Impulse withstand voltage between foil conductors on printed wiring board

The impulse flashover voltage (FOV) in air across a short gap between foil conductors on a printed wiring board was studied to obtain fundamental and remarkable characteristics that will be useful in the design of wiring on the board. Two types of conductor configuration on the test boards were studied. The studied gap distance (d) ranged from 20 mu m to 1200 mu m. The board thicknesses (t) and the foil thickness (s) were changed from 60 mu m to 800 mu m and from 6 mu m to 18 mu m, respectively. The following results were obtained in the two types of the conductor configuration. FOVs for the boards in the studied rang e are independent of the foil thickness. FOV is almost un-influenced by the board thickness in the gap distance range shorter than 30 mu m or 50 mu m. In the gap distance longer than this range, FOV characteristics strictly depend on the board thickness; FOV for t=60 mu m steeply increases with an increase in the gap distance, and FOV for t=800 mu m gradually increases with an increase in the gap distance. These experimental results were discussed basing upon the calculation results of electric field around the HV foil conductor edge.