Piezoelectric device, and method for manufacturing piezoelectric device

Abstract

To provide a piezoelectric device and a method for manufacturing a piezoelectric device that can improve reliability.SOLUTION: A piezoelectric device comprises: a first substrate 1 that has a first surface on which a piezoelectric element and a first electrode 11 connected with the piezoelectric element are arranged; and a second substrate 2 that has a second surface facing the first surface, a third surface on the opposite side of the second surface, a through hole 13 penetrating from the second surface to the third surface, and a second electrode 15 arranged in the through hole 13 and connected with the first electrode 11. The second substrate 2 is provided with a liquid reservoir part 210 having a recess connected with the third surface in at least part of a side wall of the through hole 13.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a piezoelectric device and a method for manufacturing a piezoelectric device. [Background technology]

[0002] Patent Document 1 discloses a configuration of an ultrasonic device including an ultrasonic substrate having a terminal electrically connected to a piezoelectric element, and an intermediate substrate joined to the ultrasonic substrate, in which a through hole is formed and a through electrode electrically connected to the terminal is disposed in the through hole. The through hole is formed by filling the through hole with a conductive paste using a screen printing method, for example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-106183 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the configuration of Patent Document 1, when the through-holes are filled with a conductive paste, air gets into the through-holes and remains as air bubbles, which causes a problem that the height of the through-electrodes protruding from the surface of the intermediate substrate varies due to the air bubbles. As a result, the inclination of the substrate to be joined to the intermediate substrate increases, which causes a problem of degrading the characteristics of the ultrasonic device. [Means for solving the problem]

[0005] The piezoelectric device comprises a first substrate having a first surface on which a piezoelectric element and a first electrode connected to the piezoelectric element are arranged, and a second substrate having a second surface opposite the first surface, a third surface opposite the second surface, a through hole penetrating from the second surface to the third surface, and a second electrode arranged in the through hole and connected to the first electrode, wherein the second substrate is provided with a liquid reservoir portion having a recess connected to the third surface on at least a portion of a side wall of the through hole.

[0006] A method for manufacturing a piezoelectric device includes a first substrate having a first surface on which a piezoelectric element and a first electrode connected to the piezoelectric element are arranged, a second substrate having a second surface opposite the first surface, a third surface opposite the second surface, a through hole penetrating from the second surface to the third surface, and a second electrode arranged in the through hole and connected to the first electrode, wherein the second substrate is provided with a liquid reservoir portion having a depression connected to the third surface on at least a portion of a side wall of the through hole, the method for manufacturing a piezoelectric device includes the steps of: dripping a conductive paste into the liquid reservoir portion; hardening the conductive paste that has flowed from the liquid reservoir portion to the side wall and a bottom of the through hole to form the second electrode; and joining the second substrate and a third substrate via the second electrode. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is an exploded perspective view showing a configuration of a piezoelectric device. [Diagram 2] 2 is a cross-sectional view of the piezoelectric device shown in FIG. 1 taken along line AA. [Diagram 3] 2 is a cross-sectional view of the piezoelectric device shown in FIG. 1 taken along line BB. [Figure 4] FIG. 2 is a plan view showing the configuration of a first substrate that constitutes the piezoelectric device. [Diagram 5] FIG. 2 is a plan view showing a configuration of a piezoelectric device. [Figure 6] 6 is a cross-sectional view of the piezoelectric device shown in FIG. 5 taken along the line CC. [Figure 7] 6 is an enlarged plan view of a portion D of the piezoelectric device shown in FIG. 5. [Figure 8] 7 is an enlarged cross-sectional view showing a portion E of the piezoelectric device shown in FIG. 6. [Figure 9] 5A to 5C are cross-sectional views illustrating a method for manufacturing a piezoelectric device. [Figure 10A] 5A to 5C are cross-sectional views illustrating a method for manufacturing a piezoelectric device. [Figure 10B] 5A to 5C are cross-sectional views illustrating a method for manufacturing a piezoelectric device. [Figure 10C] 5A to 5C are cross-sectional views illustrating a method for manufacturing a piezoelectric device. [Figure 10D] 5A to 5C are cross-sectional views illustrating a method for manufacturing a piezoelectric device. [Figure 10E] 5A to 5C are cross-sectional views illustrating a method for manufacturing a piezoelectric device. [Figure 11A] FIG. 13 is a plan view showing the configuration of a piezoelectric device according to a modified example. [Figure 11B] FIG. 11 is a cross-sectional view showing the configuration of a piezoelectric device according to a modified example. [Figure 12] 10A to 10C are cross-sectional views showing a method for manufacturing a piezoelectric device according to a modified example. [Figure 13A] FIG. 13 is a plan view showing the configuration of a piezoelectric device according to a modified example. [Figure 13B] FIG. 11 is a cross-sectional view showing the configuration of a piezoelectric device according to a modified example. [Figure 14] 10A to 10C are cross-sectional views showing a method for manufacturing a piezoelectric device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In the following figures, the three mutually orthogonal axes are described as the X-axis, Y-axis, and Z-axis. The direction along the X-axis is the "X-direction", the direction along the Y-axis is the "Y-direction", and the direction along the Z-axis is the "Z-direction", with the arrow direction being the + direction and the direction opposite to the + direction being the - direction. The +Z direction is sometimes called "upper" or "upper side" or "front side", and the -Z direction is sometimes called "lower" or "lower side" or "rear side", and the view from the +Z direction and -Z direction is also called a planar view or planar. The surface on the +Z side is described as the "upper surface" or "front side", and the surface on the opposite side of the -Z side is described as the "lower surface" or "rear side".

