Analytical Evaluation of Interfacial Crack Propagation in Vacuum-Based Picking-up Process

Chip picking-up with vacuum sorption is a critical technology in flip-chip packaging for separating chip intactly from donor adhesive tape. With increasing length/thickness ratio of chips, the incomplete separation affects the success rate of this process, even leads to the failure of chips. Here, we present a theoretical model with a bisection algorithm to calculate the effective size of tape that contributes to the crack growth, and introduce an energy release rate and pick-up force to evaluate the ability of thin chip picking-up. The finite-element method with a virtual crack-closure technique is constructed to validate the established process model. The effects of the type of pick-up head, length of chip, thickness, and material of tape on chip picking-up process are also revealed to improve the ability to propagate a crack in the adhesive layer. Furthermore, the crack propagation in the adhesive layer with increasing pick-up displacement is predicted to determine the critical value of the thin chip complete separation from compliant tape. These results suggest that the thinner and more compliant tape should be adopted in the chip picking-up process.