KR20040100955A - Electret condenser microphone - Google Patents

Abstract

PURPOSE: An electret condenser microphone having cup-shaped backside pole is provided to improve sensitivity and an S/N ratio by reducing a floating volume value between a capsule and a backside pole. CONSTITUTION: A capsule(11) is formed with a metal material and includes a cylindrical part and a front plate. A diaphragm(16) is adhered to one side of a diaphragm ring(15). The other side of the diaphragm ring is in contact with an inner face of the front plate. A cup-shaped backside pole(18) is formed with the metal material. An insulating spacer(17) is used for maintaining a gap between a backside pole of the cup-shaped backside pole and the diaphragm. A printed board includes an impedance converter connected to an opening portion of a cylinder part(18A) of the cup-shaped backside pole. Three or more projections are formed in a constant interval on a surrounding side of the cylinder part of the cup-shaped backside pole. Each outer surface of the projections is in contact with an inner wall face of the cylindrical part of the capsule.

Description

Electret condenser microphone {ELECTRET CONDENSER MICROPHONE}

TECHNICAL FIELD This invention relates to an electret condenser microphone. Specifically, It is related with the improvement of the electret condenser microphone which made the cup shape into the cup shape.

The present applicant has first proposed an electret condenser microphone having a structure in which a double electrode is formed in a cup shape, and a conventional double electrode supported by a double electrode holder is integrated by a double electrode and a tube portion. (Patent Document 1)

8, the structure of the previously proposed electret condenser microphone will be briefly described. In FIG. 8, 11 represents a capsule. The capsule 11 is formed of a metal material, and the front plate 12 is integrally formed on one end surface of the cylindrical portion. A center hole 13 is formed in the front plate 12, and sound is introduced into the capsule 11 through the center hole 13.

15 denotes a diaphragm ring. The diaphragm ring 15 is made of a conductive material, one surface of which is in contact with the inner surface of the front plate 12, and the other surface of the diaphragm film 6 is attached. The vibration membrane 16 is also conductive. It is formed into a film and has a structure that vibrates according to sound pressure.

Reference numeral 17 denotes a ring-shaped insulating spacer formed of an insulating material. By the thickness of this insulating spacer 17, the space | interval between the vibrating film 16 and the back electrode 18 is maintained at a predetermined value.

The back electrode 1 is constituted by a cup-shaped back electrode formed of a metal material. That is, one open end of the cup-shaped tube portion 18A is blocked by a blocking plate, and the backing plate 18 is formed by the blocking plate. An electret dielectric film 19 is formed on the outer circumferential surface of the back electrode 18 and the tube portion 18A. In the back electrode 18, a plurality of back hole holes 27 are formed, and the gap between the vibrating film 16 and the back electrode 18 is communicated with the back chamber 28 to form the vibrating film 16. Keep the vibration freely.

The open end surface of the cylinder portion 8A is blocked by the wiring board 42. On the wiring board 42, the IC element 50 constituting the impedance converter is mounted on the side of the exhaust chamber 28, and electrical signals are emitted through the IC element 50.

9 shows an example of the circuit structure of the IC element 50 constituting the impedance converter. The impedance converter is constituted by the field effect transistor 54 and the resistors 55 and 56. The back electrode 18 is electrically connected to the gate 53 of the field effect transistor 54, and the vibration membrane 16 is electrically connected to the common potential point (capsule 11). The contact piece 58 shown in FIG. 8 represents a wiring conductor for electrically connecting the back electrode 18 to the gate 53.

Moreover, the electret condenser microphone of the structure which integrated the cup shape | mold electrode 18 and the insulation spacer 17 is also proposed (patent document 2). The electret condenser microphone proposed in this patent document 2 has the effect of integrally forming a spacer on the cup-shaped double electrode surface, reducing the number of parts, and reducing the number of assembly steps.

[Patent Document 1]

Patent No. 3375284

[Patent Document 2]

Publication No. 6-2899

As described with reference to FIG. 8, in the electret condenser microphone using the cup-shaped electrode 18 proposed in Patent Literature 1, an advantage of simplifying the assembly can be obtained, while the tube portion 8A supporting the electrode 18 is obtained. ) Is disposed close to the inner wall of the capsule 11 at an interval equal to the thickness of the electret dielectric film l9, so that the capacitance value of the floating capacitance CP formed between the tube portion 8A and the capsule 11 is increased. Since the capacitance (capacitance) becomes large and this floating capacitance CP is connected in parallel with the capacitance formed between the cathode 18 and the vibrating membrane 16, as shown in Fig. 9, the presence of this floating capacitance CP is present. As a result, the voltage signal generated between the anode 18 and the vibrating membrane 16 is attenuated, causing a problem of lowering the sensitivity of the microphone.

