Large area bare Cu-Cu interconnection using micro-Cu paste at different sintering temperatures and pressures

The microstructure evolution, shear strength, and fracture behavior of large area (10 mm x 10 mm) bare Cu-Cu interconnection sintered using micro-Cu paste at different sintering temperatures (180, 200, 250, and 300 degrees C) and assistant pressures (0, 2, 5, and 10 MPa) were investigated in this study. The results showed that, as sintering temperature and assistant pressure increased, the microstructure of the sintered joints became denser, and the bonding quality of both the Cu dummy chip/Cu paste and Cu paste/Cu substrate interfaces was elevated, while more small crack or blind hole generated at the former interface. Moreover, the shear strength of the sintered joints increased with increasing sintering temperature and assistant pressure, a robust joint could be obtained under an assistant pressure of 10 MPa regardless of the sintering temperature as well as under an assistant pressure of 5 MPa at 250 and 300 degrees C. The fracture preferred at the Cu dummy chip/Cu paste interface, and the ductility of the sintered joint increased with increasing sintering temperature and assistant pressure. Accordingly, the optimized sintering temperature and assistant pressure are 250 degrees C and 10 MPa, respectively.