JP4127469B2 - Electret condenser microphone - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electret condenser microphone, and more particularly to an improvement of an external connection electrode thereof.
[0002]
[Prior art]
An electret condenser microphone applied to a cellular phone or the like is configured by housing a microphone circuit board in which an electret condenser and an impedance conversion element are mounted in a button-type casing. An external connection terminal is formed on the circuit board for microphone, and the external connection terminal is connected to an analog front end portion of the cellular phone. Conventional external connection electrodes are configured using a simple conductive pattern, a pin electrode standing and fixed on the conductive pattern, and a mechanical elastic contact electrode connected to the conductive pattern.
[0003]
[Problems to be solved by the invention]
However, in the case of a simple conductive pattern, it is necessary to realize conduction with the counterpart substrate by soldering using a lead wire. It is not easy to automate such work. In the case of a pin electrode, conduction must be realized by insertion into a through hole previously formed in the counterpart substrate. Also in this case, the direction of the pin electrode must be accurately aligned with respect to the through hole, and automation is still not easy. If an elastic contact electrode is used, low positioning accuracy can be achieved at the time of connection, but the structure of the external connection electrode becomes complicated, the number of parts increases, and the demand for cost reduction cannot be satisfied. Furthermore, the increase in the number of parts prevents the miniaturization of the microphone unit.
[0004]
An object of the present invention is to provide an electret condenser microphone suitable for being thinned or miniaturized in a mounted state on a circuit board.
[0005]
An object of the present invention is to provide an electret condenser microphone that can be easily mounted on an electronic circuit or mounted on a circuit board.
[0006]
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.
[0007]
[Means for Solving the Problems]
An electret condenser microphone according to the present invention includes a casing having openings at both ends, an electret condenser built into one end opening of the casing, and a circuit board for microphone built into the other opening of the casing. Have The microphone circuit board has a circuit component on one side facing the electret capacitor and a plurality of external connection electrodes on the other side. The other surface is recessed with respect to the peripheral edge of the other end opening of the casing. The plurality of external connection electrodes are formed of solder, and are configured by, for example, solder bump electrodes protruding from the peripheral edge of the other end opening of the casing.
[0008]
The electronic circuit and circuit board on which the electret condenser microphone should be mounted need only have a solder paste or the like printed thereon.If the external connection electrode is placed on a print pattern such as this solder paste and heated by a reflow device or the like, The external connection electrode made of solder and the solder paste are melted to achieve electrical connection and mechanical fixing.
[0009]
The microphone circuit board is recessed with respect to the peripheral edge of the other end opening of the casing, and a projecting external connection electrode is formed there, and the tip of the electrode is ahead of the peripheral edge of the other end opening. Protruding. Therefore, even if the external connection electrode becomes large in order to secure the amount of solder necessary for the fusion connection between the solders, the thickness or height at which the external connection electrode protrudes from the peripheral edge of the other end opening of the casing is small. That's it. When the external connection electrode and solder paste are melted by heating, the casing can be approached until it contacts the mating substrate, and the mounting height or thickness of the electret condenser microphone can be reduced to the casing thickness dimension of the microphone. . Since such a small mounting thickness can be realized, it is possible to contribute to the downsizing of the electronic device in which the electret condenser microphone is mounted.
[0010]
As a desirable mode, the other end opening of the casing is bent in the axial direction of the casing, and the bent portion presses and locks the microphone circuit board. In short, the microphone circuit board is fastened and fixed by the terminal edge of the other end opening of the casing. Thereby, the structure which makes the said circuit board for microphones dent with respect to the other end opening peripheral edge of the said casing can be obtained easily.
[0011]
Preferably, the casing has a circular cross section, and the plurality of protruding electrodes have a first polarity and a first external connection electrode located at a central portion of the cross section and a second external connection electrode having a second polarity. And a plurality of the second external connection electrodes are arranged radially or concentrically around the first external connection electrode. For the function of the electret condenser microphone, it is necessary and sufficient that there are two external connection electrodes. According to the above arrangement of the external connection electrodes, the electret condenser microphone is mounted in the rotational direction around the first external connection electrode. The directionality can be ignored. From the above, it becomes extremely easy to automate the mounting of the electret condenser microphone on the electronic circuit and the mounting on the circuit board in terms of directivity with respect to the rotation direction.
