Microphone assembly, printed circuit board, printed circuit board array and manufacturing method

Abstract

The present invention relates to a microphone assembly, a printed circuit board, a printed circuit board array and a manufacturing method. According to some embodiments, the present invention relates to a printed circuit board for a microphone assembly, the printed circuit board comprising a top layer, a bottom layer, at least one edge, a ground plane and a conductor electrically connected to the ground plane and the bottom layer, the structure of the top layer being designed to mount a MEMS transducer on the top layer. The MEMS transducer comprises a transducer substrate, a back plate and a diaphragm. The conductor extends vertically from the top layer of the printed circuit board to the bottom layer and extends horizontally along a portion of the length of at least one edge of the printed circuit board. The printed circuit board comprises two short edges and two long edges, and the conductor is connected to at least one of the four edges.

Description

Technical Field

[0001] The present invention relates to micro-electromechanical systems (MEMS) devices, and more particularly to printed circuit boards and methods thereof, wherein microphone device unit cells (individual packages) are cut out of the printed circuit boards. Background Art

[0002] Microphone devices that include microelectromechanical systems (MEMS) acoustic transducers convert acoustic energy into electrical signals. Microphone assemblies may be used in mobile communications devices, laptop computers and appliances, among other devices and mechanisms. An important consideration for microphone devices is the elimination of noise that is typically caused by radio frequency (RF) signal connections. As the complexity of these devices increases, the complexity of the printed circuit boards to which these devices are connected also increases, leading to design difficulties. Summary of the invention

[0003] One aspect of the present invention relates to a microphone assembly, which includes: a housing having an acoustic port and an external device electrical interface that can be surface-mounted; a micro-electromechanical system transducer, which is disposed in the housing and is configured to generate an electrical signal in response to detecting sound entering the acoustic port; and an integrated circuit, which is disposed in the housing and is connected to the micro-electromechanical system transducer and to contacts of the external device electrical interface, the housing including a printed circuit board, the printed circuit board having a conductor electrically connected to a ground plane, the conductor extending vertically from a top layer of the printed circuit board to a bottom layer of the printed circuit board, and extending horizontally along the length of at least one side of the printed circuit board.

[0004] Another aspect of the present invention relates to a printed circuit board for a microphone assembly, the printed circuit board comprising: a top layer; a bottom layer; at least one edge; a ground plane; and a conductor electrically connected to the ground plane, wherein the conductor extends vertically from the top layer of the printed circuit board to the bottom layer and extends horizontally along the length of the at least one edge of the printed circuit board; wherein the top layer and the bottom layer have ports formed through the top layer and the bottom layer.

[0005] Another aspect of the present invention relates to a method for manufacturing an externally grounded printed circuit board unit cell, the manufacturing method comprising the following steps: exposing at least one ground plane on at least one edge of the unit cell by laying out a printed circuit board wafer including the unit cell in a first direction; and electroplating a conductor on the at least one edge of the unit cell, wherein the conductor is electrically connected to the at least one ground plane and extends along the at least one edge of the unit cell in the first direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The foregoing features and other features of the present invention will become more fully apparent from the following description and the appended claims in conjunction with the accompanying drawings. These drawings only depict several embodiments according to the present invention and therefore should not be considered as limiting the scope of the present invention. Various embodiments are described in more detail below in conjunction with the accompanying drawings.

[0007] Figure 1 is a schematic diagram of multiple complex printed circuit board designs for microphone assemblies;

[0008] Figure 2A is an example diagram of a cut-away printed circuit board with external grounding;

[0009] Figure 2B is an example diagram of an acoustic transducer and an integrated circuit mounted on a Figure 2A An embodiment of the invention is an external grounding printed circuit board;

[0010] Figure 3 is an example diagram of a printed circuit board that is pre-cut during manufacturing; and

[0011] Figure 4 is a flow chart of an exemplary method of manufacturing an externally grounded printed circuit board. DETAILED DESCRIPTION

[0012] In general, an apparatus and method for producing a printed circuit board cell for a microphone assembly having an external ground to reduce radio frequency (RF) signal interference is disclosed herein. The printed circuit board includes a top layer, a bottom layer, at least one edge, a ground plane, and a conductor, and the structure of the top layer is designed to mount a MEMS transducer on the top layer. The MEMS transducer can be a capacitive acoustic transducer, which includes a fixed backplate and a movable diaphragm, and the fixed backplate and the movable diaphragm are configured to convert acoustic energy entering the diaphragm into an electrical signal. The MEMS transducer can include a transducer substrate, which includes a first port, and a diaphragm and a backplate are disposed above the first port to receive acoustic energy from an external environment. The printed circuit board can include a second port aligned with the first port to provide fluid communication from the external environment to the MEMS transducer.

