminal 11. The input signal terminal 6 stands on the input signal pad 13a shown in FIG. 3, and the output signal terminal 7 stands on the output signal pad 13b. The first reference potential terminal 8 is connected to the first reference potential pad 13c, the second reference potential terminal 9 is connected to the second reference potential pad 13d, the third reference potential terminal 10 is connected to the third reference potential pad 13e, and the fourth reference potential is connected. The terminals 11 are respectively set on the fourth reference potential pads 13f.

  Among these terminals, the input signal terminal 6, the output signal terminal 7, and the first reference potential terminal 8 are exposed from the upper surface of the protective cover 5 (surface opposite to the piezoelectric substrate 3), and a metal layer 14 described later. And are separated. On the other hand, the second reference potential terminal 9, the third reference potential terminal 10, and the fourth reference potential terminal 11 are connected to the metal layer 14. FIG. 2 shows an aspect in which the metal layer 14 and the fourth reference potential terminal 11 are connected. The second and third reference potential terminals 9 and 10 are also connected to the metal layer 14 in the same manner as the fourth reference potential terminal 11 shown in FIG.

  As shown in the cross-sectional view of FIG. 2, the first reference potential terminal 8 includes a column portion 8a that is a portion that penetrates the protective cover 5, and a land 8b that is connected to an exposed portion of the column portion 8a from the protective cover 5. have. The land 8 b has a flange laminated on the upper surface of the protective cover 5. Similarly to the first reference potential terminal 8, the input signal terminal 6 and the output signal terminal 7 have a pillar portion that is a portion penetrating the protective cover 5 and a land connected to the exposed portion of the pillar portion from the protective cover 5. Have.

  On the other hand, as shown in the cross-sectional view of FIG. 2, the fourth reference potential terminal 11 has a pillar portion that is a portion penetrating the protective cover 5 but does not have a land. Similarly, the second reference potential terminal 9 and the third reference potential terminal 10 have column portions but do not have lands.

  These terminals are formed by, for example, copper plating, and a plating base layer 35 is formed between the terminals and the protective cover 5.

  A metal layer 14 is formed on the main surface 17 a of the lid portion 17. The metal layer 14 can be formed by the same process as that of the terminal described above by, for example, copper plating.

The metal layer 14 is almost entirely covered with a thin insulating film 18. By covering the metal layer 14 with the insulating film 18, when the SAW device 1 is mounted on an external circuit board or the like, terminals exposed from the metal layer 14 and the protective cover 5 (input signal terminal 6, output signal terminal 7, It is possible to prevent the first reference potential terminal 8 from being short-circuited by a mounting bonding material such as solder, etc. The insulating film 18 is made of, for example, SiO _2, etc. 1, the window 18a is provided, and in this embodiment, three windows are provided at portions corresponding to the second reference potential terminal 9, the third reference potential terminal 10, and the fourth reference potential terminal 11. By providing such a window portion 18a, a portion exposed from the window portion 18a of the metal layer 14 and a terminal of an external circuit board on which the SAW device 1 is mounted are soldered. Connect with bonding materials such as That is, a portion exposed from the window portion 18a of the metal layer 14 can be used as a land for bonding to an external circuit board.

  Next, the positional relationship between the metal layer 14 and the vibration space 51 will be described with reference to FIG. FIG. 4 is a plan view of the SAW device 1 when the SAW device 1 is viewed from the protective cover 5 side, and the outer peripheral edge of the vibration space 51 is indicated by a one-dot chain line. In FIG. 4, the insulating film 18 is omitted and the column portion of each reference potential terminal is indicated by a two-dot chain line.

  As shown in the figure, the metal layer 14 is formed so that its outer peripheral edge is slightly larger than the outer peripheral edge of the vibration space 51. In other words, the metal layer 14 is provided so as to cover the opening of the frame portion 15 when seen in a plan view. By providing such a metal layer 14, it is possible to prevent the vibration space 51 from being greatly deformed even in a high temperature and high pressure environment such as when the entire SAW device 1 is resin-molded. The thickness of the metal layer 14 is set to 35 μm to 55 μm, for example. By forming the metal layer 14 relatively thick as described above, the effect of preventing the vibration space 51 from being deformed can be further enhanced.

