JP2952617B2 - Condenser microphone and method of manufacturing the same - Google Patents

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 for manufacturing the same, and more particularly, to a structure and a method for attaching a diaphragm to 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 fixed ring 21 holding a peripheral portion of a metal diaphragm 4 is screwed to an outer peripheral surface of a push-up ring 22. In the hollow portion of the push-up ring 22, a back electrode mounting plate 23 made of an insulating material having a base end fixed to the center of the back electrode 3 is formed on the inner peripheral surface of the push-up ring 22. It is axially positioned on the step portion 24 via the annular spacer 5 and is fitted and fixed.

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

In assembling the condenser microphone, the push-up ring 22 and the back electrode mounting plate 23 with the back electrode 3 are temporarily assembled without the spacer 7, and the leading edge of the push-up ring 22 and the back electrode 3 are connected. After the flattening process is performed on the same plane as the tip 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 plate 23
The spacer 7 is inserted between them and reassembled, and the back surface of the metal diaphragm and the front end surface of the back electrode are made parallel while maintaining the small gap.

As a countermeasure against pinholes 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 in the above-mentioned prior art has the following problems. (1) Since an appropriate tension is applied to the metal diaphragm 4 with the leading 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 metal diaphragm 4 to lose tension due to creep. (2) Since the peripheral edge of the metal diaphragm 4 is held and pulled by the annular fixing ring 21 screwed to the outer peripheral surface of the push-up ring 22, wrinkles are easily generated in the metal diaphragm 4. (3) In order to form a minute gap between the tip surface of the back electrode 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 face of the back electrode 3 are coplanar. After the drawing process, 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. High-precision parallelism with a 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. Due to the thermal expansion of the microphone 22, the minute gap between the front end surface of the back pole 3 and the plane including the front end 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 pinholes of the metal diaphragm, has poor water repellency and cannot be prevented from dew condensation on the metal diaphragm due to a rapid temperature change. As a result, dew condensation occurs on the back surface of the diaphragm. And large noise appear on the output, and the specific gravity is large, so that the vibration function of the metal diaphragm is reduced. The present invention solves the above-mentioned disadvantages of the prior art.

[0007]

SUMMARY OF THE INVENTION A condenser microphone according to the present invention is mounted on an annular body, an insulator in the annular body, and has a front end surface flush with a front end surface of the annular main body, and a radiation direction. And a metal diaphragm whose peripheral edge 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 distal end surface of the annular main body while tension is applied to the annular main body. In some cases, the metal diaphragm is coated with a thin film of a water-repellent polymeric material.

[0008] The above condenser microphone is manufactured in the following steps. (1) The annular main body and the back electrode are integrated via an insulator.
A preferred integration method is to arrange the back electrode in the annular body and integrally mold the 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 main body and the back electrode are integrated via an insulator. (2) A flat surface is formed on the front end surface of the annular main body and the front end surface of the back pole so as to be precisely flush with each other to form a reference surface. (3) Finish the annular spacer to a predetermined thickness. (4) The annular spacer is placed on the distal end surface of the annular main body, and further placed on the upper surface of the annular spacer in a state where radial tension is applied to the metal diaphragm. (5) Weld the metal diaphragm, the annular spacer and the annular body so as to be integrated.

[0009]

In the condenser microphone described above, since tension is applied to the metal diaphragm, no stress concentration occurs at the bonding portion with the annular spacer, so that the tension of the metal diaphragm due to creep is reduced. Since there is no re-assembly step to form a minute gap between the front end surface of the back electrode and the metal diaphragm, high-precision parallelism is guaranteed between the front end surface of the back electrode and the metal diaphragm, resulting in distortion in sound. Does not occur, and since the metal diaphragm is mounted via the annular spacer with the distal end surface of the annular body as the reference plane, there is almost no problem of the difference in thermal expansion between the back electrode and the annular body.

A thin film of a water-repellent polymer material, which is coated by chemical vapor deposition on the surface and / or the back surface of the metal diaphragm, fills the pinholes on the surface of the metal diaphragm and causes a rapid temperature change. Even in the case of the above, 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 effect on the vibration function of the metal diaphragm.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A condenser microphone according to an embodiment of the present invention will be described with reference to the drawings. The vertical relationship in the following description is the vertical relationship in FIG. As shown in FIG. 1, an upper annular main body 1 of a condenser microphone
The annular insulator 2 and the cylindrical back electrode 3 are concentrically integrated. The inner peripheral surface of the upper annular main body 1 and the outer peripheral surface of the annular insulator 2 are in contact, 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 main body 1 is in contact with the lower inner peripheral surface of the upper annular main body 1.

