# US 11,122,360 B2 · Microphone assembly with back volume vent > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,122,360 B2 - Document ID: US11122360B2 - Status: Granted - Kind: B2 - Application number: 16/778,061 - Filed: 2020-01-31 - Published: 2020-08-06 - Granted: 2021-09-14 - Earliest claimed: 2019-02-01 - Assignees: Knowles Electronics, LLC - Applicants: Knowles Electronics, LLC - Inventors: Michael Pedersen; Peter V. Loeppert - Web page: https://patentgrep.com/patent/US11122360B2 ## CPC - H04R 1/086: {Protective screens, e.g. all weather or wind screens} - H04R 1/2846: {Vents, i.e. ports, e.g. shape thereof or tuning thereof with damping material} - B81B 3/0027: {Structures for transforming mechanical energy, e.g. potential energy of a spring into translation, sound into translation} - B81C 1/00158: {Diaphragms, membranes (manufacture process for semi-permeable inorganic membranes B01D67/0039)} - H04R 1/04: Structural association of microphone with electric circuitry therefor (in electric hearing aids H04R25/00) - H04R 1/08: Mouthpieces; {Microphones;} Attachments therefor - H04R 1/222: {for microphones (H04R1/24, H04R1/26 take precedence)} - H04R 1/283: {using a passive diaphragm} - H04R 19/04: Microphones (H04R19/01 takes precedence) - 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)} - B81B 2201/0257: Microphones or microspeakers - B81B 2203/0127: Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function - H04R 2201/003: Mems transducers or their use - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) - B81B: MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES (piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/00, H10N35/00) - B81C: PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS (making microcapsules or microballoons B01J13/02; processes or apparatus specially adapted for the manufacture or treatment of piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/01) ## Abstract The problem of contaminants entering a microphone assembly through a pressure equalization aperture is mitigated by moving the pressure equalization aperture from a location near the acoustic port to a location on the cover of the microphone assembly. This is achieved by fabricating an aperture reduction structure using a separate dedicated die, with an aperture of diameter ˜25 microns or less disposed on the aperture reduction structure, and then coupling the aperture reduction structure to the cover of the microphone. The relatively smaller aperture on the cover after the coupling of the aperture reduction structure is used for pressure equalization of the back volume of the microphone with a pressure outside of the microphone assembly. ## Claims ### Claim 1 A microphone assembly comprising: a substrate having a port formed therein; an acoustic transducer coupled to the substrate, disposed over the port, and separating a front volume from a back volume of the microphone assembly; a cover coupled to the substrate, comprising a first aperture; and an aperture reduction structure comprising a second aperture and coupled to the cover overlapping the first aperture, wherein the second aperture is smaller than the first aperture, and wherein the second aperture overlaps the first aperture. ### Claim 2 (depends on 1) The microphone assembly of claim 1, wherein the acoustic transducer is pierce-less. ### Claim 3 (depends on 1) The microphone assembly of claim 1, wherein diameter of the second aperture is less than or equal to 25 microns. ### Claim 4 (depends on 1) The microphone assembly of claim 1, wherein the aperture reduction structure comprises an aperture reduction support member and an aperture reduction layer, wherein the aperture reduction layer comprises the second aperture. ### Claim 5 (depends on 1) The microphone assembly of claim 1, wherein a portion of the cover is indented inwards towards the substrate. ### Claim 6 (depends on 5) The microphone assembly of claim 5, wherein the aperture reduction structure is coupled to a surface of the portion of the cover indented inwards towards the substrate. ### Claim 7 (depends on 6) The microphone assembly of claim 6, wherein the surface of the portion of the cover is exposed to an outside environment of the microphone assembly. ### Claim 8 (depends on 6) The microphone assembly of claim 6, wherein a surface of the aperture reduction structure is substantially coplanar with a surface of the cover. ### Claim 9 (depends on 1) The microphone assembly of claim 1, wherein the aperture reduction structure is a flat aperture reduction layer, wherein the aperture reduction layer comprises the second aperture and is directly coupled to the cover. ### Claim 10 (depends on 9) The microphone assembly of claim 9, wherein