INVESTIGATION OF INTERFACIAL FRACTURE-BEHAVIOR OF A FLIP-CHIP PACKAGEUNDER A CONSTANT CONCENTRATED LOAD

In this paper, the interfacial fracture behavior of a flip-chip packag e subjected to a constant concentrated line load was investigated usin g a unique six-axis submicron tester coupled with a high density laser moire interferometry. The real-scale three-point bending flip-chip sp ecimen, capable of measuring the crack growth rate (along the interfac e) and the interfacial fracture toughness was developed, The results s how that the crack propagation along the interface of the passivated s ilicon chip/underfill under a constant concentrated load can be catego rized into three stages occurring in the order mentioned with obvious transition points between them: 1) stable crack propagation stage; 2) unstable crack propagation stage; 3) quasicrack arrest stage, The moir e interferometry technique was used to monitor and measure the crack l ength during the test, The crack growth rate along the interface of th e passivated silicon chip/underfill was calculated in terms of the loa d line deflection versus time curve obtained from the test, In additio n, the relationship between the crack length and the load line deflect ion was calibrated by using finite element analysis, The near tip disp lacement fields of the flip-chip package was also determined by the sa me method, The energy release rate was computed by using these near ti p displacement variables through an analytical expression derived by a uthors, The interface fracture toughness G(c) was determined by calcul ating the energy release rate corresponding to the crack length at the quasicrack arrest stage measured in the test, The underfill/chip pass ivation fracture toughness G(c) and the phase angle phi for the flip-c hip package used in our experiments are about 35 J/m(2) and -65 degree s, respectively.