Abstract:
Disclosed herein is a microphone including: a membrane; a fixed electrode part positioned at the outside of the membrane; and an elastic support part connecting the membrane and the fixed electrode part to each other so as to enable displacement of the membrane, wherein one surface of the membrane and one surface of the fixed electrode part facing each other are formed with conductive parts, respectively.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2013-0116383, filed on Sep. 30, 2013, entitled “Microphone”, and of Korean Patent Application No. 10-2013-0126091, filed on Oct. 22, 2013, entitled “Microphone” which are hereby incorporated by reference in its entirety into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a microphone. 
         [0004]    2. Description of the Related Art 
         [0005]    As portable electronic products are increased, an electrostatic microphone manufactured by a micro electro mechanical systems (MEMS) process has been widely used. 
         [0006]    More specifically, a microphone according to the prior art including the Prior Art Document is configured of a membrane, a back plate, a packaging structure, an application specific integrated circuit (ASIC), and other portions supporting the structure. 
         [0007]    In addition, the back plate and the membrane are installed so as to have a predetermined distance therebetween, and when a voltage potential is applied to the microphone, the microphone is charged with electric charges, thereby having capacitance. 
         [0008]    In addition, when a sound wave is transferred to the membrane, the membrane is deformed by pressure of the sound wave, which changes the distance between the membrane and the back plate and causes a change ΔC in a capacitance value. ΔC is electrically measured, such that the sound wave is converted into an electric signal. 
         [0009]    As described above, as the microphone according to the prior art is implemented in a manner in which the sound wave is converted into the electric signal by ΔC generated by a change in the distance between the membrane and the back plate, the microphone is structurally complicated, and ΔC is not linearly changed, such that reliability may be deteriorated. 
         [0010]    In addition, as the microphone according to the prior art is implemented in a manner in which the sound wave is converted into the electric signal due to ΔC generated by a change in the distance between the membrane and the back plate, the microphone is structurally complicated, and ΔC is not linearly changed, such that there are problems in that reliability may be deteriorated and it is impossible to implement an accurate microphone. 
       PRIOR ART DOCUMENT 
     Patent Document 
       [0011]    (Patent Document 1) U.S. Pat. No. 6,535,460 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention has been made in an effort to provide a microphone capable of more accurately converting a sound wave into an electric signal by detecting a change value of capacitance due to a change in an area of an overlapped portion between a fixed electrode part positioned in a direction perpendicular to a displacement direction of a membrane and the membrane. 
         [0013]    In addition, the present invention has been made in an effort to provide a microphone capable of being implemented without a back plate to thereby decrease a production cost, not having air-resistance or air damping by the back plate to thereby obtain high sensitivity, and linearly reacting to a sound pressure and having a simple structure to thereby have improved productivity and product reliability. 
         [0014]    Further, the present invention has been made in an effort to provide a microphone capable of more accurately converting a sound wave into an electric signal by detecting a change value of capacitance due to a change in an area of an overlapped portion between a fixed electrode part positioned in a direction perpendicular to a displacement direction of a membrane and the membrane. 
         [0015]    Furthermore, the present invention has been made in an effort to provide a microphone capable of being more accurately implemented by simultaneously detecting a change value of an area of an overlapped portion between a membrane and a fixed electrode part and a distance displacement between the membrane and a black plate, calculating a change value of the capacitance using the detected value, and converting a sound wave into an electric signal through the change value of the capacitance. 
         [0016]    According to a preferred embodiment of the present invention, there is provided a microphone including: a membrane; a fixed electrode part positioned at the outside of the membrane; and an elastic support part connecting the membrane and the fixed electrode part to each other so as to enable displacement of the membrane, wherein one surface of the membrane and one surface of the fixed electrode part facing each other are formed with conductive parts, respectively. 
         [0017]    The fixed electrode part may be positioned so as to be spaced apart from the membrane in a direction orthogonal to a displacement direction of the membrane. 
         [0018]    A side wall part may be formed at an end portion of the membrane in a direction orthogonal to a displacement direction of the membrane and a conductive part may be formed on the side wall part so as to face the fixed electrode part. 
         [0019]    The membrane may be formed of a thin film, and the side wall part is formed so as to protrude in the displacement direction of the membrane. 
         [0020]    A conductive part may be formed on the fixed electrode part so as to face the conductive part formed on the side wall part of the membrane. 
         [0021]    An end portion of the conductive part formed on the side wall part of the membrane may be positioned at the center of the conductive part of the fixed electrode part in the displacement direction of the membrane. 
         [0022]    The elastic support part may connect the membrane and the fixed electrode part to each other in a direction orthogonal to a displacement direction of the membrane. 
         [0023]    A plurality of elastic support parts may connect the membrane and the fixed electrode part to each other at equidistance. 
         [0024]    The microphone may further include a support part coupled to the fixed electrode part so as to support the fixed electrode part in the displacement direction of the membrane. 
         [0025]    According to another preferred embodiment of the present invention, there is provided a microphone including: a membrane; a fixed electrode part spaced apart from the membrane in a direction orthogonal to a displacement direction of the membrane; and an elastic support part connecting the membrane and the fixed electrode part so as to enable displacement of the membrane, wherein one surface of the membrane and one surface of the fixed electrode part facing each other are formed with conductive parts, respectively, a side wall part is formed at an end portion of the membrane in the direction orthogonal to the displacement direction of the membrane, a conductive part is formed on the side wall part so as to face the fixed electrode part, a plurality of protrusion parts protruding toward the fixed electrode part are formed at the side wall part of the membrane, and a groove part corresponding to the protrusion part is formed at the fixed electrode part. 
         [0026]    Conductive parts facing each other may be formed at the protrusion part of the side wall part and the groove part of the fixed electrode part. 
         [0027]    According to another preferred embodiment of the present invention, there is provided a microphone including: a membrane; a fixed electrode part positioned at the outside of the membrane; and a support member coupled to a central portion of the membrane so as to enable displacement of the membrane at both sides thereof, wherein one surface of the membrane and one surface of the fixed electrode part facing each other are formed with conductive parts, respectively. 
