Filter and multiplexer

Abstract

To provide a filter capable of being miniaturized.SOLUTION: A filter 100 comprises a mounting board 10 and a plurality of acoustic wave chips 30. The mounting board 10 has a top surface 11 and a normal line 41 of the top surface 11. The plurality of acoustic wave chips 30, which are serially connected to one another as a circuit and in which a normal line 40 with respect to each surface 35 is mounted perpendicular to or slantingly with respect to the normal line 41 so that a cavity 38 can be provided between themselves and the mounting board 10, each have a surface 35 and an acoustic wave resonator 32 provided on the surface 35.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to filters and multiplexers. [Background technology]

[0002] Acoustic wave resonators are used in filters and duplexers for high-frequency circuits in wireless terminals such as mobile terminals. Surface acoustic wave resonators, in which a pair of interdigital electrodes is provided on a piezoelectric substrate, are known as acoustic wave resonators (see, for example, Patent Documents 1 to 3). Also known are piezoelectric thin-film resonators, in which a lower electrode and an upper electrode are provided on a substrate with a piezoelectric film sandwiched therebetween (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-147708 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-89069 [Patent Document 3] Japanese Patent Publication No. 2022-172569 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-158161 Summary of the Invention [Problem to be solved by the invention]

[0004] A filter includes a plurality of acoustic wave resonators connected to a path between an input terminal and an output terminal, and miniaturization of such filters is desired.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to reduce the size of a filter. [Means for solving the problem]

[0006] The present invention is a filter comprising a mounting substrate having a first surface and a first normal that is normal to the first surface, and a plurality of acoustic wave chips connected in series to each other as a circuit, each having a second surface and an acoustic wave resonator provided on the second surface, and mounted such that the second normal that is normal to each of the second surfaces is perpendicular or inclined to the first normal so as to have an air gap between the mounting substrate and the acoustic wave chips.

[0007] In the above configuration, the plurality of acoustic wave chips may be mounted on the first surface with the second surfaces facing the same direction.

[0008] In the above configuration, the first surface may have a first region and a second region adjacent to the first region, and among the plurality of acoustic wave chips, the acoustic wave chips located in the first region may be mounted on the first surface with the second surface facing away from the second region, and the acoustic wave chips located in the second region may be mounted on the first surface with the second surface facing away from the first region.

[0009] In the above configuration, when directions parallel to the first surface and perpendicular to each other are defined as a first direction and a second direction, the multiple acoustic wave chips can be configured to be mounted on the first surface with portions overlapping in the first direction and aligned in the second direction.

[0010] In the above configuration, at least one pair of adjacent acoustic wave chips among the plurality of acoustic wave chips may be configured such that the acoustic wave resonators of the adjacent acoustic wave chips do not overlap but are shifted from each other in the first direction.

[0011] In the above configuration, the plurality of elastic wave chips may have at least three or more elastic wave chips, and more than half of the plurality of elastic wave chips may be arranged parallel to each other, and the remaining elastic wave chips may be arranged at an angle from the parallel state.

[0012] In the above configuration, the wiring is provided on the first surface and connected to the plurality of acoustic wave chips, and among the wiring, the ground wiring can be configured to have a larger area than the signal wiring when viewed from the first surface.

[0013] The present invention is a multiplexer comprising the filter described above. [Effects of the Invention]

[0014] According to the present invention, the filter can be made smaller. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1(a) is a plan view of the filter according to the first embodiment, and FIG. 1(b) and FIG. 1(c) are side views of the acoustic wave chip. [Figure 2] 2(a) and 2(b) are a plan view and a cross-sectional view of the acoustic wave resonator according to the first embodiment. [Figure 3] FIG. 3(a) is a plan view of a filter according to a first modified example of the first embodiment, and FIG. 3(b) is a plan view of a filter according to a second modified example of the first embodiment. [Figure 4] FIG. 4(a) is a cross-sectional view of a filter according to a third modification of the first embodiment, FIG. 4(b) is a cross-sectional view of a filter according to a fourth modification of the first embodiment, and FIG. 4(c) is a cross-sectional view of a filter according to a fifth modification of the first embodiment. [Figure 5] FIG. 5(a) is a side view of a filter according to Example 2, FIG. 5(b) is a side view of a filter according to a modified example of Example 2, and FIG. 5(c) is an enlarged view of region A in FIG. 5(b). [Figure 6] 6(a) and 6(b) are a circuit diagram and a cross-sectional view of a duplexer according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [Example]

