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DESCRIPTION JPH10145894

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DESCRIPTION JPH10145894
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
condenser microphone suitable for business use.
[0002]
2. Description of the Related Art A condenser microphone is known as a microphone, and the
microphone unit is configured as shown in FIG. 5, for example. That is, in FIG. 5, reference
numeral 30 denotes the microphone unit, and the diaphragm 31 is formed in a circular shape by
a conductive plate such as a metal plate, and is formed in an annular shape on the rear surface
by an insulating material. A back electrode (fixed electrode) 33 is provided with the spacer 32
interposed therebetween.
[0003]
The back electrode 33 is formed in a circular shape by a conductive member such as a metal
plate, and a plurality of through holes 34 are formed, and the rear surface of the diaphragm 31 is
opened to the rear of the back electrode 33 through the through holes 34. It is done.
[0004]
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Further, the air chamber member 35 is formed in a cup shape as a whole by an insulating
material, and a step 36 is formed inside the opening portion, and the back electrode 33 is located
here.
Further, the case 37 is formed in a cup shape by a conductive material such as metal, and the
through hole 38 is formed on the bottom surface thereof, and the above-mentioned components
31, 32, 33 are formed so that the diaphragm 31 faces the through hole 38. , 35 are provided
inside the case 37. Further, an annular fixing member 39 is provided in the case 37 so as to be in
contact with the rear portion of the air chamber member 35, and components provided in the
case 37 are fixed.
[0005]
Although not shown, the back electrode 33 is connected to the hot side of the front circuit
through the lead wire, and the diaphragm 31 is connected to the ground side of the front circuit
through the case 37 and through the lead wire. As an example, the diameter of the diaphragm 31
is 30 to 40 mm, and the distance between the diaphragm 31 and the back electrode 33 (the
thickness of the spacer 32) is 30 to 50 μ.
[0006]
According to such a configuration, the diaphragm 31 and the back electrode 33 constitute the
capacitor C30, and the diaphragm 31 vibrates as shown by a broken line by a sound wave, and
the capacitance of the capacitor C30 changes. At this time, the rear portion of the diaphragm 31
is opened to the air chamber (the space formed by the rear electrode 33 and the air chamber
member 35) at the rear portion of the back electrode 33 through the through hole 34. Can follow
the sound waves and vibrate.
[0007]
Therefore, if the change in capacitance of the capacitor C30 is extracted as an electric signal, the
signal is nothing other than a signal obtained by acoustic-electrical conversion of the sound wave
that has given vibration to the diaphragm 31, that is, the audio collected by the microphone unit
30. You can get a signal.
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[0008]
Incidentally, the capacitance of the capacitor C30 configured by the diaphragm 31 and the back
electrode 33 is 50 to 60 pF in the case of the above numerical example, and the capacitance
change by the sound wave is several pF.
[0009]
By the way, in the microphone unit 30 of FIG. 5, since the sound wave is converted into an audio
signal by the change in capacitance of the capacitor C30, the diaphragm 31 and the back
electrode constituting the capacitor C30 are used. Insulation between 33 is important.
That is, if the insulation is bad, the Q value of the capacitor C30 is lowered, so that the level and S
/ N of the obtained audio signal are lowered.
[0010]
However, in an actual use state, for example, as shown in the upper left portion of FIG. 5 in an
enlarged manner in FIG. 6, moisture or moisture 40 contained in the user's breath or air adheres
to the inner peripheral surface of the spacer 32. There are times when
Then, since the diaphragm 31 and the back electrode 33 are connected through the moisture 40,
the insulation resistance between the diaphragm 31 and the back electrode 33 decreases, and
the level of the audio signal to be output and the S / N Or an abnormal signal is output. And, such
a situation actually happens quite often.
[0011]
The present invention is intended to solve such problems.
[0012]
Therefore, in the present invention, a conductive diaphragm and a back electrode plate provided
on the back surface of the diaphragm are provided, and the back electrode plate is an insulating
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plate and An insulating layer is formed on the insulating plate so as to cover the electrode plate,
the electrode plate provided on the surface facing the diaphragm among the insulating plates,
and the vibration caused by the sound wave is generated. The vibration of the plate is taken as a
change in capacitance between the vibrating plate and the electrode plate.
Therefore, the insulation between the diaphragm and the electrode plate is ensured by the
insulating layer.
[0013]
DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 10 denotes a
microphone unit according to the present invention, and a diaphragm 11 is formed in a circular
shape by a conductive plate such as a metal plate, and a rear surface thereof The printed wiring
board 20 is provided with spacers 12 formed annularly of metal or the like in between.
