JP2012120097A - Piezoelectric electronic component and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric electronic component which has low-frequency characteristics, and is capable of obtaining sufficient oscillation energy.SOLUTION: The piezoelectric electronic component 1 has low-frequency characteristics, and is capable of obtaining sufficient oscillation energy by including a shim 3 having a first region 3A and a second region 3B adjacent to the first region 3A on one main surface thereof; a piezoelectric element 2 disposed in the second region 3B; a support member 4 having a part opposed to the piezoelectric element 2 and fixing the shim 3 by the first region 3A; and an elastic member 6 which is positioned between the support member 4 and the piezoelectric element 2, and is disposed in at least one of the support member 4 and the piezoelectric element 2.

Description

  The present invention relates to a piezoelectric electronic component and an electronic apparatus.

  Conventionally, piezoelectric electronic components have been used for applications such as piezoelectric exciters. For example, Patent Document 1 discloses, as such a piezoelectric electronic component, a piezoelectric element and a vibrator made of a shim material provided with piezoelectric elements on both main surfaces, and a support member that supports the vicinity of the end of the piezoelectric element. The thing of the structure which has these is described.

  In such a piezoelectric electronic component, the support member is attached to the panel of the electronic device. The vibration energy of the vibrator is transmitted to the panel through the support member, and this panel functions as a diaphragm and generates sound. According to the piezoelectric electronic component having the above configuration, since the support member directly supports the piezoelectric element, vibration energy can be transmitted to the support member without loss. Therefore, sufficient vibration energy can be extracted from the support member.

JP 2008-252878 A

  However, when the piezoelectric element is directly supported by the support member, sufficient vibration energy can be obtained, but the resonance frequency of the vibrator moves to the high frequency side. Therefore, for example, as compared with the case where a shim extended from the arrangement region of the piezoelectric element is supported, the resonance frequency moves to the high frequency side, and a sufficient low frequency characteristic cannot be obtained.

  The present invention has been made in view of the above problems, and an object thereof is to obtain a large vibration energy for a piezoelectric electronic component having a sufficiently low frequency characteristic.

  The piezoelectric electronic component of the present invention includes a shim having a first region on one main surface and a second region adjacent to the first region, a piezoelectric element provided in the second region, and the piezoelectric element. A support member that fixes the shim in the first region, and is located between the support member and the piezoelectric element, and is provided on at least one of the support member and the piezoelectric element. And an elastic member.

  An electronic apparatus according to the present invention is characterized in that the piezoelectric electronic component described above is used as a vibration source and includes a panel on which the support member is mounted.

According to the piezoelectric electronic component of the present invention, a shim having a first region and a second region adjacent to the first region on one main surface, a piezoelectric element provided in the second region, and a piezoelectric element A support member having opposing portions and fixing the shim in the first region; and an elastic member positioned between the support member and the piezoelectric element and provided on at least one of the support member and the piezoelectric element. Thus, since the first region of the shim is supported by the support member, the resonance frequency can be moved to the low frequency side. Further, vibration energy due to vibration of the piezoelectric element is transmitted not only from the first region side of the shim to the support member but also from the second region side to the support member via the elastic member. As a result, the piezoelectric electronic component having a sufficiently low frequency characteristic can be increased in vibration energy.

(A) is a side view of the piezoelectric electronic component concerning embodiment of this invention, (b) is a top view of the piezoelectric electronic component shown to (a). It is a longitudinal cross-sectional view of the piezoelectric oscillator shown in FIG. The vertical axis represents the vibration energy of the piezoelectric electronic component, and the horizontal axis represents the frequency of the input signal. It is a side view of the other example of the piezoelectric electronic component of this invention. (A), (b) is a side view of the other example of the piezoelectric electronic component of this invention.

  Hereinafter, an example of an embodiment of a piezoelectric electronic component of the present invention will be described in detail with reference to the drawings.

  The piezoelectric electronic component 1 of the example shown in FIG. 1 includes a support member 4, a piezoelectric vibrator 5 including a shim 3 and a piezoelectric element 2, an elastic member 6, and a connecting material 7 as a basic configuration. .

