JP5537096B2 - Elastic wave device and circuit board - Google Patents

Description

  The present invention relates to an elastic wave device such as a surface acoustic wave (SAW) device or a thin film acoustic resonator (FBAR).

  2. Description of the Related Art A so-called wafer level package acoustic wave device for the purpose of downsizing and the like is known. In this acoustic wave device, excitation electrodes disposed on the main surface of the element substrate are accommodated in the vibration space. The vibration space is formed by a hollow portion provided in the protective cover. In addition, columnar terminals connected to the excitation electrodes are erected on electrode pads provided on the main surface of the element substrate. As for the columnar terminal, the tip side portion (the portion opposite to the main surface of the element substrate) is exposed from the protective cover, and this exposed portion is soldered to the circuit board so that the acoustic wave device is mounted on the circuit board. (For example, refer to Patent Document 1).

JP 2007-208665 A

  By the way, in the acoustic wave device having the above-described structure, separation may occur between the substrate and the protective cover due to a difference in linear expansion coefficient between the substrate and the protective cover. Thus, when peeling arises between a board | substrate and a protective cover, peeling will reach | attain vibration space from there as a starting point. When the separation reaches the vibration space, the airtightness of the vibration space is deteriorated, and the excitation electrode is corroded. As a result, the reliability of the acoustic wave device is lowered.

  The present invention has been invented to cope with the above-described problems, and provides an elastic wave device that is less likely to be peeled off between a substrate and a protective cover and has excellent reliability.

  The acoustic wave device of the present invention includes a substrate for propagating an acoustic wave, an excitation electrode disposed on the main surface of the substrate, and standing on the main surface of the substrate and electrically connected to the excitation electrode. A plurality of first columnar conductors, a second columnar conductor standing on the main surface of the substrate and electrically floating, and a vibration space of the excitation electrode, And a protective cover that covers a side surface of the first columnar conductor and a side surface of the second columnar conductor.

  According to the present invention, it is difficult for the substrate and the protective cover to be peeled off, and it is possible to provide a highly reliable elastic wave device that maintains the airtightness of the vibration space in a good state.

(A) is a top view which shows the surface acoustic wave apparatus which concerns on embodiment of this invention, (b) is a top view of the state which removed the protective cover of the surface acoustic wave apparatus shown to Fig.1 (a). (A) is sectional drawing in the Ia-Ia line of Fig.1 (a), (b) is sectional drawing in the Ib-Ib line of Fig.1 (a). It is sectional drawing for demonstrating the manufacturing method of the surface acoustic wave apparatus which concerns on embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the surface acoustic wave apparatus which concerns on embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the surface acoustic wave apparatus which concerns on embodiment of this invention. It is sectional drawing which shows the modification of the surface acoustic wave apparatus which concerns on embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of the surface acoustic wave apparatus shown in FIG.

  FIG. 1A is a plan view showing a surface acoustic wave device 1 according to an embodiment of the present invention. FIG. 1B is a plan view of the surface acoustic wave device 1 shown in FIG. 2A is a cross-sectional view taken along line Ia-Ia in FIG. 1A, and FIG. 2B is a cross-sectional view taken along line Ib-Ib in FIG. 1 and 2 schematically show the surface acoustic wave device 1 in order to facilitate understanding of the surface acoustic wave device 1. In implementation, the size of each part of the surface acoustic wave device 1 is shown. The number, shape, etc. may be set as appropriate.

  The surface acoustic wave device 1 includes a piezoelectric substrate 3, a surface acoustic wave element 5 disposed on the piezoelectric substrate 3, a protective layer 7 and a protective cover 9 for protecting the surface acoustic wave element 5, and electrode pads 13a to 13k (hereinafter referred to as the electrode pads 13a to 13k). In addition, the electrode pads 13a to 13k may be collectively referred to as the electrode pad 13.), the first columnar conductor 15, and the second columnar conductor 16. In FIG. 1B, the first columnar conductor 15 and the second columnar conductor 16 located under the insulating film 18 are indicated by dotted lines.

