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Thermal deformations that result from mismatches of coefficients of thermal expansion (CTE) in Solder Ball Connect (SBC) assemblies were investigated. The CTE mismatches of the materials and the components in the package have both macro and micro effects on the strain distributions in the SBC interconnections. The geometry of the SBC joint also has a strong influence on the solder strains in the SBC package. An experimental technique with high sensitivity and resolution, moiré interferometry, was used to obtain whole-field displacements. Thermal strains in SBC packages, especially the strain concentrations in the SBC joints, were then determined from the displacement fields. The experimental results played an important role in failure analysis, structural design optimization, and finite element model verification in the IBM SBC program. The results also show that moiré interferometry is a very powerful and effective tool in experimental studies of electronic packaging.
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