JP6844186B2 - Piezoelectric element - Google Patents

Description

The present invention relates to a piezoelectric element.

As a conventional piezoelectric element, for example, the one described in Patent Document 1 is known. The piezoelectric element described in Patent Document 1 is arranged on a piezoelectric element, a first electrode and a second electrode for applying a voltage to the piezoelectric element, and the first electrode, and is more solder than the first electrode. It is provided with a conductive film having low wettability.

International Publication No. 2011/145453

If the solder gets wet and spreads when the piezoelectric element is mounted on a land electrode or the like, there is a risk that sufficient solder cannot be secured to join the piezoelectric element and the land electrode. If the amount of solder between one electrode and the land electrode is insufficient, the piezoelectric element may be tilted. As a result, stress is applied to the solder between the other electrode and the land electrode, which may result in mounting failure. In the conventional piezoelectric element, the wettability of the solder of the conductive film is made lower than that of the first electrode, so that when the piezoelectric element is solder-mounted, the wetting and spreading of the solder on the first electrode is suppressed. However, in the conventional piezoelectric element, since the conductive film is widely arranged on the first electrode, the conductive film may hinder the displacement of the active portion of the piezoelectric element. Therefore, with the conventional piezoelectric element, the displacement cannot be obtained efficiently.

One aspect of the present invention is to provide a piezoelectric element capable of efficiently obtaining displacement while suppressing mounting defects caused by wet spread of solder.

The piezoelectric element according to one aspect of the present invention includes a piezoelectric element, a first electrode and a second electrode arranged on the piezoelectric element and for applying a voltage to the piezoelectric element, and the first electrode and the second electrode. On at least one surface of the second electrode, a first region formed of a conductive first material and to which solder is applied at the time of mounting, and a second region adjacent to the first region and of the first material and conductive. A second region formed by including the material is provided, and the second material has a lower solder wettability than the first material.

In the piezoelectric element according to one aspect of the present invention, a first region and a second region are provided on the surface of at least one of the first electrode and the second electrode. The first region is a region to which solder is applied when the piezoelectric element is solder-mounted. The second region is provided adjacent to the first region, and is formed by mixing a first material forming the first region and a second material having a lower wettability than the first material. As a result, in the piezoelectric element, even if the solder is wetted and spread when the solder is applied to the first region, when the solder reaches the second region, the wet and spread of the solder is suppressed by the second region. Solder. Therefore, the amount of solder between the first electrode or the second electrode and the land electrode or the like can be secured, and it is possible to suppress the occurrence of inclination of the piezoelectric element due to the imbalance of the amount of solder, so that stress is applied to the solder. Can be suppressed. As a result, it is possible to suppress mounting defects caused by the wet spread of the solder. Further, in the piezoelectric element, the first material and the second material have conductivity, and the second region is provided on the surface of the electrode. That is, the second region is configured as a part of the electrode. Therefore, the second region does not inhibit the displacement of the active portion of the piezoelectric element. Therefore, in the piezoelectric element, the displacement of the active portion can be efficiently obtained.

In one embodiment, the second region may be provided at a position on the active portion of the piezoelectric element that is displaced by the application of voltage. The second region does not inhibit the displacement of the active part. Therefore, in the configuration in which the second region is provided at the position corresponding to the active portion, the configuration of the piezoelectric element is particularly effective. Further, since the position of the second region is not limited, the first region to which the solder is applied can be secured, and the solder mounting of the piezoelectric element can be reliably performed.

In one embodiment, the piezoelectric element has a substantially rectangular shape, a pair of main surfaces facing each other, a pair of end faces facing each other in the long side direction of the pair of main surfaces, and a pair of short sides of the main surface. It has a pair of sides facing each other in the direction, the first electrode is at least placed on one main surface and one end face, and the second electrode is at least placed on the other main surface and the other end face. A plurality of second regions may be provided at predetermined intervals in the opposite directions of the pair of side surfaces. In this configuration, it is possible to prevent the solder from wetting and spreading when the pair of end faces face each other. Therefore, it is possible to suppress mounting defects caused by the wet spread of the solder.