[0014]
The printed wiring board 20 is formed in the same manner as a printed wiring board used for
general circuit wiring, and the whole functions as a back electrode plate and its wiring pattern
functions as a back electrode (fixed electrode). is there.
[0015]
That is, in the printed wiring board 20, the insulating board 21 is formed in a circular shape, for
example, by a porous ceramic plate impregnated with an epoxy resin, and the glass cloth
impregnated with the epoxy resin for reinforcement on both sides thereof. A layer (not shown) is
formed.
[0016]
Then, on the surface of the insulating substrate 21 facing the diaphragm 11, a wiring pattern 22
acting as a back electrode is formed in a circular shape so as not to reach the spacer 12 with
copper foil, for example.
Further, a plurality of through holes 23 are formed in the insulating substrate 21 and the wiring
pattern 22, and the rear surface of the diaphragm 11 is opened to the rear of the printed wiring
board 20 through the through holes 23. The pattern 22 is electrically connected to the wiring
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pattern 24 on the rear surface of the insulating substrate 21 by through hole processing.
[0017]
Further, for example, as shown in FIGS. 2 and 3, a solder resist layer 26 is formed on the surface
of the insulating substrate 21 facing the diaphragm 11 so as to cover the wiring pattern 22.
Further, for example, as shown in FIGS. 3 and 4, a solder resist layer 27 is formed on the back
surface of the insulating substrate 21 so as to cover the wiring pattern 24, and a solder resist
layer is formed on the central portion 25. 27 is not formed, and the wiring pattern 24 is exposed.
[0018]
In this case, the solder resist layers 26, 27 are originally intended to prevent the solder from
adhering to the wiring pattern, but may be generally used if the insulation resistance is
sufficiently large. .
For example, liquid solder resist DSR-2200 (manufactured by Ibiden Electronics Co., Ltd.) can be
used. Also, the printed wiring board 20 as described above can be manufactured by the same
process and operation as the commonly used double-sided printed wiring board.
[0019]
Further, as shown in FIG. 1, the air chamber member 15 is formed in a cup shape as a whole by a
conductive material such as metal, and the printed wiring board 20 is positioned so as to close
the opening. Further, the case 17 is formed in a cup shape by a conductive material such as
metal, and the through hole 18 is formed on the bottom surface of the case 17 so that the
diaphragm 11 faces the through hole 18. , 15 are provided inside the case 17. Further, an
annular fixing member 19 is provided in the case 17 so as to be in contact with the rear of the air
chamber member 15, and components provided in the case 17 are fixed.
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[0020]
Then, although not shown, the exposed central portion 25 of the wiring pattern 24 is used as a
lead terminal, to which a lead wire is soldered, for example, and the lead wire is connected to the
hot side of the front circuit. . Further, the diaphragm 11 is connected to the ground side of the
front circuit through the case 17 and through the lead wire. The size of the main part is the same
as that of FIG.
[0021]
According to such a configuration, the capacitor C10 is configured by the diaphragm 11 and the
wiring pattern 22, and the diaphragm 11 is vibrated by a sound wave as indicated by a broken
line, and the capacitance of the capacitor C10 changes. At this time, the rear portion of the
diaphragm 11 is opened to the air chamber (the space formed by the printed wiring substrate 20
and the air chamber member 15) at the rear portion of the printed wiring board 20 through the
through hole 23. The plate 11 can vibrate following the sound wave.
[0022]
Therefore, if the change in capacitance of the capacitor C10 is extracted as an electric signal, the
signal is nothing other than a signal obtained by acoustic-electrical conversion of the sound wave
that has given vibration to the diaphragm 11, that is, the audio collected by the microphone unit
10. You can get a signal.
[0023]
And, in this case, according to this microphone unit 10, the wiring pattern 22 which is the back
electrode is covered with the solder resist layer 26 and exposed to the air, so moisture is
generated on the inner peripheral surface of the spacer 12 or the like. Even if it adheres, the
insulation between the diaphragm 11 and the wiring pattern 22 is secured by the solder resist
layer 26, and the insulation resistance does not decrease.
Therefore, even in a humid environment, stable microphone operation can always be realized,
and a good audio signal can be obtained.
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[0024]
Moreover, since the solder resist layer 26 can be formed in a free shape corresponding to the
shape of the wiring pattern 22, the wiring pattern 22 can be reliably covered and concealed, and
the solder resist layers 26 and 27 can be formed in a special manner. It does not require any
technical skills.
