WO2007024047A1

WO2007024047A1 - Electret condenser microphone

Info

Publication number: WO2007024047A1
Application number: PCT/KR2006/000387
Authority: WO
Inventors: Chung-Dam Song
Original assignee: BSE Co Ltd
Current assignee: BSE Co Ltd
Priority date: 2005-08-20
Filing date: 2006-02-03
Publication date: 2007-03-01
Anticipated expiration: 2008-02-20
Also published as: CN1917720A; CN1917720B; KR100632694B1

Abstract

Disclosed is an electret condenser microphone comprising: a case which is formed with a sound hole on a bottom surface thereof; an insulating base which is mounted in the case to contact the bottom surface of the case; a vibration plate which is electrically connected with the bottom surface of the case and is vibrated according to a sound pressure inputted through the sound hole; a spacer to form a gap; a back plate which faces the vibration plate with the spacer interposed therebetween, the back plate having an electret which is formed by adhering a high molecular film to an external side of a metal plate; a conductive base conducting the back plate and allowing the supporting part to support a PCB in a curling process; and the PCB whereby the conductive base supports the PCB when curling an opened end of the case after inserting the parts into the case.

Description

Description ELECTRET CONDENSER MICROPHONE

Technical Field

[1] The present invention relates to an electret condenser microphone, and, more particularly, to an electret condenser microphone for preventing deformation of parts upon a curling process and enhancing a high temperature characteristic. Background Art

[2] A typical condenser microphone consists of a voltage bias element which is generally made of electret, a pair of a vibration membrane and a back plate for forming a capacitor which is changed corresponding to a sound pressure, and a JFET for buffering an output signal. Here, the electret condenser microphone is formed with an electret on any one of the vibration membrane and the back plate thereof, wherein an electret which is formed on the vibration membrane is called a front electret, and an electret which is formed on the back plate is called a back electret. Generally, the electret is formed by forcibly applying electric charges into an organic film.

[3] Fig. 1 is a sectional side view of a condenser microphone assembly using a conventional case. The conventional microphone assembly has a case 10 which is formed with a sound hole 10c on a bottom surface thereof. The case 10 is provided with a vibration plate 12 which is consisted of a vibration membrane 12a and a polar ring 12b, a spacer 13, an insulating base 14, a back plate 15, a conductive base 16 and a PCB 18 therein. An opened end 10b of the case 10 is curled on the PCB 18.

[4] At this time, the conductive base 16 serves not only to transfer an electric signal generated from a microphone unit (that is, the vibration/back plate electret) to a JFET, an amplifier or elements having an amplifier and an AD converter, but also to mechanically fix parts inserted into the case.

[5] Further, since the conductive base 16 is higher than the insulating base 16, the PCB

18 presses the conductive base 16 if curling the case 10.

[6] However, according to the conventional microphone, in a curling process for rolling and bending the opened end of the case 10 on the PCB 18 while pressing toward the PCB 18, there happens a problem that an acoustic characteristic is deteriorated since a force for supporting the PCB 18 through the base is poor, the PCB 18 is bent due to tolerances of parts or parts within the case are deformed. Disclosure of Invention Technical Problem

[7] Accordingly, in order to solve the above problem, an object of the present invention is to provide a condenser microphone for enhancing a temperature characteristic by allowing an insulation base to surround a pair of a vibration plate and a back plate and for preventing the deformation of parts by allowing a conductive base having a broad supporting surface which is formed by a shape of "D" to support the PCB upon a curling process.

Technical Solution

[8] Further, according to one aspect of the present invention, there is provided an electret condenser microphone comprising: a case which is formed with a sound hole on a bottom surface thereof; an insulating base which is mounted in the case to contact the bottom surface of the case for electrically insulating the case and parts within the case; a vibration plate which is mounted within the insulating base and is electrically connected with the bottom surface of the case and is vibrated according to a sound pressure inputted through the sound hole; a spacer which is mounted within the insulating base to form a gap; a back plate which is mounted within the insulating base and faces the vibration plate with the spacer interposed therebetween, the back plate having an electret which is formed by adhering a high molecular film to an external side of a metal plate; a conductive base including a cylindrical body having both sides which are opened and a supporting part having a broad supporting area by allowing an upper surface of the body to be projected to the outside, thereby conducting the back plate and allowing the supporting part to support a PCB in a curling process; and the PCB which is mounted with circuit parts and is supported by the conductive base to form a back chamber inside of the case together with the back plate, whereby the conductive base supports the PCB when curling an opened end of the case after inserting the parts into the case. Brief Description of the Drawings

[9] The above and other objects and features of the invention will become apparent from the following description of preferred embodiments taken in conjunction with the accompanying drawings, in which:

[10] Fig. 1 is a sectional side view of a conventional condenser microphone assembly;

[11] Fig. 2 is a view showing to explain a spirit of the present invention;

[12] Fig. 3 is a sectional view showing a conductive base of a condenser microphone according to the present invention;

[13] Fig. 4 is a sectional side view of a condenser microphone assembly according to the present invention;

[14] Fig. 5 is a sectional side view of a condenser microphone assembly having projecting terminals according to the present invention;

[15] Fig. 6 is an external view of a condenser microphone assembly shown in Fig. 5;

[16] Fig. 7 is a sectional side view of another embodiment according to the present invention; and

[17] Fig. 8 is a flow diagram for assembling a condenser microphone according to the present invention. Best Mode for Carrying Out the Invention

[18] Hereinafter, preferred embodiments of the present invention will be explained in detail with reference to the appended drawings.

