Capacitive microphone with integrated cavity

Patent metadata

Field	Value
Publication number	US-9794711-B2
Application number	US-201615372927-A
Country	US
Kind code	B2
Filing date	Dec 8, 2016
Priority date	Apr 25, 2007
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

A capacitive microphone and method of fabricating the same are provided. One or more holes can be formed in a first printed circuit board (PCB). A diaphragm can be surface micromachined onto an interior surface of the first PCB at a region having the one or more holes. Interface electronics can also be interconnected to the interior surface of the PCB. One or more spacer PCBs can be attached to a second PCB to the first PCB, such that appropriate interconnections between interconnect vias are made. The second PCB and first PCB with spacers in between can be attached so as to create a cavity in which the diaphragm and interface electronics are located.

First claim

The invention claimed is:

1. A method of fabricating a microphone, comprising:
fabricating a backplate on a portion of a printed circuit board;
locating a diaphragm relative to the portion of the printed circuit board so as to form a first volume between the diaphragm and the back plate, wherein a front surface of the diaphragm is in contact with the first volume, wherein a back surface is in contact with a second volume, wherein one of the first volume and the second volume is in low acoustic impedance contact with the ambient acoustic environment, and the other of the first volume and second volume is in high acoustical impedance contact with the ambient acoustic environment, wherein the diaphragm flexes in response to acoustic pressure; and
producing an output signal related to the acoustic pressure on the diaphragm,
wherein the first volume is in high acoustic impedance contact with the ambient acoustic environment the second volume is in low acoustic impedance contact with the ambient acoustic environment,
further comprising:
providing an enclosure, wherein the first volume is within the enclosure,
wherein the enclosure comprises:
the printed circuit board;
a bottom printed circuit board; and
one or more spacer printed circuit boards, wherein the printed circuit board, the one or more spacer printed circuit boards, and the bottom printed circuit board are attached to form the enclosure.

2. The method according to claim 1 , wherein providing the backplate on the portion of the printed circuit board comprises patterning a conductive layer of the printed circuit board.

3. The method according to claim 1 , wherein the diaphragm comprises a conducting material, wherein the back plate comprises a conducting material, further comprising:
a bias voltage between the diaphragm and the back plate, wherein flexing of the diaphragm causes a change in electric charge across the diaphragm and the back plate, wherein the output signal is produced from the change in electric charge across the diaphragm and the back plate.

4. The method according to claim 1 , wherein the diaphragm comprises a permanent electric charge, wherein the back plate comprises a conducting material, wherein flexing of the diaphragm causes a voltage change across the diaphragm and the back plate, wherein the output signal is produced from the voltage change across the diaphragm and the back plate.

5. The method according to claim 1 , wherein the diaphragm comprises a conducting material, wherein the back plate comprises a permanent electric charge, wherein flexing of the diaphragm causes a voltage change across the diaphragm and the back plate, wherein the output signal is produced from the voltage change across the diaphragm and the back plate.

6. The method according to claim 1 , wherein the diaphragm is within the enclosure.

7. The method according to claim 1 , wherein the first volume is formed by the diaphragm and the back plate.

8. The method according to claim 1 , further comprising creating one or more apertures through the printed circuit board that allow acoustic waves to pass through the one or more apertures from the ambient acoustic environment into the second volume and from the second volume to the ambient acoustic environment.

9. The method according to claim 3 , further comprising applying a bias voltage between the back plate and the diaphragm.

10. The method according to claim 9 , wherein applying a bias voltage between the back plate and the diaphragm comprises applying a bias voltage via interface electronics.

11. The method according to claim 9 , further comprising producing the output signal via an electrical impedance buffer amplifier.

12. The method according to claim 11 , wherein the output signal related to the acoustic pressure on the diaphragm is a low impedance output signal.

13. The method according to claim 1 , wherein the diaphragm is micromachined on the printed circuit board.

14. The method according to claim 13 , wherein the diaphragm is grown or deposited onto the printed circuit board.

15. The method according to claim 1 , wherein the diaphragm is placed on the printed circuit board.

16. The method according to claim 1 ,
further comprising providing a vent passing through the enclosure that allows ambient fluid to pass back and forth between the first volume and the ambient acoustic environment while maintaining the first volume in high acoustic impedance with ambient acoustic environment.

17. The method according to claim 16 , wherein the ambient fluid is air.

18. The method according to claim 1 , further comprising:
providing a vent to allow ambient fluid to pass back and forth between the second volume and the first volume while maintaining the first volume in high acoustic impedance with the ambient acoustic environment.

19. The method according to claim 18 , wherein the ambient fluid is air.

20. A method of fabricating a microphone, comprising:
depositing a backplate on a portion of a printed circuit board;
locating a diaphragm relative to the portion of the printed circuit board so as to form a first volume between the diaphragm and the back plate, wherein a front surface of the diaphragm is in contact with the first volume, wherein a back surface is in contact with a second volume, wherein one of the first volume and the second volume is in low acoustic impedance contact with the ambient acoustic environment, and the other of the first volume and second volume is in high acoustical impedance contact with the ambient acoustic environment, wherein the diaphragm flexes in response to acoustic pressure; and
producing an output signal related to the acoustic pressure on the diaphragm,
wherein the first volume is in high acoustic impedance contact with the ambient acoustic environment the second volume is in low acoustic impedance contact with the ambient acoustic environment,
further comprising:
providing an enclosure, wherein the first volume is within the enclosure,
wherein the enclosure comprises:
the printed circuit board;
a bottom printed circuit board; and
one or more spacer printed circuit boards, wherein the printed circuit board, the one or more spacer printed circuit boards, and the bottom printed circuit board are attached to form the enclosure.

21. The method according to claim 20 , wherein providing the backplate on the portion of the printed circuit board comprises patterning a conductive layer of the printed circuit board.

22. The method according to claim 20 , wherein the diaphragm comprises a conducting material, wherein the back plate comprises a conducting material, further comprising:
a bias voltage between the diaphragm and the back plate, wherein flexing of the diaphragm causes a change in electric charge across the diaphragm and the back plate, wherein the output signal is produced from the change in electric charge across the diaphragm and the back plate.

23. The method according to claim 20 , wherein the diaphragm comprises a permanent electric charge, wherein the back plate comprises a conducting material, wherein flexing of the diaphragm causes a voltage change across the diaphragm and the back plate, wherein the output signal is produced from the voltage change across the diaphragm and the back plate.

24. The method according to claim 20 , wherein the diaphragm comprises a conducting material, wherein the back plate comprises a permanent electric charge, wherein flexing of the di

Assignees

• Univ Florida

Inventors

• Sheplak Mark
• Arnold David Patrick

Classifications

• H10W90/724

  between a chip and a stacked insulating package substrate, interposer or RDL · CPC title

• H05K2201/10083

  Electromechanical or electro-acoustic component, e.g. microphone · CPC title

• H04R1/04

  Structural association of microphone with electric circuitry therefor (in electric hearing aids H04R25/00) · CPC title

• H05K3/46

  Manufacturing multilayer circuits · CPC title

• H04R2201/02

  Details casings, cabinets or mounting therein for transducers covered by H04R1/02 but not provided for in any of its subgroups · CPC title