JPH077299U - Electret microphone - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an electret microphone having a structure that can be easily assembled. A conductor pattern serving as a back electrode plate 6 is formed on a printed circuit board 9, and an insulating spacer 7 that defines a gap between the diaphragm and the back electrode plate 6 is formed on the periphery of the back electrode plate 6 by deposition. Then, the diaphragm 4 attached to the conductive ring 5 is brought into contact with the insulating spacer. The back electrode plate 6 is connected to the input terminal of the active element 11 mounted on the printed board 9 by a wiring conductor. A front cylindrical half body 14 and a rear cylindrical half body 15 formed of a conductive resin material are formed on the front and back sides of the printed circuit board 9.
Then, the open ends of the front cylindrical half body 14 and the rear cylindrical half body 15 are welded to each other to fix and seal the printed circuit board 9 and the diaphragm 4 inside.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an electret microphone that uses an electret formed by being charged by polarization.

[0002]

[Prior art]

 FIG. 3 shows the structure of a conventional electret microphone. In the figure, 1 indicates a microphone capsule formed of a conductive plate such as aluminum. This microphone capsule 1 is formed into a cup shape by pressing, and a sound hole 2 is formed in a portion corresponding to the bottom plate of the cup, and the portion corresponding to this bottom plate is used as the front plate 1A of the microphone. The front cloth 3 is attached to the front surface of the front plate 1A.

Inside the microphone capsule 1, a microphone unit MU is arranged on the front end side. The microphone unit MU is composed of the diaphragm 4 and the back electrode plate 6. The diaphragm 4 includes a film made of a polymer material and a metal layer deposited on the film. The polymer film is polarized in the thickness direction to form an electret. The diaphragm composed of this electret. 4 is arranged with a small gap (several tens of μm) held between the back electrode plate 6 and the diaphragm 4 so that an electric signal is taken out from between the diaphragm 4 and the back electrode plate 6 by vibrating. It

The diaphragm 4 is attached to the conductive ring 5, and is electrically connected to the microphone capsule 1 through the conductive ring 5. An insulating spacer 7 for holding a gap between the diaphragm 4 and the back electrode plate 6 is interposed between the diaphragm 4 and the back electrode plate 6, and the back electrode plate 6, the spacer 7 and the diaphragm 4 The ring is pressed against the front plate 1A to hold the microphone unit MU on the front end side of the microphone capsule 1.

A back electrode holder 8 is conventionally provided to press the microphone unit MU toward the front end side in the microphone capsule 1. In this example, the back pole holder 8 is formed in a cup shape, the back pole plate 6 is supported at the opening end of the cup shape, and the microphone unit MU is pressed against the front end side of the microphone capsule 1. The bottom surface portion of the back electrode holder 8 is arranged in the opening portion of the microphone capsule 1, and the print substrate 9 is arranged outside thereof. An active element 11 for impedance conversion is housed inside the back electrode holder 8. A field-effect transistor having a high input impedance is generally used as the active element 11, a gate electrode G serving as an input terminal thereof is connected to the back electrode plate 6, and a drain electrode D and a source electrode are the bottom plate of the back electrode holder 8. It is led out to the front side of the printed circuit board 9 through the hole formed in the printed circuit board 9 and is soldered to the wiring conductor formed on the front side surface. Fig. 4 shows the electrical connection structure of the electret microphone.

[0006]

[Problems to be solved by the device]

 Since the conventional electret microphone has a structure in which the microphone unit MU is arranged on the front end side of the microphone capsule 1 and the printed circuit board 9 and the active element 11 are mounted on the rear end side, the active element 11 and the microphone unit MU are arranged. There is a drawback that the connection with and becomes a three-dimensional connection structure, which requires time and effort for assembly.

An object of the present invention is to provide an electret microphone having a structure that can be easily assembled.

[0008]

[Means for Solving the Problems]

 In this invention, the microphone unit and the active element are arranged on the same surface, and the structure is such that the microphone unit and the active element are connected by the printed wiring. More specifically, by forming a conductive pattern to be a back electrode plate on a printed circuit board and a printed wiring for mounting an active element for impedance conversion, and mounting the active element on the printed circuit board, it is inevitable. The input terminal of the active element is electrically connected to the conductive pattern to serve as the back plate. A spacer is formed on the periphery of the conductive pattern that should become the back electrode plate with insulating ink, etc., and a diaphragm supported by a conductive ring is placed on this spacer to maintain a gap corresponding to the thickness of the spacer. Face the back plate.

The conductive ring supporting the vibration plate is fitted into the recess formed in the closing plate of the resin capsule formed of the conductive resin material. As a result, the diaphragm is electrically connected to the resin capsule via the conductive ring. The resin capsule is composed of a pair of cylindrical halves whose one end is closed. That is, it is composed of a front tubular half and a rear tubular half, and the pair of tubular halves face each other with their open ends facing each other, and the open ends are welded to each other, so that the printed circuit board and the diaphragm are internally sealed. The structure is to be sealed.

Therefore, according to the structure of the present invention, the microphone unit composed of the diaphragm and the back electrode plate and the active element are mounted on the same printed circuit board, so that there is an advantage that the assembly can be easily performed.

[0011]

【Example】

 1 and 2 show an embodiment of the present invention. Portions corresponding to those in FIG. 3 are designated by the same reference numerals. That is, 9 is a printed circuit board, 11 is an active element such as an FET mounted on the printed circuit board 9, and 12 is a wiring pattern for mounting the active element 11. The structure characteristic of this invention is that a conductive pattern to be the back electrode plate 6 is formed on the printed circuit board 9, and an insulating spacer 7 is adhered and formed on the periphery of the back electrode plate 6 with insulating ink or the like. The vibrating plates 4 supported by the conductive ring 5 are disposed so as to face each other. A wiring pattern 12 connects between the back electrode plate 6, the insulating spacer 7, the conductive ring 5, and the vibration plate 4 to form a microphone unit MU and the back electrode plate 6 and the input terminal of the active element 11. That is the point.