         [0028]    The fixed electrode part may be positioned so as to be spaced apart from the membrane in a direction orthogonal to a displacement direction of the membrane. 
         [0029]    The membrane may include a center part to which the support member is coupled, and one side part and the other side part formed so as to be symmetrical to each other at both sides of the center part. 
         [0030]    Shapes of one side part and the other side part may be symmetrical to each other. 
         [0031]    A side wall part may be formed at an end portion of the membrane in a direction orthogonal to a displacement direction of the membrane, and a conductive part may be formed on the side wall part so as to face the fixed electrode part. 
         [0032]    The membrane may be formed of a thin film, and the side wall part may be formed so as to protrude in the displacement direction of the membrane. 
         [0033]    A conductive part may be formed on the fixed electrode part so as to face the conductive part formed on the side wall part of the membrane. 
         [0034]    An end portion of the side wall part of the membrane on which the conductive part is formed may be positioned at the center of the conductive part of the fixed electrode part in the displacement direction of the membrane. 
         [0035]    The support member may include: a center fixing part formed so as to correspond to the center part of the membrane; and a frame part fixedly coupled to the fixed electrode part. 
         [0036]    The microphone may further include a support part coupled to the fixed electrode part so as to support the fixed electrode part in a displacement direction of the membrane. 
         [0037]    According to another preferred embodiment of the present invention, there is provided a microphone including: a membrane; a fixed electrode part spaced apart from the membrane in a direction orthogonal to a displacement direction of the membrane; and a support member coupled to a central portion of the membrane so as to enable displacement of the membrane at both sides thereof, wherein one surface of the membrane and one surface of the fixed electrode part facing each other are formed with conductive parts, respectively, a side wall part is formed at an end portion of the membrane in the direction orthogonal to the displacement direction, a conductive part is formed on the side wall part, a plurality of protrusion parts protruding toward the fixed electrode part are formed at the side wall part of the membrane, and a groove part corresponding to the protrusion part is formed at the fixed electrode part. 
         [0038]    Conductive parts may be formed on the protrusion part of the side wall part and the groove part of the fixed electrode part so as to face each other. 
         [0039]    According to another preferred embodiment of the present invention, there is provided a microphone including: a membrane; a fixed electrode part positioned at the outside of the membrane; a back plate positioned at the outside of the membrane; and a support member coupled to a central portion of the membrane so as to enable displacement at both sides of the membrane, wherein one surface of the membrane and one surface of the fixed electrode part facing each other are formed with conductive parts, respectively, and one surface of the membrane and one surface of the back plate facing each other are formed with conductive parts, respectively. 
         [0040]    The fixed electrode part may be positioned so as to be spaced apart from the membrane in a direction orthogonal to a displacement direction of the membrane. 
         [0041]    The back plate may be positioned so as to be spaced apart from the membrane in a displacement direction of the membrane. 
         [0042]    The membrane may include a center part to which the support member is coupled, and one side part and the other side part formed so as to be symmetrical to each other at both sides of the center part. 
         [0043]    A side wall part may be formed at an end portion of the membrane in a direction orthogonal to a displacement direction of the membrane, and a first conductive part may be formed on the side wall part so as to face the fixed electrode part. 
         [0044]    The membrane may be formed of a thin film, and the side wall part may be formed so as to protrude in the displacement direction of the membrane. 
         [0045]    A conductive part may be formed on the fixed electrode part so as to face the first conductive part formed on the side wall part of the membrane. 
         [0046]    An end portion of the side wall part of the membrane on which the conductive part is formed may be positioned at the center of the conductive part of the fixed electrode part in the displacement direction of the membrane. 
         [0047]    The membrane may include a second conductive part formed so as to face the back plate in a displacement direction, and the back plate is positioned below the membrane and includes a conductive part formed so as to face the second conductive part. 
         [0048]    The back plate may include a hole formed for a flow of a sound wave and a stopper formed at one surface thereof facing the membrane. 
         [0049]    The support member may include: a center fixing part formed so as to correspond to a center part of the membrane; and a frame part fixedly coupled to the fixed electrode part. 
         [0050]    The microphone may include a support part coupled to the fixed electrode part so as to support the fixed electrode part in a displacement direction of the membrane. 
         [0051]    According to another preferred embodiment of the present invention, there is provided a microphone include: a membrane; a fixed electrode part positioned at the outside of the membrane; a back plate positioned at the outside of the membrane; and a support member coupled to a central portion of the membrane so as to enable displacement at both sides of the membrane, wherein one surface of the membrane and one surface of the fixed electrode part facing each other are formed with conductive parts, respectively, one surface of the membrane and one surface of the back plate facing each other are formed with conductive parts, respectively, the membrane includes a plurality of protrusion parts protruding toward the fixed electrode part, and the fixed electrode part includes a groove part formed therein so as to correspond to the protrusion part. 
         [0052]    The protrusion part of the membrane and the groove parts of the fixed electrode parts may be formed with conductive parts facing each other. 
         [0053]    The fixed electrode part may be positioned so as to be spaced apart from the membrane in a direction orthogonal to a displacement direction of the membrane, and the back plate may be positioned so as to be spaced apart from the membrane in the displacement direction of the membrane. 
         [0054]    The membrane may include a center part to which the support member is coupled, and one side part and the other side part formed so as to be symmetrical to each other at both sides of the center part. 
         [0055]    A side wall part protruding in a displacement direction of the membrane may be formed at an end portion of the membrane in a direction orthogonal to the displacement direction of the membrane, and a first conductive part may be formed on the side wall part so as to face the fixed electrode part. 
         [0056]    The membrane may include a second conductive part formed so as to face the back plate in a displacement direction, and the back plate may be positioned below the membrane and includes a conductive part formed so as to face the second conductive part. 
