Electret condenser microphone and method of producing same

1. An electret condenser microphone for receiving an acoustic wave to be converted to an acoustic signal indicative of said acoustic wave, comprising:

a casing member;

a circuit board disposed in said casing member and having a peripheral portion supported by said casing member, and a central portion integrally formed with said peripheral portion of said circuit board and radially inwardly extending from said peripheral portion of said circuit board;

an electrically insulating member disposed on and along said peripheral portion of said circuit board, said electrically insulating member having an outer surface opposing and spaced apart from said casing member, and an inner surface defining a central opening;

an electrode plate mounted on said electrically insulating member;

a plurality of electrically connecting members each intervening between said circuit board and said electrode plate to have said circuit board and said electrode plate electrically connected with each other, each of said electrically connecting members having a first portion disposed along said inner surface of said electrically insulating member, a second portion integrally formed with said first portion and radially outwardly extending from one end of said first portion, and a third portion integrally formed with said first portion and radially outwardly extending from the other end of said first portion; and

a diaphragm disposed along said electrode plate and spaced apart from said electrode plate at a predetermined space distance and in which

said electrically insulating member is formed with a plurality of guide grooves, and in which each of said electrically connecting members is received in each of said guide grooves of said electrically insulating member.

2. An electret condenser microphone as set forth in claim 1 , which further comprises a signal converting unit for converting an electrical capacitance between said electrode plate and said diaphragm to said acoustic signal indicative of said acoustic wave transmitted to said diaphragm, said signal converting unit being disposed on said central portion of said circuit board, in which said electrically connecting members are partly disposed on and along said peripheral portion of said circuit board.

3. An electret condenser microphone as set forth in claim 1 , in which each of said electrically connecting members is made of a metal plate having an elasticity.

4. An electret condenser microphone for receiving an acoustic wave to be converted to an acoustic signal indicative of said acoustic wave, comprising:

a casing member having a center axis passing therethrough, said casing member having an inlet portion having first and second surfaces each held in perpendicular relationship to said center axis of said casing member, a side portion integrally formed with said inlet portion of said casing member and axially extending along said center axis of said casing member from said inlet portion of said casing member, and an end portion integrally formed with said side portion of said casing member and radially inwardly extending toward said center axis of said casing member from said side portion of said casing member, said side portion of said casing member having an inner surface connected to said second surface of said inlet portion of said casing member;

a circuit board disposed in said casing member and having a peripheral portion supported by said end portion of said casing member, and a central portion integrally formed with said peripheral portion of said circuit board and radially inwardly extending from said peripheral portion of said circuit board;

an electrically insulating member disposed on and along said peripheral portion of said circuit board, said electrically insulating member having a first surface opposing and spaced apart along said center axis of said casing member from said second surface of said inlet portion of said casing member, a second surface held in contact with said circuit board, an outer surface opposing and spaced apart from said inner surface of said side portion of said casing member, and an inner surface defining a central opening;

an electrode plate mounted on said electrically insulating member;

a plurality of electrically connecting members each intervening between said circuit board and said electrode plate to have said circuit board and said electrode plate electrically connected with each other, each of said electrically connecting members having a first portion disposed along said inner surface of said electrically insulating member and having a first end section close to said electrode plate and a second end section close to said circuit board, a second portion integrally formed with said first portion and radially outwardly extending from said first end section of said first portion to be provided on said electrode plate, and a third portion integrally formed with said first portion and radially outwardly extending from said second end section of said first portion to be provided on said circuit board, said second portion of each of said electrically connecting members having an end surface opposing and spaced apart from said inner surface of said side portion of said casing member, said third portion of each of said electrically connecting members having an end surface opposing and spaced apart from said inner surface of said side portion of said casing member, and

a diaphragm disposed along said electrode plate and spaced apart along said center axis of said casing member from said electrode plate at a predetermined space distance and in which

said electrically insulating member is formed with a plurality of guide grooves, and in which each of said electrically connecting members is received in each of said guide grooves of said electrically insulating member.