In one embodiment, the piezoelectric element has a substantially rectangular shape, a pair of main surfaces facing each other, a pair of end faces facing each other in the long side direction of the pair of main surfaces, and a pair of short sides of the main surface. It has a pair of sides facing each other in the direction, the first electrode is at least placed on one main surface and one end face, and the second electrode is at least placed on the other main surface and the other end face. The second region may be continuously provided from one side surface to the other side surface in the opposite direction of the pair of side surfaces. In this configuration, it is possible to prevent the solder from wetting and spreading when the pair of end faces face each other. Therefore, it is possible to suppress mounting defects caused by the wet spread of the solder.

In one embodiment, each of the first electrode and the second electrode is configured by arranging a first layer made of Cr, a second layer made of NiCu, and a third layer made of Au in this order from the piezoelectric element side. The second region may be made of an alloy of NiCu and Au. NiCu has lower solder wettability than Au. Therefore, by melting the second layer and the third layer with a laser, for example, to form an alloy of NiCu and Au to provide the second region, the wettability of the second region can be made lower than that of the first region. Further, since the electrical connection is surely secured by the first layer, the function as an electrode can be surely secured even if the second region is provided.

In one embodiment, each of the first electrode and the second electrode is configured by arranging a first layer made of NiCr and a second layer made of Au in this order from the piezoelectric element side, and the first layer. The thickness of the second layer is larger than the thickness of the second layer, and the second region may be made of an alloy of NiCr and Au. NiCr has lower solder wettability than Au. Therefore, by melting the first layer and the second layer with a laser, for example, to form an alloy of NiCr and Au to provide the second region, the wettability of the second region can be made lower than that of the first region. Further, since the thickness of the first layer is larger than the thickness of the second layer, the first layer can surely secure the electrical connection and can surely secure the function as an electrode.

According to one aspect of the present invention, displacement can be efficiently obtained while suppressing mounting defects caused by wet spread of solder.

(A) and (b) are perspective views of the piezoelectric element according to one embodiment. It is a figure which shows the cross-sectional structure along the line II-II in FIG. 1 (a). It is a figure which shows the cross-sectional structure of a piezoelectric element partially enlarged. It is a figure which shows the mounting structure of a piezoelectric element. It is a perspective view which shows a part of the piezoelectric element in the state where the solder is wet and spread. It is a figure which shows the cross-sectional structure of the piezoelectric element which concerns on another embodiment. It is a perspective view of the piezoelectric element which concerns on another embodiment. It is a figure which shows the mounting structure of the piezoelectric element which concerns on other embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and duplicate description will be omitted.

As shown in FIG. 1, the piezoelectric element 1 includes a piezoelectric element 3, a first electrode 5, and a second electrode 7. The piezoelectric element 1 is applied to, for example, a disk device including a magnetic disk. That is, in the dual actuator type disk device, the piezoelectric element 1 is used as the second actuator other than the voice coil motor.

The piezoelectric body 3 has a pair of main surfaces 3a and 3b, a pair of end surfaces 3c and 3d, and a pair of side surfaces 3e and 3f. In the present embodiment, the piezoelectric element 3 has a rectangular parallelepiped shape. Each of the pair of main surfaces 3a and 3b has a substantially rectangular shape. The pair of end faces 3c and 3d face each other in the long side direction of the main faces 3a and 3b. The pair of side surfaces 3e and 3f face each other in the short side direction of the main surfaces 3a and 3b.

The piezoelectric element 3 is made of a piezoelectric ceramic material. Piezoelectric ceramic materials include PZT [Pb (Zr, Ti) O ₃ ], PT (PbTIO ₃ ), PLZT [(Pb, La) (Zr, Ti) O ₃ ], barium titanate (BaTIO ₃ ), and the like. Can be mentioned. In the present embodiment, the piezoelectric element 3 is configured by laminating a piezoelectric element layer which is a sintered body of a ceramic green sheet containing a piezoelectric ceramic material. In the piezoelectric body 3, the stacking direction of the plurality of piezoelectric body layers coincides with the facing direction of the pair of main surfaces 3a and 3b. In the actual piezoelectric body 3, each piezoelectric body layer is integrated to such an extent that the boundary between the piezoelectric body layers cannot be visually recognized.

