WO2015129061A1

WO2015129061A1 - Piezoelectric actuator, and piezoelectric vibration device, portable terminal, acoustic generator, acoustic generation device, and electronic device provided therewith

Info

Publication number: WO2015129061A1
Application number: PCT/JP2014/066558
Authority: WO
Inventors: 博毛利
Original assignee: 京セラ株式会社
Priority date: 2014-02-27
Filing date: 2014-06-23
Publication date: 2015-09-03
Also published as: CN105027581A; CN105027581B

Abstract

　[Problem] To provide a piezoelectric actuator which is free of disconnection even when a through-hole conductor of a flexible circuit board is arranged at a junction and which also realizes the downsizing of a piezoelectric actuator, and a piezoelectric vibration device, portable terminal, acoustic generator, acoustic generation device, and electronic device provided with the piezoelectric actuator. [Solution] A piezoelectric actuator (1) is provided with: a piezoelectric element (11) having a plate-shaped layered body (14) in which an internal electrode (12) and a piezoelectric layer (13) are stacked, and a surface electrode (15) electrically connected with the internal electrode (12) on one principal surface of the layered body (14); a flexible circuit board (2) having a wiring conductor (22) electrically connected with the surface electrode (15); and a conductive joining member (3) for electrically connecting the surface electrode (15) and the wiring conductor (22), the flexible circuit board (2) having a through-hole conductor (24) in an area in which the flexible circuit board (2) overlaps with the piezoelectric element (11), and an area for the junction of the flexible circuit board (2) and the piezoelectric element (11) by the conductive joining member (3) being provided at a position around the through-hole conductor (24) and set apart from the through-hole conductor (24) in a plan view.

Description

Piezoelectric actuator, piezoelectric vibration device including the same, portable terminal, sound generator, sound generator, electronic device

The present invention relates to a piezoelectric actuator suitable for a piezoelectric vibration device, a portable terminal, and the like, and a piezoelectric vibration device including the piezoelectric actuator, a portable terminal, an acoustic generator, an acoustic generator, and an electronic apparatus.

As the piezoelectric actuator, a bimorph type piezoelectric element in which a surface electrode is formed on the surface of a laminated body in which a plurality of internal electrodes and piezoelectric layers are laminated (see Patent Document 1), a piezoelectric element and a flexible element are used. A substrate in which a substrate is bonded with a conductive bonding material and a surface electrode of a piezoelectric element and a wiring conductor of a flexible substrate are electrically connected is known (see Patent Document 2).

JP 2002-10393 A JP-A-6-14396

Depending on the arrangement relationship between the surface electrode of the piezoelectric element and the wiring conductor provided on the flexible substrate, a through-hole conductor may be provided on the flexible substrate to route the wiring conductor. At this time, in order to reduce the size of the piezoelectric actuator, if a through-hole conductor is arranged in a region that overlaps the piezoelectric element in the flexible substrate and the entire overlapping region is to be joined, due to the stress caused by heat and pressure at the time of joining, There was a risk that the through-hole conductor would break. On the other hand, when the through-hole conductor is arranged outside the region of the flexible substrate that overlaps the piezoelectric element in order to prevent disconnection of the through-hole conductor, there is a problem that the size of the piezoelectric actuator increases because the outer dimension of the flexible substrate increases. .

The present invention has been made in view of the above circumstances, and a piezoelectric actuator that does not cause a disconnection even when a through-hole conductor is arranged in a region overlapping with a piezoelectric element on a flexible substrate, and that achieves downsizing of the piezoelectric actuator, and It is an object of the present invention to provide a piezoelectric vibration device, a portable terminal, a sound generator, a sound generation device, and an electronic device provided with the same.

The piezoelectric actuator of the present invention includes a plate-like laminate in which an internal electrode and a piezoelectric layer are laminated, and a piezoelectric element having a surface electrode electrically connected to the internal electrode on one main surface of the laminate, A flexible substrate having a wiring conductor electrically connected to the surface electrode; and a conductive bonding material that electrically connects the surface electrode and the wiring conductor, wherein the flexible substrate overlaps the piezoelectric element. A through-hole conductor is provided, and a bonding region between the flexible substrate and the piezoelectric element by the conductive bonding material is provided at a position away from the through-hole conductor around the through-hole conductor in a plan view. It is characterized by this.

The piezoelectric vibration device according to the present invention includes the piezoelectric actuator described above and a vibration plate bonded to the other main surface of the laminate.

A portable terminal of the present invention includes the piezoelectric actuator, an electronic circuit, a display, and a housing, and the other main surface of the laminate is bonded to the display or the housing. It is characterized by.

The acoustic generator according to the present invention includes a piezoelectric actuator, a diaphragm to which the piezoelectric actuator is attached, and which vibrates due to vibration of the piezoelectric actuator, and a frame body provided on an outer peripheral portion of the diaphragm. It is characterized by that.

Also, a sound generator according to the present invention is characterized by including the above-described sound generator and a housing that houses the sound generator.

According to another aspect of the invention, there is provided an electronic apparatus including the above-described acoustic generator, an electronic circuit connected to the acoustic generator, and a housing that houses the electronic circuit and the acoustic generator. It has a function of generating sound.

According to the present invention, disconnection of the through-hole conductor of the flexible wiring board can be prevented, and a highly reliable piezoelectric actuator can be obtained. Further, the flexible substrate can be miniaturized, and as a result, the piezoelectric actuator can be miniaturized. Furthermore, the piezoelectric vibration device, the portable terminal, the sound generator, the sound generation device, and the electronic device of the present invention including the piezoelectric actuator can be highly reliable and downsized.

FIG. 1A is an exploded perspective view showing an example of an embodiment of the piezoelectric actuator of the present invention, and FIG. 1B is an example of a wiring pattern on the lower surface side of the flexible substrate 2 shown in FIG. FIG. 2A is a schematic cross-sectional view taken along line AA shown in FIG. 1A, and FIG. 2B is a schematic vertical cross-sectional view taken along line BB shown in FIG. 1A. . It is a figure which shows the other example of the wiring pattern by the side of the lower surface of the flexible substrate 2 shown in FIG.1 (b). FIG. 4A is an exploded perspective view showing another example of the embodiment of the piezoelectric actuator of the present invention, and FIG. 4B is a wiring pattern on the lower surface side of the flexible substrate 2 shown in FIG. It is a figure which shows an example. FIG. 5A is an exploded perspective view showing another example of the embodiment of the piezoelectric actuator of the present invention, and FIG. 5B is a wiring pattern on the lower surface side of the flexible substrate 2 shown in FIG. It is a figure which shows an example. FIG. 6A and FIG. 6B are schematic perspective views showing variations of the formation pattern of the conductive bonding material in the piezoelectric actuator of the present invention. It is a schematic longitudinal cross-sectional view which shows the other example of embodiment of the piezoelectric actuator of this invention. It is a schematic longitudinal cross-sectional view which shows the other example of embodiment of the piezoelectric actuator of this invention. 1 is a schematic perspective view schematically showing an embodiment of a piezoelectric vibration device of the present invention. It is a schematic perspective view which shows typically embodiment of the portable terminal of this invention. It is a schematic sectional drawing cut | disconnected by the AA line shown in FIG. It is a schematic sectional drawing cut | disconnected by the BB line shown in FIG. FIG. 13 (a) is a schematic plan view showing a schematic configuration of an embodiment of the sound generator of the present invention, and FIG. 13 (b) is an example cut along line AA in FIG. 13 (a). FIG. 13C is a schematic cross-sectional view of another example cut along the line AA in FIG. 13A. It is a figure which shows the structure which concerns on embodiment of the sound generator of this invention. It is a figure which shows the structure which concerns on embodiment of the electronic device of this invention.