         [0057]    The support member may include: a center fixing part formed so as to correspond to a center part of the membrane; and a frame part fixedly coupled to the fixed electrode part. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0058]    The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0059]      FIG. 1  is a perspective view schematically showing a microphone according to a first preferred embodiment of the present invention; 
           [0060]      FIG. 2  is a schematic plan view of the microphone shown in  FIG. 1 ; 
           [0061]      FIG. 3  is a cross-sectional view showing the microphone taken along line A-A of  FIG. 1 ; 
           [0062]      FIG. 4  is a schematic cross-sectional view showing the microphone taken along line B-B of  FIG. 1 ; 
           [0063]      FIG. 5  is a view of a usage state of the microphone shown in  FIG. 1 ; 
           [0064]      FIG. 6  is a plan view schematically showing a microphone according to a second preferred embodiment of the present invention; 
           [0065]      FIG. 7  is a perspective view schematically showing a microphone according to a third preferred embodiment of the present invention; 
           [0066]      FIG. 8  is a schematic plan view of the microphone shown in  FIG. 7 ; 
           [0067]      FIG. 9  is a cross-sectional view showing the microphone taken along line A-A of  FIG. 7 ; 
           [0068]      FIG. 10  is a view of schematically showing a use state of the microphone shown in FIG.  7 ; 
           [0069]      FIG. 11  is a plan view schematically showing a microphone according to a fourth preferred embodiment of the present invention; 
           [0070]      FIG. 12  is a perspective view schematically showing a microphone according to a fifth preferred embodiment of the present invention; 
           [0071]      FIG. 13  is a schematic plan view of the microphone shown in  FIG. 12 ; 
           [0072]      FIG. 14  is a cross-sectional view showing the microphone taken along line A-A of  FIG. 12 ; 
           [0073]      FIG. 15  is a view of a usage state of the microphone shown in  FIG. 12 ; 
           [0074]      FIG. 16  is a plan view schematically showing a microphone according to a sixth preferred embodiment of the present invention; and 
           [0075]      FIG. 17  is a cross-sectional view showing the microphone taken along line A-A of  FIG. 16 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0076]    The objects, features and advantages of the present invention will be more clearly understood from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant descriptions thereof are omitted. Further, in the following description, the terms “first”, “second”, “one side”, “the other side” and the like are used to differentiate a certain component from other components, but the configuration of such components should not be construed to be limited by the terms. Further, in the description of the present invention, when it is determined that the detailed description of the related art would obscure the gist of the present invention, the description thereof will be omitted. 
         [0077]    Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. 
         [0078]      FIG. 1  is a perspective view schematically showing a microphone according to a first preferred embodiment of the present invention. As shown in  FIG. 1 , the microphone  100  includes a membrane  110 , a fixed electrode part  120 , an elastic support part  130 , and a support part  140 . 
         [0079]    In addition, when a sound wave is applied to the microphone  100  from the outside, displacement is generated in a state in which the membrane  110  is elastically supported by the elastic support part  130 , and a change in capacitance with respect to an overlapped surface of the fixed electrode part  120  and the membrane  110  by the displacement is detected, such that the sound wave is converted into an electric signal. 
         [0080]    Detailed technical configurations of the microphone according to the preferred embodiment of the present invention and systematic coupling between constituent components will be described in detail with reference to  FIGS. 2 to 4 . 
         [0081]      FIG. 2  is a schematic plan view of the microphone shown in  FIG. 1 ,  FIG. 3  is a schematic cross-sectional view showing the microphone taken along line A-A of  FIG. 1 , and  FIG. 4  is a schematic cross-sectional view showing the microphone taken along line B-B of  FIG. 1 . 
         [0082]    More specifically, the membrane  110 , which is to be displaced by the sound wave, may be formed of a thin film in a disk shape. 
         [0083]    In addition, the membrane  110  may have conductivity and be formed so that a conductive part is formed on at least some thereof. That is, the conductive part may be formed on one surface of the membrane  110  facing the fixed electrode part  120  in order to detect the change in capacitance generated at the surface facing the fixed electrode part  120 . 
         [0084]    To this end, an end portion of the membrane  110  in a direction perpendicular to a displacement direction is formed with a side wall part  111  facing the fixed electrode part. 
         [0085]    In addition, as the membrane is formed in the disk shape, the side wall part  111  may be formed in a circumferential direction at an end portion in a radical direction, and a conductive part  111   a  may be formed on the side wall part  111 . As a result, the side wall part  111  is to secure a forming region of the conductive part  111   a  for detecting the displacement of the membrane. 
         [0086]    In addition, as the membrane  110  is formed of the thin film, the side wall part  111  may be formed at the end portion of the membrane  110  so as to erect, that is, protrude in the displacement direction of the membrane  110 . 
         [0087]    Further, the conductive part  111   a  is formed on the side wall part  111  so as to face the fixed electrode part  120 . 
         [0088]    Next, the fixed electrode part  120 , which is to form ΔC with a change in an area of an overlapped portion between the fixed electrode part  120  and the membrane  110 , is positioned at an outer peripheral portion of the membrane  110 . In addition, the fixed electrode part  120  may be positioned so as to be spaced apart from the membrane in the direction orthogonal to the displacement direction of the membrane  110 . 
         [0089]    Further, the fixed electrode part  120  may be disposed to be spaced apart from the membrane  110  so as to have a predetermined gap g therebetween. The reason is to allow strong wind or low frequency flow to be discharged through the gap between the membrane  110  and the fixed electrode part  120  to thereby prevent the deformation of the membrane and allow the membrane  110  to be freely displaced by the sound wave in a vertical direction. 
         [0090]    In addition, a conductive part  121  is formed on the fixed electrode part  120  so as to face the conductive part  111   a  of the membrane. 
         [0091]    Further, as shown in an enlarged view of  FIG. 4 , an end portion of the conductive part  111   a  of the membrane  110  may be formed so as to be positioned at the center of the conductive part  121  of the fixed electrode part  120  in a vibration direction of the membrane  110 . 
         [0092]    That is, in the displacement direction of the membrane  110 , when a length of the conductive part  111   a  of the membrane  110  is defined as Lm and a length of the conductive part  121  of the fixed electrode part  120  is defined as Lb, the end portion of the conductive part  111   a  is positioned at a portion corresponding to Lb×½, which is the center of the conductive part  121 , and a distance at which the membrane  110  may be maximally moved by the sound pressure becomes Lb×½. 
