JPH053599A - Condenser microphone and its production method - Google Patents

Abstract

PURPOSE:To offer the condenser microphone preventing the tension drop of metal diaphragm and equipped with high parallel with the leading surface of the back pole. CONSTITUTION:Here is the process for producing the condenser microphone. (1) A toroidal main body 1 and a cylindrical back pole 3 are arranged concentrically. A toroidal insulator 2 is formed by a thermoplastic resin or thermosetting resin to be concentrically integrated through the back pole of the cylinder and the insulator. (2) The plane process is performed on the leading surface of the toroidal main body and the back pole to be the same plane precisely to form a reference surface. (3) A toroidal spacer 5 makes the prescribed width. (4) The toroidal spacer is put on the leading surface of the toroidal main body, further the metal diaphragm 4 is put on the upper surface of the toroidal spacer while adding the tension in the direction of the radiation. (5) The metal diaphragm 4, the toroidal spacer and the toroidal main body are welded and adhered integrally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a condenser microphone and a method of manufacturing the same, and more particularly to a vibrating membrane mounting structure and method for a condenser microphone.

[0002]

2. Description of the Related Art In a conventional condenser microphone having a metal diaphragm, as shown in FIG. 2, an annular fixing ring 21 holding the peripheral edge of the metal diaphragm 4 is screwed onto the outer peripheral surface of a push-up ring 22. In the hollow portion of the push-up ring 22, a back pole mounting plate 23 made of an insulating material, to which the base end of the back pole 3 is fixed, is formed on the inner peripheral surface of the push-up ring 22. The stepped portion 24 is positioned in the axial direction through the annular spacer 5 and fitted and fixed.

The tip surface of the back electrode 3 is drawn inward from the plane including the tip edge of the push-up ring 22, and the gap between both surfaces is a minute gap of about 20 to 25 μm. Appropriate tension is applied to the metal diaphragm 4 with the tip edge of the push-up ring 22 as a fulcrum by the relative displacement in the axial direction between the annular fixed ring 21 and the push-up ring 22 due to the relative rotation therebetween.

In the above-mentioned assembly of the condenser microphone, the push-up ring 22 and the back pole attaching plate 23 with the back pole 3 are temporarily assembled without the spacer 7, and the tip edge of the push-up ring 22 and the back pole 3 are assembled. After the flattening process is performed on the same plane as the tip end surface, the push-up ring 22 and the back electrode mounting plate 23 with the back electrode 3 are once disassembled, and then the spacer 7 having the thickness of the minute gap is pushed up. Step 24 of ring 22 and back pole mounting plate 23
The spacer 7 is inserted and reassembled between the two, and the back surface of the metal diaphragm and the front end surface of the back electrode are parallel to each other while maintaining the minute gap.

Further, as a measure against the pinhole of the metal diaphragm 4, the surface of the metal diaphragm 4 is coated with a quartz thin film by sputtering, and the back air chamber communicates with the outside through a vent hole 25.

[0006]

The condenser microphone provided with the metal diaphragm according to the above conventional technique has the following problems. (1) Since appropriate tension is applied to the metal diaphragm 4 with the tip edge of the push-up ring 22 as a fulcrum, stress concentration occurs in the metal diaphragm 4 at a portion in contact with the tip edge of the push-up ring 22. Causes the tension loss of the metal diaphragm 4 due to creep. (2) Since the annular fixing ring 21 screwed onto the outer peripheral surface of the push-up ring 22 holds and pulls the peripheral edge of the metal diaphragm 4, the metal diaphragm 4 is likely to be wrinkled. (3) To form a minute gap between the tip surface of the back pole 3 and the plane including the tip edge of the push-up ring 22, the tip edge of the push-up ring 22 and the tip surface of the back pole 3 are flush with each other. After the projecting process is performed, the push-up ring 22 and the back electrode mounting plate 23 with the back electrode 3 are once disassembled, and then the spacer 7 is inserted and reassembled. Highly precise parallelism with the plane including the leading edge of the push-up ring 22 is not guaranteed. (4) The size of the minute gap between the tip surface of the back electrode 3 and the plane including the tip edge of the push-up ring 22 is determined by the spacer 7 with reference to the fixed step portion 24 of the push-up ring 22. .
Therefore, it is extremely difficult to make the thermal expansion of the push-up ring 22 between the fixed step portion 24 and the leading edge exactly equal to the thermal expansion of the back electrode 3, so that the push-up ring between the fixed step portion 24 and the leading edge. Due to the thermal expansion of 22, the minute gap between the tip surface of the back electrode 3 and the plane including the tip edge of the push-up ring 22 changes, and the characteristics of the microphone change. (5) The coating of the quartz thin film, which is a measure against the pinhole of the metal diaphragm, has poor water repellency and cannot prevent dew condensation on the metal diaphragm due to a rapid temperature change, and as a result, dew condensation occurs on the back surface of the diaphragm. Appears as a large noise in the output, and since the specific gravity is large, the vibration function of the metal diaphragm is deteriorated. The present invention solves the above-mentioned drawbacks of the prior art.