[0009] First, the configuration of a piezoelectric device 100 will be described with reference to FIG.

[0010] As shown in FIG. 1, the piezoelectric device 100 is configured by laminating a first substrate 1, a second substrate 2, and a third substrate 3 in this order.

[0011] The first substrate 1 to the third substrate 3 have, for example, a rectangular shape in a plan view from the Z direction. The longitudinal direction of the first substrate 1 to the third substrate 3 is the X direction. The lateral direction of the first substrate 1 to the third substrate 3 is the Y direction. The first substrate 1 and the second substrate 2 have, for example, the same shape. The third substrate 3 is larger in shape than the first substrate 1 and the second substrate 2.

[0012] The first substrate 1 has a first surface 1a on the side facing the second substrate 2. Elements 7 are arranged in a matrix on the first surface 1a (see FIG. 4). The elements 7 are piezoelectric elements. The piezoelectric device 100 can vibrate the first substrate 1 and emit ultrasonic waves by applying an AC voltage to the elements 7. The first substrate 1 is also called a diaphragm.

[0013] There is no particular limitation on the number of elements 7. In this embodiment, the number of elements 7 is, for example, 16, forming an array of 4 rows and 4 columns.

[0014] In addition, first electrodes 11 and 12 electrically connected to the elements 7 are arranged on the first surface 1a of the first substrate 1. The first electrode 11 is, for example, a common terminal. The first electrode 12 is, for example, a drive terminal.

[0015] The second substrate 2 has a second surface 2a facing the first surface 1a, and a third surface 2b opposite the second surface 2a. The second substrate 2 also has through holes 13, 14 penetrating from the second surface 2a to the third surface 2b, and second electrodes 15, 16 disposed in the through holes 13, 14 and connected to the first electrodes 11, 12.

[0016] More specifically, a second electrode 15 is disposed in the through hole 13. The second electrode 15 is electrically connected to the first electrode 11. A second electrode 16 is disposed in the through hole 14. The second electrode 16 is electrically connected to the first electrode 12.

[0017] Four grooves 9 long in the Y direction are provided on the second surface 2a of the second substrate 2. The shape of the grooves 9 is approximately a parallelogram when viewed from the Z direction. The second substrate 2 is a silicon single crystal substrate. The grooves 9 are formed by wet etching. Therefore, the shape of the grooves 9 is approximately a parallelogram.

