JP3356668B2 - Thin-film electret condenser microphone and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electret condenser microphone and a method for manufacturing the same.

[0002]

2. Description of the Related Art Electret condenser microphones, which form a condenser section by a diaphragm, an electrode plate and an electret material, are roughly classified into a back electret type and a wheel electret type according to the positional relationship between the diaphragm and the electret material. What is called a scheme has also been developed by the applicant. Of these, the schematic structures of the back electret condenser microphone and the front electret condenser microphone are shown in FIGS.

As shown in FIG. 2, a back electret type condenser microphone includes a printed circuit board 2, a holder 3, a back electrode plate 4, an electret layer 5, a spacer 6, a vibrator, and the like in a capsule 1 from the rear side to the front side. The plate 7 and the ring 8 are arranged in order, and the IC element 9 is arranged inside the holder 3.

The electret layer 5 is located on the rear side of the diaphragm 7 via a space formed by the spacer 6. For this reason, this method is called a back electret method. And the electret layer 5
Are welded to the surface of the back electrode plate 4 as an electrode plate.
It is formed of a polymer film (usually FEP) of about 5 to 25 μm. The back electrode plate 4 is formed by stamping out a metal plate on which the polymer film is welded by pressing.

The IC element 9 is an FE for impedance conversion.
The input terminal 9a is connected to the back electrode plate 4 on the front side, and the output terminal 9b is connected to the printed circuit board 2 on the rear side. Reference numeral 1a denotes a sound hole formed on the front surface of the capsule 1, and 1 'denotes a front cloth adhered to the surface of the front surface.

On the other hand, as shown in FIG. 3, the condenser microphone of the front electret type includes a printed circuit board 2, a holder 3, a diaphragm 7, a spacer 6, and an electret layer 5 in a capsule 1 from the rear side to the front side. The IC elements 9 are arranged in order and the IC elements 9 are arranged inside the holder 3.

The electret layer 5 is made of a diaphragm 7 in this case.
This method is called a front electret method in that an electret layer 5 is disposed on the front side of the diaphragm 7 so as to cover the front surface of the capsule as an electrode plate located on the front side of the diaphragm. . As in the case of the back electret system, the electret layer 5 has a thickness of 12.5 to 25 welded to the back surface of the front surface of the capsule.
It is formed of a polymer film (usually FEP) of about μm.

The spacer 6 for forming a space between the electret layer 5 and the diaphragm 7 has a thickness of 3 mm formed by punching out a frame in any case.
A polymer film (usually PET) of about 0 μm is used.

In a foil electret condenser microphone, the diaphragm itself provided on the front side of the back electrode plate is formed of a polymer film having an electret effect, and the electret layer is not separated from the diaphragm. This is distinguished from the back electret type and the front electret type.

[0010]

However, the above-mentioned conventional electret condenser microphone has the following problems. That is, since the electret layer is formed of a polymer film of about 12.5 to 25 μm welded and pressed on the surface of the back electrode plate as an electrode plate, the quality and thickness of the polymer film between lots are reduced. There were individual differences in the performance of electret condenser microphones due to variations and burr of the polymer film generated during pressing of the back electrode plate.

In addition, the distance between the diaphragm and the back plate is
Since it contains the thickness of the spacer, which is a polymer film, it is substantially too large, causing a problem in performance.
That is, since the thickness of the spacer was 30 μm and the thickness of the electret layer was 12.5 to 25 μm, the interval was 42.5 to 55 μm.

The present invention has been made in view of the above circumstances, and does not cause individual differences in performance due to variations in the thickness of electret layers in electret condenser microphones as in the prior art. It is an object of the present invention to provide a thin-film electret condenser microphone that can be used as the electret condenser microphone and a method of manufacturing the same.

