Voltage breakdown of fineline flexible printed wiring

This paper presents the results of a variety of voltage breakdown measurements performed on flexible printed circuits. Data were taken for a range of linewidths and spacings, for different qualities of etched features, for a range of temperature and humidity, and for circuits with and without a protective covercoat. The speed with which the flashover process develops was also investigated. Although the primary emphasis is on fineline circuits (linewidth and spacing around 10 mils), some data is presented for spacings up to 45 mils. This program was undertaken to determine the voltage breakdown characteristics of printed backplane circuits. In certain telephone applications, such circuits may be exposed to lightning-induced surges, voltage pulses of approximately 1 kV. The results presented here should be of interest to designers concerned with the overvoltage characteristics of flexible printed wiring, and particularly to those concerned with circuit protection requirements.