Non-Newtonian Fluid Analytical Filling Time Model With Contact Line Jump Underfill Encapsulation
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Date
2019-06-01
Authors
Ng, Fei Chong
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
The analytical filling time models to predict the capillary underfill flow in flip-chip are limited in amount; while the accuracy of existing models still has room of
improvement due to the conventional porous media assumption. Moreover, the non-Newtonian behavior of underfill fluid was scarcely modelled. Therefore, this
research presents a new filling time model based on novel bump-level analysis for the non-Newtonian power-law underfill fluid. Through the regional segregation approach, the
filling times were separately studied at each filling stages. The formulation of current
model had also incorporated both the spatial considerations of meniscus evolution and
contact line jump, that were improvised in formulation and in-line to the experimental
and numerical observations. Subsequently, three past underfill experiments were
referred to validate with the current developed filling time model on top of the current
scaled-up imitated flip-chip experiment and industrial package-on-package
benchmarking. Overall, the current model predicted the filling times of least
discrepancy among other existing analytical models for all validation cases. This had
affirmed the capability of current model in terms of accuracy and versatility. Moreover,
two new temporal analyses of individual filling time component and filling efficiency
are introduced to further investigate the impact of bump pitch. Later, the well-validated
analytical model is used to study the individual variation of underfill parameters on
the filling progression. The parameters that affect the underfill flow prominently are
gap height, contact angle and bump pitch. Lastly, a generalized filling time chart was
generated using the current model to ease the direct computation of filling time.