Adhesion Strength Measurement of Multilayer Structures with Vertical Crack by Four Point Bending Test

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Current microelectronic packages consist of multilayer systems. Adhesion strength is one of the most important factors to the reliability of these systems. Previous studies have used four point bending tests as a method for characterizing the energy release rate to obtain the adhesion strength of bilayer systems. An extension of this work is proposed in this study, where a four point bending test of multilayer structures with a vertical crack is used to measure the adhesion strength, assisted by the presence of a predefined area. The predefined area allows for a weak adhesion horizontal accurate pre-crack which permits crack propagation under loading as well as reducing scatter within the values of critical loads. A numerical analysis is conducted to compute the energy release rate from the critical loads using the concept of the J-integral. Two sets of multilayer specimens were fabricated and tested in the study: one for investigating crack front behavior relative to the compliance change in the load-displacement profile by using transparent substrates, and the other using the previous set as a guideline for testing metal substrates under certain environmental conditions. Experimental results along with visual evidence support the consistent behavior between crack front behavior and compliance change. This correlation can be used as a baseline for testing other electronic packages for interfacial failure.