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JP2011254193

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DESCRIPTION JP2011254193
The present invention provides a compact microphone unit that can easily cope with
multifunctionality of a voice input device. A microphone unit 1 accommodates a first vibration
unit 13, a second vibration unit 15, a first vibration unit 13 and a second vibration unit 15, and a
first sound hole 23. And the second sound hole 25 are provided. The housing 10 includes a
mounting portion 11 having a mounting surface 11 a on which the first vibrating portion 13 and
the second vibrating portion 15 are mounted, and the housing 10 is input from the first sound
hole 23 The first sound path 41 transmitting the sound waves to one surface of the first
diaphragm 134 and transmitting the sound waves to one surface of the second diaphragm 154,
and the sound waves input from the second sound holes 25 A second sound path 42 for
transmitting to the other surface of the second diaphragm 154, and the other surface of the first
diaphragm 134 faces the closed space formed inside the housing 10 ing. [Selected figure] Figure
3
Microphone unit and voice input device provided with the same
[0001]
The present invention relates to a microphone unit having a function of converting an input
sound into an electric signal and outputting the electric signal. The invention also relates to an
audio input device comprising such a microphone unit.
[0002]
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1
Conventionally, input sound is input to various types of voice input devices (for example, voice
communication devices such as mobile phones and transceivers, information processing systems
using techniques for analyzing input voice such as voice authentication systems, recording
devices, etc.) A microphone unit having a function of converting a signal into an electrical signal
and outputting the signal is applied. Such a microphone unit may, for example, be required to
suppress background noise and pick up only the close-up sound, or to pick up not only the closeup sound but also distant sounds. is there.
[0003]
Hereinafter, a mobile phone will be described as an example of the voice input device including
the microphone unit. When making a call using a mobile phone, usually, the user holds the
mobile phone by hand and uses the mouth close to the microphone part. For this reason, as a
microphone provided in a mobile phone, a function (function as a close talk microphone) is
generally required to suppress background noise and pick up only close sounds. As such a
microphone, for example, a differential microphone as shown in Patent Document 1 is preferable.
[0004]
However, some mobile phones in recent years have a hands-free function and a function capable
of performing movie recording, for example, so as to be able to make a call without holding by
hand while driving a car or the like. When using the mobile phone using the hands-free function,
the user's mouth is located away from the mobile phone (for example, at a distance of 50 cm). It
is required to have a function of collecting sound including the sound of In addition, even when
movie recording is performed, it is necessary to record the atmosphere of the place where
recording is performed, and therefore it is required that the microphone function have a function
of collecting not only close sounds but also distant sounds. .
[0005]
That is, in recent years, due to multifunctionalization of the mobile phone, the microphone unit
mounted on the mobile phone includes the function of suppressing background noise and
collecting only the close-up sound, and the close-up sound as well as the distant sound. It is
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2
required to have both the function of picking up sound and the function of picking up sound. As
a configuration for meeting such requirements, a microphone unit having a function as a closetalking microphone and an omnidirectional microphone unit capable of picking up distant
sounds can be separately mounted on a mobile phone. .
[0006]
Moreover, applying the microphone unit disclosed by patent document 2 to a mobile telephone
as another method, for example is mentioned. The microphone unit disclosed in Patent Document
2 is configured such that one of the two openings for inputting voice can be switched between
the open state and the closed state by the open / close mechanism. The microphone unit
disclosed in Patent Document 2 functions as a bi-directional differential microphone when two
openings are open, and an omnidirectional microphone when one of the two openings is closed.
Act as.
[0007]
In the case of functioning as a bi-directional differential microphone, it is suitable for the case
where the user holds the mobile phone by hand because the user can hold only the near-field
sound by suppressing the background noise. On the other hand, when functioning as an
omnidirectional microphone, it is suitable for using the hands-free function or the movie
recording function because it can also pick up sound from a distance.
[0008]
JP, 2009-188943, A JP, 2009-135777, A
[0009]
However, when separately mounting a microphone unit having a function as a close-talking
microphone and an omnidirectional microphone unit as described above, it is necessary to
increase the area of the mounting substrate on which the microphone unit is mounted in the
mobile phone. It occurs.
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3
In recent years, there is a strong demand for downsizing of the portable telephone, and the
above-mentioned correspondence that needs to increase the area of the mounting substrate on
which the microphone unit is mounted is not desirable.
[0010]
In the case of the configuration of Patent Document 2, a mechanical mechanism is used to switch
whether to exhibit the function as a bi-directional differential microphone or to exhibit the
function as an omnidirectional microphone. . The mechanical mechanism is concerned with
durability because it is weak to a drop impact and easily worn.
[0011]
In view of the above points, an object of the present invention is to provide a compact
microphone unit that can easily cope with multifunctionalization of a voice input device. Another
object of the present invention is to provide a high quality voice input device comprising such a
microphone.
[0012]
In order to achieve the above object, in the microphone unit of the present invention, a first
vibration unit that converts a sound signal to an electric signal based on the vibration of the first
diaphragm, and a sound based on the vibration of the second diaphragm A second vibrator for
converting a signal into an electrical signal, and a first sound hole and a second sound hole which
accommodates the first vibrator and the second vibrator therein and faces the outside. And a
housing provided on the outside, the housing including a mounting portion having a mounting
surface on which the first vibration unit and the second vibration unit are mounted, the first
sound The hole and the second sound hole are provided on the back surface of the mounting
surface of the mounting portion, and in the housing, a sound wave input from the first sound
hole is one of the first diaphragms. Sound path transmitted to the first surface of the second
diaphragm and transmitted to the first surface of the second diaphragm, and sound waves input
from the second sound hole A second sound path is provided for transmission to the other
surface of the second diaphragm, and the other surface of the first diaphragm faces an enclosed
space formed inside the housing. It is characterized by
[0013]
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According to the microphone unit of this configuration, it is possible to obtain a function as an
omnidirectional microphone that can pick up not only close sounds but also distant sounds by
using the first vibrating unit, and use the second vibrating unit. Thus, it is possible to obtain a
function as a bi-directional differential microphone excellent in far-field noise suppression
performance.
For this reason, it is easy to cope with multifunctionalization of the voice input device (for
example, a mobile telephone etc.) to which a microphone unit is applied. As a specific example,
for example, in a close talk application of a mobile phone, background noise is suppressed by
utilizing a function as a bi-directional differential microphone, and in a hands-free application or
a movie recording application, a function as an omnidirectional microphone It becomes possible
to use such as In addition, since the microphone unit of this configuration has two functions, it is
not necessary to separately mount two microphone units, and it is easy to suppress the
enlargement of the voice input device.
[0014]
In the microphone unit of the above configuration, the housing is covered by the mounting
portion, and the first housing space that houses the first vibrating portion together with the
mounting portion and a second housing that houses the second vibrating portion. And a second
opening that is covered by the second vibrating part, the first opening being covered by the first
vibrating part, and a second opening that is hidden by the second vibrating part. And the first
sound path is formed in the first sound hole, the first opening, the second opening, and the inside
of the mounting portion. It is formed using the hollow space which makes 1 sound hole, said 1st
opening part, and said 2nd opening part connect, and said 2nd sound path is a penetration hole
which penetrates said mounting part It may be formed using the second sound hole and the
second accommodation space.
[0015]
According to this configuration, the hollow space is formed in the mounting portion to obtain the
sound path, and the thickness reduction of the microphone unit exhibiting the above two
functions can be easily achieved.
Moreover, according to the present configuration, the first accommodation space forms a closed
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space (back chamber) facing the other surface of the first diaphragm. This sealed space can be
formed, for example, by utilizing a recessed space provided in the lid, so it is easy to secure a
large volume. When the volume of the back chamber is increased, the vibrating membrane of the
vibrating portion is easily displaced, and the sensitivity of the vibrating portion can be improved.
Therefore, according to the present configuration, the sensitivity of the first vibration unit used
when obtaining the function as an omnidirectional microphone can be improved, whereby a high
SNR (Signal to Noise Ratio) microphone unit can be realized.
[0016]
In the microphone unit of the above configuration, the housing further includes a lid portion
which is covered by the mounting portion and which forms a housing space for housing the first
diaphragm and the second vibration portion together with the mounting portion. The mounting
surface is provided with an opening which is covered and hidden by the second vibrating portion,
and the first sound path is the first sound hole which is a through hole penetrating the mounting
portion; The second sound path is formed using the housing space, and the second sound path is
formed inside the second sound hole, the opening, and the mounting portion to form the second
sound hole and the opening. And a hollow space communicating with each other may be used.
[0017]
Also in the case of this configuration, the hollow space is formed in the mounting portion to
obtain the sound path, and it is easy to make the microphone unit having the above two
functions thin.
[0018]
The microphone unit configured as described above may include an electric circuit unit mounted
on the mounting unit and processing an electric signal obtained by the first vibrating unit and
the second vibrating unit.
In this case, the electric circuit unit includes a first electric circuit unit that processes the electric
signal obtained by the first vibration unit, and a second electric circuit unit that processes the
electric signal obtained by the second vibration unit. And the electric circuit portion of
Further, the electric signals obtained by the first vibration unit and the second vibration unit may
be processed by one electric circuit unit. Furthermore, the electric circuit portion may be formed
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monolithically on the first vibrating portion or the second vibrating portion. Further, when the
electric circuit unit is mounted on the mounting portion, an electrode for electrically connecting
to the electric circuit portion is formed on the mounting surface, and the electrode on the surface
of the mounting portion to the back surface of the mounting surface It is preferable that a back
electrode pad electrically connected to the electrode on the mounting surface is formed. This
makes it easy to mount the microphone unit on the voice input device.
[0019]
In the microphone unit having the above configuration, the back surface of the mounting surface
of the mounting portion is airtight when mounted on a mounting substrate so as to surround
each of the first sound hole and the second sound hole. A sealing portion that exerts
[0020]
According to this configuration, when mounting the microphone unit on the mounting substrate
of the voice input device, it is convenient because it is not necessary to separately prepare a
gasket for preventing acoustic leak.
[0021]
In order to achieve the above object, the voice input device of the present invention is
characterized by being a voice input device provided with the microphone unit of the above
configuration.
[0022]
According to this configuration, the use mode is used in order to combine the function as an
omnidirectional microphone capable of picking up distant sound and the function as a bidirectional differential microphone excellent in far-field noise suppression performance. It is
possible to provide a high quality voice input device that can use the microphone function
depending on the situation.
Also, such a high quality voice input device can be made compact.
[0023]
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According to the present invention, it is possible to provide a compact microphone unit which
can easily cope with multifunctionalization of the voice input device.
Further, according to the present invention, it is possible to provide a high quality voice input
device provided with such a microphone unit.
