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This paper presents experimental and simulation studies of 3-D fluid/structure interaction (FSI) of wire sweep during the encapsulation process of plastic ball grid array (PBGA) packaging in different dies (single and stacked dies). A scaled-up package is fabricated to emulate the encapsulation of PBGA packaging and to study the effects of the FSI phenomenon in the PBGA package. A 3-D model of the mold and wires is created using GAMBIT, and the FSI is simulated using FLUENT and ABAQUS software integrated with mesh-based parallel code coupling interface for the real-time calculations. The effects of the stacked die and inlet pressure of the mold cavity on the melt flow behavior and wire sweep are mainly studied. A constant viscosity of the test fluid is assumed for the experiment. The volume-of-fluid technique is applied for melt-front tracking in the analysis. The numerical results of melt-front patterns and wire sweep are compared with the experimental results and good conformity is found. It is observed that the stacked die significantly influences the melt-front profile and the eventual wire sweep; as the number of dies in the stack increases, the wire sweep also increases.