[0017] FIG. 1(a) is a plan view of a filter 100 according to a first embodiment, and FIGS. 1(b) and 1(c) are side views of an acoustic wave chip 30. In FIG. 1(a), the wiring 13 is hatched for clarity (the same applies to the following similar figures). Directions parallel to the top surface 11 of the mounting substrate 10 and perpendicular to each other are defined as the X and Y directions. A direction perpendicular to the top surface 11 is defined as the Z direction. As shown in FIGS. 1(a) to 1(c), multiple acoustic wave chips 30 are mounted on the flat top surface 11 of the mounting substrate 10. The mounting substrate 10 is, for example, a silicon substrate, a sapphire substrate, a quartz substrate, a spinel substrate, a lithium tantalate substrate, a lithium niobate substrate, or a ceramic substrate, but other substrates are also acceptable.

[0018] Wiring 13 and pads 16 are provided on the upper surface 11 of the mounting substrate 10. The pads 16 include an input terminal Tin, an output terminal Tout, and a ground terminal Gnd. The wiring 13 includes a signal wiring 14 that forms a path for transmitting a high-frequency signal between the input terminal Tin and the output terminal Tout, and a ground wiring 15 that is connected to the ground terminal Gnd. The wiring 13 and the pads 16 are formed of a metal such as gold.

[0019] The acoustic wave chip 30 includes a substrate 31, an acoustic wave resonator 32, a pad 33, and wiring 34. The acoustic wave resonator 32, the pad 33, and the wiring 34 are provided on a flat surface 35 of the substrate 31. The wiring 34 electrically connects the acoustic wave resonator 32 and the pad 33. The acoustic wave chip 30 is mounted on the upper surface 11 of the mounting substrate 10 by joining the pad 33 to the wiring 13 of the mounting substrate 10 with solder 36. The acoustic wave chip 30 is mounted on the upper surface 11 of the mounting substrate 10 such that a normal 40 to the surface 35 is perpendicular to a normal 41 to the upper surface 11 of the mounting substrate 10. The perpendicular angle allows for a tilt within the range of manufacturing error. For example, the angle θ between the normal 40 and the normal 41 is allowed to be between 85° and 95°.

[0020] One or more acoustic wave chips 30 are connected in series to a path between the input terminal Tin and the output terminal Tout, and the series resonators S1 to S6 are formed by the acoustic wave resonators 32 of these series-connected acoustic wave chips 30. Parallel resonators P1 to P5 are formed by the acoustic wave resonators 32 of one or more acoustic wave chips 30, one end of which is connected to a path between the input terminal Tin and the output terminal Tout and the other end of which is connected to a ground terminal Gnd. As described above, the filter 100 is a ladder-type filter having the series resonators S1 to S6 and the parallel resonators P1 to P5. The ground wiring 15 to which the parallel resonators P2 to P5 are commonly connected is thicker and has a larger area than the ground wiring 15 to which the signal wiring 14 and the parallel resonator P1 are connected when viewed from the top surface 11 of the mounting substrate 10.

[0021] The multiple acoustic wave chips 30 are mounted on the upper surface 11 of the mounting substrate 10 along the Y direction and are parallel to one another. The parallel orientation allows for a tilt of the order of manufacturing error. For example, a tilt of 10° or less is allowed, and preferably 5° or less. The multiple acoustic wave chips 30 are mounted on the upper surface 11 of the mounting substrate 10 so that each acoustic wave resonator 32 faces the +X direction (the direction of the arrow in the figure). The multiple acoustic wave chips 30 are also mounted on the upper surface 11 of the mounting substrate 10 lined up in the X direction so that they partially overlap in the Y direction.