Reference numerals 14 and 15 denote a front cylindrical half body and a rear cylindrical half body that form the resin capsule 16. The front tubular half body 14 and the rear tubular half body 15 are constituted by tubular half bodies whose one ends are closed by the closing plates 14A and 15A. The material is made of a conductive resin material, and the opening ends are opposed to each other and welded (for example, ultrasonic welding), and the printed board 9 and the diaphragm 4 are sealed inside by this welding.

A sound hole 2 is formed in the closing plate 14 A of the front cylindrical half body 14 at a position facing the diaphragm 4. Further, as shown in FIG. 2, a concave portion 14B is formed so as to surround the sound hole 2 on the back surface of the closing plate 14A of the front cylindrical half body 14. The position of the diaphragm 4 is fixed by fitting the conductive ring 5 into the recess 14B, and the diaphragm 4 is electrically connected to the front cylindrical half body 14, that is, the resin capsule 16. The front tubular half body 14 fitted with the conductive ring 5 supporting the diaphragm 4, the printed circuit board 9, and the rear tubular half body 15 are stacked to form a front tubular half body 14 and a rear end tubular half body. The assembly is completed by welding the body 15 and the open ends thereof. The recess 14C shown in FIG. 2 is a recess for accommodating the active element 11.

A step portion 15 B is provided on the inner circumference of the rear tubular half body 15, and the print substrate 9 is received by the step portion 15 B to form an empty space between the printed board 9 and the rear tubular half body 15. To do. Along with this, a plurality of holes 17 are formed in the portion of the printed circuit board 9 where the back electrode plate 6 is formed, and the vacant space formed between the printed circuit board 9 and the rear cylindrical half body 15 through the holes 17 is used as the vibration plate. The rear acoustic chamber is formed by communicating with the surface of No. 4.

The front acoustic chamber is formed by a gap between the diaphragm 4 and the closing plate 14A of the front cylindrical half body 14, and the volume of the front acoustic chamber and the volume of the rear acoustic chamber make the sound of the microphone sound. The resonance characteristics are set. When the characteristics of the microphone are bidirectional and unidirectional, a sound hole may be formed in a part of the closing plate 15A.

[0016]

[Effect of device]

 As described above, according to the present invention, since the microphone unit MU and the active element 11 are mounted on the same printed circuit board 9, the input terminal (gate electrode) of the active element 11 constitutes the microphone unit MU. The conductor electrically connected to the back electrode plate 6 only needs to be formed by extending the copper foil forming the back electrode plate 6 as the wiring pattern 12, and the active element 11 is soldered to this wiring pattern 12. The connection between the microphone unit MU and the active element 11 is completed only by mounting. Therefore, there is an advantage that the assembling can be easily performed and the mass production can be easily performed.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of the present invention.

FIG. 2 is a sectional view for explaining the structure of the main part of the present invention.

FIG. 3 is a cross-sectional view for explaining a conventional technique.

FIG. 4 is a connection diagram for explaining an electrical structure of an electret microphone.

[Explanation of symbols]

 2 sound hole MU microphone unit 4 diaphragm 5 conductive ring 6 back electrode plate 7 insulating spacer 9 printed circuit board 11 active element 12 wiring pattern 14 front cylindrical half body 15 rear cylindrical half body 14A, 15A closing plate 16 resin capsule 17 Hole

Claims (5)

[Scope of utility model registration request] 1. A. A printed circuit board on which a conductive pattern to serve as a back electrode plate and a conductive pattern for mounting an active element for impedance conversion are formed; An insulating spacer formed on the periphery of the conductive pattern to be the back electrode plate, for holding a gap between the diaphragm and the back electrode plate; A diaphragm that is attached to a conductive ring and is charged by applying a polarization to a film made of a polymer material; An electret microphone composed of a resin capsule formed of a conductive resin material that electrically contacts the conductive ring supporting the diaphragm and covers both the front and back surfaces of the printed circuit board. 2. The electret microphone according to claim 1, wherein a conductive pattern to serve as a back electrode plate and an input terminal of an active element are planarly connected by a wiring pattern on the printed circuit board. 3. A resin capsule is composed of a front tubular half body and a rear tubular half body whose one end is closed. The openings of these tubular half bodies are arranged to face each other, and the edges of the openings are opposed to each other. The electret microphone according to claim 1, wherein the electret microphone has a structure in which a diaphragm supported by the printed circuit board and the conductive ring is sealed inside by welding. 4. A conductive pattern that forms a back electrode plate formed on the printed circuit board while forming a sound hole in the closing plate of the front cylindrical half body that constitutes the resin capsule so as to face the diaphragm. A through hole is formed at a position to penetrate the printed circuit board, and a space formed between the diaphragm and the closing plate of the front cylindrical half body and a space between the rear cylindrical half body and the printed circuit board are formed. The electret microphone according to claim 1, wherein the front acoustic chamber and the rear acoustic chamber are configured. 5. A concave portion surrounding the sound hole is formed on the back surface of the closing plate of the front cylindrical half body, and a conductive ring supporting the diaphragm is fitted in the concave portion to form the conductive ring in the front cylindrical shape. The electret microphone according to claim 1, wherein the diaphragm is electrically connected to the half body and the diaphragm is electrically connected to the resin capsule through a conductive ring.