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JP2006319391

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DESCRIPTION JP2006319391
To solder a lead wire extended from a microphone unit, to prevent the leakage of current so that
the flux is regulated within the range of a soldered land, and to suppress the generation of noise
and Get the lead connection method. SOLUTION: A lead wire extended from a condenser
microphone unit, an impedance conversion unit 12 mounted on a circuit board 10 for converting
the impedance of an output of the microphone unit, and an output signal of the microphone unit
are input to the impedance conversion unit 12. And a soldering land 16 for soldering the lead
wire, and the flux spread by the soldering of the lead wire is regulated in the vicinity of the
soldering land 16. A masking member 20 is attached to the circuit board 10 by surrounding the
periphery of the soldering land 16 and exposing the soldering land 16. The masking member 20
may be a seal made of fluorocarbon resin. [Selected figure] Figure 1
Condenser microphone and lead wire connection method in the condenser microphone
[0001]
The present invention relates to a condenser microphone and a method of connecting a lead in
the condenser microphone, and in particular, the structure of a joint by soldering of a lead
extended for outputting an audio signal from a condenser microphone unit to a soldering land
and It relates to the connection method.
[0002]
As the condenser microphone, since the impedance of the microphone unit is high, an impedance
converter mainly composed of a field effect transistor (hereinafter referred to as "FET") is used.
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The FET, which is the main component of the impedance converter, is mounted on the circuit
board in a surface mounting manner along with other circuit components. FETs and other circuit
components are subjected to a reflow process using cream solder and simultaneously soldered.
Cream solder contains a flux, and the flux spreads on the substrate when it is soldered by reflow.
When the circuit board is placed in a high humidity environment, the flux absorbs the
surrounding moisture to reduce the surface resistance, causing a leakage current with other
circuits and causing a noise due to the leakage current. In particular, when flux remains in the
gate portion or the like of the FET having high impedance, and the flux absorbs moisture, the
surface resistance of the circuit is reduced, the influence of leakage current is large, and noise is
easily generated.
[0003]
Therefore, in the circuit board incorporated in the condenser microphone, after the circuit parts
are soldered by reflow, the flux is removed by cleaning with isopropyl alcohol (hereinafter
referred to as "IPA") or the like. However, after the above-mentioned cleaning process, it is
necessary to solder and wire the lead wire for audio signal output drawn from the condenser
microphone unit to a predetermined soldering land formed on the circuit board. In this soldering
process, a soldering iron is used to solder to a predetermined soldering land. At that time, the
flux contained in the solder spreads on the substrate, and this flux causes the above-mentioned
problems.
[0004]
FIG. 2 shows an example of a circuit board used in a conventional condenser microphone. In FIG.
2, the circuit board 10 is disposed in a condenser microphone, for example, in a microphone case
which also serves as a grip. The circuit board 10 is subjected to a reflow process together with
other circuit components 14 at the end closer to the condenser microphone unit, together with
other circuit components 14, and is simultaneously soldered and surface mounted. In addition,
after the reflow process, it is subjected to a cleaning process by IPA. On the circuit board 10, a
soldering land 16 connected to the base of the FET 12 is formed at a position closer to the
microphone unit than the FET 12. The lead wire drawn from the condenser microphone unit is
soldered to the soldering land 16. At that time, as described above, the flux contained in the
solder spreads on the substrate 10. In FIG. 2, reference numeral 18 denotes a flux spread around
the soldering land 16 on the substrate 10.
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2
[0005]
The flux 18 absorbs the moisture in the air to reduce the surface resistance, causing the current
to leak from the surrounding circuits and causing noise. In particular, since the soldering land 16
is connected to the base of the FET 12 with high impedance, the leakage of the current from the
flux 18 around the soldering land 16 is significant and causes a large noise.