[0022] The acoustic wave resonators 32 of the acoustic wave chips 30 adjacent to each other in the X direction are shifted in the Y direction and do not overlap. For example, acoustic wave chips 30 including series resonators S1 and S2 are adjacent to each other in the X direction, and the series resonators S1 and S2 are shifted in the Y direction and do not overlap. Note that there may be a pair of adjacent acoustic wave chips 30 in which the acoustic wave resonators 32 overlap each other in the Y direction.

[0023] 2(a) and 2(b) are a plan view and a cross-sectional view of an acoustic wave resonator 32 according to a first embodiment. As shown in FIG. 2(a), the acoustic wave resonator 32 may be a surface acoustic wave resonator. In this case, an IDT (Interdigital Transducer) 50 and a reflector 51 are provided on a surface 35 of a substrate 31 made of a piezoelectric material such as lithium tantalate or lithium niobate. The IDT 50 has a pair of opposing comb electrodes 52. The comb electrodes 52 have a plurality of electrode fingers 53 and a bus bar 54 to which the plurality of electrode fingers 53 are connected. The reflectors 51 are provided on both sides of the IDT 50. The plurality of electrode fingers 53 excite a surface acoustic wave on the substrate 31. The pitch of the electrode fingers 53 of one of the pair of comb electrodes 52 is approximately the wavelength λ of the acoustic wave. The wavelength λ is approximately twice the pitch D of the plurality of electrode fingers 53. The IDT 50 and the reflector 51 are formed of a metal film such as aluminum, copper, or molybdenum. A protective film or a temperature compensation film covering the IDT 50 and the reflector 51 may be provided on the surface 35 of the substrate 31. The surface of the substrate 31 opposite to the surface 35 may be bonded to a support substrate. An insulating film such as silicon oxide and / or aluminum oxide may be provided between the substrate 31 and the support substrate. That is, the substrate 31 may be bonded directly or indirectly to the support substrate.

[0024] As shown in FIG. 2( b), the acoustic wave resonator 32 may be a piezoelectric thin-film resonator. In this case, a piezoelectric layer 56 is provided on the surface 35 of a substrate 31 made of a semiconductor such as silicon or an insulator such as quartz, and a lower electrode 55 and an upper electrode 57 are provided to sandwich the piezoelectric layer 56. A gap 58 is formed between the lower electrode 55 and the substrate 31. The region where the lower electrode 55 and the upper electrode 57 face each other, sandwiching at least a portion of the piezoelectric layer 56, is a resonance region 59. In the resonance region 59, the lower electrode 55 and the upper electrode 57 excite acoustic waves in the piezoelectric layer 56. The lower electrode 55 and the upper electrode 57 are metal films, such as ruthenium films. The piezoelectric layer 56 is, for example, an aluminum nitride layer, a zinc oxide layer, a single-crystal lithium tantalate layer, or a single-crystal lithium niobate layer. An acoustic reflection film that reflects acoustic waves may be provided instead of the gap 58.

[0025] According to the first embodiment, a plurality of acoustic wave chips 30 having acoustic wave resonators 32, which are series resonators S1 to S6 or parallel resonators P1 to P5, on a surface 35 (second surface) are mounted on the upper surface 11 of the mounting substrate 10 such that a normal 40 (second normal) to the surface 35 is perpendicular to a normal 41 (first normal) to the upper surface 11 (first surface) of the mounting substrate 10, so that a gap 38 is formed between the acoustic wave chips 30 and the mounting substrate 10. In this way, by mounting the acoustic wave chips 30 upright on the mounting substrate 10, it is possible to achieve miniaturization in the XY plane.

[0026] In the first embodiment, the series resonators S1 to S6 and the parallel resonators P1 to P5 are provided on separate acoustic wave chips 30. This suppresses leakage of acoustic waves between the resonators, thereby improving the characteristics. Furthermore, it is possible to select the optimal piezoelectric material, thickness, and cut angle, the optimal IDT material and thickness, the optimal electrode finger pitch and line width, and the optimal material and thickness of the lower and upper electrodes for each resonator. Therefore, at least one of the multiple acoustic wave chips 30 may differ from the others in at least one of the above-mentioned features. This improves the characteristics. Furthermore, it is possible to mount acoustic wave chips 30 whose performance has been confirmed in advance on the mounting substrate 10, thereby improving the yield.

