JP3940679B2 - Electret condenser microphone - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to an electret condenser microphone configured by using an insulating material such as ceramic or resin as a substrate material, and more particularly, to an electret condenser microphone capable of facilitating assembling work and improving mounting accuracy by performing an integrated configuration of components. .
[0002]
[Prior art]
A conventional electret condenser microphone is disclosed in Japanese Patent Laid-Open No. 2000-50393, and will be described below with reference to FIGS. FIG. 4 is a cross-sectional view of an electret condenser microphone showing a first conventional example. 310 is a metallic back electrode, 320 is an electret layer formed on the back electrode 310, and 311 is the back electrode. An acoustic hole is formed through the electrode 310 and the electret layer 320, and the back electrode 310 and the electret layer 320 constitute a back electrode substrate 330. In the manufacturing method of the back electrode substrate 330, an electret layer is formed on the entire surface of a large metal plate to be a back electrode, and the electret layer is cut into a necessary size, and the acoustic hole 311 is removed and processed. 330.
[0003]
340 is a conductive vibration film, 350 is a metal support frame fixed to the vibration film 340, and the vibration film 340 and the support frame 350 constitute a vibration film unit 360. Then, the back electrode substrate 330 and the diaphragm unit 360 are stacked and disposed via a spacer 370 to constitute a microphone. Reference numeral 400 denotes a holder, and 410 denotes a circuit board. An electronic element 420 for processing the detection signal of the microphone is mounted on the circuit board 410. Reference numeral 500 denotes a metal case that envelops the whole and protects it electrically and mechanically.
[0004]
In the operation of the electret condenser microphone having the above configuration, the vibration film 340 having a conductive film on the surface and the back electrode 310 having the electret layer 320 formed on the surface form a capacitor with the spacer 370 interposed therebetween. When the vibrating membrane 340 is displaced by vibration of air applied from the opening of the case 500, the capacitor converts the displacement into an electric signal, which is guided to the circuit board 410 and processed by the electronic element 420. And then output from the output electrodes 430 and 440 led to the back surface of the circuit board 410. The presence of the acoustic hole 311 makes the operation of the vibrating membrane 340 smooth and ensures acoustic characteristics.
[0005]
FIG. 5 is a cross-sectional view of an electret condenser microphone composed of ceramic as a main material according to a second conventional example, and FIG. 6 is an exploded perspective view of a case portion constituting the electret condenser microphone shown in FIG. The electret condenser microphone shown in FIG. 5 includes a microphone unit 100 that performs acoustic conversion, and a case unit 200 that accommodates the microphone unit 100. The case unit 200 includes a circuit board 210 made of an insulating member, and the circuit. Covers the four frames attached to the edge of the substrate 210, that is, the first frame 220, the second frame 230, the third frame 240 , the fourth frame 250 and the upper surface side. A lid 260 is provided.
[0006]
Each member constituting the case portion 200 is composed of a circuit board 210, a first frame body 220, a second frame body 230, and a third frame body 240, which are all made of ceramic and are conductive as shown by hatching in FIG. Electrodes are formed by membranes, and the elements are mounted and connected to each other by these electrodes. Further, as will be described later, the fourth frame 250 is made of a metal material for connection to the diaphragm.
[0007]
As shown in FIG. 6, the first frame body 220, the second frame body 230, the third frame body 240, and the fourth frame body 250 all have the same outer shape, but the inner diameter is the first frame body. The third frame 240 is larger than the second frame 230, and the fourth frame 250 is larger than the third frame 240. As a result, a first step portion 230a for mounting a back electrode substrate, which will be described later, is formed on the upper portion of the second frame 230 due to the difference in inner diameter shape of each frame, and further, the upper portion of the third frame 240 Is formed with a second step portion 240a for mounting a diaphragm unit to be described later. Further, the first frame body 220 is provided with a vent hole 220a for communicating the inside and outside of the electret condenser microphone.
[0008]
Next, the microphone unit 100 includes a back electrode 110, an electret layer 120 formed on the surface of the back electrode 110, an acoustic hole 111 formed through the back electrode 110 and the electret layer 120, A diaphragm 140 attached to a ring-shaped conductive diaphragm frame 130, a lower spacer 150 interposed between the diaphragm 140 and the back electrode 110, the diaphragm 140 and the lid The upper spacer 160 is interposed between the upper spacer 160 and the upper spacer 160. As shown in FIG. 6, the circuit board 210 made of ceramic as an insulating material and the three frames, that is, the first frame 220, the second frame 230, and the third frame 240, A connection electrode is formed.
