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JP2001157297

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DESCRIPTION JP2001157297
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
condenser microphone such as a back electret microphone, and more particularly to a condenser
microphone having a reduced thickness.
[0002]
2. Description of the Related Art A conventional condenser microphone 100, as shown in FIGS. 3
and 4, is conductive in order from the side of a flat plate portion 101a with a bottom plate
portion in a cylindrical metal cap 101 with a bottom. The diaphragm 103 on which the
diaphragm ring 102 is fixed, the spacer 104, the back electrode plate 105, the insulating case
106, and the printed wiring board 107 are stacked and accommodated, and the lower end
periphery of the metal cap 101 is bent along the back surface of the printed wiring board 107 By
assembling these whole inseparable.
[0003]
The insulating case 106 supports the back electrode plate 105 at the upper side thereof, and is
formed in a cylindrical shape so that the air spring chamber 108 covered with the printed wiring
board 107 and shielded from the outside is formed on the back side of the back electrode plate
105. In the air spring chamber 108, the impedance conversion module 110 mounted on the
printed wiring board 107 is accommodated.
[0004]
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1
The impedance conversion module 110 uses, for example, an FET (field effect transistor) to
convert the vibration of the diaphragm 103 that vibrates due to the sound pressure into an
electric signal and outputs the electric signal.
Therefore, one output terminal of the FET 110 is electrically connected to the diaphragm 103 via
the conductive pattern of the printed wiring board 107, the metal cap 101, and the diaphragm
ring 102, and the other input terminal is the conductive pattern of the printed wiring board The
back plate 105 is electrically connected to the back plate 105 via contact rings 111 mounted
along the inner side surface of the insulating case 106.
[0005]
Further, in order to vibrate the diaphragm 103 by the external sound pressure, a sound hole 109
communicating the flat side of the diaphragm 103 to the outside is bored in the center of the flat
plate portion 101a. A through hole 105 a is formed to communicate the back side of the
diaphragm 103 to the air spring chamber 108.
[0006]
With such a configuration, the vibration of the sound transmitted from the outside through the
sound hole 109 is appropriate compliance of the diaphragm 103, viscous resistance due to the
gap between the diaphragm 103 and the back electrode plate 105, and the through hole The
vibration of the diaphragm 103 is efficiently transmitted by the balance of compliance by the air
spring chamber 108 communicated at 105 a.
[0007]
On the other hand, since the diaphragm 103 and the back electrode plate 105 face each other
with a slight insulating gap by the spacer 104 and act as an electrical capacitor, the vibration of
the diaphragm 103 is generated by applying a bias voltage to one of them. It can be taken out as
a voltage change at both ends.
Therefore, the FET 110 connected to the both ends converts this voltage change into a low
impedance, and outputs the vibration of the diaphragm 103 as an electric signal.
03-05-2019
2
[0008]
By the way, since the condenser microphone 100 configured in this way is widely used in
portable telephones and the like which are required to be miniaturized and thinned in recent
years, the condenser microphone itself is similarly low in height as well. Needs to be
[0009]
However, as described above, since the metal cap 101, the electrode structure of the diaphragm
103 and the back electrode plate 105, the impedance conversion module 110, and the printed
wiring board 107 are stacked, the total height of the individual components is less than The
height can not be set, and there is a limit to its height reduction.
[0010]
Further, if the height of the air spring chamber 110 is reduced to reduce the height, the volume
of the air spring chamber 108 is reduced, so it acts on the diaphragm 103 like a so-called hard
spring and the diaphragm 103 vibrates efficiently. There is a problem that the sensitivity is
deteriorated without the
[0011]
Furthermore, when the impedance conversion module 110 is taken out to reduce the height, it is
susceptible to electromagnetic noise, and it is necessary to take measures against noise
separately.
[0012]
The present invention has been made in view of the above problems, and an object of the present
invention is to provide a condenser microphone which can be reduced in height without
deteriorating sensitivity and without newly taking noise measures.
[0013]
SUMMARY OF THE INVENTION In view of the above-mentioned object, the condenser
microphone according to the first aspect of the present invention comprises an insulating case
having an electrode chamber open on the flat side, and a vibration disposed to cross the
electrode chamber. A back electrode plate having a predetermined insulation distance on the
back side of the diaphragm and arranged in the electrode chamber at a predetermined insulating
distance, and an impedance conversion module electrically connected to the diaphragm and the
back electrode plate; An insulating case in which the diaphragm and the back plate are arranged,
03-05-2019
3
and a metal cap in which a sound hole for communicating the diaphragm with the outside is
formed in a flat plate portion that accommodates the impedance conversion module and covers
the opening of the electrode chamber In the condenser microphone, the vibration of the
diaphragm is converted to an electric signal by the impedance conversion module. The capacitor
microphone is isolated from the outside on the side of the electrode chamber of the insulating
case, and the back side of the back electrode plate Forming an air spring chamber
communicating with the chamber, a portion of the air spring chamber, characterized in that to
accommodate the impedance conversion module.
