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DESCRIPTION JP2011254194

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DESCRIPTION JP2011254194
An electro-acoustic transducer mounting substrate capable of reducing the possibility of
breakdown of the electro-acoustic transducer due to dust. An electro-acoustic transducer
mounting substrate 12 has an opening 121 covered with the electro-acoustic transducer 11
formed on a mounting surface 12 a on which the electro-acoustic transducer 11 for converting a
sound signal to an electric signal is mounted. The coating process is performed on at least a part
of the wall surface 122a of the in-substrate space 122 connected to the opening 121 (the coating
layer CL is formed). [Selected figure] Figure 1
Electro-acoustic transducer mounting substrate, microphone unit, and method of manufacturing
them
[0001]
The present invention relates to an electro-acoustic transducer mounting board on which an
electro-acoustic transducer for converting a sound signal into an electric signal is mounted, and a
microphone unit including the electro-acoustic transducer mounting board. The present
invention also relates to a method of manufacturing an electroacoustic transducer mounting
substrate and a microphone unit.
[0002]
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
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devices, etc.) A microphone unit having a function of converting a signal into an electrical signal
and outputting the signal is applied.
[0003]
The microphone unit includes an electroacoustic transducer that converts a sound signal into an
electrical signal.
The electro-acoustic transducer is mounted on a substrate (electro-acoustic transducer mounting
substrate) on which a wiring pattern is to be formed, as disclosed in Patent Documents 1 and 2,
for example. The electro-acoustic transducer, as disclosed in Patent Document 1, is an opening
that is connected to the space in the substrate (sometimes functioning as a back chamber or
sometimes functioning as a sound hole (sound path)) formed on the substrate. May be mounted
on the substrate to cover the
[0004]
Here, “in-substrate space” in the present specification refers to the substrate outer surface
(assuming that the opening surface forms the outer surface for the portion where the opening is
formed) from the reference surface. Is a space formed inside the substrate.
[0005]
JP, 2008-510427, A JP, 2010-41565, A
[0006]
By the way, as the electroacoustic transducer included in the microphone unit, a micro electro
mechanical system (MEMS) chip formed by using a semiconductor manufacturing technology
may be used because the size can be reduced.
The MEMS chip includes a diaphragm, and a fixed electrode disposed opposite to the diaphragm
with a gap therebetween to form a capacitor with the diaphragm.
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[0007]
The gap formed between the diaphragm and the fixed electrode in the MEMS chip is as narrow
as, for example, 1 μm.
Therefore, if dust gets into this gap, it causes the malfunction of the MEMS chip.
[0008]
In the case of a substrate containing resin fibers such as an FR-4 substrate (glass epoxy
substrate), fiber debris (an example of dust) is easily generated from the surface cut to form, for
example, through holes and grooves. For this reason, in a microphone unit (for example,
disclosed in Patent Document 1) having a configuration in which a MEMS chip is mounted so as
to cover an opening connected to the space in the substrate (having a surface subjected to
processing such as cutting) If a substrate such as an FR-4 substrate is liable to generate dust,
there is a problem that malfunction of the MEMS chip is likely to occur.
[0009]
In view of the above points, an object of the present invention is to provide an electro-acoustic
transducer mounting substrate capable of reducing the possibility of the electro-acoustic
transducer failing due to dust. Another object of the present invention is to provide a small-sized,
high-quality microphone unit which is provided with anti-dust measures by providing such an
electro-acoustic transducer mounting substrate. Furthermore, another object of the present
invention is to provide a manufacturing method suitable for such an electro-acoustic transducer
mounting substrate and a microphone unit.
[0010]
In order to achieve the above object, in the electro-acoustic transducer mounting substrate of the
present invention, an opening covered by the electro-acoustic transducer is formed on the
mounting surface on which the electro-acoustic transducer for converting a sound signal to an
electrical signal is mounted. It is characterized in that at least a part of the wall surface of the
space in the substrate connected to the opening is coated.
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[0011]
According to this configuration, it is possible to cover the surface of the space in the substrate,
which has been subjected to processing such as cutting and cutting, with the coating layer so that
dust is less likely to be generated.
For this reason, if the electroacoustic transducer mounting substrate of this configuration is used,
it is easy to prevent the failure of the electroacoustic transducer.
[0012]
In the electro-acoustic transducer mounting substrate of the above configuration, the coating
process may be a plating process. According to this configuration, it is easy and convenient to
form the above-mentioned coating layer for preventing dust at the same time as forming, for
example, a through wiring on the electroacoustic transducer mounting substrate.
[0013]
In the electro-acoustic transducer mounting substrate of the above-described configuration, a
glass epoxy material may be used as a substrate material. As described above, the glass epoxy
substrate tends to generate dust from the surface subjected to processing such as cutting and
cutting. For this reason, in the case of this structure, the effect of the dust countermeasure by the
said coating process becomes a big thing.
[0014]
Further, in the electro-acoustic transducer mounting substrate with the above-described
configuration, the space in the substrate may not be connected to other openings other than the
opening, or may be connected to other openings other than the opening. It is also good.
Furthermore, in the case where the space in the substrate is connected to an opening other than
the opening, the other opening may be provided on the back surface of the mounting surface,
and the other opening is the mounting It may be provided on the surface. The microphone unit is
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in various forms depending on the purpose, and the electro-acoustic transducer mounting
substrate of the present invention can be widely applied to these various forms.
[0015]
In order to achieve the above object, a microphone unit according to the present invention
comprises an electro-acoustic transducer mounting substrate of the above configuration, an
electro-acoustic transducer mounted on the electro-acoustic transducer mounting substrate so as
to cover the opening, and the electricity And a lid for forming a housing space for housing the
acoustic conversion element together with the electro-acoustic conversion element mounting
substrate.
[0016]
In the microphone unit of this configuration, since the dust is less likely to be generated in the
space in the substrate, the failure of the electroacoustic transducer is less likely to occur.
That is, according to this configuration, it is possible to provide a high quality microphone unit.
[0017]
In the microphone unit of the above configuration, the electroacoustic transducer is a MEMS chip
including a diaphragm, and a fixed electrode disposed opposite to the diaphragm with a gap and
forming a capacitor with the diaphragm. It is also good. Since the MEMS chip can be formed in a
small size, this configuration makes it possible to provide a small and high quality microphone
unit.
[0018]
In order to achieve the above object, in the method of manufacturing an electroacoustic
transducer mounting substrate according to the present invention, an opening covered by the
electroacoustic transducer, a space in the substrate connected to the opening, and a through hole
for through wiring A first step of manufacturing the substrate, a second step of plating the space
in the substrate and the through holes for the through wiring, and a third step of forming a
wiring pattern on the outer surface of the substrate by performing an etching process after the
plating treatment And providing a step.
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[0019]
According to this configuration, simultaneously with the formation of the through wiring, the
wall surface of the space in the substrate connected to the opening covered by the
electroacoustic transducer can be covered with the plating layer (one form of the coating layer) It
is easy to form the acoustic conversion element mounting substrate.
[0020]
In the method of manufacturing an electroacoustic transducer mounting substrate of the above
configuration, a fourth step of bonding another substrate to the back surface of the substrate on
which the wiring pattern is formed in the third step, on which the opening is formed. A fifth step
of attaching a protective cover so as to cover the entire surface of the substrate on which the
wiring pattern is formed in three steps and the sixth step of forming a through hole for through
wiring in the other substrate; A seventh step of plating the through holes for the through wiring
formed in the sixth step after the fourth step, the fifth step and the sixth step performed in
random order are completed, and the seventh step After completion, an eighth step of forming a
wiring pattern on the other substrate by etching, and after the wiring pattern is formed on the
other substrate A ninth step of separating the protecting cover may be further provided with.
