Microphone with microhole array sound port

Abstract

A microphone includes a package, a substrate disposed in the package or forming a part of the package, a microelectromechanical system (MEMS) transducer supported by the substrate and packaged in the package, and a lid attached to the substrate to encapsulate the MEMS transducer. The microphone also includes a sound port formed in the package to couple a first side of the MEMS transducer to an ambient environment, the sound port comprising an array of holes configured to attenuate a signal level of electromagnetic interference (EMI) entering the package.

Description

MICROPHONE WITH MICROHOLE ARRAY SOUND PORTCROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. provisional application entitled “Microphone with Microhole Array Sound Port,” filed May 31 , 2024, and assigned Serial No. 63 / 654,921 , the entire disclosure of which is hereby expressly incorporated by reference.BACKGROUND OF THE DISCLOSUREField of the Disclosure

[0002] The disclosure relates generally to acoustic sensor devices that as microelectromechanical system (MEMS) microphones.Brief Description of Related Technology

[0003] MEMS microphones generally include one or more sound ports that couple one or more sides of a MEMS transducer to an ambient environment. For example, directional microphones use two sound ports to allow the MEMS transducer to measure a difference in pressure between the two sound ports. Each respective sound port couples the pressure in the ambient air to a different side of a microphone of the MEMS transducer, so that each side of the membrane is subject to a different pressure. One way to do this is to create a bottom sound port in the PCB on which the MEMS transducer is mounted. For MEMS microphones, this bottom sound port is positioned directly under the DRIE cavity in the MEMS die. The second sound port is a top sound port embedded in the metal lid of the microphone.

[0004] By placing a sound port into the metal lid of the microphone, the microphone can become more susceptible to electromagnetic interference (EMI). Electromagnetic interference in the ambient environment can couple into the microphone through the top sound port. With some directional microphones, if the transducer is compliant such that the transducer has a first resonance in the audible range of frequencies, it may be useful to have the top sound port aligned with the MEMS transducer. Additionally, the top sound port for some directional microphones may be larger than top sound ports in microphones using less compliant structures. This directly exposes the MEMS transducer, and thus an input nodeinto the ASIC, to the ambient environment. If the EMI couples onto the input node of the ASIC, the EMI can be amplified and degrade the quality of the microphone output.SUMMARY OF THE DISCLOSURE

[0005] In accordance with an aspect, a microphone includes a package, a substrate disposed in the package or forming a part of the package, a microelectromechanical system (MEMS) transducer supported by the substrate and packaged in the package, a lid attached to the substrate to encapsulate the MEMS transducer, and a sound port formed in the package to couple a first side of the MEMS transducer to an ambient environment, the sound port comprising an array of holes configured to attenuate a signal level of electromagnetic interference (EMI) entering the package.

[0006] In connection with any one of the aforementioned aspects, the acoustic system may alternatively or additionally include or involve any suitable combination of one or more of the following aspects or features. The sound port is formed in the lid over the MEMS transducer. Holes in the array are configured to have a diameter that is i) sufficiently large to provide a certain sensitivity of the MEMS transducer and ii) sufficiently small to provide a certain attenuation of the signal level of EMI entering the package. Respective holes in the array are configured to have a diameter and are spaced apart from each other with a spacing, wherein the spacing is between outer surfaces of adjacent holes, and wherein the spacing between adjacent holes is smaller than the diameter. Respective holes in the array are configured to have a diameter and are spaced apart from each other with a spacing, wherein the spacing is between centers of adjacent holes, and wherein the spacing between adjacent holes is larger than the diameter. The sound port is a first sound port configured to couple the first side of the MEMS transducer to the ambient environment, and the microphone further comprises a second sound port configured to couple a second side of the MEMS transducer to the ambient environment. The second sound port comprises a single hole coupling the second side of the MEMS transducer to the ambient environment. The first sound port has an overall diameter that is larger than an overall diameter of the second sound port. The first sound port and the second sound port are at least substantially aligned with the MEMS transducer on opposite sides of the MEMS transducer. The first sound port that comprises the array of holes is formed in the lid over the MEMS transducer. The second sound port that comprises a single hole is formed in the substrate under the MEMS transducer. The first sound port and the second sound port are aligned on opposite sides of the MEMS transducer. Respective holes in the array have a diameter less than or equal to about 200micrometers. Holes in the array are arranged in a hexagonal arrangement to maximize a number of holes of a given size within a diameter of the sound port.BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0007] For a more complete understanding of the disclosure, reference should be made to the following detailed description and accompanying drawing figures, in which like reference numerals identify like elements in the figures.

