Abstract
AbstractPlastic packaging materials tend to absorb moisture from ambient environment and get swollen, this may raise hygro-stress in plastic electronic package and redistribute the internal stress. In this paper, we reviewed the dramatic deformation of a plastic package (Flip Chip Plastic Ball Grid Array-FCPBGA) due to moisture absorption first, then hygro-thermo-mechanical stress of the plastic package and its evolution during a period of three months were investigated with finite element method, user development was performed for this investigation. The finite element model was verified with hygro-thermal deformation of the FCPBGA measured with a 3-D moiré interferometry system. Following findings were obtained: A. Thermal stress field was changed a lot due to moisture absorption; B. Thermal stress of chip was released to some extent, but peal stress up to 62.2MPa occurred to the solder bump, thus the danger of Under Bump Metal (UBM) opening increased.
Published Version
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