[0012]
Preferably, the first external connection electrode is a signal electrode, and the second external connection electrode is a circuit ground electrode. Since the signal electrode is located at the center of the casing at the position recessed from the edge of the casing, it is possible to reduce the possibility of leakage to other wiring patterns on the mounting substrate.
[0013]
In a preferred embodiment, the casing is made of metal that is electrically connected to the second external connection electrode. If the casing is electrically connected to the second external connection electrode, the casing can be used as a shield against high frequency. In this case, the first external connection electrode, which is a signal electrode, is positioned at the center of the circular cross section that is farthest from the edge of the casing, thereby preventing the first external connection electrode from leaking into the casing and causing a malfunction. It is suitable for.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a partial axial section of an example of an electret condenser microphone according to the present invention. The electret condenser microphone 1 (also simply referred to as the electret microphone 1) shown in the figure has a button-type microphone casing 11 having a circular cross section, and has a sound wave passage opening (one end) in the cylinder. A diaphragm 13 that faces one of the openings (opening) 12, a back electrode 14 that forms a counter electrode (the other pole of the capacitor) of the diaphragm 13 with a gap, and a microphone circuit board 16 are provided. Yes. The diaphragm 13 has a metal film deposited on one surface of a dielectric film such as a polyester film, the metal film is fixed to the diaphragm ring 20, and an insulating spacer 21 is fixed to the dielectric surface. The back electrode 14 is fitted and fixed substantially concentrically to the inner step portion of the insulating ring 22. A conductive connection ring 24 is inserted inside the insulating ring 22, and the conductive connection ring 24 is in contact with the microphone circuit board 16 and the back electrode 14. The other end opening 18 of the casing 11 is bent inward, and the bent peripheral edge presses and fixes the microphone circuit board 16 toward the conductive connection ring 24. In short, the conductive connecting ring is pressed against the back electrode 14 by tightening the microphone circuit board 16.
[0015]
The diaphragm 13 and the back electrode 14 constitute an electret capacitor and perform electroacoustic conversion. A circuit element 25 such as a field effect transistor used for output impedance conversion is mounted on one surface of the microphone circuit board 16 facing the electret capacitor. On the other surface of the microphone circuit board 16, a plurality of solder bump electrodes 17A and 17B are formed as external connection electrodes for outputting an impedance-converted electroacoustic signal.
[0016]
The back electrode 14 and a predetermined conductive pattern on the microphone circuit board 16 are connected through the conductive connection ring 24. The connection between the metal film of the diaphragm 13 and the predetermined conductive pattern on the circuit board 16 for the microphone is performed through a path from the diaphragm ring 20 through the peripheral surface of the casing 11 to the peripheral edge or the tightening portion. Is called. The conductive pattern formed on the front and back surfaces of the microphone circuit board 16 connects the circuit element 25 to the back electrode 14 and the diaphragm 13, and connects the circuit element 25 to the solder bump electrodes 17A and 17B. Although not particularly limited, the solder bump electrode 17B is a ground electrode (ground potential terminal) of the circuit, and the solder bump electrode 17A is a signal electrode (signal output terminal) for an electroacoustic signal.
[0017]
FIG. 2 illustrates the manufacturing process of the solder bump electrodes 17A and 17B on the circuit board 16 for microphone. As shown in (A), a circular conductive pattern 30A and a ring-shaped conductive pattern 30B are formed concentrically on the surface of the circuit board 16 for microphone. On top of that, as shown in (B), an insulating resist 31 is applied, and an insulating resist peeling portion 32 is formed at a position where the solder bump electrodes 17A and 17B are formed. As shown in (C), solder paste electrodes 17A and 17B connected to the base conductive layers 30A and 30B are formed by applying a solder paste to the peeling portion 32.