         [0093]    Next, the elastic support part  130  connects the membrane  110  and the fixed electrode part  120  to each other and allows the membrane  110  to be elastically supported by the fixed electrode part  120 . In addition, the elastic support part  130  may have a structure in which a groove is formed in a diaphragm plate. 
         [0094]    Further, the elastic support part  130  connects the membrane  110  and the fixed electrode part  120  to each other in the direction orthogonal to the displacement direction of the membrane  110 . 
         [0095]    To this end, one end of the elastic support part  130  is coupled to the side wall part  111  of the membrane  110 , and the other end of the elastic support part  130  is coupled to one surface of the fixed electrode part facing the side wall part  111 . 
         [0096]    In addition, as an example, the case in which four elastic support parts  130  are provided is shown in  FIG. 2 , and a plurality of elastic support parts may be variously formed at equidistance. 
         [0097]    Next, the support part  140  supports the fixed electrode part  120 . In addition, the support part  140  may be coupled to a lower portion of the fixed electrode part  120  in the displacement direction of the membrane. Further, the support part  140  may be formed of a silicon substrate. 
         [0098]      FIG. 5  is a view of a usage state of the microphone shown in  FIG. 1 . As shown in  FIG. 5 , in the case in which a sound wave (SW) is applied to the membrane  110  from the outside, displacement is generated therein. 
         [0099]    That is, the membrane  110  is displaced by the SW and elastically supported by the elastic support part  130 , such that a vibration property may be improved, and recovering force may be provided. 
         [0100]    In addition, in the case in which displacement of the membrane  110  is generated, the area of the overlapped portion between the conductive part  111   a  of the membrane  110  and the conductive part  121  of the fixed electrode part  120  is changed, such that capacitance is changed, thereby generating ΔC. 
         [0101]    That is, capacitance C is defined as follows. 
         [0000]    
       
      
       C=εr·εA/g  
      
     
         [0102]    (Where, εr=permittivity, ε=electric constant, A=area of overlapped portion, and g=distance between the membrane and the fixed electrode part.) 
         [0103]    In addition, as described above, as the capacitance C is changed according to the change in the area A of the overlapped portion between the conductive part  111   a  of the membrane  110  and the conductive part  121  of the fixed electrode part  120 , ΔC is obtained, such that the sound wave may be converted into the electric signal through the ΔC. 
         [0104]    Meanwhile, in the case of calculating ΔC through the change in g, which is the distance between the membrane  110  and the fixed electrode part  120 , ΔC is not linearly changed, but linearly changed according to the change in A. 
         [0105]    Therefore, in the microphone  100  according to the preferred embodiment of the present invention, as ΔC is detected through the change in the area of the overlapped portion between the conductive part  111   a  of the membrane  110  and the conductive part  121  of the fixed electrode part  120 , the sound wave may be more accurately converted into the electric signal. 
         [0106]      FIG. 6  is a plan view schematically showing a microphone according to a second preferred embodiment of the present invention. As shown in  FIG. 6 , in the microphone  200 , only shapes of a membrane and a fixed electrode part are different from those of the microphone  100  according to the first preferred embodiment of the present invention as shown in  FIG. 2 . 
         [0107]    More specifically, the microphone  200  includes a membrane  210 , a fixed electrode part  220 , an elastic support part  230 , and a support part (not shown). 
         [0108]    In addition, an end portion of the membrane  210  is provided with a side wall part  211  in a direction orthogonal to a displacement direction. In addition, as the membrane  210  has a disk shape, an end portion thereof in a radial direction is provided with the side wall part  211  in a circumferential direction. 
         [0109]    Further, a plurality of protrusion parts  211   a  protruding toward the fixed electrode part are formed at the side wall part  211  at equidistance, and one surface of the side wall part  211  including the protrusion part  211   a  facing the fixed electrode part  220  may be formed with a conductive part  211   b.    
         [0110]    Further, the protrusion part  211   a  is to further increase a formation area of the conductive part and maximize the area of the overlapped portion with the conductive part of the fixed electrode part facing the conductive part to thereby maximize the change in capacitance. In addition, although a square shaped protrusion part is shown by way of example in  FIG. 6 , the present invention is not limited thereto, but the protrusion part may be implemented in various shapes such as a semi-circular shape, or the like. 
         [0111]    In addition, as the membrane  210  is formed as the thin film, the side wall part  211  may be formed at the end portion of the membrane  210  so as to protrude in the displacement direction of the membrane  410 . 
         [0112]    Next, the fixed electrode part  220  is positioned at an outer peripheral portion of the membrane  210 . In addition, the fixed electrode part  220  may be positioned at the outer peripheral portion of the membrane in the direction orthogonal to the displacement direction of the membrane  210 . 
         [0113]    Further, the fixed electrode part  220  may be disposed to be spaced apart from the side wall part  211  of the membrane  210  so as to have a predetermined gap g therebetween. 
         [0114]    In addition, a groove part  221   a  is formed in the fixed electrode part  220  so as to correspond to the protrusion part  211   a  of the membrane  210 . 
         [0115]    Further, as shown in an enlarged view of  FIG. 6 , a conductive part  221   b  of the fixed electrode part  220  is formed so as to face the conductive part  211   b  formed on the side wall part  211  of the membrane  210 . 
         [0116]    In addition, similarly to the microphone according to the first preferred embodiment of the present invention as shown in the enlarged view of  FIG. 4 , an end portion of the conductive part  211   b  formed on the side wall part  211  of the membrane  210  may be formed so as to be positioned at the center of the conductive part  221   b  of the fixed electrode part  220  in a vibration direction of the membrane  210 . 
         [0117]    Therefore, in the microphone  200  according to the second preferred embodiment of the present invention, the area of the overlapped portion between the conductive part  211   b  of the membrane  210  and the conductive part  221   b  of the fixed electrode part  220  is maximized, and ΔC is detected through this change in the area, such that the sound wave may be more accurately converted into the electric signal. 