[0013]

A thin-film electret condenser microphone according to the present invention is formed on a diaphragm, a back plate as an electrode plate disposed on the rear side, and a surface of the back plate on the diaphragm side. in the thin-film electret condenser microphone of the back electret type that forms a capacitor portion between the electret layer, said Jer
The cullet layer is a polymer FEP on the surface of the back electrode plate on the diaphragm side.
After applying an organic solvent in which fine particles of
Heat to remove organic solvent, then immerse back plate in solution
Soak or inject cooling gas to cool and separate
It is extreme.

The thin-film electret condensate according to the present invention
The method of manufacturing the microphone is as follows.
The back electrode plate as the placed electrode plate and the diaphragm side of the back electrode plate
Capacitor part with electret layer formed on the surface of
Back electret electret forming
A condenser microphone on the surface of the back plate
Thin film forming process for forming a thin film directly with fine particles of polymer FEP
And a polarization step of performing a polarization treatment on the thin film.
In the polarization step, the back electrode plate is subjected to a solution after the thin film formation step.
For cooling on the back plate after the thin film formation process
This is done by injecting gas.

In the thin film forming step, the polymer FEP may be used.
Of applying organic solvent with fine particles dispersed on back electrode plate
And heat the back electrode plate coated with the organic solvent to dissolve the organic solvent.
The process of removing only the solvent and the back electrode from which only the organic solvent has been removed
Heat the plate at a higher temperature to form a thin film of polymer FEP
And a step of performing

An organic material in which the fine particles of the polymer FEP are dispersed
In the step of applying a solvent on the back electrode plate,
Spin-on coating of organic solvent, or the organic solvent of back electrode plate
Performed by dip into.

[0017]

FIG. 1 is a schematic explanatory view showing each step of a method for manufacturing a thin-film electret condenser microphone according to an embodiment of the present invention.

The structure of the thin-film electret condenser microphone according to the embodiment of the present invention is the same as that of the above-described conventional back electret electret condenser microphone except for the thickness of the electret film 5, and FIG. Divert.

The thin-film electret condenser microphone according to the embodiment of the present invention has a diaphragm 7, a back electrode 4 as an electrode plate disposed on the rear side, and a surface of the back electrode 4 on the diaphragm 7 side. A back electret type thin film electret condenser microphone that forms a capacitor portion with the electret layer 5 formed on the substrate, wherein the electret layer 5 is a thin film formed of fine particles of a polymer FEP and is subjected to a polarization treatment. Is what it is.

The electret layer 5 has a thickness of 1.0 formed by directly depositing FEP or the like on the surface of the back electrode plate 4. O ~
2. It is a thin film of about O μm. On the surface of the peripheral portion of the electret layer 5, a spacer 6 for forming a space between the electret layer 5 and a diaphragm disposed on the front side thereof is formed to a thickness of about 30 μm by screen printing.

The back electrode plate 4 and the electret layer 5
By using an integrated member of the spacer and the spacer 6, FIG.
The thin-film electret condenser microphone of the back electret type shown in FIG.

The electret layer 5 is formed by the following steps. First, the diameter of the polymer FEP is 0.1 μm on the surface of the back electrode plate 4 made of a brass material having excellent heat conduction.
The method comprises a thin film forming step of directly forming a thin film with fine particles of about m to 0.25 μm, and a polarizing step of performing a polarizing process on the thin film.

More specifically, the thin film forming step includes a step of applying an organic solvent 100 in which fine particles of polymer FEP are dispersed on the back electrode plate 4, and a step of applying the organic solvent 100 in which fine particles of polymer FEP are dispersed. Heating the back electrode plate 4 to remove only the organic solvent 110, and heating the back electrode plate 4 from which only the organic solvent 110 has been removed at a higher temperature to polymer FEP.
And forming a thin film.

As the fine particles of the polymer FEP, for example, ethylene tetrafluoride-propylene hexafluoride polymer fine particles are used. Examples of the organic solvent in which the fine particles of the polymer FEP are dispersed include ND-, a Neoflon (trademark) FEP dispersion manufactured by Daikin Industries, Ltd.
1 is suitable. This ND-1 has a viscosity of 10 to 30.
c. p. , 25 ° C., which is suitable for application to the back electrode plate 4.

