Flame resistance of plastics in the telecommunications industry

Five different burning tests were employed to characterize copper-clad laminates. An evaluation of the methods showed that the UL 94 vertical burning test and the needle-flame test were most difficult to pass. The glow-wire test appeared to be too insensitive to be of any practical importance. Diagrams depicting burning times versus ignition times were found to be very useful in the evaluation of the burning characteristics of laminates as well as components. Nine capacitors were investigated. It was found that smaller capacitors were more susceptible to fire than larger ones, but on the other hand they exhibited relatively short maximum burning times. The effect of ageing on flammability was evaluated for eight laminates designed for printed circuit boards. A detailed analysis of burning times showed that there was no ageing effect which was common to all materials, but on the other hand it was quite clear that ageing affected different laminates in different ways.