JP5298384B2 - Microphone unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide microphone unit achieving both of electromagnetic interference suppression and mass production property by electromagnetic shield. <P>SOLUTION: The microphone unit 120 is equipped with: a cover 200 having an opening 130 and consisting of conductive resin; a first substrate 210; a second substrate 220 having electrode pads 370, 380; a vibration unit 230 arranged in a position offset from the opening unit 130 while having a vibration plate 232; and an ASIC (application specific integrated circuit) 240 electrically connected to the vibration unit 230. In the space in the cover 200, protection films 330, 340 for preventing stripping of conductive resin which constitutes the cover 200 are formed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a microphone unit, and more particularly to a structure and a manufacturing method of a microphone unit.

  For telephone calls, voice recognition, voice recording, etc., it is preferable to collect only the target voice (speaker's voice). However, in a usage environment of a voice input device for collecting sound, there may be a sound other than the target voice such as background noise. Therefore, development of a voice input device that can accurately extract a target voice even when used in an environment where noise is present, that is, has a function of removing noise has been advanced. In recent years, electronic devices have been reduced in size, and voice input devices (hereinafter also referred to as “microphones”) have been reduced in size.

  For example, Japanese Patent Application Laid-Open No. 2007-329559 (Patent Document 1) discloses “a method for manufacturing a condenser microphone in which the mechanical strength of a diaphragm is ensured inexpensively and simply” ([Summary]). [Task]). This method is “a method of manufacturing a condenser microphone including a capacitor portion C in which a spacer member S is disposed between a diaphragm M and a back electrode plate B, and includes one surface of a substrate 1 made of single crystal silicon. A step of forming a sacrificial layer 2 on one surface of the substrate 1, a step of depositing a single crystal silicon layer 3 on the sacrificial layer 2, and a plurality of locations on the substrate 1 on the other side of the substrate 1. Etching from the surface to the sacrificial layer 2 to form a plurality of holes 7 in the substrate 1, and etching a part of the sacrificial layer 2 through the plurality of holes 7 between the substrate 1 and the single crystal silicon layer 3 By forming the space 8 in the substrate, the diaphragm M made of the single crystal silicon layer 3, the back electrode plate B made of the substrate 1 having a plurality of holes 7, and the spacer member S made of the remaining sacrificial layer 2 are formed. (Summary] [Solution]] According to the method disclosed in Japanese Patent Application Laid-Open No. 2007-329559, the condenser microphone is not an expensive substrate such as SOI, but the substrate 1 made of single crystal silicon is used as a starting material. It can be manufactured (paragraph 0028).

  Japanese Patent Application Laid-Open No. 2007-043327 (Patent Document 2) states that “a capacitor that can obtain electromagnetic shielding properties and can reduce the number of parts for maintaining electromagnetic shielding properties, resulting in cost reduction. "Microphone" ([Summary] [Problem]). This condenser microphone has the following features: “diaphragm 17, a capacitor part with back plate 15 arranged oppositely, an impedance conversion element for converting the capacitance of the capacitor part into electrical impedance, and the capacitor part and the impedance conversion element are electrically connected. And a circuit 12 that houses the capacitor unit, the impedance conversion element, and the circuit, and includes a casing 12 made of an electrical insulator, and a conductive layer 12b on the outer periphery of the casing 12. To provide electromagnetic shielding properties ”([Summary] [Solution means]).

  Japanese Patent Laying-Open No. 2008-067383 (Patent Document 3) discloses a “silicon capacitor microphone using a case having a structure in which a plating layer is formed on a resin case body” ([Summary] [Problem]). The microphone disclosed in Japanese Patent Application Laid-Open No. 2008-067383 is “a case formed by a body made of a cylindrical resin with one surface opened and a plating layer formed on the body, a MEMS microphone chip, A substrate on which a special purpose semiconductor (ASIC) chip for processing an electrical signal of the MEMS microphone chip is mounted and a connection pattern for bonding to the case is formed, and includes conductive bonding The case and the connection pattern are joined together by an agent, and the plating layer can be formed inside, outside, or on the entire surface of the body, and the open surface end of the body extends along the inner week surface. A step is formed so that the substrate is inserted into the step, facilitating molding, and can be formed on the inside, outside or the entire surface of the resin body. Forming a key layer, it is that can block external noise such as electromagnetic noise "([SOLUTION] of the Summary).

