JP3375284B2 - Electret condenser microphone - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electret condenser microphone, and more particularly, to a separate body using a constitution in which a back electrode is formed into a cup-shaped back electrode and an electret dielectric film is formed on the upper surface thereof. The present invention relates to an electret condenser microphone that does not require a back pole holder.

[0002]

2. Description of the Related Art A conventional example will be described with reference to the drawings. An embodiment of the present invention will be described with reference to FIG. In FIG. 2, the capsule 11 is made of a metal cylinder such as aluminum. One end surface of the capsule 11 is closed by the front plate 12. A center hole 13 which is a sound hole is formed at the center of the front plate 12. Inside the capsule 11, a vibrating membrane 1 attached to a vibrating membrane ring 15 made of a metal material.
6, the vibrating membrane ring 15 is in electromechanical contact with the front plate 12. An electret dielectric film 19 is deposited on the upper surface of the back electrode 18. 27 is the back pole 1
8 is a back electrode hole formed so as to penetrate therethrough. The vibration film 16 is attached to face the electret dielectric film 19 on the upper surface of the back electrode 18 via a ring-shaped spacer 17 made of an insulating material. 40 is a back pole holder made of synthetic resin. A step portion 41 is formed on the upper end portion of the back electrode holder 40 over the entire circumference, and the back electrode 18 is fitted and fixed thereto. Back pole holder 40
A back chamber 28 is formed at the center of the. Reference numeral 50 ′ is an IC chip which will be described later and is attached to the back electrode holder 40. An output terminal 51 and a ground terminal 52 are formed on the lower surface of the back electrode holder 40, and lead wires are led out from and connected to the IC chip 50 '. A gate 53 is further led out from the IC chip 50 ′ and is connected to the back electrode 18.

The back pole holder 4 will be described with reference to FIG.
The IC chip 50 'attached to 0 comprises an impedance conversion circuit. This impedance conversion circuit includes a field effect transistor 54, a resistor 55, and a resistor 56. To assemble the above electret condenser microphone, the vibrating ring 1
5, the vibrating membrane 16 and the spacer 17 are accommodated, and further the back electrode 1
The FEP film deposited on the upper surface of 8 is irradiated with an electron beam or corona discharge to form the electret dielectric film 19, and the back electrode 18 is formed by the step portion 4 of the back electrode holder 40.
1 into which the back pole holder 40 is mechanically integrated in the capsule 11 by incorporating the integrated one into the capsule 11 and bending and crimping the rear end of the capsule 11 to the lower end surface of the back pole holder 40. It is housed and fixed in.

Here, to explain the operation of the electret condenser microphone, the back electrode 18 made of a metallic material and having an electret dielectric film 19 formed on the upper surface thereof.
Constitutes one electrode, and the vibrating membrane 16 made of a metal material constitutes the other electrode. The back electrode 18, which is one of the electrodes, is connected via a gate terminal 53 to the gate of a field effect transistor 54 that constitutes an impedance conversion circuit. The vibrating membrane 16, which is the other electrode, is electrically connected to the ground terminal 52 via the vibrating membrane ring 15, which is made of a metal material, the capsule 11 and a conductor (not shown). When acoustic vibration enters into the microphone through the center hole 13 which is a sound hole, the vibrating membrane 16 vibrates due to this, and the electric capacitance between the vibrating membrane 16 and the back electrode 18 corresponding to this vibration. It changes and outputs this change as an electric signal.

[0005]

In the conventional example of the electret condenser microphone, the problem is that the back pole 18 and the back pole holder 40 are formed separately and the electret dielectric film 19 is adhered and formed. This is the point where the pole 18 is fitted and fixed to the back pole holder 40 which is a separate body. In this working process, the FEP film formed on the back electrode 18 is irradiated with an electron beam or corona discharge to change it into an electret dielectric film 19, and this is changed to a back electrode holder 40.
It is necessary to fit it into the stepped portion 41 of the and to incorporate it into the capsule 11 and other work. While performing these operations, fine dust is attached to the electret dielectric film 19 and other objects are There is a high possibility that the polarization potential will decrease due to contact, and there are many difficulties in work process control and quality control.