[0021]
For example, when the space in the substrate can not be formed simply by digging in the
substrate thickness direction, it may be convenient to form the electroacoustic transducer
mounting substrate using a plurality of substrates.
In this configuration, it is assumed that the electro-acoustic transducer mounting substrate
having the space in the substrate is formed using a plurality of substrates.
Then, in the case of forming the electroacoustic transducer mounting substrate using a plurality
of substrates, the plating treatment solution, the etching treatment solution, and the like intrude
into the space in the substrate, and the residue is finally left contaminated. There is a concern
that the electroacoustic transducer mounting substrate may be manufactured.
In this respect, in the present configuration, a protective cover is attached in advance to cover
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the inner space of the substrate in anticipation of the possibility that a plating solution or the like
may remain in the inner space of the substrate in a later step. Processing and etching are
performed. For this reason, the possibility of providing the contaminated electro-acoustic
transducer mounting substrate as described above can be reduced.
[0022]
In order to achieve the above object, in the method of manufacturing a microphone unit
according to the present invention, the method of manufacturing an electro-acoustic transducer
mounting substrate by the method of manufacturing an electro-acoustic transducer mounting
substrate of the above-mentioned configuration; The method may further include the steps of:
mounting the electroacoustic transducer so as to cover the opening; and covering a lid portion so
as to cover the electroacoustic transducer on the electroacoustic transducer mounting substrate.
[0023]
According to this configuration, since the measures against dust are taken and the
electroacoustic transducer element mounting substrate with low possibility of contamination is
manufactured, and the microphone unit is assembled using the electroacoustic transducer
element mounting substrate, It is possible to provide a high quality microphone unit.
[0024]
According to the present invention, it is possible to provide an electro-acoustic transducer
mounting substrate capable of reducing the possibility of the electro-acoustic transducer failing
due to dust.
Further, according to the present invention, by providing such an electro-acoustic transducer
mounting substrate, it is possible to provide a small-sized, high-quality microphone unit to which
a countermeasure against dust is applied.
Furthermore, according to the present invention, it is possible to provide a manufacturing
method suitable for such an electroacoustic transducer mounting substrate and a microphone
unit.
[0025]
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The schematic sectional view showing the configuration of the microphone unit of the first
embodiment to which the present invention is applied The schematic sectional view showing the
configuration of the MEMS chip included in the microphone unit of the first embodiment The
microphone substrate of the microphone unit according to the first embodiment The sectional
view for explaining the manufacturing method The outline sectional view showing the
composition of the microphone unit of a 2nd embodiment to which the present invention is
applied The sectional view for explaining the manufacturing method of the microphone substrate
with which the microphone unit of a 2nd embodiment is provided The schematic sectional view
showing the composition of the microphone unit of a 3rd embodiment to which the present
invention is applied. The sectional view for explaining the manufacturing method of the
microphone substrate provided in the microphone unit of a third embodiment. The fourth
embodiment to which the present invention is applied The microphone unit of 4th Embodiment
is provided with the schematic sectional drawing which shows the structure of the microphone
unit of a form. Sectional view for explaining a manufacturing method of the microphone
substrate
[0026]
Hereinafter, the electro-acoustic transducer mounting substrate and the microphone unit of the
present invention, and the manufacturing method thereof will be described in detail with
reference to the drawings.
[0027]
First Embodiment FIG. 1 is a schematic cross-sectional view showing a configuration of a
microphone unit according to a first embodiment to which the present invention is applied.
As shown in FIG. 1, the microphone unit 1 of the first embodiment includes a MEMS chip 11, a
microphone substrate 12 on which the MEMS chip 11 is mounted, and a cover 13.
The microphone unit 1 of the first embodiment functions as an omnidirectional microphone.
[0028]
The MEMS chip 11 composed of a silicon chip is an embodiment of the electroacoustic
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transducer of the present invention, and is a small capacitor type microphone chip manufactured
using a semiconductor manufacturing technology. FIG. 2 is a schematic cross-sectional view
showing the configuration of the MEMS chip provided in the microphone unit of the first
embodiment. The external shape of the MEMS chip 11 is a substantially rectangular
parallelepiped shape, and as shown in FIG. 2, the MEMS chip 11 includes an insulating base
substrate 111, a fixed electrode 112, an insulating intermediate substrate 113, and a diaphragm
114.
[0029]
The base substrate 111 is formed with a through hole 111a having a substantially circular shape
in plan view at a central portion thereof. The plate-like fixed electrode 112 is disposed on the
base substrate 111, and a plurality of small diameter (about 10 μm diameter) through holes
112a are formed. The intermediate substrate 113 is disposed on the fixed electrode 112, and in
the same manner as the base substrate 111, a through hole 113a having a substantially circular
shape in plan view is formed at the central portion thereof. The diaphragm 114 disposed on the
intermediate substrate 113 vibrates in response to the sound pressure (vibration in the vertical
direction in FIG. 2). Further, in the present embodiment, the thin film is a thin film which vibrates
in a substantially circular portion, has conductivity and forms one end of the electrode. The fixed
electrode 112 and the diaphragm 114, which are disposed opposite to each other so as to be in a
substantially parallel relationship with each other by opening the gap Gp due to the presence of
the intermediate substrate 113, form a capacitor.
[0030]
In the MEMS chip 11, when the diaphragm 114 vibrates due to the arrival of the sound wave, the
inter-electrode distance between the diaphragm 114 and the fixed electrode 112 changes, so that
the capacitance changes. As a result, the sound wave (sound signal) incident on the MEMS chip
11 can be extracted as an electric signal. In the MEMS chip 11, the diaphragm 114 is formed by
the presence of the through holes 111 a formed in the base substrate 111, the plurality of
through holes 112 a formed in the fixed electrode 112, and the through holes 113 a formed in
the intermediate substrate 113. The lower surface side of the is also in communication with the
space outside the MEMS chip 11.
[0031]
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The microphone substrate 12 formed in a substantially rectangular shape in plan view is an
embodiment of the electro-acoustic transducer mounting substrate of the present invention, and
the MEMS chip 11 is mounted on the upper surface 12 a thereof. Although not shown in FIG. 1,
the wiring pattern (including through wiring) necessary for applying a voltage to the MEMS chip
11 and extracting an electric signal from the MEMS chip 11 is not shown in the microphone
substrate 12. Is formed.
[0032]
Further, an opening 121 is formed in the mounting surface (upper surface) 12 a on which the
MEMS chip 11 is mounted on the microphone substrate 12, and the MEMS chip 11 is disposed
so as to cover the opening 121. The opening 121 is connected to the substantially cylindrical insubstrate space 122. The in-substrate space 122 is connected only to the opening 121 and not
connected to other openings. That is, in the microphone substrate 12, a recess is formed by the
opening 121 and the in-substrate space 122. The in-substrate space 122 is provided to increase
the volume of the back chamber (the closed space facing the lower surface of the diaphragm
114). When the back chamber volume increases, the diaphragm 114 is easily displaced, and the
microphone sensitivity of the MEMS chip 11 is improved.
[0033]
The microphone substrate 12 may be, for example, an FR-4 (glass epoxy substrate) substrate, but
may be another type of substrate.