  Japanese Patent Laying-Open No. 2008-048329 (Patent Document 4) states that “a condenser microphone and a condenser microphone that can easily exhibit an electromagnetic shielding effect while reducing the number of components and reducing the size, thereby reducing the manufacturing cost. The manufacturing method of the laminated structure is disclosed ([Summary] [Problem]). According to Japanese Patent Laid-Open No. 2008-048329, “the casing base frame 13 of the condenser microphone 10 is provided with conductive patterns 13b, 13c, 13d for electrically connecting the spacer 18 and the conductive pattern 12a of the circuit board 12, and a conductive layer. "The conductive patterns 14a and 14b provided on the top substrate 14 and the spacer 18 are electrically connected by the conductive resin 27" ([Solution] in [Summary]).

Japanese Unexamined Patent Application Publication No. 2008-011154 (Patent Document 5) discloses a technique for “miniaturizing and increasing the sensitivity of a capacitor microphone chip formed by micro-processing a silicon substrate”. According to the technology disclosed in Japanese Patent Application Laid-Open No. 2008-011154, “the silicon substrate of the microphone chip is diced so as to have a substantially hexagonal shape, preferably a regular hexagonal shape, and the back air chamber is circular or regular hexagonal. ([Solution] in [Summary]).
JP 2007-329559 A JP 2007-043327 A JP 2008-067383 A JP 2008-048329 A JP 2008-011154 A

  From the viewpoint of mass productivity, a method of separating a plurality of microphone units into a plurality of pieces by a dicing process from a sheet on which a plurality of microphones are mounted is excellent. On the other hand, in order to avoid the influence of electromagnetic interference, the cover (housing) that covers the diaphragm is preferably made of metal or metal-coated. However, it is difficult to cut (dicing) the metal cover. Further, when the metal-coated cover is diced, a problem of peeling of the metal material occurs.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a microphone unit that can achieve both electromagnetic interference suppression by an electromagnetic shield and mass productivity. . Another object is to provide a microphone unit that can prevent deterioration of acoustic characteristics.

  Another object of the present invention is to provide a method of manufacturing a microphone unit casing that can achieve both electromagnetic interference suppression by electromagnetic shielding and mass productivity. Another object of the present invention is to provide a method of manufacturing a microphone unit housing that can prevent deterioration of acoustic characteristics.

  A microphone unit according to an aspect of the present invention includes a diaphragm that converts acoustic vibration into an electrical signal, a substrate that has the diaphragm and a conductive pattern region that transmits a signal, and is bonded to the substrate and has an opening, And a cover portion surrounding the diaphragm. The cover part is formed of a conductive resin. A protective film is formed on at least the surface of the cover portion that faces the diaphragm.

Preferably, a protective film is not formed on a portion of the cover portion that is joined to the substrate portion.
Preferably, the opening portion faces a part of the substrate.

Preferably, the diaphragm is disposed so as not to face the opening.
Preferably, a part of the cover portion faces the diaphragm.

  Preferably, the portion of the cover portion that is bonded to the substrate is bonded to the ground pattern of the substrate.

  Preferably, the portion to be joined to the substrate is joined by a conductive adhesive or a conductive paste.

  Preferably, the conductive resin includes any of conductive carbon black, carbon nanofiber, carbon nanotube, or metal conductive filler dispersed in an epoxy-based resin.

Preferably, the conductive resin has a heat resistance of 200 degrees or more.
Preferably, the end surface of the cover part is a cut surface by dicing.

Preferably, the protective film is a resin.
When the other situation of this invention is followed, the manufacturing method of the housing | casing of a microphone unit is provided. The manufacturing method includes a step of molding a resin plate into a plurality of casing shapes, a step of forming a protective film on the molded resin plate, and a step of cutting the resin plate on which the protective film is formed. .

