Multi-layer PZT electrode configuration for increasing suspension stroke

Abstract

To provide a microactuator for suspensions for disk devices, and an assembly for the microactuator.SOLUTION: In a dual stage actuated (DSA) suspension 40, a piezoelectric actuator assembly 39 includes: a first PZT layer 41 including a top surface and a bottom surface; a second PZT layer 42 including a top surface and a bottom surface, the bottom surface of the second PZT layer disposed over the top surface of the first PZT layer; a third PZT layer 43 including a top surface and a bottom surface, the bottom surface of the third PZT layer disposed over the top surface of the second PZT layer; a first electrode 46A; a second electrode 46B; a third electrode 46C; and a fourth electrode 46D. The third electrode is configured to be shorter than the second electrode such that the active PZT length of the second PZT layer and the third PZT layer is shorter than the active PZT length of the first PZT layer.SELECTED DRAWING: Figure 4A

Description

Technical Field

[0001] (Cross - reference to related applications) This application claims priority from U.S. Provisional Application No. 62 / 730,979, filed on September 13, 2018, the entire contents of which are incorporated herein by reference.

[0002] (Technical Field) Embodiments of the present invention relate to the field of suspensions for disk drives. More specifically, it relates to the field of micro - actuators for suspensions for disk devices.

Background Art

[0003] A general disk drive unit includes a rotating magnetic disk containing a magnetic recording pattern of 1s and 0s that constitutes data stored on the disk drive. The magnetic disk is driven by a drive motor. The disk drive unit further includes a disk drive suspension to which magnetic read / write is attached near the distal end of a load beam. The "proximal" end in the suspension or load beam is the supported end, i.e., the end closest to the base plate that is machined or attached to the actuator arm. The "distal" end in the suspension or load beam is the end opposite the proximal end, i.e., the "distal" end is a cantilever end.

[0004] The suspension is connected to the actuator arm and is connected to a voice coil motor that moves the suspension in an arc to position the head slider above the appropriate data track of the data disk. The head slider is mounted on a gimbal that rocks the slider back - and - forth, left - and - right, so that the head slider can follow the appropriate data track of the disk while tolerating various variations such as vibrations of the disk, inertial events such as bumping, and irregularities on the disk surface.

[0005] A one-stage actuated disk drive suspension and a two-stage actuated (DSA) suspension are known. In a one-stage actuated suspension, only a voice coil motor moves the suspension.

[0006] In a DSA suspension, a small actuator disposed on the suspension moves the head slider to position the head slider above an appropriate data track. The actuator provides finer positioning of the head slider and a higher servo bandwidth than a voice coil motor. The actuator may be disposed at various locations on the suspension depending on a particular DSA suspension design. Generally, the left and right actuators act in a push-pull manner to rotate a load beam or a distal end of the load beam. Some of the early DSA suspensions disposed the actuator on a base plate and rotated the entire load beam by the operation of piezoelectric micro actuators (PZTs). The actuators used in DSA suspensions are referred to as milli actuators or micro actuators. As the data track width continues to shrink, DSA suspensions have become common in recent years. SUMMARY OF THE INVENTION

[0007] A piezoelectric actuator assembly is described. The assembly includes a first layer including a single active piezoelectric layer, the first layer including a top surface and a bottom surface. The assembly includes a single act It also includes a second layer as the piezoelectric layer. The second layer has an upper surface and a bottom surface, and the bottom surface of the second layer is disposed above the upper surface of the first layer. The assembly includes a third layer as a single active piezoelectric layer. The third layer has an upper surface and a bottom surface, and the bottom surface of the third layer is disposed above the upper surface of the second layer. The first electrode is disposed on at least a part of the bottom surface of the first layer. The second electrode is disposed on at least a part between the first layer and the second layer. The third electrode is disposed on at least a part between the second layer and the third layer. The fourth electrode is disposed on at least a part of the upper surface of the third layer. The third electrode is configured to be shorter than the second electrode such that the length of the active PZT of the second layer and the third layer is shorter than the length of the active PZT of the first layer.

[0008] The above summary is not intended to represent each embodiment or all aspects of the present disclosure. Further, the above summary merely provides some examples of the novel aspects and features shown herein. The above and other features and advantages of the present disclosure will be readily apparent from the detailed description of the embodiments and aspects for carrying out the invention when taken in conjunction with the accompanying drawings and the claims.

