Direct bonded aluminum on silicon nitride substrates via silver-aluminum interfacial reactions

Silicon nitride (Si₃N₄) ceramic substrates are widely considered as promising candidates for high-power electronic modules due to their superior mechanical properties, high thermal conductivity, and a coefficient of thermal expansion well matched to power semiconductor devices. Currently, metallized Si₃N₄ substrates are predominantly copper-clad (Cu-Si₃N₄ substrates) fabricated via the active metal brazing (AMB) process. In the context of the emerging “copper-to-aluminum substitution” trend, aluminum-clad Si₃N₄ substrates (Al-Si₃N₄) have become particularly attractive for applications such as aerospace owing to its lightweight nature, high thermal conductivity, and low cost. Nevertheless, the low melting point of Al, below the processing temperature of AMB, necessitates alternative low-temperature bonding strategies. In this study, Ti/Ag thin films were deposited on Si₃N₄ substrates via electron beam evaporation (E-beam). Robust bonding between Al and Si₃N₄ was achieved in a direct bonded aluminum on Si₃N₄ (DBA@Si₃N₄) system via Ag-Al interfacial reactions. A maximum shear strength of 61 MPa was achieved at a bonding temperature of 570 ℃ under a bonding pressure of 1 MPa for 5 min, and a dense bonding joint was formed. This work provides technical support and a theoretical foundation for the development of high-performance Al-Si₃N₄ substrates.