[0013] As the complexity of integrated circuits increases, the design of printed circuit boards is also affected, such that a single ground via may be undesirable or insufficient for the number of components and connections required to properly operate the circuit. In an attempt to optimize the space of the printed circuit board, it is often difficult to increase the number of ground vias, and reducing the number of ground vias increases the impedance to ground, thereby limiting the effectiveness of metal shielding and embedded capacitor filters. Placing the ground via directly under the MEMS transducer is not optimal because this placement will direct the RF current under the MEMS transducer and cause the RF to be coupled to the MEMS transducer. The RF coupling to the MEMS transducer results in reduced RF immunity. Similarly, power supply noise that is shunted through the embedded capacitor filter by the ground via under the MEMS transducer can be coupled to the MEMS transducer and reduce the power supply rejection ratio (PSRR). The RF signal coupled to the integrated circuit will be demodulated, and any audio present in the demodulated RF signal will appear as undesirable noise at the microphone output. In addition, power supply noise can also pass through the integrated circuit output as undesirable noise.

[0014] The solution proposed herein is to provide a low impedance path (e.g., a single low impedance path) for RF currents on the outer edge of a printed circuit board to reduce the probability of RF coupling into an integrated circuit by acting as a board-level shield to protect components on the printed circuit board. The low impedance path will be a conductor connected to the ground plane of the printed circuit board, thereby reducing the number of ground vias to a single external ground that can be used by all components. This solution will provide more room for placement options for traces, resistors, and larger capacitors as required by the integrated circuit. In addition, this method of producing printed circuit boards produces a reduced amount of cutting slurry (a waste byproduct of panel cutting), thereby reducing material loss and waste contribution. Reference will be made to Figures 1 to 4 Explain the solution further.

[0015] exist Figure 1 , an exemplary schematic diagram 100 of multiple complex printed circuit board designs for use in a microphone assembly according to some embodiments is shown. Each design includes a port 102 that is structured to align with a port of an acoustic transducer. An example outline of a MEMS acoustic transducer 104 can be seen overlaying a ground via 106. Each design also includes multiple ground vias 106 in an attempt to accommodate the necessary footprint of the MEMS transducer 104 and an integrated circuit (not shown).

[0016] exist Figure 2A and Figure 2B, an exemplary illustration of a printed circuit board unit cell 200 and various microphone assembly components mounted to the printed circuit board is shown. Figure 2A The printed circuit board unit cell 200 is illustrated without other microphone assembly components, and Figure 2B A microphone assembly is illustrated that is disposed in a housing that includes a printed circuit board unit cell 200 after components are mounted thereon. The unit cell 200 includes a port 202 and an external ground 204. The port 202 may be aligned or partially aligned with a hole of an acoustic transducer 212. The port 202 may be formed on a printed circuit board or in another portion of the housing (e.g., a cover). The external ground 204 surrounds a top layer 206 of the unit cell 200 and extends along an edge 208. According to some embodiments, the external ground 204 may extend the entire horizontal length and vertical height of the edge 208, or may extend a portion of the length of the edge 208 as shown. As shown, the edge 208 may be one of the short sides or long sides of a unit cell in the shape of a rectangular prism. In some embodiments, the unit cell 200 may be a different polygon whose structure is designed to accommodate a MEMS transducer mounted on the different polygon. The unit cell 200 may include a set of electrical connectors 210 for soldering to a MEMS transducer 214 and / or an integrated circuit component 216. The microphone assembly includes a cover 218 that encloses a volume in which the MEMS transducer 214 and the integrated circuit component 216 are disposed. The housing including the printed circuit board is surface mountable and includes an external device interface to which the integrated circuit is electrically coupled via electrical connector 210. The external device interface allows the microphone assembly to be mounted in an external device such as a phone, computer or other device capable of recording.

