CN204170914U - Piezo-activator, piezoelectric vibrating device and portable terminal - Google Patents

Abstract

Even if problem of the present utility model be to provide a kind of flexible printed circuit board being engaged in piezoelectric element long-term between drive also can not peel off from piezoelectric element and can long-term between the piezo-activator of stabilized driving, piezoelectric vibrating device and portable terminal.For this reason, the feature of the piezo-activator (1) of present embodiment is, have: piezoelectric element (10), it possesses the duplexer (4) internal electrode (2) and piezoelectric body layer (3) are laminated and the surface electrode (5) be electrically connected with internal electrode (2) at an interarea of duplexer (4); With flexible printed circuit board (6), its part is engaged with on an interarea by comprising the conductive adhesive (7) of conducting particles and resin, and possess the wiring conductor (61) be electrically connected with surface electrode (5), in the engaging zones of flexible printed circuit board (6) and piezoelectric element (10), circumference (601) at least partially compared with other parts conducting particles configure many.

Description

Piezoelectric actuator, piezoelectric vibration device, and portable terminal

technical field

The utility model relates to a piezoelectric actuator suitable for a piezoelectric vibration device, a portable terminal, a piezoelectric vibration device and a portable terminal.

Background technique

As a piezoelectric actuator, as shown in FIG. 8 , a bimorph obtained by forming a surface electrode 104 on the surface of a laminate 103 formed by laminating a plurality of internal electrodes 101 and piezoelectric layers 102 is known. type piezoelectric actuator 10 (see Patent Document 1), the flexible wiring substrate 105 is bonded to the main surface of the piezoelectric element 10 with a conductive bonding member 106, and the surface electrode 104 of the piezoelectric element 10 is connected to the A technique for electrically connecting the wiring conductors 107 of the flexible wiring substrate 105 (see Patent Document 2).

In addition, there are also known piezoelectric vibration devices in which the central portion or one end in the longitudinal direction of a bimorph piezoelectric element is fixed to a vibration plate (see Patent Documents 3 and 4).

prior art literature

patent documents

Patent Document 1: JP Unexamined Publication No. 2002-10393

Patent Document 2: JP Unexamined Patent Publication No. 6-14396

Patent Document 3: International Publication No. 2005/004535

Patent Document 4: JP Unexamined Publication No. 2006-238072

Utility model content

Problems to be solved by utility models

Here, solder or a conductive adhesive is used as the conductive joining member 106 that joins the flexible wiring board 105 and the piezoelectric element 10 .

However, in the case where solder is used as the conductive bonding member 106 for bonding, since the rigidity of the solder is high, vibrations from the outside that occur at the flexible wiring substrate 105 and resonance of the flexible wiring substrate 105 itself occur. Due to the abnormal vibration of the flexible wiring substrate 105 that does not follow the vibration of the piezoelectric actuator, stress concentration such as shearing and bending occurs near the end surface of the junction of the piezoelectric element 10 and the flexible wiring substrate 105, which may make the flexible wiring substrate 105 The wiring board 105 is peeled off from the piezoelectric element 10 .

In addition, when the piezoelectric element 10 is driven at a high speed by flowing a large current in the case of joining only with a conductive adhesive, the electrical resistance and thermal resistance of the conductive adhesive are high, and the voltage The heat generated by the vibration of the electric element 10 or the Joule's heat of the conductive adhesive itself causes thermal deterioration of the resin constituting the conductive adhesive, and the joint strength decreases. peeling off.

The present invention has been developed in view of the above-mentioned problems, and an object of the present invention is to provide a piezoelectric device that can be stably driven for a long period of time without peeling off from the piezoelectric element even if the flexible wiring substrate bonded to the piezoelectric element is driven for a long period of time. Electric actuators, piezoelectric vibration devices, and portable terminals.

means of solving problems

The piezoelectric actuator of the present invention is characterized in that it has: a piezoelectric element including a laminate formed by laminating internal electrodes and piezoelectric layers; a surface electrode electrically connected; and a flexible wiring substrate, a part of which is bonded to the one main surface through a conductive adhesive containing conductive particles and resin, and has a wiring conductor electrically connected to the surface electrode, In the bonding region between the flexible wiring board and the piezoelectric element, at least a part of the edge part is arranged more of the conductive particles than other parts.

Moreover, the piezoelectric vibration device of this invention is characterized by including the said piezoelectric actuator and the vibration plate joined to the said other main surface of the said piezoelectric element.

