JP2000050394A - Electret condenser microphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce deposition of fine dusts onto an electret dielectric film and to simplify the assembly. SOLUTION: This microphone is provided with a capsule 11 made of a metallic material and having a front plate 12, a diaphragm 16 adhered to a diaphragm ring 15, an electret dielectric film 191 adhered and formed to an outer surface of a cup shaped rear electrode 181, a ring spacer 17, a printed circuit board 42 with an IC element 50 having an impedance conversion circuit 24 mounted thereon, and the diaphragm ring 15 is in contact with the front face plate 12 and the diaphragm 16, the ring spacer 17, the cup shaped rear electrode 181 and the printed circuit board 42 are contained in the capsule 11 in this order and a rear end of the capsule 11 is bent and caulked to a lower end of the printed board 42.

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 back electrode formed by forming a back electrode into a cup-shaped back electrode and applying an electret dielectric film on an 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 formed 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. In the capsule 11, a vibrating membrane 1 attached to a vibrating membrane ring 15 made of a metal material is provided.
6 is accommodated, and the vibrating membrane ring 15 is in electromechanical contact with the front plate 12. An electret dielectric film 19 is formed on the upper surface of the back electrode 18. 27 is back pole 1
8 is a back electrode hole penetratingly formed. The vibrating film 16 is mounted 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. Reference numeral 40 denotes a back electrode holder made of a synthetic resin. At the upper end of the back electrode holder 40, a step portion 41 is formed over the entire circumference, and the back electrode 18 is fitted and fixed. Back pole holder 40
The back room 28 is formed in the center part of. Reference numeral 50 'denotes an IC chip described later, which is attached to the back pole holder 40. An output terminal 51 and a ground terminal 52 are formed on the lower surface of the back pole holder 40, and a lead wire is led out and connected from the IC chip 50 '. A gate 53 is further led out of the IC chip 50 ′ and connected to the back pole 18.

[0003] Referring 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. In order to assemble the above electret condenser microphone, the diaphragm 1
5, the diaphragm 16 and the spacer 17 are accommodated.
An electron beam or corona discharge is applied to the FEP film deposited on the upper surface of the back electrode 8 to form an electret dielectric film 19, and the back electrode 18 is connected to the step 4 of the back electrode holder 40.
1 is integrated into the capsule 11 and the back end of the capsule 11 is bent and crimped against the lower end surface of the back electrode holder 40 to mechanically move the back electrode holder 40 into the capsule 11. To be fixed.

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

[0005]

In the conventional example of the electret condenser microphone, the problem is that the back electrode 18 and the back electrode holder 40 are formed separately and the back electrode 18 on which the electret dielectric film 19 is formed is formed. The point is that the pole 18 is fitted and fixed to a separate back pole holder 40. In this operation process, the FEP film formed on the back electrode 18 is irradiated with an electron beam or corona discharge to change the FEP film into the electret dielectric film 19, and this is changed to the back electrode holder 40.
It is necessary to perform other operations such as fitting into the step portion 41 and incorporating the same into the capsule 11. During these operations, fine dust adheres to the electret dielectric film 19 and other objects are removed. There is a great risk that the polarization potential will decrease due to contact, and there are many difficulties in work process management and quality control.

The actual shape and dimensions of this electret condenser microphone are 6 mm in diameter and 1 mm in thickness.
It is a minute thing of the order of mm, and when assembling it, it is not so easy to handle a large number of minute components of the order of mm by hand. In particular, since the vibrating membrane ring 15, the vibrating membrane 16, the spacer 17, and the back electrode 18 are only small parts having a small thickness, there is a great possibility that a trouble in manufacturing will occur in an assembling operation in the vicinity thereof, and Missing or other troubles may occur.

[0007] The present invention provides an electret condenser microphone that solves the above-mentioned problems.

[0008]

Means for Solving the Problems Claims 1 includes a capsule 11 made of a metal material and having a front plate 12, a vibrating membrane 16 attached to a vibrating membrane ring 15, and an outside of a cup-shaped back electrode 181. IC element 5 including electret dielectric film 191 formed on the surface, including ring-shaped spacer 17, and impedance conversion circuit 24
0 is attached, the vibrating membrane ring 15 is brought into contact with the front plate 12, and the vibrating membrane 16, the ring-shaped spacer 17, the cup-shaped back electrode 181, and the wiring board 42 are housed in the capsule 11 in this order. An electret condenser microphone in which the rear end of the capsule 11 was bent and crimped to the lower end surface of the wiring board 42 was formed.

Claim 2: In the electret condenser microphone according to claim 1, the cup-shaped back electrode 181 is formed by coating an FEP film on one surface of a thin metal plate, and setting the FEP film on the thin metal plate with the FEP film outside. An electret condenser microphone was formed by drawing and forming into a cup, and the FEP film was electretized.

Further, in the electret condenser microphone according to the present invention, the metal thin plate is an electret condenser microphone which is an aluminum thin plate. Further, in the electret condenser microphone according to claim 3, the thickness of the aluminum thin plate is about 0.3 mm, and the thickness of the FEP film is 12.5 μm to 25 μm.
An electret condenser microphone of about a degree was constructed.