[0027] In the first embodiment, the multiple acoustic wave chips 30 are mounted on the upper surface 11 of the mounting substrate 10 with the surfaces 35 on which the acoustic wave resonators 32 are provided facing the same direction (+X direction). This positions the substrates 31 of the acoustic wave chips 30 between the acoustic wave resonators 32, thereby suppressing electromagnetic interference between the acoustic wave resonators 32. Furthermore, by mounting the multiple acoustic wave chips 30 on the mounting substrate 10 with their surfaces 35 facing the same direction, further miniaturization in the XY plane can be achieved. The surfaces 35 of the multiple acoustic wave chips 30 facing the same direction does not necessarily mean that the normals 40 of the surfaces 35 are completely parallel to each other. The normals 40 may be inclined by 10 degrees or less in the left-right and up-down directions, and preferably by 5 degrees or less.

[0028] In the first embodiment, the acoustic wave chips 30 are mounted on the upper surface 11 of the mounting substrate 10 so as to be aligned in the X direction (second direction) and partially overlap each other in the Y direction (first direction). This allows further miniaturization in the XY plane.

[0029] Furthermore, in the first embodiment, in at least one pair of adjacent acoustic wave chips 30 among the multiple acoustic wave chips 30, the acoustic wave resonators 32 are shifted in the Y direction (first direction) without overlapping with each other. This makes it possible to suppress electromagnetic interference between the acoustic wave resonators 32. From the viewpoint of suppressing electromagnetic interference between the acoustic wave resonators 32, it is preferable that at least one half of the multiple pairs of two adjacent acoustic wave chips 30 have their acoustic wave resonators 32 shifted in the Y direction without overlapping with each other, more preferably at least three-quarters, and even more preferably at least four-fifths.

[0030] Furthermore, in Example 1, the ground wiring 15 is thicker and has a larger area than the signal wiring 14 when viewed from the top surface 11 of the mounting substrate 10. This reduces the wiring resistance of the ground wiring 15, strengthening the ground and reducing loss. The thicknesses of the ground wiring 15 and the signal wiring 14 increase in accordance with the increase in the areas of the ground wiring 15 and the signal wiring 14. From the viewpoint of reducing the wiring resistance of the ground wiring 15, the thickness and area of the ground wiring 15 are preferably 1.5 times or more, more preferably 2.0 times or more, and even more preferably 2.5 times or more, of the signal wiring 14.

[0031] In the first embodiment, all of the acoustic wave chips 30 provided with the series resonators S1 to S6 and the parallel resonators P1 to P5 are mounted upright on the mounting substrate 10. However, it is acceptable if, among the acoustic wave chips 30 provided with the series resonators S1 to S6 and the parallel resonators P1 to P5, the acoustic wave chips 30 connected in series to each other as a circuit are mounted upright on the mounting substrate 10. For example, since the series resonators S1 to S6 are connected in series between the input terminal Tin and the output terminal Tout, at least two of these may be mounted upright on the mounting substrate 10. Since the series resonator S1 and the parallel resonator P1 are connected in series between the input terminal Tin and the ground terminal Gnd, these may be mounted upright on the mounting substrate 10. Since the series resonator S6 and the parallel resonator P5 are connected in series between the output terminal Tout and the ground terminal Gnd, these may be mounted upright on the mounting substrate 10.

[0032] [Variations] 3A is a plan view of a filter 110 according to a first modification of the first embodiment. As shown in FIG. 3A, in the first modification of the first embodiment, the series resonators S1 to S3 and the parallel resonators P1 and P2 included in the acoustic wave chip 30 mounted in a first region 17 located on the +X direction side of the upper surface 11 of the mounting substrate 10 face the +X direction. The series resonators S4 to S6 and the parallel resonators P3 to P5 included in the acoustic wave chip 30 mounted in a second region 19 located on the −X direction side adjacent to the first region 17 face the −X direction. That is, the series resonators S1 to S3 and the parallel resonators P1 and P2 face the same direction, the series resonators S4 to S6 and the parallel resonators P3 to P5 face the same direction, and the series resonators S1 to S3 and the parallel resonators P1 and P2 face in opposite directions to the series resonators S4 to S6 and the parallel resonators P3 to P5. The other configurations are the same as those in the first embodiment, so the description will be omitted.

