Micromachined acceleration activated mechanical switch and electromagnetic sensor

• US 6,262,463 B1
• Filed: 07/08/1999
• Issued: 07/17/2001
• Est. Priority Date: 07/08/1999
• Status: Expired due to Term

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Integrated Micromachines, Inc. (Advantest Corporation)
• Inventors: Tang, Weilong, Miu, Denny K.
• Primary Examiner(s): MINTEL, WILLIAM A
• Application Number:
  US09/349,840
• Time in Patent Office: 740 Days
• Field of Search: 257/414, 257/415, 200/83.N, 200/83.V, 335/78, 335/80, 361/819, 438/50
• US Class Current: 257/414
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2203/0127 Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function
• CPC Class Codes: B81B 2203/0361 Tips, pillars
• CPC Class Codes: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/11 by inductive pick-up
• CPC Class Codes: G01P 15/135 by making use of contacts which are actuated by a movable inertial mass
• CPC Class Codes: H01H 1/0036 Switches making use of microelectromechanical systems [MEMS] for electromagnetic relays H01H50/005; for electrostatic relays H01H59/0009
• CPC Class Codes: H01H 35/14 Switches operated by change of acceleration, e.g. by shock or vibration, inertia switch wherein the liquid constitutes a contact of the switch H01H29/002

Abstract

A micro-sensor having have a flexible monocrystalline structure that is moved by an external force. In one embodiment, one or more pole tips are mounted on the monocrystalline structure. The monocrystalline structure is suspended over one or more planar coils such that each pole tip is suspended over a corresponding planar coil. As the monocrystalline structure moves in response to the external force, the pole tips are moved in the coils, thereby changing the inductance or inducing a voltage in the coils. In another variation, a micro-switch includes a lower structural member having a pattern of raised spacer pads that laterally surround a plurality of contact pads. The lower structural member is joined to an upper structural member that includes a frame, a platform located in the frame and a plurality of spring elements which connect the frame to the platform. The upper structural member has a conductive layer formed on its planar lower surface. The lower surface of the frame is affixed to the spacer pads, such that the platform is suspended over the contact pads. An external force applied to the resulting structure causes the spring elements to flex, such that the platform moves toward the lower structural member, thereby placing the conductive layer into contact with the contact pads of the lower structural member.

Claims

1. A micro-sensor comprising:

a substrate;

one or more planar coils located entirely over a single surface of the substrate;

a flexible monocrystalline structure suspended over the substrate; and

one or more pole tips coupled to the monocrystalline structure and positioned above the one or more coils, wherein an external force applied to the flexible monocrystalline structure causes the monocrystalline structure to flex toward the substrate, thereby inserting the pole tips into the planar coils to induce a voltage in the planar coils or change the inductance of the planar coils.

2. The micro-sensor of claim 1, wherein the monocrystalline structure comprises:

a frame portion located about a perimeter of the monocrystalline structure;

a platform portion which is laterally surrounded by the frame portion, the pole piece being located on the platform portion; and

a plurality of spring elements extending between the frame portion and the platform portion.

3. The micro-sensor of claim 2, wherein the spring elements have a serpentine shape.

4. The micro-sensor of claim 2, further comprising a cover located over the monocrystalline structure.

5. The micro-sensor of claim 1, wherein the monocrystalline structure is continuous.

6. The micro-sensor of claim 2, wherein the spring elements have a thickness that is less than the thickness of the frame portion and the platform portion.

7. The micro-sensor of claim 1, wherein the substrate comprises a ferromagnetic material.

8. The micro-sensor of claim 1, wherein the substrate comprises:

a monocrystalline silicon substrate having a trench located therein; and

a layer of ferromagnetic material located in the trench.

9. The micro-sensor of claim 1, wherein the pole tips comprise a ferromagnetic material.

10. The micro-sensor of claim 1, wherein the pole tips comprise a permanent magnetic material.

11. The micro-sensor of claim 1, wherein the monocrystalline structure comprises monocrystalline silicon.

12. A micro-switch comprising:

a substrate;

a plurality of spacer pads located at the upper surface of the substrate and surrounding a central area of a substrate;

a plurality of electrically conductive contact pads located at the central area of the upper surface of the substrate, wherein the contact pads are laterally surrounded by the spacer pads;

a flexible monocrystalline structure mounted on the spacer pads and suspended over the contact pads; and

an electrically conductive bridge contact pad located on a lower surface of the monocrystalline structure, the bridge contact pad being positioned such that when the monocrystalline structure flexes toward the substrate, the bridge contact pad touches two or more of the contact pads, thereby providing an electrical connection between the two or more contact pads.

13. The micro-switch of claim 12, wherein the monocrystalline structure comprises monocrystalline silicon.

14. The micro-switch of claim 12, wherein the monocrystalline structure comprises:

frame portion located about a perimeter of the monocrystalline structure;

a platform portion which is laterally surrounded by the frame portion, the pole piece being located on the platform portion; and

a plurality of spring elements extending between the frame portion and the platform portion.

15. The micro-switch of claim 12, further comprising a cover substrate mounted over the upper surface of the monocrystalline structure.

16. The micro-switch of claim 12, further comprising:

a plurality of bonding pads located near an edge of the upper surface of the substrate, wherein each of the bonding pads is electrically connected to a corresponding one of the contact pads, and wherein each of the bonding pads is located in a groove;

an insulating layer located between the bonding pads and the lower surface of the monocrystalline structure; and

a solder ball located in each of the grooves, thereby providing an electrical connection to the bonding pads.