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DESCRIPTION JP2010074716

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DESCRIPTION JP2010074716
PROBLEM TO BE SOLVED: There is a problem that an ECM which regulates a gap between a back
electrode substrate and a vibrating membrane by using a conventional spacer block having a
three-layer structure has a problem that the accuracy of the gap is poor and the acoustic
characteristics vary. A capacitor microphone in which a back electrode substrate on which a back
electrode is formed and a vibrating film on which a counter electrode is formed is laminated via a
spacer means, wherein the spacer means is a laminated portion in which adhesive sheets are
laminated on both sides of a spacer sheet. And a spacer sheet portion from which the adhesive
sheet has been removed, the spacer sheet portion being interposed between the back electrode
and the vibrating membrane, and the laminated portion being bonded to the back electrode
substrate and the vibrating membrane It is characterized by [Selected figure] Figure 2
コンデンサマイクロホン
[0001]
The present invention relates to a back electrode substrate on which a back electrode is formed,
a diaphragm unit on which a diaphragm is fixed, and a condenser microphone having an electret
layer formed on the back electrode or the diaphragm, particularly formed on a back electrode
substrate. The present invention relates to a condenser microphone capable of precisely forming
the gap between the back electrode or the electret layer and the diaphragm.
[0002]
In recent years, electret condenser microphones (hereinafter abbreviated as ECM) have been
widely used as small-sized and high-performance mycophones widely used for mobile phones,
video cameras, digital cameras, etc., and are disclosed, for example, in Patent Document 1.
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1
[0003]
The configuration of the conventional ECM disclosed in Patent Document 1 will be described
below with reference to FIGS. 16 and 17.
FIG. 16 is a cross-sectional view of a conventional complete ECM, and in FIG. 16, 80 is an ECM.
Reference numeral 2 denotes a circuit board, and the circuit board 2 is formed of an insulating
substrate, the connection wiring 2a is formed on the upper surface side, the output electrode 2b
is formed on the lower surface side, and an integrated circuit 11 as an electronic component is
mounted. The back electrode substrate 3 has a back electrode 4 of an electrode film formed on
the upper surface side of the insulating substrate 3a, and a film of an electret layer 5 formed on
the top surface of the back electrode 4. A through hole 3 b penetrating the insulating substrate 3
a is formed outside the back electrode 4 and the electret 5. An air chamber 12 is formed between
the circuit board 2 and the back electrode board 3 by providing the board spacer 9 between the
circuit board 2 and the back electrode board 3.
[0004]
6 is a vibrating membrane unit, and the vibrating membrane unit 6 is integrated by fixing the
conductive vibrating membrane 7 on the lower surface side of the vibrating membrane support
frame 6a having a metal film formed on the surface of a metal material or insulating member It is
done. Reference numeral 18 denotes a spacer block, which has a function of accurately
determining the gap formed between the electret layer 5 formed on the upper surface of the
back electrode substrate 3 and the vibrating film 7 as described later.
[0005]
The composition of the ECM 80 is, for example, an adhesive after laminating the substrate spacer
9 between the circuit substrate 2 and the back electrode substrate 3 and the spacer block 18
between the back electrode substrate 3 and the diaphragm unit 6. As a result, the ECM 80 is
completed. The through holes 3b are formed on the outer side of the back electrode 4 in the back
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2
electrode substrate 3 to ensure ventilation between the air chamber 12 and the upper surface
side of the back electrode substrate 3 without reducing the area of the back electrode 4 Good
acoustical effects.
[0006]
Next, the operation of the ECM 80 will be described. The operation of the ECM 80 having the
above configuration forms a capacitor with the spacer block 18 interposed between the vibrating
film 7 having a conductive film on the surface and the back electrode 4 having the electret layer
5 formed on the surface. When the diaphragm 7 is displaced by air vibration of the acoustic
input signal Ps input from the upper surface side of the diaphragm 7, the capacitor converts the
displacement into an electric signal, and the electric signal is a conductive diaphragm supporting
frame. From 6a, it is led to the circuit board 2 via each connection electrode (illustration is
omitted), and after being processed by the integrated circuit 11, it is outputted from the output
electrode 2b provided on the lower surface of the circuit board 2. The vibrating action of the
vibrating membrane 7 is smoothed by the presence of the through hole 3b, and the acoustic
characteristics are secured.