The distal end surface of the upper annular main body 1 and the distal end surface of the back electrode 3 are on the same plane, and the distal end surface of the upper annular main body 1 and the peripheral portion of the metal diaphragm 4 to which appropriate tension is applied. An annular spacer 5 having a predetermined thickness (20 to 25 .mu.m) is interposed therebetween, and the upper annular body 1, the annular spacer 5, and the peripheral edge of the metal diaphragm 4 are integrally welded.

Thus, the front end face of the back electrode 3 is parallel to the metal diaphragm 4, and a small gap corresponding to the thickness of the annular spacer 5 is provided between the front end face of the back pole 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 on the intermediate inner peripheral surface of the lower annular main body 7 with a small gap, and the back pole 3 and the annular insulator 2 are provided.
A back air chamber is formed between the stepped portion 11 and the stepped portion 11 and the threaded portion 12 adjacent to the stepped portion.
Are formed, and the terminal mounting plate 6 is fixed to the fixing screw ring 10 screwed to the step portion 11 and the screw portion 12 with an appropriate minute gap therebetween. The minute gap on the outer peripheral surface of the terminal mounting plate 6 is
It may be formed by the screw surface of the thread portion 12.

The back air chamber has 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 main body 1, the upper and lower peripheral edges of the terminal mounting plate 6, and the step 11 of the annular main body 1. Communicates with the outside through a minute gap with the fixing screw ring 10, and in accordance with a pressure difference between the inside and outside of the back air chamber due to a change in atmospheric pressure or the like, air is squeezed and circulated through the minute gap, and the time constant As a result, the pressure difference between the inside and outside of the back air chamber disappears. That is, a low cut-off frequency characteristic is given to the condenser microphone.

The back electrode 3 has through holes 32, 32 # of a small diameter penetrating in the axial direction for damping adjustment. The gap space between the metal diaphragm 4 and the back electrode 3 is the back electrode 3 and the terminal. It communicates with the back air chamber between the mounting plates 6. Since an appropriate number of ventilation holes 32 can be provided at appropriate positions, appropriate damping adjustment is easy. The terminal 8 attached to the terminal attachment plate 6 and the lower end surface of the back electrode 3 are connected by a conducting wire 9.
The terminal 8 is connected to an external amplifier by a conductor.

In manufacturing the microphone, the upper annular main body 1 and the lower annular main body 7 are welded or bonded 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 condensation on the surface of the metal diaphragm 4 even in the case of a sudden temperature change.

In the above condenser microphone,
If an electret film is formed on the upper end surface of the back pole 3, an electret condenser microphone is formed.
When an electret film is used in place of the metal diaphragm 4, a front electret condenser microphone is formed.

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

In the structure shown in the figure, a step 31 is formed on the lower surface of the cylindrical back electrode 3, the small diameter portion is fitted to the annular insulator 2, and the step 31 contacts the upper surface of the annular insulator 2. And glue. In particular, a method of arranging the upper annular main body 1 and the back electrode 3 concentrically and integrally molding the annular insulator 2 with a thermoplastic resin or a thermosetting resin between the upper annular main body 1 and the annular insulator 2 -Integration of the back electrode 3 becomes easy.

Next, the tip surface of the upper annular main body 1 and the back pole 3
A flat surface is formed by lapping or the like so as to be precisely on the same plane as the front end surface of the substrate to form a reference surface. Then, an annular spacer 5 having the same shape as the distal end surface of the upper annular main body 1 is precisely finished by lapping or the like into a parallel surface of a predetermined thickness (25 to 25 μm. The annular spacer 5 is placed on the distal end surface of the upper annular main body 1. Further, the outer periphery 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 if necessary, the surface of the metal diaphragm 4 is made to have high water repellency by chemical vapor deposition to prevent dew condensation. A thin film of a molecular material (for example, Parylene (trade name)) is coated.

After the metal diaphragm 4 is placed on the upper surface of the annular spacer 5, an annular heater having the same cross section as the annular spacer 5 is pressed from above the metal diaphragm 4, and the metal diaphragm 4 and the annular spacer 5 are pressed. And the upper annular main body 1 are welded together. Then, the outer peripheral metal diaphragm 4 is removed from the outer periphery of the annular spacer 5.

