Effect of adhesive surface chemistry and morphology on package cracking in tapeless lead-on-chip (LOC) packages

The increasingly severe demands of concurrently increasing die size, while reducing package size, have made the mechanical stability of novel tapeless lead-on-chip (LOC) packaging technologies a grave concern. The dominant issue is device failure, due to package cracking, caused by interfacial delamination between the adhesive-coated chip surface and the epoxy molding compound. To investigate the effect of adhesive surface morphology and chemistry on the epoxy molding compound, devices were fabricated with different types of adhesives. The samples were characterized with scanning acoustic tomography (SAT), X-ray photo emission spectroscopy (XPS), atomic force microscopy (AFM), attenuated total reflection (ATR), peel tests, and various package-level reliability tests. The results of the characterization and an explanation of the primary factors affecting interfacial adhesion are presented in this paper.