Simulation of underfill encapsulation of electrionic packaging using the lattice-boltzmann method
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Date
2018-04-01
Authors
Gan Zhong Li
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Abstract
Many finite volume method (FVM) based studies had been conducted by researchers to optimize and improve the underfill encapsulation process. However, there are limited studies conducted using lattice-Boltzmann method (LBM) for underfill encapsulation process. In this study, LBM will be used to simulate the encapsulation process of different solder joint shapes, different solder joint arrangements and injection methods. Some of the simulation results obtained using LBM will then be compared with the results obtained from experiment using particle image velocimetry (PIV) method. High conformity were obtained from both LBM and PIV results. In terms of the solder ball arrangements, perimeter arrangement was found to give the shortest filling time compared to middle empty and full arrangements. As for different injection methods, it was found that U-type injection gives a 67% reduction of filling time compared to I-type injection. However, a huge void is formed with U-type injection. Meanwhile, L-type injection shows a 45% reduction of filling time with no macro void formed. Furthermore, the effect of different solder joint shapes are also studied. Solder joint array with hourglass shape solder joints managed to reduce the underfill filling time by around 10% while yielding a smaller void. Cylindrical shape joints did not show any significant improvement on the filling time compared to that with truncated sphere shape joints. Pressurised underfill was found to reduce filling time by up to 99% compared to conventional underfill. The maximum pressure within the flow domain was found to be approximately 2.5 to 3 times higher than the inlet pressure during pressurised underfill due to pressure build-up.