OVERDRIVE STRUCTURES FOR FLEXIBLE ELECTROSTATIC SWITCH

• US 20040017644A1
• Filed: 05/06/2002
• Published: 01/29/2004
• Est. Priority Date: 09/07/2001
• Status: Active Grant

• Current Assignee: Micross Advanced Interconnect Technology LLC
• Original Assignee: MCNC, Inc.
• Inventors: Goodwin-Johansson, Scott H.
• Granted Patent: US 6,731,492 B2
• Time in Patent Office: Days
• US Class Current: 361/233
• CPC Class Codes: H01H 1/06 characterised by the shape or structure of the contact-making surface, e.g. grooved
• CPC Class Codes: H01H 1/20 Bridging contacts for circuit breakers H01H73/045
• CPC Class Codes: H01H 2037/008 Micromechanical switches operated thermally
• CPC Class Codes: H01H 2059/0081 with a tapered air-gap between fixed and movable electrodes
• CPC Class Codes: H01H 59/0009 making use of micromechanics

Abstract

A MEMS (Micro Electro Mechanical System) electrostatically operated high voltage switch or relay device is provided. These devices can switch high voltages while using relatively low electrostatic operating voltages. The MEMS device comprises a substrate, a substrate electrode, and one or more substrate contacts. The MEMS device also includes a flexible composite overlying the substrate, one or more composite contacts, and at least one insulator. The switch or relay device is provided overdrive potential through protrusions on the contact surface of the switch or relay contacts. In one embodiment the substrate contacts define protrusions on the contact surface that extend toward the flexible composite contacts. In another embodiment the flexible composite contacts define protrusions on the contact surface that extend toward the substrate contacts.

Claims

1. A MEMS device driven by electrostatic forces, comprising:

a substrate defining a planar surface;

at least one substrate electrode disposed on the surface of said substrate;

at least one substrate contact attached to said substrate and electrically isolated from said at least one substrate electrode, wherein said at least one substrate contact defines protrusions that extend from a contact surface;

a flexible composite overlying said at least one substrate electrode and having at least one electrode element and at least one biasing element, said flexible composite having a fixed portion attached to the underlying substrate, and a distal portion movable with respect to said substrate electrode;

at least one flexible composite contact attached to said flexible composite and electrically isolated from said at least one flexible composite electrode element; and

an insulator electrically separating said substrate electrode from said flexible electrode,

whereby said at least one flexible composite contact and said at least one substrate contact is electrically connected when said flexible composite distal portion is electrostatically attracted to said substrate.

2. The MEMS device according to claim 1, wherein said protrusions on said at least one substrate contact serve to provide overdrive potential to said device.

3. The MEMS device according to claim 1, wherein said protrusions on said at least one substrate contact form an array pattern on the contact surface of the at least one substrate contact.

4. The MEMS device according to claim 1, wherein said protrusions on said at least one substrate contact are generally mound-like in shape.

5. The MEMS device according to claim 1, wherein said distal portion of said flexible composite is positionally biased with respect to said substrate.

6. The MEMS device according to claim 1, wherein said at least one substrate contact comprises a plurality of substrate contacts.

7. The MEMS device according to claim 6, wherein at least two of said plurality of substrate contacts are disposed so as to connect in series.

8. The MEMS device according to claim 6, wherein at least two of said plurality of substrate contacts are disposed so as to connect in parallel.

9. The MEMS device according to claim 1, wherein said at least one substrate electrode has a predetermined shape.

10. The MEMS device according to claim 1, wherein said at least one substrate electrode generally underlies the entire area of the distal portion of said flexible composite.

11. The MEMS device according to claim 1, wherein said insulator is attached to and overlies said at least one substrate electrode.

12. The MEMS device according to claim 1, wherein said flexible composite biasing element comprises at least one polymer film.

13. The MEMS device according to claim 1, wherein said flexible composite biasing element comprises polymer films on opposite sides of said flexible composite electrode element.