[0009] To explain how the advantages and features of the present disclosure are obtained, embodiments of the present disclosure are made with reference to specific examples shown in the accompanying drawings. These drawings show merely exemplary aspects of the present disclosure and are thus not to be regarded as limiting its scope. Those principles are shown and described with additional particularity and detail by using the following drawings.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

Figure 6

Figure 7

[0011] Embodiments of the present disclosure are described with reference to the accompanying drawings, and the same reference numerals are used throughout the drawings to indicate similar or equivalent elements. The drawings are not drawn to scale and are provided for illustrative purposes. Some aspects of the present embodiments are described below with reference to examples of applications, and are not intended to limit the scope of the present disclosure. It should be understood that many specific details, relationships, and methods are shown to provide a complete understanding of the embodiments of the present invention. However, those skilled in the art will readily recognize that the present invention can be practiced without one or more of these specific details or using other methods. In other instances, well-known structures or operations are not shown in detail to avoid obscuring the embodiments of the present invention. Embodiments of the present invention are not limited to the order of the acts or events described, since some acts may occur in a different order and / or concurrently with other acts or events. Further, not all of the acts or events described are necessary for practicing the method according to embodiments of the present invention.

[0012] Figure 1 shows a cross-sectional view of a conventional DSA suspension 10 and a microactuator assembly 9. Electrostatic actuators and other types of microactuator motors have been proposed and used, but piezoelectric elements are often used as microactuator motors. Other piezoelectric materials are also known and used, but generally the piezoelectric material used is lead zirconate titanate (PZT). In the following description and claims, for simplicity, the microactuator is often referred to in abbreviated form as "PZT", but it is recognized that the piezoelectric material need not be lead zirconate titanate. Accordingly, the term "PZT" as used herein can refer to any piezoelectric material or any piezoelectric device made of any piezoelectric material.

[0013] The microactuator assembly 9 may include a first PZT layer 11, a second PZT layer 12, and a third PZT layer 13. The first PZT layer 11 may be the bottom layer of the microactuator assembly 9. The first PZT layer 11 may have an active PZT 11A and an inactive PZT 11B. The second PZT layer 12 may be the middle layer of the microactuator assembly 9. The second PZT layer 12 may have an active PZT 12A and an inactive PZT 12B. The first PZT layer 11 may be adhered to the underside of the second PZT layer 12. The third PZT layer 13 may be the upper layer of the microactuator assembly 9. The third PZT layer 13 may have an active PZT 13A and an inactive PZT 13B. The third PZT layer 13 may be adhered to the second PZT layer 12 on the upper surface of the second PZT layer 12.

[0014] The microactuator assembly 9 is connected to the trace gimbal flexure 15 of the DSA suspension 10 using a conductive epoxy (ECA) 14. In some embodiments, the trace gimbal flexure 15 and the ECA 14 may be separated by a gold layer. The gold layer provides corrosion resistance and may improve conductivity to the trace gimbal flexure 15.

[0015] Generally, when the conventional microactuator assembly 9 is used as the DSA suspension 10, all three layers of PZT electrodes are maximized aiming for a higher stroke. Since the first PZT layer 11 is bonded to the trace gimbal strain portion 15, it has an inactive PZT portion longer than those of the second PZT layer 12 and the third PZT layer 13. FIG. 1 shows that the active length A of the first PZT layer 11 is shorter than the active length B of the second PZT layer 12 and the active length C of the third PZT layer 13.

[0016] FIG. 2 shows the conventional DSA assembly 10 in the extension mode. As described with respect to FIG. 1, since the active lengths C and B are longer than the active length A, the third PZT layer 13 and the second PZT layer 12 are assumed to extend longer than the first PZT layer 11. However, since those layers are bonded to each other, the unbalanced extension between the three PZT layers causes the PZT to curve into a convex shape as shown in FIG. 2. Furthermore, since the first PZT layer 11 is bonded to the trace gimbal strain portion 15 at the proximal and distal ends, the extension of the first PZT layer 11 is further suppressed, the convex-shaped curvature further increases, and a negative stroke displacement δ1 is brought about to reduce the total stroke under the PZT extension mode.

