Fabrication and Evaluation of Electret Condensor Microphone with Film Lamination and Silica Spacers

Abstract

The electret condenser microphones (FilmECMs) with film lamination and silica agglomerates were fabricated and the influence of the silica agglomerates on the characteristic of the FilmECM was investigated. The silica agglomerates was formed on PFA (perfluoroalkoxy) films by the application of colloidal silica using inkjet printing. The silica agglomerates for spacers formed the microgaps between the insulation films in the gap. Eventually, The silica agglomerates drastically enhanced the sensitivity of FilmECM while the resonance frequency was decreased. The size and the interval of the silica agglomerates influenced on the sensitivity and the resonance frequency. Such a influence can be explained by the density of the contact points of the films and silica agglomerates in the gap of FilmECM. Thereby the FilmECM which had the comparable sensitivity with commercial ECM was obtained. The resonant frequency was much higher than audible frequency (around 50 kHz). Hence, a wideband ECM could be obtained using FilmECM if the poor sealing of the gap and the diffraction of the sound is eliminated.

Keywords

• electret
• microphone
• silica agglomerate
• perfluoroalkoxy
• microgap