  The inventors pay attention to the metal layer 14 and intensively research whether the shape of the metal layer 14 can improve the attenuation outside the passband. The metal layer 14 and a specific reference potential terminal It has been found that the amount of attenuation outside the passband of the filter can be increased by separating.

  6 to 9 are diagrams showing the results of examining the relationship between the connection between the metal layer 14 and each reference potential terminal and the attenuation characteristics outside the passband by simulation. The simulation was performed on a filter having the configuration shown in FIG. 3, and the passband frequency is a passband frequency (1574 MHz to 1576 MHz) for GPS (Global Positioning System).

  FIG. 5 is a plan view of the SAW device of the comparative pattern F in which all reference potential terminals are connected to the metal layer 14. FIG. 6A shows the first reference potential terminal 8 among the reference potential terminals as the metal layer 14. FIG. 6 is a plan view of a SAW device having a pattern A in which a second reference potential terminal 9, a third reference potential terminal 10, and a fourth reference potential terminal 11 are connected to a metal layer 14.

  FIG. 6B compares the attenuation characteristics of the pattern A and the attenuation characteristics of the comparison pattern F. The solid line indicates the attenuation characteristics of the pattern A, and the broken line indicates the attenuation characteristics of the pattern F. As shown in the figure, it can be seen that the pattern A has a larger amount of attenuation outside the passband in the vicinity of 2 GHz required for the GPS filter than the comparison pattern F. That is, as compared with the case where all the reference potential terminals are connected to the metal layer 14, the first set up in the first region of the reference potential wiring connected in common to the plurality of parallel resonators constituting the ladder filter. It can be seen that the out-of-band attenuation is significantly improved by separating the reference potential terminal 8 from the metal layer 14.

  7A, the third reference potential terminal 10 is separated from the metal layer 14 among the reference potential terminals, and the first reference potential terminal 8, the second reference potential terminal 9, and the fourth reference potential terminal 11 are connected to the metal layer 14. FIG. It is a top view of the SAW device of connected pattern B.

  FIG. 7B compares the attenuation characteristics of the pattern B and the attenuation characteristics of the comparison pattern F. The solid line indicates the attenuation characteristics of the pattern B, and the broken line indicates the attenuation characteristics of the pattern F. As shown in the figure, there is almost no difference in out-of-band attenuation characteristics between the pattern B and the comparison pattern F. That is, even if the third reference potential terminal 10 standing in the second region of the reference potential wiring commonly connected to the plurality of parallel resonators constituting the ladder filter is separated from the metal layer 14, all the reference potential terminals As compared with the case where is connected to the metal layer 14, no significant improvement in out-of-band attenuation is observed.

  FIG. 8A shows that the first reference potential terminal 8, the third reference potential terminal 10, and the fourth reference potential terminal 11 are separated from the metal layer 14 among the reference potential terminals, and the second reference potential terminal 9 is connected to the metal layer 14. It is a top view of the SAW device of the connected pattern C.

  FIG. 8B compares the attenuation characteristic of the pattern C and the attenuation characteristic of the comparison pattern F, where the solid line indicates the attenuation characteristic of the pattern C and the broken line indicates the attenuation characteristic of the pattern F. As shown in the figure, it can be seen that the amount of attenuation outside the passband in the vicinity of 2 GHz required for the GPS filter is larger in the pattern C than in the comparison pattern F. That is, as compared with the case where all the reference potential terminals are connected to the metal layer 14, the first set up in the first region of the reference potential wiring connected in common to the plurality of parallel resonators constituting the ladder filter. By separating the reference potential terminal 8, the third reference potential terminal 10 and the fourth reference potential terminal 11 standing in the second region of the reference potential wiring from the metal layer 14, the out-of-band attenuation is remarkably improved. This result is almost the same as the result of pattern A.

