The Microstructure of Sn in Near Eutectic Sn-Ag-Cu Alloy Solder Joints and Its Role in Thermomechanical Fatigue

Copyright © (2004) by MRS. Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distrubuted for profit. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee.

During the solidification of solder joints comprised of near eutectic Sn-Ag-Cu alloys, the Sn phase grows rapidly with a dendritic growth morphology, characterized by copious branching. Notwithstanding the complicated Sn growth topology, the Sn phase demonstrates single crystallographic orientations over large regions. Typical solder Ball Grid Array (BGA) joints, 900 µm in diameter, are comprised of 1 to perhaps 12 different Sn crystallographic domains (Sn grains). When such solder joints are submitted to cyclic thermomechanical strains, the solder joint fatigue process is characterized by the recrystallization of the Sn phase in the higher deformation regions with the production of a much smaller grain size. Grain boundary sliding and diffusion in these recrystallized regions then leads to extensive grain boundary damage and results in fatigue crack initiation and growth along the recrystallized Sn grain boundaries.

By: Donald W. Henderson, James J. Woods, Timothy A. Gosselin, Jay Bartelo, David E. King, T. M. Korhonen, M. A. Korhonen, L. P. Lehman, E. J. Cotts, Sung K. Kang, Paul A. Lauro, Da-Yuan Shih, Charles Goldsmith, Karl J. Puttlitz

Published in: Journal of Materials Research, volume 19, (no 6), pages 1608-12 in 2004


This Research Report is available. This report has been submitted for publication outside of IBM and will probably be copyrighted if accepted for publication. It has been issued as a Research Report for early dissemination of its contents. In view of the transfer of copyright to the outside publisher, its distribution outside of IBM prior to publication should be limited to peer communications and specific requests. After outside publication, requests should be filled only by reprints or legally obtained copies of the article (e.g., payment of royalties). I have read and understand this notice and am a member of the scientific community outside or inside of IBM seeking a single copy only.


Questions about this service can be mailed to .