  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 first main surface 3a and a second main surface 3b on the back side. 1 and 2 exemplify the case where electrodes and the like are arranged only on the first main surface 3a, but electrodes and the like may be arranged also on the second main surface 3b.

  The surface acoustic wave element 5 has a plurality of pairs of comb-like electrodes (IDT electrodes) 6 as excitation electrodes formed on the first main surface 3 a of the piezoelectric substrate 3. The comb-like electrode 6 has a plurality of electrode fingers extending in a direction orthogonal to the propagation direction of the surface acoustic wave in the piezoelectric substrate 3 (vertical direction in the drawing of FIG. 1). The pair of comb-like electrodes 6 are formed so that the electrode fingers mesh with each other.

  FIG. 1 is a schematic diagram, and actually, a plurality of pairs of comb-like electrodes having a larger number of electrode fingers than those shown are provided. Further, a plurality of surface acoustic wave elements 5 may be connected by a system such as a series connection or a parallel connection, and a ladder type surface acoustic wave filter, a dual mode type surface acoustic wave filter, or the like may be configured. At both ends of the surface acoustic wave element 5, reflectors having comb-like electrodes (may be regarded as a part of the surface acoustic wave element 5) are provided. The surface acoustic wave element 5 is made of an Al alloy such as an Al—Cu alloy.

  As shown in FIG. 2, the protective layer 7 covers the connection conductor 11, the surface acoustic wave element 5, and the like, and contributes to preventing the surface acoustic wave element 5 from being oxidized. The protective layer 7 is made of, for example, a material having an insulating property and a mass that is light enough not to affect the propagation of the surface acoustic wave, and is made of silicon oxide, silicon nitride, silicon, or the like.

  The protective cover 9 covers the surface acoustic wave element 5 from above the protective layer 7. The protective cover 9 constitutes a vibration space 17 on the surface acoustic wave element 5 for facilitating the propagation of surface acoustic waves. In other words, the protective cover 9 includes the wall portion 19 that forms the inner wall 19 a of the vibration space 17 and the lid portion 21 that forms the ceiling 21 a of the vibration space 17.

  The thickness of the layer constituting the wall portion 19 and the thickness of the lid portion 21 may be set as appropriate. For example, the thickness is several μm to 30 μm. The wall portion 19 and the lid portion 21 are formed to have substantially the same thickness.

  The wall portion 19 and the lid portion 21 can be formed of different materials, but are preferably formed of the same material in order to increase the adhesive strength between the wall portion 19 and the lid portion 21. The wall portion 19 and the lid portion 21 are formed of, for example, a photocurable material that is cured by being irradiated with light such as ultraviolet rays or visible light, for example, a negative photoresist. As the photocurable material, a resin curable by radical polymerization such as an acrylic group or a methacrylic group can be used. More specifically, urethane acrylate, polyester acrylate, or epoxy acrylate resins can be used.

  As shown in FIG. 2A, the vibration space 17 is formed so that the cross section is substantially rectangular and the corner on the lid 21 side is rounded. In other words, the inner wall 19a and the ceiling 21a constituting the vibration space 17 are formed in an arch shape. Thereby, it can suppress that the cover part 21 bends. As a result, for example, the surface acoustic wave device 1 can be downsized by reducing the height of the vibration space 17. The planar shape of the vibration space 17 (the shape of the first main surface 3a in plan view) may be set as appropriate. FIG. 1B shows an inner wall 19a corresponding to the outer periphery of the vibration space 17 with a broken line.

  The connection conductor 11 is for connecting the surface acoustic wave element 5 and a predetermined electrode pad. The connection conductor 11 is formed on the first main surface 3 a of the piezoelectric substrate 3, for example, similarly to the surface acoustic wave element 5. As shown in FIG. 1B, the connection conductor 11 is formed in an appropriate pattern on the first main surface 3 a and is connected to the surface acoustic wave element 5. Further, in FIG. 1B, the connection conductor 11 connected to the electrode pad 13 c located at the center on the upper side among the plurality of electrode pads 13 is connected to the other connection conductor 11 and the insulating member 8. Crossed. Thus, by using the insulating member 8 to connect the connecting conductors 11 three-dimensionally, the degree of freedom of the electrode pad placement location is improved, and the acoustic wave device can be reduced in size. The insulating member 8 is made of, for example, polyimide resin.

