Evaluation of Thermal Strains in BGA Packages Using Digital Speckle Correlation Technique and FEA

A digital speckle correlation (DSC) technique was applied to second level interconnects of flip chip and wire bonded packages in order to measure in-situ deformations induced by temperature cycling. The measurements allowed for the total normal and shear strains to be evaluated at various temperatures for different package types having lead-free and Sn-Pb metallurgies. It was observed that among the flip chip packages the shear strains varied with temperature and were greater for the Sn-Pb package than for the lead-free package. As expected, the BGA package with a metal ring stiffener exhibited the lowest strains. The results from the FEA model of the wire bonded PBGA correlated well with the experimental data obtained by DSC.