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DESCRIPTION JP2000050393

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DESCRIPTION JP2000050393
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
electret condenser microphone.
[0002]
2. Description of the Related Art A conventional electret condenser microphone will be described
with reference to FIG. This conventional electret condenser microphone is mainly composed of a
microphone unit 500 which outputs an inputted sound as an electric signal, and a case unit 600
which accommodates the microphone unit 500.
[0003]
In the microphone unit 500, a fixed electrode 510 having an electret layer 511 formed on the
surface, a vibrating film 530 opposed to the fixed electrode 510 with a fixed distance through a
spacer 520, and a gate terminal 541. The fixed electrode 510 has an FET 540 as an impedance
conversion element in which the source terminal 542 is connected to an electrode layer (not
shown) of the vibrating film 530.
[0004]
The fixed electrode 510 and the electret layer 511 formed on the surface of the fixed electrode
510 have through holes 512 for communicating the space 550 between the fixed electrode 510
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and the diaphragm 530 with the back chamber 650. It has been established.
[0005]
On the other hand, the case portion 600 has a substantially bottomed cylindrical case main
portion 610 made of aluminum, which is a conductive material, and closes the open side of the
case main portion 610 while the FET 540 is mounted. And a holder portion 630 for holding the
microphone portion 500, and a conductive ring 640 interposed between the vibrating film 530
and the case main body portion 610.
The vibrating membrane 530 is attached to the ring-shaped frame 531.
[0006]
In this type of electret condenser microphone, the sound is transmitted to the vibrating
membrane 530 through the sound hole 611 formed in the case main body 610, and the electret
layer 511 of the fixed electrode 510 accompanying the vibration of the vibrating membrane 530
The change of the voltage due to the change of the capacitance of the capacitor configured as
above is output as an electric signal.
[0007]
There is also a semiconductor electret condenser microphone directed to further miniaturization.
As shown in FIG. 10, in the semiconductor electret condenser microphone, the microphone unit
700 is configured by applying a technology for forming a semiconductor element.
That is, this microphone unit 700 includes a wafer unit 710 on which an integrated circuit
including an impedance conversion element and an amplification element is formed, an electret
layer 720 formed on the surface, and a spacer formed on the electret layer 720. A through hole
711 is formed in the wafer portion 710 and the electret layer 720. The diaphragm 730 and the
vibrating membrane 740 attached to the spacer 730 are provided.
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[0008]
On the other hand, the case portion 800 has a substantially bottomed cylindrical case main
portion 810 made of aluminum, which is a conductive material, and closes the open side of the
case main portion 810. A ground plate portion 820 electrically connected to 810 and a holder
portion 830 for holding the microphone portion 700 are provided.
[0009]
A through hole 711 formed in the microphone unit 700 is in communication with a back
chamber 840 recessed in a holder unit 830 constituting the case unit 800.
[0010]
The manufacturing process of the microphone unit 700 of such a semiconductor electret
condenser microphone is as follows.
First, a large number of integrated circuits are formed on the wafer portion 710.
A silicon oxide film is formed on the side on which the integrated circuit is formed. The silicon
oxide film is electretized by an appropriate method such as heating and cooling or electron beam
irradiation to form an electret layer 720.
[0011]
Next, a through hole 711 is opened in the electret layer 720 and the wafer portion 710. The
through holes 711 are formed by laser processing or ultrasonic processing. Further, the spacer
730 is formed.
[0012]
A vibrating membrane 740 is attached to the spacer 730. Then, a space 750 corresponding to
the thickness of the spacer 730 is formed between the electret layer 720 and the vibrating
membrane 740. An electrode film 741 is formed in advance on the upper surface of the vibrating
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film 740. The vibrating membrane 740 is attached to the ring-shaped frame 742.
[0013]
A large number of microphone units 700 formed on a wafer are divided by a dicing saw. A
terminal 760 is attached to the back surface side of the wafer unit 710 of the divided
microphone unit 700, and the microphone unit 700 is completed.
