DSA suspension having multi-layer PZT microactuator with active PZT constraining layers

• US 9,330,698 B1
• Filed: 03/28/2015
• Issued: 05/03/2016
• Est. Priority Date: 03/18/2013
• Status: Active Grant

• Current Assignee: Magnecomp Corporation (TDK Corporation)
• Original Assignee: Magnecomp Corporation (TDK Corporation)
• Inventors: Hahn, Peter, Ee, Kuen Chee, Zhang, Long
• Primary Examiner(s): Garcia, Carlos E
• Application Number:
  US14/672,122
• Time in Patent Office: 402 Days
• Field of Search: 360/77.16
• US Class Current: 1/1
• 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 5/4873 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: G11B 5/596 for track following on disks G11B5/5526, G11B5/5552, G11B5/5565, G11B5/5582 take precedence
• CPC Class Codes: H10N 30/2042 Cantilevers, i.e. having one fixed end

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 most or all 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. The restraining layer can be one or more active layers of PZT material that act in the opposite direction as the main PZT layer. The restraining layer(s) may be thinner than the main PZT layer.

Claims

1. A dual stage actuated suspension for a hard disk drive, the suspension comprising:

a beam supporting a read/write head at a distal end thereof for writing data to, and reading data from, a data disk;

a multi-layer piezoelectric microactuator assembly for effecting fine positional movements of the read/write head, the microactuator assembly comprising;

a first piezoelectric layer and a second piezoelectric layer, the first layer being closest to a surface of the suspension to which the microactuator assembly is bonded;

a first electrode on a bottom side of the first piezoelectric layer;

a second electrode on a top side of the first piezoelectric layer and disposed underneath the second piezoelectric layer, there being no electrode between the first and second electrodes such that a distance between the first and second electrodes defines a thickness of the first piezoelectric layer, and such that a voltage applied across the first and second electrodes induces an electric field across the first piezoelectric layer thereby causing the first piezoelectric layer to expand or contract; and

a third electrode on a top side of the second piezoelectric layer, there being no electrode between the second and third electrodes such that a distance between the second and third electrodes defines a thickness of the second piezoelectric layer, and such that a voltage applied across the second and third electrodes induces an electric field across the second piezoelectric layer thereby causing the second piezoelectric layer to expand or contract;

wherein the second piezoelectric layer comprises the same material as the first piezoelectric layer and is thinner than the first piezoelectric layer; and

wherein the first and second piezoelectric layers are poled such that when a microactuator activation voltage is applied to the microactuator assembly, the first and second piezoelectric layers tend to act in opposite directions.

2. The suspension of claim 1 wherein when the microactuator activation voltage is applied to the microactuator assembly, the microactuator assembly acts in the direction of the first piezoelectric layer a greater overall distance than if the second piezoelectric layer were not present.

3. The suspension of claim 1 further comprising:

a third piezoelectric layer adjacent the second piezoelectric layer on a side thereof opposite the first piezoelectric layer; and

a fourth electrode on a top side of the third piezoelectric layer, with the third electrode separating the second and third piezoelectric layers, there being no electrode between the third and fourth electrodes such that a distance between the third and fourth electrodes defines a thickness of the third piezoelectric layer, and such that a voltage applied across the third and fourth electrodes induces an electric field across the third piezoelectric layer thereby causing the third piezoelectric layer to expand or contract;

wherein in response to the microactuator activation voltage, the second and third piezoelectric layers both tend to act in an opposite direction from an action of the first piezoelectric layer.

4. The suspension of claim 3 wherein the second and third piezoelectric layers are each thinner than the first piezoelectric layer.

5. The suspension of claim 3 wherein the second and third piezoelectric layers each have a thickness in the range of 5-15% of a thickness of the first piezoelectric layer.

6. The suspension of claim 1 wherein the second piezoelectric layer is less than 50% as thick as the first piezoelectric layer.

7. The suspension of claim 1 wherein the second and third piezoelectric layers are each less than 20% as thick as the first piezoelectric layer.

8. The suspension of claim 1 wherein the second piezoelectric layer has a higher coercivity than does the first piezoelectric layer.

9. A dual stage actuated suspension for a hard disk drive, the suspension comprising:

a beam supporting a read/write head at a distal end thereof for writing data to, and reading data from, a data disk;

a multi-layer piezoelectric microactuator assembly for effecting fine positional movements of the read/write head, the microactuator assembly comprising;

a first piezoelectric layer and a second piezoelectric layer, the first layer being closest to a surface of the suspension to which the microactuator assembly is bonded;

a plurality of electrodes arranged to apply first and second electric fields, respectively, across the first and second piezoelectric layers when a microactuator activation voltage is applied across the electrodes thus activating both the first and second piezoelectric layers; and

means for reducing an electric field strength across the second piezoelectric layer but not the first piezoelectric layer;

wherein the first and second piezoelectric layers are poled such that when the microactuator activation voltage is applied to the microactuator assembly, the first and second piezoelectric layers tend to act in opposite directions.

10. The suspension of claim 9 wherein the means for reducing the electric field strength comprises a pattern of voids in an electrode that is operationally associated with the second piezoelectric layer but not with the first piezoelectric layer.

11. The suspension of claim 9 wherein the means for reducing the electric field strength comprises a voltage reducer disposed between adjacent piezoelectric layers.

