JP2005057645A - Electret capacitor microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive electret capacitor microphone which is very thin and has a simple manufacturing process. <P>SOLUTION: This electret capacitor microphone includes a vibrating electrode 26 composed of a first electret dielectric film with a first electrode film formed thereon, a fixed electrode 36 including a second dielectric film 32 with a second electrode film formed thereon and a metal plate 34 holding the second electret dielectric film 32, wherein the second electret dielectric film 32 is arranged so as to face the first electret dielectric film, a circuit board 40 arranged close to or with a gap to the metal plate 34, and a semiconductor element 46 of a bare chip configuration, wherein an input terminal 46A is arranged on one surface and an output terminal 46B is arranged on the other surface, respectively, and a projecting electrode is formed on each of the surfaces. The semiconductor element 46 is provided between the fixed electrode 36 and the circuit board 40, and electrode terminals on the input terminal 46A and the fixed electrode 36, and the output terminal 46B and the circuit board 40 are respectively connected. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a condenser microphone using an electret, which is mainly used for a mobile phone or the like.

  A general electret condenser microphone (hereinafter referred to as an ECM) used for a cellular phone or the like includes a capacitor unit composed of a vibrating electrode made of an electret dielectric film and a fixed electrode, and a voltage between the vibrating electrode and the fixed electrode. It is composed of a signal amplifier circuit that amplifies the change and outputs it as an electrical signal. In addition, a filter circuit is often provided to reduce noise with respect to a signal from the ECM.

  A conventional ECM configuration will be described with reference to a cross-sectional view of FIG. 11 and an exploded perspective view of FIG. For the sake of simplicity, each drawing shows the dimension in the thickness direction enlarged.

  A voice input opening 1A is provided on one surface of the case 1 so that the voice is transmitted to the electret dielectric film, and the inner side of the voice input opening 1A is made of a metal for preventing dust. The face cloth 2 is affixed.

  Inside the case 1, a first electrode film is formed on one surface, a vibrating electrode 3 made of a first electret dielectric film that vibrates by acoustic vibration, and a conductive material for fixing the vibrating electrode 3 to the case 1. The fixed electrode 5, the fixed electrode 5 and the vibrating electrode 3 fixedly connected to each other by the electrode ring 4 and the second electret dielectric film 5A on which the second electrode film is formed and the reinforcing metal plate 5B are fixedly connected. Insulating spacers 6 inserted so as to face each other, an insulator 7 for supporting the fixed electrode 5, a semiconductor element 8 for converting an electrical signal by impedance conversion and amplification, and a capacitor 9 constituting a filter circuit And a resistor 10 are disposed.

  As the semiconductor element 8, a normally packaged field effect transistor is used. As can be seen from FIG. 12, the semiconductor element 8 has pin-shaped electrode terminals 13 A and 13 B extending from the package, and the output-side electrode terminal 13 B is connected to the electrode wiring 12 of the wiring substrate 11. On the other hand, the input-side electrode terminal 13A is bent to the upper surface side of the semiconductor element 8 and connected to the metal plate 5B of the fixed electrode 5 by a conductive adhesive or the like. The capacitor 9 and the resistor 10 are disposed on the wiring board 11 and connected to the electrode wiring 12 respectively.

  FIG. 13 is a circuit diagram for explaining the circuit configuration of the ECM. In the capacitor composed of the first electret dielectric film and the second electret dielectric film, voltage fluctuations caused by vibration of the vibrating electrode 3 due to acoustic vibration are taken out as a signal. The voltage signal is impedance-converted and amplified by the semiconductor element 8 made of a field effect transistor, and is output from the electrode terminals 15 and 16 to an external circuit (not shown) through a filter circuit formed by the capacitor 9 and the resistor 10. It has become. The electrode terminals 15 and 16 are connected to the internal electrode wiring 12 via the upper and lower connection conductors 14 provided on the wiring board 11. One of the electrode terminals 15 and 16 is electrically connected to the case 1 and connected to the earth circuit.

  Since such ECM is mainly used for mobile phones, there is a strong demand for lowering the height especially with the progress of downsizing and higher density of mobile phones. However, in the above-described conventional configuration, since the package type semiconductor element 8 is relatively thick and the pin-shaped electrode terminal 13A is bent and provided on the upper surface side, it is difficult to reduce the thickness.

  As a countermeasure for this, for example, a configuration in which an integrated circuit element (IC) including an impedance conversion circuit is used as a semiconductor element and this IC is mounted on a wiring board in a bare chip configuration is shown. The packaged IC usually has a height of 0.6 mm or more, so the thickness of the ECM is limited. However, a bare-chip IC is used, and the IC itself is 0.3 mm by flip-chip bonding. The thickness of the bare chip including the wiring board can be reduced to about 0.8 mm. As a result, the entire ECM is thinned (for example, Patent Document 1).