[0011]

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 formed of a metal cylinder such as aluminum. Capsule 1
One end face of 1 is closed by its front plate 12. A center hole 13 which is a sound hole is formed at the center of the front plate 12. A vibrating film 16 attached to a vibrating film ring 15 made of a metal material is accommodated in the capsule 11, and the vibrating film 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. An electret dielectric film 191 is formed on the outer surface of the cup-shaped back electrode 181. The cup-shaped back electrode 181 on which the electret dielectric film 191 is adhered is formed by applying a FEP film having a thickness of about 12.5 μm to 25 μm on one surface of a thin metal sheet having a thickness of about 0.3 mm, particularly an aluminum thin plate. Then, the aluminum thin plate is subjected to drawing processing with the FEP film on the outside and formed into a cup shape, and the FEP film is irradiated with an electron beam or corona discharge to convert the FEP film into an electret dielectric film 191.
It is constituted by making it. A back electrode hole 27 is formed in the cup-shaped back electrode 181 on which the electret dielectric film 191 is formed so as to penetrate both. Cup-shaped back electrode 1
The inside of 81 forms a back chamber 28.

The vibrating film 16 is mounted 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. 4
2 is a wiring board. A contact piece 58 is formed on the upper surface of the wiring board 42, and the IC element 50 is attached to the contact piece 58. 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 the IC element 50 and connected. Gate 53 from IC element 50
Is led out and connected to the cup-shaped back electrode 181 via the contact piece 58.

Referring to FIG. 3, the wiring board 42
The IC element 50 attached to the device comprises an impedance conversion circuit. This impedance conversion circuit is composed of a field effect transistor 54, a resistor 55, and a resistor 56, and further connected to a high amplification factor amplifier is an IC.
Element 50. In order to assemble the above electret condenser microphone, the diaphragm 11, the diaphragm 16, and the spacer 17 are accommodated in the capsule 11. Next, the FEP film formed 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. The cup-shaped back electrode 181 is directly encapsulated as it is. 11, and further, a wiring board 4 to which an IC element 50 is attached and connected.
2 is assembled into 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 against 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 as a cup-shaped back electrode, and the electret dielectric film 191 is formed on the upper surface thereof. . As a result, the handling of the electret dielectric film 191 in assembling the microphone converts the FEP film deposited on the upper surface of the cup-shaped back electrode 181 into an electret, and immediately incorporates the cup-shaped back electrode 181 into the capsule 11 as it is. This is greatly simplified as compared with the conventional example. As a result, the chances of fine dust adhering to the electret dielectric film 191 are reduced, and the possibility that other objects come into contact with each other to lower the polarization potential and destabilize is reduced, thereby reducing work process management and quality control. Is also convenient.

In the vicinity of the vibrating membrane ring 15, the vibrating membrane 16, the spacer 17, and the electret dielectric film 191 handling only minute components, the cup-shaped back electrode of the present invention is a back electrode holder which is conventionally a separate body. By eliminating the need for the back electrode holder, it also facilitates the assembly work and contributes to the miniaturization of the electret condenser microphone.

Further, by forming the cup-shaped back electrode 181 from a thin aluminum plate, the electret condenser microphone can withstand operation in a high temperature region.

[Brief description of the drawings]

FIG. 1 illustrates an embodiment.

FIG. 2 illustrates a conventional example.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Capsule 12 Front plate 13 Center hole 15 Vibrating film ring 16 Vibrating film 17 Spacer 18 Back electrode 181 Cup-shaped back electrode 19 Electret dielectric film 191 Electret dielectric film 27 Back electrode hole 28 Back chamber 40 Back electrode holder 41 Step 42 Wiring board 50 IC element 51 Output terminal 52 Ground terminal 53 Gate 54 Field effect transistor 55 Resistance 56 Resistance 58 Contact piece

Claims (4)

[Claims] 1. A capsule made of a metal material and having a front plate, a vibrating film attached to a vibrating film ring, and an electret dielectric film formed on an outer surface of a cup-shaped back electrode. And a ring-shaped spacer,
A wiring board equipped with an IC element having an impedance conversion circuit is provided. A vibration membrane ring is brought into contact with a front plate, and a vibration membrane, a ring-shaped spacer, a cup-shaped back electrode, and a wiring board are housed in a capsule in this order, and the wiring board is An electret condenser microphone characterized in that the rear end of the capsule is bent and crimped against the lower end surface of the electret condenser microphone. 2. The electret condenser microphone according to claim 1, wherein the cup-shaped back electrode is formed by applying an FEP film to one surface of a thin metal plate, and drawing the thin metal plate with the FEP film on the outside. An electret condenser microphone characterized in that it is formed into a cup shape and the FEP film is electretized. 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 thickness of the aluminum thin plate is about 0.3 mm,
An electret condenser microphone characterized in that the film has a thickness of about 12.5 μm to 25 μm.