JP2006157837A - Capacitor microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitor microphone which has high heat-resistant properties and can be mounted through a reflow soldering process. <P>SOLUTION: A capacitor composed of a vibrating film 35 and a back electrode 37 is built in a cylindrical capsule 31. An IC device 43, equipped with the function that converts an electrostatic capacity change in the capacitor into impedance and another function that applies a bias voltage to the capacitor, is mounted on the internal surface of a circuit board 44, which caps up the opening of the capsule 31. Since an electret which is reduced in potential and sensitivity with a rise in temperature is not used, the capacitor microphone can be mounted through a reflow soldering process, prevented from being reduced in sensitivity due to the adverse effect of a reflow heat (reflow temperature), and can be kept high in sensitivity there. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bias-type condenser microphone that does not include an electret, and particularly relates to a condenser microphone that is suitable for reflow soldering mounting without causing a decrease in sensitivity due to reflow heat.

Looking at the technological progress of condenser microphones, in which the electrode potential of a capacitor that vibrates due to sound waves is captured as a change in capacitance and converted into an electrical signal, the technology of applying a bias potential to one electrode of the capacitor and grounding the other electrode Next, the technology shifted to a technique in which an electret is provided on one electrode and the other electrode is grounded without requiring a bias potential. An electret condenser microphone using this electret is used in various directions as a condenser microphone that can be miniaturized and has high sensitivity.
FIG. 12 is a conventional cross-sectional configuration example illustrating an electret condenser microphone (hereinafter referred to as ECM), and shows a configuration described in Patent Document 1. Here, the electret condenser is built in the cylindrical capsule 11, the circuit board 12 is accommodated in the opening of the capsule 11, and the opening is covered with the circuit board 12.

The electret capacitor is composed of the vibration film 13, the back electrode 14, and the electret 15 disposed on the surface of the back electrode 14 facing the vibration film 13, so that the vibration film 13 faces the front plate 11 a of the capsule 11. Is arranged. The periphery of the vibrating membrane 13 is fixed to the vibrating membrane ring 16, and this vibrating membrane ring 16 is on the front plate 11 a side and is accommodated in the capsule 11.
A ring-shaped spacer 17 is interposed between the vibrating membrane 13 and the back electrode 14 to form a predetermined gap, and the back electrode 14 is held by a conductive cylindrical body 18 mounted on the circuit board 12. Has been. An insulating ring 19 is fitted on the outer peripheral surfaces of the back electrode 14 and the conductive cylindrical body 18.

The circuit board 12 is fixed by caulking the opening end of the capsule 11 and bending it inward, and the circuit board 12 is pressed and fixed by the bent caulking portion 11b. An IC element 21 for impedance conversion such as a FET (field effect transistor) is mounted on the inner surface (mounting surface) of the circuit board 12, and terminal electrode patterns 22 and 23 for external connection are formed on the outer surface (mounting surface). ing.
The connection between the back electrode 14 and the electrode pattern 24 on the circuit board 12 is made through the conductive cylindrical body 18, while the vibration film 13 is connected to the terminal through the vibration film ring 16, the capsule 11 and the caulking portion 11 b thereof. It is connected to the electrode pattern 23. In FIG. 12, 25 indicates a sound hole, and 26 indicates a cross.

In the structure as described above, a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) is generally used for the electret 15.
Japanese Utility Model Publication No. 5-23698

  As described above, the conventional electret condenser microphone includes the electret 15 having a residual charge as one electrode of the condenser. And as this electret 15, FEP is used, but this FEP has a low potential remaining rate due to charges at high temperature, and the potential is significantly lowered by being exposed to a high temperature such as 260 ° C. in reflow soldering, An electret condenser microphone using such FEP as an electret is not suitable for reflow soldering because it causes a significant decrease in sensitivity. In other words, a reflow device (reflow tank) is used for mounting the circuit board 12 on a counterpart mounting board. The soldering that was used cannot be applied.

  In view of such circumstances, an object of the present invention is to provide a highly heat-resistant condenser microphone that does not cause a decrease in sensitivity and can sufficiently withstand reflow soldering mounting.

    In order to achieve the above-mentioned object, the present invention includes a cylindrical capsule with a capacitor having a vibrating membrane on one electrode side and a device for equivalently converting impedance of the capacitance of the capacitor. A capacitor microphone whose opening is covered with a circuit board, wherein an IC element having a function of applying a bias voltage to the capacitor is mounted on the circuit board.