[0018] The grooves 9 are disposed in a location facing the arrangement of the elements 7. Therefore, in the locations where the elements 7 are disposed, the first substrate 1 can vibrate in the +Z direction and the -Z direction.

[0019] The second substrate 2 has an open hole 17 on the +X-direction side of the groove 9. The open hole 17 penetrates from the second surface 2a to the third surface 2b. The open hole 17 and the groove 9 are connected by a communicating groove 18. The four grooves 9 are connected to each other by a communicating groove 19.

[0020] The first substrate 1 and the second substrate 2 are fixed by adhesion. The groove 9 is not sealed because it is connected to the open hole 17 and the communicating grooves 18 and 19. When the first substrate 1 vibrates, the air in the groove 9 is connected to the outside air, so the pressure inside the groove 9 does not easily fluctuate. For this reason, the first substrate 1 is prone to vibrating.

[0021] The third substrate 3 is disposed opposite the third surface 2b of the second substrate 2. A third electrode 21 serving as a common connection terminal is disposed on the third substrate 3 at a position overlapping with the second electrode 15. In addition, a third electrode 22 serving as a drive connection terminal is disposed on the third substrate 3 at a position overlapping with the second electrode 16. The third electrode 21 is electrically connected to the second electrode 15. The third electrode 22 is electrically connected to the second electrode 16. By supplying power to the third electrodes 21 and 22, a voltage can be applied to the first electrodes 11 and 12.

[0022] The third substrate 3 includes external electrodes 23, 25 on the negative side in the X direction of the third electrodes 21, 22. The third electrode 21 and the external electrode 23 are electrically connected by a wiring 24. The third electrode 22 and the external electrode 25 are electrically connected by a wiring 26.

[0023] The wiring 24 and the wiring 26 are covered with a protective film 27. The third electrodes 21, 22 and the external electrodes 23, 25 are not covered with the protective film 27 and are exposed.

[0024] At the end of the third surface 2b of the second substrate 2 on the +X-direction side, the corner on the +Y-direction side and the corner on the -Y-direction side are fixed to the third substrate 3 by the conductive paste 28. At the end of the second substrate 2 on the -X-direction side, the periphery of the second electrodes 15, 16 is fixed to the third substrate 3 by the conductive paste 28.

[0025] Next, the configuration of the element 7 will be described with reference to FIG. 2 and FIG.

[0026] 2 and 3, the element 7 is disposed in the region overlapping with the groove 9. As described above, the element 7 is disposed on the first surface 1a of the first substrate 1. The element 7 is disposed on top of the first surface 1a on the negative side in the Z direction, and is composed of a driving electrode 7a, a piezoelectric film 7b, and a common electrode 7c.

[0027] As shown in Fig. 2, the multiple drive electrodes 7a are electrically connected to drive wiring 29 extending in the X direction. The drive electrodes 7a and the drive wiring 29 are made of the same material. As shown in Fig. 3, the multiple common electrodes 7c are electrically connected to common wiring 31 (see Fig. 3) extending in the Y direction. The common electrodes 7c and the common wiring 31 are made of the same material.

[0028] The piezoelectric film 7b is formed of, for example, a transition metal oxide having a perovskite structure. Specifically, the piezoelectric film 7b is formed of lead zirconate titanate (PZT) containing Pb, Ti, and Zr.

[0029] The first substrate 1 and the element 7 constitute an ultrasonic transducer 32. The common electrode 7c is maintained at a predetermined reference potential. Then, by inputting a drive pulse signal to the drive electrode 7a, the element 7 is deformed and the first substrate 1 vibrates. As a result, the ultrasonic transducer 32 transmits ultrasonic waves in the +Z direction.