[0009]
Next, the assembly procedure of the electret condenser microphone will be described with reference to FIG. First, the first frame body 220, the second frame body 230, the third frame body 240, and the fourth frame body 250 are laminated on the edge of the circuit board 210 on which the electric element 170 such as a semiconductor element is mounted. And attach. Next, the back electrode 110 is mounted on the first step portion 230a formed on the upper portion of the second frame 230 so that the electret layer 120 faces upward. Further, the vibration film 140 is mounted on the second step portion 240a formed on the upper portion of the third frame 240 with the lower spacer 150 and the upper spacer 160 interposed therebetween. Further, by fitting the lid 260 from above, the vibrating membrane 140 and the back electrode 110 are positioned and fixed to the case 200 to complete the electret condenser microphone.
[0010]
In the operation of the electret condenser microphone having the above configuration, the vibration film 140 having a conductive film on the surface and the back electrode 110 having the electret layer 120 formed on the surface form a capacitor with the lower spacer 150 interposed therebetween. When the vibrating membrane 140 is displaced by the vibration of air applied from the opening of the lid 260, the capacitor converts the displacement into an electrical signal, and the electrical signal is connected to the connection electrode (FIG. 6) formed on each frame. And then output to an output electrode provided on the back surface of the circuit board 210.
The internal space of the electret condenser microphone communicates with the outside through the vent hole 220a provided in the first frame body 220, and the atmospheric pressure in the internal space is adjusted.
[0011]
[Problems to be solved by the invention]
The electret condenser microphone of the conventional example shown in FIG. 4 and FIG. 5 is made by a punching method using a back electrode substrate laminated with an electret film on a back electrode of a metal plate, so A back electrode substrate support member is required, and a spacer is provided on the electret film to incorporate the diaphragm support frame. Therefore, there are problems that the number of parts increases and the number of assembling steps increases, resulting in an increase in cost. Further, since the number of parts increases, there is a problem that the assembling accuracy is lowered due to variations in each part.
[0012]
In order to solve the above problem, the present applicant has already formed a back electrode substrate and a back electrode substrate supporting member integrally with an insulating material in Japanese Patent Application Nos. 2001-147099 and 2001-269594, and this back electrode substrate. We have proposed an electret condenser microphone that has a back electrode layer and electret layer on top to reduce the number of parts and improve the accuracy of assembly.
[0013]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electret condenser microphone capable of reducing the number of parts and improving the accuracy of assembly by further improving the proposal made by the applicant who improved the prior art. .
[0014]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides an electret condenser microphone in which a back electrode substrate in which an electret layer is formed on a back electrode and a vibration film unit in which a vibration film is fixed to a support frame are stacked via a spacer. In the back electrode substrate, the back electrode, the electret layer, and the spacer are integrally formed on an insulating substrate, and a plurality of acoustic holes are provided outside a region where the back electrode is formed. It is characterized by.
[0015]
Further, the spacer is preferably provided with a vent hole for communicating the inside and outside of the electret condenser microphone, and the spacer is preferably formed on a base metal layer formed on the insulating substrate. .
[0016]
The insulating substrate constituting the back electrode substrate is preferably a ceramic substrate or a resin substrate .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a sectional view of an embodiment of an electret condenser microphone according to the present invention, and FIG. 2 is an exploded perspective view of each element constituting the electret condenser microphone shown in FIG.
[0018]
In FIG. 2, reference numeral 2 denotes a circuit board. The circuit board 2 is formed of an insulating substrate, and an electrode 2a, a connection electrode 2b, and an output electrode 2c for mounting elements are formed on the film. Reference numeral 3 denotes a back electrode substrate. The back electrode substrate 3 has a back electrode 4 formed of an electrode film on the upper surface side of an insulating substrate 3a, and an electret layer 5 is formed on the upper surface of the back electrode 4. An acoustic hole 15 penetrating the insulating substrate 3 a is formed outside the back electrode 4 and the electret layer 5.
[0019]
Further, a spacer 6 is integrally formed around the back electrode 4 and the acoustic hole 15 on the upper surface side of the insulating substrate 3a, and this spacer 6 communicates the inside and outside of the electret condenser microphone. Vent hole 6a is provided. Although a method for forming the spacer 6 will be described later, in order to improve adhesion and shape accuracy with the insulating substrate 3a, the back electrode electrode is formed in the formation area of the spacer 6 on the upper surface side of the insulating substrate 3a. The base metal layer 4a is formed simultaneously with the formation of the spacer 4, and the spacer 6 is formed on the upper surface of the base metal layer 4a.