  According to the present invention, it is a self-bias type condenser microphone that does not use an electret that lowers the potential due to reflow heat and causes a significant decrease in sensitivity. A high heat resistance type condenser microphone to which reflow soldering mounting can be applied can be obtained.

Embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 shows an embodiment of a condenser microphone according to the present invention, and FIG. 2 is an exploded view of each part. First, the configuration of each unit will be described with reference to FIG.
1 and 2, the capsule 31 has a cylindrical shape with one end face (front face) closed, and a plurality of sound holes 32 are formed in the front plate 31a closing the one end face. The capsule 31 is made of white and white in this example, and an insulating film 33 is formed on the inner surface by applying a resin material, for example, as shown in FIG.

The bias ring 34 is formed by using a metal plate, and includes a ring portion (plate surface) 34a and a plurality of leg portions 34b that are formed by protruding from the outer periphery of the ring portion 34a in a direction perpendicular to the ring portion 34a. It is supposed to be. In this example, three leg portions 34b are provided at a pitch of 120 °.
In this example, the vibration film 35 is formed of a nickel thin film having a thickness of about 1 μm, and the periphery thereof is fixedly held by a vibration film ring 36.
A large number of through holes 38 are formed in the back pole 37 as shown in FIG. A ring-shaped insulating spacer 39 is arranged on the outer periphery of the back electrode 37. In this example, the spacer 39 is formed by printing and applying polyimide.

The back electrode holder 41 is used to position and hold the back electrode 37 and has a substantially cylindrical shape. On the outer peripheral surface of the back electrode holder 41, three cutout surfaces 41a are formed corresponding to the positions of the three legs 34b of the bias ring 34. A step 41b having a slightly larger diameter is formed on the inner peripheral surface. In this example, polyphthalamide (PPA) is used as a constituent material of the back electrode holder 41.
The gate ring 42 has a cylindrical shape. The gate ring 42 and the above-described bias ring 34, diaphragm ring 36, and back electrode 37 are all made of brass.
The IC element 43 has a function of equivalently converting the change in the capacitance of the capacitor constituted by the vibration film 35 and the back electrode 37 and a function of applying a bias voltage to the capacitor. The Although not shown in detail, the IC element 43 includes a ground (GND) electrode on its bottom surface (mounting surface) and a required terminal electrode on its top surface.

The circuit board 44 is circular, and a required pattern is formed on the upper and lower surfaces (inner and outer surfaces) thereof. 3A and 3B show the inner surface (upper surface) pattern shape and outer surface (lower surface) pattern shape of the circuit board 44 together with the IC element 43, and FIG. 3B shows the outer surface pattern shape seen through from the inner surface side. ing.
As shown in FIG. 3A, an annular bias terminal pattern 45 is formed on the outer peripheral side of the inner surface of the circuit board 44, and an annular input terminal pattern 46 is formed inside the bias terminal pattern 45. A GND electrode pattern 47 is formed at the center, and an output electrode pattern 48, a power electrode pattern 49, and a relay pattern 51 are formed in a small island shape between the GND electrode pattern 47 and the input terminal pattern 46. The annular bias terminal pattern 45 and the relay pattern 51 connected thereto are connected to the leg 34b of the bias ring 34, and the input terminal pattern 46 is connected to the gate ring 42. The power supply electrode pattern 49, the input terminal pattern 46, the relay pattern 51, and the output electrode pattern 48 are connected to each terminal of the IC element 43 mounted on the GND electrode pattern 47 on the inner surface of the circuit board 44 and grounded. .

  On the other hand, an annular GND electrode pattern 52 is formed on the outer peripheral edge of the outer surface of the circuit board 44 as shown in FIG. 3B, and an output terminal pattern 53, a power source are provided in an inner region surrounded by the GND electrode pattern 52. A terminal pattern 54 and a GND terminal pattern 55 are formed. The output terminal pattern 53, the power supply terminal pattern 54, and the GND terminal pattern 55 are all circular, and the output electrode pattern 48, the power supply electrode pattern 49, and the GND electrode pattern 47 on the inner surface side and through holes (not shown), respectively. It is connected. The GND terminal pattern 55 and the GND electrode pattern 52 are connected by a connection pattern, although not shown in the drawing.

