Fracture analysis on die attach adhesives for stacked packages based on in-situ testing and cohesive zone model

Failure behaviors of die and die attach adhesives for high integration and intensive 3-dimension stacked package device were carried out by using in-situ scanning electron microscope (SEM) in three-point bending tests and finite element (FE) analysis with the cohesive zone model. These experimental results indicated that the failure model consisted mainly of discontinuous cracks bridge-link pattern between the dies for the typical package on package (PoP) specimen, in which the discontinuous crack-bridging model for different fracture toughness of die attach adhesives was demonstrated by the mixed-model in the complex stress status. And the simulation results indicated also that the cohesive zone model (CZM) with an uncoupled bilinear traction-separation law (TSL) can characterize the fracture mechanism and discontinuous crack-bridging process of these samples. Some dominated parameters in the bilinear CZM could also qualitatively describe the damage initiation and evolution of cohesive elements. Therefore, the numerical and experimental results are in good agreement.