Popcorn failure and unstable void growth in plastic electronic packages

Abstract

In order to gain some insights into popcorn failure in plastic electronic packages, the phenomenon of unstable void growth of an incompressible neo-Hookean solid under non-symmetric loading is examined. A representative material cell containing a single microvoid is employed in the numerical analysis, where the effect of moisture can be easily incorporated; this cell is subjected to combined internal vapor pressure and remote thermal stress. Results have revealed that there is a maximum allowable mean stress, referred as the critical stress, which defines the onset of unstable void growth - the precursor of popcorn failure. Locus of the critical mean stress versus internal vapor pressure is obtained for typical values of initial porosity under uniaxial, equi-biaxial and equi-triaxial strainings. Results have clearly shown that the critical stress depreciates significantly as the internal vapor pressure is increased. This critical mean stress may therefore be perceived as a suitable criterion for initiation of popcorn failure in IC packages.