JP2015026848A - Piezoelectric element and piezoelectric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric element in which variation in the adhesion of resin applied to the side face of a piezoelectric is suppressed between the elements, and to provide a piezoelectric.SOLUTION: A piezoelectric element 40 includes a piezoelectric 43 having a pair of principal surfaces (an upper surface 43a and a lower surface 43b) facing each other, and side faces 43c, 43d, 43e, 43f extending between the pair of principal surfaces so as to coupling them, and a resin 44 covering the side face of the piezoelectric 43. Since the side face of the piezoelectric 43 covered with the resin 44 is bent for the axis line in the facing direction of a pair of principal surfaces (Z direction), lowering of adhesion of the resin due to a non-contact region in a concave part or the residue is less likely to occur, and a resin adhesion of a value as just expected is obtained. As a result, variation in the adhesion between the elements is suppressed effectively in the piezoelectric element 40.

Description

  The present invention relates to a piezoelectric element and a piezoelectric body.

  A piezoelectric element having a pair of main surfaces facing each other and a side surface extending in a facing direction of the pair of main surfaces so as to connect the pair of main surfaces, and a piezoelectric body made of a piezoelectric ceramic material, and the piezoelectric body And a pair of electrodes respectively disposed on a pair of main surfaces are generally known.

  A hard disk drive (HDD) head suspension using the above-described piezoelectric element as an actuator for driving a slider is known.

  Patent Document 1 listed below discloses a technique for suppressing the separation of piezoelectric ceramic particles (generation of particles) from the side surface of such an HDD head suspension by coating a resin on the side surface of the piezoelectric element of the piezoelectric element. Has been.

International Publication No. 2011/16994 JP-A-8-319174

  The inventors have made various studies in anticipation that the generation of particles can be more effectively suppressed by improving the adhesion between the side surface of the piezoelectric body and the resin in the above-described conventional piezoelectric element. In the process, using the technique disclosed in Patent Document 2 above, the side surface of the piezoelectric body is irradiated with laser light to form a fine convex shape and a concave shape to roughen the surface, and with an enlarged surface area and anchor effect. I examined the technology to improve adhesion.

  When the resin enters the concave portion formed on the side surface of the piezoelectric body, an anchor effect can be expected, but the resin does not necessarily enter the concave portion due to various conditions such as resin viscosity, wettability, and uneven dimensions. Absent.

  And in the part where resin does not enter into a concave-shaped part, the non-contact area | region where resin and a piezoelectric material side surface do not contact arises, and it can become a cause of adhesive fall.

  In addition, when the side surface of the piezoelectric body is irradiated with laser light, a fine ceramic piece (so-called residue) that easily peels off is easily formed on the side surface of the piezoelectric body, and this residue can cause a decrease in adhesion.

  Therefore, when the side surface of the piezoelectric body is roughened by irradiating the laser beam due to the surface area expansion and the anchor effect, an unexpected decrease in adhesion occurs due to the above-described cause, and as a result, the adhesion force varies between elements. Can be considered.

  Accordingly, the present invention has been made to solve the above-described problems, and provides a piezoelectric element and a piezoelectric body in which variation in the adhesion force of the resin coated on the side surface of the piezoelectric body is suppressed between the elements. Objective.

  A piezoelectric element according to the present invention includes a piezoelectric body having a pair of main surfaces facing each other, a side surface extending so as to connect the pair of main surfaces, and a resin covering the side surface of the piezoelectric body. Then, the side surface of the piezoelectric body covered with the resin is curved with respect to the axis in the opposing direction of the pair of main surfaces.

  In this piezoelectric element, the area of the piezoelectric body side surface is expanded by making the side surface of the piezoelectric body rough and not increasing the surface area, but by bending it with respect to the axis in the opposing direction of the pair of main surfaces. Therefore, in the piezoelectric element according to the present invention, the adhesion of the resin due to the non-contact region and the residue in the concave portion is unlikely to occur, and the expected resin adhesion can be obtained. Is effectively suppressed.

