CN213426478U

CN213426478U - Microphone assembly

Info

Publication number: CN213426478U
Application number: CN201990000750.5U
Authority: CN
Inventors: N·D·塔拉格; L·博尔纳; T·利姆
Original assignee: Knowles Electronics Suzhou Co ltd
Current assignee: Knowles Electronics Suzhou Co ltd
Priority date: 2019-01-31
Filing date: 2019-12-24
Publication date: 2021-06-11
Anticipated expiration: 2029-12-24
Also published as: WO2020159652A1

Abstract

The microphone assembly includes a substrate. An acoustic transducer is disposed on the substrate and configured to generate an electrical signal in response to the acoustic signal. An integrated circuit is disposed on the substrate and electrically coupled to the acoustic transducer. The housing is disposed on the base plate and includes a body and a sidewall projecting axially from an outer edge of the body toward and in contact with the base plate in a manner such that an interior volume is defined between the housing and the base plate. The insulating layer is insert molded on the inner surface of the housing or over molded on the outer surface of the housing in such a manner that the insulating layer is not disposed on the portion of the sidewall adjacent to the substrate.

Description

Microphone assembly

Cross Reference to Related Applications

This application claims the benefit and priority of U.S. provisional patent application No.62/799,726 filed on 31.1.2019 and U.S. provisional patent application No.62/880,849 filed on 31.7.7.2019, both of which are incorporated herein by reference in their entirety.

Technical Field

The present disclosure relates generally to systems and methods for providing an insulating layer on a housing of a microphone assembly.

Background

Microphone assemblies are commonly used in electronic devices to convert acoustic energy into electrical signals. Advances in micro-and nano-fabrication technology have led to the development of smaller and smaller micro-electromechanical system (MEMS) microphone assemblies. The small size of the MEMS microphone assembly may make it prone to noise problems. In particular, temperature variations in the interior volume defined by the housing can cause noise due to heat conduction through the housing.

SUMMERY OF THE UTILITY MODEL

In some embodiments, a microphone assembly includes a substrate. An acoustic transducer is disposed on the substrate, the acoustic transducer configured to generate an electrical signal in response to an acoustic signal. An integrated circuit is disposed on the substrate and electrically coupled to the acoustic transducer. A housing is disposed on the base plate, the housing including a body and a sidewall projecting axially from an outer edge of the body toward the base plate and in contact with the base plate in a manner such that an interior volume is defined between the housing and the base plate. An insulating layer is insert molded (insert mold) on an inner surface of the housing in such a manner that the insulating layer is not disposed on a portion of the sidewall adjacent to the substrate.

In some embodiments, the housing of the microphone assembly with the insulating layer is formed by: disposing the housing in a mold cavity of a mold, the housing comprising a body and a sidewall projecting axially from an outer edge of the body; inserting an insulating material into the mold cavity through an inlet of the mold; and curing the insulating material in such a manner that the insulating layer of the insulating material is insert molded on the inner surface of the housing.

In some embodiments, a microphone assembly includes a substrate and an acoustic transducer disposed on the substrate. The acoustic transducer is configured to generate an electrical signal in response to an acoustic signal. An integrated circuit is disposed on the substrate and electrically coupled to the acoustic transducer. A housing is disposed on the substrate. The housing includes a body and a sidewall projecting axially from an outer edge of the body toward and in contact with the base plate in a manner such that an interior volume is defined between the housing and the base plate. An insulating layer is overmolded (over mold) on an outer surface of the housing in a manner such that the insulating layer is not disposed on a portion of the sidewall adjacent the substrate.

It should be understood that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided that such concepts are not mutually inconsistent) are considered to be part of the subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are considered to be part of the subject matter disclosed herein.

Drawings

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several implementations in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.

Fig. 1 is a side cross-sectional view of a microphone assembly including a housing having an insert molded insulating layer according to an embodiment.

Fig. 2A is a bottom view of the housing of fig. 1, and fig. 2B is a bottom perspective view of the housing of fig. 1, according to an embodiment.

Fig. 3 is a side cross-sectional view of a microphone assembly including a housing having an overmolded insulating layer in accordance with another embodiment.

Fig. 4A and 4B show graphs of detected electromagnetic interference (EMI) generated by radiated Radio Frequency (RF) waves through the enclosure and improved by an insert molded insulating layer disposed on an inner surface of the enclosure.

Fig. 5 is a schematic flow diagram of a method of insert molding an insulating layer on an inner surface of a housing of a microphone assembly in accordance with an embodiment.

Fig. 6 is a schematic flow diagram of a method of overmolding an insulating layer on an outer surface of a housing of a microphone assembly in accordance with an embodiment.

Throughout the following description, reference will be made to the accompanying drawings. In the drawings, like numerals generally identify like components, unless context dictates otherwise. The illustrative implementations described in the specification, drawings, and claims are not meant to be limiting. Other implementations may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and made part of this disclosure.

