Method of making stationary electrodes for electrostatic transducers

A method of forming a stationary electrode for an electrostatic acoustic transduucer, said method comprising:

• providing a frame including a planar face portion, there being a plurality of recesses distributed over said face portion;
• applying to selected areas of said face portion a conductive layer, avoiding said recesses;
• bonding to said face portion a film of a high dielectric strength polymer;
• and
• locally distorting said film into each of said recesses so as to wrap the film around the margin of each said recess and to puncture the film centrally in each recess.

A method of forming a stationary electrode for an electrostatic acoustic transducer, said method comprising:

• providing a plastic frame base including a planar face, there being a plurality of generally conical recesses distributed over said face portion;
• coating selected areas of said face portion only with a conductive layer, avoiding said recesses;
• coating said face portion including the margins of said recesses with an adhesive;
• placing over said face portion of said frame a film of a high dielectric strength polymer;
• and
• applying, to the covered face of said frame, a two stage tool including a generally conical annular portion which locally distorts said film into contact with each recess and including also a central portion which pierces the film centrally in each recess.

A method of forming a stationary electrode for an electrostatic transducer, said method comprising:

• providing a frame including a planar face portion, there being a plurality of recesses distributed over said face portion;
• providing, over said face portion, a film of a high dielectric strength polymer;
• providing, intermediate said film and said face portion, a conductive layer which avoids said recesses;
• and
• locally distorting said film into each of said recesses so as to wrap the film around the margin of each recess and to puncture the film centrally in each recess.