JP2011223138

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DESCRIPTION JP2011223138
PROBLEM TO BE SOLVED: To ensure electrical connection between a unit case and a circuit
board, to prevent noise due to electromagnetic waves and the like more reliably, and to cause a
pressure on a bent portion of an opening of the unit case to adversely affect sound collection. To
provide a condenser microphone unit that prevents the SOLUTION: A unit case 1, a diaphragm 4
stretched on a support ring 5, a fixed electrode 6 supported by an insulating seat 3, a circuit
board 2 disposed in the unit case 1, and a circuit board And an impedance converter 7 disposed
on the inner surface of 2 and connected to the fixed pole 6, wherein the edge of the opening of
the unit case 1 is bent inside the unit case 1 over the entire circumference, The shape of the bent
portion of the open edge is uneven, and each built-in component in the unit case 1 is fixed by
pressing the circuit board 2 with the concave portion 1a of the bent portion of the open edge The
concave portion 1a and the circuit board 2 are electrically connected. [Selected figure] Figure 2
コンデンサマイクロホンユニット
[0001]
The present invention relates to a condenser microphone unit, and in particular, further ensures
electrical connection between a unit case, which is a housing of a condenser microphone unit,
and a ground pattern formed on a circuit board disposed in the unit case. It relates to technology.
[0002]
The unit case of the condenser microphone unit is formed of an aluminum material or the like
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which can be processed by pressing the unit case.
For example, in FIG. 4, the unit case 1 made of aluminum material or the like has a cylindrical
shape with a bottom and a sound introduction hole 1c is drilled at one end corresponding to the
bottom and the other end is opened as an open end. In the final step, the open end edge on the
other end side is bent inward. In the unit case 1, the diaphragm 4 stretched on the support ring 5
and the fixed electrode 6 supported by the insulating seat 3 are disposed to face each other.
When the diaphragm 4 receives a sound wave, the capacitance of the diaphragm 4 and the fixed
electrode 6 changes, and the circuit board 2 for outputting this change as an audio signal is
accommodated. In the following description, the parts housed in the unit case 1 may be simply
referred to as "built-in parts".
[0003]
An impedance converter 7 connected to the fixed pole 6 through a predetermined electrical
connection means is mounted on one surface of the circuit board 2 (the surface directed to the
inside of the unit case 1; the upper surface in FIG. 4) . As shown in FIG. 3, on the other surface of
the circuit board 2 (the surface directed to the outside of the unit case; the lower surface in FIG.
4), there are soldered lands and ground patterns (grounding) for each electrode terminal of the
impedance converter. Pattern) is formed. The ground pattern is formed along the outer
peripheral edge of the circuit board 2 in order to connect to the unit case 1.
[0004]
In assembling, after housing each built-in part from the open end on the other end side of the
unit case 1, the entire circumference of the open end edge of the unit case 1 is curled toward the
inside of the unit case. The unit case and the ground pattern of the circuit board 2 are electrically
connected by the curled portion 1d. The curled portion 1d applies a suitable pressure to the
internal parts of the unit case 1 so as not to move inadvertently, and the metal deposition surface
formed on the diaphragm is supported by the support ring 5 and the unit case It is performed to
connect with the ground pattern of the circuit board 2 through 1.
[0005]
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By the way, with the spread of mobile phones, mobile phones are being used on a daily basis
near a microphone. Mobile telephones emit considerably strong electromagnetic waves (for
example, electric field strength reaching several tens of thousands times the electric field
strength generated in the city by commercial radio waves in the range of several cm to several
10 cm) when used.
[0006]
When the high frequency current due to the electromagnetic wave enters the inside of the
condenser microphone unit 20, it may be detected by the impedance converter 7 and noise at an
audible frequency may be generated. The shield of the unit case 1 plays an important role in
preventing this kind of noise generation. However, since the ground pattern of the circuit board
2 pressed by bending the open end edge of the unit case 1 is formed flat, uneven pressing force
is generated, and the contact between the unit case 1 and the ground pattern is a part Contact. In
the worst case, the unit case 1 and the ground pattern are in point contact with each other at one
point, and the shield against high frequency becomes incomplete and noise occurs frequently.
