Spring loaded bi-stable MEMS switch

• US 20030223174A1
• Filed: 05/29/2002
• Published: 12/04/2003
• Est. Priority Date: 05/29/2002
• Status: Active Grant

• Current Assignee: Superconductor Technologies Inc. (Clearday, Inc.)
• Original Assignee: Superconductor Technologies Inc. (Clearday, Inc.)
• Inventors: Prophet, Eric M.
• Granted Patent: US 6,924,966 B2
• Time in Patent Office: Days
• US Class Current: 361/115
• CPC Class Codes: H01H 1/0036 Switches making use of microelectromechanical systems [MEMS] for electromagnetic relays H01H50/005; for electrostatic relays H01H59/0009
• CPC Class Codes: H01H 2001/0042 Bistable switches, i.e. having two stable positions requiring only actuating energy for switching between them, e.g. with snap membrane or by permanent magnet
• CPC Class Codes: H01H 2057/006 Micromechanical piezoelectric relay
• CPC Class Codes: H01H 50/005 using micromechanics

Abstract

A MEMS switch assembly comprising a substrate and a resilient switching member is provided. The resilient switching member comprises a transverse torsion member having a flexible portion, and a leaf spring and cantilever that extend from the flexible portion of the torsion member. The switching assembly further comprises a first anchoring member mounting the torsion member to the stable structure, and a second anchoring member mounting the leaf spring to the stable structure. In this manner, the leaf spring has a flexible portion between the first and second anchors that can be alternately flexed in opposing directions to deflect the cantilever end in the respective opposing directions. The leaf spring can exhibit a first stable geometry (e.g., a convex geometry) when flexed in one of the opposite directions, and a second stable geometry (e.g., a concave geometry) when flexed in another of the opposite directions. Thus, the switch can be switched between two stable states using a momentary force and can maintain these two stable states without further expenditure of energy. The cantilever deflects a greater distance than that of the leaf spring, e.g., more than twice as great. Thus, in this case, the unique geometry of the switching member acts as a mechanical amplifier and allows for a large travel distance of the cantilever end, while maintaining reasonable actuation dimensions. The switching assembly can be designed to achieve any one of a variety of switching methodologies. For example, the switching assembly can be arranged as a single pole double throw (SPDT) switch, in which case, the cantilever can make electrical contact between a common terminal and one of two selected terminals, or a single pole single throw (SPST) switch, in which case, the cantilever can alternately electrically couple and decouple two terminals.

Claims

1. A micro-electro-mechanical system (MEMS) switching assembly, comprising:

a stable structure;

a switching member including a transverse torsion member having a flexible portion, a leaf spring, and an electrically conductive cantilever having a free end, the leaf spring and cantilever extending from the flexible portion of the torsion member;

a first anchoring member mounting the torsion member to the stable structure; and

a second anchoring member mounting the leaf spring to the stable structure, wherein the leaf spring has a flexible portion between the first and second anchoring members that can be alternately flexed in opposing directions to deflect the cantilever end in the respective opposing directions.

2. The switching assembly of claim 1, wherein the stable structure comprises a substrate.

3. The switching assembly of claim 1, wherein the resilient switching member comprises a planar membrane.

4. The switching assembly of claim 1, wherein the cantilever is electrically conductive.

5. The switching assembly of claim 1, wherein the switching member comprises another leaf spring extending from the flexible portion of the torsion member, the first and second leaf springs straddling the cantilever.

6. The switching assembly of claim 1, wherein the leaf spring extends from the flexible portion of the torsion member a first distance, and the cantilever extends from the flexible portion of the torsion member a second distance greater than the first distance.

7. The switching assembly of claim 1, wherein the cantilever end deflects a first distance when the leaf spring flexes a second distance, the first distance being greater than the second distance.

8. The switching assembly of claim 7, wherein the first distance is more than twice as great as the second distance.

9. The switching assembly of claim 1, wherein the leaf spring exhibits a first stable geometry when flexed in one of the opposite directions, and exhibits a second stable geometry when flexed in another of the opposite directions.

10. The switching assembly of claim 9, wherein the leaf spring has a stress gradient that maintains the leaf spring in the first and second stable geometries.

11. The switching assembly of claim 9, wherein the first stable geometry is a convex geometry and the second stable geometry is a concave geometry.

12. The switching assembly of claim 1, further comprising:

a common electrical terminal permanently electrically coupled to the cantilever;

a first electrical terminal electrically coupled to the cantilever only when the cantilever is deflected in one of the opposite directions; and

a second electrical terminal electrically coupled to the cantilever only when the cantilever is deflected in another of the opposite directions.

13. The switching assembly of claim 12, wherein the first anchoring member is electrically conductive and is mounted to the common electrical terminal.

14. The switching assembly of claim 1, further comprising:

a first electrical terminal permanently electrically coupled to the cantilever; and

a second electrical terminal electrically coupled to the cantilever only when the cantilever is deflected in one of the opposite directions.

15. The switching assembly of claim 14, wherein the first anchoring member is electrically conductive and is mounted to the first electrical terminal.

16. The switching assembly of claim 1, further comprising first and second electrical terminals electrically coupled to the cantilever only when the cantilever is deflected in one of the opposite directions.

17. The switching assembly of claim 16, wherein the cantilever comprises a shorting bar that shorts the first and second electrical terminals when the cantilever is deflected in the one opposite direction.