  The piezoelectric electronic component 1 is used as, for example, a piezoelectric exciter that utilizes bending vibration of the piezoelectric vibrator 5. The piezoelectric electronic component 1 is used as a vibration source of an electronic device having a panel. This electronic apparatus uses the piezoelectric electronic component 1 as a vibration source and has a panel on which a support member 2 is mounted.

  The support member 4 has a portion 4A facing the piezoelectric element 2 and fixes the shim 3 in the first region 3A. The support member 4 is made of a resin material such as epoxy, acrylic or polycarbonate. In the example shown in FIG. 1, the shim 3 is fixed to the first region 3 </ b> A by the connecting material 7. As the connecting material 7, an epoxy resin or the like, solder, or the like is used. The shim 3 may be directly fixed to the support member 4 without using a connecting material. Specifically, the shim 3 is brought into contact with the molten support member 4 before solidification. In this state, the support member 4 is solidified in a state where the shim 3 is fixed by performing a process such as applying heat. Further, the shim 3 may be fitted into a notch provided in the support member 4 and fixed.

  In the example shown in FIG. 1, the shim 3 has a first region 3 </ b> A and a second region 3 </ b> B adjacent to the first region 3 </ b> A on one main surface and the other main surface. The shim 3 is made of, for example, a nickel alloy such as 42 alloy or other metals. The shim 3 is a member that vibrates with the end portion supported by the support member 4 as a fixed end and the other end portion as a free end. The shim 3 has flexibility. The dimensions of the shim 3 are preferably strips having a length of 20 to 40 mm, a width of 3.5 to 5.5 mm, and a thickness of 0.2 to 0.35 mm, for example.

  As shown in FIG. 2, the piezoelectric element 2 is coated with an insulating adhesive 8 made of an epoxy resin or an acrylic resin on the main surface to be bonded to the shim 3 so as to cover the electrode 2b. The insulating adhesive 8 is attached to the main surface of the shim material 3. Affixing of the piezoelectric element 2 to the main surface of the shim 3 through the insulating adhesive 8 is performed, for example, by applying pressure at room temperature for about 2 minutes.

  In the example shown in FIG. 1, the piezoelectric element 2 is provided in the second region 3 </ b> B of one main surface (lower surface) of the shim 3, and the second main surface (upper surface) of the shim 3 The piezoelectric element 2 is further provided in a region corresponding to the region 3B.

  As in the example shown in FIG. 2, the piezoelectric element 2 is formed by laminating about 5 to 15 layers of piezoelectric substrates 2a, and an electrode 2b is provided between these substrates or between the substrates. One potential electrode 2b is connected to one end facet electrode 2c. The other potential electrode 2b is connected to the other end face electrode 2d. The end surface electrodes 2c and 2d are respectively provided on the end surfaces of the laminate composed of the piezoelectric substrate 2a and the electrode 2b.

The piezoelectric substrate 2a is lead zirconate titanate _{(PbZr 1-x Ti x O} 3), lead titanate (PbTiO _3), sodium-potassium niobate _{(Na 1-x K x NbO} 3), bismuth layered compound (e.g. : MBi ₄ Ti ₄ O ₁₅ , M: a divalent alkaline earth metal element) or the like, or a piezoelectric single crystal such as quartz or lithium tantalate (LiTaO ₃ ).

  The piezoelectric substrate 2a has, for example, a rectangular parallelepiped shape having a length of 10 to 25 mm, a width of 3 to 5 mm, and a thickness of 20 to 50 μm.

  Furthermore, for example, from the viewpoint of reducing the thickness of the entire piezoelectric electronic component 1, the thickness of the piezoelectric element 2 is preferably 5 mm or less.

  When the piezoelectric substrate 2a is made of a ceramic material, the piezoelectric substrate 2a is manufactured as follows. First, a green sheet is produced. As this method, for example, a method of adding a binder to the raw material powder and pressing it is used. Further, a method may be used in which the raw material powder is mixed with water and a dispersant using a ball mill, dried and then molded by a doctor blade method by adding a binder, a solvent, a plasticizer and the like.