  FIG. 9A is a plan view of a SAW device having a pattern D in which all reference potential terminals are separated from the metal layer 14.

  FIG. 9B compares the attenuation characteristic of the pattern D and the attenuation characteristic of the comparison pattern F, where the solid line indicates the attenuation characteristic of the pattern F and the broken line indicates the attenuation characteristic of the pattern F. As shown in the figure, there is no significant improvement in the attenuation characteristics of the pattern D compared to the comparative pattern F, and conversely, the attenuation amount outside the passband near 1800 MHz is higher in the pattern D than in the comparative pattern F. Is slightly smaller. That is, even if all the reference potential terminals are disconnected from the metal layer 14, no significant improvement is observed in the attenuation characteristics outside the passband as compared to the case where all the reference potential terminals are connected to the metal layer 14.

  From the above simulation results, the first reference potential terminal 8 set up in the first region of the reference potential wiring connected to the plurality of parallel resonators constituting the ladder type filter is separated from the metal layer 14, and the reference potential wiring By connecting at least one of the second reference potential terminal 9, the third reference potential terminal 10 and the fourth reference potential terminal 11 standing in the second region extending from the first region to the metal layer 14. It was confirmed that the attenuation outside the pass band of the SAW device can be improved.

  The reason why the attenuation characteristic outside the passband can be improved by separating the predetermined reference potential terminal from the metal layer and connecting the predetermined reference potential terminal to the metal layer is as follows. It is done.

  10A and 10B are equivalent circuit diagrams of the SAW device. FIG. 10A is an equivalent circuit diagram when all the reference potential terminals are connected to the metal layer 14, and FIG. 10B is a diagram illustrating the first reference potential terminal 8 of the metal layer 14. The equivalent circuit diagrams in the case where the second reference potential terminal 9 is connected to the metal layer 14 are shown. For simplification of description, an equivalent circuit diagram in which the third reference potential terminal 10 and the fourth reference potential terminal 11 are omitted is shown.

  In FIG. 10, L (24a) is an inductor formed in the first region 24a of the reference potential wiring 24, L (24b) is an inductor formed in the second region 24b of the reference potential wiring 24, and L (8) is the first. An inductor formed at the reference potential terminal 8, L (9) represents an inductor formed at the second reference potential terminal 9, and L (14) represents an inductor formed at the metal layer 14.

  As shown in FIG. 10A, when both the first reference potential terminal 8 and the second reference potential terminal 9 are connected to the metal layer 14, the first reference potential terminal 8 and the second reference potential terminal 8 are connected via the metal layer 14. The reference potential terminal 9 is connected at the end thereof, and it is considered that the inductor L (14) is formed at this connection portion.

  Here, considering the magnitude relationship among the inductor L (24b), the inductor L (8), the inductor L (9), and the inductor L (14), the inductor L (24b) includes the inductor L (8) and the inductor L. (9) It has a sufficiently larger inductance than the inductor L (14). Since the inductor L (24b) is formed by a thin and long wiring (second region 24b of the reference potential wiring) drawn on the piezoelectric substrate, its inductance becomes relatively large, whereas the inductor L (8 ), The inductor L (9) and the inductor L (14) are formed in a metal part having a short length and a large diameter and thickness, and their inductance is relatively small. Because.

  Assuming such a magnitude relationship of the inductance, when looking at the circuit of FIG. 10 (a), the inductor L that is much smaller than the inductor L (24b) at the end of the path on the inductor L (24b) side. Since (14) is formed, it is considered that most of the signal that has passed through the inductor L (24a) flows to the inductor L (8) side. In other words, the signal that has passed through the inductor L (24a) hardly flows to the inductor L (24b). Therefore, it is considered that a large inductance cannot be obtained in the case of the equivalent circuit diagram of FIG.

