JP2006033536A - Electret capacitor microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a low-cost high-performance electret capacitor microphone having an air-vent for communicating an internal space of the microphone with outside in a structure having a less number of components and less influences of the component variations, etc. on the acoustic characteristics. <P>SOLUTION: The microphone has a vibration film 4 vibrating by air vibration, a vibration film support frame 3 with the vibration film fixed thereto, a back board 5 having an electret layer 7 formed on the back electrode, and a circuit board 9 mounting an electronic element 10 housed in an internal space 14 formed by forming a recess 5b in the back board 5. A groove 3b is formed in the vibration film support frame 3 and an air vent 3c is provided at the top end of the groove 3b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a structure of an electret condenser microphone, and more particularly, to an electret condenser microphone that realizes excellent performance at a low price by improving a vent hole that communicates the internal space of the electret condenser microphone with the outside.

  Conventionally, an electret condenser microphone using an electret dielectric film has been used in many microphone fields because of its simple structure, easy miniaturization, and low cost. In recent years, there has been an increasing demand for further miniaturization, higher performance, and lower price as a microphone for portable devices, for which demand is rapidly increasing. In response to these requirements, a microphone unit and a case unit for housing the microphone unit are provided, and the case unit includes a base unit made of a ceramic sheet and a plurality of ceramic sheets attached to the base unit. There has been proposed an electret condenser microphone that has a frame portion and aims to simplify the manufacturing process and improve performance (see, for example, Patent Document 1). Hereinafter, a conventional electret condenser microphone will be described with reference to FIG.

  FIG. 4A is a cross-sectional view of a conventional electret condenser microphone disclosed in Patent Document 1. FIG. 4A, the electret condenser microphone includes a microphone unit 100 that performs acoustic conversion, and a case unit 200 that houses the microphone unit 100. The microphone unit 100 includes a back electrode 110, an electret layer 120 formed on the surface of the back electrode 110, an acoustic hole 111 formed through the back electrode 110 and the electret layer 120, a vibrating membrane 140, The lower spacer 150 is interposed between the vibrating membrane 140 and the back electrode 110, and the upper spacer 160 is interposed between the vibrating membrane 140 and a lid 260 described later.

  The case portion 200 includes a circuit board 210 made of an insulating member, and four frames attached to the edge of the circuit board 210, that is, a first frame body 220, a second frame body 230, and a third frame body. Frame body 240, fourth frame body 250, and lid body 260 covering the upper surface side. The circuit board 210 is mounted with an electronic element 170 made of a semiconductor element or the like. Here, each of the members constituting the case portion 200, that is, the circuit board 210, the first frame body 220, the second frame body 230, and the third frame body 240 are all made of ceramics, although not shown. Each of the frames 220 to 240 is formed with connection electrodes made of conductive films, and these connection electrodes make electrical connection to each other. The fourth frame 250 is made of a metal material for connection with the vibration film, as will be described later.

  Next, a procedure for assembling a conventional electret condenser microphone will be described with reference to FIG. First, the first frame body 220, the second frame body 230, the third frame body 240, and the fourth frame body 250 are stacked and attached to the edge of the circuit board 210 on which the electronic element 170 is mounted. Next, the back electrode 110 is mounted on the first step portion 230a formed on the upper portion of the second frame 230 so that the electret layer 120 faces upward. Further, the vibration film 140 is mounted on the second step portion 240a formed on the upper portion of the third frame 240 with the lower spacer 150 and the upper spacer 160 interposed therebetween. Further, by fitting the lid 260 from above, the vibrating membrane 140 and the back electrode 110 are positioned and fixed to the case part 200 to complete the electret condenser microphone.

  In the operation of the electret condenser microphone having the above-described configuration, the vibrating film 140 having a conductive film on the surface and the back electrode 110 on which the electret layer 120 is formed form a capacitor with the lower spacer 150 interposed therebetween. When the vibrating membrane 140 is displaced by the vibration of air applied from the opening 260a of the lid 260, the capacitance of the capacitor changes due to the displacement. Here, the vibrating membrane 140, which is one electrode of the capacitor, is connected to the circuit board 210 via a frame body 250 made of a metal material, and the back electrode 110, which is the other electrode, is connected to the connection electrode (see FIG. (Not shown) to the circuit board 210.

