Latching relay with switch bar

• US 6,876,133 B2
• Filed: 04/14/2003
• Issued: 04/05/2005
• 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): Dougherty, Thomas M.
• Application Number:
  US10/413,099
• Publication Number:
  US 20040201318A1
• Time in Patent Office: 722 Days
• Field of Search: 200/182, 200/188, 200/211, 200/214, 200/215, 310/328, 310/348, 335/47, 335/49, 335/51, 335/58
• US Class Current: 310/328
• 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 55/00 Magnetostrictive relays
• 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 switching contacts is attached to the free end of a switch bar and positioned between a pair of fixed electrical contact pads. A surface of each contact supports a droplet of a conducting liquid, such as a liquid metal. A piezoelectric actuator is energized to push or pull the switch bar and move the pair of switching contacts, closing the gap between one of the fixed contact pads and one of the switching contacts, thereby causing conducting liquid droplets to coalesce and form an electrical circuit. At the same time, the gap between the other fixed contact pad and the other switching contact is increased, causing conducting liquid droplets to separate and break an electrical circuit. The piezoelectric actuator is then de-energized and the switching 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 contact pads, each attached to the relay housing in the switching cavity and having a wettable surface;

first and second switching contacts positioned between the first and second fixed contact pads, each of the first and second switching contacts having a wettable surface;

a first conducting liquid volume in wetted contact with the first switching contact and the first fixed contact pad;

a second conducting liquid volume in wetted contact with the second switching contact and the second fixed contact pad; and

a switch bar having a fixed end coupled to the relay housing and a free end supporting the first and second switching contacts;

a piezoelectric actuator coupled to the relay housing and to the switch bar between its free end and its fixed end, the piezoelectric actuator being deformable in an extensional mode to move the free end of the switch bar in a first direction, to decrease the distance between the first switching contact and the first fixed contact pad and increase the distance between the second switching contact and the second fixed contact pad, and a second direction to increase the distance between the first switching contact and the first fixed contact pad and decrease the distance between the second switching contact and the second fixed contact pad,

wherein;

motion of the switch bar in the first direction causes the first conducting liquid volume to form a connection between the first switching contact and the first fixed contact pad and causes the second conducting liquid volume to separate into two droplets, thereby breaking a connection between the second switching contact and the second fixed contact pad; and

motion of the switch bar in the second direction causes the first conducting liquid volume to separate into two droplets, thereby breaking the connection between the first switching contact and the first fixed contact pad and causes the second conducting liquid volume to form a connection between the second switching contact and the second fixed contact pad.

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 switching contacts and the first and second fixed contact pads;

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 contact pads and the first and second switching 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 contact pads and the first and second switching 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 contact pads and the first and second switching 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 contact pads are electrically coupled to each other.

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

11. A method for switching between a first electrical circuit, between a first switching contact and a first fixed contact pad, and a second electrical circuit, between a second switching contact and a second fixed contact pad, in a relay, the relay including a switch bar 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 contact pads, the method comprising:

if the first electrical circuit is to be selected;

energizing a piezoelectric actuator to push the switch bar in a first direction, thereby moving the first switching contact towards the first fixed contact pad so that a first conducting liquid volume, supported by at least one of the first switching contact and the first fixed contact pad, wets between the first switching contact and the first fixed contact pad and completes the first electrical circuit; and

if the second electrical circuit is to be selected;

energizing the piezoelectric actuator to pull the switch bar in a second direction, thereby moving the second switching contact towards the second fixed contact pad so that a second conducting liquid volume, supported by at least one of the second switching contact and the second fixed contact pad, wets between the second switching contact and the second fixed contact pad and completes the second electrical circuit.

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

motion of the switch bar in the first direction moves the second switching contact away from the second fixed contact pad, so that the second conducting liquid volume cannot wet between the second switching contact and the second fixed contact pad, thereby breaking the second electrical circuit; and

motion of the switch bar in the second direction moves the first switching contact away from the first fixed contact pad, so that the first conducting liquid volume cannot wet between the first switching contact and the first fixed contact pad, 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 switching 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 switching contact and the second fixed contact.