Dielectric Strength and Failure Mechanism of Power Module Packaging Insulation at Ultra-High Temperature

Stricter requirements have been proposed for the safety and reliability of the power module packaging insulation as the development of power devices towards miniaturization., higher frequency., and higher power density. The dielectric insulating performance at high temperatures is one of the key measures for the reliability of packaging materials. This paper investigated the dielectric strength of the two crucial packaging insulating materials.,i.e.., encapsulation elastomer and alumina substrate., from normal to ultra-high temperatures. The thermodynamic properties of the prepared double-component vulcanizable silicone elastomer (RTV-2) were studied for the verification of its thermal stability. Then DC breakdown strength and broadband dielectric spectrum were detected for both elastomer and ceramic in a wide temperature range from 293.15 K to at least 453.15 K. The broadband dielectric spectrum showed that the dielectric loss of the elastomer
^was
very small., mainly composed of the interfacial polarization and the conductance loss. Conductance loss was also dominant in ceramics. The DC breakdown results showed that the breakdown strength of both two materials maintained basically stable at different temperatures. The critical DC breakdown strength of the silicone elastomer was about 60 kV/mm., and that of the alumina ceramic was about 80 kV/mm.