         [0118]      FIG. 7  is a perspective view schematically showing a microphone according to a third preferred embodiment of the present invention,  FIG. 8  is a schematic plan view of the microphone shown in  FIG. 7 , and  FIG. 9  is a cross-sectional view showing the microphone taken along line A-A of  FIG. 7 . As shown in  FIGS. 7 to 9 , the microphone  300  includes a membrane  310 , a fixed electrode part  320 , a support member  330 , and a support part  340 . 
         [0119]    In addition, when a sound wave is applied to the microphone  300  according to the third preferred embodiment of the present invention from the outside, displacement is generated at both sides of the membrane  310  in a state in which a central portion of the membrane  310  is fixed by the support member  330 , and a change in capacitance with respect to an overlapped surface of the fixed electrode part  320  and the membrane  310  by the displacement is detected, such that the sound wave is converted into an electric signal. 
         [0120]    More specifically, the membrane  310 , which is to be displaced by the sound wave, may be formed of a thin film in a disk shape In addition, as described above, the membrane  310  has a shape in which both side parts symmetrical to each other are connected so as to face each other based on a center part in order to generate symmetric displacement according to seesaw movement at both sides in a state in which the center part is fixed. To this end, the membrane  310  includes the central portion  310   a,  one side part  310   b,  and the other side part  310   c.    
         [0121]    In addition, the membrane  310  may have conductivity and be formed so that a conductive part is formed on at least some thereof. That is, in order to detect the change in capacitance generated at surfaces of the fixed electrode part  320  and the membrane  310  facing each other, a conductive part is formed on one surface of the membrane  310  facing the fixed electrode part  320 . 
         [0122]    To this end, a side wall part  311  is formed at an end portion of the membrane  310  in a direction orthogonal to a displacement direction, that is, an end portion thereof in a circumferential direction, and a conductive part  311   a  is formed on the side wall part  311  so as to face the fixed electrode part  320 . 
         [0123]    In addition, as the membrane  310  is formed as the thin film, the side wall part  311  may be formed at the end portion of the membrane  310  so as to protrude in the displacement direction of the membrane  410 . 
         [0124]    Next, the fixed electrode part  320 , which is to form ΔC with a change in an area of an overlapped portion between the fixed electrode part  320  and the membrane  310 , is positioned at an outer peripheral portion of the membrane  310 . 
         [0125]    In addition, the fixed electrode part  320  may be positioned at the outside of the membrane  310  in the direction orthogonal to the displacement direction of the membrane  310 . 
         [0126]    Further, the fixed electrode part  320  may be disposed to be spaced apart from the membrane  310  so as to have a predetermined gap g therebetween. The reason is to allow strong wind or low frequency flow to be discharged through the gap between the membrane  310  and the fixed electrode part  320  to thereby prevent the deformation of the membrane and allow the membrane  310  to be freely displaced by the sound wave in a vertical direction. 
         [0127]    In addition, a conductive part  321  is formed on the fixed electrode part  320  so as to face the conductive part  311   a  formed on the side wall part of the membrane  310 . 
         [0128]    Further, as shown in an enlarged view of  FIG. 9 , an end portion of the conductive part  311   a  of the membrane  310  may be formed so as to be positioned at the center of the conductive part  321  of the fixed electrode part  320  in the displacement direction of the membrane  110 . 
         [0129]    That is, in the displacement direction of the membrane  310 , when a length of the conductive part  311   a  of the membrane  310  is defined as Lm and a length of the conductive part  321  of the fixed electrode part  320  is defined as Lb, the end portion of the conductive part  311   a  is positioned at a portion corresponding to Lb×½, which is the center of the conductive part  321 , and a distance at which the membrane  310  may be maximally moved by the sound pressure becomes Lb×½. 
         [0130]    Next, the support member  330  connects the membrane  310  and the fixed electrode part  320  to each other. Further, the support member  330  is to allow displacement to be generated at both sides of the membrane  310  based on the center part thereof. In addition, symmetric displacement may be generated at both sides of the membrane  310  based on the center part thereof. 
         [0131]    To this end, the support member  330  may include a center fixing part  331  and a frame part  332 . Further, the center fixing part  331  is formed so as to correspond to the central portion  310   a  of the membrane  310 . 
         [0132]    In addition, the frame part  332  may be formed so as to correspond to the fixed electrode part  320  and fixedly coupled to the fixed electrode part  320 . 
         [0133]      FIG. 10  is a view of schematically showing a use state of the microphone shown in  FIG. 7 . As shown in  FIG. 10 , in the case in which a sound wave (SW) is applied to the membrane  310  from the outside, displacement is generated therein. That is, displacement is generated by the sound wave at one side part  310   b  and the other side part  310   c  of the membrane  310  in a state in which the center part  310   a  of the membrane  310  is fixed to the center fixing part  331  of the support member  330 . In this case, the symmetric displacement according to the seesaw movement may be generated at one side part  310   b  and the other side part  310   c.    
         [0134]    That is, when one side part  310   b  descends, the other side part  310   c  ascends, and when one side part  310   b  ascends, the other side part  310   c  descends. 
         [0135]    In addition, in the case in which displacement of the membrane  310  is generated, the area of the overlapped portion between the conductive part  311   a  of the membrane  310  and the conductive part  321  of the fixed electrode part  3201  is changed, such that capacitance is changed, and accordingly, ΔC is generated, thereby making it possible to convert the sound wave into the electric signal through ΔC. 
         [0136]      FIG. 11  is a plan view schematically showing a microphone according to a fourth preferred embodiment of the present invention. As shown in  FIG. 11 , in the microphone  400 , only shapes of a membrane and a fixed electrode part are different from those of the microphone  300  according to the third preferred embodiment of the present invention as shown in  FIG. 8 . 
         [0137]    More specifically, the microphone  400  includes a membrane  410 , a fixed electrode part  420 , a support part  430 , and a support part (not shown). 
         [0138]    In addition, when a sound wave is introduced into the microphone  400  according to the fourth preferred embodiment of the present invention from the outside, displacement is generated at both sides of the membrane  410  in a state in which a center part of the membrane  410  is fixed by the support member  430 , and a change in capacitance with respect to an overlapped surface of the fixed electrode part  420  and the membrane  410  by the displacement is detected, such that the sound wave is converted into an electric signal. 