18. The switching assembly of claim 1, further comprising an actuator operatively coupled to the leaf spring to alternately flex the leaf spring in the opposing first and second directions

19. The switching assembly of claim 18, wherein the actuator is a magnetic actuator.

20. The switching assembly of claim 19, wherein the actuator comprises:

a magnetic field coil affixed to the leaf spring; and

one or more ferrous elements placed a distance from the magnetic field coil, such that the leaf spring is flexed towards the one or more ferrous elements when electrical current with a first polarity flows through the magnetic field coil, and is flexed away from the one or more ferrous elements when electrical current with a second polarity flows through the magnetic field coil.

21. The switching assembly of claim 19, wherein the actuator comprises:

one or more ferrous elements affixed to the leaf spring; and

a magnetic field coil placed a distance from the magnetic field coil, such that the leaf spring is flexed towards the one or more ferrous elements when electrical current with a first polarity flows through the magnetic field coil, and is flexed away from the one or more ferrous elements when electrical current with a second polarity flows through the magnetic field coil.

22. A micro-electro-mechanical system (MEMS) switching assembly, comprising:

a first substrate having a common terminal and a first terminal;

a second substrate having a second terminal;

a resilient switching member including a transverse torsion member having a flexible portion, a leaf spring, and an electrically conductive cantilever having a free end, the leaf spring and cantilever extending from the flexible portion of the torsion member;

a first anchoring member mounting the torsion member to the stable structure; and

a second anchoring member mounting the leaf spring to the stable structure, wherein the leaf spring has a flexible portion between the first and second anchoring members that can be alternately flexed in opposing directions to alternately deflect the cantilever end into electrical conduction with the first and second terminals.

23. The switching assembly of claim 22, wherein the switching member comprises a planar membrane.

24. The switching assembly of claim 22, wherein the cantilever is electrically conductive.

25. The switching assembly of claim 22, wherein the switching member comprises another leaf spring extending from the flexible portion of the torsion member, the first and second leaf springs straddling the cantilever.

26. The switching assembly of claim 22, wherein the leaf spring extends from the flexible portion of the torsion member a first distance, and the cantilever extends from the flexible portion of the torsion member a second distance greater than the first distance.

27. The switching assembly of claim 22, wherein the cantilever end deflects a first distance when the leaf spring flexes a second distance, the first distance being greater than the second distance.

28. The switching assembly of claim 27, wherein the first distance is more than twice as great as the second distance.

29. The switching assembly of claim 22, wherein the leaf spring exhibits a first stable geometry when flexed in one of the opposite directions, and exhibits a second stable geometry when flexed in another of the opposite directions.

30. The switching assembly of claim 29, wherein the leaf spring has a stress gradient that maintains the leaf spring in the first and second stable geometries.

31. The switching assembly of claim 29, wherein the first stable geometry is a convex geometry and the second stable geometry is a concave geometry.

32. The switching assembly of claim 22, wherein the first anchoring member is electrically conductive and is mounted to the common terminal.

33. The switching assembly of claim 22, further comprising an actuator operatively coupled to the leaf spring to alternately flex the leaf spring in the opposing first and second directions

34. The switching assembly of claim 33, wherein the actuator is a magnetic actuator.

35. The switching assembly of claim 34, wherein the actuator comprises:

a magnetic field coil affixed to the leaf spring; and

one or more ferrous elements affixed to one of the first and second substrates, such that the leaf spring is flexed towards the one or more ferrous elements when electrical current with a first polarity flows through the magnetic field coil, and is flexed away from the one or more ferrous elements when electrical current with a second polarity flows through the magnetic field coil.

36. The switching assembly of claim 34, wherein the actuator comprises:

one or more ferrous elements affixed to the leaf spring; and

a magnetic field coil affixed to one of the first and second substrates, such that the leaf spring is flexed towards the one or more ferrous elements when electrical current with a first polarity flows through the magnetic field coil, and is flexed away from the one or more ferrous elements when electrical current with a second polarity flows through the magnetic field coil.

37. The switching assembly of claim 22, wherein first substrate comprises a coplanar waveguide coupled to the common input terminal and first terminal, and the second substrate comprises a coplanar waveguide coupled to the second terminal.

38. A switching member for a micro-electro-mechanical system (MEMS) switch assembly, comprising:

a transverse torsion member having a flexible portion;

an electrically conductive cantilever extending from the flexible portion of the torsion member, the cantilever having a free end; and

a pair of leaf springs extending from the flexible portion of the torsion member, the leaf springs straddling the cantilever, the pair of leaf springs alternately exhibiting stable first and second geometries when flexed in opposite directions to deflect the cantilever end in the respective opposing directions.

39. The switching member of claim 38, wherein the cantilever is electrically conductive.

40. The switching member of claim 38, wherein the pair of leaf springs extend from the flexible portion of the torsion member a first distance, and the cantilever extends from the flexible portion of the torsion member a second distance greater than the first distance.

41. The switching member of claim 38, wherein the cantilever end deflects a first distance when the leaf spring flexes a second distance, the first distance being greater than the second distance.

42. The switching member of claim 41, wherein the first distance is more than twice as great as the second distance.

43. The switching member of claim 38, wherein the pair of leaf springs has a stress gradient that maintains the pair of leaf springs in the stable convex and concave geometries.

44. The switching member of claim 38, wherein the first stable geometry is a convex geometry, and the second stable geometry is a concave geometry.