The contact state between the unit case 1 and the ground pattern can not be confirmed visually.
Further, even if the electrical resistance is measured by a tester or the like, accurate
determination of quality is difficult because the resistance value is low.
[0007]
Therefore, in the invention described in Patent Document 1, it is proposed that the abovementioned curled portion 1d of the open edge is subjected to ultrasonic welding and the
electrical connection is maintained with high reliability over a long period of time. There is.
However, in the invention described in Patent Document 1, the circuit board 2 is pressed with the
above-described curling shape instead of being able to maintain the electrical connection with
high reliability over a long period of time. The pressing force is applied to the entire periphery of
the circuit board 2 as indicated by. Therefore, the pressing force of the curled portion 1d on the
circuit board 2 may be increased as a whole, and the increased entire pressing force affects the
tension and the like of the diaphragm 4 as the built-in component, and in particular In the case of
a directional microphone unit or the like, there may be problems in sound collection, particularly
in the low frequency range.
[0008]
Unexamined-Japanese-Patent No. 2010-50868
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[0009]
According to the present invention, the bent portion of the open edge of the unit case securely
presses the circuit board, so that the electrical connection between the unit case and the circuit
board is secured, and the shield of the entire condenser microphone unit is reliably configured.
Noise is more reliably prevented, and the pressure from the bent part of the open edge of the
unit case does not affect the built-in parts of the condenser microphone unit, thus collecting the
sound, especially the sound in the low frequency range. It is an object of the present invention to
provide a condenser microphone unit which does not cause any problem.
[0010]
The condenser microphone unit according to the present invention has a sound introduction hole
at one end, and a unit case whose other end is an open end, a diaphragm tensioned on a support
ring, and a diaphragm disposed opposite to the diaphragm. A fixed pole supported by the
insulating seat, a circuit board disposed on the open end side of the unit case, and an impedance
converter disposed on the inner surface of the circuit board and connected to the fixed pole The
open edge of the unit case is bent inside the unit case all around, the shape of the bent part of
the open edge is uneven, and each built-in component in the unit case is an open end The
concave portion of the bent portion of the edge is fixed by pressing the circuit board, and the
concave portion of the bent portion of the open edge and the outer surface of the circuit board
are electrically connected To Also a major feature.
[0011]
According to the present invention, the shape of the bent portion of the open edge is uneven, and
each built-in component in the unit case is such that the concave portion of the bent portion of
the open edge is outside the circuit board. The shield is formed by a plurality of contact points by
fixing the depression by pressing the surface and electrically connecting the concave portion to
the outer surface of the circuit board. Even if it hits, the influence of the electromagnetic wave
can be reliably escaped to the outside of the unit case from the outer surface of the circuit board,
so the built-in parts can be protected from the electromagnetic wave, and the noise generated by
the electromagnetic wave can be prevented more reliably. be able to.
Furthermore, by the pressure by the built-in parts by the bent part of the open edge becoming
appropriate, the condenser microphone can prevent the pressure from disturbing the sound
collection of the condenser microphone unit, especially the sound collection in the low frequency
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range. A unit can be provided.
[0012]
It is a bottom view of a unit case showing an embodiment of a condenser microphone unit
concerning the present invention.
It is sectional drawing of the said Example.
It is a bottom view which shows the example of the conventional condenser microphone unit. It is
sectional drawing of the said prior art example.
[0013]
Hereinafter, embodiments of a condenser microphone unit according to the present invention
will be described with reference to the drawings. The present invention is not limited to the
configurations of the embodiments described below. In the following description, the
components housed in the unit case may be simply referred to as "built-in components". The
same reference numerals are given to members having the same configuration as the
conventional microphone shown in FIGS. 3 and 4.
