JP2013225749A - Piezoelectric device and module component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric device which preferably inhibits the inflow of a sealing material to a facing space.SOLUTION: A piezoelectric device 1 comprises: a support member 5; a SAW element 7; a bump 8 disposed between the support member 5 and the SAW element 7 and connecting the support member 5 with the SAW element 7; and a sealing part 9 provided at an outer periphery of the SAW element 7 on the support member 5. The support member 5 includes an insulation base material 11. The SAW element 7 includes: a piezoelectric substrate 19 that causes its lower surface 19a to face an upper surface 11a of the support member 5; and an excitation electrode 21 provided at the lower surface 19a side of the piezoelectric substrate 19 and facing the support member 5 through a facing space S. A cavity 11v is provided on the upper surface 11a of the insulation base material 11 and the bump 8 is housed in the cavity 11v.

Description

  The present invention relates to a piezoelectric device and a module component including a piezoelectric element such as a surface acoustic wave (SAW) element and a piezoelectric thin film resonator (FBAR).

  A piezoelectric device is known that includes a support member, a piezoelectric element mounted on the support member, and a sealing resin that covers the piezoelectric element. For example, the SAW device of Patent Document 1 includes a mounting substrate (support member), a SAW chip (piezoelectric element) surface-mounted on the mounting substrate by bumps, and a sealing resin that covers the SAW chip. The SAW chip has a surface (functional surface) on which an IDT (InterDigital Transducer) is provided facing a mounting substrate. A gap corresponding to the thickness of the bump (internal space, opposite space) is formed between the SAW chip and the mounting substrate, and the gap is not filled with sealing resin (the functional surface is sealing resin) Not covered by.). This facilitates SAW propagation (functional surface vibration) on the functional surface.

JP 2006-279484 A

  In the technique of Patent Document 1, a weir or the like for preventing the sealing resin from flowing into the facing space is not provided. Therefore, the sealing resin may flow into the facing space. In addition, when a member serving as a weir is provided on the support member or the piezoelectric element, the number of parts increases.

  The objective of this invention is providing the piezoelectric device and module component which can suppress suitably the inflow to the opposing space of a sealing material.

  A piezoelectric device according to an aspect of the present invention is provided with a supporting member having an insulating base, a piezoelectric substrate having a lower surface facing the upper surface of the insulating substrate, and a lower surface of the piezoelectric substrate, and the piezoelectric device is disposed through an opposing space. A piezoelectric element having an excitation electrode facing the support member; a joining member that is interposed between the support member and the piezoelectric element to connect them; and is provided on the outer periphery of the piezoelectric element on the support member A cavity is provided on at least one of the upper surface of the insulating base and the lower surface of the piezoelectric substrate, and at least a part of the bonding member is accommodated in the cavity.

  Preferably, the cavity is provided on the upper surface of the insulating substrate, and the excitation electrode is provided at a position facing the cavity.

  Preferably, the cavity is provided on the lower surface of the piezoelectric substrate, and the excitation electrode is provided in the cavity.

  Preferably, the upper surface of the insulating base and the lower surface of the piezoelectric substrate are in contact with each other around the cavity.

  Preferably, at least one of the insulating base and the piezoelectric substrate has a protrusion located in the cavity and in contact with the other.

  Preferably, the support member is annularly arranged on the upper surface side of the insulating base, and has a plurality of substrate pads to which the bonding member is bonded, and the piezoelectric element is annularly formed on the lower surface side of the piezoelectric substrate. A plurality of element pads are arranged and the bonding members are bonded to each other, and the substrate pads are arranged so as to be shifted to the outside of the ring with respect to the element pads.

  A module component according to an aspect of the present invention is provided with a circuit board having an insulating base, a piezoelectric substrate having a lower surface facing the upper surface of the insulating base, and a lower surface side of the piezoelectric substrate. A piezoelectric element having an excitation electrode facing the circuit board; a bonding member interposed between and connecting the circuit board and the piezoelectric element; and provided on an outer periphery of the piezoelectric element on the circuit board And an electronic element mounted on the circuit board and covered with the sealing material, and a cavity is provided on at least one of the upper surface of the insulating base and the lower surface of the piezoelectric substrate. The joining member is at least partially housed in the cavity.

  According to said structure, the inflow to the opposing space of a sealing material can be suppressed suitably.

FIG. 1A and FIG. 1B are perspective views showing the appearance of a piezoelectric device according to an embodiment of the present invention. The disassembled perspective view of the piezoelectric device of FIG. Sectional drawing of the piezoelectric device corresponding to the III-III line of FIG. 4A to 4E are cross-sectional views illustrating a method for manufacturing the piezoelectric device of FIG. Sectional drawing which shows the piezoelectric device which concerns on 2nd Embodiment. Sectional drawing which shows the piezoelectric device which concerns on 3rd Embodiment. The perspective view which shows the supporting member of the piezoelectric device which concerns on 4th Embodiment. The perspective view which shows the SAW element of the piezoelectric device which concerns on 5th Embodiment. Sectional drawing which shows the structure of the module component which concerns on 6th Embodiment. Sectional drawing which shows the structure of the module component which concerns on 7th Embodiment. FIG. 11A to FIG. 11C are cross-sectional views showing suitable examples of pad positions. FIG. 12 is a cross-sectional view showing an example of a preferable shape of the protrusion around the cavity.

