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JP2011155450

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DESCRIPTION JP2011155450
The present invention provides a microphone unit that can easily cope with the variety of voice
input devices. A microphone unit 1 includes an electric circuit unit that processes electric signals
obtained from a first vibrating unit 14, a second vibrating unit 15, a first vibrating unit 14, and a
second vibrating unit 15. A first sound hole 132, a second sound hole 101, and a third sound
hole 133 are provided while accommodating the first vibration portion 14, the second vibration
portion 15, and the electric circuit portion 16. And a housing 20. The housing 20 transmits a
sound pressure input from the first sound hole 132 to one surface 142 a of the first diaphragm
142 and transmits it to one surface 152 a of the second diaphragm 152. Sound path 41, the
second sound path 42 for transmitting the sound pressure input from the second sound hole 101
to the other surface 142b of the first diaphragm 152, and the third sound hole 133 And a third
sound path 43 for transmitting the sound pressure to the other surface 152 b of the second
diaphragm 152. [Selected figure] Figure 4
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]
Conventionally, various types of voice input devices (devices that input and process voice, for
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example, information using a technology for analyzing input voice such as a voice
communication device such as a cellular phone or transceiver, a voice authentication system, etc.
A microphone unit having a function of converting an input sound into an electric signal and
outputting the signal is applied to a processing system, a recording device, and the like) (see, for
example, Patent Documents 1 and 2).
[0003]
Applicants disclose, for example, in Patent Document 2, a microphone unit having a function of
suppressing background noise and collecting only close sounds, and suitable for close-talking
type voice input devices (for example, mobile phones etc.) doing.
In addition, the microphone unit of patent document 2 is implementing the function which
suppresses background noise and picks up only a proximity sound by making the structure into
the differential microphone unit of a directivity.
[0004]
Patent No. 3279040 gazette JP, 2008-258904, A
[0005]
By the way, when a bidirectional microphone unit as disclosed in Patent Document 2 is mounted
on a mobile phone, for example, there is a restriction in the direction in which the microphone
sensitivity becomes good, so the restriction on the arrangement of the microphone unit in the
mobile phone is It will occur.
Such restrictions are desired to be reduced as much as possible in order to deprive the freedom
of the configuration when manufacturing a voice input device such as a portable telephone.
[0006]
Also, in recent years, voice input devices are often formed in multiple functions. For example,
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some mobile phones, which are an example of a voice input device, have a function (hands-free
function) that allows a user to make a call without holding it while driving a car, in addition to
the function of holding the call by hand. In addition, some mobile phones in recent years have a
function capable of performing movie recording.
[0007]
When calling by holding the mobile phone by hand, the microphone unit provided in the mobile
phone has a function to suppress background noise and pick up only close tones in order to use
the mouth close to the microphone part (Function as a close talk microphone) is required. On the
other hand, when using the hands-free function, it is required to be able to widely collect sound
in the front direction. Further, also in the case of movie recording, it is required that the
sensitivity in the front direction is good so that sound in the subject direction can be collected.
[0008]
In order to cope with such a situation, it is conceivable to prepare a plurality of microphone units
(microphone packages) having different characteristics and mount them on the voice input
device. In this case, the microphone unit in the voice input device is mounted It is necessary to
increase the area of the mounting substrate. In recent years, the voice input device such as a
portable telephone is generally required to be compact, and the above-mentioned
correspondence that the area of the mounting substrate on which the microphone unit is
mounted needs to be expanded is not desirable. That is, there is a demand for a compact
microphone unit that can easily cope with the multifunctionality of the voice input device with
one microphone unit.
[0009]
In view of the above, it is an object of the present invention to provide a high-performance
microphone unit that can easily cope with the variety of speech input devices (for example, the
variety in design and the variety in functions). Another object of the present invention is to
provide a high quality voice input device comprising such a microphone unit.
[0010]
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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 vibration unit
that converts a signal into an electric signal; an electric circuit unit that processes an electric
signal obtained from the first vibration unit and the second vibration unit; the first vibration unit;
A housing that accommodates the second vibration unit and the electric circuit unit and is
provided with a first sound hole, a second sound hole, and a third sound hole; A first sound path
transmitting sound pressure input from the first sound hole to one surface of the first diaphragm
and transmitting the sound pressure to one surface of the second diaphragm; A second sound
path for transmitting a sound pressure input from a sound hole to the other surface of the first
diaphragm, and a sound path input from the third sound hole A third sound path for transmitting
the pressure to the other surface of the second diaphragm, is characterized in that is provided.
[0011]
According to this configuration, it is possible to realize a small-sized microphone unit provided
with two differential microphones having two different directivity that are different from each
other in the main axis direction of directivity (the axial direction in which the sensitivity is
highest).
Such a microphone unit can be functioned as a bidirectional microphone capable of controlling
the main axis direction of directivity by combining and processing signals output from two
differential microphones. Therefore, in the microphone unit of this configuration, the restriction
on the built-in position of the voice input device is reduced and it is easy to cope with the
diversity of voice input devices. Further, since the microphone unit of the present configuration
is configured to include the differential microphone with two directivity, the microphone unit is
excellent in far-field noise (background noise) suppression performance.
[0012]
Further, as described later, according to the microphone unit of the present configuration, by
using the acoustic resistance member, the function as a bi-directional differential microphone
excellent in far-field noise suppression performance and the sensitivity in the front direction are
excellent. It is also possible to provide a microphone unit that combines the function as a
unidirectional microphone.
[0013]
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In the microphone unit of the above configuration, the first sound hole and the third sound hole
are formed on the same surface of the housing, and the second sound hole is the first sound hole
of the housing. And it can be considered that it is formed in the opposing surface which opposes
the surface where the said 3rd sound hole is formed.
According to this configuration, with respect to the two bi-directional differential microphones
provided in the microphone unit, the main axis direction of the directivity can be in a different
relation (for example, a relation shifted by 90 °).
[0014]
In the microphone unit of the above configuration, the casing is covered with the first vibration
unit, the second vibration unit, and a mounting unit on which the electric circuit unit is mounted,
and the mounting unit and the mounting unit together with the mounting unit. And a lid portion
forming a housing space for housing the first vibration portion, the second vibration portion, and
the electric circuit portion, wherein the mounting portion includes a first opening and a second
opening. Part, a hollow space communicating the first opening with the second opening, a
mounting surface on which the first vibrating part, the second vibrating part, and the electric
circuit part are mounted The second sound hole passing through the back surface is formed, and
the lid portion communicates with the first sound hole, the third sound hole, and the first sound
hole. A recess space that forms the accommodation space is formed, and the first vibration unit is
configured to receive the first diaphragm. The second vibration unit is disposed on the mounting
portion so as to cover at least a part of the sound hole and to cover the second sound hole, and
the second vibration plate includes the second diaphragm of the first opening. The cover is
disposed on the mounting portion so as to cover at least a part and cover the first opening, and
the first sound path is formed using the first sound hole and the accommodation space. The
second sound path is formed using the second sound hole, and the third sound path includes the
third sound hole, the second opening, the hollow space, and the hollow space. It may be formed
using the first opening.
[0015]
According to this configuration, it is possible to avoid the configuration in which the housing of
the microphone unit that easily copes with the variety of voice input devices is made of a large
number of parts, and to easily achieve miniaturization and thinning of the microphone unit. .
[0016]
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In the microphone unit of the above configuration, the mounting portion is a base provided with
a groove portion and a base opening, and the first vibrating portion is disposed on the opposite
surface of the base that is stacked on the base and faces the base. And a microphone substrate on
which the electric circuit unit is mounted, the microphone substrate including a first substrate
opening serving as the first opening and the second opening. A second substrate opening and a
third substrate opening forming the second sound hole together with the base opening are
formed, and the hollow space is a surface facing the base of the microphone substrate The
groove may be used to form the groove.
By configuring the mounting portion as in this configuration, the hollow space formed in the
mounting portion can be easily formed.
[0017]
In the microphone unit of the above configuration, preferably, the electric circuit unit is disposed
so as to be sandwiched between the first vibrating unit and the second vibrating unit.
According to this configuration, both of the two vibration units can be disposed close to the
electric circuit unit. For this reason, according to the microphone unit of this configuration, it is
easy to secure good SNR (Signal to Noise Ratio) by suppressing the influence of electromagnetic
noise.