[0030] When an object is present on the positive side of the piezoelectric device 100 in the Z direction, the ultrasonic wave is reflected by the object. When the reflected ultrasonic wave reaches the ultrasonic transducer 32, the first substrate 1 vibrates in response to the sound pressure of the ultrasonic wave. The vibration of the first substrate 1 deforms the piezoelectric film 7b, and a potential difference is generated between the driving electrode 7a and the common electrode 7c.

[0031] As a result, a reception signal corresponding to the sound pressure of the received ultrasonic wave is output from the driving electrode 7a of the ultrasonic transducer 32. In other words, the ultrasonic wave is detected. By measuring the time from when the piezoelectric device 100 transmits the ultrasonic wave to when it receives it, the distance between the piezoelectric device 100 and the object can be measured.

[0032] Next, the configuration of the first substrate 1 will be described with reference to FIG.

[0033] As shown in Fig. 4, four drive wirings 29 extending in the X direction are arranged on the first surface 1a of the first substrate 1. The drive wirings 29 are integrated on the negative side in the X direction and electrically connected to the first electrodes 12. In addition, four common wirings 31 extending in the Y direction are arranged on the first surface 1a of the first substrate 1. The common wirings 31 are integrated on the negative side in the Y direction and electrically connected to the first electrodes 11.

[0034] Next, the configuration of the piezoelectric device 100 will be described with reference to FIGS.

[0035] 5 and 6, the piezoelectric device 100 is configured by stacking a first substrate 1, a second substrate 2, and a third substrate 3 in this order. The stacking order is illustrated in the opposite direction to that shown in FIG. 1. As described above, the first surface 1a of the first substrate 1 is disposed to face the second surface 2a of the second substrate 2. The surface of the second substrate 2 opposite to the second surface 2a is the third surface 2b.

[0036] As shown in Figure 6, the first electrode 11 arranged on the first substrate 1 is electrically connected to the third electrode 21 arranged on the third substrate 3 via the second electrode 15 arranged in the through hole 13 of the second substrate 2.

[0037] The first electrode 12 arranged on the first substrate 1 is electrically connected to a third electrode 22 arranged on the third substrate 3 via a second electrode 16 arranged in a through hole 14 of the second substrate 2.

[0038] The first electrodes 11 and 12, the second electrodes 15 and 16, and the third electrodes 21 and 22 are made of, for example, a conductive adhesive (also called conductive paste 15a). Specifically, the conductive paste 15a is, for example, a resin-based adhesive containing a silver filler. As the resin-based adhesive, for example, an epoxy resin, a urethane resin, or a silicone resin-based adhesive can be used.

[0039] The second substrate 2 is formed from a silicon single crystal substrate. The through holes 13, 14 and the grooves 9 of the second substrate 2 are formed by wet etching. The side surfaces of the through holes 13, 14 and the grooves 9 are crystal planes with a slow etching rate. Therefore, the through holes 13, 14 and the grooves 9 (see FIGS. 1 and 5) are approximately parallelograms when viewed from the Z direction.

[0040] The third substrate 3 may be a holder having rigidity such as epoxy glass or ceramic, or may be a substrate having flexibility such as an FPC (Flexible printed circuits) or a film substrate.

[0041] Next, the configuration of the connection portion 200 including the second electrode 15 will be described with reference to Fig. 7 and Fig. 8. Note that Fig. 7 and Fig. 8 show the configuration around the second electrode 15, and the third substrate 3 is omitted from the illustration.

[0042] 7 and 8, the connection portion 200 has a first substrate 1, a first electrode 11 disposed on the first substrate 1, and a second electrode 15 disposed in a through hole 13 of the second substrate 2. In this embodiment, a bonding material 11a is disposed between the first electrode 11 and the second substrate 2 to bond them to each other.

[0043] In the through hole 13 of the second substrate 2, a liquid reservoir section 210 having a depression connected to the third surface 2b is provided in a part of the side wall of the through hole 13. Specifically, the liquid reservoir section 210 is a stepped portion provided in the side wall of the through hole 13.

