Reliability enhancement of solder joints made by a void free soldering process

This paper examines microstructures and the reliability of solder joints ma de by a new void-free process and compares them to the conventional Hz proc ess. A new two step void-free process was recently developed fur enhancing the reliability of large area. high power IGBT modules. First, Arf(+) were used to clean the surface of plated Ni films on a substrates followed by co ating with 0.5 mum Ag film. and second. 50 mass% Pb-Sn solder sandwiched be tween 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 form ed by the new process was found to be 3 times longer than those made tile c onventional process. We also found the solder joints from the new process t o ha,e considerably smaller amounts of micro and interfacial voids in compa rison by those made with the conventional method.