[0008] Figure 1 depicts a microphone having an array of microholes for a sound port in accordance with one example.

[0009] Figure 2 depicts a top view of a microphone having an array of microholes for a sound port in accordance with one example.

[0010] The embodiments of the disclosed devices may assume various forms. Specific embodiments are illustrated in the drawing and hereafter described with the understanding that the disclosure is intended to be illustrative. The disclosure is not intended to limit the invention to the specific embodiments described and illustrated herein.DETAILED DESCRIPTION OF THE DISCLOSURE

[0011] Described herein are devices and methods that include or involve a sound port having an array of small (e.g., microscale) holes, as opposed to a sound port that is formed as one large hole, to maintain acoustic performance but reduce susceptibility to EMI. The sound port having the array of holes may be formed on a metal lid of a microphone, for example. The holes may be small in the sense that each individual hole in the array alone would be insufficient to support operation of the microphone. For example, if only a single hole in the array were used to support operation of the microphone, the sensitivity and thus signal-to-noise ratio (SNR) of the microphone may be greatly reduced. Further details regarding the small nature of the array microholes, according to various examples, are provided below.

[0012] Figure 1 depicts a microphone 100 having a sound ports that is formed as an array of microholes in accordance with one example. The microphone 100 includes a MEMS transducer 102 attached to or otherwise supported by a substrate 104. The substrate 104 may be or include a printed circuit board (PCB) with one or multiple layers. The MEMS transducer 102 may be patterned and etched in the substrate 104 and suspended over a cavity in the substrate 204. The microphone 100 includes an application-specific integratedcircuit (ASIC) 106 configured to read out the electrical signal(s) from the MEMS transducer 102 and is covered by a protective glop top 108 (e.g., a resin, epoxy, and / or polymer material). The ASIC 106 is also attached to, or otherwise supported by, the substrate 104 and electrically connected to conductive traces on substrate 104 by wire bonds 110. Both the MEMS transducer 102 and the ASIC 106 are encapsulated by a lid or other enclosure 112. In some examples, the lid 112 is composed of, or otherwise includes, a metal or other conductive material. The MEMS transducer 102 and the ASIC 106 may be electrically coupled to one another by wire bonds 114, either connected to each other, or to the substrate 104. In other examples, the MEMS transducer 102, ASIC 106, and / or lid 112 may be attached using other suitable techniques. For instance, in some cases, the MEMS transducer 102 may be attached to the substrate 104 (e.g., the PCB) using flip-chip technology.

[0013] A first sound port 116 (also sometimes referred to herein as “top sound port”) is embedded or disposed in the lid 112 of the microphone 100 and a second sound port 118 (also sometimes referred to herein as “bottom sound port”) is embedded or disposed in the substrate 104 (e.g., the PCB) beneath the MEMS transducer 102. The top sound port 116 is configured to couple a first side of the MEMS transducer 102 to an ambient environment. The bottom sound port 118 is configured to couple a second side of the MEMS transducer 102 to the ambient environment. The two sound ports 116 and 118 thus allow ambient sound to couple onto opposing sides of the MEMS transducer 102. Because the microphone 100 includes two sound ports 116, 118 coupling opposing sides of the MEMS transducer 102 to the ambient environment, the microphone 100 is a direction microphone that is subject to a difference in pressure between the sound ports 116 and 118. In some examples, the sound ports 116 and 118 are at least substantially aligned with the MEMS transducer 102. In an example, the sound port 116 and the sound port 118 are aligned with each other. In another example, the sound port 116 and the sound port 118 overlap, with a small offset in alignment of between the sound the sound port 116 and the sound port 118.