  Hereinafter, a piezoelectric 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. Further, in the description after the second embodiment, the same or similar configuration as the configuration of the already described embodiment may be denoted by the reference numeral of the already described embodiment, and the description will be omitted. There is.

(First embodiment)
FIG. 1A is a perspective view of the appearance of the piezoelectric device 1 according to the first embodiment of the present invention as seen from the upper surface 1a side, and FIG. 1B is a bottom view of the appearance of the piezoelectric device 1. It is the perspective view seen from the 1b side.

  The piezoelectric device 1 may have either direction upward or downward, but for convenience, the orthogonal coordinate system xyz is defined and the positive side in the z direction is upward, and the upper or lower surface of the piezoelectric device 1 is defined. Words shall be used.

  The piezoelectric device 1 is formed, for example, in a substantially rectangular parallelepiped shape, and a plurality of external terminals 3 are exposed in an appropriate shape and an appropriate number on the lower surface 1b. Although the magnitude | size of the piezoelectric device 1 may be made into an appropriate magnitude | size, the length of 1 side is 1 mm-several mm, for example.

  The piezoelectric device 1 is disposed with the lower surface 1b facing a mounting board (not shown), and a pad provided on the mounting board and a plurality of external terminals 3 are bonded to each other through bumps or the like. Implemented. The piezoelectric device 1 receives, for example, a signal from any of the plurality of external terminals 3, performs a predetermined process on the input signal, and outputs the signal from any of the plurality of external terminals 3.

  Note that the number, position, and role of the plurality of external terminals 3 may be appropriately set according to the internal configuration of the piezoelectric device 1 and the like. In this embodiment, the case where the four external terminals 3 are provided in the four corners of the lower surface 1b is illustrated.

  FIG. 2 is an exploded perspective view of the piezoelectric device 1. FIG. 3 is a cross-sectional view of the piezoelectric device 1 corresponding to line III-III in FIG.

  As shown in FIG. 2, the piezoelectric device 1 generally includes three members. That is, the piezoelectric device 1 includes a support member 5, a SAW element 7 mounted on the support member 5, and a sealing portion 9 that seals the SAW element 7. In addition, as shown in FIG. 3, the piezoelectric device 1 has bumps 8 for performing electrical connection between the support member 5 and the SAW element 7.

  The support member 5 is composed of, for example, a rigid printed wiring board, and includes an insulating base 11, an upper surface conductive layer 13A (FIG. 3) formed on the surface of the insulating base 11 on the SAW element 7 side, and an insulating base. 11, an internal conductive layer 13B (FIG. 3) formed parallel to the insulating base 11, a via conductor 15 (FIG. 3) penetrating all or part of the insulating base 11 in the vertical direction, and the insulating base 11 And the above-described external terminal 3 formed on the lower surface 11b. The support member 5 may not be provided with the internal conductive layer 13B.

  The insulating base 11 is formed in, for example, a generally thin rectangular parallelepiped shape. However, on the upper surface 11a of the insulating base 11, a cavity 11v (recessed portion, FIG. 3) is provided in the central portion of the region facing the SAW element 7. The planar shape of the cavity 11v may be an appropriate shape such as a circle, a rectangle, or a polygon, and the dimensions may be set as appropriate.

  The insulating base 11 is formed including, for example, a resin, a ceramic, and / or an amorphous inorganic material. The insulating substrate 11 may be made of a single material, or may be made of a composite material such as a substrate in which a base material is impregnated with a resin.

  The upper conductive layer 13A is provided on the bottom surface of the cavity 11v and includes a substrate pad 17 (FIG. 3) to which the bumps 8 are bonded. The via conductor 15 and the internal conductive layer 13 </ b> B include wiring that connects the substrate pad 17 and the external terminal 3. The top conductive layer 13A, the internal conductive layer 13B, and the via conductor 15 may include an inductor, a capacitor, or a circuit that performs appropriate processing. These conductive layers and the like are made of a metal such as Cu, for example. The substrate pad 17 may be plated with Ni, Au or the like in order to improve the bondability with the bumps 8.

  The SAW element 7 includes a piezoelectric substrate 19 and an element conductive layer 20 provided on the lower surface 19 a of the piezoelectric substrate 19. In addition, the SAW element 7 may have an appropriate member such as an electrode and / or a protective layer that covers the upper surface 19 b of the piezoelectric substrate 19.