         [0139]    More specifically, the membrane  410  may be displaced by the sound wave and formed of a thin film in a disk shape. In addition, as described above, the membrane  410  has a shape in which square parts symmetrical to each other are connected so as to face each other based on a center part in order to allow symmetric displacement to be generated at both sides in a state in which the center part is fixed. To this end, the membrane  410  includes the center part  410   a,  one side part  410   b,  and the other side part  410   c.    
         [0140]    In addition, an end portion of the membrane  410  in a direction orthogonal to a displacement direction may be formed with a side wall part  411 , the side wall part  411  may be formed with a plurality of protrusion parts  411   a  protruding toward the fixed electrode part at equidistance, and one surface of the side wall part  411  including the protrusion part  411   a  facing the fixed electrode part  420  may be formed with a conductive part  411   b.    
         [0141]    Further, the protrusion part  411   a  is to further increase a formation area of the conductive part and maximize the area of the overlapped portion with the conductive part of the fixed electrode part facing the conductive part to thereby maximize the change in capacitance. In addition, although a square shaped protrusion part is shown by way of example in  FIG. 11 , the present invention is not limited thereto, but the protrusion part may be implemented in various shapes such as a semi-circular shape, or the like. 
         [0142]    In addition, as the membrane  410  is formed as the thin film, the side wall part  411  may be formed at the end portion of the membrane  410  so as to protrude in the displacement direction of the membrane  410 . 
         [0143]    Next, the fixed electrode part  420  is positioned at an outer peripheral portion of the membrane  410 . In addition, the fixed electrode part  420  may be positioned at the outer peripheral portion in the direction orthogonal to the displacement direction of the membrane  410 . 
         [0144]    Further, the fixed electrode part  420  may be disposed to be spaced apart from the side wall part  411  of the membrane  410  so as to have a predetermined gap g therebetween. 
         [0145]    In addition, a groove part  421   a  is formed in the fixed electrode part  420  so as to correspond to the protrusion part  411   a  of the membrane  410 . 
         [0146]    In addition, a conductive part  421   b  is formed on a surface the fixed electrode part  420  facing the membrane  410 . Further, as shown in an enlarged view of  FIG. 11 , the conductive part  421   b  of the fixed electrode part  420  is formed so as to face the conductive part  411   b  formed on the side wall part  411  of the membrane  410 . 
         [0147]    In addition, similarly to the microphone according to the first preferred embodiment of the present invention as shown in the enlarged view of  FIG. 4 , an end portion of the conductive part  411   b  formed on the side wall part  411  of the membrane  410  may be formed so as to be positioned at the center of the conductive part  421   b  of the fixed electrode part  420  in the displacement direction of the membrane  410 . 
         [0148]    Therefore, in the microphone  400  according to the fourth preferred embodiment of the present invention, the area of the overlapped portion between the conductive part  411   b  of the membrane  410  and the conductive part  421   b  of the fixed electrode part  420  is maximized, and ΔC is detected by this change in the area, such that the sound wave may be more accurately converted into the electric signal. 
         [0149]      FIG. 12  is a perspective view schematically showing a microphone according to a fifth preferred embodiment of the present invention,  FIG. 13  is a schematic plan view of the microphone shown in  FIG. 12 , and  FIG. 14  is a cross-sectional view showing the microphone taken along line A-A of  FIG. 12 . 
         [0150]    As shown in  FIGS. 12 to 14 , the microphone  500  includes a membrane  510 , a fixed electrode part  520 , a support member  530 , a back plate  540  and a support part  550 . 
         [0151]    More specifically, when a sound wave is applied to the microphone  500  from the outside, displacement is generated at both sides of the membrane  510  in a state in which a central portion of the membrane  510  is fixed by the support member  530 , an area of an overlapped portion between the fixed electrode part  520  and the membrane  510  is changed by the displacement, and at the same time, a distance between the membrane  510  and the back plate  540  is changed. 
         [0152]    Therefore, the microphone  500  simultaneously measures the changes in the area of the overlapped portion and the distance and detects a change in capacitance according to the measured change, thereby converting the sound wave into an electric signal. 
         [0153]    To this end, the membrane  510 , which is to be displaced by the sound wave, may be formed of a thin film in a disk shape. In addition, as described above, the membrane  510  has a shape in which both side parts symmetrical to each other are connected so as to face each other based on a center part in order to allow symmetric displacement to be generated at both sides in a state in which the center part is fixed. That is, the membrane  510  includes the center part  510   a,  one side part  510   b,  and the other side part  510   c.    
         [0154]    In addition, the membrane  510  may have conductivity and be formed so that a conductive part is formed on at least some thereof. To this end, first and second conductive parts  511   a  and  511   b  are formed in the membrane  510 . 
         [0155]    In addition, the first conductive part  511   a,  which is to detect the change in the area of the overlapped portion that is a facing surface between the fixed electrode part  520  and the membrane  510 , is formed on one surface of the membrane  510  facing the fixed electrode part  520 . 
         [0156]    In addition, a side wall part  511  is formed at an end portion of the membrane  510  in a direction orthogonal to a displacement direction, that is, an end portion thereof in a circumferential direction, and the first conductive part  511   a  is formed on the side wall part  511  so as to face the fixed electrode part  520 . 
         [0157]    Further, as the membrane  510  is formed of a thin film, in order to secure a space for forming the conductive part, the side wall part  511  is formed at the end portion of the membrane so as to protrude in the displacement direction of the membrane  510 . 
         [0158]    In addition, the second conductive part  511   b,  which is to detect a change in a distance g between the back plate  540  and the membrane  510 , is formed on one surface of the membrane  510  facing the back plate  540 . That is, as the back plate  540  is positioned below the membrane  510 , the second conductive part  511   b  may be formed on a lower surface of the membrane  510  facing the back plate  540 . 
