Characterization and Reliability of Sintered Nanosilver Joints by a Rapid Current-Assisted Method for Power Electronics Packaging

A rapid current-assisted sintering technology (CAST) was used to bond electronic devices with nanosilver paste, which is a promising alternative compared with traditional solders. Instead of using an external heating source, the specimen and bonding material of nanosilver paste were heated by the alternating current whose current direction is not constant. Die-shear testing and hardness measurement were used to evaluate the bonding strength. The bonding strength and hardness increase with increasing the current and/or current-on time. CAST was able to sinter nanosilver in a very short time, i.e., less than 1 s. Scanning electron microscopy was used to characterize the microstructures of sintered silver joints. The reliability of the sintered joints by CAST was also evaluated by cyclic shearing tests. The joint by CAST could survive much longer time than that by the conventional hot pressing way. The CAST was recommended to bond two pieces of bare copper with nanosilver paste in power electronic applications without any protective gas atmosphere, e.g., bus bar connection.