[0014]
As shown in FIG. 2, the condenser microphone unit 10 basically has a unit case 1 having a sound
introduction hole 1 c at one end and an open end at the other end, and a support ring 5. A
diaphragm 4 stretched, a fixed electrode 6 disposed opposite to the diaphragm 4 and supported
by the insulating seat 3, a circuit board 2 disposed on the open end side of the unit case 1, and a
circuit An impedance converter 7 disposed on one side of the substrate 2 and connected to the
fixed pole 6 is provided.
[0015]
The unit case 1 is formed of a bottomed cylindrical body made of aluminum, and a sound
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introducing hole 1c is formed at one end (upper end in FIG. 2) corresponding to the bottom
surface of the bottomed cylinder.
The other end (lower end in FIG. 2) of the unit case 1 is an open end. The diaphragm 4 is
provided so as to be stretched with a predetermined tension on the support ring 5 made of metal,
and the disk-shaped fixed electrode 6 supported on one end side of the insulating seat 3. An
electrically insulating spacer ring (not shown) may be disposed between the diaphragm 4 and the
fixed electrode 6, and the spacer ring may not be disposed between the diaphragm 4 and the
fixed electrode 6. The built-in components may be configured to have a predetermined interval.
The open end edge of the unit case 1 is bent inward. The bent shape of the portion of the open
end edge of the unit case 1 is a concavo-convex shape (1a, 1b) in which concavities and
convexities are arranged in the circumferential direction. A feature of the condenser microphone
unit according to the present invention is that the concave portion 1a and the circuit board 2 are
electrically connected. Details will be described later.
[0016]
The diaphragm 4 is made of a thin film of synthetic resin, and although not shown, a vapor
deposited film of metal is formed on one surface thereof. In the case of the back electret type, an
electret dielectric film is provided on the surface of the fixed electrode 6 (opposite surface to the
diaphragm 4), and in the case of the film electret type, the electret dielectric is formed on the
diaphragm 4 A membrane is applied. The diaphragm 4 and the fixed pole 6 are disposed to face
each other.
[0017]
The circuit board 2 is a circular board disposed within the open end edge of the unit case 1 and
having an outer diameter slightly smaller than the inner diameter of the unit case 1, and one
surface thereof (a surface directed to the inside of the unit case 1; An FET (field effect transistor)
7 as an impedance converter is mounted on the upper surface in FIG. Of the three electrodes
provided in the FET 7, the gate electrode is connected to the fixed electrode 6 through a
predetermined electrical connection means. In this embodiment, a rod-shaped relay contact 8 is
used as the electrical connection means, and a compression coil spring 9 is provided around the
relay contact 8 in order to secure a good contact.
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[0018]
Referring to FIG. 1, in this embodiment, the other surface (the surface facing the outside of unit
case 1; the lower surface in FIG. 2) of circuit board 2 is a solder land 2a for drain electrode of
FET 7, a source electrode. Solder lands 2b and a ground pattern (ground pattern) are formed. The
ground pattern is disposed along the outer peripheral edge of the circuit board 2 and
surrounding the solder lands. Concave portions of the concavo-convex shapes 1a and 1b in which
concavities and convexities are arranged in the circumferential direction of the unit case 1 are in
contact with a ground pattern arranged along the outer peripheral edge of the circuit board 2 at
a plurality of places. For example, a feeder of a microphone cable (not shown) is connected to the
solder land 2a for drain electrode, and a signal line of the microphone cable is connected to the
solder land 2b for source electrode, and the above ground pattern is For example, a shield wire of
the microphone cable is connected. The pattern of the outer surface of the circuit board and the
connection thereof are not limited to those described above, and the unit case 1 is hit by the
electromagnetic wave because the concave portion and the outer surface of the circuit board 2
are electrically connected. However, it is possible to design appropriately so that the influence of
the electromagnetic wave can be dissipated to the outside of the unit case 1 from the outer
surface of the circuit board 2.
