Vibration device

Abstract

The vibration device of the present invention includes: a piezoelectric element having connection terminals exposed on a main surface; a resin layer having conductivity, covering the connection terminals of the piezoelectric element and electrically connected to the connection terminals; a wiring member overlapping the upper surface of the piezoelectric element and covering the resin layer, including wiring electrically connected to the resin layer, and extending beyond one end portion of the piezoelectric element when viewed in the thickness direction of the piezoelectric element; and a covering layer integrally covering the upper surface of the piezoelectric element and the wiring member from the upper surface side of the piezoelectric element, the covering layer including: a first layer directly in contact with the piezoelectric element and the wiring member, and a second layer covering the piezoelectric element and the wiring member via the first layer.

Description

Technical Field

[0001] The present disclosure relates to a vibration device. Background Art

[0002] Currently, a vibration device having a piezoelectric element is known (for example, Japanese Patent Publication No. 5909169). Summary of the Invention

[0003] Problems to be Solved by the Invention

[0004] In the vibration device as described above, it is considered that unnecessary vibration is transmitted from a wiring member attached to the piezoelectric element to the piezoelectric element. After intensive studies by the inventors, a technique has been rediscovered that can suppress the transmission of unnecessary vibration from the wiring member to the piezoelectric element.

[0005] According to one aspect of the present disclosure, there is provided a vibration device that suppresses the transmission of unnecessary vibration.

[0006] Technical Means for Solving the Problems

[0007] A vibration device according to one aspect of the present disclosure includes: a piezoelectric element having connection terminals exposed on a main surface; a first resin layer having conductivity, covering the connection terminals of the piezoelectric element and being electrically connected to the connection terminals; a wiring member overlapping the main surface of the piezoelectric element and covering the first resin layer, including wiring electrically connected to the first resin layer, and extending beyond one end portion of the piezoelectric element when viewed in the thickness direction of the piezoelectric element; and a second resin layer integrally covering the main surface of the piezoelectric element and the wiring member from the main surface side of the piezoelectric element. The second resin layer includes: a first layer directly contacting the piezoelectric element and the wiring member, and a second layer covering the piezoelectric element and the wiring member via the first layer.

[0008] In the above vibration device, the first layer of the second resin layer integrally joins the piezoelectric element and the wiring member, promotes the integral bending vibration of the piezoelectric element and the wiring member, and the second layer of the second resin layer suppresses the transmission of unnecessary vibration from the wiring member to the piezoelectric element.

[0009] In another vibration device, the thickness of the second resin layer is thinner than the thickness of the wiring member.

[0010] In another vibration device, when the thickness of the second resin layer is set to t1 and the thickness of the wiring member is set to t2, 0.25 ≤ t1 / t2 < 1.

[0011] In another vibration device, the coverage area of the second resin layer covering the main surface of the piezoelectric element is wider than the coverage area of the wiring member covering the main surface of the piezoelectric element.

[0012] In another type of vibration device, the second resin layer covers all the edges of the portion of the wiring member that covers the piezoelectric element.

[0013] Another type of vibration device further includes: a third resin layer provided on the main surface of the piezoelectric element and extending over the entire edge of one end portion of the piezoelectric element covered by the wiring member, and the first resin layer is sealed by the wiring member, the second resin layer, and the third resin layer.

[0014] In another type of vibration device, the third resin layer sandwiches the wiring member between it and the second resin layer.

[0015] In another type of vibration device, the resin material forming the wiring member is the same as the resin material of the second layer forming the second resin layer.

[0016] In another type of vibration device, the wiring member and the second resin layer are provided on the main surface of the piezoelectric element on the end portion side closer to one end than the center. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a top view of a vibration device according to an embodiment.

[0018] Figure 2 is Figure 1 an exploded perspective view of the vibration device shown.

[0019] Figure 3 is Figure 1 a cross-sectional view taken along line III-III of the vibration device shown.

[0020] Figure 4 is a graph showing the results of experiments conducted by the inventors and the like. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In addition, in the description, the same reference numerals are used for the same elements or elements having the same function, and repeated descriptions are omitted.

[0022] As Figures 1 to 3 shown, the vibration device 1 includes a piezoelectric element 10, a wiring member 20, and a covering layer 30.