Next, this green sheet is baked at a peak temperature of 1100 to 1400 ° C. for 0.5 to 8 hours to form a substrate. Next, the substrate is heated at a temperature of 80 to 200 ° C., for example, 3 to 6 kV / in the thickness direction.
A piezoelectric substrate 2a having desired piezoelectric characteristics is obtained by applying a polarization treatment by applying a voltage of mm.

  When the piezoelectric substrate 2a is made of a piezoelectric single crystal material, the piezoelectric single crystal material ingot (base material) to be the piezoelectric substrate 2a is cut so as to have a predetermined crystal direction, thereby providing desired piezoelectric characteristics. Thus obtained piezoelectric substrate 2a is obtained.

The electrode 2b and the end face electrodes 2c, 2d are preferably made of a metal film such as gold, silver, copper or aluminum from the viewpoint of conductivity. The thickness of the electrode 2b is preferably in the range of 0.1 to 5 μm. By making the metal film to be an electrode thicker than 0.1 μm, for example, when exposed to a high temperature in the atmosphere, it is possible to suppress a decrease in conductivity due to oxidation. In addition, by making the metal film thinner than 5 μm, it is possible to prevent the metal film from being peeled off by stress.

  For the deposition of the metal film to be the electrode 2b, a vacuum deposition method, a CVD (Chemical Vapor Deposition) method, a sputtering method, or the like can be used.

  At this time, in order to improve the adhesion between the piezoelectric substrate 2a and the electrode 2b, for example, a base electrode layer made of a metal having high adhesion to the ceramic material constituting the piezoelectric substrate 2a, such as chromium, is provided in advance. A desired metal film may be provided thereon.

In addition, the electrode 2b can be formed by baking a conductive paste containing a metal filler such as silver or copper and using low temperature glass as a binder at a predetermined temperature. Similarly, the end electrodes 2c and 2d are formed by baking a paste. The thickness of the electrode 2b is preferably in the range of 5 to 30 μm. By making the electrode film to be the electrode 2b thicker than 5 μm, it is possible to suppress an increase in conduction resistance due to poor contact between the metal fillers. Further, by making the thickness thinner than 30 μm, it is possible to prevent the deterioration of the vibration characteristics of the piezoelectric substrate 2a due to the mass effect of the electrode 2b.

  The dimension of the electrode 2b is appropriately set according to the dimension of the piezoelectric substrate 2a. For example, when the dimensions of the piezoelectric substrate 2a are 2 mm in length, 0.5 mm in width, and 0.2 mm in thickness, the dimension of the electrode 2b is 1.5 mm in the length direction of the piezoelectric substrate 2a. The substrate 2a has a widthwise dimension of 0.5 mm and a thickness of 1 μm.

  The elastic member 6 is preferably located between the support member 4 and the piezoelectric element 2 and provided on both the support member 4 and the piezoelectric element 2 as in the example shown in FIG. In the example shown in FIG. 1, the elastic member 6 is bonded to both the support member 4 and the piezoelectric element 2. In this case, the piezoelectric vibrator 5 can be reliably fixed to the support member 4 as compared with the case where the elastic member 6 is provided only on one of the support member 4 and the piezoelectric element 2. Therefore, it is preferable because the strength of the piezoelectric electronic component 1 can be improved.

  As this elastic member 6, a member having elasticity such as ABS resin, silicone resin, rubber or the like is used. The elastic modulus of the elastic member 6 is 1 MPa to 1 GPa. The elastic member 6 has a thickness of 30 to 200 μm. Further, the dimensions of the elastic member 6 are, for example, 1 to 4 mm in the long side direction of the piezoelectric element 2 and 2 to 6 mm in the short side direction.

  With the above configuration, since the first region 3A of the shim 3 is supported by the support member 4, it is possible to suppress the resonance frequency from moving to the high frequency side. The vibration energy of the piezoelectric vibrator 5 is transmitted from the second region 3B side of the shim 3 to the support member 4 via the elastic member 6, and also from the first region 3A side of the shim 3. Is transmitted to. Therefore, since vibration energy is transmitted to the support member 4 from a plurality of locations, sufficient vibration energy is efficiently transmitted to a panel (not shown) on which the support member 4 is mounted. Therefore, in the piezoelectric electronic component 1 having a sufficiently low frequency characteristic, vibration energy can be increased.