In this manner, the back surface of the metal diaphragm and the front end surface of the back electrode in an appropriately tensioned state are maintained parallel to each other with a precise minute gap of 20 to 25 μm by the annular spacer 5, and the metal diaphragm 4, the annular shape An 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 to the inner peripheral surface of the lower annular main body 7 and is brought into contact with the step portion 11.
Is screwed into the threaded portion 12, and the peripheral portion of the terminal mounting plate 6 is held together with the step portion 11 with an appropriate minute gap. Then, the terminal 8 attached to the terminal attachment plate 6 and the lower end surface of the back electrode 3 are connected by a conducting wire 9, and the distal end surface of the lower annular main body 7 and the lower end surface of the upper annular main body 1 are welded. Thus, the condenser microphone is assembled.

In the condenser microphone manufactured as described above and configured as shown in FIG. 1, since tension is applied to the metal diaphragm 4, stress concentration does not occur even at a bonding portion with the annular spacer 5. In addition, there is little tension loss of the metal diaphragm due to creep. Since there is no reassembly step to form a minute gap between the front end surface of the back electrode and the metal diaphragm, high-precision parallelism between the front end surface of the back electrode and the metal diaphragm is guaranteed.

[0026]

In the condenser microphone according to the present invention, a tension ring is not used for applying tension to the metal diaphragm 4 unlike the prior art.
No stress concentration occurs on the metal diaphragm. Accordingly, the tension of the metal diaphragm is hardly lost due to creep, and the sensitivity stability is excellent.

Since the metal diaphragm as in the prior art is bent at the leading edge of the push-up ring and is not squeezed and held by the annular fixing ring, no wrinkles are generated in the metal diaphragm.

Further, since there is no reassembly step as in the prior art to form a minute gap between the front end surface of the back electrode and the metal diaphragm, the front end surface of the back electrode and the metal diaphragm are highly accurate. The degree of parallelism is guaranteed, no distortion occurs in the sound, and the metal diaphragm is mounted via the annular spacer with the end surface of the annular body as the reference plane, so the problem of thermal expansion difference between the back pole and the annular body. Is almost none.

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

Further, since the countermeasures against the pinhole of the metal diaphragm are not made by the quartz coating on the metal diaphragm by sputtering in the prior art but by coating a thin film of a water-repellent polymer material on the surface of the metal diaphragm, the pinhole problem of the metal diaphragm is eliminated. In addition, water repellency is obtained, and the occurrence of dew condensation on the metal diaphragm due to a rapid temperature change is prevented. As a result, output noise due to dew condensation on the metal diaphragm hardly occurs. Moreover, since the polymer material has a low specific gravity, it has little effect on the vibration function of the metal diaphragm.

[Brief description of the drawings]

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper annular main body 2 Annular insulator 3 Back pole 11,31 step part 32 Vent hole 4 Metal diaphragm 5 Annular spacer 6 Terminal mounting plate 7 Lower annular main body 8 Terminal 9 Lead wire 10 Fixing screw ring 12 Screw part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keiji Migami 1-16-1 Hakusan, Midori-ku, Yokohama-shi, Kanagawa Prefecture Ono Sokki Technical Center Co., Ltd. (72) Inventor Tadashi Ikeda Hakusan, Midori-ku, Yokohama-shi, Kanagawa 1-1-16-1 Ono Sokki Technical Center Co., Ltd. (72) Inventor Taku Yamamoto 1-1-16 Hakusan, Midori-ku, Yokohama-shi, Kanagawa Prefecture Ono Sokki Technical Center Co., Ltd. (72) Inventor Masahisa Ohashi Kanagawa 1-16-1 Hakuyama, Midori-ku, Yokohama-shi, Japan Ono Sokki Technical Center (56) References JP-A-60-217800 (JP, A) JP-A-60-9300 (JP, A)

Claims (4)

(57) [Claims] An annular body, a back pole mounted on the annular body via an insulator, and having a distal end surface flush with the distal end surface of the annular body, and an annular body with radial tension applied thereto. Condenser microphone comprising a metal diaphragm whose peripheral edge is integrally welded to an annular main body together with an annular spacer having a predetermined thickness interposed between the distal end face of the condenser microphone and the annular spacer. 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 comprising the following steps: (1) An annular main body and a back electrode are integrated via an insulator. (2) A flat surface is formed on the front end surface of the annular main body and the front end surface of the back pole so as to be precisely flush with each other to form a reference surface. (3) Finish the annular spacer to a predetermined thickness. (4) The annular spacer is placed on the distal end surface of the annular main body, and further placed on the upper surface of the annular spacer in a state where radial tension is applied to the metal diaphragm. (5) The metal diaphragm, the annular spacer, and the annular main 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 formed of 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. 4. The method for manufacturing a condenser microphone according to claim 3, wherein the annular main body and the back electrode are integrated via an insulator.