Effect of thermal cycles on the mechanical strength of quad flat pack leads/Sn-3.5Ag-X (X = Bi and Cu) solder joints

Yoshiharu Kariya, Yasunori Hirata, Masahisa Otsuka

Research output: Contribution to journalArticle

57 Citations (Scopus)


Quad Flat Pack (QFP) Leads/Sn-3.5Ag-X (X = Bi and Cu) joint was thermally cycled between 243 K and 403 K or 273 K and 373 K, and both metallographic examination and mechanical pull test were performed to evaluate thermal fatigue damage of the joint. The addition of bismuth drastically degrades the thermal fatigue resistance of Sn-3.5Ag solder. On the other hand, the pull strength of Sn-3.5Ag-Cu solder joints slightly decreased with increasing number of thermal cycles, though it still remains higher in comparison to that for conventional Sn-37Pb or bismuth containing solder joint. The behavior observed here reflects the isothermal fatigue properties of bulk solder, because thermal fatigue crack initiates at the surface of solder fillet and propagates within the fillet in an early stage of fatigue damage. Furthermore, the lead phases lying at the interface between lead-frame and bismuth containing solder joint may promote the crack propagation at the interface, resulting in the extremely low thermal fatigue resistance of the joint.

Original languageEnglish
Pages (from-to)1263-1269
Number of pages7
JournalJournal of Electronic Materials
Issue number11
Publication statusPublished - 1999 Nov


ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering
  • Materials Chemistry

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