  As a result, the change in the capacitance of the capacitor is transmitted to the electronic element 170 mounted on the circuit board 210, converted into an electric signal by the electronic element 170, and output electrodes (not shown) provided on the back surface of the circuit board 210. Output). The internal space of the electret condenser microphone communicates with the outside through the vent hole 220a provided in the first frame body 220, and the atmospheric pressure in the internal space is adjusted.

  Since this electret condenser microphone uses ceramics for the case part 200, it is durable against high temperatures and can be mounted by reflow soldering. Further, if the case portion 200 is made of ceramics, it is advantageous from the viewpoint of manufacturing because the dimensions and manufacturing process management when forming the vent hole 220a for adjusting the pressure in the back chamber are simplified. In addition, the acoustic characteristics are improved by the vent hole 220a.

  Next, a second conventional electret condenser microphone will be described with reference to FIG. FIG. 4B is a sectional view of the electret condenser microphone of the second conventional example. The same elements as those in the conventional example of FIG. In FIG. 4B, reference numeral 140a denotes a vent hole that is opened near the center of the vibrating membrane 140. The vent hole 140a allows the internal space of the electret condenser microphone to communicate with the outside to adjust the atmospheric pressure of the internal space. Is done. Incidentally, the vent hole 220a provided in the frame body 220 in the conventional example of FIG. In the electret condenser microphone of the second conventional example, since the ventilation hole 140a is provided in the vibration membrane 140, the processing of the ventilation hole is simple, and the ventilation hole of the frame body 220 is unnecessary, so that the number of manufacturing steps is reduced. And cost reduction is possible.

JP 2000-50393 (Claims, FIG. 1)

  However, the electret condenser microphone of the first conventional example has a problem that the number of parts increases because a vent hole is provided in a part of the frame, and the number of manufacturing steps of the frame and the number of assembly steps of the case portion increase. In addition, since the number of parts is large, there is a problem that the shape of the vent hole slightly changes due to the variation in the shape of each part, and the acoustic characteristics as a microphone vary. Furthermore, since the vent hole is on the side of the electret condenser microphone, when attaching the electret condenser microphone to a portable device, etc., it is necessary to devise the mounting part etc. so as not to block the side, and the degree of freedom for attachment to the device There is also a problem of lack.

  Further, in the electret condenser microphone of the second conventional example shown in FIG. 4B, the vibration mode of the vibrating membrane slightly changes in order to open a vent hole in the vibrating membrane, and the frequency characteristics as a microphone. It is difficult to obtain optimal acoustic characteristics.

  An object of the present invention is to provide an electret condenser microphone that solves the above-described problems, consolidates the processing of the air holes into one component, and realizes cost reduction and excellent acoustic performance.

  In order to solve the above problems, the electret condenser microphone of the present invention employs the following configuration.

  The electret condenser microphone of the present invention is mounted with a vibration film that vibrates by vibration of air, a vibration film support frame that fixes the vibration film, a back substrate having an electret layer formed on a back electrode, and an electronic element. The electronic element is housed in an inner space formed with a recess formed in the back substrate or the circuit substrate, a groove is formed in the vibration film support frame, and the vibration film is formed at a tip portion of the groove. A vent hole penetrating the support frame is provided.

  With the electret condenser microphone of the present invention, a groove is formed in the diaphragm support frame, and a vent is provided at the tip of the groove, so that the processing of the vent can be consolidated into one part, reducing costs and stabilizing acoustic characteristics. Can be realized.

  The groove of the diaphragm support frame is formed from a part of a side wall of a substantially circular diaphragm hole formed at a substantially central portion of the diaphragm support frame to the vent hole, and the groove of the diaphragm support frame is formed. The interior space of the microphone is communicated with the outside by a groove.

  Thereby, since the groove is connected from the side wall to the vent hole of the diaphragm hole, the internal space of the electret condenser microphone is communicated with the outside, and the acoustic characteristics can be improved.

  The diaphragm support frame is a substrate material such as glass epoxy or BT resin.

  As a result, since the diaphragm support frame is a substrate material such as glass epoxy or BT resin, groove processing, circuit formation, lamination processing, etc. are easier than conventional ceramics, and the cost is low and the quality is excellent. Electret condenser microphone can be provided.

  The diaphragm and the diaphragm support frame are integrated to form a diaphragm unit, and the diaphragm unit is stacked on the back substrate via a spacer, and the bottom of the back substrate. The circuit board is laminated and integrated, and is incorporated in the case body.