[0014]
The microphone unit 700 thus formed is held by the holder 830 of the case 800 made of
ceramics or the like, and together with the earth plate 820 attached to the back side of the holder
830, the case body 810 Attached to At this time, the vibrating membrane 740 is made to face the
sound hole 811 of the case body 810. Further, the space 750 is in communication with the back
chamber 840 through the through hole 711.
[0015]
However, in the above-described two types of conventional electret condenser microphones, a Vshaped groove is formed in a ring-shaped frame body to which a case portion or a vibrating film
is attached. Although the back chamber is communicated with the outside through this groove,
the case part and the ring-shaped frame are made of aluminum, so in the case of a small electret
condenser microphone, management is possible in terms of dimensional accuracy. It was
difficult. Moreover, when forming a V-shaped groove in the case portion, management at the time
of caulking in the assembly process is difficult.
[0016]
The present invention has been made in view of the above circumstances, and it is an object of
the present invention to provide an electret condenser microphone which can save time and
effort in control in an assembly process.
[0017]
SUMMARY OF THE INVENTION An electret condenser microphone according to the present
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invention comprises a microphone unit for outputting input sound as an electric signal, and a
case unit for housing the microphone unit, The case portion has a base portion made of a
ceramic sheet, and a frame portion made of a ceramic sheet composed of one or more frame
members attached by being stacked on the base portion, and the microphone portion A back
electrode having an electret layer formed on the surface attached to the frame, and a vibrating
membrane attached to the back of the electret layer spaced apart from the electret layer, and the
base and the frame A conductive film for transmitting a signal from the vibrating film is formed
on the body portion.
[0018]
Further, the frame portion is formed with a vent for communicating the back chamber, which is a
space surrounded by the frame portion of the base portion and the frame portion of the frame
portion and the back electrode, with the outside.
[0019]
Further, the frame portion may be a substantially frame-shaped first frame attached to the base
portion, and a substantially frame-shaped second frame attached to the top of the first frame.
And a substantially frame-shaped third frame mounted on the second frame.
[0020]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic crosssectional view of an electret condenser microphone according to a first embodiment of the
present invention, and FIG. 2 is an electret condenser microphone according to the first
embodiment of the present invention. FIG. 3 is a schematic exploded perspective view of the case
portion other than the lid of the case portion, FIG. 3 is a case portion of the electret condenser
microphone according to the first embodiment of the present invention from which the fourth
frame and the lid are removed. FIG. 4 is a schematic cross-sectional view of an electret condenser
microphone according to a second embodiment of the present invention, and FIG. 5 is used for an
electret condenser microphone according to a third embodiment of the present invention FIG. 6
is a schematic perspective view of a first frame constituting the frame portion, and FIG. 6 is an
electret condenser microphone according to a fourth embodiment of the present invention. FIG. 7
is a schematic exploded perspective view other than a lid of a case portion constituting an
electret condenser microphone according to a fourth embodiment of the present invention, and
FIG. 8 is a first embodiment of the present invention It is a schematic perspective view of the
state which remove | eliminated the 4th frame and cover body from the case part which
comprises the electret condenser microphone which concerns on.
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[0021]
The electret condenser microphone according to the present embodiment comprises a
microphone unit 100 for outputting an input sound as an electric signal, and a case unit 200 for
housing the microphone unit 100, and the case unit 200 is It has a base portion 210 made of an
insulating member, and a frame portion 220 made up of four frames 221, 222, 223 and 224
which are attached by laminating on the edge of the base portion 210, and the microphone
portion A back electrode 110 has an electret layer (not shown) formed on the surface attached to
the frame portion 220, a vibrating membrane 120 attached with an electret layer of the back
electrode 110 and a predetermined space 150 therebetween. And transmits a signal from the
vibrating membrane 120 to the base portion 210 and the frame portion 220. In the frame
portion 220, a space surrounded by the base portion 210, the frame portion 220, and the back
electrode 110 is formed. An air vent 221a is formed to communicate a certain back chamber 300
with the outside.