In addition, the portable terminal of the present invention is characterized in that it includes the piezoelectric actuator, an electronic circuit, a display, and a frame, and the other main surface of the piezoelectric actuator is joined to the display or the frame. body.

Utility Model Effect

According to the present invention, it is possible to obtain a piezoelectric actuator in which the piezoelectric element does not vibrate abnormally and does not peel off from the piezoelectric element even when the flexible wiring board is driven for a long period of time.

Description of drawings

FIG. 1 is a schematic perspective view showing an example of an embodiment of the piezoelectric actuator of the present invention.

2( a ) is a schematic cross-sectional view taken along line A-A shown in FIG. 1( b ), and (b) is a partially enlarged plan perspective view of the piezoelectric actuator shown in FIG. 1 .

Fig. 3 is a partially enlarged plan perspective view showing another example of Fig. 2(b).

4 is a schematic perspective view schematically showing a piezoelectric vibration device according to an embodiment of the present invention.

FIG. 5 is a schematic perspective view schematically showing a mobile terminal according to an embodiment of the present invention.

Fig. 6 is a schematic cross-sectional view taken along line A-A shown in Fig. 5 .

Fig. 7 is a schematic cross-sectional view taken along line B-B shown in Fig. 5 .

8( a ) is a schematic perspective view showing an example of an embodiment of a conventional piezoelectric actuator, and ( b ) is a schematic cross-sectional view cut along line A-A shown in ( a ).

Detailed ways

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

Fig. 1 is a schematic perspective view showing an example of an embodiment of a piezoelectric actuator of the present invention, Fig. 2(a) is a schematic cross-sectional view taken along line A-A shown in Fig. 1(b), and Fig. 2(b ) is a partially enlarged plan perspective view of the piezoelectric actuator shown in FIG. 1 .

The piezoelectric actuator 1 of the present embodiment shown in FIG. 1 is characterized by having a piezoelectric element 10 including a laminated body 4 in which internal electrodes 2 and piezoelectric layers 3 are stacked, and a laminated body A surface electrode 5 whose one main surface of 4 is electrically connected to the internal electrode 2; a flexible wiring substrate 6, a part of which is bonded to one main surface by a conductive adhesive 7 containing conductive particles and resin, and has a surface electrode 5 connected to the surface electrode. In the wiring conductor 61 that is electrically connected to the flexible wiring board 6 and the piezoelectric element 10, at least a part of the peripheral portion 601 has more conductive particles than other parts.

The laminate 4 constituting the piezoelectric element 10 is formed by laminating the internal electrodes 2 and the piezoelectric layers 3 , and thus has an active portion 41 in which a plurality of internal electrodes 2 overlap in the lamination direction, and an inactive portion 42 other than the active portion. , for example formed into a long ruler shape. In the case of a piezoelectric actuator mounted on a display or a housing of a mobile terminal, the length of the laminated body 4 is preferably, for example, 18 mm to 28 mm, more preferably 22 mm to 25 mm. The width of the laminated body 4 is preferably, for example, 1 mm to 6 mm, more preferably 3 mm to 4 mm. The thickness of the laminated body 4 is preferably, for example, 0.2 mm to 1.0 mm, more preferably 0.4 mm to 0.8 mm.

The internal electrode 2 constituting the laminated body 4 is formed by simultaneous firing with the ceramics forming the piezoelectric layer 3 , and is composed of a first pole 21 and a second pole 22 . For example, the first pole 21 is a ground pole, and the second pole 22 is a positive pole or a negative pole. Piezoelectric layers 3 are sandwiched from above and below by alternate lamination with piezoelectric layers 3, and the first poles 21 and second poles 22 are arranged in the order of stacking, thereby applying pressure to the piezoelectric layers 3 sandwiched between them. driving voltage. As the forming material, for example, a conductor mainly composed of silver or a silver-palladium alloy having low reactivity with piezoelectric ceramics, or a conductor containing copper, platinum, or the like can be used, but these may also contain ceramic components or glass components.

In the example shown in FIG. 1 , the ends of the first poles 21 and the second poles 22 are respectively led out alternately to a pair of opposing side surfaces of the laminated body 4 . In the case of a piezoelectric actuator mounted on a display or housing of a mobile terminal, the length of the internal electrode 2 is preferably, for example, 17 mm to 25 mm, more preferably 21 mm to 24 mm. The width of the internal electrodes 2 is preferably, for example, 1 mm to 5 mm, more preferably 2 mm to 4 mm. The thickness of the internal electrodes 2 is preferably, for example, 0.1 to 5 μm.