[0034]
The cover 13 whose outer diameter is provided in a substantially rectangular parallelepiped
shape covers the microphone substrate 12 to form a housing space 14 for housing the MEMS
chip 11 together with the microphone substrate 12.
A sound hole 131 is formed in the cover 13 so that the sound generated outside the microphone
unit 1 can be guided to the diaphragm 114 of the MEMS chip 11. The cover 13 is an
embodiment of the lid of the present invention.
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[0035]
When the sound wave input into the housing space 14 through the sound hole 131 reaches the
diaphragm 114, the diaphragm 114 vibrates to cause a change in capacitance as described
above. The microphone unit 1 is configured to take out the change in capacitance as an electric
signal and output it to the outside. The electric circuit unit for extracting the change in
capacitance of the MEMS chip 11 as an electric signal is preferably provided in the housing
space 14, but may be provided outside the housing space 14. Further, the electric circuit portion
may be formed monolithically on the silicon substrate on which the MEMS chip 11 is formed.
[0036]
In the microphone unit 1 of the first embodiment, the wall surface 122a of the in-substrate space
122 formed in the microphone substrate 12 (in the present embodiment, the entire wall surface
of the in-substrate space 122) is covered with the coating layer CL. The coating with the coating
layer CL can be obtained, for example, by plating, and the coating layer CL can be, for example, a
metal plating layer such as Cu plating. By covering with the coating layer CL, the possibility of
dust generation in the in-substrate space 122 of the microphone substrate 12 can be reduced.
[0037]
When the microphone substrate 12 is made of, for example, a glass epoxy substrate (FR-4
substrate), fibrous dust is likely to be generated from the processed surface of the microphone
substrate 12 (the surface on which processing such as cutting or cutting has been performed). In
the case where the wall surface 122a of the in-substrate space 122 is not covered with the
coating layer CL (in the case of a configuration different from the present embodiment), the
inside of the MEMS chip 11 disposed to cover the opening 121 connected to the in-substrate
space 122 Dust easily enters the The penetration of dust into the MEMS chip 11 causes the
failure of the MEMS chip 11. As an example, dust may enter from the through hole 112 a
provided in the fixed electrode 112 and the gap Gp (see FIG. 2) between the fixed electrode 112
and the diaphragm 114 may be clogged with dust. In this respect, in the microphone unit 1
according to the first embodiment, the presence of the coating layer CL makes it difficult for dust
to be generated from the in-substrate space 122, and the possibility of failure of the MEMS chip
11 can be suppressed low.
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[0038]
Next, a method of manufacturing the above-described microphone substrate 12 and the
microphone unit 1 will be described mainly with reference to FIG. FIG. 3 is a cross-sectional view
for explaining the method of manufacturing the microphone substrate included in the
microphone unit of the first embodiment, wherein (a) to (f) show states in the process of
manufacturing, and (g) shows the completed microphone substrate. Show the condition.
[0039]
In manufacturing the microphone substrate 12, first, a substrate 12 '(flat) having its upper
surface and lower surface covered with a metallic material (conductive material) 101 such as Cu
is prepared (step a; see FIG. 3A). ). Here, the thickness of the substrate 12 ′ is, for example, 1.0
mm, and the thickness of the conductive material 101 is 0.15 μm.
[0040]
At a substantially central position of the prepared substrate 12 ', the substrate 12' is dug from
the upper surface to an intermediate position in the thickness direction (vertical direction in FIG.
3). As a result, as shown in FIG. 3B, the opening 121 with a substantially circular shape in plan
view in the substrate 12 ′ and the substantially cylindrical in-substrate space 122 connected to
the opening 121 (connected only to the opening 121, and other openings (Not connected) (step
b). The digging of the substrate 12 'is performed using, for example, an NC (Numerical Control)
device capable of cutting a three-dimensional object while controlling the coordinate position.
The size of the in-substrate space 122 is, for example, a diameter of 0.6 mm and a depth of 0.5
mm.
[0041]
In addition, although it was set as the structure obtained by utilizing NC apparatus here, the
board | substrate (board | substrate in which the recessed part was formed) in which the opening
121 and the space 122 in a board | substrate were formed is not limited to this. That is, the
opening 121 is formed by bonding a first substrate (flat plate shape) in which a through hole (the
formation thereof is formed by a drill or a laser, for example) and a second substrate (flat plate
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shape) without the through hole. Also, one substrate in which the in-substrate space 122 is
formed may be obtained.
[0042]
Next, in the substrate 12 ′ in which the opening 121 and the space 122 in the substrate are
formed, the through hole 103 (for example, as shown in FIG. Form a diameter of 0.3 mm) (step
c). For example, a drill, a laser, an NC device, or the like is used to form the through hole 103.
The part that needs to electrically connect the upper surface and the lower surface of the
substrate 12 'is appropriately determined depending on how the circuit configuration of the
microphone unit is designed. Although the location which forms the through-hole 103 is shown
as three places in FIG.3 (c), it is not the meaning limited to this. Also, the order of the process b
and the process c may be reversed.
[0043]
After the through holes 103 are formed in the substrate 12 ′, the through holes 103 are then
subjected to plating (for example, electroless copper plating) to form the through wiring 104 as
shown in FIG. d). At this time, the wall surface of the in-substrate space 122 is also plated.
Therefore, simultaneously with the formation of the through wiring 104, the entire wall surface
of the in-substrate space 122 is covered with a metal (for example, Cu) plating layer CL (coating
layer CL).
[0044]
The formation of the through wiring 104 and the process of covering the wall surface of the
space 122 in the substrate with the coating layer CL may be performed by a method other than
the plating process, for example, a method using conductive paste (filling, coating etc.) It may be
as well.
[0045]
Next, on the upper and lower surfaces of the substrate 12 ′, portions requiring a wiring pattern
are masked with the etching resist 105 as shown in FIG. 3 (e) (step e).
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At this time, the coating layer CL (for example, a Cu plated layer) applied to the wall surface of
the in-substrate space 122 is also masked with the etching resist 105.
[0046]
When the mask by the etching resist 105 is completed, the substrate 12 'is dipped in an etching
solution (step f). As a result, among the conductive materials (for example, Cu) provided on the
upper surface and the lower surface of the substrate 12 ′, the portions not covered with the
etching resist 105 are removed as shown in FIG. 3 (f).
[0047]
Here, although the configuration in which the unnecessary conductive material is removed by
etching is not limited to this, for example, the unnecessary conductive material may be removed
by laser processing or cutting.
[0048]
When the etching is completed, the substrate 12 'is cleaned and the etching resist 105 is
removed (step g).
As a result, as shown in FIG. 3G, the microphone substrate 12 provided with the opening 121
and the space 122 in the substrate whose wall surface is covered with the coating layer CL and in
which the wiring pattern (including the through wiring) is formed is obtained. Be
[0049]
The MEMS chip 11 is disposed on the upper surface 12 a of the microphone substrate 12 so as
to cover the opening 121, and the cover 13 is further covered so as to cover the MEMS chip 11.
Thus, the microphone unit 1 shown in FIG. In the MEMS chip 11, a gap can not be formed
between the bottom surface and the top surface of the microphone substrate 12 by a die bonding
material (for example, an epoxy resin type or silicone resin type adhesive or the like) so that no
acoustic leak occurs. , Is bonded to the microphone substrate 12.