5. An electret condenser microphone as set forth in claim 4 , in which said guide grooves of said electrically insulating member are disposed around said center axis of said casing member in equiangularly spaced relationship with each other.

6. An electret condenser microphone as set forth in claim 4 , in which said electrically insulating member is formed with an annular ledge, and in which said electrode plate has a peripheral portion received in said annular ledge of said electrically insulating member, and a central portion integrally formed with said peripheral portion of said electrode plate and radially inwardly extending from said peripheral portion of said electrode plate.

7. An electret condenser microphone as set forth in claim 4 , in which said inner surface of said electrically insulating member is in the form of a truncated conical shape and tapered toward said second surface of said inlet portion of said casing member.

8. An electret condenser microphone as set forth in claim 4 , in which each of said electrically connecting members is made of a metal plate and elastically restorable along said center axis of said casing member to ensure that each of said electrically connecting members is held in contact with said circuit board and said electrode plate.

9. An electret condenser microphone as set forth in claim 4 , in which said electrically connecting members are disposed around said center axis of said casing member in equiangularly spaced relationship with each other.

10. An electret condenser microphone as set forth in claim 4 , in which said second and third portions of each of said electrically connecting members are spaced apart from each other to have said electrically insulating member interposed between said second and third portions of each of said electrically connecting members.

11. An electret condenser microphone as set forth in claim 4 , in which the space distance between said end surface of said second portion of each of said electrically connecting members and said inner surface of said side portion of said casing member is smaller than or equal to the space distance between said outer surface of said electrically insulating member and said inner surface of said side portion of said casing member.

12. An electret condenser microphone as set forth in claim 4 , in which the space distance between said end surface of said third portion of each of said electrically connecting members and said inner surface of said side portion of said casing member is larger than or equal to the space distance between said outer surface of said electrically insulating member and said inner surface of said side portion of said casing member.

13. An electret condenser microphone as set forth in claim 4 , which further comprises a diaphragm supporting member provided on said second surface of said inlet portion of said casing member, in which said diaphragm has a peripheral portion supported by said diaphragm supporting member, and a central portion integrally formed with said peripheral portion of said diaphragm and radially inwardly extending from said peripheral portion of said diaphragm to be oscillatable along said center axis of said casing member with respect to said casing member.

14. An electret condenser microphone as set forth in claim 4 , which further comprises an electrically insulating spacer intervening between said electrode plate and said diaphragm to have said electrode plate and said diaphragm spaced apart from each other at a predetermined space distance.

15. An electret condenser microphone as set forth in claim 4 , in which said electrode plate and said diaphragm collectively constitute a capacitor unit to generate an electrical capacitance corresponding to the space distance between said electrode plate and said diaphragm under the state that said acoustic wave is transmitted to said diaphragm to have said diaphragm partly oscillated along said center axis of said casing member with respect to said casing member.

16. An electret condenser microphone as set forth in claim 4 , which further comprises a covering member provided on said first surface of said inlet portion of said casing member, in which said inlet portion of said casing member is formed with an acoustic aperture open at said first and second surfaces of said inlet portion of said casing member to have said acoustic wave transmitted to said diaphragm through said covering member and said acoustic aperture of said inlet portion of said casing member.

17. An electret condenser microphone as set forth in claim 4 , which further comprises a signal converting unit for converting an electrical capacitance between said electrode plate and said diaphragm to said acoustic signal indicative of said acoustic wave transmitted to said diaphragm, said signal converting unit being disposed on said central portion of said circuit board, in which said electrically connecting members are partly disposed on and along said peripheral portion of said circuit board.

18. An electret condenser microphone as set forth in claim 17 , in which said signal converting unit includes a field effect transistor, a chip capacitor, and a chip resistor.

19. An electret condenser microphone as set forth in claim 17 , in which said signal converting unit is electrically connected to said electrode plate and said diaphragm, respectively.