Effect of Moisture on Electrical Properties of Polysiloxaneimide Thin Films

Abstract

This paper focuses on the effect of moisture on dielectric properties of polysdoxaneimide thin film. Relative humidity dependenences of dielectric constant, tanδ and DC conduction current were measured and AC loss mechanism was discussed.
Dielectric constant of polysiloxaneimide film increased linearly with relative humidity in the frequency range from 50Hz to 100kHz. For instance, dielectric constant at 100kHz shows an increase of 30‰ with the change of relative humidity from 0‰ to 100‰ . This change may be attributed to the absorbed moisture in the film. Tanδ was also affected by the humidity especially at low frequency where tanδ decreased with frequency. The result was discussed in terms of the combination of dipole relaxation loss and conduction loss due to mobile carriers. Tanδ in high frequency region where tanδ increased with frequency is considered to be caused by dielectric loss due to dipole relaxatlon. Considering that both DC conduction current and tanδ in the low frequency increased with relative humidity, it is concluded that the conduction loss due to mobile carriers is dominant in this region. This conclusion is also supported by the estimation of the moisture effect on frequency dependence of the conduction loss based on the relative humidity dependence of DC conduction current.