Preferably, the step of forming the protective film includes the step of applying fine particles.
Preferably, the step of forming the protective film includes the step of attaching the resin film to the resin plate.

  Preferably, the housing has an opening. The step of forming the protective film includes the step of forming a protective film in the opening.

  Preferably, there are a plurality of openings. The step of forming a protective film in the opening includes a step of forming a protective film in each opening.

  According to the present invention, it is possible to achieve both electromagnetic interference suppression by the electromagnetic shield and mass productivity. In addition, deterioration of acoustic characteristics can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated. Further, in the case where different embodiments are described, the description of the configuration according to the embodiment will not be repeated except for the configuration unique to the embodiment.

[Usage of microphone unit]
With reference to FIG. 1, the usage mode of the microphone unit according to the embodiment of the present invention will be described. FIG. 1 is a diagram showing an outline of the configuration of a mobile phone 100 that uses a microphone unit 120. The mobile phone 100 includes a system board 110. The system board 110 includes a microphone unit 120. An opening 130 is formed in the microphone unit 120. Circuit elements for realizing the operation of the mobile phone 100 are mounted on the system board 110. The shape of the opening 130 is not limited to the shape specified from FIG. The shape of the opening 130 includes a circle, an ellipse, a rectangle, and the like.

[Configuration of microphone unit]
With reference to FIG. 2, the structure of the microphone unit 120 according to the embodiment of the present invention will be described. FIG. 2 is a diagram illustrating a state in which the upper portion of the cover unit 200 of the microphone unit 120 is cut along a plane parallel to the system board 110.

  The microphone unit 120 includes a cover unit 200, a first substrate 210, a second substrate 220, a vibration unit 230, and an ASIC (Application Specific Integrated Circuit) 240. The vibration unit 230 includes a diaphragm 232. The microphone unit 120 according to the present embodiment is, for example, a condenser microphone, but may be another microphone. In another aspect, first substrate 210 and second substrate 220 may be configured as an integrated substrate.

  The cover part 200 is comprised with electroconductive resin. The conductive resin is, for example, an epoxy resin, but may be other resins. The conductive resin is formed by dispersing, for example, conductive carbon black, carbon nanofibers, carbon nanotubes, or a metal conductive filler (filler) in an epoxy resin. Yes.

  The conductive resin preferably has heat resistance, for example, preferably has heat resistance of 200 degrees or more. By having heat resistance, it is possible to withstand heat generation during manufacturing of the cover part 200 described later. For example, heat generated when molding a plurality of cover portions 200 from one resin plate, or frictional heat generated when cutting each cover portion 200 from a plurality of cover portions 200 formed on one resin plate. Can withstand.

  Further, for the first substrate 210 and the second substrate 220, for example, by using those materials as heat-resistant materials such as FR4 (Flame Retardant 4), FR5, and BT (Bismaleimide Triazine) resin, the microphone unit. 120 can be reflow-enabled. When the microphone unit 120 is mounted on another substrate, the reflow process can be performed in the same manner as other chip components, which can contribute to the reduction in man-hours during manufacturing.

  In particular, by using carbon nanotubes as the dispersing material, it is possible to reduce the conductive resistance of the cover part 200 and improve the electromagnetic shielding effect.

  For example, the diaphragm 232 uses an inorganic piezoelectric thin film or an organic piezoelectric thin film to perform acoustic-electrical conversion by a piezoelectric effect, or uses an electret film, but is not limited to these configurations. The microphone substrate constituted by the first substrate 210 and the second substrate 220 is constituted by a material such as an insulating molded base material, fired ceramics, glass epoxy resin, plastic, etc., but the material is not limited to these, Other insulating materials may be used.

  The diaphragm 232 vibrates in the normal direction in response to the incident sound wave. The vibration unit 230 outputs an electrical signal corresponding to the sound incident on the diaphragm 232. The diaphragm 232 may be a diaphragm of various microphones such as an electrodynamic type (dynamic type), an electromagnetic type (magnetic type), and a piezoelectric type (crystal type).