  The piezoelectric substrate 19 is formed in, for example, a generally thin rectangular parallelepiped shape. Although the dimension may be set appropriately, for example, one side in a plan view is 0.6 to 0.8 mm. The size of the piezoelectric substrate 19 in plan view is smaller than the size of the support member 5 in plan view. As for the surface of the piezoelectric substrate 19, the roughness in the side surface 19c is larger than the roughness in the lower surface 19a. The piezoelectric substrate 19 is composed of a single crystal substrate having piezoelectricity, such as a lithium tantalate single crystal or a lithium niobate single crystal.

  The element conductive layer 20 includes an excitation electrode 21 for exciting SAW, an element pad 25 to which the bump 8 is bonded, and a wiring (not shown) that connects them. The element conductive layer 20 is made of, for example, a metal such as an Al—Cu alloy. The element pad 25 may be plated with Ni, Au or the like in order to improve the bondability with the bump 8.

  The excitation electrode 21 is a so-called IDT (InterDigital transducer) and includes a pair of comb electrodes 23 as shown in FIG. Each comb electrode 23 includes a bus bar 23a and a plurality of electrode fingers 23b extending from the bus bar 23a, and the pair of comb electrodes 23 are engaged with each other (a plurality of electrode fingers 23b intersect each other). Is arranged). Since FIG. 2 and the like are schematic diagrams, only one pair of comb-tooth electrodes 23 having a plurality of electrode fingers 23b is illustrated, but actually, a plurality of electrode fingers 23b having more electrode fingers 23b than this are illustrated. A pair of comb electrodes 23 may be provided. The excitation electrode 21 constitutes, for example, a SAW filter, a SAW resonator, and / or a duplexer.

  When a signal is input to one of the pair of comb electrodes 23, the signal is converted into SAW, propagates in the direction (x direction) perpendicular to the electrode finger 23b through the lower surface 19a, and is converted into a signal again. Output from the other of the comb electrodes 23. In the process, the signal is filtered.

  For example, the element pads 25 are annularly arranged on the outer peripheral side of the piezoelectric substrate 19 so as to surround the excitation electrode 21, and are connected to the excitation electrode 21 via a wiring (not shown) formed on the lower surface 19 a. One of the pair of comb electrodes 23 receives a signal through one of the plurality of element pads 25, and the other of the pair of comb electrodes 23 outputs a signal through one of the plurality of element pads 25. To do.

  The bump 8 is interposed between the element pad 25 and the substrate pad 17 to bond these pads. The bump 8 is made of, for example, solder. The solder may be a solder using lead such as Pb—Sn alloy solder, or lead-free solder such as Au—Sn alloy solder, Au—Ge alloy solder, Sn—Ag alloy solder, Sn—Cu alloy solder, etc. It may be. The bumps 8 may be made of a conductive resin.

  The sealing portion 9 covers the SAW element 7. Specifically, the sealing portion 9 is located on the upper surface 19 b of the SAW element 7 and is located on the outer periphery of the SAW element 7 on the upper surface 11 a of the support member 5. The outer shape of the sealing part 9 is formed so as to have a substantially rectangular parallelepiped shape, for example. The shape and size in plan view are the same as, for example, the planar shape of the support member 5, and the side surface 9 c of the sealing portion 9 is flush with the side surface 11 c of the support member 5 (insulating base 11). The thickness of the sealing portion 9 may be set to an appropriate size from various viewpoints such as the viewpoint of protecting the SAW element 7.

  The sealing part 9 is comprised including resin, for example. The resin is preferably a thermosetting resin, and the thermosetting resin is, for example, an epoxy resin or a phenol resin. In the resin, a filler made of insulating particles formed of a material having a lower thermal expansion coefficient than that of the resin may be mixed. Examples of the material of the insulating particles include silica, alumina, phenol, polyethylene, glass fiber, and graphite filler. In addition, the sealing part 9 may be comprised with materials other than resin, for example, the inorganic material of an amorphous state.

  As shown in FIG. 3, the cavity 11v of the support member 5 (insulating base 11) is wider than the range where the excitation electrode 21 and the element pad 25 of the SAW element 7 are provided in the xy plane, and the SAW element 7 It is formed narrower than the lower surface 19a. The SAW element 7 is disposed with respect to the support member 5 so that the excitation electrode 21 and the element pad 25 face the cavity 11v.

  Accordingly, a portion of the upper surface 11 a of the support member 5 surrounding the cavity 11 v is in contact with the lower surface 19 a of the piezoelectric substrate 19, and the depth of the cavity 11 v is between the bottom surface of the cavity 11 v and the lower surface 19 a of the piezoelectric substrate 19. Thus, a gap for accommodating the excitation electrode 21 and the element pad 25 is formed. That is, an opposing space S that facilitates SAW propagation (vibration of the lower surface 19a) is formed below the excitation electrode 21 (on the negative side in the z direction). The bump 8 is also accommodated in the cavity 11v, and the thickness thereof is equal to the depth of the cavity 11v.

  The height of the facing space S (depth of the cavity 11v) is, for example, about 20 μm. The width of the overlapping portion between the upper surface 11a of the support member 5 and the lower surface 19a of the SAW element 7 around the cavity 11v is, for example, about 50 μm.