[0017] According to some embodiments, the printed circuit board unit cell 200 includes a plurality of layers including a bottom layer, a top layer, and at least one ground plane. An external ground 204 is electrically connected to the at least one ground plane along the length of the edge 208 to provide an increased surface area to the ground plane and electrically connect the ground plane to the bottom layer. During the manufacture of the printed circuit board, the external ground 204 is created by laying out the edge 208 before the electroplating process.

[0018] Figure 32 is an exemplary embodiment of a printed circuit board panel 300 before cutting according to some embodiments. A plurality of routing lines 302 can be seen between the columns of the unit cells 200 along the edge 208. The edge 208 of the unit cell 200 is laid out along the routing lines 302 to expose the conductive layer of the printed circuit board before electroplating. In some embodiments, the laid edge 208 may appear on the short side instead of the long side shown in the figure. Laying out before electroplating makes a portion of the printed circuit board panel 300 unused, thereby reducing the number of unit cells per panel. However, the benefits of ease of design and increased trace space on each unit cell minimize production losses.

[0019] Figure 4 4 is a flow chart of an exemplary method 400 for manufacturing an externally grounded printed circuit board according to some embodiments. The method 400 begins at step 401, which includes designing a printed circuit board and pre-drilling a printed circuit board panel (wafer) to create columns of individual unit cells. Designing the printed circuit board includes determining the placement of the circuit connectors and circuit components to be routed, and generating a pattern. Pre-drilling the printed circuit board panel includes pre-drilling holes for connecting to MEMS transducers, capacitors, resistors, or other circuit component portions according to the design of the pattern. In some embodiments, the printed circuit board panel is deburred to remove excess material.

[0020] Method 400 continues with step 402, which includes: according to some embodiments, after final lamination, laying out the printed circuit board panel along a first direction on the edge of the column of cells. Laying out the printed circuit board along the first direction exposes at least one ground plane. Step 402 may include: applying a photoresist or other type of mask after laying out. The mask applied in step 402 covers the specified area of ​​the printed circuit board and prevents plating from occurring in undesired places. This ensures that short circuits do not occur on the printed circuit board.

[0021] In some embodiments, the subsequent step 403 includes electroplating the printed circuit board to electrically connect at least one ground plane to the bottom layer and the specified traces. Electroplating deposits a conductor, typically copper, nickel, tin or gold or a combination thereof, on the exposed surface of the printed circuit board. Step 403 forms a conductor on the exposed edge of the column of the unit cell. The conductor electrically connects the ground plane exposed in step 402 to the bottom layer of the printed circuit board, thereby creating an external ground. The extent of the external ground on the edge of the printed circuit board is the result of whether a mask is placed on a portion of the edge. If a mask is not placed to cover any exposed edges before electroplating, the external ground extends horizontally from the first corner to the second corner along the entire length of each unit cell, and from the top layer to the bottom layer. The external ground is electrically connected to the bottom layer of the printed circuit board unit cell, but can be electrically isolated from the top layer and all traces.

[0022] Step 403 is followed by step 404, which includes cutting the printed circuit board panel to divide the columns of the unit cell into individual unit cells. Cutting occurs in a direction perpendicular to the layout direction determined in step 402. Since the layout separates the unit cells in a first direction (e.g., vertical direction), cutting occurs only in a second (e.g., horizontal) direction along the unexposed edge of the unit cell. Between step 403 and step 404, additional steps may include adding a solder mask and final chemical nickel gold (ENIG) or chemical nickel palladium gold (ENEPIG) treatment. Before the unit cell is processed, a MEMS acoustic transducer may be mounted on the unit cell.