  A plurality of electrode pads 13 are provided. In FIG. 1B, the three electrode pads 13c, 13i, and 13j arranged on the upper side center, the lower side center, and the lower left side are ground electrode pads. The electrode pads 13a and 13e arranged on the upper left and upper right are electrode pads for input / output signals. The other electrode pads 13b, 13d, 13f, 13h, and 13k are in an electrically floating state.

  The electrode pad 13, the connecting conductor 11, and the surface acoustic wave element 5 can be manufactured by the same process using the same material, for example, and the thickness thereof is, for example, 0.1 μm to 1.0 μm. It is.

  The first columnar conductor 15 is provided on electrode pads 13 a, 13 c, 13 e, 13 g, 13 i, and 13 j that are electrically connected to the surface acoustic wave element 5. That is, the first columnar conductor 15 is electrically connected to the surface acoustic wave element 5 via the electrode pad and the connecting conductor 11, and is used to connect the surface acoustic wave element 5 to an external electric circuit or ground. It functions as a terminal.

  The second columnar conductor 16 is provided on the electrode pads 13b, 13d, 13f, 13h, and 13k that are not electrically connected to the surface acoustic wave element 5. That is, the second columnar conductor 16 is not electrically connected to the surface acoustic wave element 5. In this way, by providing the second columnar conductor 16 in addition to the normally formed first columnar conductor 15, it is possible to suppress the protective cover 9 from peeling from the piezoelectric substrate 3. This is because the shrinkage stress of the protective cover 9 caused by the difference in the linear expansion coefficient between the piezoelectric substrate 3 and the protective cover 9 is transmitted to the first columnar conductor 15 and the second columnar conductor 16 to alleviate the distortion. As a result, it is considered that the force to be peeled is suppressed to be small. In particular, since the protective cover 9 is easily peeled off in the space between the adjacent first columnar conductors 15, if the second columnar conductor 16 is provided between the adjacent first columnar conductors 15, the effect of preventing peeling. Can be further enhanced. Further, if the second columnar conductor 16 is provided corresponding to each side of the protective cover 9, peeling can be suppressed at each side, so that the airtightness of the vibration space 17 can be maintained in a good state for a longer period. Can do. In addition, the arrangement | positioning location of the 2nd columnar conductor 16 is not restricted to this. For example, in FIG. 1B, if the second columnar conductor 16 is provided also in a portion that partitions the right vibration space 17 and the left vibration space 17 of the protective cover 9, the protective cover 9 is peeled off. It can be further suppressed.

  In order to reinforce the connection between the electrode pad 13 and the terminal between the electrode pad 13 and the first columnar conductor 15 and between the electrode pad 13 and the second columnar conductor 16, respectively, chromium, nickel, gold You may interpose the connection reinforcement layer which consists of. Moreover, the 1st columnar conductor 15 and the 2nd columnar conductor 16 are formed in columnar shape, and are standingly arranged with respect to the 1st main surface 3a. The front end portion of the first columnar conductor 15 is exposed from the protective cover 9 so as to be connectable to a circuit board (not shown). On the other hand, the tip of the second columnar conductor 16 is covered with an insulating film 18 as shown in FIG. By covering the tip of the second columnar conductor 16 with the insulating film 18 in this manner, the first columnar conductor 15 and the second columnar conductor 16 are formed when the surface acoustic wave device 1 is mounted on a circuit board. It is possible to prevent a short circuit with mounting solder or the like. The insulating film 18 is made of, for example, a phenol-based or fluorine-based photosensitive resin. It should be noted that without providing the insulating film 18, the tip of the second columnar conductor 16 may be positioned in the lid portion 21, that is, the second columnar conductor 16 may be embedded in the protective cover 9. Good. Also in this case, a short circuit between the first columnar conductor 15 and the columnar conductor 8 can be prevented.

