REGISTER HERE: Seminar on Fundamentals of Electromigration in SAC305 and Sn-Bi Solder Joints
Tin-based low-temperature solder alloys were chosen as the topic of this presentation because these alloys are convenient for understanding the physical metallurgy of binary alloys. The presentation will describe the fundamental nature of the electromigration behaviors of SAC305 and eutectic Sn-Bi alloys. In both these alloys, electromigration is dominated by one element preferentially migrating in the direction of electron flow. In the case of SAC305 solder, which contains 0.5 wt. % Cu, copper atoms migrate to form the Cu6Sn5 intermetallic phase at the anode. In the case of eutectic Sn-Bi solder, bismuth atoms migrate to the anode forming a layer of a Bi-rich phase. In both cases, the phases accumulating at the anode have higher electrical resistivities than the original solder compositions and occupy large volume factions of the solder joints. This combination of higher resistivity and a larger volume fraction of the phase forming at the anode raises the electrical resistance of the joint as a function of time during high current stressing. The presentation will discuss and compare the fundamentals of the metallurgical and electromigration behavior of the two solder alloys in the early stage of electromigration before enough voids have formed at the cathode interface to coalesce and start dominating the joint resistance.
Prabjit Singh is a Senior Technical Staff Member at IBM Poughkeepsie, with 46 years of experience in the metallurgical engineering aspects of mainframe computer power, packaging, cooling, and reliability. For many years he taught a graduate course on Power Electronics at The State University of New York at New Paltz. He authored the ASHRAE book on data center gaseous and particulate contamination. He has 89 issued patents and is an IBM Master Inventor. He is a Distinguished Alumnus of the Indian Institute of Technology and an iNEMI Fellow. PJ received the B.Tech. degree in Metallurgical Engineering from the Indian Institute of Technology in 1969 followed by a M.S. and a Ph.D. in Metallurgy from the Stevens Institute of Technology, Hoboken, New Jersey, in 1973 and 1977. Later he received a M.S. in Micro-Electronic Manufacturing from the Rensselaer Polytechnic Institute, Troy, New York, and a M.S. in Electrical Engineering from Walden University, Minneapolis, Minnesota.