The piezoelectric layer 3 constituting the laminated body 4 is formed of ceramics having piezoelectric properties. As such ceramics, for example, perovskite-type oxides composed of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ), niobate Lithium (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), etc. The thickness of one piezoelectric layer 3 is preferably set to, for example, 0.01 to 0.1 mm in order to facilitate driving with a low voltage. In addition, in order to obtain a large bending vibration, it is preferable to have a piezoelectric d31 constant of 200 pm/V or more.

On one main surface of the laminated body 4, a surface electrode 5 electrically connected to the internal electrode 2 is provided. The surface electrode 5 in the form shown in FIG. 1 is composed of a large-area first surface electrode 51 , a small-area second surface electrode 52 , and a third surface electrode 53 . For example, the first surface electrode 51 is electrically connected to the internal electrode 2 that becomes the first pole 21, the second surface electrode 52 is electrically connected to the internal electrode 2 that is disposed on one main surface side and becomes the second pole 22, and the third surface electrode 53 It is electrically connected to the internal electrode 2 serving as the second pole 22 arranged on the other main surface side. In the case of a piezoelectric actuator mounted on a display or a housing of a mobile terminal, the length of the first surface electrode 51 is preferably, for example, 17 mm to 23 mm, more preferably 19 mm to 21 mm. The width of the first surface electrode 51 is preferably, for example, 1 mm to 5 mm, more preferably 2 mm to 4 mm. The lengths of the second surface electrodes 52 and the third surface electrodes 53 are preferably set to, for example, 1 mm to 3 mm. The width of the second surface electrode 52 and the third surface electrode 53 is preferably set to, for example, 0.5 mm to 1.5 mm.

In addition, the piezoelectric actuator 1 has a flexible wiring substrate 6, and a part of the flexible wiring substrate 6 is bonded to one main surface of the laminated body 4 constituting the piezoelectric element 10 via a conductive adhesive 7 made of conductive particles and resin. .

The flexible wiring board 6 includes a wiring conductor 61 , and a part of the flexible wiring board 6 is bonded to one main surface of the laminate 4 so that the surface electrode 5 and the wiring conductor 61 are electrically connected via the conductive adhesive 7 .

The flexible wiring board 6 is, for example, a flexible printed wiring board in which two wiring conductors 61 are embedded in a resin film, and a connector (not shown) for connecting to an external circuit is connected to one end thereof.

As the conductive adhesive 7, for example, conductive particles made of metal powder such as silver powder and gold powder, or resin balls subjected to conductive coating such as Au plating are dispersed in polyimide, polyamideimide, etc. , Silicone rubber, synthetic rubber and other low elastic modulus (Young's modulus) resin. Thereby, stress due to vibration can be reduced compared to solder. More preferably, the conductive adhesive 7 is also an anisotropic conductive material. The anisotropic conductive material is composed of conductive particles responsible for electrical connection and a resin adhesive responsible for bonding. The anisotropic conductive material achieves conduction in the thickness direction and insulation in the in-plane direction, so even if it is a narrow-pitch wiring, there will be no electrical short circuit between the surface electrodes of different electrodes, so that it can be connected to the flexible wiring substrate. 6. The connection part is compact.

Furthermore, in the bonding region between the flexible wiring board 6 and the piezoelectric element 10 , at least a part of the peripheral portion 601 has more conductive particles than other parts. Here, the bonding region refers to the region occupied by the conductive adhesive 7 , and the peripheral portion 601 of the bonding region refers to a region within 0.4 mm from the end surface. In addition, the phrase that conductive particles are disposed more in a part of the peripheral portion 601 than in other portions means that the conductive particles occupying the peripheral portion 601 when the flexible wiring board 6 is peeled off and the surface of the conductive adhesive 7 is observed with an electron microscope. The proportion of conductive particles per unit area is larger in some parts than in other parts.

In this way, at least a part of the peripheral portion 601 of the bonding region between the flexible wiring board 6 and the piezoelectric element 10 is arranged more conductive particles than other parts, since the thermal conductivity of this part is improved, even when a large current flows In the case of high-speed driving, the heat generation caused by the vibration of the piezoelectric element 10 or the heat conduction and diffusion of the Joule heat of the conductive adhesive 7 are also promoted, so that the generation of heat of the resin constituting the conductive adhesive 7 can be greatly reduced. degradation and peeling of the flexible wiring substrate 6 from the piezoelectric element 10 .

