HDD microactuator having reverse poling and active restraining layer

• US 9,330,694 B1
• Filed: 12/10/2014
• 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:
  US14/566,666
• Time in Patent Office: 510 Days
• Field of Search: 360/294.1
• US Class Current: 1/1
• 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

Abstract

A PZT microactuator such as for a hard disk drive is a multi-layer PZT in which a first layer of PZT material that is disposed away from the side of the microactuator that is bonded to the suspension, responds to an actuation voltage differently than does a second layer of PZT material that is closer to the suspension, thus acting as a constraining layer and thus increasing stroke sensitivity of the microactuator. The first layer of PZT material can be made to respond differently than the second layer by not being activated, by being thicker that the second layer, or by being reverse poled as compared to the second layer. The effective stroke length of the microactuator is increased by the presence and effect of constraining layer.

Claims

1. A dual stage actuated suspension for a disk drive, the suspension having a multi-layer piezoelectric microactuator, the microactuator comprising:

a first piezoelectric layer and a second piezoelectric layer, the second piezoelectric layer being closest to a surface of the suspension to which the microactuator 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 actuation voltage is applied across the electrodes thus activating both the first and second piezoelectric layers;

wherein;

the first piezoelectric layer acts in a lengthwise direction differently than does the second piezoelectric layer in response to the actuation voltage being applied across the electrodes, said difference in lengthwise actuation increasing an effective stroke sensitivity of the microactuator compared to if the first piezoelectric layer were not present;

the first and second piezoelectric layers are oppositely poled; and

the first piezoelectric layer is within the range of about 5-50% as thick as the second piezoelectric layer.

2. The dual stage actuated suspension of claim 1, wherein the first piezoelectric layer is within the range of about 20-35% as thick as the second piezoelectric layer.

3. The dual stage actuated suspension of claim 1, wherein when an actuation voltage is applied to the microactuator, the first piezoelectric layer tends to contract lengthwise while the second piezoelectric layer tends to expand lengthwise.

4. A dual stage actuated suspension for a disk drive, the suspension having a multi-layer piezoelectric microactuator, the suspension being configured such that linear expansion or contraction of the microactuator changes a linear distance across a gap in the suspension thereby arcuately moving a read/write head that is mounted to the suspension, the microactuator comprising:

a first piezoelectric layer;

a second piezoelectric layer disposed in stacked fashion over the first piezoelectric layer, the first and second piezoelectric layers having substantially coextensive footprints, the second piezoelectric layer being affixed on the suspension and the first piezoelectric layer being affixed on the second piezoelectric layer away from a surface of the suspension to which the second piezoelectric layer is affixed; and

a common electrode disposed between the first and second piezoelectric layers;

wherein;

the first piezoelectric layer is within the range of about 5-50% as thick as the second piezoelectric layer; and

a single actuation voltage and a ground applied to the microactuator causes a first one of said piezoelectric layers to tend to contract while a second one of said piezoelectric layers tends to expand, the respective actions of the two piezoelectric layers thus tending to counteract each other.

5. A dual stage actuated suspension for a disk drive, the suspension having a multi-layer piezoelectric microactuator, the microactuator comprising:

a first piezoelectric layer and a second piezoelectric layer, the second piezoelectric layer being closer to a side of the suspension to which the microactuator is bonded than is the first piezoelectric layer;

a first electrode disposed on a top of the first piezoelectric layer and on a bottom of the second piezoelectric layer; and

a second and common electrode disposed between the first and second piezoelectric layers;

wherein;

the first and second piezoelectric layers are reverse poled such that an actuation voltage applied to the microactuator across the first and second electrodes causes the first piezoelectric layer to expand in a lengthwise direction and the second piezoelectric layer to contract in a lengthwise direction, the two piezoelectric layers thereby acting in opposite directions, the action of the first piezoelectric layer thereby partially counteracting the action of the second piezoelectric layer; and

the first piezoelectric layer is 5-50% as thick as the second piezoelectric layer.

6. The dual stage actuated suspension of claim 5 wherein the first piezoelectric layer is 20-35% as thick as the second piezoelectric layer.

7. A dual stage actuated suspension for a disk drive, the suspension having a multi-layer piezoelectric microactuator, the microactuator comprising:

a first piezoelectric layer and a second piezoelectric layer, the first and second piezoelectric layers having substantially coextensive footprints, the second piezoelectric layer being closer to a side of the suspension to which the microactuator is bonded than is the first piezoelectric layer;

a first electrode disposed on a top of the first piezoelectric layer and on a bottom of the second piezoelectric layer, the first electrode comprising;

a first area of metallization on a majority of the top of the first piezoelectric layer;

a second area of metallization on a majority of the bottom of the second piezoelectric layer; and

conductive material bridging a non-conductive gap between the first and second areas of metallization, the conductive material not formed integrally with the first or second areas of metallization;

a second and common electrode disposed between the first and second piezoelectric layers;

wherein the first and second piezoelectric layers are reverse poled such that a single actuation voltage and a ground applied to the microactuator across the first and second electrodes causes the first piezoelectric layer to expand in a lengthwise direction and the second piezoelectric layer to contract in a lengthwise direction, the two piezoelectric layers thereby acting in opposite directions, the action of the first piezoelectric layer thereby partially counteracting the action of the second piezoelectric layer, the respective actions of the two layers together causing the microactuator to contract in the lengthwise direction more than if the first piezoelectric layer were not present.

8. The dual stage actuated suspension of claim 7 wherein the conductive material is conductive adhesive.

9. The dual stage actuated suspension of claim 8 wherein the conductive material mechanically and electrically bonds the microactuator to at least one of a grounded body of the suspension and an electrical circuit lead.

10. The dual stage actuated suspension of claim 7 wherein the first piezoelectric layer is thinner than the second piezoelectric layer.