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Analysis of the flow of encapsulant during underfill encapsulation of flip-chips

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2 Author(s)
Sejin Han ; Sibley Sch. of Mech. & Aerosp. Eng., Cornell Univ., Ithaca, NY, USA ; K. K. Wang

In this paper, the flow of encapsulant during the underfill encapsulation of flip-chips has been studied. Analytical as well as numerical methods have been developed to analyze the flow. For capillary-driven encapsulation (by dispensing), the capillary force at the melt-front has been calculated based on a model for the melt-front shape. A model has also been developed for the analysis of forced-injection encapsulation. The numerical analysis uses a finite-element method based on a generalized Hele-Shaw method for solving the flow field. Experiments have been performed to investigate the flow behavior using actual chips and encapsulants. Short-shot runs have been performed to observe the melt-front advancement at different flow times. In addition, measurements have been made of the material properties of the encapsulant, namely its viscosity, curing kinetics and surface-tension coefficient. The experimental and simulation results have been compared in terms of the flow-front shapes and times at different fill fractions. Such comparisons indicate that the model developed in this study is adequate to approximately simulate the flow during encapsulation of flip chips

Published in:

IEEE Transactions on Components, Packaging, and Manufacturing Technology: Part B  (Volume:20 ,  Issue: 4 )