Hard drive suspension microactuator with restraining layer for control of bending

• US 9,117,468 B1
• Filed: 03/14/2014
• Issued: 08/25/2015
• Est. Priority Date: 03/18/2013
• Status: Active Grant

• Current Assignee: Magnecomp Corporation (TDK Corporation)
• Original Assignee: Magnecomp Corporation (TDK Corporation)
• Inventors: Zhang, Long, Hahn, Peter, Ee, Kuen Chee
• Primary Examiner(s): Young, Wayne
• Assistant Examiner(s): Garcia, Carlos E
• Application Number:
  US14/214,525
• Time in Patent Office: 529 Days
• Field of Search: 360/77.16, 360/294.1, 360/294.4
• US Class Current: 1/1
• CPC Class Codes: G11B 5/48 Disposition or mounting of heads or head supports relative to record carriers mounting of head within housing G11B5/105; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed driving of both record carriers and head G11B15/18; guiding record carriers G11B15/60; head selecting circuits G11B15/12
• CPC Class Codes: G11B 5/4806 specially adapted for disk drive assemblies, e.g. assembly prior to operation, hard or flexible disk drives G11B5/488 - G11B5/54 take precedence
• CPC Class Codes: G11B 5/483 Piezoelectric devices between head and arm, e.g. for fine adjustment
• CPC Class Codes: G11B 5/4846 Constructional details of the electrical connection between arm and support
• CPC Class Codes: G11B 5/4873 the arm comprising piezoelectric or other actuators for adjustment of the arm
• CPC Class Codes: G11B 5/5552 using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means
• CPC Class Codes: H02N 2/02 producing linear motion, e.g. actuators; Linear positioners ; Linear motors
• CPC Class Codes: H10N 30/206 using only longitudinal or thickness displacement, e.g. d33 or d31 type devices

Abstract

A PZT microactuator such as for a hard disk drive has a restraining layer bonded on its side that is opposite the side on which the PZT is mounted. The restraining layer comprises a stiff and resilient material such as stainless steel. The restraining layer can cover all of the top of the PZT, or most of the top of the PZT with an electrical connection being made to the PZT where it is not covered by the restraining layer. The restraining layer reduces bending of the PZT as mounted and hence increases effective stroke length, or reverses the sign of the bending which increases the effective stroke length of the PZT even further.

Claims

1. A piezoelectric microactuator assembly having an active piezoelectric layer and having more than 50% of its top surface covered by unpoled piezoelectric material, and a bottom surface bonded to a hard disk drive suspension.

2. A dual-stage actuator suspension for a disk drive, the suspension having a microactuator assembly comprising:

a thin film PZT material, the PZT material having a first side facing the suspension and bonded thereto, and a second side facing away from the suspension and having a stiff material bonded directly to the PZT material by epoxy adhesive, the stiff material covering at least 50% of the PZT material,

wherein the PZT material has a first portion that is covered by the stiff material and a second portion that is not covered by the stiff material, and

wherein the stiff material comprises an insulating material and the insulating material has an electrically conductive via therethrough.

3. The suspension of claim 2 wherein the stiff material comprises silicon.

4. The suspension of claim 2 wherein the suspension comprises a gimbal assembly, and the thin film PZT material is attached to the suspension at the gimbal assembly.

5. The suspension of claim 2 further comprising an electrical connection to the PZT material disposed on the uncovered second portion and electrically bonded thereto.

6. A dual stage actuated suspension for a disk drive, the suspension having:

a piezoelectric microactuator having a piezoelectric material, the piezoelectric microactuator having opposite first and second faces, the piezoelectric microactuator having at least a portion of its first face bonded to the suspension at first and second ends thereof, the first and second ends spanning a gap between respective portions of the suspension, the piezoelectric microactuator and the suspension being configured so that actuation of the microactuator changes the distance of the gap to produce fine movements of a read/write head mounted to the suspension; and

a restraining layer bonded to the second face of the piezoelectric microactuator, the restraining layer comprising the same material as said piezoelectric material but being unpoled, the restraining layer altering the bending behavior of the piezoelectric microactuator so as to increase the effective stroke length of the piezoelectric microactuator compared to what the stroke length of the piezoelectric microactuator would be in the absence of the restraining layer.

7. A dual stage actuated suspension for a disk drive, the suspension having:

a piezoelectric microactuator having a piezoelectric material, the piezoelectric microactuator having opposite first and second faces, the piezoelectric microactuator having at least a portion of its first face bonded to the suspension at first and second ends thereof, the first and second ends spanning a gap between respective portions of the suspension, the piezoelectric microactuator and the suspension being configured so that actuation of the microactuator changes the distance of the gap to produce fine movements of a read/write head mounted to the suspension; and

a restraining layer having a Young'"'"'s modulus of greater than 50 GPa bonded to the second face of the piezoelectric microactuator by an adhesive without any additional layer therebetween having a stiffness that is substantially less than the stiffness of the restraining layer, the restraining layer altering the bending behavior of the piezoelectric microactuator so as to increase the effective stroke length of the piezoelectric microactuator compared to what the stroke length of the piezoelectric microactuator would be in the absence of the restraining layer.