Furthermore, by arranging a large number of conductive particles in at least a part of the peripheral portion 601 , stress concentration due to shearing and stretching due to rotation of the conductive particles and low Young's modulus is reduced. Therefore, it is possible to prevent cracks from being generated in the conductive adhesive 7 from this portion. In particular, when a force is applied to the direction in which the flexible wiring substrate 6 is connected to the outside, a large shearing and tensile stress will concentrate on the root of the joint portion of the flexible wiring substrate 6, but as described above, the conductive particles are relatively small. Many are arranged on the peripheral portion 601 , so the rotation of the conductive particles of the conductive adhesive 7 can especially suppress the concentration of shear stress, and there is no risk of the flexible wiring board 6 being peeled off due to cracks at the root of the joint. Preferably, at least a portion of the peripheral portion 601 having more conductive particles than other portions is the entire circumference of the peripheral portion 601 .

In addition, for at least a part of the peripheral portion 601 where many conductive particles are arranged, it is preferable that the number or ratio of conductive particles is 5 to 20% larger than that of other parts, for example. This ratio can be obtained by peeling off the flexible wiring board 6 and observing it with an electron microscope.

In addition, as shown in FIG. 3, by the region between the outer periphery of one main surface of the piezoelectric element 10 and the surface electrode 5, the low Young's modulus of the resin, the rotation of many conductive particles can be reduced due to Stress generated by non-following vibration of the actuator, such as external vibration and resonance of the flexible wiring board 6 itself, and the viscoelasticity of the resin can reduce the amplitude of such non-following vibration.

In addition, the thickness of the conductive adhesive 7 bonded to the region between the outer periphery of one main surface of the piezoelectric element 10 and the surface electrode 5 is smaller than that of the conductive adhesive that electrically connects the wiring conductor 61 and the surface electrode 5 to face each other. Since the thickness of the adhesive 7 is thick, the thermal resistance increases. However, by arranging many conductive particles with high thermal conductivity in this region, it is possible to provide a connection that also has the function of heat conduction that suppresses an increase in thermal resistance. As a result, the heat generated by the vibration of the piezoelectric element 10 and the Joule heat of the conductive adhesive 7 itself can be conducted/diffused, and the occurrence of cracks due to deterioration of the resin constituting the conductive adhesive 7 can be reduced.

In addition, in the above structure, when the conductive adhesive 7 is an anisotropic conductive material including, for example, gold-plated resin balls as conductive particles, the wiring conductor 61 overlaps the surface electrode 5 in plan view. The conductive particles constituting the conductive adhesive 7 in the region electrically connect the surface electrode 5 and the wiring conductor 61, and the conductive particles are in an unbonded connection form, and it is easy to form a connection with the piezoelectric element 10 and the wiring conductor in other regions. The connection form in which conductive particles that are not connected to either of 61 or are connected to only one of them are mainly present. As long as it is such a connection form, it is possible to suppress stress concentration due to shearing and tension while maintaining high heat conduction as described above, but it does not necessarily need to be a bonding material or bonding process based on an anisotropic conductive material or the like.

In order to effectively improve heat conduction and reduce stress concentration as described above, it is preferable that the conductive particles not connected to either the piezoelectric element 10 or the wiring conductor 61 account for 70% or more of the whole.

In addition, by making the other main surface of the piezoelectric element 10 flat in advance, for example, when the other main surface is attached to an object to which vibration is applied (for example, a vibrating plate, which will be described later), it is easy to contact with the object to which vibration is applied. Bending vibration is performed integrally, and the efficiency of bending vibration can be improved as a whole.

In addition, the piezoelectric actuator 1 shown in FIG. 1 is a so-called bimorph type piezoelectric actuator, and an electric signal is input from the surface electrode 5 so that one main surface and the other main surface become curved surfaces and bend. Vibration, but as the piezoelectric actuator of the present utility model, it is not limited to the bimorph type, and may also be a unimorph type, for example, by bonding (bonding) the other main surface of the piezoelectric actuator In the vibrating plate described later, flexural vibration can be performed even if it is a unimorph type.

Next, a method of manufacturing the piezoelectric actuator 1 of the present embodiment will be described.

First, a ceramic green sheet to be the piezoelectric layer 3 is produced. Specifically, a ceramic slurry is produced by mixing calcined powder of piezoelectric ceramics, a binder composed of an acrylic-based or butyral-based organic polymer, and a plasticizer. Then, a ceramic green sheet is produced using this ceramic slurry by a tape casting method using a doctor blade method, a calender roll method, or the like. As the piezoelectric ceramics, as long as it has piezoelectric properties, for example, a perovskite-type oxide composed of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ) can be used. Moreover, as a plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP), etc. can be used.