  A piezoelectric body according to the present invention is a piezoelectric body having a pair of main surfaces facing each other and side surfaces extending so as to connect between the pair of main surfaces, the side surfaces of the pair of main surfaces facing each other. Curved with respect to the axis.

  In this piezoelectric body, the area of the piezoelectric body side surface is expanded by making the side surface of the piezoelectric body rough and not bending the surface area, but by bending it with respect to the axis of the pair of main surfaces facing each other. Therefore, in the piezoelectric body according to the present invention, the adhesion of the resin due to the non-contact region and the residue in the concave portion hardly occurs and the resin adhesion as expected is obtained. Is effectively suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the piezoelectric element and piezoelectric material with which the adhesive force variation of resin coated on the side surface of a piezoelectric material was suppressed between elements are provided.

FIG. 1 is a schematic plan view showing a suspension according to an embodiment of the present invention. FIG. 2 is a plan view of the base plate shown in FIG. FIG. 3 is a plan view of the hinge component shown in FIG. FIG. 4 is an exploded perspective view of a piezoelectric element mounted on the suspension of FIG. 5 is a cross-sectional view taken along the line VV of the piezoelectric element mounted on the suspension of FIG. FIG. 6 is a diagram showing a step in manufacturing the piezoelectric element of FIG. FIG. 7 is a diagram showing a step in manufacturing the piezoelectric element of FIG. FIG. 8 is a diagram showing a step in manufacturing the piezoelectric element of FIG. FIG. 9 is a diagram showing a step in manufacturing the piezoelectric element of FIG. FIG. 10 is a diagram showing a step in manufacturing the piezoelectric element of FIG. FIG. 11 is a view showing a state in which grooves are formed in the piezoelectric substrate. 12A and 12B are SEM photographs of the side surfaces of the piezoelectric body of the piezoelectric element according to the present embodiment, and FIG. 12B is a partially enlarged photograph of FIG. FIGS. 13A and 13B are both SEM photographs of the side surface of the piezoelectric body of the piezoelectric element according to the prior art, and FIG. 13B is a partially enlarged photograph of FIG. FIG. 14 is a diagram showing a piezoelectric substrate used in an experiment for examining the surface state. FIG. 15A is a graph showing the unevenness depth of the side surface, and FIG. 15B is a graph showing the unevenness depth of the surface. FIG. 16 is a graph showing the arithmetic average roughness (Ra) of the side surface and the surface. FIG. 17 is a graph showing the maximum height roughness (Rz) of the side surfaces and the surface. FIG. 18 is an SEM photograph showing a smooth side surface. FIG. 19 is an SEM photograph showing a natural surface.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  A disk apparatus suspension 10 according to an embodiment of the present invention will be described below with reference to FIGS.

  The dual actuator type suspension 10 shown in FIG. 1 includes a load beam 11, a microactuator unit 12, a base plate 13, and a hinge member 14.

  The load beam 11 is made of a metal plate having a spring property with a thickness of, for example, about 100 μm, and a flexure 15 is attached to the load beam 11 at the tip thereof. The flexure 15 is made of a thin plate spring made of metal that is thinner than the load beam 11. A slider 16 constituting a magnetic head is provided at the front end of the flexure 15.

  As shown in FIG. 2, a circular boss hole 21 is formed in the base portion 20 of the base plate 13. Between the base portion 20 and the front end portion 22 of the base plate 13, a pair of openings 23 having a size capable of accommodating a piezoelectric element 40 described later is formed. Between the pair of openings 23, a band-shaped connecting portion 24 is provided that extends in the front-rear direction of the base plate 13 (in the axial direction of the suspension 10). The connecting portion 24 can be bent to some extent in the width direction of the base plate 13 (sway direction indicated by arrow S in FIG. 1).

