Method and apparatus for an improved micro-electrical mechanical switch

• US 6,127,744 A
• Filed: 11/23/1998
• Issued: 10/03/2000
• Est. Priority Date: 11/23/1998
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Streeter, Robert D., McMillan, Lee A.
• Primary Examiner(s): Jackson, Stephen W.
• Assistant Examiner(s): RIOS CUEVAS, ROBERTO JOSE
• Application Number:
  US09/198,669
• Time in Patent Office: 680 Days
• Field of Search: 307/125, 200/181, 361/234
• US Class Current: 307/125
• CPC Class Codes: H01G 5/18 due to change in inclination, e.g. by flexing, by spiral wrapping
• CPC Class Codes: H01G 5/40 Structural combinations of variable capacitors with other electric elements not covered by this subclass, the structure mainly consisting of a capacitor, e.g. RC combinations
• CPC Class Codes: H01H 59/0009 making use of micromechanics

Abstract

A method, device and circuit which applies an electrostatic repulsion pushing force to a MEM switch armature during an opening process. The repulsive force adds to the spring restoration force on the armature, increasing the opening speed of the switch and aids in overcoming stiction effects. The inventive switch includes a contact electrically connected to a first terminal of the switch. A throw is electrically connected to a second terminal of the switch. Finally, a mechanism is provided for opening the switch by electrostatically causing the throw to disengage the contact. In the illustrative implementation, the mechanism for opening the switch includes a first charge storage structure mounted on the throw and a second charge storage structure mounted in proximity to the first charge storage structure. When charges are applied between the first and the second charge storage structures, a force of repulsion is created or a force of attraction is created depending on the polarity of the potential.

Claims

1. An MEM switch comprising:

a cantilever beam having first and second ends;

a cantilever support member coupled to the second end of the cantilever beam;

a first insulative layer disposed on the cantilever beam;

a first control surface disposed on the first insulative layer such that the first control surface, the first insulative layer and the cantilever beam form a first capacitor having a substantially fixed capacitance;

a first conductive surface opposing the cantilever beam;

a second insulative layer disposed on the first conductive surface; and

a second control surface disposed on the second insulative surface and facing the first control surface such that the second control surface, the second dielectric layer, and the first conductive surface form a second capacitor having a substantially fixed capacitance, and the first and second control surfaces form a third capacitor having a variable capacitance that is determined by the position of the cantilever beam.

2. The switch according to claim 1, wherein the cantilever beam, the cantilever support member, and the first conductive surface are connected so as to be at the same electrical potential.

3. An MEM switch, comprising:

a cantilever support member;

a cantilever beam having first and second ends, the first end being coupled to the cantilever support member;

a contact member spaced from the cantilever support member for contacting the second end of the cantilever beam;

a first conductive surface opposing the cantilever beam;

a first dielectric layer disposed on the cantilever beam;

a first control surface disposed on the first dielectric layer, the first control surface for receiving a first control voltage;

a second dielectric layer disposed on first conductive surface; and

a second control surface disposed on the second dielectric layer such that that the first and second control surfaces face each other, the second control surface for receiving a second control voltage, wherein respective polarities of the first and second control voltages control the position of the cantilever beam for actively opening and actively closing the switch.

4. The switch according to claim 3, wherein the cantilever beam, the cantilever support member, and the first conductive surface are connected so as to be at the same electrical potential.

5. A method of controlling a micromechanical switch, comprising:

applying a first control voltage having a first polarity to a first control surface spaced from a cantilever beam by a first insulative layer, such that the first control voltage charges a first capacitor formed by the first control surface, the first insulative layer and the cantilever beam;

applying a second control voltage having a second polarity, which is opposite to that of the first control voltage, to a second control surface spaced from a first conductive layer by a second insulative layer such that the second control voltage charges a second capacitor formed by the second control surface, the second insulative layer and the first conductive layer for causing an end of the cantilever beam to touch a contact so as to close the switch; and

switching a polarity of one of the first and second control voltages so as to open the switch.

6. The method according to claim 5, further including placing cantilever beam, a cantilever support member and the first conductive surface at substantially the same electrical potential.

7. The method according to claim 5, further including providing substantially equal and opposite polarity voltages on the first and second control voltages when closing the switch.

8. The method according to claim 5, further including providing substantially equal and same polarity voltages on the first and second control voltages when opening the switch.

9. The method according to claim 5, further including connecting a low impedance circuit to at least one of the first and second capacitors for reducing a capacitor charging time.

10. The method according to claim 5, further including providing DC voltages on the first and second control voltages.

11. The method according to claim 5, further including providing AC voltages on the first and second control voltages.

12. The method according to claim 5, further including setting the first control voltage to about zero volts when closing the switch.

13. The method according to claim 5, further including setting the second control voltage to about zero volts when closing the switch.

14. The method according to claim 5, further including maintaining same polarity signals on the first and second control voltages after the switch is open.

15. The method according to claim 5, wherein the first control voltage is about positive fifty volts with respect to the cantilever beam, the cantilever support member, and the first conductive surface when closing the switch.

16. The method according to claim 15, wherein the second control voltage is about negative fifty volts with respect to the cantilever beam, the cantilever support member, and the first conductive surface when closing the switch.

17. The method according to claim 5, wherein movement of the cantilever beam towards the contact interrupts an optical path.

18. The method according to claim 5, further including coupling a load to the contact.

19. The method according to claim 18, further including coupling a load voltage to the load.