Insertion-type liquid metal latching relay

• US 6,740,829 B1
• Filed: 04/14/2003
• Issued: 05/25/2004
• Est. Priority Date: 04/14/2003
• Status: Expired due to Fees

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Wong, Marvin Glenn
• Primary Examiner(s): Donovan, Lincoln
• Assistant Examiner(s): KLAUS, LISA NHUNG
• Application Number:
  US10/412,824
• Time in Patent Office: 407 Days
• Field of Search: 200/214, 200/182, 200/190, 200/193, 200/234, 200/199, 307/409
• US Class Current: 200/214
• CPC Class Codes: H01H 1/08 wetted with mercury
• 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 2029/008 using micromechanics, e.g. micromechanical liquid contact switches or [LIMMS]
• CPC Class Codes: H01H 2057/006 Micromechanical piezoelectric relay
• CPC Class Codes: H01H 57/00 Electrostrictive relays; Piezoelectric relays

Abstract

A high frequency electrical relay uses a conducting liquid in the switching mechanism. The relay uses an actuator, such as a piezoelectric element, to cause the switch actuator to insert into a cavity in a static switch contact structure. The cavity has sides and a pad on its end that are wettable by the conducting liquid. The cavity is filled with the conducting liquid, which may be liquid metal. The volume of conducting liquid is chosen so that when the actuator returns to its rest position, the electrical contact is maintained by surface tension and by wetting of the contact pads on both the static switch contact structure and the actuator.

Claims

1. An electrical relay comprising:

a first electrical contact, having a wettable surface;

a second electrical contact with a wettable surface, at least partially lining the cavity in the second electrical contact to form a liquid well;

a well-support structure in close proximity to the first and second electrical contacts, the well-support structure having a liquid well formed within it;

a first conducting liquid volume in wetted contact with the first electrical contact;

a second conducting liquid volume in the liquid well in wetted contact with the second electrical contact; and

an actuator having a rest position at least partially within the liquid well;

wherein expansion of the actuator decreases the volume of the liquid well and displaces the second conducting liquid volume, thereby causing the first and second conducting liquid volumes to coalesce and complete an electrical circuit between the first and second electrical contacts, and contraction of the actuator increases the volume of the liquid well, thereby causing the first and second conducting liquid volumes to separate and break the electrical circuit.

2. An electrical relay in accordance with claim 1, further comprising:

a first signal conductor, electrically coupled to the first electrical contact; and

a second signal conductor, electrically coupled to the second electrical contact.

3. An electrical relay in accordance with claim 2, wherein the second signal conductor provides the well-support structure.

4. An electrical relay in accordance with claim 2, further comprising:

a ground shield, encircling the first and second electrical contacts and the first and second signal conductors;

a first dielectric layer positioned between the ground shield and the first signal conductor, the first dielectric layer electrically insulating the ground shield from the first signal conductor; and

a second dielectric layer positioned between the ground shield and the second signal conductor, the second dielectric layer electrically insulating the ground shield from the second signal conductor.

5. An electrical relay in accordance with claim 1, wherein the first electrical contact is attached to the actuator.

6. An electrical relay in accordance with claim 5, wherein expansion of the actuator moves the first electrical contact towards the second electrical contact and contraction of the actuator moves the first electrical contact away from the second electrical contact.

7. An electrical relay in accordance with claim 1, wherein the actuator comprises one of a piezoelectric actuator and a magnetorestrictive actuator.

8. An electrical relay in accordance with claim 1, wherein the first and second conducting liquid volumes are liquid metal volumes.

9. An electrical relay in accordance with claim 1, wherein the first and second conducting liquid volumes are sized such that coalesced volumes remain coalesced when the actuator is returned to its rest position, and separated volumes remain separated when the actuator is returned to its rest position.

10. An electrical relay in accordance with claim 1, further comprising a non-wetting coating partially covering the first electrical contact to prevent migration of the conducting liquid along the first electrical contact.

11. An electrical relay in accordance with claim 1, further comprising:

a circuit substrate supporting electrical connections to the actuator;

a cap layer; and

a switching layer positioned between the circuit substrate and the cap layer and having a channel formed therein;

wherein the first and second electrical contacts and the actuator are positioned within the channel.

12. An electrical relay in accordance with claim 11, wherein at least one of the electrical connections to the actuator passes through the circuit substrate.

13. An electrical relay in accordance with claim 11, wherein the electrical connections to the actuator comprise traces deposited on the surface of the circuit substrate.

14. An electrical relay in accordance with claim 11, manufactured by a method of micro-machining.

15. An electrical relay in accordance with claim 11, wherein the cap layer is fabricated from one of ceramic, glass, metal, silicon and polymer.

16. An electrical relay in accordance with claim 11, wherein the circuit substrate is fabricated from one of ceramic, glass and silicon.