Abstract
During the reflow process of In-3Ag solder ball grid array (BGA) packages with electroless nickel immersion gold (ENIG) and immersion silver (ImAg) surface finishes, continuous (Au0.9Ni0.1)In2 and scallop-shaped (Ag0.9Cu0.1)In2 intermetallic layers form at the interfaces of In-3Ag solder with Au/Ni/Cu and Ag/Cu pads, respectively. The (Au0.9Ni0.1)In2 layer breaks into clusters with increases in the aging time and temperature. Aging at 115 °C results in the formation of an additional continuous Ni10In27 layer on the Ni/Cu pads and the migration of (Au0.9Ni0.1)In2 intermetallic clusters into the solder matrix. In contrast, the (Ag0.9Cu0.1)In2 scallops grow into a continuous layer after aging treatment. Accompanying the interfacial reactions, AgIn2 precipitates in the interior of In-3Ag solder balls and coarsens during aging, causing the ball shear strengths of reflown ENIG (1.18 N) and ImAg (1.11 N)-surface-finished solder joints to decrease gradually. However, the migration of (Au0.9Ni0.1)In2 clusters into the solder matrix of ENIG-surface-finished In-3Ag packages leads to an increase in their ball shear strengths after aging at 115 °C over 300 h. Both the ENIG- and ImAg-surface-finished In-3Ag solder joints, after ball shear tests, have fractured across the solder balls with ductile characteristics.
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Acknowledgments
Sincere gratitude goes to National Taiwan University and the National Science Council, Taiwan, for sponsoring this research under Grants No. 96R0210 and No. NSC-96-2221-E002-150-MY3.
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Chuang, T.H., Jain, C.C. & Wang, S.S. Intermetallic Compounds Formed in In-3Ag Solder BGA Packages with ENIG and ImAg Surface Finishes. J. of Materi Eng and Perform 18, 1133–1139 (2009). https://doi.org/10.1007/s11665-008-9344-z
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DOI: https://doi.org/10.1007/s11665-008-9344-z