Electret condenser microphones (ECM) with perfluoroalkoxy (PFA) film lamination (FilmECMs) were fabricated and the microgap layers were formed between laminated films in the gap of FilmECM to enhance the electric field in the gap and the resonance frequency. The average sensitivity from 1 to 10 kHz and the resonance frequency of a single degree of freedom system were measured for fabricated FilmECMs. The average sensitivity of the FilmECM was increased with the increase in the number of film lamination in the gap while the resonance frequency was decreased. Moreover, the average sensitivity of FilmECM improved further by the application of boron nitride (BN) agglomerates on films in the gap. As a results, one of the fabricated FilmECMs demonstrated −54.5 dB (0 dB = 1 V/Pa) for the average sensitivity. Furthermore the significant degradation of the sensitivity was not observed up to 50 kHz for any samples though the sensitivity rising, which might be caused by the diffraction from the edge of the test fixture, was observed at around 20 kHz. Hence, FilmECM should have a great potential for a wideband mircrophone or an ultrasonic sensor.
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