JPH0739199U - microphone - Google Patents

Abstract

(57) [Abstract] [Purpose] To eliminate the soldering work for assembling a capacitor for noise prevention, to improve the efficiency of manufacturing work and improve the yield, and to reduce the cost. [Configuration] FET that functions as an impedance converter
A silicon capacitor 28 is formed by using a silicon substrate 25 forming 24. The silicon capacitor 28 is connected between the source 16 and the drain 17 of the FET 24 to prevent noise based on the high frequency signal captured by the loop portion of the circuit.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The microphone according to the present invention is a so-called electret condenser microphone, which is used in a state where it is incorporated in a wireless device such as a mobile phone or a transceiver.

[0002]

[Prior art]

 As a small microphone to be incorporated in various wireless devices, it has conventionally been equipped with a movable plate (vibration plate) and a fixed plate (back electrode), and the capacitance between these diaphragms and the back electrode due to the penetration of sound waves. An electret condenser microphone is used which converts the sound wave into an electric signal through the change of. First, the electret condenser microphone will be described with reference to FIG. 2 showing an embodiment of the present invention. The case 1 forming the microphone is formed into a cylindrical shape with a bottom by, for example, forming an aluminum alloy by drawing. A plurality of through holes 3 and 3 are formed in the end plate 2 of the case 1 corresponding to the bottom of the bottomed cylinder so that the inside and outside of the case 1 communicate with each other. A chamber 4 made of an insulating material such as Noryl is inserted in the case 1. A printed circuit board 5 is attached and supported to the outer end surface of the chamber 4 (right end surface in FIG. 2) by locking projections 6 formed on the outer end surface of the chamber 4.

On the other hand, a cylindrical portion 7 is formed in the inner half portion (left half portion in FIG. 2) of the chamber 4, and the back electrode 8 is fitted and supported at the open end of the cylindrical portion 7. ing. The back electrode 8 is made by plating brass with nickel or the like. Further, a diaphragm 9 is stretched between the inner end surface of the chamber 4 (the left end surface in FIG. 2) and the inner surface of the end plate 2. In FIG. 2, the thickness of the diaphragm 9 is exaggerated for clarity. The outer peripheral portions of both ends of the diaphragm 9 made of a polymer film are sandwiched by a spacer 10 and a ring 11.

Of these, the spacer 10 sandwiched between the inner end surface of the chamber 4 and the outer surface (right side surface of FIG. 2) of the diaphragm 9 is made of an insulating material such as polyester. A gap 12 is formed between the back electrode 8 and the diaphragm 9 by about the thickness of the spacer 10. The thickness dimension of the gap 12 is also exaggerated. The ring 11 is made of a conductive material such as iron whose surface is plated with nickel. The outer surface of the end plate 2 is covered with a cover 13 made of non-woven fabric or the like. Sound outside the end plate 2, that is, air vibration, passes through the cover 13 and the through holes 3 and 3 and enters the case 1 to vibrate the diaphragm 9.

Further, an IC 14 incorporating an FET is held inside the outer half (right half in FIG. 2) of the chamber 4. The gate 15 of the FET constituting the IC 14 which is an impedance converter is connected to the back electrode 8. The source 16 and drain 17 of this FET are connected to terminals 18a and 18b exposed on the outer surface of the printed circuit board 5.

When the microphone configured as described above is used, as shown in FIG. 3, the terminals 18 a and 18 b are connected to the power source 19 and the power source section 21 having the load resistor 20. When the diaphragm 9 vibrates in this state, the electrostatic capacitance between the diaphragm 9 and the back electrode 8 changes, and the voltage between the output terminals 22a and 22b changes. Since this change in voltage corresponds to the change in capacitance, this voltage can be used as an audio signal.

By the way, when the microphone and the power supply unit 21 are connected as shown in FIG. 3 to form a loop circuit, this loop circuit portion easily functions as an antenna for high frequency signals. In that case, an unnecessary signal will flow into the loop portion as indicated by the arrow in the figure. Since such an unnecessary signal causes noise when mixed with the FET in the IC 14, it needs to be removed.

Therefore, conventionally, as shown in FIG. 4, a noise preventing capacitor 23 having a property of easily passing a high frequency component between the source 16 and the drain 17 of the FET has been connected. There is. The capacitor 23 short-circuits the source 16 and the drain 17 in a high frequency region to prevent an unwanted signal from entering the FET.

In order to provide the capacitor 23 between the source 16 and the drain 17 as described above, the conventional method is as shown in FIGS. That is, the capacitor 23 is soldered between the terminals 18a and 18b provided on the outer surface of the printed circuit board 5.

