Study of heat-resistance property in electret condenser microphone

This paper describes an improvement in the heat-resistance of electret condenser microphones (ECMs), an application of FEP as an electret material. The sensitivity of an ECM is determined primarily by electret surface charge. The difference of the surface charge decay for some materials, charging methods, the structure of electrode and annealing conditions were investigated. Thereafter thermally-stimulated current spectra were measured. The experimental results show some differences in the heat-resistance property among those specimens. The findings of this study could be applied not only to improve heat-resistance but also to estimate long-term sensitivity stability in ECMs. Some long term data about ECMs preserved for more than 20 years and the latest ones are also shown and discussed.