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JP2010041565

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DESCRIPTION JP2010041565
[PROBLEMS] To provide a microphone unit capable of achieving both suppression of
electromagnetic interference by an electromagnetic shield and mass productivity. A microphone
unit (120) has an opening (130), a cover (200) made of conductive resin, a first substrate (210),
a second substrate (220) having electrode pads (370, 380), and an offset from the opening (130).
And an ASIC 240 electrically connected to the vibration unit 230. In the space inside the cover
200, protective films 330 and 340 for preventing the peeling of the conductive resin constituting
the cover 200 are formed. [Selected figure] Figure 3
Microphone unit and method of manufacturing housing thereof
[0001]
BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a
microphone unit, and more particularly to a structure and manufacturing method of the
microphone unit.
[0002]
It is preferable to collect only a target voice (speaker's voice) at the time of a telephone call or the
like, voice recognition, voice recording, and the like.
However, in the use environment of the voice input device for sound collection, sounds other
than the target voice such as background noise may be present. Therefore, development of a
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voice input device having a function of accurately extracting a target voice even when used in an
environment where noise is present, that is, removing noise, is in progress. Further, in recent
years, miniaturization of electronic devices has progressed, and it is also referred to as a voice
input device (hereinafter referred to as "microphone"). Miniaturization is also in progress.
[0003]
For example, Japanese Patent Laid-Open No. 2007-329559 (Patent Document 1) discloses "a
method of manufacturing a capacitor type microphone in which the mechanical strength of the
diaphragm is secured inexpensively and easily" (summary) [Task]). This method is “a method of
manufacturing a capacitor type microphone including a capacitor portion C in which the spacer
member S is disposed between the diaphragm M and the back electrode plate B, and one surface
of the substrate 1 made of single crystal silicon Forming a sacrificial layer 2 on one surface of the
substrate 1 by ion-implanting, depositing a single crystal silicon layer 3 on the sacrificial layer 2,
and forming a plurality of portions of the substrate 1 on the other side of the substrate 1. A step
of etching 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 to form a space
between the substrate 1 and the single crystal silicon layer 3 The space 8 is provided to form the
diaphragm M made of the single crystal silicon layer 3, the back electrode plate B made of the
substrate 1 having the plurality of holes 7, and the spacer member S made of the remaining
sacrificial layer 2 And the process to be done ([Summary] [Solution]) According to the method
disclosed in Japanese Patent Laid-Open No. 2007-329559, the capacitor type microphone is not
an expensive substrate such as SOI, but the substrate 1 made of single crystal silicon is the
starting material. It can be manufactured (paragraph 0028).
[0004]
Japanese Patent Application Laid-Open No. 2007-043327 (Patent Document 2) “A component
that can obtain electromagnetic shielding properties and reduce the number of parts for
maintaining the electromagnetic shielding properties, and as a result, can reduce costs.
"Microphone" is disclosed ([Summary] [Issues]). This condenser microphone includes “a
diaphragm 17 and a capacitor portion in which the back plate 15 is disposed opposite to each
other, an impedance conversion element for converting the change in electrostatic capacitance of
the capacitor portion into an electrical impedance, a capacitor portion and an impedance
conversion element Circuit including the capacitor unit, the impedance conversion element, and
the circuit, and the housing 12 made of an electrical insulator, and the conductive layer 12 b is
provided on the outer periphery of the housing 12. To provide electromagnetic shielding
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properties "([Summary] [solution]).
[0005]
Japanese Patent Application Laid-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 case body made of resin” ([Problem] [Problem]. The microphone disclosed in Japanese
Patent Application Laid-Open No. 2008-067383 includes “a case composed of a body made of a
cylindrical resin whose one surface is open and a plated layer formed on the body, a MEMS
microphone chip, A substrate on which a special purpose semiconductor (ASIC) chip for
processing electrical signals of the MEMS microphone chip is mounted, and on which a
connection pattern for bonding to the case is formed; The case and the connection pattern are
joined by an agent. The plating layer may be formed on the inside, the outside, or the entire
surface of the body, and a step is formed along an inner surface at an end of the open surface of
the body so that the substrate is the step. It is supposed to be inserted into the The molding can
be facilitated, and a plating layer can be formed on the inside, the outside, or the entire surface of
the resin body to block external noise such as electromagnetic wave noise and the like.