[0024]
The outline perspective view showing the appearance composition of the microphone unit of a
1st embodiment The disassembled perspective view showing the composition of a microphone
unit of a 1st embodiment The case where the microphone unit of a 1st embodiment is cut along
the A-A position of FIG. Schematic cross-sectional view of the schematic plan view for explaining
the configuration of the mounting portion provided in the microphone unit of the first
embodiment The schematic plan view for explaining the configuration of the lid provided in the
microphone unit of the first embodiment 10 is a schematic cross-sectional view showing the
configuration of the MEMS chip included in the microphone unit of the first embodiment. FIG. 11
is a schematic plan view of the mounting unit included in the microphone unit of the first
embodiment viewed from above. Graph showing relationship between graphic sound pressure P
and distance R from sound source showing MEMS chip and ASIC mounted The graph for
explaining the directivity characteristics of the microphone unit of one embodiment. The graph
microphone sensitivity and frequency showing the relationship between the back chamber
volume and the microphone sensitivity in the graph microphone for explaining the microphone
characteristics of the microphone unit of the first embodiment. The graph for explaining that the
relationship with the back chamber volume changes The cross section for explaining the first
modification of the microphone unit of the first embodiment of the graph The second
modification of the microphone unit of the first embodiment is explained Block diagram for
explaining the third modification of the microphone unit of the first embodiment The figure for
explaining the configuration of the third modification of the microphone unit of the first
embodiment, the microphone unit includes The schematic plan view at the time of seeing
mounting part from the top The 3rd modification of the microphone unit of a 1st embodiment
The figure for demonstrating another structure, the schematic plan view at the time of seeing the
mounting part with which a microphone unit is equipped from the top. Block diagram for
demonstrating the 4th modification of the microphone unit of a 1st embodiment. The block
diagram for demonstrating the 5th modification of a microphone unit The outline sectional view
showing the composition of the microphone unit of a 2nd embodiment The schematic
configuration of the embodiment of the portable telephone to which the microphone unit of a 1st
embodiment is applied 22 is a schematic cross-sectional view taken along the line B-B of FIG. 22.
A schematic cross-sectional view of a portable telephone in which the microphone unit disclosed
in the previous application is mounted. Schematic cross-sectional view showing the configuration
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of the microphone unit
[0025]
Hereinafter, embodiments of a microphone unit and an audio input device to which the present
invention is applied will be described in detail with reference to the drawings.
[0026]
(Microphone Unit) First, an embodiment of a microphone unit to which the present invention is
applied will be described.
[0027]
1.
Microphone Unit of First Embodiment FIG. 1 is a schematic perspective view showing the
external configuration of the microphone unit of the first embodiment, and FIG. 1 (a) is a view
from diagonally above, and FIG. 1 (b) is a diagonally from below It is the figure which looked at.
As shown in FIG. 1, the microphone unit 1 according to the first embodiment is configured to
include a substantially rectangular parallelepiped shaped housing 10 formed by a mounting
portion 11 and a lid portion 12 that covers the mounting portion 11. .
[0028]
FIG. 2 is an exploded perspective view showing the microphone unit configuration of the first
embodiment.
FIG. 3 is a schematic cross-sectional view of the microphone unit of the first embodiment taken
along the line A-A in FIG.
As shown in FIGS. 2 and 3, a first MEMS (Micro Electro Mechanical System) chip 13 and a first
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9
ASIC (Application Specific Integrated) are provided in a housing 10 including the mounting
portion 11 and the lid 12. Circuit 14, a second MEMS chip 15, and a second ASIC 16 are
accommodated. The details of each part will be described below.
[0029]
FIG. 4 is a schematic plan view for explaining the configuration of the mounting portion provided
in the microphone unit of the first embodiment, and FIG. 4 (a) is a top view of the first flat plate
constituting the mounting portion, FIG. 4 (b) FIG. 4C is a top view of a third flat plate of the
mounting portion. FIG. 4C is a top view of the second flat plate of the mounting portion. In FIG. 4,
in order to facilitate understanding of the relationship between the flat plates constituting the
mounting portion 11, the through holes provided in the flat plate disposed above the flat plate
shown in each drawing are indicated by broken lines. There is.
[0030]
As shown in FIG. 4, the three flat plates 111, 112, 113 constituting the mounting portion 11 are
all provided in a substantially rectangular shape in plan view, and the sizes in plan view are
substantially the same. As shown in FIG. 3, the third flat plate 113, the second flat plate 112, and
the first flat plate 111 are stacked in order from bottom to top, and the flat plates are bonded
together using, for example, an adhesive or an adhesive sheet. The mounting part 11 of a form is
obtained. Although the material of the flat plates 111-113 which comprise the mounting part 11
is not specifically limited, The well-known material used as a board | substrate material is used
suitably, for example, FR-4, ceramics, a polyimide film etc. are used.
[0031]
As shown in FIG. 4A, the first flat plate 111 is closer to one end in the longitudinal direction
(leftward in FIG. 4) and closer to one end in the lateral direction (downward in FIG. 4). A first
through hole 111 a having a substantially circular shape in plan view is formed. In the first flat
plate 111, a second through hole 111b having a substantially circular shape in a plan view is
formed at a position slightly shifted from the substantially central portion to the other end side
(right side in FIG. 4) in the longitudinal direction . Furthermore, the first flat plate 111 has a
substantially rectangular shape in a plan view (longitudinal direction in FIG. 4) which is a
longitudinal direction near the other end in the longitudinal direction (rightward in FIG. 4). A
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stadium type) third through hole 111c is formed.
[0032]
As shown in FIG. 4B, the second flat plate 112 has a substantially T-shape in plan view (exactly T)
from the substantially central portion thereof toward one end in the longitudinal direction
(leftward in FIG. 4). In the figure, the fourth through hole 112 a is formed. The position of the
fourth through hole 112 a is determined so as to overlap with the first through hole 111 a and
the second through hole 111 b (shown by a broken line) formed in the first flat plate 111. In
addition, the second flat plate 112 has a substantially rectangular shape in plan view in which
the short direction of the second flat plate 112 (vertical direction in FIG. 4) is a longitudinal
direction near the other end in the longitudinal direction (rightward in FIG. 4). The fifth through
hole 112 b is formed. The fifth through hole 112b is formed in the same shape and the same size
as the third through hole 111c of the first flat plate 111, and the position thereof is determined
so that the whole thereof overlaps the third through hole 111c. .
[0033]
As shown in FIG. 4C, in the third flat plate 113, the lateral direction (vertical direction in FIG. 4)
of the third flat plate 113 is the longitudinal direction toward one end in the longitudinal
direction (leftward in FIG. 4). A sixth through-hole 113a having a substantially rectangular shape
in plan view is formed. The position of the sixth through hole 113 a is determined so that the
whole thereof overlaps the fourth through hole 112 a of the second flat plate 112. In addition,
the third flat plate 113 has a substantially rectangular shape in a plan view, in which the short
direction of the third flat plate 113 (vertical direction in FIG. 4) is a longitudinal direction near
the other end in the longitudinal direction (rightward in FIG. 4). A seventh through hole 113 b is
formed. The seventh through hole 113b is formed in the same shape and size as the fifth through
hole 112b of the second flat plate 112, and the position thereof is determined so that the whole
thereof overlaps the fifth through hole 112b. .
[0034]
When the mounting portion 11 is formed by stacking the three flat plates 111 to 113 thus
formed in this order from the bottom to the top of the third flat plate 113, the second flat plate
112, and the first flat plate 111 as described above The following hollow space will be formed in
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11. That is, as shown in FIG. 3, the first opening 21 (upper surface portion of the first through
hole 111a) and the second opening 22 (second through hole 111b) provided on the upper
surface 11a of the mounting portion 11 A hollow space 24 communicating the upper surface
portion with the third opening 23 (the lower surface portion of the sixth through hole 113 a)
provided in the lower surface 11 b of the mounting portion 11 is formed inside the mounting
portion 11. When three flat plates 111 to 113 are stacked as described above to form mounting
portion 11, three through holes 111c, 112b, and 113b are connected to penetrate mounting
portion 11 in a thickness direction, and have a substantially rectangular shape in plan view. One
through hole 25 is formed (see FIG. 3).
[0035]
In addition, although the electrode pad and the electrical wiring are formed in the mounting part
11, these are mentioned later. Moreover, although it is set as the structure which obtains the
mounting part 11 by bonding three flat plates together in this embodiment, it is not limited to
this structure, the mounting part 11 may be comprised by one flat plate, Several different from
three It may be composed of a flat plate of Moreover, the shape of the mounting part 11 is not
limited to plate shape. When the non-plate-like mounting portion 11 is formed of a plurality of
members, the members constituting the mounting portion 11 may include non-flat members.
Furthermore, the shapes of the openings 21, 22, 23, the hollow space 24, and the through holes
25 formed in the mounting portion 11 are not limited to the configuration of the present
embodiment, and can be changed as appropriate.
[0036]
FIG. 5 is a schematic plan view for explaining the configuration of a lid provided in the
microphone unit of the first embodiment, and FIG. 5 (a) shows a first configuration example of
the lid, and FIG. 5 (b) is a lid The 2nd structural example of the part is shown. FIG. 5 is a view of
the lid 12 as viewed from below.
[0037]
The lid 12 is provided in a substantially rectangular parallelepiped shape (see FIGS. 1 to 3). The
length of the lid 12 in the longitudinal direction (left and right direction in FIG. 5) and the short
side direction (vertical direction in FIG. 5) is the housing when the lid 12 is placed on the
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12
mounting portion 11 to form the housing 10 The side face portions 10 are adjusted to be
substantially flush. The material constituting the lid 12 can also be, for example, a resin such as
LCP (Liquid Crystal Polymer) or PPS (polyphenylene sulfide). Here, in order to impart
conductivity to the resin, metal fillers such as stainless steel or carbon may be mixed. Moreover,
it does not matter as substrate materials, such as FR-4 grade | etc., Ceramics.
[0038]
As shown in FIG. 5, the lid 12 has two recesses 12b and 12c separated by a partition 12a.
Therefore, covering the lid 12 on the mounting portion 11 provides two spaces 121 and 122
(see FIG. 3) independent of each other. Since the two spaces 121 and 122 are used as spaces for
accommodating the MEMS chip and the ASIC as described later, the space 121 is a first
accommodation space 121 and the space 122 is a second accommodation space below. It
describes as 122.
[0039]
The concave portions 12b and 12c provided in the lid 12 may be substantially rectangular in
plan view (substantially rectangular solid shape) as shown in FIG. 5A. However, as shown in FIG.