[0033] In the first modification of the first embodiment, the top surface 11 of the mounting substrate 10 has a first region 17 and a second region 19 adjacent to the first region 17. The acoustic wave chip 30 located in the first region 17 is mounted on the mounting substrate 10 with the surface 35 on which the acoustic wave resonator 32 is provided facing away from the second region 19 (toward the +X direction), and the acoustic wave chip 30 located in the second region 19 is mounted on the mounting substrate 10 with the surface 35 on which the acoustic wave resonator 32 is provided facing away from the first region 17 (toward the −X direction). As a result, the substrates 31 of the two acoustic wave chips 30 are located between the acoustic wave resonators 32 of the acoustic wave chips 30 located near the boundary between the first region 17 and the second region 19, thereby further suppressing electromagnetic interference between the acoustic wave resonators 32.

[0034] 3B is a plan view of a filter 120 according to a second modification of the first embodiment. As shown in FIG. 3B, in the second modification of the first embodiment, the acoustic wave chip 30 on which the series resonators S1, S2, S4 to S6 and the parallel resonators P1 to P5 are provided is mounted on the upper surface 11 of the mounting substrate 10 along the Y direction and is parallel to one another. The acoustic wave chip 30 on which the series resonator S3 is provided is mounted on the upper surface 11 of the mounting substrate 10 at an angle with respect to the Y direction and is inclined relative to the acoustic wave chip 30 on which the series resonators S1, S2, S4 to S6 and the parallel resonators P1 to P5 are provided. The ground wiring 15 connected to the signal wiring 14 and the parallel resonator P1 is thick and has a large area when viewed from the upper surface 11 of the mounting substrate 10, similar to the ground wiring 15 connected to the parallel resonators P2 to P5. The other configurations are the same as those of the first embodiment, and therefore description thereof will be omitted.

[0035] In the second modification of the first embodiment, the plurality of acoustic wave chips 30 includes at least three or more acoustic wave chips 30, and at least half of the plurality of acoustic wave chips 30 are arranged parallel to one another along the Y direction, while the remaining acoustic wave chips 30 are arranged at an angle with respect to the Y direction. By thus arranging some of the acoustic wave chips 30 at an angle with respect to the other acoustic wave chips 30, it is possible to shorten the wiring 13, thereby reducing wiring resistance and loss. From the viewpoint of miniaturization, it is preferable that 70% or more of the plurality of acoustic wave chips 30 are arranged parallel to one another along the Y direction, more preferably 75% or more, and even more preferably 80% or more.

[0036] Furthermore, in the second modification of the first embodiment, in addition to the ground wiring 15 connected to the parallel resonators P2 to P5, the signal wiring 14 and the ground wiring 15 connected to the parallel resonator P1 are also formed to be thick and have a large area when viewed from the upper surface 11 of the mounting substrate 10. By mounting the acoustic wave chip 30 upright on the upper surface 11 of the mounting substrate 10, the area in which the wiring 13 can be formed is widened, and the wiring 13 can be made thicker and have a larger area. This reduces the wiring resistance of the wiring 13, thereby improving its characteristics. Furthermore, the thicker wiring 13 and the larger area can also improve heat dissipation.

[0037] FIG. 4A is a cross-sectional view of a filter 130 according to a third modification of the first embodiment. As shown in FIG. 4A, in the third modification of the first embodiment, a plurality of acoustic wave chips 30 are mounted upright on an upper surface 11 (the lower surface in FIG. 4A) of a mounting substrate 10, and a plurality of acoustic wave chips 30 are also mounted upright on a lower surface 12 (the upper surface in FIG. 4A). The acoustic wave chips 30 mounted on the upper surface 11 and the acoustic wave chips 30 mounted on the lower surface 12 are electrically connected by via wiring 18 penetrating the mounting substrate 10. The pads 16 provided on the mounting substrate 10 are joined to the pads 61 of the mounting substrate 60 by solder 70, thereby flip-chip mounting the mounting substrate 10 to the mounting substrate 60. A frame 71 is provided on the lower surface 12 of the mounting substrate 10, surrounding the plurality of acoustic wave chips 30 in a plan view seen from above the lower surface 12, and a lid 72 is provided on the frame 71. The other configurations are the same as those of the first embodiment, and therefore description thereof will be omitted.