[0007]
Next, referring to FIG. 17, the gap formed between the back electrode 4 and the electret layer 5
formed on the top surface of the back electrode substrate 3 according to the spacer block 18
generally used conventionally and the vibrating film 7 Explain how to decide. FIG. 17 is an
enlarged cross-sectional view of a portion SB in FIG. 16 and describes the configuration of the
spacer block 18 in detail. That is, the spacer block 18 has a three-layer structure in which the
upper adhesive sheet 18b and the lower adhesive sheet 18c are laminated on both surfaces of
the spacer sheet 18a.
[0008]
One example of each element constituting the spacer block 18 is shown. As the spacer sheet 18a,
a sheet of polyimide having a thickness of 75 to 85 μm is used, and an acrylic adhesive sheet
having a thickness of 12.5 μm on each side is used. The upper adhesive sheet 18b and the lower
adhesive sheet 18c are laminated.
[0009]
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When the heat press is performed in a state where the spacer block 18 having the above
configuration is interposed between the insulating substrate 3a constituting the back electrode
substrate 3 and the vibrating film 7, the upper adhesive sheet 18b which is an acrylic adhesive
sheet and the lower The side adhesive sheet 18c is bonded to and integrated with the vibration
film 7 and the insulating substrate 3a.
Since the upper adhesive sheet 18b and the lower adhesive sheet 18c are shrunk by the heat
press, the gap G formed between the vibrating membrane 7 and the electret layer 5 has a
predetermined value (for example, 20 to 20). Adjust to 25 μm).
[0010]
That is, the value of gap G is an important value that determines the capacitance value as ECM,
and in order to accurately obtain the value of gap G, the material and thickness of each element
constituting spacer block 18 are selected, and heat pressing is also performed. It is necessary to
select the condition of.
[0011]
Further, as a spacer for determining the gap G formed between the vibrating film 7 and the
electret layer 5, Patent Document 2 discloses a conventional example in which a spacer block
having a three-layer structure of a spacer sheet and an adhesive sheet is not used. .
That is, Patent Document 2 has a configuration in which a vibrating film and a back electrode
substrate are disposed opposite to each other with a spacer interposed therebetween and pressed
by a gate spring. That is, by pressing the gate spring, the diaphragm, the spacer and the back
electrode substrate are integrated to determine the gap.
[0012]
JP, 2002-345087, A JP, 2005-27182, A
[0013]
The configuration of the spacer block in the conventional ECM shown in Patent Document 1 for
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bonding the diaphragm and the back electrode substrate and defining the gap formed between
the diaphragm and the back electrode substrate is the spacer as shown in FIG. The spacer block
18 configured by laminating the upper adhesive sheet 18b and the lower adhesive sheet 18c
having the same thickness on both surfaces of the sheet 18a is indirectly crimped between the
diaphragm 7 and the back electrode substrate 3 by pressure bonding. The gap G formed between
the vibrating membrane 7 and the electret layer 5 is determined.
[0014]
However, in the method of indirectly determining the gap G in consideration of the compression
of the spacer block 18 as described above, there are the following problems.
First, according to data of the thickness of the spacer block 18, the electret layer 5 and the back
electrode 4 as elements involved in determining the gap G, the compression amount of the spacer
block 18 at which the gap G becomes a predetermined interval is determined.
Then, at the time of actual manufacturing, the gap G is formed by pressing the spacer block 18
by applying a pressing force that results in this amount of compression.
[0015]
However, in the above method, since there are variations in the thickness of the spacer block 18,
the electret layer 5 and the back electrode 4 which are elements involved in determining the gap
G, even if a predetermined pressure is applied Even if a predetermined amount of compression
can not be obtained due to the variation of the composition, or even if a predetermined amount
of compression of the spacer block 18 is obtained, the height of the gap G can be increased by
the variation of the thickness of the electret layer 5 or the back electrode 4. It results in
variations.
[0016]
In addition, the method of pressing three elements shown in Patent Document 2 by a spring has
the following problems.
