Evaluation of Cu-AlN Joint Brazed with In-Based Active Brazing Filler Metals

Abstract

The In-Ti active fillers were examined for joining metallic copper (Cu) to aluminum nitride (AlN) ceramics. Brazing was carried out with In-Ti active brazing filler metals with various compositions, and the microscopic structure and mechanical strength of the Cu-filler-AlN-filler-Cu joint at various temperatures were investigated. When brazed with an In-rich filler of In-1wt%Ti, most of In atoms in the filler were diffused into the Cu plate leaving a Ti-rich reaction layer of 2-4μm thick at the Cu-AlN joint interface. The 4-point bending strength at 500°C increases linearly with the brazing temperature, whereas the strength at room temperature saturates at 40MPa. The specimen brazed at 820°C has the strength of 58MPa and 33MPa at 500°C and 600°C, respectively. On the other hand, when using Ti-rich fillers, e.g., In-7.7wt%Ti, In-15wt%Ti and In-23.8wt%Ti (the same as Ti3In4 composition), granular Ti-rich phases were formed at the interface, and the microcracks were observed in the AlN.