  The first columnar conductor 15 and the second columnar conductor 16 are made of, for example, solder, Cu, Au, or Ni. The first and second columnar conductors 15 and 16 are preferably formed of the same metal material. By forming both terminals with the same metal material, they can be manufactured in the same process, and production efficiency is good. The first columnar conductor 15 and the second columnar conductor 16 are, for example, generally cylindrical, but the shape is not limited to this and may be a rectangular column or the like.

  The shape of the first columnar conductor 15 in a sectional view is, for example, a tapered shape in which the diameter on the first main surface 3a side is larger than that on the side opposite to the first main surface 3a. More specifically, the first taper portion on the wall portion 19 side and the second taper portion on the lid portion 21 side have a two-step taper structure, and the first taper portion has a second taper portion side. The diameter is smaller than the diameter of the second tapered portion on the first tapered portion side. The first columnar conductor 15 that functions as a terminal after the acoustic wave device is mounted on the circuit board or the like may exert a force in the pulling direction, but the first columnar conductor 15 is used as in the present embodiment. In addition, the occurrence of such drawing can be suppressed by providing a two-step tapered structure. In the present embodiment, similarly to the first columnar conductor 15, the second columnar conductor 16 is formed in a tapered shape whose diameter on the first main surface 3a side is larger than that on the side opposite to the first main surface 3a. .

  In the present embodiment, the first columnar conductor 15 and the columnar conductor 15 are formed in two stages by plating, and 2 in the middle of the thickness direction of the first columnar conductor 15 and the second columnar conductor 16. A base plating 65 for performing the plating at the stage is formed.

  A land 27 is provided at the tip of the first columnar conductor 15. For example, the land 27 has a larger area than the end surface of the first columnar conductor 15 opposite to the first main surface 3 a, and the outer peripheral portion is laminated on the protective cover 9.

  3-5 is sectional drawing explaining an example of the manufacturing method of the surface acoustic wave apparatus 1, and has shown the part corresponded in the cross section in the Ib-Ib line | wire of Fig.1 (a).

  The first manufacturing method of the surface acoustic wave device 1 can be summarized as follows: a step of forming the surface acoustic wave element 5, a step of forming the protective cover 9, and a step of forming the first columnar conductor 15 and the second columnar conductor 16. Including. Specifically, it is as follows.

  As shown in FIG. 3A, first, the connecting conductor 11, the electrode pad 13, and the surface acoustic wave element 5 (not shown in the figure) are formed on the first main surface 3a of the piezoelectric substrate 3. Is done. Specifically, first, a metal layer is formed on the first main surface 3a of the piezoelectric substrate 3 by a thin film forming method such as a sputtering method, a vapor deposition method or a CVD (Chemical Vapor Deposition) method. Next, the metal layer is patterned by a photolithography method using a reduction projection exposure machine (stepper) and an RIE (Reactive Ion Etching) apparatus. Thereby, the connection conductor 11, the electrode pad 13, and the surface acoustic wave element 5 are formed.

  Next, the protective layer 7 is formed as shown in FIG. First, a thin film to be the protective layer 7 is formed by a thin film forming method such as a CVD method or a vapor deposition method so as to cover the surface acoustic wave element 5, the connecting conductor 11, and the electrode pad 13. Next, a part of the thin film is removed by photolithography so that the electrode pad 13 is exposed. Thereby, the protective layer 7 is formed. In addition, after forming the protective layer 7, and before forming, the connection reinforcement | strengthening layer 14 is formed by laminating | stacking chromium, nickel, and gold | metal | money on the electrode pad 13 by vapor deposition etc. in order.

  Next, as shown in FIGS. 3C to 3D, the wall portion 19 is formed. Specifically, first, as shown in FIG. 3C, the wall portion constituting layer 31 that becomes the wall portion 19 is formed on the protective layer 7. The wall portion constituting layer 31 is formed, for example, by attaching a film formed of a negative type photoresist.

