Underfill Delamination of Flip Chip on Low-Cost Board
Xu Bulu, Zhang Qun, Cai Xia, Huang Weidong Xie Xiaoming, Cheng Zhaonian
(Daimler Chrysler SIM Lab, Shanghai Institute of Microsystem and Informtion Tech, Chinese Academy of Science, Shanghai 200050)

Abstract: Following thermal cycling loading standard, MIL-STD-883C, the life of two types of test chips (type B and D) are determined with electrical measure. And the delamination propagation behavior at the interface between chip and underfill is investigated and the crack propagation rates are measured by using C-SAM inspection for those samples. The material properties of SnPb eutectic solder used in simulation are modeled by the Anand viscoplastic material model. Meanwhile for underfill U8437-3, not only the Young's modulus but also the coefficients of thermal expansion are temperature-dependent. Moreover, in the related finite element simulations, the strain energy release rates near crack tip under different conditions are calculated by the J-integral in a small rectangular path near the crack tip. Then, the Paris helf-empirical equation, which can be used as a reliability design base of flip chip package, is determined through the crack propagation rates measured and the energy release rates simulated. 
Keywods: flip-chip, underfill, interfacial delamination and crack propagation, finite element simulation, fracture mechanics.