  A base portion 20 of the base plate 13 is fixed to a tip end portion of an actuator arm driven by a voice coil motor (not shown), and is turned by a voice coil motor. The base plate 13 is made of a metal plate such as stainless steel having a thickness of about 200 μm, for example. In the case of the present embodiment, the actuator base 25 is configured by the base plate 13 and the hinge member 14.

  As shown in FIG. 3, the hinge member 14 includes a base portion 30 that is fixed over the base portion 20 of the base plate 13, a band-shaped bridge portion 31 that is formed at a position corresponding to the connecting portion 24 of the base plate 13, and the base plate 13. It has an intermediate portion 32 formed at a position corresponding to the front end portion 22, a pair of flexible hinge portions 33 that can be elastically deformed in the thickness direction, a tip portion 34 fixed to the load beam 11, and the like. ing. The hinge member 14 is made of a metal plate having a spring property with a plate thickness of, for example, about 50 μm.

  The microactuator unit 12 is mounted with a pair of piezoelectric elements 40 as piezoelectric actuators. Each of the piezoelectric elements 40 has a rectangular flat plate shape, and is housed in the opening 23 of the actuator base 25 so that the longitudinal direction thereof is substantially parallel to the longitudinal direction of the base plate 13 (the axial direction of the suspension 10). Yes.

  Here, the configuration of the piezoelectric element 40 will be described with reference to FIG. For convenience of explanation, the longitudinal direction of the piezoelectric element 40 will be described as the X direction, the lateral direction as the Y direction, and the thickness direction as the Z direction as appropriate.

  The piezoelectric element 40 includes an element body 41 and a pair of electrodes 42A and 42B that cover the element body 41 from the thickness direction (Z direction).

  The element body 41 includes a piezoelectric body 43 and a resin 44.

  The piezoelectric body 43 has a rectangular flat plate shape and is made of a piezoelectric material such as PZT. That is, the piezoelectric body 43 includes an upper surface 43a and a lower surface 43b (a pair of main surfaces) facing each other in the Z direction and four side surfaces (end surfaces) 43c, 43d extending in the Z direction so as to connect the upper surface 43a and the lower surface 43b. 43e, 43f. The four side surfaces 43c, 43d, 43e, and 43f are distinguished into a first side surface pair 43c and a side surface 43d that face each other in the Y direction, and a second side surface pair 43e and a side surface 43f that face each other in the X direction. be able to. Each of the side surfaces 43c, 43d, 43e, and 43f is a smooth surface having an arithmetic average roughness (Ra) of 0.02 to 1.0 μm, and the opposing direction of a pair of main surfaces (described later) ( It is curved with respect to the axis in the Z direction).

  The resin 44 entirely covers the four side surfaces 43c, 43d, 43e, and 43f of the piezoelectric body 43 so as to surround it. The resin 44 includes a resin 45A that covers the side surfaces 43c and 43d orthogonal to the short direction (Y direction) of the piezoelectric body 43, and a resin 45B that covers the side surfaces 43e and 43f orthogonal to the longitudinal direction (X direction) of the piezoelectric body 43. It consists of The resin 45A and the resin 45B are formed at different timings as described in the manufacturing method described later. The resin 45A and the resin 45B are made of an epoxy resin, and the material of the resin 45A and the material of the resin 45B may be the same or different.

  The pair of electrodes 42A and 42B is made of a conductive material such as metal. As the electrode material, metals such as Au, Ag, Cu, Pt, Cr, Ni, and W can be used. Each electrode 42A, 42B is formed so as to cover, for example, the upper and lower surfaces of the element body 41 (that is, the upper and lower surfaces of the piezoelectric body 43 and the upper and lower surfaces of the resin 44).

  According to such a piezoelectric element 40, by applying a voltage between the pair of electrodes 42A and 42B, the piezoelectric body 43 expands and contracts in the longitudinal direction (X direction) and the short direction (Y direction). The entire piezoelectric element 40 expands and contracts in the longitudinal direction (X direction) and the lateral direction (Y direction).