[0044] The width W1 (short direction) of the through hole 13 is, for example, 340 μm. The width W2 (long direction) of the through hole 13 is, for example, 1 mm. The thickness W3 of the second substrate 2 is, for example, 400 μm. The width W4 of the liquid reservoir section 210 is, for example, 50 μm to 500 μm.

[0045] In this way, since the through-hole 13 is provided with the liquid reservoir 210 having a depression connected to the third surface 2b, for example, when forming the second electrode 15, by dropping the conductive paste 15a into the liquid reservoir 210, the conductive paste 15a can flow from the liquid reservoir 210 along the side wall of the through-hole 13, and it is possible to prevent air bubbles from entering the conductive paste 15a. Therefore, it is possible to prevent variations in the height of the second electrode 15 protruding from the third surface 2b caused by air bubbles, and it is possible to prevent the third substrate 3 bonded to the second substrate 2 from tilting.

[0046] Moreover, the liquid reservoir 210 has a bottom 2c on the second surface 2a side of the recess, and a depth W5 from the third surface 2b to the bottom 2c is preferably equal to or less than half the thickness W3 of the second substrate 2. Specifically, the depth W5 is equal to or greater than 50 μm and equal to or less than 200 μm. Moreover, the bottom 2c is preferably parallel to the third surface 2b.

[0047] In this way, the liquid reservoir section 210 has a recess with a depth W5 that is less than half the thickness W3 of the second substrate 2, and the bottom 2c of the recess is horizontal, so that the conductive paste 15a dropped into the liquid reservoir section 210 can be retained in the liquid reservoir section 210, and the conductive paste 15a accumulated in the liquid reservoir section 210 can function as part of the second electrode 15.

[0048] 9 to 10E, a method for manufacturing the piezoelectric device 100 will be described. The description will start from the steps after the first substrate 1 and the second substrate 2 are bonded together and the through hole 13 is formed. The manufacturing method for the periphery of the second electrode 15 will also be described.

[0049] 9, a liquid reservoir portion 210 having a recess connected to the third surface 2b is formed in a part of the side wall of the through hole 13. Specifically, the liquid reservoir portion 210 is formed by performing a half-etching process on a part of the through hole 13 using a wet etching method or a dry etching method.

[0050] Next, the conductive paste 15a that will become the second electrode 15 is dropped, in other words, applied (also called screen printing), into the liquid reservoir 210 using a dispenser 305. Specifically, the conductive paste 15a dropped into the liquid reservoir 210 has fluidity and flows downward from the liquid reservoir 210 along the side wall of the through hole 13. Then, it flows into the bottom of the through hole 13.

[0051] At this time, when the conductive paste 15a is flowed from the liquid reservoir 210 down the side wall to the bottom of the through hole 13, the conductive paste 15a sticks to the side wall due to surface tension and capillary action, and advances while crushing air bubbles, thereby preventing air bubbles from entering the conductive paste 15a.

[0052] Furthermore, as described above, since the depth W5 of the liquid reservoir 210 is equal to or less than half the thickness W3 of the second substrate 2, the conductive paste 15a can be retained in the liquid reservoir 210, as compared to when the depth is too deep. Therefore, the second electrode 15 that can be reliably electrically connected can be formed.

[0053] It is preferable that through-hole 13 is not completely blocked by conductive paste 15a in order to prevent air bubbles from entering through-hole 13. If air bubbles are not allowed to enter through-hole 13, it is acceptable to completely block the inside of through-hole 13.

[0054] Thereafter, the conductive paste 15a is cured to form the second electrode 15. The second electrode 15 is formed so as to protrude a predetermined amount from the third surface 2b in order to be electrically connected to the third electrode 21 of the third substrate 3. The predetermined amount is, for example, 0.04 mm.

[0055] In this way, since the second electrode 15 protrudes a predetermined amount from the third surface 2b, it is possible to suppress variation in the height of the second electrode 15 protruding from the third surface 2b, which occurs when air bubbles get into the conductive paste 15a. Therefore, it is possible to suppress tilting of the third substrate 3 when the second substrate 2 and the third substrate 3 are joined later.