Next, a conductive paste to be the internal electrode 2 is produced. Specifically, a conductive paste is prepared by adding a mixed binder and a plasticizer to silver-palladium alloy metal powder. This conductive paste was applied on the above-mentioned ceramic green sheet in the pattern of the internal electrodes 2 by a screen printing method. Furthermore, a plurality of ceramic green sheets printed with the conductive paste are laminated, subjected to binder removal treatment at a predetermined temperature, fired at a temperature of 900 to 1200° C., and subjected to grinding treatment using a surface grinder or the like to become The laminated body 4 including the internal electrodes 2 and piezoelectric layers 3 laminated alternately is manufactured.

The laminated body 4 is not limited to the production method described above, and may be produced by any production method as long as the laminated body 4 in which internal electrodes 2 and piezoelectric layers 3 are laminated in multiple layers can be produced.

Then, a conductive paste containing silver glass is prepared by adding a binder, a plasticizer, and a solvent to a mixture of conductive particles mainly composed of silver and glass, and the conductive paste is passed through a screen. The main surface and side surfaces of the laminated body 4 are printed and dried according to the pattern of the surface electrodes 5 by a printing method, and then sintered at a temperature of 650 to 750° C. to form the surface electrodes 5 .

In addition, in the case of electrically connecting the surface electrode 5 and the internal electrode 2, a via hole penetrating the piezoelectric layer 3 may be formed for connection, or a side electrode may be formed on the side surface of the laminate 4, and any manufacturing method may be used. make.

Next, the flexible wiring board 6 is connected and fixed (bonded) to the piezoelectric element 10 using the conductive adhesive 7 .

First, a conductive adhesive paste is applied to a predetermined position of the piezoelectric element 10 by screen printing or the like. Then, the flexible wiring board 6 is connected and fixed to the piezoelectric element 10 by curing the conductive adhesive paste in a state where the flexible wiring board 6 is brought into contact. In addition, the conductive adhesive paste may be applied and formed on the flexible wiring board 6 side.

When the resin constituting the conductive adhesive 7 is made of a thermoplastic resin, after applying the conductive adhesive to a predetermined position of the piezoelectric element 10 or the flexible wiring board 6, the piezoelectric element 10 and the flexible wiring board 6 are connected. When the wiring substrate 6 is in contact with the conductive adhesive, heat and pressure are applied, thereby softening and flowing the thermoplastic resin, and then returning to normal temperature, whereby the thermoplastic resin is cured again, thereby connecting and fixing the flexible wiring substrate 6 to the piezoelectric substrate. Element 10.

Here, in order to arrange a large number of conductive particles constituting the conductive adhesive 7 in the peripheral portion of the region overlapping the piezoelectric element 10 of the flexible wiring substrate 6 in a plan view, it is only necessary to prepare a A conductive adhesive paste may be used, and a conductive adhesive paste having a large content of conductive particles may be applied to the peripheral portion.

In particular, when an anisotropic conductive member is used as the conductive bonding member 7 , it is necessary to control the amount of pressure so that approaching conductive particles do not come into contact.

In addition, in the above, the method of applying and forming the conductive adhesive 7 on the piezoelectric element 10 or the flexible wiring board 6 has been shown, but it is also possible to apply the conductive adhesive 7 previously formed into a sheet. Bonding is performed by heating and pressing the sheet sandwiched between the piezoelectric element 10 and the flexible wiring board 6 .

As shown in FIG. 4 , the piezoelectric vibration device of the present invention has a piezoelectric actuator 1 and a vibration plate 81 joined to the other main surface of the piezoelectric actuator 1 .

The vibrating plate 81 has a rectangular thin plate shape. The vibrating plate 81 can be formed using a material with high rigidity and elasticity, such as acrylic resin and glass, as appropriate. In addition, the thickness of the vibrating plate 81 is set to, for example, 0.4 mm to 1.5 mm.

Vibration plate 81 is joined to the other main surface of piezoelectric actuator 1 via joining member 82 . The entire other main surface may be joined to the vibration plate 81 by the joining member 82, or substantially the entire other main surface may be joined.

