JP2008061073A - Condenser microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a condenser microphone that can achieve the reduction of a thickness and numbers of parts. <P>SOLUTION: The condenser microphone forms an electret condenser with a diaphragm (4) whose spherical edge is fixed to one end face of a diaphragm ring (7), a conical frustum section (5A) whose center portion is protruded in the form of a frustum of a cone, and a back electrode (5) having a brim (5B) at its periphery, and is characterized by a structure in which the diaphragm ring is inserted and attached in a casing (2) having an opening while the diaphragm butt-contacts with the inner end face of the casing, a protruded portion of the form of a frustum of a cone is inserted in a ring of the inserted and attached diaphragm ring, one surface of the brim butt-contacts with the other end face of the diaphragm ring, a circuit board (6) is placed on the other surface of the brim, the circuit board has circuit devices positioned in a recess part on the rear side of the protruded portion, and the circuit board is fixed to the casing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a condenser microphone having an electret condenser formed by a diaphragm and a back electrode.

  In the previous application (Patent Document 1), the present applicant has disclosed the structure of a condenser microphone in which an electret condenser is formed by making a diaphragm face a back electrode having a curved concave portion at the center. According to this, a spacer for forming a gap between the diaphragm forming the electret capacitor and the back electrode becomes unnecessary, and the number of parts can be reduced correspondingly.

JP 2003-174696 A

  However, there are other parts such as a contact ring for conducting the back electrode to the electrode pad of the circuit board, and a chamber arranged between the contact ring and the casing for suppressing a short circuit between them. The possibility of reduction remained. It was also found that the contact ring and chamber are factors that increase the thickness of the condenser microphone.

  An object of the present invention is to provide a condenser microphone capable of realizing a reduction in thickness dimension and the number of parts.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  The following is a brief description of an outline of typical inventions disclosed in the present application.

  [1] A condenser microphone according to the present invention is an electret condenser comprising a diaphragm whose peripheral part is fixed to one end face of a diaphragm ring and a back electrode whose central part protrudes in a truncated cone shape and has a flange on the peripheral part. The diaphragm ring is inserted by bringing the peripheral edge of the diaphragm into contact with the inner end surface of the casing having an opening, and the frustoconical shape is inserted into the ring of the inserted diaphragm ring. Is inserted, the other surface of the diaphragm ring is in contact with one surface of the flange, the circuit board is placed on the other surface of the flange, and the circuit board is a recessed portion on the rear surface of the protrusion. And having a circuit element, and the circuit board is fixed to a casing. According to this, since the capacitance gap of the electret capacitor can be determined by the relationship between the protruding amount of the back electrode and the thickness dimension of the diaphragm ring, a spacer used only for gap formation is not required. Moreover, since the collar part of a back electrode can be made to contact a circuit board directly, the contact ring used only for electrically connecting a back electrode to a circuit board is not required. Further, since the gap between the peripheral portion of the diaphragm and the back electrode is increased to form no capacitor, the stray capacitance that does not contribute to electroacoustic conversion is reduced, which can contribute to improvement in sensitivity. Furthermore, since the circuit element on the circuit board is located in the recessed portion on the back surface of the protruding portion without requiring a spacer, it is easy to reduce the thickness of the microphone.

  As one specific form of the present invention, a hem edge of the frustoconical protruding portion is locked by an inner diameter corner portion of the diaphragm ring, and an outer diameter of the flange portion is larger than an outer diameter of the diaphragm ring. It is made smaller. The positioning of the back electrode is easy, and the back electrode that forms one pole of the electret capacitor can suppress a short circuit with the casing that conducts to the other pole of the electret capacitor. Thus, there is no need for a chamber disposed between the casing only for suppressing short circuit.

  As a more specific form of the present invention, a polymer electret film is formed on the back electrode on the surface facing the diaphragm. Since it is not necessary to form a polymer electret film having a relatively large film thickness on the diaphragm, it is suitable for obtaining good sensitivity.

  As a more specific form of the present invention, the diaphragm has a through hole in the center, and the circuit board has a solder bump electrode as an external connection terminal. Even if the diaphragm is about to be attracted to the back electrode by heat when the condenser microphone is mounted on the mounting substrate by solder reflow, the through hole in the central portion acts to suppress the attraction.