Moreover, the electret condenser microphone proposed by patent document 2 is shape | molding the whole cup-shaped double electrode by the conductive resin material. Therefore, since the back electrode is connected to the impedance converter through this conductive resin material, the circuit shown in FIG. 9 describes a relatively large resistance value between the back electrode 18 and the gate 53 of the field effect transistor 54. The resistance (resistance of a conductive resin material) is inserted, and the SN ratio worsens.

An object of the present invention is to reduce the stray capacitance generated between the tube portion 8A and the capsule 11 in an electret condenser microphone constituted by using a cup-shaped double electrode, and has a high sensitivity and a good SN ratio. It is to provide an electret condenser microphone.

In addition, in the present invention, there is no need to insert a resistor between the cathode 18 and the gate of the field effect transistor constituting the impedance converter, and therefore, to provide an electret condenser microphone having a good SN ratio.

1 is a cross-sectional view for explaining an embodiment of the present invention.

2 is a cross-sectional view taken along the line A-A shown in FIG.

3 is a perspective view for explaining the structure of the main part of the present invention;

4 is a plan view for explaining the characteristics of the wiring board used in the present invention.

5 is a side view for explaining the operation of the main part of the present invention;

6 is a graph for explaining the frequency characteristics of an electret condenser microphone and a conventional product according to the present invention;

7 is a perspective view with a cross section a part for explaining a modified embodiment of the present invention.

8 is a cross-sectional view for explaining the conventional technology.

9 is a connection diagram for explaining the electrical structure of the electret condenser microphone having the structure shown in FIG.

<Description of the symbols for the main parts of the drawings>

1l: Capsule 27: Double hole

12: front panel 28: exhaust chamber

13: center hole 42: wiring board

15: diaphragm ring 50: IC element

16: diaphragm 51: output terminal

17: Insulation spacer 52: Earth terminal

18: polarization 53: gate

18A: Tube 58: Contact piece

18B: projection G: void

19: electret dielectric film

In claim 1 of the present invention, a capsule is formed of a metal material and has a cylindrical portion and a front plate on one end face of the cylindrical portion, and one surface of the capsule is in contact with the inner surface of the front plate of the capsule, A diaphragm ring having a vibrating membrane attached thereto, and a bipolar electrode formed of a metal material, and formed of a tube portion and a closed plate that blocks one end surface of the tube portion, and a cup-shaped electrode electrode having an electret dielectric film coated on the outer surface of the tube portion and the tube portion. And an insulating spacer interposed between the gap formed on the cup-shaped bipolar and the vibrating membrane, and maintaining a distance between the gap and the vibrating membrane at a predetermined value. In an electret condenser microphone, which is provided with a wiring board abutting the mounted surface and the other surface exposed to the opening surface of the capsule, the electret condenser microphone is placed on the circumferential surface of the cylindrical portion of the cup-shaped double electrode. Forming at least three projections with equal angular intervals in a direction, and propose the electret condenser microphone constructed to abut the outer surface of the projecting yidol group on the inner wall of the cylindrical portion of the capsule.

In the second aspect of the present invention, a capsule is formed of a metal material and has a cylindrical portion and a front plate on one end face of the cylindrical portion, and one surface of the capsule is in contact with the inner surface of the front plate of the capsule. A diaphragm ring having a vibrating membrane attached thereto, and a bipolar electrode formed of a metal material and formed of a cylinder plate and a closing plate that blocks one end surface of the tube portion, and a cup-shaped electrode electrode having an electret dielectric film coated on the outer surface of the tube portion and the tube portion. And an insulating spacer interposed between the gap formed on the cup-shaped bipolar and the vibrating membrane, and maintaining a distance between the gap and the vibrating membrane at a predetermined value. An electret condenser microphone, comprising a wiring board abutting a mounted surface and having the other surface exposed to the opening surface of the capsule, wherein the outside of the double electrode formed in the cup-shaped double electrode is provided. Forming paste coated with an insulating spacer in a ring shape to the rail edge, and a cup-like structure integral with the insulating spacer baegeuk suggests an electret condenser microphone.

In Claim 3 of this invention, the electret condenser microphone of Claim 1 or 2 WHEREIN: The electret condenser microphone which provided at least 2 or more polarization holes in the double electrode formed in the cup-shaped double electrode is proposed.

In claim 4 of the present invention, in the electret condenser microphone according to claim 1, an open end portion of the tubular portion of the cup-shaped double electrode is proposed that the electret condenser microphone contacts the arc-shaped wiring conductor formed on the wiring board.