[0017] FIG. 3 shows the conventional DSA assembly 10 in the contraction mode. Since the active lengths C and B are longer than the active length A, the third PZT layer 13 and the second PZT layer 12 are assumed to contract longer than the first PZT layer 11. However, since those layers are bonded to each other, the unbalanced contraction between the three PZT layers causes the PZT to curve into a concave shape as shown in FIG. 3. Furthermore, since the first PZT layer 11 is bonded to the trace gimbal strain portion 15 at the proximal and distal ends, the extension of the first PZT layer 11 is further suppressed, the concave-shaped curvature further increases, and a positive stroke displacement δ2 is brought about to reduce the total stroke under the PZT contraction mode. Therefore, due to the electrode length configuration in the PZT layer, the conventional microactuator The TA assembly 9 has a low stroke under PZT expansion and contraction modes. This application provides a novel configuration of the micro - actuator assembly 9 to solve the problem of stroke reduction and increase the suspension stroke.

[0018] FIG. 4A shows a cross - sectional view of a DSA suspension 40 and a micro - actuator assembly 39 according to an embodiment of the present disclosure. The micro - actuator assembly 39 may include a first PZT layer 41, a second PZT layer 42, and a third PZT layer 43. The first PZT layer 41 may have an active PZT 41A and an inactive PZT 41B. The second PZT layer 42 may have an active PZT 42A and an inactive PZT 42B. The third PZT layer 43 may have an active PZT 43A and an inactive PZT 43B.

[0019] The first PZT layer 41 may be the bottom layer of the micro - actuator assembly 39. The second PZT layer 42 may be the middle layer of the micro - actuator assembly 39. The first PZT layer 41 may be adhered to the lower side of the second PZT layer 42. The third PZT layer 43 may be the upper layer of the micro - actuator assembly 39. The third PZT layer 43 may be adhered to the second PZT layer 42 on the upper surface of the second PZT layer 42. The micro - actuator assembly 39 is electrically connected to a DSA suspension 40 including a trace gimbal flexure 45 via a conductive epoxy (ECA) 44. In some embodiments, the trace gimbal flexure 45 and the ECA 44 may be separated by a gold layer. The gold layer provides corrosion resistance and may improve conductivity to the trace gimbal flexure 45.

[0020] As shown in FIG. 4A, the lengths of the active PZT of the various layers and the lengths of the PZT electrodes 46 between those layers are different. The PZT electrode (46B) between the second PZT layer 42 and the third PZT layer 43 can be shortened so that the active length 4B of the second PZT layer 42 and the active length 4C of the third PZT layer 43 are shorter than the active length 4A of the first PZT layer 41. Since the second PZT layer 42 and the third PZT layer 43 have active lengths 4B and 4C that are shorter than the active length 4A of the first PZT layer 41, the second PZT layer 42 and the third PZT layer 43 have a shorter extension than the first PZT layer 41 in the PZT extension mode. Thereby, the microactuator 39 curves into a concave shape as shown in the upper figure of FIG. 4B, and a positive stroke displacement δ4a occurs in the extension mode to increase the total stroke. Conversely, in the PZT contraction mode, since the second PZT layer 42 and the third PZT layer 43 have active lengths 4B and 4C that are shorter than the active length 4A of the first PZT layer 41, the second PZT layer 42 and the third PZT layer 43 have a shorter contraction than the first PZT layer 41 in the PZT contraction mode. Thereby, the microactuator 39 curves into a convex shape as shown in the lower figure of FIG. 4B, and a negative stroke displacement δ4b occurs in the PZT contraction mode to increase the total stroke. In some embodiments, the PZT electrode 46B between the second PZT layer 42 and the third PZT layer 43 can be 0.05 mm to 0.15 mm shorter than the PZT electrode 46D disposed on the first PZT layer 41, and the stroke of the microactuator assembly 39 can be increased by 5 to 10%. In some embodiments, the PZT electrode 46B between the second PZT layer 42 and the third PZT layer 43 can be 0.12 mm shorter than the PZT electrode 46D disposed on the first PZT layer 41, and the stroke of the microactuator assembly 39 can be increased by 7.3%.