[0018]
In the microphone unit configured as described above, the acoustic resistance member may be
disposed to close the second sound hole. According to this configuration, as described above, the
microphone having both the function as a bi-directional differential microphone excellent in farfield noise suppression performance and the function as a uni-directional microphone excellent
in front direction sensitivity Can provide a unit. Therefore, it is possible to easily cope with the
variety (multifunction) of voice input devices (for example, mobile phones etc.) to which the
microphone unit is applied. As a specific example, for example, in close-talk mode of a mobile
phone, the function as a bi-directional differential microphone is used, and in the hands-free
mode or movie recording mode, a function as a unidirectional microphone is used. It will be
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possible. Further, since the microphone unit of this configuration has two functions, there is no
need to separately mount the two microphone units, and it is easy to suppress the enlargement
of the voice input device.
[0019]
In the microphone unit of the above configuration, a switch electrode for inputting a switch
signal from the outside may be provided, and the electric circuit unit may include a switching
circuit that performs a switching operation based on the switch signal. According to this
configuration, for example, either one of the signal corresponding to the first vibration unit and
the signal corresponding to the second vibration unit is selectively output, or the position at
which both are output is switched. It becomes possible to make it output.
[0020]
In the microphone unit configured as described above, one of the signal corresponding to the
first vibrating portion and the signal corresponding to the second vibrating portion is externally
output based on the switch signal. The switching operation may be performed so as to be output.
According to this configuration, it is not necessary to provide a switching circuit for selecting
which of the two signals to use on the audio input device side to which the microphone unit is
applied.
[0021]
In the microphone unit configured as described above, the electric circuit unit may separately
output a signal corresponding to the first vibration unit and a signal corresponding to the second
vibration unit. As in this configuration, in the case where both signals are separately output, in
the voice input device to which the microphone unit is applied, arithmetic processing using both
signals is performed to control the directivity main axis direction It is also possible to perform
switching control of directivity characteristics in some cases.
[0022]
In order to achieve the above object, the present invention is characterized in that it is an audio
input device provided with the microphone unit of the above configuration.
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[0023]
According to this configuration, since the configuration includes the microphone unit that can
easily cope with the diversity of voice input devices, the degree of freedom in design
(configuration) of the voice input device is high, and it is easy to provide a high quality voice
input device .
[0024]
In the voice input device configured as described above, the microphone unit is provided to
separately output a signal corresponding to the first vibration unit and a signal corresponding to
the second vibration unit, and the microphone unit outputs the signal from the microphone unit.
The apparatus may further include an audio signal processing unit that performs arithmetic
processing by combining a signal corresponding to the first vibration unit and a signal
corresponding to the second vibration unit.
Thus, for example, it is possible to provide a voice input device which controls the principal axis
direction of the directivity of a close talk microphone having an effect of suppressing background
noise and directs it to a close talker.
That is, it is possible to provide a voice input device capable of acquiring the voice of the speaker
with high sensitivity.
[0025]
As described above, according to the present invention, it is possible to provide a highperformance and compact microphone unit that can easily cope with the variety of voice input
devices (for example, the variety in design and the variety in functions). Further, according to the
present invention, it is possible to provide a high quality voice input device provided with such a
microphone unit.
[0026]
The outline perspective view showing the appearance composition of the microphone unit of a
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1st embodiment The exploded perspective view showing the composition of a microphone unit of
a 1st embodiment The outline top view which looked at the member which constitutes the
microphone unit of a 1st embodiment from the top A schematic sectional view at a position A-A A
schematic sectional view showing a configuration of a MEMS chip provided in the microphone
unit of the first embodiment A block diagram showing a configuration of the microphone unit
according to the first embodiment A sound pressure P and a distance R from a sound source FIG.
6 is a graph showing the relationship between the directivity characteristics of the differential
microphone configured with the first MEMS chip and the directivity characteristics of the
differential microphone configured with the second MEMS chip according to the first
embodiment A block diagram showing a configuration of a voice input device including a
microphone unit A variable (k) of calculation processing performed by a voice signal processing
unit is changed Shows how the main axis direction of the directivity of the microphone unit
functioning as a bi-directional microphone fluctuates, and the schematic configuration of the
embodiment of the portable telephone to which the microphone unit of the first embodiment is
applied The schematic sectional view in the BB position of 11 schematic sectional view showing
the composition of the microphone unit of the second embodiment The block diagram showing
the constitution of the microphone unit of the second embodiment Above the microphone
substrate provided in the microphone unit of the second embodiment Schematic plan view as
seen from the top for explaining the directivity characteristic of the microphone unit according to
the second embodiment The block diagram for explaining a modification of the microphone unit
according to the second embodiment Modification of the microphone unit according to the
second embodiment In the figure for demonstrating an example, the schematic plan view at the
time of seeing a microphone board from the top
[0027]
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.
[0028]
First Embodiment First, a first embodiment of a microphone unit and a voice input device to
which the present invention is applied will be described.
[0029]
Microphone Unit of First Embodiment FIG. 1 is a schematic perspective view showing an
appearance configuration of a microphone unit according to a first embodiment.
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FIG. 2 is an exploded perspective view showing the configuration of the microphone unit of the
first embodiment.
FIG. 3 is a schematic plan view of the members constituting the microphone unit of the first
embodiment, viewed from above, FIG. 3 (a) is a view of the lid viewed from above, and FIG. 3 (b)
is MEMS (Micro Electro) FIG. 3 (c) is a top view of the base of the microphone system on which
the mechanical system chip and the application specific integrated circuit (ASIC) are mounted.
FIG. 4 is a schematic cross-sectional view at the A-A position of FIG. FIG. 5 is a schematic crosssectional view showing the configuration of the MEMS chip provided in the microphone unit of
the first embodiment. FIG. 6 is a block diagram showing the configuration of the microphone unit
of the first embodiment. The configuration of the microphone unit 1 of the first embodiment will
be described with reference to these drawings.
[0030]
As shown in FIGS. 1 to 4, the microphone unit 1 according to the first embodiment largely
corresponds to the base 11, the microphone substrate 12 stacked on the base 11, and the upper
surface 12 a of the microphone substrate 12 (the base 11 faces And a cover 13 to be placed on
the side opposite to the side to be made.
[0031]
The base 11 is, for example, as shown in FIGS. 2 and 3C, a plate-like member having a
substantially rectangular shape in plan view.
A groove portion 111 substantially T-shaped in a plan view is formed on the upper surface 11 a
side of one end of the base 11 in the longitudinal direction. Further, at a position shifted from the
center of the base 11 to the other end side in the longitudinal direction, a base opening 112
made of a through hole having a substantially circular shape in plan view is formed. The base 11
may be formed using, for example, a glass epoxy-based substrate material such as FR-4 and BT
resin, and for example, LCP (Liquid Crystal Polymer; liquid crystal polymer), PPS (polyphenylene
sulfide), etc. It may be obtained by resin molding using a resin of When the base 11 is formed of
a substrate material such as FR-4, the groove 111 and the base opening 112 can be obtained by
machining with, for example, a router or a drill.
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[0032]
Further, the base 11 is formed in two layers, one layer is formed as a substrate in which only the
hole serving as the base opening 112 is formed, and the other layer is a substrate in which the
holes serving as the base opening 112 and the groove 111 are formed. The base 11 may be
configured by forming the base 11 and bonding the two. In this case, since any layer also
becomes a through hole, it is possible to form a hole by punching processing by punching, and
the manufacturing efficiency can be significantly improved.
[0033]
For example, as shown in FIGS. 2 and 3B, the microphone substrate 12 is formed in a
substantially rectangular shape in plan view, and the size of the plate-like surface (upper surface
12a) is that of the plate-like surface (upper surface 11a) of the base 11. It is almost the same as
the size. As shown in FIG. 2, in the microphone substrate 12, three substrate openings 121, 122,
and 123 aligned in the longitudinal direction are formed by, for example, machining.
[0034]
The first substrate opening 121 formed at a position shifted from the center of the microphone
substrate 12 to one end side (left side in FIG. 3) in the longitudinal direction is a through hole in
a substantially circular shape in plan view. The position is determined so as to overlap with a
portion of the groove 111 formed in the base 11 (more precisely, a portion extending parallel to
the longitudinal direction of the base 11) when 12 is stacked. There is. The second substrate
opening 122 formed closer to one end (left end in FIG. 3) of the microphone substrate 12 in the
longitudinal direction is such that the short direction (vertical direction in FIG. 3B) of the
microphone substrate 12 is the longitudinal direction It consists of a through-hole of planar view
substantially rectangular shape. The position of the second substrate opening 122 is determined
so as to overlap with the portion extending in the short direction of the groove 111 formed in the
base 11. The third substrate opening 123 formed at a position shifted from the center of the
microphone substrate 12 to the other end side (right side in FIG. 3) in the longitudinal direction
is a through hole having a substantially circular shape in plan view. The position of the
microphone substrate 12 is determined so as to overlap with the base opening 112 formed in the
base 11 when the microphone substrate 12 is stacked.