[0023] According to the embodiments described herein, the microphone assembly includes a housing having an acoustic port and an external device electrical interface capable of surface mounting, a MEMS transducer disposed in the housing, and an integrated circuit disposed in the housing, the housing including a printed circuit board on which the MEMS transducer is mounted. The printed circuit board includes a conductor electrically connected to a ground plane. The conductor extends vertically from a top layer of the printed circuit board to a bottom layer and extends horizontally along the length of at least one side of the printed circuit board. The conductor may extend along a portion of the length of at least one side of the printed circuit board. The printed circuit board includes two short sides and two long sides longer than the short sides. In other words, the printed circuit board is a rectangular prism or a similar three-dimensional shape. At least one side of the printed circuit board along which the conductor extends may be at least one of the long sides or at least one of the short sides. The printed circuit board may also include a single via through which a component is electrically connected to a secondary ground to connect to the integrated circuit. Depending on the needs of the microphone assembly, at least one ground plane and the secondary ground may be electrically isolated or electrically connected.

[0024] The integrated circuit is coupled to the MEMS transducer and to contacts of an external device electrical interface. The MEMS transducer includes a substrate having a hole at least partially disposed above an acoustic port, an electroacoustic conversion element, and electrical contacts coupled to the electroacoustic conversion element. The electroacoustic conversion element may be a variable capacitor, the variable capacitor including a fixed electrode and a movable electrode at least partially located above the hole of the substrate. The movable electrode is configured to move relative to the fixed electrode in response to incoming acoustic energy entering the acoustic port to generate an electrical signal. The movable electrode may include a layer of piezoelectric material.

[0025] According to the embodiments described herein, a method for manufacturing an externally grounded printed circuit board unit cell includes the following steps: exposing at least one ground plane on at least one edge of the unit cell by laying out a printed circuit board wafer containing the unit cell in a first direction so that a row of the unit cell contains the exposed edge. The manufacturing method also includes: electroplating a conductor on at least one edge of the unit cell, wherein the conductor is electrically connected to the at least one ground plane and extends along at least one edge of the unit cell in the first direction. The manufacturing method also includes: cutting the printed circuit board along an edge perpendicular to at least one plated edge of the unit cell in a second direction.

[0026] The conductor created by the manufacturing method is electrically connected to at least one ground plane and extends vertically from the bottom layer of the printed circuit board to the top layer of the printed circuit board. The conductor further extends horizontally from the first end of the plated edge to the second end. The length of at least one side of the unit cell can be the entire length or a portion of the length. At least one side of the unit cell can be one of a long side and a short side. The unit cell can include a single via through which the component can be electrically connected to the secondary ground to connect to the integrated circuit. The structure of the unit cell is designed to mount the MEMS transducer on the unit cell before the cutting step provided by the manufacturing method.

[0027] According to embodiments described herein, a printed circuit board for a microphone assembly includes a top layer, a bottom layer, at least one edge, a ground plane, and a conductor electrically connected to the ground plane. The conductor may extend vertically from the top layer to the bottom layer of a printed circuit board unit cell and horizontally along the length of at least one edge of the printed circuit board unit cell. The top layer and the bottom layer have ports formed therethrough.

[0028] The length of at least one side along which the conductor extends may be the entire length or a portion of the length. The printed circuit board includes two short sides and two long sides that are longer than the short sides. In other words, the printed circuit board is a rectangular prism or a similar three-dimensional shape. At least one side of the printed circuit board may be a long side or a short side. The printed circuit board may include a single via through which a component may be electrically connected to a secondary ground for connection to an integrated circuit, and the ground plane and the secondary ground may be electrically connected or electrically isolated.

[0029] The subject matter described in this article sometimes illustrates different components contained in or connected to different other components. It will be understood that the architecture depicted in this way is merely exemplary, and in fact, many other architectures that obtain the same function can be implemented. In a conceptual sense, any arrangement of components for achieving the same function is effectively "associated" to achieve the desired function. Thus, any two components combined in this article to obtain a specific function can be regarded as "associated" with each other to achieve the desired function, regardless of the architecture or intermediate components. Similarly, any two components associated in this way can also be regarded as "connected at work" or "connected at work" to achieve the desired function, and any two components that can be associated in this way can also be regarded as being able to "connect at work" to each other to achieve the desired function. Specific examples of connection at work include, but are not limited to, physically compatible and / or physically interacting components and / or wirelessly interactive and / or wirelessly interactive components and / or logically interactive and / or logically interactive components.

[0030] Regarding the use of plural and / or singular terms herein, those skilled in the art can translate from plural to singular and / or from singular to plural when appropriate, depending on the context and / or application. For clarity, various singular / plural permutations may be explicitly set forth herein.