[0006]
Japanese Patent Laid-Open No. 2008-048329 (Patent Document 4) “condenser microphone and
condenser microphone capable of easily achieving an electromagnetic shielding effect while
reducing the number of parts and downsizing as a result, reducing the manufacturing cost. "A
manufacturing method of laminated structure of" is disclosed ([Summary] [Issues]). According to
Japanese Patent Laid-Open No. 2008-048329, “Conductive pattern 13b, 13c, 13d for
electrically connecting the spacer 18 and the conductive pattern 12a of the circuit board 12 to
each other and the conductive layer are provided on the casing base frame 13 of the condenser
microphone 10. And “the conductive patterns 14a and 14b provided on the top substrate 14
and the spacer 18 are electrically connected by the conductive resin 27” (in [Summary]
[Solution]).
[0007]
Japanese Patent Application Laid-Open No. 2008-011154 (Patent Document 5) discloses a
technique for achieving miniaturization and high sensitivity of a condenser microphone chip
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formed by micromachining a silicon substrate. According to the technique disclosed in Japanese
Patent Application Laid-Open No. 2008-011154, “The silicon substrate of the chip for the
microphone is diced into a substantially hexagonal shape, preferably a regular hexagonal shape
to make the back air chamber circular or regular hexagonal. . [Summary] [Solution]. JP 2007329559 JP JP 2007-043327 JP JP 2008-067383 JP JP 2008-048329 JP JP 2008-011154 JP
[0008]
From the viewpoint of mass productivity, a method of separating a sheet on which a plurality of
microphones are mounted into a plurality of individual pieces of the microphone unit by a dicing
process is excellent. On the other hand, in order to avoid the influence of electromagnetic
interference, it is preferable to make the cover (housing) which covers the diaphragm be metal or
to be metal-coated. However, it is difficult to cut (dicing) the metal cover. In addition, dicing the
metal-coated cover causes a problem of peeling of the metal material.
[0009]
The present invention has been made to solve the above-mentioned problems, and an object
thereof is to provide a microphone unit capable of achieving both suppression of electromagnetic
interference by an electromagnetic shield and mass productivity. . Another object is to provide a
microphone unit capable of preventing deterioration of acoustic characteristics.
[0010]
Another object of the present invention is to provide a method of manufacturing a housing of a
microphone unit capable of achieving both suppression of electromagnetic interference by an
electromagnetic shield and mass productivity. Another object is to provide a method of
manufacturing a housing of a microphone unit that can prevent deterioration of acoustic
characteristics.
[0011]
A microphone unit according to one aspect of the present invention comprises: a diaphragm
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having acoustic vibration converted into an electrical signal; a substrate having a conductive
pattern area mounted thereon and transmitting a signal; And a cover portion surrounding the
diaphragm. The cover portion is formed of a conductive resin. A protective film is formed on at
least the surface of the cover portion facing the diaphragm.
[0012]
Preferably, no protective film is formed on the portion of the cover portion to be bonded to the
substrate portion. Preferably, the opening faces a portion of the substrate.
[0013]
Preferably, the diaphragm is offset so as not to face the opening. Preferably, a part of the cover
portion faces the diaphragm.
[0014]
Preferably, the portion of the cover portion to be bonded to the substrate is bonded to the
ground pattern of the substrate.
[0015]
Preferably, the portion to be bonded to the substrate is bonded by a conductive adhesive or a
conductive paste.
[0016]
Preferably, the conductive resin contains any of conductive carbon black, carbon nanofibers,
carbon nanotubes, or conductive filler of metal dispersed in epoxy resin.
[0017]
Preferably, the conductive resin has a heat resistance of 200 degrees or more.
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Preferably, the end face of the cover portion is a cut surface by dicing.
[0018]
Preferably, the protective film is a resin.
According to another aspect of the present invention, a method of manufacturing a housing of a
microphone unit is provided.
The manufacturing method includes the steps of molding the resin plate into the shape of a
plurality of housings, forming a protective film on the molded resin plate, and cutting the resin
plate on which the protective film is formed. .
[0019]
Preferably, the step of forming a protective film comprises the step of applying microparticles.
Preferably, the step of forming the protective film includes the step of adhering a resin film to a
resin plate.
[0020]
Preferably, the housing has an opening. Forming the protective film includes forming a protective
film in the opening.
[0021]
Preferably, the openings are multiple. The step of forming the protective film in the openings
includes the step of forming a protective film in each of the openings.
[0022]
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According to the present invention, both the suppression of electromagnetic interference and the
mass productivity can be achieved by the electromagnetic shield. In addition, the deterioration of
acoustic characteristics can be prevented.
