An investigation of diffusion barrier characteristics of an electroless Co(W,P) layer to lead-free SnBi solder

Hung Chun Pan*, Tsung-Eong Hsien

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Diffusion barrier characteristics for eutectic SnBi solder/electroless Co(W,P) couples were investigated via liquid-state aging at 250°C and solid-state aging at 120°C. At the couple interface, CoSn 3 intermetallic compound (IMC) spallation was observed for the SnBi/amorphous Co(W,P) couple subjected to liquid-state aging. In contrast, no spallation of IMCs was observed for the SnBi/amorphous Co(W,P) couples subjected to solid-state aging. For the SnBi/polycrystalline Co(W,P) couple, a thick IMC layer was observed adjacent to a tungsten-enriched amorphous interfacial layer regardless of aging conditions. IMC formation in all samples indicated that Co(W,P) is essentially a sacrificial barrier to SnBi solder. However, amorphous Co(W,P) might also exhibit stuffed-type barrier behavior due to its relatively high phosphorus (P) content. Analytical results indicated that the P content in Co(W,P) is a crucial factor affecting the structural evolution at the SnBi/electroless Co(W,P) interface.

Original languageEnglish
Pages (from-to)330-339
Number of pages10
JournalJournal of Electronic Materials
Volume40
Issue number3
DOIs
StatePublished - 1 Mar 2011

Keywords

  • Diffusion barrier
  • electroless Co(W,P)
  • intermetallic compounds
  • lead-free SnBi solder

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