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

Authors: LaLonde, A.; Emelander, D.; Jeannette, J.; Larson, C.; Rietz, W.; Swenson, D.; Henderson, D.

Source: Journal of Electronic Materials, Volume 33, Number 12, December 2004 , pp. 1545-1549(5)

Publisher: Springer

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Abstract:

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.

Keywords: Pb-free solder; Sn-Ag-Cu; dendrite orientation; β-Sn; electron backscatter diffraction; polarized light microscopy; twinning

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s11664-004-0096-8

Affiliations: 1: Email: dswenson@mtu.edu

Publication date: 2004-12-01