Popcorn cracking phenomenon in surface mounted packages is treatedby assuming an inherent edge crack at the die pad/EMC interface of aTQFP and subsequent interface delamination under thermal and/or vaporpressure loadings. Using the finite element methods and the methods ofinterface fracture mechanics, path independent energy release rate iscalculated and compared to the interface toughness which is assumed tobe a function of the phase angle. Results indicate that the edge crackpropagates toward the center leading to the delamination of the entiredie pad/EMC interface most notably for the vapor pressure loading, thenmixed loading when thermal and vapor pressure loadings are appliedsimultaneously. For the thermal loading, only the cooling process islikely to lead to the entire delamination where both the energy releaserate and interface toughness decrease with the crack length. For thevapor pressure loading, the energy release rate increases parabolicallywith the crack length but proportionally with the vapor pressure whilethe interface toughness remains almost constant. In the case of themixed loading, the energy release rate increases as in the vaporpressure loading, but the interface toughness decreases with the cracklength; Stress states near the crack tip were closer to mode II forthermal loading but to mode I for vapor pressure loading, and changedfrom mode II to mode I with the crack length for the mixed loading
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