  Further, in this example, the output terminal pattern 53, the power supply terminal pattern 54, and the GND terminal pattern 55 that form a circle are stepped 61 by increasing the plating thickness, for example, compared to the GND electrode pattern 52 located at the peripheral flat portion 60 of the outer peripheral edge. 1 (see FIG. 1) and is formed on a flat portion 62 (see FIG. 1) that protrudes toward the mounting surface side, and has a required protruding height (thickness) of 61 steps as shown in FIG. It is supposed to be. Further, a resist (insulating material) 56 is applied to portions other than the GND electrode pattern 52, the output terminal pattern 53, the power supply terminal pattern 54, and the GND terminal pattern 55 on the outer surface of the circuit board 44.

  The IC element 43 is mounted on the circuit board 44 by using, for example, a conductive adhesive. The IC element 43 is mounted on the GND electrode pattern 47 on the inner surface of the circuit board 44, and the GND electrode on the bottom surface is the GND electrode. Connected with the pattern 47. The bias terminal pattern 45, the input terminal pattern 46, the output electrode pattern 48, and the power electrode pattern 49 on the circuit board 44 are connected to the corresponding terminal electrodes on the upper surface of the IC element 43 by wire bonding. In FIG. 3A, 46a, 48a, and 49a denote wire bonding portions, and wire bonding between the IC element 43 and the bias terminal pattern 45 located on the outermost periphery is performed via the relay pattern 51. In the above description, the method of connecting the IC element 43 and each pattern on the circuit board 44 by wire bonding has been described. However, by changing the structure of each pattern to an optimum structure, it may be performed by flip chip mounting. Is possible.

Next, the incorporation of each part into the capsule 31 will be described.
First, the bias ring 34 is assembled in the capsule 31 so that the ring portion 34a faces the front plate 31a of the capsule 31, and subsequently the diaphragm ring 36 holding the diaphragm 35 and the back electrode on which the spacer 39 is disposed. 37 and the back electrode holder 41 are sequentially assembled. Then, the tips of the three leg portions 34b of the bias ring 34 are bent inward, and the back electrode holder 41 is held by the bent portions 34c as shown in FIG.
Next, the circuit board 44 on which the gate ring 42 and the IC element 43 are mounted is incorporated, and the opening end of the capsule 31 is crimped and bent inward. As a result, the circuit board 44 is pressed and fixed by the caulking portion 31b of the capsule 31, and the opening portion of the capsule 31 is covered by the circuit board 44 to complete the condenser microphone shown in FIG.

  As shown in FIG. 1, the capacitor including the vibration film 35 and the back electrode 37 is built in the capsule 31 with the vibration film 35 facing the front plate 31 a of the capsule 31, and the vibration film ring 36 is a ring portion of the bias ring 34. 34a is contacted. The back pole 37 disposed opposite to the vibrating membrane 35 via the spacer 39 is positioned and fixed at the step 41 b provided on the inner circumference of the back pole holder 41. Further, the bent portion 34c at the tip of the leg portion 34b of the bias ring 34 and the lower end of the gate ring 42 are in contact with the bias terminal pattern 45 and the input terminal pattern 46 formed on the inner surface of the circuit board 44 as described above. The In FIG. 1, illustration of each pattern formed on the inner surface of the circuit board 44 and illustration of bonding wires are omitted, and two of the three legs 34b of the bias ring 34 are for convenience. Show. In FIG. 1, reference numeral 57 denotes a solder bump.

  FIG. 4 shows the circuit configuration of the condenser microphone, and shows the connection state of the diaphragm 35, the terminal on the back electrode 37 circuit board 44, and the IC element 43. That is, the vibration film 35 is connected to the booster circuit B in one IC element 43 via the bias ring 34 and the bias terminal pattern 45 on the circuit board 44, and the booster circuit B includes the power supply electrode pattern 49 and the power supply. It is connected to the power supply Vcc via the terminal pattern 54. The back electrode 37 is connected to the gate of the FET which is an impedance conversion element in the IC element 43 via the gate ring 42 and the input terminal pattern 46 on the circuit board 44, and the source of the FET is the output electrode pattern 48 and the output. The terminal is connected to the signal output terminal OUT via the terminal pattern 53, and the drain of the FET is grounded via the GND electrode pattern 47 and the GND terminal pattern 55. In this way, a bias voltage is applied to the vibrating membrane 35 via the booster circuit B of the IC element 43, and the detection signal of the back electrode 37 is impedance-converted via the FET built in the IC element 43, and the signal output An output signal is obtained at the end OUT.