[0018]
In the example of FIG. 2, the bump electrode 17A for signal output is formed at the center of the circuit board 16 for microphone. The ground potential bump electrodes 17B are arranged radially or concentrically with the bump electrode 17A as the center.
[0019]
The heights of the solder bump electrodes 17A and 17B are as follows: the diameter of the land to which the solder bump electrodes 17A and 17B are connected in the circuit board 16 (the diameter of the peeling portion 32), and the amount of solder printed on the land (diameter and diameter). For example, when the land diameter is 0.6 mm, the solder paste diameter is 0.6 mm, and the solder paste thickness is 0.2 mm, the bump height is about 0.3 mm. This height is sufficiently larger than the depth (0.1 mm) of the clamping portion of the casing, and when placed on the counterpart mounting board, the solder bump electrodes 17A and 17B are sufficiently free from the solder paste printed on the counterpart mounting board. Touchable.
[0020]
FIG. 3 illustrates a state where the electret condenser microphone 1 is mounted on an electronic circuit or a circuit board (hereinafter also simply referred to as a mounting board). Solder pastes 4 </ b> A and 4 </ b> B are printed on the wiring pattern of the other mounting board 3 at the position where the electret condenser microphone 1 is to be mounted. The solder bump electrodes 17A and 17B are placed on the printed patterns of the solder pastes 4A and 4B. And if it heats through a reflow apparatus (not shown), solder bump electrode 17A, 17B and solder paste 4A, 4B will fuse | melt and electrical connection and mechanical fixation will be achieved. Since the microphone circuit board 16 is recessed from the other end opening edge of the casing 11 to the back of the casing 11, the solder bump electrodes 17A and 17B must be somewhat large in order to secure the amount of solder necessary for the fusion connection between the solders. Even if it is not necessary, the thickness by which the solder bump electrodes 17A and 17B protrude from the edge of the casing can be small. When the solder bump electrodes 17A and 17B and the solder paste are melted by heating, the casing 11 can be approached until it comes into contact with the counterpart substrate, and the mounting height or mounting thickness of the electret condenser microphone 1 is set to the thickness dimension of the casing 11 of the microphone 1. It is possible to make it smaller. Since such a small mounting thickness can be realized, it is possible to contribute to downsizing of an electronic device in which the electret condenser microphone 1 is mounted.
[0021]
The casing 11 has a circular axial cross section, and a plurality of, for example, three solder bump electrodes 17B as ground potential electrodes are arranged around a solder bump electrode 17A as a signal electrode. The directionality when the electret condenser microphone 1 is mounted can be ignored with respect to the rotation direction as the center. Thus, it is extremely easy to automate the mounting of the electret condenser microphone 1 on the counterpart mounting substrate 3 in terms of the directivity with respect to the rotational direction.
[0022]
Since the bump electrode 18B as the ground potential electrode is arranged around the solder bump electrode 17A as the signal electrode, the solder bump electrode 17A as the signal electrode is connected to another wiring on the other mounting board at the time of mounting. It is possible to reduce the possibility of leaking into a pattern or the like. The casing 11 is made of metal that is electrically connected to the solder bump electrode 17B. If the casing 11 is electrically connected to the solder bump electrode 17B, the casing 11 can be used as a shield against high frequency. In this case, since the solder bump electrode 17A, which is a signal electrode, is located at the center of the circular cross section farthest from the edge of the casing, it is possible to prevent the bump electrode 17A from leaking from the casing during mounting.
[0023]
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.
[0024]
For example, the structure of the electret microphone as the electroacoustic conversion component is not limited to the structure of FIG. 2 and can be changed as appropriate. The solder bump electrodes may be formed not only with solder paste but also with solder balls. There is no problem if the height of the solder is larger than the depth of the fastening portion of the casing. In the electret microphone, the solder bump electrodes need only have two electrodes, that is, a ground electrode and a signal electrode. From the viewpoint of stability, the number of bump electrodes arranged concentrically around the center is preferably 3 or more.
