Die Fracture Probability Prediction and Design Guidelines for Laminate-Based Over-Molded Packages

Abstract

Transferring molding process is widely used in the plastic IC packaging. Die cracking failures due to transfer molding process may occur. In this paper, an investigation on the die fracture and its failure probability is conducted. The approaches and results of die strength characterization, FE modeling on the laminate-based packages, and simulation-based prediction of the die fracture probability rate are presented. Weibull statistics model was used to describe the probability distribution. Model parameters were obtained by fitting to the test results. 3D parametric FE models were established to conduct numerical simulations to predict the stress field and die fracture probability caused during the tranfer molding process. For a BGA package, the influence of the solder mask opening under the die on the fracture probability was investigated. For the capped MEMS, high stress levels are induced in the cap and the MEMS die during the molding process. The cavity size, cap thickness, the molding pressure, and the wafer surface finishing process have significant influcences on the fracture failure probability. It shows that improvement of die fracture probability can be achieved by changing the designs of the die surface finishing process to meet the reliability requirements.