the aperture reduction structure is coupled to a surface of a portion of the cover indented inwards towards the substrate. ### Claim 11 (depends on 1) The microphone assembly of claim 1, wherein a ratio of a diameter of the first aperture to a diameter of the second aperture is in the range from 5 to 200. ### Claim 12 (depends on 1) The microphone assembly of claim 1, wherein the acoustic transducer comprises a pierce. ### Claim 13 (depends on 1) The microphone assembly of claim 1, wherein the aperture reduction structure comprises at least one of silicon, plastic, sheet metal, plated metal, or glass. ### Claim 14 (depends on 1) The microphone assembly of claim 1, wherein the acoustic transducer comprises a microelectromechanical systems (MEMS) acoustic transducer. ### Claim 15 (depends on 14) The microphone assembly of claim 14, wherein the microphone assembly further comprises an integrated circuit configured to generate an electrical signal indicative of acoustic activity sensed by the MEMS acoustic transducer. ### Claim 16 A microphone assembly comprising: a substrate having a port formed therein; a MEMS acoustic transducer that is pierce-less coupled to the substrate, disposed over the port, the MEMS acoustic transducer comprising: a back plate; and a diaphragm structured to vibrate in response to pressure changes through the port, the back plate and diaphragm together forming a capacitor having a capacitance that changes responsive to movement of the diaphragm; an integrated circuit coupled to the substrate configured to generate an electrical signal representative of acoustic activity based on changes in capacitance between the diaphragm and the back plate of the MEMS acoustic transducer; a cover coupled to the substrate, comprising a first aperture; and an aperture reduction structure comprising a second aperture and coupled to the cover overlapping the first aperture, wherein the second aperture is smaller than the first aperture, and wherein the second aperture overlaps the first aperture. ### Claim 17 (depends on 16) The microphone assembly of claim 16, wherein a portion of the cover is indented inwards towards the substrate. ### Claim 18 (depends on 17) The microphone assembly of claim 17, wherein the aperture reduction structure is coupled to a surface of the portion of the cover indented inwards towards the substrate. ### Claim 19 (depends on 18) The microphone assembly of claim 18, wherein a surface of the aperture reduction structure is substantially coplanar with a surface of the cover. ### Claim 20 (depends on 16) The microphone assembly of claim 16, wherein the aperture reduction structure is a flat aperture reduction layer, wherein the aperture reduction layer comprises the second aperture and is directly coupled to the cover. ### Claim 21 (depends on 20) The microphone assembly of claim 20, wherein the aperture reduction structure is coupled to a surface of a portion of the cover indented inwards towards the substrate. ### Claim 22 A method of forming a microphone assembly, the method comprising: providing a substrate having a port formed therein; coupling an acoustic transducer to a first surface of the substrate, wherein the acoustic transducer is disposed over the port; coupling a cover to the first surface of the substrate, the cover comprising a first aperture; removing contaminants from the back volume through the first aperture during coupling of the cover to the first surface of the substrate; and coupling an aperture reduction structure to the cover at a position overlapping the first aperture after removing the contaminants, the aperture reduction structure comprising a second aperture smaller than the first aperture, wherein the second aperture overlaps the first aperture. ### Claim 23 (depends on 22) The method of claim 22, the method further comprising coupling the aperture reduction structure to the cover after solder reflow. ### Claim 24 (depends on 22) The method of claim 22, further comprising forming the aperture reduction structure by: providing a silicon substrate; etching the second aperture in a first surface of the silicon substrate to form an aperture reduction layer; and etching a second surface of the silicon substrate opposing the first surface to form a cavity under a portion of the aperture reduction layer comprising the second aperture. ### Claim 25 (depends on 22) The method of claim 22, further comprising forming the aperture reduction structure by: providing a silicon substrate; etching the second aperture in a first surface of the silicon substrate; and removing material from a second surface of the silicon substrate opposing the first surface until a final height of the aperture reduction structure is reached.