  The facing space S is sealed by the sealing portion 9. The facing space S may be in a vacuum, or a gas such as air may be enclosed. When the gas is sealed, the pressure may be higher, equal, or lower than the atmospheric pressure when the temperature in the facing space S is equal to the atmospheric temperature. Good.

  FIG. 4A to FIG. 4E are cross-sectional views corresponding to FIG. 3 for explaining the method for manufacturing the piezoelectric device 1. The manufacturing process proceeds from FIG. 4A to FIG. 4E in order.

  First, as shown in FIG. 4A, the SAW element 7 is prepared, and as shown in FIG. 4B, the support member 5 is prepared.

  The SAW element 7 is manufactured, for example, by forming the element conductive layer 20 on the mother substrate that becomes the piezoelectric substrate 19 by being divided, and then performing dicing. The element conductive layer 20 is formed by forming a metal layer on the lower surface 19a by a thin film forming method such as sputtering or CVD (Chemical Vapor Deposition), and then patterning the metal layer by photolithography or the like. Formed by. Prior to dicing, the main surface of the mother substrate is polished. Therefore, the lower surface 19a constituted by the main surface has a smaller surface roughness than the side surface 19c formed by dicing.

  The support member 5 is produced, for example, in substantially the same manner as a general printed wiring board. In the steps shown in FIGS. 4B to 4E, the support member 5 is in the state of the mother substrate that becomes the support member 5 by being divided, but FIG. 4B to FIG. In e), only the part corresponding to one piezoelectric device 1 is shown.

  The cavity 11v of the support member 5 may be appropriately formed. For example, the cavity 11v may be formed by a method similar to a method of forming a via (hole) in a specific layer in a multilayer substrate. For example, when the support member 5 is formed by laminating and firing a plurality of ceramic green sheets on which conductive paste is disposed, the ceramic green sheets constituting the upper surface 11a are laminated before being laminated. On the other hand, a cavity that becomes the cavity 11v may be formed by punching or the like.

  When the support member 5 is prepared, bumps 8 are formed as shown in FIG. Specifically, for example, a solder paste to be the bumps 8 is applied onto the substrate pad 17 by an appropriate method such as a screen printing method or a dispenser method. Thereafter, an appropriate process such as a heat process for evaporating the solvent and adjusting the shape may be performed.

  When the bumps 8 are formed, the SAW element 7 is mounted on the support member 5 as shown in FIG. Specifically, the SAW element 7 is placed on the support member 5, the bumps 8 are melted by a reflow furnace or the like, and then the melted bumps 8 are solidified by cooling.

  At this time, the melted solder spreads on the substrate pad 17 and the element pad 25 due to its wettability, and attracts the SAW element 7 to the support member 5. Thereby, the lower surface 19a of the SAW element 7 abuts on the upper surface 11a of the support member 5 around the cavity 11v. Note that the SAW element 7 may be pressed toward the support member 5 by an appropriate method.

  When the SAW element 7 is mounted on the support member 5, as shown in FIG. 4E, a liquid resin 47 that becomes the sealing portion 9 is supplied. The supply of the resin 47 is performed by screen printing, for example. The supply of the resin 47 may be performed under atmospheric pressure or in a vacuum atmosphere. The supplied resin 47 is prevented from flowing into the facing space S (cavity 11v) because the upper surface 11a and the lower surface 19a are in contact with each other around the cavity 11v.

  Thereafter, the resin 47 is heated and cured. Then, the mother substrate composed of the cured resin 47 and the plurality of support members 5 is diced, and the piezo-electric device 1 is manufactured.

  As described above, in this embodiment, the piezoelectric device 1 includes the support member 5, the SAW element 7, the bumps 8 interposed between the support member 5 and the SAW element 7, and the support member 5. And a sealing portion 9 provided on the outer periphery of the SAW element 7. The support member 5 has an insulating base 11. The SAW element 7 is provided on the side of the lower surface 19a of the piezoelectric substrate 19 with the lower surface 19a facing the upper surface 11a of the support member 5, and the excitation electrode 21 facing the support member 5 via the facing space S. And have. A cavity 11v is provided on the upper surface 11a of the insulating substrate 11, and the bumps 8 are accommodated in the cavity 11v.

  Therefore, the upper surface 11a and the lower surface 19a do not face each other at a distance corresponding to the thickness of the bump 8 as in the prior art, but the upper surface 11a and the lower surface 19a can face each other at a distance smaller than the thickness of the bump 8. . As a result, for example, the piezoelectric device 1 can be thinned. Further, in the manufacturing process, the liquid resin 47 is prevented from flowing into the gap (opposed space S) between the upper surface 11a and the lower surface 19a. In addition, since the insulating substrate 11 itself functions as a weir, there is no need to provide a member that serves as a weir.