In the above description based on FIGS. 1 to 4, the bias voltage is applied to the vibration film 35 and the detection signal is obtained from the back electrode 37. However, the detection signal is obtained from the vibration film 35 and the back electrode is obtained. A configuration in which a bias voltage is applied to 37 is also possible. In this case, a signal is taken out from the bias ring 34 in FIGS. 1 and 2, and a bias voltage is applied to the gate ring 42 in FIGS. 1 and 2, or the bias terminal pattern 45 in FIG. 3 becomes an input terminal pattern. This can be realized by changing the input terminal pattern 46 to a bias terminal pattern.
In the description so far, the output terminal pattern 53, the power supply terminal pattern 54, and the GND terminal pattern 55 on the outer surface of the circuit board 44 are, for example, plated thicker than the GND electrode pattern 52 positioned on the peripheral flat portion 60. The flat part 62 (refer FIG. 1) of the shape which has the level | step difference 61 (refer FIG. 1) and protruded in the mounting surface side was formed by enlarging the height. This is because when the condenser microphone is mounted on the mounting substrate, the solder bump 57 is melted and soldered to the mounting substrate by the reflow bath, and the caulking portion 31b that assembles the entire microphone is distorted by heat. Further, the present invention addresses the problem that solder flows from the caulking portion 31b, which causes instability of the microphone assembly and lowers the sensitivity of the microphone. That is, by forming a flat portion 62 having a step 61 on the outer surface of the circuit board 44 and forming terminals and solder bumps 57 on the mounting surface side of the flat portion 62, the influence of heat on the caulking portion 31b is reduced. The solder can be prevented from flowing into the caulking portion 31b. When the height of the step 61 is larger than the thickness of the capsule 31, the above effect is remarkable.

  FIG. 5 illustrates another configuration of the circuit board 44 on the assumption that the step 61 is formed. FIG. 5 illustrates a cross section taken along the line XX in FIG. 3 of the circuit board 44 in a state where the condenser microphone is mounted on the mounting board. A circuit board 44 shown in FIG. 5 includes an upper mold body 44a and a lower mold body 44b made of a resin material. The upper mold body 44a is a resin plate having a structure in which a conductor pattern is deposited on an upper flat surface. The mold body 44b is an insert molded body made of a resin material in which an annular metal body 44c of a metal plate is arranged like a ridge. Here, the conductor pattern of the upper mold body 44a includes a bias terminal pattern 45, an input terminal pattern 46, an output electrode pattern 48, a power supply electrode pattern 49, and a GND electrode pattern 47 from the outside. In the lower mold body 44b, the annular metal body 44c is used as a peripheral flat portion 60, and a flat portion 62 protruding with a step 61 on the outer surface (mounting surface side) is molded with a resin material. An output terminal pattern 53 and a power supply terminal pattern 54 are formed on the mounting surface side of the flat portion 62. The flat surfaces of the upper mold body 44a and the lower mold body 44b are bonded together and integrated. In this case, the power electrode pattern 49 and the power terminal pattern 54 are connected by the through hole 44d, and similarly, the output electrode pattern 48 and the output terminal pattern 53 are also connected by the through hole 44e.

Thus, by forming the flat portion 62 having the step 61 made of the resin material on the outer surface of the circuit board 44 and forming the terminals and the solder bumps 57 on the mounting surface side, the influence of heat on the caulking portion 31b is reduced, It can also prevent the solder from flowing in.
FIG. 6 also illustrates another configuration of the circuit board 44 on the assumption that the step 61 is formed. FIG. 6A illustrates a state at the time of die-cutting a metal plate by a mold in manufacturing the circuit board 44. Here, a power supply electrode pattern 49, a power supply terminal pattern 54 connected to the power supply electrode pattern 49, an output electrode pattern 48, an output terminal pattern 53 connected thereto, and a GND electrode pattern 47 are provided at the center of a lead frame metal plate made of brass or phosphor bronze. A hole is formed leaving the GND terminal pattern 55 connected to this, and the GND electrode pattern 52 connected to the input terminal pattern 46, the bias terminal pattern 45, and the GND electrode pattern 47 around the hole is substantially annularly extracted. is there.

