Electret condenser microphone and method of producing same

Details Electret condenser microphone and method of producing same Electret condenser microphone and method of producing same

2001-09-19

2003-01-28

Le, Huyen (Department: 2643)

Electrical audio signal processing systems and devices

Electro-acoustic audio transducer

Microphone capsule only

C381S191000

Reexamination Certificate

active

06512833

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electret condenser microphone and a method of producing the same available for various audio equipments such as a cellular phone, and more particularly to an electret condenser microphone and a method of producing the same equipped with a condenser unit constituted by an electrode plate and a diaphragm to receive an acoustic wave to be converted to an acoustic signal indicative of the acoustic wave.
2. Description of the Related Art
Up until now, there have been proposed a wide variety of conventional electret condenser microphones each equipped with a condenser unit constituted by an electrode plate and a diaphragm to receive an acoustic wave to be converted to an acoustic signal indicative of the acoustic wave.
The conventional electret condenser microphones of this type have so far been available for various audio equipments such as a cellular phone. One typical example of the conventional electret condenser microphones is exemplified and shown in
FIGS. 8 and 9
. The conventional electret condenser microphone
900
thus proposed comprises a casing member
910
having a center axis
911
. The casing member
910
includes a circular acoustic inlet portion
912
, and a cylindrical side portion
913
integrally formed with the acoustic inlet portion
912
. The acoustic inlet portion
912
of the casing member
910
has thereon an electret film
916
to constitute an electrode plate. The side portion
913
of the casing member
910
has a first section
914
close to the acoustic inlet portion
912
of the casing member
910
, and a second section
915
remote from the acoustic inlet portion
912
of the casing member
910
and radially inwardly bent toward the center axis
911
of the casing member
910
.
The conventional electret condenser microphone
900
further comprises a covering member
920
provided on the acoustic inlet portion
912
of the casing member
910
, and a printed circuit board
960
disposed in the casing member
910
and spaced apart along the center axis
911
of the casing member
910
from the acoustic inlet portion
912
of the casing member
910
. The printed circuit board
960
is partly held in contact with the second section
915
of the side portion
913
of the casing member
910
.
The conventional electret condenser microphone
900
further comprises an electrically connecting member
940
provided on the printed circuit board
960
, and a diaphragm
930
provided on the electrically connecting member
940
. The diaphragm
930
includes a peripheral portion
931
securely retained by the electrically connecting member
940
, and a central portion
932
integrally formed with the peripheral portion
931
and radially inwardly extending from the peripheral portion
931
to be partly oscilatable along the center axis
911
of the casing member
910
with respect to the casing member
910
. The acoustic inlet portion
912
of the casing member
910
is formed with a plurality of acoustic apertures
917
to have the acoustic wave transmitted to the diaphragm
930
through the covering member
920
and the acoustic apertures
917
of the acoustic inlet portion
912
of the casing member
910
. The electrically connecting member
940
is made of a metal and intervenes between the printed circuit board
960
and the peripheral portion
931
of the diaphragm
930
to have the printed circuit board
960
and the peripheral portion
931
of the diaphragm
930
electrically connected with each other.
The conventional electret condenser microphone
900
further comprises an electrically insulating spacer
950
partly intervening between the acoustic inlet portion
912
of the casing member
910
and the diaphragm
930
to have the acoustic inlet portion
912
of the casing member
910
and the diaphragm
930
spaced apart from each other at a predetermined space distance. The acoustic inlet portion
912
of the casing member
910
, i.e., the electrode plate, and the diaphragm
930
collectively constitute a condenser unit
933
to generate an electrical capacitance corresponding to the space distance between the acoustic inlet portion
912
of the casing member
910
and the diaphragm
930
when the acoustic wave is transmitted to the diaphragm
930
to have the central portion
932
of the diaphragm
930
partly oscillated along the center axis
911
of the casing member
910
with respect to the casing member
910
.
The conventional electret condenser microphone
900
further comprises a signal converting unit
970
including a field effect transistor
971
and designed to convert the electrical capacitance generated by the condenser unit
933
to the acoustic signal indicative of the acoustic wave transmitted to the diaphragm
930
. The signal converting unit
970
is provided on the printed circuit board
960
to be electrically connected to the acoustic inlet portion
912
of the casing member
910
through the printed circuit board
960
and the side portion
913
of the casing member
910
, and to the diaphragm
930
through the printed circuit board
960
and the electrically connecting member
940
.
The following description will be directed to a method of producing the conventional electret condenser microphone
900
with reference to the drawings shown in
FIGS. 10A
,
10
B and
10
C. The method of producing the conventional electret condenser microphone
900
is performed through the steps including a preparing step, an imparting step and a releasing step as follows.
In the preparing step, the casing member
910
, the covering member
920
, the printed circuit board
960
, the electrically connecting member
940
, the diaphragm
930
, the electrically insulating spacer
950
, and the signal converting unit
970
are prepared as a partially fabricated unit. The second section
915
of the side portion
913
of the previously mentioned casing member
910
is straightly extends from the first section
914
of the side portion
913
of the casing member
910
.
In the imparting step, the second section
915
of the side portion
913
of the casing member
910
is then imparted an external force toward an imparting direction shown by an arrow
901
to assume a first state in which the second section
915
of the side portion
913
of the casing member
910
is bent toward the center axis
911
of the casing member
910
as shown in FIG.
10
B.
In the releasing step, the second section
915
of the side portion
913
of the casing member
910
is then released from the external force imparted thereto toward the imparting direction shown by the arrow
901
to assume a second state in which the second section
915
of the side portion
913
of the casing member
910
is naturally elastically restored along the center axis
911
of the casing member
910
. The conventional electret condenser microphone
900
is then produced as shown in FIG.
10
A.
The conventional electret condenser microphone, however, encounters such a problem that each of the second section
915
of the side portion
913
of the casing member
910
and the electrically connecting member
940
is spaced apart from the printed circuit board
960
in the releasing step as shown in
FIG. 10C
, resulting from the fact that the second section
915
of the side portion
913
of the casing member
910
is prevented by the electrically connecting member
940
made of a metal from being deformed toward the imparting direction shown by the arrow
901
as shown in
FIG. 10B
, and the second section
915
of the side portion
913
of the casing member
910
is naturally elastically restored along the center axis
911
of the casing member
910
as shown in FIG.
10
C.
The fact that each of the second section of the side portion of the casing member and the electrically connecting member is spaced apart from the printed circuit board leads to the fact that each of the acoustic inlet portion of the casing member, i.e., the electrode plate, and the diaphragm is electrically disconnected from the printed circuit

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