5B, the concave portion 12c forming the second accommodation space 122 (this point will be
described later) used as a sound path when the lid portion 12 is placed on the mounting portion
11 It is preferable to form in planar view substantially T shape.
[0040]
As a result, the volume of the entire second accommodation space 122 can be reduced while
securing a wide opening area of a portion (here, a portion connected to the through hole 25
here) serving as a sound entrance for the second accommodation space 122. The acoustic
resonance frequency of the second accommodation space 122 can be set to the high frequency
side. In this case, the microphone characteristic using the second MEMS chip 15 (see FIG. 3)
accommodated in the second accommodation space 122 can be made favorable (noise can be
appropriately suppressed on the high frequency side).
[0041]
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13
Here, the resonant frequency will be additionally described. In general, when considering a model
in which the second accommodation space 122 and a sound entrance connected thereto are
present, the model has an acoustic resonance frequency specific to the model. This resonance
frequency is called Helmholtz resonance. In this model, qualitatively, the larger the area S of the
sound inlet and / or the smaller the volume V of the second accommodation space 122, the
higher the resonance frequency. Conversely, the smaller the area S of the sound inlet and / or the
larger the volume V of the second accommodation space 122, the lower the resonant frequency.
When the resonance frequency becomes low and comes close to the audio frequency band (~10
kHz), the frequency characteristics and sensitivity characteristics of the microphone are
adversely affected. Therefore, it is desirable to set the resonance frequency as high as possible.
[0042]
In the above, the recess 12c forming the second accommodation space 122 is substantially Tshaped in a plan view, but is not limited to this shape, and the second accommodation may be
performed depending on the arrangement of the MEMS chip and the ASIC. It is desirable to
design so that the volume V of the space 122 is minimized. In addition, when the mounting part
11 is comprised, the reason for having formed the through-hole 112a of planar view
substantially T-shape about the 2nd flat plate 112 among three flat plates is the same reason.
The volume of the hollow space 24 is reduced and the resonance frequency is set high while
securing a wide opening area of a portion (a portion connected to the sixth through hole 113a)
as an entrance of sound.
[0043]
As shown in FIGS. 2 and 3, in the microphone unit 1, two MEMS chips of the first MEMS chip 13
and the second MEMS chip 15 are mounted on the mounting portion 11. The two MEMS chips
13 and 15 are both silicon chips, and the configuration is the same. Therefore, taking the case of
the first MEMS chip 13 as an example, the configuration of the MEMS chip included in the
microphone unit 1 will be described with reference to FIG. 6 is a schematic cross-sectional view
showing the configuration of the MEMS chip provided in the microphone unit of the first
embodiment. Further, in FIG. 6, reference numerals shown in parentheses correspond to the
second MEMS chip 15. Also, the MEMS chip is an embodiment of the vibration unit of the
present invention.
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14
[0044]
As shown in FIG. 6, the first MEMS chip 13 includes an insulating first base substrate 131, a first
fixed electrode 132, a first insulating layer 133, and a first diaphragm 134. Have.
[0045]
A through hole 131 a having a substantially circular shape in plan view is formed in a central
portion of the first base substrate 131.
The first fixed electrode 132 is disposed on the first base substrate 131, and the first fixed
electrode 132 is formed with a plurality of small diameter through holes 132a. The first
insulating layer 133 is disposed on the first fixed electrode 132, and similarly to the first base
substrate 131, a through hole 133a having a substantially circular shape in a plan view is formed
in the central portion thereof. The first diaphragm 134 disposed on the first insulating layer 133
is a thin film that vibrates (vibrates in the vertical direction in FIG. 6) by receiving sound
pressure, and has conductivity to form one end of the electrode. doing. The first fixed electrode
132 and the first diaphragm 134, which are disposed opposite to each other so as to be
substantially parallel to each other with a gap Gp due to the presence of the first insulating layer
133, form a capacitor.
[0046]
The presence of the through holes 131 a formed in the first base substrate 131, the plurality of
through holes 132 a formed in the first fixed electrode 132, and the through holes 133 a formed
in the first insulating layer 133 The sound wave arrives at the first diaphragm 134 not only from
above but also from below.
[0047]
Thus, in the first MEMS chip 13 configured as a capacitor type microphone, when the first
diaphragm 134 vibrates due to the arrival of the sound wave, the space between the first
diaphragm 134 and the first fixed electrode 132 is generated. Capacitance changes.
As a result, the sound wave (sound signal) incident on the first MEMS chip 13 can be extracted as
04-05-2019
15
an electric signal. Similarly, the second MEMS chip 15 including the second base substrate 151,
the second fixed electrode 152, the second insulating layer 153, and the second diaphragm 154
also receives the incident sound wave (sound Signal) can be taken out as an electrical signal. That
is, the first MEMS chip 13 and the second MEMS chip 15 have a function of converting a sound
signal into an electric signal.
[0048]
The configuration of the MEMS chips 13 and 15 is not limited to the configuration of the present
embodiment, and the configuration may be changed as appropriate. For example, in the present
embodiment, the diaphragms 134 and 154 are higher than the fixed electrodes 132 and 152, but
the opposite relationship (the relationship in which the diaphragm is lower and the fixed
electrode is higher) It may be configured to be
[0049]
The first ASIC 14 is an integrated circuit that amplifies an electrical signal extracted based on a
change in capacitance of the first MEMS chip 13 (derived from the vibration of the first
diaphragm 134). The second ASIC 16 is an integrated circuit that amplifies an electrical signal
extracted based on a change in capacitance of the second MEMS chip 15 (derived from the
vibration of the second diaphragm 154). ASIC is an embodiment of the electric circuit unit of the
present invention.
[0050]
As shown in FIG. 7, the first ASIC 14 includes a charge pump circuit 141 that applies a bias
voltage to the first MEMS chip 13. The charge pump circuit 141 boosts the power supply voltage
VDD (for example, about 1.5 to 3 V) (for example, about 6 to 10 V) and applies a bias voltage to
the first MEMS chip 13. The first ASIC 14 also includes an amplifier circuit 142 that detects a
change in capacitance of the first MEMS chip 13. The electrical signal amplified by the amplifier
circuit 142 is output from the first ASIC 14 (OUT1). Similarly, the second ASIC 16 also applies a
charge pump circuit 161 that applies a bias voltage to the second MEMS chip 15 and an
amplifier circuit 162 that detects a change in electrostatic capacitance and outputs an amplified
electrical signal. Prepare. FIG. 7 is a block diagram showing the configuration of the microphone
unit of the first embodiment.
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16
[0051]
Here, referring mainly to FIG. 8, the positional relationship and electrical connection relationship
of the two MEMS chips 13 and 15 and the two ASICs 14 and 16 in the microphone unit 1 will be
described. FIG. 8 is a schematic plan view of the mounting portion provided in the microphone
unit of the first embodiment as viewed from above (from the mounting surface side), showing a
state in which the MEMS chip and the ASIC are mounted.
[0052]
The two MEMS chips 13 and 15 are mounted on the mounting portion 11 in a posture (see FIG.
3) in which the diaphragms 134 and 154 are substantially parallel to the mounting surface
(upper surface) 11 a of the mounting portion 11. Then, as shown in FIG. 8, the first MEMS chip
13 and the first ASIC 14 are mounted side by side in the lateral direction near one end in the
longitudinal direction of the mounting portion 11 (leftward in FIG. 8) Ru. In addition, the second
MEMS chip 15 is mounted at a position slightly shifted from the substantially central portion of
the mounting portion 11 to the other end side (right side in FIG. 8) in the longitudinal direction.
Further, the second ASIC 16 is mounted on the other end side (the right side in FIG. 8) of the
mounting portion 11 with respect to the second MEMS chip 15 in the longitudinal direction.
[0053]
The first MEMS chip 13 is mounted on the mounting portion 11 so as to cover the first opening
21 (see FIGS. 2 and 3) formed in the mounting surface (upper surface) 11 a of the mounting
portion 11. There is. The second MEMS chip 15 is mounted on the mounting portion 11 so as to
cover the second opening 22 (see FIGS. 2 and 3) formed in the upper surface 11 a of the
mounting portion 11.
[0054]
Further, the arrangement of the two MEMS chips 13 and 15 and the two ASICs 14 and 16 is not
limited to the configuration of the present embodiment, and can be changed as appropriate. For
04-05-2019
17
example, the MEMS chip and the ASIC may be arrayed in the longitudinal direction or may be
arrayed in the lateral direction in each of the groups configured by the MEMS chip and the ASIC.
[0055]
The two MEMS chips 13 and 15 and the two ASICs 14 and 16 are mounted on the mounting
portion 11 by die bonding and wire bonding. In detail, the first MEMS chip 13 and the second
MEMS chip 15 are formed of a die bonding material (for example, an epoxy resin type or silicone
resin type adhesive, etc.) (not shown) with their bottom surface and the top surface 11 a of the
mounting portion 11. Are joined to the upper surface 11 a of the mounting portion 11 so as to
make no gap between them. By bonding in this manner, a situation in which sound leaks from a
gap formed between the upper surface 11 a of the mounting portion 11 and the bottom surface
of the MEMS chip 13 or 15 does not occur. Also, as shown in FIG. 8, the first MEMS chip 13 is
electrically connected to the first ASIC 14, and the second MEMS chip 15 is electrically
connected to the second ASIC 16 by wires 17 (preferably gold wires). It is done.
[0056]
Further, in each of the two ASICs 14 and 16, a bottom surface facing the mounting surface
(upper surface) 11 a of the mounting portion 11 is joined to the upper surface 11 a of the
mounting portion 11 by a die bonding material (not shown). As shown in FIG. 8, the first ASIC 14
is electrically connected to each of the plurality of electrode terminals 18 a, 18 b and 18 c
formed on the upper surface 11 a of the mounting portion 11 by the wires 17. The electrode
terminal 18a is a power supply terminal for inputting a power supply voltage (VDD), the
electrode terminal 18b is a first output terminal for outputting the electric signal amplified by the
amplifier circuit 142 of the first ASIC 14, and the electrode terminal 18c is GND terminal for
ground connection.
[0057]
Similarly, the second ASIC 16 is electrically connected to each of the plurality of electrode
terminals 19 a, 19 b, 19 c formed on the upper surface 11 a of the mounting portion 11 by the
wire 17. The electrode terminal 19a is a power supply terminal for inputting a power supply
voltage (VDD), the electrode terminal 19b is a second output terminal for outputting the electric
signal amplified by the amplifier circuit 162 of the second ASIC 16, and the electrode terminal
04-05-2019
18
19c is GND terminal for ground connection.
[0058]
As shown in FIG. 1B and FIG. 3, an external connection electrode pad 20 is formed on the back
surface (lower surface of the mounting portion 11) 11 b of the mounting surface 11 a of the
mounting portion 11. The external connection electrode pad 20 includes a power supply
electrode pad 20a, a first output electrode pad 20b, a second output electrode pad 20c, a GND
electrode pad 20d, and a sealing electrode pad 20e.