[19] Fig. 2 is a view showing to explain a spirit of the present invention. A first enlarged drawing within a circle conceptually shows that a PCB 18 within a conventional condenser microphone is bent upon a curling process. Then, a second enlarged drawing within a circle conceptually shows that a PCB 114 is prevented from being bent by allowing a conductive base 112 having a shape of "D" to support the PCB 114 upon a curling process according to the present invention.

[20] Referring to Fig. 2, since a conventional conductive base 16 which supports the

PCB 18, as shown in the first enlarged drawing, has a linear upper end portion, an end surface area for supporting the PCB 18 is narrow, whereby an end of the PCB 18 is bent inward by a pressing force in the curling process of folding an opened end 10b of the case and bending toward the PCB 18. As a result, an acoustic path is changed, whereby a sound quality is deteriorated. Further, the parts which are mounted within the case are damaged. However, according to the present invention, as shown in the second enlarged drawing, an upper supporting surface which contacts a surface of a PCB 114 is projected outwardly in a shape of "D", thereby broadly supporting the surface of PCB 114 upon curling an opened end 102b of the case. As a result, the PCB 114 is prevented from being bent.

[21] Fig. 3 is a sectional view showing a conductive base of a condenser microphone ac cording to the present invention.

[22] The conductive base 112, as shown in Fig. 3, includes a body 112a which has a cylindrical shape having both sides which are opened, and a supporting part 112b which forms a broad flat area for supporting the PCB 114 by projecting an upper surface of the body 112a outwardly to has a left sectional shape of "D" and a right sectional shape of " p" As such, according to the conductive base 112 of the present invention, the supporting part 112b for supporting the PCB 114 is broadly expanded compared with the body 112a, thereby enlarging a supporting area in the curling process and thus preventing the PCB 114 from being bent.

[23] Fig. 4 is a sectional side view of an electret condenser microphone assembly according to the present invention.

[24] A condenser microphone which is assembled using the inventive conductive base

112, as shown in Fig. 4, has a structure for inserting the insulating base 110 into the hollow case 102 having an opened side and a bottom side which is formed with the sound hole 102a, inserting a vibration plate 104 having a polar ring 104a and a vibration membrane 104b to be served as a movable electrode, a spacer 106 for forming a gap, a back plate 108 which is formed with a sound hole 108a and is served as a fixing electrode, and a conductive base 112 for providing a conductive function to the back plate 108 into the insulating base 110, and then curling the opened end 102b of the case after inserting the PCB 114 which is mounted with parts. At this time, the back plate 108 is formed with an electret by pressing an organic film 108b on a metal plate 108b and forcibly injecting electric charges to the organic film 108b.

[25] The insulating base 110, as shown in Fig. 4, is longer than the conventional base to reach a bottom surface of the case 102. The vibration plate 104 faces the back plate 108 with the spacer 106 interposed between the vibration plate 104 and the back plate 108 in the insulating base 110. As such, according to the electret condenser microphone 100 of the present invention, the insulating base 110 surrounds the vibration plate 104 and the back electret, thereby protecting the electret upon the reflow process in a high temperature for a SMT. The insulating base 110, preferably, is made of a material having thermal resistance and tolerance such as fluoroplastic series, polymer series or plastic series.

[26] Fig. 5 is a sectional side view of a condenser microphone assembly having projecting terminals according to the present invention. When comparing with the structure in Fig. 4, the projecting terminals 114a and 114b are projected from an exposed surface of the PCB 114 higher than the curled surface 102b

[27] Referring to Fig. 5, the connecting terminals 114a and 114b which is projected from the exposed surface of the PCB 114 higher than the curled surface 102b of the case 102 allows the microphone 100 to be bonded to another PCB (for example, PCB of a mobile phone) in the SMD process. The connecting terminals 114a and 114b, as shown in Fig. 6, are consisted of the circular terminal 114a for a Vdd connection which is positioned inside of the PCB 114 and the circular ground terminal 114b which is spaced from the terminal 114a to the outside. Although there is not shown in the drawing, if necessary, the ground terminal 114b may be separated by a gas discharging recess to discharge a gas generated when bonding in the SMD process.

