Evaluation of Interfacial Fracture Toughness of a Bi-Material System Under Thermal Loading Conditions

In this paper, the interfacial fracture toughness of a bi-material (molding compound/silicon) specimen subjected to a series of thermal loads was evaluated using a high density laser moiré interferometry coupled with FEA technique. The moiré interferometry technique was used to monitor and measure the crack length during the test. A finite element technique was simultaneously used to determine the near crack tip displacement fields of the bi-material specimen. The interfacial fracture toughness and phase angle were computed by using these near tip displacement variables through the analytical energy release rate and phase angle expressions derived by authors. The results show that the interfacial fracture toughness of the bi-material specimen considered is strongly related to the phase angle in terms of the defined phase angle expression in this paper. The interfacial fracture toughness Gc and the phase angle ϕ of the tested bi-material specimen at the interface corresponding to the crack length a = 3.0mm under the temperature rise thermal load from room temperature (20° C) to 120° C are 13.64 J/m and −54.28° respectively, while the interfacial fracture toughness Gc and the phase angle ϕ of the tested bi-material specimen at the interface of the molding compound/silicon with the crack length a = 3.3mm under the temperature rise thermal load from room temperature (20° C) to 138° C are 20.02 J/m2 and −54.8° respectively.