12. A dual stage actuated suspension for a hard disk drive, the suspension comprising:

a beam supporting a read/write head at a distal end thereof for writing data to, and reading data from, a data disk;

a multi-layer piezoelectric microactuator assembly for effecting fine positional movements of the read/write head, the microactuator assembly comprising;

a first piezoelectric layer adjacent a surface of the suspension to which the microactuator assembly is bonded; and

a plurality of restraining piezoelectric layers bonded to the first piezoelectric layer, each of the restraining piezoelectric layers being farther away from the surface of the suspension to which the microactuator assembly is bonded, and each of the piezoelectric restraining layers having an associated pair of electrodes with one electrode disposed between adjacent restraining piezoelectric layers, the restraining piezoelectric layers tending to act in an opposite direction as the first piezoelectric layer when a microactuator activation voltage is applied to the microactuator assembly.

13. The suspension of claim 12 wherein when the microactuator activation voltage is applied to the microactuator assembly, the microactuator assembly acts in the direction of the first piezoelectric layer a greater overall distance than if the plurality of restraining piezoelectric layers were not present.

14. The suspension of claim 12 wherein each of the restraining piezoelectric layers is thinner than the first piezoelectric layer.

15. The suspension of claim 12 wherein each of the restraining piezoelectric layers is less than 50% as thick as the first piezoelectric layer.

16. A dual stage actuated suspension for a hard disk drive, the suspension comprising:

a beam supporting a read/write head for reading data from a data disk;

a multi-layer piezoelectric microactuator assembly for effecting fine positional movements of the read/write head, the microactuator assembly comprising;

a first piezoelectric layer, the first piezoelectric layer tending to act in a first linear direction when a voltage is applied across a pair of electrodes of the microactuator assembly;

a plurality of opposing piezoelectric layers bonded to the first piezoelectric layer, the first piezoelectric layer and the plurality of opposing piezoelectric layers being disposed in stacked planar relationships to one other, the first piezoelectric layer being disposed closer to a surface of the suspension to which the microactuator assembly is bonded; and

conductive electrode layers disposed between respective pairs of said piezoelectric layers including between pairs of adjacent opposing piezoelectric layers;

wherein the opposing piezoelectric layers are poled so that they act in a linear direction generally opposite the first linear direction when said voltage is applied across said pair of electrodes.

17. The suspension of claim 16 wherein said opposing piezoelectric layers are thinner than the first piezoelectric layer.

18. The suspension of claim 16 wherein said opposing piezoelectric layers are, taken together, thinner than the first piezoelectric layer.

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

a beam supporting a read/write head at a distal end thereof for writing data to, and reading data from, a data disk;

a multi-layer piezoelectric microactuator assembly for effecting fine positional movements of the read/write head, the microactuator assembly comprising;

a first piezoelectric layer and a second piezoelectric layer, the first layer being closest to a surface of the suspension to which the microactuator assembly is bonded; and

a plurality of electrodes arranged to apply first and second electric fields, respectively, across the first and second piezoelectric layers when a microactuator activation voltage is applied across the electrodes thus activating both the first and second piezoelectric layers;

wherein the first and second piezoelectric layers are poled such that when the microactuator activation voltage is applied to the microactuator assembly, the first and second piezoelectric layers tend to act in opposite directions; and

wherein the piezoelectric layers were poled using at least three voltages applied to three separate electrodes, and then after poling selected ones of the electrodes were electrically ganged.

20. A dual stage actuated suspension for a hard disk drive, the suspension comprising:

a beam supporting a read/write head for reading data from a data disk;

a multi-layer piezoelectric microactuator assembly for effecting fine positional movements of the read/write head, the microactuator assembly comprising;

a first piezoelectric layer, the first piezoelectric layer tending to act in a first linear direction when a voltage is applied across a pair of electrodes of the microactuator assembly;

a plurality of opposing piezoelectric layers bonded to the first piezoelectric layer, the first piezoelectric layer and the plurality of opposing piezoelectric layers being disposed in stacked planar relationships to one other; and

conductive electrode layers disposed between respective pairs of said piezoelectric layers;

wherein the opposing piezoelectric layers are poled so that they act in a linear direction generally opposite the first linear direction when said voltage is applied across said pair of electrodes; and

wherein two of said conductive electrode layers are electrically ganged by conductive adhesive that bonds the microactuator assembly to the suspension.

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

a beam supporting a read/write head for reading data from a data disk;

a multi-layer piezoelectric microactuator assembly for effecting fine positional movements of the read/write head, the microactuator assembly comprising;

a first piezoelectric layer, the first piezoelectric layer tending to act in a first linear direction when a voltage is applied across a pair of electrodes of the microactuator assembly;

a plurality of opposing piezoelectric layers bonded to the first piezoelectric layer, the first piezoelectric layer and the plurality of opposing piezoelectric layers being disposed in stacked planar relationships to one other;

conductive electrode layers disposed between respective pairs of said piezoelectric layers; and

means for reducing an electric field strength across at least one of the opposing piezoelectric layers, the means for reducing electric field strength being integrally formed with the piezoelectric microactuator assembly;

wherein the opposing piezoelectric layers are poled so that they act in a linear direction generally opposite the first linear direction when said voltage is applied across said pair of electrodes.