  Alternatively, the diaphragm 232 may be a diaphragm of a semiconductor film (for example, a silicon film) or a silicon microphone (Si microphone). By using the silicon microphone, the microphone unit 120 can be reduced in size and performance. The shape of the diaphragm 232 is not particularly limited. For example, the outer shape of the diaphragm 232 may be a circle, an ellipse, a polygon, or the like.

  With reference to FIG. 3, the configuration of microphone unit 120 according to the present embodiment will be further described. FIG. 3 is a diagram illustrating a state in which the microphone unit 120 is cut along a plane perpendicular to the system board 110. The cover unit 200 is configured to surround the vibration unit 230, the diaphragm 232, and the ASIC 240. The vibration unit 230 and the ASIC 240 are attached to the first substrate. The opening 130 is configured at a position offset with respect to the diaphragm 232. With such an arrangement, even when a minute object such as dust enters from the opening 130, it is difficult to reach the diaphragm 232, and thus the vibration of the diaphragm 232 is hardly affected. As a result, deterioration of acoustic characteristics due to minute objects is prevented.

  Inside the cover part 200, protective films 330 and 340 are formed on the surface of the cover part 200. In one aspect, the protective films 330 and 340 are formed by immersing a single resin in which a plurality of cover portions 200 are molded in a liquid tank in which a material constituting the protective film is melted. The protective films 330 and 340 prevent part of the members constituting the cover unit 200 from being peeled off or worn out.

  Note that it is preferable that a protective film is not formed at the joint portion between the cover portion 200 and the first substrate 210. If the protective film is not formed, the height of the cover part 200 is easily kept within a certain range. Thereby, the joining precision of the cover part 200 and the 1st board | substrate 210 can be raised, and mass-productivity can be improved.

  The cover part 200 and the first substrate 210 are joined by, for example, a conductive adhesive, a conductive paste, or the like. The conductive adhesive is not particularly limited, and may be an adhesive mixed with a material having good conductivity such as silver powder, copper powder, or carbon fiber. The kind of conductive paste is not limited.

  Conductive patterns 350 and 360 are formed between the first substrate 210 and the second substrate 220. Conductive pattern 350 is electrically coupled to ASIC 240. The conductive pattern 360 is connected to the ground. Similarly, the support portion of the vibration unit 230 and the ASIC 240 are electrically connected by a conductive pattern. The acoustic vibration in the diaphragm 232 is converted into an electric signal in the vibration unit 230, and the signal is sent to the ASIC 240 via the conductive pattern 352.

  Electrode pads 370 and 380 are formed on the back surface of the second substrate 220. The electrode pads 370 and 380 are electrically connected to terminals (not shown) provided on the system board 110.

[Production method]
With reference to FIG. 4 and FIG. 5, the manufacturing method of the microphone unit 120 according to the present embodiment will be described. FIG. 4 is a diagram showing the resin plate 400 on which a plurality of microphone units 120 are molded from the top.

  The resin plate 400 includes a plurality of microphone units 120-1, 120-2, 120-3 and the like formed by injection molding. Cutting regions 401, 402, 403 and the like are formed between adjacent microphone units. Each cutting area is used for dicing described later.

  When the plurality of microphone units 120 and the cutting region are formed on the resin plate 400, the resin plate 400 is placed in a liquid bath in which the material of the protective film is melted in order to form the protective film on the surface. . Note that the method of forming the protective film is not limited to this. For example, in another aspect, instead of putting the resin plate 400 in the liquid tank, the material constituting the protective film is attached to the back surface of the resin plate 400 (the surface facing the vibration plate 232) by spraying. Also good.

  In addition, in order to form a protective film only on one surface of the resin plate 400, the other surface that does not require the protective film is masked in advance, and the mask is removed after the process of forming the protective film is performed. May be performed.