The actual shape and dimensions of this electret condenser microphone are 6 mm in diameter and 1 in thickness.
Since it is a minute component of the order of mm, it is not so easy to handle a large number of minute components of the order of mm by hand when assembling this. Particularly, since the vibrating membrane ring 15, the vibrating membrane 16, the spacer 17, and the back electrode 18 are only minute parts having a small thickness, there is a great possibility that a manufacturing trouble will occur in the assembly work in the vicinity, and If you forget to put it in, other troubles may occur.

The present invention provides an electret condenser microphone which solves the above problems.

[0008]

According to a first aspect of the present invention, there is provided a capsule 11 made of a metallic material and having a front plate 12, a vibrating membrane 16 attached to a vibrating membrane ring 15, and a cup-shaped back electrode 181. An IC element 5 having an electret dielectric film 191 deposited on the surface, having a ring-shaped spacer 17, and having an impedance conversion circuit 24.
0 is attached to the wiring board 42, and the vibrating membrane ring 15 is brought into contact with the front plate 12 to house the vibrating membrane 16, the ring-shaped spacer 17, the cup-shaped back electrode 181, and the wiring board 42 in this order in the capsule 11. An electret condenser microphone in which the rear end portion of the capsule 11 is bent and crimped to the lower end surface of the wiring board 42 is configured.

According to a second aspect of the present invention, in the electret condenser microphone according to the first aspect, the cup-shaped back electrode 181 is formed by depositing an FEP film on one side of a thin metal plate, and the FEP film is placed outside the thin metal plate. An electret condenser microphone, which is a FEP film electretized, was formed by performing a drawing process into a cup shape.

According to a third aspect of the present invention, in the electret condenser microphone according to the second aspect, the metal thin plate is an aluminum thin plate. Furthermore, in the electret condenser microphone according to claim 4, the aluminum thin plate has a thickness of about 0.3 mm, and the FEP film has a thickness of 12.5 μm to 25 μm.
An electret condenser microphone was constructed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIG. In FIG. 1, reference numerals common to those of the conventional example indicate common members. The capsule 11 is made of a metal cylinder such as aluminum. Capsule 1
One end face of 1 is closed by the front plate 12. A center hole 13 which is a sound hole is formed at the center of the front plate 12. A vibrating membrane 16 attached to a vibrating membrane ring 15 made of a metal material is housed in the capsule 11, and the vibrating membrane ring 15 is in electromechanical contact with the front plate 12.

Reference numeral 181 denotes a cup-shaped back electrode according to the present invention. The cup-shaped back electrode 181 has an electret dielectric film 191 deposited on the outer surface thereof. The cup-shaped back electrode 181 having the electret dielectric film 191 deposited thereon has a metal thin plate having a thickness of about 0.3 mm, particularly an FEP film having a thickness of about 12.5 μm to 25 μm formed on one side of an aluminum thin plate. Then, the FEP film is squeezed to the aluminum thin plate outside to form a cup shape, and the FEP film is irradiated with an electron beam or corona discharge to change the FEP film to the electret dielectric film 191.
It is configured by. A back electrode hole 27 is formed through the cup-shaped back electrode 181 on which the electret dielectric film 191 is formed. Cup-shaped back pole 1
The inside of 81 forms the back chamber 28.

The vibrating film 16 is attached to face the electret dielectric film 191 on the upper surface of the cup-shaped back electrode 181 via a ring-shaped spacer 17 made of an insulating material. Four
2 is a wiring board. The contact piece 58 is formed on the upper surface of the wiring board 42, and the IC element 50 is attached thereto. An output terminal 51 and a ground terminal 52 are formed on the lower surface of the wiring board 42, and lead wires are led out from and connected to the IC element 50. Gate 53 from IC element 50
Is led out and connected to the cup-shaped back electrode 181 via the contact piece 58.

