Constant-current corona charging of Teflon PFA

Experiments in which 25-μm-thick films of tetrafluoroethylene-per-fluoromethoxyethylene copolymer (Teflon PFA) were charged positively and negatively with a constant-current corona at different temperatures and subsequently discharged are discussed. The time behaviors of surface potential, total current, and conduction current during constant-current and constant-voltage charging are compared. The mean charge depth is found to increase with negative constant-current and constant-voltage charging at elevated temperatures. It is shown that, compared with constant-voltage charging, constant-current charging leads to a more prominent mean-charge-depth shift towards the back electrode and to an improved charge stability in Teflon PFA, since a large amount of the deeper bulk traps is being filled