# US 10,373,636 B2 · Suspension having a stacked D33 mode PZT actuator with constraint layer

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- Number: US 10,373,636 B2
- Document ID: US10373636B2
- Status: Granted
- Kind: B2
- Application number: 15/727,306
- Filed: 2017-10-06
- Published: 2018-02-01
- Granted: 2019-08-06
- Earliest claimed: 2016-01-27
- Assignees: Magnecomp Corporation
- Applicants: Magnecomp Corporation
- Inventors: Kuen Chee Ee
- Web page: https://patentgrep.com/patent/US10373636B2

## CPC

- G11B 5/5552: {using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means}
- G11B 5/483: {Piezoelectric devices between head and arm, e.g. for fine adjustment}
- G11B 5/4873: {the arm comprising piezoelectric or other actuators for adjustment of the arm}
- H02N 2/02: producing linear motion, e.g. actuators; Linear positioners {; Linear motors}
- H10N 30/20: with electrical input and mechanical output, e.g. functioning as actuators or vibrators
- H10N 30/2023: {having polygonal or rectangular shape}
- H10N 30/2041: {Beam type}
- H10N 30/206: {using only longitudinal or thickness displacement, e.g. d33 or d31 type devices}
- H10N 30/87: Electrodes or interconnections, e.g. leads or terminals
- G11B 5/4833: {Structure of the arm assembly, e.g. load beams, flexures, parts of the arm adapted for controlling vertical force on the head (G11B5/484 takes precedence)}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- H02N: ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

A microactuator for a dual stage actuated suspension for a hard disk drive is constructed as a longitudinal stack of piezoelectric (PZT) elements acting in the d33 mode, expanding or contracting longitudinally when an electric field is applied across them in the longitudinal direction. The microactuator has interlaced electrode fingers that separate and define the individual PZT elements, and apply the electric field. A stiff constraint layer having a high Young's modulus is affixed to the microactuator on the side opposite the suspension to which the microactuator is bonded. The constraint layer may be a layer of substantially inactive PZT material that is formed integrally with the PZT elements but without electrodes in the inactive PZT layer. The presence of the stiff constraint layer increases the effective stroke length of the microactuator.

## Claims

### Claim 1

A piezoelectric (PZT) actuator, the PZT actuator comprising:
a PZT layer;
a first electrode having a plurality of first electrode fingers extending into the PZT layer;
a second electrode having a plurality of second electrode fingers extending into the PZT layer;
the first electrode fingers and the second electrode fingers interlaced to define a plurality of interlacing fingers, the interlacing fingers configured to define a plurality of PZT elements within the PZT layer and between the interlaced fingers, the PZT elements successively located in a longitudinal direction;
the PZT elements poled such that when a voltage is applied across the first and second electrodes, the PZT elements are configured to expand or contract in the longitudinal direction; and
a stiff constraint layer located on a top side of the PZT actuator away from an opposite bottom side of the PZT actuator at which the PZT actuator is bonded to a suspension, the constraint layer configured to oppose expansion or contraction of the PZT elements.

### Claim 2 (depends on 1)

The PZT actuator claim 1 wherein the constraint layer comprises a material having a Young's modulus of greater than 50 GPa.

### Claim 3 (depends on 2)

The PZT actuator of claim 2 wherein the constraint layer is adhered to the PZT elements.

### Claim 4 (depends on 1)

The PZT actuator of claim 1 wherein the constraint layer includes inactive PZT material.

### Claim 5 (depends on 1)

The PZT actuator of claim 1 wherein the constraint layer includes inactive PZT material that is formed integrally with and above the PZT elements.

### Claim 6 (depends on 1)

The PZT actuator of claim 1 wherein the constraint layer includes PZT material that has no electrodes for inducing a significant electric field therein.