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[0035]
In addition, although the material which comprises the microphone board | substrate 12 is not
specifically limited, A well-known material is suitably used as a substrate material, For example,
FR-4, ceramics, a polyimide film etc. are used.
[0036]
As shown in FIG. 3B and FIG. 4, the first MEMS chip 14, the second MEMS chip 15, and the ASIC
16 are mounted on the upper surface 12 a of the microphone substrate 12.
Here, the configurations of the MEME chips 14 and 15 and the ASIC 16 mounted on the
microphone substrate 12 will be described.
[0037]
The first MEMS chip 14 and the second MEMS chip 15 are both silicon chips, and their
configurations are the same. Therefore, the configuration of the MEMS chip will be described by
taking the case of the first MEMS chip 14 as an example. In FIG. 5, reference numerals shown in
parentheses correspond to the second MEMS chip 15.
[0038]
As shown in FIG. 5, the first MEMS chip 14 includes an insulating first base substrate 141, a first
diaphragm 142, a first insulating layer 143, and a first fixed electrode 144. Are stacked. In the
first base substrate 141, an opening 141a having a substantially circular shape in plan view is
formed. The first diaphragm 142 provided on the first base substrate 141 is a thin film that
vibrates (vibrates in the vertical direction in FIG. 5) by receiving sound pressure, and has
conductivity to form one end of the electrode. ing.
[0039]
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The first insulating layer 143 is provided such that the first diaphragm 142 and the first fixed
electrode 114 are disposed at an interval Gp, and the through-hole 143a having a substantially
circular shape in plan view is provided at the central portion thereof. Is formed. The first fixed
electrode 144 disposed on the first insulating layer 143 is disposed opposite to the first
diaphragm 142 in a substantially parallel state, and the first diaphragm 142 and the first fixed
electrode are disposed. A capacitance of between 144 and 144 is formed. A plurality of through
holes 144a are formed in the first fixed electrode 144 so that sound waves can pass through, and
sound waves coming from the upper side of the first diaphragm 142 are formed on the upper
surface 142a of the first diaphragm 142. It is supposed to reach you.
[0040]
Thus, in the first MEMS chip 14 configured as a capacitor type microphone, when the first
diaphragm 142 vibrates due to the arrival of the sound wave, the first diaphragm 142 and the
first fixed electrode 144 The capacitance between them changes. As a result, the sound wave
(sound signal) incident on the first MEMS chip 14 can be extracted as an electric signal. Similarly,
the second MEMS chip 15 including the second base substrate 151, the second diaphragm 152,
the second insulating layer 153, and the second fixed electrode 154 also receives an incident
sound wave (sound Signal) can be taken out as an electrical signal. That is, the first MEMS chip
14 and the second MEMS chip 15 have a function of converting a sound signal into an electric
signal.
[0041]
The configuration of the MEMS chips 14 and 15 is not limited to the configuration of the present
embodiment. For example, in the present embodiment, the diaphragms 142 and 152 are lower
than the fixed electrodes 144 and 154, but the opposite relationship (the diaphragm is on the
upper side and the fixed electrode is on the lower side) It may be configured to be
[0042]
The ASIC 16 changes the capacitance of the second MEMS chip 15 as well as the electrical signal
extracted based on the change of the capacitance of the first MEMS chip 14 (due to the vibration
of the first diaphragm 142). It is an integrated circuit that amplifies the electrical signal extracted
based on the vibration (derived from the vibration of the second diaphragm 152).
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[0043]
As shown in FIG. 6, the ASIC 16 includes a charge pump circuit 161 that applies a bias voltage to
the first MEMS chip 14 and the second MEMS chip 15.
The charge pump circuit 161 boosts a power supply voltage (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 14 and the second
MEMS chip 15. The ASIC 16 also includes a first amplifier circuit 162 that detects a change in
capacitance in the first MEMS chip 14 and a second amplifier circuit 163 that detects a change in
capacitance in the second MEMS chip 15. And. The electrical signals amplified by the first
amplifier circuit 162 and the second amplifier circuit 163 are independently output from the
ASIC 16.
[0044]
Here, the charge pump circuit 161 is configured to apply a common bias voltage to the first
MEMS chip 14 and the second MEMS chip 15. Generally, a large capacitor capacity is required to
form charge pump circuit 161, and a large semiconductor chip area is consumed. By sharing the
bias for the first MEMS chip 14 and the second MEMS chip 15 and supplying them from one
charge pump power source, the chip area of the semiconductor is reduced and the size of the
ASIC 16 is reduced, and thus the microphone unit 1 It is possible to reduce the size of the
[0045]
In the present embodiment, a common bias voltage is applied to the first MEMS chip 14 and the
second MEMS chip 15, but the present invention is not limited to this configuration. For example,
two charge pump circuits 161 may be provided to apply bias voltages separately to the first
MEMS chip 14 and the second MEMS chip 15. This configuration can reduce the possibility of
crosstalk between the first MEMS chip 14 and the second MEMS chip 15.
[0046]
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In the microphone unit 1, as shown in FIG. 4, the two MEMS chips 14 and 15 are mounted on the
microphone substrate 12 such that the diaphragms 142 and 152 are substantially parallel to the
upper surface 12 a of the microphone substrate 12. In the microphone unit 1, the MEMS chips
14 and 15 and the ASIC 16 are mounted in a line in the longitudinal direction of the upper
surface 12 a of the microphone substrate 12 (FIG. 3 (b), in the left and right direction in FIG. The
order is the first MEMS chip 14, the ASIC 16, and the second MEMS chip 15 in order from the
right side with reference to FIGS. 3 and 4.
[0047]
The first MEMS chip 14 is a microphone such that the first diaphragm 142 covers the third
substrate opening 123 formed in the microphone substrate 12 as can be seen with reference to
FIGS. 3 (b) and 4. It is disposed on the upper surface 12 a of the substrate 12 and covers the
third substrate opening 123. In addition, as shown in FIG. 3B and FIG. 4, in the second MEMS
chip 15, the second diaphragm 152 covers the first substrate opening 121 formed in the
microphone substrate 12. The microphone substrate 12 is disposed on the upper surface 12 a of
the microphone substrate 12 so as to cover and hide the first substrate opening 121.
[0048]
In the present embodiment, the MEMS chips 14 and 15 covering the substrate openings 121 and
123 are mounted on the microphone substrate 12 so that the diaphragms 142 and 152 cover
the entire substrate openings 121 and 123. However, the present invention is not limited to this
configuration, and the MEMS chips 14 and 15 which cover the substrate openings 121 and 123
are mounted on the microphone substrate 12 so that the diaphragms 142 and 152 cover part of
the substrate openings 121 and 123. May be
[0049]
The two MEMS chips 14 and 15 and the ASIC 16 are mounted on the microphone substrate 12
by die bonding and wire bonding. In detail, the first MEMS chip 14 and the second MEMS chip
15 have a bottom surface facing the top surface 12 a of the microphone substrate 12 by a die
bonding material (for example, an epoxy resin type or silicone resin type adhesive or the like) not
shown. The whole is joined without gaps. By bonding in this manner, a situation in which sound
leaks from the gap formed between the upper surface 12 a of the microphone substrate 12 and
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the lower surface of the MEMS chips 14 and 15 does not occur. Also, as shown in FIG. 3 (b), each
of the two MEMS chips 14, 15 is electrically connected to the ASIC 16 by the wire 17.
[0050]
Further, in the ASIC 16, a bottom surface facing the top surface 12 a of the microphone substrate
12 is joined by a die bonding material (not shown). Further, as shown in FIG. 3B, the ASIC 16 is
electrically connected to each of the plurality of electrode terminals 18a, 18b, 18c, 18d formed
on the upper surface 12a of the microphone substrate 12 by the wire 17. The plurality of
electrode terminals 18 a to 18 d formed on the microphone substrate 12 are first terminals for
outputting a power signal (a power supply terminal for inputting a power supply voltage (VDD))
and an electric signal amplified by the first amplifier circuit 162 of the ASIC 16. And a second
output terminal 18c for outputting the electric signal amplified by the second amplifier circuit
163 of the ASIC 16, and a GND terminal 18d for ground connection.