An example of an embodiment of a piezoelectric actuator of the present invention will be described in detail with reference to the drawings.

FIG. 1A is an exploded perspective view showing an example of an embodiment of the piezoelectric actuator of the present invention, and FIG. 1B is an example of a wiring pattern on the lower surface side of the flexible substrate 2 shown in FIG. FIG. 2A is a schematic cross-sectional view taken along line AA shown in FIG. 1A, and FIG. 2B is a schematic cross-sectional view taken along line BB shown in FIG. 1A. is there.

The piezoelectric actuator 1 according to the present embodiment shown in FIGS. 1 and 2 includes a plate-like laminate 14 in which an internal electrode 12 and a piezoelectric layer 13 are laminated, and the internal electrode 12 and the electrical surface on one main surface of the laminate 14. The piezoelectric element 11 having the surface electrode 15 connected to the surface, the flexible substrate 2 having the wiring conductor 22 electrically connected to the surface electrode 15, and the conductive junction for electrically connecting the surface electrode 15 and the wiring conductor 22. The flexible substrate 2 has a through-hole conductor 25 in a region overlapping with the piezoelectric element 11 and is electrically conductively bonded at a position away from the through-hole conductor 25 around the through-hole conductor 25 in plan view. A bonding region 30 between the flexible substrate 2 and the piezoelectric element 11 made of the material 3 is provided.

The piezoelectric actuator 1 of this example has a piezoelectric element 11, and the piezoelectric element 11 of this example has a rectangular shape in which one main surface has a length direction and a width direction. The laminated body 14 constituting the piezoelectric element 11 is formed by laminating the internal electrode 12 and the piezoelectric layer 13 in a plate shape. The piezoelectric actuator 1 has an active portion in which a plurality of internal electrodes 12 overlap in the stacking direction and an inactive portion other than the active portion, and is formed in a long shape, for example. In the case of a piezoelectric actuator attached to a display or casing of a portable terminal, the length of the laminate 14 is preferably, for example, 18 mm to 28 mm, and more preferably 22 mm to 25 mm. For example, the width of the laminate 14 is preferably 1 mm to 6 mm, and more preferably 3 mm to 4 mm. The thickness of the laminate 14 is preferably, for example, 0.2 mm to 1.0 mm, and more preferably 0.4 mm to 0.8 mm.

The internal electrode 12 constituting the laminate 14 is formed by simultaneous firing with the ceramic forming the piezoelectric layer 13 and includes a first internal electrode and a second internal electrode. Piezoelectric layers 13 are alternately stacked and sandwich the piezoelectric layers 13 from above and below, and the first internal electrode and the second internal electrode are arranged in the stacking order, so that the piezoelectric body is sandwiched between them. A driving voltage is applied to the layer 13. As this forming material, for example, a conductor mainly composed of silver or a silver-palladium alloy having a low reactivity with piezoelectric ceramics, or a conductor containing copper, platinum, or the like can be used. You may make it contain.

In the example shown in FIGS. 1 and 2, the end portions of the first internal electrode and the second internal electrode are led out alternately to a pair of side surfaces facing each other of the laminate 14. In the case of a piezoelectric actuator attached to a display or casing of a mobile terminal, the length of the internal electrode 12 is preferably, for example, 17 mm to 25 mm, and more preferably 21 mm to 24 mm. For example, the width of the internal electrode 12 is preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. The thickness of the internal electrode 12 is preferably 0.1 μm to 5 μm, for example.

The piezoelectric layer 13 constituting the laminated body 14 is formed of ceramics having piezoelectric characteristics. As such ceramics, for example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ), Lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), or the like can be used. The thickness of one layer of the piezoelectric layer 13 is preferably set to 0.01 to 0.1 mm, for example, so as to be driven at a low voltage. In order to obtain a large bending vibration, it is preferable to have a piezoelectric constant d31 of 200 pm / V or more.

A surface electrode 15 electrically connected to the internal electrode 12 is provided on one main surface of the laminate 14. The surface electrode 15 in the form shown in FIG. 1 includes a first surface electrode 151 having a large area, a second surface electrode 152 and a third surface electrode 153 having a small area. For example, the first surface electrode 151 is electrically connected to the internal electrode 12 serving as the first internal electrode, and the second surface electrode 152 is, for example, the internal electrode 12 serving as the second internal electrode disposed on one main surface side. The third surface electrode 153 is electrically connected to the internal electrode 12 serving as a second internal electrode disposed on the other main surface side, for example. In the case of a piezoelectric actuator attached to a display or casing of a portable terminal, the length of the first surface electrode 151 is preferably 17 mm to 23 mm, for example, and more preferably 19 mm to 21 mm. For example, the width of the first surface electrode 151 is preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. The lengths of the second surface electrode 152 and the third surface electrode 153 are preferably 1 mm to 3 mm, for example. The width of the second surface electrode 152 and the third surface electrode 153 is preferably 0.5 mm to 1.5 mm, for example.

Moreover, the piezoelectric actuator 1 has a flexible substrate 2 electrically joined to the surface electrode 15. Specifically, for example, the flexible substrate 2 is provided with a wiring conductor 22 and a through-hole conductor 25 as wiring on a resin base film 21, a cover film 23 is provided on the upper surface thereof, and overlaps with the piezoelectric element 11 on the lower surface. The cover film 23 is provided in the area except for the area and the vicinity thereof. Here, the through-hole conductor 25 shown in the figure has a configuration in which a conductor layer is provided on the inner wall surface of a hole penetrating the base film 21. The through-hole conductor 25 is provided in a region overlapping the piezoelectric element 11 in the flexible substrate 2. The wiring conductor 22 electrically connected to the first surface electrode 151 of the piezoelectric element 11 is routed from the lower surface of the base film 21 to the upper surface of the base film 21 through the through-hole conductor 25. On the other hand, the wiring conductor 22 electrically connected to the second surface electrode 152 of the piezoelectric element 11 and the wiring conductor 22 electrically connected to the third surface electrode 153 are provided on the lower surface of the base film 21. Thus, by dividing the wiring conductor 22 above and below the base film 21, the width of the flexible substrate 2 can be reduced and the piezoelectric actuator 1 can be reduced. The through-hole conductor is not limited to the one shown in the figure, and may be one in which a conductor is filled in the hole. In addition, the upper and lower wiring conductors 22 may overlap in plan perspective, but may not be overlapped as illustrated in view of the increase in thickness. FIG. 1A shows an example of a wiring pattern when the flexible substrate 2 is viewed from above, and FIG. 1B shows an example of a wiring pattern when the flexible substrate 2 is viewed from below.

Here, the end portion of the wiring conductor 22 to be joined to the surface electrode 15 should be wide, and further, as shown in FIG. 3, a slit is provided at the end portion of the wide wiring conductor 22. It is preferable that the ends have a comb-teeth shape, whereby the conductive bonding material 3 and the wiring conductor 22 are three-dimensionally bonded, and the bonding strength between the flexible substrate 2 and the piezoelectric element 11 is improved. . Moreover, it can also contribute to prevention of the flow of the conductive bonding material 3.

The cover film 23 provided on the lower surface of the flexible substrate 2 may be provided in a region excluding the bonding region with the surface electrode 15 of the wiring conductor 22 on the lower surface of the flexible substrate 2, but overlaps the piezoelectric element 11. Since the cover film 23 is not provided in the region and the vicinity thereof, a reliable electrical connection can be obtained without being affected by the thickness of the cover film 23. For example, the flexible substrate 2 is joined to the piezoelectric element 11 at one end, and joined to an external circuit (connector) at the other end.

