At&t Bell Laboratories

Bell Telephone Laboratories

Stephen Reed Whitesell

Alex Michael Brzezinski

John C Baumhauer, Jr

Harold J Hershey

Joe Edward Warren

A transducer embodying the present invention is assembled on a discrete electrically conductive frame (100) that has been formed to provide both leads (120-140) and a backplate (110). An integrated circuit chip (200) is bonded to one of the leads, and a dielectric inner housing member (300) is molded about the backplate and the portion of the leads adjacent to it. The inner housing member encapsulates the chip, embraces the perimeter of the backplate, and provides a cylindrical opening (310) that extends on each side of the backplate. A conductive outer housing member (400) is subsequently molded about the perimeter of the inner housing member, and a spacer (500), electret diaphragm assembly (600), and conductive gasket (700) are sequentially positioned in the opening on one side of the backplate. Conductive front and back covers (800,900) are thereafter bonded to the outer housing to close the opening and to complete a conductive enclosure that provides electrostatic shielding for the transducer. In addition, electrical continuity is provided between a metalized surface on the electret diaphragm and the conductive enclosure by means of the gasket.

Electroacoustic transducer

An electroacoustic transducer in accordance with the present invention comprises a perforated backplate having a plurality of upstanding parallel ribs between which conductive surfaces are situated. The conductive surfaces are electrically interconnected with one another and with a contact surface on a relieved shoulder at one end of the backplate. This shoulder is engaged by a bifurcated contact spring that (1) electrically connects the conductive surfaces to the input of an integrated preamplifier circuit deposited on a substrate and (2) holds the substrate in place on the underside of the backplate. An electret diaphragm having a metallized surface is tensioned across the ribs of the backplate with the metallized surface facing away from the backplate, and while so tensioned, the ends of the diaphragm are clamped against the backplate by a conductive intermediate member that makes electrical contact with the diaphragm. The intermediate member is held in place by a conductive spring member that wraps around the sides of the foregoing assembly and presses the intermediate member and the substrate toward one another. The spring member provides the clamping force necessary to retain the desired tension on the diaphragm and at the same time further secures the substrate in place. In addition, the spring member includes a terminal that is located in engagement with the ground lead of the preamplifier circuit and thus in combination with the intermediate member provides a conductive path to ground for the conductive surface of the diaphragm. Finally, the spring member serves to provide additional electrostatic shielding for the electret.

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Indianapolis, IN, United States of America

Stephen Reed Whitesell