Fracture Mechanics Parameters Governing Delamination of IC Packages Subjected to Non-Steady Thermal Stress

摘要

In the reflow soldering process, the IC package is heated over 270 deg C by the infrared rays. N a delamination interface, the stress field near a crack tip will always be in a mixed-mode state. It was assumed that the initial defects were generated among the corner part of die pad and epoxy molding compound. The 3-D finite element analysis was carried out to evaluate the stain energy release rate of delamination interface in IC packages subjected to non-steady thermal stress. The strain energy release rate of mixed mode was evaluated by the modified crack-closure integral and virtual crack extension method. The maximum difference of strain energy release rate between the modified crack-closure integral and virtual crack extension method was about 8 percent. Therefore, it is considered that the modified crack-closure integral is useful as a simple evaluation method of the strain energy release rate. The stress intensity factor K was examined from 3-D and 2-D virtual crack extension method. The virtual crack extension method can evaluate stress intensity factors of the interface crack under a mixed-mode loading accurately.