The bonding member 82 has a film-like shape. Furthermore, the bonding member 82 is made of a softer and more easily deformable material than the vibrating plate 81 , and has smaller elastic modulus and rigidity such as Young's modulus, rigidity modulus, and bulk modulus than the vibrating plate 81 . That is, the joining member 82 is deformable, and deforms more than the vibrating plate 81 when the same force is applied. In addition, the other main surface (the main surface on the −z direction side in the drawing) of the piezoelectric actuator 1 is integrally fixed to one main surface (the main surface on the +z direction side in the figure) of the joining member 82, and A part of one main surface (principal surface on the +z direction side in the drawing) of the diaphragm 81 is fixed to the other main surface (the main surface on the −z direction side in the drawing) of the member 82 .

The joining member 82 may be a single member or a complex of several members. As such joining member 82 , for example, a double-sided tape in which an adhesive is adhered to both surfaces of a substrate made of nonwoven fabric or the like, various elastic adhesives that are elastic adhesives, and the like can be suitably used. In addition, the thickness of the joining member 82 is preferably larger than the amplitude of the bending vibration of the piezoelectric actuator 1, but if it is too thick, the vibration will be attenuated, so it is set to, for example, 0.1 mm to 0.6 mm. However, in the piezoelectric vibration device of the present invention, the material of the joining member 82 is not limited, and the joining member 82 may be formed of a material that is harder and less deformable than the vibration plate 81 . In addition, depending on circumstances, a structure not having the joining member 82 may be used.

The piezoelectric vibration device of this example having such a structure functions as a piezoelectric vibration device that vibrates the vibration plate 81 by applying an electric signal to cause the piezoelectric actuator 1 to bend and vibrate. In addition, the other end in the longitudinal direction of the vibrating plate 81 (the end in the y direction in the figure, the peripheral edge of the vibrating plate 81 , etc. may be supported by a support member not shown.

The piezoelectric vibration device of this example is configured using the piezoelectric actuator 1 that reduces the generation of unnecessary vibrations, so it can be a piezoelectric vibration device that reduces the generation of unnecessary vibrations.

In addition, in the piezoelectric vibration device of this example, the vibration plate 81 is bonded to the other flat main surface of the piezoelectric actuator 1 . Accordingly, it is possible to obtain a piezoelectric vibration device in which the piezoelectric actuator 1 and the vibration plate 81 are firmly bonded.

As shown in Figures 5 to 7, the portable terminal of the present invention has a piezoelectric actuator 1, an electronic circuit (not shown), a display 91 and a frame 92, and the other main surface of the piezoelectric actuator 1 is joined in frame 92. In addition, FIG. 5 is a schematic perspective view schematically showing a portable terminal of the present invention, FIG. 6 is a schematic cross-sectional view cut along the line A-A shown in FIG. 5 , and FIG. 7 is cut along the line B-B shown in FIG. 5 a schematic cross-section of the .

Here, it is preferable to join the piezoelectric actuator 1 and the housing 92 using a deformable joining member. That is, the joint member 82 is a deformable joint member in FIGS. 6 and 7 .

By joining the piezoelectric actuator 1 to the frame body 92 with the deformable bonding member 82 , the deformable bonding member 82 deforms more than the frame body 92 when vibration is transmitted from the piezoelectric actuator 1 .

At this time, since the anti-phase vibration reflected from the frame body 92 can be moderated by the deformable joint member 82 , the piezoelectric actuator 1 can transmit strong vibration to the frame body 92 without being affected by surrounding vibrations.

Among them, since at least a part of the joint member 82 is made of a viscoelastic body, the strong vibration from the piezoelectric actuator 1 can be transmitted to the frame body 92, and the weak vibration reflected from the frame body 92 can be absorbed by the joint member 82. This is preferable. For example, a double-sided tape having an adhesive attached to both sides of a substrate made of nonwoven fabric or a bonding member having a structure including an elastic adhesive can be used, and their thickness can be, for example, 10 μm to 2000 μm.

In addition, in this example, the piezoelectric actuator 1 is attached to a part of a housing 92 serving as a cover of the display 91 , and a part of the housing 92 functions as a vibrating plate 922 .

In addition, in this example, a case where the piezoelectric actuator 1 is joined to the housing 92 is shown, but the piezoelectric actuator 1 may be joined to the display 91 .

The frame body 92 has a box-shaped frame body body 921 with one surface open, and a vibration plate 922 closing the opening of the frame body body 921 . The housing 92 (the housing main body 921 and the vibrating plate 922 ) can be suitably formed using a material such as a synthetic resin with high rigidity and high modulus of elasticity.

