Bonding Mechanisms in Silicon Nitride Brazing

Abstract

We investigated the wetting behavior and reactions of different metals on Si 3 N 4 using sessile drop measurements, analysis of reaction layers, and measurements of strengths of joined bars. Active metals, such as Al and Ti, and alloys that contain them react with Si 3 N 4 and cause wetting and spreading at the interface. Al‐Si 3 N 4 reaction at 900°C produced a thin layer of Al 2 O 3 at the interface. Reaction between Si 3 N 4 and Ag‐Cu‐To braze alloys at 900°C resulted in a complex microstructure in the reaction zone that contained TiN and titanium silicides. Breaking strengths of Si 3 N 4 bars joined with the Ag‐Cu‐Ti braze alloys were higher than those for Si 3 N 4 joined with Al, primarily because of the better wetting by the Ag‐Cu‐Ti alloys. Nonreactive metals and alloys such as Sn, In, Ag‐Cu, and Ag‐Cu‐Sn neither wet, spread, nor adhere to Si 3 N 4 substrates.