JP2012039489A - Capacitor microphone unit and method for producing the same - Google Patents

Abstract

In a condenser microphone unit that takes out a change in electrostatic capacitance between a diaphragm and a fixed pole as a voltage change, electrical insulation between the diaphragm and the fixed pole is ensured to generate a leakage current. To prevent the microphone sensitivity from decreasing.
A diaphragm 14 stretched on a support ring 13, a fixed pole 16 disposed opposite to the diaphragm, and an insulating seat 2 that supports the periphery of the fixed pole, and a lower surface of the support ring. And a capacitor ring unit in which a predetermined gap is formed between the diaphragm and the fixed pole by sandwiching a spacer ring 17 between the diaphragm and the upper surface of the insulating seat. An insulating film 3a having a predetermined film thickness is formed on the upper surface of the fixed pole disposed, and an annular groove 2a is formed along the periphery of the fixed pole on the upper surface of the insulating seat in the periphery of the fixed pole. An insulating layer 3b having a predetermined thickness is formed in the annular groove.
[Selection] Figure 1

Description

  The present invention relates to a condenser microphone unit that takes out a change in capacitance between a diaphragm and a fixed pole as a voltage change, and in particular, a capacitor that can prevent generation of a leakage current between the fixed pole and the diaphragm. The present invention relates to a microphone unit and a manufacturing method thereof.

  The capacitor microphone includes a capacitor microphone unit in which a diaphragm and a fixed pole are arranged to face each other via a spacer ring, and outputs an audio signal via an impedance converter such as an FET (field effect transistor).

A schematic configuration of a conventional condenser microphone unit will be described. FIG. 3 is a partially cutaway side view of a conventional condenser microphone unit, and FIG. 4 is a cross-sectional view showing the configuration of the main part (acoustoelectric transducer).
A condenser microphone unit 10 shown in FIG. 3 has a cylindrical housing 11 with both ends open. In the figure, an electrostatic acoustoelectric transducer 20 is held by an annular frame 12 disposed at the upper end. Yes.
The acoustoelectric converter 20 includes a support ring 13, a diaphragm 14 stretched on the support ring 13, and a fixed pole 16 supported by an electrically insulating insulating seat 15. As shown in FIG. 4, the diaphragm 14 and the fixed pole 16 are disposed to face each other via an electrically insulating annular spacer ring 17.

A cover body 18 provided with a plurality of holes (acoustic terminals) 18a is placed on the frame body 11. When this cover body 18 is coupled to the upper end opening of the housing 11 by, for example, screwing, a support ring is provided. 13 and the insulating seat 15 are in close contact with the spacer ring 17 and sandwiched therebetween. A circuit board (not shown) on which an FET as an impedance converter is mounted is disposed at the lower part of the housing 11, and the fixed pole 16 is electrically connected to the circuit board.
The configuration of such a condenser microphone unit is described in Patent Document 1.

JP 2010-50869 A

By the way, as described above, the condenser microphone unit 10 includes the acoustoelectric converter 20 having a very small capacitance between the diaphragm 14 and the fixed electrode 16, so that the impedance converter (FET) having an extremely high input impedance. An audio signal is output via
However, since a polarization voltage (DC voltage) is applied to both electrodes through a high impedance, a leakage current is generated when the electrical insulation between the diaphragm 14 and the fixed electrode 16 is reduced, and this is accompanied by this. There was a problem that large noise was generated.

In order to solve the above problem, it is necessary to ensure electrical insulation between the diaphragm 14 and the fixed pole 16.
However, in the insulating seat 15 and the spacer ring 17 formed of a plastic material such as polycarbonate or PET, the volume resistivity is very high, but the surface resistivity is easily affected by humidity in the air, When the resistance decreased, noise due to the leakage current was generated. Specifically, since the creeping distance around the fixed pole 16 incorporated in the insulating seat 15 (the creeping distance passing through the insulating seat 15 and the spacer ring 17) is short, a reduction in surface resistance at that portion is a problem. It was.

  The present invention has been made by paying attention to the above points, and in a condenser microphone unit that takes out a change in capacitance between the diaphragm and the fixed pole as a voltage change, between the diaphragm and the fixed pole. It is an object of the present invention to provide a condenser microphone unit and a method of manufacturing the same that can prevent the occurrence of leakage current while suppressing the decrease in microphone sensitivity.