[0023] The piezoelectric element 10 has a rectangular flat-plate shape and is composed of a piezoelectric layer and an electrode layer that overlap in the plate thickness direction. The piezoelectric element 10 includes at least a pair of electrode layers that overlap in the plate thickness direction and a piezoelectric layer sandwiched between the pair of electrode layers. The piezoelectric element 10 may be a single-layer structure including one piezoelectric layer, or may be a multi-layer structure in which a plurality of piezoelectric layers and a plurality of electrode layers are alternately laminated. The piezoelectric layer can be composed of a piezoelectric ceramic material such as PZT, for example. The piezoelectric element 10 may also have a rectangular flat-plate shape with chamfered corners and edges, or may have a rectangular flat-plate shape with rounded corners and edges. Figure 1 The symbol C shown represents the center of the piezoelectric element 10 when viewed from above.

[0024] A pair of connection terminals 12 are exposed on the upper surface 10a (main surface) of the piezoelectric element 10. Each connection terminal 12 is electrically connected to the electrode layer constituting the piezoelectric element 10, for example, to each of the pair of electrode layers sandwiching the piezoelectric layer. When a periodic voltage signal is input between the pair of connection terminals 12, the piezoelectric layer of the piezoelectric element 10 expands or contracts repeatedly, and the entire piezoelectric element 10 vibrates. Vibration related to the plate thickness direction is mainly generated in the piezoelectric element 10.

[0025] As Figure 2 shown, the pair of connection terminals 12 are located at one end portion 11 of the piezoelectric element 10. More specifically, the pair of connection terminals 12 are separated from the edge 11a of the one end portion 11 and arranged along the edge 11a of the one end portion 11. In the present embodiment, each connection terminal 12 has a rectangular shape when viewed from above. Each connection terminal 12 may also be circular or elliptical when viewed from above.

[0026] On the upper surface 10a of the piezoelectric element 10, a pair of resin layers 41 (first resin layers) are provided so as to cover each of the pair of connection terminals 12. Each resin layer 41 has conductivity and is composed of, for example, an anisotropic conductive adhesive material (ACP). When viewed from above, the size of the resin layer 41 is substantially the same as the size of the connection terminal 12.

[0027] On the upper surface 10a of the piezoelectric element 10, on the side closer to the one end portion 11 than the pair of resin layers 41, a sealing resin layer 42 (third resin layer) is also provided. The sealing resin layer 42 has a shape extending in one direction, for example, a rectangular shape. The sealing resin layer 42 extends along the edge 11a of the one end portion 11 of the piezoelectric element 10. The sealing resin layer 42 may also be separated from the edge 11a of the one end portion 11 of the piezoelectric element 10 or may not be separated. The sealing resin layer 42 is composed of, for example, nitrile gum. The sealing resin layer 42 has at least the functions of adhesion and moisture resistance.

[0028] The wiring member 20 is a strip-shaped member extending in the same direction as the extending direction of the piezoelectric element 10, and is designed to be narrower in width than the piezoelectric element 10. As Figure 1 shown, the wiring member 20 overlaps with the piezoelectric element 10 at the end portion 23, covering the upper surface 10a of the piezoelectric element 10. The wiring member 20 is located closer to the end portion 11 than the center C with respect to the piezoelectric element 10. The end portions 11 and 23 of both the piezoelectric element 10 and the wiring member 20 overlap with each other, and when viewed from the thickness direction of the piezoelectric element 10, the wiring member 20 extends beyond one end portion 11 of the piezoelectric element 10.

[0029] The wiring member 20 is constituted by a pair of wirings 21 and a resin sheet 22 that holds the wirings 21. The wiring member 20 is, for example, a flexible printed circuit board (FPC). In the present embodiment, the wiring 21 is made of Cu, and the resin sheet 22 is made of a polyimide resin.

[0030] The wiring member 20 integrally covers a pair of resin layers 41 and a sealing resin layer 42 provided on the upper surface 10a of the piezoelectric element 10. The wiring member 20 is bonded to the piezoelectric element 10 by the pair of resin layers 41 and the sealing resin layer 42. Since the width of the wiring member 20 is narrower than that of the piezoelectric element 10, the upper surface 10a between the side edges 11b and 11c opposite to each other in the extending direction of the edge 11a of one end portion 11 of the piezoelectric element 10 is exposed. More specifically, when the wiring member 20 is mounted on one end portion 11 of the piezoelectric element 10, as Figure 1 shown, the upper surface 10a around the end portion 23 of the wiring member 20 is exposed in a U-shape. The sealing resin layer 42, when covered by the wiring member 20, extends over the entire area (the entire edge) of the edge 11a of one end portion 11 of the piezoelectric element 10.

