Evaluation of high temperature reliability of SiC die attached structure with sinter micron-size Ag particles paste on Ni-P/Pd/Au plated substrates

Abstract

Next generation power modules empowered by wide bandgap semiconductors like SiC and GaN can operate for a higher power than Si-based semiconductors at a high temperature over 250 °C. Ag sinter joining as a die attach material with a high melting point and good thermal conductive properties have obtained many attentions for the next generation power modules. This study investigated the bonding properties and the high temperature reliability of Ag sinter joining on ENEPIG (Electroless Ni plating (EN), Electroless palladium plating (EP) and immersion gold plating (IG)) metallized DBA substrates. The initial die shear strength for SiC (3x3 mm2) power modules was 33.9 MPa at 250°C sintering without assisted pressure in air conduction. The high temperature reliability of Ag sinter joint structure was evaluated at 250°C aging for 1000 h. The Ag-Au interface bonding mechanism, fracture behaviors and microstructure evolution of sinter Ag-Au joint were systematically analyzed. In addition, the connected Ag particles change to coarse with pore size increase during the aging process. The Ag-Au inter-diffusion layer also increased with the aging time but not clearly delamination occurrence. The die shear strength was slightly increased from the initial to 36.5 MPa after aging 1000 h, which meaning the Ag-Au joint possessed a good high temperature reliability. This study should add the understanding of the reliability issues of Ag sinter joining on Au finished substrate for its applications at high temperature.