  In addition, it is preferable that a protective film is not formed at a joint portion between the cover portion 200 and the first substrate 210. Therefore, after the protective film is formed on the resin plate 400, a step of polishing the resin plate 400 may be performed in order to remove the protective film formed in the region corresponding to the joint portion.

  FIG. 5 is a flowchart showing a part of the method for manufacturing microphone unit 120 according to the present embodiment.

  In step S510, one resin panel (for example, resin plate 400) is molded as a panel including a plurality of cover portions (for example, a plurality of microphone units 120).

  In step S520, a protective film is formed on one surface of the molded panel (for example, the surface facing diaphragm 232). The formation of the protective film is realized, for example, by placing the panel in a liquid layer constituting the protective film and then drying the panel. Alternatively, in another aspect, liquid particles constituting the protective film may be applied to one surface of the panel. Alternatively, in still another aspect, a thin film constituting the protective film may be attached to the panel. In this case, instead of the process of attaching the thin film after the process of step S510, the molding process in step S510 may be performed after attaching the thin film. If it does in this way, the fall of the processing precision of the case formed may be prevented.

  In step S530, the panel on which the protective film is formed is cut (diced) for each cover portion (for each microphone unit 120). Thereby, each microphone unit is generated.

[Effect of the embodiment]
As described above, microphone unit 120 according to the embodiment of the present invention has a housing formed of a conductive resin. The housing is made of a conductive resin. A protective film is formed on the surface of the housing. In this way, the conductive resin is prevented from being peeled off, so that it is possible to prevent a decrease in acoustic performance due to the peeled particles adhering to the diaphragm 232 or the like.

  Further, since the casing of the microphone unit 120 is made of a conductive resin, electromagnetic interference due to the electromagnetic shield can be suppressed. In addition, since the casing is made of resin, processing is facilitated, and for example, a plurality of casings can be cut out from a single panel by dicing. Thereby, mass productivity improves.

  In addition, as described above, by forming the protective films 330 and 340 on the surface of the conductive resin of the cover part 200, conductive carbon black, carbon nanofibers dispersed in the conductive resin, When dust such as carbon nanotubes or metal fillers scatters and adheres to or sticks to the diaphragm, the vibration characteristics of the vibration unit 230 change and the acoustic characteristics deteriorate, or an electrical short circuit occurs, resulting in a diaphragm or It is possible to prevent the ASIC 240 from being damaged.

  Further, the first substrate 210 and the second substrate 220 are also made of a heat-resistant material such as FR4, FR5, BT resin, etc., so that the microphone unit 120 can be reflow-compatible. Is possible. When the microphone unit 120 is mounted on the system board 110, the reflow process can be performed in the same manner as other chip components, which can contribute to the reduction of man-hours during manufacturing.

<Modification>
Hereinafter, modifications of the embodiment of the present invention will be described. The microphone unit 620 according to this modification is different from the microphone unit 120 described above in that it has a so-called differential microphone configuration. The same components as those of the microphone unit 120 described above are denoted by the same reference numerals. Their functions are the same. Therefore, description of the same component is not repeated.

[Constitution]
With reference to FIG. 6, a configuration of microphone unit 620 according to the present embodiment will be described. FIG. 6 is a diagram illustrating a state in which the microphone unit 620 is cut along a plane perpendicular to the system board 110.

  The microphone unit 620 further includes an opening 132 in addition to the configuration of the microphone unit 120 shown in FIG. Protective films 310 and 320 are formed on the surface of the cover part 200 in the opening part 132. The protective films 310 and 320 are formed in the same manner as the protective films 330 and 340.

  According to such a configuration, the material of the surface of the cover part 200 is peeled off, and the peeled material is less likely to adhere to the upper and lower surfaces of the diaphragm 232. Therefore, the acoustic vibration in the diaphragm 232 is not affected by such a peeled object. As a result, a decrease in sound characteristics of the microphone unit 620 is prevented.

  As described above, the microphone unit 620 according to the modification of the embodiment of the present invention has a housing formed of a conductive resin. The housing is made of a conductive resin. A protective film is formed on the surface of the housing. In this way, the conductive resin is prevented from being peeled off, so that it is possible to prevent a decrease in acoustic performance due to the peeled particles adhering to the diaphragm 232 or the like.