14. The MEMS device according to claim 1, wherein said flexible composite biasing element and said flexible composite electrode element have different thermal coefficients of expansion, urging said flexible composite to curl.

15. The MEMS device according to claim 1, wherein said flexible composite biasing element comprises at least two polymer films of different thicknesses, urging said flexible composite to curl.

16. The MEMS device according to claim 1 wherein said flexible composite biasing element comprises at least two polymer films of different coefficients of expansion, urging said flexible composite to curl.

17. The MEMS device according to claim 1, wherein the distal portion of said flexible composite curls out of the plane defined by the upper surface of said flexible composite when no electrostatic force is created between said at least one composite electrode and said at least one flexible composite electrode.

18. The MEMS device according to claim 1, wherein said at least one flexible composite contact comprises a plurality of contacts.

19. The MEMS device according to claim 18, wherein at least two of said plurality of flexible composite contacts are disposed so as to connect in series

20. The MEMS device according to claim 18, wherein at least two of said plurality of flexible composite contacts are disposed so as to connect in parallel.

21. The MEMS device according to claim 20, wherein said at least one substrate electrode generally encompasses said at least one substrate contact.

22. The MEMS device according to claim 1, wherein said at least one flexible composite electrode layer generally encompasses said at least one flexible composite contact.

23. The MEMS device according to claim 1, further comprising a source of electrical energy electrically connected to at least one of said at least one substrate contacts and one of said at least one flexible composite contacts.

24. The MEMS device according to claim 23, further comprising at least one device electrically connected to at least one of said at least one substrate contacts and one of said at least one flexible composite contacts.

25. The MEMS device according to claim 1, further comprising a source of electrical energy electrically connected to at least one of said at least one substrate electrodes and one of said at least one flexible composite electrodes.

26. The MEMS device according to claim 25, further comprising a switching device electrically connected to at least one of said at least one substrate electrodes and one of said at least one composite electrodes.

27. A MEMS device driven by electrostatic forces, comprising:

a substrate defining a planar surface;

at least one substrate electrode disposed on the surface of said substrate;

at least one substrate contact attached to said substrate and electrically isolated from said at least one substrate electrode;

a flexible composite overlying said at least one substrate electrode and having at least one electrode element and at least one biasing element, said flexible composite having a fixed portion attached to the underlying substrate, and a distal portion movable with respect to said substrate electrode;

at least one flexible composite contact attached to said flexible composite and electrically isolated from said at least one flexible composite electrode element, wherein said at least one flexible composite contact defines protrusions that extend from a contact surface; and

an insulator electrically separating said substrate electrode from said flexible electrode,

whereby said at least one flexible composite contact and said at least one substrate contact is electrically connected when said flexible composite distal portion is electrostatically attracted to said substrate.

28. The MEMS device according to claim 27, wherein said protrusions on said at least one flexible composite contact serve to provide overdrive potential to said device.

29. The MEMS device according to claim 27, wherein said protrusions on said at least one flexible composite contact form an array pattern on the contact surface of the at least one flexible composite contact.

30. The MEMS device according to claim 27, wherein said protrusions on said at least one flexible composite contact are generally mound-like in shape.

31. The MEMS device according to claim 27, wherein said distal portion of said flexible composite is positionally biased with respect to said substrate.

32. The MEMS device according to claim 27, wherein said at least one substrate contact comprises a plurality of substrate contacts.

33. The MEMS device according to claim 32, wherein at least two of said plurality of substrate contacts are disposed so as to connect in series.

34. The MEMS device according to claim 32, wherein at least two of said plurality of substrate contacts are disposed so as to connect in parallel.

35. The MEMS device according to claim 27, wherein said at least one substrate electrode has a predetermined shape.

36. The MEMS device according to claim 27, wherein said at least one substrate electrode generally underlies the entire area of the distal portion of said flexible composite.