  Thereby, since each component is laminated | stacked and integrated and integrated in a case body, the electret condenser microphone excellent in assemblability can be provided.

  Furthermore, the case body has a sound hole for transmitting air vibration to the vibration film on the upper surface portion, the back substrate has an acoustic hole penetrating the back substrate, and the internal space and the outside of the microphone are The sound holes of the case body, the grooves of the diaphragm support frame, the vent holes of the diaphragm support frame, and the acoustic holes of the back substrate are communicated with each other.

  As a result, the internal space of the microphone communicates with the outside through the sound holes arranged on the upper surface of the case body through the grooves of the diaphragm support frame, the vent holes of the diaphragm support frame, and the acoustic holes of the back substrate. Therefore, it is possible to provide an electret condenser microphone with improved acoustic characteristics, low cost and excellent quality.

  As described above, according to the present invention, a groove and a vent hole for communicating the inside space of the electret condenser microphone with the outside can be formed by the diaphragm supporting frame which is one part, so that the number of parts can be reduced and the assembly process can be reduced. Simplification is possible, and it also helps to improve and stabilize acoustic characteristics.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of an electret condenser microphone according to an embodiment of the present invention. FIG. 2A is a top view of the diaphragm unit according to the embodiment of the present invention. FIG. 2B is a top view showing another form of the diaphragm unit according to the embodiment of the present invention. FIG. 3 is an exploded perspective view showing an assembly process of the electret condenser microphone according to the embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes an electret condenser microphone of the present invention. Reference numeral 2 denotes a diaphragm unit. The diaphragm unit 2 includes a diaphragm support frame 3 made of a substrate material such as glass epoxy and BT resin, and a circular diaphragm hole provided in the center of the diaphragm support frame 3. 3a is formed by a conductive vibration film 4 formed as a film, and the vibration film support frame 3 is integrated by fixing and supporting the vibration film 4. In addition, although mentioned later for details, 3b is a groove | channel formed in the diaphragm support frame 3, 3c is a ventilation hole.

  Reference numeral 5 denotes a back substrate, and a back electrode 6 made of a conductive film is formed on the back substrate upper surface portion 5a of the back substrate 5, and an electret layer 7 made of an electret dielectric film is formed on the top surface of the back electrode 6. . In addition, a recess 5b is provided in the lower part of the back substrate 5, and an inner space 14 that is an air layer is formed by the recess 5b. Reference numeral 8 denotes a plurality of acoustic holes provided in the back substrate 5. One or more acoustic holes are arranged outside the back electrode 6 and the electret layer 7, penetrate the back substrate 5, and air layers on the top surface of the back substrate 5. And the internal space 14 which is an air layer on the lower surface portion of the back substrate 5 are communicated with each other. Reference numeral 9 denotes a circuit board made of an insulating material, and connection electrodes 9 a and 9 b are formed on a part of the upper surface of the circuit board 9. Reference numeral 10 denotes an electronic element constituted by a semiconductor element or the like. The electronic element 10 is accommodated in an internal space 14 formed by the concave portion 5 b of the back substrate 5, and the connection electrodes 9 a and 9 b of the circuit substrate 9 are formed by solder 11. To be implemented.

  A spacer 12 is disposed between the diaphragm unit 2 and the back substrate 5, and the diaphragm 4 and the back electrode 6 on which the electret layer 7 is formed face each other to form a capacitor. Although not shown, the spacer 12 has an electrode formed on the surface in contact with the vibration film 4 and is electrically connected to the connection electrode 9 a of the circuit board 9 through the back substrate 5. Similarly, although not shown, a part of the back electrode 6 is also electrically connected to the connection electrode 9 b of the circuit board 9 through the back substrate 5.

  Reference numeral 13 denotes a substantially cubic case body that covers the casing and covers the diaphragm unit 2, the spacer 12, the back substrate 5, and the circuit substrate 9. Reference numeral 13a denotes a sound hole opened in the upper surface portion of the case body 13, and the vibration film 4 can pick up vibrations of external air through the sound hole 13a. The internal space 14 is routed from the sound hole 13a of the case body 13, the groove 3b of the diaphragm support frame 3, the vent hole 3c of the diaphragm support frame 3, and the acoustic hole 8 of the back substrate 5 to the outside of the electret condenser microphone 1. Communicated with. In this embodiment, the internal space 14 is formed by the recess 5b provided in the back substrate 5. However, the present invention is not limited to this structure. For example, the back substrate 5 has a flat plate shape. The internal space 14 may be formed by providing a concave portion on the circuit board 9. Alternatively, the internal space 14 may be formed by providing recesses in the lower part of the back substrate 5 and the upper part of the circuit board 9.