[0051]
Note that each of the plurality of electrode terminals 18a to 18d provided on the upper surface
12a of the microphone substrate 12 is a lower surface 11b of the base 11 (including through
wiring) formed on the microphone substrate 12 and the base 11 (not shown). There is an
external connection electrode 19 (in detail, a power supply electrode 19a, a first output electrode
19b, a second output electrode 19c, and a GND electrode 19d (see FIG. 6) formed in FIG. 4).
Electrically connected). The external connection electrode 19 is used to connect to a connection
terminal formed on the mounting substrate on which the microphone unit 1 is mounted.
[0052]
Although the two MEMS chips 14 and 15 and the ASIC 16 are mounted by wire bonding in the
above, the present invention is not limited to this configuration, and the two MEMSs 14 and 15
and the ASIC 16 may of course be flip chip mounted.
[0053]
As shown in FIGS. 1 to 4, the lid 13 has a substantially rectangular parallelepiped outer shape,
and a substantially rectangular parallelepiped recessed space 131 is formed.
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The recess space 131 extends to the vicinity of one end side (right side in FIG. 4) of the lid 13 in
the longitudinal direction but does not extend to the vicinity of the other end side (left side in
FIG. 4). The lid 13 is in a posture in which the recess space 131 and the microphone substrate 12
face each other so that the recess space 131 and the microphone substrate 12 form a storage
space for storing the two MEMS chips 14 and 15 and the ASIC 16. Then, the microphone
substrate 12 is covered.
[0054]
The lengths of the lid 13 in the longitudinal direction (left and right direction in FIG. 3A) and in
the lateral direction (vertical direction in FIG. 3A) are substantially the same as the size of the
upper surface 12a of the microphone substrate 12. It is done. Accordingly, the side surface
portions of the microphone unit 1 formed by laminating the microphone substrate 12 and the lid
13 on the base 11 are substantially flush.
[0055]
At one end side (right side in FIG. 3A) in the longitudinal direction of the lid upper surface 13a,
the first lid opening 132 having a substantially elliptical shape in plan view in which the short
direction of the lid 13 is the long axis direction. Is formed. The first lid opening 132 is in
communication with the recess space 131 of the lid 13 as shown in FIG. 4, for example. Further,
on the other end side in the longitudinal direction of the lid upper surface 13a (left side in FIG.
3A), a second lid opening of a substantially elliptical shape in plan view in which the short
direction of the lid 13 is the long axis direction. The part 133 is formed. The second lid opening
portion 133 is a through hole penetrating from the upper surface 13 a to the lower surface 13 b
of the lid 13 as shown in FIG. 4, for example.
[0056]
The second lid opening 133 communicates with the second substrate opening 122 formed in the
microphone substrate 12 when the lid 13 is placed on the microphone substrate 12. So that its
position has been adjusted.
[0057]
04-05-2019
17
The lid 13 may be formed using, for example, a glass epoxy-based substrate material such as FR4 and BT resin, which is the same substrate material as the microphone substrate 12, or, for
example, using a resin such as LCP or PPS. You may obtain by resin molding.
When the base 11 is formed of a substrate material such as FR-4, the recess space 131, the first
lid opening 132, and the second lid opening 133 can be obtained by machining using, for
example, a router or a drill.
[0058]
In addition, the lid 13 is formed in two layers, one layer is formed as a substrate on which a hole
to be the first lid opening 132 and the second lid opening 133 is formed, and the other layer is
the recess space 131 The lid 13 may be configured by forming a substrate in which a hole to be
the second lid opening 133 is formed and bonding the two together. In this case, since any layer
also becomes a through hole, it is possible to form a hole by punching processing by punching,
and the manufacturing efficiency can be significantly improved.
[0059]
The above base 11, the microphone substrate 12 (where the two MEMS chips 14 and 15 and the
ASIC 16 are mounted), and the lid 13 are sequentially stacked in this order from the bottom, and
the respective members are bonded with an adhesive or the like. Thus, a microphone unit 1 as
shown in FIG. 1 is obtained. In the microphone unit 1, as shown in FIG. 4, the sound wave input
from the outside through the first lid opening 132 is a storage space (the recess space 131 of the
lid 13 and the upper surface 12 a of the microphone substrate 12 The upper surface 142a of the
first diaphragm 142 and the upper surface 152a of the second diaphragm 152 are reached
through the space formed therebetween. Further, the sound wave input from the outside through
the base opening 112 and the third substrate opening 123 reaches the lower surface 142 b of
the first diaphragm 142. Further, the sound wave input from the outside through the second lid
opening 133 is formed by using the second substrate opening 122, the hollow space (the groove
111 of the base 11 and the lower surface 12b of the microphone substrate 12) Space), and
reaches the lower surface 152 b of the second diaphragm 152 through the first substrate
opening 121.
04-05-2019
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[0060]
In other words, the sound pressure input from the first lid opening 132 functioning as the first
sound hole is transmitted to one surface (upper surface 142 a) of the first diaphragm 142 in the
microphone unit 1. Sound pressure input from the first sound path 41 transmitted to one surface
(upper surface 152 a) of the second diaphragm, the base opening 112 functioning as the second
sound hole, and the third substrate opening 123 Of the sound pressure input from the second
sound path 42 transmitting the second diaphragm 142 to the other surface (the lower surface
142b) of the first diaphragm 142 and the second lid opening 133 functioning as the third sound
hole. And a third sound path 43 to be transmitted to the other surface (lower surface 152 b) of
the diaphragm 152.
[0061]
Hereinafter, the first lid opening 132 may be expressed as the first sound hole 132, and the
second lid opening 133 may be expressed as the third sound hole 133.
Also, a sound hole formed by the base opening 112 and the third substrate opening 123 may be
expressed as a second sound hole 101.
[0062]
The first MEMS chip 14 is an embodiment of the first vibrating portion of the present invention.
The second MEMS chip 15 is an embodiment of the second vibrator of the present invention. The
ASIC 16 is an embodiment of the electrical circuitry of the present invention. The combination of
the base 11, the microphone substrate 12 and the lid 13 is an embodiment of the housing of the
present invention. The combination of the base 11 and the microphone substrate 12 is an
embodiment of the mounting portion of the present invention. The hollow space of the present
invention (this space communicates the first substrate opening 121 and the second substrate
opening 122) using the groove 111 of the base 11 and the lower surface 12 b of the microphone
substrate 12. Embodiments are obtained.
[0063]
04-05-2019
19
Further, in the microphone unit 1 of the present embodiment, the base 11, the microphone
substrate 12, and the lid 13 constituting the housing 20 are all made of FR-4 which is a substrate
material. As described above, when the materials constituting the housing 20 are unified to the
same material, it is possible to suppress the occurrence of warpage in the microphone substrate
12 due to the difference in expansion coefficient between the two when reflow mounting the
microphone unit 1 on the mounting substrate. This can prevent unnecessary stress from being
applied to the MEMS chips 14 and 15 mounted on the microphone substrate 12. That is,
deterioration of the characteristics of the microphone unit 1 can be avoided.
[0064]
Moreover, although the base 11 which comprises the mounting part 10 is made into the flat
plate in this embodiment, it is not the meaning limited to this shape. That is, for example, the
shape of the base may be a box shape or the like having an accommodation recess for
accommodating the microphone substrate 12 and the lid 13. With this configuration, alignment
of the base 11, the microphone substrate 12, and the lid 13 can be facilitated, and the assembly
of the microphone unit 1 is facilitated.
[0065]
Moreover, in this embodiment, although the shape of the groove part 111 formed in the base 11
was made into the substantially T shape in planar view, it is not the meaning limited to this
structure. That is, for example, it may be a substantially rectangular shape in plan view (a
configuration shown by a broken line in FIG. 3C) or the like. However, by configuring as in the
present embodiment, it is possible to increase the area for supporting the microphone substrate
12 by the base 11 while securing the cross-sectional area of the space to be the sound path to
some extent. As a result, it is possible to avoid the situation in which the cross-sectional area of
the hollow space formed by utilizing the lower surface 12b of the microphone substrate 12 and
the groove portion 111 of the base 11 is reduced by bending the microphone substrate 12.
