Pressureless sintering performance enhancement of Ag pastes by surface modification of Ag nanoparticles with tert-dodecyl mercaptan.

A rising variety of power devices based on wide-bandgap (WBG) semiconductors are employed in products that can service at high temperatures consistently for extending the working life. Traditional tin–lead and lead-free solders are no longer suitable for power device packaging. Recently, nano-Ag pressureless sintering technology has attracted widespread attention for high-temperature application. When commercial Ag powders are applied, satisfactory sintering quality is often not obtained due to unstable product batches, unknown surface cladding, and poor sintering performance. In this work, Ag nanoparticles are surface modified with tert-dodecyl mercaptan (TDM) to prevent agglomeration at room temperature for improving pressureless sintering performance. We systematically introduced the modification process of Ag nanoparticles and Ag paste preparation and sintering process and compared the changes in the sintering performance of modified Ag nanoparticles with different TDM contents. With a minor amount of TDM, 1.5% of the total weight of Ag, the sintering performance of the Ag paste can be effectively improved and the porosity reduced. The highest average shear strength of the bonded joints based on modified Ag nanoparticles is up to 46.82 MPa with only 6.1% porosity by pressureless and low-temperature sinter at 250 °C for 10 min in ambient air, and the sintering morphology is better than the joints without nanoparticle modification. At the same time, increasing the sintering time does not have much effect on the bond strength, which indicated that 10 min already formed a high-quality joint. The analysis reveals that TDM molecules can be absorbed on the surface of Ag nanoparticles by headgroups to form a coating layer. The mechanism of TDM modification to enhance the sintering performance is also proposed, which provides theoretical support for the practical application of the pressureless Ag sintering technology. [ABSTRACT FROM AUTHOR]