[0059]
The power supply terminals 18a and 19a provided on the upper surface 11a of the mounting
portion 11 are electrically connected to the power supply electrode pads 20a via unshown wiring
(including through wiring) formed on the mounting portion 11. The first output terminal 18 b
provided on the upper surface 11 a of the mounting portion 11 is electrically connected to the
first output electrode pad 20 b via a wiring (including a through wiring) formed on the mounting
portion 11. The second output terminal 19 b provided on the upper surface 11 a of the mounting
portion 11 is electrically connected to the second output electrode pad 20 c via a wiring
(including a through wiring) (not shown) formed on the mounting portion 11. The GND terminals
18c and 19c provided on the upper surface 11a of the mounting portion 11 are electrically
connected to the GND electrode pad 20d through unshown wiring (including through wiring)
formed on the mounting portion 11. Through wiring can be formed by a through hole via
generally used in substrate manufacture.
[0060]
The sealing electrode pad 20 e is used to maintain air tightness when the microphone unit 1 is
mounted on a mounting substrate of a voice input device such as a portable telephone, and the
details will be described later.
[0061]
In the present embodiment, although two MEMS chips 13 and 15 and two ASICs 14 and 16 are
wire-bonded and mounted, two MEMS chips 13 and 15 and two ASICs 14 and 16 are flip-chip
04-05-2019
19
mounted. Of course it does not matter.
In this case, electrodes are formed on the lower surfaces of the MEMS chips 13 and 15 and the
ASICs 14 and 16, and electrode pads corresponding thereto are disposed on the upper surface of
the mounting portion 11, and these wiring patterns are formed on the mounting portion 11 To
do.
[0062]
The lid portion 12 is mounted on the mounting portion 11 (which is configured by bonding of
the substrates in this embodiment and may be expressed as a substrate portion) on which the
two MEMS chips 13 and 15 and the two ASICs 14 and 16 are mounted. When bonding is
performed so as to hermetically seal (for example, an adhesive or an adhesive sheet is used), the
first MEMS chip 13, the first ASIC 14, the second MEMS chip 15, and the second , And an ASIC
16 of the present invention. In the microphone unit 1, as shown in FIG. 3, the first MEMS chip 13
and the first AISC 14 are accommodated in the first accommodation space 121, and the second
MEMS chip 15 is accommodated in the second accommodation space 122. And the second ASIC
16 are accommodated.
[0063]
In the microphone unit 1, as shown in FIG. 3, the sound wave input from the outside through the
third opening 23 passes through the hollow space 24 and the first opening 21 to the first
diaphragm 134. The lower surface of the second diaphragm 154 is reached through the hollow
space 24 and the second opening 22. In addition, the sound wave input from the outside through
the through hole 25 passes through the second accommodation space 122 and reaches the
upper surface of the second diaphragm 154. In addition, since the third opening 23 and the
through hole 25 are used to input sound waves into the housing 10, the third sound opening 23
is penetrated through the third opening 23 below. The hole 25 is expressed as a second sound
hole 25.
[0064]
From the above, in the microphone unit 1, the sound wave input from the first sound hole 23 is
04-05-2019
20
transmitted to one surface (lower surface) of the first diaphragm 134 and one of the second
diaphragm 154 is transmitted. A first sound path 41 transmitting to the surface (lower surface),
and a second sound path 42 transmitting the sound wave input from the second sound hole 25
to the other surface (upper surface) of the second diaphragm 154 It can be said that, is provided.
Further, in the microphone unit 1, a sound wave is not input from the outside to the other
surface (upper surface) of the first diaphragm 134, and an enclosed space (back chamber) free of
acoustic leaks is formed. .
[0065]
The distance (center-to-center distance) between the first sound hole 23 and the second sound
hole 25 provided in the microphone unit 1 is preferably 3 mm or more and 10 mm or less, and
more preferably 4 mm or more and 6 mm or less preferable. If the distance between the two
sound holes 23 and 25 is too wide, the phase difference of the sound waves input from the
respective sound holes 23 and 25 and reaching the second diaphragm 154 becomes large, and
the microphone characteristics deteriorate (noise suppression performance) In order to prevent
such a situation, In addition, if the distance between the two sound holes 23 and 25 is too
narrow, the difference in sound pressure applied to the upper and lower surfaces of the second
diaphragm 154 becomes smaller, and the amplitude of the second diaphragm 154 becomes
smaller. The signal to noise ratio (SNR) of the electrical signal output from the ASIC 16 is
degraded, and this is intended to suppress such a situation.
[0066]
Also, in order to obtain a high noise suppression effect in a wide frequency range, the sound
propagates from the first sound hole 23 to the second diaphragm 154 through the first sound
path 41 (see FIG. 3). The distance and the propagation distance of the sound from the second
sound hole 25 to the second diaphragm 154 through the second sound path 42 (see FIG. 3) are
designed to be approximately equal. preferable.
[0067]
Moreover, in the microphone unit 1, although the 1st sound hole 23 and the 2nd sound hole 25
which are provided in the housing | casing 10 become a long hole shape, it is not limited to this
structure, For example, planar view abbreviation It may be a circular hole or the like.
04-05-2019
21
However, as in the present configuration, the long hole shape suppresses the increase in the
length of the longitudinal direction of the microphone unit 1 (corresponding to the horizontal
direction in FIG. 3), for example, while reducing the package size. It is preferable because the
cross-sectional area of the sound hole can be increased. The effects of increasing the crosssectional area of the sound hole are as described above. Since the resonance frequency can be
increased as the cross-sectional area of the sound hole is increased, flat performance can be
obtained over a wide band as the microphone.
[0068]
Further, the amplifier gain of the amplifier circuit 142 that detects a change in capacitance in the
first MEMS chip 13 and the amplifier gain of the amplifier circuit 162 that detects a change in
capacitance in the second MEMS chip 15 are different. May be set to gain. Since the second
diaphragm 154 of the second MEMS chip 15 vibrates due to the sound pressure difference
applied to both surfaces (upper surface and lower surface), the vibration amplitude is the
vibration of the first diaphragm 134 of the first MEMS chip 13 It becomes smaller than the
amplitude. Therefore, for example, the amplifier gain of the amplifier circuit 162 of the second
ASIC 16 may be larger than the amplifier gain of the amplifier circuit 142 of the first ASIC 14.
More specifically, when the center-to-center distance between the two sound holes 23 and 25 is
about 5 mm, the amplifier gain of the amplifier circuit 162 of the second ASIC 16 is the amplifier
gain of the amplifier circuit 142 of the first ASIC 14 It is preferable to set to a value higher than
that by about 6 to 14 dB. As a result, the output signal amplitudes from the two amplifier circuits
142 and 162 can be made substantially equal, so that a large output amplitude change can be
suppressed when the user selects and switches the outputs from both amplifiers. it can.
[0069]
Next, the operation and effect of the microphone unit 1 of the first embodiment will be described.
[0070]
When sound is generated outside the microphone unit 1, the sound wave input from the first
sound hole 23 reaches the lower surface of the first diaphragm 134 by the first sound path 41,
and the first diaphragm 134 vibrates. Do.
04-05-2019
22
As a result, a change in capacitance occurs in the first MEMS chip 13. The electrical signal
extracted based on the change in capacitance of the first MEMS chip 13 is amplified by the
amplifier circuit 142 of the first ASIC 14 and finally output from the first output electrode pad
20 b. (See above, refer to FIG. 3 and FIG. 7).
[0071]
In addition, when sound is generated outside the microphone unit 1, the sound wave input from
the first sound hole 23 reaches the lower surface of the second diaphragm 154 by the first sound
path 41 and the second sound hole The sound wave input from 25 reaches the upper surface of
the second diaphragm 154 by the second sound path 42. For this reason, the second diaphragm
154 vibrates due to the sound pressure difference between the sound pressure applied to the
upper surface and the sound pressure applied to the lower surface. As a result, a change in
capacitance occurs in the second MEMS chip 15. The electrical signal extracted based on the
change in capacitance of the second MEMS chip 15 is amplified by the amplifier circuit 162 of
the second ASIC 16 and finally output from the second output electrode pad 20c. (See above,
refer to FIG. 3 and FIG. 7).
[0072]
As described above, in the microhonin unit 1, the signal obtained using the first MEMS chip 13
and the signal obtained using the second MEMS chip 15 are separately output to the outside. It
has become. The microphone unit 1 exhibits different properties in the case of using only the
first MEMS chip 13 and the case of using only the second MEMS chip 15. This will be described
below.
[0073]
Before the explanation, the nature of the sound wave is explained. FIG. 9 is a graph showing the
relationship between the sound pressure P and the distance R from the sound source. As shown
in FIG. 9, the sound wave attenuates as it travels through a medium such as air, and the sound
pressure (intensity / amplitude of the sound wave) decreases. The sound pressure is inversely
proportional to the distance from the sound source, and the relationship between the sound
pressure P and the distance R can be expressed as the following equation (1). In addition, k in
Formula (1) is a proportionality constant. P=k/R (1)
04-05-2019
23
[0074]
As is clear from FIG. 9 and the equation (1), the sound pressure is rapidly attenuated (at the left
of the graph) at a position close to the sound source and is gradually attenuated (at the right of
the graph) as it gets farther from the sound source. That is, the sound pressure transmitted to
two positions (R1 and R2 and R3 and R4) different in distance from the sound source by Δd is
largely attenuated (P1-P2) in R1 to R2 where the distance from the sound source is small. There
is little attenuation in R3 to R4 where the distance from the sound source is large (P3-P4).
[0075]
FIG. 10 is a diagram for explaining the directivity characteristic of the microphone unit of the
first embodiment, and FIG. 10 (a) is a diagram for explaining the directivity characteristic when
using the first MEMS chip 13 side. 10 (b) is a diagram for explaining the directivity characteristic
in the case of using the second MEMS chip 15 side. In FIG. 10, the attitude of the microphone
unit 1 is assumed to be the same as that shown in FIG.
[0076]
If the distance from the sound source to the first diaphragm 134 is constant, the sound pressure
applied to the first diaphragm 134 is constant regardless of the direction of the sound source.
That is, when using the first MEMS chip 13 side, as shown in FIG. 10A, the microphone unit 1
exhibits an omnidirectional characteristic that uniformly receives a sound wave incident from
any direction.
[0077]
On the other hand, when the second MEMS chip 15 is used, the microphone unit 1 does not
exhibit omnidirectional characteristics, but exhibits bidirectional characteristics as shown in FIG.
10B. If the distance from the sound source to the second diaphragm 154 is constant, the sound
pressure applied to the second diaphragm 154 is maximum when the sound source is in the
direction of 0 ° or 180 °. This is because the difference between the distance from the first
04-05-2019
24
sound hole 23 to the lower surface of the second diaphragm 154 and the distance from the
second sound hole 25 to the upper surface of the second diaphragm 154 is It is because it
becomes the largest.