A part of the flexible substrate 2 is bonded to one main surface of the multilayer body 14 constituting the piezoelectric element 11 via the conductive bonding material 3, and the wiring conductor 22 is connected to the surface electrode 15 via the conductive bonding material 3. Electrically connected. Here, as described later, a bonding region 30 between the flexible substrate 2 and the piezoelectric element 11 is provided at a position around the through-hole conductor 25 in a plan view and away from the through-hole conductor 25.

Although the number of through-hole conductors 25 is not limited, a plurality of through-hole conductors 25 are preferably provided as shown in the figure in order to suppress disconnection and reduce conduction resistance. Further, the pattern of the wiring conductor 22 is not limited, but for example, by providing the wiring conductor 22 around the opening of the through-hole conductor 25, a strong electrical connection with the through-hole conductor 25 can be obtained. preferable.

As the conductive bonding material 3, a conductive adhesive, solder, or the like is used, but a conductive adhesive is preferable. For example, conductive particles 31 made of, for example, gold, copper, nickel, or gold-plated resin balls are dispersed in a resin adhesive 32 such as acrylic resin, epoxy resin, silicone resin, polyurethane resin, or synthetic rubber. This is because the use of an adhesive can reduce stress caused by vibration compared to solder. More preferably, the conductive adhesive is preferably an anisotropic conductive material. The anisotropic conductive material is composed of conductive particles 31 responsible for electrical bonding and a resin adhesive 32 responsible for adhesion, and one conductive particle 31 is in contact with the surface electrode 15 and the wiring conductor 22. That is, the respective conductive particles 31 between the surface electrode 15 and the wiring conductor 22 are in contact with the surface electrode 15 and the wiring conductor 22. Since this anisotropic conductive material can conduct in the thickness direction and insulate in the in-plane direction (plane direction parallel to the one main surface of the laminate 14), the wiring pattern pitch of the flexible substrate 2 and the piezoelectric element Even if the pattern pitch of the surface electrode 15 of 11 is narrowed, an electrical short circuit does not occur and the junction region 30 can be made small. In the example illustrated in FIG. 1, a configuration using an anisotropic conductive material as the conductive bonding material 3 is illustrated.

Although not shown, the piezoelectric actuator 1 may include a reinforcing plate provided at least in a region overlapping with the piezoelectric element 11 when viewed from above the flexible substrate 2. The reinforcing plate is used to reinforce the region of the flexible substrate 2 that overlaps the piezoelectric element 11, for example, a resin such as glass epoxy (FR-4), composite (CEM-3), polyetherimide, polyimide, polyester, A metal such as stainless steel, aluminum, and alloys thereof, for example, having a thickness of 50 to 200 μm.

In the present invention, as described above, the flexible substrate 2 has the through-hole conductor 25 in the region overlapping the piezoelectric element 11, and is separated from the through-hole conductor 25 around the through-hole conductor 25 in plan view. A bonding region 30 between the flexible substrate 2 and the piezoelectric element 11 made of the conductive bonding material 3 is provided at the above position.

Here, the bonding region 30 is a conductive bonding material 3 between the surface of the piezoelectric element 11 including the surface (upper surface) of the surface electrode 15 and the surface of the flexible substrate 2 including the surface (lower surface) of the wiring conductor 22. It means the area that is filled. In addition, in this joining area | region 30, when the area where the conductive bonding material 3 contacts the flexible substrate 2 and the area where the piezoelectric element 11 contacts are different, for example, the cross section of the conductive bonding material 3 has a trapezoidal shape. Cases are also included. Even in such a case, the region where the conductive bonding material 3 and the flexible substrate 2 are in contact with each other only needs to be separated from the through-hole conductor 25, and such a form is also included in the present invention. Further, as a distant position, it is preferable that the distance is 200 to 600 μm away from the opening of the through hole (through hole conductor 25). Further, as will be described later, it is sufficient that the space is provided to such an extent that stress is not easily applied to the through-hole conductor 25.

With this configuration, a space (gap) is formed between the through-hole conductor 25 and the piezoelectric element 11 in the flexible substrate 2. Therefore, even when the flexible substrate 2 is bonded to the piezoelectric element 11 and in use, the through-hole conductor 25 is less likely to be stressed, and the through-hole conductor 25 can be prevented from being disconnected.

Further, since a space (gap) is formed between the through-hole conductor 25 and the piezoelectric element 11 in the flexible substrate 2, the flexible substrate 2 can easily follow the deformation of the piezoelectric element 11 and hardly obstruct the deformation of the piezoelectric element 11. Therefore, it can vibrate efficiently and the sound pressure of a portable terminal or a sound generator can be improved.

Here, as shown in FIG. 4, it is preferable that a plurality of bonding regions 30 made of the conductive bonding material 3 are provided.

By adopting such a configuration, the bonding strength between the flexible substrate 2 and the piezoelectric element 11 is improved by making the thickness of the conductive bonding material 3 in the bonding region 30 uniform without increasing so much.

Moreover, since the piezoelectric element 11 self-heats due to vibration, the temperature of the bonding region 30 due to the conductive bonding material 3 increases, and the bonding strength may decrease. Therefore, when the piezoelectric element 11 is continuously driven, the conductive bonding material 3 may be peeled off and the reliability may be lowered. On the other hand, by reducing the bonding area and volume of the conductive bonding material 3, the surface area of the conductive bonding material 3 that comes into contact with the atmosphere (air) is increased and the heat dissipation effect is increased. It can be suppressed and the reliability in continuous driving can be improved.

Furthermore, since the bonding area of the conductive bonding material 3 is reduced and the mass of the conductive bonding material 3 can be reduced, the vibration of the piezoelectric element 11 is hardly damped and the piezoelectric element 11 can be vibrated efficiently. Therefore, the diaphragm can be excited efficiently, and the sound pressure of the portable terminal and the sound generator can be improved.

In particular, it is preferable that one main surface of the laminate 14 is rectangular, and the bonding region 30 by the conductive bonding material 3 is provided apart in the length direction of the one main surface of the piezoelectric element 11. Since the piezoelectric element 11 mainly bends and vibrates so that the end portion in the length direction moves up and down, according to this configuration, the bonding region 30 by the conductive bonding material 3 is separated in the length direction. The vibration of the piezoelectric element 11 becomes less likely to be damped, and the piezoelectric element 11 can be flexibly vibrated more efficiently.

Specifically, as shown in FIG. 4, one main surface of the laminate 14 is rectangular, and the surface electrode 15 includes a first surface electrode 151, a second surface electrode 152, and a third surface electrode 153. The second surface electrode 152 and the third surface electrode 153 are provided apart from each other in the width direction of the one main surface, and the first surface electrode 151 is provided in the length direction of the one main surface. The bonding region 30 includes a first bonding region 301, a second bonding region 302, and a third bonding region 303, and the first bonding region 301 is the first bonding region 301. The first surface electrode 151 is provided, the second bonding region 302 is provided on the second surface electrode 152, and the third bonding region 303 is provided on the third surface electrode 153. It is done.

At this time, the wiring conductor 22 of the flexible substrate 2 includes a first wiring conductor 221 connected to the through-hole conductor 25, and a second wiring conductor 222 and a third wiring conductor 223 that are not connected to the through-hole conductor 25. The first surface electrode 151 is connected to the first wiring conductor 221 via the first bonding region 301, and the second surface electrode 152 is connected to the second wiring conductor 222 via the second bonding region 302. The third surface electrode 153 is connected to the third wiring conductor 223 through the third bonding region 303.

