Development of insulating system with low dielectric constant, high dielectric strength a-C:F film coated conductor prepared by plasma CVD as alternatives to SF_6

点击翻译按钮获取中文摘要

In order to reduce the usage of SFs insulation gas, which has high GWP (global warming potential), the present project proposed to use a-C:F film coated conductor prepared by RF plasma CVD method for insulation of electric power systems as alternatives of SF_6. This project was motivated because we had experienced very high deposition rates in RF plasma if per-fluorocarbon vapors were used. The main results are listed as follows.l. The deposition rate on Si and A1 substrates was > 100-200nm/min, which is a few tens times higher than those obtained by conventional CF_4 and C_2F_6 gases.2. The a-C:F film, which is composed of C-C and C-F bonds, was excellent insulation properties (dielectric constant 【approximately equal】 2) with high density and good thermal strength.3. The breakdown voltage V_s of N_2, Ar and He between the a-C:F film coated Al electrodes were 3 times larger than that between Al ones in low p(pressure)d(gap length) region. For pd<20 Torr/cm the V_s was rather higher than that of SFs.4. Reason of the enhancement of V_s was explained by the fact that secondary electron emission rate was reduced significantly by this film coating.5. Effect of decomposed species in the plasma on the a-C:F film properties was tried to examine, but in this project term it was not really cleared.