[0031] Those skilled in the art will understand that, in general, the terms used herein, and especially in the appended claims (e.g., the bodies of the appended claims), are generally intended to be “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “comprising” should be interpreted as “including but not limited to,” etc.).

[0032] Although the drawings and description can illustrate a specific order of method steps, unless otherwise specified above, the order of these steps may be different from the steps depicted and described. In addition, unless otherwise specified above, two or more steps may be performed simultaneously or partially simultaneously. Such variations may, for example, depend on the selected software and hardware systems and the designer's choice. All of these variations are within the scope of the present invention. Similarly, software implementations of the described methods may be accomplished using standard programming techniques with rule-based logic and other logic to accomplish various connection steps, processing steps, comparison steps, and decision steps.

[0033] Those skilled in the art will further understand that if a specific number of a recited claim is intended to be stated, such intent will be explicitly stated in the claim, and in the absence of such a statement, no such intent exists. For example, to aid understanding, the following appended claims may contain the use of the introductory phrases "at least one" and "one or more" to introduce claim statements. However, the use of these phrases should not be interpreted as implying that the reference to a claim by the indefinite article "a" or "an" will limit any particular claim containing such a recited claim statement to an invention containing only one such statement, even if the same claim includes the introductory phrases "one or more" or "at least one", and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should generally be interpreted as meaning "at least one" or "one or more"); the same is true for the use of definite articles used to refer to claim statements. In addition, even if a specific number of recited claim statements is explicitly stated, those skilled in the art will recognize that such a statement should generally be interpreted as meaning at least the stated number (e.g., a detailed statement of "two statements" without other modifiers generally means at least two statements, or two or more statements).

[0034] Furthermore, in those cases where a convention similar to “at least one of A, B, and C, etc.” is used, generally speaking, such construction is intended in the sense that one skilled in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include, but is not limited to, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). In those cases where a convention similar to “at least one of A, B, or C, etc.” is used, generally speaking, such construction is intended in the sense that one skilled in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include, but is not limited to, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). One skilled in the art would further understand that any disjunctive words and / or phrases that actually present two or more alternative terms, whether in the specification, claims, or drawings, should be understood to contemplate the possibility of including one, either, or both of these terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

[0035] Additionally, use of the terms "approximately," "about," "approximately," "substantially," etc. means plus or minus ten percent unless otherwise indicated.

[0036] The foregoing description of exemplary embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or limited to the precise form disclosed, and modifications and variations may be made in light of the above teachings or may be acquired from practice of the disclosed embodiments. The scope of the invention is intended to be defined by the appended claims and their equivalents.

Claims

1. A microphone assembly, comprising: a housing having an acoustic port and an external device electrical interface for surface mounting; a micro-electromechanical systems transducer disposed in the housing and configured to generate an electrical signal in response to detecting sound entering the acoustic port; as well as an integrated circuit, the integrated circuit being disposed in the housing, the integrated circuit being coupled to the micro-electromechanical system transducer and to contacts of the external device electrical interface, The housing includes a printed circuit board having a conductor that electrically connects the ground plane to an external ground, the conductor extending vertically from a top layer of the printed circuit board to a bottom layer of the printed circuit board and extending horizontally along a length of at least one side of the printed circuit board, wherein the area of ​​the printed circuit board is below the micro-electromechanical system transducer, and The conductor provides a low impedance path away from the area of ​​the printed circuit board underneath the MEMS transducer, wherein the low impedance path is used to pass radio frequency current to the ground plane.

2. The microphone assembly according to claim 1, wherein: The length of the at least one side of the printed circuit board is the entire length of the at least one side of the printed circuit board.

3. The microphone assembly according to claim 1, wherein: The printed circuit board comprises two short sides and two long sides longer than the two short sides, and wherein the at least one side of the printed circuit board along which the conductor extends is at least one of the two long sides.

4. The microphone assembly according to claim 1, wherein: The printed circuit board includes two short sides and two long sides that are longer than the two short sides, and wherein the at least one side of the printed circuit board along which the conductor extends is at least one of the two short sides.

