Published online by Cambridge University Press: 26 October 2005
This paper examines the role of interfaces in the polymericinsulating films under the scope of their dielectric strength. PET(Polyethylene terephthalate) films of different thickness are puttogether forming a planar sample of a typical thickness of $200~\mu$ m and subjected to AC ramp voltage, until the dielectricbreakdown. The role of interface as a potential barrier forelectrons was examined as well as the influence of interfacenumber for a standard thickness. Experiments were also executedfor investigating the role of the position of the first, thesecond and the last interface in the sample. All the experimentswere executed with the same voltage rising rate, the breakdown ACvoltage V b was measured and the dielectric strength F b was calculated. It was shown that interfaces act as deep trappingcenters for electrons giving rise to the sample dielectricstrength for sort time experiments. Moreover the thinner the firstfilm, the higher the dielectric strength for the sample. It wasalso found that the position of the second interface does not playan important role in the process.