Brazed metal-ceramic components play an important role in the manufacturing of specialized scientific instruments for space applications, where a compact, lightweight, and robust construction is always needed. Soldering and brazing are the best joining techniques if dissimilar materials are involved. For the current ESA mission JUICE, an optimized ion source main structure consisting of a stack of concentric metal electrodes and ceramic rings was to be brazed in vacuum. In the improved design one-piece electrodes manufactured from a molybdenum-copper composite were used having the same coefficient of thermal expansion as alumina. Different coating systems were evaluated for the composite material. The effectiveness of TiAlN as diffusion barrier for gold could be demonstrated in a first brazing test between the coated Mo85Cu15 and metallized Al₂O₃ parts joined with Incusil® ABATM. Several main structures satisfying all technical requirements were successfully brazed.