Further, in the front electret condenser microphone, paying attention to the fact that the ratio of the thickness of the wiring board to the total thickness is high, a first wiring board on which wiring conductors for electrically connecting and supporting the semiconductor elements are formed; A configuration is shown in which the second wiring substrate is formed by being stacked on the first wiring substrate and formed with an opening through which the semiconductor element penetrates, thereby achieving a reduction in thickness. Thus, a condenser microphone having an outer diameter of 6 mmφ and a thickness of 1 mm can be manufactured (for example, Patent Document 2).
JP-A-11-266499 JP 2001-95097 A

  In the first example described above, a holder for electrically connecting the electret dielectric film and the wiring board at the same time as holding the electret dielectric film is provided. This holder is composed of an insulator as a whole, and it is necessary to form a conductive layer from a part of the upper end surface to a part of the inner side surface and the lower end surface. The process of forming such a conductive layer is relatively There was a problem that it was complicated and resulted in high costs.

  Further, in the second example, the processing and assembly of the wiring board can be performed because two wiring boards having different shapes are attached to each other and the wiring board inside the case requires an opening. It becomes relatively complicated. Furthermore, since the capacitor and the semiconductor element are mounted in the opened region, there is a problem that the mounting work becomes complicated.

  The present invention solves such a conventional problem, and an object of the present invention is to provide a low-cost ECM that is very thin and has a simple manufacturing process.

  In order to solve the above problems, an ECM according to the present invention includes a vibrating electrode made of a first electret dielectric film having a first electrode film formed on one surface and a second electrode film formed on one surface. Two electret dielectric films and a holding plate for holding the second electret dielectric film, the other surface of the second electret dielectric film being disposed so as to face the other surface of the first electret dielectric film. A fixed electrode, a wiring board disposed in close contact with or with a gap between the holding plate, an input terminal on one surface, and an output terminal on the other surface, respectively, and an input terminal and an output terminal, respectively. A semiconductor element that impedance-converts and amplifies a bare-chip electrical signal having a protruding electrode formed thereon, and the semiconductor element is disposed between the fixed electrode and the wiring board. Consists structure fixed electrode and the input terminal, and an output terminal and the electrode terminal on the wiring substrate are connected via the protruding electrode, respectively.

  With this configuration, since the semiconductor element having the bare chip configuration is connected to the fixed electrode and the electrode terminal of the wiring board by the protruding electrodes provided on both sides, the space for arranging the semiconductor element can be very small. Further, since the fixed electrode is directly connected to the semiconductor element and the semiconductor element is directly connected to the wiring substrate, the connection can be made with the shortest wiring length. Further, it is not necessary to form a wiring for connecting from the fixed electrode to the wiring board as in the prior art.

  The ECM of the present invention comprises a metal plate in which the holding plate of the fixed electrode is conductively joined to the second electrode film, and the wiring board is disposed with a gap at least larger than the thickness of the semiconductor element. The terminal is connected to the metal plate via the protruding electrode, and the output terminal is connected to the electrode terminal on the wiring board via the protruding electrode.

  With this configuration, since the fixed electrode is held by the metal plate, even if a load pressing the metal plate is applied when the input terminal of the semiconductor element is connected to the metal plate, the influence on the characteristics is reduced. As a result, an ECM with a high yield and high reliability can be easily obtained.

  The ECM according to the present invention includes an insulating plate in which a holding plate for a fixed electrode is bonded to the second electrode film and an opening having a shape for housing a semiconductor element is provided, and the wiring board is in close contact with the insulating plate. The semiconductor device is disposed in the opening, the input terminal is connected to the second electrode film via the protruding electrode, and the output terminal is connected to the electrode terminal on the wiring board via the protruding electrode. Consists of.

  With this configuration, since a space for housing the semiconductor element is provided in the holding plate, the thickness can be further reduced. Further, since the space area where the semiconductor element is exposed is small, the semiconductor element can be easily sealed and protected, and the reliability of the semiconductor element having the bare chip configuration can be improved.

  The ECM of the present invention comprises an insulating plate in which a holding plate for a fixed electrode is bonded via a metal plate conductively bonded to the second electrode film, and an opening having a shape for housing a semiconductor element is provided. The wiring board is disposed in close contact with the insulating plate, the semiconductor element is accommodated in the opening, the input terminal is connected to the metal plate via the protruding electrode, and the output terminal is connected to the electrode terminal on the wiring board via the protruding electrode. Connected to each other.

  With this configuration, since a space for housing the semiconductor element is provided in the holding plate, the thickness can be further reduced. Further, since the space area where the semiconductor element is exposed is small, the semiconductor element can be easily sealed and protected, and the reliability of the semiconductor element having the bare chip configuration can be improved. Further, when connecting the protruding electrode of the semiconductor element to the metal plate, the influence on the characteristics is reduced even if a load pressing the metal plate is applied. As a result, an ECM with a high yield and high reliability can be easily obtained.

  The ECM of the present invention has a configuration in which the protruding electrode of the input terminal of the semiconductor element and the fixed electrode are connected by a conductive adhesive. With this configuration, the connection process of the semiconductor element can be simplified by connecting the semiconductor element and the fixed electrode at a low temperature of about room temperature. Further, when the wiring board is inserted into the case, it can be connected at the same time.