37. The MEMS device according to claim 27, wherein said insulator is attached to and overlies said at least one substrate electrode.

38. The MEMS device according to claim 27, wherein said flexible composite biasing element comprises at least one polymer film.

39. The MEMS device according to claim 27, wherein said flexible composite biasing element comprises polymer films on opposite sides of said flexible composite electrode element.

40. The MEMS device according to claim 27, wherein said flexible composite biasing element and said flexible composite electrode element have different thermal coefficients of expansion, urging said flexible composite to curl.

41. The MEMS device according to claim 27, wherein said flexible composite biasing element comprises at least two polymer films of different thickness, urging said flexible composite to curl.

42. The MEMS device according to claim 27, wherein said flexible composite biasing element comprises at least two polymer films of different coefficients of expansion, urging said flexible composite to curl.

43. The MEMS device according to claim 27, wherein the distal portion of said flexible composite curls out of the plane defined by the upper surface of said flexible composite when no electrostatic force is created between said at least one composite electrode and said at least one flexible composite electrode.

44. The MEMS device according to claim 27, wherein said at least one flexible composite contact comprises a plurality of contacts.

45. The MEMS device according to claim 44, wherein at least two of said plurality of flexible composite contacts are disposed so as to connect in series.

46. The MEMS device according to claim 44, wherein at least two of said plurality of flexible composite contacts are disposed so as to connect in parallel.

47. The MEMS device according to claim 27, wherein said at least one substrate electrode generally encompasses said at least one substrate contact.

48. The MEMS device according to claim 27, wherein said at least one flexible composite electrode layer generally encompasses said at least one flexible composite contact.

49. The MEMS device according to claim 27, further comprising a source of electrical energy electrically connected to at least one of said at least one substrate contacts and one of said at least one flexible composite contacts.

50. The MEMS device according to claim 49, further comprising at least one device electrically connected to at least one of said at least one substrate contacts and one of said at least one flexible composite contacts.

51. The MEMS device according to claim 27, further comprising a source of electrical energy electrically connected to at least one of said at least one substrate electrodes and one of said at least one flexible composite electrodes.

52. The MEMS device according to claim 51, further comprising a switching device electrically connected to at least one of said at least one substrate electrodes and one of said at least one composite electrodes.

53. A method of using a MEMS device having a substrate including at least one substrate electrode and at least one substrate contact defining protrusions on a contact surface, and a flexible composite having at least one electrode element, at least one biasing element and at least one flexible composite contact, said flexible composite movable in response to an electrostatic force created between the at least one substrate electrode and the at least one electrode layer, the method comprising the steps of:

electrically isolating at least one of the substrate contacts or the composite contacts from their respective associated substrate electrodes or composite electrodes,

selectively generating an electrostatic force between the at least one substrate electrode and the at least electrode element of said flexible composite;

moving said flexible composite toward the substrate;

electrically connecting the at least one substrate contact and the at least one flexible composite contact in a circuit electrically isolated from at least one of the substrate electrodes or composite electrodes; and

overdriving the at least one substrate contact into the at least one flexible composite contact so as to minimize contact resistance.

54. A method of using a MEMS device having a substrate including at least one substrate electrode and at least one substrate contact, and a flexible composite having at least one electrode element, at least one biasing element and at least one flexible composite contact defining protrusions on a contact surface, said flexible composite movable in response to an electrostatic force created between the at least one substrate electrode and the at least one electrode layer, the method comprising the steps of:

electrically isolating at least one of the substrate contacts or the composite contacts from their respective associated substrate electrodes or composite electrodes,

selectively generating an electrostatic force between the at least one substrate electrode and the at least electrode element of said flexible composite;

moving said flexible composite toward the substrate;

electrically connecting the at least one substrate contact and the at least one flexible composite contact in a circuit electrically isolated from at least one of the substrate electrodes or composite electrodes; and

overdriving the at least one flexible composite contact into the at least one substrate composite contact so as to minimize contact resistance.