Reliability of Silver Sintering on DBC and DBA Substrates for Power Electronic Applications

In terms of reliability standard power electronic modules are at their limit regarding robustness aspects. As a high reliable alternative for assembly processes such as Sn-based soldering and aluminum wire bonding, the assembly with nano silver sintering technology on different substrate materials has been investigated in this work. The reliability of silver sintered top and bottom side interconnects has been determined by end-of-life active power cycling testing with 50 mm(exp 2) commercial diodes from Infineon sintered on DBC (direct bonded copper) and DBA (direct bonded aluminum) substrates with a sintered silver ribbon for the top side connect. The setup with DBC substrate showed a 17 times, the one with DBA substrates a 2.7 times higher statistical lifetime than the soldered and wire bonded reference. Delamination of the sintered layers and with a progressing aging in active temperature cycles also showed oxidized cracks in the Cu metallization of the substrate as new failure mechanisms of the DBC samples with double sided sinter technology. For DBA assemblies a formation of hillocks on the Al surface underneath the diode could be detected next to delamination of the sinter layer.