WO2007097519A1

WO2007097519A1 - Electret condenser microphone and assembling method thereof

Info

Publication number: WO2007097519A1
Application number: PCT/KR2006/005863
Authority: WO
Inventors: Kyung-Hwan Kang; Kyoung-Ku Han
Original assignee: Bse Co., Ltd
Priority date: 2006-02-21
Filing date: 2006-12-29
Publication date: 2007-08-30
Also published as: KR20070084700A; KR100758515B1

Abstract

Provided is an electret condenser microphone including a diaphragm for replacing a spacer ring. The electret condenser microphone includes: a diaphragm vibrating in response to sound pressure; and a dielectric plate disposed to face the diaphragm. The diaphragm includes a protrusion protruding from at least one side of the diaphragm to a predetermined thickness and contacting the dielectric plate. Accordingly, the protrusion fromed on the diaphragm can replace the spacer ring.

Description

ELECTRET CONDENSER MICROPHONE AND ASSEMBLING

METHOD THEREOF

Technical Field

[1] The present invention relates to an electret condenser microphone, and more particular, to an electret condenser microphone having a diaphragm capable of replacing a spacer ring. Background Art

[2] With recent development of information communication devices, e.g., mobile phones, telephones, MP3 players, etc., a sound wave device such as an amplifier has been rapidly developed. Thus, extensive research is being conducted to improve the performance of a subminiature electret condenser microphone mounted in the sound wave device.

[3] The electret condenser microphone includes a dielectric plate and a diaphragm and converts an audio signal into an electric signal using an electrostatic field formed between the dielectric plate and the diaphragm. The dielectric plate includes a high polymer film into which a semipermanent electric charge (called an electret) is injected. The diaphragm is manufactured by attaching a metal polar ring to a vibrating membrane formed of a polyethylen terephtalate (PET) film.

[4] Such a conventional electret condenser microphone uses a spacer ring to prevent electric contact between the dielectric plate and the diaphragm so as to use them as two terminals of a capacitor, to adjust the sensitivity of the electret condenser microphone through the adjustment of a gap between the two terminals, and to provide a space for the vibration of the diaphragm.

[5] In manuacturing the spacer ring, a film roll formed of an insulating material such as an acrylic resin is cut off in the shape of the spacer ring using a spacer insertion mold and then is inserted into the electret condenser microphone.

[6] The process of inserting the cut-off spacer ring into the electret condenser microphone, however, has problems that causes the breakdown or malfunction of the electret condenser microphone. If the spacer ring is incompletely cut off, for example, it is torn or cut larger than designed, the dielectric plate and the diaphragm do not maintain a constant gap in parallel, causing the electrical contact therebetween and/or noise.

[7] In addition, during the process of cutting the film roll, blurrs are formed in an inner or outer circumference of a cut-off surface of the spacer ring. If the burred spacer ring is inserted between the dielectric plate and the diaphragm, a portion of the diaphragm is deformed or torn. Consequently, the diaphragm may abnormally transmit an external audio signal to the dielectric plate, causing noise or malfunction of the electret condenser microphone.

[8] Finally, when the spacer ring is incompletely cut off from the film roll and therefore still remains in the spacer insertion mold or the film roll during an automatic assembling process, the spacer ring is not inserted into the electret condenser microphone. In this case, both a current electret condenser microphone product and a next electret condenser microphone product may be defective. Disclosure of Invention Technical Problem

[9] Accordingly, the present invention is directed to an electret condenser microphone that substantially obviates one or more problems due to limitations and disadvantages of the related art.

[10] An object of the present invention is to provide an electret condenser microphone having a protrusion formed on a polar ring of a diaphragm, and an assembling method thereof.

[11] Another object of the present invention is to provide an electret condenser microphone and an assembling method thereof, which can prevent a breakdown of the microphone due to the tearing of a spacer ring during an insertion process, the generation of burrs on the inner and outer circumferences of the spacer ring, and the non-insertion of the spacer ring.

[12] A further object of the present invention is to provide an electret condenser microphone and an assembling method thereof, in which an inserting process of a spacer ring separately manufactured into the microphone can be omitted by adding a forging process with the thickness of a spacer ring to a polar ring manufacturing process. Therefore, the whole manufacturing process of the microphone is simplified.

