The changes in microstructure and microhardness of Sn-0.5Ag, Sn-1.0Ag, and Sn-0.7Cu Pb-free solders were investigated during high temperature aging at 150°C and 200 °C. As-solidified microstructures, revealed by cross-polarized light microscopy, consist of relatively large Sn grains in both Sn-Ag and Sn-Cu solders. Upon aging at 200 °C, 2h, Sn grains become smaller compared to the as-solidified ones. In addition, the microhardness of Sn-Ag solders increases after 200 °C, 2h aging, while that of Sn-Cu solder decreases. Detailed observation of the coarsening and redistribution of intermetallic particles in each system further explains this response of mechanical properties during high temperature aging. To investigate the effect of aging temperature, solders were aged at a lower temperature, 150 °C for up to 1000h and compared with the aged at 200 °C. The microstructure changes during the high temperature aging were characterized in terms of Sn grain size, crystal orientation, and IMC growth kinetics, and were further correlated with the changes of their mechanical properties.
By: Sun-Kyoung Seo; Sung K. Kang; Da-Yuan Shih; Hyuck Mo Lee
Published in: RC24579 in 2008
LIMITED DISTRIBUTION NOTICE:
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 reports@us.ibm.com .