Detailed Description

Embodiments described herein relate generally to a housing for a microphone assembly that includes an insulating layer that is insert molded or over molded on the housing that reduces heat transfer to an interior volume of the housing.

The small MEMS microphone assembly allows for the incorporation of such microphone assemblies into compact devices, such as mobile phones, laptop computers, wearable devices, television/set-top box remote controls, and the like. The MEMS microphone industry is faced with a continuing need to reduce footprint, package volume, power consumption, and cost while improving performance and reliability. Typically, the enclosure (can) or housing that houses the components of the microphone assembly is filled with air. The miniaturization of the MEMS microphone assembly allows the housing of the MEMS microphone assembly to be very small (e.g., at 1 mm)³-5mm³Within) of the container. The housing provides an electromagnetic shield and a protective cover for the components of the microphone assembly.

However, such MEMS microphone assemblies present other unique challenges, particularly due to the small size of such microphone assemblies. For example, the housing may not provide sufficient electromagnetic compatibility (EMC) for RF signals to which the microphone assembly may be subjected. RF signals that may be generated by other components of the system in which the microphone assembly is disposed may impinge upon and be absorbed in the housing, thereby causing the housing to increase in temperature. This heat is conducted into the interior volume defined by the housing, resulting in an increase in air disposed in the interior volume, which results in acoustic noise (e.g., due to changes in density and thus partial pressure of air present in the interior volume). In other cases, the housing may be subjected to radiant heat (e.g., generated by other components of the system including the microphone assembly), which may also cause the housing to heat.

In contrast, embodiments of the diaphragm assemblies and acoustic transducers described herein may provide one or more benefits, including, for example: (1) providing an insulating layer on an inner surface or an outer surface of a housing of the microphone assembly, thereby reducing heat conduction and noise; (2) overmolding or insert molding the insulating layer on the housing, thereby allowing mass manufacturing of the housing with the insulating layer in a smart, fast, and cost-effective manner; (3) providing an insulating layer in continuous contact with the housing, thereby providing better insulation; and (4) allowing the height of the insulating layer to be controlled so that a portion of the sidewall of the housing that is joined to the substrate of the microphone assembly is not covered so as to prevent the insulating layer from interfering with the joining of the housing and the substrate.

Fig. 1 is a side cross-sectional view of a microphone assembly 100 according to a particular embodiment. The microphone assembly 100 may be used to convert acoustic signals into electrical signals in any device, such as, for example, a mobile phone, a laptop computer, a television/set-top box remote control, a tablet computer, an audio system, a headset, a wearable device, a portable speaker, a car audio system, or any other device that uses a microphone assembly.

The microphone assembly 100 includes a substrate 102, a sound transducer 110, an integrated circuit 120, and a housing or cover 130. The substrate 102 may be formed of a material (e.g., plastic) used in Printed Circuit Board (PCB) manufacturing. For example, substrate 102 may include a PCB configured to mount acoustic transducer 110, integrated circuit 120, and housing 130. An acoustic port 104 is formed through the substrate 102. Acoustic transducer 110 is located on acoustic port 104 and is configured to generate an electrical signal in response to an acoustic signal received through acoustic port 104.

In fig. 1, acoustic transducer 110 and integrated circuit 120 are shown disposed on a surface of substrate 102, but in other implementations, one or more of these components may be disposed on housing 130 (e.g., disposed on an interior surface of housing 130) or on a sidewall of housing 130 or stacked on each other. In some implementations, the substrate 102 includes an external device interface having a plurality of contacts that are coupled to the integrated circuit 120, e.g., to connection pads (e.g., bond pads) that may be disposed on the integrated circuit 120. The contacts may be embodied as pins, pads, bumps (bump) or balls, among other known or future mounting structures. The function and number of contacts on the external device interface depends on the protocol or protocols implemented and may include power contacts, ground contacts, data contacts, clock contacts, and the like. The external device interface allows the microphone assembly 100 to be integrated with a host device using reflow soldering, fusion bonding, or other assembly processes.

In various implementations, acoustic transducer 110 may include a diaphragm 112 and a back plate 114 disposed over diaphragm 112. A diaphragm 112 and a backplate 114 may be disposed on the transducer substrate 111. The thickness of the diaphragm 112 may be in the range of 1 micron to 10 microns. As shown in fig. 1, the diaphragm 112 separates a front cavity volume 105 defined between the diaphragm 112 and the acoustic port 104 from an interior volume 107, the interior volume 107 forming a back cavity volume of the microphone assembly 100 between the housing 130 and the diaphragm 112. Thus, the microphone assembly 100 is a bottom port microphone assembly in which the acoustic port 104 is defined in the substrate 102 such that the interior volume 107 of the housing 130 defines a back volume. It should be understood that in other embodiments, the concepts described herein may be implemented in a top port microphone assembly in which the acoustic port is defined in the housing 130 of the microphone assembly 100.