The method of applying the organic solvent 100 in which the fine particles of the polymer FEP are dispersed to the back electrode plate 4 is as shown in FIG.
As shown in (A), there is a spin-on coating method. In this case, the back electrode plate 4 is
This is carried out by dropping the organic solvent 100 onto the back electrode plate 4 while rotating at rpm. About 10 to 20 seconds is suitable for one back electrode plate 4. By doing so, as shown in FIG.
The organic solvent 100 is applied to a thickness of μm.

Next, as shown in FIG. 1 (C), the back electrode plate 4 coated with the organic solvent 100 is heated. Of about 100 to 120 ° C. and heating for about 5 minutes. This heating removes only the organic solvent 110, and deposits 130 of fine particles of the polymer FEP form the back electrode plate 4.
Formed on

Further, in order to reduce the thickness of the polymer FEP, that is, a deposit 130 of the polymer FEP fine particles.
In order to reduce the film thickness, the ambient temperature higher than the preliminary firing,
For example, main firing is performed at 380 to 450 °. This main firing is performed for about 10 minutes. By this baking, a thin film 120 of the polymer FEP is formed.

After the main firing, a polarization step is performed. In the polarization step, the back electrode plate 4 is cooled after the thin film formation step. For example, the back electrode plate 4 is immersed in water as a solution 200 and rapidly cooled. With this quenching,
The molecular orientation of the polymer FEP thin film 120 changes, and the thin film 120 functions as the electret layer 5.

The electret layer 5 thus obtained is formed to a thickness of 1.0 to 2.0 μm, and has a surface resistance of 2.0 μm and 1 × 10 ¹³ Ω. Was. Here, if the FEP film is welded to the surface of the back electrode plate 4 as in the related art, the thickness is 1 × 10 ¹³ Ω and 2 × 10 ¹³ Ω. In other words, when manufactured by the manufacturing method according to the present embodiment, an extremely thin electret layer 5 can be formed while having the same resistance value.

In the above-described embodiment, in the thin film forming step, the organic solvent 10 in which the polymer FEP is dispersed is used.
0 was applied by the spin-on coating method, but may be applied by dipping the back electrode plate 4 in the organic solvent 100. That is, the back electrode plate 4 is applied by dipping in the organic solvent 100. In this case, the workability is superior to the spin-on coating method.

In the above-described embodiment, the back electrode 4 is rapidly cooled in the polarization step by immersing the back electrode 4 in water as a solution 200. However, methyl alcohol is used instead of water. You may. When methyl alcohol is used, it is superior in orientation in comparison with the case where water is used.

Further, the rapid cooling in the polarization step is performed as shown in FIG.
(F) As shown in FIG.
For example, it may be performed by injecting cold air 300. It is air-cooled, so to speak. In this case, workability is superior to the case where the solution 200 is used.

[0033]

The thin-film electret condenser microphone according to the present invention comprises a diaphragm, a back plate as an electrode plate disposed on the rear side, and an electret layer formed on the surface of the back plate on the diaphragm side. In the back electret type thin film electret condenser microphone that forms a capacitor portion with the above, the electret layer is
Fine particles of polymer FEP are dispersed on the surface of the back electrode plate on the diaphragm side
After applying the organic solvent, the back electrode plate is heated to
Remove the medium and then immerse the back plate in the solution, or
Polarized by cooling by injecting a cooling gas
You.

Therefore, there is no variation in the quality and thickness of the electret layer as in the conventional thin film electret condenser microphone in which the FEP film is welded to the back electrode plate, so that the quality can be made uniform. In addition, since it is not necessary to press work after welding the polymer FEP film to the back electrode plate, there is no problem that a burr of the film which causes deterioration of the performance occurs as in the related art. In addition, polarization work
If the back electrode plate is cooled after the thin film forming process,
The poles are easily formed, but the cooling of the back plate is
Immerse the back electrode plate in the solution, or back electrode after the thin film forming process
Injecting the cooling gas into the plate is simple equipment.
The electret layer can be polarized.