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[0050]
The cover 13 is also bonded to the upper surface of the microphone substrate 12 using, for
example, an adhesive or an adhesive sheet so as to hermetically seal. When the electric circuit
unit is mounted on the microphone substrate 12, the cover 13 is bonded to the upper surface
(mounting surface of the MEMS chip 11 or the like) of the microphone substrate 12 after the
MEMS chip 11 and the electric circuit unit are bonded to the microphone substrate 12. Be done.
The wiring pattern formed on the lower surface of the microphone substrate 12 is used as an
external electrode.
[0051]
Although the wiring pattern provided on the microphone substrate 12 has been described above
as being formed by the subtraction method using the etching method, the present invention is
not limited to this. That is, the wiring pattern provided on the microphone substrate 12 may be
formed by an addition method such as printing or embedding method.
[0052]
Second Embodiment FIG. 4 is a schematic cross-sectional view showing a configuration of a
microphone unit according to a second embodiment to which the present invention is applied. As
shown in FIG. 4, the microphone unit 2 of the second embodiment includes a MEMS chip 21, a
microphone substrate 22 on which the MEMS chip 21 is mounted, and a cover 23. The
microphone unit 2 of the second embodiment functions as an omnidirectional microphone.
[0053]
The configuration of the MEMS chip 21 (an embodiment of the electroacoustic transducer of the
present invention) having the fixed electrode 212 (having a plurality of through holes 212a) and
the diaphragm 214 is the same as that of the MEMS chip 11 of the first embodiment. Detailed
description will be omitted as it is present.
[0054]
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The configuration of the microphone substrate 22 (the embodiment of the electro-acoustic
transducer mounting substrate of the present invention) is substantially the same as that of the
microphone substrate 12 of the first embodiment, but formed on the mounting surface (upper
surface) 22 a of the microphone substrate 22 This is different from the configuration of the first
embodiment in that the in-substrate space 222 connected to the first opening 221 is connected
to the second opening 223 formed on the back surface (lower surface) 22b of the mounting
surface of the microphone substrate 22. There is.
That is, the through hole penetrating the microphone substrate 22 in the thickness direction is
formed in the microphone substrate 22 not by the recess as in the first embodiment but by the
first opening 121, the in-substrate space 122 and the second opening 223. . Further, the cover
23 (the embodiment of the lid portion of the present invention) also has substantially the same
configuration as the cover 13 of the first embodiment, but differs from the configuration of the
first embodiment in that a sound hole is not provided. .
[0055]
The microphone substrate 22 may be, for example, an FR-4 (glass epoxy substrate) substrate, but
may be another type of substrate.
[0056]
In the microphone unit 2 of the second embodiment, the MEMS chip 21 is disposed to cover the
first opening 221 formed in the mounting surface 22 a of the microphone substrate 22.
The through hole formed by the first opening 221, the space 222 in the substrate, and the
second opening 223 functions as a sound hole. That is, the sound waves generated outside the
microphone unit 2 reach the lower surface of the diaphragm 214 through the second opening
223, the space 222 in the substrate, and the first opening 221.
[0057]
As a result, the diaphragm 214 vibrates to cause a change in capacitance. The microphone unit 2
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is configured to take out the change in capacitance as an electric signal and output it to the
outside. The notes on the arrangement of the electric circuit unit for taking out the change of the
electrostatic capacitance in the MEMS chip 21 as an electric signal are the same as in the case of
the first embodiment.
[0058]
The microphone unit 2 of the second embodiment is configured to use the sealed space 24
(storage space for storing the MEMS chip 21) formed by the microphone substrate 22 and the
cover 23 as a back chamber, thereby increasing the volume of the back chamber. It's easy to do.
Because of this, it is easy to improve the microphone sensitivity.
[0059]
Also in the microphone unit 2 of the second embodiment, the wall surface 222a of the insubstrate space 222 formed in the microphone substrate 22 (in the present embodiment, the
entire wall surface of the in-substrate space 222) is covered with the coating layer CL. The
coating with the coating layer CL can be obtained, for example, by plating, and the coating layer
CL can be, for example, a metal plating layer such as Cu plating. The effect of the coating by the
coating layer CL is the same as that of the first embodiment, and even in the microphone unit 2
of the second embodiment, the generation of dust in the in-substrate space 222 is prevented and
the failure of the MEMS chip 21 is achieved. It can be reduced.
[0060]
Next, a method of manufacturing the microphone substrate 22 and the microphone unit 2 as
described above will be described mainly with reference to FIG. FIG. 5 is a cross-sectional view
for explaining the method of manufacturing the microphone substrate included in the
microphone unit of the second embodiment, wherein (a) to (f) show states in the middle of
manufacturing, and (g) shows the completed microphone substrate. Show the condition.
[0061]
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In order to manufacture the microphone substrate 22, first, a substrate 22 '(flat plate) whose
upper and lower surfaces are covered with a metal material (conductive material) 201 such as Cu
is prepared (step a; see FIG. 5A). ). The thicknesses of the substrate 22 ′ and the conductive
material 201 can be the same as in the first embodiment.
[0062]
At a substantially central position of the prepared substrate 22 ', a hole (for example, a diameter
of 0.6 mm) penetrating from the upper surface to the lower surface along the thickness direction
of the substrate 22' (vertical direction in FIG. 5) is drilled, laser, NC Open using equipment etc.
Thus, the first opening 221 having a substantially circular shape in plan view on the upper
surface of the substrate 22 ′, the substantially cylindrical in-substrate space 222 connected to
the first opening 221, and the lower surface of the substrate 22 ′ are provided. The second
opening 223 having a substantially circular shape in a plan view connected to the second
opening 223 is formed (step b; see FIG. 5B).
[0063]
Thereafter, the same processing as that of the first embodiment is sequentially performed.
[0064]
First, as shown in FIG. 5C, a through hole 203 is formed in a portion where the upper surface and
the lower surface need to be electrically connected (step c).
The order of the step b and the step c may be reversed. Then, plating is performed to form a
through wiring 204 as shown in FIG. 5D (step d). At this time, the wall surface of the substrate
inner space 222 is also plated, and the entire wall surface of the substrate inner space 222 is
covered with a metal (for example, Cu) plating layer CL (coating layer CL). The formation of the
through wiring 204 and the process of covering the wall surface of the in-substrate space 222
with the coating layer CL may be another method as in the first embodiment.
[0065]
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Next, on the upper and lower surfaces of the substrate 22 ′, portions requiring a wiring pattern
are masked with the etching resist 205 as shown in FIG. 5E (step e). At this time, the coating
layer CL (for example, a Cu plated layer) applied to the wall surface of the in-substrate space 222
is also masked with the etching resist 205.
[0066]
When the mask by the etching resist 205 is completed, the substrate 22 'is immersed in an
etching solution to remove unnecessary conductive material (for example, Cu) as shown in FIG.
5F (step f), and then cleaning and etching resist A removal of 205 is performed (step g). Thus, as
shown in FIG. 5G, the microphone provided with the first opening 221, the space 222 in the
substrate covered with the coating layer CL, and the second opening 223, and having the wiring
pattern (including the through wiring) formed therein. A substrate 22 is obtained.
[0067]
The MEMS chip 21 is disposed on the upper surface 22a of the microphone substrate 22 so as to
cover the opening 221, and the cover 23 is further covered so as to cover the MEMS chip 21.
