A combined simulation and experimental study on cracking and delamination behavior at the Cu/Polyimide interface of RDLs in chiplet package subjected to thermo-mechanical loads

In this work, experimental characterization by double cantilever beam (DCB) and three-point bending (TPB) tests combined with finite element simulations are conducted to obtain the cohesive zone model (CZM) parameters at the interface between the Cu trace and the polyimide (Cu/PI), and then the crack initiation and delamination behaviors at the Cu/PI interface in redistribution layers (RDLs) of chiplet packages under thermo-mechanical loads are studied. The influence of the layers and width of Cu trace on the interface reliability is also investigated. The results show that crack initiation and delamination mainly occur at the interface between the uppermost layer Cu trace and PI. The reduction of width of Cu trace has little effect on the interface reliability, while increasing the number of layers of Cu trace leads to an increased reliability of the uppermost Cu/PI interface.