Multi-layer PZT microactuator 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 microactuator assembly comprising:
a multi-layer piezoelectric element including a first layer and a second layer connected to the first layer, the first layer configured to be closer to a surface to which the microactuator assembly is bonded than is the second layer;
a first electrode configured to be disposed on and partially cover a bottom side of the first layer, configured to be disposed on a first side of the first layer and the second layer, and configured to be disposed on and partially cover a top side of the second layer;
a second electrode configured to be disposed on and partially cover the top side of the second layer, configured to be disposed between the first layer and the second layer, configured to be disposed on and partially cover the bottom side of the first layer, and configured to be disposed on a second side of the first layer and the second layer, opposite the first side; and
a constraint layer electrically ganged by conductive adhesive to the first electrode and the second layer of the multi-layer piezoelectric element.
2. The microactuator assembly of claim 1 , wherein the first layer and the second layer of the multi-layer piezoelectric element are formed from a poled piezoelectric material.
3. The microactuator assembly of claim 1 , wherein the first electrode is configured to be electrically connected to a first voltage and the second electrode is configured to be electrically connected to a second voltage.
4. The microactuator assembly of claim 1 , wherein the first layer and the second layer have equal thicknesses.
5. The microactuator assembly of claim 1 , wherein the constraint layer is formed of an unpoled piezoelectric material.
6. The microactuator assembly of claim 1 , wherein the constraint layer includes a stainless steel layer.
7. The microactuator assembly of claim 1 , wherein the constraint layer includes silicon.
8. The microactuator assembly of claim 1 , wherein the first electrode is formed by sputtering and/or electrodeposition.
9. The microactuator assembly of claim 1 , wherein the second electrode is formed by sputtering and/or electrodeposition.
10. An 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 including:
a multi-layer piezoelectric element including a first layer and a second layer connected to the first layer, the first layer configured to be closer to a surface to which the microactuator assembly is bonded than is the second piezoelectric layer;
a first electrode configured to be disposed on and partially cover a bottom side of the first layer, configured to be disposed on a first side of the first layer and the second layer, and configured to be disposed on and partially cover a top side of the second layer;
a second electrode configured to be disposed on and partially cover the top side of the second layer, configured to be disposed between the first layer and the second layer, configured to be disposed on and partially cover the bottom side of the first layer, and configured to be disposed on a second side of the first layer and the second layer, opposite the first side; and
a constraint layer electrically ganged by conductive adhesive to the first electrode and the second layer of the multi-layer piezoelectric element.
11. The actuated suspension of claim 10 , wherein the first layer and the second layer of the multi-layer piezoelectric element are formed of a poled piezoelectric material.
12. The actuated suspension of claim 10 , wherein
the first electrode is configured to be electrically connected to a first voltage and the second electrode is configured to be electrically connected to a second voltage such that a first voltage differential applied across the multi-layer piezoelectric element causes the multi-layer piezoelectric element to expand or contract.
13. The actuated suspension of claim 10 , wherein the first layer and the second layer have equal thicknesses.
14. The actuated suspension of claim 10 , wherein the constraint layer includes an unpoled piezoelectric material.
15. The actuated suspension of claim 10 , wherein the constraint layer includes a stainless steel layer.
16. The actuated suspension of claim 10 , wherein the constraint layer includes silicon.
17. The actuated suspension of claim 10 , wherein the first electrode is formed by sputtering and/or electrodeposition.
18. The actuated suspension of claim 10 , wherein the second electrode is formed by sputtering and/or electrodeposition.