Thus, the microphone unit 2 shown in FIG. The bonding method of the MEMS chip 21 and the
cover 23 and the precautions in the case of mounting the electric circuit unit on the microphone
substrate 22 are the same as those in the first embodiment. Further, the wiring pattern provided
on the microphone substrate 22 may be formed not by the subtraction method but by the
addition method as in the case of the first embodiment.
[0068]
Third Embodiment FIG. 6 is a schematic cross-sectional view showing the configuration of a
microphone unit according to a third embodiment of the present invention. As shown in FIG. 6,
the microphone unit 3 of the third embodiment includes a MEMS chip 31, a microphone
substrate 32 on which the MEMS chip 31 is mounted, and a cover 33. The microphone unit 3 of
the third embodiment functions as an omnidirectional microphone.
[0069]
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19
The configuration of a MEMS chip 31 (an embodiment of the electroacoustic transducer of the
present invention) having a fixed electrode 312 (having a plurality of through holes 312a) and a
diaphragm 314 is the same as that of the MEMS chip 11 of the first embodiment. Therefore, the
detailed description is omitted. Further, the configuration of the cover 33 (the embodiment of the
lid portion of the present invention) in which the sound hole 331 is formed is also the same as
that of the cover 13 of the first embodiment, so the detailed description is omitted.
[0070]
The configuration of the microphone substrate 32 (the embodiment of the electroacoustic
transducer of the present invention) is different from the configuration of the first embodiment.
For this reason, the microphone unit 3 of the third embodiment is different from the microphone
unit 1 of the first embodiment in the configuration of the back room.
[0071]
The microphone substrate 32 formed in a substantially rectangular shape in plan view is formed
by bonding three substrates 32a, 32b, and 32c as shown in FIG. Although not shown in FIG. 6,
the microphone substrate 32 is a wire necessary for applying a voltage to the MEMS chip 31
mounted on the upper surface 32 d thereof and extracting an electrical signal from the MEMS
chip 31. A pattern (including a through wiring) is formed.
[0072]
Further, an opening 321 is formed in the mounting surface (upper surface) 32 d on which the
MEMS chip 31 is mounted on the microphone substrate 32, and the MEMS chip 31 is disposed
so as to cover the opening 321. The opening 321 is connected to the in-substrate space 322
which is substantially L-shaped in cross section. The in-substrate space 322 is connected only to
the opening 321 and not connected to other openings. As described above, since the microphone
substrate 32 is configured by bonding a plurality of substrates, the in-substrate space 322 having
a substantially L shape in cross section can be easily obtained. The microphone substrate 32 may
be, for example, an FR-4 (glass epoxy substrate) substrate, but may be another type of substrate.
18-04-2019
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[0073]
The substrate interior space 322 is provided to increase the volume of the back chamber (a
closed space facing the lower surface of the diaphragm 314). The in-substrate space 322 of the
present embodiment can have a larger volume than the in-substrate space 122 of the first
embodiment because of its shape (generally L-shaped in cross section). For this reason, the
microphone unit 3 of the third embodiment can be expected to improve the microphone
sensitivity as compared with the microphone unit 1 of the first embodiment. The substrate
internal space 322 may be configured to have a hollow space connected to digging in the
substrate thickness direction so as to increase the volume of the back chamber, and is not limited
to the configuration of the present embodiment. It does not matter even if it has a shape.
[0074]
In the microphone unit 3 of the third embodiment, when a sound wave input into the
accommodation space 34 (formed by the microphone substrate 32 and the cover 33) of the
MEMS chip 21 via the sound hole 331 reaches the diaphragm 314, The diaphragm 314 vibrates
to cause a change in capacitance. The microphone unit 3 is configured to take out the change in
capacitance as an electric signal and output it to the outside. The notes on the arrangement of
the electric circuit unit for taking out the change of the electrostatic capacitance in the MEMS
chip 31 as an electric signal are the same as those in the first embodiment.
[0075]
By the way, in the microphone unit 3 of the third embodiment, a part of the wall surface 322a of
the in-substrate space 322 formed in the microphone substrate 32 (a part excluding the bottom
wall of the in-substrate space 322) is covered with the coating layer CL. There is. The coating
with the coating layer CL can be obtained, for example, by plating, and the coating layer CL can
be, for example, a metal plating layer such as a Cu plating layer. The effect of the coating by the
coating layer CL is the same as that of the first embodiment, and even in the microphone unit 3
of the third embodiment, generation of dust in the in-substrate space 322 is prevented, and
failure of the MEMS chip 31 is prevented. It can be reduced.
[0076]
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21
Of course, the bottom wall of the substrate inner space 322 may also be covered with the coating
layer CL. In the present embodiment, the microphone substrate 32 is formed by bonding a
plurality of substrates 32a to 32c, and the bottom wall of the in-substrate space 322 is formed
by the upper surface of the substrate 32c. The upper surface of the substrate 32c is not a surface
on which processing such as cutting or cutting has been performed, so dust is less likely to be
generated. Therefore, in the present embodiment, the bottom wall of the substrate inner space
322 is not covered with the coating layer CL.
[0077]
Next, a method of manufacturing the microphone substrate 32 and the microphone unit 3 as
described above will be described mainly with reference to FIG. FIG. 7 is a cross-sectional view
for explaining the method of manufacturing the microphone substrate included in the
microphone unit of the third embodiment, wherein (a) to (o) show the state in the middle of
manufacturing, and (p) shows the completed microphone substrate. Show the condition.
[0078]
In manufacturing the microphone substrate 32, first, a first substrate 32a (flat plate shape)
whose upper surface is covered with a metal material (conductive material) 301 such as Cu, for
example, is prepared. Then, along the thickness direction of the first substrate 32a (vertical
direction in FIG. 7), the first through hole 302 having a substantially circular shape in plan view
penetrating from the upper surface to the lower surface using a drill, a laser, an NC device, etc.
Open (step a; see FIG. 7 (a)). The formation position of the first through hole 302 is substantially
at the center of the first substrate 32a. The thickness of the first substrate 32a is, for example,
0.3 mm, and the thickness of the conductive material 301 is 0.15 μm. Further, the diameter of
the first through hole 302 is 0.6 mm.
[0079]
In addition, a second substrate 32b (flat plate shape) whose lower surface is covered with a metal
material (conductive material) 301 such as Cu, for example, is prepared. The thicknesses of the
second substrate 32b and the conductive material 301 are the same as those of the first
substrate 32a. Then, along the thickness direction of the second substrate 32b (vertical direction
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in FIG. 7), the second through hole 303 having a substantially circular shape in plan view
penetrating from the upper surface to the lower surface using a drill, a laser, an NC device, etc.
Open (step b; see FIG. 7 (b)). The second through hole 303 is provided at a position overlapping
the first through hole 302, and the diameter thereof is provided larger than that of the first
through hole 302. Of course, the order of the step a and the step b may be reversed.
[0080]
Next, an adhesive is applied to at least one of the lower surface of the first substrate 32a and the
upper surface of the second substrate 32b, and pressed to bond the first substrate 32a and the
second substrate 32b (step c; FIG. 7) (C)). As a result, the opening 321 of the mounting surface
on which the MEMS chip 31 is mounted, and the in-substrate space 322 (substantially L-shaped
in cross section) connected to the opening 321 can be obtained. In addition, an adhesive sheet
(for example, a thermoplastic sheet having a thickness of about 50 μm) may be used instead of
the adhesive, or the first substrate 32a and the second substrate 32b may be pasted together by
thermal compression.