[0014] The MEMS transducer 102 may include a cantilever-based structure 120. As the microphone 100 is subjected to a difference in pressure between the sound ports 116 and 118, the cantilever-based structure 120 vibrates, generating a signal that is amplified by the ASIC 106. By having a cantilever-based configuration, the structure 120 is relatively compliant and may have a resonance in the audible range of frequencies. In some examples, the cantilever structure 120 may have a resonance between about 1 kHz and about 5kHz. In other examples, the cantilever structure 120 may have a resonance above about 8kHz, such as about 10kHz.

[0015] The top sound port 116 includes an array of microholes 122 (sometimes referred to herein as “holes”). The array of holes 122 is configured to attenuate a signal level (e.g., amplitude, power, voltage, etc.) of electromagnetic interference (EMI) entering the package of the microphone 100. Respective microholes 122 in the array have a diameter and are spaced from each other with a spacing 124. The spacing 124 may be defined as a spacing between outer surfaces of adjacent holes 122. For example, the spacing 124 corresponds to a straight shortest line drawn from a point on a circumference of one hole 122 to a point on a circumference of an adjacent hole 122. If either each individual hole 122 or, collectively, the array of holes 122, is too small, then the top sound port 116 can reduce the microphone sensitivity. On the other hand, if the individual holes 122 are too big, then the holes 122 may result in insufficient attenuation of EMI. Thus, in various examples, the microholes 122 of the array, and the array collectively, are designed to be correctly sized. For example, the microholes 122 of the array, and the array collectively, may be designed such that i) the microholes 122 are sufficiently large to provide a certain microphone sensitivity and ii) the microholes 122 are sufficiently small to provide a certain attenuation of EMI. As the total or collective open area in the top sound port 116 increases, the sensitivity and thus signal-to- noise-ratio (SNR) of the microphone 100 improves. Thus, in various examples, the spacing 124 between adjacent holes in the array of holes 122 is minimized while still maintaining structural integrity. Small spacings in the arrays of microholes 122 may also lead to fabrication challenges. Because a portion of the area of the top sound port 116 is closed, by the lid material between the array of holes 122, the overall diameter of the top sound port 116 may be larger than it would be if the top sound port 116 was instead configured as one large hole to compensate for the decrease in open area. Thus, in some examples, the diameter of the top sound port 116 may be larger than the diameter of the bottom sound port 118. In an example, the total open area of the top sound port 116 is less than the open area of the bottom sound port 118. For example, the total open area of the top sound port 116 is about half of the open area of the bottom sound port 118. In another example, the total open area of the top sound port 116 is more than half of the open area of the bottom sound port 118 but less than the entire open area of the bottom sound port 118. In yet another example, the total open area of the top sound port 116 is about the same as the open area of the bottom sound port 118.

[0016] In an example, the diameter of the top sound port 116 is about 1 .45 millimeters (mm) and the diameter of the bottom sound port 118 is less than 1 .45 millimeters. In some examples, each hole in the array of holes 122 may have a diameter between about 120 micrometers (urn) and about 250 urn. In an example, each hole in the array of holes 122may have a diameter less than or equal to about 200 urn. In some examples, the diameter of the total top sound port 116 may be between about 1 mm and about 1 .8 mm. In some examples, the holes 122 may have a spacing between about 40 urn and about 120 urn. In some examples, the spacing 124 may be less than the radius of the microholes 122. As just an example, the microholes 122 may have a diameter of about 180 urn (or another diameter less than or equal to about 200 urn) and a spacing 124 of about 150 urn.

