subject: Electret Condenser Microphone And Method Of Producing Same [print this page] Herein disclosed is an electret condenser microphone which comprises a casing member having a center axis and including a circular acoustic inlet portion and a cylindrical side portion integrally formed with the acoustic inlet portion, the side portion of the casing member having a first section close to the acoustic inlet portion of the casing member and a second section remote from the acoustic inlet portion of the casing member.
The second section of the side portion of the casing member radially inwardly bent toward the center axis of the casing member, a printed circuit board disposed in the casing member and held in contact with the second section of the side portion of the casing member, an electrically insulating member provided on the printed circuit board, an electrode plate provided on the electrically insulating member, and an electrically connecting member intervening between the printed circuit board and the electrode plate to have the printed circuit board and the electrode plate electrically connected with each other.
An electret condenser microphone for receiving an acoustic wave to be converted to an acoustic signal indicative of said acoustic wave, comprising:
Casing member having a center axis and including a circular acoustic inlet portion and a cylindrical side portion integrally formed with said acoustic inlet portion, said side portion of said casing member having a first section close to said acoustic inlet portion of said casing member and a second section remote from said acoustic inlet portion of said casing member, said second section of said side portion of said casing member radially inwardly bent toward said center axis of said casing member;
A printed circuit board disposed in said casing member and held in contact with said second section of said side portion of said casing member, said casing member and said printed circuit board collectively forming a cylindrical casing space;an electrically insulating member accommodated in said casing space and provided on said printed circuit board, said electrically insulating member having an inner surface;an electrode plate provided on said electrically insulating member; and
An electrically connecting member having a peripheral surface and intervening between said printed circuit board and said electrode plate to have said printed circuit board and said electrode plate electrically connected with each other under the state that said peripheral surface of said electrically connecting member is held in contact with said inner surface of said electrically insulating member.
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, 10B and 10C. 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.