In order to solve the above-described problems, a condenser microphone unit according to the present invention includes a diaphragm stretched on a support ring, a fixed pole disposed opposite to the diaphragm, and an insulation that supports the periphery of the fixed pole. A condenser microphone unit in which a predetermined gap is formed between the diaphragm and the fixed pole by sandwiching a spacer ring between the lower surface of the support ring and the upper surface of the insulating seat An insulating film having a predetermined thickness having electrical insulation is formed on the upper surface of the fixed pole disposed opposite to the diaphragm, and the fixed surface is formed on the upper surface of the insulating seat in the periphery of the fixed pole. An annular groove is formed along the periphery of the pole, and an insulating layer having a predetermined thickness having electrical insulation is formed in the annular groove.
Moreover, it is desirable that the insulating film and the insulating layer are formed of a fluorine-based coating agent.

With such a configuration, even when the diaphragm is in contact with the fixed pole, the insulation film is interposed, and therefore, generation of noise accompanying the movement of charges can be prevented. Moreover, by forming an insulating film with a fluorine-based coating agent, the film thickness can be made very thin, and a decrease in microphone sensitivity can be suppressed.
In addition, by providing an annular groove on the upper surface of the insulating seat, the creeping distance around the fixed pole (the creepage distance passing through the insulating seat and the spacer ring) becomes longer, and the fluorine-based coating has excellent moisture resistance in the annular groove. By providing the insulating layer made of the agent, it is possible to prevent the surface resistance from being lowered due to the humidity change in the air. That is, it is possible to suppress the generation of leakage current due to a decrease in surface resistance, and to prevent the generation of noise due to it.

In order to solve the above-described problems, a method of manufacturing a condenser microphone unit according to the present invention supports a lower surface of a support ring on which a diaphragm is stretched and a periphery of a fixed pole that is disposed to face the diaphragm. A capacitor microphone unit manufacturing method in which a spacer ring is sandwiched between the upper surface of the insulating seat and a predetermined gap is formed between the diaphragm and the fixed pole, wherein the insulating seat is formed in the step of forming the insulating seat. A step of providing an annular groove along a peripheral edge of the fixed pole on an upper surface of the insulating seat which is a peripheral portion of the fixed pole when the fixed pole is supported; and a step of arranging the fixed pole on the insulating seat Polishing and flattening the upper surfaces of the insulating seat and the fixed electrode, applying a fluorine-based coating agent to the upper surfaces of the insulating seat and the fixed electrode, and applying the applied coating Volatilizing a solvent contained in the base coating agent, forming an insulating film having a predetermined thickness on at least the upper surface of the fixed electrode, and forming an insulating layer having a predetermined thickness in the annular groove; It is characterized by including.
In the step of applying a fluorine-based coating agent to the upper surface of the insulating seat and the fixed electrode, it is preferable that the fluorine coating agent is accumulated in the annular groove.

  By performing the process including the steps, the condenser microphone unit according to the present invention can be obtained, and the effects described above can be obtained.

  According to the present invention, in a condenser microphone unit that takes out a change in electrostatic capacitance between a diaphragm and a fixed pole as a voltage change, the electrical insulation between the diaphragm and the fixed pole is ensured and leakage current is ensured. It is possible to obtain a condenser microphone unit and a method for manufacturing the same that can prevent the occurrence of noise and suppress a decrease in microphone sensitivity.

FIG. 1 is a cross-sectional view showing the overall configuration of an acoustoelectric transducer provided in a condenser microphone unit according to the present invention. FIG. 2 is a flowchart showing a flow of a method for manufacturing an acoustoelectric converter included in the condenser microphone unit according to the present invention. FIG. 3 is a partially cutaway side view of a conventional condenser microphone unit. FIG. 4 is a cross-sectional view showing a configuration of an acoustoelectric converter included in a conventional condenser microphone unit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the overall configuration of an acoustoelectric converter 1 provided in a condenser microphone unit according to the present invention.
In FIG. 1, members that are the same as or correspond to those shown in the conventional example described with reference to FIGS. 3 and 4 are denoted by the same reference numerals.