[0066]
Moreover, in this embodiment, although the shape of two sound holes 132 and 133 formed in
the lid 13 was made into the long hole shape, it is not the meaning limited to this, for example, as
a sound hole etc. I don't care. However, as in the present configuration, the cross-sectional area
04-05-2019
20
of the sound hole can be reduced while suppressing the length of the longitudinal direction of the
microphone unit 1 (corresponding to the left and right direction in FIG. 4) from becoming long. It
is preferable because it can be enlarged.
[0067]
And although the 2nd board | substrate opening part 122 provided in the microphone board |
substrate 12 is also made into the long hole shape by the meaning similar to this, this shape can
also be changed suitably. In the present embodiment, the passage of the sound wave input from
the third sound hole 133 (the second lid opening 133) is formed by one large through hole (the
second substrate opening 122). There is. However, the present invention is not limited to this
configuration, and, for example, a plurality of small (compared to the size of the second substrate
opening 122 of this embodiment) aligned along the short side direction of the microphone
substrate 12 (vertical direction in FIG. The configuration may be made of a small through hole.
With this configuration, it is easy to form a through hole provided in the microphone substrate
12 in order to secure the passage of the sound wave input from the third sound hole 133. A
plurality of through holes is provided to increase the cross-sectional area of the sound path. The
shape of the through hole is not particularly limited, but can be, for example, a round hole
(generally circular in plan view). The round holes can be easily formed by drilling, so that the
manufacturing efficiency can be improved. In addition, since the maximum pore size of each
individual decreases, there is also an effect of preventing the entry of dust.
[0068]
Moreover, although it was set as the structure arrange | positioned so that ASIC16 may be
pinched | interposed between two MEMS chips 14 and 15 in this embodiment, it is not
necessarily limited to this structure. However, when the ASIC 16 is configured to be sandwiched
between the two MEMS chips 14 and 15 as in the present embodiment, it is easy to electrically
connect the MEMS chips 14 and 15 to the ASIC 16 by the wires 17. In addition, since the
distance between each of the MEMS chips 14 and 15 and the ASIC 16 becomes short, the
influence of electromagnetic noise can be suppressed for the signal output from the microphone
unit 1, and a good SNR can be easily ensured.
[0069]
Next, the operation and effect of the microphone unit 1 of the first embodiment will be described.
04-05-2019
21
[0070]
When a sound is generated outside the microphone unit 1, the sound wave input from the first
sound hole 132 reaches the upper surface 142 a of the first diaphragm 142 by the first sound
path 41, and the second sound hole 101. The sound wave input from the second sound path 42
reaches the lower surface 142 a of the first diaphragm 142.
For this reason, the first diaphragm 142 vibrates due to the sound pressure applied to the upper
surface 142a and the sound pressure difference applied to the lower surface 142b. As a result, a
change in capacitance occurs in the first MEMS chip 14. The electric signal extracted based on
the change in capacitance of the first MEMS chip 14 is amplified by the first amplifier circuit 162
and output from the first output electrode 19 b (FIGS. 4 and 6) reference).
[0071]
Further, when sound is generated outside the microphone unit 1, the sound wave input from the
first sound hole 132 reaches the upper surface 152 a of the second diaphragm 152 by the first
sound path 41, and the third sound is generated. The sound wave input from the hole 133
reaches the lower surface 152 b of the second diaphragm 152 by the third sound path 43. For
this reason, the second diaphragm 152 vibrates due to the sound pressure difference between
the sound pressure applied to the upper surface 152a and the sound pressure applied to the
lower surface 152b. As a result, a change in capacitance occurs in the second MEMS chip 15. The
electric signal extracted based on the change in capacitance of the second MEMS chip 15 is
amplified by the second amplifier circuit 163 and output from the second output electrode 19c
(FIGS. 4 and 6) reference).
[0072]
As described above, in the microhonin unit 1, the signal obtained using the first MEMS chip 14
and the signal obtained using the second MEMS chip 15 are separately output to the outside. It
has become. By the way, each of the first MEMS chip 14 and the second MEMS chip 15 in the
microphone unit 1 exhibits a function as a bi-directional differential microphone. Hereinafter, the
characteristics of the microphone unit 1 configured as described above will be described with
04-05-2019
22
reference to FIGS. 7 and 8.
[0073]
FIG. 7 is a graph showing the relationship between the sound pressure P and the distance R from
the sound source. FIG. 8 is a diagram for explaining the directivity characteristic (dotted line) of
the differential microphone formed of the first MEMS chip and the directivity characteristic (solid
line) of the differential microphone formed of the second MEMS chip It is. In FIG. 8, the attitude
of the microphone unit 1 is assumed to be the same as the attitude shown in FIG.
[0074]
As shown in FIG. 7, the sound wave attenuates as it travels through a medium such as air, and the
sound pressure (the strength and 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)
[0075]
As apparent from FIG. 7 and the equation (1), the sound pressure is rapidly attenuated (left side
of the graph) at a position close to the sound source, and is gradually attenuated (right side of the
graph) as it is separated 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).
[0076]
Here, it is assumed that the distance from the sound source of the target sound to be picked up
by the microphone unit 1 is different between the first sound hole 132 and the second sound
hole 101. In this case, the sound pressure of the target sound generated in the vicinity of the
microphone unit 1 is largely attenuated between the upper surface 142a and the lower surface
04-05-2019
23
142b of the first diaphragm 145 and transmitted to the upper surface 142a of the first
diaphragm 142. And the sound pressure transmitted to the lower surface 142b of the first
diaphragm 142 are largely different. On the other hand, background noise (far noise) hardly
attenuates between the upper surface 142a and the lower surface 142b of the first diaphragm
142 because the sound source is at a position farther than the target sound, and the first
vibration is generated. The sound pressure difference between the sound pressure transmitted to
the upper surface 142 a of the plate 142 and the sound pressure transmitted to the lower
surface 142 b of the first diaphragm 142 becomes very small.
[0077]
Since the sound pressure difference of the background noise received by the first diaphragm 142
is very small, the sound pressure of the background noise is substantially canceled by the first
diaphragm 142. On the other hand, since the sound pressure difference of the target sound
received by the first diaphragm 142 is large, the sound pressure of the target sound is not
canceled by the first diaphragm 142. Therefore, the signal obtained by the vibration of the first
diaphragm 142 can be regarded as the signal of the target sound from which the background
noise has been removed. Therefore, the differential microphone configured by the first MEMS
chip 14 is excellent in far-field noise suppression performance. Similarly, the differential
microphone constituted by the second MEMS chip 15 is also excellent in far-field noise
suppression performance.
[0078]
As described above, although the differential microphone composed of the first MEMS chip 14
and the differential microphone composed of the second MEMS chip 15 both exhibit directivity,
as shown in FIG. The main axis direction of the directivity is shifted by about 90 °.
[0079]
In the differential microphone configured by the first MEMS chip 14, when the distance from the
sound source to the first diaphragm 142 is constant, the first diaphragm 142 is when the sound
source is in the direction of 90 ° or 270 °. The sound pressure applied to the
This is because the distance between the sound wave from the first sound hole 132 to the upper
surface 142 a of the first diaphragm 142 and the distance between the sound wave from the
04-05-2019
24
second sound hole 101 to the lower surface 142 b of the first vibration plate 142 This is because
the difference is the largest. On the other hand, the sound pressure applied to the first diaphragm
142 when the sound source is in the direction of 0 ° or 180 ° is minimum (0). This is because
the distance between the sound wave from the first sound hole 132 to the upper surface 142 a
of the first diaphragm 142 and the distance between the sound wave from the second sound hole
101 to the lower surface 142 b of the first vibration plate 142 This is because the difference is
almost zero. That is, the differential microphone formed by the first MEMS chip 14 is easily
received by the sound waves incident from the directions of 90 ° and 270 °, and is hard to
receive the sound waves incident from the directions of 0 ° and 180 °. Show.
[0080]
On the other hand, in the differential microphone configured by the second MEMS chip 15, if the
distance from the sound source to the second diaphragm 152 is constant, the second vibration
occurs when the sound source is in the direction of 0 ° or 180 °. The sound pressure applied
to the plate 152 is maximized. This is because the distance between the sound wave from the
first sound hole 132 to the upper surface 152 a of the second diaphragm 152 and the distance
between the sound wave from the third sound hole 133 to the lower surface 152 b of the second
vibration plate 152 This is because the difference is the largest. On the other hand, the sound
pressure applied to the second diaphragm 152 is minimum (0) when the sound source is in the
90 ° or 270 ° direction. This is because the distance between the sound wave from the first
sound hole 132 to the upper surface 152 a of the second diaphragm 152 and the distance
between the sound wave from the third sound hole 133 to the lower surface 152 b of the second
vibration plate 152 This is because the difference is almost zero. That is, the differential
microphone configured by the second MEMS chip 15 has a property that it is easy to receive the
sound waves incident from the directions of 0 ° and 180 °, and hard to receive the sound
waves incident from the directions of Show.
