B. Han, E. Stellrecht, and M. Pecht
CALCE Electronic Products and Systems Center
University of Maryland
College Park, MD 20742
The hygroscopic swelling of five commercially available mold compounds is analyzed and the coefficient of hygroscopic swelling is determined for each mold compound using moire interferometry. The results indicate that the deformation caused by hygroscopic swelling can be as significant as the deformation caused by a thermal expansion of 90oC. The comparison indicates that hygroscopic strains must be considered for accurate reliability assessment when plastic encapsulated microcircuits (PEMs) are subjected to environments where the relative humidity fluctuates.
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