[0078]
On the other hand, the sound pressure applied to the second diaphragm 154 is minimum (0)
when the sound source is in the 90 ° or 270 ° direction. This is because the difference
between the distance from the first sound hole 23 to the lower surface of the second diaphragm
154 and the distance from the second sound hole 25 to the upper surface of the second
diaphragm 154 is It is because it becomes almost zero. That is, when the second MEMS chip 15
side is used, the microphone unit 1 has high sensitivity to the sound waves incident from the
directions of 0 ° and 180 °, and the sound waves incident from the directions of 90 ° and
270 ° Show low sensitivity characteristics (bidirectional).
[0079]
FIG. 11 is a graph for explaining the microphone characteristics of the microphone unit of the
first embodiment, the horizontal axis representing the distance R from the sound source as a
logarithmic axis, and the vertical axis the sound pressure applied to the diaphragm of the
microphone unit Indicates the level (dB). In FIG. 11, A indicates the microphone characteristic of
the microphone unit 1 when using the first MEMS chip 13 side, and B indicates the microphone
characteristic of the microphone unit 1 when using the second MEMS chip 15 side. Show.
[0080]
In the first MEMS chip 13, the first diaphragm 134 vibrates due to the sound pressure applied to
one surface (lower surface), but in the second MEMS chip 15, the second diaphragm 154 has
both surfaces (upper surface and lower surface) Vibrate due to the difference in sound pressure
applied to the The distance attenuation characteristics attenuate the sound pressure level by 1 /
R when using the first MEMS chip 13 side, but when using the second MEMS chip 15 side, the
first MEMS chip 13 characteristics The characteristic is obtained by differentiating the distance R
and the sound pressure level is attenuated by 1 / R <2>. For this reason, as shown in FIG. 11, in
the case of using the second MEMS chip 15 side as compared with the case of using the first
MEMS chip 13 side, the decrease of the vibration amplitude with respect to the distance from the
04-05-2019
25
sound source is rapid. And the distance attenuation is increased.
[0081]
In other words, in the case of using the first MEMS chip 13 side, the microphone unit 1 is far
from the microphone unit 1 in the far distance sound source where the sound source is located
as compared with the case of using the second MEMS chip 15 side. Excellent in the ability to pick
up sound. On the other hand, when the second MEMS chip 15 side is used, the microphone unit
1 efficiently picks up the target sound generated in the vicinity of the microphone unit 1 and
indicates the background noise (a sound that is not the target sound) Excellent in the function of
removing
[0082]
The latter will be further described. The sound pressure of the target sound generated in the
vicinity of the microphone unit 1 is largely attenuated between the first sound hole 23 and the
second sound hole 25 and transmitted to the upper surface of the second diaphragm 154 There
is a large difference between the pressure and the sound pressure transmitted to the lower
surface of the second diaphragm 152. On the other hand, background noise hardly attenuates
between the first sound hole 23 and the second sound hole 25 in order to position the sound
source farther than the target sound, and the second vibration is generated. The sound pressure
difference between the sound pressure transmitted to the upper surface of the plate 154 and the
sound pressure transmitted to the lower surface of the second diaphragm 154 is very small.
Here, it is assumed that the distance from the sound source to the first sound hole 23 and the
distance from the sound source to the second sound hole 25 are different.
[0083]
Since the sound pressure difference of the background noise received by the second diaphragm
154 is very small, the sound pressure of the background noise is substantially canceled by the
second diaphragm 154. On the other hand, since the sound pressure difference of the target
sound received by the second diaphragm 154 is large, the sound pressure of the target sound is
not canceled by the second diaphragm 154. Therefore, the signal obtained by the vibration of the
second diaphragm 154 can be regarded as the signal of the target sound from which background
noise has been removed. Therefore, when the second MEMS chip 15 side is used, the microphone
04-05-2019
26
unit 1 is excellent in the function of removing background noise from the target sound generated
in the vicinity and collecting the target sound.
[0084]
As described above, in the microphone unit 1, the signal extracted from the first MEMS chip 13
and the signal extracted from the second MEMS chip 15 are separately processed (amplified) and
separately output to the outside. It is designed to output. For this reason, in the voice input
device to which this microphone unit 1 is applied, the signals output from any one of the MEMS
chips 13 and 15 are appropriately selected according to the purpose of either the close sound
source collection or the distant sound source collection. By selecting and using it, it is possible to
support multiple functions of the voice input device.
[0085]
As a specific example, a case where the microphone unit 1 is applied to a mobile phone (an
example of a voice input device) will be described. When talking on a mobile phone, the user
usually speaks with the mouth close to the microphone unit 1. For this reason, as a function at
the time of a telephone call of a mobile telephone, it is desirable that background noise be
removed and only a target sound can be collected. For this reason, for example, during a call, of
the signals output from the microhonin unit 1, the signal extracted from the second MEMS chip
15 may be used.
[0086]
As described above, recent mobile phones have a hands-free function and a movie recording
function. When used in such a mode, it is necessary to be able to pick up a sound far from the
microphone unit 1. For this purpose, for example, in the case of using the hands-free function or
movie recording function of the portable telephone, it is possible to use the signal extracted from
the first MEMS chip 13 among the signals output from the microhonin unit 1. Just do it. Here,
since a distant sound has a relatively low input sound pressure with respect to a close sound, a
high SNR is required.
[0087]
04-05-2019
27
As described above, the microphone unit 1 according to the present embodiment has a function
(near-field sound pickup function) as a differential microphone with bi-directional characteristics
excellent in far-field noise suppression performance and a sound source located at a distance
from the microphone unit 1 It is configured to have a function (far-field sound pickup function)
as an omnidirectional microphone capable of picking up a certain distance sound. For this
reason, according to the microphone unit 1 of this embodiment, it is easy to cope with
multifunctionalization of the voice input device to which the microphone unit is applied.
[0088]
In the microphone unit 1 of the present embodiment, the sound path to the first diaphragm 134
and the sound path to the second diaphragm 154 are partially shared, and the space of the
housing is shared. We are trying to miniaturize the package. Specifically, in the conventional
microphone Z as shown in FIG. 26 having the function of only a close-talking microphone, the
first sound hole Z3 and the second sound hole Z4 (both are formed on the lower surface side of
the mounting portion Z1 A fixed distance (for example, 5 mm) is physically required. For this
reason, a useless area which is not acoustically used in the lid portion Z2 occurs at the upper
portion of the first sound hole Z3. In the microphone unit 1 of the present embodiment, the first
accommodation space 121 is provided in this area, and the first MEMS chip 13 and the first ASIC
14 are disposed and effectively used to realize miniaturization of the microphone unit. doing. In
FIG. 26, reference symbol Z5 denotes a MEMS chip, and reference symbol Z6 denotes an ASIC.
[0089]
Further, in order to combine the two functions described above, the microphone unit 1 of the
present embodiment does not need to separately mount two microphone units having different
functions, as in the related art. Therefore, when manufacturing a multi-functional voice input
device, it is possible to reduce the number of members used and to reduce the mounting area for
mounting the microphone (suppress the enlargement of the voice input device).
[0090]
Further, in the microphone unit 1 of the present embodiment, since the closed space (back
04-05-2019
28
chamber) facing the upper surface of the first diaphragm 134 is obtained by using the recess 12
b formed in the lid 12, It is easy to increase the volume of the back room. This contributes to the
improvement of the SNR of the microphone.
[0091]
FIG. 12 is a graph showing the relationship between back chamber volume and microphone
sensitivity in the microphone. FIG. 12 shows that the microphone sensitivity improves as the
back chamber volume increases, and the sensitivity drops sharply as the back chamber volume
decreases. When dealing with a small microphone, it is difficult to secure a sufficient volume of
the back chamber, and it is often designed in a region where the sensitivity change with respect
to the back chamber volume is large. In such a case, it can be seen that the microphone
sensitivity is significantly improved by increasing the volume of the back chamber.
[0092]
Moreover, FIG. 13 is a graph for demonstrating that the relationship between microphone
sensitivity and a frequency changes with back chamber volumes. It can be understood from FIG.
13 that the microphone sensitivity is improved as the back chamber volume is increased, and
that the microphone sensitivity is attenuated in the low frequency range when the back chamber
volume is small. The above characteristics are determined by the balance between the spring
coefficient of the diaphragm and the spring coefficient of the air in the housing space. As
described above, in the microphone unit 1 of the first embodiment, it is easy to secure a large
volume of the back chamber facing the upper surface of the first diaphragm 134, and it is easy to
improve the microphone sensitivity. Therefore, when using the first MEMS chip 13 to pick up a
far-distance sound having a sound source located at a distance from the microphone unit 1, high
SNR can be achieved for the signal output from the microphone unit 1.
[0093]
Further, in the microphone unit 1 of the present embodiment, the lid 12 is made of resin such as
LCP and PPS, glass epoxy such as FR-4, and ceramic, in addition to conductive materials such as
aluminum, brass, iron and copper. It is also possible to use a metal material having a metal
material. By connecting the metal part to the mounting part 11 or the GND part of the user
substrate, the effect of the electromagnetic shield can be obtained. In addition, even if it is an
04-05-2019
29
insulating material such as a resin material, a glass epoxy material, and a ceramic material, it is
possible to obtain the same electromagnetic shielding effect as metal by applying a conductive
plating treatment to the surface. Specifically, conductive plating (metal plating) is applied to the
outer wall surfaces of the upper and side portions of the lid portion 12 and connected to the
mounting portion 11 or the GND portion of the user substrate to obtain an electromagnetic
shielding effect. It is possible.
[0094]
In order to make the microphone unit thinner, it is necessary to reduce the thickness of each
component, but when the resin material and glass epoxy material have a thickness of 0.2 mm or
less, they become very weak in strength, and the wall has an external sound The pressure causes
the outer wall to vibrate and adversely affects the microphone's original sound collecting
function. By forming a conductive metal film on the outer wall surface of the lid 12, the
mechanical strength of the lid 12 can be enhanced to enhance the resistance to external stress,
and by suppressing unnecessary vibration, the microphone can be A sound collecting function
can be exhibited.
[0095]
Here, a modified example of the microphone unit 1 of the first embodiment is shown.
[0096]
FIG. 14 is a cross-sectional view for explaining a first modification of the microphone unit of the
first embodiment.
FIG. 14 is a cross-sectional view similar to FIG. In the first modified example of the microphone
unit 1, the coating layer 43 is formed on the inner wall surface of the sound path provided in the
mounting portion 11 constituting the housing 10 and the inner wall of the lid portion 12.