  Next, the structure of the grooves and vent holes formed in the diaphragm supporting frame 3 will be described with reference to FIG. 2A is a top view of the vibrating membrane unit 2. In FIG. 2A, the vibrating membrane support frame 3 has the vibrating membrane hole 3a as described above, and the vibrating membrane 4 has the vibrating membrane hole 3a. A film is formed entirely. The groove 3b is formed in an arc shape from a part of the side wall of the diaphragm hole 3a along the outer periphery of the diaphragm hole 3a, and further, a vent hole 3c penetrating the diaphragm support frame 3 at the tip of the groove 3b. Is formed. As a result, the side wall of the vibrating membrane hole 3a and the vent hole 3c are connected by the groove 3b, and the internal space 14 of the electret condenser microphone 1 is communicated with the outside. Note that FIG. 1 described above is sectioned along the center line indicated by the arrow A in FIG.

  Next, FIG. 2 (b) shows another form of the diaphragm unit 2, that is, the groove 3b that communicates the side wall of the diaphragm hole 3a and the vent hole 3c is not arcuate but bent substantially at a right angle. Formed in shape. As described above, the shape of the groove 3b formed in the diaphragm support frame 3 is not limited and may be any shape, and the acoustic characteristics as a microphone are corrected by adjusting the width and length of the groove 3b. Can be improved.

  Next, a schematic assembly process of the electret condenser microphone 1 will be described with reference to FIG. FIG. 3 is an exploded perspective view of the electret condenser microphone according to the embodiment of the present invention, illustrating the assembly process. First, in step (a), a sound hole 13a is processed in the upper surface of the case body 13 as a previous step.

  Next, in step (b), the diaphragm unit 2 in which the diaphragm 4 and the diaphragm support frame 3 are integrated is assembled into the case body 13. At this time, the vibration film support frame 3 is formed with the grooves 3b and the vent holes 3c as described above.

  Next, in step (c), the spacer 12 is fixed to the upper surface of the back substrate 5 and is assembled into the case body 13 in a form of being laminated on the lower surface side of the vibration membrane unit 2 that has already been incorporated into the case body 13. . The back substrate 5 is formed with a back electrode 6 and an electret layer 7, and one or more acoustic holes 8 are formed by pre-processing.

  Next, in the step (d), the circuit board 9 on which the electronic element 10 is mounted is incorporated into the case body 13 in a form of being laminated on the lower surface side of the back substrate 5 already incorporated into the case body 13. As a result, the vibrating membrane unit 2, the back substrate 5, and the circuit board 9 are stacked and incorporated in the case body 13 in this order, and the electret condenser microphone 1 shown in FIG. 1 is completed. The circuit board 9 has a pair of output electrodes 9c and 9d in addition to the connection electrodes 9a and 9b described above, and the output electrodes 9c and 9d are connected to the electronic element 10 by solder (not shown). Although not shown, the output electrodes 9c and 9d are formed up to the back surface of the circuit board 9 and serve as output terminals to the outside.

  Next, the operation of the electret condenser microphone 1 will be described with reference to FIG. 1 and FIG. First, when the vibration film 4 is vibrated and displaced by the vibration of air applied from the sound hole 13a of the case body 13, the capacitor formed by the vibration film 4 and the back electrode 6 has a capacitance due to this displacement. Change. As described above, the vibrating membrane 4 which is one electrode of the capacitor is connected to the connection electrode 9a of the circuit board 9, and the back electrode 6 which is the other electrode is connected to the connection electrode 9b. The change in capacitance is input to the electronic element 10.

  The electronic element 10 converts the change in capacitance into an electric signal inside and outputs it to the outside from the back surface of the circuit board 9 by the output electrodes 9c and 9d. As described above, the internal space 14 of the electret condenser microphone 1 and the outside are communicated with each other by the groove 3b and the air vent 3c formed in the diaphragm support frame 3, so that the atmospheric pressure of the internal space 14 is adjusted. The acoustic characteristics as a microphone can be improved.