[0038] In the third modification of the first embodiment, the acoustic wave chips 30 are mounted upright on both the upper surface 11 and the lower surface 12 of the mounting substrate 10. By mounting the multiple acoustic wave chips 30 separately on the top and bottom of the mounting substrate 10 in this manner, further miniaturization in the XY plane direction can be achieved.

[0039] 4(b) is a cross-sectional view of a filter 140 according to a fourth modification of the first embodiment. As shown in FIG. 4(b), in the fourth modification of the first embodiment, a recess 62 is provided in a mounting substrate 60, and the mounting substrate 10 is flip-chip mounted to the mounting substrate 60 so that the acoustic wave chip 30 is disposed in the recess 62. This makes it possible to reduce the size in the XY plane and the height in the Z direction. The other configurations are the same as those of the first embodiment, and therefore a description thereof will be omitted.

[0040] 4(c) is a cross-sectional view of a filter 150 according to a fifth modification of the first embodiment. As shown in FIG. 4(c), in the fifth modification of the first embodiment, the acoustic wave chip 30 is joined to the wiring 13 of the mounting substrate 10 by solder 36, and is also joined to the metal film 63 of the mounting substrate 60 by solder 73. This increases the mechanical strength of the acoustic wave chip 30. The other configurations are the same as those of the first embodiment, and therefore will not be described again. [Example]

[0041] Fig. 5(a) is a side view of a filter 200 according to a second embodiment. As shown in Fig. 5(a), in the second embodiment, the acoustic wave chip 30 is mounted on the upper surface 11 of the mounting substrate 10 at an angle relative to the upper surface 11. That is, the acoustic wave chip 30 is mounted on the upper surface 11 of the mounting substrate 10 at an angle relative to a normal 40 of a surface 35 on which the acoustic wave resonator 32 is provided, with respect to a normal 41 of the upper surface 11 of the mounting substrate 10. The other configurations are the same as those of the first embodiment, and therefore description thereof will be omitted.

[0042] In the first embodiment, as shown in FIG. 1B, the acoustic wave chip 30 is mounted on the upper surface 11 of the mounting substrate 10 such that the normal 40 to the surface 35 on which the acoustic wave resonator 32 is provided is perpendicular to the normal 41 to the upper surface 11 of the mounting substrate 10. However, as in the second embodiment, the acoustic wave chip 30 may be mounted on the upper surface 11 of the mounting substrate 10 such that the normal 40 to the surface 35 is inclined with respect to the normal 41 to the upper surface 11 of the mounting substrate 10. Even in this case, miniaturization in the XY plane can be achieved. From the viewpoints of both miniaturization in the XY plane and reduction in height in the Z direction, the angle θ between the normal 40 and the normal 41 is preferably 30° to 60°, more preferably 35° to 55°, and even more preferably 40° to 50°.

[0043] Fig. 5(b) is a side view of a filter 210 according to a modification of the second embodiment, and Fig. 5(c) is an enlarged view of region A in Fig. 5(b). In Fig. 5(c), the end face 37 of the acoustic wave chip 30 is indicated by a thick line. As shown in Figs. 5(b) and 5(c), in the modification of the second embodiment, the end face 37 of the acoustic wave chip 30 has a tapered shape. The other configurations are the same as those of the second embodiment, and therefore description thereof will be omitted.