[13] A still further object of the present invention is to provide an electret condenser microphone and an assembling method thereof, in which an integrated base ring forming process is added to a protrusion forming process on a polar ring to replace a spacer ring. An integrated base ring includes an insulating base ring and a conductive base ring. Accordingly, a whole manufacturing process of the electret condenser microphone can be simplified, thereby enhancing the production yield of the electret condenser microphone. Technical Solution

[14] According to an aspect of the present invention, there is provided an electret condenser microphone, including: a diaphragm vibrating in response to sound pressure; and a dielectric plate disposed to face the diaphragm, wherein the diaphragm includes a protrusion protruding from at least one side of the diaphragm to a predetermined thickness and contacting the dielectric plate. [15] It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Brief Description of the Drawings [16] FIG. 1 is an exploded perspective view of an electret condenser microphone according to an embodiment of the present invention.

[17] FIG. 2 is an exploded perspective view of a diaphragm shown in FIG. 1.

[18] FIG. 3 is a rear view of the diaphragm shown in FIG. 2.

[19] FIG. 4 is a sectional assembled view of an electret condenser microphone according to an embodiment of the present invention. [20] FIGs. 5 and 6 are a front view and a rear view of a polar ring having a circular rim according to an embodiment of the present invention, respectively. [21] FIG. 7 is a perspective view of a polar ring having a rectangular rim according to an embodiment of the present invention. [22] FIG. 8 is an exploded perspective view of a hexahedral electret condenser microphone including the polar ring shown in FIG. 7. [23] FIG. 9 is an exploded perspective view of an electret condenser microphone i ncluding an integrated base ring, with the absence of a spacer ring, according to an embodiment of the present invention. [24] FIG. 10 is a sectional assembled view of the electret condenser microphone shown in FIG. 9.

[25] FIG. 11 is an exploded perspective view of another type of an integrated base ring.

[26] FIG. 12 is a sectional assembled view of an electret condenser microphone including the integrated base ring shown in FIG. 11. [27] FIG. 13 is a flowchart illustrating an assembling method of an electret condenser microphone according to an embodiment of the present invention. [28] DESCRIPTION OF THE SYMBOLS IN MAIN PORTIONS OF THE

DRAWINGS>

[29] 100: case 120: sound hole

[30] 200: diaphragm 220: protrusion

[31] 250: polar ring 270: vibrating membrane

[32] 300: dielectric plate 350: electret

[33] 400: conductive base ring 500: insulating base ring

[34] 600: PCB 700: integrated base ring

[35] 730: via hole 900: back chamber Best Mode for Carrying Out the Invention

[36] Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

[37] FIG. 1 is an exploded perspective view of an electret condenser microphone according to an embodiment of the present invention.

[38] Referring to FIG. 1, an electret condenser includes a printed circuit board (PCB)

600, an insulating base ring 500, a conductive base ring 400, a dielectric plate 300, a diaphragm 200, and a case 100.

[39] The case 100 includes a sound hole 120 through which external sound is transmitted to the diaphragm 200, and receives components of the electret condenser microphone, for example, the PCB 600, the insulating base ring 500, the conductive base ring 400, the dielectric plate 300, and the diaphragm 200. Therefore, the case 100 can protect or shield the componets from external impact or external electronic noise. The case 100 provides a conduction path between the PCB 600 and the diaphragm 200. Since the case 100 is curled at an end of its opening, electrical connections between the components are tightened. To this end, the case 100 is formed of a conductive material selected from the group consisting of nickel, copper, aluminum, and an alloy thereof. The case 100 can also be plated with gold so as to increase its conductivity.

[40] The PCB 600 transmits an electric signal of the dielectric plate 300 to external devices (not shown) through the conductive base ring 400. The PCB 600 includes a field effect transistor (FET) for amplifying the electric signal, a multilayer ceramic capacitor (MCC) for filtering the amplified electric signal, and a circuit pattern for providing an electric path between the FET and the MCC. The PCB 600 is electrically connected to the dielectric plate 300 through the conductive base ring 400 and to the diaphragm 200 through the case 100, so that the electret condenser microphone operates as a capacitor.