  Next, as shown in FIG. 3D, exposure processing is performed by irradiating the wall constituting layer 31 with light L such as ultraviolet rays through a photomask 33. The photomask 33 is configured, for example, by forming a light shielding layer 37 on a transparent substrate 35. The light shielding layer 37 is disposed at a position corresponding to the position where the wall portion constituting layer 31 is to be removed. Specifically, it is disposed at a location corresponding to the formation position of the vibration space 17, the formation position of the first columnar conductor 15, and the second columnar conductor 16. The exposure may be projection exposure, proximity exposure, or close exposure.

  Thereafter, as shown in FIG. 4A, development processing is performed to leave a portion irradiated with light in the wall portion constituting layer 31 and remove a portion not irradiated with light. As a result, an opening (not shown) that becomes the vibration space 17, the first hole 41 in which the first columnar conductor 15 is disposed, and the second columnar conductor 16 are disposed in the wall portion constituting layer 31. The second hole portion 42 is formed, and the wall portion 19 is completed.

  Here, in the edge part of the area | region where the light of the wall part structure layer 31 is irradiated, since the irradiated light will diverge to the area | region where the light of the wall part structure layer 31 is not irradiated, it is 1st main surface. Light does not reach the 3a side sufficiently. Therefore, the edge part of the area | region where the light of the wall part structure layer 31 is irradiated is removed without fully hardening the 1st main surface 3a side. As a result, the first hole portion 41 and the second hole portion 42 are formed in a tapered shape (forward tapered shape) whose diameter increases toward the first main surface 3a side.

  Next, the lid portion 21 is formed. Specifically, first, as shown in FIG. 4 (b), the lid portion constituting layer 43 constituting the lid portion 21 is formed on the wall portion 19. The lid portion constituting layer 43 is formed, for example, by attaching a film formed of a negative type photoresist. By forming the lid constituting layer 43, the opening of the wall portion 19 is closed and the vibration space 17 is formed. The wall portion constituting layer 31 and the lid portion constituting layer 43 are joined by being heated.

  Next, as shown in FIG. 4C, exposure processing is performed by irradiating the lid constituting layer 43 with light L such as ultraviolet rays through a photomask 45. Similar to the photomask 33, the photomask 45 is configured by forming a light shielding layer 49 on the transparent substrate 47. The light shielding layer 49 is disposed at a position corresponding to the position where the lid portion constituting layer 43 should be removed. In other words, the first columnar conductor 15 and the second columnar conductor 16 are disposed at locations corresponding to the formation positions. The exposure may be projection exposure, proximity exposure, or close exposure.

  Thereafter, as shown in FIG. 4D, development processing is performed to leave a portion irradiated with light, and remove a portion not irradiated with light, from the lid constituting layer 43. As a result, a third hole 51 is formed on the first hole 41, and a first columnar conductor forming hole 61 composed of the first hole 41 and the third hole 51 is formed. . A fourth hole 52 is formed on the second hole 42, and a second columnar conductor forming hole 62 composed of the second hole 42 and the fourth hole 52 is formed. In this way, the lid portion 21 is completed. By forming the lid portion 21, the protective cover 9 including the wall portion 19 and the lid portion 21 is completed.

  When the protective cover 9 is formed, the first columnar conductor 15 and the second columnar conductor 16 are formed as shown in FIG. Specifically, first, as shown in FIG. 5A, a plating base layer 55 and a plating resist layer 57 are formed.

  The plating base layer 55 is formed so as to cover the protective cover 9. The plating base layer 55 is also formed on the bottom surface of the first columnar conductor forming hole 61, the bottom surface of the second columnar conductor forming hole 62, and the inner peripheral surface thereof. The plating underlayer 55 is a suitable example formed of a Ti—Cu alloy or the like, for example, by flash plating.

  The plating resist layer 57 is formed on the plating base layer 55. The plating resist layer 57 is formed on the substrate by a technique such as spin coating.