  On the other hand, in the case of the circuit of FIG. 10B, since the first reference potential terminal 8 is disconnected from the metal layer 14, a bypass path (inductor L (14)) having a small inductance is not formed. The signal that has passed through 24a) passes through the inductor L (24b) having a certain degree of inductance. Accordingly, it is considered that a relatively large inductance can be obtained in the equivalent circuit diagram of FIG.

  However, when all the reference potential terminals are separated from the metal layer 14, the metal layer 14 is in an electrically floating state, and unnecessary capacitance is generated between the metal layer 14 and various electrodes constituting the filter unit. It is considered that the filter characteristics are deteriorated as in the simulation result shown in the pattern D SAW device.

  Next, a preferred example of the shape of the metal layer 14 when the terminal and the metal layer 14 are separated will be described with reference to FIGS.

  11 corresponds to the plan view of the SAW device shown in FIG. 6, and the shape of the metal layer 14 is different from that of FIG. Specifically, in the SAW device 1 shown in FIG. 6, when the metal layer 14 is viewed in plan, the input signal terminal 6, the output signal terminal 7, and the first reference that are not connected to the metal layer 14. Whereas the potential terminal 8 is formed so as to surround approximately half of these terminals, in the SAW device 1 shown in FIG. 11, the metal layer 14 is formed so as to surround the entire terminals. Has been. From another point of view, in the SAW device 1 shown in FIG. 11, the metal layer 14 is disposed at the location where the input signal terminal 6, the output signal terminal 7, and the first reference potential terminal 8 are arranged. It is formed over substantially the entire upper surface of the lid portion 17 with a circular window portion that is slightly larger than the signal terminal 7 and the first reference potential terminal 8.

  By forming the metal layer 14 in the shape as shown in FIG. 11, it is possible to suppress the generation of cracks in the lid portion 17, particularly the peripheral portion of the terminal that is not connected to the metal layer 14. This is confirmed from the result of examining the state of change of the stress generated in the lid portion 17 due to the difference in the shape of the metal layer 14 by simulation.

12A and 12B are plan views of the SAW device 1 used in the simulation model. FIG. 12A is a diagram in which the metal layer 14 is formed so as not to surround the dummy terminals 31, and FIG. 12B is a diagram in which the metal layer 14 is a dummy. It is formed so as to surround the terminal 31. In the model of FIG. 12A and the model of (b), all the conditions other than the shape of the metal layer 14 were the same. Specifically, the piezoelectric substrate 3 is made of LiTaO ₃ , the protective cover 5 is made of a photosensitive acrylate resin, and the metal layer 14 and the dummy terminal 31 are made of Cu. The model is obtained by halving the SAW device 1.

  FIG. 13 shows the result of simulation performed on the model of FIG. FIG. 13 (a) shows the state of stress generated in the lid portion 17 corresponding to the model of FIG. 12 (a), and FIG. 13 (b) corresponds to the model of FIG. 12 (b). The state of the stress generated in the lid portion 17 is shown. The simulation was performed by setting the temperature load to −125 ° C. in a state where the SAW device 1 having the model shown in FIG. 12 is solder-mounted on another substrate. The simulation used here is a thermal stress simulation by a finite element method.

  In FIG. 13, the magnitude of the stress is represented by color shading, and the darker the color, the greater the stress that is generated. As is apparent from the results shown in FIG. 13, in the case of (a), a relatively large stress is generated around the dummy terminal 31, whereas in the case of (b), compared with that of (a). Thus, the stress generated around the dummy terminal 31 is reduced. In the case of (a), the maximum value of the generated stress was 28.11 MPa, whereas in the case of (b), the maximum value of the generated stress was 23.14 MPa, which was reduced by about 18%. It had been.

  From the above results, it can be said that by forming the metal layer 14 so as to surround the terminals as shown in FIG. 11, it is possible to suppress the occurrence of cracks in the lid portion 17 constituting the cover 5.