On the other hand, as shown in FIG. 5, one main surface of the laminate 14 is rectangular, and the surface electrode 15 includes a first surface electrode 151, a second surface electrode 152, and a third surface electrode 153, and the second surface The electrode 152 and the third surface electrode 153 are provided apart from each other in the width direction of the one main surface, and the first surface electrode 151 is disposed in the length direction of the one main surface. 153, the bonding region 30 includes a first bonding region 301 and a second bonding region 302, the first bonding region 301 is provided on the first surface electrode 151, and The two bonding regions 302 may be provided across the second surface electrode 152 and the third surface electrode 153.

At this time, the wiring conductor 22 of the flexible substrate 2 includes a first wiring conductor 221 connected to the through-hole conductor 25 and a second wiring conductor 222 not connected to the through-hole conductor 25, and the first surface electrode 151. Is connected to the first wiring conductor 221 via the first bonding region 301, and the second surface electrode 152 and the third surface electrode 153 are connected to the second wiring conductor 222 via the second bonding region 302. It is the composition which is.

Further, effectively, as shown in FIG. 6A, one main surface of the laminate 14 is rectangular, and the bonding region 30 (the first bonding region 301 and the second bonding region 302) On the other hand, a configuration that extends in the width direction of the main surface and has a band shape when seen through the plane is preferable. Specifically, in FIG. 6A, three rows of conductive bonding materials 3 extending in a band shape in the width direction are disposed on the first surface electrode 151, and the second surface electrode 152 An example is shown in which three rows of conductive bonding materials 3 extending in a band shape in the width direction from the top to the third surface electrode 153 are arranged. According to this configuration, the vibration of the piezoelectric element 11 becomes more difficult to be damped with respect to bending vibration in which the end portion in the length direction mainly moves up and down, and the piezoelectric element 11 can be vibrated more efficiently. it can.

Further, as shown in FIG. 6B, one main surface of the laminate 14 is rectangular, and a plurality of the bonding regions 30 (the first bonding region 301 and the second bonding region 302) are the one main surface. A configuration may also be employed in which the surfaces are arranged side by side in the width direction of the surface. Specifically, in FIG. 6B, three conductive bonding materials 3 arranged at intervals in the width direction are arranged on the first surface electrode 151, and the second surface An example in which three conductive bonding materials 3 are arranged from the top of the electrode 152 to the third surface electrode 153 is shown. According to this configuration, the vibration of the piezoelectric element 11 is less likely to be damped with respect to the bending vibration in the width direction, and the piezoelectric element 11 can be vibrated more efficiently.

In the case where there is a region where the surface electrode where the piezoelectric layer 13 is exposed is not provided between the first surface electrode 151, the second surface electrode 152, and the third surface electrode 153, a through hole is directly above this region. The conductor 25 is preferably located. That is, it is preferable that the surface of the piezoelectric layer 13 is exposed in a region overlapping with the through-hole conductor 25 on the one main surface when seen in a plan view. The area where the flexible substrate 2 and the piezoelectric element 11 overlap is reduced, and the electrical connection between the wiring conductor 22 and the first surface electrode 151, the second surface electrode 152, and the third surface electrode 153 by the conductive bonding material 3 is performed. Since a large area can be secured and a space (gap) between the through-hole conductor 25 and the piezoelectric element 11 can be sufficiently secured, the flexible substrate 2 can easily follow the deformation of the piezoelectric element 11, and the piezoelectric element 11 can be further improved. It becomes difficult to inhibit the deformation. Therefore, the sound pressure of the portable terminal or the sound generator can be improved by vibrating more efficiently.

Further, since the first surface electrode 151, the second surface electrode 152, and the third surface electrode 153 of the piezoelectric element 11 generate heat due to vibration, the through-hole conductor 25 becomes the first surface electrode 151, the second surface electrode 152, and the third surface electrode. If it is directly above the electrode 153, the heat is easily transferred to the through-hole conductor 25. Therefore, when continuously driven, there is a risk of disconnection due to a difference in thermal expansion between the through-hole conductor 25 and the base film 21, and reliability is reduced. Therefore, the surface of the piezoelectric layer 13 is exposed in a region that overlaps the through-hole conductor 25 on one main surface when seen in a plan view, so that it is difficult to be affected by heat generated by continuous driving. Disconnection is suppressed and reliability is improved.

Since the flexible substrate 2 is also deformed by the vibration of the piezoelectric element 11, the through-hole conductor 25 electrically connected to the first surface electrode 151 is connected to the surface electrode on the other pole side (second surface electrode 152 and third surface electrode 153. The surface electrode with the piezoelectric layer 13 exposed between the first surface electrode 151, the second surface electrode 152, and the third surface electrode 153 is surely eliminated. When there is a region that is not provided, it is effective to arrange the through-hole conductor 25 immediately above this region or directly above the first surface electrode 151.

Further, as shown in FIG. 7, the conductive bonding material 3 is preferably provided so as to extend to a region where the flexible substrate 2 extends from the piezoelectric element 11. By adopting such a configuration, a meniscus is formed by the protruding conductive bonding material 3, for example, and the bonding area between the conductive bonding material 3 and the piezoelectric element 11 or the conductive bonding material 3 and the flexible substrate 2. As a result, the bonding strength of the flexible substrate 2 is further improved. Further, the exposed wiring conductor 22 is also covered and protected.

Further, as shown in FIG. 8, the side of the through-hole conductor 25 facing the piezoelectric element 11 is preferably covered with a cover film 23. With such a configuration, it is possible to reliably prevent the conductive bonding material 3 from entering the through-hole 24 and to prevent the through-hole conductor 25 from being disconnected by generating no stress due to hardening shrinkage or the like.

Next, a method for manufacturing the piezoelectric actuator 1 according to this embodiment will be described.

First, a ceramic green sheet to be the piezoelectric layer 13 is produced. Specifically, a ceramic slurry is prepared by mixing a calcined powder of piezoelectric ceramic, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer. And a ceramic green sheet is produced using this ceramic slurry by using tape molding methods, such as a doctor blade method and a calender roll method. As the piezoelectric ceramic, any material having piezoelectric characteristics may be used. For example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ) can be used. As the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP), or the like can be used.

Next, a conductive paste to be the internal electrode 12 is produced. Specifically, a conductive paste is prepared by adding and mixing a binder and a plasticizer to a metal powder of a silver-palladium alloy. This conductive paste is applied on the ceramic green sheet in the pattern of the internal electrodes 12 using a screen printing method. Further, a plurality of ceramic green sheets on which the conductive paste is printed are laminated, subjected to binder removal treatment at a predetermined temperature, fired at a temperature of 900 to 1200 ° C., and then subjected to a predetermined grinding using a surface grinder or the like. By performing a grinding process so as to have a shape, a laminated body 14 including the internal electrodes 12 and the piezoelectric body layers 13 that are alternately laminated is manufactured.

The laminated body 14 is not limited to the one produced by the above manufacturing method, and any production method can be used as long as the laminated body 14 formed by laminating a plurality of internal electrodes 12 and piezoelectric layers 13 can be produced. It may be produced.

Thereafter, a silver glass-containing conductive paste prepared by adding a binder, a plasticizer, and a solvent to a mixture of conductive particles mainly composed of silver and glass is used as a main electrode of the laminate 14 in a pattern of the surface electrode 15. After the surface and side surfaces are printed by a screen printing method or the like and dried, a baking process is performed at a temperature of 650 to 750 ° C. to form the surface electrode 15.

When the surface electrode 15 and the internal electrode 12 are electrically connected, a via that penetrates the piezoelectric layer 13 may be formed or connected, or a side electrode may be formed on the side surface of the multilayer body 14, It may be produced by any manufacturing method.

For example, the flexible substrate 2 is a polyimide film as a sheet in which a large number of base films 21 are arranged (a multi-sheet for base film), and a copper foil to be a wiring conductor 22 is attached to both surfaces of the base film 21 using an adhesive. Put on. Next, a conductor pattern of the wiring conductor 22 is formed by a photolithography technique. At this time, the end portion of the wiring conductor 22 in the bonding area with the piezoelectric element 11 may have a comb-like shape.