[0006]
In order to prevent the above problems, it is sufficient to secure a large space to the extent that
the flux 18 does not contact other circuits even if the flux 18 spreads. However, since ordinary
microphones are designed to be small, the spacing between soldered lands is also designed to be
narrow, and it is difficult to secure a large space to the extent that flux 18 does not contact other
circuits. In order to remove the flux 18, it may be considered to be subjected to the washing step
again, but it can not be subjected to the washing step by IPA in the state where the microphone
unit is connected. Further, in the case of the electret condenser microphone, there is a problem
that the surface voltage of the electret is attenuated by the vapor when IPA is used. Even in a
condenser microphone unit that requires a bias voltage, there is a problem that when the IPA
flows into the inside of the microphone unit, the microphone unit is broken.
[0007]
The present invention aims to solve the problems inherent to the condenser microphone as
described above. Prior art for such purpose could not be found. In the prior art which is
considered to be relatively close to the present invention, the steps of printing a soldering flux
consisting of metal powder having a melting point higher than that of the flux and solder on the
foundation electrode, and the foundation electrode printed with the soldering flux There has
been proposed a method of forming a solder bump in which a step of mounting a solder ball on
the upper side and a step of melting the solder ball by heat treatment are provided, and the
printing step is performed by screen printing using a screen mask (for example, Patent Document
1).
[0008]
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As another prior art, the solder particle is placed on the electrode, and the solder particle is
pressed toward the electrode while applying ultrasonic vibration to the tool by the bonding tool
having the concave portion formed at the tip, thereby the solder particle Crushing the contact
area between the electrode and the solder particle while breaking the oxide film on the electrode
surface and the solder particle surface, bringing the electrode into contact with the new surface
of the solder particle and bonding, and then forming a hemispherical bump by reflow A
semiconductor device manufacturing method has been proposed in which solder particles are
arranged with high positional accuracy by covering a predetermined mask when arranging
solder particles on the electrodes (see, for example, Patent Document 2).
[0009]
The inventions described in Patent Document 1 and Patent Document 2 each relate to a
technique for forming solder bumps on a circuit board before mounting a circuit component,
focusing on problems unique to condenser microphones as in the present invention. It is not
intended to solve it.
[0010]
JP, 2002-224884, A JP, 11-121495, A
[0011]
According to the present invention, in soldering the lead wire extended from the condenser
microphone unit to a predetermined soldering land in order to input the output of the condenser
microphone unit to the impedance conversion unit, the flux is regulated within the range of the
soldering land It is an object of the present invention to provide a condenser microphone and a
method of connecting leads in the condenser microphone which can prevent current leakage and
suppress noise generation due to the current leakage.
[0012]
According to the present invention, a lead wire extended from a condenser microphone unit, an
impedance conversion unit mounted on a circuit board for converting the impedance of an
output of the condenser microphone unit, and the lead for inputting an output signal of the
condenser microphone unit to the impedance conversion unit It has the soldering land which
solders a wire, and it makes it the main features that the flux which spreads by soldering of the
above-mentioned lead is regulated near the above-mentioned soldering land.
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In order to regulate the flux spread by the soldering of the lead wire to the vicinity of the
soldering land, it is preferable to surround the soldering land and expose the soldering land to
bond the masking member to the circuit board.
The masking member may be a seal made of fluorocarbon resin.
[0013]
According to the condenser microphone of the present invention, the flux spreading when
soldering the lead wire of the condenser microphone unit to the soldering land is limited to the
vicinity of the soldering land, and the output signal of the condenser microphone unit is
otherwise There is an advantage in that the circuit of (1) can not leak and noise generation due to
the leak current can be prevented.
If the surrounding of the soldering land is surrounded and the soldering land is exposed and the
masking member made of fluorine resin is stuck on the circuit board, the masking member made
of fluorine resin does not need to be removed purposely, and the manufacturing process can be
simplified.
[0014]
Hereinafter, an embodiment of a condenser microphone and a method of connecting lead wires
in the condenser microphone according to the present invention will be described with reference
to FIG.
The same components as those of the conventional example shown in FIG. 2 are denoted by the
same reference numerals.
