Microstructure evolution during Cu/AlN vacuum brazing using Ag–29.5Cu–3Sn–1.5Ti filler sheet: electron energy-loss spectroscopic study

AlN was brazed to Cu using Ag 66 Cu 29.5 Sn 3 Ti 1.5 filler sheets at various brazing temperatures and holding times. The brazeability of the filler sheet was investigated using constant-depth mode scanning acoustic microscopy analysis and cross-sectional observation. The microstructural evolution was clarified through detailed analyses using scanning electron microscopy and transmission electron microscopy. In particular, the reaction phase formed at the filler/AlN brazed interface was analyzed using electron energy-loss spectroscopy which is suitable for analyzing Ti N compounds. The experimental results indicated that the brazeability of the filler improved at higher brazing temperatures. Defect-free interface was achieved at brazing temperatures of 1123 and 1173 K. In addition, interdiffusion between Cu and the filler was observed. A coarse granular τ 1 -CuTi 5 Sn 3 and a fine crystalline NaCl-type TiN were observed at the filler and AlN brazed interface, suggesting that the brazing was achieved by formation of TiN through the reaction between Ti in the filler and AlN. • Defect-free interface between Cu and AlN was achieved via Ag-based filler. • Cu/AlN brazed interface was studied by advanced microscopic techniques. • TiN was formed at the filler/AlN interface. • Microstructural evolution mechanism during the Cu/AlN brazing was clarified.