  Further, the ECM of the present invention has a configuration in which the protruding electrode of the input terminal of the semiconductor element and the fixed electrode are electrically connected by pressure contact. With this configuration, after the semiconductor element is connected and fixed on the wiring board, the wiring board is inserted into the case, and at the same time, the protruding electrode and the fixed electrode of the semiconductor element can be connected. For this reason, ECM with an easy assembly process can be realized.

  Further, the ECM of the present invention has a vibrating electrode made of a first electret dielectric film having a first electrode film formed on one surface and a second electrode film formed on one surface, and is at least larger than a semiconductor element. A second electret dielectric film having an opening or notch, and an input-side electrode terminal electrically connected to the second electrode film and extending to the opening or notch, and provided in the opening or notch A wiring board on which the output-side electrode terminals are formed, an input terminal and an output terminal on one surface, and an electric signal of a bare chip configuration in which a protruding electrode is formed on each of the input terminal and the output terminal. The second electret dielectric film is bonded and fixed to the wiring board, and the second electrode film and the input-side electrode terminal are connected to each other. The input terminal of the semiconductor element and the input-side electrode terminal of the wiring board, and the output terminal and the output-side electrode terminal are respectively connected, and the surface of the second electret dielectric film and the surface of the first electret dielectric film are predetermined. It consists of the structure arrange | positioned in the position which opposes at intervals.

  With this configuration, the fixed electrode holding plate and the wiring substrate are integrated, and a thinner ECM can be realized. Further, since the ECM can be manufactured by connecting the semiconductor element and the second electret dielectric film to the wiring board in advance and then inserting and fixing the wiring board in the case, the assembly process can be greatly simplified.

  The ECM of the present invention has a configuration in which a filter circuit composed of one or more electronic components selected from a capacitor, a resistor, and an inductor is formed on a wiring board by a film manufacturing technique. With this configuration, the thickness can be significantly reduced as compared with the case where a chip component is used, and the thickness can be more effectively realized when a semiconductor element having a bare chip configuration is used.

  As described above, according to the present invention, a bare chip configuration semiconductor element in which an input terminal and an output terminal are disposed on opposite surfaces is disposed between a fixed electrode and a wiring board, and the input terminal and the fixed electrode, The output terminal and the electrode terminal on the wiring board are connected to each other.

  With this configuration, since the semiconductor element having the bare chip configuration is connected to the fixed electrode and the electrode terminal of the wiring board by the protruding electrodes provided on both sides, the space for arranging the semiconductor element can be very small. Further, since the fixed electrode is directly connected to the semiconductor element and the semiconductor element is directly connected to the wiring substrate, the connection can be made with the shortest wiring length. Further, it is not necessary to form a wiring for connecting from the fixed electrode to the wiring board as in the prior art. As a result, an ECM that is thin and easy to assemble can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. For ease of understanding, the dimension in the thickness direction of each drawing is shown enlarged.

(First embodiment)
FIG. 1 is a cross-sectional view of an ECM 20 according to the first embodiment of the present invention, and FIG. 2 is an exploded perspective view. The case 22 has a cylindrical shape made of, for example, aluminum (Al), and an audio input opening 22A is provided on one surface so that the audio is transmitted to the electret dielectric film. A metal face cloth 24 for preventing dust is affixed to the inner side of the voice input opening 22A.

  Inside the case 22, the vibration electrode 26, the conductive electrode ring 28 for fixing the vibration electrode 26 to the case 22, the fixed electrode 36, and the fixed electrode 36 and the vibration electrode 26 face each other with a predetermined interval. The insulating spacer 30 inserted in this manner, the insulator 38 for supporting the fixed electrode 36, the semiconductor element 46, the capacitor 42 and the resistor 44 constituting the filter circuit, and the wiring board 40 on which these are mounted are provided. The lower surface of the case 22 is caulked.

  The vibrating electrode 26 has a configuration in which a first electrode film (not shown) is formed on one surface of the first electret dielectric film. The fixed electrode 36 includes a second electret dielectric film 32 having a second electrode film (not shown) formed on one surface thereof, and a metal plate 34 that is conductively joined to the second electrode film. Yes.

  The wiring board 40 has an electrode wiring 40A formed on the inner side surface of the case 22, and electrode terminals are formed at predetermined positions of the electrode wiring 40A. The capacitor 42, the resistor 44, the semiconductor element 46, etc. Are connected to an electronic component (not shown). Furthermore, an electrode terminal 40B for connecting to an external device is formed on the outer surface via the vertical connection conductor 40C. The electrode terminals 40B are formed concentrically in accordance with the outer shape of the ECM 20, but are not necessarily concentric.

  In this embodiment, the semiconductor element 46 uses a field-effect transistor having a bare chip configuration. The input terminal 46 </ b> A is formed with a protruding electrode on the upper surface side of the semiconductor element 46, that is, on the surface of the fixed electrode 36 facing the metal plate 34. The output terminal 46B is similarly formed on the surface facing the wiring substrate 40 with a protruding electrode. The input terminal 46 </ b> A and the output terminal 46 </ b> B having protruding electrodes are connected to the electrode terminals of the metal plate 34 and the wiring board 40 by, for example, a conductive adhesive.