  Then, after the punching of the metal plate, as apparent from FIG. 6B shown in the YY line cross section of FIG. 6A, each connection line 50 is bent and output to the output electrode pattern 48 facing the inner surface of the condenser microphone. The connection line 50 is bent so that the terminal pattern 53 faces the outer surface on the mounting side, the connection line 50 is bent so that the power terminal pattern 54 faces the outer surface on the mounting side with respect to the power electrode pattern 49 facing the inner surface, and For the GND electrode pattern 47 that faces the inner surface, the connecting line 50 is bent so that the GND terminal pattern 55 and the GND electrode pattern 52 face the outer surface on the mounting side. This operation can be performed by molding with a pressing die, for example. Thus, the bias terminal pattern 45, the input terminal pattern 46, the GND electrode pattern 47, the output electrode pattern 48, and the power supply electrode pattern 49 face the inner surface, and the GND electrode pattern 52, the output terminal pattern 53, the power supply terminal pattern 54, and the GND The terminal pattern 55 can face the mounting surface side. FIG. 6B is also a diagram applied to the capsule 31 of the condenser microphone, and shows a state in which the resin is molded by insert molding. Here, the step 61 has a dimension higher than the thickness of the caulking portion 31 b of the capsule 31 to form the flat portion 62.

FIG. 7 shows still another example for forming the step 61 of the circuit board 44. In FIG. 7, the entire condenser microphone is shown. As the circuit board 44, the original board 44A is used for the step 61. The substrate 44B is laminated. In this case, a through hole 44f connected to the solder bump 57 is formed in the substrate 44B. Again, the step 61 has a dimension higher than the thickness of the caulking portion 31 b of the capsule 31.
(Second Embodiment)
The structure of the condenser microphone shown in FIGS. 1 and 2 shows a structure in which the back electrode 37 and the vibrating membrane 35 are individually provided. The structure shown in FIGS. The structure also serves as the capsule 31, and the IC element is divided into two, and is divided into an IC element 43a having a function of applying a bias voltage and an IC element 43b having an impedance conversion function. An example in which an IC element is configured is shown. That is, in FIGS. 8 and 9, the capsule 31 has a cylindrical shape with one end face (front face) closed, and a plurality of sound holes 32 are formed in the front plate 31a closing the one end face. The insulating film 33 is formed by applying a resin material, for example. A ring-shaped insulating spacer 39 is disposed on the inner peripheral edge of the front plate 31a. In this example, the spacer 39 is formed by printing and applying polyimide. A vibrating membrane ring 36 positioned inside the spacer 39 is fixed and held. A vibrating membrane 35 made of a nickel thin film having a thickness of about 1 μm is stretched on the vibrating membrane ring 36 in this example.
In this case, the front plate 31a also serves as a back electrode with a grounded structure. The gate ring 42 has a cylindrical shape. The gate ring 42 and the diaphragm ring 36 are all made of brass.

The IC element 43b has a function of equivalently impedance-converting a change in the capacitance of the capacitor constituted by the vibration film 35 and the capsule front plate 31a. The IC element 43a has a bias voltage applied to the capacitor. It has a function to apply. Although not shown in detail, both IC elements 43a and 43b include ground (GND) electrodes on their bottom surfaces (mounting surfaces).
The circuit board 44 is circular, and a required pattern is formed on the upper and lower surfaces (inner and outer surfaces) thereof. 3A and 3B show the inner surface (upper surface) pattern shape and outer surface (lower surface) pattern shape of the circuit board 44 together with the IC element 43, and FIG. 3B shows the outer surface pattern shape seen through from the inner surface side. ing.

