MEMS microphone system for harsh environments

• US 8,841,738 B2
• Filed: 10/01/2012
• Issued: 09/23/2014
• Est. Priority Date: 10/01/2012
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Harney, Kieran P., Gao, Jia, Khenkin, Aleksey S.
• Primary Examiner(s): Green, Telly
• Assistant Examiner(s): Hillman, Damian A
• Application Number:
  US13/632,205
• Publication Number:
  US 20140091406A1
• Time in Patent Office: 722 Days
• Field of Search: 257/416, 257/777, 257/778
• US Class Current: 257/416
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H04R 1/086 Protective screens, e.g. all weather or wind screens
• CPC Class Codes: H04R 19/005 using semiconductor materials
• CPC Class Codes: H04R 19/04 Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 31/00 Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor manufacture of microstructural arrangements of deformable or non-deformable structures in general B81C1/00182

Abstract

A MEMS microphone system suited for harsh environments. The system uses an integrated circuit package. A first, solid metal lid covers one face of a ceramic package base that includes a cavity, forming an acoustic chamber. The base includes an aperture through the opposing face of the base for receiving audio signals into the chamber. A MEMS microphone is attached within the chamber about the aperture. A filter covers the aperture opening in the opposing face of the base to prevent contaminants from entering the acoustic chamber. A second metal lid encloses the opposing face of the base and may attach the filter to this face of the base. The lids are electrically connected with vias forming a radio frequency interference shield. The ceramic base material is thermally matched to the silicon microphone material to allow operation over an extended temperature range.

Claims

1. A microphone system in an integrated circuit package comprising:

a package base including opposing first and second faces, the package base including a cavity in the first face;

a first metal lid coupled to the first face of the package base covering the cavity and forming an acoustic chamber, the package base including an aperture through the second face of the package base for receiving an audio signal into the acoustic chamber;

a filter covering the aperture in the second face of the package base;

a silicon microphone secured to the package base about the aperture within the acoustic chamber; and

a second metal lid enclosing the second face of the package base and the filter, the second metal lid electrically connected to the first metal lid, the second metal lid including an opening for allowing the audio signal to reach the acoustic chamber.

2. The microphone system as defined by claim 1 wherein the package base material is a ceramic.

3. The microphone system as defined by claim 1 wherein the package base material is chosen from a group consisting of alumina and aluminum nitride.

4. The microphone system as defined by claim 1 wherein the filter is attached to the package base by the second metal lid.

5. The microphone system as defined by claim 1 wherein the second metal lid includes the filter.

6. The microphone system as defined by claim 1 wherein the filter comprises a polyetheretherketone fabric.

7. The system as defined by claim 1 wherein the filter is chosen from a group consisting of a polytetrafluoroethylene fabric and a sintered metal mesh.

8. The microphone system as defined by claim 1 wherein the filter has a controlled acoustic impedance.

9. The microphone system as defined by claim 1 further comprising a processing element secured within the acoustic chamber, the processing element electrically communicating with the silicon microphone.

10. The microphone system as defined by claim 1 further comprising in-line package leads side-brazed to a lead frame.

11. The microphone system as defined by claim 1 further comprising J-lead package leads.

12. The microphone system as defined by claim 1 further comprising gull-wing package leads.

13. The microphone system as defined by claim 1 where the integrated circuit package is surface-mounted.

14. The microphone system as defined by claim 1 wherein the first metal lid and the second metal lid are connected with vias, where the vias are spaced such that radio frequency interference is reduced.

19. The microphone system as defined by claim 1 wherein the silicon microphone being positioned between the cavity and the filter.

20. The microphone system as defined by claim 1 wherein the silicon microphone being secured to the package base about the aperture within the acoustic chamber.

21. The microphone system as defined by claim 1 wherein the silicon microphone including a diaphragm and an electrode capacitively coupled together.

22. The microphone system as defined by claim 1 wherein the filter being positioned between the aperture and the second metal lid.

23. The microphone system as defined by claim 1 wherein the filter being positioned in a manner such as to avoid contamination.

24. The microphone system as defined by claim 1 further including a microphone die situated between the cavity and the aperture and implemented as an application specific integrated circuit (ASIC), the ASIC being attached to the first face of the package base within the cavity.

25. The microphone system as defined by claim 1 wherein the first and second metal lids form an EMI shield.

15. A method of forming a microphone system, the method comprising:

providing a package base including opposing first and second faces, the base including a cavity in the first face, vias, and an aperture through the second face;

securing a MEMS microphone about the package base aperture;

securing a first metal lid to the first face of the package base to form an acoustic chamber including the cavity, wherein the acoustic chamber contains the microphone;

attaching a filter to the second face of the package base wherein the filter covers the aperture; and

attaching a second metal lid to the second face of the base; and

electrically connecting the vias to each of the first metal lid and the second metal lid such that the first metal lid and the second metal lid are electrically connected.

16. The method of claim 15 wherein the package base is ceramic.

17. The method of claim 15 wherein the first and second metal lids are attached to the package base by seam welding.

18. The method of claim 15 wherein the first and second metal lids are attached to the package base by soldering.

26. The method of claim 15 wherein the filter being positioned sufficiently away from the microphone to avoid contamination thereof.