In some implementations, the acoustic transducer 110 can include a MEMS transducer embodied as a condenser-type transducer having a diaphragm 112 (e.g., a diaphragm) that is movable relative to a backplate 114 in response to acoustic pressure changes. Alternatively, the MEMS acoustic transducer 110 may comprise a piezoelectric device, or some other known or future electro-acoustic transduction device implemented using MEMS technology. In still other implementations, the acoustic transducer 110 is a non-MEMS device, for example embodied as an electret or other known or future non-MEMS type transducing device.

In some implementations, the acoustic transducer 110 can be formed of a dielectric material and/or a conductive material (e.g., silicon oxide, silicon nitride, silicon carbide, gold, aluminum, platinum, etc.). Movement of the diaphragm 112 in response to the acoustic signal may generate an electrical signal (e.g., a voltage corresponding to a change in its capacitance) that may be measured and representative of the acoustic signal. In some implementations, vibration of the diaphragm relative to the backplate 114 (e.g., a fixed backplate) causes a change in capacitance between the diaphragm 112 and the backplate 114 and a corresponding change in the generated electrical signal. In other implementations, the acoustic transducer 110 may be formed from piezoelectric materials (e.g., quartz, lead titanate, group III-V and group II-VI semiconductors (e.g., gallium nitride, indium nitride, aluminum nitride, zinc oxide, etc.), graphene, ultra-nanodiamonds, polymers (e.g., polyvinylidene fluoride), or any other suitable piezoelectric material). In such implementations, the acoustic transducer 110 may generate an electrical signal (e.g., a piezoelectric current or voltage) representative of the acoustic signal in response to the vibration of the acoustic signal. In some embodiments, a perforation or through hole is defined through the diaphragm 112 to provide pressure equalization between the front volume 105 and the back volume 107. In other embodiments, a vent may be defined in the housing 130 to allow for pressure equalization.

The backplate 114 is disposed above the diaphragm 112 such that the backplate 114 is spaced apart from the diaphragm 112. A plurality of apertures 116 are defined in the backing plate 114. The backplate 114 may be formed of polysilicon, silicon nitride, other suitable materials (e.g., silicon oxide, silicon, ceramic, etc.), or interlayers thereof. Vibration of the diaphragm 112 relative to a backplate 114, the backplate 114 being substantially fixed (e.g., substantially non-bending relative to the diaphragm 112), in response to acoustic signals received at the diaphragm 112, results in a change in capacitance between the diaphragm 112 and the backplate 114 and a corresponding change in the generated electrical signal. Although the backplate 114 is disposed above the diaphragm 112 as shown in fig. 1, in other embodiments, the backplate 114 may be disposed below the diaphragm 112, or in a dual-diaphragm acoustic transducer or any other acoustic transducer, the backplate 114 may be disposed between a first diaphragm and a second diaphragm, each of which includes the diaphragm 112.

Integrated circuit 120 is located on substrate 102. The integrated circuit 120 is electrically coupled to the acoustic transducer 110, for example, via a first electrical lead 124, and is also electrically coupled to the substrate 102 via a second electrical lead 126 (e.g., electrically coupled to traces or other electrical contacts disposed on the substrate 102). Integrated circuit 120 receives the electrical signal from acoustic transducer 110 and may amplify and condition the signal before outputting a digital or analog electrical signal, as is well known. Integrated circuit 120 may also include a protocol interface (not shown) depending on the desired output protocol. Integrated circuit 120 may also be configured to allow programming or interrogation thereof, as described herein. Exemplary protocols include, but are not limited to, PDM, PCM, SoundWire, I2C, I2S, and SPI, among others.

Integrated circuit 120 may include one or more components, such as a processor, memory, and/or a communication interface. The processor may be implemented as one or more general-purpose processors, Application Specific Integrated Circuits (ASICs), one or more Field Programmable Gate Arrays (FPGAs), Digital Signal Processors (DSPs), a set of processing elements, or other suitable electronic processing elements. In other implementations, the DSP may be separate from the integrated circuit 120, and in some implementations, the DSP may be stacked on the integrated circuit 120. In some embodiments, one or more processors may be shared by multiple circuits and may execute stored instructions or be accessed via different memory regions. Alternatively or additionally, one or more processors may be configured to perform or otherwise perform certain operations independently of one or more coprocessors. In other example embodiments, two or more processors may be coupled via a bus to implement independent, parallel, pipelined, or multi-threaded instruction execution. All such variations are intended to fall within the scope of the present disclosure. For example, the circuitry described herein may include one or more transistors, logic gates (e.g., nand, and, nor, or, xor, nor, xnor, etc.), resistors, multiplexers, registers, capacitors, inductors, diodes, wiring, and the like.

In some implementations, the protective coating 122 can be disposed on the integrated circuit 120. The protective coating 122 may include, for example, a silicone gel, a laminate, or any other protective coating configured to protect the integrated circuit 120 from moisture and/or temperature variations.