The condenser microphone unit according to the present invention has a configuration in which the acoustoelectric transducer 20 in the configuration shown in FIG. 3 is replaced with the acoustoelectric transducer 1 shown in FIG.
That is, an annular frame 12 is disposed at one end of a cylindrical housing 11 with both ends open, and the electrostatic acoustoelectric transducer 1 is held by the frame 12.
The acoustoelectric transducer 1 is fixed in the housing 11 by, for example, screwing the lid 18 shown in FIG. 3 to the upper end opening of the housing 11.

As shown in FIG. 1, the acoustoelectric converter 1 includes an annular support ring 13, a diaphragm 14 stretched with a predetermined tension on the lower surface thereof, and an insulating seat 2 made of an electrically insulating material (for example, made of polycarbonate). And a fixed pole 16 supported on the surface.
An electrically insulating spacer ring 17 (for example, made of PET) is disposed between the support ring 13 and the insulating seat 2, and a predetermined gap is formed between the diaphragm 14 and the fixed pole 16. .

  In addition, an insulating film 3a of an electrically insulating thin film (for example, 1 μm or less) is formed on the upper surface of the fixed electrode 16 and the upper surface of the insulating seat 2 on which the fixed electrode 16 is supported. The insulating film 3a is formed of a fluorine-based coating agent having excellent moisture resistance and high volume resistivity and surface resistivity (for example, Fluorobarrier-FP-1054E manufactured by ING Corp.).

  The fixed pole 16 is provided with a plurality of sound holes 16a for allowing sound waves from the acoustic terminal 18a to act on the back surface side of the diaphragm 14, but in the example shown in FIG. Since the insulating film 3a on the top surface of the pole 16 is a very thin film, it is formed in a state of closing the sound hole 16a. However, the insulating film 3 a may be formed only on the upper surface of the fixed electrode 16 excluding the sound hole 3 in that sound waves are applied to the back side of the diaphragm 14.

Further, as shown in FIG. 1, in the state where the insulating seat 2 supports the fixed pole 16, the periphery of the fixed pole 16 on the upper surface of the insulating seat 2 is concentric with the support ring 13 and the spacer ring 17, An annular groove 2 a having a predetermined width and depth is formed along the periphery of the fixed pole 16. An electrically insulating insulating layer 3b having a thickness greater than that of the insulating film 3a is formed in the annular groove 20.
The insulating layer 3b is formed of a fluorine-based coating agent similarly to the insulating film 3a, and the insulating film 3a and the insulating layer 3b are continuously formed along the surface.

When the thus configured acoustoelectric converter 1 is arranged in the housing 11 and the lid 18 is screwed to the housing 11, the support ring 13 and the insulating seat 2 are in close contact with the spacer ring 17, respectively. It becomes the structure which holds this.
That is, a predetermined gap space is formed between the diaphragm 14 and the upper surface of the fixed pole 16 by the spacer ring 17, but a thin insulating film 3 a is interposed there.

The acoustoelectric converter 1 is configured through the steps shown in FIG.
That is, when forming the insulating seat 2, the annular groove 2a is provided (step S1 in FIG. 2). For example, as shown in FIG. 1, the annular groove 2 a is formed in a stepped shape at the upper end edge on the inner peripheral side of the insulating seat 2, and the fixed pole 16 is disposed on the insulating seat 2, thereby forming a concave groove. The That is, the upper end outer peripheral surface of the fixed pole 16 is a peripheral wall on the inner diameter side of the annular groove 2a as illustrated.

Next, the fixed pole 16 is disposed on the insulating seat 2 (step S2 in FIG. 2), and a polishing process is performed so that the upper surfaces of the insulating seat 2 and the fixed pole 16 become flat surfaces (step S3 in FIG. 2).
When the upper surfaces of the insulating seat 2 and the fixed electrode 16 are made flat, a predetermined amount of a fluorine coating agent (for example, Fluorobarrier-FP-1054E manufactured by ING Corp.) is applied thereto (see FIG. 2 step S4).
In this application process, the fluorine coating agent is accumulated in the annular groove 2a.