  Further, since the casing of the microphone unit 620 is made of a conductive resin, electromagnetic interference due to the electromagnetic shield can be suppressed. In addition, since the casing is made of resin, processing is facilitated, and for example, a plurality of casings can be cut out from a single panel by dicing. Thereby, mass productivity improves. Since the microphone unit 620 includes the two openings 130 and 132, noise is canceled out. As a result, it is possible to provide a microphone unit that prevents deterioration in acoustic characteristics while maintaining mass productivity.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The microphone unit according to this embodiment can be applied to a mobile phone, a voice recorder, and other small voice input devices.

It is a figure showing the outline of a structure of the mobile telephone 100 which uses the microphone unit 120 which concerns on embodiment of this invention. FIG. 4 is a diagram illustrating a state in which an upper portion of a cover unit 200 of the microphone unit 120 is cut along a plane parallel to the system board 110. 2 is a diagram illustrating a state in which a microphone unit 120 is cut along a plane perpendicular to a system board 110. FIG. It is a figure showing the resin board 400 in which the several microphone unit 120 was shape | molded from the upper surface. 5 is a flowchart showing a part of a method for manufacturing microphone unit 120. FIG. 10 is a diagram illustrating a state where a microphone unit 620 according to a modification of the present embodiment is cut along a plane perpendicular to the system board 110.

Explanation of symbols

  100 cellular phone, 110 system board, 120, 620 microphone unit, 130, 132 opening, 200 cover, 210 first substrate, 220 second substrate, 230 vibration unit, 232 vibration plate, 240 ASIC, 400 resin plate, 310, 320, 330, 340 Protective film, 350, 352, 360 Conductive pattern, 370, 380 Electrode pad, 401-406, 411-415 Cutting region.

Claims (11)

A diaphragm that converts acoustic vibrations into electrical signals;
A first substrate having a conductive pattern region mounted with the diaphragm and transmitting the electrical signal;
A cover portion that covers the first substrate and is joined to the first substrate;
The cover part is formed of a resin in which a conductive filler is dispersed,
A protective film for preventing scattering of the conductive filler is formed on at least the surface of the cover portion facing the diaphragm ,
A second substrate bonded to the first substrate;
In the first substrate, a first hole portion and a second hole portion are formed,
The diaphragm is disposed so as to cover the first hole portion,
When the first substrate and the second substrate are joined, the surface of the second substrate is formed so that a space connecting the first hole portion and the second hole portion is formed. Configured,
The cover portion has a first opening and a second opening,
The second opening portion is connected to the first surface of the diaphragm through the second hole portion inside the cover portion,
The microphone unit , wherein the first opening is connected to the second surface opposite to the first surface inside the cover . The microphone unit according to claim 1 , wherein a protective film that prevents the conductive filler from scattering is formed on an inner wall of the second opening of the cover . The microphone unit according to claim 1 or 2, wherein the first and second openings are opposed to a part of the first substrate . The microphone unit according to claim 1 or 2, wherein the diaphragm is arranged so as not to be opposed to the first and second openings . The microphone unit according to claim 1, wherein a part of the cover portion faces the diaphragm . The microphone unit according to any one of claims 1 to 5, wherein the conductive filler is any one of carbon black, carbon nanofiber, carbon nanotube, or metal . The microphone unit according to any one of claims 1 to 6 , wherein the protective film is not formed at a portion where the cover portion and the first substrate are joined . Said first portion is bonded to the substrate of said cover portion, said being joined to the ground pattern of the first substrate, the microphone unit according to any of claims 1 to 7. The microphone unit according to claim 8, wherein the portion to be joined to the first substrate is joined by a conductive adhesive or a conductive paste . The microphone unit according to claim 1 , wherein the resin has a heat resistance of 200 degrees or more . The microphone unit according to any one of claims 1 to 10, wherein the protective film is a resin .

Images