[0031] The covering layer 30 (second resin layer) integrally covers the piezoelectric element 10 and the wiring member 20 from the upper surface 10a side of the piezoelectric element 10. The covering layer 30 also covers the U-shaped area of the upper surface 10a around the end portion 23 of the above-mentioned wiring member 20. The covering layer 30 covers all the edges of the end portion 23 of the wiring member 20 that covers the piezoelectric element 10 (in the present embodiment, all three edges in a U-shape). The covering area of the covering layer 30 covering the upper surface 10a of the piezoelectric element 10 is designed to be wider than the covering area of the wiring member 20 covering the upper surface 10a of the piezoelectric element 10. The covering layer 30, like the wiring member 20, is located closer to the end portion 11 than the center C with respect to the piezoelectric element 10. The covering layer 30 has at least the functions of adhesion and moisture resistance.

[0032] The cover layer 30 is composed of a plurality of resin layers. In the present embodiment, it is composed of a double layer of a first layer 31 and a second layer 32. The first layer 31 is directly in contact with the piezoelectric element 10 and the wiring member 20. In particular, the first layer 31 integrally joins the piezoelectric element 10 and the wiring member 20 to promote the integral vibration (bending vibration) of the piezoelectric element 10 and the wiring member 20. The first layer 31 can be made of, for example, acrylic resin, silicone, etc. The second layer 32 indirectly covers the piezoelectric element 10 and the wiring member 20 via the first layer 31. The second layer 32 suppresses the propagation of unnecessary vibration from the wiring member 20 to the piezoelectric element 10. The second layer 32 is made of, for example, polyimide resin, and can also be made of other resins (such as polyester resin, fluororesin), glass cloth, etc. That is, in the present embodiment, the second layer 32 of the cover layer 30 is made of the same material (i.e., polyimide resin) as the resin material of the resin sheet 22 constituting the wiring member 20. The thickness t1 of the cover layer 30 is designed to be thinner than the thickness t2 of the wiring member 20. The thickness t1 of the cover layer 30 and the thickness t2 of the wiring member 20 can be designed to satisfy the relationship of 0.25≦t1 / t2<1.

[0033] As described above, the vibration device 1 includes: a piezoelectric element 10 having connection terminals 12 exposed on the upper surface 10a; a resin layer 41 having conductivity, covering the connection terminals 12 of the piezoelectric element 10 and electrically connected to the connection terminals 12; a wiring member 20 overlapping the upper surface 10a of the piezoelectric element 10 and covering the resin layer 41, including wiring 21 electrically connected to the resin layer 41, and extending beyond one end portion 11 of the piezoelectric element 10 when viewed from the thickness direction of the piezoelectric element 10; and a cover layer 30 integrally covering the upper surface 10a of the piezoelectric element 10 and the wiring member 20 from the upper surface 10a side of the piezoelectric element 10. The cover layer 30 includes a first layer 31 directly in contact with the piezoelectric element 10 and the wiring member 20 and a second layer 32 covering the piezoelectric element 10 and the wiring member 20 via the first layer 31.

[0034] In the vibration device 1, the first layer 31 of the cover layer 30 integrally joins the piezoelectric element 10 and the wiring member 20 to promote the integral vibration (bending vibration) of the piezoelectric element 10 and the wiring member 20, and the second layer 32 of the cover layer 30 suppresses the propagation of unnecessary vibration from the wiring member 20 to the piezoelectric element 10.

[0035] In particular, the second layer 32 of the cover layer 30 cooperates with the resin sheet 22 of the wiring member 20 to suppress the unnecessary vibration propagating to the piezoelectric element 10. Therefore, by making the second layer 32 of the cover layer 30 of the same material as the constituent material of the resin sheet 22, the unnecessary vibration propagating to the piezoelectric element 10 can be effectively suppressed.

[0036] In addition, in the vibration device 1, asFigure 3 As shown, the resin layer 41 is sealed by the wiring member 20, the cover layer 30, and the sealing resin layer 42, achieving an improvement in moisture resistance and effectively suppressing the deterioration of the resin layer 41.