[0056] The resistance of the second electrode 15 is preferably, for example, 1Ω or less, and is 0.1Ω in this embodiment.

[0057] 10A, the first substrate 1, the second substrate 2, and the third substrate 3, which have been divided and separated, are attached to the mounting machine 300. Specifically, the first substrate 1 and the second substrate 2 are joined to the lower fixing part 310 of the mounting machine 300, and the third substrate 3 is fixed to the upper fixing part 320 of the mounting machine 300. For example, a vacuum suction method is used as a fixing method. Next, the second substrate 2 and the third substrate 3 are aligned by a coaxial camera.

[0058] 10B, the third substrate 3 is mounted on the second substrate 2. Specifically, the third substrate 3 adsorbed to the upper fixing portion 320 is released from the vacuum at a certain position by Z position control.

[0059] 10C, the upper fixing portion 320 is released. Specifically, the second substrate 2 and the third substrate 3 are bonded by the weight of the third substrate 3. Since there is little variation in the amount that the second electrode 15 protrudes from the third surface 2b, bonding by the weight of the third substrate 3 is possible without controlling the height of the third substrate 3.

[0060] 10D, the second substrate 2 and the third substrate 3 are heated in a bonded state, and the conductive paste 15a hardens and shrinks to self-control the posture, completing the bonding of the second substrate 2 and the third substrate 3. As a result, the second substrate 2 and the third substrate 3 are electrically connected via the second electrode 15, and the piezoelectric device 100 is completed (see FIG. 10E). The dispenser 305 is not limited to being a separate device, and may be provided in the mounting machine 300.

[0061] As described above, the piezoelectric device 100 of this embodiment comprises a first substrate 1 having a first surface 1a on which a piezoelectric element as an element 7 and a first electrode 11 connected to the piezoelectric element are arranged, and a second substrate 2 having a second surface 2a opposite to the first surface 1a, a third surface 2b opposite to the second surface 2a, a through hole 13 penetrating from the second surface 2a to the third surface 2b, and a second electrode 15 arranged in the through hole 13 and connected to the first electrode 11. The second substrate 2 is provided with a liquid reservoir portion 210 having a recess connected to the third surface 2b on at least a portion of the side wall of the through hole 13.

[0062] According to this configuration, since the through-hole 13 is provided with the liquid reservoir 210 having a depression connected to the third surface 2b, for example, when forming the second electrode 15, by dropping the conductive paste 15a into the liquid reservoir 210, the conductive paste 15a can flow from the liquid reservoir 210 along the side wall of the through-hole 13, and it is possible to prevent air bubbles from entering the conductive paste 15a. Therefore, it is possible to prevent variations in the height of the second electrode 15 protruding from the third surface 2b caused by air bubbles, and it is possible to prevent the third substrate 3 bonded to the second substrate 2 from tilting.

[0063] Furthermore, in the piezoelectric device 100 of this embodiment, it is preferable that the liquid reservoir 210 has a bottom 2c in the recess, and the depth W5 from the third surface 2b to the bottom 2c is equal to or less than half the thickness W3 of the second substrate 2. With this configuration, since the liquid reservoir 210 has a recess with a depth equal to or less than half the thickness W3 of the second substrate 2, it is possible for the conductive paste 15a dropped into the liquid reservoir 210 to be retained in the liquid reservoir 210, and the conductive paste 15a retained in the liquid reservoir 210 can function as a part of the second electrode 15.

[0064] In addition, in the piezoelectric device 100 of this embodiment, the bottom 2c is preferably parallel to the third surface 2b. With this configuration, the bottom 2c of the recess is parallel to the third surface 2b, so that the conductive paste 15a can be retained at the bottom 2c.