[0017] In some examples, the size of each of the microholes 122 and / or spacing 124 may be equal. In other examples, the size of at least one of the microholes 122 and / or at least one spacing 124 between two microphones may be different. The microholes 122 may have any geometrical shape to establish a collective open area of the top sound port 116.

[0018] When moving from a single, large circular sound port to an array of holes 122, the sensitivity of the microphone 100 may be reduced. As the thickness of the lid 112 decreases, the impact to sensitivity arising from the array of holes 122 may diminish. Additionally, thinner lids may address the above-referenced fabrication challenges in forming a small array of holes 122 through processes such as mechanical stamping or laser drilling. In some examples, the lid 112 may have a thickness between about 50 urn and about 100 urn.

[0019] In alternative embodiments, the sound ports 116 and 118 of microphone 100 may not be aligned (non-aligned). For example, the top sound port 116 may be closer to (e.g., more closely aligned with) the ASIC 106 than the MEMS transducer 102. The top sound port 116 may thus be positioned farther away from the input node into the ASIC 106.

[0020] Figure 2 depicts a top view of a microphone 200 having an array of microholes for a sound port in accordance with one example. The microphone 200 is the same as or similar to the microphone 100 of Figure 1 and includes like-numbered elements with the microphone 100 of Figure 1 . The microphone 200 includes a lid 212 that encapsulates the MEMS transducer and ASIC and is supported by substrate 204. In some examples, the lid 212 may be composed of, or otherwise include, a metal or conductive material. A top sound port 216 is embedded or disposed in the lid 212 and includes an array of microholes 222. Adjacent holes 222 in the array have a spacing 228 therebetween. In the example microphone 200 of Figure 2, the spacing 228 is defined as the spacing between the center of one microhole 222 to the center of an adjacent microhole 222. In an example, the spacing 228 may be larger than a diameter of the microholes 222. For example, the microholes 222 may have a diameter less than or equal to about 200 urn, and the spacing 228 may be between about 150 urn and about 350 urn. In some cases, the diameter of the microholes 222 may be about 180 urn (or another diameter less than or equal to about 200 urn) and thespacing 228 may be about 260 urn. In some examples, the spacing 228 between the microholes 222 may be less than 2x the diameter of the microholes 222. In other examples, the spacing 228 between the microholes 222 may be less than 1 ,5x the diameter of the microholes 222.

[0021] The collective open area of the top sound port 216 may be maximized for a given size of microhole 222. For instance, in some examples, the array of microholes 222 may be arranged in a hexagonal arrangement, as this maximizes the number of microholes 222 of a given size that can be positioned within the diameter of top sound port 216. In other examples, the microholes 222 may be arranged in a rectangular or other geometric pattern.

[0022] In some examples, the size of each of the microholes 222 and / or spacing 224 may be equal. In other examples, the size of at least one of the microholes 222 and / or at least one spacing 228 between two microphones may be different. The microholes 222 may have any geometrical shape to establish a collective open area of the top sound port 216.

[0023] The term ''microscale" and prefix "micro-" are used herein to describe or otherwise refer to features having a dimension less than 1 millimeter.

[0024] The term "about" is used herein in a manner to include deviations from a specified value that would be understood by one of ordinary skill in the art to effectively be the same as the specified value due to, for instance, the absence of appreciable, detectable, or otherwise effective difference in operation, outcome, characteristic, or other aspect of the disclosed methods and devices.

[0025] The present disclosure has been described with reference to specific examples that are intended to be illustrative only and not to be limiting of the disclosure. Changes, additions and / or deletions may be made to the examples without departing from the spirit and scope of the disclosure.

[0026] The foregoing description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom.