An annular bias terminal pattern 45, an input terminal pattern 46, and a GND electrode pattern 47 are formed on the inner surface of the circuit board 44 as shown in FIG. 10 similar to FIG. 3A, and the GND electrode pattern 47 and the input terminal pattern 46 are formed. The output electrode pattern 48, the power supply electrode pattern 49, and the relay pattern 51 are formed in a small island shape.
For example, a conductive adhesive is used to mount the IC elements 43a and 43b on the circuit board 44. The IC elements 43a and 43b are mounted on the GND electrode pattern 47 on the inner surface of the circuit board 44. The GND electrode is connected to the GND electrode pattern 47. The bias terminal pattern 45 of the circuit board 44 is not used because it is the same as the input terminal pattern 46 here, but a structure similar to FIG. 3A is shown for convenience of manufacturing. Here, the IC element 43 a is connected to the power electrode pattern 49 and the input terminal pattern 46, and the IC element 43 b connected to the IC element 43 a is connected to the output electrode pattern 48. The connection between the output electrode pattern 48, the power supply electrode pattern 49 and the input terminal pattern 46 and the corresponding terminal electrodes on the upper surfaces of the IC elements 43a and 43b is performed by wire bonding. In the above description, the method of connecting the IC elements 43a, 43b and the respective patterns on the circuit board 44 by wire bonding has been shown. However, the structure of each pattern is changed to an optimum structure by flip chip mounting. It is possible.

  FIG. 11 shows a circuit configuration of a condenser microphone similar to that in FIG. 4, and shows a connection state of the vibrating membrane 35 and the IC elements 43a and 43b. That is, the vibration film 35 is connected to the booster circuit B in the IC element 43a via the gate ring 42 and the input terminal pattern 46 on the circuit board 44 shown in FIG. The power supply terminal pattern 54 (see FIG. 3B) is connected to the power supply Vcc. For the FET which is the impedance conversion element in the IC element 43b connected to the IC element 43a via a DC cut capacitor, the source of the FET outputs a signal via the output electrode pattern 48 and the output terminal pattern 53 (see FIG. 3B). Connected to the end OUT, the drain of the FET is grounded via the GND electrode pattern 47 and the GND terminal pattern 55 (see FIG. 3B). In this way, a bias voltage is applied to the vibration film 35 via the booster circuit B of the IC element 43a, and the detection signal of the vibration film 35 is impedance-converted via the FET built in the IC element 43b, and the signal output. An output signal is obtained at the end OUT. The capsule front plate 31a forming the back pole 37 is grounded.

Also in the second embodiment, in order to form the step 61 and the flat portion 62, FIG. 8 shows a structure in which, for example, the plating thickness is increased similarly to FIG. 1, but the structure of the step 61 is shown in FIG. The structure shown in FIG. 7 can be applied.
Further, in the first embodiment, one IC element 43 including a function of applying a bias voltage and an impedance conversion function will be described, and in the second embodiment, an IC element 43a having a function of applying a bias voltage and an impedance conversion are described. The two IC elements divided into the functional IC element 43b have been described, but the first embodiment may be two IC elements and the second embodiment may be one IC element.

  The condenser microphone configured as described above does not use an electret as in the prior art, and has a function of equivalently impedance-converting a change in the capacitance of the capacitor including the vibrating membrane 35 and the back electrode 37, and An IC element 43 having a function of applying a bias voltage to the capacitor, or an IC element 43b equivalently impedance-converting a change in the capacitance of the capacitor serving as a back electrode and a capsule, and a bias voltage applied to the capacitor It is a self-bias type condenser microphone provided with an IC element 43a for applying.

  Further, the problem that the sensitivity is lowered due to reflow heat unlike the electret condenser microphone does not occur, and a high heat resistance type condenser microphone that can sufficiently withstand reflow soldering mounting can be obtained. In addition, by using the self-bias type, it is not necessary to apply a bias from the outside, and a capacitor microphone that is easy to handle can be obtained. Further, when the IC element 43 having both functions as described above is used, the size does not increase as a whole, that is, the capsule 31 does not need to be enlarged, and in that respect, downsizing as much as the electret condenser microphone is achieved. Is possible.

In the first embodiment, the spacer 39 and the back electrode holder 41 are each made of polyimide and PPA having excellent heat resistance, the vibration film 35 is made of a nickel thin film whose resonance frequency does not change by heating, and the capsule 31 is also heat resistant. In this respect, the structure is suitable for reflow soldering mounting.
In the first and second embodiments, the output terminal pattern 53, the power supply terminal pattern 54, and the GND terminal pattern 55 of the circuit board 44 have the required height having the step 61 as shown in FIGS. The capsule 31 protrudes with a height equal to or higher than the height of the caulking portion 31b of the capsule 31 with respect to the outer surface of the circuit board 44, and the protruding flat portion 62 serves as a reflow soldering surface. It is something that can be done. In this respect, the same can be said for the examples of FIGS.