[0019]
The condenser microphone unit 1 in this embodiment is provided with the rear acoustic terminal
2 d on the circuit board 2 since it has a single directivity, and the insulating seat 3 and the fixed
pole 6 have sound holes (sound introducing holes) 3 a and 6 a respectively. Is drilled. Thereby,
the sound wave from the rear acoustic terminal 2 d acts on the back surface of the diaphragm 4
through the sound holes 3 a and 6 a. A predetermined acoustic resistance material 11 is disposed
between the fixed pole 6 and the sound hole 3a. In order to assemble the condenser microphone
unit 10, as an example, the support ring 5 with the diaphragm 4 stretched, the insulating seat 3
with the fixed pole 6 attached, the relay contact 8 and the circuit board 2 in the unit case 1 Store
in this order.
[0020]
The open end edge on the other end side of the unit case 1 is plastically deformed into
continuous irregularities by transferring the shape of a tool such as a bevel gear like a knurling
over the entire circumference, The open end can be bent inside the unit case 1. Thus, as shown in
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FIGS. 1 and 2, the open end edge of the unit case 1 is folded to the outer surface side of the
circuit board 2 to form a concave portion 1a which contacts the ground pattern of the circuit
board, and It comes to have continuously the convex part 1b which protrudes on the opposite
side to the surface side. By this processing, the outer surface of the circuit board 2 and the
concave portion 1a are electrically connected at a plurality of places. In FIGS. 1 and 2, the shapes
of the uneven portions 1a and 1b can be any suitable shape that allows the concave portion 1a
and the outer surface of the circuit board 2 to be electrically connected. is there. For example, as
shown in FIG. 1 and FIG. 2, the shape of the uneven portions 1 a and 1 b may be peak-and-valley
with a sharp tip, and the tip may be rounded. The formation method of the uneven ¦ corrugated
shape mentioned above can use not only the above-mentioned thing but an appropriate thing.
Each built-in component in the unit case 1 is fixed by pressing the circuit board 2 with the
concave portion 1 a of the bent portion. As described above, while each built-in component is
fixed in the unit case 1, the unit case 1 contacts the ground pattern at the periphery of the circuit
board 2 at a plurality of places, and the concave portion 1a and the circuit board 2 are
electrically Connected.
[0021]
As described above, the electrical connection between the unit case 1 and the ground pattern of
the circuit board 2 is surely made, and the shape of the bent portion of the open end is a
concavo-convex shape (1a, 1b). Each of the internal components is fixed by pressing the outer
surface of the circuit board 2 with the concave portion 1a of the bent portion of the open edge,
and the concave surface 1a and the outer surface of the circuit board 2 are electrically Since it is
possible to ensure that the influence of the electromagnetic wave can be dissipated to the outside
of the unit case 1 from the outer surface of the circuit board 2 even if the electromagnetic wave
strikes the unit case 1 because the connection is surely made. Can be protected from
electromagnetic waves, and noise generated by electromagnetic waves can be more reliably
prevented. Furthermore, the pressure on the built-in parts by the bent portion of the open edge
becomes appropriate, so that it is possible to prevent the pressure from disturbing the sound
collection of the condenser microphone unit 10, particularly the sound collection in the low
frequency range. In particular, a condenser microphone unit having a property of being easily
disturbed by the above-mentioned pressure due to the tension of the diaphragm 4 and the
structure of the rear acoustic terminal, such as a unidirectional microphone unit, can be used in
the unit case 1 as in the embodiment of the present invention. It is preferred to make the bent
portion of the open edge uneven.
[0022]
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As mentioned above, although an example of embodiment of this invention was described, this
invention is not limited to the structure of this Example, A design change can be carried out in
the range which does not deviate from the technical idea described in the claim. For example, the
uneven shape of the unit case according to the above embodiment of the present invention may
be used for a nondirectional microphone unit as well as a unidirectional microphone unit.
[0023]
DESCRIPTION OF SYMBOLS 1 unit case 1a concave part 1b convex part 1c sound introduction
hole 2 circuit board 3 insulator seat 4 diaphragm 5 support ring 6 fixed pole 7 impedance
converter (FET) 8 relay contact 10 capacitor microphone unit
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