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That is, although the configuration is such that the vibrating membrane and the back electrode
substrate are positioned via the spacer, this is a method in which the above three elements are
pressed by a spring and three elements are not fixed. The gap may be formed in an inclined
manner, and the capacity of the ECM results in a dispersion. In addition, since the three elements
are not fixed, there is a problem that the gap is changed by the external impact.
[0017]
The object of the present invention has been made in view of the above circumstances, and even
if there are variations in the spacer block, the electret layer, the thickness of the back electrode,
etc. which are elements determining the gap G of ECM, the gap G of ECM can be accurately
determined. It is possible to provide an ECM that can be managed and has stable capacitor
characteristics.
[0018]
The configuration of the ECM according to the present invention for achieving the above object is
a capacitor microphone in which a back electrode substrate having a back electrode formed
thereon and a vibrating film having a counter electrode formed thereon are laminated via a
spacer means. It has a lamination part which laminated an adhesion sheet on both sides of a
sheet, and a spacer sheet part which removed an adhesion sheet, the spacer sheet part intervenes
between the back electrode and a diaphragm, and the lamination part is the back. It is
characterized in that it is bonded to the electrode substrate and the vibrating film.
[0019]
According to the above configuration, the gap between the back electrode and the vibrating
membrane can be determined only by the thickness of the spacer sheet, so that the gap G of the
ECM can be accurately managed, and the ECM having a stable capacitor characteristic can be
obtained. It can be mass-produced.
[0020]
An electret layer is formed on the back electrode of the back electrode substrate, and the spacer
sheet portion is interposed between the electret layer and the vibrating film.
[0021]
The region in which the spacer sheet portion is interposed between the electret layer and the
vibrating membrane is a part of the outer periphery of the electret layer.
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[0022]
The region in which the spacer sheet portion is interposed between the electret layer and the
diaphragm is a corner of four corners of the electret layer having a substantially rectangular
shape.
[0023]
According to the above configuration, the detection sensitivity can be enhanced by increasing the
effective area of the vibrating diaphragm to vibrate by reducing the region where the spacer
sheet portion is interposed between the electret layer and the vibrating diaphragm. Furthermore,
the floating capacity as ECM can be reduced.
[0024]
In the two adhesive sheets laminated on both sides of the spacer sheet, the thickness of the lower
adhesive sheet adhered to the back electrode substrate is larger than the thickness of the upper
adhesive sheet adhered to the vibrating film. Do.
[0025]
As described above, according to the present invention, since the gap between the back electrode
and the vibrating membrane can be determined only by the thickness of the spacer sheet, the gap
G of the ECM can be accurately managed, and the capacitor characteristics are stable. Mass
production of ECM.
[0026]
The configuration of the ECM according to the first embodiment of the present invention will be
described below with reference to FIGS.
1 is a cross-sectional view of a completed ECM, FIG. 2 is an enlarged cross-sectional view of an
SB portion which is a junction of the ECM shown in FIG. 1, and FIG. 3 is a cross-sectional view
showing a first laminated structure of the junction shown in FIG. 4 is a cross-sectional view
showing a second laminated structure of the joint portion shown in FIG. 2, FIG. 5 is a developed
view of each sheet constituting the spacer block, and FIG. 6 is a plan view showing a laminated
state of the spacer block shown in FIG. 7 is a sectional view taken along the line AA of the spacer
block shown in FIG. 6, FIG. 8 is a developed view of the spacer block and the back electrode
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substrate, and FIG. 9 is a plan view showing a laminated state of the spacer block and the back
electrode substrate shown in FIG. 10 is a sectional view taken along the line A-A in FIG. 9, and
FIG. 11 is a sectional view in which the shield case is attached to the ECM shown in FIG.
[0027]
Next, the specific configuration of the ECM according to the first embodiment of the present
invention will be described with reference to FIGS.
In FIG. 1, 10 is an ECM, and the basic configuration is the same as the ECM 80 of FIG.
That is, the circuit board 2 is formed of an insulating substrate, the connection wiring 2a is
formed on the upper surface side, the output electrode 2b is formed on the lower surface side,
and the integrated circuit 11 which is an electronic component is mounted.
