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

Journal Article · Mon Nov 01 04:00:00 EST 1999 · Journal of Electronic Materials

DOI:https://doi.org/10.1007/s11664-999-0166-z· OSTI ID:20001752

Kariya, Yoshiharu; Hirata, Yasunori; Otsuka, Masahisa

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.

• Research Organization: Shibaura Inst. of Tech., Tokyo (JP)
• OSTI ID: 20001752
• Journal Information: Journal of Electronic Materials, Journal Name: Journal of Electronic Materials Journal Issue: 11 Vol. 28; ISSN JECMA5
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BISMUTH ALLOYS
COPPER ALLOYS
CRACK PROPAGATION
INTERFACES
METALLOGRAPHY
SILVER ALLOYS
SOLDERED JOINTS
THERMAL CYCLING
THERMAL FATIGUE
TIN ALLOYS