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Recently, the research and development activities for replacing Pb-containing solders with Pb-free solders have been intensified due to both competitive market pressures and environmental issues. As a result of these activities, a few promising candidate solder alloys have been identified, mainly, Sn-based alloys. A key issue affecting the integrity and reliability of solder joints is the interfacial reactions between a molten solder and surface finishes in the solder joint structures. In this paper, a fundamental study of the interfacial reactions between several Pb-free candidate solders and surface finishes commonly used in printed-circuit cards is reported. The Pb-free solders investigated include Sn-3.5Ag, Sn-3.8Ag-0.7Cu, and Sn-3.5Ag-3.0Bi. The surface finishes investigated include Cu, Au/Ni(P), Au/Pd/Ni(P), and Au/Ni (electroplated). The reaction kinetics of the dissolution of surface finishes and intermetallic compound growth have been measured as a function of reflow temperature and time. The
intermetallic compounds formed during reflow reactions have been identified by SEM with Energy Dispersive X-ray Spectroscopy.
By: S. K. Kang, D. Y. Shih, K. Fogel, P. Lauro, M. J. Yim, G. Advocate (IBM Microelectronics), M. Griffin (IBM Microelectronics), C. Goldsmith (IBM Microelectronics), D. W. Henderson (IBM Microelectronics), T. Gosselin (IBM Microelectronics), D. King (IBM Microelectronics), J. Konrad (IBM Microelectronics), A. Sarkhel (IBM Microelectronics), K. J. Puttlitz (IBM Corporate Staff)
Published in: IEEE Transactions on Electronics Packaging Manufacturing, volume 25, (no 3), pages 155-61 in 2002
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