  The assembly of the ECM 20 of the present embodiment is performed as follows, for example. A capacitor 42, a resistor 44, a semiconductor element 46, and necessary electronic components are connected to the wiring board 40 in advance by solder or a conductive adhesive. On the other hand, the face cloth 24, the vibration electrode 26, the fixed electrode 36, the electrode ring 28, the spacer 30 and the insulator 38 are disposed in the case 22. After this state, a conductive adhesive is applied to the protruding electrode of the input terminal 46A of the semiconductor element 46, the wiring board 40 is inserted into the case 22, and the lower surface portion of the case 22 is caulked to thereby input the input terminal 46A. The protruding electrode and the metal plate 34 are electrically and mechanically connected. Thereby, the assembly of the ECM 20 is completed. For this reason, the insulator 38 is formed to be slightly thicker than the semiconductor element 46 including the protruding electrodes.

  The operation of this ECM will be described. A sound vibration is applied to the vibration electrode 26, and a voltage generated by a capacitor composed of the vibration electrode 26 and the fixed electrode 36 is input to the semiconductor element 46 from the fixed electrode 36, and impedance conversion and amplification are performed. This signal is output to the wiring board 40. The signal output to the wiring board 40 is output from the electrode terminal 40B of the wiring board 40 to an external device (not shown) through a filter circuit including a capacitor 42 and a resistor 44. On the other hand, the vibration electrode 26 is connected to the ground electrode terminal of the electrode terminals 40B of the wiring board 40 via the conductor ring 28 and the case 22, and is similarly connected to the ground terminal of the external device. . Through the above operation, sound can be converted into an electrical signal and output to an external device.

  The capacitor 42 and the resistor 44 constituting the filter circuit may be mounted with chip parts, but if formed by a film production technique such as a thin film formation technique or a print formation technique, a plurality of capacitors or resistors are incorporated. Since it is also easy, it is possible to realize an even thinner and higher-performance ECM. Since the filter circuit formed by such a film manufacturing technique can have a thickness of about several tens of μm, noise can be efficiently prevented without increasing the thickness of the ECM 20.

  Since the ECM 20 according to the present embodiment uses a semiconductor element 46 having a bare chip configuration and having an input terminal 46A and an output terminal 46B having protruding electrodes on both sides, the thickness thereof is 0.1 mm to 0.3 mm. Can be about. Further, since no pin-shaped electrode terminals are used, the thickness of mounting the semiconductor element 46 can be significantly reduced as compared with the conventional case. Therefore, the thickness of the entire ECM can be reduced as compared with the conventional one.

  Furthermore, according to the ECM 20 of the present embodiment, the connection between the input terminal 46A of the semiconductor element 46 and the metal plate 34 of the fixed electrode 36 is performed by applying a conductive adhesive on the protruding electrode, Since it is only necessary to insert the case 22 and caulk the lower surface portion of the case 22, the assembly process can be simplified. In addition, since it is not necessary to provide a wiring for connecting the fixed electrode 36 to the wiring board 40, the insulator 38 can be manufactured at low cost.

  In the present embodiment, the semiconductor element 46 is mounted on the wiring board 40 together with the capacitor 42 and the resistor 44 in advance, and then connected to the metal plate 34 of the fixed electrode 36 with a conductive adhesive. This is not a limitation. For example, the case 22 may be crimped and assembled so that the semiconductor element 46 is in a state of being crimped to the metal plate 34. Further, the connection between the semiconductor element 46 and the wiring board 40 may be performed using a conductive adhesive at the same time when the semiconductor element 46 is connected to the metal plate 34.

  Furthermore, in this embodiment, the space where the semiconductor element 46, the capacitor 42, and the resistor 44 are mounted is not particularly positively sealed, but the present invention is not limited to this. . For example, after applying an insulating resin on the surface of the wiring board 40 except for the region where the semiconductor element 46 is mounted, the wiring board 40 is inserted into the case 22 and the input terminal 46A of the semiconductor element 46 is connected. Simultaneously with the connection with the metal plate 34, the space may be filled with resin so as to surround the semiconductor element 46 and shielded from the outside air. Alternatively, an adhesive is applied to the outer peripheral portion of the wiring substrate 40, and when the lower surface portion of the case 22 is caulked, the outer peripheral portion of the wiring substrate 40 and the insulator 38 are bonded, thereby removing the space portion from the outside air. You may make it shield. By doing so, the reliability of the semiconductor element 46 having a bare chip configuration can be further improved.

(Second Embodiment)
FIG. 3 is a cross-sectional view of an ECM 50 according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected about the same element as FIG. 1 and FIG.

  As with the ECM 20 of the first embodiment, the case 22 has a cylindrical shape made of aluminum (Al), for example, and is provided with an audio input opening 22A. A metal face cloth 24 is attached to the inner surface of the voice input opening 22A to prevent dust from entering the inside.