[0023]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings. In the following description, the same components are denoted by the same reference
numerals. Their names and functions are also the same. Therefore, detailed description about
them will not be repeated. Further, when a different embodiment is described, the description of
the configuration according to the embodiment will not be repeated except for the configuration
unique to the embodiment.
[0024]
[Use Mode of Microphone Unit] A use mode of the microphone unit according to the embodiment
of the present invention will be described with reference to FIG. FIG. 1 is a diagram schematically
showing the configuration of mobile phone 100 using microphone unit 120. Referring to FIG.
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. On system board
110, circuit elements for realizing the operation of mobile phone 100 are mounted. 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.
[0025]
[Configuration of Microphone Unit] The configuration of the microphone unit 120 according to
the embodiment of the present invention will be described with reference to FIG. FIG. 2 is a view
showing a state in which the upper portion of the cover unit 200 of the microphone unit 120 is
cut in a plane parallel to the system board 110. As shown in FIG.
[0026]
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The microphone unit 120 includes a cover unit 200, a first substrate 210, a second substrate
220, a vibration unit 230, and an application specific integrated circuit (ASIC) 240. The vibrating
unit 230 includes a vibrating plate 232. The microphone unit 120 according to the present
embodiment is, for example, a condenser microphone, but may be another microphone. In
another aspect, the first substrate 210 and the second substrate 220 may be configured as an
integral substrate.
[0027]
The cover 200 is made of a conductive resin. The conductive resin is, for example, an epoxy
resin, but may be another resin. The conductive resin is constituted, for example, by dispersing
any of conductive carbon black, carbon nanofibers, carbon nanotubes, and metal conductive filler
(filler) in an epoxy resin. There is.
[0028]
The conductive resin preferably has heat resistance, and for example, preferably has heat
resistance of 200 degrees or more. By having heat resistance, it can endure the heat generation
at the time of manufacture of cover part 200 mentioned below. For example, heat generation
when molding a plurality of cover portions 200 from a single resin plate, or frictional heat when
cutting each cover portion 200 from a plurality of cover portions 200 formed on a single resin
plate Can withstand.
[0029]
Furthermore, for the first substrate 210 and the second substrate 220, for example, the
microphone unit can be formed by using a heat-resistant material such as FR4 (Flame Retardant
4), FR5, BT (Bismaleide Triazine) resin, etc. It is possible to make 120 compatible with reflow.
When the microphone unit 120 is mounted on a separate substrate, the reflow process can be
performed like other chip components, which can contribute to reduction in the number of
manufacturing steps.
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[0030]
Further, in particular, by using carbon nanotubes as the dispersing material, it is possible to
reduce the conductive resistance of the cover portion 200 and to improve the effect of the
electromagnetic shield.
[0031]
The vibrating plate 232 has a configuration for performing acousto-electrical conversion by a
piezoelectric effect using, for example, an inorganic piezoelectric thin film or an organic
piezoelectric thin film, or a configuration using an electret film, but is not limited to these
configurations.
The microphone substrate configured by the first substrate 210 and the second substrate 220 is
formed of, for example, a material such as an insulating molded substrate, a fired ceramic, a glass
epoxy resin, or a plastic, but the material is not limited thereto. Other insulating materials may be
used.
[0032]
The diaphragm 232 vibrates in the normal direction in response to the sound wave incident. The
vibration unit 230 outputs an electrical signal according to the sound incident on the diaphragm
232. The diaphragm 232 may be, for example, a diaphragm of various microphones such as an
electrodynamic type (dynamic type), an electromagnetic type (magnetic type), and a piezoelectric
type (crystal type).
[0033]
Alternatively, the diaphragm 232 may be a semiconductor film (for example, a silicon film) or a
diaphragm of a silicon microphone (Si microphone). By using a silicon microphone,
miniaturization and high performance of the microphone unit 120 can be realized. The shape of
the diaphragm 232 is not particularly limited. For example, the outer shape of the diaphragm
232 may be circular, elliptical, polygonal or the like.
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[0034]
The configuration of microphone unit 120 according to the present embodiment will be further
described with reference to FIG. FIG. 3 is a diagram showing the microphone unit 120 cut in a
plane perpendicular to the system board 110. As shown in FIG. 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 minute objects
such as dust enter from the opening 130, they hardly reach the diaphragm 232, so that the
vibration of the diaphragm 232 is hardly affected. As a result, the deterioration of the acoustic
characteristics due to the minute objects is prevented.
