JP2014078624A - Piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric element in which dispersion of adhesion force of a resin coated on a side face of a piezoelectric material is suppressed between elements.SOLUTION: A piezoelectric element 40 includes: a piezoelectric material 43 having a pair of principal faces (upper face 43a and lower face 43b) which face each other and sides 43c, 43d, 43e and 43f extending to couple a pair of principal faces; a resin 44 for covering the side faces of the piezoelectric material 43; and electrodes 42A and 42B arranged on the principal faces of the piezoelectric material 43. Since the principal faces 43a and 43b where the electrodes 42A and 42B are arranged are smooth faces of Ra0.01 to 0.2 μm, there are very few residues existing on the principal faces 43a and 43b compared to a case where roughening processing is performed, and deterioration of adhesion property of the electrode due to the residues is difficult to occur. Thus, electrode adhesion force which is the same as an expected value, is obtained and dispersion of the adhesion force between the elements is effectively suppressed.

Description

  The present invention relates to a piezoelectric element.

  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

  In the conventional piezoelectric element described above, particles can be generated not only from the side surface of the piezoelectric body but also from the main surface of the piezoelectric body.

  In view of this, the inventors have repeated various studies from the prediction that the generation of particles can be effectively suppressed by improving the adhesion between the piezoelectric main surface and the electrodes in the above-described conventional piezoelectric element. It was. In the process, using the technique disclosed in Patent Document 2 above, the main 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 the adhesion accompanying the increase in surface area I examined the improvement.

  However, when the main surface is roughened by laser light irradiation or polishing, fine ceramic pieces (so-called residues) that easily peel off are easily formed on the main surface, and this residue is formed between the main surface and the electrode. May cause a decrease in adhesion. Therefore, it is considered that an unexpected decrease in adhesion occurs due to the residue, and as a result, the adhesion force varies between elements.

  Accordingly, the present invention has been made to solve the above-described problem, and an object thereof is to provide a piezoelectric element that suppresses variations in adhesion between electrodes disposed on the principal surface of the piezoelectric body between elements. To do.

  A piezoelectric element according to the present invention includes a piezoelectric body having a pair of main surfaces facing each other and side surfaces extending so as to connect the pair of main surfaces, a resin covering the side surfaces of the piezoelectric body, and at least a piezoelectric body. An electrode disposed on each main surface, wherein the main surface on which the electrode is disposed is a smooth surface of Ra 0.01 to 0.2 μm.

  In the piezoelectric element of the present invention, the main surface of the piezoelectric body on which the electrodes are arranged is a smooth surface, and the roughening process is not performed on the main surface. Therefore, the residue existing on the main surface is extremely small, and the electrode adhesion due to the residue is less likely to occur. Therefore, the electrode adhesion force as expected is obtained, and the variation in adhesion force between elements is effectively suppressed.

  Further, the surface roughness (Ra) of the main surface of the piezoelectric body on which the electrode is disposed may be smaller than the surface roughness of the natural surface of the piezoelectric body, and the main surface of the piezoelectric body on which the electrode is disposed is polished. The aspect which is the grinding | polishing surface to which the process was given may be sufficient.

  ADVANTAGE OF THE INVENTION According to this invention, the piezoelectric element which suppressed the contact | adhesion power variation of the electrode arrange | positioned at the main surface of a piezoelectric material between elements is 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.

  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 30 that is fixed to be overlapped with the base 20 of the base plate 13, a strip-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 can be 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. it can. The upper surface 43a and the lower surface 43b are polished surfaces that have been subjected to a polishing process as will be described later, and each has a smooth surface with an arithmetic average roughness (Ra) of 0.01 to 0.2 μm (for example, 0.02 μm). is there. This surface roughness was measured at a cut-off wavelength of 0.025 mm using a surface roughness profile measuring machine (SURFCOM) manufactured by Tokyo Seimitsu Co., Ltd. Since the surface roughness of the natural surface of a general PZT piezoelectric substrate is about Ra 0.35 μm, the surface roughness of the upper surface 43a and the lower surface 43b is smaller than the surface roughness of the natural surface.

  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.).

  Furthermore, the piezoelectric substrate 62 is thinned along a plane (XY plane) orthogonal to the thickness direction 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. For example, a 1500-th wheel is used for the polishing, and as a result, the upper surface 43a and the lower surface 43b are smooth surfaces of Ra 0.01 to 0.2 μm (for example, 0.02 μm).

  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.

  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. A piezoelectric element comprising: a piezoelectric body 43 having 43e and 43f; a resin 44 covering a side surface of the piezoelectric body 43; and electrodes 42A and 42B disposed on the respective main surfaces of the piezoelectric body 43, The main surfaces 43a and 43b on which 42A and 42B are arranged are smooth surfaces.

  That is, the main surfaces 43a and 43b on which the electrodes 42A and 42B are arranged are smooth surfaces, and the main surfaces 43a and 43b are not subjected to roughening treatment such as laser light irradiation or polishing. Therefore, compared to the case where the roughening treatment is performed, the residue existing on the main surfaces 43a and 43b is extremely small, and the adhesion of the electrode due to the residue is less likely to occur. Therefore, the electrode adhesion force as expected is obtained, and the variation in adhesion force between elements is effectively suppressed.

  The electrodes 42A and 42B do not necessarily need to be formed so as to cover the upper and lower surfaces of the element body 41, but cover only the upper and lower surfaces 43a and 43b of the piezoelectric body 43 and do not cover the upper and lower surfaces of the resin 44. There may be. However, when the piezoelectric element 40 is manufactured according to the manufacturing method described above, the electrodes 42A and 42B are preferably formed so as to cover the upper and lower surfaces of the element body 41 from the viewpoint of ease of manufacture.

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 (3)

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;
Electrodes arranged on at least the main surfaces of the piezoelectric body;
A piezoelectric element comprising:
A piezoelectric element, wherein a main surface on which the electrode is disposed is a smooth surface having a Ra of 0.01 to 0.2 μm.   2. The piezoelectric element according to claim 1, wherein a surface roughness (Ra) of a main surface of the piezoelectric body on which the electrodes are arranged is smaller than a surface roughness of a natural surface of the piezoelectric body. 3. The piezoelectric element according to claim 1, wherein a main surface of the piezoelectric body on which the electrode is disposed is a polished surface subjected to a polishing process.

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