  When the fluorine coating agent is applied to the upper surfaces of the insulating seat 2 and the fixed electrode 16, it is left for a predetermined time, and the solvent in the fluorine coating agent is volatilized (step S5 in FIG. 2). Thereby, the fluorine coating agent applied to the upper surfaces of the insulating seat 2 and the fixed electrode 16 becomes the insulating film 3a having a predetermined film thickness (1 μm or less), and the fluorine coating agent stored in the annular groove 2a is the insulating film 3a. A thicker insulating layer 3b is obtained.

  In this way, when the insulating film 3a is formed on the upper surface of the insulating seat 2 and the fixed pole 16, and the insulating film 3b is formed in the annular groove 2a, the diaphragm 14 stretched on the support ring 13 is replaced with the spacer 17. The acoustoelectric converter 1 is configured to be disposed opposite to the upper surface of the fixed pole 16 (step S6 in FIG. 2).

  As described above, according to the embodiment of the present invention, the thin insulating film 3 a is provided on the upper surface of the fixed electrode 16. An annular groove 2a is formed around the fixed pole 16, and an insulating layer 3b having a thickness larger than that of the insulating film 3a is provided there. Furthermore, the insulating film 3a and the insulating layer 3b are formed of a fluorine-based coating agent having excellent moisture resistance and high volume resistivity and surface resistivity.

With this configuration, even when the diaphragm 14 is in contact with the fixed pole 16, since the insulating film 3a is interposed, it is possible to prevent the generation of noise accompanying the movement of charges. Moreover, since the insulating film 3a is formed by the fluorine-based coating agent, the film thickness can be made very thin (for example, 1 μm or less), and the decrease in microphone sensitivity can be suppressed.
Further, the provision of the annular groove 2a in the insulating seat 2 increases the creeping distance around the fixed pole 16 (the creeping surface passing through the insulating seat 2 and the spacer ring 17), and the annular groove 2a has excellent moisture resistance. Since the insulating layer 2b made of a system coating agent is provided, it is possible to prevent a decrease in surface resistance caused by a change in humidity in the air. That is, it is possible to suppress the generation of leakage current due to a decrease in surface resistance, and to prevent the generation of noise due to it.

DESCRIPTION OF SYMBOLS 1 Acoustoelectric transducer 2 Insulating seat 2a Annular groove 3a Insulating film 3b Insulating layer 11 Housing 13 Support ring 14 Diaphragm 16 Fixed pole 17 Spacer ring 18 Lid

Claims (4)

A diaphragm stretched on a support ring; a fixed pole disposed opposite to the diaphragm; and an insulating seat that supports the periphery of the fixed pole; and a lower surface of the support ring and an upper surface of the insulating seat A capacitor microphone unit in which a predetermined gap is formed between the diaphragm and the fixed pole by sandwiching a spacer ring therebetween,
An insulating film having a predetermined thickness having electrical insulation is formed on the upper surface of the fixed pole disposed opposite to the diaphragm.
An annular groove is formed along the periphery of the fixed pole on the upper surface of the insulating seat in the periphery of the fixed pole, and an insulating layer having a predetermined thickness having electrical insulation is formed in the annular groove. Condenser microphone unit characterized by   The condenser microphone unit according to claim 1, wherein the insulating film and the insulating layer are formed of a fluorine-based coating agent. A spacer ring is sandwiched between the lower surface of the support ring on which the diaphragm is stretched and the upper surface of the insulating seat that supports the periphery of the fixed pole that is disposed to face the diaphragm, and the diaphragm and the fixed pole A method of manufacturing a condenser microphone unit in which a predetermined gap is formed,
In the step of forming the insulating seat, when the fixed pole is supported, a step of providing an annular groove along the peripheral edge of the fixed pole on the upper surface of the insulating seat serving as a peripheral portion of the fixed pole;
Disposing the fixed pole on the insulating seat;
Polishing and flattening the upper surface of the insulating seat and the fixed pole;
Applying a fluorine-based coating agent to the upper surface of the insulating seat and the fixed electrode;
Volatilizes the solvent contained in the applied fluorine-based coating agent, and forms an insulating film having a predetermined film thickness on at least the upper surface of the fixed electrode,
And a step of forming an insulating layer having a predetermined thickness in the annular groove. In the step of applying a fluorine-based coating agent to the upper surface of the insulating seat and the fixed electrode,
4. The method of manufacturing a condenser microphone unit according to claim 3, wherein the fluorine coating agent is accumulated in the annular groove.

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