The piezoelectric body 3 includes an internal electrode 9 and an internal electrode 11. Each of the internal electrodes 9 and 11 has a substantially rectangular shape, for example, in a plan view. Each of the internal electrodes 9 and 11 is made of a conductive material (for example, Ni, Pt, Pd, etc.) usually used as an internal electrode of a laminated electronic element. Each of the internal electrodes 9 and 11 is configured as a sintered body of a conductive paste containing the above conductive material.

As shown in FIG. 1 or 2, the first electrode 5 has a first electrode portion 5a and a second electrode portion 5b. The first electrode portion 5a is arranged on one main surface 3a. The end portion of the first electrode portion 5a on the other end surface 3d side is located on one end surface 3c side with respect to the other end surface 3d. That is, the length of the pair of end faces 3c and 3d of the first electrode portion 5a in the opposite direction is shorter than the length between the pair of end faces 3c and 3d. As a result, the end portion of the first electrode portion 5a on the other end surface 3d side is separated from the end portion of the second electrode portion 7 described later on the one end surface 3c side of the third electrode portion 7c. The second electrode portion 5b is arranged on one end surface 3c. The first electrode portion 5a and the second electrode portion 5b are integrally formed. The second electrode portion 5b is in physical contact with one end of the internal electrode 9. As a result, the first electrode 5 is electrically connected to the internal electrode 9.

The first electrode 5 is composed of a first layer 15, a second layer 17, and a third layer 19. The first layer 15, the second layer 17, and the third layer 19 are arranged (laminated) in this order from the piezoelectric element 3 side. The first layer 15 is made of Cr. The second layer 17 is made of NiCu. The third layer 19 is made of Au. In the present embodiment, the thicknesses of the first layer 15, the second layer 17, and the third layer 19 are, for example, the same.

The second electrode 7 has a first electrode portion 7a, a second electrode portion 7b, and a third electrode portion 7c. The first electrode portion 7a is arranged on the other main surface 3b. The end portion of the first electrode portion 7a on the one end surface 3c side is located closer to the other end surface 3d than the one end surface 3c. That is, the length of the pair of end faces 3c and 3d of the first electrode portion 7a in the opposite direction is shorter than the length between the pair of end faces 3c and 3d. As a result, the end portion of the first electrode portion 7a on the one end surface 3c side is separated from the end portion of the first electrode 5 on the other main surface 3b side of the second electrode portion 5b. The second electrode portion 7b is arranged on the other end face 3d. The third electrode portion 7c is arranged on one main surface 3a. The end portion of the third electrode portion 7c on the one end surface 3c side is separated from the end portion of the first electrode portion 5 of the first electrode 5 on the other end surface 3d side. The second electrode portion 7b is in physical contact with one end of the internal electrode 11. As a result, the second electrode 7 is electrically connected to the internal electrode 11.

The second electrode 7 is composed of a first layer 21, a second layer 23, and a third layer 25. The first layer 21, the second layer 23, and the third layer 25 are arranged in this order from the piezoelectric element 3 side. The first layer 21 is made of Cr. The second layer 23 is made of NiCu. The third layer 25 is made of Au. In the present embodiment, the thicknesses of the first layer 21, the second layer 23, and the third layer 25 are, for example, the same.

The first electrode 5 and the second electrode 7 function as electrodes for applying a voltage to the piezoelectric element 3 via the internal electrodes 9 and 11. In the piezoelectric element 1, the region of the piezoelectric element 3 sandwiched between the first electrode portion 5a of the first electrode 5 and the internal electrode 11, the region sandwiched between the internal electrode 9 and the internal electrode 11, and the second The region sandwiched between the second electrode portion 7b of the electrode 7 and the internal electrode 9 becomes an active portion and is displaced when a voltage is applied.

In the present embodiment, the surface 5s of the first electrode 5 is provided with the first region A1 and the second region A2. The first region A1 is a region on the one end surface 3c side of the first electrode portion 5a. As shown in FIG. 4, the first region A1 is a region in which the piezoelectric element 1 is arranged to face the land electrodes L2 and the solder S2 is applied when the piezoelectric elements 1 are mounted on the land electrodes L1 and L2. The first region A1 is formed by the surface of the third layer 19, which is the outermost layer of the first electrode 5. That is, the first region A1 is formed of Au (first material).