5. The microphone assembly according to claim 1, wherein: The micro-electromechanical system transducer comprises: a substrate comprising an aperture at least partially aligned with the acoustic port; an electroacoustic transducing element at least partially located over the aperture and coupled to the substrate; and an electrical contact coupled to the electroacoustic transducing element, The electroacoustic conversion element is a variable capacitor, which includes a back plate and a diaphragm, and the diaphragm is at least partially located above the hole of the substrate.

6. The microphone assembly according to claim 1, wherein: The micro-electromechanical system transducer comprises: a substrate comprising an aperture at least partially aligned with the acoustic port; an electroacoustic transducing element at least partially located over the aperture and coupled to the substrate; and an electrical contact coupled to the electroacoustic transducing element, The electroacoustic conversion element includes a back plate and a diaphragm, the diaphragm includes a piezoelectric material layer, and the piezoelectric material layer is at least partially located above the hole of the substrate.

7. A printed circuit board for a micro-electromechanical system microphone assembly, the printed circuit board comprising: Top floor; bottom layer; At least one edge; Ground plane; as well as a conductor electrically connecting the ground plane to an external ground, wherein the conductor extends vertically from the top layer of the printed circuit board to the bottom layer of the printed circuit board and extends horizontally along the length of the at least one side of the printed circuit board; wherein the top layer and the bottom layer have ports formed through the top layer and the bottom layer, wherein the port provides acoustic energy to a MEMS transducer of the MEMS microphone assembly, wherein the area of ​​the printed circuit board is below the micro-electromechanical system transducer, and wherein the conductor provides a low impedance path coupled between the ground plane and the external ground, away from the area of ​​the printed circuit board below the MEMS transducer, wherein the low impedance path is used to pass radio frequency current to the ground plane.

8. The printed circuit board according to claim 7, wherein: The length of the at least one side is the entire length or a portion of the entire length.

9. The printed circuit board according to claim 7, wherein: The printed circuit board further comprises two short sides and two long sides longer than the two short sides, and wherein the at least one side of the printed circuit board along which the conductor extends is at least one of the two long sides.

10. The printed circuit board according to claim 7, wherein: The printed circuit board further comprises two short sides and two long sides longer than the two short sides, and wherein the at least one side of the printed circuit board along which the conductor extends is at least one of the two short sides.

11. A printed circuit board array, wherein: The printed circuit board array comprises a plurality of printed circuit boards according to claim 7 that are non-unitary and arranged in an array.

12. A method for manufacturing a printed circuit board unit cell with external grounding, the manufacturing method comprising the following steps: exposing at least one ground plane on at least one side of a unit cell by laying out a printed circuit board wafer containing the unit cell in a first direction, wherein the unit cell includes a top layer structured such that a micro-electro-mechanical system transducer is mounted on the top layer; and electroplating a conductor on the at least one side of the unit cell, wherein the conductor is electrically connected to the at least one ground plane and extends along the at least one side of the unit cell in the first direction, wherein the area of ​​the printed circuit board is below the area where the micro-electromechanical system transducer is mounted, and The conductor provides a low impedance path away from an area of ​​the printed circuit board below an area where the micro-electromechanical system transducer is mounted, wherein the low impedance path is used to pass radio frequency current to the at least one ground plane.

13. The manufacturing method according to claim 12, further comprising the following steps: The printed circuit board is cut in a second direction along an edge perpendicular to at least one plated edge of the unit cell.

14. The manufacturing method according to claim 12, wherein: The conductor is electrically connected to the at least one ground plane, the conductor extending vertically from a bottom layer of the unit cell to a top layer of the unit cell and extending horizontally from a first end of the plated side to a second end of the plated side.

15. The manufacturing method according to claim 12, wherein: The length of the at least one side of the unit cell is the entire length or a portion of the entire length.

16. The manufacturing method according to claim 12, wherein: The at least one side of the unit cell is one of a long side and a short side.

17. The manufacturing method according to claim 12, wherein: The unit cell includes a single via electrically connected to a secondary ground for connection to an integrated circuit.

18. The manufacturing method according to claim 12, wherein: The unit cell is configured such that a micro-electro-mechanical system transducer is mounted on the unit cell prior to dicing.

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