### Claim 7 (depends on 1)

The PZT actuator of claim 1 further comprising an insulating layer on the bottom side, the insulating layer configured to cover a bottom side of most of the interlaced fingers but leaving a portion of the first electrode and a portion of the second electrode electrically accessible from the bottom side.

### Claim 8

A piezoelectric (PZT) actuator, the PZT actuator comprising:
a plurality of PZT elements;
first and second electrodes defining a plurality of interlaced fingers, the fingers configured to extend between individual ones of the PZT elements;
the PZT elements poled and arranged such that when a voltage is applied across the first and second electrodes, the individual ones of the PZT elements between the interlaced fingers are configured to expand or contract in their d33 mode, the expanding or contracting adding serially such that an overall expansion or contraction of the PZT actuator generally equals a cumulative expansion or contraction of the individual ones of the PZT elements; and
a stiff constraint layer located on a top side of the PZT actuator away from an opposite bottom side of the PZT actuator at which the PZT actuator is affixed to a suspension, the constraint layer configured to oppose the overall expansion or contraction of the PZT actuator and thus to increase an effective stroke length of the PZT actuator as compared to if the PZT actuator lacked the constraint layer.

### Claim 9 (depends on 8)

The PZT actuator of claim 8 wherein the stiff constraint layer includes substantially inactive PZT material.

### Claim 10 (depends on 9)

The PZT actuator of claim 9 wherein the inactive PZT material of the constraint layer is formed integrally with the individual PZT elements.

### Claim 11 (depends on 9)

The PZT actuator of claim 9 wherein the inactive PZT material of the constraint layer is formed by applying PZT material in fluid form over the interlacing fingers and thereafter hardened.

### Claim 12 (depends on 9)

The PZT actuator of claim 9 wherein said expansion or contraction occurs in a longitudinal direction, and the interlacing fingers do not extend vertically into the substantially inactive PZT material.

### Claim 13

A piezoelectric (PZT) actuator, the PZT actuator comprising:
a first section of PZT material;
a second section of PZT material on the first section of PZT material and affixed thereto; and
first and second electrodes, each of the electrodes having fingers that extend laterally into the first section of PZT material, the portions of PZT material within the first section and between fingers that are adjacent in a longitudinal direction configured to define individual PZT elements;
wherein:
the PZT elements within the first section are poled such that, when an activation voltage is applied across the first and second electrodes,. electric fields in the longitudinal direction are applied across the PZT elements causing the PZT elements to expand or contract in the longitudinal direction, and such that the overall first section of PZT material expands or contracts in the longitudinal direction; and
when the activation voltage is applied across the first and second electrodes, the second section of PZT material is configured to act differently than the first section of PZT material thus configured to oppose the expansion or contraction of the first section of PZT material.

### Claim 14 (depends on 13)

The PZT actuator of claim 13 wherein the second section of PZT material is formed integrally with the first section of PZT material and above the electrode fingers.

### Claim 15 (depends on 13)

The PZT actuator of claim 13 wherein the second section of PZT material is substantially unpoled PZT material.

### Claim 16 (depends on 13)

The PZT actuator of claim 13 wherein the second section of PZT material has no electrode fingers extending laterally therein.

### Claim 17 (depends on 13)

The PZT actuator of claim 13 wherein the second section of PZT material has fewer electrode fingers extending laterally therein than the first section.

### Claim 18 (depends on 13)

The PZT actuator of claim 13 wherein the second section of PZT material has electrode fingers extending therein that are shorter than the electrode fingers extending into the first section.

### Claim 19 (depends on 13)

The PZT actuator of claim 13 wherein the electrode fingers in the first section of PZT material have an average vertical height, the second section of PZT material has no electrode fingers therein, and the second section of PZT material has a thickness that is at least as great as the average vertical height of the electrode fingers in the first section of PZT material.

### Claim 20 (depends on 13)

The PZT actuator of claim 13 wherein the electrode fingers extend vertically through the first section of PZT material but do not extend vertically through the second section of PZT material.