[0044] As in the modified example of the second embodiment, the end face 37 of the acoustic wave chip 30 is inclined in a tapered manner relative to the surface 35, which makes it easy to mount the acoustic wave chip 30 at an angle relative to the upper surface 11 of the mounting substrate 10. By setting the taper angle α of the end face 37 to a desired angle, the angle θ between the normal line 40 and the normal line 41 can be easily set to a desired angle. [Example]

[0045] 6(a) is a circuit diagram of a duplexer 300 according to a third embodiment. As shown in FIG. 6(a), a transmit filter 80 is connected between a common terminal Ant and a transmit terminal Tx. A receive filter 82 is connected between the common terminal Ant and a receive terminal Rx. The transmit filter 80 passes, to the common terminal Ant as a transmit signal, signals in the transmit band among the high-frequency signals input from the transmit terminal Tx, and suppresses signals of other frequencies. The receive filter 82 passes, to the receive terminal Rx as a receive signal among the high-frequency signals input from the common terminal Ant, signals in the receive band, and suppresses signals of other frequencies.

[0046] 6(b) is a cross-sectional view of a duplexer 300 according to a third embodiment. As shown in FIG. 6(b), a transmit filter 80 and a receive filter 82 are formed on separate mount substrates 10. At least one of the transmit filter 80 and the receive filter 82 is any of the filters shown in the first, second, and their modifications. The mount substrate 10 on which the transmit filter 80 is formed and the mount substrate 10 on which the receive filter 82 is formed are both mounted on a single mounting substrate 60 by solder 70.

[0047] Although a duplexer has been shown as an example of a multiplexer, a triplexer or a quadplexer may also be used.

[0048] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0049] 10...mounting substrate, 11...upper surface, 12...lower surface, 13...wiring, 14...signal wiring, 15...ground wiring, 16...pad, 17...first region, 18...via wiring, 19...second region, 30...acoustic wave chip, 31...substrate, 32...acoustic wave resonator, 33...pad, 34...wiring, 35...surface, 36...bonding member, 37...end surface, 38...air gap, 40...normal, 41...normal, 50...IDT, 51...reflector, 52...comb-shaped electrode, 5 3...electrode finger, 54...bus bar, 55...lower electrode, 56...piezoelectric layer, 57...upper electrode, 58...gap, 59...resonance region, 60...mounting substrate, 61...pad, 62...recess, 63...metal film, 70...bonding member, 71...frame, 72...lid, 73...bonding member, 80...transmitting filter, 82...receiving filter, 100, 110, 120, 130, 140, 150, 200, 210...filter, 300...duplexer

Claims

1. a mounting substrate having a first surface and a first normal that is a normal to the first surface; a plurality of acoustic wave chips connected in series to each other as a circuit, each having a second surface and an acoustic wave resonator provided on the second surface, and mounted such that a second normal, which is a normal to each of the second surfaces, is perpendicular to or inclined from the first normal so as to have a gap between the chips and the mounting substrate.

2. The filter according to claim 1 , wherein the plurality of acoustic wave chips are mounted on the first surface with the second surfaces facing the same direction.

3. the first surface has a first region and a second region adjacent to the first region, 2. The filter of claim 1, wherein among the plurality of acoustic wave chips, the acoustic wave chips located in the first region are mounted on the first surface with the second surface facing away from the second region, and the acoustic wave chips located in the second region are mounted on the first surface with the second surface facing away from the first region.

4. 3. The filter of claim 1, wherein when directions parallel to the first surface and perpendicular to each other are defined as a first direction and a second direction, the plurality of acoustic wave chips are mounted on the first surface with some overlapping in the first direction and aligned in the second direction.

5. The filter according to claim 4 , wherein the acoustic wave resonators of at least one pair of adjacent acoustic wave chips among the plurality of acoustic wave chips are shifted from each other in the first direction without overlapping with each other.

6. The filter of claim 1 or 2, wherein the plurality of acoustic wave chips include at least three or more acoustic wave chips, and more than half of the plurality of acoustic wave chips are arranged parallel to each other, and the remaining acoustic wave chips are arranged at an angle from the parallel state.

7. wiring provided on the first surface and connected to the plurality of acoustic wave chips; 3. The filter according to claim 1, wherein the ground wiring of said wirings has a larger area than the signal wiring when viewed from said first surface.

8. A multiplexer comprising a filter according to claim 1 or 2.

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