Bottom port surface mount MEMS microphone

• US 9,051,171 B1
• Filed: 01/07/2014
• Issued: 06/09/2015
• Est. Priority Date: 11/28/2000
• Status: Expired due to Fees

• Current Assignee: Knowles Electronics Llc (Knowles Corporation)
• Original Assignee: Knowles Electronics Llc (Knowles Corporation)
• Inventors: Minervini, Anthony D.
• Primary Examiner(s): Chambliss, Alonzo
• Application Number:
  US14/149,525
• Time in Patent Office: 518 Days
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/0257 Microphones or microspeakers
• CPC Class Codes: B81B 2207/092 Buried interconnects in the substrate or in the lid
• 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: B81B 7/0038 using materials for controlling the level of pressure, contaminants or moisture inside of the package, e.g. getters
• 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: B81B 7/0061 suitable for fluid transfer from the MEMS out of the package or vice versa, e.g. transfer of liquid, gas, sound
• CPC Class Codes: B81B 7/0064 for protecting against electromagnetic or electrostatic interferences
• CPC Class Codes: B81B 7/007 Interconnections between the MEMS and external electrical signals
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: B81C 1/00301 Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias
• CPC Class Codes: B81C 3/00 Assembling of devices or systems from individually processed components
• CPC Class Codes: H01L 21/78 with subsequent division of the substrate into plural individual devices cutting to change the surface-physical characteristics or shape of semiconductor bodies H01L21/304
• CPC Class Codes: H01L 23/10 characterised by the material or arrangement of seals between parts, e.g. between cap and base of the container or between leads and walls of the container
• CPC Class Codes: H01L 23/15 Ceramic or glass substrates H01L23/142, H01L23/145, H01L23/147 take precedence
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/1461 MEMS
• CPC Class Codes: H04R 1/04 Structural association of microphone with electric circuitry therefor in deaf-aid sets H04R25/00
• CPC Class Codes: H04R 1/222 for microphones H04R1/24, H04R1/26 take precedence
• CPC Class Codes: H04R 1/2892 Mountings or supports for transducers
• CPC Class Codes: H04R 19/005 : using semiconductor materials
• CPC Class Codes: H04R 19/016 : for microphones
• CPC Class Codes: H04R 19/04 : Microphones H04R19/01 takes precedence
• CPC Class Codes: H04R 2201/003 : Mems transducers or their use
• CPC Class Codes: H04R 2225/49 : Reducing the effects of electromagnetic noise on the functioning of hearing aids, by, e.g. shielding, signal processing adaptation, selective (de)activation of electronic parts in hearing aid
• CPC Class Codes: H04R 23/00 : Transducers other than those covered by groups H04R9/00 - H04R21/00 diaphragms for transducers of the distributed-mode type H04R7/045
• CPC Class Codes: H04R 2410/03 : Reduction of intrinsic noise in microphones
• CPC Class Codes: H04R 3/00 : Circuits for transducers , loudspeakers or microphones
• CPC Class Codes: H04R 31/006 : Interconnection of transducer parts of diaphragm and outer suspension by moulding H04R31/003
• CPC Class Codes: Y10T 29/49005 : Acoustic transducer
• CPC Class Codes: Y10T 29/4908 : Acoustic transducer
• CPC Class Codes: Y10T 29/49798 : Dividing sequentially from leading end, e.g., by cutting or breaking

Abstract

A bottom port, surface mount package for a micro-electro-mechanical system (MEMS) microphone die is disclosed. The surface mount package features a substrate with metal pads for surface mounting the package to a device'"'"'s printed circuit board and for making electrical connections between the microphone package and the device'"'"'s circuit board. The surface mount microphone package has a cover, and the MEMS microphone die is substrate-mounted and acoustically coupled to the acoustic port in the substrate. The substrate and the cover are joined together to form the MEMS microphone, and the substrate and cover cooperate to form an acoustic chamber for the substrate-mounted MEMS microphone die.