[41] The insulating base ring 500 insulates teh case 100 from the conductive dielectric plate 300 and protects the dielectric plate 300 from external impact and heat. The insulating base ring 500 may be formed of a thermosetting plastic material.

[42] The conductive base ring 400 provides a conduction path through which the electric signal of the dielectric plate 300 is transmitted to the PCB 600. The conductive base ring 400 may be formed of a metal, e.g., copper, silver, nickel, etc. In this embodiment of the present invention, copper is suitable because of its cost efficency and easy pro- cessability.

[43] The capacitance of the dielectric plate 300 is changed due to the change of the vibration (i.e., the change of a distance between the vibrating membrane 270 and the dielectric plate 300) which is transmitted from the diaphragm 200. Thus, the amount of accumulated electric charges on the dielectric plate 300 is changed. That is, the current of the dielectric plate 300 varies according to the change of an audio signal, such that the audio signal is converted into the electric signal. The dielectric plate 300 is manufactured by thermally laminating an electret film (e.g., fluoronate ethylen pprophylen (FEP), polytetrafluorethylene (PTFE), perfluoroalkoxy (PFA), etc.) on a metal plate (e.g., gold, bronze, brass, phosphor bronze, etc.) using a laminating machine. Then, an electric charge is injected into the electret film using a charge injector. The dielectric plate 300 has a semipermanent electric charge, forms an electrostatic field, is connected to the PCB 600 through the conductive base ring 400, and serves as one terminal of the capacitor

[44] The vibrating membrane 270 vibrates in respond to sound pressure of external sound introduced through the sound hole 120 of the case 100, leading to the change of a distance between the dielectric plate 300 and the vibrating membrane, that is, the change of capacitance. The diaphragm 200 is formed by attaching the PET film (the vibrating membrane 270) to the metal plate (i.e., the polar ring 250) formed of gold, bronze, brass, or phosphor bronze. The diaphragm 200 is formed by combining the vibrating membrane 270 and the polar ring 250. Due to the formation of a protrusion 220 in the polar ring 250, the diaphragm 200 can replace a spacer ring. The diaphragm 200 will be described later with reference to FIG. 2. The diaphragm 200 is electrically connected to the PCB 600 through the case 100 and serves as the other terminal of the capacitor.

[45] FIG. 2 is an exploded perspective view of the diaphragm shown in FIG. 1, and FIG.

3 is a rear view of the diaphragm shown in FIG. 2.

[46] Referring to FIGs. 2 and 3, the polar ring 250 has a protrusion 220 defining a space to replace the spacer ring. The protrusion 220 is formed by forging the rear side of the polar ring 250 using a press. More specifically, at least one surface of the polar ring 250 between the inner diameter and the outer diameter of the polar ring 250 extends towards the dielectric plate 300 to form the protrusion 220. That is, as at least one surface of the polar ring 250 disposed on the bottom surface of the case 100 is forged, the other surface of the polar ring 250 extends to form the protrusion 220. A forged width of the protrusion 220 may be similar to a thickness of the spacer ring in order to maintain a distance from the dielectric plate 300. Although the protrusion 220 is formed using a forging process, it can also be formed using a molding process.

[47] The vibrating membrane 270 is disposed on the extended surface of the polar ring

250, that is, the protrusion 220. The vibrating membrane 270 is attached on one surface of the polar ring 250 with the protrusion. Accordingly, the protrusion (220) region and the vibrating membrane (270) region attached thereto are higher than other regions. That is, the vibrating membrane 270 has a recess at its center in order to maintain a predetermined gap between the vibrating membrane 270 and the dielectric plate 300 and ensure a predetermined space for the vibration of the vibrating membrane 270. The dielectric plate 300 and the vibrating membrane 270 are attached to each other. However, the dielectric plate 300 must be insulated from the diaphragm 200 so that they can serve as two terminals of the capacitor. The vibrating membrane 270 may be formed of an insulating material.

[48] FIG. 4 is a sectional assembed view of an electret condenser microphone according to an embodiment of the present invention.