  Next, as shown in FIG. 5B, the exposed plating underlayer 55 is plated. As a result, the first and second columnar conductor forming holes 61 and 62 are filled with metal. Then, the first columnar conductor 15 and the second columnar conductor 16 are completed by filling the first columnar conductor forming hole 61 and the second columnar conductor forming hole 62 with metal.

  Next, after removing the plating resist layer 57, as shown in FIG. 5C, the plating resist layer 67 in which the land hole 69 is formed so that the tip of the first columnar conductor 15 is exposed. Form. At this time, the tip of the second columnar conductor 16 is covered with a plating resist layer 67. In this state, the ground layer 65 for plating is formed on the bottom surface of the land hole 69, and then the land 27 is formed by filling the land hole 69 with metal by plating. In the land hole 69, the metal does not need to be filled up to the surface of the plating resist layer 67, and the metal may be filled to an appropriate depth in the land hole 69. The plating method may be appropriately selected, but the electroplating method is preferable.

  Thereafter, the plating resist layer 67 is removed. Finally, a photosensitive resin such as phenol resin or fluorine resin is applied on the protective cover by screen printing or spin coating, and the applied resin film is patterned by photolithography or the like so that the land 27 is exposed. The surface acoustic wave device 1 shown in FIGS. 1 and 2 is completed.

  The plating resist layers 57 and 67 described above can be removed by using an organic solvent such as acetone or IPA or an alkaline organic solvent such as dimethyl sulfoxide. When Cu is used as the plating base layer, the plating base layer can be removed by, for example, ferric chloride, a mixed solution of phosphoric acid and hydrogen peroxide solution. Further, when Ti is used as the plating base layer, it can be removed with, for example, dilute hydrofluoric acid or a mixed solution of ammonia and hydrogen peroxide.

(Modification)
FIG. 6 is a cross-sectional view of a surface acoustic wave device 2 as a modification of the surface acoustic wave device 1 described above, and corresponds to a cross section of the same portion as FIG. In the surface acoustic wave device 1, the tip of the second columnar conductor 16 is covered with the insulating film 18, whereas in the surface acoustic wave device 2 shown in FIG. 6, the tip of the second columnar conductor 16 is exposed as it is. I am letting. Thus, if the front-end | tip part of the 2nd columnar conductor 16 is exposed, when mounting the surface acoustic wave apparatus 2 on a circuit board etc., the 2nd columnar conductor 16 can also be utilized as a dummy terminal. For example, if the ground pad of the circuit board and the second columnar conductor 16 are joined by solder or the like, the connection strength of the surface acoustic wave device 2 to the circuit board can be strengthened.

  In the case of the surface acoustic wave device 2, the manufacturing process can be simplified. FIG. 7 is a cross-sectional view showing an example of the manufacturing process of the surface acoustic wave device 2. FIG. 7 shows a stage corresponding to FIG. The difference from the state shown in FIG. 5A is that land holes 69 are provided in the plating resist layer 57 at this stage. In this state, the first columnar conductor 15 and the land 27 are continuously connected by plating the first columnar conductor forming hole 61, the second columnar conductor forming hole 62, and the land hole 69. Can be formed. That is, as shown in FIG. 5C and FIG. 5D, the process for forming the land 27 after forming the first columnar conductor 15 can be omitted, so that the manufacturing process is simplified. And production efficiency is good.

  The present invention is not limited to the above embodiment, and may be implemented in various aspects.

  The acoustic wave device is not limited to a surface acoustic wave device. For example, the acoustic wave device may be a piezoelectric thin film resonator. In the acoustic wave device, the protective layer (7) and the connection reinforcing layer (13) may be omitted, or conversely, other appropriate layers may be formed. Further, the first columnar conductor 15 is not limited to a tapered one, and can have any shape as long as it is columnar.