  In the first and second embodiments described above, a nickel thin film is used for the vibration film 35. For example, a film obtained by forming a metal film such as Ni or Al on one surface of a polyphenylene sulfide (PPS) film is used. May be. In this case, the vibration film using the PPS film changes in the resonance frequency due to the reflow heat, and the change is not uniform due to factors such as the assembly accuracy and the component accuracy of each condenser microphone, that is, the propagation of the reflow heat. Since the difference is not uniform and a stable performance cannot be obtained, a material that has been previously annealed at a temperature corresponding to a reflow soldering temperature (for example, 260 ° C.) is used. By doing so, it is possible to realize a condenser microphone having a stable performance with little change in sensitivity even if the resonance frequency is passed through the reflow device.

  The constituent materials of the spacer 39 and the back electrode holder 41 are not limited to polyimide and PPA, respectively. For example, both may be polyimide, or both may be PPA. Furthermore, although the spacer 39 is printed on the back electrode 37 in the above-described example, it may be configured as a separate part by using, for example, a polyimide film. In addition, when forming by printing, it does not need to be ring-shaped, and a plurality of island-shaped spacers may be formed on the outer peripheral portion of the back electrode 37 at a predetermined angular pitch.

1 is a cross-sectional view showing a first embodiment of a condenser microphone according to the present invention. The exploded perspective view of FIG. The figure which shows the pattern shape of the circuit board in FIG. 1, A shows an upper surface pattern, B shows a lower surface pattern. FIG. 2 is a circuit diagram of the condenser microphone shown in FIG. 1. Sectional drawing which shows an example of a circuit board. The top view and sectional drawing at the time of the punching which show the other example of a circuit board. Sectional drawing which shows the further another example of a circuit board. Sectional drawing which shows 2nd Embodiment of the condenser microphone by this invention. The exploded perspective view of FIG. The figure which shows the upper surface pattern shape of the circuit board in FIG. FIG. 9 is a circuit diagram of the condenser microphone shown in FIG. 8. Sectional drawing which shows the example of a conventional structure of an electret condenser microphone.

Claims (9)

A capacitor with a vibrating membrane on one electrode side in a cylindrical capsule and a device for equivalent impedance conversion of a change in capacitance of the capacitor are built in, and a capacitor whose capsule opening is covered by a circuit board A microphone,
A capacitor microphone, wherein an IC element having a function of applying a bias voltage to the capacitor is mounted on the circuit board. In the condenser microphone according to claim 1,
A condenser microphone comprising the IC element including the impedance converting device. In the condenser microphone according to claim 1,
The capacitor microphone is characterized in that the device for impedance conversion is constituted by an IC element separate from the IC element. The condenser microphone according to any one of claims 1 to 3, further comprising a capacitor having a vibrating membrane on one electrode side and a back electrode on the other electrode in a cylindrical capsule.
A first ring for electrically connecting the vibrating membrane and the circuit board is provided, and a second ring for electrically connecting the back electrode and the circuit board is provided. Condenser microphone. The condenser microphone according to claim 4, wherein
A bias ring having a plurality of legs projecting in the vertical direction from the plate surface of the first ring from the outer periphery of the first ring,
A bias terminal pattern in which the first ring is in contact with a diaphragm ring holding the periphery of the diaphragm, and the leg portion is formed on the inner periphery of the circuit board and connected to the bias terminal of the IC element A condenser microphone characterized by being in contact with the condenser microphone. The condenser microphone according to claim 4 or 5,
A capacitor microphone, wherein a spacer interposed between the vibrating membrane and a back electrode and a back electrode holder for holding the back electrode are made of polyimide or polyphthalamide (PPA). The condenser microphone according to any one of claims 1 to 3, further comprising a capacitor having a vibrating membrane as one electrode side and a cylindrical capsule itself as a back electrode as the other electrode.
A condenser microphone comprising a ring interposed between the vibrating membrane and the circuit board to electrically connect them, and the back electrode grounded.   8. The condenser microphone according to claim 1, wherein an outer surface of the circuit board has a flat portion having an external terminal in a shape in which a central portion protrudes toward the mounting surface with respect to the peripheral flat portion. . The condenser microphone according to any one of claims 1 to 8,
The vibration film is a vibration film in which a metal film is formed on one surface of a polyphenylene sulfide (PPS) film, and the vibration film is annealed at a temperature corresponding to a reflow soldering temperature. Microphone.

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