| 摘要 |
PURPOSE:To make mass production of microphone units through an automatic assembling system easy by fixing a printed base board at a hollow part of the bottom of an insulator and to smooth insertion of the base board into a cylindrical metallic case. CONSTITUTION:A vibration film 4 made of an electret material and containing a metal vapor-deposited on a single side is stretched to a metallic ring 3. An insulator 7 fixes a fixed electrode 6 and forms a back air room 7a. An input lead 8a of a field effect transistor TR8 which performs the electric impedance conversion is connected to the electrode 6 by a spot welding process, etc. A hollow part 12 is formed at the bottom of a pot-shaped insulator 7. The width of the part 12 is a little larger than a printed base board 9. Then the board 9 is put into the part 12 and fixed there, and a copper foil pattern 9a of the board 9 is connected to an output lead 8b of the TR8 by soldering 10. In such a constitution, the insulator 7, the board 9, etc. can be put smoothly into a cylindrical metallic case 2 with no hitch to the edge part 11 of the case 2. |
