Microscopic experimental investigation on shear failure of solder joints

K. J. Lau, Chak Yin Tang, P. C. Tse, C. L. Chow, S. P. Ng, Chi Pong Tsui, B. Rao

Research output: Journal article publicationJournal articleAcademic researchpeer-review

13 Citations (Scopus)

Abstract

A microscopic investigation has been made on the shearing of one leaded and two lead-free solders by using an in situ SEM method. A shear lap joint specimen is designed and fabricated to accommodate a thin layer of solder alloy between copper strips. A non-contact method that measures strains in a very narrow area in the solder was applied. A laser grid was also used on the copper strip for measuring the back-face strain. Simultaneously micrographs at various stages were also taken. Where in situ measurements and micrographs are recorded they can reveal the continual development of damage and fracture mechanisms consistent with observations generated by low-cycle fatigue loading. This means that the shear test can be used as an alternative test to fatigue loading tests. By comparison, two lead-free solder specimens showed much smaller elongation to failure than the leaded solder, although all specimens showed similar sequence of events leading to final failure, including the boundary layer fracture phenomenon. The back-face strain indicator for the formation of a macro crack is due to the shifting of high stress concentration area from the joint-edge region to outside the joint region as revealed by a damage-coupled finite element procedure. The procedure also provides an estimate on the critical back-face strain.
Original languageEnglish
Pages (from-to)617-634
Number of pages18
JournalInternational Journal of Fracture
Volume130
Issue number3
DOIs
Publication statusPublished - 1 Dec 2004

Keywords

  • Back-face strain
  • In situ measurements
  • Microstructures under shear
  • Solder joint

ASJC Scopus subject areas

  • Computational Mechanics
  • Modelling and Simulation
  • Mechanics of Materials

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