Analysis of interfacial delamination in IC packaging: Use stress or fracture mechanics?

After encapsulation, thermo-mechanical deformation builds up within the electronic packages due to temperature coefficient of expansion mismatch between the respective materials within the package as it cools to room temperature. The maximum Von Mises stress or principle stress criterion based on stress analysis and maximum energy release rate criterion based on fracture mechanics are two of the most popular criteria for failure prediction. However, it is well known that the stress calculation based on finite element analysis (FEA) is mesh dependent and stress fields around bonded corners showed singular behaviors. The objective of this work is to investigate a few interface delamination cases in IC packaging using stress analysis and fracture mechanics respectively. The approach is to quantify the stress, energy release rate and corresponding phase angle at room temperature and lead-free solder reflow temperature. A suitable criterion for the estimation of interface delamination will be proposed based on FEA and the results based on simulation will be compared with experiment study.