[0081]
As described above, the microphone unit 1 is configured to include two bi-directional differential
microphones having different principal axis directions of directivity. Then, as described above, in
the microphone unit 1, the signal extracted from the first MEMS chip 14 and the signal extracted
from the second MEMS chip 15 are separately processed (amplified) and output to the outside It
is supposed to be. In this case, the microphone unit 1 can be made to function as an
omnidirectional microphone whose directivity main axis direction can be controlled by
combining two separately output signals and performing predetermined arithmetic processing.
04-05-2019
25
This will be described with reference to FIGS. 9 and 10.
[0082]
(Voice Input Device Including Microphone Unit of First Embodiment) FIG. 9 is a block diagram
showing a configuration of a voice input device including the microphone unit of the first
embodiment. As shown in FIG. 9, the audio input device 5 according to the first embodiment
includes a microphone unit 1 and an audio signal processing unit 6 that combines two signals
output from the microphone unit 1 and performs predetermined arithmetic processing. Prepare.
[0083]
In the present embodiment, the audio signal processing unit 6 executes, for example, the
arithmetic processing shown in the following equation (2). In Equation (2), OUT1 is a signal
output (output from the first output electrode 19b) corresponding to the first MEMS chip 14, and
OUT2 is a signal output (second output) corresponding to the second MEMS chip 15. Output
from the second output electrode 19c). Further, in equation (2), k is a variable for weighting.
(1−|k|)×OUT2−k×OUT1 (2)
[0084]
FIG. 10 is a diagram showing how the main axis direction of the directivity of the microphone
unit functioning as a bi-directional microphone changes by changing the variable (k) of the
arithmetic processing performed by the audio signal processing unit. As shown in FIG. 10, the
main axis direction of the microphone unit 1 is selected from the X direction which is the
longitudinal direction of the microphone unit 1 and the Y direction which is the thickness
direction of the microphone unit 1 by selecting the value of k in equation (2). It is possible to
control rotation around the axis of the Z axis orthogonal to
[0085]
For example, in the case of k = -1 or k = 1, the main axis direction of the directivity of the
microphone unit 1 becomes parallel to the Y direction which is the thickness direction of the
microphone unit 1, and when k = 0, the directivity of the microphone unit 1 The main axis
direction of X is the X direction which is the longitudinal direction of the microphone unit 1.
04-05-2019
26
[0086]
When the voice input device 5 is configured in this way, the principal axis direction of directivity
can be controlled by changing the variable k value in Equation (2), so the mounting position of
the microphone unit 1 in the voice input device 5 is changed by design convenience. Even by
setting the value of the variable k appropriately, the speech of the close talker can be obtained
with high sensitivity.
Also, when using the voice input device, it is possible to change the variable k in accordance with
the position of the close talker to control the main axis direction of directivity, and to obtain the
voice of the speaker with high sensitivity.
[0087]
Here, a configuration example in which a microphone unit is applied to a mobile phone (an
example of a voice input device) having a function as a voice input device will be described with
reference to FIGS. 11 and 12. FIG. FIG. 11 is a view showing a schematic configuration of an
embodiment of a mobile phone to which the microphone unit of the first embodiment is applied.
FIG. 12 is a schematic cross-sectional view at a position B-B in FIG.
[0088]
As shown in FIGS. 11 and 12, two sound holes 511 and 512 are provided on the lower side of the
surface 51 a of the case 51 of the mobile phone 5. Further, as shown in FIG. 12, one sound hole
513 is provided on the back surface 51 b of the casing 51 of the mobile phone 5. Then, the
user's voice is input to the microphone unit 1 disposed inside the housing 51 through the three
sound holes 511, 512, 513.
[0089]
The microphone unit 1 is mounted on the mobile telephone 5 in a state of being mounted on the
04-05-2019
27
mounting substrate 52 provided in the housing 51 of the mobile telephone 5 as shown in FIG.
The mounting substrate 52 is provided with the above-mentioned audio signal processing unit 6
(not shown in FIG. 12). The mounting substrate 52 is provided with a plurality of electrode pads
electrically connected to the plurality of external connection electrodes 19 provided in the
microphone unit 1, and the microphone unit 1 is mounted on the mounting substrate 52 using,
for example, solder or the like. And electrically connected. Then, the power supply voltage is
applied to the microphone unit 1, and the electrical signal output from the microphone unit 1 is
sent to the audio signal processing unit 6.
[0090]
In the microphone unit 1, the first sound hole 132 is overlapped with the sound hole 511 formed
in the housing 51 of the mobile phone 5, and the second sound hole 101 is provided in the
mounting substrate 52. The third sound hole 133 is disposed so as to overlap with the sound
hole 513 formed in the case 51 of the telephone 5 and the sound hole 512 formed in the case 51
of the mobile telephone 5.
[0091]
Therefore, the sound generated outside the housing 51 of the mobile phone 5 passes through the
first sound path 41 provided in the microphone unit 1 and is transmitted to the upper surface
142 a of the first diaphragm 142 of the first MEMS chip 14. At the same time, it reaches the
lower surface 142 b of the diaphragm 142 of the first MEMS chip 14 through the second sound
path 42.
Further, the sound generated outside the casing 51 of the mobile phone 5 passes through the
first sound path 41 provided in the microphone unit 1 and reaches the upper surface 152 a of
the second diaphragm 152 of the second MEMS chip 15. Then, the lower surface 152 b of the
second diaphragm 152 of the second MEMS chip 15 is reached through the third sound path 43.
[0092]
In the mobile phone 5 of the present embodiment, an elastic body (gasket) 53 is disposed
between the housing 51 and the microphone unit 1. The elastic body 53 has an opening 531, so
that voice generated outside the housing 51 can be efficiently and independently input
04-05-2019
28
corresponding to the two sound paths 41 and 43 provided in the microphone unit 1. 532 is
formed. The elastic body 53 is provided so as to maintain airtightness without causing an
acoustic leak. The material of the elastic body 53 is preferably, for example, butyl rubber or
silicone rubber.
[0093]
Further, for the purpose of keeping the air tightness without causing the acoustic leak, the air
tightness is provided between the microphone unit 1 and the mounting substrate 52 so as to
surround the substrate through hole 521 provided in the second sound hole 101 and the
mounting substrate 52. A section 54 is provided. The airtight portion 54 is obtained, for example,
by joining an airtight terminal provided in the microphone unit 1 and an airtight terminal
provided in the mounting substrate 52 by soldering or the like. Further, in order to maintain
airtightness without causing acoustic leakage, an elastic body is provided between the mounting
substrate 52 and the housing 51 so as to surround the substrate through-hole 521 of the
mounting substrate 52 and the sound hole 513 of the housing 51. A (gasket) 55 is disposed.
[0094]
Further, in this example, the microphone unit 1 is arranged on the lower side of the mobile
phone 1, but as described above, the main axis direction of directivity of the microphone unit 1
functioning as a bi-directional microphone can be controlled is there. For this reason, not only
the lower side of the mobile phone 1 but the arrangement of the microphone unit 1 can be easily
changed.
[0095]
(Summary and Remarks of First Embodiment) As described above, the microphone unit 1
according to the first embodiment includes two differential microphones having high directivity
and excellent in far-field noise suppression performance, and these two differential microphones
The main axis directions of the directivity of (1) are different from each other (in this example,
they are shifted by 90 °, but are not necessarily limited to 90 °). By performing predetermined
arithmetic processing using signals output from the two differential microphones, the
microphone unit 1 can be made to function as one microphone, and directivity can be
appropriately changed by appropriately changing variables during arithmetic processing. Can
04-05-2019
29
control the main axis direction of Therefore, the microphone unit 1 of the present embodiment
can easily cope with the design diversity of the voice input device.
[0096]
Further, in the microphone unit 1 of the first embodiment, the first sound path 41, the second
sound path 42 and the third sound path 43 are formed by three members such as the base 11,
the microphone substrate 12 and the lid 13. The structure is simple, easy to assemble, and easy
to miniaturize and thin.
