Reliability Enhancement of Solder Joints Made by a Void Free Soldering Process

摘要

This paper examines microstructures and the reliability of solder joints made by a new void-free process and compares them to the conventional H_2 process. A new two step void-free process was recently developed for enhancing the reliability of large area, high power IGBT modules. First, Ar~+ were used to clean the surface of plated Ni films on a substrates followed by coating with 0.5 #mu#m Ag film, and second, 50 mass percent Pb-Sn solder sandwiched between the two substrates was heated at 503 K in vacuum for 5 min. and then cooled in a N_2 atmosphere. The fatigue life time of the solder joints formed by the new process was found to be 3 times longer than those made the conventional process. We also found the solder joints from the new process to have considerably smaller amounts of micro and interfacial voids in comparison by those made with the conventional method.