[0020]
That is, the back electrode substrate 3 is a single component in which the insulating substrate 3a that also functions as a back electrode substrate support member, the back electrode 4, the electret layer 5, and the spacer 6 are integrally formed. In this embodiment, the upper surface of the back electrode substrate 3 has a rectangular shape, and the back electrode 4 and the electret layer 5 are formed in a circular shape on the upper surface of the back electrode substrate 3, The acoustic hole 15 is formed at a position corresponding to the corner portion of the back electrode substrate 3 outside the region where the back electrode 4 is formed, thereby efficiently using the area of the upper surface of the back electrode substrate 3.
[0021]
Reference numeral 7 denotes a diaphragm unit. The diaphragm unit 7 is integrated by attaching a conductive diaphragm 10 to a diaphragm mounting electrode formed on the lower surface side of a diaphragm support frame 8 made of an insulating substrate. Has been. Reference numeral 16 denotes a metal shield case.
[0022]
Next, the configuration of the electret condenser microphone 1 will be described with reference to FIG. The back substrate 3 and the diaphragm unit 7 are laminated on the circuit board 2 on which the elements such as the integrated circuit 11 are mounted on the electrode 2a, and are fixedly integrated with an adhesive or the like, and are then casing in a shield case 16. That is, when the shield case 16 is removed, the electret condenser microphone 1 can be completed by positioning and incorporating only three components.
[0023]
In the operation of the electret condenser microphone 1 having the above configuration, the vibration film 10 having a conductive film on the surface and the back electrode 4 having the electret layer 5 formed on the surface form a capacitor with the spacer 6 interposed therebetween. When the vibrating membrane 10 is displaced by the vibration of air, the capacitor converts the displacement into an electric signal, and the electric signal is guided to the circuit board 2 through each connection electrode (not shown), and the integrated circuit 11 Is output from the output electrode 2 c provided on the back surface of the circuit board 2. The presence of the acoustic hole 15 makes the operation of the vibrating membrane 10 smooth, ensuring acoustic characteristics, and adjusting the static pressure in the electret condenser microphone 1 by the vent hole 6 a provided in the spacer 6.
[0024]
In the above-described configuration, the operable range of the diaphragm 10 constituting the diaphragm unit 7 is not constrained by the diaphragm support frame 8 of the diaphragm 10 at the center of the upper surface of the insulating substrate 3a constituting the back electrode 3. The back electrode 4 and the electret layer 5 having a slightly smaller area than the area of the range) are formed, and further outside the region where the back electrode 4 and the electret layer 5 of the insulating substrate 3a are formed (the back electrode 4). And the spacer 6 ) are provided with acoustic holes 15.
[0025]
As a result, the formation of the capacitance in the electret condenser microphone 1 is only the effective capacitance formed in the portion where the back electrode 4 and the vibrating membrane 10 face each other, and the vibrating membrane as in the conventional example shown in FIGS. Since there is no stray capacitance formed by 10 non-operating regions and no loss capacitance lost by the acoustic hole 15, extremely high sensitivity characteristics can be obtained.
[0026]
FIG. 3 is an exploded perspective view for explaining a method of manufacturing the back electrode substrate 3. In the present embodiment, an epoxy resin containing glass (hereinafter abbreviated as glass epoxy) is used as the insulating substrate 3a constituting the back electrode substrate 3. FIG. The method used will be described. First, in step (a), the insulating substrate 3a is manufactured by resin molding of glass epoxy. Next, in step (b), the back electrode 4 and the base metal layer 4a are formed on the upper surface of the insulating substrate 3a. These metal layers may be divided into the back electrode 4 and the base metal layer 4a by a patterning technique after the metal layer is formed on the entire upper surface of the insulating substrate 3a by a plating technique, or simultaneously formed by mask plating. May be. Further, as the metal layer, for example, a Ni / Au layer may be formed on a copper base layer.
[0027]
Next, the acoustic hole 15 is processed in step (c). Next, in step (d), a spacer 6 is formed on the base metal layer 4a. The spacer 6 is formed by attaching a film resist (a film that can be patterned with photolithography) to the entire upper surface of the insulating substrate 3a and patterning the back electrode 4, the acoustic holes 15, and the air holes 6a. The part of is removed. The material of the spacer 6 is not limited to the film resist, but may be patterned using a liquid resist, or may be formed by mask printing. Next, the back electrode substrate 3 is completed by forming the electret layer 5 on the back electrode 4 in the step (e).
