JPS59171300A - Condenser microphone - Google Patents

Abstract

PURPOSE:To prevent a resonance frequency from being lowered at a high ambient temperature by inserting a metallic thin film spacer having lots of through- holes and an insulator between a metallic diaphragm and a back electrode. CONSTITUTION:The condenser microphone consists of a diaphragm 6 made of metallic foil, a spacer 9 comprising metallic thin film having plural through- holes 7, the metallic back electrode 5 and an insulating film 10. In this constitution, a DC bias voltage is impressed between the diaphragm 6 and the back electrode 5 and a sound pressure P is applied to the diaphragm 6, then the length of the through-holes 7 is changed and a capacitance between the diaphragm 6 and the back electrode 5 is changed and this is extracted as a voltage change. Since a metallic foil having a less expansion coefficient than a plastic film by nearly 1 digit is used in this way, no deflection is produced in a high ambient temperature and the resonance frequency is not decreased. Since the spacer 9 is also the metallic thin film, the holes 7 are formed with high precision and the control of the resonance frequency is easy.

Description

[Detailed description of the invention] Industrial application field of the present invention
(1) It should be used as a condenser microphone, which is used as a condenser microphone.
Figure υ (, j: S2-, this vapor-deposited electrode 1 is placed on one side (-i wave number emitting surface side), and this steam swamp dragon ball 1 is electrically connected to the gold 1-column ring 2 with -, i3j+ ・1] A plastic vibrating wire (1), which is stretched over a plastic vibrator (1), is closely spaced on the back (51) with a plurality of concave holes (4), and a DC bias voltage is applied between the evaporation electrode (1) and one pole (5). It has a structure that applies (7).And when the sound pressure P is applied to the vibrating membrane 3 (・), the sound pressure P is applied (・).
Due to the corresponding displacement of the filament membrane 3, the vapor electrode 1 and the back electrode 5 are
The distance d between the parts including the recesses 2 and the gaps 4 changes, and this electrostatic tolerance change is taken out to an external electric circuit (not shown).

Here, the surface of the back electrode 5 (5) has a concentric groove 4-1 as shown in FIG. As shown in Figure 4,
Each independent circle with 7'j Fn number 4-2. Square 4-3
It may also be a void that has the shape of 1,111 stones.

-(stationary wave number)'r[1(z]4
The tension of the membrane is given as T[:N7m], the areal density is given as Ml, A9/nl'', 11 and S, but the conventional content ν-type microphone for ultra-violet ultra-f waves is Since a plastic film is used as the vibrating membrane 3, when the ambient temperature becomes high, the vibrating membrane 3
As a result, the tension T of the diaphragm 3 becomes smaller than the initial setting value at room temperature, and as a result, the
) has the disadvantage that the resonance frequency shown by the equation decreases.

In order to eliminate this drawback, as shown in FIG. 6, a metal vibrating membrane 6 made of titanium alloy or the like with a small coefficient of thermal expansion is used, and an insulating film made of a plastic thin film with a thickness of several thousand 1 tm or less and having a plurality of through holes 7 is used. A configuration in which the vibrating membrane 6 faces the back electrode 6 in close contact with the body spacer 8 has been considered, but since the insulator spacer 8 is a thin plastic film, it is difficult to handle, and the resonance circumference number is several hundreds. In the case of KHz or more, the cross-sectional dimension of the insulator spacer 80 through hole 7 is on the order of 0.1 mm, and it is not easy to perform microfabrication of about 0.1 mm on a plastic thin film with a thickness of several tens of μm or less. .

Purpose of the Invention The present invention has been made in view of the above problems.
It is an object of the present invention to provide a capacitor type microphone which prevents a drop in common frequency in a high temperature atmosphere, improves the dimensional accuracy of an insulating spacer, and is easy to handle.

Structure of the Invention In order to achieve the above object, the present invention interposes a metal thin film spacer having a large number of through holes and an insulator between a metal vibrating membrane and a back electrode.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

FIG. 6 is a configuration diagram showing an embodiment of the present invention, in which a vibrating membrane 6 made of metal foil such as titanium alloy is made of a metal thin film with a thickness of several tens of μm or less with a plurality of minute through holes 7 formed therein. Spacer consisting of9. Metal back electrode6. An insulating film 10 made of a plastic film or the like for insulating the spacer 9 and the back electrode 3.
A vibrating membrane holding ring 2 on which the vibrating membrane 6 is stretched. and a shield case 11. Vibrating membrane retaining ring 2
is made of metal and is electrically connected to the vibrating membrane 6.
The vibrating membrane 6 stretched on the vibrating membrane holding ring 2 is connected to a spacer 9
The diaphragm 6 and the spacer 9 do not necessarily need to be electrically conductive, but they should be brought into close contact with each other to ensure electrical continuity in order to reduce the stray capacitance between the electrodes. is desirable.

In the above configuration, a DC bias voltage is applied between the movable membrane 6 and the back electrode 6. When sound pressure P is applied to the diaphragm 6, the height of the through hole 7 provided in the spacer 9 changes, and therefore the interelectrode capacitance between the diaphragm θ and the back electrode 5 changes, which is caused by a voltage change. In Fig. 6, titanium foil with a thickness of 2 μm is used for the vibrating membrane 6, stainless steel foil with a thickness of 3.011 m is used for the spacer 9, and the spacer 9 has a radius of 0.2 TII by etching.
A large number of through holes 7 are provided, and the vibration membrane 6 (Tension of the tensile strength of titanium (T = 500 N/m)
When adding, M=9X10-'Nori/m' and the (
1) According to the formula, the resonant frequency fr is approximately 450 KHz.
As explained above, in this embodiment, the vibrating membrane 6 uses metal foil such as titanium or titanium alloy, which has a linear expansion coefficient about one order of magnitude smaller than that of a plastic film, so the vibrating membrane 6 will sag even in a high-temperature atmosphere. Therefore, the resonant frequency does not decrease. Also spacer 9
Since this uses metal foil such as stainless steel, a large number of extremely small through holes 7 can be formed with high dimensional accuracy by methods such as etching, making it possible to control the resonance frequency with high precision. be. Furthermore, since metal foil with a spacer is used, it is easier to handle than wrinkles, etc., compared to when a plastic thin film is used.

As described in detail, according to the present invention, since the diaphragm is made of a thin metal film, the diaphragm does not sag even in a high-temperature atmosphere, resulting in a reduction in the resonance frequency. Therefore, the through holes can be formed with high precision, the resonance frequency can be easily controlled within 1 lilJ, and wrinkles are less likely to occur (easy to handle).

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a conventional condenser type microphone using a plastic diaphragm, and Figs. 2 to 4 show the shape of the back electrode. i'
6 is a cross-sectional view showing a unidirectional membrane condenser microphone.
FIG. 3 is a sectional view showing the embodiment. 2... Shaking GLH membrane retaining ring, 6...
Back electrode, 6... Vibration membrane, 7... Negative through hole, 9
...Spacer, 21o...Insulator. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3-2 Figure 5 Figure 6

Claims (1)

[Claims] A large number of through holes are formed, and a spacer made of a metal thin film 1P is formed.
[2] / Tenza type microphone cophone, which forms a back 1j that constitutes an inward 1F pole with the diaphragm.