  The cavity 11v is provided on the upper surface 11a of the support member 5, and the excitation electrode 21 is provided at a position facing the cavity 11v. Therefore, the distance between the lower surface 19a and the upper surface 11a in the periphery is made as small as possible while ensuring the height of the facing space S for facilitating SAW propagation (vibration on the lower surface 19a of the piezoelectric substrate 19) by the excitation electrode 21. can do. As a result, the effects of the above-described thinning and suppression of the inflow of the resin 47 are improved. Further, since the cavity 11v is provided in the support member 5, the distance between the substrate pad 17 and the external terminal 3 can be shortened, and the wiring length can be shortened.

  The upper surface 11a of the support member 5 and the lower surface 19a of the piezoelectric substrate 19 are in contact with each other around the cavity 11v. Therefore, the inflow of the resin 47 is more reliably suppressed. Further, since the force for supporting the piezoelectric substrate 19 is dispersed around the entire circumference of the piezoelectric substrate 19, the bending of the lower surface 19a through which the SAW propagates is suppressed, and as a result, the electrical characteristics of the piezoelectric device 1 are expected to be stable.

  Further, the side surface 19c of the piezoelectric substrate 19 has a larger surface roughness than the lower surface 19a. Therefore, the resin 47 tends to stay on the side surface 19 c and does not easily penetrate between the lower surface 19 a and the upper surface 11 a of the support member 5.

(Second Embodiment)
FIG. 5 is a cross-sectional view similar to FIG. 3 showing the piezoelectric device 201 according to the second embodiment.

  In the first embodiment, the cavity 11 v is formed in the support member 5. On the other hand, in the second embodiment, the support member 205 has no cavity and the SAW element 207 has a cavity 219v. Other than that, it is almost the same as the first embodiment.

  The excitation electrode 21, the element pad 25, and the wiring (not shown) of the SAW element 207 are provided on the bottom surface of the cavity 219v. As in the first embodiment, the bump 8 is accommodated in the cavity 219v, and the lower surface 219a of the piezoelectric substrate 219 and the upper surface 211a of the insulating base 211 are in contact with each other around the cavity 219v. Thereby, the opposing space S is formed below the excitation electrode 21.

  The size and shape of the cavity 219v may be the same as the cavity 11v of the first embodiment. For example, the height of the opposing space S (depth of the cavity 219v) is about 20 μm. The width of the overlapping portion of the upper surface 211a of the support member 205 and the lower surface 219a of the SAW element 207 on the outer periphery of the cavity 219v is, for example, about 50 μm (one side of the piezoelectric substrate 219 is 0.6 to 0.8 mm).

  The method for manufacturing the piezoelectric device 201 may be substantially the same as in the first embodiment. However, the cavity 219v is formed in the piezoelectric substrate 219 in the process of manufacturing the SAW element 207, and the cavity is not formed in the insulating substrate 211 in the process of manufacturing the support member 205. A method of forming the cavity 219v in the piezoelectric substrate 219 may be an appropriate method such as dry etching, ion etching, cutting, or laser processing.

  Also in the second embodiment, since the cavity 219v is provided and the bump 8 is accommodated in the cavity 219v, the same effect as in the first embodiment can be obtained. That is, the distance between the upper surface 211a of the support member 205 and the lower surface 219a of the SAW element 207 can be made smaller than the thickness of the bumps 8. As a result, the piezoelectric device 1 can be made thinner and the liquid resin 47 can be opposed to the opposing space S. The effect of suppressing the inflow of water is exerted.

  In the second embodiment, the cavity 219v is provided on the lower surface 219a of the piezoelectric substrate 219, and the excitation electrode 21 is provided in the cavity 219v. Therefore, as in the first embodiment, the distance between the lower surface 219a and the upper surface 211a in the periphery can be made as small as possible while ensuring the height of the facing space S.

  Further, by providing the cavity 219v not on the support member 5 but on the piezoelectric substrate 219, an effect that is not achieved in the first embodiment is also achieved. Specifically, it is as follows.

  The piezoelectric substrate 219 can also be regarded as a protrusion 219w (protrusion) that protrudes toward the support member 205 on the outer periphery of a conventional rectangular parallelepiped piezoelectric substrate. In this case, compared to the conventional case, the sectional moment of the piezoelectric substrate 219 is increased without changing the distance from the upper surface 211a of the support member 205 to the upper surface 219b of the piezoelectric substrate 219, and the bottom surface (functional surface) of the cavity 219v. That is, it was possible to suppress the bending of. Further, by suppressing the bending of the functional surface, the influence of the bending on the propagation of the SAW is reduced, and the electrical characteristics of the piezoelectric device 201 are stabilized.

  Further, when the cavity 219v is formed in the piezoelectric substrate 219, the path along the surface of the piezoelectric substrate 219 from the edge portion (corner portion with the side surface 219c) of the lower surface 219a of the piezoelectric substrate 219 to the excitation electrode 21 is the first path. It is longer than that of the embodiment, and includes a portion (side surface of the cavity 219v) that is directed from the lower side to the upper side. Therefore, the probability that the resin 47 reaches the excitation electrode 21 along the upper surface of the piezoelectric substrate 219 is reduced.