[0025]
【The invention's effect】
In the electret condenser macrophone according to the present invention, the external connection electrode is composed of a solder bump electrode or the like, so if the external connection electrode is placed on a printed pattern such as a solder paste of the other party to be mounted and heated by a reflow device or the like The external connection electrode made of solder and the solder paste are melted, and electrical connection and mechanical fixing can be easily achieved.
[0026]
The external connection electrode protrudes from the circuit board for microphone that is recessed from the peripheral edge of the opening of the casing, and its tip protrudes forward from the peripheral edge of the opening of the casing. Even if the external connection electrode is increased in order to ensure the amount of solder, the thickness or height at which the external connection electrode protrudes from the peripheral edge of the other end opening of the casing may be small. Therefore, when the external connection electrode and solder paste are melted by heating, the casing can be approached until it contacts the mating substrate, and the mounting height or mounting thickness of the electret condenser microphone can be reduced to the casing thickness dimension of the microphone. It is. As described above, since a small mounting thickness can be realized, it is possible to contribute to miniaturization of an electronic device in which the electret condenser microphone is mounted.
[0027]
By arranging a plurality of radial or concentric areas around the first external connection electrode, the directivity when mounting the electret condenser microphone can be ignored with respect to the rotation direction about the first external connection electrode. become. From the above, it becomes extremely easy to automate the mounting of the electret condenser microphone on the electronic circuit and the mounting on the circuit board in terms of directivity with respect to the rotation direction.
[0028]
From the above, according to the electret condenser microphone according to the present invention, it is suitable for thinning or miniaturization in the mounting state on the circuit board, and it is easy to automate mounting on the counterpart electronic circuit and mounting on the circuit board. It is.
[Brief description of the drawings]
FIG. 1 is a partial axial sectional view showing an example of an electret condenser microphone according to the present invention.
FIG. 2 is an explanatory view exemplifying a manufacturing process of a solder bump electrode on a circuit board for a microphone.
FIG. 3 is a front view illustrating a state when an electret condenser microphone is mounted on a mounting substrate.
[Explanation of symbols]
1 Electret condenser microphone 3 Mounting board 4A, 4B
11 Casing 12 Sound wave passage opening (one end opening)
13 Diaphragm 14 Back electrode 16 Microphone circuit board 17A, 17B Solder bump electrode 18 Opening at the other end 20 Diaphragm ring 24 Conductive connection ring 25 Circuit element

Claims (5)

A casing having openings at both ends, an electret condenser built in facing the one end opening of the casing, and a microphone circuit board built in facing the other end opening of the casing;
The microphone circuit board has a circuit component on one surface facing the electret capacitor, and a plurality of conductive patterns connected to the circuit component are formed on the other surface on the back side ,
A plurality of solder bump electrodes used for surface mounting on the plurality of conductive patterns;
The other surface of the microphone circuit board is located behind the opening surface of the other end opening of the casing ,
Wherein the plurality of solder bump electrodes are protruded from the opening surface, it is to be placed on the wiring pattern of the mounting substrate, an electret condenser microphone, characterized in that.   2. The electret condenser microphone according to claim 1, wherein the other end opening of the casing is bent in the axial direction of the casing, and the bent portion presses and locks the microphone circuit board. Said casing is a shaft circular section, said plurality of solder bump electrodes in a first solder bump electrode positioned in the shaft the cross-sectional center portion having a first polarity, and a second solder bump electrodes having a second polarity 3. The electret condenser microphone according to claim 2, wherein a plurality of the second solder bump electrodes are arranged radially or concentrically around the first solder bump electrode. 4. The electret condenser microphone according to claim 3, wherein the first solder bump electrode is a signal electrode, and the second solder bump electrode is a ground electrode of a circuit. 5. The electret condenser microphone according to claim 4, wherein the casing is made of a metal that is electrically connected to the second solder bump electrode.

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