Thermomechanical reliability of low-temperature sintered silver die-attachment

Abstract

In this paper, we present a thermomechanical reliability study on the low-temperature sintered silver die-attachment for packaging semiconductor devices. The die-attachment was formed by sintering nanoscale silver paste at 300degC for 40 minutes to develop full adhesion strength between silver-coated direct-bond-copper (DBC) or copper substrates and silver-metallized SiC devices. A strong bond was formed between the die and substrate with the die-shear strength reaching 40 MPa. Using a 50% drop in the die-shear strength as the failure criterion, accelerated temperature-cycling test between 50degC and 250degC showed that the sintered silver die-attachment on DBC substrates can survive beyond 4000 cycles, indicating high reliability at the temperature cycling range. Scanning electron microscopy (SEM) observations suggest that the die-attachment failure is due to ductile fracture in the silver attachment as micro-cavities were nucleated at grain boundaries during temperature cycling. Results obtained in this study demonstrate that the low-temperature sintered silver is a promising lead-free and reliable die-attach solution for semiconductor devices. Additionally, the silver die-attachment is a potential solution for high-temperature electronics packaging because its high-temperature reliability exhibited during the temperature cycling