Effect of combination between various polyimide coating materials and molding compounds on the reliability of integrated circuits (ICs)

Various polyimide coatings used on integrated circuits (ICs) were investigated for crack and molding compound interface separation caused by heat stress. As factors influencing the occurrence of cracking or delamination, the authors examined heat resistance, mechanical properties, moisture absorption, and adhesion strength to the silicon wafer or molding compound of four polyimide resins, both photosensitive and non-photosensitive. The crack occurrence and interface adhesion properties of conventional IC packaging containing polyimide-coated chips and an epoxy molding compound were also investigated. It was found that every polyimide studied had good adhesion strength to silicon wafers and to the molding compound and that the coating of IC chips with polyimides reduced package cracking considerably. However, there were some differences in properties among these polyimide types; the ester-type photosensitive polyimide resin had very poor mechanical properties and large internal stress