The back electrode substrate 3 has a back electrode 4 of an electrode film formed on the upper
surface side of the insulating substrate 3a, and a film of an electret layer 5 formed on the top
surface of the back electrode 4. A through hole 3 b penetrating the insulating substrate 3 a is
formed outside the back electrode 4 and the electret 5.
An air chamber 12 is formed between the circuit board 2 and the back electrode board 3 by
providing the board spacer 9 between the circuit board 2 and the back electrode board 3.
[0028]
6 is a vibrating membrane unit, and the vibrating membrane unit 6 is integrated by fixing the
conductive vibrating membrane 7 on the lower surface side of the vibrating membrane support
frame 6a having a metal film formed on the surface of a metal material or insulating member It is
done.
A spacer block 8 has a function of accurately determining the gap formed between the electret
layer 5 formed on the upper surface of the back electrode substrate 3 and the vibrating film 7 as
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described later.
Also, the operation of the ECM 10 is basically the same as the operation of the ECM 80 described
in FIG.
[0029]
Next, FIG. 2 illustrates a method of determining the gap formed between the back electrode 4
and the electret layer 5 formed on the top surface of the back electrode substrate 3 according to
the spacer block 8 of the present invention and the vibrating film 7. Do.
FIG. 2 is an enlarged cross-sectional view of a portion SB in FIG. 1 and describes the
configuration of the spacer block 8 in detail.
That is, the spacer block 8 has a three-layer structure in which the upper adhesive sheet 8b and
the lower adhesive sheet 8c are laminated on both surfaces of the spacer sheet 8a.
[0030]
The spacer block 8 has a three-layered laminated portion 8d in which the upper adhesive sheet
8b and the lower adhesive sheet 8c are laminated on both surfaces of the spacer sheet 8a, and a
spacer sheet portion from which the upper adhesive sheet 8b and the lower adhesive sheet 8c
are removed. 8e, and the spacer sheet portion 8e is interposed between the back electrode 4 and
the vibrating membrane 7, and the laminated portion 8d is bonded to the back electrode
substrate 3 and the vibrating membrane 7 so that the back surface is formed. Since the gap G
formed between the electret layer 5 formed on the upper surface of the electrode substrate 3 and
the vibrating film 7 can be determined only by the thickness of the spacer sheet portion 8e, the
gap G of the ECM 10 can be accurately managed. can do.
[0031]
Next, the method of forming the lamination by the spacer block 8 and the gap G will be described
with reference to FIGS.
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FIG. 3 shows the first laminated state, and the dimensional relationship of the three elements
constituting the spacer block 8 is that the length of the spacer sheet 8a is longer than the upper
adhesive sheet 8b and the lower adhesive sheet 8c, and the upper adhesive sheet 8b. The length
of the lower adhesive sheet 8c is substantially the same in the present embodiment. Furthermore,
the thickness of the lower side adhesive sheet 8c is larger than the thickness of the upper side
adhesive sheet 8b. In the first laminated state, the spacer sheet 8 a and the upper adhesive sheet
8 b are adhered to the vibration film 7, and the lower adhesive sheet 8 c is adhered to the back
electrode substrate 3.
[0032]
Next, in the second laminated state shown in FIG. 4, the spacer sheet 8a and the lower adhesive
sheet are formed by laminating and pressurizing the vibrating film 7 side and the back electrode
substrate 3 side which are block-formed in the first laminated state. 8c is adhered and the whole
is integrated. In this state, due to the difference in length between the spacer sheet 8a and the
upper adhesive sheet 8b and the lower adhesive sheet 8c, a laminated portion 8d in which the
upper adhesive sheet 8b and the lower adhesive sheet 8c are laminated on both sides of the
spacer sheet 8a A spacer sheet portion 8e is formed by removing the adhesive sheet 8b and the
lower adhesive sheet 8c, and the spacer sheet portion 8e is interposed between the electret layer
5 provided on the back electrode 4 and the vibrating film 7, By bonding the laminated portion 8d
to the back electrode substrate 3 and the vibrating film 7, the gap G between the electret layer 5
and the vibrating film 7 is accurately formed only by the thickness of the spacer sheet 8a.
