FEM based enhancement of system lifetime by improvement of the die top connection of power electronic semiconductors

Abstract:
In 2014 Danfoss Silicon Power introduced the Danfoss Bond Buffer(r) Technology, which is now made commercially available to third parties through the so called Die Top System - DTS(TM), produced and provided by Heraeus Deutschland. In comparison to conventional packages, based on die-attach soldering and Al-wire bond technology, modules with a Die Top System - DTSTM composition actually show significantly higher lifetime. In addition you can find a new failure mechanism in the aluminum based top metallization of the die. Due to thermo mechanical stress, a degradation occurs in the aluminum which can be seen by cracks in the material. For packages using an aluminum based NiAu top metallized semiconductor a virtual FEM DoE (virtual power cycle) was carried out to identify the most potential adjustable design parameters. The source of most influence, the sinter layer porosity, was investigated focussing on application processes and reliability (power cycling test). On the one hand, in the course of initial power cycling tests, the extremely high reliability of DTS (Exp TM) based systems was confirmed, but on the other hand, a significant effect on the package reliability through an increase to the layer porosity was not observed. Nevertheless, a change within the failure mechanism was detected, and in addition an influence on manufacturing processes was observed. For a middle- and long-term perspective further investigations will take place to foster the understanding of failure mechanisms, simulation and reliability for innovative and high reliable packaging technologies.