[0037] In addition, in the vibration device 1, the thickness t1 of the cover layer 30 is designed to be thinner than the thickness t2 of the wiring member 20. The inventors and the like conducted experiments as shown below to confirm the influence of the relationship between the thickness t1 of the cover layer 30 and the thickness t2 of the wiring member 20 on the vibration device. That is, specimens with different ratios of t1 / t2 (Examples 1 to 3, Comparative Examples 1 to 3) were prepared, and the total harmonic distortion (THD) was measured for each specimen, and the presence or absence of peeling of the cover layer after the measurement was confirmed. The ratios of t1 / t2 in Examples 1 to 3 were set to 1, 0.5, and 0.25, respectively. In addition, as Comparative Example 1, the total harmonic distortion was measured for a specimen without a cover layer. The ratios of t1 / t2 in Comparative Examples 2 and 3 were set to 1.25 and 0.2, respectively. The experimental results are shown in Table 1 and Figure 4 the chart shown below.

[0038]

Table 1

[0039] Comparative Example t1 / t2 Total Harmonic Distortion [dB] Peeling Example 1 1 8 None Example 2 0.5 13 None Example 3 0.25 19 None Comparative Example 1 NA 33 NA Comparative Example 2 1.25 25 Yes Comparative Example 3 0.2 22 None

[0040] According to Table 1 and Figure 4 the chart shown below, it can be seen that in Examples 1 to 3 where the relationship of 0.25 ≤ t1 / t2 < 1 is satisfied, it is confirmed that the total harmonic distortion is suppressed below 20 dB in the range of 100 to 2000 Hz, and good vibration characteristics (such as sound accuracy) are obtained, and no peeling of the cover layer is confirmed. On the other hand, in Comparative Examples 1 to 3, the total harmonic distortion exceeds 20 dB in the range of 100 to 2000 Hz. In addition, in the specimen of Comparative Example 2, peeling of the cover layer was confirmed.

[0041] Therefore, by making the thickness t1 of the cover layer 30 and the thickness t2 of the wiring member 20 satisfy the relationship of 0.25 ≤ t1 / t2 < 1, peeling of the cover layer can be suppressed and good vibration characteristics can be obtained. When the thickness of the cover layer 30 is too thick (for example, t1 ≥ t2), peeling of the cover layer 30 is likely to occur, and when the thickness of the cover layer 30 is too thin (for example, t1 / t2 < 0.25), it is difficult to obtain good vibration characteristics.

Claims

1. A vibration device, wherein, comprises: a piezoelectric element having connection terminals exposed on a main surface; a first resin layer having conductivity, covering the connection terminals of the piezoelectric element and electrically connected to the connection terminals; a wiring member overlapping the main surface of the piezoelectric element and covering the first resin layer, including wiring electrically connected to the first resin layer, and extending beyond one end portion of the piezoelectric element when viewed from the thickness direction of the piezoelectric element; and a second resin layer integrally covering the main surface of the piezoelectric element and the wiring member from the main surface side of the piezoelectric element, the second resin layer includes: a first layer directly contacting the piezoelectric element and the wiring member, and a second layer covering the piezoelectric element and the wiring member via the first layer, the second resin layer covers all edges of the portion of the wiring member covering the piezoelectric element, further comprises: a third resin layer provided on the main surface of the piezoelectric element and extending over the entire edge of the one end portion of the piezoelectric element covered by the wiring member, the first resin layer is sealed by the wiring member, the second resin layer, and the third resin layer.

2. The vibration device according to claim 1, wherein, the thickness of the second resin layer is thinner than the thickness of the wiring member.

3. The vibration device according to claim 2, wherein, when the thickness of the second resin layer is set to t1 and the thickness of the wiring member is set to t2, 0.25 ≦ t1 / t2 < 1.

4. The vibration device according to any one of claims 1 to 3, wherein, the coverage area of the main surface of the piezoelectric element covered by the second resin layer is wider than the coverage area of the main surface of the piezoelectric element covered by the wiring member.

5. The vibration device according to claim 1, wherein, the third resin layer sandwiches the wiring member between the third resin layer and the second resin layer.

6. The vibration device according to any one of claims 1 to 5, wherein, the resin material constituting the wiring member and the resin material of the second layer constituting the second resin layer are the same.

7. The vibration device according to any one of claims 1 to 6, wherein, the wiring member and the second resin layer are provided on the main surface of the piezoelectric element on the side closer to the one end portion than the center.

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