S. Nishimotoab, S.A. Moeinib, T. Ohashia, Y. Nagatomoa, and P. McCluskeyb
aCentral Research Institute, Mitsubishi Materials Corporation, 1-600, Kitabukuro-cho, Omiya-Ku, Saitama 330-8508, Japan
bCenter for Advan.ced Life Cycle Engineering (CALCE), Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, United States
Currently, Ag die-attach techniques, using nano-silver particles, are of high interest for manufacturing of wideband-gap(WBG) power module due to their high-temperature operation capability. However, the high cost of silver and complicated processing requirements are the main driving force in the search for simpler and more cost-effective attached technologies. In this study, a new die-attach technique based on silver die-attach, without conventional Ag-paste, for high-temperature applications is developed. Glass containing Ag paste was pre-sintered on the OBA substrates, and later on, semiconductor dies were simply placed on this pre-sintered Ag layer and attached under heat and pressure. The samples were tested under shear and thermal cycling loadings ( -45 oC/250 oC) to evaluate the quality and reliability. Destructive and non-destructive analysis methods, such as Scanning Acoustic Tomography and cross-section observation, were used to identify fracture modes. The samples demonstrated sufficient shear strength and high thermal reliability. Furthermore, the effects of Ag recrystallization, grain growth and rearrangement of the voids are considered to be the main fracture factor of conventional Ag die-attach joints based on sample's cross-sections.