Strain and Deformation of Flip Chip with Underfill at High Temperature: In-situ Characterization and Finite Element Analysis

Since the finite element analysis (FEA) has been widely used in material design and reliability assessment of electronic packaging, whether FEA captures the characteristics of the behaviors of a practical encapsulation is crucial in material optimization and reliability evaluation. In this study, the thermomechanical behavior of a flip-chip package with underfill between 25-200 degrees C has been investigated by an in-situ 2D digital image correlation (DIC) experiment and FEA, the strains and deformation behavior of a cross section of the encapsulation during thermal loading have been analyzed and comparison between experiment and simulation have been made. Results show that our FE model reproduced the general characteristics of the behaviors of solder bumps observed in the in-situ experiment at temperature below Tg, improvements of the model are needed to reproduce the behaviors of the encapsulation at temperature above Tg, and more carefully experimental study on the physical properties of the underfill and more representative model are needed to improve the FEA accuracy in underfill design and selection. This result is of great importance in improving the FEA accuracy in underfill design of flip-chip package and would trigger more experimental study on improving reliability assessment of electronic packaging by FEA.