[0007]

A condenser microphone according to the present invention is mounted on an annular main body, an insulator inside the annular main body, and an end surface thereof is flush with the distal end surface of the annular main body. It is composed of a metal diaphragm whose peripheral portion is integrally welded to the annular main body together with an annular spacer having a predetermined thickness interposed between the annular main body and the tip surface of the annular main body under tension. In some cases, the metal diaphragm is coated with a thin film of water repellent polymeric material.

The above condenser microphone is manufactured in the following steps. (1) The annular body and the back electrode are integrated with each other through an insulator.
A preferable integration method is to arrange a back electrode in the annular body and integrally mold an annular insulator between the inner peripheral surface of the annular body and the outer peripheral surface of the back electrode with a thermoplastic resin or a thermosetting resin. Then, the annular body and the back electrode are integrated with each other through the insulator. (2) The reference surface is formed by performing flattening processing so that the tip surface of the annular main body and the tip surface of the back electrode are precisely flush with each other. (3) Finish the annular spacer to a predetermined thickness. (4) The annular spacer is placed on the front end surface of the annular body, and is further placed on the upper surface of the annular spacer while tension is applied to the metal diaphragm in the radial direction. (5) Weld the metal diaphragm, the annular spacer, and the annular body so that they are integrated.

[0009]

In the above condenser microphone, since tension is applied to the metal diaphragm, stress concentration does not occur even at the bonding portion with the annular spacer, so that the tension loss of the metal diaphragm due to creep is small. Moreover, since there is no reassembly process to form a minute gap between the tip surface of the back electrode and the metal diaphragm, a high degree of parallelism is guaranteed between the tip surface of the back electrode and the metal diaphragm, which causes distortion in the sound. In addition, since the metal diaphragm is mounted via the annular spacer with the front end surface of the annular body as a reference surface, there is almost no problem of difference in thermal expansion between the back electrode and the annular body.

Further, the thin film of the water-repellent polymer material coated on the front surface and / or the back surface of the metal diaphragm by chemical vapor deposition fills the pinholes on the surface of the metal diaphragm and causes a rapid temperature change. Even in the case, the occurrence of dew condensation on the surface of the metal diaphragm is prevented. Moreover, since the polymer material has a low specific gravity, it has little influence on the vibration function of the metal diaphragm.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A condenser microphone according to an embodiment of the present invention will be described with reference to the drawings. Note that the vertical relationship in the following description is the vertical relationship in FIG. As shown in FIG. 1, the upper annular body 1 of the condenser microphone
The annular insulator 2 and the cylindrical back electrode 3 are concentrically integrated with each other. The inner peripheral surface of the upper annular body 1 is in contact with the outer peripheral surface of the annular insulator 2, and the inner peripheral surface of the annular insulator 2 is in contact with the outer peripheral surface of the back electrode 3. In the illustrated example, the small diameter portion of the cylindrical back electrode 3 having the step portion 31 formed on the lower surface is in contact with the inner peripheral surface of the annular insulator 2, and the step portion 31 is in contact with the upper surface of the annular insulator 2. The outer peripheral surface of the annular insulator 2 lower than the upper annular body 1 is in contact with the lower inner peripheral surface of the upper annular body 1.

The tip surface of the upper annular body 1 and the tip surface of the back electrode 3 are on the same plane, and the tip surface of the upper annular body 1 and the peripheral portion of the metal diaphragm 4 in a state where an appropriate tension is applied. An annular spacer 5 having a predetermined thickness (20 to 25 μm) is interposed between the upper annular body 1, the annular spacer 5 and the peripheral portion of the metal diaphragm 4 to be integrally welded.

Thus, the tip surface of the back electrode 3 and the metal diaphragm 4 are parallel to each other, and a minute gap corresponding to the thickness of the annular spacer 5 is provided between the tip surface of the back electrode 3 and the back surface of the metal diaphragm 4. Is held.

Further, a terminal mounting plate 6 made of an insulating material (eg, glass, ceramics, etc.) is fitted to the intermediate inner peripheral surface of the lower annular main body 7 with a minute gap, and the back electrode 3 and the annular insulator 2 are attached.
A back air chamber is formed between the stepped portion 11 and the threaded portion 12 adjacent to the stepped portion 11 on the intermediate inner peripheral surface of the lower annular main body 7.
The terminal mounting plate 6 is fixed by being sandwiched by a fixing screw ring 10 screwed into the step portion 11 and the screw portion 12 with an appropriate minute gap. The small gap on the outer peripheral surface of the terminal mounting plate 6 is
It may be formed by the threaded surface of the thread portion 12.

