Electret microphone

DETAILED DESCRIPTION The foregoing problems are solved in accordance with an embodiment of the invention wherein an electret transducer comprises a uniformly radially tensioned electret diaphragm having a thin metal layer deposited on one of its major surfaces; and a ring-shaped metal washer bonded to the metallized layer of the electret diaphragm by means of a lightly metal-filled adhesive.
In one illustrative embodiment of the invention, the thin metallized layer is selected from the group comprising chromium, gold, aluminum and silver.
In accordance with a preferred embodiment of the invention, the metal washer is made of a nickel-plated brass material and the lightly metal-filled adhesive is an epoxy comprising approximately 4% nickel.
In accordance with one embodiment of the invention, a method for forming an electrically conductive bond between a thin metallized film of insulating material and a metal ring comprises the steps of depositing on an annular surface of the metal ring a predetermined quantity of a lightly metal-filled adhesive; contacting the metallized portion of the film with the adhesive-coated annular surface of the ring; and applying a clamping force between the film and the metal ring while curing the adhesive.
In accordance with a further embodiment of the invention, a method for forming a plurality of electret transducers comprises the steps of forming a matrix array of photodefined ring-shaped metal washers on a carrier; screen printing a lightly metal-filled adhesive on the washers of the array; contacting the metallized surface of a sheet of electret material with the adhesive-coated washers of the matrix array; and applying a clamping force between the carrier and the electret sheet while curing the adhesive.