Numerical study on effect of gap thickness, surface roughness, solder bump placements and temperature on underfill flow
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Date
2019-07
Authors
Mohamad Afiq Bin Mohamad Zulkefflee
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Abstract
In this research, the effects of the epoxy underfill flow such as distance gap, surface roughness, solder bump placements and temperature on the flip-chip packaging industry can be known. This research is done by simulation using ANSYS Fluent software with the dimension of substrate of 5cm x 5cm, to find behavior and also to determine the flow time, average velocity and strain rate when the epoxy underfill is filling the substrate in simulation. The surface roughness was modified by using different sandpaper of different grain sizes. Then, the samples were analyzed by using the Atomic Fourier Microscopy (AFM) machine. The model that been used in ANSYS Fluent is laminar model, due to nature of epoxy underfill will flow through a closed channel such as a pipe or between two flat plates, with the effect of energy equation, gravity, ambient temperature with certain velocity that has been calculated in Laplace –Young equation for capillary flow, for each distance gap. Before that, the meshing analysis has been done to replicate real life behavior of fluid, make sure that the flow behavior is controlled in ANSYS Fluent using water as medium, as the water behave in Newtonian fluid. The results found out that: 1) The biggest gap, 5mm thickness has the least flow time compare 3mm and 1mm, and has the highest velocity and strain rate for both experiment and simulation. 2) The surface roughness with very rough surface roughness has the least flow time compare to smooth and rough surface roughness, and has the most accumulated average velocity, while the smooth surface roughness has the most strain rate. 3) The uniform and middle placement solder bumps has the least flow time and has the most average velocity and the most strain rate. 4) The temperature of 80OC shows the critical temperature for the epoxy underfill, as it has the least flow time.