[0021] Figure 5 shows another embodiment of the microactuator assembly 39 as part of the DSA suspension 40. As shown in Figure 5, the lengths of the active PZT in various layers and the length of the PZT electrode 46 are different. The PZT electrode 46A disposed on the active PZT 43A of the third PZT layer 43 is short so that the active length 5C of the third PZT layer 43 is shorter than the active length 5B of the second PZT layer 42 and the active length 5A of the first PZT layer 41. In some embodiments, the PZT electrode 46A disposed on the active PZT 43A of the third PZT layer 43 can be 0.10 - 0.30 mm shorter than the PZT electrode 46C disposed on the active PZT 41A of the first PZT layer 41. When the PZT electrode 46A disposed on the active PZT 43A of the third PZT layer 43 is short within this range, the stroke of the microactuator assembly 39 can increase by 15 - 25%. According to some embodiments, the PZT electrode 46A disposed on the active PZT 43A of the third PZT layer 43 can be 0.2 mm shorter than the PZT electrode 46C disposed on the active PZT 41A of the first PZT layer 41, and the stroke of the microactuator assembly 39 can increase by 18.6%. When the electrode 46A is short within this range, the stroke of the microactuator assembly 39 can increase by 15 - 25%. According to some embodiments, the PZT electrode 46A disposed on the active PZT 43A of the third PZT layer 43 can be 0.2 mm shorter than the PZT electrode 46C disposed on the active PZT 41A of the first PZT layer 41, and the stroke of the microactuator assembly 39 can increase by 18.6%.

[0022] Figure 6 shows a cross-sectional view of a two-layer microactuator assembly 60 according to an embodiment of the present disclosure. The microactuator assembly 60 includes a first PZT layer 61 and a second PZT layer 62. The first PZT layer 61 is configured to have an active PZT 61A and an inactive PZT 61B. The second PZT layer 62 is configured to have an active PZT 62A and an inactive PZT 62B.

[0023] As shown in FIG. 6, the lengths of the active PZT of the various layers and the lengths of the PZT electrodes 66 therebetween are different. The PZT electrode (66B) between the first PZT layer 61 and the second PZT layer 62 is configured such that the active length 68A of the second PZT layer 62 is shorter than the active length 68B of the first PZT layer 61. As a result, as described herein, in the PZT extension mode, a beneficial curvature profile such as a concave shape is enabled. Conversely, the microactuator 60 in the PZT contraction mode is configured to curve in a convex shape to increase the total stroke, as described herein. Embodiments of the microactuator 60 include PZT layers and PZT electrodes configured using the techniques described herein.

[0024] FIG. 7 shows a cross-sectional view of a four-layer microactuator assembly 70 according to an embodiment of the present disclosure. The microactuator assembly 70 includes a first PZT layer 71, a second PZT layer 72, a third PZT layer 73, and a fourth PZT layer 74. The first PZT layer 71 is configured to have an active PZT 71A and an inactive PZT 71B. The second PZT layer 72 is configured to have an active PZT 72A and an inactive PZT 72B. The third PZT layer 73 is configured to have an active PZT 73A and an inactive PZT 73B. The fourth PZT layer 74 is configured to have an active PZT 74A and an inactive PZT 74B.

[0025] As shown in FIG. 7, the lengths of the active PZT of the various layers are different from the lengths of the PZT electrodes 76 therebetween. The PZT electrode 76 is configured such that the active length 78B of the fourth PZT layer 74 is shorter than the active length 78C of the first PZT layer 71. The PZT electrode 76 is further configured such that the active length 78B of the fourth PZT layer 74 is shorter than the active length 78A of the second PZT layer 72. The PZT electrode 76 is further configured such that the active length 78B of the fourth PZT layer 74 is shorter than the active length 78D of the third PZT layer 73. As a result, as described herein, a beneficial curved profile such as a concave shape is enabled under the PZT extension mode. Conversely, the microactuator assembly 70 is configured to curve in a convex shape in order to increase the total stroke under the PZT contraction mode. Embodiments of the microactuator 70 include PZT layers and PZT electrodes configured using the techniques described herein.