[0033]
Next, one example of the conditions of each element that makes up the spacer block 8 and the
pressing conditions for forming the gap G will be described. First, as each element constituting
the spacer block 8 in the present embodiment, a polyimide sheet of 20 to 25 μm as the spacer
sheet 8 a, an acrylic adhesive sheet of 12.5 μm as the upper adhesive sheet 8 b, and an acrylic
of 75 μm as the lower adhesive sheet 8 c. A system adhesive sheet was used.
[0034]
The upper adhesive sheet 8b is compressed to about 1⁄4 and compressed from 12.5 μm to 3
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μm under the pressure in the first laminated state shown in FIG. 3, but in this state the spacer
sheet 8a and the vibrating film 7 are still There is a slight gap between the Next, in pressurization
in the second lamination state shown in FIG. 4, the spacer sheet 8a and the lower side are
laminated by pressurizing and laminating the diaphragm 7 side and the back electrode substrate
3 side which are block-formed in the first lamination state. The side adhesive sheet 8c is adhered
and the whole is integrated. In this state, the lower adhesive sheet 8c is compressed to about 3⁄5
and compressed from 75 μm to 60 μm. The upper adhesive sheet 8b is also further
compressed, and the gap between the spacer sheet 8a and the vibrating film 7 completely
disappears, and the electret in which the spacer sheet portion 8e formed only of the spacer sheet
8a is provided on the back electrode 4 A gap G is formed between the layer 5 and the vibrating
membrane 7.
[0035]
That is, as in the above configuration, the thickness of the lower adhesive sheet 8c adhered to the
back electrode substrate 3 is adhered to the vibrating film 7 in each thickness of the two
adhesive sheets laminated on both sides of the spacer sheet 8a. By making the thickness of the
upper adhesive sheet 8b larger than the thickness of the upper adhesive sheet 8b, the lower
adhesive sheet 8c absorbs the laminated thickness of the back electrode 4 and the electret layer
5, and the upper adhesive sheet 8b is completely compressed. A gap G is formed between the
electret layer 5 provided on the back electrode 4 and the diaphragm 7. The gap G at this time is
formed to be 20 to 25 μm by the thickness of the spacer sheet 8 a constituting the spacer sheet
portion 8 e.
[0036]
Next, the shape of the spacer block 8 will be described with reference to FIGS. FIG. 5 is a plan
view of each of the elements constituting the spacer block 8, and is an upper adhesive sheet
having a rectangular window portion 8bm having a rectangular outer shape above and below the
spacer sheet 8a having a rectangular outer window portion 8am. 8b and a lower adhesive sheet
8c having a rectangular outer shape and a rectangular window 8 cm. In the present embodiment,
the outer shapes of the spacer sheet 8a, the upper adhesive sheet 8b, and the lower adhesive
sheet 8c are the same, and the windows 8bm and 8 cm of the upper adhesive sheet 8b and the
lower adhesive sheet 8c are the same. .
[0037]
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FIG. 6 is a plan view of the spacer block 8 in which the spacer sheet 8a, the upper adhesive sheet
8b, and the lower adhesive sheet 8c shown in FIG. 5 are laminated, and the spacer sheet 8a is
shown in the window 8bm of the upper adhesive sheet 8b. An oval window 8am is disposed.
Here, the lower adhesive sheet 8c is hidden behind and not visible. 7 is a cross-sectional view of
the spacer block 8 shown in FIG.
[0038]
Next, the laminated structure of the spacer block 8 and the back electrode substrate 3 will be
described with reference to FIGS. 8 and 9. FIG. 8 is a plan view of the spacer block 8 and the back
electrode substrate 3, and FIG. 9 is a plan view showing a laminated structure of the spacer block
8 and the back electrode substrate 3. In FIG. 8, in the spacer block 8, the oval window 8am of the
spacer sheet 8a is disposed in the window 8bm of the upper adhesive sheet 8b (the window 8cm
of the lower adhesive sheet 8c has the same shape as well) and The outer shape of the electret
layer 5 formed on the electrode substrate 3 is substantially the same as the shape of the window
8bm of the upper adhesive sheet 8b, and the size is slightly smaller.
