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

Abstract

This paper examines microstructures and the reliability of solder joints made by a new void-free process and compares them to the conventional H₂ 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 \\micron Ag film, and second, 50 mass% Pb–Sn solder sandwiched between the two substrates was heated at 503 K in vacuum for 5 min. and then cooled in a N₂ 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.