  Next, a driving method for the case where the piezoelectric electronic component 1 is used as a piezoelectric exciter will be described below. Lead electrodes (not shown) are connected to the end face electrodes 2c and 2d of the piezoelectric element 2, respectively. The lead electrode having one end connected to the end surface electrode 2c has the other end connected to one side of a drive power source (not shown). Further, the lead electrode having one end connected to the end face electrode 2d has the other end connected to the other side of the drive power supply (not shown). The drive power supply supplies an alternating current having a predetermined frequency.

  The present invention is not limited to the embodiments described above, and various changes and improvements can be made without departing from the scope of the present invention.

  For example, FIG. 1 shows an example in which the piezoelectric elements 2 are provided on both main surfaces of the shim 3, but these are provided on one main surface of the shim 3 as shown in FIG. It may be only.

In the example shown in FIG. 1, the elastic member 6 is located between the support member 4 and the piezoelectric element 2 and is provided in both the support member 4 and the piezoelectric element 2. However, as long as the elastic member 6 is located between the support member 4 and the piezoelectric element 2, it does not depend on this configuration. For example, as shown in FIG. 5A, the elastic member 6 is preferably provided only on the support member 4. In this case, when the amplitude of the piezoelectric oscillator 5 is small, the piezoelectric element 2 does not contact the elastic member 6. Therefore, when the amplitude of the piezoelectric oscillator 5 is small, the piezoelectric oscillator 5 is supported only by the shim 3. Therefore, in this case, a lower frequency characteristic can be obtained. On the other hand, when the amplitude of the piezoelectric oscillator 5 is large, the piezoelectric element 2 comes into contact with the elastic member 6. Therefore, the vibration energy that cannot be transmitted only on the first region 3A side of the shim 3 can be transmitted to the support member 2 via the elastic member 6 also from the second region 3B side of the shim 3.

  Further, as shown in FIG. 5B, it is preferable that the elastic member 6 is provided only on the piezoelectric element 2 because the same effect as the example shown in FIG. 5A can be obtained.

  The elastic member 6 is preferably provided on the first region 3 </ b> A side from the central portion of the piezoelectric element 2. In particular, the elastic member 6 is preferably provided at the end of the piezoelectric element 2 on the first region 3A side as in the example shown in FIG. In this case, it is suppressed that the elastic member 6 prevents the vibration of the piezoelectric element 2. Therefore, it becomes easy to obtain a desired frequency characteristic.

  Further, as in the example shown in FIG. 1, the end face of the elastic member 6 and the end face of the piezoelectric element 2 may be aligned so as to be substantially in the same plane. The end face of the elastic member 6 preferably extends beyond the end face of the piezoelectric element 2 on the first region 3A side. In this case, the adhesion area between the elastic member 6 and the facing portion 4A of the support member 4 can be increased without increasing the adhesion area between the elastic member 6 and the piezoelectric element 2. Therefore, without interfering with the vibration of the piezoelectric element 2, the adhesive strength between the elastic member 6 and the support member 4 can be increased, and peeling of both can be prevented.

  The elastic member 6 preferably has a lower elastic modulus than the adhesive 7 described above. In this case, the adhesive 7 has a higher fixing force than the elastic member 6. Therefore, the piezoelectric vibrator 5 is fixed by the support member 4 via the adhesive 7 mainly at the end portion of the shim 3. Therefore, the fixing force of the piezoelectric element 2 by the elastic member 6 is smaller than that of the shim 3. Therefore, the resonance frequency of the piezoelectric vibrator 5 can be further suppressed from moving to the high frequency side. The elastic modulus of the elastic member 6 is appropriately selected from the range of 1 MPa to 1 GPa, and the elastic modulus of the connecting member 7 is appropriately selected from the range of 100 MPa to 100 GPa.

  Differences in characteristics between the piezoelectric electronic component 1 and the comparative piezoelectric electronic component will be described below with reference to the drawings. First, the piezoelectric electronic component 1 will be described.