8. The dual stage actuated suspension of claim 7 wherein the restraining layer is bonded to the second face of the piezoelectric microactuator by said adhesive without any additional layer therebetween having Young'"'"'s modulus that is less than 50 GPa.

9. The dual stage actuated suspension of claim 7 wherein the restraining layer is bonded to the second face of the piezoelectric microactuator by said adhesive without any additional layer therebetween of a material having a Young'"'"'s modulus that is less than 20 GPa.

10. The dual stage actuated suspension of claim 7 wherein the restraining layer has a Young'"'"'s modulus of greater than 100 GPa.

11. The dual stage actuated suspension of claim 7 wherein the restraining layer comprises stainless steel.

12. The dual stage actuated suspension of claim 7 wherein the restraining layer comprises a ceramic material.

13. The dual stage actuated suspension of claim 7 wherein the restraining layer has a Young'"'"'s modulus of greater than 100 GPa and the restraining layer is bonded directly to the second face of the piezoelectric microactuator by epoxy adhesive without any organic material between the epoxy adhesive and the restraining layer.

14. The dual stage actuated suspension of claim 7 wherein when the piezoelectric microactuator is activated so as to cause it to expand, the piezoelectric microactuator bends such that the second face assumes a concave shape.

15. The dual stage actuated suspension of claim 7 wherein when the piezoelectric microactuator is activated so as to cause it to contract, the piezoelectric microactuator bends such that the second face assumes a convex shape.

16. The dual stage actuated suspension of claim 7 wherein the piezoelectric material has a first portion that is covered by the restraining layer and a second portion that is not covered by the restraining layer.

17. The dual stage actuated suspension of claim 7 wherein the piezoelectric material has a first portion that is covered by the restraining layer and a second portion that is not covered by the restraining layer, and an electrical connection to the piezoelectric material is disposed on the uncovered second portion and electrically bonded thereto.

18. The dual stage actuated suspension of claim 17 wherein the electrical connection on the uncovered first portion rises to a height that is no higher than the restraining layer.

19. A dual stage actuated suspension for a disk drive, the suspension having:

a linear piezoelectric element having a top face and a bottom face, at least a portion of the bottom face being bonded to the suspension, the piezoelectric element and the suspension being configured so that actuation of the piezoelectric element moves a transducer head mounted on the suspension;

the top face of the piezoelectric element having a material having a Young'"'"'s modulus of greater than 50 GPA affixed thereto;

wherein;

when the piezoelectric element is actuated by a voltage that causes the piezoelectric element to expand, the piezoelectric element bends in a direction that causes the top face to become more concave; and

when the piezoelectric element is actuated by a voltage that causes the piezoelectric element to contract, the piezoelectric element bends in a direction that causes the top face to become more convex.

20. The dual stage actuated suspension of claim 19 wherein:

when the piezoelectric element is actuated by a voltage that causes the piezoelectric element to expand, the piezoelectric element bends in a direction that causes the top face to become net concave in shape; and

when the piezoelectric element is actuated by a voltage that causes the piezoelectric element to contract, the piezoelectric element bends in a direction that causes the top face to become net convex in shape.

21. A dual stage actuated suspension for a disk drive, the suspension having:

a piezoelectric microactuator having a piezoelectric material, the piezoelectric microactuator having opposite first and second faces, the piezoelectric microactuator having at least a portion of its first face bonded to the suspension at first and second ends thereof, the first and second ends spanning a gap between respective portions of the suspension, the piezoelectric microactuator and the suspension being configured so that actuation of the microactuator changes the distance of the gap to produce fine movements of a read/write head mounted to the suspension; and

a restraining layer bonded to the second face of the piezoelectric microactuator, the restraining layer being smaller than the second face leaving a portion of the second face uncovered by the restraining layer;

wherein the restraining layer and its bonding comprises at least one of;

a stainless steel layer bonded directly to the second face of the piezoelectric microactuator by epoxy adhesive; and

an unactivated piezoelectric layer affixed to the piezoelectric material, the unactivated piezoelectric layer exhibiting less than 10% as much piezoelectric behavior as the piezoelectric material when the microactuator is activated by application of a voltage thereto;

wherein the restraining layer alters the bending behavior of the piezoelectric microactuator so as to increase the effective stroke length of the piezoelectric microactuator compared to what the stroke length of the piezoelectric microactuator would be in the absence of the restraining layer.

22. The dual stage actuated suspension of claim 21 further comprising:

an electrical connection to the piezoelectric material physically and electrically bonded to the uncovered portion of the piezoelectric microactuator'"'"'s second face.