[0097]
Also, although the case where the microhonin unit 1 is used as a close-talking microphone of a
portable telephone has been illustrated above, the microhonin unit 1 can perform control of the
principal axis direction of directivity, for example, perform sound source estimation. It is easy to
apply to the device etc.
[0098]
Further, in the first embodiment, although the audio signal processing unit for controlling the
main axis direction of directivity is provided outside the microphone unit 1, this signal
processing unit is provided inside the ASIC 16 included in the microphone unit 1. It may be
provided.
In this case, a control signal corresponding to a weighting coefficient (k in equation (2)) for
adding the outputs of two differential microphones is externally input to the microphone unit 1
and the method of arithmetic processing is switched inside the ASIC 16 Control of the main axis
direction of the
[0099]
Second Embodiment Next, a second embodiment of the microphone unit and the voice input
device to which the present invention is applied will be described.
[0100]
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30
Microphone Unit of Second Embodiment The majority of the configuration of the microphone
unit of the second embodiment is the same as that of the microphone unit 1 of the first
embodiment.
Only the differences will be described below.
The same parts as those of the microphone unit 1 of the first embodiment will be described with
the same reference numerals.
[0101]
FIG. 13 is a schematic cross-sectional view showing the configuration of the microphone unit of
the second embodiment. As shown in FIG. 13, the microphone unit 2 of the second embodiment
is different from the microphone unit 1 of the first embodiment in that the acoustic resistance
member 21 is provided to close the second sound hole 101. The acoustic resistance member 21
is formed of, for example, a felt or the like, and delays the phase of the sound wave input from
the second sound hole 101. In the microphone unit 2 of the second embodiment, the
configuration of the acoustic resistance member 21 is adjusted such that the first MEMS chip 14
functions as a unidirectional microphone.
[0102]
FIG. 14 is a block diagram showing the configuration of the microphone unit of the second
embodiment. As shown in FIG. 14, in the microphone unit 2 of the second embodiment, a switch
electrode 19e for inputting a switch signal from the outside (a voice input device on which the
microphone unit 2 is mounted) is provided. It differs from the microphone unit 1 of the first
embodiment in that the switching circuit 164 provided in the ASIC 16 is operated by a switch
signal supplied via the electrode 19 e.
[0103]
Since the switch electrode 19e is provided, the switch terminal 18e is provided on the upper
surface 12a of the microphone substrate 12, as shown in FIG.
04-05-2019
31
[0104]
As shown in FIG. 14, the switching circuit 164 switches which of the signal output from the first
amplifier circuit 162 and the signal output from the second amplifier circuit 163 is to be output
to the outside. It is a circuit.
That is, in the microphone unit 2 of the second embodiment, the signal output from the
microphone unit 2 is one of the signal extracted from the first MEMS chip 14 and the signal
extracted from the second MEMS chip 15. Only one or the other is output.
[0105]
Therefore, unlike the microphone unit 1 of the first embodiment, in the microphone unit 2 of the
second embodiment, one output electrode is included in the external connection electrode 19
provided on the lower surface 11 b of the base 11 (first And the output electrode 19b). Further,
in relation to this, as shown in FIG. 15, only the first output terminal 18b is provided on the
upper surface 12a of the microphone substrate 12, and the second output terminal 18c is
eliminated (see FIG. 15). See also 3 (b)).
[0106]
The switching operation of the switching circuit 164 by the switch signal may be configured to
use, for example, H (high level) or L (low level) of the signal.
[0107]
The operation and effect of the microphone unit 2 of the second embodiment configured as
described above will be described.
[0108]
FIG. 16 is a diagram for explaining the directivity characteristic of the microphone unit of the
second embodiment.
04-05-2019
32
In FIG. 16, the attitude of the microphone unit 2 is assumed to be the same as the attitude shown
in FIG.
[0109]
In the microphone unit 2 of the second embodiment, the first MEMS chip 14 is configured as a
differential microphone, but due to the presence of the acoustic resistance member 21, the single
directivity as shown in FIG. It functions as a microphone.
In detail, the sensitivity to the sound having the sound source on one surface side (the upper
surface side in FIG. 13) of the microphone unit 1 is good, and the sensitivity to the sound having
the sound source on the other surface side (the lower surface side in FIG. 13) is extremely low.
ing. On the other hand, since the second MEMS 15 configured as a differential microphone is not
influenced by the acoustic resistance member 21, the difference in the directivity between the
far-apart noise suppression performance is excellent as in the microphone unit 1 of the first
embodiment. Demonstrates the function as a dynamic microphone. Note that the main axis of
directivity of the omnidirectional microphone using the second MEMS chip 15 is the longitudinal
direction of the microphone unit 2 (the left-right direction in FIG. 13).
[0110]
As described above, in the microphone unit 2 of the second embodiment, the electric signal
extracted based on the change in capacitance of the first MEMS chip 14 and the change in
capacitance of the second MEMS chip 15 And the electric signal extracted based on is selectively
outputable by the switching circuit 164. That is, the microphone unit 2 can be used by switching
between the function as a unidirectional microphone using the first MEMS chip 14 and the
function as a bidirectional microphone using the second MEMS chip 15 It has become. For this
reason, the microphone unit 2 of the second embodiment can easily cope with the multiple
functions of the voice input device.
[0111]
(Voice Input Device Including Microhonin Unit of Second Embodiment) The microphone unit of
the second embodiment is applied to, for example, a cellular phone (an example of a voice input
04-05-2019
33
device). The configuration in the case of applying the microphone unit 2 of the second
embodiment to a mobile phone can be, for example, the same configuration as that of the first
embodiment (a configuration similar to the configuration shown in FIGS. 11 and 12). The
description is omitted.
[0112]
A mobile phone to which the microphone unit 2 is applied is configured to have multiple
functions, and includes, for example, a hands-free function and a movie recording function. When
the control unit (not shown) of the mobile phone recognizes which of the close talk mode, hands
free mode and movie recording mode is used, the control unit (not shown) inputs a
corresponding switch signal to the microphone unit 2. Then, the switching circuit 164 performs
switching operation so that one of the signal corresponding to the first MEMS chip 14 and the
signal corresponding to the second MEMS chip 15 can be output by the switch signal. Do.
[0113]
Specifically, when the portable telephone is used in the close-talk mode, a signal corresponding
to the second MEMS chip 15 is output from the microphone unit 2 by the function of the
switching circuit 164, and audio signal processing of the portable telephone is performed. The
unit (having the function different from that of the audio signal processing unit 6 of the first
embodiment) performs processing using a signal corresponding to the second MEMS chip 15. As
described above, when the second MEMS chip 15 is used, high-quality signals suitable for close
talk can be obtained because of excellent distance noise suppression performance.
[0114]
On the other hand, when the mobile phone is used in the hands-free mode or the movie
recording mode, the signal corresponding to the first MEMS chip 14 is output from the
microphone unit 2 by the function of the switching circuit 164. The audio signal processing unit
performs processing using a signal corresponding to the first MEMS chip 14. As described above,
when the first MEMS chip 14 is used, it is desirable to collect sound because the sensitivity on
the surface side (front side) on which the first sound hole 132 and the third sound hole 133 are
provided is excellent. It is possible to pick up the voice by narrowing down to the voice of the
direction. That is, desirable signal processing can be performed in each mode.
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[0115]
(Summary and Remarks of Second Embodiment) As described above, the microphone unit 2
according to the second embodiment has a function as a differential microphone with bidirectional characteristics excellent in far-field noise suppression performance, and sound
collection sensitivity on the front side. And the function as a single directional microphone. For
this reason, according to the microphone unit of this embodiment, it is easy to correspond to the
multiple functions of the voice input device to which the microphone unit is applied. Since the
microphone unit 1 of the present embodiment has two functions, it is not necessary to separately
mount two microphone units as in the prior art, and it is easy to suppress the enlargement of the
voice input device.
[0116]
Also, although the microphone unit 2 of the present embodiment is configured to have two
MEMS chips 14 and 15, a bi-directional differential microphone unit excellent in far-field noise
suppression performance (a microphone previously developed by the present inventors) The
MEMS chip is additionally disposed in a space originally provided in the unit), and a sound hole
(closed by the acoustic resistance member 21) is provided on the lower side of the additionally
disposed MEMS chip. For this reason, it is possible to avoid the upsizing of the microphone unit
previously developed by the present inventors. This will be described below.