Action

According to the present invention, since a plurality of projections facing outward are formed on the peripheral surface of the tubular portion constituting the double pole, and the projecting surface of the protrusion is brought into contact with the inner wall surface of the capsule, the peripheral surface of the cylindrical portion other than the protrusion is encapsulated. It is laid apart from the inner wall of the. As a result, the stray capacitance value formed between the capsule and the tubular portion of the back electrode can be made small, whereby the sensitivity can be improved.

In addition, in the present invention, since the cathode and the cylinder are integrally formed by the metal material, the anode and the gate of the field effect transistor are electrically connected by the metal material. Therefore, since the resistance value between the polarization and the gate of the field effect transistor can be reduced, an electret condenser microphone with a good SN ratio can be provided.

<Embodiment of the Invention>

1 to 3 show one embodiment of the present invention. In Fig. 1 to Fig. 3, the parts corresponding to those in Fig. 8 are denoted by the same reference numerals, and the description thereof will be omitted. However, as shown in Fig. 1, the capsule 11 is formed in a cup shape by a metal material. The diaphragm ring 15 is in contact with the inner surface of the front plate 12 of the capsule 1l, the diaphragm 16 is affixed to the other side, and the back electrode 18 is made of, for example, a metal material. It consists of a blocking plate which is formed of a silver and closed the open end of one side of the cylinder portion 18A. An electret dielectric film 19 is formed on the outer circumferential surface of these electrodes 18 and the tube portion 8A. In addition, an insulating spacer 17 is sandwiched between the spacer 18 and the vibrating membrane 16, and the gap between the vibrating membrane 16 and the spacer 18 is determined by the insulating spacer 17. The structure to be maintained is the same as that described using FIG.

The structure characterized by the present invention is that at least three or more projections 18B are formed on the circumferential surface of the tube portion 18A integrally formed with the electrode 18 at equal intervals in the circumferential direction. 2 and 3 show the case where three projections 18B are formed on the circumferential surface of the cylinder portion 18A. The protruding amount of these protruding surfaces of the projections 18B is the protruding amount of each protruding surface of the projections 18B exactly contacting the inner wall surface of the capsule 11, and the protruding surface of the protruding surfaces 18B is formed of the capsule 11. By contacting the inner wall surface, the center of the back electrode 18 is supported without shaking in accordance with the center position of the hollow portion of the capsule ll.

By forming the projection 18B, as shown in FIG. 2, as shown in FIG. 2, a gap G is formed between the outer circumferential surface of the tube portion 18A of the cup-shaped electrode and the inner wall surface of the capsule 11. By forming this gap G, the value of the floating volume CP (refer FIG. 9) formed between the capsule 11 and the cylinder part 18A can be made small. As a result, the vibration film 16 vibrates to reduce the amount of attenuation of the voltage signal (variable components of static electricity generated by the electret dielectric film 19) generated between the vibration film 16 and the back electrode 18. As a result, an audio signal having a good SN ratio can be obtained.

Further, since the gap G is formed, an arc-shaped wiring conductor 59 in contact with the opening end of the tube portion 8A, as shown in FIG. 4, shows the wiring conductor connecting the anode 18 to the gate of the IC element 50. It is possible to stabilize the electrical connection state between the polarization 18 and the IC element 50.

That is, according to the structure demonstrated using FIG. 8, the outer periphery surface of the cylinder part 18A is arrange | positioned near the inner wall surface of the capsule 11. For this reason, when the wiring conductor which contacts the opening end of the cylinder part 18A with the structure shown in FIG. 8 in circular arc shape, since the wiring conductor will also contact the inner wall surface of the capsule 11, it will form circularly. There is no number. For this reason, in the example shown in FIG. 8, only the contact piece 58 formed in the radial direction of the wiring board 42 is in contact with the tube portion 18A. According to this connection method, since the contact area of the contact piece 58 and the cylinder part 18A is small, the fault of low contact reliability arises.

On the other hand, according to this invention, since the arc shaped wiring conductor 59 can be formed, the reliability of the connection between the cylinder part 18A and the gate 53 can be improved. In the embodiment shown in FIG. 4, the case where the arc-shaped wiring conductor 59 is formed in a circle is shown. However, the shape is not limited to the circle but may be partially cut.

In addition, according to the present invention, the diameter of the tube portion 18A is reduced on average, which results in a decrease in the contents of the exhaust chamber 28 and a decrease in the contents of the exhaust chamber 28. As the opening end portion in which the projections 18B are formed is slightly flipped as shown in FIG. 5, a gap S is generated between the wiring board 42 and the gap in the volume of the exhaust chamber 28 through this gap S. Since the volume of the portion of G is added, substantially no decrease in sensitivity is seen.