  [2] A condenser microphone according to another aspect of the present invention has a conductive diaphragm whose peripheral portion is fixed to one end face of the diaphragm ring, a central portion protruding into a trapezoidal cross section, and a flange portion at the peripheral portion. An electret capacitor is formed by a back electrode, and a diaphragm ring is inserted by bringing a peripheral edge of the diaphragm into contact with an inner end surface of a conductive casing having an opening, and the diaphragm is inserted A protruding portion having a trapezoidal cross-sectional shape is inserted into the ring of the ring, one surface of the flange portion is brought into contact with the other end surface of the diaphragm ring, a circuit board is placed on the other end surface of the flange portion, and the circuit The substrate has a structure in which a circuit element is located in a recessed portion on the rear surface of the protruding portion, and the circuit substrate is fixed to a casing. The back electrode has a polymer electret film formed on the surface facing the diaphragm, and the opposite surface has conductivity. The hem edge of the frustoconical protruding portion is locked by the inner diameter corner portion of the diaphragm ring, and the outer diameter of the flange portion is made smaller than the outer diameter of the diaphragm ring.

  The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.

  That is, it is possible to reduce the thickness of the condenser microphone and the number of parts.

  FIG. 1 shows a cross section of a condenser microphone according to the present invention. The condenser microphone 1 shown in the figure is not particularly limited, but has a button-type microphone casing 2 having a circular cross section, and a diaphragm 4 is disposed in the cylinder so as to face the sound wave passage opening 3. A back electrode 5 is disposed with a predetermined gap from the diaphragm 4 and a circuit board 6 for a microphone is provided. The size of the condenser microphone 1 is, for example, φ4 × 1 mm.

  The diaphragm 4 has a metal film deposited on the front and back surfaces of a dielectric film such as a polyester film, and is formed in a circular shape with a constant thickness in the range of 2 to 4 μm. The peripheral edge of the diaphragm 4 is bonded and fixed to one end surface of the conductive diaphragm ring 7.

  The back electrode 5 is formed by providing a polymer electret film 11 on one surface of the stainless steel plate 10, the central portion projects in a truncated cone shape, forms a truncated cone portion 5A, and has a flange portion 5B at the peripheral portion. A polymer electret film 11 is opposed to the diaphragm 4. The polymer electret film 11 is composed of, for example, a 25 μm Teflon (registered trademark) film. The stainless steel surface of the back electrode 5 is a conductive surface, and the polymer electret film surface of the back electrode 5 is an insulating surface. The back electrode 5 forms an electret capacitor with the diaphragm 4.

  A diaphragm ring 7 is inserted into the inner end surface of the casing 2 having the sound wave passage hole 3 with the peripheral edge of the diaphragm 4 in contact therewith. The truncated cone part 5A is inserted into the inserted ring of the diaphragm ring 7, and the insulating surface of the flange part 5B is brought into contact with the other end face of the diaphragm ring 7. A circuit board 6 is placed on the conductive surface of the flange portion 5B. The circuit board 6 has circuit elements 12 and 13 located in a recessed portion on the back side of the truncated cone part 5B. It is fixed by caulking at the end of the casing 2. The back electrode 5 constituting one pole of the electret capacitor is electrically connected to the wiring pattern on the one surface 6A of the circuit board 6 through the conductive surface of the flange portion 5B. The diaphragm 4 forming the other pole of the electret capacitor is electrically connected to the wiring pattern on the other surface 6B of the circuit board 6 through the casing 2. The bottom edge 5C of the truncated cone portion 5A is locked by the inner diameter corner portion 7A of the diaphragm ring 7, the outer diameter of the flange portion 5B is made smaller than the outer diameter of the diaphragm ring, and the back electrode collar The outer peripheral surface of the part 5 </ b> B is not in contact with the inner peripheral surface of the casing 2.

  The circuit elements 12 and 13 mounted on the circuit board 6 are, for example, a JFET for impedance conversion and a capacitor for noise removal. The gate of the JFET is connected to the back electrode, the source is the ground, and the drain is the output terminal. The capacitor is connected between the source and drain. The diaphragm is connected to the ground. An electroacoustic signal is output from the output terminal.

  According to the electret capacitor 1, since the capacity gap of the electret capacitor can be determined by the relationship between the protruding amount of the truncated cone part 5A and the thickness dimension of the diaphragm ring 7, a spacer used only for gap formation is necessary. And not. Further, since the flange portion 5B of the back electrode 4 can be brought into direct contact with the wiring pattern of the circuit board 6, a contact ring used only for conducting the back electrode 5 to the circuit board 6 is not required. In addition, since the gap between the diaphragm 4 and the back electrode 5 becomes large at the peripheral portion of the diaphragm 4 so as not to form a capacitor, stray capacitance that does not contribute to electroacoustic conversion is reduced, which can contribute to improvement in sensitivity. Further, since the circuit elements 12 and 13 on the circuit board 6 are located in the recessed portions of the truncated cone portion 5A without the spacer, the thickness of the microphone 1 is reduced. Since the bottom edge 5C of the truncated cone part 5B is locked by the inner diameter corner part 7A of the diaphragm ring 7, the positioning of the back electrode 5 is easy, and the outer diameter of the flange part 5B is the diaphragm ring 7 Therefore, it is possible to suppress a situation in which the back electrode 5 forming one pole of the electret capacitor is short-circuited with the casing 2 conducting to the other pole of the electret capacitor. It is not necessary to place a chamber between the casing only for such short-circuit suppression. FIG. 3 illustrates a condenser microphone that requires a spacer, a contact ring, and a chamber as a comparative example. 20 is a diaphragm, 21 is a diaphragm ring, 22 spacer, 23 is a back electrode, 24 is a contact ring, and 25 is a chamber.