  Inside the case 22, a vibrating electrode 26 made of a first electret dielectric film having a first electrode film (not shown) formed on one surface, and conductivity for fixing the vibrating electrode 26 to the case 22. The electrode ring 28, the fixed electrode 58, the insulating spacer 30 for arranging the fixed electrode 58 and the vibrating electrode 26 to face each other with a predetermined distance, and the wiring board 40 maintain a predetermined positional relationship. And electrical connection is made.

  In the present embodiment, the fixed electrode 58 includes a second electret dielectric film 52 having a second electrode film 54 formed on one surface, and a reinforcing plate 56 made of a resin or the like adhered to the second electrode film 54. It is configured. As shown in FIG. 4, the reinforcing plate 56 is provided with an opening 56 </ b> A having a shape slightly larger than that of the semiconductor element 46. On the wiring board 40 having the same configuration as that of the first embodiment, a capacitor 60 and a resistor 62 formed by thin film technology are provided. In the semiconductor element 46, the electrode terminal provided in the electrode wiring 40 </ b> A and the output terminal 46 </ b> B of the semiconductor element 46 are connected on the wiring substrate 40 at a position corresponding to the opening 56 </ b> A of the reinforcing plate 56. Further, the input terminal 46A of the semiconductor element 46 and the second electrode film 54 of the fixed electrode 58 are connected by a conductive adhesive.

  The method for assembling the ECM 50 can be performed in the same manner as in the first embodiment, and thus description thereof is omitted.

  In the ECM 50 of the present embodiment, the opening 56A is provided in the reinforcing plate 56, and the semiconductor element 46 is accommodated in the opening 56A. Therefore, the space portion as in the case of the ECM 20 of the first embodiment is used. Can be further reduced.

  Since the thickness of the second electret dielectric film 52 of the fixed electrode 58 is 2 μm to 5 μm and the second electrode film 54 is about 0.1 μm to 0.5 μm, the input terminal 46A of the semiconductor element 46 is connected. Sometimes heavy loads can cause damage. For this reason, it is desirable to apply a conductive adhesive on the protruding electrode so that the conductive adhesive is connected and fixed to the second electrode film 54 exposed in the opening 56A in a wide area. .

  Further, FIG. 5 shows a cross-sectional configuration of the ECM 70 of a modified example of the ECM 50 of the present embodiment. In addition, the same code | symbol is attached | subjected about the same element as FIG. 3 and FIG.

  The ECM 70 shown in FIG. 5 is different from the ECM 50 shown in FIG. 3 in the configuration of the fixed electrode 66. That is, in the case of the ECM 70 of this modification, the fixed electrode 66 includes the second electret dielectric film 52, the second electrode film 54 formed on one surface thereof, the reinforcing plate 56 provided with the opening 56A, and the second It is composed of a metal plate 64 having a thickness of about 0.05 mm that is conductively joined to the electrode film 54. The reinforcing plate 56 is bonded to the metal plate 64. Other configurations are the same as those of the ECM 50 shown in FIG.

  Thus, by inserting the metal plate 64 between the second electrode film 54 and the reinforcing plate 56, the protruding electrode provided on the input terminal 46A of the semiconductor element 46 and the metal plate 64 may be connected by pressure contact. This makes it possible to prevent the manufacturing yield of the ECM 70 from being reduced by the weight applied when caulking at the lower surface of the case 22.

(Third embodiment)
FIG. 6 shows a cross-sectional view of an ECM 80 according to a third embodiment of the present invention. In addition, the same code | symbol is attached | subjected about the same element as the element shown in FIGS.

  The ECM 80 of the present embodiment is different from the ECMs of the first embodiment and the second embodiment in the configuration of the fixed electrode 88, and therefore, the configuration of the fixed electrode 88 will be mainly described.

  FIG. 7 is an external perspective view of the fixed electrode 88. In the present embodiment, as can be seen from FIGS. 6 and 7, the second electret dielectric film 82 having the second electrode film 84 formed on one surface has a part of a circular outer peripheral region cut out. ing.

  The wiring board 86 has a capacitor (not shown) and a resistor (not shown) formed on the surface thereof by a thin film technique or a print forming technique, and an electrode wiring 86A is further formed on the surface layer. An electrode terminal 86C for connecting to an external device (not shown) is provided on the outer surface via the electrode wiring 86A and the vertical connection conductor 86D. The electrode wiring 86A is processed to have a shape slightly larger than that of the second electret dielectric film 82, and is electrically connected to the second electrode film 84 on the entire surface excluding the region connected to the input terminal 90A of the semiconductor element 90. . Further, a part of the film is exposed even after the second electret dielectric film 82 is attached, and is connected to the input terminal 90A of the semiconductor element 90 in this region. Further, an electrode wiring 86B for connecting to the output terminal 90B of the semiconductor element 90 is formed on the same surface as the electrode wiring 86A and at a position facing it.

  In the second electret dielectric film 82, the second electrode film 84 and the electrode wiring 86 </ b> A are conductively bonded and fixed to the wiring substrate 86.