[0097]
For example, when a substrate material such as FR4 is used as the material of the mounting
04-05-2019
30
portion 11 and the lid portion 12, fibrous dust is likely to be generated from the cut surface
(processed surface). For example, when such dust penetrates into the space between the
electrodes from the through holes 132a and 152a (see FIG. 6) provided in the fixed electrodes
132 and 152 of the MEME chips 13 and 15, the fixed electrodes 132 and 152 and the
diaphragm 134, The gap between the MEMS chip 13 and the chip 154 may be clogged, causing a
problem that the MEMS chips 13 and 15 may not function properly. In this respect, when the
coating layer 43 is applied as in the first modified example, the generation of minute dust can be
prevented and the above-mentioned problems can be solved.
[0098]
The coating layer 43 may be obtained by using a plating technique which is often used in
substrate production, and more specifically, the coating layer 43 may be obtained by, for
example, Cu plating or Cu + Ni plating. Also, the coating layer 43 may be obtained by coating an
exposure-developable resist material. The coating layer 43 may be composed of a plurality of
layers, and may be obtained, for example, by further coating the resist material after Cu plating.
In the microphone unit 1, a sealing electrode pad 20 e is formed around the first sound hole 23
and the second sound hole 25 (see FIG. 1 (b) or the like). In this configuration, when the
microphone unit 1 is mounted on a voice input device such as a mobile phone, solder flows into
the first sound hole 23 and the second sound hole 25 to narrow or close the sound path. There is
a possibility of In order to prevent this, it is effective to code a material that repels solder such as
a resist on Cu plating to prevent the penetration of the solder.
[0099]
In the configuration of the first modification shown in FIG. 14, the coating layer 43 (Cu plating as
a specific example) provided on the mounting portion 11 and the lid portion 12 may be
connected to a fixed potential (GND or power supply) . The coating layer 43 provided on the
mounting portion 11 can improve resistance to an external electromagnetic field from below the
MEMS chips 13 and 15. Further, the coating layer 43 provided on the lid 12 can improve
resistance to an external electromagnetic field coming from above the MEMS chips 13 and 15. As
a result, it becomes possible to electromagnetically shield the MEMS chips 13 and 15 from both
upper and lower sides, and it is possible to greatly improve the resistance from the external
electromagnetic field (prevent the mixing of external electromagnetic field noise) .
[0100]
04-05-2019
31
Further, in the first modification, the coating layer 43 is provided on the mounting portion 11
and the lid portion 12, but the configuration is not limited to this. For example, only the
mounting portion 11 is provided (ie, a sound path provided in the mounting portion 11 The
coating layer 43 may be provided only on the wall surface of
[0101]
FIG. 15 is a perspective view for explaining a second modification of the microphone unit of the
first embodiment.
In the second modified example of the microphone unit 1, a shield cover 44 is provided so as to
cover the case 10 (consisting of the mounting portion 11 and the lid portion 12) that constitutes
the microphone unit 1.
[0102]
The shield cover 44 made of a conductive material (metal) is provided in a substantially box
shape, is covered from the lid 12 side so as to cover the housing 10, and is connected to a fixed
potential (GND). The shield cover 44 is fixed to the housing 10 by caulking, and the shield cover
44 is provided with a caulking area 44 a. By thus covering the case 10 with the shield cover 44,
it is possible to improve the resistance to the external electromagnetic field (prevent the mixing
of the external electromagnetic field noise). The thickness of the metal is suitably about 50 to
200 μm. In this modification, since the entire structure of the microphone housing is covered
with a metal plate, a high electromagnetic shielding effect can be obtained.
[0103]
FIG. 16 is a block diagram for explaining a third modification of the microphone unit of the first
embodiment. In the third modification of the microphone unit 1, the first ASIC 14 accommodated
in the first accommodation space 121 (see FIG. 3) and the second ASIC 16 accommodated in the
second accommodation space 122 (see FIG. 3) And the number of ASICs is taken as one (with
space reduction effect).
04-05-2019
32
[0104]
An example of the arrangement of the MEMS chip and the ASIC on the mounting portion 11 at
this time is shown in FIG. FIG. 17 is a view for explaining the configuration of a third modification
of the microphone unit of the first embodiment, and is a schematic plan view when the mounting
portion provided in the microphone unit is viewed from above. In FIG. 17, the housing spaces
121 and 122 are also shown in order to facilitate understanding. The first MEMS chip 13 and the
ASIC 45 are disposed in the first accommodation space 121, and the second MEMS chip 15 is
disposed in the second accommodation space 122. In this configuration, since the ASIC 45 and
the MEMS chip 15 can not be directly connected by a wire, the wire extracted from the second
MEMS chip 15 is connected to the electrode terminal 19 d on the mounting portion 11 and
extracted from the ASIC 45 A wire may be connected to the electrode terminal 18d on the
mounting portion 11, and the electrode terminal 18d and the electrode terminal 19d may be
connected by the wiring pattern PW (shown by a dotted line) formed in the mounting portion 11.
The ASIC 45 may be disposed in the second accommodation space 122.
[0105]
Also, another arrangement example of the MEMS chip and the ASIC is shown in FIG. FIG. 18 is a
view for explaining another configuration of the third modified example of the microphone unit
of the first embodiment, and is a schematic plan view when the mounting portion provided in the
microphone unit is viewed from above. In FIG. 18, similarly to FIG. 17, the accommodation
spaces 121 and 122 are also shown. The first MEMS chip 13 and the ASIC 45 are disposed in the
first accommodation space 121, and the second MEMS chip 15 is disposed in the second
accommodation space 122. In this configuration, since the electrical connection between the
ASIC 45 and the MEMS chip 15 can not be directly connected by wires, all of the first MEMS chip
13, the second MEMS chip 15, and the ASIC 14 are flipped to the mounting portion 11. It is in
the form of chip mounting. An electrode pad is provided on the back surface of the chip, and an
electrode is provided on the side of the mounting portion 11 so as to face the electrode pad of
the chip, and both are joined by solder or the like. The mounting portion 11 is provided with a
wiring pattern PW (shown by a dotted line) for connecting these electrodes.
[0106]
The ASIC 45 includes a charge pump circuit 451 that applies a bias voltage to the first MEMS
chip 13 and the second MEMS chip 15. The charge pump circuit 451 boosts the power supply
04-05-2019
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voltage VDD (for example, about 1.5 to 3 V) (for example, about 6 to 10 V) and applies a bias
voltage to the first MEMS chip 13 and the second MEMS chip 15. The ASIC 45 further includes a
first amplifier circuit 452 that detects a change in capacitance in the first MEMS chip 13 and a
second amplifier circuit 453 that detects a change in capacitance in the second MEMS chip 15.
And. The electric signals amplified by the first amplifier circuit 452 and the second amplifier
circuit 453 are output from the ASIC 45 independently.
[0107]
In the microphone unit 1 of the third modified example, the electric signal extracted based on the
change in capacitance of the first MEMS chip 13 is amplified by the first amplifier circuit 452,
and finally the first Is output from the output electrode pad 20b. Further, the electric signal
extracted based on the change in capacitance of the second MEMS chip 15 is amplified by the
second amplifier circuit 452, and finally output from the second output electrode pad 20c. Ru.
[0108]
Although a common bias voltage is applied to the first MEMS chip 13 and the second MEMS chip
15 here, the present invention is not limited to this configuration. For example, two charge pump
circuits may be provided and bias voltages may be separately applied to the first MEMS chip 13
and the second MEMS chip 15. This configuration can reduce the possibility of crosstalk between
the first MEMS chip 13 and the second MEMS chip 15.
[0109]
Also, the amplifier gains of the two amplifier circuits 452 and 453 may be set to different gains.
Here, it is preferable to make the amplifier gain of the second amplifier circuit 453 larger than
the amplifier gain of the first amplifier circuit 452.
[0110]
FIG. 19 is a block diagram for explaining a fourth modification of the microphone unit of the first
embodiment. As in the case of the third modification, the number of ASICs is one, as in the case
04-05-2019
34
of the third modification. However, it differs from the third modification in the following point.
That is, in the microphone unit 1 of the fourth modification, a switch electrode pad 20g for
inputting a switch signal from the outside (a voice input device on which the microphone unit 1
is mounted) is provided (a housing as an external connection electrode pad). It differs from the
configuration of the third modification in that a switching circuit 454 provided in the ASIC 45 is
operated by a switch signal provided outside the body 10) and the switch electrode pad 20g.
Moreover, it differs from the third modification also in that one output electrode pad for output
to the outside is provided (output electrode pad 20f).
[0111]
As shown in FIG. 19, the switching circuit 454 switches which of the signal output from the first
amplifier circuit 452 and the signal output from the second amplifier circuit 453 is to be output
to the outside. It is a circuit. That is, in the microphone unit 1 of the fourth modification, only one
of the signal extracted from the first MEMS chip 14 and the signal extracted from the second
MEMS chip 15 is an output electrode pad It is output to the outside through 20f. When
configured as in the fourth modified example, it is not necessary to perform switching operation
of which one of the two input audio signals is used on the audio input device side on which the
microphone unit 1 is mounted.
[0112]
The switching operation of the switching circuit 454 by the switch signal may be configured to
use, for example, H (high level) or L (low level) of the signal. Further, in the configuration of the
fourth modification, a common bias voltage is applied to the first MEMS chip 13 and the second
MEMS chip 15, but the present invention is not limited to this, and other configurations are
possible. Good. That is, for example, it is possible to switch which of the first MEMS chip 13 and
the second MEMS chip 15 is electrically connected to the charge pump circuit 451 using a switch
signal and a switching circuit. Good. In this way, the possibility of crosstalk between the first
MEMS chip 13 and the second MEMS chip 15 can be reduced.
[0113]
FIG. 20 is a block diagram for explaining a fifth modification of the microphone unit of the first
embodiment. Similar to the fourth modification, the microphone unit 1 of the fifth modification is
04-05-2019
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a switch electrode pad 20g for inputting a switch signal from the outside and a switch provided
on the ASIC 45 and provided via the switch electrode pad 20g. And a switching circuit 454 that
performs switching operation according to a signal. However, unlike the case of the fourth
modified example, two output electrode pads (a first output electrode pad 20b and a second
output electrode pad 20c) for output to the outside are provided.
[0114]
In the switching circuit 454, which of the two output electrode pads 20 b and 20 c the signal
output from the first amplifier circuit 452 and the signal output from the second amplifier circuit
453 are output from Is configured to be switched.
[0115]
That is, when the switching circuit 454 is set to the first mode by the switch signal input from
the switch electrode pad 20e, a signal corresponding to the first MEMS chip 13 from the first
output electrode pad 20b. Is outputted, and a signal corresponding to the second MEMS chip 15
is outputted from the second output electrode pad 20c.
On the other hand, when the switching circuit 454 is set to the second mode by the switch signal,
the first output electrode pad 20b outputs a signal corresponding to the second MEMS chip 15,
and the second output A signal corresponding to the first MEMS chip 13 is output from the
electrode pad 20c.