[0065] In addition, in the piezoelectric device 100 of this embodiment, the width W4 of the liquid reservoir 210 as viewed from the third surface 2b side is preferably 50 μm or more. With this configuration, since the width W4 of the liquid reservoir 210 is 50 μm or more, for example, when the conductive paste 15a is dropped into the liquid reservoir 210, the conductive paste 15a can be retained in the liquid reservoir 210 and can flow slowly along the side wall of the through hole 13. This makes it possible to prevent air bubbles from entering the conductive paste 15a.

[0066] Furthermore, a method for manufacturing the piezoelectric device 100 of this embodiment includes a first substrate 1 having a first surface 1a on which a piezoelectric element as an element 7 and a first electrode 11 connected to the piezoelectric element are arranged, a second substrate 2 having a second surface 2a opposed to the first surface 1a, a third surface 2b on the opposite side to the second surface 2a, a through hole 13 penetrating from the second surface 2a to the third surface 2b, and a second electrode 15 arranged in the through hole 13 and connected to the first electrode 11, a liquid reservoir portion 210 having a depression connected to the third surface 2b on at least a portion of a side wall of the through hole 13, the method for manufacturing the piezoelectric device 100 comprising the steps of: dripping conductive paste 15a into the liquid reservoir portion 210; hardening the conductive paste 15a that has flowed from the liquid reservoir portion 210 to the side wall and the bottom of the through hole 13 to form a second electrode 15; and joining the second substrate 2 and the third substrate 3 via the second electrode 15.

[0067] According to this method, conductive paste 15a is dropped into liquid reservoir 210, so that conductive paste 15a can flow from liquid reservoir 210 down the side wall of through hole 13 to the bottom of through hole 13. This makes it possible to prevent air bubbles from entering conductive paste 15a, and suppresses variations in the height of second electrode 15 protruding from third surface 2b caused by air bubbles. This makes it possible to suppress tilting of third substrate 3 bonded to second substrate 2.

[0068] Modifications of the above embodiment will now be described.

[0069] As described above, the liquid reservoir portion 210 is not limited to being formed in a portion of the side wall of the through hole 13, but may be formed around the entire periphery of the side wall as shown in FIGS. 11A and 11B.

[0070] 11A and 11B, the liquid reservoir 210A of the modified example has a liquid reservoir 210A of width W6 added to other regions in addition to the liquid reservoir 210 of the above embodiment. The width W6 is preferably, for example, 50 μm or more and 200 μm or less.

[0071] In the manufacturing method of the second electrode 15 in the liquid reservoir 210A of the modified example, i.e., the manufacturing method of the piezoelectric device 100, as shown in Fig. 12, a dispenser 305 is operated along the entire circumference of the side wall of the through-hole 13 (see Fig. 11A) to apply the conductive paste 15a to the liquid reservoir 210A. Note that even in the liquid reservoir 210A, a portion of width W4 is drawn slowly, and other portions are drawn quickly.

[0072] Since conductive paste 15a has viscosity (e.g., 30 Pa·S), it takes longer for it to flow into through hole 13 than it takes to apply it. Therefore, by providing liquid reservoir 210A around the entire side wall of through hole 13, it is possible to increase the application area and shorten the application time. In addition, since liquid reservoir 210A is provided around the entire side wall, conductive paste 15a can flow along the side wall no matter which part of the side wall from which conductive paste 15a is dropped, and it is possible to prevent air bubbles from entering conductive paste 15a.

[0073] Thus, in the piezoelectric device 100 of this modified example, the liquid reservoir portion 210A is preferably provided around the entire periphery of the side wall of the through hole 13. With this configuration, since the liquid reservoir portion 210A is provided around the entire periphery of the side wall, the conductive paste 15a can flow along the side wall no matter where the conductive paste 15a is dropped from, and it is possible to prevent air bubbles from entering the conductive paste 15a.

[0074] As described above, the liquid reservoir 210 is not limited to having a width W4 (see FIG. 7) formed in a portion of the side wall of the through hole 13, and as shown in FIG. 13A and FIG. 13B, the liquid reservoir 210B may have a width W7 larger than width W1. In addition, the liquid reservoir 210B of the modified example may be formed around the entire periphery of the side wall of the through hole 13.

