Parametric analysis of steam driven delamination in electronics packages

Steam driven delamination between molding compound and substrate is analytically modeled. Pressure based delamination criterion and steam evaporation based criterion are examined as a function of crack size. Comparison with reported experimental trends revealed that steam based delamination criterion N/sub c/ is more descriptive of the stable and fast fracture regimes in steam driven delamination in electronics packages during solder reflow heat treatment. Following the establishment of the criterion, the driving force for delamination N/sub s/ is modeled. Delamination occurs when N/sub s/ equals or exceeds N/sub c/. Parametric investigations on the influence of molding compound thickness, defect size, elastic modulus, and critical strain energy released rate with and without humidity pre-conditioning were conducted using the analytical model. The study revealed that the critical delamination temperature is controlled by the defect size and the decrease in the critical strain energy released rate resulting from exposure to a humid environment. To minimize steam driven delamination, defect size and water degradation of critical strain energy released rate should be minimized.