  Next, how the piezoelectric element 40 is mounted on the suspension 10 will be described with reference to FIG.

  When the piezoelectric element 40 is mounted on the suspension 1, the piezoelectric element 40 is accommodated in the opening 23 of the base plate 13 so that the longitudinal direction (X direction) of the piezoelectric element 40 is along the front-rear direction of the base plate 13 (the axial direction of the suspension 10). . At this time, the front end portion of the piezoelectric element 40 is bonded and fixed by the adhesive 50 so as to be supported by the intermediate portion 32 of the hinge member 14. Similarly, the rear end portion of the piezoelectric element 40 is fixed to the base portion 30 of the hinge member 14. It is fixed with an adhesive 50 so as to be supported.

  In order to apply a voltage between the electrodes 42A and 42B of the piezoelectric element 40, electric wirings (not shown) are provided on the electrodes 42A and 42B, respectively. Note that a conductive adhesive may be used as the adhesive 50 described above, and the adhesive 50 may be used as part of the electrical wiring.

  When the pair of piezoelectric elements 40 are mounted on the suspension 10, the voltage applied to the pair of piezoelectric elements 40 is controlled to expand one piezoelectric element 40 by a predetermined length in the longitudinal direction and the other piezoelectric element 40 can be contracted by a predetermined length in the longitudinal direction. Thus, in the suspension 10, the load beam 11 side can be displaced by a desired amount in the width direction (sway direction S) by controlling the expansion and contraction of each of the pair of piezoelectric elements 40.

  Next, a procedure for manufacturing the piezoelectric element 40 will be described with reference to FIGS.

  When the piezoelectric element 40 is manufactured, first, a piezoelectric substrate 62 to be the piezoelectric body 43 is held on a plate-like or tape-like substrate 60, and as shown in FIG. A plurality of grooves 62a arranged in parallel at the same interval G1 are formed. The extending direction of the plurality of grooves 62a corresponds to the longitudinal direction (X direction) of the produced piezoelectric element 40, and the gap G1 of the grooves 62a corresponds to the short direction length (Y direction length) of the piezoelectric body 43. To do. A generally used cutting tool (such as a dicing saw) can be used to form the groove 62a, and the groove 62a is cut to a depth that does not reach the lower surface of the piezoelectric substrate 62. As a cutting tool, a blade having a count of 1000 or smaller (for example, 1500) is used, and the inner surface of the groove 62a is made a smooth surface of Ra 0.02 to 1.0 μm. In addition, the piezoelectric substrate 62 uses a substrate having a thickness of 0.05 to 3 mm, and the substrate is prepared by cutting out from a sheet method or a sintered body.

  Next, as shown in FIG. 7, the upper surface of the piezoelectric substrate 62 is covered with a thermosetting resin 64 to be the resin 45A by a printing method or the like. Thereby, the resin 64 is filled in each of the plurality of grooves 62 a formed on the upper surface of the piezoelectric substrate 62. After filling, the resin 64 is cured by heating at a predetermined thermosetting temperature (for example, 80 ° C.).

  Subsequently, as shown in FIG. 8, a plurality of parallel lines arranged at the same interval G2 on the upper surface of the piezoelectric substrate 62 covered with the resin 64 along the direction (Y direction) orthogonal to the extending direction of the groove 62a. The groove 62b is formed. The extending direction of the plurality of grooves 62b corresponds to the short direction (Y direction) of the piezoelectric element 40 to be manufactured, and the interval G2 between the grooves 62b corresponds to the length in the longitudinal direction of the piezoelectric body 43 (length in the X direction). To do. As in the formation of the groove 62a, a generally used cutting tool can be used to form the groove 62b, and the groove 62b is cut to substantially the same depth as the groove 62a. At that time, as shown in FIG. 8, the piezoelectric substrate 62 and the resin 64 are integrally cut. Similarly to the formation of the groove 62a, the groove 62b is formed using a blade having a count of 1000 or finer (for example, 1500) as a cutting tool, and the inner surface of the groove 62b is Ra 0.02 to 1.0 μm. Make the surface smooth.