The wiring board 42 will be described with reference to FIG.
The IC element 50 attached to is composed of an impedance conversion circuit. This impedance conversion circuit is composed of a field effect transistor 54, a resistance 55, and a resistance 56, and a high amplification factor amplifier is further connected to this impedance conversion circuit.
The element 50. To assemble the above electret condenser microphone, the vibrating membrane ring 15, the vibrating membrane 16 and the spacer 17 are housed in the capsule 11. Next, the FEP film deposited on the upper surface of the cup-shaped back electrode 181 is irradiated with an electron beam or corona discharge to form an electret dielectric film 191, and the cup-shaped back electrode 181 is immediately encapsulated as it is. Wiring board 4 built in 11 and further having IC element 50 attached and connected
2 is assembled in the capsule 11 with the contact piece 58 in contact with the cup-shaped back electrode 181, and the rear end of the capsule 11 is bent and crimped to the lower surface of the wiring board 42. Thereby, all the components are mechanically housed and fixed in the capsule 11.

[0015]

As described above, according to the present invention, the back electrode is formed into a cup-shaped back electrode and the electret dielectric film 191 is formed on the upper surface of the cup electrode. . Accordingly, when the electret dielectric film 191 is handled in assembling the microphone, the FEP film formed on the upper surface of the cup-shaped back electrode 181 is electretized, and the cup-shaped back electrode 181 is immediately incorporated into the capsule 11 as it is. This is a big simplification as compared with the case of the conventional example. As a result, the chance that fine dust adheres to the electret dielectric film 191 is reduced, and the possibility of destabilization due to a decrease in the polarization potential caused by contact with other objects is reduced, and in terms of work process control and quality control. Is also convenient.

In the vicinity of the vibrating ring 15, the vibrating membrane 16, the spacer 17, and the electret dielectric film 191, which handle only minute parts, the cup-shaped back pole of the present invention is a separate back pole holder. By eliminating the back pole holder, the assembly work is facilitated and the electret condenser microphone is miniaturized.

Further, the cup-shaped back electrode 181 is made of a thin plate of aluminum so that the electret condenser microphone can withstand operation in a high temperature region.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example.

FIG. 2 is a diagram illustrating a conventional example.

FIG. 3 is a diagram illustrating an electric circuit of an electret condenser microphone.

[Explanation of symbols]

11 capsules 12 Front plate 13 Center hole 15 Vibrating membrane ring 16 vibrating membrane 17 Spacer 18 back pole 181 cup-shaped back pole 19 Electret dielectric film 191 electret dielectric film 27 back pole hole 28 back room 40 back pole holder 41 steps 42 wiring board 50 IC element 51 output terminal 52 Ground terminal 53 gates 54 Field effect transistor 55 Resistance 56 resistance 58 Contact piece

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04R 19/04

Claims (4)

(57) [Claims] 1. A capsule comprising a front plate made of a metal material, comprising a vibrating membrane attached to a vibrating membrane ring, and comprising an electret dielectric film deposited on the outer surface of the cup-shaped back electrode. Equipped with a ring spacer,
The wiring board is provided with an IC element having an impedance conversion circuit, and the diaphragm is brought into contact with the front plate to house the diaphragm, the ring spacer, the cup-shaped back electrode, and the wiring board in this order in a capsule. An electret condenser microphone characterized in that the rear end of the capsule is bent and crimped to the lower end surface of the. 2. The electret condenser microphone according to claim 1, wherein the cup-shaped back electrode is formed by depositing an FEP film on one surface of a thin metal plate, and subjecting the thin metal plate to the FEP film on the outside for drawing. An electret condenser microphone, which is formed in a cup shape and is an electret FEP film. 3. The electret condenser microphone according to claim 2, wherein the metal thin plate is an aluminum thin plate. 4. The electret condenser microphone according to claim 3, wherein the thin aluminum plate has a thickness of about 0.3 mm, and the FEP
The electret condenser microphone, wherein the film thickness is about 12.5 μm to 25 μm.