[0035]
In the inside of the cover portion 200, protective films 330 and 340 are formed on the surface of
the cover portion 200. In one aspect, the protective films 330 and 340 are formed by immersing
a single resin in which a plurality of cover parts 200 are formed into a liquid bath in which the
material constituting the protective film is melted. The protective films 330 and 340 prevent part
of the members constituting the cover 200 from peeling or wearing off.
[0036]
Note that it is preferable that a protective film is not formed at the bonding portion between the
cover portion 200 and the first substrate 210. If the protective film is not formed, the height of
the cover portion 200 can be easily accommodated within a certain range. Thereby, the bonding
accuracy between the cover portion 200 and the first substrate 210 can be improved, and mass
productivity can be improved.
[0037]
The cover portion 200 and the first substrate 210 are bonded by, for example, a conductive
adhesive, a conductive paste, or the like. The conductive adhesive is not particularly limited, and
may be, for example, an adhesive in which a material having good conductivity such as silver
powder, copper powder, or carbon fiber is mixed. The type of conductive paste is also not limited.
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[0038]
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. The support of the vibration unit 230 and the ASIC 240
are similarly electrically connected by the conductive pattern. The acoustic vibration in the
diaphragm 232 is converted to an electrical signal in the vibrating unit 230, and the signal is
sent to the ASIC 240 via the conductive pattern 352.
[0039]
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.
[0040]
[Manufacturing Method] A method of manufacturing the microphone unit 120 according to the
present embodiment will be described with reference to FIGS. 4 and 5. FIG. 4 is a top view
showing a resin plate 400 in which a plurality of microphone units 120 are formed.
[0041]
The resin plate 400 includes a plurality of microphone units 120-1, 120-2, 120-3 and the like
formed by injection molding. Between the microphone units adjacent to each other, cutting
regions 401, 402, 403 and the like are formed. Each cutting area is used in dicing described
later.
[0042]
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When the plurality of microphone units 120 and the cutting area are formed on the resin plate
400, the resin plate 400 can be put in a liquid bath in which the material of the protective film is
melted in order to form the above-described 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 by spray to the back surface of the resin plate 400 (the surface facing the
diaphragm 232). It is also good.
[0043]
In addition, in order to form a protective film only on one side of the resin plate 400, the other
surface not requiring a protective film is masked in advance, and after the process of forming the
protective film is performed, the mask is removed May be performed.
[0044]
In addition, it is preferable that a protective film is not formed on the bonding portion between
the cover portion 200 and the first substrate 210.
Therefore, after the protective film is formed on the resin plate 400, the process of polishing the
resin plate 400 may be performed in order to remove the protective film formed in the region
corresponding to the bonding portion.
[0045]
FIG. 5 is a flowchart showing a part of the method of manufacturing the microphone unit 120
according to the present embodiment.
[0046]
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).
[0047]
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In step S520, a protective film is formed on one surface of the molded panel (for example, the
surface facing the diaphragm 232).
The formation of the protective film is realized, for example, by putting the panel in a liquid layer
constituting the protective film and then drying the panel.
Alternatively, in another aspect, liquid particles constituting a protective film may be applied to
one surface of the panel. Alternatively, in still another aspect, a thin film constituting a protective
film may be attached to the panel. In this case, the forming process in step S510 may be
performed after the thin film is attached instead of the step of attaching the thin film after the
process in step S510. In this way, a reduction in the processing accuracy of the formed casing
can be prevented.
[0048]
In step S530, the panel on which the protective film is formed is cut (diced) for each cover (for
each microphone unit 120). Thus, each microphone unit is generated.
[0049]
[Effects of the Embodiment] As described above, the microphone unit 120 according to the
embodiment of the present invention has the housing formed of the conductive resin. The
housing is made of conductive resin. A protective film is formed on the surface of the housing. In
this way, since peeling of the conductive resin is prevented, it is possible to prevent a decrease in
acoustic performance due to, for example, adhesion of the peeled particles to the diaphragm 232.
[0050]
In addition, since the housing of the microphone unit 120 is made of a conductive resin,
electromagnetic interference due to the electromagnetic shield can be suppressed. Further, when
the case is made of resin, processing is facilitated, and for example, a plurality of cases can be cut
out from one panel by dicing. This improves mass productivity.
