Double layered sintered silver die bonding technology with superior mechanical reliability

Abstract

In recent years, the sintering and bonding technology of silver (Ag) nanoparticles has been attracting attention in the bonding of SiC power devices. This is because Ag nanoparticles enable us to do sintering and bonding at relatively low temperatures. However, the vacancies encapsulated in the sintered Ag layer become a source of stress concentration of the cyclic thermal stress, which generates cracks leading to failure. In this paper, a new paste, hybrid paste (HYP) containing Ag and copper oxide (CuO) nanoparticles, is introduced firstly. Then, to suppress cracking, a double layered Ag/HYP sintering technique is proposed. The effectiveness of the technique towards long-term reliability of the die attach assemblies under thermal shock test (TST) is discussed based on cross sectional scanning electron microscope (SEM) images, finite element analysis (FEA), and material testing results.