[0116]
If the manufacturer of the microphone unit and the voice input device is different, it is assumed
that the following types of persons exist as the manufacturer of the voice input device. (A) A
person who wants to output both the signal corresponding to the first MEMS chip 13 and the
signal corresponding to the second MEMS chip 15 from the microphone unit. (B) A person who
wants to output one of the signal corresponding to the first MEMS chip 13 and the signal
corresponding to the second MEMS chip 15 from the microphone unit by switching with the
switch signal.
[0117]
04-05-2019
36
In this point, according to the microphone unit 1 of the fifth modified example, it is convenient
because it can correspond to any one of the above (A) and (B).
[0118]
A sixth modified example of the microphone unit 1 of the first embodiment will be described.
In the sixth modification, the sealing electrode pad 20 e is used, for example, as a GND electrode
pad or a power electrode pad for inputting a power supply voltage (VDD). Specific examples
include a configuration in which both of the two sealing electrode pads 20e are used as GND
electrode pads, and a configuration in which one is used as a GND electrode pad and the other is
used as a power supply electrode pad.
[0119]
With this configuration, it is possible to reduce the number of external connection electrode pads
20 formed on the outer surface (the lower surface 11 b of the mounting portion 11) of the
housing 10. When the number of the external connection electrode pads 20 is reduced, the size
of each electrode pad provided on the outer surface of the housing 10 can be increased, so
bonding of each electrode pad to the mounting substrate of the voice input device (mobile phone
etc.) The strength can be increased. Further, in the configuration in which both of the two sealing
electrode pads 20 e are used as the GND electrode pads, the sealing electrode pads 20 e provided
around the sound holes 23, 25 are continuously formed to the inside of the sound holes 23, 25.
It is also possible to strengthen the GND by applying through-hole plating to the inner walls of
the sound holes 23 and 25 to improve the resistance to the external electromagnetic field
(prevent the mixing of external electromagnetic field noise).
[0120]
The configuration of the sixth modification is advantageous over the configuration in which the
shield cover 44 as shown in the second modification is placed on the housing 10 (see FIG. 15).
That is, when the housing 10 is small, it is difficult to secure the caulking area 44a. However, in
the configuration of the sixth modification, in order to reduce the number of the external
connection electrode pads 20, securing of the caulking area 44a is facilitated.
04-05-2019
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[0121]
2. Microphone Unit of Second Embodiment Next, a microphone unit of the second embodiment
will be described. FIG. 21 is a schematic cross-sectional view showing the configuration of the
microphone unit of the second embodiment. The cutting position of FIG. 21 is the same position
as that of FIG. The same parts as those of the microphone unit 1 of the first embodiment will be
described with the same reference numerals.
[0122]
Similarly to the microphone unit 1 of the first embodiment, the microphone unit 2 of the second
embodiment also includes the first MEMS chip 13 and the first MEMS chip 13 in the housing 50
configured by the mounting portion 51 and the lid 52. The ASIC 14, the second MEMS chip 15,
and the second ASIC 16 are accommodated. The configurations of the MEMS chips 13 and 15
and the ASICs 14 and 16 and their positions and connection relationships are the same as those
of the microphone unit 1 according to the first embodiment, and thus the detailed description
thereof is omitted.
[0123]
The mounting unit 51 is formed, for example, by bonding a plurality of flat plates together in the
same manner as the microphone unit 1 of the first embodiment.
[0124]
A through hole is formed through the mounting surface (upper surface) 51a on which the MEMS
chips 13, 15 and ASICs 14 and 16 are mounted and the back surface (lower surface) 51b on one
end of the mounting portion 51 in the longitudinal direction (rightward in FIG. 21). 61 (generally
rectangular in plan view) are formed.
The through hole 61 is a sound hole for inputting a sound into the inside of the housing 10 and
will be expressed as a first sound hole 61 below. The shape and the position of the first sound
hole 61 are the same as those of the second sound hole 25 of the first embodiment.
04-05-2019
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[0125]
Further, the mounting portion 51 is provided with an opening 62 (generally circular in plan view)
covered by the second MEMS chip 15 substantially at the center of the mounting surface 51a
(more precisely, slightly right from the center in the longitudinal direction). There is. Further, on
the back surface 51b of the mounting surface 51a of the mounting portion 51, an opening 63
having a substantially rectangular shape in plan view (hereinafter referred to as a second sound
hole 63) to be a second sound hole is formed. In the mounting portion 51, a hollow space 64
(generally T-shaped in plan view) communicating the opening 62 and the second sound hole 63
is formed. The shapes of the opening 62, the second sound hole 63, and the hollow space 64 are
respectively the second opening 22, the first sound hole 23, and the hollow space 24 of the
microphone unit 1 of the first embodiment. Is the same as
[0126]
In the mounting portion 51, the same wirings and electrode pads (including the sealing electrode
pad 20e) as those of the mounting portion 11 of the microphone unit 1 of the first embodiment
are formed.
[0127]
The outer shape of the lid 52 is provided in a substantially rectangular parallelepiped shape, and
the lengths of the longitudinal direction (left and right direction in FIG. 21) and the latitudinal
direction (direction perpendicular to the sheet of FIG. 21) When the housing 50 is configured to
cover the housing 51, the side surface portion of the housing 50 is adjusted to be substantially
flush.
Unlike the lid 12 of the microphone unit 1 according to the first embodiment, no partition is
provided inside, and the lid 52 has only one recess. For this reason, as shown in FIG. 21, by
covering the mounting portion 51 with the lid 52, one accommodation space 521 for
accommodating the two MEMS chips 13 and 15 and the two ASICs 14 and 16 is obtained.
[0128]
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39
In the microphone unit 2 of the second embodiment configured as described above, as shown in
FIG. 21, the sound wave input from the first sound hole 61 passes through the accommodation
space 521 and the sound wave of the first diaphragm 134. While reaching one surface (upper
surface), it reaches one surface (upper surface) of the second diaphragm 154. In addition, the
sound wave input from the second sound hole 63 reaches the other surface (lower surface) of the
second diaphragm 154 through the hollow space 64 and the opening 62.
[0129]
That is, in the microphone unit 2, the sound wave input from the first sound hole 61 is
transmitted to one surface of the first diaphragm 134 and is also transmitted to one surface of
the second diaphragm 154. The sound path 71 is formed by using the first sound hole 61 and
the accommodation space 521. Further, the second sound path 72 for transmitting the sound
wave input from the second sound hole 63 to the other surface of the second diaphragm 154
includes the second sound hole 63, the hollow space 64, and the opening portion. And 62. FIG. A
sound wave is not input from the outside on the other surface of the first diaphragm 134, and a
sealed space (back chamber) free of acoustic leaks is formed.
[0130]
When a sound is generated outside the microphone unit 2, the sound wave input from the first
sound hole 61 reaches the upper surface of the first diaphragm 134 by the first sound path 71,
and the first diaphragm 134 vibrates. Do. As a result, a change in capacitance occurs in the first
MEMS chip 13. The electric signal extracted based on the change of the capacitance of the first
MEMS chip 13 is present on the first ASIC 14 (not shown in FIG. ) And finally output from the
first output electrode pad 20b.
[0131]
When sound is generated outside the microphone unit 2, the sound wave input from the first
sound hole 61 reaches the upper surface of the second diaphragm 154 by the first sound path
71, and the second sound hole The sound wave input from 63 reaches the lower surface of the
second diaphragm 154 by the second sound path 72. For this reason, the second diaphragm 154
vibrates due to the sound pressure difference between the sound pressure applied to the upper
04-05-2019
40
surface and the sound pressure applied to the lower surface. As a result, a change in capacitance
occurs in the second MEMS chip 15. The electrical signal extracted based on the change in
capacitance of the second MEMS chip 15 is amplified by the amplifier circuit 162 of the second
ASIC 16 and finally output from the second output electrode pad 20c. Ru.
[0132]
Like the microphone unit 1 of the first embodiment, the microphone unit 2 of the second
embodiment has a function as a differential microphone of two directional characteristics
excellent in far-field noise suppression performance (a signal extracted from the second MEMS
chip 15 And the function as an omnidirectional microphone capable of picking up far-distance
sound (obtained by using a signal extracted from the first MEMS chip 13). It has become. For this
reason, the microphone unit 2 of the second embodiment also easily copes with
multifunctionalization of the voice input device to which the microphone unit is applied.
[0133]
Also, in order to combine the two functions described above, the microphone unit 2 according to
the second embodiment needs to separately mount two microphone units having different
functions so as to ensure these two functions as in the prior art. There is no Therefore, when
manufacturing a multi-functional voice input device, it is possible to reduce the number of
members used and to reduce the mounting area for mounting the microphone (suppress the
enlargement of the voice input device).
[0134]
In the microphone unit 2 of the second embodiment, the modified examples 1 to 6 shown in the
first embodiment can be appropriately applied.
[0135]
(Voice Input Device to which Microphone Unit of the Present Invention is Applied) Next, a
configuration example of a voice input device to which the microphone unit of the present
invention is applied will be described.
04-05-2019
41
Here, the case where the voice input device is a mobile phone will be described as an example.
Moreover, the case where a microphone unit is the microphone unit 1 of 1st Embodiment is
demonstrated to an example.
[0136]
FIG. 22 is a plan view showing a schematic configuration of an embodiment of a mobile phone to
which the microphone unit of the first embodiment is applied. FIG. 23 is a schematic crosssectional view at a position B-B in FIG. As shown in FIG. 22, two sound holes 811 and 812 are
provided on the lower side of the casing 81 of the mobile phone 8, and the user's voice is casing
81 via the two sound holes 811 and 812. It is designed to be input to the microphone unit 1
disposed inside.
[0137]
As shown in FIG. 23, a mounting substrate 82 on which the microphone unit 1 is mounted is
provided in a housing 81 of the mobile phone 8. The mounting substrate 82 is provided with a
plurality of electrode pads electrically connected to the plurality of external connection electrode
pads 20 (including the sealing electrode pad 20 e) included in the microphone unit 1. For
example, it is fixed to the mounting substrate 82 in a state of being electrically connected to the
mounting substrate 82 using solder or the like. Then, the power supply voltage is applied to the
microphone unit 1, and the electric signal output from the microphone unit 1 is sent to an audio
signal processing unit (not shown) provided on the mounting substrate 82.
[0138]
The mounting substrate 82 is provided with through holes 821 and 822 at positions
corresponding to the two sound holes 811 and 812 provided in the casing 81 of the mobile
phone 8. In addition, a gasket 83 is disposed between the housing 81 of the mobile phone 8 and
the mounting substrate 82 so as to maintain airtightness without causing an acoustic leak. The
gasket 83 is provided with through holes 831 and 832 at positions corresponding to the two
sound holes 811 and 812 provided in the casing 81 of the mobile phone 8.