Claims

What is Claimed is:

1. A microphone, comprising: a package; a substrate disposed in the package or forming a part of the package; a microelectromechanical system (MEMS) transducer supported by the substrate and packaged in the package; a lid attached to the substrate to encapsulate the MEMS transducer; and a sound port formed in the package to couple a first side of the MEMS transducer to an ambient environment, the sound port comprising an array of holes configured to attenuate a signal level of electromagnetic interference (EMI) entering the package.

2. The microphone of claim 1 , wherein the sound port is formed in the lid over the MEMS transducer.

3. The microphone of claim 1 , wherein holes in the array are configured to have a diameter that is i) sufficiently large to provide a certain sensitivity of the MEMS transducer and ii) sufficiently small to provide a certain attenuation of the signal level of EMI entering the package.

4. The microphone of claim 1 , wherein respective holes in the array are configured to have a diameter and are spaced apart from each other with a spacing, wherein the spacing is between outer surfaces of adjacent holes, and wherein the spacing between adjacent holes is smaller than the diameter.

5. The microphone of claim 1 , wherein respective holes in the array are configured to have a diameter and are spaced apart from each other with a spacing, wherein the spacing is between centers of adjacent holes, and wherein the spacing between adjacent holes is larger than the diameter.

6. The microphone of claim 1 , wherein: the sound port is a first sound port configured to couple the first side of the MEMS transducer to the ambient environment; and the microphone further comprises a second sound port configured to couple a second side of the MEMS transducer to the ambient environment.

7. The microphone of claim 6, wherein the second sound port comprises a single hole coupling the second side of the MEMS transducer to the ambient environment.

8. The microphone of claim 7, wherein the first sound port has an overall diameter that is larger than an overall diameter of the second sound port.

9. The microphone of claim 7, wherein the first sound port and the second sound port are at least substantially aligned with the MEMS transducer on opposite sides of the MEMS transducer.

10. The microphone of claim 7, wherein: the first sound port that comprises the array of holes is formed in the lid over the MEMS transducer; and the second sound port that comprises a single hole is formed in the substrate under the MEMS transducer.11 . The microphone of claim 7, wherein the first sound port and the second sound port are aligned on opposite sides of the MEMS transducer.

12. The microphone of claim 1 , wherein respective holes in the array have a diameter less than or equal to about 200 micrometers.

13. The microphone of claim 1 , wherein holes in the array arranged in a hexagonal arrangement to maximize a number of holes of a given size within a diameter of the sound port.

14. An microphone, comprising: a package; a substrate disposed in the package or forming a part of the package; a microelectromechanical system (MEMS) transducer supported by the substrate and packaged in the package; a lid attached to the substrate to encapsulate the MEMS transducer; and a first sound port formed in the package to couple a first side of the MEMS transducer to an ambient environment, the first sound port comprising an array of holes configured to attenuate a signal level of electromagnetic interference (EMI) entering the package; and a second sound port formed in the package, the second sound port configured to couple a second side of the MEMS transducer to the ambient environment.

15. The microphone of claim 14, wherein respective holes in the array are configured to have a diameter and are spaced apart from each other with a spacing, wherein the spacingis between outer surfaces of adjacent holes, and wherein the spacing between adjacent holes is smaller than the diameter.

16. The microphone of claim 14, wherein respective holes in the array are configured to have a diameter and are spaced apart from each other with a spacing, wherein the spacing is between centers of adjacent holes, and wherein the spacing between adjacent holes is larger than the diameter.

17. The microphone of claim 14, wherein the second sound port comprises a single hole coupling the second side of the MEMS transducer to the ambient environment.

18. The microphone of claim 14, wherein the first sound port has an overall diameter that is larger than an overall diameter of the second sound port.

19. The microphone of claim 14, wherein: the first sound port that comprises the array of holes is formed in the lid over the MEMS transducer; and the second sound port that comprises a single hole is formed in the substrate under the MEMS transducer.

20. The microphone of claim 14, wherein holes in the array arranged in a hexagonal arrangement to maximize a number of holes of a given size within a diameter of the first sound port.

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