[0117]
In the microphone unit 2 of the present embodiment, when the first MEMS chip 14, the second
sound hole 101 and the acoustic resistance member 21 are removed, a differential microphone
unit having excellent directivity in far-field noise suppression can be obtained. In this
microphone unit, the distance between the centers of the two sound holes 132 and 133 is
preferably about 5 mm. This is due to the following reason.
[0118]
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If the distance between the two sound holes 132 and 133 is too short, the difference in sound
pressure applied to the upper surface 152a and the lower surface 152b of the second diaphragm
152 becomes smaller, and the amplitude of the second diaphragm 152 becomes smaller. SNR of
the electrical signal being Therefore, it is preferable to increase the distance between the two
sound holes 132 and 133 to some extent. On the other hand, when the center-to-center distance
between the two sound holes 132 and 133 becomes too large, the time difference until the sound
waves emitted from the sound source reach the second diaphragm 152 through the respective
sound holes 132 and 133, The phase difference is increased, and the noise removal performance
is reduced. Therefore, the distance between the centers of the two sound holes 132 and 133 is
preferably 4 mm or more and 6 mm or less, and more preferably about 5 mm.
[0119]
By the way, the length of the longitudinal direction (the direction parallel to the line connecting
the centers of the two sound holes 132 and 133, the left and right direction in FIG. 13) of the
MEMS chips 14 and 15 used for the microphone unit 2 of this embodiment is The length in the
longitudinal direction of the ASIC 16 is, for example, about 0.7 mm. When functioning as a
differential microphone, the time for the sound wave to reach from the first sound hole 132 to
the upper surface 152 a of the second diaphragm 152 and the sound wave from the third sound
hole 133 to the second diaphragm 152 It is preferable that the time taken to reach the lower
surface 152b be approximately the same. Therefore, the second MEMS chip 15 is located away
from the first sound hole 132 of the accommodation space (the space formed between the recess
space 131 of the lid 13 and the upper surface 12 a of the microphone substrate 12) (see FIG. At
13, the position is placed at the left side of the accommodation space).
[0120]
Therefore, a space in which the first MEMS chip 14 can be disposed originally exists in the
accommodation space of the bi-directional differential microphone unit having excellent far-field
noise suppression performance. Therefore, the microphone unit 1 of this embodiment has a
function as a unidirectional microphone excellent in sound collection sensitivity on the front side
added to a function as a bi-directional differential microphone excellent in far-field noise
suppression performance. The addition of the MEMS chip can make the microphone unit small
without increasing the size.
[0121]
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In this embodiment, a switching circuit 164 is provided downstream of the two amplifier circuits
162 and 163 to switch and output a signal corresponding to the first MEMS chip 14 and a signal
corresponding to the second MEMS chip 15. It was composition. This is intended to switch
between a signal corresponding to the first MEMS chip 14 and a signal corresponding to the
second MEMS chip 15 and output the signal to the outside. Other configurations can be adopted.
That is, for example, one amplifier circuit may be provided, and a switching circuit that performs
switching operation by a switch signal may be disposed between the amplifier circuit and the two
MEMS chips 14 and 15.
[0122]
Further, when two amplifier circuits 162 and 163 are provided as in the present embodiment,
the amplifier gains of the two amplifier circuits 162 and 163 may be set to different gains.
[0123]
Further, in the present embodiment, a common bias voltage is applied to the first MEMS chip 14
and the second MEMS chip 15. However, the present invention is not limited to this and another
configuration may be adopted.
That is, for example, it is possible to switch which of the first MEMS chip 14 and the second
MEMS chip 15 is electrically connected to the charge pump circuit 161 using a switch signal and
a switching circuit. Good. In this way, the possibility of crosstalk between the first MEMS chip 14
and the second MEMS chip 15 can be reduced.
[0124]
In addition, the microphone unit 2 of the present embodiment is configured to selectively output
one of the signal corresponding to the first MEMS chip 14 and the signal corresponding to the
second MEMS chip 15 to the outside. . However, the configuration is not limited to this. That is,
for example, as in the case of the microphone unit 1 of the first embodiment (see FIG. 6), both
signals may be separately and independently output to the outside (microphone unit 2 of the
second embodiment) Modified example A). In this case, the voice input device having the
microhonin unit may select which one of the two signals is to be used. Moreover, as another form
04-05-2019
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(modification B of the microphone unit 2 of the second embodiment), the configuration as shown
in FIGS. 17 and 18 may be adopted.
[0125]
As shown in FIG. 17, in the microphone unit of the modified example B, a switch electrode 19e
for inputting a switch signal from the outside (a voice input device on which the microphone unit
is mounted) is provided. A switching circuit 164 provided in the ASIC 16 is operated by a switch
signal supplied via the switching circuit 164. Since the switch electrode 19e is provided, the
switch terminal 18e is provided on the upper surface 12a of the microphone substrate 12, as
shown in FIG.
[0126]
In the switching circuit 164, the signal output from the first amplifier circuit 162 and the signal
output from the second amplifier circuit 163 are two output electrodes 19b and 19c (part of the
external connection electrode 19). Among these, it is configured to be able to switch from which
of the two (it has a function different from the switching circuit of the microphone unit 2 of the
second embodiment described above).
[0127]
That is, when the switching circuit 164 is in the first mode by the switch signal input from the
switch electrode 19e, a signal corresponding to the first MEMS chip 14 is output from the first
output electrode 19b. A signal corresponding to the second MEMS chip 15 is output from the
second output electrode 19c.
On the other hand, when the switching circuit 164 enters the second mode by the switch signal,
the first output electrode 19b outputs a signal corresponding to the second MEMS chip 15, and
the second output electrode A signal corresponding to the first MEMS chip 14 is output from
19c.
[0128]
The switching operation of the switching circuit 164 by the switch signal may be configured to
use, for example, H (high level) or L (low level) of the signal.
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[0129]
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) As in the microphone unit 2 of the second embodiment, either one of the signal
corresponding to the first MEMS chip 14 and the signal corresponding to the second MEMS chip
15 is switched by the switch signal. , Those who want to output from the microphone unit. (B) As
in the modified example A of the microphone unit 2 of the second embodiment, both the signal
corresponding to the first MEMS chip 14 and the signal corresponding to the second MEMS chip
15 are independently and independently from the microphone unit Those who want them to
output.
[0130]
In this point, according to the modified example B of the microphone unit 2 of the second
embodiment, it is convenient because it can correspond to any one of the above (A) and (B).
[0131]
In the second embodiment, the signal corresponding to the first MEMS chip 14 and the signal
corresponding to the second MEMS chip 15 are used independently.
However, the present invention is not limited to this configuration, and the configuration may be
such that both signals are combined by the audio signal processing unit to perform arithmetic
processing (addition, subtraction, etc.). By performing such processing, it is possible to control to
switch the directivity characteristic of the microphone unit 2 to various types.
[0132]
(Others) The embodiment described above is an example of the configuration to which the
present invention is applied, and the scope of application of the present invention is not limited
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to the embodiment described above. That is, various changes may be made to the embodiment
described above without departing from the object of the present invention.
[0133]
For example, in the embodiment described above, the first vibrating portion and the second
vibrating portion of the present invention are configured as the MEMS chips 14 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.
[0134]
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.
[0135]
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.
[0136]
The microphone unit of the present invention can be widely applied to a voice input device that
inputs voice and performs processing, and is suitable for, for example, a cellular phone or the
like.
[0137]
1, 2 microphone unit 5 mobile phone (voice input device) 6 audio signal processing unit 10
mounting unit 11 base (part of housing, part of mounting unit) 11b lower surface of base (back
surface of mounting surface of mounting unit) 12 Microphone substrate (part of housing, part of
mounting portion) 12a Upper surface of microphone substrate (mounting surface of mounting
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portion) 13 lid (lid) 14 first MEMS chip (first vibrating portion) 15 second MEMS chip (second
vibrating portion) 16 ASIC (electric circuit portion) 19 e switch electrode 20 case 41 first sound
path 42 second sound path 43 third sound path 101 second sound hole 111 groove portion
(Component of hollow space) 112 Base opening (component of second sound hole) 121 first
substrate opening 122 second substrate opening 123 third substrate opening (configuration of
second sound hole Element: 131 Recess space (accommodation Components between) 132 first
lid opening (first sound hole) 133 second lid opening (third sound hole) 142 first diaphragm
142a top surface of first diaphragm (one Face) 142b Lower surface of the first diaphragm (other
surface) 152 Second diaphragm 152a Upper surface of the second diaphragm (one surface)
152b Lower surface of the second diaphragm (other surface) 164 Switching circuit
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