Effect of ILU dispensing types for different solder bump arrangements on CUF encapsulation process

Underfill encapsulation play an important role to improve the reliability of flip chip package, yet the conventional underfill (CUF) encapsulation process is subjected to several drawbacks such as extended filling time, incomplete filling and voids formation. Therefore, the focal point of this project is on the study of different CUF dispensing method for different types of ball grid array (BGA) orientations. The experimental works and numerical simulations were performed to predict the interaction of fluid on the structure and the results from both studies have reached a good agreement. This paper explores the effect of BGA orientations and dispensing types namely I, L and U on the behavior of underfill flow and the filling time. This study reveals the potential of both aspects in improving the efficiency of CUF encapsulation. The findings show that of all 9 different combinations of orientations and dispensing type, the fastest filling time is achieved by combining perimeter orientations with U-type flow. However, it suffers from racing effect that might lead to possible voids formation. The findings are then applied on real size 16×16 BGA and it was found that the flow front propagation changed from concave to convex shape for small size BGA and the filling time is also highly dependent on the BGA size and the solder ball count. Display Omitted This paper study the effect of I, L and U dispensing types on three common BGA orientations in terms of its flow attributes.3D multiphase setup of ILU dispensing encapsulation process based on scale up and real size BGA models for 6×6 and 16×16 BGA.Combination of U-type perimeter orientation has the fastest filling time and the slowest is given by I-type full orientation.Flow front propagation changed from concave to convex shape for small size BGA.The overall filling time and flow characteristics are highly dependent on the BGA size and the solder ball count.