(Third embodiment)
FIG. 6 is a cross-sectional view similar to FIG. 3 illustrating a piezoelectric device 301 according to the third embodiment.

  In the first embodiment, the cavity 11 v is formed over the arrangement range of the bumps 8 and the excitation electrodes 21. On the other hand, in the third embodiment, the cavity 311v is not formed in the arrangement range of the excitation electrodes 21, but is formed only in the arrangement range of the bumps 8.

  The cavity 311v is smaller than the total thickness of the bump 8, the substrate pad 17, and the element pad 25. Accordingly, the upper surface 311a of the support member 305 (insulating base 311) and the lower surface 19a of the SAW element 7 are spaced apart from each other by a predetermined distance, thereby forming a facing space S below the excitation electrode 21. The height of the facing space S is smaller than the height of the facing space S in the first and second embodiments, and is, for example, 7 to 8 μm.

  The sealing portion 9 is formed by supplying a liquid resin 47 around the SAW element 7 mounted on the support member 305, as in the first embodiment. However, as the resin 47, a resin having a certain degree of viscosity (for example, 120 Pa · s) is used, thereby suppressing the resin 47 from flowing into the gap between the upper surface 311 a and the lower surface 19 a formed relatively narrow. Is done. The viscosity of the resin 47 is adjusted by the composition of the resin 47, the content of the effect accelerator, and the curing temperature.

  Also in the third embodiment, since the cavity 311v is provided and a part of the bump 8 is accommodated in the cavity 311v, the same effect as in the first embodiment can be obtained. That is, the distance between the upper surface 311a of the support member 305 and the lower surface 19a of the SAW element 7 can be made smaller than the thickness of the bumps 8. As a result, the piezoelectric device 1 can be made thinner and the liquid resin 47 can be opposed to the opposing space S. Is expected to be suppressed.

(Fourth embodiment)
FIG. 7 is a perspective view showing a support member 405 of the piezoelectric device according to the fourth embodiment.

  The piezoelectric device according to the fourth embodiment is different from the first embodiment only in the shape of the insulating base 411 of the support member 405. In addition, about other members, it is the same as that of 1st Embodiment, and the code | symbol of FIGS. 1-4 may be referred in the following description.

  As in the first embodiment, the support member 405 has a cavity 411v formed in a range extending from the excitation electrode 21 and the substrate pad 17 in a plan view. However, a protrusion 411p is formed in the cavity 411v so as to protrude upward (on the SAW element 7 side) from the bottom surface thereof.

  For example, the height of the protrusion 411p is equal to the depth of the cavity 411v. Accordingly, although not particularly illustrated, the lower surface 19a of the SAW element 7 is in contact with the upper surface 411a of the support member 405 around the cavity 411v and also in the protrusion 411p.

  The position of the protrusion 411p may be an appropriate position in the cavity 411v, and is preferably located closer to the center side (excitation electrode 21 side) of the cavity 411v than the plurality of substrate pads 17. The planar shape of the protrusion 411p may be an appropriate shape such as a column shape or a wall shape. In FIG. 7, a protrusion 411 p formed in a wall shape surrounding a region facing the excitation electrode 21 inside the substrate pad 17 is illustrated.

  Also in the fourth embodiment, the cavity 411v is provided, and the bump 8 is accommodated in the cavity 411v, so that the same effect as that of the first embodiment is obtained. That is, it is expected that the piezoelectric device 1 is thinned and the inflow of the liquid resin 47 into the facing space S is suppressed.

  Furthermore, the protrusion 411p provided in the cavity 411v abuts on the lower surface 19a of the SAW element 7, so that the bending of the lower surface 19a (functional surface) is suppressed. As a result, the characteristics of the SAW element 7 are stabilized. Further, as illustrated in FIG. 7, the protrusion 411 p is provided so as to surround the excitation electrode 21, so that the liquid resin 47 can be more reliably suppressed from reaching the excitation electrode 21.

(Fifth embodiment)
FIG. 8 is a perspective view showing the SAW element 507 of the piezoelectric device according to the fifth embodiment.

  The piezoelectric device of the fifth embodiment is different from the second embodiment only in the shape of the piezoelectric substrate 519 of the SAW element 507. Other members are the same as those in the second embodiment, and the reference numerals in FIG. 5 may be referred to in the following description.

  As in the second embodiment, the piezoelectric substrate 519 has a cavity 519v formed in a range extending over the excitation electrode 21 and the element pad 25. However, similarly to the fourth embodiment, a protrusion 519p is formed in the cavity 519v so as to protrude downward (on the support member 205 side) from its bottom surface.

  The height of the protrusion 519p is equal to the depth of the cavity 519v, for example. Therefore, although not particularly illustrated, the upper surface 211a of the support member 205 is in contact with the lower surface 519a of the piezoelectric substrate 519 around the cavity 519v and also in the protrusion 519p.