  Further, in this embodiment, the bare chip-structured semiconductor element 90 is formed on the same surface for both the input terminal 90A and the output terminal 90B, and is provided with a protruding electrode (not shown). The semiconductor element 90 has an input terminal 90A connected to the electrode wiring 86A and an output terminal 90B connected to the electrode wiring 86B through the protruding electrodes. This connection may be a method using a conductive adhesive, or may be a method such as solder bonding or gold-tin (Au-Sn) bonding in which protruding electrodes are formed of solder or gold (Au). Also good. In this way, in addition to the second electret dielectric film 82, a fixed electrode including a capacitor (not shown), a resistor (not shown), and the like constituting a semiconductor element 90 and a filter circuit on the wiring board 86. 88 is configured.

  If the fixed electrode 88 is opposed to the vibrating electrode 26 via a spacer 92 so as to maintain a predetermined distance and the lower surface portion of the case 22 is crimped, the assembly is completed and the ECM 80 is obtained.

  As described above, according to the present embodiment, the wiring board 86 also serves as a reinforcing plate for the second electret dielectric film 82, and the semiconductor element 90 includes the vibrating electrode 26 and the second electret dielectric film 82. Since it is housed in the created space, the whole can be made thinner. In the present embodiment, since almost all components including the second electret dielectric film 82 and the semiconductor element 90 are mounted on the wiring board 86 and then inserted into the case 22, the assembly process can be simplified. It becomes possible.

  In the present embodiment, in order to mount the semiconductor element 90, a part of the outer periphery of the second electret dielectric film 82 is cut out, but the present invention is not limited to this. For example, the semiconductor element 90 may be mounted by providing an opening in the second electret dielectric film 82 and forming the electrode wirings 86A and 86B on the wiring substrate 86 located in the opening.

  In the first to third embodiments, the ECM is assembled by caulking the lower surface portion of the case. However, the present invention is not limited to this. For example, a cylindrical case is used, a wiring board is fitted into the lower surface of the case, a fixed electrode, a vibration electrode, an electrode ring, a spacer and an insulator are then disposed, and finally a face cloth is attached. It is good.

  In the above embodiment, the face cloth 24 is shown inside the case 22, but it may be outside the case 22.

  In this example, an ECM 200 according to a modification in which the ECM 20 of the first embodiment is used as a base and the filter circuit configuration is partially changed will be described. FIG. 8 is a diagram showing a cross-sectional configuration of the ECM 200 of the present embodiment. FIG. 9 is a plan view showing a filter circuit configuration on the wiring board 140. FIG. 10 is a circuit diagram illustrating the circuit configuration of the ECM 200 according to the present embodiment. In addition, the same code | symbol is attached | subjected about the same element as FIG. 1 and FIG.

  In this example, the structure of the wiring board 140 is different from the ECM 20 described in the first embodiment, and therefore this wiring board 140 will be mainly described. In the wiring substrate 140, lower electrode wirings 182 a, 182 b, 182 c, and 182 d are formed on the surface of the resin base material 181 that faces the fixed electrode 36. The lower electrode wiring 182a also serves as a lower capacitor electrode layer, and a dielectric layer 184 is formed so that this electrode terminal portion is exposed. Further, upper capacitor electrode layers 185 a and 185 b are formed on the dielectric layer 184. The first capacitor 190 is constituted by the lower layer electrode wiring 182a, the dielectric layer 184 and the upper capacitor electrode layer 185a. Similarly, the second capacitor 195 is formed by the lower layer electrode wiring 182a, the dielectric layer 184 and the upper capacitor electrode layer 185b. Has been. Resistance layers 186a and 186b are formed between the lower layer electrode wirings 182b and 182c and between the lower layer electrode wirings 182b and 182d. The first resistor 100 and the second resistor 100 including the lower layer electrode wirings 182b, 182c and 182d The resistor 105 is configured. These two resistors and two capacitors constitute the filter circuit of this embodiment.

  In addition, electrode terminals 146 and 148 for connecting to an external device (not shown) are formed on the outer surface of the resin base material 181. These electrode terminals 146 and 148 are connected to lower layer electrode wirings 182c and 182a by upper and lower connection conductors 142 and 144, respectively.

Hereinafter, a specific manufacturing process of the wiring board 140 will be described. As the resin substrate 181, a glass epoxy substrate having a thickness of 0.13 mm was used. A copper (Cu) thin film was formed on the glass epoxy substrate to a thickness of about 200 nm by sputtering, and predetermined pattern processing was performed to form lower layer electrode wirings 182a, 182b, 182c, and 182d. Next, after masking so that only the electrode terminal portion of this lower layer electrode wiring 182a was exposed, a silicon dioxide (SiO ₂ ) thin film was formed to a thickness of about 100 nm by a sputtering method to form a dielectric layer 184. Further, a copper (Cu) thin film was similarly formed on the dielectric layer 184 by sputtering to a thickness of about 200 nm, and predetermined processing was performed to form upper capacitor electrode layers 185a and 185b. By this step, the first capacitor 190 and the second capacitor 195 are formed.

