2 TEST SPECIMENS FOR DETERMINING THE INTERFACIAL FRACTURE-TOUGHNESS IN FLIP-CHIP ASSEMBLIES

Two test specimens are developed to measure interfacial fracture tough ness in flip-chip assemblies. The specimens consist of three layers: s ilicon chip, underfill, and circuit board. Two symmetric edge cracks a re embedded along the interface, either between the chip and the under fill or between the underfill and the circuit board. The specimens are subjected to four-point-bend lending and critical loads are obtained. Analytical solutions for energy release rate have been derived for th ese two specimens and used to obtain the toughness from the measured c ritical loads. These specimens have been used to evaluate material com binations of chip passivation, underfill and solder mask for desired i nterfacial strength.