A Mass Spectrometric Study of Dielectric Breakdown

The volatile degradation materials from a polyimide insulation on magnet wire was studied under thermal stress alone and in the presence of both thermal and electrical stress. Both types of experiments were carried out under vacuum with the apparatus connected directly to a mass spectrometer. The combination of thermal and electrical stress led to a different mass spectrometric pattern than that for thermal stress alone. The most marked difference was the sharp increase in water peaks. The possible interpretations are discussed.