[0022]
First, the base portion 210 is made of a ceramic sheet which becomes ceramic when fired, and is
cut into a desired shape.
Three external terminals 211 of the electret condenser microphone are formed on the top
surface and the back surface of the base portion 210 from the front surface to the front surface.
The external terminal 211 is formed of a conductive film formed by metal plating.
[0023]
A substantially frame-shaped first frame body 221 is attached to the upper edge portion of the
base portion 210.
This first frame body 221 is also made of a ceramic sheet in the same manner as the base portion
210.
In addition, the first frame body 221 is formed with a notch portion 221A which becomes the
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vent hole 221a.
Further, on the back surface from the top surface of the first frame body 221 through the inner
surface, three conductive portions 221B electrically connected to the external terminal 211 are
formed of a conductive film by metal plating.
[0024]
Further, on the first frame 221, a substantially frame-like second frame 222 is attached.
The second frame 222 is also made of a ceramic sheet, as with the base 210 and the like.
Further, the second frame 222 is formed thicker than the first frame 221. This is to prevent the
integrated circuit 400 mounted on the base portion 210 from coming out of the second frame
222. Therefore, the thickness dimension of the second frame 222 is set larger than the thickness
dimension of the integrated circuit 400 in combination with the first frame 221.
[0025]
Also, on the back surface of the second frame 222 from the upper surface to the inner surface,
three conductive portions 222B electrically connected to the external terminal 211 are formed of
a conductive film by metal plating.
[0026]
Further, on the second frame body 222, a substantially frame-like third frame body 223 is
attached.
The outer diameter of the third frame 223 is set to be the same as that of the first frame 221 and
the second frame 222, but the inner diameter is larger than that of the first frame 221 and the
second frame 222. It is set large. Therefore, when the third frame 223 is mounted on the second
frame 222, the back electrode step 222A is formed. The back electrode step 222A is a portion to
which a back electrode 110 described later is attached. The thickness dimension of the third
frame 223 is set to be the same as the thickness dimension of the back electrode 110.
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[0027]
Also in the third frame 222, a conductive portion 223B electrically connected to the external
terminal 211 is formed of a conductive film by metal plating. However, the conductive portion
223B of the third frame 223 is also electrically connected to a fourth frame 224 described later.
[0028]
The case 200 also has a lid 230 and a fourth frame 224 in addition to the members described
above.
[0029]
The fourth frame body 224 constitutes a part of the frame portion 220.
However, unlike the first to third frames 221 to 223, the fourth frame 224 is made of steel. The
outer diameter of the fourth frame 224 is set to be the same as that of the first to third frames
221 to 223, but the inner diameter is set larger than that of the third frame 223. Therefore,
when the fourth frame body 224 is attached to the third frame body 223, the diaphragm portion
223A is formed.
[0030]
The lid 230 constitutes the case portion 200 together with the base portion 210 and the frame
portion 220. A sound hole 231 is opened in the lid 230, and a protrusion 232 is formed on the
back outer peripheral edge side. When the lid 230 is attached, the protrusion 232 closely
contacts the inside of the fourth frame body 224.
[0031]
On the other hand, the microphone unit 100 includes a back electrode 110, a diaphragm 120
attached to a ring-shaped conductive frame 121, and a lower portion interposed between the
diaphragm 120 and the back electrode 110. A side spacer 130 and an upper spacer 140
interposed between the vibrating membrane 120 and the lid 230 are provided.
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[0032]
An electret layer (not shown) is formed on the surface of the back electrode 110, and a through
hole 111 is formed together with the electret layer.
By attaching the back electrode 110 to the back electrode step 222A, a back chamber 300
surrounded by the base portion 210, the first to third frame portions 221 to 223, and the back
electrode 110 is formed.