Claims

1. A solder reflow surface mount micro-electro-mechanical system (MEMS) microphone, the microphone comprising:

a rectangular substrate comprising;

a rigid base layer comprised of multiple sub-layers of non-conductive material, each sub-layer having a predetermined coefficient of thermal expansion, wherein the base layer has a planar top surface and a planar bottom surface, the top surface having an interior region and an attachment region, the attachment region disposed between the interior region and the edges of the base layer, and completely bounding the interior region;

a first plurality of flat metal pads disposed on the top surface of the base layer and defined by a first solder mask layer;

a second plurality of flat metal pads disposed on the bottom surface of the base layer and defined by a second solder mask layer, the second plurality of metal pads arranged to be within a perimeter of the bottom surface of the base layer;

one or more electrical pathways disposed completely within the base layer, wherein the pathways electrically couple one or more of the first plurality of metal pads on the top surface of the base layer to one or more of the second plurality of metal pads on the bottom surface of the base layer; and

an acoustic port disposed in the interior region of the base layer and passing completely through the base layer, wherein the acoustic port is disposed in a position offset from a centerpoint of the substrate, and wherein one of the second plurality of metal pads is a metal ring that completely surrounds the acoustic port in the base layer and has an inner diameter that is greater than a diameter of the acoustic port;

a MEMS microphone die mounted to the top surface of the substrate and electrically coupled to at least one of the first plurality of metal pads on the top surface of the substrate, the MEMS microphone die being disposed directly over the acoustic port in the base layer; and

a solid single-piece rectangular cover having a predetermined shape, the rectangular cover comprising a top portion and a substantially vertical and continuous sidewall portion that adjoins the top portion at an angle and that completely surrounds and supports the top portion, the sidewall portion having a predetermined height, an exterior sidewall surface, an interior sidewall surface, and an attachment surface,

wherein the attachment surface of the sidewall portion of the cover is aligned with and attached to the attachment region of the top surface of the base layer of the substrate, and

wherein the predetermined height of the sidewall portion of the cover, the interior sidewall surface of the sidewall portion of the cover, and the interior surface of the top portion of the cover, in cooperation with the interior region of the top surface of the base layer, define an acoustic chamber for the MEMS microphone die and provide a protective enclosure for the MEMS microphone die to reduce electromagnetic interference.

2. A solder reflow surface mount MEMS microphone according to claim 1, further comprising at least one passive electrical element electrically coupled between one of the first plurality of metal pads and one of the second plurality of metal pads.

3. A solder reflow surface mount MEMS microphone according to claim 2, wherein the at least one passive electrical element is disposed within the base layer of the substrate.

4. A solder reflow surface mount MEMS microphone according to claim 3, wherein the at least one passive electrical element comprises a dielectric or resistive material that is different from the sub-layers of non-conductive material in the base layer of the substrate.

5. A solder reflow surface mount MEMS microphone according to claim 1, wherein the substrate further comprises an acoustic material that substantially blocks contaminants from passing through the acoustic port.

6. A solder reflow surface mount MEMS microphone according to claim 1, wherein the first plurality of metal pads further comprises a metal pad with an opening, wherein the opening surrounds the acoustic port in the base layer, and the metal pad is interposed between the MEMS microphone die and the top surface of the base layer.

7. A solder reflow surface mount MEMS microphone according to claim 1, wherein the first plurality of metal pads further comprises a metal pad with an opening, wherein the opening surrounds the acoustic port in the base layer, and the MEMS microphone die contacts the metal pad when mounted.

8. A solder reflow surface mount MEMS microphone according to claim 1, wherein one or more sub-layers of the base layer comprise FR-4 printed circuit board material.

9. A solder reflow surface mount MEMS microphone according to claim 1, wherein the enclosure protects the MEMS microphone die from at least one of light and physical damage.

10. A solder reflow surface mount MEMS microphone according to claim 1, wherein a diaphragm of the MEMS microphone die defines a front volume and a back volume within the acoustic chamber, and the acoustic port disposed in the base layer of the substrate is acoustically coupled to the front volume.