  Then, as shown in FIG. 9, the upper surface of the piezoelectric substrate 62 covered with the resin 64 is covered with a thermosetting resin 66 to be the resin 45B by a printing method or the like. Thereby, the resin 66 is filled in each of the plurality of grooves 62b described above. After filling, the resin 66 is cured by heating at a predetermined thermosetting temperature (for example, 80 ° C.).

  Further, the piezoelectric substrate 62 is thinned along a plane (XY plane) orthogonal to the thickness direction, for example, by polishing, and a thin plate 68 having a thickness D shown in FIG. 10 is taken out. The thickness D of the thin plate 68 obtained at this time corresponds to the thickness of the piezoelectric body 43 of the manufactured piezoelectric element 40. Since the thin plate 68 is taken out at a position shallower than the grooves 62 a and 62 b formed in the piezoelectric substrate 62, the piezoelectric substrate 62 is partitioned by the resin 64 and the resin 66 in a lattice shape in the thin plate 68.

  Thereafter, electrode films (not shown) to be the electrodes 42A and 42B are formed on the upper and lower surfaces of the thin plate 68 by sputtering or plating, and along the intermediate line L1 of the resin 64 and the intermediate line L2 of the resin 66. Cut into a grid to make chips. Thereby, the piezoelectric element 40 shown in FIG. 4 is obtained. For the electrode shape, a method such as sputtering, plating or baking is appropriately selected. After the electrode is formed, it is polarized. Depending on the application, it may be a piezoelectric element array.

  In FIG. 6, the groove 62a of the piezoelectric substrate 62 is illustrated in the form of a square groove, but the cutting tool used in the present embodiment is gradually narrower toward the tip as shown in FIG. Therefore, the inner surface of the groove 62a is curved similarly to the blade shape. That is, the groove 62a of the piezoelectric substrate 62 is curved with respect to the axis line in the depth direction (Z direction) so that the width becomes gradually narrower in the depth direction. Therefore, when the thin plate 68 is taken out from the piezoelectric substrate 62, the surface is curved, and the side surface 43c (and the side surface 43d) of the piezoelectric body 43 is curved. A similar U-shaped blade 70 is used to form the groove 62b shown in FIG. 8, and the side surfaces 43e and 43f of the piezoelectric body 43 are also curved.

  As described above in detail, the piezoelectric element 40 according to this embodiment includes a pair of main surfaces (upper surface 43a and lower surface 43b) facing each other and side surfaces 43c, 43d extending so as to connect the pair of main surfaces. 43e and 43f, and a piezoelectric element 43 including a resin 44 covering the side surface of the piezoelectric body 43. The side surface of the piezoelectric body 43 covered with the resin 44 has an arithmetic mean roughness (Ra ) Is a smooth surface of 0.02 to 1.0 μm.

  FIG. 12 shows an SEM photograph of the side surface of the piezoelectric body having an arithmetic average roughness (Ra) of 0.5 μm, and FIG. 13 shows a piezoelectric body according to the prior art having an arithmetic average roughness (Ra) of 2.0 μm. A side SEM photograph is shown. As shown in FIG. 12, a smooth surface having an arithmetic average roughness (Ra) in the range of 0.02 to 1.0 μm is finer on the side surface of the piezoelectric body than the side surface of the piezoelectric body according to the prior art shown in FIG. There are very few concave shapes.