The peripheral portion of the vibrating plate 922 is attached to the frame main body 921 in a vibrating manner via the joint 93 . The joint member 93 is made of a softer and more easily deformable material than the vibrating plate 922 , and has smaller elastic modulus and rigidity than the vibrating plate 922 such as Young's modulus, rigidity modulus, and bulk modulus. That is, the joint 93 is deformable, and deforms more than the vibrating plate 922 when the same force is applied.

The joining member 93 may be a single member or a composite body composed of several members. As such a bonding material 93 , for example, a double-sided tape in which an adhesive is adhered to both surfaces of a base material made of nonwoven fabric or the like can be suitably used. The thickness of the bonding material 93 is set so as not to attenuate vibration due to excessive thickness, and is set to, for example, 0.1 mm to 0.6 mm. However, in the portable terminal of the present invention, the material of the joint member 93 is not limited, and the joint member 93 may be formed of a material that is harder and less deformable than the vibrating plate 922 . In addition, depending on circumstances, a structure not including the joint 93 may be used.

As an electronic circuit (not shown), for example, a circuit for processing image information displayed on the display 91 or audio information transmitted through a mobile terminal, a communication circuit, and the like can be exemplified. At least one of these circuits may be used, or all circuits may be included. In addition, a circuit having other functions may also be used. Furthermore, it is also possible to have a plurality of electronic circuits. In addition, the electronic circuit and the piezoelectric actuator 1 are connected by unillustrated connection wiring.

The display 91 is a display device having a function of displaying image information, and known displays such as a liquid crystal display, a plasma display, and an organic EL display, for example, can be suitably used. In addition, the display 91 may have an input device such as a touch panel. In addition, the cover (vibration plate 922) of the display 91 may have an input device such as a touch panel. Moreover, the whole display 91 or a part of the display 91 may function as a diaphragm.

Furthermore, the mobile terminal of the present invention is characterized in that the display 91 or the housing 92 is vibrated to transmit sound information through ear cartilage or air conduction. The mobile terminal of this example can transmit sound information by bringing the vibrating plate (display 91 or housing 92 ) into contact with the ear directly or via other members to transmit vibration to the cartilage of the ear. That is, by directly or indirectly contacting the vibrating plate (display 91 or housing 92 ) with the ear, it is possible to transmit vibration to the cartilage of the ear and thereby transmit sound information. Thereby, for example, a mobile terminal capable of delivering audio information even when the surroundings are noisy can be obtained. In addition, the member interposed between the vibrating plate (display 91 or frame 92) and the ear may be, for example, a cover of a portable terminal, or a headphone (headphone) or an earphone (earphone), as long as it can transmit vibration. Any kind of component can be used. In addition, it may be a portable terminal that transmits sound information by propagating sound generated from a vibrating plate (display 91 or housing 92 ) in the air. Furthermore, it may be a portable terminal that transmits audio information via a plurality of paths.

The portable terminal of this example transmits audio information using the piezoelectric actuator 1 that reduces the occurrence of unnecessary vibrations, so that high-quality audio information can be transmitted.

【Example】

A specific example of the piezoelectric actuator of the present invention will be described. Specifically, the piezoelectric actuator shown in FIG. 1 was manufactured as follows.

The piezoelectric element was in the shape of a cuboid with a length of 23.5 mm, a width of 3.3 mm, and a thickness of 0.5 mm. In addition, the piezoelectric element has a structure in which piezoelectric layers having a thickness of 30 μm and internal electrodes are alternately laminated, and the total number of piezoelectric layers is 16. The piezoelectric layer is formed of lead zirconate titanate. An alloy of silver palladium is used for the internal electrodes.

The ceramic green sheets on which the conductive paste made of silver and palladium was printed were laminated, pressed to make them stick together, degreased at a predetermined temperature, and then fired at 1000° C. to obtain a laminated sintered body.

Next, the surface electrodes were printed so that both ends in the width direction were 1 mm longer than the internal electrodes.

The piezoelectric element was polarized by applying a voltage with an electric field strength of 2 kV/mm between the internal electrodes (between the first and second electrodes) via the surface electrodes.

Then, a conductive adhesive containing gold-plated resin balls as conductive particles was applied to the surface of the piezoelectric element bonded to the flexible wiring board. At this time, a conductive adhesive containing 20 vol % of conductive particles was applied to a region of 0.3 mm in width at the periphery of the overlapping region of the flexible wiring board and the piezoelectric element, and a conductive adhesive was applied to the inner region of the region. Conductive adhesive containing 10vol% conductive particles.