11. A solder reflow surface mount MEMS microphone according to claim 10, wherein the interface between the attachment surface of the sidewall portion of the cover and the attachment region of the top surface of the base layer of the substrate is sealed to maintain acoustic pressure within the back volume.

12. A solder reflow surface mount MEMS microphone according to claim 1, wherein the MEMS microphone die is a pressure-equalizing MEMS microphone die.

13. A solder reflow surface mount MEMS microphone according to claim 5, wherein the acoustic material is a film of polymeric material.

14. A solder reflow surface mount MEMS microphone according to claim 5, wherein the acoustic material is hydrophobic.

15. A solder reflow surface mount MEMS microphone according to claim 3, wherein the at least one passive electrical element filters one or more of an input signal, an output signal, or input power.

16. A solder reflow surface mount micro-electro-mechanical system (MEMS) microphone, the microphone comprising:

a rectangular base portion comprising;

a rigid base layer comprised of multiple sub-layers of printed circuit board material, each sub-layer having a predetermined coefficient of thermal expansion, wherein the base layer has a substantially flat upper surface and a substantially flat lower surface, the upper surface having an inner area and a coupling area, the coupling area located between the inner area and edges of the base layer, and completely surrounding the inner area;

a plurality of flat metal pads located on the upper surface of the base layer and defined by a first solder mask layer;

a plurality of flat solder pads located on the lower surface of the base layer and defined by a second solder mask layer, the plurality of solder pads arranged to be within a perimeter of the lower surface of the base layer;

one or more electrical connections passing through the base layer, wherein the connections electrically couple one or more of the plurality of metal pads on the upper surface of the base layer to one or more of the plurality of solder pads on the lower surface of the base layer;

an acoustic port located in the inner area of the base layer and passing completely through the base layer, wherein the acoustic port is disposed in a position offset from a centerpoint of the base portion, and wherein one of the plurality of solder pads is a solder pad ring that completely surrounds the acoustic port in the base layer and has an inner diameter that is greater than the diameter of the acoustic port; and

at least one passive electrical element disposed within the base layer and electrically coupled between one of the plurality of metal pads and one of the plurality of solder pads, wherein the at least one passive electrical element comprises a dielectric or resistive material that is different from the sub-layers of printed circuit board material;

a MEMS microphone die mounted to the upper surface of the base portion and electrically coupled to at least one of the plurality of metal pads on the upper surface of the base layer of the base portion, the MEMS microphone die being disposed directly over the acoustic port in the base layer of the base portion; and

a rectangular cover portion, formed from a single piece of solid material and having a predetermined shape, the cover portion comprising a top portion and a substantially vertical and continuous sidewall portion that adjoins the top portion at an angle and that completely surrounds and supports the top portion, the sidewall portion having a predetermined height, an exterior sidewall surface, an interior sidewall surface, and a coupling surface,

wherein the coupling surface of the sidewall portion of the cover portion is aligned with and mechanically coupled to the coupling area of the base layer of the base portion;

wherein the predetermined height and interior surface of the sidewall portion of the cover portion, and interior surface of the top portion of the cover portion, in cooperation with the interior region of the upper surface of the base layer of the base portion, define an acoustic chamber for the MEMS microphone die and provide a protective enclosure for the MEMS microphone die; and

wherein the respective overall lengths of the base portion and the cover portion are substantially equal, and the respective overall widths of the base portion and the cover portion are substantially equal.

17. A solder reflow surface mount MEMS microphone according to claim 16, wherein the plurality of metal pads further comprises a metal pad with an opening, wherein the opening surrounds the acoustic port in the base layer of the base portion, and the metal pad is interposed between the MEMS microphone die and the upper surface of the base layer of the base portion.

18. A solder reflow surface mount MEMS microphone according to claim 16, wherein the enclosure protects the MEMS microphone die from at least one of light, electromagnetic interference, and physical damage.

19. A solder reflow surface mount MEMS microphone according to claim 16, wherein the base layer of the base portion further comprises an acoustic material that substantially blocks contaminants from passing through the acoustic port.

