A Multichip Phase-Leg IGBT Module Using Nanosilver Paste by Pressureless Sintering in Formic Acid Atmosphere

This paper proposed a new approach to attach power devices on nonmetallized direct bonding copper (DBC) substrates by pressureless sintering of nanosilver paste in poor-oxygen sintering atmosphere and formic acid reduction atmosphere. The average shear strength of die-attach joints could reach 25 MPa, and the copper oxidation issue of the nonmetallized DBC substrates was avoided. Based on the pressureless sintering approach of nanosilver paste, insulated-gate bipolar transistor (IGBT) modules were prototyped to verify the feasibility of this approach for mass production of power modules. The electrical and thermal characteristics of the IGBT modules bonded with sintered nanosilver were then compared with those of the commercialized ones using Pb92.5Sn5Ag2.5 solder alloy. This approach could extend the applications to bonding power devices on nonmetallized DBC substrates by nanosilver paste, and guide fabricating power modules in a mass productive, low facility costs, and high-yield way.