A Low-Temperature Alumina/Copper Diffusion Bonding Process using La-Doped Titanium Interlayers

Ceramic-to-metal heterojunctions have been established to improve high-temperature stability for applications in aerospace and harsh environments. In this work, we employed low-temperature diffusion bonding to realize an alumina/Cu heterogeneous joint. Using a thin layer of lanthanum-doped titanium (La-doped Ti) to metallize the alumina surface, we achieved the bonding at a temperature range of 250-350 degrees C. We produced a uniform, thermally stable, and high-strength alumina/Cu joint after a hot-press process in vacuum. Signals from X-ray diffraction (XRD) suggested the successful diffusion of Ti and La into the alumina substrate, as Ti can easily substitute Al in alumina, and La has a better oxygen affinity than that of Al. The transmission electron microscopy and XRD results also showed the existence of CuxTiyO phases without CuxTiy or LaOx . In addition, the bonding strength of alumina/copper hot-pressed at 250, 300, and 350 degrees C were 7.5, 9.8 and 15.0 MPa, respectively. The process developed in this study successfully lowered the bonding temperature for the alumina/copper joint.