The warpage of a thin quad flat pack (TQFP), particularly the warpage as a result of instability of the structure, is analyzed. The package under investigation is a 144 pin TQPP measured 20 m× 20 mm with a thickness of 1.4 mm. The difference inmechanical properties (typically coefficient of thermal expansion and Young's modulus) of different materials used in the package, causes the package to warp when it is subjected to a temperature change in the assembly processes. As future packages willmove in the ultra thin direction by the demand of applications in PCMCIA devices, the warpage may cause open circuit during solder reflow. As a result, the future package design must take the warpage into consideration.The present work models the warpage of TQFP as a function of temperature using dimensional analysis and finite element simulation methods. Two different types of instability are revealed. The first instability leads to symmetric warpage. The second,usually occurs after the first instability, leads to non-symmetric saddle-shaped warpage (buckling). Using dimensional analysis method and finite element simulation, an empirical equation for critical buckling load (temperature increase) is determined innon-dimensional form as a function of structure's geometric and material parameters.
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