High frequency latching relay with bending switch bar

• US 6,900,578 B2
• Filed: 04/14/2003
• Issued: 05/31/2005
• 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:
  US10/413,237
• Publication Number:
  US 20040201321A1
• Time in Patent Office: 778 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 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 moveable switching contacts is attached to the free end of a switch bar and positioned between a pair of fixed electrical contact pads. The connections to the switching contacts and the fixed contact pads are shielded by ground traces. 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 comprises:

a cap layer;

a circuit substrate;

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

first and second electrical traces formed on the circuit substrate and terminating at first and second fixed contact pads, respectively, in the switching cavity;

a switch bar having a fixed end coupled to the relay housing and a free end;

first and second switching contacts attached to the free end of the switch bar and positioned between the first and second fixed contact pads;

a third electrical trace formed on the circuit substrate and electrically coupled to at least one of the first and second switching contacts;

a first plurality of ground traces formed on the circuit substrate to provide electrical shielding to the first, second and third electrical traces;

a piezoelectric actuator coupled to the switching layer and to the switch bar between its free end and its fixed end, the piezoelectric actuator being deformable in an extensional mode to displace the switch bar and move the switching contacts between the fixed contact pads;

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

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

wherein;

motion of the switching contacts in a 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 switching contacts in a 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 droplets remain separated when the switch bar is not displaced.

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

a first moveable contact supported by the switch bar and electrically coupled to at least one of the first and second switching contacts;

a third fixed contact pad positioned in proximity to the first moveable contact and electrically coupled to the third electrical trace; and

a third conducting liquid volume in wetted contact with and forming an electrical connection between the first moveable contact and the third fixed contact pad,

wherein the third conducting liquid volume is sized so that the electrical connection between the first moveable contact and the third fixed contact pad is maintained when the switch bar is displaced.

5. An electrical relay in accordance with claim 1, wherein at least one of the first, second and third electrical traces terminates at an edge of the circuit substrate.

6. An electrical relay in accordance with claim 1, further comprising a second plurality of ground traces deposited on the lower surface of the circuit substrate, the first plurality of ground traces being electrically connected to the second plurality of ground traces by one or more vias passing through the circuit substrate.

7. An electrical relay in accordance with claim 1, wherein the relay is manufactured by a method of micro-machining.

8. An electrical relay in accordance with claim 1, wherein the fixed end of the switch bar is rigidly fixed to the switching layer.

9. An electrical relay in accordance with claim 1, wherein the fixed end of the switch bar is hinged to the switching layer.

10. An electrical relay in accordance with claim 1, wherein the first and second switching contacts are separated by a surface that is not wettable by conducting liquid.

11. An electrical relay in accordance with claim 1, wherein all of the ground traces of the first plurality of ground traces are electrically coupled to each other.

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

13. An electrical relay in accordance with claim 1, wherein the third electrical trace is electrically coupled to the first switching contact and further comprising a fourth electrical trace formed on the circuit substrate and electrically coupled to the second switching contact.

14. An electrical relay in accordance with claim 1, wherein the conducting liquid droplet is mercury.

15. An electrical relay in accordance with claim 1, wherein the conducting liquid droplet is a gallium alloy.