Study of Charge Accumulation Properties of Polycristalline Alumina Used in Power Electronics Components

Because of its good physical properties (high ac dielectric strength and high thermal conductivity), the polycrystalline Al₂O₃ is used in IGBT power modules packaging as interface between the electronics device and the cooling system. The various constraints (electrical, thermal and mechanical) undergone by the Al₂O₃ substrates in service can lead to charge development in surface (surface discharges) or in the bulk of the material (space charge accumulation). These phenomena may ultimately lead to dielectric breakdown and thus to general failure of the power electronics component. In order to increase the knowledge of the physical mechanisms involved during the ageing, this work is focused on the charge accumulation study in alumina. The results presented in this paper have been obtained on 96 and 99.6% alumina. The charge trapping and de-trapping phenomena have been investigated by using characterization techniques such as space charge measurements and thermally stimulated current measurements.