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|Behaviors of QFN Packages on a Substrate Strip|
|Keywords: Mold Compound, QFN, FEM|
|To lower the manufacturing cost of QFN (quad flat no-lead) packages, the number of QFN packages on a substrate must be increased. However, the increased number of packages or changes to the layout of QFN packages on the substrate can impact the mold compound flow behavior, which will, in turn, affect warpage, the generation of voids inside the mold compound, and the sweeping of bonding wires. In this paper, both simulation and experiment approaches were conducted to study the impact of the layout of QFN packages. For simulation, we will demonstrate and present an analysis methodology to account for the in-line processing parameters, especially the step of manufacturing and processing of mold compound material to form the QFN packages on a substrate strip. The in-line manufacturing parameters, such as pressure, temperature, shrinkage, and processing timing, were all considered and modeled. A commercial finite element tool was used. For experiment, we varied the number of QFN packages, the runner sizes, and the layout configurations, such as 1 UP or 2 UP distributions, on a substrate strip. The warpage along the long and short edges of the substrate strip, the wire sweeping and the voids generation of QFN packages at different locations on the substrate strip are studied. Various mold compound processing parameters were controlled and monitored to check their impact on the warpage, the voids, and the wire sweeping. In conclusion, the experiment vs. modeling data is correlated, and the study has proved to be very useful for the prediction of warpage, void generations, and wire sweeping.|
|Eric Ouyang, Deputy Director