Manufacturing method for multi-layer PZT microactuator having a poled but inactive PZT constraining layer
A multi-layer piezoelectric microactuator assembly has at least one poled and active piezoelectric layer and one poled but inactive piezoelectric layer. The poled but inactive layer acts as a constraining layer in resisting expansion or contract of the first piezoelectric layer.
1. A method of manufacturing a piezoelectric microactuator assembly, the method comprising:
forming a top electrode layer onto a top face of a PZT element;
placing a mask at different locations on the top electrode layer to form a space between at least two portions of mask;
applying a conductive epoxy in the space between the at least two portions of the mask;
applying a constraint layer to the conductive epoxy;
removing the mask leaving the constraint layer on the conductive epoxy;
forming a bottom electrode layer onto a bottom face of the PZT element opposite the top electrode layer; and
polarizing the PZT element to form an active piezoelectric layer.
2. The method of claim 1 , further comprising placing the PZT element onto a first transfer tape prior to forming the top electrode layer.
3. The method of claim 2 , further comprising removing the first transfer tape when removing the at least two masks.
4. The method of claim 1 , wherein the top electrode layer is formed by sputtering and/or electrodeposition.
5. The method of claim 1 , wherein the space between the at least two portions of the mask covers more than 50% of a surface of the top electrode.
6. The method of claim 1 , wherein the constraint layer includes unpoled piezoelectric material.
7. The method of claim 1 , wherein the constraint layer includes a stainless steel layer.
8. The method of claim 1 , further comprising applying a second transfer tape to the constraint layer after applying the constraint layer to the conductive epoxy.
9. The method of claim 1 , wherein the bottom electrode layer is formed by sputtering and/or electrodeposition.
10. The method of claim 1 , wherein the constraint layer includes silicon.
11. The method of claim 1 , wherein applying the constraint layer to the conductive epoxy includes bonding the constraint layer to the conductive epoxy without any additional layer between the constraint layer and the conductive epoxy, the constraint layer having a Young's modulus that is equal to or less than 50 GPa.
12. The method of claim 1 , wherein applying the constraint layer to the conductive epoxy includes bonding the constraint layer to the conductive epoxy without any additional layer between the constraint layer and the conductive epoxy, the constraint layer having a Young's modulus that is greater than 50 GPa.
13. The method of claim 1 , wherein the constraint layer has a Young's modulus of greater than 100 GPa.
14. The method of claim 1 , wherein the constraint layer has a Young's modulus of greater than 100 GPa and the constraint layer is applied directly to the conductive epoxy without any organic material between the conductive epoxy and the constraint layer.
15. The method of claim 1 , wherein the active piezoelectric layer has a first portion that is covered by the constraint layer and a second portion that is not covered by the constraint layer.
16. The method of claim 15 , further comprising disposing and electrically bonding an electrical connection to the active piezoelectric layer on the uncovered second portion.
17. The method of claim 16 , wherein the electrical connection on the uncovered second portion rises to a height that is no higher than the constraint layer.
18. The method of claim 1 , wherein the active piezoelectric layer is configured to be actuated by a voltage that causes the active piezoelectric layer to expand and bend in a direction that causes the top face of the PZT element to become net concave in shape.
19. The method of claim 1 , wherein the active piezoelectric layer is configured to be actuated by a voltage that causes the active piezoelectric layer to contract, the piezoelectric element bends in a direction that causes the top face of the PZT element to become net convex in shape.