[0015]
In FIG. 1, the circuit board 10 is disposed in a condenser microphone, for example, in a
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microphone case which also serves as a grip. In FIG. 1, the upper side is the rear end side of the
microphone case, ie, the side on which the connector for connecting the microphone cable is
disposed, and the lower side is the front end side of the microphone case, ie, the microphone unit
arrangement side. The circuit board 10 has an FET 12 serving as the main body of an impedance
converter surface-mounted at the end closer to the condenser microphone unit, that is, the lower
end in FIG. The FET 12 is subjected to a reflow process along with various other circuit
components 14 and is simultaneously soldered and surface mounted. In addition, after the reflow
process, it is subjected to a cleaning process with IPA, and the flux spread on the surface by the
reflow soldering is removed. On the circuit board 10, a soldering land 16 connected to the base
of the FET 12 is formed at a position closer to the microphone unit than the FET 12. Lead wires
(not shown) drawn from the condenser microphone unit are soldered to the soldering lands 16.
At this time, as described above, since the flux contained in the solder tends to spread on the
substrate 10, the spread of the flux is regulated in the vicinity of the soldering land 16 in this
embodiment.
[0016]
In order to regulate the spread of the flux in the vicinity of the soldering land 16, in the
embodiment shown in FIG. 1, a masking member 20 surrounding the periphery of the soldering
land 16 is attached to the circuit board 10. The masking member 20 comprises an annular seal
having a circular hole in the center. Further, the masking member 20 is also circular in outer
shape, and has a donut shape as a whole. By attaching the masking member 20 to the circuit
board 20, the circular soldering lands 16 are exposed. The masking member 20 is formed of an
annular adhesive seal, and the adhesive seal is configured by applying an adhesive material on
the back surface of a seal made of fluorocarbon resin, and the adhesive surface is attached to the
circuit board 10.
[0017]
As described above, the masking member 20 is attached, and the lead wire drawn from the
condenser microphone unit is soldered to the soldering land 16 exposed from the central hole of
the masking member 20. By soldering, the flux contained in the solder tends to spread on the
substrate 10. However, when the masking member 20 is made of a fluorocarbon resin seal, the
flux is repelled by the fluorocarbon resin, and the spread of the flux is regulated within the
soldering land 16 or in the vicinity of the soldering land 16. Therefore, even if the flux absorbs
moisture in the air and is in a hygroscopic state, the range in which the insulation resistance
decreases is limited to the vicinity of the soldering land 16, and the output signal of the
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microphone unit does not leak to other circuits. Noise generation due to leakage current can be
prevented.
[0018]
The masking member 20 does not have to be a fluorine resin. When the masking member 20
does not have the property of repelling flux, the flux spreads on the masking member 20 when
soldering the lead wire drawn from the condenser microphone unit to the exposed soldering land
16. Therefore, after the lead wire is soldered, a process of removing the masking member 20 is
provided. By doing this, an area where the spread of the flux is blocked, ie, an area where there is
no flux, is formed around the soldering land 16, and the output signal of the microphone unit
does not leak to other circuits, which causes leakage. Noise generation due to current can be
prevented.
[0019]
According to the embodiment described above, even if it can not be subjected to the cleaning
process after soldering, the spreading of the flux due to soldering can be regulated around the
soldering land, so the surface due to the spreading of the flux The reduction in resistance can be
avoided, and the generation of noise due to signal leakage due to the reduction in surface
resistance can be prevented. In particular, the output signal of the condenser microphone unit
has a characteristic that the impedance is high and noise is easily generated due to signal
leakage, but by applying the structure or method according to the present invention, the
decrease in surface resistance is effectively avoided. The noise generation prevention effect can
be enhanced. In addition, by applying the structure or method according to the present invention
when the cleaning process can not be performed after soldering, it is possible to effectively avoid
the reduction in surface resistance and to enhance the noise generation preventing effect. If the
masking member is formed of a seal made of fluorocarbon resin, the step of removing the
masking member after soldering to the soldering land can be omitted, so the manufacturing step
of the condenser microphone or the connection step of the lead wire can be simplified. Benefits.
[0020]
It is the top view which showed the Example of the connection method of the lead wire in the
condenser microphone concerning this invention, and the condenser microphone. It is the top
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view which showed the example of the connection method of the lead wire in the conventional
condenser microphone and a condenser microphone.
Explanation of sign
[0021]
10 circuit board 12 FET 14 circuit element 16 soldering land 20 masking member
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