Initiation and propagation of interface delamination in plastic IC packages

Abstract

This paper describes a finite element computational model for the study of the initiation of interface decohesion and subsequent delamination propagation in plastic IC packages. The effects of thermal loading and vapor-induced pressure on IC package failure are investigated using an interface traction-separation law. This law, characterized by interface adhesion energy and interface adhesion strength, is augmented by a micro-mechanics model describing interface softening that is caused by vapor pressure-driven void growth. Parametric studies on delamination failure in IC packages were carried out to understand the role of three parameter groups: intrinsic interface parameters, thermal/vapor pressure loading, and the layered structure geometry. Results showed that small changes in the interface adhesion strength would exert a pronounced effect on the extrinsic delamination toughness. Under thermal loading alone, interface delamination would progress in a stable fashion. On the contrary, vapor pressure would cause delamination to progress in a highly unstable manner, resulting in catastrophic popcorn failure. Results also showed that the initiation sites of decohesion, and subsequent delamination, are influenced by the geometry of the die, the die-pad and the molding compound.