Active brazing filler alloys promote wetting and good capillary action on surfaces that would otherwise be difficult to braze. These include important non-metal materials, such as ceramics, aluminum oxide (sapphire), and diamond.

The "working" elements of active brazing alloys are titanium and zirconium. Because Ti and Zr are very strong acceptors of oxygen (and there is obviously a lot of oxygen present in oxide-form within the sintered matrix of oxide-base ceramic materials), the joining process will depend very much on the ability of titanium/zirconium to react (at brazing temperature) with oxides that are present in the ceramics. To keep the titanium addition as "active" as possible during this high-temperature joining process, it is necessary to use a good vacuum brazing furnace, since a good, clean, tight vacuum furnace is the best way to exclude oxygen throughout the brazing cycle. Vacuum levels on the order of 10^-5 to 10^-6 Torr are often used, and the vacuum furnace leak-up rate should be less than 5 millitorr per hour. The vacuum furnace should be very clean, with no significant contamination on the inner cold-walls of the chamber because of condensation of outgassing materials from previous furnace cycles.