[49] Referring to FIG. 4, a vibrating membrane 270 is attached to a polar ring 250 and is in contact with a dielectric plate 300. The vibrating membrane 270 includes a supporter 275 supporting an electret 350 of the dielectric plate 300 and a vibrator 276 vibrating in response to external sound. A space between the dielectric plate 300 and the vibrator 276 A is defined by a height difference between the supporter 275 and the vibrator 276. Accordingly, the vibrating membrane 270 does not contact the dielectric plate 300 even when it vibrates in response to external sound.

[50] FIGs. 5 and 6 are a front view and a rear view of a polar ring having a rim according to an embodiment of the present invention.

[51] Referring to FIGs. 5 and 6, a rim 220a may be formed extending along the periphery of a polar ring 250. That is, the rim 220a may be formed by extending the polar ring 250 by a predetermined width. The shape of the polar ring 250 may have a polygonal shape, e.g., a hexagonal shape, as well as an oval shape.

[52] FIG. 7 is a perspective view of a polar ring having a rectangular rim according to an embodiment of the present invention, and FIG. 8 is an exploded perspective view of a hexahedral electret condenser microphone including the polar ring shown in FIG. 7.

[53] Referring to FIGs. 7 and 8, a rim 220b of a polar ring 250 may be formed in a rectangular shape. Preferably, a vibrating membrane 270a and the polar ring 250a may be formed in a rectangular shape. Referring to FIG. 8, the electret condenser microphone having a diaphragm 200a includes a hollow case 100a having a rectangular pillar shape, the rectangular diaphragm 200a, a dielectric plate 300a, an insulating base ring 500a, a conductive base ring 400a, and a PCB 600a. Although the insulating base ring 500a, a conductive base ring 400a and a dielectric plate 300a are formed in an oval shape, the present invention is not limited thereto. For example, they can also be formed in various shapes, e.g., a rectangular shape, a hexagonal shape, etc.

[54] In the above-described embodiments of the present invention, the conductive base ring and the insulating base ring are included in the electret condenser microphone as separate components. However, the electret condenser microphone may include an integrated base ring, instead of the two separate base rings. The integrated base ring is provided by forming the conductive and insulating base rings as one body. The electret condenser microphone including the integrated base ring will now be described with reference to FIGs. 9 to 12.

[55] FIG. 9 is an exploded perspective view of an electret condenser microphone including an integrated base ring, with the abscence of the spacer ring, according to an embodiment of the present invention. FIG. 10 is a sectional assembled view of the electret condenser microphone shown in FIG. 9.

[56] Referring to FIGs 9 and 10, an electret condenser microphone includes a diaphragm

200b having a protrusion, an insulating ring 800, a dielectric plate 300b, an integrated base ring 700, and a PCB 600b, which are sequentially stacked in a case 100b. Because the components other than the integrated base ring 700 and the insulating ring 800 are identical to those of FIGs. 1 to 8, their detailed description will be omitted.

[57] The integrated base ring 700 is formed by a PCB fabrication technology, not by a molding. The integrated base ring 700 includes a hollow cylindrical insulating body 750. Upper and lower surfaces of the hollow cylindrical insulating body 750 are metal- plated to form metal-plated layers 770. A conduction pattern is formed on the inner surface of the hollow cylindrical insulating body 750 so that the metal-plated layers 770 are electrically connected to each other. Accordingly, the integrated base ring 700 can serve as both an insulating base ring and a conductive base ring. An insulating body of the integrated base ring 700 is provided with an insulating printed board formed of a glass epoxy based material, a resin based material, or a polyvinyl chloride (PVC) based material.

[58] The dielectric plate 300b is insulated from the case 100b because it is surrounded by an insulating ring 800. The inner diameter of the insulating ring 800 is larger than that of the integrated base ring 700. Accordingly, the dielectric plate 300b may be formed to have an outer diameter larger than the inner diameter of the integrated base ring 700.

[59] In the electret condenser microphone, the protrusion 220c is formed in a polar ring

250b and the diaphragm 200b is formed by placing an insulating vibrating membrane 270b on the protrusion 220c. Alternatively, the diaphragm 200b is formed by attaching the polar ring 250b to the vibrating membrane 270b and then the protrusion 220c is formed. Subsequently, the dielectric plate 300b, the integrated base ring 700, and the PCB 600b are sequentially stacked on the diaphragm 200b. Therefore, the electret condenser microphone can use both the integrated base ring 700 and the diaphragm 200b replacing a spacer ring.