  The position and planar shape of the protrusion 519p may be set appropriately as in the protrusion 411p of the fourth embodiment. However, since the wiring (not shown) that connects the excitation electrode 21 and the element pad 25 preferably does not straddle the protrusion 411p (step), the protrusion 519p is formed avoiding the arrangement position of the wiring. (It is preferable to avoid an annular wall surrounding the excitation electrode 21 inside the element pad 25 as illustrated in FIG. 7).

  Also in the fifth embodiment, the cavity 519v is provided, and the bump 8 is accommodated in the cavity 519v, so that the same effect as in the first and second embodiments can be obtained. That is, it is expected that the piezoelectric device 1 is thinned and the inflow of the liquid resin 47 into the facing space S is suppressed. Further, by providing the protrusion 519p, the functional surface of the piezoelectric substrate 519 is suppressed from being bent as in the fourth embodiment, and the liquid resin 47 can more reliably reach the excitation electrode 21. It is suppressed.

(Sixth embodiment)
FIG. 9 is a cross-sectional view showing a module component 600 according to the sixth embodiment.

  In the sixth embodiment, in addition to the SAW element 7, the electronic component 31 is mounted on the support member 605 (circuit board), and only the SAW element 7 and the electronic component 31 are sealed together by the sealing portion 609. Is different from the first embodiment.

  The electronic component 31 is, for example, an IC, a resistor, a capacitor, or an inductor, and is surface-mounted on the support member 605. The electronic component 31 may be connected to the SAW element 7 or another electronic component 31 via the support member 605, or is simply connected to an external terminal, like the SAW element 7 of the first embodiment. Just be fine.

  The basic configurations of the SAW element 7 and the support member 605 are substantially the same as those in the first embodiment. That is, a cavity 611v is formed in the support member 605 (insulating base 611), and the bumps 8 are accommodated in the cavity 611v.

  Note that the module component 600 and the module component 700 described later may be regarded as a piezoelectric device as a whole, or may be regarded as including a piezoelectric device in part.

  In the sixth embodiment, the same effect as that of the first embodiment is achieved. That is, it is expected that the module component 600 is thinned, the functional surface of the piezoelectric substrate 19 is prevented from being bent, the liquid resin 47 is prevented from flowing into the facing space S, and the wiring penetrating through the support member 605 is shortened.

(Seventh embodiment)
FIG. 10 is a cross-sectional view showing a module component 700 according to the seventh embodiment.

  In the seventh embodiment, in addition to the SAW element 7, the electronic component 31 is mounted on the support member 705, and only the second point is that the SAW element 207 and the electronic component 31 are sealed together by the sealing portion 709. It is different from the embodiment.

  The basic configuration of the SAW element 207 and the support member 705 is substantially the same as in the second embodiment. That is, the cavity 219v is formed in the SAW element 207 (piezoelectric substrate 219), and the bumps 8 are accommodated in the cavity 219v.

  In the seventh embodiment, the same effects as those of the second embodiment are achieved. That is, it is expected to reduce the thickness of the module component 700, suppress the bending of the functional surface of the piezoelectric substrate 219, suppress the inflow of the liquid resin 47 into the facing space S, and the like.

(Position, size or shape of details)
FIG. 11A to FIG. 11C are cross-sectional views showing preferable examples of the positions and sizes of the substrate pads 17 and the element pads 25. In these drawings, it is assumed that the left side of the drawing is the outside of the cavity (11v, etc.). In these drawings, the reference numerals of the first embodiment are used, but the same applies to other embodiments.

  In the example of FIG. 11A, the substrate pad 17 is wider than the element pad 25, and as a whole (for example, when the positions of centroids in a plan view are compared), the cavity 11v is located with respect to the element pad 25. It is shifted outward.

  Accordingly, the molten solder that becomes the bumps 8 extends in and out of the cavity 11v in order to wet the substrate pads 17 and the element pads 25, while trying to shrink to reduce the surface area. And a tensile force that brings the element pad 25 closer.

  Here, as shown in FIG. 2, a plurality of substrate pads 17 and element pads 25 are provided, and are arranged annularly on the outer peripheral side of the piezoelectric substrate 19. Therefore, the tensile force is canceled out between the plurality of substrate pads 17 and the element pads 25 in the direction along the xy plane, while acting as a force for attracting the SAW element 7 toward the support member 5 in the z direction. To do.

  In this manner, among the plurality of substrate pads 17 and element pads 25 arranged in an annular shape, the substrate pad 17 is arranged so as to be shifted to the outside of the ring with respect to the element pad 25, whereby the SAW element 7 and the support member 5 are arranged. It is easy to make the gap small or to bring them into contact with each other. The above effect can be obtained by shifting the element pad 25 to the outside of the ring with respect to the substrate pad 17.

  In the example of FIG. 11B, the substrate pad 17 has the same area as the element pad 25, but as a whole, the substrate pad 17 is shifted to the outside of the cavity 11v with respect to the element pad 25. . Accordingly, as in FIG. 11A, the SAW element 7 is easily attracted to the support member 5 by the bumps 8.

