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JPS5585198

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DESCRIPTION JPS5585198
Description 1, title of the invention
Microphone manufacturing method
3. Detailed Description of the Invention The present invention relates to a method of
manufacturing a microphone using a polymeric piezoelectric film as a vibrating film, and in
particular to provide a method of manufacturing a microphone that is resistant to temperature
changes in the environment using the microphone and is easy to manufacture. It is a thing. A
conventional microphone of this type will be described with reference to FIG. A vibrating film 1 is
formed of a polymeric piezoelectric film 21 having a metal electrode on both sides. 2 is a frame
made of metal, and the frame 2 is curved so as to obtain desired frequency characteristics and
sensitivity, and the polymer piezoelectric film 1 is attached to the frame 3 in a tensioned state
along the curvature The lead 3 is taken out from one side of the vibrating membrane surface and
the frame 2. Now, when the sound pressure P is applied, the vibrating membrane 1 bends, a
potential is generated on both sides of the vibrating membrane 1, and an output can be taken out
from the lead 3. However, in the conventional configuration, since the expansion coefficient of
the diaphragm 1 is larger than that of the frame 2 because the frame 2 is metal, for example, the
expansion of the diaphragm 1 becomes larger than that of the frame 2 when the temperature
rises. There was a defect that the tension of the membrane 1 changed. The situation is shown in
Fig. 2a and b. Fig. 2 shows a state where the temperature rises from the state of Fig. 1, and the
vibrating membrane 1 changes the curvature of the sagging vibrating membrane 1, and therefore
both the frequency characteristics and the sensitivity change and become unstable. Met.
Therefore, in order to solve such a problem, an ?End-up: 1-frame? that is made of plastic has
been developed, but this is a method of attaching a piezoelectric film to a plastic flat frame and
then bending the frame. As a result, the shape of the piezoelectric film in the completed state
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becomes a bowl shape, and as a result, the frequency characteristics and the sensitivity are
lowered as in the conventional one described above. The present invention is intended to
eliminate the above-mentioned conventional defects, and is configured such that the curvature of
the vibrating film surface does not change with temperature change. FIG. 3 shows an
embodiment of the present invention, in which 4 is a vibrating film made of a piezoelectric film
having metal electrodes 8 and 8 'on both sides, and 5 is a frame made of resin and has desired
frequency characteristics and sensitivity. It is pre-curved to be obtained. The vibrating membrane
4 is attached while tension is applied along the curvature of the frame 6. The bonding may be
performed by applying an adhesive and applying pressure to conduct one of the metal electrodes
8 'of the vibrating membrane 4 with the metal layer 6 of claim 6, and a shielded conductive
adhesive may be used.
?? A is a lead wire, and the lead wire 7 is connected to the metal layer 6 of the frame 5, and the
other lead wire 7 ? is connected to one electrode 8 of the vibrating membrane 4. As is well
known, this type of microphone using a polymeric piezoelectric film has its curvature related to
frequency characteristics and sensitivity. For example, the sensitivity and the resonance
frequency are represented by the following equations. Here, R is the curvature of the vibrating
film, ? is the dielectric constant of the material, d is the piezoelectric constant of the material, E
is the Young's modulus of the material, and ? is the density of the material. That is, both the
sensitivity and the resonance frequency are related to the curvature of the vibrating film except
for the material constant of the polymer film. Conversely, if the curvature changes, the sensitivity
and the resonant frequency are greatly affected. Now, if the thermal expansion coefficient of the
frame material is different from the thermal expansion coefficient of the vibrating membrane, the
curvature of the vibrating membrane changes because the elongation of the frame and the
vibrating membrane is different due to temperature change, as described in the conventional
example. Frequency characteristics change. In the present invention, by selecting a material
having approximately the same linear expansion coefficient as that of the polymeric piezoelectric
film and the linear expansion coefficient of the frame material, it is possible to make the
elongation of the frame and the vibrating film caused by temperature change almost the same.
The curvature of the film does not change, and both the frequency characteristics and sensitivity
are stable against temperature changes. As a material of the frame, any material may be used as
long as it has a coefficient of expansion similar to that of the vibrating film, is tough and is
capable of metal plating. For example, ABS (acrylonitrile, butadiene, styrene, etc. combination)
can do. Then, in the present invention, the material selected in this manner is processed with a
curvature so as to obtain desired properties, and then metal plating is applied to the frame, and
tension is applied along the curvature of the frame. It is a method of sticking a polymeric
piezoelectric film in the applied state. In FIG. 6, a microphone is attached to the opening of the
case 9 having the microphones shown in FIGS. 3 and 4, and the sound absorbing material 10 is
accommodated in the case 9 to form a back cavity. As described above, according to the method
of manufacturing a microphone of the present invention, the following effects can be obtained.
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(1) Since the frame is made of resin, the curvature of the polymeric piezoelectric film does not
change even if the ambient temperature changes, and the frequency characteristics, sensitivity,
etc. of the microphone change due to the ambient temperature change. I am angry. In addition,
after the frame is formed into a desired shape with a curvature and molded, metal plating is
applied and the piezoelectric film is attached, so that a microphone having good frequency
characteristics and sensitivity can be obtained.
Since metal plating is applied to the frame made of (turned) resin, if a polymeric piezoelectric
film provided with electrodes on both sides is attached to the frame, one of the electrodes of the
polymeric piezoelectric film and the frame are electrically connected Since the conduction is
obtained, the connection of the lead wires is facilitated. ???????? ?
4. Brief Description of the Drawings FIG. 1 is a perspective view of a conventional microphone,
FIGS. 2a and 2b are sectional views of the conventional microphone, and FIG. 3 is obtained by the
method of manufacturing a microphone according to an embodiment of the present invention.
FIG. 4 is an enlarged view of a portion A of FIG. 3 and FIG. 5 is a cross-sectional view showing the
same microphone incorporated in a case. 4 ииииии Vibrating film (polymer piezoelectric film), 5 иии
Frame и и и и и и и и и и и и и и и и и и и 7, 7 'и и и и и и и и Lead wire, 8.8 '...... electrode, 9 ...... case, 1o ...... intake
?r material. Name of agent Attorney Nakao and others 1 person Figure 1 Figure 2 EndPage: ?
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