Multi-layer PZT microacuator with active PZT constraining layers for a DSA suspension
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.
1. A 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 configured to be closest to a surface of the suspension to which the microactuator is bonded;
a first electrode partially disposed on a top of the first piezoelectric layer and partially disposed on a bottom of the second piezoelectric layer;
a second electrode partially disposed on a top of the first piezoelectric layer, partially disposed on a bottom of the second piezoelectric layer, and partially disposed therebetween the first piezoelectric layer and the second piezoelectric layer; and
a restraining layer bonded to the first electrode and the top of the first piezoelectric layer by an adhesive, the restraining layer configured to increase the effective stroke length of the piezoelectric.
2. The suspension of claim 1 , the first electrode comprising:
a first area of metallization on a majority of the top of the first piezoelectric layer; and
a second area of metallization on a majority of the bottom of the second piezoelectric layer.
3. The suspension of claim 2 , the second electrode comprising:
a first area of metallization on a minority of the top of the first piezoelectric layer;
a second area of metallization on a minority of the bottom of the second piezoelectric layer; and
a third area of metallization partially extending therebetween the first piezoelectric layer and the second piezoelectric layer.
4. The suspension of claim 1 , wherein the first electrode and the second electrode are 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.
5. The suspension of claim 1 , wherein the restraining layer includes a stainless steel layer bonded directly to the first electrode and the top of the first piezoelectric layer by epoxy adhesive.
6. The suspension of claim 1 , wherein the restraining layer includes an unactivated piezoelectric, the unactivated piezoelectric layer exhibiting less than 10% as much piezoelectric behavior as the first and second piezoelectric layers when the microactuator is activated by application of a voltage thereto.
7. The suspension of claim 1 , wherein the restraining layer includes a ceramic material.
8. The suspension of claim 1 , wherein the first piezoelectric layer is configured to contract lengthwise and the second piezoelectric layer is configured to expand lengthwise when an actuation voltage is applied to the microactuator.
9. The suspension of claim 1 , wherein the first piezoelectric layer and the second piezoelectric layer have coextensive footprints.
10. The suspension of claim 1 , wherein the restraining layer has a Young's modulus of greater than 50 GPa.
11. A suspension for a disk drive, the suspension comprising:
a beam supporting a read/write head at a distal end; and
a multi-layer piezoelectric microactuator assembly for effecting fine positional movements of the read/write head, the microactuator assembly including:
a first piezoelectric layer and a second piezoelectric layer, the second piezoelectric layer configured to be closest to a surface of the suspension to which the microactuator is bonded;
a first electrode partially disposed on a top of the first piezoelectric layer and partially disposed on a bottom of the second piezoelectric layer;
a second electrode partially disposed on a top of the first piezoelectric layer, partially disposed on a bottom of the second piezoelectric layer, and partially disposed therebetween the first piezoelectric layer and the second piezoelectric layer; and
a restraining layer bonded to the first electrode and the top of the first piezoelectric layer by an adhesive, the restraining layer configured to increase the effective stroke length of the piezoelectric microactuator.
12. The suspension of claim 11 , the first electrode comprising:
a first area of metallization on a majority of the top of the first piezoelectric layer; and
a second area of metallization on a majority of the bottom of the second piezoelectric layer.
13. The suspension of claim 12 , the second electrode comprising:
a first area of metallization on a minority of the top of the first piezoelectric layer;
a second area of metallization on a minority of the bottom of the second piezoelectric layer; and
a third area of metallization partially extending therebetween the first piezoelectric layer and the second piezoelectric layer.
14. The suspension of claim 11 , wherein the first electrode and the second electrode are 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.
15. The suspension of claim 11 , wherein the restraining layer includes a stainless steel layer bonded directly to the first electrode and the top of the first piezoelectric layer by epoxy adhesive.
16. The suspension of claim 11 , wherein the restraining layer includes an unactivated piezoelectric, the unactivated piezoelectric layer exhibiting less than 10% as much piezoelectric behavior as the first and second piezoelectric layers when the microactuator is activated by application of a voltage thereto.
17. The suspension of claim 11 , wherein the restraining layer includes a ceramic material.
18. The suspension of claim 11 , wherein when an actuation voltage is applied to the microactuator, the first piezoelectric layer is configured to contract lengthwise while the second piezoelectric layer is configured to expand lengthwise.
19. The suspension of claim 11 , wherein the first piezoelectric layer and the second piezoelectric layer have coextensive footprints.
20. The suspension of claim 11 , wherein the restraining layer has a Young's modulus of greater than 50 GPa.