FSI Simulation of Wire Sweep PBGA Encapsulation Process Considering Rheology Effect

This paper presents a 3-D fluid-structure interaction (FSI) technique using mesh-based parallel code coupling interface (MpCCI) for the visualization of wire sweep during encapsulation of the plastic ball grid array packaging, considering the polymer rheology effect. In the molding process, the encapsulant flow behavior is modeled by the Castro-Macosko viscosity model including the curing effect and volume of fluid technique for melt-front tracking. The viscosity model is written in C language and compiled using user-defined functions into the FLUENT analysis. Wire sweep behavior is analyzed by ABAQUS and integrated with FLUENT software by MpCCI as an interface of fluid and solid interaction. Three types of epoxy molding compound (EMC), namely, Cases 1-3, were utilized for the study of fluid flow inside the mold cavity. The melt-front profiles and viscosity versus shear rate for all cases are analyzed and presented. The degree of conversion of the molding compound during the encapsulation process at the top view of the package for different EMCs is also studied. Pressure distribution around the wire region and wire sweep profiles within the mold are presented. The numerical results of the melt-front behavior and wire sweep are compared with the previous experimental results and found in good conformity. In the present case, Case 2 with a lower viscosity shows lower air trap, lower pressure distributions, and lower wire deformation. Therefore, the strength of MpCCI in handling FSI problems is proven to be excellent. The work presented in this paper is expected to be a reference and guide for the microelectronics industry.

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