The back air chamber includes a minute gap between the outer peripheral surface of the terminal mounting plate 6 and the intermediate inner peripheral surface (screw surface) of the annular body 1, the upper and lower peripheral surfaces of the terminal mounting plate 6 and the stepped portion 11 of the annular body 1.・ Communicating with the outside through a minute gap with the fixing screw ring 10, air squeezes in the minute gap according to the pressure difference between the inside and outside of the back air chamber due to changes in atmospheric pressure, etc. The pressure difference between the inside and outside of the back air disappears. That is, the condenser microphone is given a low cutoff frequency characteristic.

The back pole 3 is penetrated by ventilation holes 32, 32 with a small diameter in the axial direction for adjusting the damping, and the gap space between the metal diaphragm 4 and the back pole 3 is the back pole 3 and the terminal. It communicates with the back air chamber between the mounting plates 6. Since the ventilation hole 32 can be provided in an appropriate number at an appropriate position, an appropriate damping adjustment can be easily performed. The terminal 8 attached to the terminal attaching plate 6 and the lower end surface of the back electrode 3 are connected by a conductor 9.
The terminal 8 is connected to an external amplifier by a conductor.

In manufacturing the microphone, the upper annular body 1 and the lower annular body 7 are welded or bonded to each other at the time of assembly to be integrated. If necessary, the surface of the metal diaphragm 4 and the upper end surface of the back electrode 3 are coated with a thin film of a water-repellent polymer material (for example, parylene (trade name)) by chemical vapor deposition. This thin film fills the pinholes on the surface of the metal diaphragm 4, and prevents the occurrence of dew condensation on the surface of the metal diaphragm 4 even in the case of a sudden temperature change.

In the above condenser microphone,
By forming an electret film on the upper end surface of the back electrode 3, an electret-type condenser microphone is constructed.
If an electret film is used instead of the metal diaphragm 4, a front electret type condenser microphone is constructed.

A method of manufacturing the above condenser microphone will be described. The lower inner peripheral surface of the upper annular body 1 is in contact with the outer peripheral surface of the annular insulator 2 which is lower than the upper annular body 1, and the inner peripheral surface of the annular insulator 2 is in contact with the outer peripheral surface of the cylindrical back electrode 3 to form the three members. It is integrated with an adhesive or the like.

In the illustrated structure, a step portion 31 is formed on the lower surface of the cylindrical back electrode 3, and a small diameter portion is fitted into the annular insulator 2, and the step portion 31 abuts on the upper surface of the annular insulator 2. Let it adhere. In particular, a method of arranging the upper annular body 1 and the back electrode 3 in a concentric state and integrally molding the annular insulator 2 with a thermoplastic resin or a thermosetting resin between the upper annular body 1 and the annular insulator 2 is described. -The back pole 3 can be easily integrated.

Next, the tip surface of the upper annular body 1 and the back electrode 3
The reference surface is formed by performing flattening processing so as to be precisely on the same plane by lapping processing or the like with respect to the front end surface of. Then, an annular spacer 5 having the same shape as the tip surface of the upper annular body 1 is precisely finished by lapping into a parallel surface having a predetermined thickness (25 to 25 μm. The annular spacer 5 is placed on the tip surface of the upper annular body 1. In addition, the peripheral edge of the metal diaphragm 4 is held by a retainer in a state where tension is applied to the metal diaphragm 4 in the radial direction, and chemical vapor deposition is performed on the surface of the metal diaphragm 4 as necessary to prevent dew condensation. A thin film of a molecular material (for example, Parylene (trade name)) is coated.

Then, the metal diaphragm 4 is placed on the upper surface of the annular spacer 5, and then the annular heating element having the same cross-section as the annular spacer 5 is pressed from above the metallic diaphragm 4 to press the metallic diaphragm 4 and the annular spacer 5. And the upper annular body 1 is welded to be integrated. Then, the metal diaphragm 4 in the outer region is removed from the outer periphery of the annular spacer 5.

In this way, the back surface of the metal diaphragm and the tip surface of the back electrode, which are appropriately tensioned, are maintained in parallel with each other by the annular spacer 5 with a precise gap of 20 to 25 μm, and the metal diaphragm 4 and the annular member The upper structure of the condenser microphone including the spacer 5 and the upper annular body 1 is assembled.

Next, the terminal mounting plate 6 is fitted on the inner peripheral surface of the lower annular main body 7 and brought into contact with the stepped portion 11, and further the fixing screw ring 10 is attached.
Is screwed into the threaded portion 12 to hold the peripheral portion of the terminal mounting plate 6 together with the stepped portion 11 with an appropriate minute gap. Then, the terminal 8 attached to the terminal mounting plate 6 and the lower end surface of the back electrode 3 are connected by the conductive wire 9, and the tip end surface of the lower annular main body 7 and the lower end surface of the upper annular main body 1 are welded together. Thus, the condenser microphone is assembled.