The second region A2 is provided adjacent to the first region A1. The second region A2 is arranged at a position on the active portion of the piezoelectric element 1, that is, at a position where the piezoelectric element 3 is sandwiched between the internal electrodes 11. In the present embodiment, the second region A2 is on the surface 5s of the first electrode portion 5a, one end surface 3c side of the central portion of the lengths of the pair of end faces 3c and 3d of the first electrode portion 5a in the opposite direction. Is located in. The second region A2 is provided from one side surface 3e to the other side surface 3f in the opposite direction of the pair of side surfaces 3e and 3f. The width of the second region A2 (the length of the pair of end faces 3c and 3d in the opposite direction) is smaller than the width of the first region A1.

The second region A2 is formed of a material (second material) having a lower wettability of the solder than Au forming the first region A1. Specifically, as shown in FIG. 3, the second region A2 is formed on the surface of the mixing portion 20 made of an alloy of NiCu forming the second layer 17 and Au forming the third layer 19. Has been done. NiCu has lower solder wettability than Au. The mixing portion 20 is formed, for example, by irradiating a laser. Specifically, the laser is irradiated along the opposite directions of the pair of side surfaces 3e and 3f. At this time, the laser is irradiated from the third layer 19 side so that the laser reaches the second layer 17 and the third layer 19 (so that the first layer 15 is not melted). As a result, NiCu in the second layer 17 and Au in the third layer 19 are melted and mixed by a laser to form a mixing portion 20 made of an alloy. The intensity of the laser is appropriately set according to the characteristics (material, thickness, etc.) of the first electrode 5.

As shown in FIG. 4, the piezoelectric element 1 is mounted on the land electrodes L1 and L2 with solders S1 and S2. Specifically, the third electrode portion 7c of the second electrode 7 of the piezoelectric element 1 and the land electrode L1 are arranged so as to face each other, and the first electrode portion 5a of the first electrode 5 and the land electrode L2 face each other. Arrange as follows. The third electrode portion 7c and the land electrode L1 are joined by the solder S1, and the first electrode portion 5a and the land electrode L2 are joined by the solder S2.

As shown in FIG. 5, when the first electrode portion 5a and the land electrode L2 are joined by the solder S2, the solder S2 wets and spreads in the first region A1 of the first electrode portion 5a (solder S2 in FIG. 5). Is shown with a black fill). When the solder S2 that has spread in the first region A1 reaches the second region A2, the solder S2 has low wettability in the second region A2, so that the solder S2 is suppressed from spreading. Although not shown in FIG. 5, the solder S2 can also wet and spread to the second electrode portion 5b.

As described above, in the piezoelectric element 1 according to the present embodiment, the first region A1 and the second region A2 are provided on the surface 5s of the first electrode 5. The first region A1 is a region to which the solder S2 is applied when the piezoelectric element 1 is solder-mounted. The second region A2 is provided adjacent to the first region A1, and the first material (Au in the present embodiment) forming the first region A1 and the second material having lower wettability than the first material. (NiCu in this embodiment) is mixed and formed. As a result, in the piezoelectric element 1, when the solder S2 is applied to the first region A1, even if the solder S2 gets wet and spreads, when the solder S2 reaches the second region A2, the second region A2 causes the solder S2. Wetting and spreading of the solder S2 is suppressed. Therefore, the amount of the solder S2 between the first electrode 5 and the land electrode L2 can be secured, and it is possible to suppress the occurrence of inclination of the piezoelectric element 1 due to the imbalance between the amount of the solder S1 and the amount of the solder S2. It is possible to suppress the application of stress to the solder S1. As a result, it is possible to suppress mounting defects caused by the wetting and spreading of the solder S2.

Further, in the piezoelectric element 1, the first material and the second material have conductivity, and the second region A2 is provided on the surface 5s of the first electrode 5. That is, the second region A2 is configured as a part of the first electrode 5. Therefore, the second region A2 does not hinder the displacement of the active portion of the piezoelectric element 3. Therefore, in the piezoelectric element 1, the displacement of the active portion can be efficiently obtained.

