Determination of fracture toughness of underfill/chip interface with digital image speckle correlation technique

Layered packages are prone to multi-mode damage and failure when they are subjected to complicated and coupled environmental loading. As a result, fracture toughness is usually used as a fracture criterion to evaluate the reliability of the polymer/inorganic interface. In this study, an in-situ/real-time micro-digital image speckle correlation (μ-DiSC) system was established and employed to determine the fracture toughness of the underfill/chip interface involved in flip chip assembly. The tests were carried out over a wide range of temperatures and at various loading angles. In order to verify the findings of the μ-DiSC technique, an interface fracture mechanics based FEM is implemented into ANSYS to calculate the values of CTOD of the underfill/chip joint under different loading configurations. The results obtained from the simulation are found to be in good agreement with those measured by the μ-DiSC system, indicating that the system can be used as an accurate and effective experimental tool for electronic packages. The fractographs with respect to different temperatures and loading angles are further discussed.