Then, by heating and pressing the flexible wiring substrate in contact with it, the flexible wiring substrate was conducted and fixed to the piezoelectric element, thereby producing the piezoelectric actuator of the embodiment of the present invention (Sample No. .1). In addition, as the above-mentioned conductive adhesive, an anisotropic conductive material that conducts in the thickness direction and does not conduct in the in-plane direction is used.

In addition, as a comparative example, except that the flexible wiring substrate was bonded to the piezoelectric element with solder, a piezoelectric actuator outside the scope of the present invention having the same structure as the above-mentioned sample No. 1 was produced (sample No. .2).

Then, for each piezoelectric actuator, a sine wave signal with a frequency of 1kHz and an effective value of ±10Vrms was applied to the piezoelectric element through the flexible wiring substrate, and a driving test was carried out. The displacement of the bending vibration.

Next, a sine wave signal with an effective value of 3V whose frequency was changed between 0.2 and 5000 Hz was input to confirm whether abnormal vibrations due to cracks in the joint surface of the flexible wiring board occurred. In the piezoelectric actuator of sample No. 1, abnormal vibration was not observed except vibrations at the resonance and anti-resonance frequencies of the piezoelectric element. On the other hand, in the piezoelectric actuator of Sample No. 2, which is outside the scope of the present invention, abnormal vibration was measured at frequencies other than the vibration originating in the piezoelectric element.

Then, a driving test was performed by continuously applying a sine wave signal of an effective value ±10 Vrms for 100,000 cycles. Sample No. 2 outside the scope of the present invention vibrated abnormally, and the flexible wiring board peeled off from the piezoelectric element at 90,000 cycles.

On the other hand, the piezoelectric actuator of Sample No. 1 of the embodiment of the present invention continued to drive without generating abnormal vibration even after 100,000 cycles. In addition, no cracks, cracks, etc. were observed in the conductive adhesive for connecting and fixing the flexible wiring board, and no peeling of the flexible wiring board was observed.

By using the piezoelectric actuator of the present invention, abnormal vibration does not occur, and even if it is driven continuously for a long period of time, there is no such problem that the flexible wiring board is peeled off from the piezoelectric element, and it is excellent in durability. Sex is confirmed.

Symbol Description

1: Piezoelectric Actuator

2: Internal electrodes

21: 1st pole

22: 2nd pole

3: Piezoelectric layer

4: laminated body

41: Active Department

42: Inactive Department

5: Surface electrode

51: 1st surface electrode

52: 2nd surface electrode

53: 3rd surface electrode

6: Flexible wiring substrate

61: wiring conductor

601: peripheral part

602: the area between the periphery of one main surface and the surface electrode

7: Conductive adhesive

81: Vibration plate

82: Joining components

91: display

92: frame

921: Frame body

922: Vibration plate

93: Joints

Claims (8)

1. A piezoelectric actuator, characterized in that it has: A piezoelectric element comprising a laminate formed by laminating internal electrodes and piezoelectric layers, and a surface electrode electrically connected to the internal electrode on one main surface of the laminate; and A flexible wiring substrate, a part of which is bonded to the one main surface with a conductive adhesive containing conductive particles and resin, and has a wiring conductor electrically connected to the surface electrode, In the bonding region between the flexible wiring board and the piezoelectric element, at least a part of the peripheral part is arranged more of the conductive particles than other parts. the 2. The piezoelectric actuator according to claim 1, characterized in that, The part is located in a region between the outer periphery of the one main surface and the surface electrode. the 3. The piezoelectric actuator according to claim 1 or 2, characterized in that, The conductive adhesive is an anisotropic conductive material. the 4. A piezoelectric vibration device, characterized in that, The piezoelectric actuator according to any one of claims 1 to 3, and a vibration plate joined to the other main surface of the piezoelectric element. the 5. piezoelectric vibration device according to claim 4, is characterized in that, The piezoelectric actuator and the vibrating plate are joined using a deformable joining member. the 6. A portable terminal, characterized in that, Have the piezoelectric actuator, electronic circuit, display and frame according to any one of claims 1 to 3, The other main surface of the piezoelectric actuator is joined to the display or the housing. the 7. The portable terminal according to claim 6, characterized in that, The piezoelectric actuator and the display or the housing are joined using a deformable joining member. the 8. The portable terminal according to claim 6 or 7, characterized in that, The display or the frame generates vibrations that transmit sound information through ear cartilage or air conduction. the