[0039]
FIG. 9 is a plan view showing a laminated structure of the spacer block 8 and the back electrode
substrate 3. The arc shape SP at four corners of the electret layer 5 indicated by hatching is a
laminate of the spacer sheet 8e and the electret layer 5 in the spacer sheet 8a. It is a part that is
being That is, in the present embodiment, by combining the rectangular electret layer 5 and the
window 8am of the elliptical spacer sheet 8a, the region in which the spacer sheet portion 8e is
interposed between the electret layer 5 and the vibrating film 7 is It is a corner of four corners of
the electret layer 5 having a substantially rectangular shape (rectangle).
[0040]
As described above, the region in which the spacer sheet portion 8 e is interposed between the
electret layer 5 and the vibrating membrane 7 is not the whole of the outer periphery of the
electret layer 5 but a part of the effective area where the vibrating membrane 7 can vibrate. By
increasing the sensitivity of the ECM as the ECM and reducing the area of the electret layer 5 and
the diaphragm 7 facing each other across the spacer sheet 8a, the stray capacitance of the ECM
can be reduced. .
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12
[0041]
FIG. 10 is a cross-sectional view showing a configuration in which the back electrode substrate 3,
the spacer block 8 and the vibrating membrane unit 6 are stacked, and shows an AA cross
section of FIG. 9.
11 is a cross-sectional view of the configuration in which the shield case 15 is attached to the
ECM 10 shown in FIG. 1. The acoustic input signal Ps is applied to the diaphragm 7 through the
acoustic hole 15a provided in the shield case 15. That is, the ECM 10 may be incorporated into
the inside of the apparatus in the state shown in FIG. 1, or the shield case 15 may be attached
and used as shown in FIG.
[0042]
FIG. 12 is a cross-sectional view of an ECM in the second embodiment of the present invention,
and the basic configuration is the same as that of the ECM 10 shown in FIG. The ECM 20 differs
from the ECM 10 in the configuration of the back electrode substrate. In the ECM 20, the back
electrode substrate 3 and the substrate spacer 9 in the ECM 10 are one member, and a U-shaped
back electrode substrate 23 is used.
[0043]
FIG. 13 is a cross-sectional view of an ECM in the third embodiment of the present invention, and
the basic configuration is the same as that of the ECM 10 shown in FIG. The structure of the ECM
30 is the same as that of the ECM 10 in the laminated structure of the circuit board 2, the back
electrode board 3, the diaphragm unit 6, the spacer block 38 and the board spacer 9, except for
the circuit board 2 and the back electrode board 3. The size of the diaphragm unit 6, the spacer
block 38, and the substrate spacer 9 is slightly larger than that of the ECM 10, and an acoustic
hole 30a is provided in the enlarged portion, and the penetrating acoustic hole 30a is the
vibration. The upper surface side of the membrane 7 is communicated with the outside.
Furthermore, in order to form an air gap between the vibration film 7 and the upper surface of
the shield case 35, the air gap spacer 13 is provided on the vibration film support frame 6a, and
each element is integrally fixed by an adhesive or the like and covered with the shield case 35. By
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doing this, the ECM 30 is completed. That is, although the laminated structure of each element of
the ECM 30 has substantially the same configuration as that of the ECM 10, it differs from the
ECM 10 in that the circuit board 2 has the acoustic holes 30a and the shield case 35 is not
provided with the acoustic holes.
[0044]
FIG. 14 is a cross-sectional view showing the ECM 30 shown in FIG. 13 attached to the main
circuit board 100. The ECM 30 is set on the lower surface side of the main circuit board 100
having the acoustic holes 100a. The output electrode 2 b is soldered and attached to the lower
surface side of the main circuit substrate 100 in a state of being aligned with the acoustic hole
100 a of the substrate 100.
[0045]
Next, the operation of the ECM 30 will be described.
