Dielectric and thermal properties of Polyamide-imide (PAI) films

Polyamide-imide (PAI) materials appear as potential candidates for the encapsulation of wide band gap semiconductor power devices operating at high temperature (>200°C). However, electrical properties of PAIs are under-known compared to those of polyimides (Pis). We propose to evaluate the dielectric properties of two PAI materials with two different glass transition temperatures Tg. The aim is to observe the benefit of increasing T_g, from 280 up to 335°C for a novel kind of PAIs. So, the broadband dielectric relaxation spectroscopy has been used for measuring the dielectric parameters versus temperature. This paper highlights the role of the glass transition phenomenon in the dielectric properties evolution of PAIs at high temperature. It appears that the glass transition temperature has a strong influence in both the increase of the permittivity, the loss factor and the dc conductivity of several orders of magnitude, and in the characteristic temperature shift when these increases occur.