Evaluation of interfacial fracture toughness of a flip-chip package and a bimaterial system by a combined experimental and numerical method

In this paper, the interfacial fracture toughness of a flip-chip package su bjected to a constant concentrated line load and a bimaterial system under thermal loading condition were evaluated using a unique six-axis submicron tester, a thermal vacuum chamber and FEM modeling coupled with a high densi ty laser moire interferometry. The six-axis submicron tester was used to pr ovide a constant concentrated line load, whereas the moire interferometry t echnique was used to monitor the crack length during the test. In addition, a finite element technique was simultaneously used to determine the near c rack tip displacement fields of the specimens. The interfacial fracture tou ghness and phase angle were computed by using these near tip displacement v ariables through the analytical energy release rate and phase angle express ions derived by authors. The interfacial fracture toughness and the phase a ngle of the flip-chip package considered at the interface where the passiva ted silicon chip meets the underfill are 35 J/m(2) and -65 degrees, respect ively, while the interfacial fracture toughness and the phase angle of the tested bimaterial specimen at the interface of the molding compound/silicon with the crack length of 3.3 mm under the temperature rise thermal load fr om room temperature (20 degrees C) to 138 degrees C are 20.02 J/m(2) and -5 4.8 degrees, respectively. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.