Intermetallic compounds formed in In-3Ag solder BGA packages with ENIG and ImAg surface finishes
Journal
Journal of Materials Engineering and Performance
Journal Volume
18
Journal Issue
8
Pages
1133-1139
Date Issued
2009
Author(s)
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 (Au 0.9Ni 0.1)In 2 and scallop-shaped (Ag 0.9Cu 0.1)In 2 intermetallic layers form at the interfaces of In-3Ag solder with Au/Ni/Cu and Ag/Cu pads, respectively. The (Au 0.9Ni 0.1)In 2 layer breaks into clusters with increases in the aging time and temperature. Aging at 115 °C results in the formation of an additional continuous Ni 10In 27 layer on the Ni/Cu pads and the migration of (Au 0.9Ni 0.1)In 2 intermetallic clusters into the solder matrix. In contrast, the (Ag 0.9Cu 0.1)In 2 scallops grow into a continuous layer after aging treatment. Accompanying the interfacial reactions, AgIn 2 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 (Au 0.9Ni 0.1)In 2 clusters into the solder matrix of ENIG-surfacefinished 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. © ASM International.
Type
journal article