Abstract
Nano-sized, nonreacting, noncoarsening Al 2O 3 particles have been incorporated into eutectic Sn–Zn solder alloys to investigate the microstructure, hardness and shear strength on Au/Ni metallized Cu pads ball grid array substrate (BGA). In the plain Sn–Zn solder joint and solder joints containing Al 2O 3 nano-particles, a scallop-shaped AuZn 3 intermetallic compound layer was found at the interfaces. In the solder joints containing Al 2O 3 nano-particles, a fine acicular-shaped Zn-rich phase and Al 2O 3 nano-particles were found to be homogeneously distributed in the β-Sn matrix. The shear strengths and hardness of solder joints containing higher percentage of Al 2O 3 nano-particles exhibited consistently higher value than those of plain solder joint and solder joints containing lower percentage of Al 2O 3 nano-particles due to control the fine microstructure as well as homogeneous distribution of Al 2O 3 nano-particles acting as a second phase dispersion strengthening mechanism. The fracture surfaces of plain Sn–Zn solder joints exhibited a brittle fracture mode with smooth surfaces while Sn–Zn solder joints containing Al 2O 3 nano-particles showed a typical ductile failure with very rough dimpled surfaces.
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