  In the electret condenser microphone according to the embodiment of the present invention, the outer shape of the case body is substantially a cube. However, the shape is not limited to this, and may be a cylindrical shape or any other shape. The assembly process shown in FIG. 3 is assembled while sequentially incorporating the elements into the case body 13, but is not limited to the order of the processes. For example, after the elements are stacked and integrated, the case body 13 may be incorporated.

  As described above, according to the embodiment of the present invention, since the groove 3b and the vent hole 3c can be processed and formed in the diaphragm support frame 3, there is no need to increase the number of parts in order to provide the vent hole, and the number of parts can be reduced. In addition, the assembly process can be simplified and the cost can be reduced. Further, since the vent hole can be formed only by the diaphragm support frame 3 which is one part, the shape variation of the vent hole is small compared with the case where the vent hole is formed by a plurality of parts. An electret condenser microphone with stable characteristics and high reliability can be provided.

  In addition, by adjusting the width and length of the groove formed in the diaphragm support frame 3, the acoustic characteristics of the microphone can be arbitrarily modified and improved to some extent, so an electret condenser microphone having acoustic characteristics according to the application can be obtained. Can be provided. In addition, since the diaphragm support frame 3 is a substrate material such as glass epoxy or BT resin, it is easier to process grooves and the like, and it is possible to provide an electret condenser microphone that is low in cost and excellent in quality as compared with conventional ceramics. .

It is sectional drawing of the electret condenser microphone which is embodiment of this invention. It is a top view of the diaphragm unit which is an embodiment of the present invention. It is a top view which shows the other form of the diaphragm unit which is embodiment of this invention. It is a disassembled perspective view which shows the assembly process of the electret condenser microphone which is embodiment of this invention. It is sectional drawing of the electret condenser microphone which is a 1st prior art example. It is sectional drawing of the electret condenser microphone which is a 2nd prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electret condenser microphone 2 Vibrating membrane unit 3 Vibrating membrane support frame 3a Vibrating membrane hole 3b Groove 3c, 140a, 220a Vent hole 4, 140 Vibrating membrane 5 Back substrate 5a Rear substrate upper surface portion 5b Recessed portion 6, 110 Back electrode 7, 120 Electret Layer 8, 111 Acoustic hole 9, 210 Circuit board 9a, 9b Connection electrode 9c, 9d Output electrode 10, 170 Electronic element 11 Solder 12 Spacer 13 Case body 13a, 260a Sound hole 14 Internal space 100 Microphone part 150 Lower surface spacer 160 Upper surface spacer 200 Case part 220 First frame body 230 Second frame body 230a First step part 240 Third frame body 240a Second step part 250 Fourth frame body 260 Lid

Claims (5)

A vibration film that vibrates by vibration of air, a vibration film support frame that fixes the vibration film, a back substrate having an electret layer formed on a back electrode, and a circuit board on which an electronic element is mounted, The electronic element is accommodated in an internal space formed by providing a recess in the back substrate or the circuit board, a groove is formed in the diaphragm supporting frame, and a vent hole penetrating the diaphragm supporting frame is formed at a tip of the groove. An electret condenser microphone is provided. The groove of the diaphragm support frame is formed from a part of a side wall of a substantially circular diaphragm hole formed at a substantially central portion of the diaphragm support frame to the vent hole, and the groove of the diaphragm support frame is formed by the groove of the diaphragm support frame. The electret condenser microphone according to claim 1, wherein the internal space of the microphone communicates with the outside. 3. The electret condenser microphone according to claim 1, wherein the vibration film support frame is a substrate material such as glass epoxy or BT resin. The diaphragm and the diaphragm support frame are integrated to form a diaphragm unit, and the diaphragm unit is stacked with the back substrate via a spacer, and is disposed below the back substrate. 4. The electret condenser microphone according to claim 1, wherein the circuit boards are laminated and integrated, and are incorporated in the case body. 5. Furthermore, the case body has a sound hole for transmitting air vibration to the vibration film on the upper surface portion, the back substrate has an acoustic hole penetrating the back substrate, and the internal space and the outside of the microphone are 5. The sound hole of the case body, the groove of the diaphragm supporting frame, the vent hole of the diaphragm supporting frame, and the route of the acoustic hole of the back substrate are communicated with each other. Electret condenser microphone.

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