Referring now also to fig. 2A-2B, a housing 130 is positioned on the substrate 102. The housing 130 defines an interior volume 107, with at least the integrated circuit 120 and the acoustic transducer 110 located within the interior volume 107. For example, as shown in fig. 1, the housing 130 is positioned on the substrate 102, and the substrate 102 and the housing 130 collectively define an interior volume 107. As previously described herein, the interior volume 107 defines a back volume of the microphone assembly 100. The housing 130 may be formed of a suitable material, such as, for example, a metal (e.g., aluminum, copper, stainless steel, brass, etc.), and is coupled to the substrate 102 at a joint 128. The joint 128 may include, for example, an adhesive, solder, or fusion bond. The housing 130 includes a body 132 and a sidewall 134, the sidewall 134 axially protruding from an outer edge of the body 132 toward the substrate 102 and contacting the substrate 102, wherein an end 133 of the sidewall 134 contacting the substrate 102 is coupled to the substrate 102 by a joint 128.

In some cases, the microphone assembly 100 may be exposed to RF signals generated by, for example, other components of a system that includes the microphone assembly 100. The RF signal may be absorbed in the housing 130 and cause the housing 130 to heat up. The heat is conducted into the interior volume 107 (i.e., the back volume) and heats the air contained therein, which results in acoustic noise.

To reduce heat conduction from the housing 130 to the interior volume 107, the insulating layer 140 is insert molded onto the interior surface 131 of the housing 130 in a manner such that the insulating layer 140 is not disposed on the portion 136 of the sidewall 134 adjacent the substrate 102. Specifically, the insulating layer is not provided on the portion of the sidewall 134 between the end 133 of the sidewall 134 that is in contact with the substrate 102 and the outer end 143 of the insulating layer 140 that is near the substrate 102. For example, as shown in fig. 1, the height of sidewall 134 is H1, and the height of the portion of insulating layer 140 disposed on sidewall 134 is H2, which height H2 is selected such that insulating layer 140 is not disposed on portion 136 of sidewall 134. In some embodiments, the height H of the portion 136 is less than three-quarters (3/4) times the height H1 of the side wall 134. For example, the height of the portion 136 may be equal to or less than 100 microns.

Some conventional housings used with microphone assemblies may have a pre-formed insert coupled to an inner surface of the housing via an adhesive. Disadvantages of this approach include that on the part of the inner surface of such a housing where no adhesive is present, a gap remains between the preformed insulation layer and the corresponding surface of the housing, which may result in heat leakage into the inner volume of the housing, thus providing poor thermal insulation. In addition, since the housing of the microphone assembly has a small size (e.g., 1 mm)³To 5mm³) Thus, therefore, it isAccurately positioning such preformed inserts into the housing is cumbersome and prone to error. Complex clamps and fixtures may be required, which greatly increases manufacturing complexity and cost.

In contrast, the surface 141 of the insulating layer 140 is in continuous contact with the corresponding inner surface 131 of the housing 130, which is a benefit provided by insert molding the insulating layer directly onto the inner surface 131 of the housing 130. Accordingly, the insulating layer 140 is directly formed on the inner surface 131 of the housing 130 in one molding step, and when the insulating material forming the insulating layer 140 is cured during the molding process, the insulating material adheres to the inner surface 131 of the housing 130.

In this manner, the complex steps of alignment, positioning and adhesion used with pre-formed inserts are eliminated, thereby reducing manufacturing complexity and cost. Furthermore, the continuous contact of the insulating layer 140 with the inner surface of the housing 130 provides excellent thermal insulation. In addition, the molding process can expose portions 136 of the sidewalls without the need for additional etching or material removal processes. This facilitates the bonding of the end 133 of the side wall 134 of the housing 130 to the substrate 102 via the bonding portion 128 without the insulating layer 140 interfering with the bonding process.

Further, the insulating layer 140 may act as a barrier to the solder material that may be used to form the joint 128 to couple the housing 130 to the substrate 102 so that the solder material does not flow up the side wall 134 of the housing 130. For example, in a conventional housing that does not include an insert molded insulating layer, the solder material present on the substrate 102 and serving as the bond pads of the housing 130 is heated to a temperature in the range of 220 degrees celsius to 270 degrees celsius. This melts the weld material, which when cooled to its solidification temperature forms a joint 128 with the housing 130. In some cases, the molten weld material may flow up the side wall 134 along the inner surface 131 of the outer shell 130. The molten solder material may flow to the top of the housing 130 and then fall as small solder particles onto the acoustic transducer 110, the integrated circuit 120, and other components of the microphone assembly 100 disposed within the housing 130, which may damage these components. In contrast, the insert molded insulating layer 140 acts as a physical barrier that restricts the flow of solder material to the portion 136, thereby preventing the solder material from flowing to the top of the housing 130 and landing on the components of the microphone assembly 100.