  In the example of FIG. 11C, the substrate pad 17 is displaced to the outside of the cavity 11v as a whole with respect to the element pad 25 and the inner wall of the cavity 11v, as in FIGS. 11A and 11B. It is provided up to. Therefore, the same effect as in FIGS. 11A and 11B is further expected.

  FIG. 12 is a cross-sectional view illustrating an example of a preferable shape of a cavity (a protrusion around the cavity) when the cavity is formed on the piezoelectric substrate as in the second embodiment. In the figure, the reference numerals of the second embodiment are used, but the same applies to other embodiments in which a cavity is formed in the piezoelectric substrate.

  The inner wall of the cavity 219v is formed so as to be inclined so that the protrusion 219w becomes thinner toward the tip. Such an inclined surface is formed, for example, by appropriately setting etching conditions such as a composition ratio of etching gas and an applied voltage when the cavity 219v is formed by etching such as reactive ion etching.

  When the protrusion 219w becomes thinner toward the tip in this manner, when a load from above to below is applied to the piezoelectric substrate 219, the load is easily absorbed by the deformation of the protrusion 219w, and the functional surface of the piezoelectric substrate 219 is improved. Deflection is suppressed. As a result, the characteristics of the SAW element are stabilized.

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

The piezoelectric element is not limited to a SAW element. The piezoelectric element may be one that does not use elastic waves, or one that uses elastic waves other than SAW, such as a piezoelectric thin film resonator. The specific configuration of the SAW element is not limited to that exemplified in the embodiment. For example, the SAW element may have a protective layer made of SiO ₂ or the like that covers the excitation electrode.

  The cavity may be provided not only in one of the support member and the piezoelectric element but also in both the support member and the piezoelectric element. In this case, the cavity provided in the support member and the cavity provided in the piezoelectric element may or may not partially overlap each other.

  The protrusion located in the cavity is not limited to the support member and the piezoelectric element provided on the member on the side where the cavity is formed, but provided on the other member and inserted into the cavity to support the load. It may be.

  When the opposing space is formed by the cavity (the first and second embodiments and the like), the upper surface of the support member and the lower surface of the piezoelectric element do not have to be in contact with each other around the cavity. That is, even when the cavity is provided, a gap may be formed between the upper surface and the lower surface as in the third embodiment, and the inflow may be suppressed by the viscosity of the resin.

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric device, 5 ... Support member, 11 ... Insulating base | substrate, 11a ... Upper surface, 7 ... SAW element (piezoelectric element), 8 ... Bump (joining member), 9 ... Sealing part (sealing material), 11v ... Cavity 19 ... Piezoelectric substrate, 19a ... lower surface, 21 ... excitation electrode.

Claims (7)

A support member having an insulating substrate;
A piezoelectric substrate having a piezoelectric substrate having a lower surface opposed to the upper surface of the insulating substrate, and an excitation electrode provided on the lower surface side of the piezoelectric substrate and opposed to the support member via a facing space;
A joining member interposed between the support member and the piezoelectric element to connect them;
A sealing material provided on an outer periphery of the piezoelectric element on the support member;
Have
A cavity is provided in at least one of the upper surface of the insulating base and the lower surface of the piezoelectric substrate,
At least a part of the joining member is accommodated in the cavity. Piezoelectric device. The cavity is provided on an upper surface of the insulating substrate;
The piezoelectric device according to claim 1, wherein the excitation electrode is provided at a position facing the cavity. The cavity is provided on a lower surface of the piezoelectric substrate;
The piezoelectric device according to claim 1, wherein the excitation electrode is provided in the cavity. The piezoelectric device according to claim 2, wherein an upper surface of the insulating base and a lower surface of the piezoelectric substrate are in contact with each other around the cavity. The piezoelectric device according to claim 4, wherein at least one of the insulating base and the piezoelectric substrate has a protrusion that is located in the cavity and contacts the other. The support member is annularly arranged on the upper surface side of the insulating base, and has a plurality of substrate pads to which the bonding member is bonded,
The piezoelectric element has a plurality of element pads that are annularly arranged on the lower surface side of the piezoelectric substrate and to which the bonding member is bonded.
The piezoelectric device according to claim 4, wherein the substrate pad is arranged so as to be shifted to the outside of the ring with respect to the element pad. A circuit board having an insulating substrate;
A piezoelectric substrate having a piezoelectric substrate having a lower surface opposed to the upper surface of the insulating substrate, and an excitation electrode provided on the lower surface side of the piezoelectric substrate and opposed to the circuit substrate via a facing space;
A bonding member interposed between the circuit board and the piezoelectric element to connect them;
A sealing material provided on an outer periphery of the piezoelectric element on the circuit board;
An electronic element mounted on the circuit board and covered with the sealing material;
Have
A cavity is provided in at least one of the upper surface of the insulating base and the lower surface of the piezoelectric substrate,
A module component in which at least a part of the joining member is housed in the cavity.

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