         [0159]    Next, the fixed electrode part  520 , which is to form ΔC through a change in the area of the overlapped portion between the fixed electrode part  520  and the membrane  510 , is positioned at an outer peripheral portion of the membrane  510 . 
         [0160]    In addition, the fixed electrode part  520  may be positioned at the outside of the membrane  510  in the direction orthogonal to the displacement direction of the membrane  510 . 
         [0161]    Further, the fixed electrode part  520  may be disposed to be spaced apart from the membrane  510  so as to have a predetermined gap therebetween. The reason is to allow strong wind or low frequency flow to be discharged through the gap between the membrane  510  and the fixed electrode part  520  to thereby prevent the deformation of the membrane and allow the membrane  510  to be freely displaced by the sound wave in a vertical direction. 
         [0162]    In addition, a conductive part  521  is formed on the fixed electrode part  520  so as to face the first conductive part  511   a  formed on the side wall part of the membrane  510 . 
         [0163]    Further, as shown in an enlarged view of  FIG. 14 , an end portion of the conductive part  511   a  of the membrane  510  may be formed so as to be positioned at the center C of the conductive part  521  of the fixed electrode part  520  in the displacement direction of the membrane  510 . 
         [0164]    That is, in the displacement direction of the membrane  510 , when a length of the first conductive part  511   a  of the membrane  510  is defined as Lm and a length of the conductive part  521  of the fixed electrode part  520  is defined as Lb, the end portion of the first conductive part  511   a  is positioned at a portion corresponding to Lb×½, which is the center of the conductive part  521 , and a distance at which the membrane  510  may be maximally moved by the sound pressure becomes Lb×½. 
         [0165]    Next, the support member  530  connects the membrane  510  and the fixed electrode part  520  to each other. Further, the support member  530  is to allow displacement to be generated at both sides of the membrane  510  based on the center part thereof. In addition, symmetric displacement may be generated at both sides of the membrane  510  based on the center part thereof. 
         [0166]    To this end, the support member  530  may include a center fixing part  531  and a frame part  532 . In addition, the center fixing part  531  may be formed so as to correspond to the center part  510   a  of the membrane  510  and coupled to the center part  510   a.    
         [0167]    In addition, the frame part  532  may be formed so as to correspond to the fixed electrode part  520  and fixedly coupled to the fixed electrode part  520 . 
         [0168]    Next, the back plate  540  is to detect the change value of the capacitance through the change in the distance between the back plate  540  and the membrane  510 . To this end, the back plate  540  is positioned so as to have the predetermined gap g with the membrane  510  in the displacement direction of the membrane  510 . In addition, a conductive part  541  is formed on the back plate  540  so as to face the second conductive part  511   b  of the membrane  510 . In addition, a hole  542  is formed in the back plate  540  for a flow of the sound wave, and a stopper  543  may be formed at one surface facing the membrane. 
         [0169]    Further, the stopper  543 , which is to limit excessive displacement of the membrane  510 , may be formed so as to face the end portion of the membrane  510  at which maximum displacement is generated. 
         [0170]      FIG. 15  is a view of a usage state of the microphone shown in  FIG. 12 . As shown in  FIG. 15 , in the case in which the sound wave (SW) is applied to the membrane  510  from the outside, displacement is generated therein. That is, displacement is generated at one side part  510   b  and the other side part  510   c  of the membrane  510  in a state in which the center part  510   a  of the membrane  510  is fixed to the center fixing part  531  of the support member  530 . In this case, symmetric displacement according to the seesaw movement may be generated at one side part  510   b  and the other side part  510   c.  That is, when one side part  510   b  descends, the other side part  510   c  may ascend, and when one side part  510   b  ascends, the other side part  510   c  may descend. 
         [0171]    In addition, in the case in which displacement of the membrane  510  is generated, the area of the overlapped portion between the first conductive part  511   a  of the membrane  510  and the conductive part  521  of the fixed electrode part  520  is changed. 
         [0172]    In addition, a distance between the second conductive part  511   b  of the membrane  510  and the conductive part  541  of the back plate  540  is changed. 
         [0173]    That is, capacitance C is defined as follows. 
         [0000]    
       
      
       C=εr·ε·A/g  
      
     
         [0174]    (Where, εr=permittivity, ε=electric constant, A=area of overlapped portion, and g=distance between the membrane and the back plate.) 
         [0175]    Here, as the area A of the overlapped portion and the distance g are changed, the capacitance is changed and ΔC is calculated, such that the sound wave may be converted into the electric signal through ΔC. 
         [0176]    As described above, the microphone  500  according to the fifth preferred embodiment of the present invention may be implemented as a more accurate microphone by simultaneously detecting the displacement of the area of the overlapped portion between the membrane  510  and the fixed electrode part  520  and distance displacement between the membrane  510  and the black plate to calculate ΔC and converting the sound wave into the electric signal through the calculated ΔC. 
         [0177]      FIG. 16  is a plan view schematically showing a microphone according to a sixth preferred embodiment of the present invention, and  FIG. 17  is a cross-sectional view showing the microphone taken along line A-A of  FIG. 16 . As shown in  FIGS. 16 and 17 , in the microphone  600 , only shapes of a membrane and a fixed electrode part are different from those of the microphone  500  according to the fifth preferred embodiment of the present invention as shown in  FIG. 13 . 
         [0178]    More specifically, the microphone  600  includes a membrane  610 , a fixed electrode part  620 , a support member  630 , a back plate  640  and a support part  650 . 
         [0179]    In addition, when a sound wave is introduced to the microphone  600  according to the sixth preferred embodiment of the present invention from the outside, displacement is generated at both sides of the membrane  610  in a state in which a center part thereof is fixed by the support member  630 , and a change value in capacitance with respect to an overlapped surface of the fixed electrode part  620  and the membrane  610  by the displacement is detected, such that the sound wave is converted into an electric signal. 
         [0180]    More specifically, the membrane  610  may be displaced by the sound wave and formed of a thin film in a disk shape. In addition, as described above, the membrane  610  has a shape in which both side parts symmetrical to each other are connected so as to face each other based on the center part in order to allow symmetric displacement to be generated at both sides in a state in which the center part is fixed. To this end, the membrane  610  includes the center part  610   a,  one side part  610   b,  and the other side part  610   c.    