  Therefore, according to the SAW device 1 shown in FIG. 11, since it is possible to suppress the occurrence of cracks in the lid portion 17, the state of the atmosphere of the vibration space 51 changes due to the occurrence of cracks. The electrical characteristics of the SAW device 1 can be stabilized. The input signal terminal 6 and the output signal terminal 7 are one embodiment of the signal terminal of the present invention. The type of terminal surrounded by the metal layer 14 is not limited to the signal terminal, and various terminals (for example, a reference potential terminal or an electrically floating dummy that is not connected to the upper surface of the metal layer 14 and the lid portion 17). It is needless to say that the occurrence of cracks can be suppressed around the terminals, etc. by forming the metal layer 14 so as to surround the terminals.

  The present invention is not limited to the above embodiments and modifications, and may be implemented in various ways.

  In the above-described embodiment, the first reference potential terminal 8 is disconnected from the metal layer 14 and the other reference potential terminals are connected to the metal layer 14. However, the reference potential terminal and the metal layer 14 are connected and disconnected. The reference potential terminal raised in the first region 24 a of the reference potential wiring 24 is connected to the metal layer 14, and the reference potential terminal raised in the second region 24 b of the reference potential wiring 24 is connected to the metal layer 14. Any aspect may be used as long as it is separated from the above. For example, in the above-described embodiment, if at least one of the second reference potential terminal 9, the third reference potential terminal 10, and the fourth reference potential terminal 11 is connected to the metal layer 14, the other reference potential terminals are connected. It may be separated from the metal layer 14. However, in order to effectively use the inductor formed in the second region 24 b of the reference potential wiring 24, the second reference potential terminal 9 disposed at the terminal portion of the second region 24 b is connected to the metal layer 14. It is preferable to keep it.

  In the above-described embodiment, one vibration space 51 is provided. However, the vibration space 51 may be divided into a plurality of sections. In other words, a plurality of vibration spaces may be provided. In this case, one vibration space is reduced and mold resistance is improved.

DESCRIPTION OF SYMBOLS 1 ... SAW device 3 ... Piezoelectric substrate 5 ... Protective cover 6 ... Input signal terminal 7 ... Output signal terminal 8 ... First reference potential terminal 9 ... Second reference Potential terminal 10 ... third reference potential terminal 11 ... fourth reference potential terminal 12 ... filter portion 14 ... metal layer 15 ... frame portion 17 ... lid portion 18 ... insulating film

Claims (5)

A piezoelectric substrate;
A ladder-type filter unit including a plurality of parallel resonators provided on the piezoelectric substrate;
A protective cover having a frame portion arranged on the main surface of the piezoelectric substrate so as to surround the plurality of parallel resonators and a lid portion that closes an opening of the frame portion;
A reference potential wiring having a first region provided on the piezoelectric substrate and connected in common to the plurality of parallel resonators and a second region extending from the first region;
A first reference potential terminal provided upright in the first region of the reference potential wiring and penetrating the frame portion and the lid portion;
A second reference potential terminal provided upright in the second region of the reference potential wiring and penetrating the frame portion and the lid portion;
A metal layer provided on the main surface of the lid, connected to the second reference potential terminal and not connected to the first reference potential terminal;
A surface acoustic wave device comprising:   The second region is entirely formed along the outer periphery of the main surface of the piezoelectric substrate, and has a gap so that both ends are not connected to each other. The second reference potential terminal is the second reference potential terminal. The surface acoustic wave device according to claim 1, wherein the surface acoustic wave device is disposed at a distal end portion extending from the first region of the region.   The surface acoustic wave device according to claim 1, further comprising an insulating film covering the metal layer.   The surface acoustic wave device according to claim 3, wherein the insulating film is provided with a window portion exposing a part of the metal layer. A signal terminal for inputting or outputting a signal to the filter unit;
The signal terminal passes through the frame portion and the lid portion,
5. The surface acoustic wave device according to claim 1, wherein the metal layer surrounds the signal terminal and is spaced apart from the signal terminal when the metal layer is viewed in plan.