The shim 3 was a strip shape having a length of 35 mm, a width of 4.5 mm, and a thickness of 0.3 mm, and the material was 42 alloy. The piezoelectric element 2 had a length of 31 mm, a width of 4.1 mm, and a thickness of 0.55 μm. The piezoelectric element 2 is disposed on both main surfaces of the shim 3. The electrode 2b of the piezoelectric element 2 had a length of 30.4 mm, a width of 3.5 mm, and a thickness of 2 μm.

In the portion where the support member 4 and the shim 3 are bonded, the length direction of the shim 3 is 2 mm, and the width direction of the shim 3 is 4.5 mm. In the portion where the facing portion 4A of the support member 4 and the piezoelectric element 2 are bonded, the length direction of the piezoelectric element 2 is 2.5 mm, and the width direction of the piezoelectric element 2 is 4.1 mm.

In the supporting member 4, the portion 4 </ b> A facing the piezoelectric element 2 is 3 mm in the length direction of the shim 3 and 4.5 mm in the width direction of the shim 3. The connecting material 7 has an elastic modulus of 2 GPa and a thickness of 5
An epoxy resin of 0 μm was used. As the elastic member 6, a silicone resin having an elastic modulus of 30 MPa and a thickness of 100 μm was used.

Next, a piezoelectric electronic component of a comparative example will be described. The support member for the piezoelectric electronic component does not have the elastic member 6 in the piezoelectric electronic component 1. Other dimensions and shapes of the piezoelectric electronic component were the same as those of the piezoelectric electronic component 1.

  An alternating current having a predetermined frequency was applied to each of the piezoelectric electronic component 1 and the piezoelectric electronic component of the comparative example, and the generated vibration energy was measured. The frequency of the alternating current to be applied was changed within a predetermined range as shown on the horizontal axis of FIG.

  In addition, the drive method of the piezoelectric electronic component 1 in the application of a voltage is shown below. First, lead electrodes were connected to the end face electrodes 2c and 2d of the piezoelectric element 2, respectively. The lead electrode having one end connected to the end face electrode 2c has the other end connected to one side of the drive power source. Further, the lead electrode having one end connected to the end face electrode 2d was connected to the other side of the drive power source (not shown). The same driving method was used for the piezoelectric electronic component of the comparative example.

  In FIG. 3, the broken line is the vibration mode of the piezoelectric electronic component of the comparative example, and the solid line is the vibration mode of the piezoelectric electronic component 1.

In the broken line vibration mode, the resonance frequency on the low frequency side was about 550 Hz. At this resonance frequency, the vibration energy was about -21 dBN. On the other hand, in the solid line vibration mode, the resonance frequency on the low frequency side is about 550 Hz, and the vibration energy is about −8 d at this resonance frequency.
It was BN. Therefore, the vibration mode indicated by the broken line and the vibration mode indicated by the solid line have substantially the same resonance frequency on the low frequency side. On the other hand, the vibration energy of the resonance frequency on the low frequency side was about 13 dBN greater in the vibration mode indicated by the solid line than in the vibration mode indicated by the broken line. As a result, it has been found that the vibration energy of the piezoelectric electronic component 1 is larger at substantially the same resonance frequency as compared with the piezoelectric electronic component of the comparative example.

1: piezoelectric electronic component 2: piezoelectric element 2a: piezoelectric substrate 2b: electrode 2c, 2d: end face electrode 3: shim material 4: support member 5: piezoelectric oscillator 6: elastic member

Claims (5)

A shim having a first region on one main surface and a second region adjacent to the first region;
A piezoelectric element provided in the second region;
A support member having a portion facing the piezoelectric element and fixing the shim in the first region;
A piezoelectric electronic component comprising: an elastic member positioned between the support member and the piezoelectric element and provided on at least one of the support member and the piezoelectric element.   The piezoelectric electronic component according to claim 1, wherein the elastic member is provided on both the support member and the piezoelectric element.   The piezoelectric electronic component according to claim 1, wherein the elastic member is provided closer to the first region than a central portion of the piezoelectric element.   The piezoelectric electronic component according to claim 1, wherein a piezoelectric element is further provided in a region corresponding to the second region on the other main surface of the shim.   An electronic apparatus comprising the piezoelectric electronic component according to claim 1 as a vibration source and a panel on which the support member is mounted.

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