  Next, a nickel-chromium (Ni—Cr) alloy is formed by a sputtering method, and a rectangular resistance layer 186a having a sheet resistance value of 1000Ω / □ between the lower electrode wiring 182b and the lower electrode wiring 182c, 182d, 186b was formed. By this step, the first resistor 100 and the second resistor 105 are formed.

  Note that the capacitance values of the first capacitor 190 and the second capacitor 195 in this embodiment are 100 pF and 10 pF, respectively, and the resistance values of the first resistor 100 and the second resistor 105 are both 150Ω. I did it.

After that, a protection composed of a two-layer structure of a silicon dioxide (SiO ₂ ) thin film and a silicon nitride (Si ₃ N ₄ ) thin film on the entire surface except for the electrode terminal portions of the lower layer electrode wirings 182 a and 182 d connected to the output terminal 46 B of the semiconductor element 46. A layer (not shown) was similarly formed by sputtering. Thereby, the wiring board 140 is completed.

  The shape of the case 22 is 7 mm in diameter and 0.4 mm in thickness. As the vibrating electrode 26, a first electret dielectric film made of polyphenylene sulfide having a thickness of 2 μm was used, and a first electrode film was formed on one surface by vapor deposition. The vibrating electrode 26 was bonded on the outer peripheral surface of the spacer 30 by hot pressing. The spacer 30 has a thickness of 0.1 mm. The thickness of the electrode ring 28 was 0.2 mm. The semiconductor element 46 is a bare-chip field effect transistor having a thickness of 0.1 mm, and protruding electrodes formed on the input terminal 46A and the output terminal 46B are formed to a thickness of about 30 μm by gold (Au) plating. .

  The ECM 200 assembled as described above can not only have a thickness of about 0.8 mm, but can also incorporate a filter circuit including two capacitors and two resistors. The noise removal performance of this ECM200 was evaluated. The evaluation method was performed by inputting 115 dBμV noise to the input of the semiconductor element 46, which is a field effect transistor, and measuring an output noise level of 500 MHz or higher. As a result, the average noise level in the case of the conventional ECM was 40 dBmV, whereas in the case of the ECM200 of the present embodiment, it was 85 dBmV. Further, as a result of evaluating the degree of deterioration of the sound volume by an acceleration test, it was recognized that only about 20% of the fluctuation occurred even when used for 5 years under a temperature condition of 30 ° C., and good results were obtained.

  In this embodiment, the lower electrode wirings 182a, 182b, 182c, and 182d made of a copper (Cu) thin film are formed on the resin substrate 181, but a nickel (Ni) thin film is further formed on the copper (Cu) thin film. It is desirable to form a laminated film made of a gold (Au) thin film because the moisture resistance is further improved. Alternatively, instead of the copper (Cu) thin film, aluminum (Al) is deposited and subjected to heat treatment at 180 ° C. for 10 hours, and then the dielectric layer 184 and the resistance layers 186a and 186b are formed. Good.

  Moreover, as the resin base material 181, it is not limited to a glass epoxy base material, For example, you may use a polyimide base material. Furthermore, as the electret dielectric film, a syndiotactic polystyrene film having the same thickness may be used instead of polyphenylene sulfide.

  Further, as the dielectric layer 184, divinyl biphenyl monomer may be applied and cured by electron beam irradiation, and then thermally cured at 240 ° C. for use.

  Further, the ECM of the present invention may have a structure in which at least one of the first electret dielectric film or the second electret dielectric film is interposed between the first electrode film and the second electrode film. In particular, since the second electret dielectric film does not vibrate directly, electretization is facilitated. Also, when an aluminum foil having a thickness of more than 50 μm is used as the second electrode film, unlike the aluminum vapor deposition film, stable polarization treatment is performed without worrying about thermal contraction or fast cooling of the second electret dielectric film. be able to. Further, when the volume of the first electrode film and the second electrode film is too small and the audio signal is distorted, the second electret dielectric film is made smaller to release the sound pressure, and the second electrode film is included. It is good also as a structure which provides a through-hole and releases sound pressure to the exterior below. The through-hole at that time may penetrate through the wiring board in the region where there is no electronic component or electrical wiring.

  The ECM according to the present invention can reduce the space in which the semiconductor element is arranged, can be connected with the shortest wiring length, and does not require the formation of wiring for connecting from the fixed electrode to the wiring board. In addition, since it is possible to realize an ECM that is easy to assemble, it can be applied to applications such as mobile phones.