  Therefore, in the piezoelectric element 40, even if the resin 44 does not enter the concave portion, since the number of fine concave shapes is small in the first place, the resin 44 and the piezoelectric side surfaces 43c, 43d, 43e, 43f Non-contact areas that do not contact are less likely to occur. Also, from FIG. 12, the piezoelectric side surfaces 43c, 43d, 43e, and 43f are not rough surfaces (that is, not roughened by laser irradiation or the like), and therefore, compared with the piezoelectric side surfaces according to the prior art shown in FIG. It is also clear that very little residue is present on the sides.

  Therefore, in the piezoelectric element 40, the resin adhesiveness is hardly reduced due to the non-contact region and the residue in the concave portion, and the resin adhesive force as expected can be obtained. As a result, in the piezoelectric element 40, variation in adhesion between elements is effectively suppressed.

  Moreover, in the piezoelectric element 40, as described with reference to FIG. 11, the side surfaces 43c, 43d, 43e, and 43f of the piezoelectric body 43 are curved with respect to the axis in the depth direction (Z direction). In this case, the area expansion of the side surface of the piezoelectric body is realized as compared with the surface that is not curved straight with respect to the axis in the depth direction (Z direction). That is, since the side surfaces 43c, 43d, 43e, and 43f are not roughened, the area cannot be enlarged by roughening, but the area can be enlarged by curving as described above. The contact area between the piezoelectric body and the side surface of the piezoelectric body is increased to improve the adhesion.

  The inventors conducted the following experiment in order to examine the surface roughness of the side surface of the piezoelectric body in more detail.

That is, a fired piezoelectric substrate 80 made of PZT (solid solution of PbZrO ₃ —PbTiO ₃ , 55C) as shown in FIG. Then, the surface roughness of the exposed side surface 80a was measured (according to JISB 0601: 2001). As a comparison target, a natural substrate surface 80b was adopted. For measurement, a three-dimensional measuring machine was used to measure the unevenness depth of the side surface 80a and the surface 80b under the conditions of a cutoff wavelength of 0.08 mm, a measurement length of 1 mm, and a measurement pitch of 1 μm.

  The measurement results were as shown in the graph of FIG. In the graph relating to the side surface 80a shown in FIG. 15A, the ratio of the dents having a depth of 1 μm or more was low, and the frequency was 6.8 per 100 μm length. On the other hand, in the graph relating to the surface 80b shown in FIG. 15B, the ratio of dents having a depth of 1 μm or more was high, and the frequency was 7.8 per 100 μm length. From this result, it was found that the smooth side surface obtained by the 1000th blade has a lower frequency of dents of 1 μm or more than the natural surface.

  Moreover, when the surface roughness (Ra, Rz) of the side surface 80a and the surface 80b was calculated | required, it was as the graph of FIG. As described above, the arithmetic average roughness (Ra) and the maximum height roughness (Rz) were both rougher on the side surface 80a than on the surface 80b.

  Furthermore, the results of observing the surface with a scanning electron microscope (SEM) are as shown in FIGS. The SEM photograph in FIG. 18 shows the smooth side obtained with the 1500th blade. The SEM photograph in FIG. 19 shows the natural surface.

DESCRIPTION OF SYMBOLS 10 ... Suspension, 40 ... Piezoelectric element, 42A, 42B ... Electrode, 43 ... Piezoelectric body, 43a ... Upper surface, 43b ... Lower surface, 43c, 43d, 43e, 43f ... Side surface, 44, 45A, 45B ... Resin.

Claims (2)

A piezoelectric body having a pair of main surfaces facing each other and a side surface extending so as to connect between the pair of main surfaces;
A resin covering the side surface of the piezoelectric body;
A piezoelectric element comprising:
A piezoelectric element, wherein a side surface of the piezoelectric body covered with the resin is curved with respect to an axis in a direction opposite to a pair of main surfaces. A piezoelectric body having a pair of main surfaces facing each other and a side surface extending so as to connect between the pair of main surfaces,
The piezoelectric body, wherein the side surface is curved with respect to an axis in a direction opposite to the pair of main surfaces.