Thermal deformation measurement and stress analysis of PQFP assembly during power cycling

The three-dimensional displacements fields in a surface mounted plastic-quad-flat-pack (PQFP) asserrbly are measured during power cycl ing usi ng a combination of hd ographic interferorretry and high sensiti vity moire i nterferorretry. Detailed in-plane and out-of-plane whole-field displacerrent data of the top and bottom ends of the gull wing leads and their distri butions along the edge of PQFP are provi ded. The maximum deforrrations of the gull wing leads occur at the four corners of the PQFP. The experirrental results are used as displacerrent boundary condition in a linear-el asti c analysis of the therrral stresses of the corner lead and its solder joint using a 3-D finite element method (FEM). The highest stresses occur in the area connecti ng the I ead and the solder joint. The results should be useful in the evaluati on of therrral fatigue damage of surface mount assembl ies.