In the piezoelectric element 1 according to the present embodiment, the second region A2 is provided at a position on the active portion of the piezoelectric element 3 that is displaced by applying a voltage. The second region A2 does not inhibit the displacement of the active portion. Therefore, the configuration of the piezoelectric element 1 is particularly effective in the configuration in which the second region A2 is provided at a position corresponding to the active portion. Further, since the position of the second region A2 is not limited, the first region A1 to which the solder S2 is applied can be secured, and the piezoelectric element 1 can be reliably soldered.

In the piezoelectric element 1 according to the present embodiment, the second region A2 is continuously provided from one side surface 3e to the other side surface 3f in the opposite direction of the pair of side surfaces 3e and 3f. In this configuration, it is possible to prevent the solder S2 from spreading wet on the pair of end faces 3c and 3d facing each other. Therefore, it is possible to suppress mounting defects caused by the wetting and spreading of the solder S2.

In the piezoelectric element 1 according to the present embodiment, the first electrode 5 and the second electrode 7 are the first layers 15 and 21 made of Cr, the second layers 17 and 23 made of NiCu, and the like, respectively, from the piezoelectric element 3 side. The third layers 19 and 25 made of Au are arranged and configured in this order. The second region A2 is made of an alloy of NiCu and Au. NiCu has lower solder wettability than Au. Therefore, by melting the second layer 17 and the third layer 19 with a laser to form an alloy of NiCu and Au to provide the second region A2, the wettability of the second region A2 is lower than that of the first region A1. it can. Further, since the electrical connection is surely secured by the first layer 15, even if the second region A2 is provided, the function as an electrode in the first electrode 5 can be surely secured.

Although the embodiments of the present invention have been described above, the present invention is not necessarily limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof.

In the above embodiment, the first electrode 5 is composed of the first layer 15, the second layer 17, and the third layer 19, and the second electrode 7 is composed of the first layer 21, the second layer 23, and the third layer 25. It was explained as an example. However, the configuration of the first electrode 5 and the second electrode 7 is not limited to this.

For example, as shown in FIG. 6, the first electrode 5 (second electrode 7) of the piezoelectric element 1A may be composed of the first layer 18 and the second layer 19A. The first layer 18 and the second layer 19A are arranged in this order from the piezoelectric element 3 side. The first layer 18 is made of NiCr. The second layer 19A is made of Au. The thickness T1 of the first layer 18 is thicker than the thickness T2 of the second layer 19A. For example, the thickness T1 is twice the thickness T2.

In the piezoelectric element 1A, the second region A2 provided on the surface 5As of the first electrode 5A is a mixing portion 20A made of an alloy of NiCr forming the first layer 18 and Au forming the second layer 19A. It is formed on the surface. NiCr has lower solder wettability than Au. The mixing portion 20A is formed, for example, by irradiation with a laser. Specifically, the laser is irradiated along the opposite directions of the pair of side surfaces 3e and 3f. At this time, the laser is irradiated from the second layer 19A side so that the laser reaches a part of the first layer 18 and the second layer 19A (so as not to melt a part of the first layer 18). As a result, NiCr of the first layer 18 and Au of the second layer 19A are melted and mixed by a laser to form a mixing portion 20A made of an alloy.

In the above embodiment, a mode in which the second region A2 is continuously provided from one side surface 3e to the other side surface 3f in the opposite direction of the pair of side surfaces 3e and 3f has been described as an example. However, the form of the second region is not limited to this. For example, as shown in FIG. 7, a plurality of second regions A2 of the piezoelectric element 1B are provided at predetermined intervals in the opposite directions of the pair of side surfaces 3e and 3f. The second region A2 is provided by forming a mixing portion by, for example, spot irradiation of a laser. In this configuration, the surface tension of the solder S2 in the plurality of second regions A2 can suppress the wetting and spreading of the solder S2. Therefore, it is possible to suppress mounting defects caused by the wetting and spreading of the solder S2.

In the above embodiment, a mode in which the first electrode 5 is provided with the first region A1 and the second region A2 will be described as an example. However, the first region A1 and the second region A2 may be provided on the second electrode 7. Alternatively, as shown in FIG. 8, in the piezoelectric element 1C, the first region A1 and the second region A2 may be provided on the first electrode 5 and the second electrode 7. By providing the second region A2 on the second electrode 7, it is possible to suppress the creeping up of the solder S1. The second region A2 may be provided at a position where the wet spread of the solder should be suppressed according to the shape of the electrode.

