Characterizations of Nanosilver Joints by Rapid Sintering at Low Temperature for Power Electronic Packaging

摘要

Nanosilver paste is a promising lead-free die-attach material suitable for power electronic packaging, particularly for high-temperature applications. Compared with traditional hot pressing to sinter nanosilver, rapid sintering by a pulse current is able to sinter nanosilver in less than a second. To investigate the nanosilver sintering process during rapid sintering, we characterize the temperature field of a nanosilver joint by using an infrared camera. The temperature field is analyzed as a function of current magnitude and current-on time. The relationship between the temperature field and the shear strength of joint is discussed to optimize the rapid sintering parameters. Results show that the joint's temperature–time curve varies with the current-on time. The shear strength can be up to 40 MPa, which is comparable to the robust hot-press sintered joint, when the peak temperature reaches above 400 $^{circ}hbox{C}$. The microstructure of these joints is porous with a particle diameter of $sim$400 nm, and this aids in releasing the internal stresses resulting in higher shear strength.