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[0051]
Further, as described above, by forming the protective films 330 and 340 on the surface of the
conductive resin of the cover portion 200, conductive carbon black, carbon nanofibers, and the
like dispersed in the conductive resin, Dust such as carbon nanotube or metal filler is scattered
and attached to or stuck in the diaphragm, the vibration characteristic of the vibration unit 230
is changed and the acoustic characteristic is deteriorated, or an electrical short is generated, and
the diaphragm or It is possible to prevent the ASIC 240 from being damaged.
[0052]
Further, the material of the first substrate 210 and the second substrate 220 is also made of a
heat-resistant material such as, for example, FR4, FR5, or BT resin, thereby enabling the
microphone unit 120 to be compatible with reflow. Is possible.
When the microphone unit 120 is mounted on the system board 110, the reflow process can be
performed like other chip components, which contributes to the reduction of the number of
manufacturing steps.
[0053]
<Modifications> Hereinafter, modifications of the embodiment of the present invention will be
described. The microphone unit 620 according to the present modification differs from the
above-described microphone unit 120 in that it has a so-called differential microphone
configuration. The same components as those of the above-described microphone unit 120 are
denoted by the same reference numerals. Their functions are also the same. Therefore, the
description of the same components will not be repeated.
[0054]
[Configuration] The configuration of microphone unit 620 according to the present embodiment
will be described with reference to FIG. FIG. 6 is a diagram showing the microphone unit 620 cut
in a plane perpendicular to the system board 110. As shown in FIG.
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[0055]
Microphone unit 620 further includes an opening 132 in addition to the configuration of
microphone unit 120 shown in FIG. Protective films 310 and 320 are formed on the surface of
the cover 200 at the opening 132. The protective films 310 and 320 are formed in the same
manner as the protective films 330 and 340.
[0056]
According to such a configuration, the material of the surface of the cover portion 200 peels off,
and the peeled off substance hardly adheres to the upper surface and the lower surface of the
diaphragm 232. Therefore, the acoustic vibration in the diaphragm 232 is not affected by such a
separation. As a result, deterioration of the sound characteristics of the microphone unit 620 is
prevented.
[0057]
As described above, the microphone unit 620 according to the modification of the embodiment
of the present invention has a housing formed of conductive resin. The housing is made of
conductive resin. A protective film is formed on the surface of the housing. In this way, since
peeling of the conductive resin is prevented, it is possible to prevent a decrease in acoustic
performance due to, for example, adhesion of the peeled particles to the diaphragm 232.
[0058]
Further, since the housing of the microphone unit 620 is made of conductive resin,
electromagnetic interference due to the electromagnetic shield can be suppressed. Further, when
the case is made of resin, processing is facilitated, and for example, a plurality of cases can be cut
out from one panel by dicing. This improves mass productivity. The microphone unit 620 has
two openings 130 and 132 so that noise is canceled out. As a result, it is possible to provide a
microphone unit in which a decrease in acoustic characteristics is prevented while maintaining
mass productivity.
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[0059]
It should be understood that the embodiments disclosed herein are illustrative and nonrestrictive in every respect. The scope of the present invention is indicated not by the above
description but by the claims, and is intended to include all the modifications within the meaning
and scope equivalent to the claims.
[0060]
The microphone unit according to the present embodiment is applicable to a small-sized voice
input device such as a cellular phone, a voice recorder, and the like.
[0061]
It is a figure showing the outline of composition of cellular phone 100 which uses microphone
unit 120 concerning an embodiment of the invention.
FIG. 7 is a diagram showing a state in which the upper portion of the cover unit 200 of the
microphone unit 120 is cut in a plane parallel to the system board 110. FIG. 7 is a diagram
showing a state in which the microphone unit 120 is cut in a plane perpendicular to the system
board 110. It is a figure showing the resin board 400 in which the some microphone unit 120
was shape | molded from an upper surface. 15 is a flowchart showing a part of a method of
manufacturing the microphone unit 120. It is a figure showing the state which cut | disconnected
the microphone unit 620 which concerns on the modification of this Embodiment by the surface
perpendicular | vertical to the system board 110. FIG.
Explanation of sign
[0062]
DESCRIPTION OF SYMBOLS 100 mobile phone, 110 system board, 120, 620 microphone unit,
130, 132 opening part, 200 cover, 210 1st board | substrate, 220 2nd board | substrate, 230
vibration unit, 232 diaphragm, 240 ASIC, 400 resin plate, 310, 320, 330, 340 protective film,
350, 352, 360 conductive pattern, 370, 380 electrode pad, 401-406, 411-415 cut area.
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