[0033]
An electrode film (not shown) is formed on the back surface of the vibrating film 120 in advance.
Then, a space 150 corresponding to the thickness of the lower spacer 130 described later is
formed between the electret layer and the vibrating membrane 120. As the vibrating film 120, a
PPS film or the like is used. The vibrating film 120 is attached to the ring-shaped frame 121
having conductivity as described above.
[0034]
The lower spacer 130 is attached to the vibrating membrane step 223A, and the vibrating
membrane 120 is attached on the lower spacer 130. Then, a space 150 corresponding to the
thickness dimension of the lower spacer 130 is formed between the electret layer of the back
electrode 110 and the vibrating membrane 120. That is, a capacitor is formed between the
electret layer and the vibrating film 120.
[0035]
When the lid 230 is attached with the upper spacer 140 placed on the vibrating membrane 120,
the projection 232 is attached to the fourth frame 224 in a state where the upper spacer 140 is
held down.
[0036]
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The electrode film of the vibrating film 120 is made of the frame 121 → the fourth frame 224 →
the conductive film 223B of the third frame 223 → the conductive film 222B of the second
frame 222 → the first frame 221 The conductive film 221 B of the second embodiment → the
external terminal 211 of the base portion 210 is conducted.
[0037]
The electret condenser microphone configured as described above is integrated by firing the
base portion 210 and the first to third frame portions 221 to 223 constituting the case portion
200.
[0038]
Next, the operation of the electret condenser microphone configured as described above will be
described.
A sound wave penetrates the space 160 between the lid 230 of the case 200 and the vibrating
membrane 120 through the sound hole 231 to vibrate the vibrating membrane 120.
The vibration of the vibrating membrane 120 changes the volume of the space 150 between the
vibrating membrane 120 and the electret layer, and the capacitance between the vibrating
membrane 120 and the electret film changes with this change.
Then, the change in capacitance is output to the external terminal 211 through the path as a
change in voltage.
[0039]
Further, the pressure generated by the change of the capacity of the space 150 due to the
vibration of the vibrating membrane 120 is transmitted to the outside through the vent hole
221a which is the notch portion 221A formed in the first frame body 221. By this, sound
correction can be performed.
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[0040]
In the embodiment described above, the notch 221A is formed in the first frame 221, and it is
made the air hole 221a, but as shown in FIG. 5, the groove is formed in the first frame 221. It is
also possible to form 221C and use it as the air hole 221a. Thus, it is advantageous to merely
form the groove portion 221C in the first frame body 221, since the strength of the first frame
body 221 can be increased more than in the case of the notch portion 221A.
[0041]
Further, the size of the vent hole 221a greatly depends on the acoustic characteristics,
particularly the low frequency characteristic of 500 Hz or less, and therefore, should be
determined appropriately according to the required specification.
[0042]
Furthermore, in the embodiment described above, although the frame portion 220 is composed
of four frames, the first to fourth frames 221 to 224, as shown in FIG. It is also possible to make
up the body 220 'from three frames 211'-223'.
That is, the frame 221 'in which the first frame 221 and the second frame 222 are integrated is
used. Accordingly, a groove 221A 'forming the vent hole 221a' is formed on the back surface
side of the frame body 221 '.
[0043]
The other frames 222 'and 223' are equivalent to the third frame 223 'and the fourth frame 224'
in the above-described embodiment.
[0044]
In the embodiment described above, the first frame body 221, 221 'is provided with the notch
portion 221A and the groove portion 221'A to be the vent holes 221a, 221'a, but as shown in
FIGS. You may
[0045]
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That is, as shown in FIG. 7, the inner edge portions of the four frames 221, 222, 223 and 224
constituting the frame portion 220 communicate with each other when they are stacked, and the
vent holes 221 "a The concave portions 221C, 222C, 223C, and 224C that form the
In addition, the lid 230 is also formed with a recess 233 communicating with the recesses 221C,
222C, 223C, and 224C.
