Microphone assembly with barrier to prevent contaminant infiltration

• US 9,078,063 B2
• Filed: 08/06/2013
• Issued: 07/07/2015
• Est. Priority Date: 08/10/2012
• Status: Active Grant

• Current Assignee: Knowles Electronics Llc (Knowles Corporation)
• Original Assignee: Knowles Electronics Llc (Knowles Corporation)
• Inventors: Loeppert, Peter V., McCall, Ryan M., Giesecke, Daniel, Vos, Sandra F., Szczech, John B., Lee, Sung Bok, Van Kessel, Peter
• Primary Examiner(s): NGUYEN, TUAN DUC
• Application Number:
  US13/960,392
• Publication Number:
  US 20140044297A1
• Time in Patent Office: 700 Days
• Field of Search: 381/355, 381/369, 381/174, 381/175, 257/416, 257/254, 257/678, 257/685, 257/686, 438 50- 53
• US Class Current: 1/1
• CPC Class Codes: H04R 1/04 Structural association of microphone with electric circuitry therefor in deaf-aid sets H04R25/00
• CPC Class Codes: H04R 1/08 Mouthpieces; Microphones; Attachments therefor
• CPC Class Codes: H04R 1/086 Protective screens, e.g. all weather or wind screens
• CPC Class Codes: H04R 2201/003 Mems transducers or their use of the electrostatic type H04R19/005

Abstract

A microphone assembly includes a cover, a base coupled to the cover, a microelectromechanical system (MEMS) device disposed on the base. An opening is formed in the base and the MEMS device is disposed over the opening. The base includes a barrier that extends across the opening and is porous to sound. The remaining portions of the base do not extend across the opening.

Claims

1. A microphone assembly comprising:

a cover;

a base comprising;

a first material layer having an upper surface and a lower surface, and an acoustic port;

a second material layer disposed on the upper surface of the first material layer, wherein the second material layer has an opening that is larger than the acoustic port in the first material layer, and an axis of the opening in the second material layer is aligned with an axis of the acoustic port in the first material layer; and

a barrier layer comprised of multiple ports, wherein the multiple ports are offset from the axis of the acoustic port, the barrier layer cooperating with the first and second material layers to form an internal cavity in the base;

wherein the multiple ports of the barrier layer and the acoustic port of the first material layer are acoustically coupled to the internal cavity, thereby providing a path for sound from the exterior of the microphone assembly;

a microelectromechanical system (MEMS) device having an internal chamber and disposed on the base, wherein the MEMS device is disposed such that its internal chamber is acoustically coupled to the multiple ports of the barrier layer; and

a cover attached to the base, wherein the cover cooperates with the base to form an acoustic chamber for the MEMS device.

2. The microphone assembly of claim 1 further comprising an integrated circuit coupled to the MEMS device.

3. The microphone assembly of claim 2 wherein the integrated circuit is an application specific integrated circuit (ASIC).

4. The microphone assembly of claim 1, wherein the barrier layer has a hydrophobic coating.

5. The microphone assembly of claim 1, wherein the barrier layer comprises a patterned flex printed circuit board (PCB).

6. The microphone assembly of claim 5 wherein the patterned flex PCB comprises a polyimide film.

7. The microphone assembly of claim 1, wherein the multiple ports of the barrier layer are sized to limit the ingress of particulates into the acoustic chamber.

8. A microphone assembly comprising:

a base comprised of;

a first circuit board layer having a plurality of ports;

a second circuit board layer having an acoustic port; and

a core layer of non-conductive material, the core layer having an opening formed at a predetermined location,

wherein the first circuit board layer, the second circuit board layer, and the core layer, when joined together, cooperate to form an internal cavity,

wherein the plurality of ports in the first circuit board layer and the acoustic port in the second circuit board layer are acoustically coupled to the internal cavity, thereby providing a path for sound from the exterior of the microphone assembly, and

wherein the axes of the plurality of ports in the first circuit board layer and the axis of the acoustic port in the second circuit board layer are not aligned with each other;

a microelectromechanical system (MEMS) device disposed on the base, wherein an internal chamber of the MEMS device is aligned over the plurality of ports in the first circuit board layer such that the axis of the acoustic port is aligned with the axis of the internal chamber of the MEMS device; and

a cover attached to the base, wherein the cover provides an acoustic chamber for the MEMS device.

9. The microphone assembly of claim 8, wherein the internal cavity has straight walls.

10. The microphone assembly of claim 8, wherein the internal cavity has a plurality of curved walls.

11. A microphone assembly comprising:

a base having an upper surface and a lower surface, the base further comprising an acoustic port;

a microelectromechanical system (MEMS) device having an internal chamber, wherein the MEMS device is disposed on the upper surface of the base and the internal chamber of the MEMS device is aligned with the acoustic port;

a barrier element disposed on the upper surface of the base and covering the acoustic port, wherein the barrier element is disposed within the internal chamber of the MEMS device, wherein the barrier element is porous to sound but does not allow particulates to pass through the acoustic port; and

a cover attached to the upper surface of the base.

12. The microphone assembly of claim 11, wherein the barrier element comprises an elongated tunnel with a plurality of turns, wherein one port of the elongated tunnel is acoustically coupled to the acoustic port in the base, and the other port of the elongated tunnel is acoustically coupled to the internal chamber of the MEMS device.

13. The microphone assembly of claim 12, wherein the port of the elongated tunnel that is acoustically coupled to the acoustic port in the base has a diameter that is smaller than the diameter of the acoustic port.

14. The microphone assembly of claim 12, wherein the barrier element is comprised of silicon and the elongated tunnel is formed by one of stealth dicing or chemical etching.