[0081]
The substrate formed by bonding the first substrate 32a and the second substrate 32b shown in
FIG. 7C may be formed of one substrate. In this case, a substrate provided with a conductive
material on the upper and lower surfaces is prepared. Then, the substrate is dug from the upper
surface side and the lower surface side using an NC device. If the area for forming the digging is
changed between the digging formed from the upper surface side and the digging formed from
the lower surface side, the same substrate as shown in FIG. 7C can be obtained.
[0082]
Next, a third through hole 304 (for example, 0.3 mm in diameter) is formed where electrical
connection is required between the upper surface of the first substrate 32 a and the lower
surface of the second substrate 32 b (step d; FIG. d) see). For example, a drill, a laser, an NC
device, or the like is used to form the third through hole 304.
[0083]
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23
Next, the third through hole 304 is plated (for example, electroless copper plating) to form a first
through wiring 305 as shown in FIG. 7E (step e). At this time, the wall surface of the in-substrate
space 322 is also plated, and the entire wall surface of the in-substrate space 322 is covered with
a metal (for example, Cu) plating layer CL (coating layer CL). The formation of the first through
wiring 305 and the process of covering the wall surface of the space 322 in the substrate with
the coating layer CL may be performed by a method other than plating. For example, conductive
paste is used (embedded, coated, etc. ) May be used.
[0084]
Next, on the upper surface of the first substrate 32a and the lower surface of the second
substrate 32b, the portion requiring the wiring pattern formation is masked with the etching
resist 306 (step f; see FIG. 7F). At this time, the coating layer CL (for example, a Cu plating layer)
applied to the wall surface of the in-substrate space 322 is also masked with the etching resist
306.
[0085]
Next, the first substrate 32a and the second substrate 32b, which are bonded to each other, are
immersed in an etching solution. As a result, of the conductive material (for example, Cu)
provided on the substrate, a portion not covered with the etching resist 306 is removed (step g;
see FIG. 7G). Here, although the configuration in which the unnecessary conductive material is
removed by etching is not limited to this, for example, the unnecessary conductive material may
be removed by laser processing or cutting.
[0086]
Next, the substrate immersed in the etching solution is cleaned, and then the etching resist 306 is
removed (step h; see FIG. 7 (h)). Then, a third substrate 32c (an embodiment of another substrate
of the present invention) whose lower surface is covered with the conductive material 301 is
attached to the lower surface of the second substrate 32b (step i; see FIG. 7 (i)). The thicknesses
of the third substrate 32c and the conductive material are the same as in the case of the first
substrate 32a and the second substrate 32b. Bonding of the third substrate 32c to the second
18-04-2019
24
substrate 32b may be performed by the same method as bonding of the first substrate 32a and
the second substrate 32b.
[0087]
Next, a protective cover 307 covering and sealing the entire top surface of the first substrate 32a
is attached (step j; see FIG. 7 (j)). In the present embodiment, the protective cover 307 has a box
shape, and the outer edge portion 307a is adhesively fixed to the first substrate 32a in a state in
which the opening of the box is directed downward. A gap is formed between the first substrate
32 a and the protective cover 307 at a position other than the outer edge portion 307 a. The
shape of the protective cover 307 is not limited to this shape, and may be flat. When the
protective cover 307 is flat, the entire surface may be adhered to the upper surface of the first
substrate 32a.
[0088]
In the process of attaching the protective cover 307, the purpose is to prevent the substrate
processing liquid from intruding into the in-substrate space 322 and contaminating the electroacoustic transducer mounting substrate 32 finally obtained in the subsequent substrate
manufacturing process. Provided in In detail, when the protective cover 307 is not provided, the
plating solution or the etching solution may intrude into the space 322 in the substrate during
the plating, etching, and cleaning steps, and the residue may remain to contaminate the
substrate. In this respect, by attaching the protective cover 307 as in the present embodiment,
the contamination of the substrate can be prevented.
[0089]
Next, a fourth through hole 308 having a substantially circular shape in plan view is made in the
third substrate 32c from the lower surface of the third substrate 32c to the lower surface of the
second substrate 32b (step k; see FIG. 7K). The fourth through hole 308 can be, for example, a
laser, an NC device, or the like, and its diameter can be about 0.5 mm. Note that the order of step
i to step k may be changed as appropriate.
[0090]
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25
Next, the fourth through hole 308 is plated (for example, electroless copper plating) to form a
second through wire 309 as shown in FIG. 7L (step l). As a result, electrical connection is made
between the wiring pattern on the lower surface of the second substrate 32b and the conductive
material 301 on the lower surface of the third substrate 32c. In the plating process, the presence
of the protective cover 307 prevents the plating solution from intruding into the in-substrate
space 322. The formation of the second through wiring 309 may be performed by a method
other than the plating process, and examples thereof include a method using (such as filling and
coating) a conductive paste.
[0091]
Next, on the lower surface of the third substrate 32c, a portion requiring a wiring pattern is
masked with the etching resist 306 (step m; see FIG. 7 (m)). Next, the substrate (the first
substrate 32a, the second substrate 32b, and the third substrate 32c are bonded together) is
immersed in an etching solution to remove unnecessary conductive material (for example, Cu) on
the lower surface of the third substrate 32c. (Step n; see FIG. 7 (n)). At this time, the presence of
the protective cover 307 prevents the etchant from intruding into the space 322 in the substrate.
[0092]
Here, although the configuration in which the unnecessary conductive material is removed by
etching is not limited to this, for example, the unnecessary conductive material may be removed
by laser processing or cutting.
[0093]
When the etching is completed, the substrate is cleaned, and then the etching resist 306 is
removed (step o; see FIG. 7 (o)).
And finally, as shown in FIG. 7 (p), the adhesion part of the protective cover 307 is removed and
the protective cover 307 is separated (process p). Thereby, the microphone substrate 32
provided with the opening 321 and the space 322 in the substrate in which a part of the wall
surface is covered with the coating layer CL is formed, and the wiring pattern (including the
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through wiring) is formed.
[0094]
The MEMS chip 31 is disposed on the upper surface 32 d of the microphone substrate 32 so as
to cover the opening 321, and the cover 33 is further covered so as to cover the MEMS chip 31.
Thus, the microphone unit 3 shown in FIG. The bonding method of the MEMS chip 31 and the
cover 33 and the precautions in the case of mounting the electric circuit portion on the
microphone substrate 32 are the same as those in the first embodiment. Further, the wiring
pattern provided on the microphone substrate 32 may be formed not by the subtraction method
but by the addition method as in the case of the first embodiment.
[0095]
Fourth Embodiment FIG. 8 is a schematic cross-sectional view showing a configuration of a
microphone unit according to a fourth embodiment to which the present invention is applied. As
shown in FIG. 8, the microphone unit 4 of the fourth embodiment includes a MEMS chip 41, a
microphone substrate 42 on which the MEMS chip 41 is mounted, and a cover 43. The
microphone unit 4 of the fourth embodiment functions as a bi-directional differential
microphone.
[0096]
The configuration of a MEMS chip 41 (an embodiment of the electroacoustic transducer of the
present invention) having a fixed electrode 412 (having a plurality of through holes 412a) and a
diaphragm 414 is the same as that of the MEMS chip 11 of the first embodiment. Detailed
description will be omitted as it is present.
[0097]
The configuration of the microphone substrate 42 (the embodiment of the electroacoustic
transducer of the present invention) is different from the configurations of the first, second and
third embodiments.