In the above embodiment, an example of the material forming the first electrode 5 and the second electrode 7 has been described. However, the material forming the electrode is not limited to the material described in the above embodiment. In the piezoelectric element, the material forming the second region may have a lower wettability than the material forming the first region.

In the above embodiment, a mode in which the mixing portions 20 and 20A are formed by laser irradiation has been described as an example. However, the method for forming the mixing portions 20 and 20A may be another method.

1,1A, 1B, 1C ... Piezoelectric element, 3 ... Piezoelectric element, 3a, 3b ... Main surface, 3c, 3d ... End surface, 3e, 3f ... Side surface, 5 ... First electrode, 5s, 5As ... Surface, 7 ... 2nd electrode, 15, 21 ... 1st layer, 17, 23, 19A ... 2nd layer, 19, 25 ... 3rd layer, A1 ... 1st region, A2 ... 2nd region.

Claims (6)

Piezoelectric body and
A first electrode and a second electrode, which are arranged on the piezoelectric element and for applying a voltage to the piezoelectric element, are provided.
On the surface of at least one of the first electrode and the second electrode, a first region formed of a conductive first material and to which solder is applied at the time of mounting, and a first region adjacent to the first region and described above. A second region formed by including one material and a conductive second material is provided.
The second material has a lower wettability of the solder than the first material.
At least one of the first electrode and the second electrode is configured such that the first layer and the second layer are arranged in this order from the piezoelectric element side.
The second region is a piezoelectric element made of an alloy of the first layer and the material forming the second layer. The piezoelectric element according to claim 1, wherein the second region is provided at a position on an active portion of the piezoelectric body that is displaced by applying the voltage. The piezoelectric elements have a substantially rectangular shape and face each other with a pair of main surfaces, a pair of end faces facing each other in the long side direction of the pair of main surfaces, and a pair of end faces facing each other in the short side direction of the main surfaces. With a pair of opposing sides,
The first electrode is arranged at least on one of the main surfaces and one of the end surfaces.
The second electrode is at least arranged on the other main surface and the other end surface.
The piezoelectric element according to claim 1 or 2, wherein a plurality of the second regions are provided at predetermined intervals in a pair of opposite directions of the side surfaces. The piezoelectric elements have a substantially rectangular shape and face each other with a pair of main surfaces, a pair of end faces facing each other in the long side direction of the pair of main surfaces, and a pair of end faces facing each other in the short side direction of the main surfaces. With a pair of opposing sides,
The first electrode is arranged at least on one of the main surfaces and one of the end surfaces.
The second electrode is at least arranged on the other main surface and the other end surface.
The piezoelectric element according to claim 1 or 2, wherein the second region is continuously provided from one side surface to the other side surface in a direction opposite to the pair of side surfaces. Piezoelectric body and
A first electrode and a second electrode, which are arranged on the piezoelectric element and for applying a voltage to the piezoelectric element, are provided.
On the surface of at least one of the first electrode and the second electrode, a first region formed of a conductive first material and to which solder is applied at the time of mounting, and a first region adjacent to the first region and described above. A second region formed by including one material and a conductive second material is provided.
The second material has a lower wettability of the solder than the first material.
At least one of the first electrode and the second electrode is configured by arranging the first layer, the second layer, and the third layer in this order from the piezoelectric element side.
Configuration wherein each of the first electrode and the second electrode, wherein the piezoelectric element side, wherein the first layer of Cr, the third layer of the second layer and Au consisting NiCu is arranged in this order Has been
The second region is a piezoelectric element made of an alloy of NiCu, which is a material forming the second layer, and Au, which is a material forming the third layer. Each of the first electrode and the second electrode is configured by arranging the first layer made of NiCr and the second layer made of Au in this order from the piezoelectric element side.
The thickness of the first layer is larger than the thickness of the second layer.
The piezoelectric element according to any one of claims 1 to 4, wherein the second region is made of an alloy of NiCr and Au.

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