Effect of Interfacial Hardness on Failure Modes of Liquid Phase Diffusion Bonded Sn/Sn with Bi Filler

Abstract

To examine the effect of Bi ller metal on bond strength of the Sn/Sn bonded joint interface, the interfacial microstructures and fractured surfaces of joint were observed by using SEM. After Bi ller metal had been deposited to the surface, the diffusion bonding was carried out in a vacuum chamber at bonding temperature of 413~463 K. The application of ller has decreased bonding temperature by 20 K or more which the bonded joints obtained bond strength comparable to the base metal. As the bonding temperature increases, the thickness of the Bi diffusion layer increases as well. Moreover, the interfacial hardness has decreased with a rise in bonding temperature, and the failure mode changes from brittle to ductile. The changes in the interfacial eutectic reaction layer between Sn and Bi accompanied by the expansion of the contact area between Sn metal surfaces are considered as the contributing factor to the increase in the bond strength.