The insulating layer 140 may be formed of any suitable material (e.g., liquid crystal polymer, molding compound, or engineering plastic). In a particular embodiment, the insulating layer is formed from a liquid crystal polymer. The liquid crystal polymer may have a melting temperature in a range of 250 degrees celsius to 400 degrees celsius. In some embodiments, the liquid crystalline polymer comprises an aromatic polyester (such as under the trade name

The aromatic polyester provided). In particular embodiments, the liquid crystalline polymer comprises a high melting temperature

LCP, its melting temperature is about 335 degrees celsius. In various embodiments, the liquid crystal polymer may be reinforced with glass. In other embodiments, the liquid crystalline polymer comprises

In still other embodiments, the insulating layer 140 may be formed from a molding compound, such as an engineered molded epoxy resin (e.g., an epoxy cresol novolac cured with a novolac, etc.). In still other embodiments, the insulating polymer is an engineering plastic, such as low density polyethylene, polypropylene, polystyrene, acrylonitrile butadiene styrene, acetal, and the like.

In some embodiments, the thickness of the insulating layer 140 is in the range of 50 microns to 100 microns. For example, the thickness of the insulating layer 140 may be in a range of 55 microns to 90 microns, 60 microns to 80 microns, 70 microns to 100 microns, or any other suitable thickness. In a particular embodiment, the thickness of the insulating layer 140 is about 70 microns.

In some embodiments, insulating layer 140 further includes a mold gate 142, the mold gate 142 protruding from a surface of insulating layer 140 disposed on main body 132 of housing 130 and protruding away from main body 132. Mold gate 142 corresponds to the portion of the insulating material disposed in the gate or opening of the mold through which the insulating material is poured into the mold cavity of the mold. The housing 130 is located in a mold cavity and an insulating material (e.g., a liquid crystal polymer or any other molten or liquefied insulating material) is inserted into the mold cavity via a gate. The portion of the insulating material remaining in the gate solidifies to form mold gate 142 and can remain protruding from insulating layer 140 once housing 130, in which insulating layer 140 is insert molded, is removed from the mold.

As shown in fig. 1 and 2A-2B, mold gate 142 is relative to a longitudinal axis a of microphone assembly 100_LRadially offset. For example, the inlet or gate of a mold used to insert mold insulating layer 140 on inner surface 131 of housing 130 may be offset from the longitudinal axis (i.e., center) of housing 130 such that mold gate 142 is offset from longitudinal axis a once insulating layer 140 is molded_LOffset (e.g., located near a side or corner of the housing 130). This may prevent mold gate 142 from interfering with (i.e., contacting) components of microphone assembly 100 (e.g., acoustic transducer 110 or integrated circuit 120) located within the interior volume of housing 130 and/or provide space to form indicia (e.g., stamped or laser etched product numbers, serial numbers, lot numbers, etc.) on the interior surface of insulating layer 140, which is typically formed near the center of housing 130.

In some embodiments, a shielding layer 150 of shielding material is also disposed on at least the outer surface 135 of the housing 130. In some embodiments, the shield layer 150 may also be disposed on the portion 136 of the sidewall 134 of the housing 130, or in implementations where the shield layer 150 is disposed on the housing 150, such as after the insulating layer 140 is insert molded onto the housing 150, the shield layer 150 may be disposed on any other exposed portion of the housing 130 where the insulating layer 140 is not disposed. In other embodiments, the shield layer 150 may be disposed on the housing 130 before the insulating layer 140 is insert molded on the housing 130. In such embodiments, the shielding layer 150 is disposed on each of the inner surface 131 and the outer surface 135 of the housing 130 and is interposed between the insulating layer 140 and the housing 130.

The shielding material forming the shielding layer 150 may include copper, nickel, tin, chromium, gold, silver, or any other suitable material. The shielding layer is configured to provide additional electromagnetic shielding, for example to improve signal-to-noise ratio. The shield layer 150 may be disposed on the housing 130 using electroplating, electroless plating, vacuum deposition, or any other suitable deposition process.

Fig. 3 is a side cross-sectional view of a microphone assembly 200 according to another embodiment. The microphone assembly 200 may be used to convert acoustic signals into electrical signals in any device, such as, for example, a mobile phone, a laptop computer, a television/set-top box remote control, a tablet computer, an audio system, a headset, a wearable device, a portable speaker, a car audio system, or any other device that uses a microphone assembly.

The microphone assembly 200 includes the substrate 102 defining the acoustic port 104, the acoustic transducer 210, the integrated circuit 120, the housing or cover 130, and generally includes the same components as described in detail with respect to the microphone assembly 200 of fig. 1. In fig. 3, acoustic transducer 110 and integrated circuit 120 are shown disposed on a surface of substrate 102, but in other implementations, one or more of these components may be disposed on housing 130 (e.g., disposed on an inner surface of housing 130) or on a sidewall of housing 130 or stacked on each other. Further, while fig. 3 shows a bottom port microphone assembly 200, in other embodiments, the concepts described herein may be implemented in a top port microphone assembly in which an acoustic port is defined in the housing 130 of the microphone assembly 200.