         [0181]    In addition, the membrane  610  may have conductivity and be formed so that a conductive part is formed on at least some thereof. To this end, first and second conductive parts  611   b  and  611   c  are formed in the membrane  610 . 
         [0182]    A side wall part  611  is formed at an end portion of the membrane  610  in a direction orthogonal to a displacement direction, and a plurality of protrusion parts  611   a  protruding toward the fixed electrode part are formed at the membrane  610  at equidistance. In addition, the side wall part  611  including the protrusion part  611   a  may include the first conductive part  611   b  formed on one surface thereof facing the fixed electrode part  620 . 
         [0183]    Further, the protrusion part  611   a  is to further increase a formation area of the conductive part and maximize an area of an overlapped portion with a conductive part of the fixed electrode part facing the conductive part to thereby maximize a change in capacitance. In addition, although a square shaped protrusion part is shown by way of example in  FIG. 16 , the present invention is not limited thereto, but the protrusion part may be implemented in various shapes such as a semi-circular shape, or the like. 
         [0184]    In addition, as the membrane  610  is formed as the thin film, the side wall part  611  may be formed at the end portion of the membrane  610  so as to protrude in the displacement direction of the membrane  610 . 
         [0185]    In addition, the second conductive part  611   c,  which is to detect a change in a distance g between the back plate  640  and the membrane  610 , is formed on one surface of the membrane  610  facing the back plate  640 . That is, as the back plate  640  is positioned below the membrane  610 , the second conductive part  611   c  may be formed on a lower surface of the membrane  610  facing the back plate  640 . 
         [0186]    Next, the fixed electrode part  620  is positioned at an outer peripheral portion of the membrane  610 . In addition, the fixed electrode part  620  may be positioned at the outer peripheral portion in the direction orthogonal to the displacement direction of the membrane  610 . 
         [0187]    Further, the fixed electrode part  620  may be disposed to be spaced apart from the side wall part  611  of the membrane  610  so as to have a predetermined gap therebetween. 
         [0188]    In addition, a groove part  621   a  is formed in the fixed electrode part  620  so as to correspond to the protrusion part  611   a  of the membrane  610 . 
         [0189]    In addition, a conductive part  421   b  is formed on a surface of the fixed electrode part  620  facing the membrane  610 . Further, as shown in an enlarged view of  FIG. 16 , the conductive part  621   b  of the fixed electrode part  620  is formed so as to face the first conductive part  611   b  formed on the side wall part  611  of the membrane  610 . 
         [0190]    In addition, an end portion of the first conductive part  611   b  formed on the side wall part  611  of the membrane  610  may be formed so as to be positioned at the center C of the conductive part  621   b  of the fixed electrode part  620  in the displacement direction of the membrane  610 . Next, the support member  630  connects the membrane  610  and the fixed electrode part  620  to each other. Further, the support member  630  is to allow displacement to be generated at both sides of the membrane  610  based on the center part thereof. In addition, symmetric displacement may be generated at both sides of the membrane  610  based on the center part thereof. 
         [0191]    To this end, the support member  630  may include a center fixing part  631  and a frame part  632 . In addition, the center fixing part  631  may be formed so as to correspond to the center part  610   a  of the membrane  610  and coupled to the center part  610   a.    
         [0192]    In addition, the frame part  632  may be formed so as to correspond to the fixed electrode part  620  and fixedly coupled to the fixed electrode part  620 . 
         [0193]    Next, the back plate  640  is to detect the change value of the capacitance through the change in the distance between the back plate  640  and the membrane  610 . To this end, the back plate  640  is positioned so as to have the predetermined gap g with the membrane  610  in the displacement direction of the membrane  610 . In addition, the back plate  640  may be positioned below the membrane. Further, a conductive part  641  is formed on the back plate  640  so as to face the second conductive part  611   c  of the membrane  610 . In addition, the back plate  640  may include a hole  642  formed therein for a flow of the sound wave and a stopper  643  formed at an end portion thereof. 
         [0194]    Further, the stopper  643 , which is to limit excessive displacement of the membrane  610 , may be formed to face both end portions of the membrane at which maximum displacement is generated. 
         [0195]    Through the above-mentioned configurations, the microphone  600  according to the sixth preferred embodiment of the present invention may be implemented as a more accurate microphone by maximizing the area of the overlapped portion between the first conductive part  611   b  of the membrane  610  and the conductive part  621   b  of the fixed electrode part  620 , detecting ΔC by the displacement of the area of the overlapped portion between the membrane  610  and the fixed electrode part  620  and distance displacement between the membrane  610  and the black plate  640 , and converting the sound wave into the electric signal through the detected ΔC. 
         [0196]    According to the present invention, it is possible to obtain the microphone capable of more accurately converting the sound wave into the electric signal by detecting the change value of the capacitance through the change in the area of the overlapped portion between the fixed electrode part positioned in the direction orthogonal to the displacement direction of the membrane and the membrane, decreasing the production cost by being implemented without the back plate, obtaining high sensitivity without air-resistance or air damping by the back plate, and linearly reacting to the sound pressure and having a simple structure to thereby have improved productivity and product reliability. 
         [0197]    In addition, according to the present invention, it is possible to obtain the microphone capable of more accurately converting the sound wave into the electric signal by detecting the change value of the capacitance through the change in the area of the overlapped portion between the fixed electrode part positioned in the direction orthogonal to the displacement direction of the membrane and the membrane, and capable of being more accurately implemented by simultaneously detecting the change value of the area of the overlapped portion between the membrane and the fixed electrode part and the distance displacement between the membrane and the black plate, calculating the change value of the capacitance using the detected value, and converting the sound wave into the electric signal through the change value of the capacitance. 
         [0198]    Although the embodiments of the present invention have been disclosed for illustrative purposes, it will be appreciated that the present invention is not limited thereto, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention. 
         [0199]    Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the invention, and the detailed scope of the invention will be disclosed by the accompanying claims.