A 12*12 stiffness matrix was obtained for the gull-wing lead and solder joint in a plastic quad flat pack (PQFP) surface-mount assembly, using a three-dimensional finite element method. Deformation of the composite structure for each imposed unit displacement (or rotation) was then obtained. It is shown that the whole-field stress distributions in the gull-wing lead provide a better understanding of their mechanical characteristics. The metallurgical response of the solder joints was not measured in this study.>
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Lau et al. (1990) studied this question.