As shown in fig. 3, housing 130 defines an interior volume 107, with at least integrated circuit 120 and acoustic transducer 110 located within interior volume 107. The interior volume 107 forms the back volume of the microphone assembly 200. The housing 130 includes a body 132 and a sidewall 134, the sidewall 134 axially protruding from an outer edge of the body 132 toward the substrate 102 and contacting the substrate 102, wherein an end 133 of the sidewall 134 contacting the substrate 102 is coupled to the substrate 102 by a joint 128.

Unlike the microphone assembly 100, the microphone assembly 200 includes an insulating layer 240 overmolded onto the outer surface 135 of the housing 130 in a manner such that the insulating layer 240 is disposed outside of the interior volume 107 defined by the housing 130. The insulating layer 240 is not disposed on the portion 136 of the sidewall 134 of the housing 130 adjacent the substrate 102 between the end 133 of the sidewall 134 that contacts the substrate 102 and the outer end 243 of the insulating layer 240 adjacent the substrate 102. For example, as shown in fig. 3, the height of the sidewall 134 is H1, and the height of the portion of the insulating layer 240 disposed on the sidewall 134 is H2, such that the insulating layer 240 is not disposed on the portion 136 of the sidewall 134. In some embodiments, the height H of the portion 136 is less than 3/4 times the height H1 of the side wall 134. For example, the thickness of the portion 136 excluding the insulating layer 240 may be equal to or less than 100 micrometers.

Surface 245 of insulating layer 140 is in continuous contact with corresponding outer surface 135 of housing 130. Accordingly, in one molding step, the insulating layer 240 is formed directly on the outer surface 135 of the outer shell 130, and when the insulating material forming the insulating layer 240 is cured during the molding process, the insulating material adheres to the outer surface 135 of the outer shell 130.

Insulating layer 240 may be formed of any suitable material as described in detail with respect to insulating layer 140. In some embodiments, the thickness of the insulating layer 240 is in a range of 50 microns to 100 microns. For example, the thickness of the insulating layer 240 may be in a range of 55 microns to 90 microns, 60 microns to 80 microns, 70 microns to 100 microns, or any other suitable thickness. In a particular embodiment, the thickness of the insulating layer 240 is about 70 microns.

In some embodiments, insulating layer 240 further includes a mold gate 242, the mold gate 242 protruding from a surface of insulating layer 240 disposed on main body 132 of housing 130 and protruding away from main body 132. The mold gate 242 is oriented with respect to the longitudinal axis a of the microphone assembly 100_LRadially offset. This may provide space to form indicia (e.g., laser etched product numbers, serial numbers, lot numbers, etc.) on the outer surface of the insulating layer 240 adjacent the center of the housing 130.

Furthermore, as described with respect to the microphone assembly 100, the shield layer 250 is also disposed on at least the inner surface 131 of the housing 130 opposite the outer surface 135. In some embodiments, the shielding layer 250 may also be disposed on the portion 136 of the sidewall 134. The shield layer 250 is substantially similar to the shield layer 150 and therefore will not be described in detail herein.

Fig. 4A and 4B are graphs illustrating detected electromagnetic interference (EMI) generated by radiated Radio Frequency (RF) waves through a housing of a microphone assembly and providing EMI improvement through an insert molded insulating layer disposed on an inner surface of the housing. The insulating layer includes a liquid crystal polymer having a thickness in a range of about 70 microns to 100 microns. In FIG. 4A, the RF source is positioned at an angle of zero degrees with respect to the housing, and in FIG. 4B, the RF source is positioned at an angle of 90 degrees with respect to the housing. The RF source is scanned over a frequency range from 0.7GHz to 2.2 GHz. When the insulating layer was insert molded on the inner surface of the case, an EMC improvement of 10dB-15dB (i.e., an EMI improvement of 10dB-15dB) was observed.

Fig. 5 is a schematic flow diagram of a method 300 of insert molding an insulating layer on an inner surface of a housing (e.g., housing 130) of a microphone assembly (e.g., microphone assembly 100). The method 300 includes providing a housing at 302. For example, a housing 130 is provided, the housing 130 including a main body 132 and a sidewall 134 axially protruding from an outer edge of the main body 132.

At 304, a housing is disposed in a mold cavity of a mold. The mold cavity may be configured to allow insert molding of the insulating layer on an inner surface (e.g., inner surface 131) of the housing (e.g., housing 130).

At 306, an insulating material is inserted into the mold cavity through an inlet or gate of the mold. At 308, the insulating material is cured in a manner such that an insulating layer of insulating material (e.g., insulating layer 140) is insert molded over the inner surface of the housing.