1. Surface acoustic wave device (elastic wave device)
3 ... Piezoelectric substrate (substrate)
3a ... 1st main surface (main surface)
6 ... Comb electrode (excitation electrode)
7 ... Protective layer 8 ... Insulating member 9 ... Protective cover 11 ... Connecting conductor 15 ... First columnar conductor 16 ... Second columnar conductor 17 ... Vibration space 18 ... Insulating films

Claims (15)

A substrate that propagates elastic waves;
An excitation electrode disposed on a main surface of the substrate;
A plurality of first columnar conductors standing on the main surface of the substrate and electrically connected to the excitation electrode;
A second columnar conductor that is erected on the main surface of the substrate and is electrically floating;
A protective cover that forms a vibration space of the excitation electrode and covers a side surface of the first columnar conductor and a side surface of the second columnar conductor;
The second columnar conductor is an acoustic wave device in which a tip portion opposite to the main surface is positioned on the upper surface side of the protective cover with respect to the vibration space in the thickness direction. 2. The acoustic wave device according to claim 1, wherein the second columnar conductor has a tapered portion whose diameter on the principal surface side is larger than that on the opposite side to the principal surface. A substrate that propagates elastic waves;
An excitation electrode disposed on a main surface of the substrate;
A plurality of first columnar conductors standing on the main surface of the substrate and electrically connected to the excitation electrode;
A second columnar conductor that is erected on the main surface of the substrate and is electrically floating;
A protective cover that forms a vibration space of the excitation electrode and covers a side surface of the first columnar conductor and a side surface of the second columnar conductor;
The second columnar conductor is an acoustic wave device having a tapered portion whose diameter on the principal surface side is larger than that on the opposite side to the principal surface. Before SL tapered portion, a first tapered portion whose diameter increases in the main surface side, located on the opposite side of the first of said major surface relative to the tapered portion, the diameter increases to the main surface The elastic wave device according to claim 2, which has two tapered portions.   The elastic wave device according to any one of claims 1 to 4, wherein the protective cover has a rectangular planar shape, and the second columnar conductor is provided corresponding to each side of the protective cover.   The elastic wave device according to any one of claims 1 to 5, wherein the second columnar conductor has a tip portion opposite to the main surface covered with an insulating material. A substrate that propagates elastic waves;
An excitation electrode disposed on a main surface of the substrate;
A plurality of first columnar conductors standing on the main surface of the substrate and electrically connected to the excitation electrode;
A second columnar conductor that is erected on the main surface of the substrate and is electrically floating;
A protective cover that forms a vibration space of the excitation electrode and covers a side surface of the first columnar conductor and a side surface of the second columnar conductor;
The second columnar conductor is an acoustic wave device in which a tip portion opposite to the main surface is covered with an insulating material. A substrate that propagates elastic waves;
An excitation electrode disposed on a main surface of the substrate;
A plurality of first columnar conductors standing on the main surface of the substrate and electrically connected to the excitation electrode;
A second columnar conductor that is erected on the main surface of the substrate and is electrically floating;
A protective cover that forms a vibration space of the excitation electrode and covers a side surface of the first columnar conductor and a side surface of the second columnar conductor;
The protective cover is an elastic wave device in which a planar shape is rectangular, and the second columnar conductor is provided corresponding to each side of the protective cover. 9. The acoustic wave device according to claim 7, wherein the second columnar conductor has a tapered portion whose diameter on the main surface side is larger than that on the opposite side to the main surface.   The elastic wave device according to claim 1, wherein the second columnar conductor is disposed between the adjacent first columnar conductors.   The elastic wave device according to any one of claims 1 to 10, wherein the first columnar conductor and the second columnar conductor are made of the same metal material. The elastic wave device according to any one of claims 1 to 11, wherein the first columnar conductor has a tapered portion whose diameter on the principal surface side is larger than that on the opposite side to the principal surface. Any said substrate is a piezoelectric substrate, the excitation electrode, of the claims 1 to 12 is a comb-shaped electrode comprising a plurality of electrode fingers extending in a direction perpendicular to the propagation direction of the surface acoustic wave propagating piezoelectric substrate The elastic wave apparatus of crab. The elastic wave device according to any one of claims 1 to 13 ,
And a second substrate on which the acoustic wave device is mounted. The second substrate has a pad,
The circuit board according to claim 14 , wherein the elastic wave device is such that the second columnar conductor is joined to the pad.

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