[0010]

[Problems to be solved by the device]

 The microphone of the present invention eliminates the need for soldering work for assembling a capacitor for noise prevention, thereby improving the efficiency of microphone manufacturing work. That is, like the above-described conventional structure, after the main body of the microphone is completed, the work of soldering the capacitor 23 to the outside of the main body is troublesome and difficult to automate. For this reason, in the past, this soldering work was performed manually, which not only complicates the microphone manufacturing work, but also causes a decrease in yield due to an increase in the defective product generation rate and a cause of an increase in product cost. Was becoming. The microphone of the present invention was devised in view of such circumstances.

[0011]

[Means for Solving the Problems]

 The microphone of the present invention, like the conventional microphone described above, has a case formed with a through hole that communicates the inside and the outside, and is stretched in the case, and is based on air vibrations that enter the case through the through hole. A vibrating diaphragm, a back electrode held in the case with a minute gap interposed between the vibrating plate, an impedance converter having its gate connected to the back electrode, and this impedance converter. And a capacitor provided between the source and the drain.

In particular, the microphone of the present invention is characterized in that the capacitor is formed on a semiconductor substrate that constitutes the impedance converter.

[0013]

[Action]

 The operation itself when the microphone of the present invention as described above converts the sound, which is vibration of the air, into an electric signal and outputs it as an audio signal is the same as that of the conventional microphone described above. In particular, in the case of the microphone of the present invention, a capacitor for noise prevention can be integrated with the impedance converter and can be manufactured at the same time when the impedance converter is manufactured, so that it is not necessary to solder the capacitor later. . Therefore, the efficiency of the microphone manufacturing work and the yield can be improved.

[0014]

【Example】

 1 and 2 show an embodiment of the present invention. The feature of the present invention is that the capacitor for preventing the noise due to the high frequency signal is integrated with the impedance converter to facilitate the manufacturing work, and the other parts are configured. And the operation is the same as the above-mentioned conventional structure. Therefore, the duplicated description of the parts equivalent to the conventional structure will be omitted, and the characteristic parts of the present invention will be described below.

An FET (including an IC 14 including the FET, which is the same throughout this specification) 24 that constitutes an impedance converter is formed on a substrate 25 of silicon (Si) and is shown in FIG. 2, it has a gate 15, a source 16 and a drain 17. As shown in FIG. 1, an aluminum foil 27 is laminated on a part of the substrate 25 through a dielectric 26 to form a silicon capacitor 28.

Both ends of the silicon capacitor 28 are electrically connected to the source 16 and the drain 17, respectively, through a circuit printed on the substrate 25. Therefore, also in the microphone circuit of the present invention, as in the case of the conventional structure described above, as shown in FIG. 4, the high frequency signal captured in the loop portion of the circuit enters the FET 24 by the capacitor (silicon capacitor 28). Can be prevented.

As described above, since the silicon capacitor 28 for noise prevention can be manufactured integrally with the FET 24 at the same time when the FET 24 is manufactured, the capacitor 23 (see FIGS. ) Need not be soldered. Therefore, the efficiency of microphone manufacturing work and the yield can be improved. The FETs forming the impedance converter include, for example, those formed on a silicon substrate as described above, and those formed on a germanium (Ge) substrate, for example. Even in such an FET, a capacitor for noise prevention can be integrally formed on the substrate.

[0018]

[Effect of device]

 Since the microphone of the present invention is constructed and operates as described above, a highly reliable microphone can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a FET incorporated in the microphone of the present invention.
And a schematic view of the capacitor part.

FIG. 2 is a sectional view of the microphone of the present invention.

FIG. 3 is a circuit diagram showing a state in which a microphone and a power supply unit are combined.

FIG. 4 is a circuit diagram showing a state in which a noise prevention capacitor is incorporated.

FIG. 5 is a side view showing a microphone in which a noise preventing capacitor is assembled by a conventional structure.

FIG. 6 is a view seen from the right side of FIG.

[Explanation of symbols]

 1 Case 2 End Plate 3 Through Hole 4 Chamber 5 Printed Circuit Board 6 Locking Protrusion 7 Cylindrical Part 8 Back Electrode 9 Vibration Plate 10 Spacer 11 Ring 12 Gap 13 Cover 14 IC 15 Gate 16 Source 17 Drain 18a, 18b Terminal 19 Power supply 20 Load resistance 21 Power supply section 22a, 22b Output terminal 23 Capacitor 24 FET 25 Substrate 26 Dielectric 27 Aluminum foil 28 Silicon capacitor

Claims (1)

[Scope of utility model registration request] 1. A case having a through hole for communicating the inside and the outside, a diaphragm stretched in the case and vibrating based on air vibrations entering the case through the through hole, and the diaphragm. A back electrode held in the case with a minute gap therebetween, an impedance converter having its gate connected to this back electrode, and a capacitor provided between the source and drain of this impedance converter. In a microphone with and
A microphone formed on a semiconductor substrate that constitutes the impedance converter.