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The microphone substrate 42 formed in a substantially rectangular shape in plan view is formed
by bonding three substrates 42a, 42b and 42c as shown in FIG. Although not shown in FIG. 8, the
microphone substrate 42 is a wire necessary for applying a voltage to the MEMS chip 41
mounted on the upper surface 42 d thereof and extracting an electrical signal from the MEMS
chip 41. A pattern (including a through wiring) is formed.
[0098]
Further, in the microphone substrate 42, a first opening 421 is formed near the center of the
mounting surface (upper surface) 42d on which the MEMS chip 41 is mounted, and the MEMS
chip 41 is disposed so as to cover the first opening 421. Ru. The first opening 421 is connected
to the in-substrate space 422 substantially U-shaped in cross section. The in-substrate space 422
is connected not only to the first opening 421 but also to a second opening 423 formed in the
mounting surface 42 d of the microphone substrate 42. As described above, since the
microphone substrate 42 is configured by bonding a plurality of substrates, the configuration
including the first opening 421, the in-substrate space 422, and the second opening 423 can be
easily obtained. The microphone substrate 42 may be, for example, an FR-4 (glass epoxy
substrate) substrate, but may be another type of substrate.
[0099]
The cover 43, whose outer diameter is provided in a substantially rectangular parallelepiped
shape, covers the microphone substrate 42 to form a housing space 44 for housing the MEMS
chip 41 together with the microphone substrate 42. The cover 43 is provided with a first sound
hole 431 communicating with the accommodation space 44. Further, the cover 43 is formed with
a second sound hole 432 communicating with the in-substrate space 422 through the second
opening 423. The cover 43 is an embodiment of the lid of the present invention.
[0100]
In the microphone unit 4 of the fourth embodiment, the sound wave input into the
accommodation space 44 via the first sound hole 431 reaches the upper surface of the
diaphragm 414. Also, the sound wave input to the in-substrate space 422 via the second sound
hole 432 reaches the lower surface of the diaphragm 414. Therefore, when sound is generated
outside the microphone unit 4, the diaphragm 414 vibrates due to the difference between the
18-04-2019
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sound pressure applied to the upper surface and the sound pressure applied to the lower surface.
[0101]
The sound pressure of a sound wave (the amplitude of the sound wave) is inversely proportional
to the distance from the sound source. Then, the sound pressure attenuates sharply at a position
close to the sound source, and gently attenuates as it gets away from the sound source.
Therefore, when the distance from the sound source to the upper surface of the diaphragm 414
is different from the distance from the lower surface to the lower surface, the user's voice
generated near the microphone unit 4 and incident on the upper and lower surfaces of the
diaphragm 414 A large sound pressure difference is generated between the upper surface and
the lower surface to vibrate the diaphragm. On the other hand, noise incident on the upper
surface and the lower surface of the diaphragm 414 from a distance is almost the same sound
pressure and cancels each other to hardly vibrate the diaphragm.
[0102]
Therefore, the electrical signal extracted by the vibration of the diaphragm 414 can be regarded
as an electrical signal representing the user's voice from which noise has been removed. That is,
the microphone unit 4 of the present embodiment is suitable for a close talk type microphone
which is required to suppress distant noise and collect close sounds.
[0103]
An electric circuit unit for extracting a change in capacitance of the MEMS chip 41 as an electric
signal may be provided, for example, in the housing space 44 or may be provided outside the
microphone unit. Further, the electric circuit portion may be monolithically formed on the silicon
substrate on which the MEMS chip 41 is formed.
[0104]
By the way, in the microphone unit 4 of the fourth embodiment, a part of the wall surface 422a
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of the in-substrate space 422 formed in the microphone substrate 42 is covered with the coating
layer CL. The coating with the coating layer CL can be obtained, for example, by plating, and the
coating layer CL can be, for example, a metal plating layer such as a Cu plating layer. The effect
of the coating by the coating layer CL is the same as that of the first embodiment, and even in the
microphone unit 4 of the fourth embodiment, generation of dust in the in-substrate space 422 is
prevented, and failure of the MEMS chip 41 is prevented. It can be reduced.
[0105]
Of course, the entire wall surface forming the in-substrate space 422 may be covered with the
coating layer CL. In the present embodiment, the microphone substrate 42 is formed by bonding
a plurality of substrates 42 a to 42 c. The portion (wall surface) where the coating layer CL is not
provided in the in-substrate space 422 is formed by the upper surface of the third substrate 42c.
Since this portion is not a surface on which processing such as cutting or cutting has been
performed, dust is less likely to be generated. Therefore, in the present embodiment, a part of the
wall surface of the in-substrate space 422 is not covered with the coating layer CL.
[0106]
Next, a method of manufacturing the microphone substrate 42 and the microphone unit 4 as
described above will be described mainly with reference to FIG. FIG. 9 is a cross-sectional view
for explaining the method of manufacturing the microphone substrate included in the
microphone unit of the fourth embodiment, wherein (a) to (o) show the state in the middle of
manufacturing, and (p) shows the completed microphone substrate. Show the condition.
[0107]
In manufacturing the microphone substrate 42, first, a first substrate 42a (flat plate shape)
whose upper surface is covered with a metal material (conductive material) 401 such as Cu, for
example, is prepared. Then, the first through holes 402 and the second through holes 403 in a
substantially circular shape in plan view penetrating from the upper surface to the lower surface
along the thickness direction (vertical direction in FIG. 9) of the first substrate 42a are, for
example, drills, lasers, Open using an NC device or the like (step a; see FIG. 9 (a)). The thickness
of the first substrate 42a is, for example, 0.3 mm, and the thickness of the conductive material
401 is 0.15 μm. Further, the diameters of the first through holes 402 and the second through
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holes 403 are 0.6 mm. Here, the first through holes 402 and the second through holes 403 have
the same shape, but may have different shapes.
[0108]
In addition, a second substrate 42b (flat plate shape) whose lower surface is covered with a metal
material (conductive material) 401 such as Cu, for example, is prepared. The thicknesses of the
second substrate 42b and the conductive material 401 are the same as those of the first
substrate 42a. Then, the third through hole 404 having a substantially rectangular shape in plan
view penetrating from the upper surface to the lower surface along the thickness direction
(vertical direction in FIG. 9) of the second substrate 42b, using, for example, a drill, a laser, or an
NC device Open (step b; see FIG. 7 (b)). The third through hole 404 is provided to overlap the
first through hole 402 and the second through hole 403.
[0109]
In the present embodiment, the right end of the third through hole 404 is at the same position as
the right end of the first through hole 402, and the left end of the third through hole 404 is at
the same position as the left end of the second through hole 403. Although not limited to this
configuration. For example, the left and right ends of the third through hole 404 may be further
expanded to the left and right than in the present embodiment. Further, the shape of the third
through hole 404 is not limited to the shape of the present embodiment (a substantially
rectangular shape in plan view), and can be changed as appropriate. Also, the order of the step a
and the step b may of course be reversed.
[0110]
Next, the lower surface of the first substrate 42a and the upper surface of the second substrate
42b are bonded (Step c; see FIG. 9C). Thus, the first opening 421 of the mounting surface on
which the MEMS chip 41 is mounted, the in-substrate space 422 connected to the first opening
421 (substantially U-shaped in cross section), and the mounting surface on which the MEMS chip
41 is mounted The second opening 423 is provided separately from the one opening 421 and
connected to the in-substrate space 422. The bonding of the first substrate 42a and the second
substrate 42b may be performed in the same manner as the bonding of the first substrate 32a
and the second substrate 32b in the third embodiment. Further, as in the case of the third
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31
embodiment, the substrate shown in FIG. 9C (the substrate formed by bonding the first substrate
42a and the second substrate 42b) is formed of one substrate. It is also good.
