Study on the Impacts of Clamping Process Defects to the Reliability of Press-Pack IGBTs

As press-pack IGBTs (PP IGBTs) have been introduced to improve reliability and lifetime of IGBT module via avoiding the susceptibility of wire-bonded IGBTs due to thermo-mechanical stress, the corresponding reliability of PP IGBTs has attracted the attention by both manufacturers and end users. In this paper, during the product validation phase, three cases of PP IGBTs with the failure modes relevant closely to the clamping process defects have been collected to understand the impacts to the reliability and lifetime. Base on the cases study, deformation and burnout of the metallization / dielectric layer, cracking of the active layer at the edge, mechanical damage of the dielectric / active layer, burnout on the dielectric / active layer were identified via failure analysis step by step, which can be ascribed to improper applied clamping force, non-coplanar clamping force, faulty protrusion of the clamping heads, respectively. Therefore, regarding these negative impacts of clamping process defects, corresponding improvement and optimization of clamping process should be scheduled during the process development phase, which is crucial to the product launching and designed lifetime.