The Interfacial Delamination and Fracture Behavior of Cu-filled Through Glass Vias (TGVs) Interposer Package with Multi-Layer RDLs under Thermo-mechanical Loads

This study investigates the interfacial delamination and fracture behavior of Cu-filled through-glass vias (TGVs) in glass interposer package with multilayer redistribution layers (RDLs) under thermo-mechanical loads by means of finite element simulation using the virtual crack closure technique (VCCT). The strain energy release rate (ERR) is calculated to evaluate the crack driving force for four representative cracks in the package structure: a vertical crack at the Cu/PI interface on the pad edge, a horizontal crack at the Cu/glass interface beneath the pad, a bulk crack in the glass near the pad edge and an interface edge crack at the TGV/glass boundary (i.e., Crack 1 to Crack 4). Results show that an interface edge crack near the left edge of the corner TGV exhibits the highest ERR, indicating a higher risk of interfacial delamination in the region. Temperature rise results in a significant increase in ERR, especially for an interface edge crack, which exhibits a near-doubling in ERR with every 50–60 °C increment. While the number of RDL layers has a limited impact on ERR, a higher Cu trace density leads to increase in crack-driving force. Increase of CTE of the glass substrate brings about significant reduction of ERR for all the cracks. In addition, conformal TGV structures with thinner metal layers prove beneficial in reducing ERR, meaning a low risk of fracture and interfacial delamination.