20. A solder reflow surface mount MEMS microphone according to claim 19, wherein the acoustic material is a film of polymeric material.

21. A solder reflow surface mount MEMS microphone according to claim 19, wherein the acoustic material is hydrophobic.

22. A solder reflow surface mount MEMS microphone according to claim 16, wherein a diaphragm of the MEMS microphone die defines a front volume and a back volume within the acoustic chamber, and the acoustic port disposed in the base layer of the base portion is acoustically coupled to the front volume;

and

wherein the interface between the coupling surface of the sidewall portion of the cover portion and the coupling area of the upper surface of the base layer of the base portion is sealed to maintain acoustic pressure within the back volume.

23. A solder reflow surface mount MEMS microphone according to claim 16, wherein the at least one passive electrical element filters one or more of an input signal, an output signal, or input power.

24. A solder reflow surface mount micro-electro-mechanical system (MEMS) microphone, the microphone comprising:

a rectangular base element comprising;

a rigid core layer comprised of multiple sub-layers of FR-4 printed circuit board material, each sub-layer having a predetermined coefficient of thermal expansion, wherein the core layer has a substantially flat top surface and a substantially flat bottom surface, the top surface having a die mount region and an attachment region, the attachment region positioned between the die mount region and edges of the core layer, and completely surrounding the die mount region;

a plurality of flat metal pads located on the top surface of the core layer and defined by a first solder mask layer;

a plurality of flat solder pads located on the bottom surface of the core layer and defined by a second solder mask layer, the plurality of solder pads arranged to be within a perimeter of the bottom surface of the core layer, wherein the solder pads are plated with at least one metal;

a plurality of electrical connections passing through the core layer that electrically couple one or more of the plurality of metal pads on the top surface of the core layer to one or more of the plurality of solder pads on the bottom surface of the core layer;

an acoustic port located in the interior region of the core layer and passing completely through the core layer, wherein the acoustic port is disposed in a position offset from a centerpoint of the base element, and wherein one of the second plurality of solder pads is a solder pad ring that completely surrounds the acoustic port in the base element and has an inner diameter that is greater than the diameter of the acoustic port; and

at least one passive electrical element disposed within the core layer and electrically coupled between one of the plurality of metal pads and one of the plurality of solder pads, wherein the at least one passive electrical element comprises a dielectric or resistive material that is different from the sub-layers of printed circuit board material; and

a pressure-equalizing MEMS microphone die having an internal acoustic channel mounted in the die mount region of the core layer, and electrically coupled to one or more of the metal pads on the top surface of the core layer, the internal acoustic channel of the MEMS microphone die being arranged directly over the acoustic port in the core layer;

a solid single-piece rectangular cover element having a predetermined shape, the cover element comprising a top region and a continuous wall region, the wall region supporting the top region and adjoining the top region at a substantially perpendicular angle and having a predetermined height, an exterior surface, and an interior surface, an attachment surface;

wherein the cover element is attached to the base element such that the attachment surface of the wall region of the cover element is aligned with and physically attached to the attachment region of the top surface of the core layer of the base element, thereby providing a protective enclosure for the MEMS microphone die,

wherein the interior of the protective enclosure is an acoustic chamber having a volume defined by the predetermined height of the wall region of the cover element, and the width and length of the top region of the cover element,

wherein a diaphragm of the MEMS microphone die defines a front volume and a back volume within the acoustic chamber, and the acoustic port disposed in the base element is acoustically coupled to the diaphragm, and

wherein an interface between the attachment surface of the wall region of the cover element and the attachment area of the top surface of the core layer of the base element is sealed to maintain acoustic pressure within the back volume.

25. A solder reflow surface mount MEMS microphone according to claim 24, wherein the at least one passive electrical element filters one or more of an input signal, an output signal, or input power.

26. A solder reflow surface mount MEMS microphone according to claim 24, wherein the enclosure protects the MEMS microphone die from at least one of light, electromagnetic interference, and physical damage.

