Vapor Pressure Assisted Interface Delamination and Failure of Plastic IC Packages: A Micromechanics Approach

Insights into delamination and popcorn cracking in plastic IC packages can be gained by studying the vapor pressure assisted void growth and coalescence at critical interfaces. The interface of interest for this paper is the die-pad/molding compound interface which is a site that is highly susceptible to delamination. A mechanism-based approach is adopted to simulate the initiation of debonding at the interface, and its subsequent growth. A layer of voided cells, governed by the extended Gurson constitutive law with vapor pressure incorporated as an internal variable, is embedded along the initially intact interface. Simulations are carried out under conditions similar to the specifications stated by the Moisture Sensitivity Test (MST). The extent of damage across the die-pad/molding compound interface is examined, and subsequent cracking is modeled. A full field analysis is carried out to investigate the moisture-induced damage in the entire molding compound as well.