The insulating material may comprise a liquid crystal polymer, a molding compound, or an engineering plastic. In a particular embodiment, the insulating layer is formed from a liquid crystal polymer. The liquid crystal polymer may have a melting temperature in a range of 250 degrees celsius to 400 degrees celsius. In some embodiments, the liquid crystalline polymer comprisesAromatic polyesters (such as those sold under the trade name

In other embodiments, the insulating layer may be formed from a molding compound, such as an engineered molded epoxy resin (e.g., an epoxy cresol novolac cured with a novolac, etc.). In still other embodiments, the insulating polymer is an engineering plastic, such as low density polyethylene, polypropylene, polystyrene, acrylonitrile butadiene styrene, acetal, and the like.

In some embodiments, the insulating material comprises a liquid crystal polymer inserted in a liquid phase into the mold cavity at a temperature in a range of 250 degrees celsius to 400 degrees celsius and a pressure of up to 30 bar. In some embodiments, the liquid crystalline polymer may be melted by heating to the melting temperature of the liquid crystalline polymer, and then solidified by cooling to a temperature below the melting temperature (e.g., to room temperature). In some embodiments, the liquid crystal polymer may have a melting temperature in a range of 250 degrees celsius to 400 degrees celsius. In a particular embodiment, the temperature of the liquid crystal polymer is in a range of 330 degrees celsius to 350 degrees celsius. In other embodiments, the liquid crystal polymer may be inherently liquid and cure upon exposure to an appropriate stimulus (e.g., heat or ultraviolet light), which causes the liquid crystal polymer to crosslink within the mold, forming a solid insulating layer on the housing. In some embodiments, the curing time is in the range of 4 hours to 6 hours.

In some embodiments, the thickness of the insulating layer (e.g., insulating layer 140) is in the range of 50 microns to 100 microns. For example, the thickness of the insulating layer may be in a range of 55 microns to 90 microns, 60 microns to 80 microns, 70 microns to 100 microns, or any other suitable thickness. In a particular embodiment, the thickness of the insulating layer is about 70 microns.

In some embodiments, the insulating layer further includes a mold gate (e.g., mold gate 142) that protrudes from a surface of the insulating layer disposed on the body of the housing and away from the body. The mold gate corresponds to a portion of the insulating material disposed in an entrance or gate of the mold through which the insulating material is poured into the mold cavity of the mold. The mold gate is radially offset from the longitudinal axis of the microphone assembly, as previously described herein.

In some embodiments, at 310, a mark is formed on a portion of the insulating layer that is located near a central portion of a body (e.g., body 132) of the housing (e.g., housing 130 adjacent the longitudinal axis). As previously described herein, the indicia may be formed, for example, via laser etching, stamping, or any other suitable process. Radially offsetting the mold gate relative to the longitudinal axis advantageously allows for indicia to be formed near a central portion of the body without the mold gate interfering with the formation of such indicia.

At 312, a shielding layer of shielding material is disposed on at least an outer surface of the housing opposite the inner surface. For example, the shield 150 is disposed on the outer surface 135 of the housing 130 and may also be disposed on the portion 136 of the sidewall 134 of the housing 130. The shield layer 150 may be disposed using electroplating, electroless plating, vacuum deposition, or any other suitable deposition process. Although described as being deposited after the insert molding of the insulating layer 140, in other embodiments, the shield layer 150 may be deposited on the housing 130 prior to the insert molding process (i.e., prior to operation 304).

In particular embodiments, disposing the shield layer 150 may include rinsing the housing 130 with the insulating layer 140 disposed thereon (e.g., ultrasonic rinsing in deionized water), followed by electrolytic cleaning and acid cleaning (e.g., in sulfuric acid). A first shielding material (e.g., a first metal (e.g., nickel, zinc, etc.)) can be deposited on the housing 130 and then electroplated or electrolessly plated. A second shielding material, such as a second metal (e.g., gold, copper, silver, platinum, etc.), may be deposited over the first metal. This is followed by one or more rinsing operations (e.g., ultrasonic rinsing in deionized water) followed by one or more drying operations (e.g., spin drying and/or oven baking). The shield plating process results in a shield layer (e.g., shield layer 150) being deposited on the exposed surfaces of the housing 130 (i.e., the surface or surfaces on which the insulating layer 140 is not disposed).

Fig. 6 is a schematic flow diagram of a method 300 of overmolding an insulating layer on an exterior surface of a housing (e.g., housing 130) of a microphone assembly (e.g., microphone assembly 200). The method 300 includes providing a housing at 402. For example, a housing 130 is provided, the housing 130 including a main body 132 and a sidewall 134 axially protruding from an outer edge of the main body 132.

At 404, a housing is disposed in a mold cavity of a mold. The mold cavity may be configured to allow for overmolding of the insulating layer on an outer surface of the housing (e.g., outer surface 135).

At 406, an insulating material is inserted into the mold cavity through an inlet or gate of the mold. At 408, the insulating material is cured in a manner such that an insulating layer of the insulating material (e.g., insulating layer 240) is overmolded onto the outer surface of the housing. The insulating material may comprise a liquid crystal polymer, a molding compound or an engineering plastic or any other suitable material, as previously described herein. In particular embodiments, the insulating layer may be formed from a liquid crystal polymer using similar process parameters as described with respect to method 300.