[0028]
The steps are not limited to this order. For example, the electret layer 5 may be formed before the spacer 6 is formed, or the acoustic hole 15 is processed before the metal layer is formed. You can keep it. Furthermore, the spacer 6 is formed on the base metal layer 4a as in the present embodiment to improve the adhesion and the shape accuracy, but is not limited to this, and may be formed directly on the insulating substrate 3a.
[0029]
Further, when ceramic is used as the insulating substrate 3a constituting the back electrode substrate 3, it can be performed by the above steps (a) to (e), but in the case of ceramic, it can be fired at a high temperature. A method of using a bakable conductive paste such as silver palladium for forming the back electrode 4 or a method of printing the glass paste with a glass paste to form the spacer 6 is also possible.
[0030]
As described above, in the present invention, the back electrode substrate 3 is formed by laminating the back electrode 4 and the electret layer 5 on the upper surface of the insulating substrate 3a having a U-shaped cross section, and the spacer 6 is integrated. Further, since the diaphragm unit 7 is also integrated by fixing the conductive diaphragm 10 to the diaphragm support frame 8 made of an insulating substrate, the basic configuration is the circuit board 2, the back electrode board. 3 and the vibration membrane unit 7 are simplified to three bodies.
[0031]
Furthermore, in the above configuration, since the spacer 6 is integrated with the insulating substrate 3a by a formation method with high positional accuracy and shape accuracy, the distance between the back electrode 4 and the vibrating membrane 10 can be kept with high accuracy. The acoustic characteristics as a microphone can be enhanced.
[0032]
Furthermore, by forming the air holes 6a in the spacers 6 provided in the vicinity of the vibration film 10 , it is possible to enhance the effect of preventing the deformation of the vibration film 10 due to the static pressure. This is because conventional built-in type spacers have a thin ring shape, so if grooves are formed in such spacers, the ring shape will collapse and the built-in property will deteriorate, and the accuracy of the shape of the spacer will deteriorate. In contrast to the problem, in the present invention, since the spacer 6 is integrated on the insulating substrate 3a, the vent hole 6a can be provided without impairing the assembling property and the shape accuracy.
[0033]
The insulating substrate in the present invention needs to be a material that can be easily shaped and can be patterned with an electrode film including a through hole. For example, a ceramic or a resin material is suitable. In addition, it is desirable that the material is highly rigid for miniaturization and thinning. In this respect, ceramic is a good material, and good results can be obtained by using a ceramic substrate. In addition, it is desirable that the resin material contains glass fiber in order to increase rigidity, and as a result of using a glass-filled epoxy resin, good results have been obtained.
[0034]
【The invention's effect】
As described above, according to the present invention, by integrating the back electrode and the spacer on the back substrate, in addition to reducing the number of parts and improving the mounting accuracy, the distance between the back electrode and the diaphragm is reduced. It was possible to maintain high accuracy, and the static pressure could be adjusted well by providing a vent hole in the integrated spacer.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of an electret condenser microphone of the present invention.
2 is an exploded perspective view of each element constituting the electret condenser microphone of FIG. 1. FIG.
FIG. 3 is a perspective view showing a manufacturing process of the back electrode substrate of the present invention.
FIG. 4 is a cross-sectional view of a conventional electret condenser microphone.
FIG. 5 is a cross-sectional view of a conventional electret condenser microphone.
6 is an exploded perspective view of a case portion constituting the electret condenser microphone shown in FIG. 5. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electret condenser microphone 2, 210, 410 Circuit board 3, 330 Back electrode board 4, 110, 310 Back electrode 4a Base metal layer 5, 120, 320 Electret layer 6, 370 Spacer 6a Vent hole 7, 360 Vibration membrane unit 10 140,340 Vibration membrane 15, 111, 311 Acoustic hole

Claims (5)

In an electret condenser microphone in which a back electrode substrate having an electret layer formed on a back electrode and a vibration membrane unit having a vibration film fixed to a support frame are stacked via a spacer, the back electrode substrate is placed on an insulating substrate. The electret condenser microphone, wherein the back electrode, the electret layer, and the spacer are integrally formed, and a plurality of acoustic holes are provided outside a region where the back electrode is formed .   2. The electret condenser microphone according to claim 1, wherein the spacer is provided with a vent hole for communicating the inside and the outside of the electret condenser microphone.   The electret condenser microphone according to claim 1, wherein the spacer is formed on a base metal formed on the insulating substrate. The electret condenser microphone according to any one of claims 1 to 3, wherein the insulating substrate constituting the back electrode substrate is a ceramic substrate. 4. The electret condenser microphone according to claim 1 , wherein the insulating substrate constituting the back electrode substrate is a resin substrate.

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