[0025]
Furthermore, in the microphone unit 30 of FIG. 5, a member for determining the relative position
between the diaphragm 31 and the spacer 33 must be an insulating material, but generally the
insulating material has a low processing accuracy, so the capacity of the capacitor C30 is It will
scatter.
However, in the microphone unit 10 of FIG. 1, since the back electrode plate is constituted by the
printed wiring board 20, as shown also in FIG. 1, the spacer 12, etc. which determines the
capacity of main components, particularly the capacitor C10. Can be formed of any metal by any
processing method, and can be formed with high accuracy.
[0026]
Therefore, since the variation in the capacitance of the capacitor C10 can be suppressed, the
variation in the level of the output audio signal can be suppressed, and the signal level and the S
/ N of the design target can be obtained.
[0027]
In addition, since the insulation substrate 21 of the printed wiring board 20 which can originally
ensure sufficient insulation insulates the wiring pattern 22 acting as the back electrode, the
insulation between the back electrode (wiring pattern) 22 and other portions Can be secured
enough.
Furthermore, since the back electrode plate is configured by the printed wiring board 20, the
wiring pattern 22 acting as the back electrode can be formed with sufficient accuracy for the
shape required electrically, and at the same time the insulating substrate 21 is also It can be
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formed in a shape required to support the wiring pattern 22. Therefore, excellent characteristics
can be obtained also from this point as a microphone unit of a condenser microphone.
[0028]
Furthermore, if there is variation in the diameter of the insulating substrate 21 of the printed
wiring board 20, the printed wiring board 20 will be assembled unevenly in the left and right
direction in FIG. 1, but the capacity of the capacitor C10 is determined The area of the wiring
pattern 22 facing the diaphragm 11 can be formed with sufficient accuracy, so that the variation
in the diameter of the printed wiring board 20 does not matter. Further, even if the thickness of
the insulating substrate 21 varies, the distance between the wiring pattern 22 and the diaphragm
11 is not affected, so that the variation of the thickness of the insulating substrate 21 does not
matter. Furthermore, as apparent from FIG. 1, the structure or shape of each part can be
simplified, and the processing of each part is simple.
[0029]
In the microphone unit 10 described above, in order to convert the change in capacitance of the
capacitor C10 into an audio signal, a series circuit of the capacitor C10 and a resistor having a
relatively large value may be connected to a DC power supply. That is, if so, an audio signal can
be obtained from the resistor.
[0030]
Alternatively, the capacitor C10 is connected to the resonance circuit of the oscillation circuit,
and the oscillation frequency is FM-modulated by the capacitance change of the capacitor C10,
and the FM signal is FM-demodulated to obtain an audio signal.
[0031]
The wiring patterns 22 and 24 can also be formed by applying a conductive paint or the like in a
plate shape.
Furthermore, instead of the solder resist layers 26 and 27, a paint for marking the device name
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etc. on the printed wiring board can be used.
[0032]
According to the present invention, since the back electrode is provided on the insulating plate
and the back electrode is covered with the insulating layer, insulation between the diaphragm
and the back electrode can be secured. Even under a high humidity environment, stable
microphone operation can be realized at all times. In addition, since the insulating layer can be
formed in a free shape corresponding to the shape of the back electrode, the back electrode can
be reliably covered. In addition, no special technology is required to form the insulating layer.
[0033]
Furthermore, in order to provide insulation between the diaphragm and the back electrode, the
microphone unit can be realized with a simpler structure without the need to use a complicatedshaped insulating part. In addition, the positional relationship between the diaphragm and the
back electrode can be obtained with sufficient accuracy, and a good output signal can be
obtained.
[0034]
Furthermore, since the back electrode plate and the back electrode are configured by the printed
wiring board, each can be made into a free shape, and the position of the back electrode in the
back electrode plate can also be made arbitrary.
[0035]
Brief description of the drawings
[0036]
1 is a cross-sectional view showing an embodiment of the present invention.
[0037]
2 is a front view showing an embodiment of the main part of the present invention.
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[0038]
3 is a cross-sectional view showing an embodiment of the main part of the present invention.
[0039]
4 is a rear view showing an embodiment of the main part of the present invention.
[0040]
5 is a cross-sectional view for explaining the present invention.
[0041]
6 is an enlarged cross-sectional view of a portion of FIG.
[0042]
Explanation of sign
[0043]
10 = microphone unit, 11 = diaphragm, 12 = spacer, 15 = air chamber member, 17 = case, 18 =
through hole, 19 = fixing member, 20 = printed wiring board, 21 = insulating substrate, 22 and
24 = Wiring pattern, 23 = through hole, 26 and 27 = solder resist layer
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