Then, a through hole for the through-hole conductor 25 is formed by drilling in a region where the flexible substrate 2 and the piezoelectric element 11 overlap. Next, copper plating is simultaneously performed on the wiring conductor 22 and the inner wall of the through hole by electrolytic plating, so that the through-hole conductor 25 is produced and bonded to the wiring conductor 22. For insulation and protection of the wiring conductor 22, a polyimide film to be the cover film 23 is attached to both surfaces of the base film 21 with a thermosetting adhesive. Further, the cover film 23 may be attached so as to cover the through-hole conductor 25 formed in the bonding area with the piezoelectric element 11.

After the nickel conductor and the gold conductor are plated on the junction area with the piezoelectric element 11 and the connection conductor 22 with the mother board such as a portable terminal, a polyimide sheet with a thickness of 150 μm which becomes a reinforcing plate 26 if necessary (multiple sheet for reinforcing plate) ) At a predetermined position with a thermosetting adhesive, and punched into a desired shape by die press processing, the flexible substrate 2 can be produced.

Next, the flexible substrate 2 is connected and fixed (bonded) to the laminate 14 using, for example, a conductive adhesive as the conductive bonding material 3. First, a conductive bonding paste is applied and formed at a predetermined position of the laminated body 14 by using a method such as screen printing or dispensing. At this time, the conductive bonding material 3 is applied and formed at a position away from the position where the through-hole conductor 25 of the flexible substrate 2 is provided. The shape of the applied conductive bonding material 3 is, for example, divided into two parts so as to be separated from the through-hole conductor 25 in the bonding region, and encloses the periphery of the through-hole conductor 25. Any shape can be used as long as the material 3 does not come into contact with or after joining. The conductive adhesive may be applied and formed on the flexible substrate 2 side.

Then, the flexible substrate 2 is connected and fixed to the piezoelectric element 11 by curing the conductive adhesive paste while the flexible substrate 2 is in contact therewith.

When the resin constituting the conductive adhesive is made of a thermoplastic resin, the conductive adhesive is applied and formed on a predetermined position of the laminate 14 or the flexible substrate 2 and then the laminate 14 and the flexible substrate 2 are made conductive. The thermoplastic resin softens and flows by being heated and pressed in a state of being brought into contact with the adhesive, and then returned to room temperature, so that the thermoplastic resin is cured again, and the flexible substrate 2 is connected and fixed to the laminate 14. Is done. At this time, the indenter to be heated and pressurized has a shape that avoids the through hole of the flexible substrate 2, and the through hole conductor 25 is not directly heated and pressurized. However, the coated conductive bonding material 3 can be reliably heated and pressed.

Also, when an anisotropic conductive material is used as the conductive bonding material, it is necessary to control the amount of pressurization so that adjacent conductive particles do not come into contact with each other.

In order to make the conductive bonding material 3 extend from the bonding region 30 to a region where the flexible substrate 2 extends from the piezoelectric element 11, a conductive bonding material such as an anisotropic conductive material is used. 3 is applied and formed in a predetermined position on the laminate 14 or the flexible substrate 2, and then the laminate 14 and the flexible substrate 2 may be pressure-bonded so that the conductive bonding material 3 is extended. At this time, the thickness of the coating is preferably 30 μm or more.

In particular, the conductive bonding material 3 extends around the side surface of the piezoelectric element 11, extends around the side surface of the flexible substrate 2, or covers the wiring conductor 22 exposed from the cover film 23. For this purpose, a particularly large amount of coating may be applied at these sites.

Similarly, the conductive bonding material 3 extends in the extending direction of the flexible substrate 2 or extends from one end of the piezoelectric element 11. In particular, a large amount of coating may be applied.

As shown in FIG. 9, the piezoelectric vibration device according to the present embodiment includes a piezoelectric actuator 1 and a vibration plate 81 joined to the other main surface of the multilayer body 14 constituting the piezoelectric element 11 included in the piezoelectric actuator 1. Is. Note that the flexible substrate 2 bonded to one main surface of the laminate 14 constituting the piezoelectric element 11 is omitted in FIG.

The diaphragm 81 is, for example, a rectangular thin plate. The diaphragm 81 can be preferably formed using a material having high rigidity and elasticity, such as acrylic resin or glass. The thickness of the diaphragm 81 is set to 0.4 mm to 1.5 mm, for example.

The diaphragm 81 is joined to the other main surface of the multilayer body 14 constituting the piezoelectric element 11 via a joining member 82. The entire surface of the other main surface may be bonded to the vibration plate 81 via the bonding member 82, or the substantially entire surface may be bonded.

The joining member 82 has a film shape. Further, the joining member 82 is formed of a material that is softer and more easily deformed than the vibration plate 81, and has a smaller elastic modulus and rigidity such as Young's modulus, rigidity, and bulk elastic modulus than the vibration plate 81. That is, the joining member 82 can be deformed when the diaphragm 81 is vibrated by driving the piezoelectric actuator 1 (piezoelectric element 11), and deforms more greatly than the diaphragm 81 when the same force is applied. is there. Then, the other main surface (main surface on the −z direction side in the drawing) of the laminate 14 is fixed to the one main surface (main surface on the + z direction side in the drawing) of the bonding member 82 as a whole. A part of one main surface (main surface on the + z direction side in the drawing) of the diaphragm 81 is fixed to the other main surface (main surface on the −z direction side in the drawing).

By joining the laminate 14 and the diaphragm 81 with the deformable joining member 82, the deformable joining member 82 is larger than the diaphragm 81 when vibration is transmitted from the piezoelectric actuator 1 (piezoelectric element 11). Deform.

At this time, the anti-phase vibration reflected from the vibration plate 81 can be mitigated by the deformable joining member 82, so that the piezoelectric actuator 1 (piezoelectric element 11) is not affected by the surrounding vibration and the vibration plate 81. Strong vibrations can be transmitted.

In particular, since at least a part of the joining member 82 is made of a viscoelastic body, strong vibration from the piezoelectric actuator 1 (piezoelectric element 11) is transmitted to the vibration plate 81, while weak vibration reflected from the vibration plate 81. Is preferable in that the bonding member 82 can absorb. For example, a double-sided tape in which a pressure-sensitive adhesive is attached to both surfaces of a base material made of a nonwoven fabric or the like, or a joining member including an elastic adhesive can be used, and the thickness thereof is, for example, 10 μm to 2000 μm. Can be used.

The joining member 82 may be a single member or a composite body composed of several members. As such a joining member 82, for example, a double-sided tape in which a pressure-sensitive adhesive is attached to both surfaces of a substrate made of a nonwoven fabric or the like, various elastic adhesives that are adhesives having elasticity, and the like can be suitably used. The thickness of the joining member 82 is preferably larger than the amplitude of the bending vibration of the piezoelectric actuator 1 (piezoelectric element 11). However, if the thickness is too thick, the vibration is attenuated. Is set. However, in the piezoelectric vibration device of the present invention, the material of the bonding member 82 is not limited, and the bonding member 82 may be formed of a material that is harder and more difficult to deform than the vibration plate 81. Moreover, depending on the case, the structure which does not have the joining member 82 may be sufficient.

The piezoelectric vibration device of this example having such a configuration functions as a piezoelectric vibration device that flexibly vibrates the piezoelectric actuator 1 (piezoelectric element 11) by applying an electric signal, and thereby vibrates the vibration plate 81. Note that the other end of the diaphragm 81 in the length direction (the end in the −y direction in the figure, the peripheral edge of the diaphragm 81, etc.) may be supported by a support member (not shown).