[0014]
An air spring chamber is formed on the side of the electrode chamber in which the diaphragm
and back electrode plate are arranged, and the impedance conversion module is accommodated
in a part of the air chamber, so the volume of the air spring chamber is maintained at a
predetermined size. , Can reduce the overall height.
[0015]
Since the impedance conversion module is housed in the metal cap, it is less susceptible to
external noise.
[0016]
The condenser microphone according to claim 2 is characterized in that the back side of the air
spring chamber is covered by a printed wiring board on which the impedance conversion module
is mounted.
[0017]
The impedance conversion module can be accommodated in the air spring chamber only by
covering the back side of the air spring chamber with the printed wiring board on which the
impedance conversion module is mounted.
[0018]
By accommodating the impedance conversion module on the side of the electrode chamber, the
input terminal can be disposed at a position where it abuts on the back electrode plate, and a
contact for electrically connecting the back electrode plate and the input terminal Parts such as
rings are unnecessary.
03-05-2019
4
[0019]
The capacitor microphone according to claim 3 is characterized in that the periphery of the metal
cap is folded along the back surface of the printed wiring board, the printed wiring board is fixed
to the insulating case, and the metal cap electrically connected to the diaphragm is one of the
impedance conversion modules. And electrically connected to the conductive pattern of the
printed wiring board connected to the terminal of.
[0020]
In the step of bending the peripheral edge of the metal cap along the back surface of the printed
wiring board, the work of assembling the internal parts and the work of electrically connecting
one terminal of the impedance conversion module to the diaphragm are performed.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to FIGS. 1 and 2. FIG.
[0022]
FIG. 1 is an exploded perspective view showing an embodiment of a condenser microphone 1
according to the present invention, and FIG. 2 is a longitudinal cross-sectional view of the
condenser microphone 1. With the upper side.
[0023]
In FIG. 1, reference numeral 2 denotes a metal cap formed in a cylindrical shape with a bottom
by drawing, and the diaphragm ring 3, the diaphragm 4, and the insulating spacer 5 inward with
the bottom plate as the flat plate portion 2a on the flat side. The backplate 6, the insulating case
7, the FET (field effect transistor) 10 as an impedance conversion module, and the printed wiring
board 11 are accommodated.
[0024]
The insulating case 7 is formed of an insulating synthetic resin in a cylindrical shape that fits on
the inner side surface of the metal cap 2, and the electrode chamber 8 and the air spring
chamber 9 are provided outside the central axis of the insulating case 7. It is formed.
[0025]
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5
The electrode chamber 8 is formed in a cylindrical shape that opens on the flat side and the back
side, and along the edge on the back side, the flange piece 8a whose diameter on the back side is
slightly smaller is integrally formed with the insulating case 7 There is.
The back electrode plate 6, the insulating spacer 5, the diaphragm 4, and the diaphragm ring 3
are sequentially stacked on the flange piece 8a with the surface side of the electrode chamber 8
upward, and these components are peeled off in the electrode chamber 8 It is accommodated
without a hitch.
[0026]
Therefore, the outer shapes of the diaphragm ring 3, the diaphragm 4, the insulating spacer 5,
and the back electrode plate 6 are formed in a circular shape with the same outer diameter so as
to fit loosely in the electrode chamber 8, and the sum of these thicknesses is the electrode The
length is slightly longer than the height from the flange portion 8a of the chamber 8 to the plane
side opening surface.
[0027]
The diaphragm ring 3 is a conductive ring body held between the periphery of the diaphragm 4
and the flat plate portion 2 a of the metal cap 2 as shown in FIG. A gap for vibrating the
diaphragm 4 is formed between the flat plate portion 2 a and the flat plate portion 2 a.
The gap with the flat plate portion 2a communicates with the outside through the sound hole 12
formed in the flat plate portion 2a of the metal cap 2, and the vibration of the sound transmitted
from the outside is transmitted to the diaphragm 4 There is.
In addition, a metal vapor deposition surface is formed around the flat side of the diaphragm 4 in
contact with the diaphragm ring 3, and the diaphragm ring 3 is held between the diaphragm 4
and the flat plate portion 2 a to form a diaphragm ring. The diaphragm 4 and the metal cap 2 are
electrically connected via 3.
[0028]
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6
The vibrating plate 4 electrically acts as one electrode of a capacitor, and is separated by a ringshaped insulating spacer 5 from a slight insulating gap of, for example, 30 μm, so as to face the
back electrode plate 6 serving as the other electrode. Be placed.
An electret dielectric film 6 a such as Teflon is attached to the opposite surface (surface on the
flat side) of the back electrode plate 6 facing the diaphragm 4, and the back electrode plate 6 has
a gap with the diaphragm 4. The through holes 13 are formed at four positions so as to
communicate the back side of the through holes 13.
[0029]
On the back side of the back electrode plate 6, an air gap 15 is formed by the above-mentioned
flange piece 8a, and this air gap 15 is respectively surrounded by the conduction holes 14
formed by cutting out the flange piece 8a at three positions. It communicates with air spring
chambers 91, 92, 93 divided into three chambers.