[0046]
When the vent holes 221a and 221'a are formed on the side surface of the case portion 200 as
in the embodiment described above, the vent holes 221a and 221'a are formed depending on the
relationship with other electronic components and the like disposed on the side surface.
However, it is usual that the other electronic components are not installed above the electret
condenser microphone, so the vent holes 221′′a opened on the upper surface of the case 200
are other electronic components. There is no risk of being blocked by
Therefore, the vent hole 221′′a for connecting the back chamber 300, which is a space
surrounded by the base portion 210, the frames 221, 222, 223 and 224 of the frame portion
220 and the back electrode 110, to the outside is assuredly ensured. Therefore, the low-pass
characteristics are unlikely to be different from those designed.
[0047]
The electret condenser microphone according to the present invention comprises a microphone
unit for outputting the input sound as an electric signal, and a case unit for housing the
microphone unit, and the case unit is The microphone unit has a base portion made of a ceramic
sheet and a frame portion made of a ceramic sheet composed of one or more frame members
attached by being stacked on the base portion. A back electrode having an electret layer formed
on the surface to be attached to the portion, and a vibrating membrane attached with the back
surface electret layer spaced apart from the electret layer, and the base portion and the frame
portion , And a conductive film for transmitting a signal from the vibrating film.
[0048]
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Therefore, in this electret condenser microphone, since ceramics is used in the case portion, it
can be of the surface mounting type.
That is, since the case part is made of ceramics and can withstand high temperatures of 250 ° C.
to 300 ° C., mounting by reflow soldering becomes possible. In addition, when the case portion
is made of ceramic, the control of dimensions and manufacturing process at the time of forming
the vent for adjusting the air pressure in the back chamber is greatly simplified, which is
advantageous from the viewpoint of manufacturing.
[0049]
Further, the frame portion is formed with an air vent for connecting the back chamber, which is a
space surrounded by the frame portion of the base portion and the frame portion of the frame
portion and the back electrode, to the outside. It is possible to set the characteristic of to any one.
[0050]
Further, the frame portion is a substantially frame-shaped first frame attached to the base
portion, and a substantially frame-shaped second frame attached to the top of the first frame.
And a substantially frame-shaped third frame mounted on the second frame.
When the frame portions are laminated in this way, the frame portions can be manufactured with
high accuracy.
[0051]
Brief description of the drawings
[0052]
1 is a schematic cross-sectional view of an electret condenser microphone according to a first
embodiment of the present invention.
[0053]
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2 is a schematic exploded perspective view other than the lid of the case portion of the electret
condenser microphone according to the first embodiment of the present invention.
[0054]
3 is a schematic perspective view of a state in which the fourth frame and the lid are removed
from the case portion of the electret condenser microphone according to the first embodiment of
the present invention.
[0055]
4 is a schematic cross-sectional view of an electret condenser microphone according to a second
embodiment of the present invention.
[0056]
5 is a schematic perspective view of a first frame constituting the frame used in the electret
condenser microphone according to the third embodiment of the present invention.
[0057]
6 is a schematic cross-sectional view of an electret condenser microphone according to a fourth
embodiment of the present invention.
[0058]
7 is a schematic exploded perspective view other than the lid of the case portion constituting the
electret condenser microphone according to the fourth embodiment of the present invention.
[0059]
8 is a schematic perspective view of a state in which the fourth frame and the lid are removed
from the case portion of the electret condenser microphone according to the first embodiment of
the present invention.
[0060]
9 is a schematic cross-sectional view of a conventional electret condenser microphone.
[0061]
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10 is a schematic cross-sectional view of a conventional electret condenser microphone.
[0062]
Explanation of sign
[0063]
DESCRIPTION OF SYMBOLS 100 Microphone part 110 Back pole 120 Vibrating film 150 Space
200 Case part 210 Base part 220 Frame body part 221a Air vent 300 Back room
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