Also, in the piezoelectric vibration device of this example, a diaphragm 81 is joined to the other flat main surface of the piezoelectric element 11. Thereby, it can be set as the piezoelectric vibration apparatus with which the laminated body 14 and the diaphragm 81 were joined firmly.

Since the piezoelectric vibration device of this example is configured using the highly reliable and small piezoelectric actuator 1, it can be a highly reliable and small piezoelectric vibration device.

As shown in FIGS. 10 to 12, the portable terminal of the present embodiment includes the piezoelectric actuator 1, an electronic circuit (not shown), a display 91, and a casing 92. The other main surface of the laminated body 14 to be configured is joined to the housing 92. 10 is a schematic perspective view schematically showing the portable terminal of the present invention, FIG. 11 is a schematic cross-sectional view taken along line AA shown in FIG. 10, and FIG. 12 is a line BB shown in FIG. It is the schematic sectional drawing cut | disconnected by. The flexible substrate joined to one main surface of the laminated body 14 is omitted in FIGS. 11 and 12.

Here, it is preferable that the laminated body 14 and the housing 92 are joined using a deformable joining member. That is, in FIG. 11 and FIG. 12, the joining member 82 is a deformable joining member.

By joining the laminate 14 and the housing 92 with the deformable joining member 82, the deformable joining member 82 is larger than the housing 92 when vibration is transmitted from the piezoelectric actuator 1 (piezoelectric element 11). Deform.

At this time, the antiphase vibration reflected from the casing 92 can be mitigated by the deformable joining member 82, so that the piezoelectric actuator 1 (piezoelectric element 11) is not affected by the surrounding vibration and the casing 92 is not affected. Strong vibrations can be transmitted.

In particular, since at least a part of the joining member 82 is formed of a viscoelastic body, strong vibration from the piezoelectric actuator 1 (piezoelectric element 11) is transmitted to the housing 92, while weak vibration reflected from the housing 92. Is preferable in that the bonding member 82 can absorb. For example, a double-sided tape in which a pressure-sensitive adhesive is attached to both surfaces of a base material made of a nonwoven fabric or the like, or a joining member including an elastic adhesive can be used, and the thickness thereof is, for example, 10 μm to 2000 μm. Can be used.

In this example, the laminate 14 is attached to a panel that is a part of the casing 92 that is a cover of the display 91, and a part of the casing 92 functions as the diaphragm 922.

In this example, the laminated body 14 is bonded to the housing 92, but the laminated body 14 may be bonded to the display 91.

The housing 92 includes a box-shaped housing main body 921 having one surface opened, and a diaphragm 922 that closes the opening of the housing main body 921. The casing 92 (the casing main body 921 and the diaphragm 922) can be formed preferably using a material such as a synthetic resin having high rigidity and elastic modulus.

The peripheral edge of the diaphragm 922 is attached to the housing main body 921 via a bonding material 93 so as to vibrate. The bonding material 93 is formed of a material that is softer and easier to deform than the diaphragm 922, and has a smaller elastic modulus and rigidity such as Young's modulus, rigidity, and bulk modulus than the diaphragm 922. That is, the bonding material 93 can be deformed, and deforms more greatly than the diaphragm 922 when the same force is applied.

The bonding material 93 may be a single material or a composite made up of several members. As such a bonding material 93, for example, a double-sided tape in which an adhesive is attached to both surfaces of a base material made of a nonwoven fabric or the like can be suitably used. The thickness of the bonding material 93 is set so that the vibration is not attenuated due to being too thick, and is set to, for example, 0.1 mm to 0.6 mm. However, in the mobile terminal of the present invention, the material of the bonding material 93 is not limited, and the bonding material 93 may be formed of a material that is harder than the vibration plate 922 and hardly deforms. Moreover, depending on the case, the structure which does not have the joining material 93 may be sufficient.

Examples of the electronic circuit (not shown) include a circuit for processing image information to be displayed on the display 91 and audio information transmitted by the portable terminal, a communication circuit, and the like. At least one of these circuits may be included, or all the circuits may be included. Further, it may be a circuit having other functions. Furthermore, you may have a some electronic circuit. The electronic circuit and the piezoelectric actuator 1 are connected by a connection wiring (not shown).

The display 91 is a display device having a function of displaying image information. For example, a known display such as a liquid crystal display and an organic EL display can be suitably used. The display 91 may have an input device such as a touch panel. Moreover, the cover (diaphragm 922) of the display 91 may have an input device such as a touch panel. Further, the entire display 91 or a part of the display 91 may function as a diaphragm.

Since the portable terminal of this example is configured using the highly reliable and small piezoelectric actuator 1, it can be a highly reliable and small portable terminal.

In addition, the mobile terminal according to the present embodiment is characterized in that the display 91 or the casing 92 generates vibrations that transmit sound information through the ear cartilage or air conduction. The portable terminal of this example can transmit sound information by transmitting a vibration to the cartilage of the ear by bringing the diaphragm (display 91 or housing 92) into contact with the ear directly or via another object. That is, sound information can be transmitted by bringing a vibration plate (display 91 or housing 92) into direct or indirect contact with the ear and transmitting vibration to the cartilage of the ear. Thereby, for example, even when the surroundings are noisy, sound information can be transmitted clearly, and a portable terminal capable of recognizing voice even by a hearing impaired person can be obtained. Note that the object interposed between the diaphragm (display 91 or housing 92) and the ear may be, for example, a cover of a mobile terminal, a headphone or an earphone, and any object that can transmit vibration. Anything can be used. Further, it may be a portable terminal that transmits sound information by propagating sound generated from the diaphragm (display 91 or housing 92) in the air. Furthermore, it may be a portable terminal that transmits sound information via a plurality of routes.

Since the portable terminal of this example is configured using the highly reliable and small piezoelectric actuator 1, it can transmit high-quality sound information with high reliability and small size.

Further, as shown in FIG. 13, the acoustic generator 10 of the present embodiment is provided with the piezoelectric actuator 1 described above and the piezoelectric actuator 1, and a diaphragm 20 that vibrates with the piezoelectric actuator 1 due to the vibration of the piezoelectric actuator 1. And a frame 30 as a support body that is provided on at least a part of the outer peripheral portion of the diaphragm 20 and supports the diaphragm 20.

The piezoelectric actuator 1 is an exciter that excites the diaphragm 20 by vibrating under application of a voltage. The main surface of the piezoelectric actuator 1 and the main surface of the vibration plate 20 are joined by an adhesive such as an epoxy resin, and the piezoelectric actuator 1 bends and vibrates. Sound can be generated.

The diaphragm 20 is fixed to the frame 30 in the tensioned state, and vibrates with the piezoelectric actuator 1 by the vibration of the piezoelectric element actuator 1. The diaphragm 20 can be formed using various materials such as resin and metal. For example, the diaphragm 20 can be made of a resin film such as polyethylene, polyimide, or polypropylene having a thickness of 10 to 200 μm. Since the resin film is a material having a lower elastic modulus and mechanical Q value than a metal plate or the like, the diaphragm 20 is made of a resin film, so that the diaphragm 20 bends and vibrates with a large amplitude, thereby reducing the sound pressure. It is possible to reduce the difference between the resonance peak and the dip by widening the width of the resonance peak and reducing the height in the frequency characteristics.

The frame body 30 functions as a support body that supports the diaphragm 20 at the peripheral edge of the diaphragm 20, and can be formed using various materials such as metals such as stainless steel and resins. The frame 30 may be composed of one frame member (upper frame member 301) as shown in FIG. 13 (b), and two frame members (upper frame member 301 and upper frame member 301 and The lower frame member 302) may be used. In this case, the tension of the diaphragm 20 can be stabilized by sandwiching the diaphragm 20 between the two frame members. The upper frame member 301 and the lower frame member 302 have a thickness of, for example, 100 to 5000 μm.