In some embodiments, the thickness of the insulating layer (e.g., insulating layer 240) is in a range of 50 microns to 100 microns. For example, the thickness of the insulating layer may be in a range of 55 microns to 90 microns, 60 microns to 80 microns, 70 microns to 100 microns, or any other suitable thickness. In a particular embodiment, the thickness of the insulating layer is about 70 microns.

In some embodiments, the insulating layer further includes a mold gate (e.g., mold gate 242) that protrudes from a surface of the insulating layer disposed on the body of the housing and away from the body. The mold gate is radially offset from the longitudinal axis of the microphone assembly, as previously described herein. In some embodiments, at 410, a mark is formed on a portion of the insulating layer that is located near a central portion of a body (e.g., body 132) of the housing (e.g., housing 130 adjacent the longitudinal axis). As previously described herein, the indicia may be formed, for example, via laser etching, stamping, or any other suitable process. Radially offsetting the mold gate relative to the longitudinal axis advantageously allows for indicia to be formed near a central portion of the body without the mold gate interfering with the formation of such indicia.

At 412, a shield is disposed on at least an inner surface of the housing. For example, shield layer 250 is disposed on inner surface 131 of housing 130, and may also be disposed on portion 136 of sidewall 134, using similar processes as described with respect to method 300. Although described as being deposited after the overmolding of the insulating layer 140, in other embodiments, the shielding layer 250 may be deposited on the housing 130 prior to the overmolding process (i.e., prior to operation 404).

The subject matter described herein sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being "operably connected," or "operably coupled," to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being "operably couplable," to each other to achieve the desired functionality. Specific examples of operatively coupled include, but are not limited to, physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interacting and/or logically interactable components.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. Various singular/plural permutations may be expressly set forth herein for clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "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 "includes" should be interpreted as "includes but is not limited to," etc.).

It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same is true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations).

Further, in those instances where a convention analogous to "at least one of A, B and C, etc." is used, in general such a configuration is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B and C" would include but not be limited to systems that have 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 instances where a convention analogous to "A, B or at least one of C, etc." is used, in general such a configuration is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B or C" would include, but not be limited to, systems that have 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.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "a or B" will be understood to include the possibility of "a" or "B" or "a and B". Moreover, unless otherwise specified, the use of the words "about," "approximately," and the like means plus or minus ten percent. The foregoing description of the exemplary embodiments has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to be limited to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosed embodiments. It is intended that the scope of the invention be defined by the following claims and their equivalents.

Claims

1. A microphone assembly, comprising:

a substrate;

an acoustic transducer disposed on the substrate, the acoustic transducer configured to generate an electrical signal in response to an acoustic signal;

an integrated circuit disposed on the substrate and electrically coupled to the acoustic transducer; and

a housing disposed on the substrate, the housing comprising:

a main body, and

a sidewall projecting axially from an outer edge of the body toward the base plate and in contact with the base plate in a manner such that an interior volume is defined between the housing and the base plate; and

an insulating layer insert molded on an inner surface of the housing in such a manner that the insulating layer is not disposed on a portion of the sidewall adjacent to the substrate.

2. The microphone assembly of claim 1, wherein a surface of the insulating layer is in continuous contact with a corresponding surface of the housing.

3. The microphone assembly of claim 1, wherein the height of the portion is less than three-quarters of the height of the sidewall.

4. The microphone assembly of claim 1, wherein the insulating layer has a thickness in a range of 50 microns to 100 microns.

5. The microphone assembly of claim 1, wherein the insulating layer comprises a liquid crystal polymer.

6. The microphone assembly of claim 5, wherein the liquid crystal polymer comprises an aromatic polyester.

7. The microphone assembly of claim 1 wherein the insulating layer further comprises a mold gate projecting from a surface of the insulating layer disposed on the body, the mold gate projecting away from the body.

8. The microphone assembly of claim 7 wherein the mold gate is radially offset from a longitudinal axis of the microphone assembly.

9. The microphone assembly of claim 1, further comprising a shielding material disposed at least on an outer surface of the housing opposite the inner surface.

10. The microphone assembly of claim 9 wherein the shielding material is further disposed on the portion of the sidewall adjacent the substrate.

11. A microphone assembly, comprising:

a substrate;

a housing disposed on the substrate, the housing comprising:

a main body, and

an insulating layer overmolded on an outer surface of the housing in a manner such that the insulating layer is not disposed on a portion of the sidewall adjacent the substrate.

12. The microphone assembly of claim 11 wherein a surface of the insulating layer is in continuous contact with a corresponding surface of the housing.

13. The microphone assembly of claim 11 wherein the insulating layer comprises a liquid crystal polymer.

14. The microphone assembly of claim 11 further comprising a shielding material disposed at least on an inner surface of the housing opposite the outer surface.