27. A solder reflow surface mount MEMS microphone according to claim 24, wherein the core layer of the base element further comprises an acoustic material that substantially blocks contaminants from passing through the acoustic port.

28. A solder reflow surface mount MEMS microphone according to claim 27, wherein the acoustic material is a film of polymeric material.

29. A solder reflow surface mount MEMS microphone according to claim 27, wherein the acoustic material is hydrophobic.

30. A solder reflow surface mount MEMS microphone according to claim 24, wherein the plurality of metal pads further comprises a metal pad with an opening, wherein the opening surrounds the acoustic port in the base layer, and the metal pad is interposed between the MEMS microphone die and the top surface of the base layer.

31. A solder reflow surface mount micro-electro-mechanical system (MEMS) microphone, the microphone comprising:

a pressure-equalizing MEMS microphone die having an internal acoustic channel;

a protective housing for the MEMS microphone die comprising;

a first housing element having a rectangular shape comprising;

a rigid core layer comprised of multiple layers of FR-4 printed circuit board material, each layer of FR-4 material having a predetermined coefficient of thermal expansion, wherein the core layer has a substantially flat top surface and a substantially flat bottom surface, wherein the top surface has a die mount region and an attachment region, the attachment region being arranged between the die mount region and edges of the core layer, and the attachment region completely surrounds the die mount region;

a plurality of flat metal pads disposed on the top surface of the core layer and defined by a first solder mask layer, wherein the metal pads are plated with at least one metal;

a plurality of flat solder pads disposed on the bottom surface of the core layer and defined by a second solder mask layer, the plurality of solder pads arranged to be within a perimeter of the bottom surface of the core layer, wherein the solder pads are plated with at least one metal;

one or more electrical vias located inside the core layer, wherein the vias electrically couple one or more of the plurality of metal pads on the top surface of the core layer to one or more of the plurality of solder pads on the bottom surface of the core layer; and

an acoustic port located in the die mount region of the core layer and passing completely through the core layer, wherein the acoustic port is disposed in a position offset from a centerpoint of the first housing element, and wherein one of the plurality of solder pads is a solder pad ring that completely surrounds the acoustic port in the core layer and has an inner diameter that is greater than the diameter of the acoustic port; and

at least one passive electrical element disposed within the core layer and electrically coupled between one of the plurality of metal pads and one of the plurality of solder pads, wherein the at least one passive electrical element comprises a dielectric or resistive material that is different from the printed circuit board material in the core layer; and

a second housing element, having a rectangular shape and formed from a single piece of solid material, the second housing element comprising a substantially flat top region and a continuous wall region, the wall region supporting the top region and adjoining the top region at a substantially perpendicular angle, the wall region having a predetermined height, an exterior surface, an interior surface, and an attachment surface;

wherein the MEMS microphone die is disposed in the die mount region of the core layer, and electrically coupled to one or more of the metal pads on the top surface of the core layer, the internal acoustic channel of the MEMS microphone die being arranged directly over the acoustic port in the core layer;

wherein the attachment surface of the wall region of the second housing element is aligned with and physically coupled to the attachment region of the top surface of the core layer of the first housing element, thereby forming a protective enclosure for the MEMS microphone die, and

wherein the interior of the protective enclosure is an acoustic chamber having a volume defined by the predetermined height of the wall region of the second housing element, and a width and a length of the top region of the second housing element.

32. A solder reflow surface mount MEMS microphone according to claim 31, wherein the enclosure protects the MEMS microphone die from at least one of light, electromagnetic interference, and physical damage.

33. A solder reflow surface mount MEMS microphone according to claim 31, wherein the core layer of the first housing element further comprises an acoustic material that substantially blocks contaminants from passing through the acoustic port.

34. A solder reflow surface mount MEMS microphone according to claim 33, wherein the acoustic material is a film of polymeric material.

35. A solder reflow surface mount MEMS microphone according to claim 33, wherein the acoustic material is hydrophobic.

36. A solder reflow surface mount MEMS microphone according to claim 31, wherein the at least one passive electrical element filters one or more of an input signal, an output signal, or input power.