Electromigration in Pb-Free Solder Joints in Electronic Packaging

Chih Chen*, Shih Wei Liang, Yuan Wei Chang, Hsiang Yao Hsiao, Jung Kyu Han, King-Ning Tu

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

Abstract

Pb-free solders have been adopted to replace Pb-containing SnPb solders in the electronic packaging industry due to environmental concerns. Electromigration is one of the critical reliability issues for fine-pitch Pb-free solder bumps. This chapter reviews the unique features of electromigration in flip-chip solder bumps, emphasizing the effects of current crowding and Joule heating. It also describes the changes in the physical properties of the solder bumps during electromigration, such as bump-resistance changes, the redistribution of temperature, and the enhanced brittle mechanical behavior. In addition, the challenges for a better understanding of electromigration in Pb-free solder microbumps are discussed. As the dissolution rates of Ni and Cu in Pb-free solders are much higher than those in Pbcontaining solders, fast dissolution of Cu and Ni from the under-bump metallization into the solder bump under electromigration may endanger the solder bump reliability because of the anisotropic nature of Sn microstructure in Pb-free solder microbumps.

Original languageEnglish
Title of host publicationLead-free Solders
Subtitle of host publicationMaterials Reliability for Electronics
PublisherWiley-Blackwell
Pages375-399
Number of pages25
ISBN (Electronic)9780470971826
ISBN (Print)9781119966203
DOIs
StatePublished - 15 Mar 2012

Keywords

  • Critical reliability issue
  • Crowding, Joule heating
  • EM behavior, flip chip
  • EM changes
  • EM reliability
  • Flip chip joints
  • Solder bump
  • TSV, microbump

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