In the acoustic generator 10 of this example, as shown in FIGS. 13B and 13C, the piezoelectric actuator 1 to at least a part of the surface of the diaphragm 20 (for example, the peripheral portion of the piezoelectric actuator 1). It is preferable to further have a resin layer 40 provided so as to cover it. As the resin layer 40, for example, an acrylic resin can be used. By embedding the piezoelectric actuator 1 (piezoelectric element 11) in the resin layer 40, an appropriate damper effect can be induced, so that the resonance phenomenon is suppressed and the peak or dip in the frequency characteristic of the sound pressure is reduced. Can do. 13B and 13C, the resin layer 40 may be formed to have the same height as the upper frame member 301.

Since the sound generator 10 of this example is configured using the highly reliable and small piezoelectric actuator 1, it can be a highly reliable and small sound generator.

Next, an example of an embodiment of the sound generator of the present invention will be described.

The sound generation device 80 is a sound generation device such as a so-called speaker, and includes, for example, a sound generator 10 and a housing 70 that houses the sound generator 10 as shown in FIG. The housing 70 resonates the sound generated by the sound generator 10 and radiates sound to the outside from an opening (not shown) formed in the housing 70. By having such a housing | casing 70, the sound pressure in a low frequency band can be raised, for example.

Such a sound generator 80 can be used alone as a speaker, and can be suitably incorporated into a portable terminal, a thin-screen TV, a tablet terminal, or the like, as will be described later. Moreover, it can also be incorporated into home appliances that have not been prioritized in terms of sound quality, such as refrigerators, microwave ovens, vacuum cleaners, and washing machines.

Since the sound generator 80 of the present invention uses the highly reliable and small sound generator 10, a highly reliable and small sound generator can be obtained.

Next, an electronic device equipped with an acoustic generator will be described with reference to FIG. FIG. 15 is a diagram illustrating a configuration of the electronic device 50 according to the embodiment. In the figure, only components necessary for explanation are shown, and descriptions of general components are omitted.

As shown in FIG. 15, the electronic device 50 of this example includes an acoustic generator 10, an electronic circuit 60 connected to the acoustic generator 10, and a housing 70 that houses the electronic circuit 60 and the acoustic generator 10. And having a function of generating sound from the sound generator 10.

The electronic device 50 includes an electronic circuit 60. The electronic circuit 60 includes, for example, a controller 50a, a transmission / reception unit 50b, a key input unit 50c, and a microphone input unit 50d. The electronic circuit 60 is connected to the sound generator 10 and has a function of outputting an audio signal to the sound generator 10. The sound generator 10 generates sound based on the sound signal input from the electronic circuit 60.

Further, the electronic device 50 includes a display unit 50e, an antenna 50f, and the sound generator 10. Further, the electronic device 50 includes a housing 70 that accommodates these devices. Although FIG. 15 shows a state in which each device including the controller 50a is accommodated in one casing 70, the accommodation form of each device is not limited. In the present embodiment, it is only necessary that at least the electronic circuit 60 and the sound generator 10 are accommodated in one housing 70.

The controller 50 a is a control unit of the electronic device 50. The transmission / reception unit 50b transmits / receives data via the antenna 50f based on the control of the controller 50a. The key input unit 50c is an input device of the electronic device 50 and accepts a key input operation by an operator. The microphone input unit 50d is also an input device of the electronic device 50, and accepts a voice input operation by an operator. The display unit 50e is a display output device of the electronic device 50, and outputs display information based on the control of the controller 50a.

The sound generator 10 operates as a sound output device in the electronic device 50. The sound generator 10 is connected to the controller 50a of the electronic circuit 60, and emits sound upon application of a voltage controlled by the controller 50a.

In FIG. 15, the electronic device 50 is described as a portable terminal device. However, the electronic device 50 is not limited to the type of the electronic device 50, and may be applied to various consumer devices having a function of emitting sound. . For example, flat-screen televisions and car audio devices can of course be used for products having a function of generating sound, for example, various products such as vacuum cleaners, washing machines, refrigerators, microwave ovens, and the like.

Since such an electronic device 50 is configured using the highly reliable and small piezoelectric actuator 1, it can be a highly reliable and small electronic device.
As described above, since the acoustic generator 10 using the highly reliable and small piezoelectric actuator 1 is included, it has excellent durability and can be driven stably for a long period of time. In addition, by providing the housing 70, it is possible to increase the low-frequency sound pressure.

Next, a specific example of the piezoelectric actuator of the present invention will be described.

A piezoelectric actuator was manufactured as shown below.

The piezoelectric element had a long shape with a length of 23.5 mm, a width of 3.3 mm, and a thickness of 0.5 mm. The piezoelectric element has a structure in which piezoelectric layers having a thickness of 30 μm and internal electrodes are alternately stacked, and the total number of piezoelectric layers is 16. The piezoelectric layer was formed of lead zirconate titanate in which part of Zr was replaced with Sb. As the internal electrode, an alloy of silver palladium was used.

After laminating ceramic green sheets on which a conductive paste made of silver palladium was printed, they were pressed and adhered, degreased at a predetermined temperature, and fired at 1000 ° C. to obtain a laminated sintered body.

Next, using a conductive paste made of silver, the surface electrode was printed so as to be 1 mm longer at both ends in the width direction than the internal electrode to obtain a surface electrode.

A voltage with an electric field strength of 2 kV / mm was applied between the internal electrodes (between the first electrode and the second electrode) via the surface electrode to polarize the piezoelectric element.

Moreover, the flexible substrate was produced as follows. First, the copper foil used as a wiring conductor was stuck on both surfaces of the base film using the adhesive to the polyimide film as a sheet | seat with which many base films were arranged (multiple-sheet for base films). Next, a conductor pattern of the wiring conductor was formed by a photolithography technique. The end portion of the wiring conductor in the bonding area with the piezoelectric element was shaped like a comb. A through hole for a through-hole conductor was formed by drilling in a region where the flexible substrate and the piezoelectric element overlap. Next, by simultaneously plating the wiring conductor and the inner wall of the through hole by electrolytic plating, a through-hole conductor is produced and bonded to the wiring conductor. A polyimide film serving as a cover film was affixed to both surfaces of the base film with a thermosetting adhesive for insulation and wiring conductor protection. Also, a cover film was attached so as to cover the through-hole conductor formed in the bonding area with the piezoelectric element. Next, after the nickel conductor and the gold conductor are plated on the bonding region with the piezoelectric element and the wiring conductor for connection to a mother board such as a portable terminal, a polyimide sheet (a multi-sheet for reinforcing plate) having a thickness of 150 μm that serves as a reinforcing plate Was stuck at a predetermined position with a thermosetting adhesive, and was punched into a desired shape by die pressing to produce a flexible substrate.

An anisotropic conductive material containing anisotropic conductive particles was used to electrically connect the wiring conductor of the flexible substrate and the surface electrode. Anisotropic conductive particles are particles having a particle diameter of about 30 μm, and a particle body made of acrylic resin coated with gold plating with Ni plating applied as a base coat. The conductive paste as the anisotropic conductive material is a paste in which the anisotropic conductive particles are dispersed in a synthetic rubber adhesive, and is printed on the surface electrode by screen printing and then dried by drying. A material was formed. In order to form the anisotropic conductive material at a position away from the through-hole conductor forming position of the flexible substrate, the printed pattern was divided into two in the bonding area. In a state where the flexible substrate was brought into contact with the bonding region of the piezoelectric element via the anisotropic conductive material, the anisotropic conductive material was softened and flowed by heating and pressing, and both were bonded to produce a piezoelectric actuator. The heating and pressurization is performed from the reinforcing plate side of the flexible substrate with an indenter divided into two in the same way as the anisotropic conductive material formed on the piezoelectric element, and without applying stress to the through-hole conductor and the anisotropic conductive material The whole was heated and pressurized to produce the piezoelectric actuator of the embodiment of the present invention.

