Bending-mode latching relay

• US 20040201315A1
• Filed: 04/14/2003
• Published: 10/14/2004
• Est. Priority Date: 04/14/2003
• Status: Active Grant

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Wong, Marvin Glenn
• Granted Patent: US 6,882,088 B2
• Time in Patent Office: Days
• US Class Current: 310/328
• 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

An electrical relay that uses a conducting liquid in the switching mechanism. In the relay, a pair of moveable electrical contacts is attached to the free end of a piezoelectric actuator and positioned between pair of fixed electrical contacts. The contacts each support a droplet of a conducting liquid, such as a liquid metal. The piezoelectric actuator is energized to deform in a bending mode and move the pair of moveable contacts, closing the gap between one of the fixed contacts and one of the moveable contacts, thereby causing conducting liquid droplets to coalesce and form an electrical circuit. At the same time, the gap between the other fixed contact and the other moveable contact is increased, thereby causing conducting liquid droplets to separate and break an electrical circuit. The piezoelectric actuator is then de-energized and the moveable electrical contacts return to their starting positions. The volume of liquid metal is chosen so that liquid metal droplets remain coalesced or separated because of surface tension in the liquid. The relay is amenable to manufacture by micro-machining techniques.

Claims

1. An electrical relay comprising:

a relay housing containing a switching cavity;

first and second fixed electrical contacts attached to the relay housing in the switching cavity each having a wettable surface;

first and second moveable electrical contacts positioned between the first and second fixed electrical contacts, the first and second moveable electrical contacts, each having a wettable surface;

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

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

a piezoelectric actuator in a rest position having fixed end attached to the relay housing and a free end supporting the first and second moveable electrical contacts, the piezoelectric actuator being operable to move the free end in a first direction, to reduce the distance between the first moveable electrical contact and the first fixed electrical contact and increase the distance between the second moveable electrical contact and the second fixed electrical contact, and in a second direction to increase the distance between the first moveable electrical contact and the first fixed electrical contact and decrease the distance between the second moveable electrical contact and the second fixed electrical contact,

wherein;

motion of the free end of the piezoelectric actuator in the first direction causes the first conducting liquid volume to form a connection between the first moveable electrical contact and the first fixed electrical contact and breaks a connection formed by the second conducting liquid volume between the second moveable electrical contact and the second fixed electrical contact; and

motion of the free end of the piezoelectric actuator in the second direction breaks the connection formed by the first conducting liquid volume between the first moveable electrical contact and the first fixed electrical contact and causes the second conducting liquid to form a connection between the second moveable electrical contact and the second fixed electrical contact.

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

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

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

a circuit substrate supporting electrical connections to the piezoelectric actuator, the first and second moveable electrical contacts and the first and second fixed electrical contacts;

a cap layer; and

a switching layer positioned between the circuit substrate and the cap layer and having the switching cavity formed therein.

5. An electrical relay in accordance with claim 4, wherein at least one of the electrical connections to the first and second fixed electrical contacts and the first and second moveable electrical contacts passes through the circuit substrate and terminates in a solder ball.

6. An electrical relay in accordance with claim 4, wherein at least one of the electrical connections to the first and second fixed electrical contacts and the first and second moveable electrical contacts is a trace deposited on the surface of the circuit substrate.

7. An electrical relay in accordance with claim 4, wherein at least one of the electrical connections to the first and second fixed electrical contacts and the first and second moveable electrical contacts terminates at an edge of the switching layer.

8. An electrical relay in accordance with claim 4, manufactured by a method of micro-machining.

9. An electrical relay in accordance with claim 1, wherein the first and second fixed electrical contacts are electrically coupled to each other.

10. An electrical relay in accordance with claim 1, wherein the first and second moveable electrical contacts are electrically coupled to each other.

11. A method for switching between a first electrical circuit, between a first movable contact and a first fixed contact, and a second electrical circuit, between a second moveable contact and a second fixed contact, in a relay, the relay including a piezoelectric actuator having a fixed end attached to the relay and a free end supporting the first and second switching contacts between the first and second fixed contacts, the method comprising:

if the first electrical circuit is to be selected;

energizing the piezoelectric actuator to deform in a bending mode and move the free end of the piezoelectric actuator in a first direction, thereby moving the first moveable contact towards the first fixed contact so that a first conducting liquid, supported by at least one of the first moveable contact and the first fixed contact, wets between the first moveable contact and the first fixed contact and completes the first electrical circuit; and

if the second electrical circuit is to be selected;

energizing the piezoelectric actuator to deform in a bending mode and move the free end of the piezoelectric actuator in a second direction, thereby moving the second moveable contact towards the second fixed contact so that a second conducting liquid, supported by at least one of the second moveable contact and the second fixed contact, wets between the second moveable contact and the second fixed contact and completes the second electrical circuit.

12. A method in accordance with claim 11, wherein:

motion of the free end of the piezoelectric actuator in the first direction moves the second moveable contact away from the second fixed contact, so that the second conducting liquid cannot wet between the second moveable contact and the second fixed contact, thereby breaking the second electrical circuit; and

motion of the free end of the piezoelectric actuator in the second direction moves the first moveable contact away from the first fixed contact, so that the first conducting liquid cannot wet between the first moveable contact and the first fixed contact, thereby breaking the first electrical circuit.

13. A method in accordance with claim 11, further comprising:

if the first electrical circuit is to be selected;

de-energizing the piezoelectric actuator after the first conducting liquid wets between the first moveable contact and the first fixed contact; and

if the second electrical circuit is to be selected;

de-energizing the piezoelectric actuator after the second conducting liquid wets between the second moveable contact and the second fixed contact.