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Interfacial reactions of BGA Sn-3.5%Ag-0.5%Cu and Sn-3.5%Ag solders during high-temperature aging with Ni/Au metallization

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

Abstract

The joint strength and the microstructure of Sn-3.5Ag and Sn-3.5Ag-0.5Cu (wt.%) solders on Cu/Ni/Au ball-grid-array (BGA) pad metallization were investigated after high-temperature solid-state aging at 190°C (around 0.86Tm of solder alloys). Sn-Ag solder gave better results in terms of shear strength on high-temperature aging than Sn-Ag-Cu. Very high consumption of Ni was observed in the case of Sn-Ag-Cu solder alloys. After 16 days of aging at the afore mentioned temperature, 5 μm Ni layer was fully consumed from the substrate pad and a thick layer of Cu-Sn intermetallic compounds (IMCs) was found at the base of the interfacial IMCs. Much less consumption of Ni substrate was observed for Sn-3.5Ag solder during high-temperature aging for longer time. The mean thickness of the intermetallics at the interface was higher for Sn-Ag-Cu solder alloy. For both cases Ni diffused through the interfacial MCs and formed quaternary compounds for Sn-Ag-Cu system and ternary compounds for Sn-Ag system within the bulk solder. It appeared that Sn-Ag-Cu solder alloy was more vulnerable in high-temperature solid-state aging. © 2004 Elsevier B.V. All rights reserved.
Original languageEnglish
Pages (from-to)184-189
JournalMaterials Science and Engineering B: Solid-State Materials for Advanced Technology
Volume113
Issue number3
DOIs
Publication statusPublished - 15 Nov 2004

Research Keywords

  • Au/Ni/Cu substrate
  • Intermetallic compounds
  • Ni consumption
  • Sn-based lead-free solder

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