Determination of interface fracture parameters by shear testing using different theoretical approaches
Simple adhesion tests like the pull-out test or the button shear tests have been used in industry for decades. They offer a great potential for comparison of different molding compounds, encapsulants, or adhesives on different types of sub-strates with or without surface treatment. However, for theoretical prediction purposes, interface fracture mechanics parameters are needed. Quantitative evaluations of the test applied to molding compound (MC)-button on Cu-leadframe by different fracture- and damage mechanical approaches are the subjects of the paper. Defect tolerant methodologies like the "virtual crack closure technique" (VCCT), which consider the interface initially delaminated, are compared to the damage methodology "cohesive zone modelling (CZM)", which needs no initial crack and can track the delamination progress. Calculated fracture parameters, in particular the energy release rates and mode mixity are compared. Effects on these parameters are discussed for d ifferent button shapes. In-situ tracking of delamination progress for a cubic button is shown using the optical correlation technique microDAC.