[28] According to the condenser microphone 100 of the present invention, if air is flown through the sound hole 102a of the case 102 into the microphone by an external sound wave, the vibration membrane 104b is vibrated by a sound pressure and then the air is flown through through-holes 108a of the back plate 108 into a back chamber which is formed between the PCB 114 and the back plate.108. At this time, if the vibration membrane 104b is vibrated by the sound pressure which is applied through the sound hole 102a, a gap between the vibration membrane 104b and the back plate 108 is changed. Then, if the gap is changed by the sound pressure, electrostatic capacity which is formed by the vibration plate 104b and the back plate 108 is changed, thereby obtaining a change of an electrical signal (that is, voltage) according to the sound wave. Then, the electrical signal is transferred to an IC, for example, JFET and so on which are mounted on the PCB 114, and then is amplified. Finally, the amplified signal is transferred through a connecting terminal (not shown) to the outside.

[29] Fig. 7 is a sectional side view of another embodiment according to the present invention, wherein the position of the vibration plate 104 and the back plate 108 within the insulating base 110 is reversed with the spacer interposed between them when comparing with the structure in Fig. 4.

[30] The insulating base 110, as shown in Fig. 7, is longer than the conventional base to reach a bottom surface of the case 102. The vibration plate 104 faces the back plate 108 with the spacer 106 interposed between the vibration plate 104 and the back plate 108 in the insulating base 110.

[31] As such, according to the electret condenser microphone 100' of the present invention, the insulating base 110 surrounds the electret, thereby protecting the electret upon the reflow process in a high temperature for a SMT. The insulating base, preferably, is made of a material having thermal resistance and tolerance such as fluo- roplastic series, polymer series or plastic series.

[32] Fig. 8 is a flow diagram for assembling a condenser microphone according to the present invention.

[33] Referring to Fig. 8, an assembling process according to the present invention including the steps of preparing the case 102 (Sl), inserting the insulating base 110 into the case 102 (S2), inserting the vibration plate 104, the spacer 106 and the back plate 108 in turn into the insulating base 110 in case of a first structure shown in Fig.4 or inserting the back plate 108, the spacer 106, and the vibration plate 104 in turn into the insulating base 110 in case of a second structure shown in Fig. 7 (S6 to S8), inserting a T typed metal base (that is, conductive base 112) (S9), inserting the PCB 114 (SlO), and curling the case 102 (SI l). Industrial Applicability

[34] From the foregoing, according to the condenser microphone of the present invention, there is provided the microphone for allowing the conductive base having the wide supporting surface to broadly support the PCB in the process for curling the opened end of the case, thereby preventing the PCB from being bent or preventing the other parts to be deformed due to a stress on the other parts and thus providing a superior acoustic characteristic.

[35] Further, according to the electret condenser microphone of the present invention, the insulating base surrounds the pair of the vibration plate and the back plate, thereby preventing the electret characteristic from being deteriorated upon the reflow process in a high temperature.

[36] While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the present invention is not limited to the disclosed embodiment, but, on the contrary, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

[1] An electret condenser microphone comprising: a case which is formed with a sound hole on a bottom surface thereof; an insulating base which is mounted in the case to contact the bottom surface of the case for electrically insulating the case and parts within the case; a vibration plate which is mounted within the insulating base and is electrically connected with the bottom surface of the case and is vibrated according to a sound pressure inputted through the sound hole; a spacer which is mounted within the insulating base to form a gap; a back plate which is mounted within the insulating base and faces the vibration plate with the spacer interposed therebetween, the back plate having an electret which is formed by adhering a high molecular film to an external side of a metal plate; a conductive base including a cylindrical body having both sides which are opened and a supporting part having a broad supporting area by allowing an upper surface of the body to be projected to the outside, thereby conducting the back plate and allowing the supporting part to support a PCB in a curling process; and the PCB which is mounted with circuit parts and is supported by the conductive base to form a back chamber inside of the case together with the back plate, whereby the conductive base supports the PCB when curling an opened end of the case after inserting the parts into the case.

[2] An electret condenser microphone comprising: a case which is formed with a sound hole on a bottom surface thereof; an insulating base which is mounted in the case to contact the bottom surface of the case for electrically insulating the case and parts within the case; a back plate which is mounted within the insulating base and has an electret which is formed by adhering a high molecular film to an external side of a metal plate, the back plate being formed with a sound hole; a spacer which is mounted within the insulating base to form a gap; a vibration plate which is mounted within the insulating base and faces the back plate with the spacer interposed between the vibration plate and the back plate, the vibration plate being vibrated according to a sound pressure inputted through the sound hole; a conductive base including a cylindrical body having both sides which are opened and a supporting part having a broad supporting area by allowing an upper surface of the body to be projected to the outside, thereby conducting the vibration plate and allowing the supporting part to support a PCB in a curling process; and the PCB which is mounted with circuit parts and is supported by the conductive base to form a back chamber inside of the case together with the vibration plate, whereby the conductive base supports the PCB when curling an opened end of the case after inserting the parts into the case.

[3] The electret condenser microphone according to claim 1 or 2, wherein the conductive base has any one of a cylinderical shape and a rectangular parallelepiped shape.

[4] The electret condenser microphone according to claim 1 or 2, wherein the PCB has connecting terminals projected from an exposed surface thereof to connect with an external device.