Development of compliant coating system for transfer molding of sensitive silicon dice

Exposed-die type packaging requires molding process capability to provide mold flash free situation. Presently, the trend is in adopting transfer molding to encapsulate the silicon device with epoxy molding compound, which involves high transfer pressure. Hence, to avoid any epoxy bleed on the exposed die region a novel method of applying a soft coating on the mold surface is adopted. The coating is designed to act as a leakproof sealant to resist the high packing pressure during molding and can accommodate die height variations and minimizes the clamping stress passed to the silicon die, thus avoiding any chances of die cracking. This paper describes the use of Mooney-Rivlin hyperelastic model based finite element method (FEM) in the design of soft coating so as to minimize die stress under clamping and molding.