Sectional drawing of ECM concerning the 1st Embodiment of this invention The exploded perspective view of ECM in the embodiment Sectional drawing of ECM concerning the 2nd Embodiment of this invention The perspective view of the reinforcement board used for ECM of the embodiment Sectional drawing of ECM of the modification in the embodiment Sectional drawing of ECM concerning the 3rd Embodiment of this invention External perspective view of fixed electrode of ECM of same embodiment Sectional drawing of ECM concerning the Example of this invention The top view which shows the shape which comprises a filter circuit on the wiring board of ECM in the Example The circuit diagram explaining the circuit structure of ECM in the same Example Sectional drawing for demonstrating the conventional ECM structure Exploded perspective view of the ECM Circuit diagram for explaining the circuit configuration of the ECM

Explanation of symbols

1, 22 Case 1A, 22A, 56A Opening 2, 24 Face cloth 3, 26 Vibration electrode 4, 28 Electrode ring 5, 36, 58, 66, 88 Fixed electrode 5A, 32, 52, 82 Second electret dielectric film 5B, 34, 64 Metal plate 6, 30, 92 Spacer 7, 38 Insulator 8, 46, 90 Semiconductor element 9, 42, 60 Capacitor 10, 44, 62 Resistance 11, 40, 86, 140 Wiring board 12, 40A, 86A, 86B Electrode wiring 13A, 13B, 15, 16, 40B, 86C, 146, 148 Electrode terminal 20, 50, 70, 80, 200 Electret condenser microphone (ECM)
40C, 86D, 142, 144 Upper and lower connecting conductors 46A, 90A Input terminal 46B, 90B Output terminal 54, 84 Second electrode film 56 Reinforcing plate 100 First resistor 105 Second resistor 181 Resin substrate 182a, 182b, 182c, 182d Lower layer electrode wiring 184 Dielectric layer 185a, 185b Upper capacitor electrode layer 190 First capacitor 195 Second capacitor 186a, 186b Resistance layer

Claims (8)

A vibrating electrode comprising a first electret dielectric film having a first electrode film formed on one surface;
A second electret dielectric film having a second electrode film formed on one surface thereof; and a holding plate for holding the second electret dielectric film, wherein the other surface of the second electret dielectric film is the first electret dielectric film. A fixed electrode disposed to face the other surface of the electret dielectric film;
A wiring board disposed in close contact with or with a gap to the holding plate;
An input terminal on one surface, an output terminal on the other surface, and a semiconductor element for impedance-converting and amplifying an electric signal of a bare chip configuration in which a protruding electrode is formed on each of the input terminal and the output terminal; Including
The semiconductor element is disposed between the fixed electrode and the wiring board, and the input terminal and the fixed electrode, and the output terminal and the electrode terminal on the wiring board are connected via the protruding electrodes, respectively. An electret condenser microphone characterized by The holding plate of the fixed electrode is made of a metal plate that is conductively joined to the second electrode film,
The wiring board is disposed with an interval at least larger than the thickness of the semiconductor element,
The input terminal of the semiconductor element is connected to the metal plate via the protruding electrode, and the output terminal is connected to the electrode terminal on the wiring board via the protruding electrode. Item 2. An electret condenser microphone according to Item 1. The holding plate of the fixed electrode is composed of an insulating plate that is bonded to the second electrode film and provided with an opening having a shape for housing the semiconductor element,
The wiring board is disposed in close contact with the insulating plate,
The semiconductor element is housed in the opening, the input terminal is connected to the second electrode film via the protruding electrode, and the output terminal is connected to the electrode terminal on the wiring substrate via the protruding electrode. The electret condenser microphone according to claim 1, wherein the electret condenser microphone is provided. The holding plate of the fixed electrode is composed of an insulating plate that is bonded via a metal plate that is conductively bonded to the second electrode film, and that is provided with an opening having a shape that houses the semiconductor element,
The wiring board is disposed in close contact with the insulating plate,
The semiconductor element is housed in the opening, the input terminal is connected to the metal plate via the protruding electrode, and the output terminal is connected to the electrode terminal on the wiring board via the protruding electrode. The electret condenser microphone according to claim 1, wherein: The electret condenser microphone according to any one of claims 1 to 4, wherein the protruding electrode of the input terminal of the semiconductor element and the fixed electrode are connected by a conductive adhesive. 5. The electret condenser microphone according to claim 2, wherein the protruding electrode and the fixed electrode of the input terminal of the semiconductor element are electrically connected by pressure contact. A vibrating electrode comprising a first electret dielectric film having a first electrode film formed on one surface;
A second electret dielectric film having a second electrode film formed on one surface and having at least a larger opening or notch than the semiconductor element;
An input-side electrode terminal electrically connected to the second electrode film and extending to the opening or the notch, and an output-side electrode terminal provided in the opening or the notch are formed. A wiring board;
An input terminal and an output terminal on one side, and a semiconductor element that impedance-converts and amplifies an electric signal of a bare chip configuration in which a protruding electrode is formed on each of the input terminal and the output terminal,
The second electret dielectric film is bonded and fixed to the wiring board, the second electrode film and the input side electrode terminal are connected, and the input terminal of the semiconductor element and the input side electrode of the wiring board A terminal, and the output terminal and the output-side electrode terminal are connected to each other, and the surface of the second electret dielectric film and the surface of the first electret dielectric film are opposed to each other with a predetermined interval. An electret condenser microphone characterized by being arranged. 8. The circuit board according to claim 1, wherein a filter circuit including one or more electronic components selected from a capacitor, a resistor, and an inductor is formed on the wiring board by a film manufacturing technique. The electret condenser microphone described in 1.

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