  FIG. 2 shows another example of the condenser microphone according to the present invention. 1 differs from FIG. 1 in that the diaphragm 5 has a through hole 5D in the center, and the circuit board 6 has a solder bump electrode 6C as an external connection terminal. Even if the diaphragm 4 tries to be attracted to the back electrode 5 by heat when the condenser microphone 1 is mounted on the mounting substrate by solder reflow, the suction is suppressed by the through hole 5D at the center. Since other configurations are the same as those in FIG. 1, a detailed description thereof will be omitted.

  Although the invention made by the present inventor has been specifically described based on the embodiments, it is needless to say that the present invention is not limited thereto and can be variously modified without departing from the gist thereof.

  For example, the condenser microphone is not limited to a circle but may be a polygon. In this case, the back electrode may have a central portion protruding in a trapezoidal cross-sectional shape and a flange portion on the peripheral edge portion.

It is sectional drawing which shows an example of the condenser microphone which concerns on this invention. It is sectional drawing which shows another example of the condenser microphone which concerns on this invention. It is sectional drawing of the condenser microphone which concerns on the comparative example which requires a spacer, a contact ring, and a chamber.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor microphone 2 Casing 3 Sound wave passage opening 4 Diaphragm 5 Back electrode 5A Frustum part 5B Gutter part 5C Bottom edge of the frustum 5D Central part through-hole 6 Circuit board 7 Diaphragm ring 7A Inner angle part of the diaphragm ring 10 Stainless steel plate 11 Polymer electret film 12, 13 Circuit element 20 Diaphragm 21 Diaphragm ring 22 Spacer 25 Chamber

Claims (5)

A condenser microphone that forms an electret condenser by a diaphragm having a peripheral portion fixed to one end face of the diaphragm ring and a back electrode having a central portion protruding in a truncated cone shape and having a flange on the peripheral portion,
A diaphragm ring is inserted by bringing the peripheral edge of the diaphragm into contact with an inner end surface of a casing having an opening, and the frustoconical protruding portion is inserted into the ring of the inserted diaphragm ring, One surface of the flange portion is brought into contact with the other end surface of the diaphragm ring, and a circuit board is placed on the other end surface of the flange portion, and the circuit board is located in a recessed portion on the rear surface of the projecting portion to place a circuit element. A condenser microphone having the circuit board fixed to a casing.   2. The condenser microphone according to claim 1, wherein a bottom edge of the frustoconical protruding portion is locked by an inner diameter corner portion of the diaphragm ring, and an outer diameter of the flange portion is made smaller than an outer diameter of the diaphragm ring. .   The condenser microphone according to claim 2, wherein a polymer electret film is formed on a surface of the back electrode facing the diaphragm.   The condenser microphone according to claim 3, wherein the diaphragm has a through hole in a central portion, and the circuit board has a solder bump electrode as an external connection terminal. A condenser microphone in which an electret condenser is formed by a conductive diaphragm having a peripheral portion fixed to one end face of a diaphragm ring and a back electrode having a central portion protruding in a trapezoidal cross section and having a flange portion on the peripheral portion. ,
A diaphragm ring is inserted by bringing the peripheral edge of the diaphragm into contact with an inner end surface of a conductive casing having an opening, and the protruding portion of the trapezoidal cross section is inserted in the ring of the inserted diaphragm ring. Inserted, the other surface of the diaphragm ring is brought into contact with one surface of the flange portion, a circuit board is placed on the other surface of the flange portion, and the circuit board is located in a recessed portion on the rear surface of the protruding portion. Having a circuit element, the circuit board is fixed to the casing,
The back electrode has a polymer electret film formed on the surface facing the diaphragm, and the opposite surface has conductivity,
A condenser microphone in which a bottom edge of the frustoconical protruding portion is locked by an inner diameter corner portion of the diaphragm ring, and an outer diameter of the flange portion is made smaller than an outer diameter of the diaphragm ring.

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