Role of design factors for improving moisture performance of plastic packages

The authors investigated both the chemical and physical nature of mold compound adhesion to the leadframe with the 32 lead SOP and 32 lead TSOP as the primary vehicles. The choice of molding compound is shown to be, a significant factor in enhancing the performance of plastic packages with respect to package cracking. The molding compound primarily determines the chemical adhesion between the leadframe and the molding compound, which prevents the initiation of delamination which eventually can result in package cracking. In terms of improving the mechanical adhesion between the molding compound and the leadframe, round and square shaped dimples if properly spaced seem to provide adequate mechanical adhesion to prevent delamination as well as package cracking in normal surface mount use conditions