[0075] In this manner, by forming the liquid reservoir section 210B having a width W7 larger than the width W1, it is possible to enlarge the contact point when connecting with the third electrode 21 of the third substrate 3, thereby ensuring electrical conduction.

[0076] In the manufacturing method of the second electrode 15 in the liquid reservoir portion 210B of the modified example, that is, the manufacturing method of the piezoelectric device 100, the range of the half-etching process of a part of the through-hole 13 is made wider than that in the above embodiment, as shown in FIG.

[0077] A method for manufacturing the second electrode 15 in the liquid reservoir 210B of the modified example, i.e., a method for manufacturing the piezoelectric device 100, is as follows: as shown in FIG. 14, a dispenser 305 is operated along the entire periphery of the side wall of the through hole 13 (see FIG. 13A) to apply the conductive paste 15a to the liquid reservoir 210B.

[0078] Furthermore, as described above, the second electrode 15 is not limited to being formed by providing the liquid reservoir 210, but the liquid reservoir 210 may be applied to other contact electrodes, wiring, and the like. [Explanation of symbols]

[0079] 1...First substrate, 1a...First surface, 2...Second substrate, 2a...Second surface, 2b...Third surface, 2c...Bottom, 3...Third substrate, 7...Element, 7a...Drive electrode, 7b...Piezoelectric film, 7c...Common electrode, 9...Groove , 11,12...first electrode, 11a...bonding material, 13,14...through hole, 15,16...second electrode, 15a...conductive paste, 17...open hole, 18,19...communicating groove, 21,22...third electrode Electrode, 23, 25...external electrode, 24...wiring, 26...wiring, 27...protective film, 28...conductive paste, 29...drive wiring, 31...common wiring, 32...ultrasonic transducer, 100...piezoelectric device, 200...connection portion, 210...liquid reservoir portion, 210A...liquid reservoir portion, 210B...liquid reservoir portion, 300...mounting machine, 305...dispenser, 310...lower fixing portion, 320...upper fixing portion.

Claims

1. a first substrate having a first surface on which a piezoelectric element and a first electrode connected to the piezoelectric element are arranged; a second substrate having a second surface opposite to the first surface, a third surface opposite to the second surface, a through hole penetrating from the second surface to the third surface, and a second electrode disposed in the through hole and connected to the first electrode; Equipped with The second substrate is provided with a liquid reservoir portion having a depression connected to the third surface on at least a portion of a side wall of the through hole.

2. 2. The piezoelectric device according to claim 1 , The liquid reservoir is provided around the entire periphery of the side wall of the through hole.

3. 2. The piezoelectric device according to claim 1 , The liquid reservoir has a bottom in the recess, A piezoelectric device, wherein a depth from the third surface to the bottom is equal to or less than half the thickness of the second substrate.

4. 4. The piezoelectric device according to claim 3, The bottom is parallel to the third surface.

5. 2. The piezoelectric device according to claim 1 , A piezoelectric device, wherein the liquid reservoir has a width of 50 μm or more when viewed from the third surface side.

6. a first substrate having a first surface on which a piezoelectric element and a first electrode connected to the piezoelectric element are arranged; a second substrate having a second surface opposite to the first surface, a third surface opposite to the second surface, a through hole penetrating from the second surface to the third surface, and a second electrode disposed in the through hole and connected to the first electrode; Equipped with a liquid reservoir portion having a depression connected to the third surface, the liquid reservoir portion being provided on at least a portion of a side wall of the through hole, the liquid reservoir portion including: Dropping a conductive paste into the liquid reservoir; hardening the conductive paste that has flowed from the liquid reservoir to the side wall and the bottom of the through hole to form the second electrode; bonding the second substrate and a third substrate together via the second electrode; The method for manufacturing a piezoelectric device includes the steps of:

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