[60] The insulating ring 800 is inserted between the dielectric plate 300b and the case

100b to insulate the dielectric plate 300b from the case 100b. Since the insulating ring 800 replacing the insulating base ring is smaller than the insulating base ring, the size of the dielectric plate 300b can be increased, thereby enhancing its performance. [61] FIG. 11 is an exploded perspective view of another type of an integrated base ring, and FIG. 12 is a sectional assembled view of an electret condenser microphone including the integrated base ring shown in FIG. 11.

[62] Referring to FIGs. 11 and 12, an integrated base ring 700b may have a via hole 730 penetrating into an insulating body 750b and providing a conduction path to a metal- plated layer 770b. Therefore, it is unnecessary to form the metal-plated layers 770b on the upper and lower surfaces of the integrated base ring 700b and the metal-plate layer 770b on an inner surface of the insulating body 750b of the integrated base ring 700b. The via hole 730 is formed by boring a through hole in the insulting body 750 and metal-plating the inner surface of the through hole. Due to the via hole 730, the conduction path is provided between a dielectric plate 300b and the metal-plated layer 770b, without forming the metal-plated layer 770b on the inner surface of the insulating body 750b of the integrated base ring 700b. Therefore, a back chamber space 900 can be enlarged.

[63] FIG. 13 is a flowchart illustrating an assembling method of an electret condenser microphone according to an embodiment of the present invention.

[64] The assembling method of the electret condenser microphone will be described below in detail with reference to FIG. 13.

[65] In step SlOl, a protrusion is formed on a diaphragm.

[66] The protrusion is formed on a polar ring, and a vibrating membrane is attached to the polar ring where the protrusion is formed. Alternatively, a protrusion can be formed after a vibrating membrane is attached to a polar ring. The diaphragm having the protrusion may replace a spacer ring used in the conventional electret condenser microphone.

[67] Meanwhile, in order to form the protrusion on the polar ring, the rear side of the polar ring is forged in a press, so that the other side of the polar ring extends, thereby forming the protrusion. A predetermined space is defined by a height difference between the protrusion and the polar ring. The predetermined space allows the vibrating membrane to vibrate. In order to ensure the predetermined space, a length of a protruding surface extending from an outer diameter to an inner diameter must be smaller than a distance between the outer diameter and the inner diameter of the polar ring. The electret condenser microphone may be manufactured in various shapes, e.g., a circular shape, a rectangular shape or a hexagonal shape according to the characteristic of products where the electret condenser microphones are mounted. Likewise, the vibrating membrane and the polar ring may also be formed in various shapes, e.g., a circular shape, a square shape or a hexagonal shape.

[68] In step S 102, the diaphragm is inserted into a case.

[69] The diaphragm with the protrusion is inserted into the case, such that it is disposed on a sound hole.

[70] In step S 103, a dielectric plate is disposed on the diaphragm.

[71] The dielectric plate is disposed on the diaphragm, without the separate process of inserting the spacer ring.

[72] In step S 104, an insulating base ring and a conductive base ring are inserted.

[73] The insulating base ring is inserted into the outer diameter to insulate the dielectric plate from the case. Also, the conductive base ring is disposed on the dielectric plate to transmit an electric signal of the dielectric plate to the PCB. On the other hand, instead of the conductive base ring and the insulating base ring, the integrated base ring may be used in the assembling process of the present invention. That is, the insulating base ring is formed in a hollow cylindrical or a hollow polygonal shape. Metal-plated layers are formed on the upper and lower surfaces of the insulating base ring, and another metal-plated layer is formed on the inner surface of the insulating base ring or the via hole is formed in the body of the insulating base ring, such that the metal-plated layers serve as the conductive base ring.

[74] Furthermore, to prevent an electrical contact between the case and the metal-plated layer, the outer diameter of the metal-plated layer is smaller than that of the insulating base ring.

[75] In step S 105, the PCB is placed on the conductive base ring.

[76] A circuit pattern of the PCB contacts the conductive base ring. The circuit pattern amplifies the electric signal transmitted from the conductive base ring using a FET of the PCB, filters the electric signal using a MLCC, and outputs the electric signal to an external device.

[77] In step S 106, the opening of the case is curled.

