Abstract

Pop-corn package cracking in thin quad flatpack packages (TQFP) during surface mount solder reflow can be minimized by adopting precautionary measures such as design changes, selection of new grades of epoxy mold compound (EMC) with lower affinity for moisture and lower expansivity, shipment and storage of epoxy mold compound under dry pack, as well as drying of plastic package prior to solder reflow. This paper investigates, using thermal analysis techniques, the cause of pop-corning phenomenon from pad-plastic interface in a particular batch of TQFPs despite the precautionary measures adopted. By comparing the difference in EMC properties between a control and reject batch of TQFP, this study suggest that ensuring optimum degree of polymerization or cure of the epoxy encapsulant can also assist in minimizing package delamination and pop-corn cracking.

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