THERMAL MECHANICAL ISOLATOR FOR VACUUM PACKAGING OF A DISC RESONATOR GYROSCOPE

• US 20100251817A1
• Filed: 04/01/2009
• Published: 10/07/2010
• Est. Priority Date: 04/01/2009
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Ge, Howard H., Challoner, A. Dorian
• Granted Patent: US 8,322,028 B2
• Time in Patent Office: Days
• US Class Current: 73/504.120
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 7/0058 for protecting against damages due to external chemical or mechanical influences, e.g. shocks or vibrations
• CPC Class Codes: G01C 19/5684 the devices involving a micromechanical structure
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: Y10T 29/49117 Conductor or circuit manufacturing
• CPC Class Codes: Y10T 29/49124 On flat or curved insulated base, e.g., printed circuit, etc.
• CPC Class Codes: Y10T 29/49128 Assembling formed circuit to base
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base

Abstract

A single layer micromachined thermal and mechanical isolator may be bonded between a microelectromechanical system (MEMS) die and package. Small bond pads of the isolator are attached to the periphery of the die. The isolator material may be chosen to match that of the die, reducing CTE mismatch. Long thin isolation beams can be used to provide thermal isolation against external temperature changes, which may be conducted through the package. Weak and flexible beams can be used to tolerate large displacements with very little resistance. Thus, excessive stress or distortion to the package, from either CTE mismatch or external stress, may be absorbed by the isolator and will not be transmitted to the MEMS die. Beam rigidity may be designed to attenuate vibration of particular frequency range. The isolator can be readily inserted into an existing disc resonator gyroscope package in one thermal compression bond step.

Claims

1. An apparatus comprising:

a single layer comprising a central region and a plurality of substantially radial isolation beams, each extending from the central region to a separate radial symmetric pad;

a vacuum package bonded to the central region of the single layer; and

a microelectromechanical system (MEMS) die bonded to each separate radial symmetric pad at a periphery of the MEMS die;

wherein the vacuum package is bonded to a bottom side of the single layer and the MEMS die is bonded to a top side of the single layer.

2. The apparatus of claim 1, wherein each of the plurality of substantially radial isolation beams comprises a plurality of circumferential segments and radial segments connected in series.

3. The apparatus of claim 2, wherein each of the plurality of substantially radial isolation beams includes three circumferential segments and four radial segments alternately interconnected in series.

4. The apparatus of claim 3, wherein there are three substantially radial isolation beams.

5. The apparatus of claim 1, wherein beam width of the substantially radial top layer isolation beams is selected to provide vibration isolation.

6. The apparatus of claim 1, wherein there are three substantially radial isolation beams.

7. The apparatus of claim 1, wherein the MEMS die comprises a disc resonator having embedded electrostatic electrodes having sidewalls that interact with interior sidewalls of the disc resonator such that vibration modes of the disc resonator are driven and sensed with the embedded electrostatic electrodes to measure motion of the disc resonator;

and

a baseplate having a topside bonded to support the disc resonator and having electrical traces coupled from the embedded electrostatic electrodes and to a baseplate periphery;

wherein a bottom side of the baseplate is bonded to the separate radial symmetric pad of each of the plurality of substantially radial isolation beams.

8. The apparatus of claim 7, wherein the vacuum package comprises electrical feedthroughs where the electrical feedthroughs are coupled to wire bonds that are coupled in turn to the electrical traces at the baseplate periphery.

9. The apparatus of claim 8, wherein the vacuum package comprises a lid including a getter material activated to assist producing a vacuum within the vacuum package and the lid is bonded to close out the vacuum package.

10. The apparatus of claim 1, wherein the single layer comprises a semiconductor material selected from the group consisting of silicon and fused silica.

11. A method of producing an isolator for a microelectromechanical system (MEMS) die, comprising:

etching a single layer comprising a central region and a plurality of substantially radial isolation beams, each extending from the central region to a separate radial symmetric pad;

bonding a vacuum package to the central region of the single layer at a bottom side of the single layer; and

bonding a MEMS die to each separate radial symmetric pad at a periphery of the MEMS die at a top side of the single layer.

12. The method of claim 11, wherein each of the plurality of substantially radial isolation beams comprises a plurality of circumferential segments and radial segments connected in series.

13. The method of claim 12, wherein each of the plurality of substantially radial isolation beams includes three circumferential segments and four radial segments alternately interconnected in series.

14. The method of claim 13, wherein there are three substantially radial isolation beams.

15. The method of claim 11, wherein beam width of the substantially radial top layer isolation beams is selected to provide vibration isolation.

16. The method of claim 11, wherein there are three substantially radial isolation beams.

17. The method of claim 11, wherein the MEMS die comprises a disc resonator having embedded electrostatic electrodes having sidewalls that interact with interior sidewalls of the disc resonator such that vibration modes of the disc resonator are driven and sensed with the embedded electrostatic electrodes to measure motion of the disc resonator;

and

a baseplate having a topside bonded to support the disc resonator and having electrical traces coupled from the embedded electrostatic electrodes and to a baseplate periphery;

wherein a bottom side of the baseplate is bonded to the separate radial symmetric pad of each of the plurality of substantially radial isolation beams.

18. The method of claim 17, wherein the vacuum package comprises electrical feedthroughs where the electrical feedthroughs are coupled to wire bonds that are coupled in turn to the electrical traces at the baseplate periphery.

19. The method of claim 18, wherein the vacuum package comprises a lid including a getter material activated to assist producing a vacuum within the vacuum package and the lid is bonded to close out the vacuum package.

20. The method of claim 11, wherein the single layer comprises a semiconductor material selected from the group consisting of silicon and fused silica.

21. A disc resonator gyroscope, comprising:

a single layer comprising a central region and a plurality of substantially radial isolation beams, each extending from the central region to a separate radial symmetric pad;

a disc resonator means for measuring motion attached to each separate radial symmetric pad of the single layer at a top side of the single layer.

22. The apparatus of claim 21, further comprising a vacuum package means for enclosing the disc resonator means in a vacuum, the vacuum package means bonded to a bottom side of the single layer.