In the condenser microphone manufactured as described above and having the structure as shown in FIG. 1, stress is not applied to the metal diaphragm 4 even at the bonding portion with the annular spacer 5, although tension is applied to the metal diaphragm 4. Low tension loss of metal diaphragm due to creep. Since there is no reassembly process to form a minute gap between the tip surface of the back electrode and the metal diaphragm, the tip surface of the back electrode and the metal diaphragm are guaranteed to have a high degree of parallelism.

[0026]

In the condenser microphone according to the present invention, since a tension ring is applied to the metal diaphragm 4, a push-up ring unlike the prior art is not used,
No stress concentration on the metal diaphragm. Therefore, the tension loss of the metal diaphragm due to creep is small, and the sensitivity stability is excellent.

Since the metal diaphragm of the prior art is bent at the leading edge of the push-up ring and is not pulled and held by the annular fixing ring, the metal diaphragm is not wrinkled.

Further, since there is no reassembly process as in the prior art for forming a minute gap between the tip surface of the back electrode and the metal diaphragm, the tip surface of the back electrode and the metal diaphragm are highly accurate. Since the parallelism is guaranteed, the sound is not distorted, and the metal diaphragm is mounted via the annular spacer with the tip surface of the annular body as the reference surface, the problem of the difference in thermal expansion between the back pole and the annular body. There is almost no.

In order to concentrically integrate the annular main body and the cylindrical back pole with an insulator, the annular main body and the cylindrical back pole are arranged concentrically, and the annular insulator is heated between them. The method of molding with a plastic resin or a thermosetting resin facilitates integration, is excellent in mass productivity, and reduces production cost.

Further, as a countermeasure against the pinhole of the metal diaphragm, the surface of the metal diaphragm is coated with a thin film of a water-repellent polymer material, not the quartz coating on the metal diaphragm by sputtering in the prior art, so that the pinhole problem of the metal diaphragm is solved. It also eliminates dew condensation and provides water repellency to prevent condensation on the metal diaphragm due to rapid temperature changes. As a result, output noise due to dew condensation on the metal diaphragm is unlikely to occur. Moreover, since the polymer material has a low specific gravity, it has little influence on the vibration function of the metal diaphragm.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of a condenser microphone according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a configuration of a conventional condenser microphone.

[Explanation of symbols] 1 Upper annular body 2 ring insulator 3 back pole 11, 31 steps 32 vents 4 metal diaphragm 5 annular spacer 6 terminal mounting plate 7 Lower annular body 8 terminals 9 conductors 10 Fixing screw ring 12 Thread

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Keiji Mikami             1-16-1, Shirayama, Midori-ku, Yokohama-shi, Kanagawa Stock             Ono Sokki Technical Center (72) Inventor Tadashi Ikeda             1-16-1, Shirayama, Midori-ku, Yokohama-shi, Kanagawa Stock             Ono Sokki Technical Center (72) Inventor Taku Yamamoto             1-16-1, Shirayama, Midori-ku, Yokohama-shi, Kanagawa Stock             Ono Sokki Technical Center (72) Inventor Masahashi Ohashi             1-16-1, Shirayama, Midori-ku, Yokohama-shi, Kanagawa Stock             Ono Sokki Technical Center

Claims (4)

[Claims] 1. An annular main body, a back electrode mounted in the annular main body via an insulator and having a tip end surface flush with the tip end surface of the annular main body, and an annular main body with tension applied in the radial direction. Microphone composed of a metal diaphragm whose peripheral portion is integrally welded to an annular body together with an annular spacer having a predetermined thickness interposed between the distal end surface and the 2. The condenser microphone according to claim 1, wherein the metal diaphragm is coated with a thin film of a water-repellent polymer material. 3. A method of manufacturing a condenser microphone including the following steps: (1) An annular body and a back electrode are integrated via an insulator. (2) The reference surface is formed by performing flattening processing so that the tip surface of the annular main body and the tip surface of the back electrode are precisely flush with each other. (3) Finish the annular spacer to a predetermined thickness. (4) The annular spacer is placed on the front end surface of the annular body, and is further placed on the upper surface of the annular spacer while tension is applied to the metal diaphragm in the radial direction. (5) The metal diaphragm, the annular spacer, and the annular body are welded or bonded so as to be integrated. 4. A back electrode is arranged in an annular body, and an annular insulator is integrally molded with a thermoplastic resin or a thermosetting resin between an inner peripheral surface of the annular body and an outer peripheral surface of the back electrode. The method of manufacturing a condenser microphone according to claim 3, wherein the annular main body and the back electrode are integrated via an insulator.