[78] All components of the electret condenser microphone are inserted into the case.

Thereafter, the opening of the case is curled so that electric connections between internal components are tightened.

[79] In the structure of the diaphragm and the assembling method of the electret condenser microphone according to the embodiments of the present invention, the protrusion or the rim is formed on the polar ring so as to replace the spacer ring. However, the present invention can also be changed or modified in various forms in materials and processes.

[80] The diaphragm with the protrusion or rim and the integrated base ring can be applied to a back type electret condenser microphone, a front type electret condenser microphone, and a foil type electret condenser microphone. In the case of the front type electret condenser microphone, the dielectric plate is disposed in front of the diaphragm. In the case of the foil type electret condenser microphone, the electret is formed on the vibrating membrane. Industrial Applicability

[81] In the electret condenser microphone and the assembling method thereof according to the embodiments of the present invention, the spacer ring is replaced by the diaphragm having the protrusion.

[82] The present invention can prevent the tearing of the spacer ring during the insertion process, the generation of burrs on the inner and outer circumferences of the spacer ring, and the non-insertion of the spacer ring or duplicate insertion of the spacer rings, thereby reducing the failure rate of the electret condenser microphone.

[83] The process of inserting the spacer ring into the electret condenser microphone can be omitted by an additional process of forming the protrusion to a backplate manufacturing process. Thus, the manufacturing process of the electret condenser microphone can be simplified.

[84] The integrated base ring forming process is added to the protrusion forming process on the polar ring to replace the spacer ring. The integrated base ring includes the insulating base ring and the conductive base ring. Accordingly, a whole manufacturing process of the microphone can be simplified, thereby enhancing the production yield. In addition, a back chamber space is enlarged, thereby improving the sensitivity and frequency response characteristics of the electret condenser microphone.

[85]

Claims

[1] An electret condenser microphone, comprising: a diaphragm vibrating in response to sound pressure; and a dielectric plate disposed to face the diaphragm, wherein the diaphragm includes a protrusion protruding from at least one side of the diaphragm to a predetermined thickness and contacting the dielectric plate. [2] The electret condenser microphone of claim 1, wherein the diaphragm includes: a polar ring with at least one protrusion; and a vibrating membrane disposed on one side of the polar ring. [3] The electret condenser microphone of claim 2, wherein the protrusion includes at least one side of the polar ring being protruded. [4] The electret condenser microphone of claim 2, wherein the polar ring is formed in a hollow circular shape or a hollow polygonal shape. [5] The electret condenser microphone of any one of claims 1 to 4, further comprising: a case for receiving the dielectric plate and the diaphragm; an insulating base ring for insulating the dielectric plate and the case; a conductive base ring contacting the dielectric plate to provide a conduction path; and a printed circuit board (PCB) for transmitting an electric signal of the dielectric plate to the outside. [6] The electret condenser microphone of claim 5, wherein the insulating base ring and the conductive base ring are integrally formed. [7] The electret condenser microphone of claim 5, wherein the insulating base ring includes at least one of a first metal-plated layer formed on the top and bottom thereof, a second metal-plated layer formed on the inside surface thereof, and a via hole formed in an inside thereof, and the outer diameter of the first metal- plated layer is smaller than that of the insulating base ring. [8] A method of assembling an electret condenser microphone, comprising the step of: forming a protrusion on a diaphragm; inserting the diaphragm in a case; disposing a dielectric plate on the top of the diaphragm; inserting an insulating base ring and a conductive base ring in the case; disposing a PCB on the top of the conductive base ring; and curling the case at an opening thereof. [9] The method of claim 8, wherein the step of forming the protrusion comprises the steps of: forging at least one side of a polar ring to form the protrusion; and diposing a vibrating membrane on the side on which the protrusion is formed. [10] The method of claim 8, wherein the step of forming the protrusion comprises the steps of: disposing a vibrating membrane on one side of a polar ring; and forming the protrusion towards the disposed vibrating membrane. [11] The method of any one of claims 8 to 10, wherein the diaphragm is formed in at least one of an oval shape and a polygonal shape including a rectangular shape and a hexagonal shape. [12] The method of any one of claims 8 to 10, wherein the conductive base ring and the insulating base ring are integrally formed into an integrated base ring.