In addition, the frequency characteristics of the electret condenser microphone described in Fig. 8 and the electret condenser microphone according to the present invention are shown in Fig. 6. In Fig. 6, the curve A shows the frequency characteristics of the electret condenser microphone according to the present invention, and the curve B shows the frequency characteristics of the electret condenser microphone having the structure shown in Fig.8. As is apparent from Fig. 6, the electret condenser microphone according to the present invention has an improved sensitivity of about 2 to 3 dB than the conventional product. In addition, when the SN ratio was measured, the conventional product was 62.0 dB, but the electret condenser microphone according to the present invention was found to have an SN ratio of about 6 dB to about 2 dB.

7 shows a modified embodiment of the present invention. In this embodiment, the case where the insulation spacer 17 is insert molded integrally with the cup-shaped electrode 18 is shown. That is, an aluminum thin plate coated with the electret dielectric film 19 is formed into a cup shape, and an insulating spacer (eg, a liquid crystal polymer or polyvinyl chloride) is formed on the outer circumference of the cup-shaped double electrode 18. 17) and integrally formed by insert formation.

By integrating the back electrode 18 and the insulation spacer 17, the back electrode 18, the back electrode holder, the gate ring, and the insulation spacer 17 are substantially integrated, and the number of assembling steps is reduced, thereby reducing the assembly cost. can do. In addition, there is an advantage that fewer misses during assembly. In addition, the integrated production reduces the imbalance between components, and can also provide an advantage of providing a product with high sensitivity.

As described above, according to the embodiment shown in Figs. 1 to 5 of the present invention, the floating capacitance value generated between the capsule ll and the double electrode 18 is higher than that of the electret microphone having the structure shown in Fig. 8. Since it can be made small, compared with the electret condenser microphone of the structure shown in FIG. 8, the sensitivity can be improved and SN ratio can be improved.

Further, in the present invention, since the electrode 18 is formed to be electrically connected to the gate 53 of the IC element 50 via the tube portion 18A formed of a metal material, the electret microphone disclosed in Patent Document 2 is disclosed. In comparison with this, the resistance value sandwiched between the gap 18 and the gate 53 can be reduced. In this respect, the electret condenser microphone of which the SN ratio is better than the electret condenser microphone of the structure of patent document 2 can be obtained.

In addition, according to the embodiment shown in FIG. 7 of this invention, since the number of parts can be reduced, the assembly becomes easy and the advantage which can provide the electret condenser microphone with the characteristic provided can be acquired.

Claims (4)

A capsule formed by a metal material and having a cylindrical portion and a front plate on one end face of the cylindrical portion, and a vibrating membrane in which one surface is in contact with the inner surface of the front plate of the capsule and the vibrating membrane is attached to the other surface. A cup-shaped electrode having a ring formed by a metal material and formed of a tube portion and a closing plate which blocks one end face of the tube portion, and having an electret dielectric film coated on the electrode and an outer surface of the tube portion, and the cup-shaped electrode; An insulating spacer which is sandwiched between the formed double electrode and the vibrating membrane, and maintains a distance between the double electrode and the vibrating membrane at a predetermined value, and a surface on which the opening end of the tube portion of the cup-shaped double electrode is mounted with an impedance converter. In the electret condenser microphone which is provided with a wiring board which abuts on the other side and is exposed to the opening surface of the said capsule, At least three projections are formed on the circumferential surface of the cylindrical portion of the cup-shaped bipolar at equal intervals in the circumferential direction, and the protruding outer surface of the projection abuts against the inner wall surface of the cylindrical portion of the capsule. Electret condenser microphone. A capsule formed by a metal material and having a cylindrical portion and a front plate on one end face of the cylindrical portion, and a vibrating membrane in which one surface is in contact with the inner surface of the front plate of the capsule and the vibrating membrane is attached to the other surface. A cup-shaped anode formed of a ring, a metal material, and formed of a cylinder portion and a closing plate that blocks one end surface of the cylinder portion, the electrode having a cuplet electrode having an electret dielectric film coated on the electrode and an outer surface of the tube portion; An insulating spacer interposed between the gap formed in the circuit and the vibration membrane to maintain a distance between the gap and the vibration membrane at a predetermined value, and a surface on which the opening end of the tube portion of the cup-shaped gap is mounted with an impedance converter. In the electret condenser microphone which is provided with a wiring board which abuts on the other side and is exposed to the opening surface of the said capsule, An electret condenser microphone according to claim 1, wherein the insulating spacer is formed by attaching the insulating spacer to a ring-shaped outer edge of the double electrode formed on the cup-shaped double electrode, and the cup-shaped double electrode and the insulating spacer are integrated. The electret condenser microphone according to claim 1 or 2, wherein at least two or more polarization holes are formed in the polarization formed in the cup-shaped polarization. The electret condenser microphone according to claim 1, wherein the opening end of the tubular portion of the cup-shaped electrode contacts the arc-shaped wiring conductor formed on the wiring board.