Simulation and Experimental Study of the Warpage of Fan-Out Wafer-Level Packaging: The Effect of the Manufacturing Process and Optimal Design

摘要

In this paper, warpage of fan-out wafer-level packaging (FOWLP) throughout the manufacturing process is investigated to minimize the warpage. FOWLP technology has the advantages of low cost, small form factor, efficient electrical performance, and increased input-output counts. The main benefit of fan-out packaging is that it utilizes the redistribution layer to interconnect the die and solder joints instead of using the substrate. However, warpage control is still a critical issue in the wafer molding process. Warpage is induced by the coefficient of thermal expansion mismatch between the die and the molding compound. Throughout the manufacturing process, the warpage of each step was recorded by utilizing the continuity simulation. The debonding process, grinding process, and annealing process at room temperature were analyzed via the simulation results and the experimental results. To simulate the wafer molding process in a continuous manner, the element birth and death technique was employed using finite-element modeling. This method can be used to reactive and deactivate elements when the material is added to or removed from the system. The results of the measurement and simulation were highly similar, with a difference of less than 10%. However, the results differed considerably when the wafer thickness was small. The results revealed a gap between the experimental testing and simulation modeling. Because of the wafer stiffness, the wafer is too thin to support the gravity force in the experimental testing process. Therefore, it is important to determine the calibration factor to decrease the gap between experimental testing and simulation modeling. In addition, it is crucial to determine the key factor controlling the warpage behavior and to minimize the warpage by evaluating the die arrangement and the die size in this paper. Overall, the simulation modeling represents a feasible approach for predicting the warpage during the manufacturing process.