The thin-film electret condensate according to the present invention
The method of manufacturing the microphone is as follows.
The back electrode plate as the placed electrode plate and the diaphragm side of the back electrode plate
Capacitor part with electret layer formed on the surface of
Back electret electret forming
A condenser microphone on the surface of the back plate
Thin film forming process for forming a thin film directly with fine particles of polymer FEP
And a polarization step of performing a polarization treatment on the thin film.
In the polarization step, the back electrode plate is subjected to a solution after the thin film formation step.
For cooling on the back plate after the thin film formation process
This is done by injecting gas.

After the polarization step, the back electrode plate is cooled after the thin film forming step.
Otherwise, polarization occurs easily, but cooling of the back plate
Dipping the back electrode plate after the thin film formation process
Injecting a cooling gas to the back electrode plate after the film formation process
Then, the electret layer can be polarized with simple equipment.
You.

In the thin film forming step, the polymer FEP is used.
Of applying organic solvent with fine particles dispersed on back electrode plate
And heat the back electrode plate coated with the organic solvent to dissolve the organic solvent.
The process of removing only the solvent and the back electrode from which only the organic solvent has been removed
Heat the plate at a higher temperature to form a thin film of polymer FEP
A uniform electret layer.
Can be easily formed.

Further, the fine particles of the polymer FEP are dispersed.
In the process of applying the organic solvent to the back plate,
The spin-on coating of the organic solvent, or the back electrode plate
If performed by dipping in organic solvent, uniform
The lectret layer can be easily formed.

[0039]

[0040]

[0041]

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing each step of a method for manufacturing a thin-film electret condenser microphone according to an embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional view of a conventional electret condenser microphone (back electret system).

FIG. 3 is a schematic longitudinal sectional view of a conventional electret condenser microphone (front electret system).

[Explanation of symbols]

 Reference Signs List 4 back electrode plate 5 electret layer 100 organic solvent in which fine particles of polymer FEP are dispersed 110 organic solvent 120 thin film

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04R 19/01 H04R 31/00

Claims (4)

(57) [Claims] 1. A back electret system in which a capacitor portion is formed by a diaphragm, a back plate as an electrode plate disposed on the rear surface side, and an electret layer formed on the surface of the back plate on the diaphragm side. In the thin film electret condenser microphone of the above, the electret layer is a back electrode plate
Fine particles of polymer FEP were dispersed on the surface on the diaphragm side
After applying the organic solvent, the back electrode plate is heated to remove the organic solvent.
And then immerse the back plate in the solution or
It is cooled and polarized by injecting gas.
Thin film electret condenser microphone that. 2. A diaphragm and an electrode disposed on a rear surface side thereof.
The back electrode plate as a plate and the surface formed on the diaphragm side of the back electrode plate
To form a capacitor with the electret layer
Electret condenser my of electret type
And a polymer FEP on the surface of the back electrode plate.
A thin film forming step of directly forming a thin film with fine particles;
And a polarization step of performing a polarization process on the substrate.
In the process, the back electrode plate is immersed in the solution after the thin film formation process
Or, inject cooling gas to back plate after thin film formation process
Film electret core characterized by performing
Method for manufacturing a condenser microphone. 3. The method according to claim 1, wherein the step of forming a thin film comprises the step of
A step of applying an organic solvent having dispersed particles on a back electrode plate,
The back electrode plate coated with the organic solvent is heated to remove the organic solvent.
Process and the back plate from which only the organic solvent has been removed.
Heat at higher temperature to form polymer FEP thin film
3. The method of manufacturing a thin-film electret condenser microphone according to claim 2, comprising the steps of : 4. Fine particles of the polymer FEP according to claim 3.
In the process of applying an organic solvent in which
Spin-on coating of the organic solvent on the electrode plate, or back electrode plate
Is carried out by dipping in the organic solvent.
Of manufacturing a thin film electret condenser microphone.