[0030]
The central air spring chamber 92 is formed in a rectangular parallelepiped shape so that the
FET 10 can be accommodated therein, and the air spring chambers 91 and 93 on both sides
thereof are formed in the remaining portion of the insulating case 7 on both sides of the
electrode chamber 8 Be done.
The central air spring chamber 92 and the air spring chambers 91 and 93 on both sides thereof
also communicate with each other by a conduction hole 14 formed by cutting out a part of a
partition separating these.
[0031]
The air spring chambers 91, 92, 93 are formed by penetrating the plane side and the back side
of the insulating case 7, respectively, but the plane side is formed by the flat plate portion 2a of
the metal cap 2, It is covered by the printed wiring board 11 which covers the whole rear surface
side of the insulating case 7, and the air gap 15 and the air spring room 9 whole become a closed
space intercepted from the outside.
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7
[0032]
The printed wiring board 11 is formed in a disk shape so as to cover the entire rear surface side
of the cylindrical insulating case 7, and the FET 10 is mounted at a position covering the central
air spring chamber 92.
The FET 10 includes an input terminal 10a and two other output terminals 10b and 10c. The
input terminal 10a extends toward the center of the printed wiring board 11, and the other two
output terminals 10b and 10c are printed wiring. It is soldered to a ground pattern (not shown)
of the substrate 11.
[0033]
As described above, after assembling each component in the electrode chamber 8 as described
above, the insulating case 7 is covered with the printed wiring board 11, and the back side
peripheral edge 2b of the metal cap 2 is placed on the back of the printed wiring board 11.
Assemble by folding and crimping along.
[0034]
As shown in FIG. 2, in the assembled state, the input terminal 10 a of the FET 10 extends from
the air spring chamber 92 to the air gap 15 along the conduction hole 14 and abuts on the back
surface of the back electrode plate 6. Electrically connected to board 6
Therefore, electrical connection between the back electrode plate 6 and the FET 10 is easily
made during a series of assembly operations.
[0035]
Further, the peripheral edge 2b of the metal cap 2 is crimped so as to be electrically connected to
the input pattern of the printed wiring board 11, whereby the output terminal 10b of the FET 10
has the ground pattern of the printed wiring board 11, the metal cap 2 and the vibration.
Electrical connection is made to the diaphragm 4 via the plate ring 3.
[0036]
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8
On the other hand, the surface side of the diaphragm 4 communicates with the outside through
the sound hole 12 as described above, and the back side communicates with the air gap 15
which is a closed space through the through hole 13 of the back electrode plate 6.
Since the air gap 15 and the air spring chamber 9 communicate with each other through the
conduction hole 14, the volume can be made large as a whole, and the back chamber of the back
electrode plate 6 becomes a back chamber of a corresponding volume.
[0037]
Therefore, the diaphragm 4 has an appropriate compliance of the diaphragm 4, a viscous
resistance due to the gap between the diaphragm 4 and the back electrode plate 6, and a balance
of compliance due to the gap 15 communicated with the through hole 13 and the air spring
chamber 9. And vibrate efficiently with respect to the vibration of sound transmitted from the
outside through the sound hole 12.
[0038]
The vibration of the diaphragm 4 causes the diaphragm 4 and the back electrode plate 6 to
function as electrodes of a capacitor facing each other with an insulating gap, so that a bias of 200 V is applied to the dielectric film 6a deposited on the back electrode plate 6. By applying a
voltage and causing permanent charging, the voltage change between the back electrode plate 6
and the diaphragm 4 is taken out.
Since the input terminal 10a and the output terminal 10b are connected to these electrodes, the
FET 10 converts this voltage change into a low impedance, and outputs the vibration of the
diaphragm 4 as an electrical signal from the other output terminal 10c.
[0039]
According to this embodiment, the height of the condenser microphone, which could not be
reduced in height from the height of 2 mm conventionally, can be set to 1 mm without degrading
the sensitivity.
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9
[0040]
The present invention is not limited to the above-described embodiment. For example, although
the above-described embodiment covers the back side of the air spring chamber 9 with the
printed wiring board 11, the insulating case 7 The back side may be covered.
In addition, the shape and number of the air spring chambers 9 are not limited as long as an
appropriate capacity can be obtained.
[0041]
As described above, according to the present invention, the overall thickness of the condenser
microphone can be reduced without affecting the vibration of the diaphragm 4.
[0042]
Furthermore, since the space for housing the impedance conversion module is also used as part
of the back chamber, the air spring chamber can be efficiently formed without increasing the size
of the insulating case.
[0043]
Further, according to the invention of claim 2, it becomes possible to arrange the input terminal
of the impedance conversion module in a position in contact with the back electrode plate, and a
contact ring or the like for electrically connecting the back electrode plate and the input terminal
Parts are not required.
[0044]
Further, according to the invention of claim 3, in one step of bending the peripheral edge of the
metal cap along the back surface of the printed wiring board, the assembly operation of the
internal parts and the electrical connection operation of the terminal of the impedance
conversion module and the diaphragm are performed. be able to.
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