Package warpage evaluation for multi-layer molded PQFP

Finite element analyses (FEAs) together with molding experimentation with various mold chases were conducted to evaluate the mechanisms for package warpage and leadframe deflection of multi-layer PQFP (plastic quad flat pack) packages. The leadframe downset structure is identified as the major factor contributing to the package warpage. It is demonstrated that package warpage can be eliminated by properly tailoring the top and bottom mold cavity depths. The post mold cure, which raises the T_g of the molding compound, also helps reduce the package warpage. FEA calculations of package warpage at room temperature are in good agreement with experimental data. The leadframe deflection is also due primarily to its downset structure and may be reduced by preheating the leadframe before the encapsulation