Silver sintering die attach process for IGBT power module production

Abstract

Silver sinter technology is a very promising lead free interconnection method with high operating temperature, high thermal and electrical conductivity. In high power semiconductor modules the die attach material connects the die to the insulating substrate. These die attach materials need to be optimized to provide low electrical resistance and high thermal conductivity. Various silver sinter materials, such as micro or nano sized Ag paste, pressure-less or pressure assisted Ag paste or Ag film and the necessary sinter equipment are being developed to accelerate the industrialization of silver sinter technology. In this paper, we report the results of a silver sinter film based die attach process evaluation, suitable for IGBT power module production. The proposed process has very good controllability and has the potential for large scale production. The Ag sinter joint porosity and bondline were analyzed by cross section SEM. Thermal shock and cumulative structure function from T3ster measurement both showed superior performance than conventional solder die attach. Thermal structure function analysis showed that Ag sinter die attach layer is a high thermal conductivity region in a IGBT power module system, unlike solder die attach layer which is traditionally accepted as a low thermal conductivity region in a power module system.