On the other hand, as a comparative example, the same flexible substrate and piezoelectric element are used, the anisotropic conductive material and the indenter for heating and pressing are not divided into two, and the anisotropic conductive material is provided without being separated from the through-hole conductor, A piezoelectric actuator was fabricated by applying stress to the through-hole conductor during bonding.

For these piezoelectric actuators, first, 20 pieces of each of the flexible substrates were checked for peel strength. In the piezoelectric actuator of the comparative example, the average was 5N, but in the piezoelectric actuator of the example of the present invention, it was confirmed that the average was 10N, which was about twice as strong.

Next, a drive test was performed in which each piezoelectric actuator was attached to the diaphragm and a sine wave signal having an effective value of ± 10 Vrms was applied at a frequency of 1 kHz. Both piezoelectric actuators were confirmed to vibrate with a vibration plate displacement of 4 μm. Thereafter, a reliability test in which a noise signal having an effective value ± 10 Vrms was continuously applied for 168 hours was performed. After the test, in the piezoelectric actuator of the comparative example, the value of the capacitance measurement through the flexible substrate was 0 nF, but in the piezoelectric actuator of the embodiment of the present invention, a capacitance of 2,500 nF was confirmed. When the inside of the piezoelectric actuator of the comparative example was analyzed, the through-hole conductor of the flexible substrate was disconnected and no voltage was applied. On the other hand, in the piezoelectric actuator of the present invention, no disconnection of the through-hole conductor was observed. With respect to the piezoelectric actuator of the comparative example, it can be presumed that micro cracks are generated in the conductor by applying stress to the through-hole conductor, and the wire is completely disconnected by performing a reliability test.

It was confirmed that by using the piezoelectric actuator of the present invention, the bonding strength between the flexible substrate and the piezoelectric element is high and the through-hole conductor of the flexible substrate does not break even when continuously driven.

1: Piezoelectric actuator 11: Piezoelectric element 12: Internal electrode 13: Piezoelectric layer 14: Laminate 15: Surface electrode 2: Flexible substrate 21: Base film 22: Wiring conductor 23: Cover film 25: Through-hole conductor 26: Reinforcing plate 3: Conductive bonding material 31: Conductive particles 32: Resin adhesive 81: Vibration plate 82: Bonding member 91: Display 92: Housing 921: Housing main body 922: Vibration plate 93: Bonding material 10: Sound generator 20: Diaphragm 30: Frame 301: Upper frame member 302: Lower frame member 40: Resin layer 50: Electronic device 60: Electronic circuit 70: Housing 80: Sound generator

Claims

A plate-like laminate in which an internal electrode and a piezoelectric layer are laminated, a piezoelectric element having a surface electrode electrically connected to the internal electrode on one main surface of the laminate, and the surface electrode electrically A flexible substrate having a connected wiring conductor; and a conductive bonding material for electrically connecting the surface electrode and the wiring conductor;
The flexible substrate has a through-hole conductor in a region overlapping with the piezoelectric element, and the flexible substrate is formed by the conductive bonding material at a position away from the through-hole conductor around the through-hole conductor when viewed through a plane. A piezoelectric actuator comprising a bonding region between the piezoelectric element and the piezoelectric element.
2. The piezoelectric actuator according to claim 1, wherein a plurality of the bonding regions are provided.
3. The piezoelectric actuator according to claim 2, wherein one main surface of the laminate is rectangular and the joining region is provided apart in the length direction of the one main surface.
One main surface of the laminate is rectangular, the surface electrode includes a first surface electrode, a second surface electrode, and a third surface electrode, and the second surface electrode and the third surface electrode are the one main surface. The first surface electrodes are provided away from the second surface electrode and the third surface electrode in the length direction of the one main surface;
The bonding region includes a first bonding region, a second bonding region, and a third bonding region, and the first bonding region is provided on the first surface electrode, and the second bonding region 3 is provided on the second surface electrode, and the third bonding region is provided on the third surface electrode.
The wiring conductor of the flexible substrate includes a first wiring conductor connected to the through-hole conductor, a second wiring conductor and a third wiring conductor not connected to the through-hole conductor, and the first surface electrode is The third surface is connected to the first wiring conductor via the first bonding region, the second surface electrode is connected to the second wiring conductor via the second bonding region, and the third surface. The piezoelectric actuator according to claim 4, wherein an electrode is connected to the third wiring conductor via the third bonding region.
One main surface of the laminate is rectangular, the surface electrode includes a first surface electrode, a second surface electrode, and a third surface electrode, and the second surface electrode and the third surface electrode are the one main surface. The first surface electrodes are provided away from the second surface electrode and the third surface electrode in the length direction of the one main surface;
The bonding region includes a first bonding region and a second bonding region, the first bonding region is provided on the first surface electrode, and the second bonding region is the second surface electrode. 3. The piezoelectric actuator according to claim 2, wherein the piezoelectric actuator is provided across the upper surface and the third surface electrode.
The wiring conductor of the flexible board includes a first wiring conductor connected to the through-hole conductor and a second wiring conductor not connected to the through-hole conductor, and the first surface electrode is connected to the first bonding conductor. It is connected to the first wiring conductor via a region, and the second surface electrode and the third surface electrode are connected to the second wiring conductor via the second bonding region, The piezoelectric actuator according to claim 6.
3. The laminated body according to claim 2, wherein one main surface of the laminate is rectangular, and the joining region extends in the width direction of the one main surface, and has a band shape when seen in a plan view. Piezoelectric actuator.
3. The piezoelectric actuator according to claim 2, wherein one main surface of the laminated body is rectangular, and a plurality of the joining regions are provided side by side in the width direction of the one main surface. .
10. The surface of the piezoelectric layer is exposed in a region overlapping the through-hole conductor on the one main surface when viewed through a plane. 10. Piezoelectric actuator.
11. The piezoelectric according to claim 1, wherein the conductive bonding material is provided to extend from the bonding region to a region where the flexible substrate extends from the piezoelectric element. Actuator.
12. The piezoelectric actuator according to claim 1, wherein a side of the through-hole conductor facing the piezoelectric element is covered with a cover film.
The piezoelectric actuator according to claim 1, wherein the conductive bonding material is an anisotropic conductive material.
The piezoelectric actuator according to any one of claims 1 to 13, wherein an end portion of the wiring conductor joined to the surface electrode has a comb shape.
15. A piezoelectric vibration device comprising: the piezoelectric actuator according to claim 1; and a vibration plate joined to the other main surface of the laminate.
A piezoelectric actuator according to any one of claims 1 to 14, an electronic circuit, a display, and a housing, wherein the other main surface of the laminate is on the display or the housing. A portable terminal characterized by being joined.
The piezoelectric actuator according to any one of claims 1 to 14, the diaphragm to which the piezoelectric actuator is attached, which vibrates due to the vibration of the piezoelectric actuator, and a frame body provided on an outer peripheral portion of the diaphragm. And an acoustic generator.
The acoustic generator according to claim 17, further comprising a resin layer provided so as to cover at least a part of a surface of the piezoelectric actuator and the diaphragm.
A sound generator comprising: the sound generator according to claim 17 or claim 18; and a housing that houses the sound generator.
19. A sound generator according to claim 17 or claim 18, an electronic circuit connected to the sound generator, and a housing for housing the electronic circuit and the sound generator, wherein the sound is generated from the sound generator. An electronic device having a function of generating