[0111]
Hereinafter, although there is a difference in the shape of the substrate, the microphone
substrate 42 is manufactured in the same procedure as in the case of the third embodiment. The
points overlapping with the third embodiment are omitted or briefly described.
[0112]
Where electrical connection is required between the upper surface of the first substrate 42a and
the lower surface of the second substrate 42b, for example, a fourth through hole 405 (for
example, 0.3 mm in diameter) is formed using a drill, a laser, an NC device or the like. Form (step
d; see FIG. 9 (d)). Subsequently, the fourth through holes 405 are plated (for example, electroless
copper plating) to form a first through wiring 406 as shown in FIG. 9E (step e). At this time, the
wall surface of the in-substrate space 422 is also plated, and the entire wall surface of the insubstrate space 422 is covered with the metal plating layer CL (coating layer CL).
[0113]
The formation of the through wiring 406 and the process of covering the wall surface of the insubstrate space 422 with the coating layer CL may be performed by a method other than plating
as in the case of the third embodiment.
[0114]
Next, on the upper surface of the first substrate 42a and the lower surface of the second
substrate 42b, the portion requiring the wiring pattern formation is masked with the etching
resist 407 (step f; see FIG. 9F).
At this time, the coating layer CL applied to the wall surface of the in-substrate space 422 is also
masked with the etching resist 407. Then, removal of the unnecessary conductive material 401
by the etching solution (step g; see FIG. 9G), cleaning after etching and removal of the etching
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32
resist 407 are performed (step h; see FIG. 9H).
[0115]
Here, although the configuration in which the unnecessary conductive material is removed by
etching is not limited to this, for example, the unnecessary conductive material may be removed
by laser processing or cutting.
[0116]
Next, a third substrate 42c (an embodiment of another substrate of the present invention) whose
lower surface is covered with the conductive material 401 is attached to the lower surface of the
second substrate 42b (step i; see FIG. 9I).
Next, a protective cover 408 covering and sealing the entire top surface of the first substrate 42a
is attached (step j; see FIG. 9 (j)). The shape and mounting method of the protective cover 408
and the reason for using the protective cover 408 are the same as in the third embodiment. Next,
the fifth through hole 409 having a substantially circular shape in plan view from the lower
surface of the third substrate 42c to the lower surface of the second substrate 400b is opened in
the fourth substrate 42c using, for example, a laser or an NC device k; see FIG. 9 (k)). Note that
the order of step i to step k may be changed as appropriate.
[0117]
Next, the fourth through hole 409 is plated (for example, electroless copper plating) to form a
second through wire 410 as shown in FIG. 9L (step 1). Thereby, the electrical connection
between the wiring pattern on the lower surface of the second substrate 42b and the conductive
material 401 on the lower surface of the third substrate 42c is performed. In the plating process,
the presence of the protective cover 408 prevents the plating solution from intruding into the insubstrate space 422. The formation of the second through wiring 410 may be performed by a
method other than plating, as in the third embodiment.
[0118]
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33
Next, on the lower surface of the third substrate 42c, a portion requiring a wiring pattern is
masked with the etching resist 407 (step m; see FIG. 9 (m)), and the substrate (made by bonding
three substrates 400a to 400c) Is immersed in an etching solution to remove unnecessary
conductive material (eg, Cu) on the lower surface of the third substrate 42c (step n; see FIG. 9
(n)). At this time, the presence of the protective cover 408 prevents the etchant from intruding
into the in-substrate space 422.
[0119]
Here, although the configuration in which the unnecessary conductive material is removed by
etching is not limited to this, for example, the unnecessary conductive material may be removed
by laser processing or cutting.
[0120]
When the etching is completed, the substrate is cleaned, and then the etching resist 407 is
removed (step o; see FIG. 9 (o)).
Finally, as shown in FIG. 9 (p), the bonded portion of the protective cover 408 is removed to
separate the protective cover 408 (step p). Thus, the microphone substrate 42 provided with the
first opening 321, the second opening 423, and the in-substrate space 422 in which a part of the
wall surface is covered with the coating layer CL is formed, and the wiring pattern (including the
through wiring) is formed. can get.
[0121]
The MEMS chip 41 is disposed on the upper surface 42 d of the microphone substrate 42 so as
to cover the first opening 421, and the cover 43 is further covered so that the second sound hole
432 overlaps the second opening 423. By putting it on, the microphone unit 4 shown in FIG. 8 is
obtained. The bonding method of the MEMS chip 41 and the cover 43 and the precautions in the
case of mounting the electric circuit unit on the microphone substrate 42 are the same as those
in the first embodiment. Further, the wiring pattern provided on the microphone substrate 42
may be formed not by the subtraction method but by the addition method as in the case of the
first embodiment.
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[0122]
(Others) The microphone units 1 to 4 of the embodiment described above, the electroacoustic
transducer mounting substrate (microphone substrate) 12, 22, 32, 42, and their manufacturing
method are merely examples of the present invention, 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.
[0123]
For example, in the embodiment described above, the electro-acoustic transducer is a MEMS chip
formed by using a semiconductor manufacturing technology, but the present invention is not
limited to this configuration. The present invention is preferably applied because the
electroacoustic transducer composed of the MEMS chip is particularly vulnerable to dust, but the
present invention is also applicable when an electroacoustic transducer other than the MEMS
chip is used. .
[0124]
In the above embodiments, the case where the electroacoustic transducer is a so-called capacitor
type microphone has been described, but in the present invention, the electroacoustic transducer
is a component microphone other than a capacitor type microphone (for example, an
electrodynamic (dynamic type) The present invention is also applicable to the case of an
electromagnetic type (magnetic type), a microphone such as a piezoelectric type, and the like.
[0125]
Moreover, although the above embodiment demonstrated the case where the coating layer
provided in the space in the board | substrate of an electroacoustic transducer mounting
substrate was metal layers, such as a plating layer, it is not the meaning limited to this.
The point is that the coating layer provided in the space in the substrate may be other than the
metal layer as long as it has a function of suppressing dust that may be generated in the space in
the substrate.
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[0126]
Besides, the shapes of the electroacoustic transducer and the microphone unit (including the
openings provided in them, the space in the substrate, and the like) are not limited to the shapes
of the present embodiment, and of course can be changed into various shapes. It is.
[0127]
The present invention is suitable, for example, for a microphone unit provided in an audio input
device such as a mobile phone.
[0128]
1, 2, 3, 4 Microphone units 11, 21, 31, 41 MEMS chips (electroacoustic transducers) 12, 22, 32,
42 Microphone substrates (electroacoustic transducers mounted substrate) 12a, 22a, 32d, 42d
mounting surface 13, 23, 33, 43 Cover (lid part) 14, 24, 34, 44 Housing space 22b Back surface
of mounting surface 31c, 41c Third substrate (other substrate) 103, 203, 304, 308, 405, 409
Through wiring Through holes 112, 212, 312, 412 fixed electrodes 114, 214, 314, 414
diaphragms 121, 221, 321, 322 openings or first openings 122, 222, 322, 422 spaces in the
substrate 122a, 222a, 322a, 422a Wall in the space in the substrate 223, 423 second opening
(other opening) 307, 408 protective cover CL Computing layer
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