04-05-2019
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[0139]
The microphone unit 1 is disposed such that the first sound hole 23 overlaps the through hole
821 provided in the mounting substrate 82 and the second sound hole 25 overlaps the through
hole 822 provided in the mounting substrate 82. When the microphone unit 1 is mounted on the
mounting substrate 82, the sealing electrode pads 20e disposed around each of the first sound
hole 23 and the second sound hole 25 are also soldered to the mounting substrate 82. . For this
reason, airtightness is maintained between the microphone unit 1 and the mounting substrate 82
without causing acoustic leak.
[0140]
Since the mobile phone 8 is configured as described above, the voice generated outside the
housing 81 of the mobile phone 8 is input from the sound hole 811 of the mobile phone 8 and is
passed through the through hole 831 (provided in the gasket 83). , And reaches the first sound
hole 23 of the microphone unit 1 through the through hole 821 (provided in the mounting
substrate 82), and further passes through the first sound path 41 to form the first MEMS chip 13
of the first. It reaches one surface (upper surface in FIG. 23) of the diaphragm 134 and reaches
one surface (upper surface in FIG. 23) of the second MEMS chip 15. Further, the sound generated
outside the casing 81 of the mobile phone 8 is input from the sound hole 812 of the mobile
phone 8, and the through hole 832 (provided in the gasket 83) and the through hole 822
(provided in the mounting substrate 82). Reaches the second sound hole 25 of the microphone
unit 1 through the second sound path 42, and the other surface (the lower surface in FIG. 23) of
the second diaphragm 154 of the second MEMS chip 15. To reach).
[0141]
As shown in FIG. 22, the cellular phone 8 of the present embodiment is provided with a mode
switching button 84 for switching between the close talk mode and the handsfree mode (a movie
recording mode may be included). In the audio signal processing unit (not shown) provided on
the mounting substrate 82, when the close talk mode is selected by the mode switching button
84, the second MEMS chip among the signals output from the microphone unit 1 Perform
processing using a signal corresponding to 15. In addition, when the handsfree mode (or movie
recording mode) is selected by the mode switching button 84, processing using the signal
corresponding to the first MEMS chip 13 among the signals output from the microphone unit 1
is performed. Do. Thereby, preferable signal processing can be performed in each mode.
04-05-2019
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[0142]
By the way, the present applicant has previously made a patent application (Japanese Patent
Application No. 2009-293989) disclosing another form of a microphone unit capable of
switching between the close talk mode and the hands free mode, for example. FIG. 24 is a
schematic cross-sectional view of a mobile phone in which the microphone unit disclosed in the
prior application is mounted. The microphone unit X disclosed in the previous application is not
the mounting portion X1 on which the MEMS chip X3, X4 or the like is mounted, but a sound
hole (first sound hole X5, second sound) in the lid portion X2 which is put on the mounting
portion X1. It differs from the microphone unit of the present application in that a hole X6) is
provided.
[0143]
In the microphone unit X disclosed in the previous application, using the first sound hole X5
formed in the lid X2, and the accommodation space X7 formed by covering the lid X2 on the
upper surface of the mounting portion X1. While transmitting the sound wave input from the
first sound hole X5 to one surface (upper surface in FIG. 24) of the first diaphragm X31, one
surface (upper surface in FIG. 24) of the second diaphragm X41 A first sound path P1 to be
transmitted to the vehicle is formed. In addition, the second sound hole X6 formed in the lid
portion X2, and the first opening X11, the hollow space X12, and the second opening X13
formed in the mounting portion X1 are used as the second sound hole. The second sound path
P2 is formed to transmit the sound wave input from the sound hole X6 of the second
embodiment to the other surface (the lower surface in FIG. 24) of the second diaphragm X41. A
sound wave is not input from the outside on the other surface (lower surface) of the first
diaphragm X31, and a sealed space (back chamber) free of acoustic leaks is formed.
[0144]
The microphone unit X disclosed in the prior application is mounted on a mounting substrate Y2
provided in a case Y1 of a mobile telephone Y as shown in FIG. The mounting substrate Y2 is
provided with a plurality of electrode pads electrically connected to the plurality of external
connection electrode pads X8 provided in the microphone unit X, and the microphone unit X is
mounted on the mounting substrate Y2 using, for example, solder or the like. And electrically
04-05-2019
44
connected. Then, the power supply voltage is applied to the microphone unit X, and the electrical
signal output from the microphone unit X is sent to an audio signal processing unit (not shown)
provided on the mounting substrate Y2.
[0145]
In the microphone unit X, the first sound hole X5 overlaps the sound hole Y11 formed in the
case Y1 of the mobile phone Y, and the second sound hole X6 is formed in the case Y1 of the
mobile phone Y1. It is arranged to overlap the. A gasket G is disposed between the housing Y1 of
the mobile phone Y and the microphone unit X so as to maintain airtightness without causing
acoustic leak. In the gasket G, a through hole G1 is formed so as to overlap with the sound hole
Y11 of the case Y1 of the mobile phone Y, and a through hole G2 is formed so as to overlap with
the sound hole Y12 of the case Y1 of the mobile phone Y .
[0146]
The advantages of the microphone units 1 and 2 of the present embodiment (hereinafter,
referred to as lower hole products) with respect to the microphone unit X (hereinafter, referred
to as upper hole products) configured as described above will be described.
[0147]
The lower hole product can narrow the gap d (see FIGS. 23 and 24) between the housing of the
mobile phone and the mounting substrate as compared with the upper hole product, so it is easy
to realize thinning of the mobile phone.
Moreover, in the case of the upper hole product, when the microphone unit X is attached to the
mounting substrate Y2 with inclination, the airtightness may not be sufficiently secured by the
gasket G, but in the lower hole product Problem does not occur.
[0148]
Further, in the case of the upper hole product, when the microphone unit X is mounted on the
mounting substrate Y2, an assembly error may occur in the in-plane direction or the thickness
04-05-2019
45
direction of the mounting substrate Y2. In consideration of the occurrence of the error in the inplane direction, in the upper hole product, for example, it is necessary to increase the opening
area of the through holes G1 and G2 provided in the gasket G, which is disadvantageous. If the
opening area of the through holes G1 and G2 of the gasket G is too large, the contact area
between the gasket G and the microphone unit X can not be sufficiently ensured, and the
airtightness may be insufficiently maintained. In addition, even when the error in the thickness
direction occurs, the airtightness may not be sufficiently secured, and the thickness of the gasket
G needs to be designed to be thick. In the case of the lower hole product, the design margin of
the gasket 83 is increased because the gasket 83 can be designed without concern for the
assembly error of the microphone units 1 and 2 as described above.
[0149]
Furthermore, in the case of the upper-hole product, when it is mounted on the cellular phone Y,
the MEMS chip X3 and X4 are stressed because the microphone unit X is configured to be held
down by the elastic gasket G. The sensitivity of X4 may change. On the other hand, in the lower
hole product, since the mounting substrate 82 with high rigidity is interposed between the gasket
83 and the microphone units 1 and 2, the stress as described above is not easily applied to the
MEMS chips 13 and 15.
[0150]
(Others) The microphone units 1 and 2 and the voice input device 8 according to the
embodiments described above are merely examples of the present invention, and the scope of
application of the present invention is not limited to the embodiments described above. . That is,
various changes may be made to the embodiment described above without departing from the
object of the present invention.
[0151]
For example, although the ASICs 14 and 16 (electric circuit units) are included in the microphone
units 1 and 2 in the embodiment described above, the electric circuit units may be disposed
outside the microphone units. Also, in the embodiment described above, the MEMS chips 13 and
15 and the ASICs 14 and 16 are configured as separate chips, but the integrated circuit mounted
on the ASICs 14 and 16 is on the silicon substrate forming the MEMS chips 13 and 15 It may be
04-05-2019
46
formed monolithically.
[0152]
In the embodiment described above, an example is shown in which the acoustic sealing portion
around the first sound hole 23 and the second sound hole 24 doubles as an electrode pad and is
realized by soldering. By attaching a thermoplastic adhesive sheet around the first sound hole 23
and the second sound hole 24, the structure may be such that seal bonding is performed
simultaneously with solder reflow.
[0153]
Further, in the embodiment described above, the first vibrating portion and the second vibrating
portion of the present invention are configured as the MEMS chips 13 and 15 formed using
semiconductor manufacturing technology, but this configuration It is not the meaning limited to
For example, the first vibrating unit and / or the second vibrating unit may be a condenser
microphone or the like using an electret film.
[0154]
Further, in the above embodiment, a so-called condenser type microphone is adopted as the
configuration of the first vibrating portion and the second vibrating portion of the present
invention. However, the present invention can also be applied to a microphone unit adopting a
configuration other than a condenser microphone. For example, the present invention can be
applied to a microphone unit in which an electrodynamic (dynamic), electromagnetic (magnetic),
piezoelectric or the like microphone is adopted.
[0155]
In addition, as a modification of the voice input device (mobile phone 8) on which the
microphone unit 1 of the present embodiment described above is mounted, the signal
corresponding to the first MEMS chip 13 and the second MEMS chip 15 are supported. The
audio signal processing unit 85 (see FIG. 25) may perform addition, subtraction, or filter
processing on the received signal.
04-05-2019
47
[0156]
By performing such processing, it is possible to control the directivity characteristics of the voice
input device (for example, a mobile phone) and to pick up voice of a specific area.
For example, arbitrary directivity characteristics such as omnidirectionality, hypercardioid,
supercardioid, unidirectionality can be realized.
[0157]
Although the process of controlling the directivity is performed by the voice input device here,
the ASIC of the microphone unit may be one chip, and the ASIC may be provided with a
processing unit capable of performing the process of controlling the directivity. .
[0158]
Besides, the shape of the microphone unit is not intended to be limited to the shape of the
present embodiment, and of course can be changed to various shapes.
[0159]
The microphone unit of the present invention can be suitably used, for example, in a mobile
phone.
[0160]
1, 2 microphone unit 8 mobile phone (voice input device) 10, 50 housing 11, 51 mounting
portion 11a, 51a mounting surface 11b, 51b mounting surface back surface 12, 52 lid 13 first
MEMS chip (first Vibrating portion 14 First ASIC (first electric circuit portion) 15 Second MEMS
chip (second vibrating portion) 16 Second ASIC (second electric circuit portion) 18a to 18c, 19a
to 19c Electrode Terminal (electrode on mounting surface) 20 Electrode pad for external
connection (back surface electrode pad) 20 e Electrode pad for sealing (sealing portion) 21 first
opening 22 second opening 23, 61 first sound hole 24, 64 Hollow space 25, 63 second sound
hole 41, 71 first sound path 42, 72 second sound path 45 ASIC (electric circuit portion) 62
opening 82 mounting substrate 121 first housing Space 122 second accommodation space 134
first diaphragm 154 second diaphragm 521 accommodation space
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