15. The microphone assembly of claim 11, wherein the barrier element is a non-conductive material and comprises:

an internal channel;

a first trench opening disposed on a bottom side of the barrier element, the first trench opening acoustically coupled to the acoustic port in the base; and

a second trench opening disposed on a top side of the barrier element, the second trench opening acoustically coupled to the internal chamber of the MEMS device,

wherein the internal channel acoustically couples the first trench opening to the second trench opening, thereby allowing sound to reach the MEMS device through the acoustic port and substantially blocking particulates from passing through the acoustic port.

16. The microphone assembly of claim 15, wherein the internal channel of the barrier element is curved or straight.

17. The microphone assembly of claim 15, wherein the internal channel of the barrier element is formed by one of stealth dicing or chemical etching and the first and second trenches are formed by dry etching.

18. The microphone assembly of claim 11, wherein the barrier element is a non-conductive material and comprises:

a first trench traversing the length of a bottom surface of the barrier element, wherein the bottom surface of the barrier element is coupled to the upper surface of the base, the first trench acoustically coupled to the acoustic port in the base; and

a second trench traversing the length of the bottom surface of the barrier element, the second trench acoustically coupled to the acoustic port in the base,

wherein the first trench and the second trench intersect each other at a predetermined angle, and

wherein acoustic pressure entering the microphone assembly is transferred through the first and second trenches and exits the barrier element through the respective trench openings in the sidewalls of the barrier element.

19. The microphone assembly of claim 18, wherein the first trench is a plurality of first trenches, and the second trench is a plurality of second trenches.

20. The microphone assembly of claim 18, wherein the respective openings of the first and second trenches in the sidewalls of the barrier element are acoustically coupled to the internal chamber of the MEMS device.

21. The microphone assembly of claim 11, wherein the barrier element is a porous ceramic material having pore sizes in the range of 1 to 100 microns.

22. The microphone assembly of claim 21, wherein the barrier element has pore sizes in the range of 2 to 20 microns.

23. The microphone assembly of claim 21, wherein the barrier element further comprises an impervious surface on a portion of a top surface of the barrier element.

24. A microphone assembly comprising:

a base;

a microelectromechanical system (MEMS) device disposed on the base; and

a solid cover attached to the base and forming an acoustic chamber for the MEMS device, wherein the solid cover is comprised of;

a metal mesh layer having a predetermined shape with an interior surface and an exterior surface; and

a layer of epoxy material covering the exterior surface of the metal mesh layer, wherein the epoxy material is patterned to form an acoustic port that exposes a portion of the underlying metal mesh layer, wherein the exposed portion of the metal mesh layer allows sound to pass there through but not allowing particulates to pass there through.

25. The microphone assembly of claim 24 further comprising an integrated circuit coupled to the MEMS device.

26. The microphone assembly of claim 24 wherein the integrated circuit is an application specific integrated circuit (ASIC).

27. The microphone assembly of claim 24, wherein the shaped metal mesh of the solid cover provides radio frequency protection for the MEMS device.

28. The microphone assembly of claim 24, wherein the exposed metal mesh in the acoustic port in the solid cover has openings of 50 microns or less.

29. The microphone assembly of claim 24, wherein the exposed metal mesh in the acoustic port in the solid cover is coated with a hydrophobic material.

30. A microphone assembly comprising:

a base;

a microelectromechanical system (MEMS) device disposed on the base; and

a solid cover attached to the base and forming an acoustic chamber for the MEMS device, wherein the solid cover is comprised of;

a layer of epoxy material formed into a predetermined shape having an interior surface and an exterior surface, and having an acoustic port in an upper portion of the predetermined shape; and

a layer of metal mesh disposed on the interior surface of the epoxy material layer, wherein the metal mesh layer completely covers the acoustic port and allows sound to pass through the acoustic port but not allowing particulates to pass through.

31. The microphone assembly of claim 30, further comprising an integrated circuit coupled to the MEMS device.

32. The microphone assembly of claim 31, wherein the integrated circuit is an application specific integrated circuit (ASIC).

33. The microphone assembly of claim 30, wherein the exposed metal mesh in the acoustic port in the solid cover has openings of 50 microns or less.

34. The microphone assembly of claim 30, wherein the exposed metal mesh in the acoustic port in the solid cover is coated with a hydrophobic material.

35. The microphone assembly of claim 30, wherein the porosity of the acoustic portion of the solid cover is controlled to dampen the frequency response of the microphone assembly.

36. A microphone assembly comprising:

a base;

a microelectromechanical system (MEMS) device disposed on the base; and

a solid cover attached to the base and forming an acoustic chamber for the MEMS device, wherein the solid cover is comprised of;

sidewall portions comprised of a fused material without voids; and

an acoustic portion comprised of a partially fused material containing voids, wherein the sidewall portions and the acoustic portion cooperate to provide the acoustic chamber, wherein the acoustic portion allows sound to pass there through but not allowing particulates to pass there through.

37. The microphone assembly of claim 36, further comprising an integrated circuit coupled to the MEMS device.

38. The microphone assembly of claim 37, wherein the integrated circuit is an application specific integrated circuit (ASIC).

39. The microphone assembly of claim 36, wherein the acoustic portion of the solid cover comprises a cover comprises partially fused or sintered metal.

40. The microphone assembly of claim 36, wherein the acoustic portion of the solid cover is coated with a hydrophobic material.

41. The microphone assembly of claim 36, wherein the sidewall portions and the acoustic portion of the solid cover are constructed from metal to provide protection against radio frequency interference for the MEMS device.