The acoustic input signal Ps input through the acoustic hole 100a of the main circuit board 100
and the acoustic hole 30a penetrated by the ECM 30 from the upper surface side of the main
circuit board 100 is the diaphragm 7 formed of the air gap spacer 13 and the shield It is led to
the gap between the cases 35. When the diaphragm 7 is displaced by air vibration of the acoustic
input signal Ps, the capacitor converts the displacement into an electric signal, and the electric
signal is transmitted from the conductive diaphragm supporting frame 6a to each connection
electrode (not shown). And is processed by the integrated circuit 11 and output from an output
electrode 2 b provided on the lower surface side of the circuit board 2. Then, the presence of the
through hole 3b formed in the back electrode substrate 3 makes the operation of the diaphragm
7 smooth and secures the acoustic characteristics.
[0046]
As described above, by providing the acoustic holes 30 a in the circuit board 2, the ECM 30 can
take in an acoustic signal from the main circuit board 100 side, so that it is possible to make the
mobile phone etc. smaller and thinner.
[0047]
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FIG. 15 is a cross-sectional view of an ECM according to the fourth embodiment of the present
invention, and the basic configuration is the same as that of the ECM 10 shown in FIG.
What is different from the ECM 10 of the ECM 40 is that the vibrating membrane 47 is formed of
an electret sheet. That is, the electrode film is vapor-deposited on the electret sheet to form the
vibrating film 47, and only the back electrode 4 is provided on the back electrode substrate 3.
Therefore, the spacer block 48 forms a gap G between the back electrode 4 on the back electrode
substrate 3 and the vibrating film 47. For this reason, although the spacer sheet 8 a and the
upper adhesive sheet 8 b are identical to the spacer block 8 in the configuration of the spacer
block 48, the electret layer in which the thickness of the lower adhesive sheet 8 c is formed on
the back electrode 4 It is thinner by 5 thickness.
[0048]
As described above, the ECM of the present invention can improve gap management accuracy
while using the conventional three-layer spacer block, and can provide ECM having good acoustic
characteristics without increasing the cost. . In each of the above embodiments, although the case
of the diaphragm having a rectangular shape has been described, the present invention is not
limited to this, and it is natural that the present invention can be applied to a diaphragm having a
conventional circular shape or an elliptical shape. is there.
[0049]
It is sectional drawing of ECM10 in 1st Embodiment of this invention. It is an expanded sectional
view of the junctional part of ECM10 shown in FIG. It is sectional drawing which shows the 1st
laminated structure of the junctional part shown in FIG. It is sectional drawing which shows the
2nd laminated structure of the junctional part shown in FIG. It is an expanded view of each sheet
| seat which comprises the spacer block in 1st Embodiment of this invention. It is a top view
which shows the lamination | stacking state of the spacer block shown in FIG. FIG. 7 is a crosssectional view of the spacer block shown in FIG. It is an expanded view of the spacer block and
back electrode substrate in 1st Embodiment of this invention. It is a top view which shows the
lamination | stacking state of the spacer block and back surface electrode board | substrate
which are shown in FIG. It is AA sectional drawing of FIG. It is sectional drawing which attached
the shield case to ECM10 shown in FIG. It is sectional drawing of ECM in 2nd Embodiment of this
invention. It is sectional drawing of ECM in 3rd Embodiment of this invention. FIG. 14 is a crosssectional view showing the ECM 30 shown in FIG. 13 attached to the main circuit board 100. It is
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sectional drawing of ECM in 4th Embodiment of this invention. FIG. 1 is a cross-sectional view of
a conventional completed ECM. FIG. 17 is an enlarged cross-sectional view of a joint portion of
the ECM 80 shown in FIG. 16;
Explanation of sign
[0050]
Reference Signs List 2 circuit board 2a connection wiring 2b output electrode 3 back electrode
substrate 3a insulating substrate 3b through hole 4 back electrode 5 electret layer 6 vibrating
membrane unit 6a vibrating membrane supporting frame 7 vibrating membrane 8, 18, 38, 48
spacer block 8a, 18a spacer Sheet 8b, 18b Upper adhesive sheet 8c, 18c Lower adhesive sheet
8d Stacking part 8e Spacer sheet part 9 Substrate spacer 10, 20, 30, 40, 80, ECM 11 Integrated
circuit 12 Air chamber 13 Air gap spacer 15, 35 Shield case 15a , 30a, 100a acoustic hole 100
main circuit board
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