Quantitative metallography of β-Sn dendrites in Sn-3.8Ag-0.7Cu ball grid array solder balls via electron backscatter diffraction and polarized light microscopy
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Electron backscatter diffraction and polarized light microscopy have been used to quantify the number of crystallographically independent β-Sn dendrites present in near-eutectic, ball grid array Sn-Ag-Cu (SAC) solder balls as a function of cooling rate (0.35–3.0°C/s). Based on these data, it is estimated that a single 900-µm-diameter solder ball contains on average eight individual β-Sn dendrites, independent of cooling rate. Specific orientation relationships were also found to be prevalent between neighboring β-Sn dendrites. These results confirm and expand upon recent research, and further emphasize the probable anisotropic nature of SAC solder joints.
Key WordsPb-free solder Sn-Ag-Cu dendrite orientation β-Sn electron backscatter diffraction polarized light microscopy twinning
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