[0026] The embodiments described herein solve the problems with conventional multi-layer PZT electrode configurations that can produce low stroke. Those configurations result in a low total stroke because the PZT can deform into a convex shape in the extension mode and into a concave shape in the contraction mode. Conversely, the present invention allows the PZT to deform into a concave shape in the extension mode and into a convex shape in the contraction mode in order to increase the total stroke.

[0027] The foregoing description of the disclosure is provided to enable a person skilled in the art to make or use the disclosure. . Various modifications to the disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the disclosure. Accordingly, the disclosure is not intended to be limited to the embodiments and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein that do not conflict with each other.

Claims

1. A piezoelectric actuator assembly having a first end portion and a second end portion, comprising a first layer including a single active piezoelectric layer and having a top surface and a bottom surface, a second layer including a single active piezoelectric layer and having a top surface and a bottom surface, the bottom surface of which is disposed above the top surface of the first layer, a first electrode disposed on at least a part of the bottom surface of the first layer, a second electrode disposed on at least a part between the first layer and the second layer, and a third electrode disposed on at least a part of the top surface of the second layer, wherein the third electrode is configured to be shorter than the first electrode such that the length of the active piezoelectric layer of the second layer is shorter than the length of the active piezoelectric layer of the first layer, the second electrode is configured to be longer than the first electrode and the third electrode, the second layer has a shorter elongation than the first layer in the PZT elongation mode, whereby the piezoelectric actuator assembly is curved into a concave shape and the stroke is increased, the second layer has a shorter contraction than the first layer in the PZT contraction mode, whereby the piezoelectric actuator assembly is curved into a convex shape and the stroke is increased,

2. each of the first layer and the second layer includes an inactive portion, and the inactive portions of each of the first layer and the second layer are disposed at the first end portion of the piezoelectric actuator assembly. The piezoelectric actuator assembly according to claim 1.

3. The piezoelectric actuator assembly according to claim 1, wherein the first electrode and the third electrode are connected at the first end portion of the piezoelectric actuator assembly to cover the first end portions of the first layer and the second layer.

4. The piezoelectric actuator assembly according to claim 1, wherein the second electrode covers the second end portions of the first layer and the second layer and the second end portion of the piezoelectric actuator assembly so as to be disposed on the top surface of the second layer and a part of the bottom surface of the first layer.

5. The piezoelectric actuator assembly according to claim 1, wherein the third electrode is configured to be 0.05 to 0.15 mm shorter than the second electrode.

6. The piezoelectric actuator assembly according to claim 5, wherein the third electrode is configured to be 0.12 mm shorter than the second electrode.

7. A microactuator, A first layer including a single active piezoelectric layer and having an upper surface and a bottom surface, A second layer including a single active piezoelectric layer and having an upper surface and a bottom surface, the bottom surface being disposed above the upper surface of the first layer, A first electrode disposed on at least a part of the bottom surface of the first layer, A second electrode disposed on at least a part between the first layer and the second layer, A third electrode disposed on at least a part of the upper surface of the second layer, and The third electrode is configured to be shorter than the first electrode such that the length of the active piezoelectric layer of the second layer is shorter than the length of the active piezoelectric layer of the first layer, The second electrode is configured to be longer than the first electrode and the third electrode, a micro actuator.

8. The second layer has a shorter elongation than the first layer in the PZT elongation mode, whereby the micro actuator curves into a concave shape and the stroke increases, The second layer has a shorter contraction than the first layer in the PZT contraction mode, whereby the micro actuator curves into a convex shape and the stroke increases, the micro actuator according to claim 7.

9. The third electrode is configured to be 0.05 to 0.15 mm shorter than the second electrode, the micro actuator according to claim 7.

10. The third electrode is configured to be 0.12 mm shorter than the second electrode, the micro actuator according to claim 7.

11. Each of the first layer and the second layer includes an inactive portion, The inactive portion of each of the first layer and the second layer is disposed at a first end of the micro actuator, the micro actuator according to claim 7.

12. The first electrode and the third electrode are connected at a first end of the micro actuator to cover the first ends of the first layer and the second layer, the micro actuator according to claim 7.

13. The second electrode covers the second ends of the first layer and the second layer and covers the second end of the micro actuator so as to be disposed on an upper surface of the second layer and a part of the bottom surface of the first layer, the micro actuator according to claim 7.

Images